KR20060012990A - Backlight driving circuit in fs-lcd - Google Patents

Abstract

The present invention relates to a circuit for driving R, G, and B backlights used as a light source of a field-sequential liquid crystal display device. The backlight driving circuit of the present invention provides light for one frame divided into at least two subframes. In a backlight driving circuit having at least two backlights emitting light, the backlights being sequentially driven in corresponding subframes to emit light of different colors, wherein each backlight is provided with a different driving current. It emits light with brightness and provides different PWM signals to each backlight to adjust the chromaticity of the light emitted from each backlight.

LCD, backlight, drive current, PWM

Description

BACKLIGHT DRIVING CIRCUIT {BACKLIGHT DRIVING CIRCUIT IN FS-LCD}

1 is a view showing a pixel of a conventional TFT-LCD.

2 is a view for explaining a method of driving the R, G, B backlight used in the conventional field-sequential driving LCD.

3 shows a schematic configuration diagram of a LCD of a conventional field sequential driving method.

4 is a schematic configuration diagram illustrating an operation principle of a backlight driving circuit used in a liquid crystal display device having a field sequential driving method according to an embodiment of the present invention.

5 is a detailed configuration diagram of a backlight driving circuit according to an embodiment of the present invention.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device and a driving method thereof, and more particularly, to a liquid crystal display device having a field sequential driving method and a driving method thereof.

Recently, display devices are also required to be lighter and thinner in accordance with the light weight and thickness of personal computers and televisions, and according to such demands, flat displays such as liquid crystal displays (LCDs) instead of cathode ray tubes (CRTs) are required. Panel type displays are being developed.

An LCD applies an electric field to a liquid crystal material having an anisotropic dielectric constant injected between two substrates, and adjusts the intensity of the electric field to control the amount of light transmitted to the substrate from an external light source (backlight). A display device for obtaining an image signal.

Such LCDs are typical of portable flat panel displays, and among them, TFT-LCD using a thin film transistor (TFT) as a switching element is mainly used.

In the TFT-LCD, each pixel can be modeled as a liquid crystal capacitor because electrodes (pixel electrodes and common electrodes) are disposed to face each other with a liquid crystal interposed therebetween. In such LCDs, each pixel is represented by an equivalent circuit as shown in FIG. Can be.

As shown in Fig. 1, each pixel of the liquid crystal display device has a drain electrode of a TFT 10 and a TFT 10 having a source electrode connected to a data line Dm, and a gate electrode connected to a scan line Sn. The liquid crystal capacitor Cl is connected between the common electrode Vcom and a storage capacitor Cst is connected to the drain electrode of the TFT 10.

The TFT 10 provides the pixel electrode (not shown) with the data voltage Vd supplied from the data line Dm in response to the scan signal from the scan line Sn. The electric field corresponding to the difference between the data voltage provided to the pixel electrode (ie, the pixel voltage Vp and the common voltage Vcom applied to the common electrode (not shown) is equivalent to that of the liquid crystal capacitor (FIG. 1). The liquid crystal adjusts the transmittance of light according to the intensity of the applied electric field, and the storage capacitor Cst uses the pixel voltage provided to the liquid crystal capacitor Cl to the next data voltage Vd. The light is transmitted for a predetermined time by maintaining it until it is supplied.

In general, the LCD can be divided into two methods, a color filter method and a field sequential driving method, according to a method of displaying a color image.

The color filter LCD forms a color filter layer consisting of three primary colors of red (R), green (G) and blue (B) on the upper substrate of the panel, and adjusts the amount of light transmitted through the color filter layer. The desired image is displayed. However, the color filter LCD requires unit pixels corresponding to each of the red (R), green (G), and blue (B) regions, and thus requires three times as many pixels as those for displaying black and white. Therefore, in order to obtain high resolution images, sophisticated manufacturing technology of LCD panels is required. In addition, in the color filter type LCD, red (R), green (G) and blue (B) color filters must be formed on the upper substrate, which is cumbersome in manufacturing, and the light transmittance of the color filter itself must be improved. There is a problem.

On the other hand, the LCD of the field sequential driving method periodically turns on independent light sources of red (R), green (G), and blue (B) colors sequentially, and supplies pixel voltages (Vp) to each pixel at each lighting cycle. Displays a color image. That is, a field-sequential driving LCD does not divide one pixel into unit pixels of red (R), green (G), and blue (B), and red (R), green (G), and blue in one pixel. (B) Color images are displayed using the afterimage effect of the eyes by sequentially displaying the light of the three primary colors supplied from each backlight in time division.

