KR20130018493A - Display device and driving method thereof - Google Patents

Abstract

The present invention relates to a display device and a driving method thereof capable of preventing a defect in visibility, a change in luminance, and flicker visibility while reducing power consumption. The display device according to an embodiment of the present invention provides a still image and a moving picture. A display panel for displaying; A signal controller configured to control signals for driving the display panel; And a graphic processing unit which transmits input image data to the signal controller, wherein the signal controller includes a frame memory for storing the input image data, and wherein the display panel displays the video at a first frequency. And is driven at a second frequency lower than the first frequency when displaying the still image.

Description

DISPLAY DEVICE AND DRIVING METHOD THEREOF [0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display device and a driving method thereof, and more particularly, to a display device and a driving method thereof capable of preventing a defect in visibility, a change in luminance, and visibility of flicker while reducing power consumption.

Display devices are required for computer monitors, televisions, mobile phones, etc., which are widely used today. The display device includes a cathode ray tube display device, a liquid crystal display device, and a plasma display device.

Such a display device includes a graphics processing unit (GPU), a display panel, and a signal control unit. The graphic processing apparatus transmits the image data of the screen to be displayed on the display panel to the signal control section, and the signal control section generates a control signal for driving the display panel and transmits the control signal to the display panel together with the image data to drive the display device.

The image displayed on the display panel is largely divided into a still image and a moving image. The display panel displays several frames per second, and when the image data of each frame is the same, a still image is displayed. If the image data of each frame is different, the video is displayed.

In this case, the signal controller may receive the same image data from the graphics processing apparatus every frame not only when the display panel displays a moving image but also when displaying a still image, thereby consuming a lot of power.

Recently, many studies have been attempted to reduce power consumption of display devices. As one of such methods, a method has been proposed in which a frame memory is added to a signal control unit to store image data in a still image, and a stored image data is provided to a display panel while a still image is displayed. This is called a panel self refresh (PSR) method. Since the image data is not transmitted from the graphic processing apparatus while displaying a still image, power consumption can be reduced by deactivating the graphics processing apparatus.

However, when driving in the PSR method, there is a problem in that power consumption increases as frame memory is added.

The present invention has been made to solve the above problems, and an object thereof is to provide a display device and a driving method thereof capable of reducing power consumption and preventing defects in visibility.

In addition, an object of the present invention is to provide a display device and a driving method thereof capable of preventing a change in luminance while reducing power consumption.

Another object of the present invention is to provide a display device and a method of driving the same, which can prevent flicker from being recognized while reducing power consumption.

Another object of the present invention is to provide a display device and a method of driving the same, which can reduce flicker due to an increase in leakage current while reducing power consumption.

According to an aspect of the present invention, there is provided a display device including: a display panel configured to display a still image and a moving image; A signal controller configured to control signals for driving the display panel; And a graphic processing unit which transmits input image data to the signal controller, wherein the signal controller includes a frame memory for storing the input image data, and wherein the display panel displays the video at a first frequency. And is driven at a second frequency lower than the first frequency when displaying the still image.

The graphic processing apparatus may transmit a still image start signal and a still image end signal to the signal controller.

The signal controller may store the input image data in the frame memory when the still image start signal is applied, and output the stored image data stored in the frame memory to the display panel at the second frequency. You can disable the transfer.

The signal controller may activate transmission of the input image data when the still image end signal is applied, and output the input image data to the display panel at the first frequency.

The length of the vertical blank section when driven at the second frequency may be longer than the length of the vertical blank section when driven at the first frequency.

After the still image start signal is applied, the display panel may be driven at a frequency higher than the second frequency and lower than the first frequency during the S1 frame.

During the S1 frame, the length of the vertical blank section may be gradually increased.

After the still image termination signal is applied, the display panel may be driven at a frequency higher than the second frequency and lower than the first frequency during the S2 frame.

During the S2 frame, the length of the vertical blank section may be gradually shortened.

The display panel includes a substrate; A gate line and a data line formed on the substrate; A switching element connected to the gate line and the data line; And a pixel electrode connected to the switching element, and a gate signal including a gate on voltage and a gate off voltage may be applied to the gate line.

The clock frequency of the gate signal when driven at the second frequency may be lower than the clock frequency of the gate signal when driven at the first frequency.

The length of the vertical blank section when driven at the second frequency may be longer than the length of the vertical blank section when driven at the first frequency.

The display panel may be driven at the second frequency until the frame to which the still image end signal is applied ends.

The display panel includes a gate driver including a gate line and a data line to drive the gate line; And a data driver for driving the data line, wherein the signal controller may transmit an STV signal and a CPV signal to the gate driver.

The signal controller may transmit the STV signal to the gate driver at the start of one frame except for the point where the second frequency is changed from the second frequency to the first frequency.

The signal controller may control the width of the CPV signal when the display panel is driven at the first frequency and when the display panel is driven at the second frequency.

The signal controller has a width equal to p clock signals when the display panel is driven at the first frequency and has a width equal to p clock signals when the display panel is driven at the second frequency. It can be controlled to have the same width as the clock signal of less than p times.

The signal controller may gamma-correct the image data when the display panel is driven at the second frequency and transmit the corrected image data to the display panel.

The signal controller counts the number of still image continuous frames input after the still image start signal is applied and before the still image end signal is applied, and when the still image start signal is applied after the still image end signal is applied. The apparatus may further include a frame counting unit for counting the number of continuous frames inputted until.

The signal controller may store the input image data in the frame memory when the number of the continuous image continuous frames is greater than or equal to x, disable transmission of the input image data, and transmit the input image data when the number of the continuous image frames is greater than y. Can be activated.

The signal controller outputs the stored image data stored in the frame memory to the display panel when the number of the continuous image frames is greater than or equal to x. May be output at the first frequency.

A display device according to an embodiment of the present invention includes a light source unit for irradiating light to the display panel; And a light source driver configured to control signals for driving the light source unit.

The light source driver may drive the light source unit at a first ratio when the display panel is driven at a first frequency, and may drive the light source unit at a second ratio when the display panel is driven at a second frequency.

The second ratio may have a lower value than the first ratio when the display panel is in the normally black mode, and the second ratio may have a higher value than the first ratio when the display panel is in the normally white mode. have.

The signal controller may include a signal receiver configured to receive the input image data from the graphic processing apparatus; And a driving frequency selector configured to select the first frequency when displaying the still image and to select the second frequency when displaying the video.

The light source driver may include a driving frequency receiver configured to receive a driving frequency of the display panel from the signal controller; A light source unit drive ratio selector configured to determine a drive ratio of the light source unit according to the drive frequency; And a light source driving signal generator configured to generate a signal for driving the light source according to the driving ratio of the light source unit.

The light source driver may maintain a constant driving ratio of the light source unit when the display panel is driven at the first frequency, and periodically change a driving ratio of the light source unit when the display panel is driven at the second frequency. have.

The display panel is in a normally black mode, and the light source driver drives the light source unit at a first ratio when the display panel is driven at the first frequency, and the light source unit when the display panel is driven at the second frequency. May be driven at a rate that is sequentially lowered from the first ratio and the first ratio.

The display panel includes a gate driver including a gate line and a data line to drive the gate line; And a data driver for driving the data line, wherein the signal controller may transmit an STV signal to the gate driver at the start of every frame.

When the display panel is driven at the second frequency, the light source driving unit drives the light source unit at the first rate at the point where the STV signal is transmitted, and the light source unit is driven from the first ratio until the next STV signal is transmitted. It can be driven at a rate that sequentially decreases.

A transmission period of the STV signal when the display panel is driven at the first frequency may be the same as a change period of a driving ratio of the light source unit when the display panel is driven at the second frequency.

The display panel is in a normally white mode, and the light source driving unit drives the light source unit at a first ratio when the display panel is driven at the first frequency, and the light source unit when the display panel is driven at the second frequency. May be driven at a first rate and a rate that increases sequentially from the first rate.

The display panel includes a substrate; A gate line, a data line, and a storage electrode line formed on the substrate; A first switching element connected to the gate line and the data line; And a sustain capacitor connected to the first switching element and the sustain electrode line, wherein the common voltage input to the sustain electrode line has a constant value when the display panel is driven at the first frequency. When driven at this second frequency, the common voltage may have a value that changes with time.

The display panel may include a second switching element and a third switching element formed between the storage electrode line and the storage capacitor; And a sustain electrode control line formed on the substrate, wherein the second switching element and the third switching element each include a control terminal, an input terminal, and an output terminal. An input terminal of a switching element is connected to the sustain electrode line, an output terminal of the second switching element and the third switching element is connected to the sustain capacitor, and a control terminal of the second switching element is connected to the gate line The control terminal of the third switching element may be connected to the sustain electrode control line.

The common voltage may have a first voltage in a first section and a second voltage higher than the first voltage in a second section when the display panel is driven at the second frequency.

One frame may include a valid section in which image data is transmitted and a vertical blank section in which image data is not transmitted, the first section may be the valid section, and the second section may be the vertical blank section.

The control voltage input to the sustain electrode control line may have a gate-off voltage in the first section and a gate-on voltage in the second section.

The common voltage may have a third voltage higher than the second voltage in a third section when the display panel is driven at the second frequency.

One frame includes a valid section in which image data is transmitted and a vertical blank section in which image data is not transmitted, the first section is the valid section, and the second section is a portion of the vertical blank section, and the third The section may be the remaining part of the vertical blank section.

The common voltage may have a first voltage in a first section when the display panel is driven at the second frequency, and may swing to the first voltage and a second voltage higher than the first voltage in a second section.

The common voltage may gradually change with a value between the first voltage and the second voltage when changing from the first voltage to the second voltage.

A display device according to an embodiment of the present invention includes a gate driver for driving the gate line; And a data driver configured to drive the data line, wherein the signal controller comprises: a calculator configured to calculate a representative value of stored image data stored in the frame memory; A line memory for storing the representative value; And a kickback correction unit configured to generate the auxiliary image data by correcting the representative value according to a kickback voltage, wherein the data driver is further configured to output an auxiliary voltage corresponding to the auxiliary image data in a vertical blank period when displaying the still image. Can be applied to the line.

The data line may include a plurality of data lines, and the calculator may calculate a representative value of the stored image data for each data line.

The representative value may be an average gray value of the stored image data.

The representative value may be an average gray value of upper t bits of the stored image data.

The representative value may be an intermediate value between the maximum gray value and the minimum gray value of the stored image data.

(Ga: 상기 보조 영상 데이터의 계조값, Gr: 상기 대표값, dG: 상기 대표값에 따른 킥백 보상 계조값)에 따라 생성될 수 있다.The auxiliary image data

(Ga: gray value of the auxiliary image data, Gr: the representative value, dG: kickback compensation gray value based on the representative value).

The kickback compensation gray value may be a value stored in the form of a lookup table or calculated by a function.

When the kickback compensation gradation value is a value calculated by a function, the function calculates the kickback compensation gradation value at the minimum gradation, the kickback compensation gradation value at the maximum gradation, and the gradation value when the magnitude of the kickback compensation gradation value is the maximum. Can be made by linear interpolation.

The display panel may include a gate line and a data line; A switching device having a control terminal connected to the gate line and an input terminal connected to the data line; And a pixel electrode connected to an output terminal of the switching element, wherein a gate signal including a gate on voltage and a gate off voltage is applied to the gate line, and the display panel is driven at the second frequency. The gate-off voltage is Va-0.2 kVa k <Voff2 <Va + 0.2 kVa (Voff2: the gate-off voltage when the display panel is driven at the second frequency, Va: a positive pixel on the pixel electrode Leakage current flowing between the input terminal and the output terminal of the switching element when a voltage is applied and Leakage flowing between the input terminal and the output terminal of the switching element when a negative pixel voltage is applied to the pixel electrode The voltage of the control terminal of the switching element when the current is the same.

When the display panel is driven at the second frequency, the gate-off voltage is set to Va−0.1┃Va┃ ≦ Voff2 ≦ Va + 0.1┃Va┃ (Voff2: when the display panel is driven at the second frequency, the gate off voltage is obtained. Voltage, Va: The leakage current flowing between the input terminal and the output terminal of the switching element when the positive pixel voltage is applied to the pixel electrode and the negative current of the switching element when the negative pixel voltage is applied to the pixel electrode. And a voltage of the control terminal of the switching element when the leakage current flowing between the input terminal and the output terminal is the same.

The gate-off voltage when the display panel is driven at the first frequency is Va−0.2 kVa┃ ≦ Voff1 ≦ Va + 0.2 kVa ′ (Voff1: when the display panel is driven at the first frequency. Gate-off voltage, Va: The switching when the leakage current flowing between the input terminal and the output terminal of the switching element when the positive pixel voltage is applied to the pixel electrode and the negative pixel voltage is applied to the pixel electrode. And a voltage of the control terminal of the switching element when the leakage current flowing between the input terminal and the output terminal of the element is the same.

The gate-off voltage when the display panel is driven at the first frequency is Va−0.1 μs Va ′ ≦ Voff1 ≦ Va + 0.1 μs Va ′ (Voff1: when the display panel is driven at the first frequency Gate-off voltage, Va: The switching when the leakage current flowing between the input terminal and the output terminal of the switching element when the positive pixel voltage is applied to the pixel electrode and the negative pixel voltage is applied to the pixel electrode. And a voltage of the control terminal of the switching element when the leakage current flowing between the input terminal and the output terminal of the element is the same.

The gate off voltage when the display panel is driven at the first frequency may be the same as the gate off voltage when the display panel is driven at the second frequency.

The gate off voltage when the display panel is driven at the first frequency may be lower than the gate off voltage when the display panel is driven at the second frequency.

A display device according to an embodiment of the present invention includes a gate driver for driving the gate line; And a data driver configured to drive the data line, wherein the signal controller stores the input image data in the frame memory when the still image start signal is applied, and stores the stored image data stored in the frame memory. The data driver may be applied to the data driver to deactivate the transmission of the input image data.

When the still image end signal is applied, transmission of the input image data may be activated, and the input image data may be applied to the data driver.

The gate driver may be attached to one side of the display panel.

The gate driver may be mounted in the display panel together with the gate line, the data line, and the switching element.

A method of driving a display device according to an embodiment of the present invention includes a display panel for displaying a moving image and a still image, and a signal controller for controlling signals for driving the display panel. Transmitting image data and driving the display panel at a first frequency; Applying a still image start signal; Changing a driving frequency of the display panel to a second frequency lower than the first frequency; Applying a still image end signal; And changing a driving frequency of the display panel to the first frequency.

When the still image start signal is applied, the input image data may be stored in a frame memory, the transmission of the input image data may be deactivated, and the stored image data stored in the frame memory may be output to the display panel at the second frequency. Can be.

When the still image end signal is applied, the transmission of the input image data may be activated and the input image data may be output to the display panel at the first frequency.

The length of the vertical blank section when driven at the second frequency may be longer than the length of the vertical blank section when driven at the first frequency.

After the still image start signal is applied, the display panel may be driven at a frequency higher than the second frequency and lower than the first frequency during the S1 frame.

During the S1 frame, the length of the vertical blank section may be gradually increased.

After the still image end signal is applied, the display panel may be driven at a frequency higher than the second frequency and lower than the first frequency during the S2 frame.

During the S2 frame, the length of the vertical blank section may be gradually shortened.

The display panel includes a substrate; A gate line and a data line formed on the substrate; A switching element connected to the gate line and the data line; And a pixel electrode connected to the switching element, and applying a gate signal including a gate on voltage and a gate off voltage to the gate line.

The clock frequency of the gate signal when driven at the second frequency may be lower than the clock frequency of the gate signal when driven at the first frequency.

The length of the vertical blank section when driven at the second frequency may be longer than the length of the vertical blank section when driven at the first frequency.

The display panel is driven at the second frequency until the frame to which the still image end signal is applied ends, and the driving frequency of the display panel is changed to the first frequency in the next frame to which the still image end signal is applied. Can be.

The display panel includes a gate driver including a gate line and a data line to drive the gate line; And a data driver for driving the data line, wherein the signal controller may transmit an STV signal and a CPV signal to the gate driver.

The signal controller may transmit the STV signal to the gate driver at the start of every frame except for the point where the second frequency is changed from the second frequency to the first frequency.

The signal controller may control the width of the CPV signal when the display panel is driven at the first frequency and when the display panel is driven at the second frequency.

The signal controller has a width equal to p clock signals when the display panel is driven at the first frequency and has a width equal to p clock signals when the display panel is driven at the second frequency. It can be controlled to have the same width as the clock signal of less than p times.

The signal controller may gamma-correct the image data when the display panel is driven at the second frequency and transmit the corrected image data to the display panel.

Counting the number of continuous image continuous frames input after the still image start signal is applied but before the still image end signal is applied; And counting the number of continuous video frames inputted after the still image end signal is applied until the still image start signal is applied.

The signal controller may store the input image data in the frame memory when the number of the continuous image continuous frames is greater than or equal to x, disable transmission of the input image data, and transmit the input image data when the number of the continuous image frames is greater than y. Can be activated.

The signal controller outputs the stored image data stored in the frame memory to the display panel when the number of the continuous image frames is greater than or equal to x. May be output at the first frequency.

The light source unit may be driven at a first ratio when the display panel is driven at a first frequency, and the light source unit may be driven at a second ratio when the display panel is driven at a second frequency.

The second ratio may have a lower value than the first ratio when the display panel is in the normally black mode, and the second ratio may have a higher value than the first ratio when the display panel is in the normally white mode. have.

The selection of the driving ratio of the light source unit according to the driving frequency of the display panel may be performed using a lookup table or a function.

Switching of the driving frequency of the display panel and the driving ratio of the light source unit may be performed in the vertical blank period.

The driving ratio of the light source unit may be kept constant when the display panel is driven at the first frequency, and the driving ratio of the light source unit may be periodically changed when the display panel is driven at the second frequency.

The display panel is in a normally black mode, and the light source unit is driven at a first ratio when the display panel is driven at the first frequency, and the light source unit is driven at a first ratio when the display panel is driven at the second frequency. And a rate that is sequentially lowered from the first ratio.

