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WO2016095309A1 - 液晶显示装置、背光模块及其背光源驱动电路 - Google Patents

液晶显示装置、背光模块及其背光源驱动电路 Download PDF

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Publication number
WO2016095309A1
WO2016095309A1 PCT/CN2015/070966 CN2015070966W WO2016095309A1 WO 2016095309 A1 WO2016095309 A1 WO 2016095309A1 CN 2015070966 W CN2015070966 W CN 2015070966W WO 2016095309 A1 WO2016095309 A1 WO 2016095309A1
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WIPO (PCT)
Prior art keywords
current
comparator
light emitting
resistor
emitting unit
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PCT/CN2015/070966
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English (en)
French (fr)
Inventor
张华�
曹丹
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TCL China Star Optoelectronics Technology Co Ltd
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Shenzhen China Star Optoelectronics Technology Co Ltd
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Priority to US14/417,669 priority Critical patent/US9672779B2/en
Publication of WO2016095309A1 publication Critical patent/WO2016095309A1/zh
Anticipated expiration legal-status Critical
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    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
    • H05B45/30—Driver circuits
    • H05B45/37—Converter circuits
    • H05B45/3725—Switched mode power supply [SMPS]
    • H05B45/38—Switched mode power supply [SMPS] using boost topology
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
    • G09G3/34—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source
    • G09G3/36—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source using liquid crystals
    • G09G3/3611—Control of matrices with row and column drivers
    • G09G3/3648—Control of matrices with row and column drivers using an active matrix
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
    • H05B45/40—Details of LED load circuits
    • H05B45/44—Details of LED load circuits with an active control inside an LED matrix
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2330/00—Aspects of power supply; Aspects of display protection and defect management
    • G09G2330/12—Test circuits or failure detection circuits included in a display system, as permanent part thereof
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
    • G09G3/34—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source
    • G09G3/3406—Control of illumination source
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B20/00—Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps
    • Y02B20/30—Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]

Definitions

  • the present invention relates to the field of liquid crystal display technologies, and in particular, to a liquid crystal display device, a backlight module, and a backlight driving circuit thereof.
  • LCDs liquid crystal displays
  • the LCD panel Since the liquid crystal itself does not emit light, the LCD panel itself does not have the characteristics of light emission, and therefore an illumination source such as a backlight module is required.
  • the imaging principle of the liquid crystal display is that after the electrodes in the panel are energized, the liquid crystal molecules will be twisted after the electrodes are energized, so that the light of the backlight module can pass and realize illumination.
  • Backlight is an optical component that provides a back light source in LCD display products. Therefore, the quality of the backlight determines the brightness of the LCD display screen, the uniformity of the emitted light, the color gradation and other important parameters, which largely determines The luminous effect of the LCD display.
  • LED Light-Emitting Diode
  • CCFLs Cold Cathode Fluorescent Lamps
  • FIG. 1 is a schematic diagram of a backlight driving circuit in the prior art.
  • the LED constant current drive IC is constant
  • the LED constant current drive IC internal feedback amplifier feedback resistor R voltage, and then adjust the LED string negative terminal MOS transistor Q2 conduction, to determine the current flowing between the source and drain of MOS transistor Q2, That is, the LED string current size.
  • the ability of the LED constant current driver IC to regulate the current is limited. After exceeding its capability range, the LED constant current driver IC can no longer be adjusted to the set current level, and the above circuit will The current flowing in the LED has a large error with the set value.
  • One of the technical problems to be solved by the present invention is to provide a backlight driving circuit capable of making the LED current reach a range that can be adjusted by the circuit, and making the current flowing in the LED closer to the set value. The error between the two.
  • a liquid crystal display device and a backlight module are also provided.
  • the present invention provides a backlight driving circuit, comprising: a boosting circuit that boosts an input voltage to a desired operating voltage; and an illumination unit electrically connected to the boosting circuit Working on the operating voltage from the boosting circuit; a current detecting resistor connected in series with the light emitting unit; an automatic regulating current circuit electrically connected to the current detecting resistor to detect the detected Comparing the voltage of the current-sense resistor with the set reference voltage value to adjust the magnitude of the resistor connected in series with the light-emitting unit to regulate the current of the light-emitting unit; a controller electrically connected to the light-emitting unit and detecting The relationship between the actual voltage corresponding to the current fed back by the light-emitting unit and its internal set voltage value to generate a pulse width modulation signal to regulate the current of the light-emitting unit.
  • the auto-adjusting power supply circuit further includes: a first comparator that compares the detected voltage of the current-sense resistor with the set first reference voltage value, and outputs the result according to the comparison result.
