KR20050063567A - Method and apparatus for driving liquid crystal display device - Google Patents

Abstract

The present invention relates to a method and apparatus for driving a liquid crystal display device to reduce heat generation and power consumption of a driving circuit.

The method and apparatus for driving the liquid crystal display determine the type of the input image, and if the input image is a video, modulate the data of the input image into preset modulation data, and if the still image is not, do not modulate the data of the input image.

Description

TECHNICAL AND APPARATUS FOR DRIVING LIQUID CRYSTAL DISPLAY DEVICE}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and more particularly, to a method and apparatus for driving a liquid crystal display device to reduce heat generation and power consumption of a driving circuit.

Liquid crystal displays display an image by adjusting light transmittance of liquid crystal cells according to a video signal.

Among the liquid crystal display devices, an active matrix type liquid crystal display device in which switching elements are formed for each liquid crystal cell is advantageous in implementing a moving image because active control of the switching element is possible. As a switching element used in an active matrix type liquid crystal display device, a thin film transistor (hereinafter, referred to as TFT) is mainly used.

As the liquid crystal display device can be seen in Equations 1 and 2, the response speed is slow due to the inherent viscosity and elasticity of the liquid crystal.

Where τr is the rising time when voltage is applied to the liquid crystal, Va is the applied voltage, VF is the Freederick Transition Voltage at which the liquid crystal molecules start the tilt motion, and d is the liquid crystal. The cell gap of the cell, (gamma) means rotational viscosity of liquid crystal molecules, respectively.

Here, τf denotes a falling time during which the liquid crystal is restored to its original position by the elastic restoring force after the voltage applied to the liquid crystal is turned off, and K denotes an elastic modulus inherent to the liquid crystal.

Although the liquid crystal response speed of the TN mode (Twisted Nematic mode), which has been the most commonly used liquid crystal display device, can vary depending on the physical properties of the liquid crystal material and the cell gap, the rising time is 20-80 ms and the polling time is generally 20-30 ms. The response speed of the liquid crystal is longer than one frame period (NTSC: 16.67ms). For this reason, as shown in FIG. 1, since the voltage charged in the liquid crystal cell reaches the next voltage, the motion blurring phenomenon occurs in which the screen is blurred in the video.

Referring to FIG. 1, in the conventional LCD, when the data VD changes from one level to another level due to a slow response speed, the corresponding display luminance BL does not reach the desired luminance. Will not be represented. As a result, the motion blurring phenomenon appears in the moving image, and the image quality is deteriorated due to the decrease in the contrast ratio.

In order to solve the slow response speed of the liquid crystal display device, U.S. Patent No. 5,495,265 and PCT International Publication No. WO 99/05567 use a lookup table to modulate the data according to whether or not the data is changed (hereinafter, 'high speed driving'). Has been proposed. This high speed driving method modulates data in the same principle as in FIG. 2.

Referring to FIG. 2, the high speed driving method modulates the input data VD into preset modulation data MVD and applies the modulation data MVD to the liquid crystal cell to obtain a desired luminance MBL. This high-speed driving method uses Equation 1 based on whether or not the data changes so as to obtain a desired luminance corresponding to the luminance value of the input data within one frame period. To make it larger. Therefore, the liquid crystal display device using the high speed driving method compensates for the late response speed of the liquid crystal by modulating the data value, thereby alleviating the motion blur phenomenon in the video.

In other words, the high speed driving method compares data between the previous frame and the current frame and modulates the data of the current frame with preset modulation data if there is a change between the data. The high speed drive device in which the high speed drive method is implemented may be implemented as shown in FIG. 3.

Referring to FIG. 3, the high speed drive device includes first and second frame memories 43a for storing data from the data input line 42 and a modulator 44 for modulating the data.

The first and second frame memories 43a and 43b alternately store data in units of frames in accordance with the pixel clock, and alternately output the stored data to the modulator 44, that is, the n-1 th frame data ( Fn-1) is supplied.

