KR20080049338A - Apparatus and method for driving lcd - Google Patents

Abstract

An apparatus and a method for driving an LCD device are provided to display optimal color on a screen by adjusting full white color displayed by the highest level gray data. An apparatus for driving an LCD(Liquid Crystal Display) device includes a timing controller(310), a switch(320), and a data driver(330). The timing controller receives video data, outputs plural gray data, outputs simultaneously black and white variable gray data, and generates gray control signals. The switch switches gray data excepting the lowest and highest level gray data of the plural gray data, selectively switches the lowest level gray data and the black variable gray data, and selectively switches the highest level gray data and the white variable gray data. The data driver displays gray data switched through the switch in the LCD panel.

Description

Driving apparatus and method of liquid crystal display device {Apparatus and method for driving LCD}

1 is an equivalent circuit diagram of a pixel formed in a general liquid crystal display device.

2 is a configuration diagram of a general liquid crystal display device.

3 is a configuration diagram of a driving device of a conventional liquid crystal display device.

4 is a configuration diagram of a driving device of a liquid crystal display device according to an exemplary embodiment of the present invention.

<Description of Symbols for Main Parts of Drawings>

100: liquid crystal display device 110: liquid crystal display panel

120, 230, 330: data driver 130: gate driver

140: gamma reference voltage generator 150: backlight assembly

160: inverter 170: common voltage generator

180: gate driving voltage generator 190, 220, 310: timing controller

200, 300: driving device of the liquid crystal display 210: frame storage unit

320: switch

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and more particularly, to a driving device and a method of a liquid crystal display device capable of adjusting a full white color displayed by highest level gray data.

A liquid crystal display device displays an image by adjusting light transmittance of liquid crystal cells according to a video signal, and an active matrix type liquid crystal display device in which a switching element is formed for each liquid crystal cell enables active control of the switching element. This is advantageous for video implementation. As the switching element used in the active matrix liquid crystal display device, a thin film transistor (hereinafter referred to as TFT) is mainly used as shown in FIG. 1.

Referring to FIG. 1, an active matrix type liquid crystal display converts digital input data into an analog data voltage based on a gamma reference voltage and supplies it to the data line DL and simultaneously supplies scan pulses to the gate line GL. The liquid crystal cell Clc is charged.

The gate electrode of the TFT is connected to the gate line GL, the source electrode is connected to the data line DL, and the drain electrode of the TFT is connected to the pixel electrode of the liquid crystal cell Clc and one electrode of the storage capacitor Cst. Connected.

The common voltage Vcom is supplied to the common electrode of the liquid crystal cell Clc.

The storage capacitor Cst charges a data voltage applied from the data line DL when the TFT is turned on, thereby maintaining a constant voltage of the liquid crystal cell Clc.

When the scan pulse is applied to the gate line GL, the TFT is turned on to form a channel between the source electrode and the drain electrode so that the voltage on the data line DL is applied to the pixel electrode of the liquid crystal cell Clc. Supply. At this time, the liquid crystal molecules of the liquid crystal cell Clc modulate the incident light by changing the arrangement by the electric field between the pixel electrode and the common electrode.

A configuration of a general liquid crystal display device having pixels having such a structure will be described with reference to FIG. 2.

2 is a configuration diagram of a general liquid crystal display device.

Referring to FIG. 2, in the general liquid crystal display device 100, a thin film transistor for driving the liquid crystal cell Clc at the intersection of the data lines DL1 to DLm and the gate lines GL1 to GLn. (TFT: Thin Film Transistor), a liquid crystal display panel 110, a data driver 120 for supplying data to the data lines DL1 to DLm of the liquid crystal display panel 110, and the liquid crystal display panel 110 A gate driver 130 for supplying scan pulses to the gate lines GL1 to GLn, a gamma reference voltage generator 140 for generating a gamma reference voltage, and supplying the gamma reference voltage to the data driver 120; The backlight assembly 150 for irradiating light to the display panel 110, the inverter 160 for applying an alternating voltage and current to the backlight assembly 150, and the common voltage Vcom are generated to generate a liquid crystal display panel ( Common voltage generator for supplying the common electrode of the liquid crystal cell Clc of 110 The gate 170 and the gate driving voltage generator 180 for generating and supplying the gate high voltage VGH and the gate low voltage VGL to the gate driver 130, the data driver 120 and the gate driver A timing controller 190 for controlling 130.

