CN101521968B - Current regulator and control method thereof - Google Patents

Abstract

A current regulator and its control method, including a current source and a brightness controller, characterized by that, the current source provides a direct proportion ((L + a)/b)ⁿWherein L is the brightness, a, b and n are constants; the brightness controller determines the value of L to generate a current to drive the white LED, and the relation curve between the current and the dimming step is equal to or similar to the relation curve between the brightness and the brightness in human eyes, so that when the dimming step is changed, the human eyes can observe that the brightness of the white LED is changed linearly.

Description

Current regulator and its control method

technical field

The invention relates to a current regulator for driving a white light LED, in particular to a current regulator and a control method thereof which can make the brightness change of the white light LED change linearly in human eyes.

Background technique

Due to the advantages of low power consumption, long life, small size and low cost, light-emitting diodes (LEDs) are attracting more and more attention. 1 shows a known current regulator 10 for driving a white LED 20, which includes a current source 12 for supplying a current IREF, a drain of a transistor 16 connected to the current IREF and a non-inverting input of an operational amplifier 14, the source of which is connected to ground. Terminal GND, its gate is connected to the output of the operational amplifier 14, the drain of the transistor 18 is connected to the inverting input of the LED20 and the operational amplifier 14, its source is connected to the ground terminal GND, its gate is connected to the output of the operational amplifier 14, and the transistor 18 mirror Current IREF injected through transistor 16 generates DC drive current ILED to white LED 20 . Figure 2 shows the relationship curve between the current IREF and the dimming step. Since the dimming step and the current IREF have a linear relationship, the current can be obtained

IREF＝K1×STEP Formula 1

It is characterized in that K1 is a constant, and STEP is the number of dimming steps. Figure 3 shows the relationship curve between the DC driving current ILED and the dimming step. Since the DC driving current ILED is generated by the mirror current IREF, there is also a linear relationship between the dimming step and the DC driving current ILED, so the DC drive current

ILED＝K1×K2×STEP Formula 2

Wherein, K2 is the ratio of the sizes of the transistors 16 and 18 . Fig. 4 shows the relationship curve between the luminous intensity of the white LED20 and the DC drive current ILED, when the DC drive current ILED increases, the luminous intensity of the LED20 also increases, in other words, the brightness of the LED20 and the dimming step There is a linear relationship between them.

Although the brightness of the white LED 20 is proportional to the dimming step, the brightness produced by the white LED 20 is not linear to human eyes. Fig. 5 shows the relationship curve 30 between the luminance (luminance) and the lightness (lightness) of the white light LED 20 and the relationship curve 32 between the luminance and the lightness in the human eye, wherein, the luminance of the vertical axis represents the actual luminance, and the horizontal axis The brightness of the horizontal axis represents the brightness perceived by human eyes. For the curve 30 , the brightness of the horizontal axis can represent the dimming step. Conventionally, when the value is 0, it means completely black, and when the value is 100, it means completely white. Whenever the brightness of the white LED 20 changes ΔY, the human eye should feel the brightness change ΔL, as shown in the curve 30. In fact, the structure of the human eye is complex, and when the brightness is high, a large brightness change is required. On the contrary, when the brightness is low, the human eye will feel the change of brightness with a little brightness change, as shown in curve 32. Therefore, every time a dimming step is changed to make When the brightness of the LED 20 changes by ΔY, the brightness change perceived by the human eye is not a fixed value. In other words, the dimming step of the current regulator 10 is not linearly related to the brightness perceived by the human eye. Fig. 6 shows the error value of the luminance between curve 30 and 32 in Fig. 5, can obviously find out from here, when same shading degree, the luminance that LED20 sends and the luminance required by human eyes have very big disparity, especially It's around a value of 50.

In the known current regulator 10, if the brightness perceived by human eyes is to change linearly, it is necessary to properly select the dimming step. The brightness of the LED20 will change, so there are fewer dimming steps in the low current area. On the contrary, in the high current area, the brightness of LED20 must be greatly changed, so that the human eye can feel the change in brightness. , so there are many dimming steps that can be selected. However, no matter in the low current region or the high current region, some dimming steps must be unused, thus causing waste. In addition, complex calculations are required to select an appropriate dimming step, which also increases the difficulty of design.

The known current regulator therefore suffers from the above-mentioned inconveniences and problems.

Contents of the invention

The object of the present invention is to propose a current regulator and its control method that can make the brightness of white LEDs change linearly in human eyes.