2 is a view for explaining a method of driving the R, G, B backlight used in the conventional field-sequential driving LCD.

Referring to FIG. 2, a conventional backlight driving circuit includes a backlight 20 sequentially emitting light of three primary colors of R, G, and B, and the R, G, B backlights 22, 23, and 24. A driving current generator 21 is provided to provide the same driving current ILED in common.

The backlight 20 includes an R backlight 22 that emits R light, a G backlight 23 that emits G light, and a B backlight 24 that emits B light. The R backlight 22 is composed of one R light emitting diode (RLED1) for emitting R light, and the G backlight 23 is composed of one G light emitting diode (GLED1) for emitting G light, The B backlight 24 is composed of one B light emitting diode BLED1 for emitting B light.

The driving current generator 21 generates driving currents (ILED) having the same level as all of the R, G, and B backlights 22, 23, and 24 constituting the backlight 20. 22, a driving current ILED is provided to the anode electrode of the R light emitting diode RLED1, a driving current IELD is provided to the G electrode 23 as an anode electrode of the G light emitting diode GLED1, and a B backlight ( 24, a driving current ILED is provided to the anode electrode of the B light emitting diode BLED1, respectively.

In addition, the conventional backlight driving circuit further comprises a brightness control means for controlling the brightness of the light emitted from the backlight 20 is connected in series between the backlight 20 and the ground. The brightness control means includes a first variable resistor RVR connected between the cathode of the R LED 22 of the R backlight 22 and the ground to adjust the brightness of the light emitted from the R backlight 22; A second variable resistor GVR connected between the cathode electrode of the G LED 1 of the backlight 23 and the ground to adjust the luminance of the light emitted from the G backlight 23, and the B of the B backlight 24. A third variable resistor BVR is connected between the cathode of the light emitting diode BLED1 and the ground to adjust the brightness of light emitted from the B backlight 24.

Conventionally, although the forward driving currents (RIf, GIf, BIf) of the light emitting diodes (RLED, GLED, BLED) of the R, G, and B backlights 22, 23, and 24 are different from each other, the driving current generator The same drive current, for example, 20 mA, is provided from 21 to the R, G, or B backlights 22, 23, 24. For example, R LEDs require 10 mA of forward driving current (RIf), G LEDs (GLED) require 17 mA of forward driving current (GIf), and B LEDs (BLEDs) of 18 mA. Forward drive current BIf is required.

Conventionally, since R, G, and B backlights 22, 23, and 24 are all provided with the same driving current (ILED) of 20 mA, a variable resistor (RVR) is required to drive the R light emitting diode (RLED1). ), A forward driving current (RIf) of 10 mA is applied to the R light emitting diode RLED1 to adjust the luminance of light emitted from the R backlight 22.

On the other hand, when the G light emitting diode GLED1 is to be driven, the luminance of light emitted from the G backlight 23 is applied by applying a 17 mA forward driving current GIf to the G light emitting diode GLED1 using the variable resistor GVR. Adjust it. In addition, when driving the B LED1, the luminance of the light emitted from the B backlight 24 is applied by applying a 18 mA forward driving current BIf to the B LED 1 using the variable resistor BVR. Adjust it.

Therefore, the conventional backlight driving circuit as described above is provided with the same driving current of 20 mA regardless of the R, G, B light emitting diodes driven by different driving currents. That is, since the same driving current is applied to one frame during the three sub-frames for driving the R, G, and B light emitting diodes, the power consumption is not only increased, but also the driving current required for the R, G, and B light emitting diodes. There was a problem that the driving current generation circuit should generate a driving current corresponding to the largest driving current.

In addition, there is a problem in that the forward driving current provided to the R, G, and B light emitting diodes is manually adjusted by using a variable resistor for each subframe, and when the driving current of the light emitting diode is large, Manual adjustment alone has a problem in that it is difficult to provide a forward driving current suitable for each of the R, G, and B light emitting diodes.

SUMMARY OF THE INVENTION The present invention has been made in an effort to solve the problems of the prior art, and provides a backlight driving circuit capable of reducing power consumption and maximizing efficiency by providing a driving current suitable for each light emitting diode.

In addition, to provide a backlight driving circuit that can optimize the color purity by using a different PWM value for each light emitting diode.