The display panel may include a gate line and a data line, and the display device may include a gate driver configured to drive the gate line; And a data driver for driving the data line, wherein the signal controller may transmit an STV signal to the gate driver at the start of every frame.

When driving the display panel at the second frequency, the light source unit is driven at a first rate at the point where the STV signal is transmitted, and the light source unit is sequentially lowered from the first rate until the next STV signal is transmitted. Can be driven at a rate.

The transmission period of the STV signal when the display panel is driven at the first frequency may be the same as the change period of the driving ratio of the light source unit when the display panel is driven at the second frequency.

The display panel is in a normally white mode, and the light source unit is driven at a first ratio when the display panel is driven at the first frequency, and the light source unit is driven at a first ratio when the display panel is driven at the second frequency. And driving at a rate sequentially increasing from the first ratio.

When driving the display panel at the first frequency, the signal controller applies a common voltage having a constant value to the display panel, and when driving the display panel at the second frequency, the signal controller is configured to change a value. The branch may apply a common voltage to the display panel.

When the display panel is driven at the second frequency, the signal controller may apply a common voltage having a first voltage in a first section and having a second voltage higher than the first voltage in a second section.

One frame may include a valid section in which image data is transmitted and a vertical blank section in which image data is not transmitted, the first section may be the valid section, and the second section may be the vertical blank section.

When the display panel is driven at the second frequency, the signal controller may apply a common voltage having a third voltage higher than the second voltage to the display panel in a third section.

One frame includes a valid section in which image data is transmitted and a vertical blank section in which image data is not transmitted, the first section is the valid section, and the second section is a portion of the vertical blank section, and the third The section may be the remaining part of the vertical blank section.

When the display panel is driven at the second frequency, the signal controller has a first voltage in a first section and swings to the first voltage and a second voltage higher than the first voltage in a second section. Can be applied.

The common voltage may gradually change with a value between the first voltage and the second voltage when changing from the first voltage to the second voltage.

According to an exemplary embodiment, there is provided a method of driving a display device, comprising: storing the input image data in a frame memory when the still image start signal is applied; Calculating a representative value of the stored image data stored in the frame memory; Generating auxiliary image data by correcting the representative value according to a kickback voltage; And applying an auxiliary voltage corresponding to the auxiliary image data to a data line in a vertical blank period.

The data line may include a plurality of data lines, and the representative value of the stored image data may be calculated for each data line.

The representative value may be an average gray value of the stored image data.

The representative value may be an average gray value of upper t bits of the stored image data.

The representative value may be an intermediate value between the maximum gray value and the minimum gray value of the stored image data.

(Ga: 상기 보조 영상 데이터의 계조값, Gr: 상기 대표값, dG: 상기 대표값에 따른 킥백 보상 계조값)에 따라 생성될 수 있다.The auxiliary image data

(Ga: gray value of the auxiliary image data, Gr: the representative value, dG: kickback compensation gray value based on the representative value).

The kickback compensation gray value may be a value stored in the form of a lookup table or calculated by a function.

When the kickback compensation gradation value is a value calculated by a function, the function calculates the kickback compensation gradation value at the minimum gradation, the kickback compensation gradation value at the maximum gradation, and the gradation value when the magnitude of the kickback compensation gradation value is the maximum. Can be made by linear interpolation.

When the display panel is driven at the second frequency, the signal controller is set to Va-0.2 의 Va┃ ≦ Voff2 ≦ Va + 0.2┃Va┃ (Voff2: gate off when the display panel is driven at the second frequency). Voltage, Va: The leakage current flowing between the input terminal and the output terminal of the switching element when the positive pixel voltage is applied to the pixel electrode and the negative current of the switching element when the negative pixel voltage is applied to the pixel electrode. A gate off voltage having a range of the voltage of the control terminal of the switching element when the leakage current flowing between the input terminal and the output terminal is the same may be applied to the display panel.

When the display panel is driven at the second frequency, the signal controller includes Va−0.1 μVa μ ≦ Voff 2 ≦ Va 0.1 μVa μV (Voff2: gate off voltage when the display panel is driven at the second frequency). Va: the leakage current flowing between the input terminal and the output terminal of the switching element when a positive pixel voltage is applied to the pixel electrode and the negative current of the switching element when a negative pixel voltage is applied to the pixel electrode. A gate-off voltage having a range of the voltage of the control terminal of the switching element when the leakage current flowing between the input terminal and the output terminal is the same may be applied to the display panel.

When the display panel is driven at the first frequency, the signal controller includes Va-0.2┃Va┃ ≦ Voff1 ≦ Va + 0.2┃Va┃ (Voff1: gate off when the display panel is driven at the first frequency). Voltage, Va: The leakage current flowing between the input terminal and the output terminal of the switching element when the positive pixel voltage is applied to the pixel electrode and the negative current of the switching element when the negative pixel voltage is applied to the pixel electrode. And a voltage of the control terminal of the switching element when the leakage current flowing between the input terminal and the output terminal is the same.

When the display panel is driven at the first frequency, the signal controller includes Va-0.1┃Va┃ ≦ Voff1 ≦ Va + 0.1┃Va┃ (Voff1: gate off when the display panel is driven at the first frequency). Voltage, Va: The leakage current flowing between the input terminal and the output terminal of the switching element when the positive pixel voltage is applied to the pixel electrode and the negative current of the switching element when the negative pixel voltage is applied to the pixel electrode. And a voltage of the control terminal of the switching element when the leakage current flowing between the input terminal and the output terminal is the same.

The gate off voltage when the display panel is driven at the first frequency may be the same as the gate off voltage when the display panel is driven at the second frequency.

The gate off voltage when the display panel is driven at the first frequency may be lower than the gate off voltage when the display panel is driven at the second frequency.

The display device and the driving method thereof according to the exemplary embodiment of the present invention as described above have the following effects.

The display device and the driving method thereof according to an embodiment of the present invention have an effect of reducing power consumption by driving at a lower frequency when displaying a still image than when displaying a moving image. At this time, by lowering the frequency in the still image, the power consumption can be reduced by more than an increase in power consumption as the frame memory is added.

In addition, by displaying a still image at a point where the still image is converted to a moving image, it is possible to prevent a defect in visibility due to a frequency change.

In addition, even when the frequency is changed, the width of the CPV signal is set to be constant or by gamma correction, thereby preventing the defect of visibility due to the frequency change.

In addition, by dimming and driving the light source unit according to the change of the frequency, there is an effect of preventing the luminance change caused by the change of the frequency.

Also, by changing the driving frequency of the display panel when the number of still image continuous frames and the number of moving image continuous frames is equal to or greater than a predetermined number, there is an effect that the luminance change due to the change of the frequency can be further prevented.

When the display panel is driven at the second frequency, the common voltage is changed to change the luminance, thereby preventing the flicker from being viewed.

In addition, when the display panel is driven at the second frequency, a leakage current is calculated by calculating a value representing the stored image data for each data line in the vertical blank period and applying an auxiliary voltage corresponding to the kickback correction value to the data line. And thus, flicker can be reduced.

In addition, the range of the gate-off voltage when the display panel is driven at the second frequency is determined by the leakage current of the switching element when the positive pixel voltage is applied to the pixel electrode and the switching element when the negative pixel voltage is applied to the pixel electrode. By setting the leakage current at the same point as the reference, flicker can be reduced.

1 is a block diagram of a display device according to a first embodiment of the present invention.
2 is a block diagram illustrating a signal controller of a display device according to a first exemplary embodiment of the present invention.
3 is a diagram illustrating control signals of a display device according to a first exemplary embodiment of the present invention.
4 is a diagram illustrating control signals of a display device according to a first exemplary embodiment of the present invention.
5 illustrates a DE signal and a Vsync signal used in the display device according to the first embodiment of the present invention.
6 illustrates a gate signal and an STV signal when the display panel is driven at a first frequency in the display device according to the first exemplary embodiment of the present invention.
7 to 9 illustrate gate signals and STV signals when a display panel is driven at a second frequency in the display device according to the first exemplary embodiment of the present invention.
FIG. 10 is a diagram illustrating a clock signal and a CPV signal when driven at a first frequency in the display device according to the first embodiment of the present invention.
FIG. 11 is a diagram illustrating a clock signal and a CPV signal when driven at a second frequency in the display device according to the first embodiment of the present invention.
12 is a flowchart illustrating a method of correcting image data in the display device according to the first embodiment of the present invention.
13 is a block diagram of a display device according to a second exemplary embodiment of the present invention.
14 is a block diagram illustrating a light source driver of a display device according to a second exemplary embodiment of the present invention.
15 is a flowchart illustrating a method of driving a display device according to a second exemplary embodiment of the present invention.
16 to 18 are block diagrams of signal controllers illustrating, in sequence, a method of driving a display device according to a second exemplary embodiment of the present invention.
19 and 20 are block diagrams illustrating a light source driving unit in a step-by-step manner, in a sequence, of a method of driving a display device according to a first embodiment of the present invention.
21 is a block diagram of a signal controller according to a third embodiment of the present invention.
22 is a flowchart illustrating a method of driving a display device according to a third exemplary embodiment of the present invention.
23 to 26 are block diagrams of signal controllers illustrating, in sequence, a method of driving a display device according to a third exemplary embodiment of the present invention.
27 is a flowchart illustrating a method of driving a display device according to a fourth embodiment of the present invention.
28 and 29 illustrate driving ratios of an STV signal and a light source unit of a display device according to a fourth exemplary embodiment of the present invention.
30 is an equivalent circuit diagram of one pixel of the display device according to the fifth exemplary embodiment of the present invention.
31 is a diagram illustrating control signals when a display panel of a display device according to a fifth exemplary embodiment displays a still image.
32 is a diagram illustrating control signals when a display panel of a display device according to a fifth exemplary embodiment displays a still image.
33 is an equivalent circuit diagram of one pixel of the display device according to the sixth exemplary embodiment.
34 is a diagram illustrating control signals when a display panel of a display device according to a sixth exemplary embodiment displays a still image.
35 is a diagram illustrating control signals when a display panel of a display device according to a sixth exemplary embodiment displays a still image.
36 is a graph illustrating power consumption according to driving frequency.
FIG. 37 is a graph illustrating the voltage at one terminal of the sustain capacitor when the display panel is driven at 60 Hz.
38 is a graph illustrating the voltage at one terminal of the sustain capacitor when the display panel is driven at 10 Hz.
FIG. 39 is a graph illustrating voltages of one terminal of the sustain capacitor when the display panel is driven at 10 Hz according to the fifth exemplary embodiment of the present invention.
40 is a block diagram illustrating a signal controller of a display device according to a seventh exemplary embodiment of the present invention.
FIG. 41 is a graph illustrating a kickback voltage based on a gray value of image data. FIG.
42 is a graph illustrating a kickback compensation gray value based on the gray value of the image data.
43 is an equivalent circuit diagram of one pixel of the display device according to the seventh embodiment of the present invention.
44 is a diagram illustrating a leakage current when a predetermined voltage is applied during a vertical blank period in the display device according to the seventh exemplary embodiment of the present invention.
45 is a diagram illustrating one pixel of a display device according to an eighth exemplary embodiment of the present invention.
46 is a graph illustrating current between an input terminal and an output terminal according to a gate voltage in a switching element of a display device according to an eighth exemplary embodiment of the present invention.
47 is a diagram illustrating luminance characteristics when displaying a still image in the display device according to the prior art.
48 is a diagram illustrating luminance characteristics when displaying a still image in the display device according to the eighth embodiment of the present invention.
49 is a graph illustrating a flicker value according to a gate off voltage value when displaying a still image in the display device according to the eighth exemplary embodiment of the present invention.
50 is a graph illustrating the intensity of light emitted from another display panel at time.
FIG. 51 shows equipment used for flicker measurement. FIG.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

In the drawings, the thickness of layers, films, panels, regions, etc., are exaggerated for clarity. Like parts are designated with like reference numerals throughout the specification. When a part of a layer, film, region, plate, etc. is said to be "on" another part, this includes not only the other part being "right over" but also another part in the middle. On the contrary, when a part is "just above" another part, there is no other part in the middle.

First, a display device according to a first exemplary embodiment of the present invention will be described with reference to the accompanying drawings.

1 is a block diagram of a display device according to a first embodiment of the present invention.

As shown in FIG. 1, the display device according to the first exemplary embodiment includes a display panel 300 displaying an image, a signal controller 600 controlling signals for driving the display panel 300, and an input image. The graphic processing apparatus 700 transmits data to the signal controller 600.

The display panel 300 may receive the image data DAT from the signal controller 600 to display a still image and a video. If a plurality of consecutive frames have the same image data DAT, a still image is displayed, and if they have different image data DAT, a moving image is displayed.

The display panel 300 includes a plurality of gate lines G1 -Gn and a plurality of data lines D1 -Dm, the plurality of gate lines G1 -Gn extend in a horizontal direction, and the plurality of data lines D1-Dm extends in the vertical direction while crossing the plurality of gate lines G1-Gn.

One gate line G1 -Gn and one data line D1 -Dm are connected to one pixel, and one pixel line is connected to the gate line G1 -Gn and data line D1 -Dm. A switching element Q. The control terminal of the switching element Q is connected to the gate lines G1-Gn, the input terminal is connected to the data lines D1-Dm, and the output terminals are the liquid crystal capacitor C _lc and the sustain capacitor C. _st ).

Although the display panel 300 of FIG. 1 is illustrated as a liquid crystal display panel, the display panel 300 to which the present invention can be applied may include various displays such as an organic light emitting display panel, an electrophoretic display panel, and a plasma display panel in addition to the liquid crystal display panel. Panels can be used.

The signal controller 600 may receive the input image data received from the graphics processing apparatus 700 and control signals thereof, for example, a vertical synchronization signal Vsync, a horizontal synchronization signal Hsync, a main clock signal MCLK, and data in In response to the enable signal DE or the like, the input image data and the control signal are processed to suit the operating conditions of the liquid crystal display panel 300, and then the gate control signal CONT1 and the data control signal CONT2 are generated and output.

The gate control signal CONT1 is a vertical synchronization start signal STV for indicating the start of output of the gate-on pulse (high period of the gate signal GS), a gate clock signal CPV for controlling the output timing of the gate-on pulse, and the like. It includes.

The data control signal CONT2 includes a horizontal synchronization start signal STH indicating the start of input of the image data DAT, a load signal TP for applying a corresponding data voltage to the data lines D1 -Dm, and the like.

The graphic processing apparatus 700 transmits input image data to the signal controller 600. When the display panel 300 displays a video, the graphic processing apparatus 700 transmits input image data to the signal controller 600 every frame. When the display panel 300 displays a still image, the signal controller 600 stores the input image data received from the graphic processing apparatus 700 and transmits the input image data to the display panel 300. The input image data is not transmitted to the signal controller 600. That is, when the display panel 300 displays a still image, the graphic processing apparatus 700 is deactivated.

The graphic processing apparatus 700 transmits a still image start signal to the signal controller 600 at a switching time point at which the input image data displaying the moving image is transmitted while the input image data displaying the moving image is transmitted. Also, the graphic processing apparatus 700 transmits a still image end signal to the signal controller 600 at a switching time point during which the input image data displaying the still image is transmitted while the input image data displaying the still image is transmitted.

The display device according to the first exemplary embodiment of the present invention may further include a gate driver 400 driving the gate lines G1 -Gn and a data driver 500 driving the data lines D1 -Dm.

The plurality of gate lines G1 -Gn of the display panel 300 are connected to the gate driver 400, and the gate driver 400 is gated on in response to the gate control signal CONT1 applied from the signal controller 600. The voltage Von and the gate off voltage Voff are alternately applied to the gate lines G1 -Gn.

The display panel 300 may be formed of two substrates facing each other and bonded to each other, and the gate driver 400 may be formed to be attached to one edge of the display panel 300. In addition, the gate driver 400 may be mounted on the display panel 300 along with the gate lines G1 -Gn, the data lines D1 -Dm, and the switching element Q on the display panel 300. That is, the gate driver 400 may also be formed in the process of forming the gate lines G1 -Gn, the data lines D1 -Dm, and the switching element Q.

The plurality of data lines D1 -Dm of the display panel 300 are connected to the data driver 500, and the data driver 500 receives the data control signal CONT2 and the image data DAT from the signal controller 600. Received. The data driver 500 converts the image data DAT into a data voltage using the gray voltage generated by the gray voltage generator 800, and transfers the image data DAT to the data voltages D1 -Dm.

Next, the signal controller of the display device according to the first embodiment of the present invention will be described.

2 is a block diagram illustrating a signal controller of a display device according to a first exemplary embodiment of the present invention.

The signal controller 600 selects a first frequency when displaying a video signal, a signal receiver 610 that receives various signals from the graphic processing apparatus 700, a frame memory 640 that stores input image data, and a moving image. It may include a driving frequency selection unit 650 for selecting the second frequency when displaying.

The signal receiver 610 receives the input image data, the still image start signal, and the still image end signal from the graphic processing apparatus 700. Although not shown, the signal receiver 610 is connected to the graphic processing apparatus 700 by a main link and an auxiliary link. The signal receiver 610 receives input image data from the graphic processing apparatus 700 through a main link. In addition, the signal receiver 610 receives a still image start signal and a still image end signal from the graphic processing apparatus 700 through an auxiliary link, and outputs a signal indicating a driving state of the display panel 300 to the graphic processing apparatus 700. To send.

The frame memory 640 receives and stores input image data from the signal receiver 610. The frame memory 640 is not used when the display panel displays a moving picture. When the display panel displays a still image, the input image data is stored in the frame memory 640, and the stored image data stored in the frame memory 640 is output to the display panel 300.

The driving frequency selector 650 selects a first frequency when the display panel displays a moving image and selects a second frequency when displaying a still image. When displaying a video, the input image data is received from the signal receiver 610 and output to the display panel 300 at a first frequency. When displaying a still image, the storage image data is received from the frame memory 640 and output to the display panel 300 at a second frequency.