Another object of the present invention is to provide a current regulator and a control method thereof that can make the brightness of the white LED vary almost linearly in human eyes.

For realizing the above object, technical solution of the present invention is:

A current regulator, including a current source and a brightness controller, is characterized in that:

The current source provides a drive current proportional to ((L+a)/b) ⁿ , where L is lightness, a, b and n are constants and;

The shading controller determines the value of L;

Wherein, the relationship curve between the driving current and the brightness is close to the relationship curve between the brightness and the brightness in human eyes.

The current regulator of the present invention can also be further realized by adopting the following technical measures.

In the aforementioned current regulator, the constant a is 16, the constant b is 116, and the constant n is 3.

The aforementioned current regulator, wherein the current source comprises:

A first function circuit that generates a current proportional to ((L+a)/b) according to an input signal; and

A second function circuit for generating a current proportional to ((L+a)/b) ² according to the output of the first function circuit.

In the aforementioned current regulator, the current source further includes a third function circuit, which generates a current proportional to ((L+a)/b) ³ according to the output of the second function circuit.

The aforementioned current regulator, wherein the current source further includes:

A first resistor whose resistance value is proportional to ((L+16)/116);

A second resistor, the resistance value of which has a proportional relationship with ((L+16)/116);

A third resistor, the resistance value of which is proportional to ((L+16)/116);

a second current source, supplying the first current to the first resistor to generate a first voltage

a first voltage-to-current converter for converting the first voltage into a second current;

a first current mirror mirroring the second current to generate a third current to the second resistor to generate a second voltage;

a second voltage-to-current converter for converting the second voltage into a fourth current;

a second current mirror mirroring the fourth current to generate a fifth current to the third resistor to generate a third voltage;

a third voltage-to-current converter for converting the third voltage into a sixth current; and

A third current mirror mirrors the sixth current to generate a driving current.

In the aforementioned current regulator, wherein the first, second and third resistors have the same resistance value.

The aforementioned current regulator, wherein the current source further includes:

a current mirror mirroring a reference current to generate the drive current;

a voltage-to-current converter that converts a reference voltage into a reference current; and

a switch controlled by a control signal to control the conduction time of the reference current, the control signal includes a main period with a duty cycle ratio of ((L+16)/116), in the main period A first sub-cycle has a duty cycle ratio of ((L+16)/116) in the working time, and a second sub-cycle has a duty cycle ratio of ((L) in the working time of the first sub-cycle +16)/116).

The aforementioned current regulator, wherein the current source further includes:

A first resistor whose resistance value is proportional to ((L+16)/116);

A second resistor, the resistance value of which has a proportional relationship with ((L+16)/116);

a second current source, supplying a first current to the first resistor to generate a first voltage;

a first voltage-to-current converter for converting the first voltage into a second current;

a first current mirror mirroring the second current to generate a third current to the second resistor to generate a second voltage;

a second voltage-to-current converter for converting the second voltage into a fourth current;

a second current mirror, mirroring the fourth current to generate a driving current;

A switch is controlled by a control signal for controlling the conduction time of the fourth current, and the control signal has a duty cycle ratio of ((L+16)/116).

In the aforementioned current regulator, wherein the first and second resistors have the same resistance value.

The aforementioned current regulator further includes a low-dropout current source to generate an output current to the LED according to the driving current.

The aforementioned current regulator, wherein the low dropout current source comprises:

An operational amplifier having a first input, a second input and an output;

A first transistor has a drain connected to the drive current and the first input, a source connected to a reference voltage, and a gate connected to the output;

a second transistor having a drain connected to the light-emitting diode and the second input, a source connected to the reference voltage, and a gate connected to the output for mirroring the driving current through the first transistor to generate the output current.

In the aforementioned current regulator, the current source provides a driving current that varies with the dimming step, and the first relational curve between the driving current and the dimming step approximates the difference between brightness and darkness in human eyes. The second relationship curve between; and

The output circuit generates an output current to the LED according to the driving current.

In the aforementioned current regulator, wherein the output circuit includes a second current source that mirrors the driving current to generate the output current.

The aforementioned current regulator, wherein the current source further includes:

a current mirror, used to mirror a reference current to generate a driving current;

a variable resistor whose resistance value is determined by the dimming step;

a transistor connected between the variable resistor and the current mirror; and

An operational amplifier, with two inputs respectively connected to a variable voltage that changes with the dimming step and the variable resistor, and an output connected to the gate of the transistor, the operational amplifier provides the variable voltage to the The variable resistor is used to generate the reference current.

