KR20050112951A - Method and apparatus for driving liquid crystal display - Google Patents

Abstract

The present invention relates to a driving device of a liquid crystal display device which changes the brightness of a backlight corresponding to data when a moving image is displayed and maintains the brightness of the backlight constant when a still image is displayed.

A driving device of the liquid crystal display device of the present invention includes a liquid crystal panel; A backlight for supplying light to the liquid crystal panel; An image quality improving unit for identifying an image attribute of data supplied from the outside and generating an image quality control signal corresponding to the identified image attribute; The controller may be configured to determine whether an image displayed on the liquid crystal panel is a moving image or a still image using data, and to control the luminance of the backlight regardless of the image quality control signal when the still image is displayed.

Description

Driving method and driving device of liquid crystal display device {Method and Apparatus for Driving Liquid Crystal Display}

The present invention relates to a driving method and a driving device of a liquid crystal display device. In particular, the luminance of the backlight is changed in response to data when a moving image is displayed, and the luminance of the backlight can be kept constant when a still image is displayed. The present invention relates to a driving method and a driving device of a liquid crystal display device.

The liquid crystal display device displays an image by adjusting light transmittance of liquid crystal cells according to a video signal. The liquid crystal display device is implemented in an active matrix type in which switching elements are formed in each cell, and is applied to display devices such as computer monitors, office equipment, and cellular phones. As a switching element used in an active matrix liquid crystal display device, a thin film transistor (hereinafter, referred to as TFT) is mainly used.

1 schematically shows a driving device of a conventional liquid crystal display.

Referring to FIG. 1, in a driving apparatus of a conventional liquid crystal display, m × n liquid crystal cells Clc are arranged in a matrix type, m data lines D1 to Dm and n gate lines G1 to A liquid crystal panel 2 having Gn intersected and a TFT formed at an intersection thereof, a data driver 4 for supplying a data signal to the data lines D1 to Dm of the liquid crystal panel 2, and gate lines. The gate driver 6 for supplying the scan signal to the G1 to Gn, the gamma voltage supply unit 8 for supplying the gamma voltage to the data driver 4, and the synchronization signal supplied from the system 20 are used. To generate the voltages supplied to the liquid crystal panel 2 by using the timing controller 10 for controlling the data driver 4 and the gate driver 6 and the voltage supplied from the power supply 12. DC conversion unit (hereinafter referred to as "DC / DC conversion unit") 14, and back light An inverter 16 for driving the bite 18 is provided.

The system 20 supplies the vertical / horizontal synchronization signals Vsync and Hsync, the clock signal DCLK, the data enable signal DE, and the data R, G, and B to the timing controller 10.

The liquid crystal panel 2 includes a plurality of liquid crystal cells Clc disposed in a matrix at the intersections of the data lines D1 to Dm and the gate lines G1 to Gn. Each TFT formed in the liquid crystal cell Clc supplies a data signal supplied from the data lines D1 to Dm to the liquid crystal cell Clc in response to a scan signal supplied from the gate line G. In addition, a storage capacitor Cst is formed in each of the liquid crystal cells Clc. The storage capacitor Cst is formed between the pixel electrode of the liquid crystal cell Clc and the front gate line, or is formed between the pixel electrode of the liquid crystal cell Clc and the common electrode line to maintain a constant voltage of the liquid crystal cell Clc. Let's do it.

The gamma voltage supply unit 8 supplies a plurality of gamma voltages to the data driver 4.

The data driver 4 converts the digital video data R, G, and B into analog gamma voltages (data signals) corresponding to the gray scale values in response to the control signal CS from the timing controller 10. The gamma voltage is supplied to the data lines D1 to Dm.

The gate driver 6 sequentially supplies scan pulses to the gate lines G1 to Gn in response to the control signal CS from the timing controller 10 to supply a horizontal signal to the liquid crystal panel 2. Select.

The timing controller 10 uses a control signal for controlling the gate driver 6 and the data driver 4 by using the vertical / horizontal synchronization signals Vsync and Hsync and the clock signal DCLK input from the system 20. Generate CS). The control signal CS for controlling the gate driver 6 includes a gate start pulse (GSP), a gate shift clock (GSC), a gate output enable (GOE), and the like. Included. The control signal CS for controlling the data driver 4 includes a source start pulse (GSP), a source shift clock (SSC), a source output signal (SOC), and Polarity signal (POL) is included. The timing controller 10 rearranges the data R, G, and B supplied from the system 20 and supplies the data driver 4 to the data driver 4.

The DC / DC converter 14 boosts or reduces the voltage of 3.3V input from the power supply 12 to generate the voltage supplied to the liquid crystal panel 2. The DC / DC converter 14 generates a gamma reference voltage, a gate high voltage VGH, a gate low voltage VGL, a common voltage Vcom, and the like.

The inverter 16 supplies a driving voltage (driving current) for driving the backlight 18 to the backlight 18. The backlight 18 generates light corresponding to a driving voltage (or driving current) supplied from the inverter 16 and supplies the light to the liquid crystal panel 2.

In order to display a vivid image in the liquid crystal panel 2 driven as described above, contrast (brightness and darkness) must be sharply corresponding to data. However, since the backlight 18 shown in FIG. 1 always generates light having a constant brightness regardless of data, it is difficult to display a vivid and dynamic screen.