At this time, the second frequency has a lower value than the first frequency.

For example, the first frequency may be 60 Hz, which refers to playing 60 frames per second to display a screen. Also, the second frequency may be 10 Hz, which refers to displaying 10 frames by reproducing 10 frames per second. In this case, when displaying a still image, power consumption is reduced to about 1/6 as compared with displaying a moving image. Therefore, by setting the frequency at the time of displaying a still image to a certain ratio or less than when displaying a moving image, the power consumption can be reduced by more than the increase in power consumption due to the addition of the frame memory.

When displaying a video, there is a problem that the movement looks unnatural when the frequency is lowered. However, when displaying a still image, a frame having the same image data (DAT) is repeatedly played. Is not. However, since the flicker increases when the frequency is lowered, it is desirable to lower the frequency so that the flicker is not recognized.

Hereinafter, a method of driving the display device according to the first exemplary embodiment of the present invention will be described with reference to FIGS. 1 and 3.

3 is a diagram illustrating control signals of a display device according to a first exemplary embodiment of the present invention.

First, the first frame is a frame displaying a video, and the graphic processing apparatus 700 transmits the image data DAT in the video to the signal controller 600, and the signal controller 600 transmits the gate control signal CONT1. Is transmitted to the gate driver 400, and the image data DAT and the data control signal CONT2 are transmitted to the data driver 500. In this case, the display panel 300 displays the video at the first frequency in the first frame. For example, when the first frequency is 60 Hz, the screen is displayed for 1/60 second in the first frame.

That is, the graphic processing apparatus 700 recognizes that the first frame is a moving picture, supplies the image data DAT, and the display panel 300 displays the moving picture at the first frequency.

Subsequently, the second frame is a frame displaying a still image, and the graphic processing apparatus 700 transmits the image data DAT in the still image to the signal controller 600 together with the still image start signal indicating that the still image starts. do. The signal controller 600 recognizes that the still image is started by receiving a still image start signal, and stores the image data DAT of the still image in the frame memory. In addition, the signal controller 600 deactivates the graphic processing apparatus 700 such that the graphic processing apparatus 700 no longer transmits the image data DAT in the still image.

The signal controller 600 transmits the image data DAT in the still image stored in the frame memory to the data driver 500. In this case, the display panel 300 displays the video at the second frequency in the second frame. For example, if the second frequency is 40 Hz, the screen is displayed for 1/40 seconds in the second frame.

That is, in the second frame, the graphic processing apparatus 700 recognizes that the second frame is a still image and is deactivated, and the display panel 300 displays the still image at the second frequency.

Although not illustrated, the display panel 300 displays the still image at the second frequency, as in the second frame, from the third frame to the n-1th frame.

Subsequently, the n-th frame is a frame corresponding to a point of switching from a still image to a moving image, and the graphic processing apparatus 700 controls the image data DAT in the moving image together with the still image ending signal indicating that the still image ends. Send to 600.

In this case, the display panel 300 is driven at the second frequency up to the previous frame of the nth frame, and the graphic processing apparatus 700 recognizes that the display panel 300 is driven at the first frequency. At the midpoint of the frequency shift occurs. In addition, a time delay occurs while the image data DAT in the moving image is transmitted from the graphic processing apparatus 700. Therefore, in order to prevent the defect of visibility caused by this, the image data DAT in the still image is displayed at the second frequency until the n-th frame to which the still image end signal is applied is terminated.

That is, the display panel 300 stops at the second frequency even though it is a section in which a moving picture is to be displayed after the still image end signal is applied at the middle point of the nth frame until the nth frame ends. Display the video.

Subsequently, the n + 1th frame is a frame for displaying a video, and the graphic processing apparatus 700 transmits the image data DAT in the video to the signal controller 600, and the display panel 300 at the first frequency. Display the video.

Hereinafter, another method of driving the display device according to the first exemplary embodiment of the present invention will be described with reference to FIGS. 1 and 4.

4 is a diagram illustrating control signals of a display device according to a first exemplary embodiment of the present invention.

Since the same parts as the above-described driving method are equivalent, the description thereof will be omitted and only the differences will be described below.

The driving method of the display device in the first frame, the second frame, and the nth frame is the same as described above.

In the n + 1th frame, the graphic processing apparatus 700 recognizes the n + 1th frame as a frame displaying the moving image, and transmits the image data DAT in the moving image to the signal controller 600.

The signal controller 600 transmits the STV signal to the gate driver 400 at the start of each frame, and then the gate driver 400 receives the CPV signal from the signal controller 600 and then switches the switching elements (eg, the display elements of the display panel 300). Turn on Q). However, the signal controller 600 does not transmit the STV signal to the gate driver 400 at the start point of the n + 1 frame, which is the point of change from the second frequency to the first frequency. Therefore, even when the CPV signal is applied to the gate driver 400 in the n + 1th frame, the STV signal is not applied, so that the switching element Q of the display panel 300 is turned off.

That is, since the switching element Q is not turned on in the n + 1th frame, the pixel is not charged and is maintained at the voltage charged in the nth frame so that the display panel 300 displays a still image.

Subsequently, the n + 2 frame is a frame displaying a video, and the graphic processing apparatus 700 transmits the image data DAT in the video to the signal controller 600, and the display panel 300 moves the video at a first frequency. Is displayed.

The signal controller 600 of the display device according to the first exemplary embodiment may implement the first frequency and the second frequency in various ways.

For example, there is a method of changing the clock frequency of the gate signal, a method of changing the length of the vertical blank section, and a method of changing the length of the vertical blank section at the same time as the clock frequency of the gate signal. A description with reference to 5 to 9 are as follows.

5 is a diagram illustrating a DE signal and a Vsync signal used in the display device according to the first embodiment of the present invention, and FIG. 6 is a display panel driven at a first frequency in the display device according to the first embodiment of the present invention. 7 to 9 illustrate a gate signal and an STV signal when the display panel is driven at a second frequency in the display device according to the first exemplary embodiment of the present invention. to be.

As illustrated in FIG. 5, one frame includes a valid period in which image data is transmitted and a vertical blank period in which image data is not transmitted. Image data of two neighboring frames may be distinguished by the vertical blank period.

As shown in FIG. 6, when the display panel 300 is driven at the first frequency, a gate signal is provided to enable the pixel voltage corresponding to the image data to be applied in the effective period. The gate off is maintained in the vertical blank section.

As shown in FIG. 7, when the display panel 300 is driven at the second frequency, the length of one frame is longer than when the display panel 300 is driven at the first frequency. For example, when the first frequency is 60 Hz and the second frequency is 20 Hz, as shown, when driven at the second frequency, the length of one frame is three times longer than when driven at the first frequency. In this case, the second frequency may be implemented by making the length of the effective section when driven at the second frequency longer than three times the length of the effective section when driven at the first frequency. In order to increase the length of the effective period, the clock frequency of the gate signal may be increased by about three times or more. There is almost no difference in the length of the vertical blank section when driven at the first frequency and when driven at the second frequency.

In FIG. 8, when the display panel 300 is driven at the second frequency, the length of one frame is three times longer than when the display panel 300 is driven at the first frequency. Unlike the case of FIG. 7, the length of the effective section when driven at the second frequency is almost the same as the length of the effective section when driven at the first frequency. However, the second frequency may be implemented by increasing the length of the vertical blank period when driven at the second frequency by a length corresponding to two frames when driven at the first frequency.

In FIG. 9, when the display panel 300 is driven at the second frequency, the length of one frame is three times longer than when the display panel 300 is driven at the first frequency, as in the case of FIGS. 7 and 8. Unlike the case of FIGS. 7 and 8, in FIG. 9, the length of the effective section when driven at the second frequency is longer than the length of the effective section when driven at the first frequency, and the length of the vertical blank section also increases. That is, the length of the effective section when driven at the second frequency has a length corresponding to about two frames when driven at the first frequency, and the length of the vertical blank section when driven at the second frequency is zero. The second frequency may be implemented by having a length corresponding to one frame when driven at one frequency.

As such, when the still image is displayed, power consumption may be reduced by lowering the frequency driving the display panel 300.

When the still image start signal is applied, the signal controller 600 adjusts the signals so that the display panel 300 is driven at the second frequency. In this case, the display panel 300 may be driven at the first frequency and then immediately switched to the second frequency when the still image start signal is applied. Alternatively, after the still image start signal is applied, the display panel 300 may be driven at a frequency higher than the second frequency and lower than the first frequency during the S1 frame. That is, after the still image start signal is applied, the signal may be switched to the second frequency after the S1 frame passes through the transient period during the S1 frame. To implement this, the length of the vertical blank section may be gradually increased during the S1 frame after the still picture start signal is applied.

When the still image end signal is applied, the signal controller 600 adjusts the signals so that the display panel 300 is driven at the first frequency. In this case, the display panel 300 may be driven at the second frequency and then immediately switched to the first frequency when the still image termination signal is applied. Alternatively, after the still image end signal is applied, the display panel 300 may be driven at a frequency higher than the second frequency and lower than the first frequency during the S2 frame. That is, after the still image end signal is applied, the signal may be switched to the first frequency after the S2 frame passes through the transient period during the S2 frame. To implement this, the length of the vertical blank period may be gradually shortened during the S2 frame after the end of the still image is applied.

As described above, the display device according to the first exemplary embodiment uses different clock signals to drive still images and moving images at different frequencies. Hereinafter, the width of the CPV signal according to the use of different clock signals in still and moving images will be described with reference to FIGS. 10 and 11.

FIG. 10 is a view illustrating a clock signal and a CPV signal when the display device is driven at a first frequency in accordance with a first embodiment of the present invention, and FIG. 11 is a second view of the display device according to the first embodiment of the present invention. A diagram illustrating a clock signal and a CPV signal when driven at a frequency. The clock signal is represented by CLK and the CPV signal is represented by CPV.

As shown in FIG. 10, the width w3 of the CPV signal when driven at the first frequency in the display device according to the first exemplary embodiment corresponds to six clock signals. If the CPV signal is set to have a width corresponding to six clock signals even when the display panel is driven at the second frequency, the clock signals when driven at the first frequency and at the second frequency are different. The width of the CPV signal is also changed.

As shown in FIG. 11, the width w4 of the CPV signal when driven at the second frequency in the display device according to the first exemplary embodiment has a width corresponding to three clock signals. Therefore, even if the clock speed when driven at the second frequency is lower than the clock speed when driven at the first frequency, the width of the CPV signal when driven at the first frequency and when driven at the second frequency is set. By setting the parameters to be separate, the width of the CPV signal can be kept the same.

That is, the signal controller sets the width w3 of the CPV signal when the display panel is driven at the first frequency to have the same width as the clock signal of p times, and sets the width of the CPV signal when the display panel is driven at the second frequency ( w4) is set to have the same width as q clock signals less than p. In this case, p and q may be set such that the width w3 of the CPV signal when the display panel is driven at the first frequency and the width w4 of the CPV signal when the display panel is driven at the second frequency are the same.

Therefore, the difference in visibility can be prevented by making the filling rate of the pixel the same when a display panel displays a still image and when displaying a moving image.

Another method for preventing the difference in visibility between still images and moving images is described with reference to FIG. 12.

12 is a flowchart illustrating a method of correcting image data in the display device according to the first embodiment of the present invention.

As shown in FIG. 12, the signal controller first determines whether the display panel is driven at the first frequency or the second frequency in the corresponding frame. (S110)

In this case, even though the charging rate of the pixels is different in the frame driven at the first frequency and the frame driven at the second frequency, the images actually displayed are different from each other even though they have the same image data DAT. Therefore, a gamma correction is performed to correct the characteristics of the gray level to compensate for the luminance difference caused by different filling rates of the pixels in the frame driven at the first frequency and the frame driven at the second frequency. (S120)

Subsequently, the gamma-corrected image data DAT is output in the frame driven at the second frequency, and the image data DAT is output without the gamma correction step in the frame driven at the first frequency. (S130)

That is, the gamma correction is performed on the image data DAT in a frame driven at the second frequency, so that a difference in visibility occurs even when the display panel displays a still image and a pixel charge rate is different when displaying a video. Can be prevented.

Next, a display device according to a second exemplary embodiment of the present invention will be described with reference to FIGS. 13 and 14 as follows.

FIG. 13 is a block diagram of a display device according to a second embodiment of the present invention, and FIG. 14 is a block diagram showing a light source driver of the display device according to the second embodiment of the present invention.

Since the display device according to the second embodiment of the present invention is substantially the same as the display device according to the first embodiment, description thereof will be omitted and only differences will be described below.

As shown in FIG. 13, the display device according to the second exemplary embodiment of the present invention includes a light source unit 900 for irradiating light to the display panel 300 and a light source driver 910 for controlling signals for driving the light source unit 900. ) May be further included.

The light source unit 900 supplies light to the inside of the display panel 300, and the supplied light comes out of the liquid crystal display panel 300 to display a screen. The light source unit 900 may be formed of various light sources, for example, a light emitting diode (LED), a cold cathode fluorescent lamp (CCFL), an external electrode fluorescent lamp (EEFL), or the like. This can be used. In addition, the light source unit 900 is classified into a metering type and a direct type according to its arrangement.

The light source driver 910 controls the light source 900 to be dimmed. Dimming driving is a technique for controlling the amount of light of the light source in consideration of the brightness of the image in order to prevent the contrast ratio (CR) of the image is reduced and to minimize the power consumption.

As illustrated in FIG. 14, the light source driver 910 adjusts the driving ratio of the light source unit 900 according to the driving frequency and the driving frequency receiver 912 that receives the driving frequency of the display panel 300 from the signal controller 600. And a light source driving signal generator 916 for generating a signal for driving the light source 900 according to the driving ratio of the light source unit 900.

The driving frequency receiver 912 receives a first frequency from the signal controller 600 when displaying a video, and receives a second frequency from the signal controller 600 when displaying a still image.

The driving ratio selector 914 receives a driving frequency from the driving frequency receiver 912 and selects a ratio of driving the light source unit. The driving ratio of the light source unit may be selected differently according to the driving frequency.

For example, the selection of the driving ratio of the light source unit 900 according to the driving frequency of the display panel 300 may be performed using a look up table. The driving ratio selector 914 selects a driving ratio of the light source unit as the first ratio when the driving frequency is the first frequency using a look-up table as shown in Table 1, and drives the light source unit when the driving frequency is the second frequency. The ratio is chosen as the second ratio. That is, when displaying a moving image, the light source unit is driven at the first ratio, and when displaying a still image, the light source unit is driven at the second ratio.

Drive frequency (Hz) Driving ratio of light source unit (%) First frequency First ratio Second frequency Second ratio

When the frequency driving the display panel 300 is changed and lowered, the time for charging each pixel becomes long, and the amount of charge charged increases. Accordingly, the brightness before and after the change of the frequency may change. In a normally black mode display device, the brightness increases as the amount of charged charge increases, and in a normally white mode display device, the brightness decreases as the amount of charged charge increases.

Therefore, when the second frequency has a value lower than the first frequency, the display device in the normally black mode sets the second ratio to a value lower than the first ratio to compensate for the increased luminance. At this time, the power consumption can be reduced by lowering the driving ratio of the light source unit.

On the contrary, in the normally white mode display device, the second ratio is set to a value higher than the first ratio to compensate for the reduced luminance.

In the above description, the selection of the driving ratio of the light source unit 900 according to the driving frequency of the display panel 300 is performed by using a look-up table. However, the present invention is not limited thereto, and a function of the form y = f (x) is provided. It is also possible to use a method of selecting a driving ratio using.

The light source driving signal generator 916 receives the driving ratio of the light source selected by the driving ratio selector 914 and generates a signal capable of driving the light source unit at the first ratio or a signal capable of driving the second ratio at the second ratio. To 900. In this case, the signal generated by the light source driving signal generator 916 may be various signals such as a PWM signal, a communication protocol such as I ² C, and the like.

Hereinafter, a driving method of a display device according to a second exemplary embodiment of the present invention will be described.

FIG. 15 is a flowchart illustrating a method of driving a display device according to a second exemplary embodiment of the present invention, and FIGS. 16 to 18 are diagrams illustrating a method of driving a display apparatus according to a second exemplary embodiment of the present invention, in order of steps. 19 and 20 are block diagrams of a signal controller according to a sequence of a method of driving a display device according to a first exemplary embodiment of the present invention.

First, as illustrated in FIG. 16, the graphic processing apparatus transmits input image data to the signal receiver 610 of the signal controller 600. (S1110)

It is determined whether a still image start signal is applied to the signal receiver 610 (S1120), and if the still image start signal is not applied, the input image data is output to the display panel. (S1190)

If the still image start signal is applied, the input image data is stored in the frame memory 640 as shown in FIG. (S1140)

18, the graphics processing apparatus is deactivated so that the graphics processing apparatus does not transmit the input image data, and the stored image data stored in the frame memory 640 is output. When the still image start signal is applied, the driving frequency selector 650 selects the second frequency and outputs the stored image data to the display panel at the second frequency. In this case, the display panel displays a still image and is driven at the second frequency.

At the same time, the light source driver 910 receives the second frequency f ₂ at the driving frequency as the driving frequency receiver 912 as shown in FIG. 2 Select the ratio (P ₂ ).

The driving ratio of the light source unit may be differently selected according to the driving frequency. In this case, the selection of the driving ratio of the light source unit 900 according to the driving frequency of the display panel may be performed by using a look-up table or a function of y = f (x) form.

The light source driving signal generator 916 generates a light source driving signal capable of driving the light source unit at the second ratio P ₂ and outputs the light source driving signal to the light source unit. In this case, the light source driving signal may be various signals such as a PWM signal and a communication protocol such as I ² C.

Subsequently, it is determined whether the still image end signal is applied (S1160). If the still image end signal is not applied, the stored image data is continuously output at the second frequency and the light source unit is driven at the second ratio. (S1150)

If the still image end signal is applied, as shown in FIG. 16, the graphics processing apparatus is reactivated to transmit the input image data. (S1180)

When the still image end signal is applied, the driving frequency selector 650 selects the first frequency, and outputs the input image data to the display panel at the first frequency. In this case, the display panel displays a video and is driven at the first frequency.