  • a second comparator which compares the detected voltage of the current-sense resistor with the set second reference voltage value, and outputs a switch signal according to the comparison result;
  • a first switch the control end thereof The first comparator is electrically connected, performing on and off according to a switch signal from the first comparator; a first resistor connected in parallel with the first switch, together with the first switch a current detecting resistor is connected in series; a second switch having a control end electrically connected to the second comparator, performing on and off according to a switching signal from the second comparator; and a second resistor, the The two switches are connected in series, together with the second switch, in parallel with the current detecting resistor, wherein the voltage of the current detecting resistor is higher than the first reference voltage When the value is large, the first comparator outputs a first
  • a third switch is further included, which is electrically connected to the light emitting unit and the controller, respectively.
  • the light emitting unit is a string of light emitting diodes.
  • the size of the first reference voltage of the first comparator is greater than 5% of the internal set voltage value of the controller; the size of the second reference voltage of the second comparator is greater than the control The internal set voltage value is 5% smaller.
  • the self-regulating current circuit further includes two resistors connected in series, and the junction point is electrically connected to the control end of the first switch, wherein one end of one resistor is connected to the DC voltage, and one end of the other resistor is connected. Ground.
  • a backlight module includes: a backplane having a space; a backlight driving circuit disposed in the space, the backlight driving circuit comprising: a boosting circuit, It boosts the input voltage to a desired operating voltage; an illumination unit electrically coupled to the boost circuit, operating based on an operating voltage from the boost circuit; and a current-sense resistor in series with the illumination unit Connected; an automatic current adjustment circuit electrically connected to the current detecting resistor, comparing the detected voltage of the current detecting resistor with a set reference voltage value to adjust a resistance in series with the light emitting unit The size further controls the current of the light emitting unit; a controller electrically connected to the light emitting unit, by detecting a relationship between an actual voltage corresponding to the current fed back by the light emitting unit and an internal set voltage value thereof to generate A pulse width modulated signal is used to regulate the current of the light emitting unit.
  • the auto-adjusting power supply circuit further includes: a first comparator that compares the detected voltage of the current-sense resistor with the set first reference voltage value, and outputs the result according to the comparison result.
  • a second comparator which compares the detected voltage of the current-sense resistor with the set second reference voltage value, and outputs a switch signal according to the comparison result;
  • a first switch the control end thereof The first comparator is electrically connected, performing on and off according to a switch signal from the first comparator; a first resistor connected in parallel with the first switch, together with the first switch a current detecting resistor is connected in series; a second switch having a control end electrically connected to the second comparator, performing on and off according to a switching signal from the second comparator; and a second resistor, the The second switch is connected in series with the second switch in parallel with the current detecting resistor, wherein when the voltage of the current detecting resistor is greater than the first reference voltage value, the first comparator outputs a shutdown signal;
  • a third switch is further included, which is electrically connected to the light emitting unit and the controller, respectively.
  • the size of the first reference voltage of the first comparator is greater than 5% of the internal set voltage value of the controller; the size of the second reference voltage of the second comparator is greater than the control The internal set voltage value is 5% smaller.
  • a liquid crystal display device includes: a liquid crystal display panel; a backlight module disposed opposite to the liquid crystal display panel, wherein the backlight module includes the backlight driving circuit described above .
  • One or more embodiments of the present invention may have the following advantages over the prior art.
  • the invention increases the automatic adjustment current circuit in the backlight driving circuit.
  • the LED current exceeds the adjustment range of the controller (for example, the LED constant current driving IC)
  • the circuit changes the resistance value in series with the LED, thereby changing the flow rate.
  • the size of the LED current is such that it can be adjusted within the range of the LED constant current drive IC, and the current flowing through the LED can be brought closer to the set value (operating voltage) to reduce the error.
  • FIG. 1 is a circuit diagram of a backlight driving circuit in the prior art
  • FIG. 2 is a schematic structural view of a liquid crystal display device according to an embodiment of the invention.
  • FIG. 3 is a functional schematic diagram of a backlight driving circuit according to an embodiment of the invention.
  • FIG. 4 is a circuit diagram of the backlight driving circuit shown in FIG.
  • FIG. 2 is a schematic structural view of a liquid crystal display device according to an embodiment of the present invention, and various constituent structures of the liquid crystal display device will be described below with reference to FIG.
  • the liquid crystal display device includes a liquid crystal display panel 21 and a backlight module 22.
  • the backlight module 22 is opposite to the liquid crystal display panel 21, and the backlight module 22 has a back plate 221 and a backlight driving circuit 222.
  • the backplane 221 has a space, and the backlight driving circuit 222 is disposed in the space.
  • the backlight driving circuit 222 is for supplying the liquid crystal display panel 21 with its required light source.