The modulator 44 compares the n th frame data Fn from the data input line 43 with the n-1 th frame data Fn from the first and second frame memories 43a and 43b and compares them. The modulation data (MRGB) corresponding to is selected from a lookup table shown in Table 1 to modulate the data. The lookup table is stored in a read only memory (ROM).

division 0 One 2 3 4 5 6 7 8 9 10 11 12 13 14 15 0 0 2 3 4 5 6 7 9 10 12 13 14 15 15 15 15 One 0 One 3 4 5 6 7 8 10 12 13 14 15 15 15 15 2 0 0 2 4 5 6 7 8 10 12 13 14 15 15 15 15 3 0 0 One 3 5 6 7 8 10 11 13 14 15 15 15 15 4 0 0 One 3 4 6 7 8 9 11 12 13 14 15 15 15 5 0 0 One 2 3 5 7 8 9 11 12 13 14 15 15 15 6 0 0 One 2 3 4 6 8 9 10 12 13 14 15 15 15 7 0 0 One 2 3 4 5 7 9 10 11 13 14 15 15 15 8 0 0 One 2 3 4 5 6 8 10 11 12 14 15 15 15 9 0 0 One 2 3 4 5 6 7 9 11 12 13 14 15 15 10 0 0 One 2 3 4 5 6 7 8 10 12 13 14 15 15 11 0 0 One 2 3 4 5 6 7 8 9 11 13 14 15 15 12 0 0 One 2 3 4 5 6 7 8 9 10 12 14 15 15 13 0 0 One 2 3 3 4 5 6 7 8 10 11 13 15 15 14 0 0 One 2 3 3 4 5 6 7 8 9 11 12 14 15 15 0 0 0 One 2 3 3 4 5 6 7 8 9 11 13 15

In Table 1, the leftmost column is data of the previous frame Fn-1, and the uppermost row is data of the current frame Fn.

During the nth frame period, the nth frame data Fn is stored in the first frame memory 43a and supplied to the modulator 44 at the same pixel clock as indicated by the solid line. At the same time, the second frame memory 43b supplies the n−1 th frame data Fn−1 to the modulator 44 during the n th frame period.

In contrast, during the n + 1 th frame period, the current n + 1 th frame data (Fn + 1) is stored in the second frame memory 43b at the same time as the dotted pixel clock as shown by the dotted line. Supplied to. At the same time, the first frame memory 43b supplies the nth frame data Fn to the modulator 44 during the n + 1th frame period.

However, since the high speed driving device modulates data for all input data, there is a disadvantage in that a large amount of heat is generated and power consumption is high in a memory and an integrated circuit.

Accordingly, an object of the present invention is to provide a method and apparatus for driving a liquid crystal display device to reduce heat generation and power consumption of a driving circuit.

In order to achieve the above object, the driving method of the liquid crystal display device according to an embodiment of the present invention comprises the steps of determining the type of the input image; Modulating data of the input image into preset modulation data if the input image is a moving image as a result of the image determination; Bypassing data of the input image when the input image is a still image as a result of the image determination.

The method of driving the liquid crystal display device comprises the steps of: receiving a user command; The method may further include determining whether to modulate the data according to the user command.

The modulating of the data may include delaying the data of the input image by one frame period by storing and outputting the data of the input image in a frame memory; And comparing the current frame data of the input image with the delayed previous frame data and modulating the current frame data using the modulation data set based on the change of the current frame data and the previous frame data.

The driving method of the liquid crystal display device may further include not performing data comparison if the input image is a still image.

The method of driving the liquid crystal display device comprises the steps of: receiving a user command; The method may further include determining whether to compare the data according to the user command.

According to another exemplary embodiment of the present invention, there is provided a method of driving a liquid crystal display device, including determining a type of an input image; Modulating the data of the input image into preset modulation data if the input image is a television image as a result of the image determination; And bypassing the data of the input image if the input image is a computer image as a result of the image determination.