At the same time, as shown in FIG. 20, the light source driver 910 receives the first frequency f ₁ at the drive frequency by the drive frequency receiver 912, and the light source drive ratio selector 914 sets the light source drive ratio as the light source drive ratio. 1 Select the ratio (P ₁ ).

The light source driving signal generator 916 generates a light source driving signal capable of driving the light source unit at the first ratio P ₁ and outputs the light source driving signal to the light source unit.

When displaying a moving image in the method of driving the display device according to the second embodiment of the present invention, the display panel is driven at the first frequency and the light source unit is driven at the first ratio. In addition, when displaying a still image, the display panel is driven at the second frequency, and the light source unit is driven at the second ratio.

At this time, the second frequency has a lower value than the first frequency. In still images, the same image is displayed every frame, and thus a low driving frequency can be realized. However, the charging time of the pixel according to the change of the driving frequency is changed, and the charge amount is also changed. Accordingly, the change in luminance can be visually recognized.

Therefore, by dimming the light source unit, it is possible to prevent such luminance change from being visually recognized. Specifically, the light source unit is driven at the first ratio when the display panel is driven at the first frequency, and the light source unit is driven at the second ratio when the display panel is driven at the second frequency.

In a display device in a normally black mode, the second ratio is set to a value lower than the first ratio. At this time, the first ratio and the second ratio are set to values that can compensate for the increased luminance when displaying the still image than when displaying the moving image.

In a display device in a normally white mode, the second ratio is set to a value higher than the first ratio. At this time, the first ratio and the second ratio are set to a value capable of compensating for the luminance lowered when displaying the still image than when displaying the moving image.

When changing the driving frequency of the display panel and changing the driving ratio of the light source unit when switching from a still image to a moving image, the luminance change can be prevented from being further recognized by matching the vertical blank period (V-blank time). .

Next, a display device according to a third exemplary embodiment of the present invention will be described with reference to FIGS. 13, 14, and 21.

21 is a block diagram of a signal controller according to a third embodiment of the present invention. Since the display device according to the third exemplary embodiment of the present invention is the same as the second exemplary embodiment except for the signal controller, the display device will be described with reference to FIGS. 13 and 14.

Since the display device according to the third exemplary embodiment of the present invention is substantially the same as the display device according to the second exemplary embodiment, a description thereof will be omitted and only differences will be described below. The biggest difference from the second embodiment is that the signal controller further includes a frame counting unit, which will be described in more detail below.

As shown in FIG. 13, the display device according to the third embodiment of the present invention includes a display panel 300 for displaying an image, a signal controller 600 for controlling signals for driving the display panel 300, and an input image. A graphic processing apparatus 700 for transmitting data to the signal controller 600, a light source unit 900 for irradiating light to the display panel 300, and a light source driver 910 for controlling signals for driving the light source unit 900. It is the same as the display device according to the second embodiment in that it includes.

The signal controller 600 may include a signal receiver 610 that receives various signals from the graphic processing apparatus 700, a frame counter 620 that counts the number of frames, a frame memory 640 that stores input image data, and a video. The display apparatus may include a driving frequency selector 650 that selects a first frequency when displaying and selects a second frequency when displaying a still image.

The signal receiver 610 receives the input image data, the still image start signal, and the still image end signal from the graphic processing apparatus 700. Although not shown, the signal receiver 610 is connected to the graphic processing apparatus 700 by a main link and an auxiliary link. The signal receiver 610 receives input image data from the graphic processing apparatus 700 through a main link. In addition, the signal receiver 610 receives a still image start signal and a still image end signal from the graphic processing apparatus 700 through an auxiliary link, and outputs a signal indicating a driving state of the display panel 300 to the graphic processing apparatus 700. To send.

The frame counting unit 620 counts the number of continuous frame continuous images input after the still image start signal is applied and before the still image end signal is applied, and until the still image start signal is applied after the still image end signal is applied. Count the number of consecutive frames of video that are input.

The frame counting unit 620 transmits input image data to the frame memory 640 when the number of still image continuous frames is x or more. In addition, the graphics processing apparatus 700 deactivates the graphics processing apparatus 700 so as not to transmit the input image data. On the contrary, if the number of still image continuous frames is less than x, the input image data is not transmitted to the frame memory 640 but transmitted to the driving frequency selector 650 so that the input image data is output. In addition, the graphic processing apparatus 700 is not deactivated so that input image data is continuously transmitted.

This is to prevent switching from a moving picture to a still picture when the number of still picture continuous frames is less than x. In the case where the still image is processed for a short time and then converted into a moving image, if the driving frequency is changed accordingly, the effect of reducing power consumption is not large. Therefore, the luminance is maintained by maintaining the driving frequency. Even when the light source unit is dimmed and driven according to the change of the driving frequency, the change in luminance may be partially recognized. Therefore, when the still image is displayed for a short time, the luminance change may be prevented by maintaining the driving frequency of the display panel 300 and the driving ratio of the light source unit 900 unchanged.

The frame counting unit 620 activates the graphic processing apparatus 700 so that the graphic processing apparatus 700 transmits the input image data when the number of moving image continuous frames is y or more. On the contrary, if the number of moving picture continuous frames is less than y, the graphic processing apparatus 700 is left in an inactive state.

This is to prevent switching from a still image to a moving image when the number of continuous frames of moving images is less than y. If the moving image is converted to a still image after a short time, and the driving frequency is changed accordingly, the effect of reducing the power consumption is not large. Therefore, the luminance is maintained by maintaining the driving frequency. That is, when the moving image is displayed for a short time, the luminance change may be prevented by maintaining the driving frequency of the display panel 300 and the driving ratio of the light source unit 900 unchanged.

At this time, the values of x and y may be appropriately selected and set in consideration of the effect of power consumption reduction and the visibility problem caused by the luminance change.

The frame memory 640 receives and stores input image data when the number of still image continuous frames is greater than x from the frame counting unit 620.

The driving frequency selector 650 selects a second frequency when the display panel 300 continuously displays at least x frames of the still image, and displays the first frequency when the display panel 300 continuously displays at least y frames of the moving image. Select a frequency. The driving frequency selector 650 outputs the stored image data stored in the frame memory 640 to the display panel 300 at the second frequency when the number of still image continuous frames is equal to or greater than x. The driving frequency selector 650 outputs the input image data to the display panel 300 at a first frequency when the number of continuous video frames is y or more.

Accordingly, the light source driver 910 receives the second frequency from the signal controller 600 when the number of the continuous image continuous frames is x or more, and drives the light source 900 at the second ratio. When the number of moving picture frames is y or more, the first frequency is received from the signal controller 600 to drive the light source unit 900 at the first ratio.

Hereinafter, a driving method of a display device according to a third exemplary embodiment of the present invention will be described.

FIG. 22 is a flowchart illustrating a method of driving a display device according to a third exemplary embodiment of the present invention, and FIGS. 23 to 26 are diagrams illustrating a method of driving a display apparatus according to a third exemplary embodiment of the present invention, in order of steps. A block diagram of a signal controller.

Since the driving method of the display device according to the third exemplary embodiment of the present invention is substantially the same as the driving method of the display device of the third exemplary embodiment, the description thereof will be omitted and the following description will be mainly given of differences.

First, as illustrated in FIG. 23, the graphic processing apparatus transmits input image data to the signal receiver 610 of the signal controller 600. (S2110)

In operation S2120, it is determined whether the still image start signal is applied to the signal receiver 610, and if the still image start signal is not applied, the input image data is output to the display panel. In this case, the display panel displays a video and is driven at the second frequency.

If the still image start signal is applied, the frame counting unit 620 counts the number of continuous image continuous frames input after the still image start signal is applied and before the still image end signal is applied. In this case, the frame counting unit 620 determines whether the number of still image continuous frames is more than x. If the number of still image continuous frames is less than x, the input image data is output to the display panel as in the case where the still image start signal is not applied. In this case, the display panel displays a still image and is driven at the first frequency.

If the number of still image continuous frames is x or more, the input image data is stored in the frame memory 640 as shown in FIG. (S2140)

Next, as shown in FIG. 25, the graphics processing apparatus is deactivated so that the graphics processing apparatus does not transmit the input image data, and the stored image data stored in the frame memory 640 is output. When the number of still image continuous frames is x or more, the driving frequency selecting unit 650 selects the second frequency and outputs the stored image data to the display panel at the second frequency. In this case, the display panel displays a still image and is driven at the second frequency.

At the same time, the light source driver receives the second frequency at the driving frequency and drives the light source unit at the second ratio.

The driving ratio of the light source unit may be differently selected according to the driving frequency. In this case, the selection of the driving ratio of the light source unit according to the driving frequency of the display panel may be performed using a look-up table or a function of y = f (x) form.

Subsequently, it is determined whether the still image end signal is applied (S2160). If the still image end signal is not applied, the stored image data is continuously output at the second frequency, and the light source unit is driven at the second ratio. In this case, the display panel displays a still image and is driven at the second frequency.

As shown in FIG. 26, if the still image end signal is applied, the frame counting unit 620 counts the number of continuous video frames input after the still image end signal is applied and before the still image start signal is applied. In this case, the frame counting unit 620 determines whether the number of continuous video frames is y or more. If the number of moving picture continuous frames is less than y, the stored video data is output at the second frequency as in the case where the moving picture start signal is not applied, and the light source unit is driven at the second ratio. (S2150)

If the still image end signal is applied but the number of continuous video frames is less than y, the graphic processing apparatus is activated and the input image data is transmitted to the signal receiver 610. However, by outputting the stored image data, the display panel displays the still image and is driven at the second frequency.

If the number of continuous video frames is y or more, as shown in FIG. 23, the graphics processing apparatus is reactivated to transmit the input image data. (S2180)

When the number of moving picture frames is y or more, the driving frequency selector 650 selects the first frequency, and outputs the input image data to the display panel at the first frequency. In this case, the display panel displays a video and is driven at the first frequency.

At the same time, the light source driver receives the first frequency at the driving frequency and drives the light source unit at the first ratio.

In the driving method of the display device according to the third exemplary embodiment of the present invention, when the still image is continuous for more than x frames, the display panel is driven at the second frequency and the light source unit is driven at the second ratio. In addition, when the moving image continues for more than y frames, the display panel is driven at the first frequency, and the light source unit is driven at the first ratio.

At this time, the second frequency has a lower value than the first frequency. In still images, the same image is displayed every frame, and thus a low driving frequency can be realized. However, the charging time of the pixel according to the change of the driving frequency is changed, and the charge amount is also changed. Accordingly, the change in luminance can be visually recognized.

Therefore, by dimming the light source unit, it is possible to prevent such luminance change from being visually recognized. In detail, when the display panel is driven at the second frequency, the light source unit is driven at the second ratio, and when the display panel is driven at the first frequency, the light source unit is driven at the first ratio.

In addition, when the still image is not continuous for more than x frames and the video is not continuous for more than y frames, the change in luminance can be prevented from occurring by maintaining the driving frequency of the display panel and the driving ratio of the light source unit unchanged.

When the still image end signal is applied but the number of continuous video frames is less than y, the display panel outputs the stored image data to display the still image and is driven at the second frequency. However, the present invention is not limited thereto. In contrast, when a still image end signal is applied but the number of continuous video frames is less than y, the input image data may be output at a first frequency and the light source may be driven at a first ratio. In this case, the display panel displays a video and is driven at the first frequency.

Next, a driving method of the display device according to the fourth exemplary embodiment of the present invention will be described with reference to FIGS. 27 to 29. Since the structure of the display device according to the fourth embodiment of the present invention is the same as that of the display device according to the second embodiment, a description thereof will be omitted.

27 is a flowchart illustrating a method of driving a display device according to a fourth exemplary embodiment of the present invention, and FIGS. 28 and 29 are diagrams illustrating driving ratios of an STV signal and a light source unit of a display apparatus according to a fourth exemplary embodiment of the present invention. .

First, the graphic processing apparatus transmits input image data to the signal receiver 610 of the signal controller 600. (S3110)

It is determined whether the still image start signal is applied to the signal receiving unit 610 (S3120), and if the still image start signal is not applied, the input image data is output to the display panel. (S3190)

If the still image start signal is applied, the input image data is stored in the frame memory 640. (S3140)

Subsequently, the graphics processing apparatus is deactivated so that the graphics processing apparatus does not transmit the input image data, and the stored image data stored in the frame memory 640 is output. When the still image start signal is applied, the driving frequency selector 650 selects the second frequency and outputs the stored image data to the display panel at the second frequency. In this case, the display panel displays a still image and is driven at the second frequency.

At the same time, the light source driver 910 receives the second frequency f ₂ as the driving frequency receiving unit 912 as the driving frequency, and the light source unit driving rate selector 914 selects a rate that periodically changes to the light source unit driving rate.

Hereinafter, the periodic change of the driving ratio of the light source unit will be described with reference to FIG. 28.

STV1 in FIG. 28 is an STV signal when driving the display panel at the first frequency, and STV2 is an STV signal when driving the display panel at the second frequency.

For example, when the first frequency is 60 Hz and the second frequency is 10 Hz, STV2 is applied once during the time that STV1 is applied six times. Therefore, when driving at the first frequency, the brightness of the screen changes more frequently than when driving at the second frequency, and thus, flicker is relatively difficult to see. Therefore, the display device according to the fourth exemplary embodiment of the present invention is characterized in that the driving ratio of the light source unit is changed at the same period as the application period of the STV1 signal when driven at the first frequency.

First, when the STV2 is applied, the light source unit driving ratio selector 914 selects the first ratio as the light source unit driving ratio.

The light source driving signal generator 916 generates a light source driving signal capable of driving the light source unit at a first ratio and outputs the light source driving signal to the light source unit. In this case, the light source driving signal may be various signals such as a PWM signal and a communication protocol such as I ² C.

When one frame is divided into first to sixth sections having the same length, the light source unit is driven at a first ratio in the first section.

Subsequently, when using a display device in a normally black mode, the light source unit driving ratio selector 914 selects a second ratio lower than the first ratio as the light source unit driving ratio at the time when the second section starts. The light source unit is driven at the second ratio.

Subsequently, at the start of the third section, the light source unit driving ratio selector 914 selects a third ratio lower than the second ratio as the light source driving ratio and drives the light source unit at the third ratio.

Subsequently, when the fourth section starts, the light source unit driving ratio selecting unit 914 selects a fourth ratio lower than the third ratio as the light source unit driving ratio and drives the light source unit at the fourth ratio.

Subsequently, when the fifth section starts, the light source unit driving ratio selector 914 selects a fifth ratio lower than the fourth ratio as the light source driving ratio, and drives the light source unit at the fifth ratio.

Subsequently, when the sixth section starts, the light source unit driving ratio selector 914 selects a sixth ratio lower than the fifth ratio as the light source unit driving ratio and drives the light source unit at the sixth ratio.

Subsequently, at the time when the next frame starts, the light source unit driving ratio selector 914 selects the first ratio again as the light source unit driving ratio and drives the light source unit at the first ratio.

That is, the light source unit is driven at a rate sequentially lowered from the first ratio and the first ratio within one frame. At the point where the STV2 signal is transmitted, the light source unit is driven at a first rate, and the light source unit is driven at a rate that is sequentially lowered from the first ratio until the next STV2 signal is transmitted. In this case, the change period of the driving ratio of the light source unit may be set to be the same as the transmission period of the STV1 signal. Therefore, even when the display panel is driven at a second frequency lower than the first frequency, the flicker is not viewed by increasing the luminance change period as in the case of driving the first frequency.

Subsequently, it is determined whether the still image end signal is applied (S3160). If the still image end signal is not applied, the stored image data is continuously output at the second frequency, and the light source unit is driven at a rate that changes periodically. (S3150)

If the still image end signal is applied, the graphic processing apparatus is reactivated to transmit the input image data. (S3180)

When the still image end signal is applied, the driving frequency selector 650 selects the first frequency, and outputs the input image data to the display panel at the first frequency. In this case, the display panel displays a video and is driven at the first frequency.

At the same time, as shown in FIG. 20, the light source driver 910 receives the first frequency at the driving frequency by the driving frequency receiver 912, and selects the first ratio by the light source driving ratio by the light source driving ratio selecting unit 914. do.

The light source driving signal generator 916 generates a light source driving signal capable of driving the light source unit at a first ratio and outputs the light source driving signal to the light source unit.

In the method of driving the display device according to the fourth embodiment of the present invention, when displaying a moving image, the display panel is driven at the first frequency and the light source unit is driven at the first ratio. In addition, when displaying a still image, the display panel is driven at a second frequency, and the light source unit is driven at a rate that varies periodically.

In the above, the case of using the display device in the normally black mode has been described. In the following, the periodic change of the driving ratio of the light source unit when the display device in the normally white mode is used is described. A description with reference to FIG. 29 is as follows.

When the STV2 is applied, the light source unit driving ratio selector 914 selects the first ratio as the light source unit driving ratio and drives the light source unit at the first ratio.

Subsequently, at the start of the second section, the light source unit driving ratio selector 914 selects a second ratio having a high light source unit driving ratio from the first ratio and drives the light source unit at the second ratio.

Subsequently, the light source unit is driven while changing at a rate gradually higher than the second ratio in the third to sixth sections.

That is, when driving the display panel at the second frequency, the display device of the normally black mode drives the light source unit at a rate which is sequentially lowered from the first ratio and the first ratio within one frame, In the display device, the light source unit is driven at a rate that sequentially increases from the first ratio and the first ratio within one frame.

Next, a display device according to a fifth embodiment of the present invention will be described with reference to FIGS. 1, 2, and 30.

30 is an equivalent circuit diagram of one pixel of the display device according to the fifth exemplary embodiment of the present invention.