  • FIG. 3 is a functional schematic diagram of a backlight driving circuit according to an embodiment of the invention
  • FIG. 4 is a circuit diagram of the backlight driving circuit shown in FIG.
  • the backlight driving circuit 222 includes a boosting circuit 222a, a light emitting unit 222b, a current detecting resistor (not shown), an automatic regulating current circuit 222c, and a controller 222d.
  • the boosting circuit 222a is electrically connected to the light emitting unit 222b
  • the current detecting resistor is connected in series with the light emitting unit 222b
  • the controller 222d is electrically connected to the boosting circuit 222a and the light emitting unit 222b, respectively, and automatically adjusts the current circuit 222c and the light emitting unit 222b.
  • Sexual connection is possible connection.
  • the boosting circuit 222a is an inductive boosting circuit for boosting the input voltage signal to a desired operating voltage.
  • the boosting circuit 222a includes an inductor and a switching transistor Q1. Diode and a capacitor.
  • the inductor is an energy conversion device that converts electrical energy and magnetic field energy into each other.
  • the switching transistor Q1 When the switching transistor Q1 is closed, the inductor converts the electrical energy into a magnetic field energy storage and stores it.
  • the switching transistor Q1 When the switching transistor Q1 is turned off, the inductor converts the stored magnetic field energy into electric field energy, and this energy is superimposed on the input voltage and then filtered by the diode and the capacitor to obtain a smooth DC voltage to be supplied to the load. Since this voltage is formed by the superposition of the input voltage and the magnetic field of the inductor into electrical energy, the output voltage is higher than the input voltage.
  • the light-emitting unit 222b is configured as a light-emitting diode string.
  • those skilled in the art can set a plurality of light-emitting diode strings as needed, which is easy to understand, and is required for each LED string. Add the corresponding automatic regulation current circuit.
  • the controller 222d is an LED constant current driving IC.
  • the auto-regulating current circuit 222c includes a comparator 1, a comparator 2, a switch Q3, a switch Q4, a resistor R1, and a resistor R2.
  • the comparator 1 is electrically connected to the control terminal (gate) of the switch Q4; the switch Q4 is connected in parallel with the resistor R2, and is further connected in series with the current-sense resistor R together with the resistor R2; the control terminal of the comparator 2 and the switch Q3 (gate)
  • the terminal is electrically connected, and the switch Q3 is connected in series with the resistor R1, and is further connected in parallel with the current-sense resistor R together with the resistor R1.
  • a switch Q2 is further included, which is electrically connected to the light emitting unit 222b and the controller 222d, respectively.
  • the boost circuit 222a receives an input voltage and boosts it to the desired operating voltage output.
  • the lighting unit 222b operates in accordance with the operating voltage from the boost circuit 222a to achieve the desired luminance.
  • the magnitude of the current-sense resistor R is selected, and when the LED constant current driving IC operates, the voltage on the resistor R is adjusted.
  • the voltage value V1 is set internally thereto so that the current flowing through the LED string is the required current.
  • the adjustment range of the LED constant current driving IC is limited, and only within the adjustment range, the accurate current can be obtained, otherwise a large error will occur.
  • the automatic regulating current circuit 222c also starts operating during the operation of the light emitting unit 222b.
  • the negative inputs of these two comparators are connected to the upper end of the current-sense resistor R.
  • the output of the comparator 1 is connected to the gate of the MOS transistor Q4, and the output of the comparator 2 is connected to the gate of the MOS transistor Q3. It is easy to understand that although the values of Vref1 and Vref2 are set as described above, other values may be used depending on actual needs.
  • the comparator 1 and the comparator 2 detect the voltage on the current detecting resistor R. If the voltage exceeds (1+5%) V1, the comparator 1 outputs a low level, and the MOS transistor Q4 does not conduct, and the resistor R2 and The current-sense resistor R is connected in series to the line of the LED string to increase the resistance value, thereby reducing the LED current to a range that can be adjusted by the constant current driving IC; when the voltage on the resistor R is lower than (1-5%) V1 When the comparator 2 outputs a high level, the MOS transistor Q3 is turned on, and the resistor R1 and the current-sense resistor R are connected in parallel to the line of the LED string to reduce the resistance value, thereby increasing the current flowing through the LED string to The LED constant current drive IC can be adjusted within the range.
  • the comparator 1 outputs a high level, the MOS transistor Q4 is turned on, so that the resistor R2 is short-circuited, the comparator 2 outputs a low level, and the MOS transistor Q3 is turned off, so that the resistor R1 is turned off.
  • the self-regulating current circuit 222c further includes two resistors connected in series, and the junction point thereof is electrically connected to the gate of the switch Q4, wherein one end of one resistor is connected to the DC voltage of 5V, and one end of the other resistor is grounded.