An apparatus for driving a liquid crystal display according to an exemplary embodiment of the present invention includes an image determining unit which determines a type of an input image; A modulator configured to modulate data of the input image into preset modulation data when the input image is determined to be a moving image by the image determining unit; And a selector for selecting data of the input image when the input image is a still image by the image determining unit and selecting data modulated by the modulator when the input image is a moving image.

The image determining unit generates a control signal indicating a type of the input projection.

The driving device of the liquid crystal display device further includes a mode selection unit for receiving a user command.

The image determiner determines whether to modulate the data in response to a signal from the mode selector.

The liquid crystal display driving device includes: a frame memory for delaying data of the input image by a frame period; And a memory controller for controlling data input / output of the frame memory in response to the control signal.

The modulator compares the current frame data of the input image with the delayed previous frame data and modulates the current frame data using the modulation data set based on the change of the current frame data and the previous frame data.

The frame memory supplies the previous frame data in the moving image to the modulator under the control of the memory controller while the frame memory does not supply the previous frame data in the still image to the modulator.

The driving device of the liquid crystal display device further includes a data switch for forming a transmission path of the current frame data supplied to the modulator in the moving image and blocking the transmission path of the data in the still image in response to the control signal.

The selector outputs data modulated by the modulator in the moving image and the current frame data unmodulated in the still image in response to the control signal.

The driving apparatus of the liquid crystal display device includes a liquid crystal display panel in which liquid crystal cells are arranged in a matrix type and a plurality of data lines and a plurality of gate lines intersect with each other; A data driver configured to supply the modulated data and the unmodulated data to the data lines; A gate driver supplying scan pulses to gate lines of the liquid crystal display panel; And a timing controller configured to supply the modulated data and the unmodulated data to the data driver and to control the data driver and the gate driver.

In accordance with another aspect of the present invention, there is provided a driving apparatus of a liquid crystal display device comprising: an image determining unit determining a type of an input image; A modulator for modulating data of the input image into preset modulation data when the input determining unit determines that the input image is a television image; And a selector for selecting data of the input image when the input image is determined to be a computer image and selecting data modulated by the modulator when the input image is a television image.

Other objects and features of the present invention in addition to the above objects will become apparent from the description of the embodiments with reference to the accompanying drawings.

Hereinafter, exemplary embodiments of the present invention will be described with reference to FIGS. 4 to 7.

Referring to FIG. 4, in the liquid crystal display according to the exemplary embodiment of the present invention, a liquid crystal display panel in which a data line 55 and a gate line 56 cross each other and a TFT for driving the liquid crystal cell Clc is formed at an intersection thereof. 57, a modulator 52 for modulating digital video data RGB to preset modulation data MRGB only in a moving picture or a television image, and a data driver for data (RGB or MRGB) from the modulator 52. A timing controller 51 for supplying to the 53 and controlling the data driver 53 and the gate driver 54 is provided.

In the liquid crystal display panel 57, liquid crystal is injected between two glass substrates, and the data lines 55 and the gate lines 56 are orthogonal to each other on the lower glass substrate. The TFT formed at the intersection of the data lines 55 and the gate lines 56 causes the liquid crystal cell Clc to supply data from the data lines 55 in response to a scan pulse from the gate line 56. do. For this purpose, the gate electrode of the TFT is connected to the gate line 56 and the source electrode is connected to the data line 55. The drain electrode of the TFT is connected to the pixel electrode of the liquid crystal cell Clc. In addition, a storage capacitor Cst is formed on the lower glass substrate of the liquid crystal display panel 57 to maintain the voltage of the liquid crystal cell Clc. The storage capacitor Cst may be formed between the liquid crystal cell Clc and the front gate line 56 or may be formed between the liquid crystal cell Clc and a separate common line.

The modulator 52 analyzes the input image and inputs the input digital video data using the modulation data MRGB set under the conditions of Equation 3 to 5 in consideration of the change in the data value between the previous frame and the current frame in the moving image or TV image. Modulates (RGB). The modulation data MRGB is listed in a lookup table stored in an electrically erased and programmable ROM (EEPROM).