In the liquid crystal display panel 110, liquid crystal is injected between two glass substrates. The data lines DL1 to DLm and the gate lines GL1 to GLn are orthogonal to the lower glass substrate of the liquid crystal display panel 110. TFTs are formed at intersections of the data lines DL1 to DLm and the gate lines GL1 to GLn. The TFT supplies the data on the data lines DL1 to DLm to the liquid crystal cell Clc in response to the scan pulse. The gate electrodes of the TFTs are connected to the gate lines GL1 to GLn, and the source electrodes of the TFTs are connected to the data lines DL1 to DLm. The drain electrode of the TFT is connected to the pixel electrode of the liquid crystal cell Clc and the storage capacitor Cst.

The TFT is turned on in response to the scan pulse supplied to the gate terminal via the gate lines GL1 to GLn. When the TFT is turned on, video data on the data lines DL1 to DLm is supplied to the pixel electrode of the liquid crystal cell Clc.

The data driver 120 supplies data to the data lines DL1 to DLm in response to the data driving control signal DDC supplied from the timing controller 190. Here, the data driver 120 samples and latches the digital video data RGB supplied from the timing controller 190, and then the liquid crystal display panel 110 based on the gamma reference voltage supplied from the gamma reference voltage generator 140. In the liquid crystal cell Clc of FIG. 1, the grayscale is converted into an analog data voltage that can express gray levels, and is supplied to the data lines DL1 to DLm.

The gate driver 130 sequentially generates scan pulses, that is, gate pulses, in response to the gate driving control signal GDC and the gate shift clock GSC supplied from the timing controller 190 to generate the gate lines GL1 to GLn. Feed the fields. In this case, the gate driver 130 determines the high level voltage and the low level voltage of the scan pulse based on the gate high voltage VGH and the gate low voltage VGL supplied from the gate driving voltage generator 180.

The gamma reference voltage generator 140 receives a high potential power supply voltage VDD to generate a positive gamma reference voltage and a negative gamma reference voltage and output the same to the data driver 120.

The backlight assembly 150 is disposed on the rear surface of the liquid crystal display panel 110 and emits light by an AC voltage and a current supplied from the inverter 160 to irradiate light to each pixel of the liquid crystal display panel 110.

The inverter 160 converts the square wave signal generated therein into a triangular wave signal and compares the triangular wave signal with a DC power supply voltage (VCC) supplied from the system to generate a burst dimming signal proportional to the comparison result. . When a burst dimming signal determined according to an internal square wave signal is generated, a driving IC (not shown) for controlling the generation of AC voltage and current in the inverter 160 is supplied to the backlight assembly 150 according to the burst dimming signal. Control the generation of alternating voltage and current.

The common voltage generator 170 receives the high potential power voltage VDD to generate the common voltage Vcom and supplies the common voltage Vcom to the common electrodes of the liquid crystal cells Clc of each pixel of the liquid crystal display panel 110.

The gate driving voltage generator 180 receives the high potential power voltage VDD to generate the gate high voltage VGH and the gate low voltage VGL to supply the gate driver 130 to the gate driver 130. Here, the gate driving voltage generation unit 180 generates a gate high voltage VGH that is greater than or equal to the threshold voltage of the TFTs provided in each pixel of the liquid crystal display panel 110, and the gate low voltage that is less than or equal to the threshold voltage of the TFT. VGL). The gate high voltage VGH and the gate low voltage VGL generated in this way are used to determine the high level voltage and the low level voltage of the scan pulse generated by the gate driver 130, respectively.

The timing controller 190 supplies the digital video data RGB supplied from the system to the data driver 120 and controls the data driving by using the horizontal / vertical synchronization signals H and V according to the clock signal CLK. The signal DDC and the gate driving control signal GDC are generated and supplied to the data driver 120 and the gate driver 130, respectively. The data driving control signal DDC includes a source shift clock SSC, a source start pulse SSP, a polarity control signal POL, a source output enable signal SOE, and a gate driving control signal GDC. ) Includes a gate start pulse (GSP) and a gate output enable (GOE).

In general liquid crystal display having such a configuration and function, when the data changes from one level to another level due to the slow response speed when the video is implemented, the corresponding display luminance does not reach the desired luminance and thus does not express the desired color and luminance. I can't. As a result, the motion blurring phenomenon occurs in the liquid crystal display, and the display quality is degraded due to the decrease in the contrast ratio.