  • the LED constant current driving IC Based on the operation of the above circuit, the LED constant current driving IC detects the actual voltage corresponding to the current fed by the light emitting unit 222b and the value of the internal set voltage value in real time, and then generates a pulse width modulation signal to regulate the switch Q2 and thereby regulate the light emitting unit. Current of 222b. Due to the operation of the auto-regulating current circuit 222c, the current of the LED string is always within the range that the LED constant current driving IC can adjust, and the error is also reduced.
  • the liquid crystal display device, the backlight module and the backlight driving circuit thereof of the present invention change the relationship with the reference voltage by detecting the relationship between the voltage of the current-sense resistor connected in series with the light-emitting unit and the reference voltage.
  • the resistance value in series changes the current flowing through the light-emitting unit, effectively avoiding large errors caused by the current of the light-emitting unit exceeding the adjustment range of the controller.

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  • Physics & Mathematics (AREA)
  • Computer Hardware Design (AREA)
  • General Physics & Mathematics (AREA)
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  • Crystallography & Structural Chemistry (AREA)
  • Circuit Arrangement For Electric Light Sources In General (AREA)

Abstract

一种液晶显示装置、背光模块及其背光源驱动电路，背光源驱动电路（222）包括：升压电路（222a）、发光单元（222b）、自动调节电流电路（222c）和控制器（222d）。通过背光源驱动电路（222）中的自动调节电流电路（222c），当LED电流大小超过控制器（222d）的调节范围时，自动调节电流电路（222c）改变流过LED电流的大小，使其达到控制器（222d）能够调节的范围内。

Description

液晶显示装置、背光模块及其背光源驱动电路
相关申请的交叉引用
本申请要求享有2014年12月18日提交的名称为“液晶显示装置、背光模块及其背光源驱动电路”的中国专利申请CN201410798135.7的优先权，该申请的全部内容通过引用并入本文中。
技术领域
本发明涉及液晶显示技术领域，尤其涉及一种液晶显示装置、背光模块及其背光源驱动电路。
背景技术
近年来，随着薄型化的显示趋势，液晶显示器(Liquid Crystal Display，简称LCD)已广泛使用在各种电子产品的应用中，例如手机、笔记本计算机以及彩色电视机等。
由于液晶自身不会发光，LCD面板本身也不具备发光的特性，因此需要照明光源，例如背光模组。液晶显示的成像原理是靠面板中的电极通电后，液晶分子在电极通电之后会发生扭转，从而让背光模组的光线能够通过并实现发光。背光源(Backlight)是提供LCD显示器产品中一个背面光源的光学组件，因而，背光源的质量决定了LCD显示器屏幕的亮度、出射光均匀度、色阶等重要参数，在很大程度上决定了LCD显示器的发光效果。