Fn (RGB) <Fn-1 (RGB) ---> Fn (MRGB) <Fn (RGB)

Fn (RGB) = Fn-1 (RGB) ---> Fn (MRGB) = Fn (RGB)

Fn (RGB)> Fn-1 (RGB) ---> Fn (MRGB)> Fn (RGB)

As shown in Equations 3 to 5, the modulation data MRGB is larger than the current frame Fn when the pixel data value of the same pixel is larger in the current frame Fn than in the previous frame Fn-1. On the other hand, if the value is smaller in the current frame Fn than the previous frame Fn-1, the value is smaller than the current frame Fn. The modulation data MRGB is set to the same value as the current frame Fn if the pixel data value of the same pixel is the same in the previous frame Fn-1 and the current frame Fn.

The timing controller 51 controls the gate driver 54 by using the vertical / horizontal synchronization signals V and H, the pixel clock CLK, and a data enable signal Data Enable (DE) indicating a period in which data exists. A gate control signal GDC for controlling and a data control signal DDC for controlling the data driver 53 are generated. The timing controller 51 samples the data RGB or MRGB from the modulator 52 in accordance with the pixel clock CLK in the data enable signal DE section and converts the data RGB or MRGB into the data driver. Supply to 53.

The data driver 53 stores the shift register, a register for temporarily storing data (RGB or MRGB) from the timing controller 51, and stores data one line by one line in response to a clock signal from the shift register. A latch for outputting data at the same time, a digital / analog converter for selecting an analog positive / negative gamma compensation voltage corresponding to the digital data value from the latch, and a data line to which a positive / negative gamma compensation voltage is supplied. 55) and a multiplexer for selecting and an output buffer connected between the multiplexer and the data line. The data driver 53 receives data RGB or MRGB from the timing controller 51 and receives the data RGB or MRGB from the data lines of the liquid crystal display panel 57 under the control of the timing controller 51. 55).

The gate driver 54 shifts the shift register which sequentially generates scan pulses in response to the gate control signal GDC from the timing controller 51, and the swing width of the scan pulses to a level suitable for driving the liquid crystal cell Clc. Level shifter, output buffer, and so on. The gate driver 54 turns on the TFTs connected to the gate line 56 by supplying scan pulses to the gate line 56 so that the pixel voltage of the data, that is, the analog gamma compensation voltage, is supplied. The liquid crystal cells Clc of one horizontal line to be selected are selected. Data generated from the data driver 53 is supplied to the liquid crystal cell Clc of one horizontal line selected by being synchronized with the scan pulse.

5 shows a first embodiment of the modulator 52.

Referring to FIG. 5, the modulator 52 includes a video determining unit 61, a memory controller 62, first and second frame memories 63 and 64, a modulator 65, an EEPROM 66, and a selector ( 67 and a data switch 68.

The video determining unit 61 judges the video by comparing the luminance information of the partial region of the screen between frames without judging the video through the frame-to-frame data comparison for the entire screen. ) To determine whether the video. This video determination method is described in detail in Korean Patent Application No. 2003-0081172 filed by the applicant of the present application. In addition, the video determining unit 61 generates a video / still image indicating signal MV / ST indicating whether the input digital video data RGB is a video. This moving picture / still picture indication signal MV / ST is supplied to the memory controller 62, the selector 65, and the data switch 68.

The memory controller 62 controls the first and second frame memories 63 and 64 according to the moving picture / still picture indication signal MV / ST from the moving picture determining unit 61.