As shown in FIG. 1, the display device according to the fifth embodiment of the present invention includes a display panel 300, a signal controller 600, and a graphics processing apparatus 700, and the signal controller 600 is illustrated in FIG. 2. As shown, the signal receiver 610, the frame memory 640, and the driving frequency selector 650 are included.

Since the display panel 300, the signal controller 600, and the graphic processing apparatus 700 of the display device according to the fifth embodiment of the present invention are the same as those of the first embodiment, detailed description thereof will be omitted.

In the display panel of the display device according to the fifth exemplary embodiment, as illustrated in FIG. 30, the gate line G and the data line D cross each other to define pixels. Although not shown, a layout view and a cross-sectional view are omitted, the gate line G and the data line D are formed on a substrate and may be formed on different layers so as to be separated from each other. As shown in FIG. 1, the gate line G and the data line D may be formed in plural, and since only one pixel is shown in FIG. 30, only one gate line G and one data line D are shown. It is.

The first switching element Q1 is formed to be connected to the gate line G and the data line D. The first switching element Q1 is a three-terminal element such as a thin film transistor. The control terminal is connected to the gate line G, the input terminal is connected to the data line D, and the output terminal is the liquid crystal capacitor Clc. ) And sustain capacitor Cst.

The storage electrode line SL and the storage electrode control line SCL may be further formed on the substrate, and the storage electrode line SL and the storage capacitor Cst are connected to the second switching element Q2 and the third switching element Q3. Is connected by. That is, the second switching element Q2 and the third switching element Q3 are formed between the storage electrode line SL and the storage capacitor Cst.

The second switching element Q2 is a three-terminal element such as a thin film transistor. The control terminal is connected to the gate line G, the input terminal is connected to the storage electrode line SL, and the output terminal is the storage capacitor Cst. )

The third switching element Q3 is a three-terminal element such as a thin film transistor, the control terminal is connected to the sustain electrode control line SCL, the input terminal is connected to the sustain electrode line SL, and the output terminal is the sustain capacitor. Is connected to (Cst).

Hereinafter, the voltage relationship when the display panel of the display device according to the fifth exemplary embodiment displays a still image will be described.

31 is a diagram illustrating control signals when a display panel of a display device according to a fifth exemplary embodiment displays a still image.

In the display device according to the fifth exemplary embodiment of the present invention, when the video is displayed, the display device is driven at the first frequency, and when the still image is displayed, the display device is driven at a second frequency lower than the first frequency. In this case, the length of the vertical blank period may be increased than when driving at the first frequency to implement the second frequency.

For example, in order to change the frequency to 10 Hz while driving at 60 Hz, the length of the vertical blank section between two adjacent frames can be changed to 5 times the length of one frame when driving at 60 Hz. In this case, the speed of applying the data enable signal DE is the same both when driving at 60 Hz and when driving at 10 Hz.

When displaying the still image by driving at the second frequency, if the gate-on voltage is first applied to the gate line G in the effective period of the n-th frame, the first switching element Q1 and the second switching element Q2 are It turns on. Subsequently, when a data voltage is applied to the data line D, the liquid crystal capacitor Clc and the sustain capacitor Cst are charged through the first switching element Q1.

In this case, one terminal of the storage capacitor Cst is connected to the first switching element Q1 to represent a data voltage, and the other terminal is connected to the second switching element Q2 to be applied to the storage electrode line SL. The voltage V _SL is represented. The common voltage V _SL has a constant value during the nth frame to which the data enable signal is applied.

After the data voltage is applied to each pixel, the gate-off voltage is applied to the gate line G, and the first switching element Q1 and the second switching element Q2 are turned off. Subsequently, a vertical blank period starts, and a gate-on voltage is applied to the sustain electrode control line SCL. Accordingly, the third switching element Q3 connected to the sustain electrode control line SCL is turned on, and a common voltage is applied from the sustain electrode line SL.

The common voltage V _SL in the vertical blank period has a voltage higher than the common voltage V _SL in the effective period. When the common voltage V _SL in the effective period is the first voltage, the common voltage V _SL changes to a second voltage higher than the first voltage after the vertical blank period starts. Thereafter, the common voltage V _SL after a predetermined time in the vertical blank period has a third voltage higher than the second voltage. The time when the second voltage is applied to the sustain electrode line SL and the time when the third voltage is applied may be set to be the same.

When the common voltage V _SL is changed from the first voltage to the second voltage and when the second voltage is changed from the second voltage to the third voltage, the voltage of one terminal of the sustain capacitor Cst is discharged and the original voltage and the predetermined voltage are applied. It can be set to coincide with the point at which the abnormal difference occurs.

Subsequently, the vertical blank period ends, and a gate-off voltage is applied to the sustain electrode control line SCL. As a result, the third switching element Q3 connected to the sustain electrode control line SCL is turned on.

At the same time, the n + 1th frame starts, and a gate-on voltage is applied to the gate line G. Accordingly, the first switching element Q1 and the second switching element Q2 are turned on. Subsequently, a data voltage is applied to the data line D, and the liquid crystal capacitor Clc and the sustain capacitor Cst are charged. At this time, since the still image is shown, the data voltages in the nth frame and the n + 1th frame are the same.

When the n + 1th frame starts, the common voltage V _SL applied to the storage electrode line SL falls back to the first voltage and is transferred to the other terminal of the storage capacitor Cst through the second switching element.

As described above, the common voltage V _SL applied to the storage electrode line SL has a value that changes when the display panel is driven at the second frequency. That is, the common voltage V _SL has the first voltage in the valid period of the nth frame and the valid period of the n + 1th frame, and in the vertical blank period between the nth frame and the n + 1th frame, It has a second voltage higher than one voltage, and then has a third voltage higher than the second voltage. For example, the first voltage may be set to 7.5V, the second voltage to 7.6V, and the third voltage to 7.7V.

According to the change of the common voltage V _SL , the voltage of the other terminal of the sustain capacitor Cst connected to the second switching element Q2 and the third switching element Q3 changes. In addition, the voltage at one terminal of the sustain capacitor Cst connected to the first switching element Q1 is also changed.

For example, when the voltage of one terminal of the sustain capacitor Cst connected to the first switching element Q1 becomes 10.5V by the application of the data voltage in the effective period of the nth frame, the first switching element Q1 Is turned off and the voltage drops when a predetermined time passes.

The voltage of one terminal of the storage capacitor (Cst) in a vertical blank interval dropping to about 10.4V, the third switching device (Q3) is in the on state when the storage capacitor (Cst) common voltage (V _SL of 7.6V to the other terminal of the ) Is applied. At this time, as the voltage of the other terminal of the sustain capacitor Cst increases, the voltage of one terminal of the sustain capacitor Cst also rises to 10.5V.

When a predetermined time passes and the voltage of one terminal of the storage capacitor Cst drops to about 10.4V, the common voltage V _SL applied to the other terminal of the storage capacitor Cst may increase to 7.7V. At this time, as the voltage of the other terminal of the sustain capacitor Cst increases, the voltage of one terminal of the sustain capacitor Cst also rises to 10.5V.

Thereafter, when the n + 1th frame starts, the same data voltage as that of the nth frame is applied to one terminal of the sustain capacitor Cst.

As such, the voltage of one terminal of the sustain capacitor Cst may be changed in the vertical blank period through the change of the common voltage V _SL , thereby changing the luminance.

When displaying moving images, the display panel is driven at a frequency relatively faster than when displaying still images, so that the period of the luminance change is short, so that flicker is not recognized. When displaying still images, the flicker is well recognized because the display panel is driven at a relatively slower frequency than when displaying a moving image. In the fifth exemplary embodiment of the present invention, the flicker may not be visually recognized as the video is displayed by inducing the luminance change through the change of the common voltage V _SL .

In the fifth exemplary embodiment of the present invention, since flicker is hardly recognized without inducing a luminance change, a common voltage V _SL having a constant value is supplied to the sustain electrode line SL.

In the above, when the still image is displayed, that is, when the display panel is driven at the second frequency, the common voltage V _SL is changed from the first voltage to the second voltage and from the second voltage to the third voltage, and then again. Explained as coming back. However, the present invention is not limited thereto, and the change in the common voltage V _SL may be implemented in various ways.

For example, the common voltage V _SL may vary as shown in FIG. 32.

32 is a diagram illustrating control signals when a display panel of a display device according to a fifth exemplary embodiment displays a still image.

When the display panel is driven at the second frequency, the common voltage V _SL has a first voltage in the valid period of the nth frame and the valid period of the n + 1th frame, and the validity of the nth frame and the n + 1th frame. The second blank may have a second voltage higher than the first voltage in the vertical blank period between the sections. That is, after the common voltage V _SL rises from the first voltage to the second voltage, the common voltage V _SL may be maintained at the second voltage and then fall back to the first voltage when the next frame starts.

In addition, unlike FIG. 32, when the display panel is driven at the second frequency, the common voltage V _SL has a first voltage in an effective period of the nth frame and an effective period of the n + 1th frame, and the nth The second voltage is higher than the first voltage in the vertical blank period between the frame and the effective period of the n + 1 frame, and then the common voltage V _SL after the predetermined time in the same vertical blank period is greater than the second voltage. It may have a high third voltage. Thereafter, the common voltage V _SL after a predetermined time in the same vertical blank period may have a fourth voltage higher than the third voltage. That is, the common voltage V _SL may change from the first voltage to the second voltage, the second voltage to the third voltage, the third voltage to the fourth voltage, and may fall back to the first voltage when the next frame starts. .

If the vertical blank period is relatively short, the flicker is hardly seen even if the number of voltage changes is set small. On the contrary, when the vertical blank period is relatively long, flicker is better recognized, and therefore, it is preferable to set the number of times of voltage change more.

Next, a display device according to a sixth exemplary embodiment of the present invention will be described with reference to FIG. 33.

33 is an equivalent circuit diagram of one pixel of the display device according to the sixth exemplary embodiment.

Since the display device according to the sixth embodiment of the present invention is substantially the same as the display device according to the fifth embodiment, descriptions and drawings thereof will be omitted and only differences will be described below.

In the display device according to the sixth exemplary embodiment, unlike the fifth exemplary embodiment, the second switching element, the third switching element, and the sustain electrode control line are not formed. In addition, the form of the common voltage applied to the sustain electrode line is different from that of the fifth embodiment.

In the display panel of the display device according to the sixth exemplary embodiment, as illustrated in FIG. 33, the gate line G and the data line D cross each other to define pixels. The gate line G and the data line D may be formed in plural, and a plurality of pixels may be formed, and only one pixel is shown in FIG. 33.

The first switching element Q1 is formed to be connected to the gate line G and the data line D. The first switching element Q1 is a three-terminal element such as a thin film transistor. The control terminal is connected to the gate line G, the input terminal is connected to the data line D, and the output terminal is the liquid crystal capacitor Clc. ) And sustain capacitor Cst.

In addition, the storage electrode line SL may be further formed, and the storage electrode line SL is connected to the storage capacitor Cst.

That is, in the above embodiment, the storage electrode line SL and the storage capacitor Cst are connected by the switching element, whereas in the present embodiment, the storage electrode line SL and the storage capacitor Cst are directly connected.

Hereinafter, the voltage relationship when the display panel of the display device according to the sixth exemplary embodiment displays a still image will be described.

34 is a diagram illustrating control signals when a display panel of a display device according to a sixth exemplary embodiment displays a still image.

In the display device according to the sixth exemplary embodiment of the present invention, when the moving picture is displayed, the display device is driven at the first frequency, and when the still image is displayed, the display device is driven at the second frequency lower than the first frequency. In this case, the length of the vertical blank period may be increased than when driving at the first frequency to implement the second frequency.

When displaying the still image by driving at the second frequency, if the gate-on voltage is first applied to the gate line G in the valid period of the n-th frame, the first switching element Q1 is turned on. Subsequently, when a data voltage is applied to the data line D, the liquid crystal capacitor Clc and the sustain capacitor Cst are charged through the first switching element Q1.

In this case, one terminal of the storage capacitor Cst is connected to the first switching element Q1 to represent a data voltage, and the other terminal is connected to the storage electrode line SL, thereby applying a common voltage applied to the storage electrode line SL. V _SL ). The common voltage V _SL has a constant value during the nth frame to which the data enable signal is applied.

After the data voltage is applied to each pixel, the gate off voltage is applied to the gate line G, and the first switching element Q1 is turned off. Then, the vertical blank period starts, and the common voltage V _SL is changed. The common voltage (V _SL) at the vertical blank interval is the swinging in the same voltage and the common voltage (V _SL) of the useful portion common voltage and a higher voltage than the validity period (V _SL) at.

When the common voltage V _SL in the effective period is the first voltage, when the vertical blank period starts, the common voltage V _SL may change to a second voltage higher than the first voltage and then fall back to the first voltage. Thereafter, after a predetermined time passes in the vertical blank period, the common voltage V _SL may change back to the second voltage and then fall back to the first voltage. The time when the common voltage V _SL has the second voltage in the vertical blank period may be set to be shorter than the time having the first voltage.

The time point at which the common voltage V _SL changes from the first voltage to the second voltage may be set to coincide with the time point at which the voltage at one terminal of the sustain capacitor Cst is discharged to be different from the originally applied data voltage by a predetermined voltage or more. have.

FIG. 34 shows the number of times that the common voltage V _SL changes from the first voltage to the second voltage and returns to the first voltage in the vertical blank period between two adjacent frames. However, the present invention is not limited thereto, and the number of times may be variously set. For example, the number of times that the common voltage V _SL changes from the first voltage to the second voltage and returns to the first voltage in the vertical blank period between the effective periods of two frames may be set only once. It can also be set to times, four times, or the like.

If the vertical blank period is relatively short, the flicker is hardly seen even if the number of voltage changes is set small. On the contrary, when the vertical blank period is relatively long, flicker is better recognized, and therefore, it is preferable to set the number of times of voltage change more.

Subsequently, the vertical blank period ends, and the common voltage V _SL applied to the sustain electrode line SL is constantly maintained at the first voltage.

At the same time, the n + 1th frame starts, and a gate-on voltage is applied to the gate line G. As a result, the first switching element Q1 is turned on. Subsequently, a data voltage is applied to the data line D, and the liquid crystal capacitor Clc and the sustain capacitor Cst are charged. At this time, since the still image is shown, the data voltages in the nth frame and the n + 1th frame are the same.

As described above, the common voltage V _SL applied to the storage electrode line SL has a value that changes when the display panel is driven at the second frequency. That is, the common voltage V _SL has the first voltage in the valid period of the nth frame and the valid period of the n + 1th frame, and in the vertical blank period between the nth frame and the n + 1th frame, Swing to a first voltage and a second voltage higher than the first voltage. For example, the first voltage may be set to 7.5V and the second voltage to 7.6V.

As the common voltage V _SL changes, the voltage of the other terminal of the storage capacitor Cst connected to the storage electrode line SL changes. In addition, the voltage at one terminal of the sustain capacitor Cst connected to the first switching element Q1 is also changed.

For example, when the voltage of one terminal of the sustain capacitor Cst connected to the first switching element Q1 becomes 10.5V by the application of the data voltage in the effective period of the nth frame, the first switching element Q1 Is turned off and may drop to about 10.4V after a predetermined time.

When the common voltage V _SL input to the storage electrode line SL increases from 7.5V to 7.6V, the voltage of the other terminal of the storage capacitor Cst increases to 7.6V. At this time, as the voltage of the other terminal of the sustain capacitor Cst increases, the voltage of one terminal of the sustain capacitor Cst also rises to 10.5V. Next, the common voltage V _SL is dropped back to 7.5V.

When a predetermined time passes and the voltage of one terminal of the storage capacitor Cst drops to about 10.4V, the common voltage V _SL applied to the other terminal of the storage capacitor Cst may increase from 7.5V to 7.6V. At this time, as the voltage of the other terminal of the sustain capacitor Cst increases, the voltage of one terminal of the sustain capacitor Cst also rises to 10.5V.

Thereafter, when the n + 1th frame starts, the same data voltage as that of the nth frame is applied to one terminal of the sustain capacitor Cst.

As described above, the voltage of one terminal of the sustain capacitor Cst may be changed in the vertical blank period through the change of the common voltage V _SL , thereby shortening the period of the luminance change and preventing the flicker from being recognized.

In the above description, the common voltage V _SL is instantaneously increased from the first voltage to the second voltage, and after a predetermined time, the common voltage V _SL is instantaneously lowered from the second voltage to the first voltage. However, the present invention is not limited thereto, and a change form of the common voltage V _SL may be implemented in various ways.

For example, the common voltage V _SL may vary as shown in FIG. 35.

35 is a diagram illustrating control signals when a display panel of a display device according to a sixth exemplary embodiment displays a still image.

When the display panel is driven at the second frequency, the common voltage V _SL has a first voltage in the valid period of the nth frame and the valid period of the n + 1th frame, and the validity of the nth and n + 1th frames. In the vertical blank period between the sections, the first voltage and the second voltage higher than the first voltage may swing. In this case, when the common voltage V _SL changes from the first voltage to the second voltage, the common voltage V _SL may gradually change while having a value between the first voltage and the second voltage. Also, when the common voltage V _SL changes from the second voltage to the first voltage, the common voltage V _SL may gradually change while having a value between the first voltage and the second voltage.

Unlike in FIG. 35, when the common voltage V _SL changes from the first voltage to the second voltage, the common voltage V _SL gradually changes while having a value between the first voltage and the second voltage, and changes from the second voltage to the first voltage. It may fall momentarily. In addition, when the common voltage V _SL changes from the first voltage to the second voltage, the voltage rises momentarily, and when the common voltage V _{SL changes} from the second voltage to the first voltage, it gradually changes while having a value between the first voltage and the second voltage. It may be.

Hereinafter, power consumption which is reduced in the display device according to the fifth and sixth embodiments of the present invention will be described.

36 is a graph illustrating power consumption according to driving frequency. In detail, when the power consumption when driving at 60 Hz is 100%, when the five different screens are driven at 60 Hz to 10 Hz, the ratio of the relative power consumption to the power consumption when driving at 60 Hz is shown. . In addition, the average value of the power consumption ratio of five different screens is also shown. In five different screens, the first screen is a screen that displays white, the second screen is a screen that displays black, and the third and fourth screens are screens that display different colors by dividing the entire area into a plurality of areas. The fifth screen is the Windows desktop.