The backlight driving circuit according to one feature of the present invention for achieving the above object is

A backlight driving circuit having at least two backlights emitting light during one frame divided into at least two subframes, wherein the backlight is sequentially driven in a corresponding subframe to emit light of different colors.

A driving current generator for providing different driving currents to the backlights so that each backlight emits light having a predetermined brightness; And

It includes a PWM generator for providing a different PWM signal to each backlight to adjust the chromaticity of the light emitted from each backlight.

DETAILED DESCRIPTION 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. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. In the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention. Like parts are designated by like reference numerals throughout the specification.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

3 shows a schematic configuration diagram of a LCD of a conventional field sequential driving method.

Referring to FIG. 3, the liquid crystal display includes a lower substrate 101 having a TFT array (not shown) arranged with a plurality of gate lines, a plurality of data lines, and a plurality of switching thin film transistors connected to a plurality of common lines. Liquid crystal including an upper substrate 102 having a common electrode (not shown) for providing a common voltage to a line, and a liquid crystal (not shown) injected between the upper and lower substrates 102 and 101. The panel 100 is provided.

In addition, the liquid crystal display device includes a gate line driver circuit 110 for providing scan signals to a plurality of gate lines of the liquid crystal panel 100, and a data line for providing R, G, and B data signals to the data lines. A driving system 120 and a backlight system 130 for providing light of three primary colors of R, G, and B to the liquid crystal panel 100 are further provided.

The backlight system 130 includes three R, G, and B backlights 131, 132, and 133 for providing R, G, and B lights, respectively, and the respective R, G, and B backlights 131. And a light guide plate 134 for providing R, G, and B light emitted from the light emitting elements 132 and 133 to the liquid crystal of the liquid crystal panel 100.

In general, the time interval of one frame driven at 60 Hz is 16.7 ms (1/60 s). Thus, in the field sequential liquid crystal display in which one frame is divided into three sub-frames, one sub-frame is 5.56 ms (1). / 180s). The time interval of one subframe is a very short time and the field change is not recognized by the human eye. Therefore, the human eye is recognized as an integrated time of 16.7 ms, and the synthesized colors of the three primary colors of R, G, and B are recognized.

Therefore, the field sequential driving method can realize three times the resolution of the same size panel as the color filter method, and the light efficiency is increased due to the absence of the color filter, and the same color reproduction and high-speed moving picture as the color television can be achieved. On the other hand, since one frame is divided into three subframes and driven, the driving frequency is required to be six times higher than the color filter driving method, and therefore, high speed operation characteristics are required.

Therefore, in order for the liquid crystal display device to obtain high-speed operating characteristics, not only the response speed of the liquid crystal should be fast but also the on / off switching speed of the R, G, and B backlights must be relatively fast.

4 is a schematic configuration diagram illustrating an operation principle of a backlight driving circuit used in a liquid crystal display device having a field sequential driving method according to an embodiment of the present invention.

Referring to FIG. 4, the backlight driving circuit of the present invention has a forward direction suitable for each of R, G, and B light emitting diodes (RLED, GLED, and BLED) in R, G, and B backlights 201, 202, and 203, respectively. The driving current is sequentially generated, and each of the R, G, and B light emitting diodes (RLED, GLED, and BLED) is driven by the forward driving current to realize a color whose luminance is controlled. In addition, it adjusts the different PWM values (RPWM, GPWM, BPWM) suitable for R, G, B LEDs (RLED, GLED, BLED) to optimize the white balance of the implemented color. At this time, the pulse width modulation (PWM) value has a different value for each of the R, G, and B light emitting diodes (RLED, GLED, BLED).

For example, when one frame consists of three subframes to sequentially drive R, G, and B light emitting diodes (RLED, GLED, and BLED) for each subframe, the first subframe is suitable for an R LED. Each of the forward driving currents RIf is provided to drive the R LEDs. Subsequently, in the second sub frame, each of the forward driving currents GIf suitable for the G LED is provided to drive the G light emitting diode GLED, and in the third sub frame, the forward driving suitable for the B light emitting diode BLED is performed. A current BIf is provided to drive the B light emitting diodes BLEDs, respectively.