The aforementioned current regulator, wherein the resistance value of the variable resistor is a power of 2.

The aforementioned current regulator, wherein the current source further includes:

A current mirror mirrors a reference current to generate a driving current;

a voltage-to-current converter that converts a reference voltage into a reference current; and

A switch, controlled by a control signal, is used to control the conducting time of the reference current, and the working time of the control signal and the reference voltage are determined by the dimming step.

The aforementioned current regulator, wherein the working time is a power of 2.

The aforementioned current regulator, wherein the second current source comprises:

An operational amplifier having a first input, a second input and an output;

A first transistor having a drain connected to the driving current and the first input, a source connected to a reference voltage, and a gate connected to the output;

a second transistor having a drain connected to the LED and a second input, a source connected to the reference voltage, and a gate connected to the output for mirroring the drive through the first transistor current produces the output current.

In the aforementioned current regulator, the error value between the first relationship curve and the second relationship curve is lower than 10%.

The aforementioned current regulator, wherein the second relational curve is Y/Yn=((L+16)/116) ³ , wherein Y is the brightness, Yn is the brightness when it is completely white, and L is the brightness.

A control method for a current regulator, comprising the following steps:

The first step: providing a driving current that varies with the dimming step, a first relationship curve between the driving current and the dimming step approximates a second relationship curve between brightness and darkness in human eyes; and

The second step: generating an output current to the LED according to the driving current.

In the aforementioned method for controlling a current regulator, the second step includes mirroring the driving current to generate an output current.

The control method of the aforementioned current regulator, wherein the first step includes:

providing a variable voltage varying with the dimming step to a variable resistor varying with the dimming step to generate a reference current; and

Mirroring the reference current generates a drive current.

In the control method of the aforementioned current regulator, wherein the resistance value of the variable resistor is a power of 2.

The control method of the aforementioned current regulator, wherein the first step further includes:

converting a reference voltage into a reference current;

mirroring the reference current to generate a drive current; and

controlling the conduction time of the reference current;

Both the conduction time of the reference current and the reference voltage are determined by the dimming steps.

In the aforementioned control method of the current regulator, the conduction time of the reference current is a power of 2.

In the control method of the aforementioned current regulator, the error value between the first relationship curve and the second relationship curve is lower than 10%.

In the control method of the aforementioned current regulator, the second relational curve is Y/Yn=((L+16)/116) ³ , where Y is the brightness, Yn is the brightness when it is completely white, and L is the brightness.

After adopting the above technical solution, the current regulator of the present invention has the following advantages:

(1). It can make the brightness change of white LED change linearly in human eyes.

(2). It can make the brightness change of white light LED almost linear in human eyes.

Description of drawings

Figure 1 shows a known current regulator for driving white LEDs;

Figure 2 shows the relationship curve between the current IREF and the dimming step in Figure 1;

Figure 3 shows the relationship curve between the DC drive current ILED and the dimming step in Figure 1;

Fig. 4 shows the relationship curve between the light intensity of the white LED and the DC driving current ILED;

Fig. 5 shows the relationship curve between the luminance and the shading of the white LED 20 and the relationship curve between the luminance and the shading in human eyes;

Fig. 6 shows the error value of brightness between curves 30 and 32 in Fig. 5;

Fig. 7 is the first embodiment of the present invention;

FIG. 8 shows the relationship curve between the current of the current source 42 and the dimming step in FIG. 7;

Figure 9 shows the relationship between the current ILED and the dimming step;

Fig. 10 shows the relationship curve between the brightness of LED48 in Fig. 7 and the lightness and the relationship curve between the brightness and the lightness in the human eye;

Fig. 11 is the second embodiment of the present invention;

Fig. 12 shows the embodiment of control signal PWM;

Fig. 13 is the third embodiment of the present invention;

FIG. 14 shows an embodiment of the control signal PWM in FIG. 13;

Fig. 15 is the fourth embodiment of the present invention;

Fig. 16 shows the relationship curve between brightness and shade in human eyes and the brightness of LED48 in the current regulator 70 and the relationship curve between shade;

Figure 17 shows the error value between the two curves 74 and 76 in Figure 16;

Fig. 18 is the fifth embodiment of the present invention;

Fig. 19 shows the relationship curve between brightness and shade in human eyes and the relationship curve between the brightness and shade of LED48 in the current regulator 80; and

FIG. 20 shows the error value between the two curves 84 and 86 in FIG. 19 .