Since the power consumption when driving the display panel at 10 Hz is about 60%, the power consumption by about 40% is reduced compared to when driving the display panel at 60 Hz. Therefore, by setting the driving frequency at the time of displaying a still image to a certain ratio or less than at the time of displaying a moving image, power consumption can be reduced more than the increase of the power consumption according to addition of a frame memory.

When displaying a video, there is a problem that the movement looks unnatural when the driving frequency is lowered.However, when displaying a still image, the frame is reproduced repeatedly with the same image data. none.

However, when driving at a low driving frequency, flicker is well recognized. Hereinafter, when the flicker is recognized according to the fifth embodiment of the present invention, the flicker is recognized and compared with the related art.

FIG. 37 is a graph showing the voltage at one terminal of the sustain capacitor when driving the conventional display panel at 60 Hz, and FIG. 38 is a graph showing the voltage at one terminal of the sustain capacitor when driving the conventional display panel at 10 Hz. 39 is a graph illustrating the voltage at one terminal of the sustain capacitor when the display panel according to the fifth embodiment of the present invention is driven at 10 Hz.

Referring to FIG. 37 and FIG. 38, when the display panel is driven at 10 Hz, the period of voltage change at one terminal of the sustain capacitor is longer than that at 60 Hz, and the period of luminance change is also longer. Therefore, the lower the driving frequency, the better the flicker is recognized. Referring to FIG. 39, in the fifth embodiment of the present invention, when displaying a still image at a low driving frequency, the common voltage is changed to reduce the period of the voltage change at one terminal of the sustain capacitor to 60 Hz. Can be. As a result, the period of the luminance change is shortened so that the flicker is not visually recognized.

Next, a display device according to a seventh exemplary embodiment of the present invention will be described with reference to FIGS. 1 and 40.

40 is a block diagram illustrating a signal controller of a display device according to a seventh exemplary embodiment of the present invention.

As shown in FIG. 1, the display device according to the seventh embodiment of the present invention includes a display panel 300, a signal controller 600, and a graphics processing apparatus 700.

Since the display panel 300 and the graphic processing apparatus 700 of the display device according to the seventh embodiment of the present invention are the same as those of the first embodiment, detailed description thereof will be omitted.

As shown in FIG. 40, the signal controller 600 of the display device according to the seventh embodiment of the present invention calculates a representative value of the frame memory 640 for storing input image data and the stored image data stored in the frame memory. The operation unit 620 may include a line memory 630 for storing the representative value, and a kickback correction unit 660 for correcting the representative value to generate auxiliary image data.

The frame memory 640 stores input image data received from the graphics processing apparatus 700. The frame memory 640 is not used when the display panel displays moving images, but is used when displaying still images. When the still image start signal is applied, the input image data is stored in the frame memory 640, and the display panel 300 is driven using the stored image data stored in the frame memory 640.

The calculator 620 receives the stored image data from the frame memory 640 and calculates a representative value representing the stored image data. At this time, the representative value is calculated for each data line D1 -Dm.

The frame memory 640 stores stored image data representing one frame, and the stored image data is separated for each data line D1 -Dm. For example, the stored image data corresponding to the data voltage to be applied to the first data line D1, the stored image data corresponding to the data voltage to be applied to the second data line D2, and the third data line D3. Storage image data corresponding to the data voltage to be applied, storage image data corresponding to the data voltage to be applied to the m-th data line Dm, and the like are separated.

The calculation unit 620 receives the stored image data for each data line D1 -Dm and calculates a representative value representing them. For example, the first representative value representing the stored image data corresponding to the data voltage to be applied to the first data line D1 is calculated, and the stored image corresponding to the data voltage to be applied to the second data line D2 is calculated. A second representative value representing data is calculated. In this manner, the third representative value, the mth representative value, and the like are calculated.

The representative value representing the stored image data may be calculated in various ways.

Hereinafter, a method of calculating a representative value will be described with reference to Table 2.

Table 2 is a table showing gray scale values of the stored image data corresponding to the data voltage to be applied to the first data line D1. The number of stored image data corresponding to the data voltage applied to one data line D1 -Dm is the same as the number of gate lines D1 -Dm.

Save image data Gradation d11 00100110 d12 00101010 d13 00111101 d14 00111011 d15 00111011 d16 00101101 d1n 00110001

In the first method, the average gradation value of the stored image data may be represented as a representative value, and may be calculated according to Equation 1.

[Equation 1]

(Gr: representative value, n: number of stored video data)

In Table 2, assuming n is 7, and the average gray value is calculated, 00110010 is obtained.

In the second method, the average gray value of the upper t bits of the stored image data may be represented as a representative value. At this time, the t value can be set in various ways, and a smaller value of t makes the operation simpler. For example, when the stored image data is 8 bits, the t value may be set to 3 or 4.

Assuming a t value of 4 and extracting the upper 4 bits of the stored image data, it is as follows. d11, d12, d13, d14, d15, d16, and d17 have upper four-bit grayscale values of 0010, 0010, 0011, 0011, 0011, 0010, and 0011. Their average value is 0011, and the representative value is 00110000.

In a third method, the representative value may be a median value of the maximum gray value and the minimum gray value of the stored image data. In Table 2, the maximum gray value of the stored image data is 00111101, and the minimum gray value is 00100110. Calculating their median yields 00110010.

Representative values calculated in three ways are 00110010, 00110000, and 00110010, respectively. Therefore, the representative values are not significantly different according to either method. While following the first approach can compute the most appropriate representative value, the computation is complicated. In addition, according to the second and third methods, the calculation is simple, while the suitability of the representative value may be lower than that of the first method.

The line memory 630 receives and stores a representative value from the calculator 620. At this time, since the representative value exists for each data line, the representative value is stored for each data line. The first representative value, the second representative value, the third representative value, the mth representative value, and the like are stored, respectively.

The kickback correction unit 660 generates auxiliary image data by correcting the representative value stored in the line memory 630 according to the kickback voltage.

Each pixel connected to the gate lines G1 -Gn and the data lines D1 -Dm is charged with a data voltage applied from the data lines D1 -Dm, and the charged voltage is referred to as a pixel voltage. The pixel voltage is reduced by the parasitic capacitance and the like as the switching element Q is turned off, and the reduced voltage is referred to as a kick-back voltage.

The kickback correction unit 660 generates auxiliary image data having a value closest to the grayscale value corresponding to the pixel voltage charged in the pixel column connected to one data line D1 -Dm when the switching element Q is in the off state. do. That is, the auxiliary image data has a value close to the grayscale value corresponding to the pixel voltage lowered by the kickback voltage.

The kickback voltage depends on the magnitude of the data voltage applied to the pixel. That is, the kickback voltage varies according to the gray value of the image data corresponding to the data voltage, and can be confirmed through FIG. 41.

FIG. 41 is a graph illustrating a kickback voltage based on a gray value of image data. FIG.

Referring to FIG. 41, it can be seen that the larger the gray value of the image data, the larger the kickback voltage. For example, the kickback voltage at zero gradation is about 1.0V and the kickback voltage at 256 gradations is about 1.2V. The kickback voltage according to the gray value of the image data illustrated in FIG. 41 is merely an example, and may be a value that may vary according to specifications of the display device.

Although the kickback voltage is different depending on the gray value of the image data, it can be seen that the difference is not large. Therefore, the voltage for correction according to the kickback voltage may be set to the same voltage. For example, the kickback voltage may be assumed to be 1V regardless of the size of the image data.

However, even if the kickback voltage is assumed to be 1V regardless of the size of the image data, the gray value corresponding to 1V may vary according to the gray value of each image data. This is because voltage and transmittance have a nonlinear relationship. Accordingly, the gray scale value corresponding to the kickback voltage, that is, the kickback compensation gray scale value, may be obtained according to the gray scale value of the image data from the voltage-transmittance curve V-T curve of each display device.

Hereinafter, a method of obtaining a kickback compensation gray value will be described with reference to FIG. 42.

42 is a graph illustrating a kickback compensation gray value based on the gray value of the image data. The dotted line represents the calculated value obtained by the calculation, and the solid line represents the approximation made using the calculated value.

First, the method for obtaining the kickback compensation gray value by calculation is as follows.

The second image data corresponding to the second data voltage obtained by subtracting the kickback voltage from the first data voltage corresponding to the arbitrary first image data is obtained. The kickback compensation gray value is obtained by subtracting the gray value of the second image data from the gray value of the first image data. In this manner, the kickback compensation gray values for all the first image data can be obtained and represented as a lookup table. In addition, when the kickback compensation gray value obtained by the calculation is represented graphically, it is drawn as a dotted line in FIG.

The kickback compensation gray value according to the representative value of the stored image data may be obtained using the lookup table generated by the calculation.

Next, a method of calculating the kickback compensation gray value by approximation using the calculated value is as follows.

Referring to FIG. 42, when the image data is about 175 gray levels, the kickback compensation gray value is the largest. Also, in the range where the image data is less than about 175 gradations, the smaller the gradation value is, the smaller the kickback compensation gradation value becomes, and in the range where the image data is greater than about 175, the larger the gradation value, the smaller the kickback compensation gradation value is. At this time, the change of the kickback compensation gray value according to the gray value of the image data is nonlinear but has a form close to linear.

Accordingly, a function of the kickback compensation gray value according to the gray value of the image data may be generated using linear interpolation. At this time, the kickback compensation gray value y1 at the minimum gray level x1, the kickback compensation gray value x3 at the maximum gray level x3, and the grayscale value y2 when the magnitude of the kickback compensation gray value is at maximum (y2). ) Can be used to generate a function such as Equation 2.

&Quot; (2) &quot;

When the representative value of the stored image data is input to x in the function of Equation 2, the y value becomes the kickback compensation gray value.

Hereinafter, a method of generating auxiliary image data using the kickback compensation gray value will be described.

As shown in Equation 3, a value obtained by subtracting the kickback compensation gray value according to the representative value from the representative value of the stored image data is the gray value of the auxiliary image data.

&Quot; (3) &quot;

(Ga: gray value of auxiliary image data, Gr: representative value, dG: kickback compensation gray value according to the representative value)

The kickback correction unit 660 transmits the auxiliary image data generated using Equation 3 to the data driver 500, and the data driver 500 corresponds to the auxiliary image data in the vertical blank section when displaying the still image. An auxiliary voltage is applied to the data lines D1 -Dm.

If the signal controller 600 organizes the image data transmitted to the data driver 500 according to each case is as follows.

When displaying a video, the signal controller 600 transmits input image data received from the graphic processing apparatus 700 to the data driver 500 to drive the display panel 300 at a first frequency. When the still image is displayed, the signal controller 600 transmits the stored image data stored in the frame memory 640 to the data driver 500 to drive the display panel 300 at the second frequency. In addition, when displaying a still image, the auxiliary image data having corrected the representative value of the stored image data in the vertical blank period is transmitted to the data driver 500 so that the auxiliary voltage is applied to the data line.

Next, a principle of reducing leakage current by inputting auxiliary image data in a vertical blank period when displaying a still image in the display device according to the seventh exemplary embodiment of the present invention will be described with reference to FIGS. 43 and 44. .

FIG. 43 is an equivalent circuit diagram of one pixel of the display device according to the seventh embodiment of the present invention, and FIG. 44 is a view illustrating a case in which a predetermined voltage is applied during a vertical blank period in the display device according to the seventh embodiment of the present invention. It is a figure which shows the leakage current.

As illustrated in FIG. 43, a switching element Q is formed so that one pixel of the display device according to the seventh exemplary embodiment is connected to the gate line Gn and the data line Dm. The switching element Q is a three-terminal element such as a thin film transistor, the control terminal is connected to the gate line Gn, the input terminal is connected to the data line Dm, and the output terminal is connected to the liquid crystal capacitor Clc. It is connected.

When the gate-on voltage is applied to the gate line Gn and the data voltage is applied to the data line Dm, the liquid crystal capacitor Clc is charged. Subsequently, when the gate-off voltage is applied to the gate line Gn, and the switching element Q is turned off, no current should flow between the input terminal and the output terminal of the switching element Q. However, due to the characteristics of the switching element Q such as a thin film transistor, a leakage current Idp flowing from the output terminal of the switching element Q to the input terminal is generated. The leakage current Idp is proportional to the difference between the voltage Vd of the input terminal of the switching element Q and the voltage Vp of the output terminal.

In general, since the data voltage is not input in the vertical blank period between two adjacent frames, the voltage difference between the input terminal and the output terminal of the switching element Q is large. When the length of the vertical blank section between the two frames is driven at a low frequency, the leakage current due to the voltage difference between the input terminal and the output terminal of the switching element Q becomes larger.

In the present invention, the leakage current can be reduced by driving the display panel at a low frequency when displaying a still image and applying a predetermined voltage to the data line in the vertical blank period.

As shown in FIG. 44, it can be seen that the leakage current changes when the data voltage corresponding to the black gray and the data voltage corresponding to the white gray are applied to the data line in the vertical blank period.

In this case, the predetermined voltage applied to the data line is preferably set to the value closest to the pixel voltage charged in the liquid crystal capacitor Clc of each pixel, that is, the voltage of the output terminal of the switching element Q.

In the present invention, a value representative of the stored image data is calculated for each data line, corrected according to the kickback voltage to generate auxiliary image data, and then a corresponding auxiliary voltage is applied to the data line. Therefore, it is possible to minimize the voltage between the input terminal and the output terminal of the switching element (Q), thereby minimizing the leakage current.

Next, a display device according to an eighth embodiment of the present invention will be described.

Since the display device according to the eighth embodiment of the present invention is the same as the structure of the display device according to the first embodiment, a detailed description thereof will be omitted.

Hereinafter, a gate voltage applied to the gate line of the display device according to the eighth embodiment of the present invention will be described with reference to FIGS. 45 and 46.

45 is a view illustrating one pixel of a display device according to an eighth embodiment of the present invention, and FIG. 46 is a diagram illustrating an input terminal and an output terminal according to a gate voltage in a switching element of a display device according to an eighth embodiment of the present invention. Is a graph showing the current.

One pixel of the display device according to the eighth embodiment of the present invention is a switching element Q connected to a gate line Gn and a data line Dm and a liquid crystal capacitor Clc connected to a switching element Q. And a holding capacitor Cst. In this case, the control terminal of the switching element Q is connected to the gate line Gn, the input terminal is connected to the data line Dm, and the output terminal is connected to the liquid crystal capacitor Clc and the sustain capacitor Cst.

The gate on voltage and the gate off voltage are alternately applied to the gate line Gn to adjust the on / off state of the switching element Q.

When the gate-on voltage is applied to the gate line Gn, the switching element Q is turned on, and the current Ids flows between the input terminal and the output terminal. Therefore, the pixel electrode is charged to the pixel voltage Vp by the data voltage Vd supplied through the data line Dm.

When the gate-off voltage is applied to the gate line Gn, the switching element Q is turned off, and the current Ids between the input terminal and the output terminal hardly flows. However, a voltage difference is formed between the data voltage Vd and the pixel voltage Vp, so that a leakage current is generated between the input terminal and the output terminal. Therefore, the gate off voltage is preferably selected to a voltage value that can minimize such leakage current.

As shown in FIG. 46, it can be seen that a difference occurs in the leakage current when the pixel voltage Vp charged in the pixel electrode is positive and negative.

46 illustrates the current Ids between the input terminal and the output terminal according to the gate voltage Vg input to the control terminal of the switching element Q when the pixel voltage Vp is negative and when it is positive. When the pixel voltage Vp is negative, the pixel voltage Vp is 0V, the data voltage Vd is 10V. When the pixel voltage Vp is positive, the pixel voltage Vp is 20V and the data voltage Vd is 10V. It is shown.

If the voltage for minimizing the current Ids between the input terminal and the output terminal of the switching element Q when the pixel voltage Vp is negative is selected as the gate-off voltage, between the positive pixel and the negative pixel Differences in leakage current occur, resulting in different luminance characteristics. Further, even when the voltage for minimizing the current Ids between the input terminal and the output terminal of the switching element Q when the pixel voltage Vp is positive is selected as the gate-off voltage, the positive pixel and the negative pixel Differences in leakage current occur between them, resulting in different luminance characteristics.

Therefore, in the display device according to the eighth embodiment of the present invention, the voltage of the control terminal of the switching element Q is changed when the leakage current is the same when the pixel voltage Vp charged to the pixel electrode is positive and negative. It can be selected as the gate-off voltage. For example, the gate off voltage may be set to −4 V according to the experimental result shown in FIG. 46. Of course, these values are values that can vary as the experimental conditions change.

Hereinafter, the flicker is improved in the display device according to the eighth exemplary embodiment of the present invention with reference to FIGS. 47 and 48.

47 is a diagram illustrating luminance characteristics when displaying a still image in the display device according to the related art, and FIG. 48 is a diagram illustrating luminance characteristics when displaying a still image in the display device according to the eighth embodiment of the present invention. Drawing. Specifically, FIG. 47 illustrates luminance characteristics when a voltage for minimizing the current Ids between the input terminal and the output terminal of the switching element Q when the pixel voltage Vp is negative is selected as the gate-off voltage. FIG. 48 is a diagram showing luminance characteristics when the voltage of the control terminal of the switching element Q is selected as the gate-off voltage when the leakage current is the same when the pixel voltage Vp is positive and negative. .

When displaying a still image, the same image is displayed every frame, so that the luminance of each pixel does not change in theory.

As shown in FIG. 47, when the pixel voltage Vp is negative, a display according to the related art, which selects a voltage for minimizing the current Ids between the input terminal and the output terminal of the switching element Q as the gate-off voltage. In the device, when the still image is displayed, the brightness of the entire screen is repeatedly increased and decreased every frame, and thus flicker may be visually recognized.