The first and second frame memories 63 and 64 alternately store current frame data RGB (Fn) in a moving image under the control of the memory controller 62, and store the data RGB (Fn) for one frame period. Delay and supply the previous frame data (RGB (Fn-1)) which has already been stored to the modulator 65. The first and second frame memories 62 alternately store the current frame data RGB (Fn) in the still image under the control of the memory controller 62, and delay the data RGB (Fn) by one frame period. It does not output the previous frame data RGB (Fn-1) that has already been stored. That is, the first and second frame memories 62 store only the data RGB (Fn-1) every frame by overwriting the data RGB (Fn) in the still image and transmit the stored data RGB (Fn-1) to the modulator 65. Do not supply

The data switch 68 is a data bus of the current frame data RGB (Fn) connected to the data input terminal of the modulator 65 in response to the moving picture / still picture indicating signal MV / ST from the moving picture determining unit 61. Switch to. This data switch 68 connects the data bus of the current frame data RGB (Fn) connected to the data input terminal of the modulator 65 to supply the current frame data RGB (Fn) to the modulator 65 in the video. On the other hand, in the still image, the data bus is switched to block transmission of the current frame data RGB (Fn) supplied to the modulator 65.

The modulator 65 loads the modulation data lookup table stored in the EEPROM 66 into the internal static random access memory (SRAM) and supplies the current frame data (RGB (Fn)) supplied from the data switch 68. And the current frame data RGB (Fn) are modulated by selecting the modulation data MRGB in accordance with the comparison result of the previous frame data RGB (Fn-1) from the frame memories 63 and 64. The modulator 65 performs data comparison and modulation on the data of the moving image, but no data is supplied from the still image, and no data comparison and modulation is performed on the data of the still image.

The selector 67 outputs data MRGB modulated by the modulator 65 in response to the video / still image indicating signal MV / ST from the video determining unit 61, or the current frame data RGB which is not modulated. (Fn)) is output. The selector 67 supplies the modulation data MRGB from the modulator 65 to the timing controller 51 in the moving picture under the control of the moving picture determining unit 61, while the unmodulated data RGB (Fn) in the still picture is supplied. ) Is supplied to the timing controller 51.

6 shows a second embodiment of the modulator 52. In FIG. 6, components having substantially the same functions as the circuit configuration shown in FIG. 5 are denoted by the same reference numerals and detailed description thereof will be omitted.

Referring to FIG. 6, the modulator 52 may include a video determining unit 71, a memory controller 72, first and second frame memories 63 and 64, a modulator 65, an EEPROM 66, and a selector ( 77, a data switch 78, and a mode selector 69.

The mode selector 69 may be implemented as a receiving circuit of an external switch unit, an on screen display (OSD), or a remote controller. The mode selector 69 supplies the video selection unit 71 with a mode selection signal of a user input through a user interface such as an external switch, an on-screen display, or a remote controller. By using the mode selection unit 69, the user can select whether to modulate the data.

The video determining unit 71 determines whether the video of the input digital video data RGB is determined by comparing the luminance information of the partial region of the screen between frames to determine the video. The video determining unit 71 instructs the modulator 65 not to perform data comparison and modulation in response to the mode selection signal from the mode selector 69, and instructs the modulator 65 to perform data comparison and modulation. A moving picture / still picture indication signal (MV / ST) for performing data comparison and modulation only on a moving picture is supplied to the memory controller 72, the selector 77, and the data switch 78.

The method and apparatus for driving a liquid crystal display device according to the first and second embodiments of the present invention improve the display quality in a video by improving the response speed of the liquid crystal through data modulation in the video, and do not perform data comparison and data modulation in the still image. By doing so, the heat generation and the power consumption of the modulator 52 are lowered.

7 shows a third embodiment of the modulator 52.

Referring to FIG. 7, the modulator 52 includes a TV signal / PC signal determiner 81, a memory controller 82, first and second frame memories 83 and 84, a modulator 85, and an EEPROM 86. ), A selector 87, a data switch 88, and a mode selector 89.

The mode selector 89 supplies the user's mode selection signal input to the video determining unit 81 through a user interface such as an external switch, an on-screen display, or a remote controller. By using the mode selection unit 89, the user can select whether to modulate data.