Detailed ways

The present invention will be further described below in conjunction with embodiment and accompanying drawing.

In the known literature, the conversion formula between brightness Y and lightness L

L＝116f(Y/Yn)-16 Formula 1

Among them, Yn is the brightness when it is completely white. f(Y/Yn)=(Y/Yn)1/3 when (Y/Yn)>0.008856, otherwise f(Y/Yn)=7.787(Y/Yn)+16/116. It can be deduced from formula 1

f(Y/Yn)＝((L+16)/116) Formula 2

Since the range of (Y/Yn)<0.008856 is very small, it is negligible, so it can be further deduced

(Y/Yn)=((L+16)/116) ³ Formula 3

Therefore, as long as the brightness emitted by the light-emitting diode conforms to formula 3, it can conform to the brightness change perceived by human eyes. For more details, please refer to the webpage http://en.wikipedia.org/wiki/Lab_color_space.

First please refer to FIG. 7 , which is a diagram of the first embodiment of the present invention. As shown in the figure, in the current regulator 40, the current source 42 provides a driving current IREF=K1×((L+16)/116) ³ , where K1 is a constant, and the brightness controller 44 is used to determine the brightness The value of L, where the brightness L is the dimming step, the low dropout current source 46 generates an output current ILED to the LED 48 according to the current IREF, the low dropout current source includes an operational amplifier 4602 and transistors 4604 and 4606, wherein, The transistor 4604 is connected between the current ILED and the ground terminal GND, the transistor 4606 is connected between the LED48 and the ground terminal GND, the non-inverting input and the inverting input of the operational amplifier 4602 are respectively connected to the drains of the transistors 4604 and 4606, and the operational amplifier 4602 The output of is connected to the gates of transistors 4604 and 4606.

FIG. 8 shows the relationship between the current in the current source 42 and the dimming step. In the current source 42, the variable resistors 4204, 4210 and 4216 have the same resistance value ((L+16)/116)×R, and the current source 4202 provides the current I1 to the variable resistor 4204 to generate the voltage VI=((L +16)/116)×R×I1, voltage current converter 4206 converts voltage V1 to current I2=((L+16)/116)×I1, current mirror 4208 mirrors current I2 to generate current I3=((L +16)/116)×I1×n1 is given to resistor 4210 to generate voltage V2=((L+16)/116) ² ×R×I1×n1, the curve of current I3 is as shown in curve 50 of Figure 8, voltage-current Converter 4212 converts voltage V2 into current I4=((L+16)/116) ² ×I1×n1, and current mirror 4214 mirrors current I4 to generate current I5=((L+16)/116) ² ×I1× n1×n2 is given to resistor 4216 to generate voltage V3=((L+16)/116) ³ ×R×I1×n1×n2, the curve of current I5 is as shown in curve 52 of Figure 8, and voltage-to-current converter 4218 converts the voltage V3 is converted into current I6=((L+16)/116) ³ ×I1×n1×n2, current mirror 4220 mirrors current I6 to generate current IREF=K1×((L+16)/116) ³ , as shown in Figure 8 As shown in the curve 54, here K1=I1×n1×n2×n3.

Figure 9 shows the relationship between current ILED and dimming steps. In low dropout current source 46, operational amplifier 4602 makes the voltage between the gate and drain of transistor 4604 equal to the voltage between the gate and drain of transistor 4606, so transistor 4606 will mirror the current IREF through transistor 4604, assuming transistors 4604 and 4606 The size ratio between them is 1:K2, then the current ILED=K1×K2×((L+16)/116) ³ can be obtained, as shown in FIG. 9 . Fig. 10 shows the relationship curve between the luminance and shading of LED48 in Fig. 7 and the relationship curve between luminance and shading in human eyes, wherein the two curves overlap, therefore, every time one dimming step L is changed, the human The brightness change perceived by the eyes is a constant value, so the dimming step of the current regulator 40 has a linear relationship with the brightness perceived by the human eye, so there is no need to select an appropriate dimming step through complicated calculations to make the human eye The brightness change of the observed LED is linear, and there is no waste of dimming steps being idle.