The reason why the flicker occurs is because the sum of the luminance of the pixels to which the positive pixel voltage is applied and the pixels to which the negative pixel voltage is applied is not constant. The luminance of the pixel to which the positive pixel voltage is applied and the luminance of the pixel to which the negative pixel voltage is applied are different from each other. The sum of the luminance of the pixels to which the positive pixel voltage is applied and the pixel to which the negative pixel voltage is applied changes every frame, so that the brightness of the entire screen also changes every frame.

As shown in FIG. 48, the eighth embodiment of the present invention selects the voltage of the control terminal of the switching element Q as the gate-off voltage when the leakage current is the same when the pixel voltage Vp is positive and negative. In the display device, the luminance of the entire screen is kept constant when displaying a still image.

In the display device according to the eighth embodiment of the present invention, the leakage current generated in the pixel to which the positive pixel voltage is applied and the leakage current generated in the pixel to which the negative pixel voltage is applied are the same while displaying a still image. By doing so, the sum of the luminance of the pixel to which the positive pixel voltage is applied and the luminance of the pixel to which the negative pixel voltage is applied can be kept constant. Therefore, the brightness of the entire screen is kept constant, so that flicker is not visually recognized.

In the above, the characteristic that the flicker can be reduced by setting the gate-off voltage to the voltage of the control terminal of the switching element when the leakage current is the same in the positive pixel and the negative pixel is described.

Furthermore, by setting the gate-off voltage to be within a predetermined range based on the voltage of the control terminal of the switching element when the leakage current is the same in the positive pixel and the negative pixel, the same or similar effects can be obtained. The range will be described with reference to 3 and FIG. 49.

Table 3 is a table showing flicker values according to the gate off voltage values when displaying a still image in the display device according to the eighth exemplary embodiment of the present invention, and FIG. 49 is a graph showing Table 3 graphically. That is, FIG. 49 is a graph illustrating a flicker value according to the gate off voltage when displaying a still image in the display device according to the eighth exemplary embodiment of the present invention.

As shown in Table 3 and FIG. 49 when the display device according to the eighth embodiment of the present invention changes the length of the vertical blank section or changes the magnitude of the clock frequency to lower the frequency and displays a still image at a lower frequency. The flicker value changes according to the gate-off voltage.

In the experimental example illustrated in FIG. 46, when the leakage current is the same in the positive pixel and the negative pixel, the voltage of the control terminal of the switching element Q is -4V. Therefore, the flicker was measured by setting the lower voltage and the higher voltage as the gate-off voltage based on -4V, and the results are shown in Table 3 and FIG. 49.

Gate off voltage (V) Flicker value (dB) Change vertical blank section Clock frequency change -6.5 -37.9 -36.7 -6 -40 -39.5 -5.5 -42.7 -42.4 -5 -46.2 -45 -4.5 -49.4 -46.3 -4 -51.4 -46.4 -3.5 -52.4 -45.6 -3 -52.5 -44.7 -2.5 -53.5 -43.7

Referring to Table 3 and FIG. 49, the flicker value when the gate-off voltage is -4V has a value similar to the flicker value when the gate-off voltage is changed by about -20% or + 20% based on -4V. You can see that. Even when the gate-off voltage has a value of about + 20% or more based on -4V, the flicker value may have a value similar to or lower than that when the gate-off voltage is -4V. However, when the gate-off voltage is set to a value that is too high, problems such as color leakage may occur as the leakage current increases.

Therefore, the gate-off voltage is set to have a range of about -20% to + 20% based on the voltage of the control terminal of the switching element Q when the leakage current is the same in the positive pixel and the negative pixel. desirable. In addition, the gate-off voltage is set so as to have a range of about -10% to + 10% based on the voltage of the control terminal of the switching element Q when the leakage current is the same in the positive pixel and the negative pixel. More preferred.

Based on this, the range of the gate-off voltage is expressed by the following equation.

In the display device according to the eighth embodiment of the present invention, the gate-off voltage applied to the gate line Gn when the display panel is driven at the second frequency may be set to have the range of Equation 4 below.

&Quot; (4) &quot;

Va-0.2┃Va┃≤ Voff2≤ Va + 0.2┃Va┃

(Voff2: the gate-off voltage when the display panel is driven at the second frequency, Va: leakage flowing between the input terminal and the output terminal of the switching element when a positive pixel voltage is applied to the pixel electrode) Voltage of the control terminal of the switching element when the current and the leakage current flowing between the input terminal and the output terminal of the switching element are equal when a negative pixel voltage is applied to the pixel electrode)

More preferably, in the display device according to the eighth embodiment of the present invention, the gate-off voltage applied to the gate line Gn when the display panel is driven at the second frequency may be set to have the range of Equation 5 below. .

[Equation 5]

Va-0.1┃Va┃≤ Voff2≤ Va + 0.1┃Va┃

(Voff2: the gate-off voltage when the display panel is driven at the second frequency, Va: leakage current flowing between the input terminal and the output terminal of the switching element when a positive pixel voltage is applied to the pixel electrode) And a voltage of the control terminal of the switching element when the leakage current flowing between the input terminal and the output terminal of the switching element is the same when a negative pixel voltage is applied to the pixel electrode.

Since the display device according to the eighth embodiment of the present invention is driven at a low frequency when displaying a still image, a gate-off voltage is set according to Equation 4 or 5 to prevent flicker.

When displaying a moving image in the display device according to the eighth embodiment of the present invention, since the flicker is hardly recognized because the driving is performed at a high frequency, the gate-off voltage can be set to a lower value. That is, the gate-off voltage when the display panel is driven at the first frequency may be set lower than the gate-off voltage when the display panel is driven at the second frequency.

Alternatively, the gate off voltage when the display panel is driven at the first frequency may be set to be the same as the gate off voltage when the display panel is driven at the second frequency. In this case, the range of the gate-off voltage is expressed by the following equation.

&Quot; (6) &quot;

Va-0.2┃Va┃≤ Voff1≤ Va + 0.2┃Va┃

(Voff1: the gate-off voltage when the display panel is driven at the first frequency, Va: leakage flowing between the input terminal and the output terminal of the switching element when a positive pixel voltage is applied to the pixel electrode) Voltage of the control terminal of the switching element when the current and the leakage current flowing between the input terminal and the output terminal of the switching element are equal when a negative pixel voltage is applied to the pixel electrode)

More preferably, in the display device according to the eighth embodiment of the present invention, the gate-off voltage applied to the gate line Gn when the display panel is driven at the first frequency may be set to have the range of Equation 7 below. .

[Equation 7]

Va-0.1┃Va┃≤ Voff1≤ Va + 0.1┃Va┃

(Voff1: the gate-off voltage when the display panel is driven at the first frequency, Va: leakage flowing between the input terminal and the output terminal of the switching element when a positive pixel voltage is applied to the pixel electrode) Voltage of the control terminal of the switching element when the current and the leakage current flowing between the input terminal and the output terminal of the switching element are equal when a negative pixel voltage is applied to the pixel electrode)

Hereinafter, a method of calculating the flicker value will be described with reference to FIGS. 50 and 51 as follows.

FIG. 50 is a graph showing the intensity of light emitted from another display panel at time, and FIG. 51 is a diagram illustrating equipment used for flicker measurement.

Flicker refers to a phenomenon in which light flicker is felt because the intensity of light emitted from the screen is not constant but changes periodically with time. When the display device is driven at 60 Hz, 60 flickers occur 1 second.

Referring to FIG. 50, it can be seen that light intensity changes with time. Light intensity changes periodically with values between Vmax and Vmin.

As a first method of calculating the flicker value, there is a method of calculating the ratio of an AC component to a DC component. After measuring the Vmax and Vmin values, the flicker value may be calculated using Equation 8 below.

[Equation 8]

(F: 플리커값)

(F: flicker value)

The sensitivity of the eye changes according to the intensity of light, and the amount of change has nonlinearity, so it is necessary to take this into account when calculating the flicker value. Since the first method does not consider this, it is not easy to derive an accurate flicker value, but the calculation method is simple.

Hereinafter, a second method used to derive a more accurate flicker value in consideration of a change in sensitivity of an eye according to light intensity will be described.

As illustrated in FIG. 51, a luminance meter 20 capable of measuring luminance may be disposed on a surface where light is emitted from the display device 10. The luminance meter 20 can use BM-7 etc., for example. In addition, a dynamic signal analyzer 30 (DSA) which receives and processes a signal from the luminance meter 20 is connected to the luminance meter 20.

First, the light is emitted from the display device 10, and the luminance of the light emitted from the display device 10 is measured using the luminance meter 20. The luminance of the light measured by the luminance meter 20 has an analog value, which is transmitted to the dynamic signal analyzer 30. The dynamic signal analyzer 30 reads rms value (root mean square value) of 0 Hz component and 30 Hz component in decibels from the analog value.

After reading the effective values of the 0 Hz component and the 30 Hz component from the dynamic signal analyzer 30, the flicker value may be calculated using Equation 9 below. Equation 6 is made in consideration of the amount of change in the size of the pupil with respect to the intensity of light, the intensity of light passing through the pupil for the amount of change in the size of the pupil, and the eye's responsiveness to the intensity of light passing through the pupil.

&Quot; (9) &quot;

F = 1000 * (A-B)

,(

,

,

,

,

,

,

,

0 Hz: RMS value of the 0 Hz component of the luminance of the light,

30 Hz: RMS value of the 30 Hz component of the luminance of the light,

a: proportional constant between the luminance of light incident on the luminance meter 20 and the output voltage,

b: reference voltage for calculating the voltage input to the dynamic signal analyzer 30 in decibels (dB)

In the case of the second method, the calculation method is more complicated, but the calculation method takes into account various variables acting on the change of the flicker value, so that a more accurate value can be calculated.

Flicker values shown in Table 3 and FIG. 49 of the present invention are the values calculated using the second method.

Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concepts of the present invention defined in the following claims are also provided. It belongs to the scope of rights.

10: display device 20: luminance meter
30: dynamic signal analyzer 300: display panel
400: gate driver 500: data driver
600: signal controller 610: signal receiver
620: frame counting unit 630: line memory
640: frame memory 650: drive frequency selector
660: kickback correction unit 700: graphics processing unit
800: gray voltage generator 900: light source
910: light source driver 912: driving frequency receiver
914: light source driving rate selector 916: light source driving signal generation unit

Claims (110)

A display panel displaying still images and moving images;
A signal controller configured to control signals for driving the display panel; And
A graphic processing apparatus for transmitting input image data to the signal controller;
The signal controller includes a frame memory that stores the input image data.
In the display panel,
Is driven at the first frequency when displaying the video,
Driven at a second frequency lower than the first frequency when displaying the still image;
Display device.
The method according to claim 1,
The graphic processing apparatus transmits a still image start signal and a still image end signal to the signal controller.
Display device.
The method of claim 2,
The signal control unit,
When the still image start signal is applied, the input image data is stored in the frame memory, the stored image data stored in the frame memory is output to the display panel at the second frequency, and the transmission of the input image data is deactivated. ,
Display device.
The method of claim 3,
The signal control unit,
When the still image end signal is applied, the transmission of the input image data is activated, and the input image data is output to the display panel at the first frequency.
Display device.
The method of claim 2,
The length of the vertical blank section when driven at the second frequency is longer than the length of the vertical blank section when driven at the first frequency,
Display device.
6. The method of claim 5,
The display panel is driven at a frequency higher than the second frequency and lower than the first frequency during the S1 frame after the still image start signal is applied.
Display device.
The method of claim 6,
During the S1 frame, the length of the vertical blank section is gradually longer,
Display device.
6. The method of claim 5,
The display panel is driven at a frequency higher than the second frequency and lower than the first frequency during the S2 frame after the stop image termination signal is applied.
Display device.
The method of claim 8,
During the S2 frame, the length of the vertical blank section is gradually shortened,
Display device.
The method of claim 2,
In the display panel,
Board;
A gate line and a data line formed on the substrate;
A switching element connected to the gate line and the data line; And
A pixel electrode connected to the switching element,
A gate signal including a gate on voltage and a gate off voltage is applied to the gate line.
Display device.
The method of claim 10,
The clock frequency of the gate signal when driven at the second frequency is lower than the clock frequency of the gate signal when driven at the first frequency,
Display device.
12. The method of claim 11,
The length of the vertical blank section when driven at the second frequency is longer than the length of the vertical blank section when driven at the first frequency,
Display device.
The method of claim 2,
The display panel is driven at the second frequency until the frame to which the still image end signal is applied ends.
Display device.
The method of claim 13,
The display panel includes a gate line and a data line.
A gate driver for driving the gate line; And
Further comprising a data driver for driving the data line,
The signal controller transmits an STV signal and a CPV signal to the gate driver.
Display device.
15. The method of claim 14,
The signal controller transmits the STV signal to the gate driver at the start of one frame except for the point where the second frequency is changed from the second frequency to the first frequency.
Display device.
The method of claim 15,
The signal control unit,
Controlling the width of the CPV signal to be equal to each other when the display panel is driven at the first frequency and the second frequency;
Display device.
17. The method of claim 16,
The signal control unit,
When the display panel is driven at the first frequency, a width of the CPV signal has the same width as p clock signals.
When the display panel is driven at the second frequency, the width of the CPV signal is controlled to have the same width as q clock signals less than p.
Display device.
The method of claim 15,
The signal control unit,
Gamma correcting the image data when the display panel is driven at the second frequency, and transmitting the corrected image data to the display panel;
Display device.
The method of claim 2,
The signal control unit,
The number of still image continuous frames input after the still image start signal is applied and before the still image end signal is applied, and after the still image end signal is applied, until the still image start signal is applied. Further comprising a frame counting unit for counting the number of consecutive frames,
Display device.
The method of claim 19,
The signal control unit,
When the number of still image continuous frames is equal to or greater than x, the input image data is stored in the frame memory, and the transmission of the input image data is deactivated.
Activating the transmission of the input image data when the moving picture continuous frame number is y or more;
Display device.
21. The method of claim 20,
The signal control unit,
Outputting stored image data stored in the frame memory to the display panel at the second frequency when the number of still image continuous frames is equal to or greater than x,
Outputting the input image data to the display panel at the first frequency when the moving picture continuous frame number is y or more;
Display device.
The method of claim 2,
A light source unit radiating light onto the display panel; And
Further comprising a light source driver for controlling signals for driving the light source unit,
Display device.
The method of claim 22,
The light source driver,
When the display panel is driven at a first frequency, the light source is driven at a first ratio,
Driving the light source unit at a second ratio when the display panel is driven at a second frequency;
Display device.
24. The method of claim 23,
When the display panel is in the normally black mode, the second ratio has a lower value than the first ratio.
When the display panel is in the normally white mode, the second ratio has a higher value than the first ratio.
Display device.
25. The method of claim 24,
The signal control unit,
A signal receiving unit receiving the input image data from the graphic processing apparatus; And
The display apparatus may further include a driving frequency selector configured to select the first frequency when displaying the still image and to select the second frequency when displaying the video.
Display device.
25. The method of claim 24,
The light source driver,
A driving frequency receiving unit receiving a driving frequency of the display panel from the signal controller;
A light source unit drive ratio selector configured to determine a drive ratio of the light source unit according to the drive frequency; And
Including a light source driving signal generation unit for generating a signal for driving the light source in accordance with the driving ratio of the light source unit,
Display device.
The method of claim 22,
The light source driver,
When the display panel is driven at the first frequency, the driving ratio of the light source unit is kept constant.
Periodically changing a driving ratio of the light source unit when the display panel is driven at the second frequency;
Display device.
28. The method of claim 27,
The display panel is in a normally black mode,
The light source driver,
When the display panel is driven at the first frequency, the light source is driven at a first ratio,
When the display panel is driven at the second frequency, the light source is driven at a rate that is sequentially lowered from the first ratio and the first ratio.
Display device.
29. The method of claim 28,
The display panel includes a gate line and a data line.
A gate driver for driving the gate line; And
Further comprising a data driver for driving the data line,
The signal controller transmits an STV signal to the gate driver at the start of every frame,
Display device.
30. The method of claim 29,
The light source driver,
When the display panel is driven at the second frequency,
At the point where the STV signal is transmitted, the light source unit is driven at a first ratio,
To drive the light source unit at a rate sequentially lowered from the first ratio until the next STV signal is transmitted,
Display device.
31. The method of claim 30,
The transmission period of the STV signal when the display panel is driven at the first frequency is the same as the change period of the driving ratio of the light source unit when the display panel is driven at the second frequency,
Display device.
28. The method of claim 27,
The display panel is in a normally white mode,
The light source driver,
When the display panel is driven at the first frequency, the light source is driven at a first ratio,
When the display panel is driven at the second frequency, driving the light source unit at a rate that increases sequentially from the first ratio and the first ratio;
Display device.
The method of claim 2,
In the display panel,
Board;
A gate line, a data line, and a storage electrode line formed on the substrate;
A first switching element connected to the gate line and the data line; And
A sustain capacitor connected to the first switching element and the sustain electrode line;
When the display panel is driven at the first frequency, the common voltage input to the sustain electrode line has a constant value.
When the display panel is driven at the second frequency, the common voltage has a value that changes with time.
Display device.
The method of claim 33, wherein
In the display panel,
A second switching element and a third switching element formed between the sustain electrode line and the sustain capacitor; And
A sustain electrode control line formed on the substrate;
The second switching element and the third switching element each include a control terminal, an input terminal, an output terminal,
Input terminals of the second switching element and the third switching element are connected to the sustain electrode line,
An output terminal of the second switching element and the third switching element is connected to the sustain capacitor,
The control terminal of the second switching element is connected to the gate line,
The control terminal of the third switching element is connected to the sustain electrode control line,
Display device.
The method of claim 34, wherein
The common voltage is driven when the display panel is driven at the second frequency.
Having a first voltage in a first section,
Having a second voltage higher than the first voltage in a second period,
Display device.
36. The method of claim 35 wherein
One frame consists of a valid section in which video data is transmitted and a vertical blank section in which video data is not transmitted.
The first section is the valid section,
The second section is the vertical blank section,
Display device.
37. The method of claim 36,
The control voltage input to the sustain electrode control line is
Has a gate-off voltage in the first section,
Having a gate on voltage in the second section,
Display device.
36. The method of claim 35 wherein
The common voltage is driven when the display panel is driven at the second frequency.
Having a third voltage higher than the second voltage in a third section,
Display device.
The method of claim 38, wherein
One frame consists of a valid section in which video data is transmitted and a vertical blank section in which video data is not transmitted.
The first section is the valid section,
The second section is part of the vertical blank section,
The third section is the remaining part of the vertical blank section,
Display device.
The method of claim 33, wherein
The common voltage is driven when the display panel is driven at the second frequency.
Having a first voltage in a first section,
Swinging to the second voltage higher than the first voltage and the first voltage in a second period,
Display device.
41. The method of claim 40 wherein
The common voltage is
When changing from the first voltage to the second voltage,
Gradually varying with a value between the first voltage and the second voltage,
Display device.
The method of claim 2,
A gate driver for driving the gate line; And
Further comprising a data driver for driving the data line,
The signal control unit,
A calculator configured to calculate a representative value of the stored image data stored in the frame memory;
A line memory for storing the representative value; And
A kickback correction unit configured to generate auxiliary image data by correcting the representative value according to a kickback voltage;
When the data driver displays the still image, the data driver applies an auxiliary voltage corresponding to the auxiliary image data to the data line in a vertical blank period.
Display device.
The method of claim 42, wherein
The data line is composed of a plurality,
The calculator calculates a representative value of the stored image data for each of the data lines.
Display device.
44. The method of claim 43,
The representative value is an average gradation value of the stored image data.
Display device.
44. The method of claim 43,
The representative value is an average gray value of upper t bits of the stored image data.
Display device.
44. The method of claim 43,
The representative value is an intermediate value between the maximum gray value and the minimum gray value of the stored image data.
Display device.
44. The method of claim 43,
The auxiliary image data,