As such, when a driving current (RIf) suitable for the R LED is generated and driven in the first sub-frame, the PWM value (RPWM) suitable for the R LED is adjusted to adjust the chromaticity of the R color. In the second sub-frame, when a driving current (GIf) suitable for the G light emitting diode (GLED) is generated and driven, the chromaticity of the G color is adjusted by providing a PWM value (GPWM) suitable for the G light emitting diode (GLED). In the third sub-frame, when a driving current BIf suitable for the B light emitting diode BLED is generated and driven, the chromaticity of the B color is adjusted by providing a PWM value BPWM suitable for the B light emitting diode BLED.

Accordingly, R, G, and B light emitting diodes (RLED, GLED, BLED) generate a suitable forward driving current, respectively, to implement R, G, and B colors having desired luminance, and R, which is driven according to each forward driving current, The white balance is adjusted using the PWM values of the G and B light emitting diodes (RLED, GLED, BLED). Therefore, it is possible to provide a color having an optimized chromaticity with a predetermined luminance.

5 illustrates a detailed configuration diagram of a backlight driving circuit according to an exemplary embodiment of the present invention.

Referring to FIG. 5, the backlight driving circuit according to the present invention includes a backlight 200 for generating R, G, and B light, and a driving current generator 210 for generating a driving current ILED through the backlight 200. ) And a LED controller 220 for controlling the operation of the backlight 200 according to the LED control signal LED_CTRL and a PWM to the backlight 200 according to the output signal provided from the LED controller 220. And a PWM generator 230 for generating a signal.

The backlight 200 includes an R backlight 201 that emits light of R color, a G backlight 202 that emits light of G color, and a B backlight 203 that emits light of B color.

The R backlight 201 includes an R LED and a forward driving current required for driving the R LED from the output terminal ILED of the driving current generator 210 using the R LED. (RIf) is supplied.

The G backlight 202 includes one G light emitting diode (GLED), and a forward direction required for driving the G light emitting diode from the output terminal (ILED) of the driving current generator 210 is used as the G light emitting diode (GLED). The drive current GIf is supplied.

The B backlight 203 includes a B light emitting diode (BLED), and an anode electrode of the B light emitting diode (BLED) is required to drive the B light emitting diode from an output terminal (ILED) of the driving current generator 210. Forward drive current BIf is supplied.

In the exemplary embodiment of the present invention, the backlight 200 includes only R, G, and B light emitting diodes, but may also include R, G, and B light emitting diodes, and a W light emitting diode emitting W (white) colors. In addition, although the R, G, and B backlights each consist of one backlight, one or more backlights may be configured.

The driving current generating unit 210 is a forward driving current (RIf), (GIf), (BIf) suitable for the R, G, B backlight 201, 202, (203) constituting the backlight 200 ) Are sequentially generated, and consist of registers for storing forward driving currents (RIf), (GIf), and (BIf) of the R, G, and B backlights.

Accordingly, the driving current generator 210 generates a driving current (RIf) suitable for the R light emitting diode as an anode electrode of the R light emitting diode (RLED) in the R subframe for driving the R light emitting diode, and drives the G light emitting diode. In the G subframe, a driving current (GIf) suitable for the G light emitting diode is generated as an anode electrode of the G light emitting diode (GLED), and in the B subframe for driving the B light emitting diode, the anode of the B light emitting diode (BLED) is used. The electrode generates a driving current BIf suitable for the B light emitting diode.

Meanwhile, according to another embodiment of the present invention, when the plurality of R, G, and B backlights is configured, the driving current generator 210 may have the same driving currents RIf_1,..., RIf_n for each of the plurality of R, G, and B backlights. ), (GIf_1, ..., Gif_n), and (BIf_1, ..., BIf_n).

In this case, when the distribution of driving current of each light emitting diode is uneven, different driving currents (RIf_1, ..., RIf_n) suitable for a plurality of R backlights are provided, and different driving currents (GIf_1, ..., GIF_n, and different driving currents BIf_1, ..., BIf_n suitable for a plurality of B backlights may be provided, respectively.

In addition, the driving currents RIf_1, ..., RIf_n, (GIf_1, ..., Gif_n), and (BIf_1, ..., BIf_n) provided by the plurality of R, G, and B backlights are provided with different levels of current. The driving currents (RIf_1, ..., RIf_n), (GIf_1, ..., Gif_n), (BIf_1, ..., BIf_n) provided to the R, G, and B backlights are all different from each other, or at least one of the R, G, and B backlights In addition, different driving currents may be provided to only one backlight.

The LED controller 220 outputs a signal for driving a corresponding backlight among R, G, and B backlights in a corresponding frame among a plurality of subframes constituting a frame according to the LED control signal LED_CTRL.