作为LCD显示器的背光源，发光二极管(Light-Emitting Diode，LED)现在已显露出取代冷阴极荧光灯管(Cold Cathode Fluorescent Lamp，CCFL)的趋势。发光二极管具有色域宽、色彩还原性好、可控性强、寿命长、不含汞蒸气和其他有害气体等优点。由于LED是一个低压非线性半导体器件，LED的正向电压会随着电流和温度的变化而变化，需要有驱动电路才能保证其稳定可靠地工作，因此，研究背光源用LED驱动电路是本领域技术人员所致力的主要课题。
图1为现有技术中的背光源驱动电路的示意图。在图1中，LED恒流驱动IC的恒定 电压V1以及在LED串的负端设置的电阻R决定LED串中电流幅值大小，即I＝V1/R。LED恒流驱动IC内部的运算放大器反馈电阻R上的电压，再通过调节LED串负端MOS管Q2的导通情况，来决定MOS管Q2的源极和漏极之间流过的电流大小，即LED串电流大小。
然而，受半导体制程、以及价格因素的限制，LED恒流驱动IC调节电流的能力有限，超出其能力范围后，LED恒流驱动IC就无法再调整到设定的电流大小，并且上述电路会使LED中流过的电流与设定值的误差较大。
因此，如何解决上述问题，能够将LED电流调节到设定值，并且使LED中流过的电流更接近设定值的大小，减小二者之间的误差，乃业界所致力的课题之一。
发明内容
本发明所要解决的技术问题之一是需要提供一种背光源驱动电路，该电路能够使将LED电流达到电路能够调节的范围内，并且使LED中流过的电流更接近设定值的大小，减小二者之间的误差。另外，还提供了一种液晶显示装置和背光模块。
为了解决上述技术问题，本发明提供了一种背光源驱动电路，包括：一升压电路，其将输入电压升压至所需的工作电压；一发光单元，其与该升压电路电性连接，基于来自该升压电路的工作电压工作；一检流电阻，其与所述发光单元串联连接；一自动调节电流电路，其与所述检流电阻电性连接，将侦测到的所述检流电阻的电压与设定的参考电压值进行比较以调节与所述发光单元串联的电阻的大小进而调控所述发光单元的电流；一控制器，其与该发光单元电性连接，通过检测所述发光单元反馈的电流所对应的实际电压和其内部设定电压值的关系，以产生一脉冲宽度调制信号来调控所述发光单元的电流。
在一个实施例中，所述自动调节电源电路进一步包括：一第一比较器，其比较侦测到的所述检流电阻的电压和设定的第一参考电压值，并根据比较的结果输出开关信号；一第二比较器，其比较侦测到的所述检流电阻的电压和设定的第二参考电压值，并根据比较的结果输出开关信号；一第一开关，其控制端与所述第一比较器电性连接，根据来自所述第一比较器的开关信号执行开启与关闭；一第一电阻，其与所述第一开关并联，同所述第一开关一起与所述检流电阻串联；一第二开关，其控制端与所述第二比较器电性连接，根据来自所述第二比较器的开关信号执行开启与关闭；一第二电阻，其与所述第二开关串联，同所述第二开关一起与所述检流电阻并联，其中，在所述检流电阻的电压比第一参考电压 值大时，所述第一比较器输出关闭信号；在所述检流电阻的电压比第二参考电压值小时，所述第二比较器输出开启信号。
在一个实施例中，进一步包括一第三开关，其分别电性连接所述发光单元和所述控制器。
在一个实施例中，所述发光单元为发光二极管串。
在一个实施例中，所述第一比较器的第一参考电压的大小比所述控制器内部设定电压值大5％；所述第二比较器的第二参考电压的大小比所述控制器内部设定电压值小5％。
在一个实施例中，所述自动调节电流电路还包括两个串联的电阻，二者结合点与第一开关的控制端电性连接，其中一电阻的一端连接一直流电压，另一电阻的一端接地。
根据本发明的另一方面，还提供了一种背光模块，包括：一背板，具有一空间；一背光源驱动电路，设置在该空间中，该背光源驱动电路包括：一升压电路，其将输入电压升压至所需的工作电压；一发光单元，其与该升压电路电性连接，基于来自该升压电路的工作电压工作；一检流电阻，其与所述发光单元串联连接；一自动调节电流电路，其与所述检流电阻电性连接，将侦测到的所述检流电阻的电压与设定的参考电压值进行比较以调节与所述发光单元串联的电阻的大小进而调控所述发光单元的电流；一控制器，其与该发光单元电性连接，通过检测所述发光单元反馈的电流所对应的实际电压和其内部设定电压值的关系，以产生一脉冲宽度调制信号来调控所述发光单元的电流。
在一个实施例中，所述自动调节电源电路进一步包括：一第一比较器，其比较侦测到的所述检流电阻的电压和设定的第一参考电压值，并根据比较的结果输出开关信号；一第二比较器，其比较侦测到的所述检流电阻的电压和设定的第二参考电压值，并根据比较的结果输出开关信号；一第一开关，其控制端与所述第一比较器电性连接，根据来自所述第一比较器的开关信号执行开启与关闭；一第一电阻，其与所述第一开关并联，同所述第一开关一起与所述检流电阻串联；一第二开关，其控制端与所述第二比较器电性连接，根据来自所述第二比较器的开关信号执行开启与关闭；一第二电阻，其与所述第二开关串联，同所述第二开关一起与所述检流电阻并联，其中，在所述检流电阻的电压比第一参考电压值大时，所述第一比较器输出关闭信号；在所述检流电阻的电压比第二参考电压值小时，所述第二比较器输出开启信号。