11 is a second embodiment of the present invention, the current regulator 60 includes a current source 62, a brightness controller 64 and a low-dropout current source 46, and the current source 62 provides a current IREF=K1×((L+16)/ 116) ³ , as shown in the curve 54 of FIG. 8 , the shading controller 64 is used to determine the value of the shading L, where the shading L is a dimming step, and the low-dropout current source 46 generates a current ILED according to the current IREF, As shown in Figure 9. In the current source 62, the voltage-to-current converter 6202 converts the voltage VREF into a current I1, and the PWM signal generator 6204 generates a control signal PWM according to the output L of the brightness controller 64, and is connected between the voltage-to-current converter 6202 and the ground terminal GND. Between the switch S1, thereby controlling the conduction time of the current I1, the current mirror 6206 mirrors the current I1 to generate the current IREF. Figure 12 shows an embodiment of the control signal PWM, wherein the control signal PWM includes the main cycle T1 with a duty cycle ratio ((L+16)/116), and the duty time of the main cycle T1 includes the first sub-cycle T2 with a duty cycle ratio ((L+16)/116), the working time of the first sub-period T2 includes ((L+16)/116) in the second sub-period, therefore, it can be known that the average current of the current IREF is equal to K1×(( L+16)/116) ³ , where K1=I1. Since the current IREF is proportional to ((L+16)/116) ³ , the current ILED is also proportional to ((L+16)/116) ³ , in other words, the relationship curve between the brightness and darkness of LED48 in Fig. 11 And the relationship curves between brightness and darkness in human eyes overlap, as shown in FIG. 10 , so the dimming step of the current regulator 60 has a linear relationship with the brightness perceived by human eyes.

Fig. 13 is the third embodiment of the present invention, and described current regulator 66 comprises current source 68, shading controller 69 and low dropout current source 46, and current source 68 provides current IREF=K1*((L+16)/ 116) ³ , as shown in the curve 54 of FIG. 8 , the brightness controller 69 is used to determine the value of the brightness L, where the brightness L is a dimming step, and the low dropout current source 46 generates the current ILED according to the current IREF. In the current source 68, the variable resistors 6804 and 6810 have the same resistance value ((L+16)/116)×R, the current source 6802 provides the current I1 to the variable resistor 6804 to generate the voltage V1=((L+16 )/116)×R×I1, voltage-current converter 6806 converts voltage V1 to current I2=((L+16)/116)×I1, current mirror 6808 mirrors current I2 to generate current I3=((L+16 )/116)×I1×n1 is given to resistor 6810 to generate voltage V2=((L+16)/116) ² ×R×I1×n1, voltage-to-current converter 6812 converts voltage V2 into current I4=((L+ 16)/116) ² ×I1×n1, the switch S1 is connected between the voltage-current converter 6812 and the ground terminal GND, the PWM signal generator 6816 generates the control signal PWM switch S1 according to the output L of the brightness controller 69, as shown in Fig. 14 shows an embodiment of the control signal PWM in FIG. 13, which includes a period T1 with a duty cycle ratio ((L+16)/116), and the current mirror 6814 mirrors the current on its reference branch to generate a current IREF, due to the control signal PWM The duty cycle ratio is ((L+16)/116), so it can be known that the average current of the current IREF is equal to I4×n2×((L+16)/116), and the current I4 is equal to ((L+16)/116 ) ² ×I1×n1, so the average current of the current IREF is equal to K1×((L+16)/116) ³ , where K1=I1×n1×n2.

15 is a fourth embodiment of the present invention, the current regulator 70 includes a current source 72 to provide a current IREF and a low-dropout current source 46 to generate a current ILED to the LED48 according to the current IREF. This embodiment uses a piecewise linear approximation (piecewise linear approach) to obtain a curve approximate to formula 3. In the current source 72, the voltage-to-current converter 7201 converts the variable voltage V1=(N/40)×VREF into the current I1, and the current mirror 7206 mirrors the current I1 to generate the current IREF. In the voltage-to-current converter 7201, the operational amplifier The 7202 has a non-inverting input and an inverting input respectively connected to the variable voltage V1 and node A to provide the voltage V1 to the node A, where N is the dimming step, in this embodiment, N is equal to 21-40 A plurality of resistors R with the same resistance value are connected in parallel between the node A and the ground terminal GND to form an equivalent resistance 7204, and each of the plurality of switches S1-S16 is connected in series with a resistor, so switching the switches S1-S16 can change the equivalent resistance The resistance value of the resistor 7204, the equivalent resistor 7204 generates the current I1 in response to the voltage V1. FIG. 16 shows a relationship curve 74 between brightness and shade in human eyes and a relationship curve 76 between brightness and shade of LED 48 in the current regulator 70 . 15 and 16, in this embodiment, the curve 76 is divided into 5 sections, and the number of dimming steps N is 20, so each section includes 4 dimming steps, in each section, etc. The resistance value of the effective resistor 7204 will change to change the slope of the current ILED, as shown in Figure 16, in the first paragraph, the switch S1 is turned on (turn on) and the rest is turned off (turn off), the resistance value of the equivalent resistor 7204 is R, in the second section, the switches S1 and S2 are open and the rest are closed, and the resistance value of the equivalent resistance 7204 becomes R/2. In the third section, the switches S1~S4 are open and the rest are closed, so the equivalent resistance 7204 The resistance value of the resistor is R/4. In the fourth section, the switches S1~S8 are turned on and the rest are turned off, so the resistance value of the equivalent resistor 7204 is R/8. In the fifth section, the switches S1~S16 are all turned on, so The resistance value of the equivalent resistance 7204 is R/16, obviously, the resistance value of the equivalent resistance 7204 is a power of 2. In other embodiments, as long as the reference voltage VREF, the number of dimming steps, and the resistor R are properly selected, the number of segments of the curve 76 of the current ILED can be changed. As the number of segments increases, the curve 76 of the current ILED can be closer to Curve 74. Figure 17 shows the error value between the two curves 74 and 76 in Figure 16, wherein the error value between the two curves 74 and 76 does not exceed 10%, obviously the two curves 74 and 76 are quite similar, so when the dimming step N When changing, the brightness change of LED 48 is nearly linear to the human eye.