The PWM generator 230 is a PWM signal (RPWM), (GPWM), (R, G, B backlight 201, 202, (203) corresponding to the output signal of the LED controller 220 ( BPWM), which is composed of registers for storing PWM signals of each of the R, G, and B backlights.

Accordingly, the PWM generator 230 generates the PWM signal RWM by the cathode electrode of the light emitting diode RLED of the R backlight 201 in the R subframe among the plurality of frames constituting one frame, respectively. ). In the G subframe, the PWM signal GPWM is generated to the cathode of the light emitting diode GLED of the G backlight 202 to drive the G backlight 202. In the B subframe, the PWM signal BPWM is generated to the cathode of the light emitting diode BLED of the B backlight 203 to drive the B backlight 203.

In the embodiment of the present invention, since the R, G, and B backlights each consist of one backlight 201, 202, and 203, the PWM generation unit 230 includes R, G, and B light emitting diodes (RLEDs). PWM signals (RPWM), (GPWM), and (BPWM) are generated for, (GLED) and (BLED), respectively.

On the other hand, the PWM generator 230 according to another embodiment of the present invention, when there are a plurality of backlights, the same PWM signal (RPWM_1, ..., RPMW_n), a plurality of R light emitting diodes (RLED_1, ..., RLED_n) The same PWM signal (GPWM_1, ..., GPWM_n) for the G light emitting diodes (GLED_1, ..., GLED_n) and the same PWM signal (BPWM_1, ..., BWWM_n) may be provided for the plurality of B light emitting diodes (BLED_1, ..., BLED_n), respectively. have.

At this time, when the distribution of the driving current of each light emitting diode is non-uniform, the PWM generator 230 may use different PWM signals (RPWM_1, RPWM_n) and G light emitting diodes suitable for the R LEDs (RLED_1, ..., RLED_n). Different PWM signals GPWM_1, GPWM_n suitable for (GLED_1, ..., GLED_n) and different PWM signals (BPWM_1, ..., BWWM_n) suitable for B light emitting diodes (BLED_1, ..., BLED_n) may be provided, respectively. .

In this case, when different driving currents are provided to each of the R, G, and B light emitting diodes, different driving currents are provided to all of the R, G, and B light emitting diodes, or at least one of the R, G, and B light emitting diodes is provided. Different driving currents may be provided only for each.

  The operation of the backlight driving circuit having the above configuration will be described in more detail as follows.

In an embodiment of the present invention, one frame includes three subframes, that is, an R subframe for driving an R backlight, a G subframe for driving a G backlight, a B subframe for driving a B backlight, and R, Assume that G and B backlights are sequentially driven for one frame.

Accordingly, the driving current generator 210 generates a driving current, for example, a forward driving current RIf of 20 mA in the R light emitting diode RLED in the R subframe. In this case, an LED control signal LED_CTRL in an on or off state is applied to the LED controller 220 to drive the R backlight 201. Accordingly, the LED controller 220 generates an output signal for driving the R backlight 201 among the R, G, and B backlights 200 to the PWM generator 230.

In the exemplary embodiment of the present invention, the R backlight 201 uses one R light emitting diode, and a current of 20 mA is provided from the driving current generator 210.

Accordingly, the PWM generator 230 generates a PWM signal RPWM for driving the R backlight 201 through the output terminal R_OUT by the output signal provided from the LED controller 320. Therefore, the R backlight 201 has a corresponding forward driving current (RIf) applied to the anode of the light emitting diode (RLED) and a driving current corresponding to the corresponding PWM signal (RPWM) applied to the cathode of the light emitting diode (RLED). And flows, thereby emitting light of R color having a predetermined brightness and chromaticity.

Subsequently, the driving current generator 210 generates a driving current, for example, a forward driving current GIf of 17 mA in the G backlight 202 in the G subframe. In this case, an LED control signal LED_CTRL in an on or off state is applied to the LED controller 220 to drive the G backlight 202. Accordingly, the LED controller 220 generates an output signal for driving the G backlight among the R, G, and B backlights to the PWM generator 230.

Therefore, the PWM generator 230 generates a PWM signal GPWM for driving the G backlight 202 by the output signal provided from the LED controller 220 through the output terminal G_OUT. Therefore, the G backlight 202 corresponds to a corresponding forward drive current GIf applied to the anode of the light emitting diode GLED and a drive current corresponding to a corresponding PWM signal GPWM applied to the cathode of the light emitting diode GLED. Is caused to emit light of G color having a predetermined brightness and chromaticity.