In order to solve the slow response speed of the liquid crystal display, U.S. Patent No. 5,495,265 and PCT International Publication No. WO 99/09967 use a lookup table to modulate the data depending on whether or not the data is changed (hereinafter referred to as 'high speed driving'). Is proposed.

A driving device of the conventional liquid crystal display device to which the high speed driving method is applied will be described with reference to FIG. 3.

3 is a configuration diagram of a driving device of a conventional liquid crystal display device.

Referring to FIG. 3, the driving apparatus 200 of the conventional LCD device includes a frame storage unit 210 for storing a previous frame of an input current frame, a timing controller 220 for controlling high-speed driving of data, The data driver 230 may drive the gray data V0 to V255 from the timing controller 220 to the liquid crystal display panel 110 under the control of the timing controller 220. Here, V0 to V255 are 0 gray data to 255 gray data, respectively. V0 is the lowest level gray data among the gray data implemented in the liquid crystal display panel 110, and V255 is the highest level gray data among the gray data implemented in the liquid crystal display panel 110.

The frame storage unit 210 temporarily stores the previous frame and outputs the timing frame to the timing controller 220, where the previous frame is transmitted to the timing controller 220 simultaneously with the current frame.

The timing controller 220 compares the inputted previous frame with the most significant bit data MSB of the current frame, and if there is a change between the most significant bit data MSB, selects a corresponding modulation data Mdata from a predetermined lookup table and modulates it. The data Mdata and the input real data Rdata are sequentially output to the data driver 230. The timing controller 220 controls driving timing of the data driver 230.

The data driver 230 drives the gray data V0 to V255 corresponding to the actual data Rdata and the modulation data Mdata sequentially input to the liquid crystal display panel 110 under the control of the timing controller 220. Let's do it.

Since the color displayed on the liquid crystal display driven by the conventional driving device of the liquid crystal display is largely dependent on the color filter and the backlight, a desired color is sensed when the thickness of the RGB color filters is uniformly exposed in the exposure process. Is not displayed, and this causes a color difference between the desired color and the color actually displayed.

In addition, since the driving device of the conventional liquid crystal display cannot implement gray data higher than 255-level gray data, even if the full white color displayed by the 255-level gray data is not displayed in the desired full white color, it cannot be improved. I have a problem.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a driving apparatus and method of a liquid crystal display device capable of adjusting the full white color displayed by the highest level gray data.

SUMMARY OF THE INVENTION An object of the present invention is to provide a driving apparatus and method for a liquid crystal display device capable of displaying the best color on a screen by adjusting the full white color displayed by the highest level gray data.

In order to achieve the above object, the driving apparatus of the liquid crystal display according to the exemplary embodiment of the present invention receives video data, outputs a plurality of gray data, and simultaneously outputs black variable gray data and white variable gray data. A timing controller generating a gray control signal; In response to the gray control signal, switching all gray data except the lowest level gray data and the highest level gray data among the plurality of gray data, selectively switching the lowest level gray data and the black variable gray data, A switch for selectively switching the highest level gray data and the white variable gray data; And a data driver for implementing gray data switched through the switch in the liquid crystal display panel.

A method of driving a liquid crystal display according to an exemplary embodiment of the present invention includes generating black variable gray data and white variable gray data while generating a plurality of gray data while receiving video data, and generating a gray control signal. ; In response to the gray control signal, switching all gray data except the lowest level gray data and the highest level gray data among the plurality of gray data, selectively switching the lowest level gray data and the black variable gray data, Selectively switching the highest level gray data and the white variable gray data; And implementing the switched gray data on the liquid crystal display panel.

According to another aspect of the present invention, there is provided a driving apparatus of a liquid crystal display, comprising: a timing controller configured to receive video data, output a plurality of gray data, output white variable gray data, and generate a gray control signal; A switch for switching all gray data except the highest level gray data among the plurality of gray data and selectively switching the highest level gray data and the white variable gray data in response to the gray control signal; And a data driver for implementing gray data switched through the switch in the liquid crystal display panel.

According to another aspect of the present invention, there is provided a method of driving a liquid crystal display device, the method comprising: generating a plurality of gray data while receiving video data, generating white variable gray data, and generating a gray control signal; In response to the gray control signal, switching all gray data except the highest level gray data among the plurality of gray data, and selectively switching the highest level gray data and the white variable gray data; And implementing the switched gray data on the liquid crystal display panel.