(Ga: gray value of the auxiliary image data, Gr: the representative value, dG: kickback compensation gray value according to the representative value)
Generated according to,
Display device.
The method of claim 47,
The kickback compensation gray value is a value stored in the form of a lookup table or calculated by a function,
Display device.
49. The method of claim 48 wherein
When the kickback compensation gray value is a value calculated by a function,
The function is
Created by linear interpolation using the kickback compensation gradation value at the minimum gradation, the kickback compensation gradation value at the maximum gradation, and the gradation value when the magnitude of the kickback compensation gradation value is maximum,
Display device.
The method of claim 2,
In the display panel,
Gate lines and data lines;
A switching device having a control terminal connected to the gate line and an input terminal connected to the data line; And
A pixel electrode connected to an output terminal of the switching element,
A gate signal including a gate on voltage and a gate off voltage is applied to the gate line,
The gate-off voltage when the display panel is driven at the second frequency is
Va-0.2┃Va┃≤ Voff2≤ Va + 0.2┃Va┃
(Voff2: the gate-off voltage when the display panel is driven at the second frequency, Va: leakage flowing between the input terminal and the output terminal of the switching element when a positive pixel voltage is applied to the pixel electrode) Voltage of the control terminal of the switching element when the current and the leakage current flowing between the input terminal and the output terminal of the switching element are equal when a negative pixel voltage is applied to the pixel electrode)
With a range of
Display device.
51. The method of claim 50,
When the display panel is driven at the second frequency, the gate off voltage is
Va-0.1┃Va┃≤ Voff2≤ Va + 0.1┃Va┃
(Voff2: the gate-off voltage when the display panel is driven at the second frequency, Va: leakage current flowing between the input terminal and the output terminal of the switching element when a positive pixel voltage is applied to the pixel electrode) And a voltage of the control terminal of the switching element when the leakage current flowing between the input terminal and the output terminal of the switching element is the same when a negative pixel voltage is applied to the pixel electrode.
With a range of
Display device.
51. The method of claim 50,
The gate-off voltage when the display panel is driven at the first frequency is
Va-0.2┃Va┃≤ Voff1≤ Va + 0.2┃Va┃
(Voff1: the gate-off voltage when the display panel is driven at the first frequency, Va: leakage flowing between the input terminal and the output terminal of the switching element when a positive pixel voltage is applied to the pixel electrode) Voltage of the control terminal of the switching element when the current and the leakage current flowing between the input terminal and the output terminal of the switching element are equal when a negative pixel voltage is applied to the pixel electrode)
With a range of
Display device.
The method of claim 52, wherein
The gate-off voltage when the display panel is driven at the first frequency is
Va-0.1┃Va┃≤ Voff1≤ Va + 0.1┃Va┃
(Voff1: the gate-off voltage when the display panel is driven at the first frequency, Va: leakage flowing between the input terminal and the output terminal of the switching element when a positive pixel voltage is applied to the pixel electrode) Voltage of the control terminal of the switching element when the current and the leakage current flowing between the input terminal and the output terminal of the switching element are equal when a negative pixel voltage is applied to the pixel electrode)
With a range of
Display device.
51. The method of claim 50,
The gate-off voltage when the display panel is driven at the first frequency is the same as the gate-off voltage when the display panel is driven at the second frequency,
Display device.
51. The method of claim 50,
The gate-off voltage when the display panel is driven at the first frequency is lower than the gate-off voltage when the display panel is driven at the second frequency,
Display device.
The method of claim 2,
A gate driver for driving the gate line; And
Further comprising a data driver for driving the data line,
The signal control unit,
When the still image start signal is applied, the input image data is stored in the frame memory, the stored image data stored in the frame memory is applied to the data driver, and the transmission of the input image data is deactivated.
Display device.
The method of claim 56, wherein
When the still image end signal is applied, the transmission of the input image data is activated, and the input image data is applied to the data driver.
Display device.
The method of claim 56, wherein
The gate driver is attached to one side of the display panel.
Display device.
The method of claim 56, wherein
The gate driver is mounted in the display panel together with the gate line, the data line, and the switching element.
Display device.
A method of driving a display device, comprising: a display panel displaying a moving image and a still image; and a signal controller configured to control signals for driving the display panel.
Transmitting input image data and driving the display panel at a first frequency;
Applying a still image start signal;
Changing a driving frequency of the display panel to a second frequency lower than the first frequency;
Applying a still image end signal; And
Changing a driving frequency of the display panel to the first frequency;
A method of driving a display device.
61. The method of claim 60,
When the still image start signal is applied, storing the input image data in a frame memory, deactivating transmission of the input image data, and outputting the stored image data stored in the frame memory to the display panel at the second frequency. ,
A method of driving a display device.
62. The method of claim 61,
When the still image end signal is applied, the transmission of the input image data is activated, and the input image data is output to the display panel at the first frequency.
A method of driving a display device.
61. The method of claim 60,
The length of the vertical blank section when driven at the second frequency is longer than the length of the vertical blank section when driven at the first frequency,
A method of driving a display device.
The method of claim 63, wherein
Driving the display panel at a frequency higher than the second frequency and lower than the first frequency during the S1 frame after the still image start signal is applied;
A method of driving a display device.
65. The method of claim 64,
During the S1 frame, the length of the vertical blank section is gradually longer
A method of driving a display device.
The method of claim 63, wherein
Driving the display panel at a frequency higher than the second frequency and lower than the first frequency during the S2 frame after the stop image termination signal is applied;
A method of driving a display device.
67. The method of claim 66 wherein
During the S2 frame, the length of the vertical blank section is gradually shortened,
A method of driving a display device.
61. The method of claim 60,
In the display panel,
Board;
A gate line and a data line formed on the substrate;
A switching element connected to the gate line and the data line; And
A pixel electrode connected to the switching element,
Applying a gate signal including a gate on voltage and a gate off voltage to the gate line;
A method of driving a display device.
The method of claim 68, wherein
The clock frequency of the gate signal when driven at the second frequency is lower than the clock frequency of the gate signal when driven at the first frequency,
A method of driving a display device.
The method of claim 69, wherein
The length of the vertical blank section when driven at the second frequency is longer than the length of the vertical blank section when driven at the first frequency,
A method of driving a display device.
61. The method of claim 60,
The display panel is driven at the second frequency until the frame to which the still image end signal is applied ends.
Changing the driving frequency of the display panel to the first frequency in the next frame to which the still image end signal is applied;
A method of driving a display device.
The method of claim 71, wherein
The display panel includes a gate line and a data line.
A gate driver for driving the gate line; And
Further comprising a data driver for driving the data line,
The signal controller transmits an STV signal and a CPV signal to the gate driver.
A method of driving a display device.
73. The method of claim 72,
The signal controller transmits the STV signal to the gate driver at the start of every frame except for the point where the second frequency is changed from the second frequency to the first frequency.
A method of driving a display device.
The method of claim 73,
The signal control unit,
Controlling the width of the CPV signal to be equal to each other when the display panel is driven at the first frequency and the second frequency;
A method of driving a display device.
The method of claim 74, wherein
The signal control unit,
When the display panel is driven at the first frequency, a width of the CPV signal has the same width as p clock signals.
When the display panel is driven at the second frequency, the width of the CPV signal is controlled to have the same width as q clock signals less than p.
A method of driving a display device.
74. The method of claim 73 wherein
The signal control unit,
Gamma correcting the image data when the display panel is driven at the second frequency, and transmitting the corrected image data to the display panel;
A method of driving a display device.
61. The method of claim 60,
Counting the number of continuous image continuous frames input after the still image start signal is applied but before the still image end signal is applied; And
And counting the number of continuous video frames inputted after the still image end signal is applied until the still image start signal is applied.
A method of driving a display device.
78. The method of claim 77 wherein
The signal control unit,
When the number of still image continuous frames is equal to or greater than x, the input image data is stored in the frame memory, and the transmission of the input image data is deactivated.
Activating the transmission of the input image data when the moving picture continuous frame number is y or more;
A method of driving a display device.
The method of claim 78,
The signal control unit,
Outputting stored image data stored in the frame memory to the display panel at the second frequency when the number of still image continuous frames is equal to or greater than x,
Outputting the input image data to the display panel at the first frequency when the moving picture continuous frame number is y or more;
A method of driving a display device.
61. The method of claim 60,
The light source unit is driven at a first ratio when the display panel is driven at a first frequency.
Driving the light source unit at a second ratio when driving the display panel at a second frequency;
A method of driving a display device.
81. The method of claim 80,
When the display panel is in the normally black mode, the second ratio has a lower value than the first ratio.
When the display panel is in the normally white mode, the second ratio has a higher value than the first ratio.
A method of driving a display device.
81. The method of claim 80,
The selection of the driving ratio of the light source unit according to the driving frequency of the display panel is performed using a look up table or a function.
A method of driving a display device.
81. The method of claim 80,
The switching of the driving frequency of the display panel and the driving ratio of the light source unit is performed in the vertical blank period.
A method of driving a display device.
61. The method of claim 60,
When driving the display panel at the first frequency, the driving ratio of the light source unit is kept constant.
Periodically changing a driving ratio of the light source unit when driving the display panel at the second frequency;
A method of driving a display device.
85. The method of claim 84,
The display panel is in a normally black mode,
Driving the light source unit at a first ratio when driving the display panel at the first frequency;
When driving the display panel at the second frequency, driving the light source unit at a rate sequentially lowered from the first ratio and the first ratio;
A method of driving a display device.
92. The method of claim 85,
The display panel includes a gate line and a data line.
The display device includes:
A gate driver for driving the gate line; And
Further comprising a data driver for driving the data line,
The signal controller transmits an STV signal to the gate driver at the start of every frame,
A method of driving a display device.
87. The method of claim 86,
When driving the display panel at the second frequency,
Driving the light source unit at a first rate at a point where the STV signal is transmitted;
Driving the light source unit at a rate sequentially lowered from the first ratio until the next STV signal is transmitted;
A method of driving a display device.
88. The method of claim 87 wherein
The transmission period of the STV signal when the display panel is driven at the first frequency is the same as the change period of the driving ratio of the light source unit when the display panel is driven at the second frequency.
A method of driving a display device.
85. The method of claim 84,
The display panel is in a normally white mode,
Driving the light source unit at a first ratio when driving the display panel at the first frequency;
When driving the display panel at the second frequency, the light source is driven at a rate that increases sequentially from the first ratio and the first ratio,
A method of driving a display device.
61. The method of claim 60,
When driving the display panel at the first frequency,
The signal controller applies a common voltage having a constant value to the display panel,
When driving the display panel at the second frequency,
The signal controller applies a common voltage having a variable value to a display panel.
A method of driving a display device.
91. The method of claim 90,
When driving the display panel at the second frequency,
The signal control unit,
Having a first voltage in a first section,
Applying a common voltage having a second voltage higher than the first voltage in a second period,
A method of driving a display device.
92. The method of claim 91 wherein
One frame consists of a valid section in which video data is transmitted and a vertical blank section in which video data is not transmitted.
The first section is the valid section,
The second section is the vertical blank section,
A method of driving a display device.
92. The method of claim 91 wherein
When driving the display panel at the second frequency,
The signal control unit,
In the third section, a common voltage having a third voltage higher than the second voltage is applied to the display panel.
A method of driving a display device.
94. The method of claim 93,
One frame consists of a valid section in which video data is transmitted and a vertical blank section in which video data is not transmitted.
The first section is the valid section,
The second section is part of the vertical blank section,
The third section is the remaining part of the vertical blank section,
A method of driving a display device.
91. The method of claim 90,
When driving the display panel at the second frequency,
The signal control unit,
Having a first voltage in a first section,
Applying a common voltage swinging to the first voltage and the second voltage higher than the first voltage in a second section,
A method of driving a display device.
97. The method of claim 95,
The common voltage is
When changing from the first voltage to the second voltage,
Gradually varying with a value between the first voltage and the second voltage,
A method of driving a display device.
61. The method of claim 60,
Storing the input image data in a frame memory when the still image start signal is applied;
Calculating a representative value of the stored image data stored in the frame memory;
Generating auxiliary image data by correcting the representative value according to a kickback voltage; And
The method may further include applying an auxiliary voltage corresponding to the auxiliary image data to a data line in a vertical blank period.
A method of driving a display device.
97. The method of claim 97,
The data line is composed of a plurality,
Calculating a representative value of the stored image data for each data line;
A method of driving a display device.
99. The method of claim 98,
The representative value is an average gradation value of the stored image data.
A method of driving a display device.
99. The method of claim 98,
The representative value is an average gray value of upper t bits of the stored image data.
A method of driving a display device.
99. The method of claim 98,
The representative value is an intermediate value between the maximum gray value and the minimum gray value of the stored image data.
A method of driving a display device.
99. The method of claim 98,
The auxiliary image data,

(Ga: gray value of the auxiliary image data, Gr: the representative value, dG: kickback compensation gray value according to the representative value)
Generated according to,
A method of driving a display device.
103. The method of claim 102,
The kickback compensation gray value is a value stored in the form of a lookup table or calculated by a function,
A method of driving a display device.
103. The method of claim 103,
When the kickback compensation gray value is a value calculated by a function,
The function is
Created by linear interpolation using the kickback compensation gradation value at the minimum gradation, the kickback compensation gradation value at the maximum gradation, and the gradation value when the magnitude of the kickback compensation gradation value is maximum,
A method of driving a display device.
61. The method of claim 60,
When driving the display panel at the second frequency,
The signal control unit,
Va-0.2┃Va┃≤ Voff2≤ Va + 0.2┃Va┃
(Voff2: gate-off voltage when the display panel is driven at the second frequency, Va: leakage current flowing between the input terminal and the output terminal of the switching element when a positive pixel voltage is applied to the pixel electrode) And a voltage of the control terminal of the switching element when the leakage current flowing between the input terminal and the output terminal of the switching element is the same when a negative pixel voltage is applied to the pixel electrode.
Applying a gate-off voltage having a range of to the display panel,
A method of driving a display device.
105. The method of claim 105,
When driving the display panel at the second frequency,
The signal control unit,
Va-0.1┃Va┃≤ Voff2≤ Va + 0.1┃Va┃
(Voff2: gate-off voltage when the display panel is driven at the second frequency, Va: leakage current flowing between the input terminal and the output terminal of the switching element when a positive pixel voltage is applied to the pixel electrode) Voltage of the control terminal of the switching element when the leakage current flowing between the input terminal and the output terminal of the switching element is the same when a negative pixel voltage is applied to the pixel electrode)
Applying a gate-off voltage having a range of to the display panel,
A method of driving a display device.
105. The method of claim 105,
When driving the display panel at the first frequency,
The signal control unit,
Va-0.2┃Va┃≤ Voff1≤ Va + 0.2┃Va┃
(Voff1: Gate-off voltage when the display panel is driven at the first frequency, Va: Leakage current flowing between the input terminal and the output terminal of the switching element when a positive pixel voltage is applied to the pixel electrode) And a voltage of the control terminal of the switching element when the leakage current flowing between the input terminal and the output terminal of the switching element is the same when a negative pixel voltage is applied to the pixel electrode.
With a range of
A method of driving a display device.
108. The method of claim 107 wherein
When driving the display panel at the first frequency,
The signal control unit,
Va-0.1┃Va┃≤ Voff1≤ Va + 0.1┃Va┃
(Voff1: Gate-off voltage when the display panel is driven at the first frequency, Va: Leakage current flowing between the input terminal and the output terminal of the switching element when a positive pixel voltage is applied to the pixel electrode) And a voltage of the control terminal of the switching element when the leakage current flowing between the input terminal and the output terminal of the switching element is the same when a negative pixel voltage is applied to the pixel electrode.
With a range of
A method of driving a display device.
105. The method of claim 105,
The gate-off voltage when the display panel is driven at the first frequency is the same as the gate-off voltage when the display panel is driven at the second frequency,
A method of driving a display device.
105. The method of claim 105,
The gate-off voltage when the display panel is driven at the first frequency is lower than the gate-off voltage when the display panel is driven at the second frequency,
A method of driving a display device.

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