在一个实施例中，进一步包括一第三开关，其分别电性连接所述发光单元和所述控制器。
在一个实施例中，所述第一比较器的第一参考电压的大小比所述控制器内部设定电压值大5％；所述第二比较器的第二参考电压的大小比所述控制器内部设定电压值小5％。
根据本发明的另一方面，还提供了一种液晶显示装置，包括：一液晶显示面板；一背光模块，其与该液晶显示面板相对设置，其中该背光模块包括以上所述的背光源驱动电路。
与现有技术相比，本发明的一个或多个实施例可以具有如下优点。
本发明通过在背光源驱动电路中增加自动调节电流电路，当LED电流大小超过控制器(例如，LED恒流驱动IC)的调节范围时，该电路改变与LED串联的电阻值，进而改变流过LED电流的大小，使其达到LED恒流驱动IC能够调节的范围内，并且也能够使LED中流过的电流更接近设定值(工作电压)大小，减小误差。
本发明的其它特征和优点将在随后的说明书中阐述，并且，部分地从说明书中变得显而易见，或者通过实施本发明而了解。本发明的目的和其他优点可通过在说明书、权利要求书以及附图中所特别指出的结构来实现和获得。
附图说明
附图用来提供对本发明的进一步理解，并且构成说明书的一部分，与本发明的实施例共同用于解释本发明，并不构成对本发明的限制。在附图中：
图1是现有技术中一背光源驱动电路的电路示意图；
图2是根据本发明一实施例的液晶显示装置的结构示意图；
图3是根据本发明一实施例的背光源驱动电路的一功能示意图；
图4是图3所示的背光源驱动电路的电路示意图。
具体实施方式
为使本发明的目的、技术方案和优点更加清楚，以下结合附图对本发明作进一步地详细说明。
图2是根据本发明一实施例的液晶显示装置的结构示意图，下面参考图2来说明该液晶显示装置的各个组成结构。
如图2所示，该液晶显示装置包括一液晶显示面板21和一背光模块22。该背光模块 22与液晶显示面板21相对设置，该背光模块22具有一背板221和一背光源驱动电路222。其中该背板221具有一空间，而该背光源驱动电路222设置在该空间中。背光源驱动电路222用于给液晶显示面板21提供其所需的光源。
下面参考图3和图4来详细说明本发明一实施例的背光源驱动电路。图3是根据本发明一实施例的背光源驱动电路的一功能示意图，图4是图3所示的背光源驱动电路的电路示意图。
如图3所示，背光源驱动电路222包括一升压电路222a、一发光单元222b、一检流电阻(未示出)、一自动调节电流电路222c以及一控制器222d。升压电路222a与发光单元222b电性连接，检流电阻与发光单元222b串联连接，控制器222d分别与该升压电路222a和发光单元222b电性连接，自动调节电流电路222c与发光单元222b电性连接。
如图4所示，升压电路222a为一电感型升压电路，其用于将输入的电压信号升压至所需的工作电压，该升压电路222a包括一电感、一开关晶体管Q1、一二极管和一电容。
具体地，在该升压电路222a中，电感是将电能和磁场能相互转化的能量转换器件，当开关晶体管Q1闭合后，电感将电能转换为磁场储能存储起来。当开关晶体管Q1断开后，电感将存储的磁场能转换成为电场能，且这个能量和输入电压叠加后通过二极管和电容的滤波得到平滑的直流电压提供给负载。由于这个电压是输入电压和电感的磁场能转换成为电能的叠加后形成的，所以输出电压要高于输入电压。
在本实施例中，为了便于说明，将发光单元222b设置为一个发光二极管串，当然，本领域技术人员根据需要可以设置多个发光二极管串，容易理解的，对应每个发光二极管串，还需要增加相应的自动调节电流电路。
控制器222d为一LED恒流驱动IC。自动调节电流电路222c包括比较器1、比较器2、开关Q3、开关Q4、电阻R1和电阻R2。其中，比较器1与开关Q4的控制端(栅极)电性连接；开关Q4与电阻R2并联，进而同该电阻R2一起与检流电阻R串联；比较器2与开关Q3的控制端(栅极)电性连接，开关Q3与电阻R1串联，进而同该电阻R1一起与检流电阻R并联。另外还包括一开关Q2，其分别电性连接发光单元222b和控制器222d。
再请参考图4，详细说明整个背光源驱动电路222的执行流程。升压电路222a接收一输入电压并将其升压至所需的工作电压输出，发光单元222b根据来自该升压电路222a的工作电压进行工作来达到所需的发光亮度。
在现有技术中，根据所需LED串的电流大小，即I＝V1/R，选定检流电阻R值的大小，在LED恒流驱动IC工作时，会努力将电阻R上的电压调整到其内部设定电压值V1，使得流过LED串的电流即为所需的电流。但是，LED恒流驱动IC的调整范围有限，只有在其调整范围之内，才能够得到准确的电流大小，否则会产生较大的误差。