Hereinafter, with reference to the accompanying drawings will be described in detail a preferred embodiment of the present invention.

4 is a configuration diagram of a driving device of a liquid crystal display according to an exemplary embodiment of the present invention.

Referring to FIG. 4, the driving device 300 of the liquid crystal display according to the present invention controls the timing of supplying gray data and displays the color displayed by the lowest level gray data V0 and the highest level gray data V255. The timing controller 310 to adjust, the switch 320 to switch the gray data (V_V0, V0 to V255, V_V255) from the timing controller 310, and the gray data (V_V0 switched through the switch 320) Or a data driver 330 for implementing V0, V1 to V254, V255, or V_V255 on the liquid crystal display panel 110.

The timing controller 310 receives RGB video data from the system and outputs a plurality of gray data V0 to V255 to the switch 320, and simultaneously outputs the black variable gray data V_V0 and the white variable gray data V_V255. A gray control signal GVS controlling the output of the gray data V_V0, V0 to V255, and V_V255 is generated and output to the switch 320. Here, the black variable gray data V_V0 has a gray level lower than the lowest level gray data V0, and the white variable gray data V_V255 has a gray level higher than the highest level gray data V255.

The timing controller 310 compares the level of the lowest level gray data V0 and the predetermined reference black gray data Vbref among the plurality of gray data V0 to V255 corresponding to the input RGB data, according to a comparison result. The gray control signal GVS instructing to selectively switch the black variable gray data V_V0 or the lowest level gray data V0 is output to the switch 320. As a result of the comparison, when the level of the lowest level gray data V0 is not higher than the level of the predetermined reference black gray data Vbref, the timing controller 310 determines the lowest of the black variable gray data V_V0 and the lowest level gray data V0. The gray control signal GVS instructing to switch the level gray data Vo is output to the switch 320. As a result of the comparison, when the level of the lowest level gray data V0 is higher than the level of the predetermined reference black gray data Vbref, the timing controller 310 changes the black among the black variable gray data V_V0 and the lowest level gray data V0. The gray control signal GVS instructing to switch the gray data V_V0 is output to the switch 320.

The timing controller 310 compares the level of the highest level gray data V255 and the predetermined reference white gray data Vwref among the gray data V0 to V255 corresponding to the input RGB data, according to a comparison result. The gray control signal GVS instructing to selectively switch the white variable gray data V_V255 or the highest level gray data V255 is output to the switch 320. As a result of the comparison, when the level of the highest level gray data V255 is not lower than the level of the predetermined reference white gray data Vwref, the timing controller 310 is the highest among the white variable gray data V_V255 and the highest level gray data V255. The gray control signal GVS instructing to switch the level gray data V255 is output to the switch 320. As a result of the comparison, when the level of the highest level gray data V255 is lower than the level of the predetermined reference white gray data Vwref, the timing controller 310 determines whether the white level among the white variable gray data V_V255 and the highest level gray data V255 is white. The gray control signal GVS indicating to switch the variable gray data V_V255 is output to the switch 320.

In addition, the timing controller 310 generates a data driving control signal DDC using the horizontal / vertical synchronization signals H and V from the system according to the clock signal CLK from the system to generate the data driving control signal DDC. Supply. The data driving control signal DDC includes a source shift clock SSC, a source start pulse SSP, a polarity control signal POL, a source output enable signal SOE, and the like.

The switch 320 is the lowest level gray data V0 and the highest level gray among the gray data V0 to V255 output from the timing controller 310 in response to the gray control signal GVS from the timing controller 310. All gray data V1 to V254 except the data V255 are switched to the data driver 330. The switch 320 selectively switches the lowest level gray data V0 and the black variable gray data V_V0 from the timing controller 310 to the data driver 330 in response to the gray control signal GVS. The highest level gray data V255 and the white variable gray data V_V255 from the timing controller 310 are selectively switched to the data driver 330.

More specifically, under the condition that the level of the lowest level gray data V0 is not higher than the level of the predetermined reference black gray data Vbref, the switch 320 responds to the gray variable gray data (VS) in response to the gray control signal GVS. Among the V_V0 and the lowest level gray data V0, the lowest level gray data V0 is switched to the data driver 330. On the contrary, in a condition where the level of the lowest level gray data V0 is higher than the level of the predetermined reference black gray data Vbref, the switch 320 responds to the gray control signal GVS and the black variable gray data V_V0. ) And the black variable gray data V_V0 among the lowest level gray data V0 is switched to the data driver 330.