FIG. 18 is a fifth embodiment of the present invention. The current regulator 80 includes a current source 82 to provide a current IREF and a low-dropout current source 46 to generate a current ILED to the LED48 according to the current IREF. This embodiment also uses a segmented linear approximation method to achieve A curve approximating Equation 3 is obtained. In the current source 82, the voltage-to-current converter 8202 converts the variable voltage V1=(N/40)×VREF into a current I1, and the switch S1 is connected between the voltage-to-current converter 8202 and the ground terminal GND, and is controlled by a control signal PWM, used to control the conduction time of the current I1, the current mirror 8204 mirrors the current I1 to generate the current IREF. FIG. 19 shows the relationship curve 84 between brightness and darkness in human eyes and the relationship curve 86 between the brightness and brightness of LED 48 in the current regulator 80 . Referring to Figures 18 and 19, in this embodiment, the curve 86 of the current ILED is also divided into 5 sections, and the number of dimming steps N is 20 in total, so each section includes 4 dimming steps, and in each section Among them, the control signal PWM has different working hours. It can be seen from Fig. 19 that the duty cycle ratios of the control signal PWM in each segment are (1/16), (2/16), (4/16), (8/ 16) and (16/16), the operating time of the control signal PWM is a power of 2, and whenever the operating time of the control signal PWM increases, the slope of the curve 86 also increases. In other embodiments, as long as the reference voltage VREF, the number of dimming steps and the resistor R are properly selected, the number of segments of the curve 86 of the current ILED can be changed. As the number of segments increases, the curve 86 of the current ILED can be closer to Curve 84. Figure 20 shows the error value between the two curves 84 and 86 in Figure 19, wherein the error value between the two curves 84 and 86 does not exceed 10%, obviously the two curves 84 and 86 are quite similar, so when the dimming step N When changing, the brightness change of LED 48 is nearly linear to the human eye.

The above embodiments are only for illustrating the present invention, rather than limiting the present invention. Those skilled in the relevant technical field can also make various transformations or changes without departing from the spirit and scope of the present invention. Therefore, all equivalent technical solutions should also belong to the category of the present invention and should be defined by each claim.

Claims (23)

1. a current regulator, comprises one first current source and a shading value controller, it is characterized in that:

Described the first current source provides one to be proportional to ((L+16)/116) ³drive current, wherein L is shading value,

Described shading value controller determines the value of L;

Wherein, the relation curve between described drive current and shading value with the error amount of the relation curve between brightness in human eye and shading value lower than 10%;

Described the first current source comprises:

One first resistance, its resistance value has proportionate relationship with ((L+16)/116);

One second resistance, its resistance value has proportionate relationship with ((L+16)/116);

One the 3rd resistance, its resistance value has proportionate relationship with ((L+16)/116);

One second current source, supply one first electric current to described the first resistance to produce one first voltage;

One first voltage current adapter, in order to being one second electric current by described the first voltage transitions;

One first current mirror, described in mirror the second electric current produce one the 3rd electric current to described the second resistance to produce a second voltage;

One second voltage current converter, in order to be converted to described second voltage in one the 4th electric current;

One second current mirror, described in mirror the 4th electric current produce one the 5th electric current to described the 3rd resistance to produce a tertiary voltage;

One tertiary voltage current converter, in order to be converted to described tertiary voltage in one the 6th electric current; And

One the 3rd current mirror, the 6th electric current produces described drive current described in mirror.