因此，为了防止流过LED串的电流超出LED恒流驱动IC的调节范围，在发光单元222b工作期间，自动调节电流电路222c也开始工作。
如图4所示，比较器1的正输入端接入恒定电压Vref1＝(1+5％)V1，比较器2的正输入端接入恒定电压Vref2＝(1-5％)V1，其中，V1为LED恒流驱动IC内设定电压值(也可认为是LED串所需的工作电压)。这两个比较器的负输入端都连接到检流电阻R的上端。比较器1的输出端连接到MOS管Q4的栅极，比较器2的输出端连接到MOS管Q3的栅极。容易理解，虽然Vref1和Vref2的值如上述那样设定，但是根据实际需要也可以设为其他的值。
具体地，比较器1和比较器2侦测检流电阻R上的电压，若超过(1+5％)V1，则比较器1输出低电平，MOS管Q4不导通，则电阻R2与检流电阻R串联接入到LED串的线路中，使电阻值增加，进而使LED电流降低到恒流驱动IC能够调节的范围内；当电阻R上的电压低于(1-5％)V1时，比较器2输出高电平，MOS管Q3导通，电阻R1与检流电阻R并联接入到LED串的线路中，使电阻值减小，进而使流经LED串的电流增大到LED恒流驱动IC能够调节的范围内。
若检流电阻R上的电压在小于(1+5％)V1且大于(1-5％)V1的范围内，则没有任何外加的电阻与检流电阻R串联或并联。换言之，比较器1输出高电平，MOS管Q4导通，使得电阻R2短接，比较器2输出低电平，MOS管Q3截止，使得电阻R1断开。
另外在自动调节电流电路222c中还包括两个串联的电阻，其结合点与开关Q4的栅极电性连接，其中一电阻的一端连接一直流电压5V，另一电阻的一端接地。
基于上述电路的工作，LED恒流驱动IC在实时检测发光单元222b所反馈的电流所对应的实际电压与其内部设定电压值的大小，然后产生一脉冲宽度调制信号来调控开关Q2进而调控发光单元222b的电流。由于自动调节电流电路222c的工作，就会使得LED串的电流一直处于LED恒流驱动IC能够调节的范围内，并且也减少了误差。
综上所述，本发明的液晶显示装置、背光模块及其背光源驱动电路是利用自动调节电流电路检测与发光单元串联的检流电阻的电压与参考电压之间的关系，来改变与发光单元 串联的电阻值，进而改变流过发光单元的电流，有效避免由于发光单元电流大小超出控制器的调节范围而引起的大误差。
以上所述，仅为本发明较佳的具体实施方式，但本发明的保护范围并不局限于此，任何熟悉该技术的人员在本发明所揭露的技术范围内，可轻易想到的变化或替换，都应涵盖在本发明的保护范围之内。因此，本发明的保护范围应该以权利要求的保护范围为准。

Claims (16)

  1. 一种背光源驱动电路，包括：
    一升压电路，其将输入电压升压至所需的工作电压；
    一发光单元，其与该升压电路电性连接，基于来自该升压电路的工作电压工作；
    一检流电阻，其与所述发光单元串联连接；
    一自动调节电流电路，其与所述检流电阻电性连接，将侦测到的所述检流电阻的电压与设定的参考电压值进行比较以调节与所述发光单元串联的电阻的大小进而调控所述发光单元的电流；
    一控制器，其与该发光单元电性连接，通过检测所述发光单元反馈的电流所对应的实际电压和其内部设定电压值的关系，以产生一脉冲宽度调制信号来调控所述发光单元的电流。
  2. 根据权利要求1所述的背光源驱动电路，其中，所述自动调节电源电路进一步包括：
    一第一比较器，其比较侦测到的所述检流电阻的电压和设定的第一参考电压值，并根据比较的结果输出开关信号；
    一第二比较器，其比较侦测到的所述检流电阻的电压和设定的第二参考电压值，并根据比较的结果输出开关信号；
    一第一开关，其控制端与所述第一比较器电性连接，根据来自所述第一比较器的开关信号执行开启与关闭；
    一第一电阻，其与所述第一开关并联，同所述第一开关一起与所述检流电阻串联；
    一第二开关，其控制端与所述第二比较器电性连接，根据来自所述第二比较器的开关信号执行开启与关闭；
    一第二电阻，其与所述第二开关串联，同所述第二开关一起与所述检流电阻并联，
    其中，在所述检流电阻的电压比第一参考电压值大时，所述第一比较器输出关闭信号；在所述检流电阻的电压比第二参考电压值小时，所述第二比较器输出开启信号。
  3. 根据权利要求2所述的背光源驱动电路，其中，进一步包括一第三开关，其分别电性连接所述发光单元和所述控制器。
  4. 根据权利要求1所述的背光源驱动电路，其中，所述发光单元为发光二极管串。
  5. 根据权利要求2所述的背光源驱动电路，其中，
    所述第一比较器的第一参考电压的大小比所述控制器内部设定电压值大5％；
    所述第二比较器的第二参考电压的大小比所述控制器内部设定电压值小5％。
  6. 根据权利要求2所述的背光源驱动电路，其中，所述自动调节电流电路还包括两个串联的电阻，二者结合点与第一开关的控制端电性连接，其中一电阻的一端连接一直流电压，另一电阻的一端接地。