The TV signal / PC signal determination unit 81 determines whether the digital video data RGB currently inputted is a TV (Television) video signal having mostly moving images or a PC (Personal Computor) video signal having mostly still images. In general, an external TV video signal input terminal and an external PC video signal input terminal are separated. Accordingly, the TV signal / PC signal determination unit 81 may detect the TV input signal and the PC video signal with respect to the currently input video by detecting the data input path. In addition, the TV signal / PC signal determination unit 81 generates a TV signal / PC signal indicating signal (TV / PC) indicating whether the input digital video data RGB is a TV video signal or a PC video signal. The TV signal / PC signal support signal TV / PC is supplied to the memory controller 82, the selector 85, and the data switch 88.

The memory controller 82 controls the first and second frame memories 83 and 84 according to the TV signal / PC signal support signal TV / PC from the TV signal / PC signal determination unit 81.

The first and second frame memories 83 and 84 alternately store current frame data RGB (Fn) of the TV signal under the control of the memory controller 82, and store the data RGB (Fn) in one frame period. Delay and supply the previous frame data (RGB (Fn-1)) which has already been stored to the modulator 85. The first and second frame memories 82 alternately store current frame data RGB (Fn) of the PC signal under the control of the memory controller 82, and store the data RGB (Fn) for one frame period. Delay and do not output the previous frame data (RGB (Fn-1)) already stored. That is, the first and second frame memories 82 store and store only the data (RGB (Fn-1) every frame by overwriting the data RGB (Fn) of a relatively large number of PC signals. ) Is not supplied to the modulator 85.

The data switch 88 is connected to the data input terminal of the modulator 85 in response to the TV signal / PC signal support signal TV / PC from the TV signal / PC signal determination unit 81 (RGB (Fn). Switch the data bus of)). The data switch 88 connects the data bus of the current frame data RGB (Fn) connected to the data input terminal of the modulator 85 in the TV image, and transmits the current frame data RGB (Fn) to the modulator 85. On the other hand, in the PC image, the data bus is switched to block transmission of the current frame data RGB (Fn) supplied to the modulator 85.

The modulator 85 loads the modulation data lookup table stored in the EEPROM 86 into the internal SRAM and transfers the current frame data RGB (Fn) supplied from the data switch 88 and the frame memories 83 and 64. The current frame data RGB (Fn) is modulated by selecting the modulation data MRGB according to the comparison result of the frame data RGB (Fn-1). The modulator 85 performs data comparison and modulation on the data of the TV image, but no data is supplied from the PC image, and data comparison and modulation is not performed on the data of the PC image.

The selector 87 outputs or unmodulated data MRGB modulated by the modulator 85 in response to the TV signal / PC signal support signal TV / PC from the TV signal / PC signal determination section 81. The current frame data RGB (Fn) is output. The selector 87 supplies modulation data MRGB from the modulator 85 to the timing controller 51 in the TV image under the control of the TV signal / PC signal determination unit 81 while not being modulated in the PC image. The data RGB (Fn) is supplied to the timing controller 87.

A method and apparatus for driving a liquid crystal display device according to a third exemplary embodiment of the present invention improve the display quality in a TV image including mostly moving images by improving the response speed of the liquid crystal through data modulation in a TV image, and compare data and data in a PC image. By not modulating, heat generation and power consumption of the modulator 52 are reduced.

On the other hand, the modulation method of the modulator and the modulation data (Mdata) listed in the lookup table of the EEPROM are disclosed in Patent Application No. 10-2001-028907, Patent Application No. 10-2001-032464, and Patent Application No. 10-2001-054123, Patent application 10-2001-054124, Patent application 10-2001-054125, Patent application 10-2001-054327, Patent application 10-2001-054889, Patent application 10 -2001-054127, Patent Application No. 10-2001-054128, Patent Application No. 10-2001-057119, Patent Application No. 10-2001-056235, Patent Application No. 10-2001-079008, Patent Application No. 10 And a modulator and modulation data disclosed in -2001-078449, Patent Application No. 10-2002-046858, and Patent Application No. 10-2002-074366, respectively.

As described above, the method and apparatus for driving the liquid crystal display according to the present invention can increase the display quality in the moving image and reduce the heat generation and power consumption of the driving circuit by performing data comparison and modulation on the moving image or TV image. have.