2. current regulator as claimed in claim 1, is characterized in that, described first, second and third resistance has same resistance value.

3. current regulator as claimed in claim 1, more comprises that a low voltage difference current source produces an output current to light-emitting diode according to described drive current.

4. current regulator as claimed in claim 3, is characterized in that, described low voltage difference current source comprises:

One operational amplifier, has one first input, one second input and an output;

One the first transistor, has that a drain connects described drive current and the first input, one source pole connects a reference voltage and a gate and connects output;

One transistor seconds, has that a drain connects described light-emitting diode and the second input, one source pole connects described reference voltage and a gate and connects output, and the described drive current in order to mirror by described the first transistor produces described output current.

5. a current regulator, comprises one first current source and a shading value controller, it is characterized in that:

Described the first current source provides one to be proportional to ((L+16)/116) ³drive current, wherein L is shading value, described shading value controller determines the value of L;

Wherein, the relation curve between described drive current and shading value with the error amount that approaches the relation curve between brightness and shading value in human eye lower than 10%;

Described the first current source comprises:

One current mirror, mirror one reference current produces described drive current;

One voltage current adapter, is converted to described reference current by a reference voltage; And

One switch, be controlled by a control signal, in order to control the ON time of described reference current, described control signal comprises a primary period, the described primary period has the work period than being ((L+16)/116), in the operating time in described primary period, comprise one first subcycle, described the first subcycle has the work period than being ((L+16)/116), in the operating time of described the first subcycle, comprise one second subcycle, described the second subcycle has the work period than being ((L+16)/116).

6. current regulator as claimed in claim 5, more comprises that a low voltage difference current source produces an output current to light-emitting diode according to described drive current.

7. current regulator as claimed in claim 6, is characterized in that, described low voltage difference current source comprises:

One operational amplifier, has one first input, one second input and an output;

One the first transistor, has that a drain connects described drive current and the first input, one source pole connects a reference voltage and a gate and connects output;

One transistor seconds, has that a drain connects described light-emitting diode and the second input, one source pole connects described reference voltage and a gate and connects output, and the described drive current in order to mirror by described the first transistor produces described output current.

8. a current regulator, comprises one first current source and a shading value controller, it is characterized in that:

Described the first current source provides one to be proportional to ((L+16)/116) ³drive current, wherein L is shading value, described shading value controller determines the value of L;

Wherein, the relation curve between described drive current and shading value with the error amount of the relation curve between brightness in human eye and shading value lower than 10%;

Described the first current source comprises:

One first resistance, its resistance value has proportionate relationship with ((L+16)/116);

One second resistance, its resistance value has proportionate relationship with ((L+16)/116);

One second current source, supply one first electric current to described the first resistance to produce one first voltage;

One first voltage current adapter, in order to being one second electric current by described the first voltage transitions;

One first current mirror, described in mirror the second electric current produce one the 3rd electric current to described the second resistance to produce a second voltage;

One second voltage current converter, in order to be converted to described second voltage in one the 4th electric current;

One second current mirror, the 4th electric current produces described drive current described in mirror; And

One switch, is controlled by a control signal, and in order to control the ON time of described the 4th electric current, described control signal has the work period than being ((L+16)/116).

9. current regulator as claimed in claim 8, is characterized in that, described first and second resistance has same resistance value.

10. current regulator as claimed in claim 8, more comprises that a low voltage difference current source produces an output current to light-emitting diode according to described drive current.

11. current regulators as claimed in claim 10, is characterized in that, described low voltage difference current source comprises:

One operational amplifier, has one first input, one second input and an output;

One the first transistor, has that a drain connects described drive current and the first input, one source pole connects a reference voltage and a gate and connects output;

One transistor seconds, has that a drain connects described light-emitting diode and the second input, one source pole connects described reference voltage and a gate and connects output, and the described drive current in order to mirror by described the first transistor produces described output current.