  7. 一种背光模块，包括：
    一背板，具有一空间；
    一背光源驱动电路，设置在该空间中，该背光源驱动电路包括：
    一升压电路，其将输入电压升压至所需的工作电压；
    一发光单元，其与该升压电路电性连接，基于来自该升压电路的工作电压工作；
    一检流电阻，其与所述发光单元串联连接；
    一自动调节电流电路，其与所述检流电阻电性连接，将侦测到的所述检流电阻的电压与设定的参考电压值进行比较以调节与所述发光单元串联的电阻的大小进而调控所述发光单元的电流；
    一控制器，其与该发光单元电性连接，通过检测所述发光单元反馈的电流所对应的实际电压和其内部设定电压值的关系，以产生一脉冲宽度调制信号来调控所述发光单元的电流。
  8. 根据权利要求7所述的背光模块，其中，所述自动调节电源电路进一步包括：
    一第一比较器，其比较侦测到的所述检流电阻的电压和设定的第一参考电压值，并根据比较的结果输出开关信号；
    一第二比较器，其比较侦测到的所述检流电阻的电压和设定的第二参考电压值，并根据比较的结果输出开关信号；
    一第一开关，其控制端与所述第一比较器电性连接，根据来自所述第一比较器的开关信号执行开启与关闭；
    一第一电阻，其与所述第一开关并联，同所述第一开关一起与所述检流电阻串联；
    一第二开关，其控制端与所述第二比较器电性连接，根据来自所述第二比较器的开关信号执行开启与关闭；
    一第二电阻，其与所述第二开关串联，同所述第二开关一起与所述检流电阻并联，
    其中，在所述检流电阻的电压比第一参考电压值大时，所述第一比较器输出关闭信号；在所述检流电阻的电压比第二参考电压值小时，所述第二比较器输出开启信号。
  9. 根据权利要求8所述的背光模块，其中，进一步包括一第三开关，其分别电性连接所述发光单元和所述控制器。
  10. 根据权利要求8所述的背光模块，其中，
    所述第一比较器的第一参考电压的大小比所述控制器内部设定电压值大5％；
    所述第二比较器的第二参考电压的大小比所述控制器内部设定电压值小5％。
  11. 一种液晶显示装置，包括：
    一液晶显示面板；
    一背光模块，其与该液晶显示面板相对设置，其中该背光模块包括背光源驱动电路，该背光源驱动电路，包括：
    一升压电路，其将输入电压升压至所需的工作电压；
    一发光单元，其与该升压电路电性连接，基于来自该升压电路的工作电压工作；
    一检流电阻，其与所述发光单元串联连接；
    一自动调节电流电路，其与所述检流电阻电性连接，将侦测到的所述检流电阻的电压与设定的参考电压值进行比较以调节与所述发光单元串联的电阻的大小进而调控所述发光单元的电流；
    一控制器，其与该发光单元电性连接，通过检测所述发光单元反馈的电流所对应的实际电压和其内部设定电压值的关系，以产生一脉冲宽度调制信号来调控所述发光单元的电流。
  12. 根据权利要求11所述的液晶显示装置，其中，所述自动调节电源电路进一步包括：
    一第一比较器，其比较侦测到的所述检流电阻的电压和设定的第一参考电压值，并根 据比较的结果输出开关信号；
    一第二比较器，其比较侦测到的所述检流电阻的电压和设定的第二参考电压值，并根据比较的结果输出开关信号；
    一第一开关，其控制端与所述第一比较器电性连接，根据来自所述第一比较器的开关信号执行开启与关闭；
    一第一电阻，其与所述第一开关并联，同所述第一开关一起与所述检流电阻串联；
    一第二开关，其控制端与所述第二比较器电性连接，根据来自所述第二比较器的开关信号执行开启与关闭；
    一第二电阻，其与所述第二开关串联，同所述第二开关一起与所述检流电阻并联，
    其中，在所述检流电阻的电压比第一参考电压值大时，所述第一比较器输出关闭信号；在所述检流电阻的电压比第二参考电压值小时，所述第二比较器输出开启信号。
  13. 根据权利要求12所述的液晶显示装置，其中，进一步包括一第三开关，其分别电性连接所述发光单元和所述控制器。
  14. 根据权利要求11所述的液晶显示装置，其中，所述发光单元为发光二极管串。
  15. 根据权利要求12所述的液晶显示装置，其中，
    所述第一比较器的第一参考电压的大小比所述控制器内部设定电压值大5％；
    所述第二比较器的第二参考电压的大小比所述控制器内部设定电压值小5％。
  16. 根据权利要求12所述的液晶显示装置，其中，所述自动调节电流电路还包括两个串联的电阻，二者结合点与第一开关的控制端电性连接，其中一电阻的一端连接一直流电压，另一电阻的一端接地。
PCT/CN2015/070966 2014-12-18 2015-01-19 液晶显示装置、背光模块及其背光源驱动电路 Ceased WO2016095309A1 (zh)

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