In the condition that the level of the highest level gray data V255 is not lower than the level of the predetermined reference white gray data Vwref, the switch 320 is the highest with the white variable gray data V_V255 in response to the gray control signal GVS. The highest level gray data V255 among the level gray data V255 is switched to the data driver 330. On the contrary, in a condition where the level of the highest level gray data V255 is lower than the level of the predetermined reference white gray data Vwref, the switch 320 responds to the gray control signal GVS and the white variable gray data V_V255. And the white variable gray data V_V255 among the highest level gray data V255 are switched to the data driver 330.

The data driver 330 displays the gray data V_V0 or V0, V1 to V254, V255 or V_V255 switched through the switch 320 in response to the data driving control signal DDC from the timing controller 310. The panel 110 is implemented.

Here, when the black variable gray data V_V0 is implemented in the liquid crystal display panel 110 instead of the lowest level gray data V0, the full black color displayed by the lowest level gray data V0 is further increased. Darkens. When the desired full black color is not displayed due to a cause caused by a color filter, the black variable gray data V_V0 having a lower level than the lowest level gray data V0 is implemented to display the desired full black color.

When the white variable gray data V_V255 is implemented in the liquid crystal display panel 110 instead of the highest level gray data V255, the full white color displayed by the highest level gray data V255 becomes brighter. When the desired full white color is not displayed due to a cause caused by a color filter, the white variable gray data V_V255 having a higher level than the highest level gray data V255 is implemented to display the desired full white color.

As described above, the present invention discloses a technique for improving a full black color and a full white color at the same time, but is not limited thereto. As another embodiment, the present invention may disclose only a technique for improving full white color, in which case the highest level gray data V255 and the white variable gray data V_V255 are alternatively implemented, but the black variable gray data ( V_V0) is not implemented.

As described above, according to the present invention, the best color can be displayed on the screen by adjusting the full white color displayed by the highest level gray data.

Although the technical spirit of the present invention has been described in detail according to the above-described preferred embodiment, it should be noted that the above-described embodiment is for the purpose of description and not of limitation. In addition, those skilled in the art will understand that various embodiments are possible within the scope of the technical idea of the present invention.

Claims (26)