Finally, the driving current generator 210 generates a driving current, for example, a forward driving current BIf of 18 mA in the B backlight 203 in the B subframe. In this case, an LED control signal LED_CTRL in an on or off state for driving the B backlight 203 is applied to the LED controller 220. Accordingly, the LED controller 220 generates an output signal for driving the B backlight 203 among the R, G, and B backlights to the PWM generator 230.

Therefore, the PWM generator 230 generates a PWM signal BPWM for driving the B backlight 203 through the output terminal B_OUT by the output signal provided from the LED controller 220. Therefore, the B backlight 203 corresponds to a corresponding forward driving current BIf applied to the anode of the light emitting diode BLED and a driving current corresponding to the corresponding PWM signal BPWM applied to the cathode of the light emitting diode BLED. Is caused to emit light of B color having a predetermined brightness and chromaticity.

Therefore, the forward driving currents (RIf), (GIf), (BIf) of the R. G, B backlights generated from the driving current generator 210 during one frame, and the R, G, generated from the PWM generator 230 Since a driving current corresponding to the PWM signals RPWM, GPWM, and BPWM of the B backlight flows, light having a predetermined brightness and chromaticity is emitted.

In the present invention, one frame is divided into three subframes, and the R, G, and B light emitting diodes are sequentially driven for each subframe. However, one frame is divided into four or more subframes, and the three subframes are R, The G and B light emitting diodes may be sequentially driven, and in the other frame, all of the R, G and B light emitting diodes may be driven, or one or more of the R, G and B light emitting diodes may be driven. Meanwhile, the backlight may be configured of R, G, B, and W light emitting diodes, driving R, G, and B light emitting diodes in three of the four subframes, and configuring a W light emitting diode in the other frame. .

In the exemplary embodiment of the present invention, the R, G, and B LEDs (RLED, GLED, BLED) are controlled to emit light in the order of R, G, and B in each subframe in one frame, but in order to obtain an optimal brightness and chromaticity, the LEDs The light emission order of can be arbitrarily changed. In addition, according to an embodiment of the present invention, one subframe is divided into two sections to select a forward driving current suitable for R, G, and B light emitting diodes in the first section, and the forward driving selected in the first section in the second section. A method of driving each light emitting diode by generating a current is illustrated, but is not necessarily limited thereto.

 Although the above has been described with reference to embodiments of the present invention, those skilled in the art will be able to variously modify and change the present invention without departing from the spirit and scope of the invention as set forth in the claims below. It will be appreciated.

As described above, according to the present invention, the backlight driving circuit stores forward driving currents suitable for each of the R, G, and B light emitting diodes in a register, and also converts PWM values suitable for the R, G, and B light emitting diodes into another register. In addition, since each subframe generates forward driving currents and PWM signals corresponding to R, G, and B light emitting diodes, light having optimal brightness and chromaticity can be emitted as well as efficiency can be increased.

Claims (8)

A backlight driving circuit having at least two backlights emitting light during one frame divided into at least two subframes, wherein the backlights are sequentially driven in a corresponding subframe to emit light of different colors. A driving current generator for providing different driving currents to the backlights so that each backlight emits light having a predetermined brightness; And PWM generator that controls the chromaticity of light emitted from each backlight by providing different PWM signals to each backlight Backlight driving circuit comprising a. The method of claim 1, And said backlight comprises at least two light emitting diodes emitting light of R, G, B and W colors. The method of claim 1, The backlight driving circuit, characterized in that each of the one or more R, G, B backlight. The method of claim 1, And when the backlight is composed of two or more R, G and B backlights, the same driving current is provided to each of the two or more R, G and B backlights from the driving current generator. The method of claim 1, And when the backlight is composed of two or more R, G and B backlights, the same PWM signal is provided from each of the two or more R, G and B backlights from the PWM generator. The method of claim 1, The driving current generating unit is a backlight driving circuit, characterized in that each of the driving current corresponding to the R, G, B backlight is set in advance and stored. The method of claim 1, The PWM generation unit is a backlight driving circuit, characterized in that each of the PWM signal corresponding to the R, G, B backlight is made of a predetermined preset stored. The method of claim 1, And a LED controller for providing a signal for driving only one light emitting diode of the two or more light emitting diodes to the PWM generator according to a control signal for controlling the light emitting diodes. .

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