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the technical spirit of the present invention. Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification but should be defined by the claims.

1 is a waveform diagram showing a change in luminance according to data in a conventional liquid crystal display.

2 is a waveform diagram showing an example of a luminance change caused by data modulation in the high speed driving method.

3 is a view showing an example of a high speed drive device.

4 is a block diagram illustrating a liquid crystal display according to an exemplary embodiment of the present invention.

5 is a block diagram illustrating a modulator according to a first embodiment of the present invention.

6 is a block diagram illustrating a modulator according to a second exemplary embodiment of the present invention.

7 is a block diagram illustrating a modulator according to a third exemplary embodiment of the present invention.

<Description of Symbols for Main Parts of Drawings>

51: timing controller 52: modulator

53: data driver 54: gate driver

55: data line 56: gate line

57: liquid crystal display panel 61, 71: moving picture determination unit

62, 72, 82: memory controller 63, 64, 83, 84: frame memory

65, 85: modulator 66, 86: EEPROM

67, 77, 87: selector 68, 78, 88: data switch

69, 89: mode selector 81: TV signal / PC signal determination unit

Claims (13)

Determining a type of the input image; Modulating data of the input image into preset modulation data if the input image is a moving image as a result of the image determination; And bypassing the data of the input image if the input image is a still image as a result of the image determination. The method of claim 1, Receiving a user command; And determining whether to modulate the data according to the user command. The method of claim 1, Modulating the data, Delaying the data of the input image by one frame period by storing and outputting the data of the input image in a frame memory; Comparing the current frame data of the input image with the delayed previous frame data and modulating the current frame data by using the modulation data set based on the change of the current frame data and the previous frame data. A method of driving a liquid crystal display device. The method of claim 3, wherein And not comparing the data if the input image is a still image. The method of claim 4, wherein Receiving a user command; And determining whether or not to compare the data according to the user command. Determining a type of the input image; Modulating the data of the input image into preset modulation data if the input image is a television image as a result of the image determination; And if the input image is a computer image, bypassing data of the input image as a result of the image determination. An image determination unit determining a type of an input image; A modulator configured to modulate data of the input image into preset modulation data when the input image is determined to be a moving image by the image determining unit; And a selector for selecting data of the input image when the input image is a still image by the image determining unit and selecting data modulated by the modulator when the input image is a moving image. Drive. The method of claim 7, wherein And the image determining unit generates a control signal indicating a type of the input projection. The method of claim 7, wherein A mode selection unit for receiving a user command; And the image determiner determines whether to modulate the data in response to a signal from the mode selector. The method of claim 8, A frame memory for delaying data of the input image by a frame period; And a memory controller for controlling data input / output of the frame memory in response to the control signal. The modulator compares the current frame data of the input image with the delayed previous frame data and modulates the current frame data using the modulation data set based on the change of the current frame data and the previous frame data. And the frame memory supplies the previous frame data in the moving image to the modulator under the control of the memory controller, while the previous frame data is not supplied to the modulator in the still image. The method of claim 10, And a data switch configured to form a transmission path of the current frame data supplied to the modulator in the moving image and to block a transmission path of the data in the still image in response to the control signal; And the selector outputs data modulated by the modulator in the moving image and outputs the current frame data unmodulated in the still image in response to the control signal. The method of claim 11, A liquid crystal display panel in which liquid crystal cells are arranged in a matrix type and in which a plurality of data lines and a plurality of gate lines cross each other; A data driver configured to supply the modulated data and the unmodulated data to the data lines; A gate driver supplying scan pulses to gate lines of the liquid crystal display panel; And a timing controller for supplying the modulated data and the unmodulated data to the data driver and controlling the data driver and the gate driver. An image determination unit determining a type of an input image; A modulator for modulating data of the input image into preset modulation data when the input determining unit determines that the input image is a television image; And a selector for selecting data of the input image when the input image is determined to be a computer image by the image determining unit and selecting data modulated by the modulator when the input image is a television image. Device driving device.