A timing controller configured to receive video data, output a plurality of gray data, output black variable gray data and white variable gray data, and generate a gray control signal; In response to the gray control signal, switching all gray data except the lowest level gray data and the highest level gray data among the plurality of gray data, selectively switching the lowest level gray data and the black variable gray data, A switch for selectively switching the highest level gray data and the white variable gray data; And Data driver for implementing gray data switched through the switch to the liquid crystal display panel Driving device for a liquid crystal display device comprising a. The method of claim 1, The black variable gray data has a gray level lower than the lowest level gray data, And the white variable gray data has a gray level higher than the highest level gray data. The method of claim 1, The timing controller compares the level of the lowest level gray data with a predetermined reference black gray data and outputs the gray control signal instructing to selectively switch the black variable gray data or the lowest level gray data according to a comparison result. A drive device for a liquid crystal display device, characterized in that outputted by a switch. The method of claim 3, wherein If the level of the lowest level gray data is not higher than the level of the predetermined reference black gray data, the timing controller instructs to switch the lowest level gray data among the black variable gray data and the lowest level gray data. And a control signal is output to the switch. The method of claim 3, wherein If the level of the lowest level gray data is higher than the level of the predetermined reference black gray data, the timing controller instructs to switch the black variable gray data among the black variable gray data and the lowest level gray data. And a signal is outputted to the switch. The method of claim 1, The timing controller compares the level of the highest level gray data with the predetermined reference white gray data and supplies the gray control signal instructing to selectively switch the white variable gray data or the highest level gray data according to a comparison result. And a liquid crystal display device for driving the switch. The method of claim 6, If the level of the highest level gray data is not lower than the level of the predetermined reference white gray data, the timing controller instructs to switch the highest level gray data among the white variable gray data or the highest level gray data. And a control signal is output to the switch. The method of claim 6, If the level of the highest level gray data is lower than the level of the predetermined reference white gray data, the timing controller instructs to switch the white variable gray data among the white variable gray data and the highest level gray data. And a control signal is output to the switch. Generating a plurality of gray data and generating black variable gray data and white variable gray data at the same time as receiving video data, and generating a gray control signal; In response to the gray control signal, switching all gray data except the lowest level gray data and the highest level gray data among the plurality of gray data, selectively switching the lowest level gray data and the black variable gray data, Selectively switching the highest level gray data and the white variable gray data; And Implementing the switched gray data on a liquid crystal display panel; Method of driving a liquid crystal display comprising a. The method of claim 9, The black variable gray data has a gray level lower than the lowest level gray data, And the white variable gray data has a gray level higher than the highest level gray data. The method of claim 9, In the gray control signal generation step, And comparing the level of the lowest level gray data with a predetermined reference black gray data to generate the gray control signal instructing to selectively switch the black variable gray data or the lowest level gray data according to a comparison result. A driving method of a liquid crystal display device. The method of claim 11, If the level of the lowest level gray data is not higher than the level of the predetermined reference black gray data, the gray control signal instructing to switch the lowest level gray data among the black variable gray data and the lowest level gray data is generated. A driving method of a liquid crystal display device, characterized in that. The method of claim 11, When the level of the lowest level gray data is higher than the level of the predetermined reference black gray data, the gray control signal for instructing to switch the black variable gray data among the black variable gray data and the lowest level gray data is generated. A method of driving a liquid crystal display device, characterized in that. The method of claim 9, In the gray control signal generation step, And comparing the level of the highest level gray data with the predetermined reference white gray data to generate the gray control signal instructing to selectively switch the white variable gray data or the highest level gray data according to a comparison result. A method of driving a liquid crystal display device. The method of claim 14, When the level of the highest level gray data is not lower than the level of the predetermined reference white gray data, the gray control signal instructing to switch the highest level gray data among the white variable gray data or the highest level gray data is generated. A driving method of a liquid crystal display device, characterized in that. The method of claim 14, When the level of the highest level gray data is lower than the level of the predetermined reference white gray data, the gray control signal instructing to switch the white variable gray data among the white variable gray data and the highest level gray data is generated. A driving method of a liquid crystal display device, characterized in that. A timing controller configured to receive video data, output a plurality of gray data, output white variable gray data, and generate a gray control signal; A switch for switching all gray data except the highest level gray data among the plurality of gray data and selectively switching the highest level gray data and the white variable gray data in response to the gray control signal; And Data driver for implementing gray data switched through the switch to the liquid crystal display panel Driving device for a liquid crystal display device comprising a. The method of claim 17, And the white variable gray data has a gray level higher than the highest level gray data. The method of claim 17, The timing controller compares the level of the highest level gray data with the predetermined reference white gray data and supplies the gray control signal instructing to selectively switch the white variable gray data or the highest level gray data according to a comparison result. And a liquid crystal display device for driving the switch. The method of claim 19, If the level of the highest level gray data is not lower than the level of the predetermined reference white gray data, the timing controller instructs to switch the highest level gray data among the white variable gray data or the highest level gray data. And a gray control signal is outputted to the switch. The method of claim 19, If the level of the highest level gray data is lower than the level of the predetermined reference white gray data, the timing controller instructs to switch the white variable gray data among the white variable gray data and the highest level gray data. And a control signal is output to the switch. Generating video data and generating white variable gray data at the same time, and generating a gray control signal; In response to the gray control signal, switching all gray data except the highest level gray data among the plurality of gray data, and selectively switching the highest level gray data and the white variable gray data; And Implementing the switched gray data on a liquid crystal display panel; Method of driving a liquid crystal display comprising a. The method of claim 22, And the white variable gray data has a gray level higher than the highest level gray data. The method of claim 22, In the gray control signal generation step, And comparing the level of the highest level gray data with the predetermined reference white gray data to generate the gray control signal instructing to selectively switch the white variable gray data or the highest level gray data according to a comparison result. A method of driving a liquid crystal display device. The method of claim 24, When the level of the highest level gray data is not lower than the level of the predetermined reference white gray data, the gray control signal instructing to switch the highest level gray data among the white variable gray data or the highest level gray data is generated. A driving method of a liquid crystal display device, characterized in that. The method of claim 24, When the level of the highest level gray data is lower than the level of the predetermined reference white gray data, the gray control signal instructing to switch the white variable gray data among the white variable gray data and the highest level gray data is changed. A driving method of a liquid crystal display device, characterized in that generated.

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