12. 1 kinds of current regulators, comprise one first current source and an output circuit, it is characterized in that:

Described the first current source, one drive current with light modulation step change is provided, the first relation curve between described drive current and described light modulation step is with the error amount of the second relation curve between brightness in human eye and shading value lower than 10%, and described the first current source comprises:

One first current mirror, produces drive current in order to mirror one reference current;

One variable resistor, its resistance value is determined by described light modulation step;

One the first transistor, is connected between described variable resistor and described the first current mirror; And

One first operational amplifier, have two inputs and connect respectively the gate that a variable voltage changing with described light modulation step and described variable resistor and an output connect described the first transistor, described the first operational amplifier offers described variable resistor to produce described reference current by described variable voltage; And

Described output circuit, produces an output current to light-emitting diode according to described drive current, and described output circuit comprises described in one second current source mirror that drive current produces described output current, and described the second current source comprises:

One second operational amplifier, has one first input, one second input and an output;

One transistor seconds, has the first input, the one source pole that a drain connects described drive current and described the second operational amplifier and connects the output that a reference voltage and a gate connect described the second operational amplifier; And

One the 3rd transistor, have the second input, the one source pole that a drain connects described light-emitting diode and described the second operational amplifier and connect the output that described reference voltage and a gate connect described the second operational amplifier, the described drive current in order to mirror by described transistor seconds produces described output current.

13. current regulators as claimed in claim 12, is characterized in that, the power side that described variable-resistance resistance value is 2.

14. current regulators as claimed in claim 12, is characterized in that, described the second relation curve is Y/Yn=((L+16)/116) ³, it is characterized in that, Y is brightness, brightness when Yn is complete white, L is shading value.

15. 1 kinds of current regulators, comprise one first current source and an output circuit, it is characterized in that:

Described the first current source, one drive current with light modulation step change is provided, the first relation curve between described drive current and described light modulation step is with the error amount of the second relation curve between brightness in human eye and shading value lower than 10%, and described the first current source also comprises:

One current mirror, mirror one reference current produces described drive current;

One voltage current adapter, is converted to described reference current by a reference voltage; And

One switch, is controlled by a control signal, and in order to control the ON time of described reference current, the operating time of described control signal and described reference voltage are all determined by described light modulation step; And

Described output circuit, produces an output current to light-emitting diode according to described drive current, and described output circuit comprises described in one second current source mirror that drive current produces described output current, and described the second current source comprises:

One operational amplifier, has one first input, one second input and an output;

One the first transistor, have a drain connect described drive current and first input, one source pole connects a reference voltage and a gate connects described output; And

One transistor seconds, has that a drain connects described light-emitting diode and the second input, one source pole connects described reference voltage and a gate connects described output, and the described drive current in order to mirror by described the first transistor produces described output current.

16. current regulators as claimed in claim 15, is characterized in that, the power side that the described operating time is 2.

17. current regulators as claimed in claim 15, is characterized in that, described the second relation curve is Y/Yn=((L+16)/116) ³, it is characterized in that, Y is brightness, brightness when Yn is complete white, L is shading value.

The control method of 18. 1 kinds of current regulators, is characterized in that, comprises the following steps:

First step: a drive current with light modulation step change is provided, the first relation curve between described drive current and described light modulation step with the error amount of the second relation curve between brightness in human eye and shading value lower than 10%; And

Second step: described in mirror, drive current produces an output current to light-emitting diode;

Wherein, described first step comprises:

Provide a variable resistor changing with described light modulation step with the variable voltage to of described light modulation step change to produce a reference current; And

Described in mirror, reference current produces described drive current.

19. control methods as claimed in claim 18, is characterized in that, the power side that described variable-resistance resistance value is 2.

20. control methods as claimed in claim 18, is characterized in that, described the second relation curve is Y/Yn=((L+16)/116) ³, wherein Y is brightness, brightness when Yn is complete white, and L is shading value.

The control method of 21. 1 kinds of current regulators, is characterized in that, comprises the following steps:

First step: a drive current with light modulation step change is provided, the first relation curve between described drive current and described light modulation step with the error amount of the second relation curve between brightness in human eye and shading value lower than 10%; And

Second step: described in mirror, drive current produces an output current to light-emitting diode;

Wherein, described first step also comprises:

One reference voltage is converted to a reference current;

Described in mirror, reference current produces described drive current; And

Control the ON time of described reference current;

The ON time of described reference current and described reference voltage are all determined by described light modulation step.

22. control methods as claimed in claim 21, is characterized in that, the power side that the ON time of described reference current is 2.

23. control methods as claimed in claim 21, is characterized in that, described the second relation curve is Y/Yn=((L+16)/116) ³, wherein Y is brightness, brightness when Yn is complete white, and L is shading value.

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