In order to overcome this problem, a method of changing the luminance of the backlight 18 in response to data has been proposed. In other words, when the bright image is displayed on the liquid crystal panel 2, the brightness of the backlight 18 is increased, and when the dark image is displayed on the liquid crystal panel 2, the brightness of the backlight 18 is reduced, thereby providing a vivid and dynamic screen. Suggested on how to mark it. However, if the luminance of the backlight 18 is changed corresponding to the data, the luminance of the backlight 18 is changed even when displaying a still image, thereby causing a problem of deterioration of display quality.

In fact, when the liquid crystal panel 2 is used as a monitor, a case where a still image and a moving image are simultaneously displayed is generated. As such, when the still image is displayed on the liquid crystal panel 2, the luminance of the backlight 18 must be kept constant. However, in the related art, since the luminance of the backlight 18 changes in response to a moving image, it causes inconvenience to the user. For example, if the brightness of the backlight 18 is changed when the user is working on the document, a problem occurs that causes inconvenience to the user and decreases the eyesight of the user.

Accordingly, an object of the present invention is to drive and drive a liquid crystal display device to change the luminance of the backlight in response to data when a moving image is displayed and to maintain the luminance of the backlight constantly when a still image is displayed. To provide.

In order to achieve the above object, the driving apparatus of the liquid crystal display device of the present invention comprises a liquid crystal panel; A backlight for supplying light to the liquid crystal panel; An image quality improving unit for identifying an image attribute of data supplied from the outside and generating an image quality control signal corresponding to the identified image attribute; The controller may be configured to determine whether an image displayed on the liquid crystal panel is a moving image or a still image using data, and to control the luminance of the backlight regardless of the image quality control signal when the still image is displayed.

When the video is displayed, the backlight controller controls the brightness of the backlight in response to an image quality control signal.

When the still image is displayed, the backlight controller controls to generate light having a predetermined brightness in the backlight regardless of the image quality control signal.

The backlight controller may include a scaler for extracting only a luminance component of some data among one frame of data input to the frame, a high pass filter for extracting a high frequency component from the luminance component supplied from the scaler, and a high pass filter. A storage unit for storing at least two frames of high frequency components, a comparison unit for determining whether an image displayed on the liquid crystal panel is a moving picture or a still image by comparing the high frequency components of at least two frames stored in the storage unit; Video backlight control unit for controlling the backlight so that light of the brightness corresponding to the image quality control signal is supplied when the control signal is input from the unit, and light of a predetermined brightness when the control signal is input from the comparator And a still image backlight controller for controlling the backlight.

The comparison unit supplies a control signal to the moving image backlight control unit when the image displayed on the liquid crystal panel is determined to be a moving image, and supplies the control signal to the still image backlight control unit in other cases.

The scaler converts a plurality of preset pixel data of one frame of data input to the luminance component into a luminance component, and supplies only the luminance component of the intermediate gray level to the high pass filter.

The scaler converts luminance components of a plurality of preset pixel data among data of one frame inputted to the average into an average value and supplies the average to a high pass filter.

The backlight controller detects the resolution of data input to the outside from the outside, and supplies the data to the scaler when the detected resolution is larger than the preset resolution, and converts the data into the luminance component in other cases to supply the high pass filter. It further comprises a resolution detector for.

The driving method of the liquid crystal display device of the present invention comprises the steps of determining the image attribute of the data supplied from the outside, and using the data to determine whether the image displayed on the liquid crystal panel is a moving image or a still image, Controlling the luminance of the backlight regardless of the image attribute of the data when the image is displayed; and controlling the luminance of the backlight in response to the image attribute of the data when the video is displayed on the liquid crystal panel.

When the still image is displayed on the liquid crystal panel, the backlight is controlled to supply light having a predetermined luminance.

The step of determining whether the moving picture or the still image is a first step of extracting only a luminance component of some data of one frame of data input to the self, a second step of extracting a high frequency component from the luminance component, and a second A third step of storing high frequency components of at least two frames extracted in the step; and a fourth step of determining whether an image displayed on the liquid crystal panel is a moving image or a still image using the high frequency components of at least two frames stored in the third step It includes.

In the first step, a plurality of preset pixel data of one frame of data input to the user are converted into a luminance component, and only the luminance component of the intermediate gray level is extracted therefrom.

In the first step, the luminance components of a plurality of preset pixel data among the data for one frame input to the first frame are converted into an average value and supplied to the second step.

Determining whether the moving image or the still image is the step of detecting the resolution of data input from the outside, and if the detected resolution is larger than the preset resolution, the data is supplied to the first step, otherwise the data is luminance And converting the component into a second step.

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. 2 to 5.

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

Referring to FIG. 2, in the driving apparatus of the liquid crystal display according to the exemplary embodiment of the present invention, m × n liquid crystal cells Clc are arranged in a matrix type, m data lines D1 to Dm and n gates are provided. A liquid crystal panel 22 having lines G1 to Gn intersected and TFTs formed at the intersections thereof, and a data driver 24 for supplying data signals to the data lines D1 to Dm of the liquid crystal panel 22. A gate driver 26 for supplying a scan signal to the gate lines G1 to Gn, a gamma voltage supply unit 28 for supplying a gamma voltage to the data driver 24, and a synchronization signal supplied thereto. Using the timing controller 30 to control the data driver 24 and the gate driver 26 and the voltage supplied from the power supply unit 32 to generate the voltages supplied to the liquid crystal panel 22. DC / DC converter 34 is provided.

In addition, the driving apparatus of the liquid crystal display device according to the embodiment of the present invention includes an image quality improvement unit 42 for generating an image quality control signal corresponding to input data, and an image displayed on the liquid crystal panel 22 is a still image or a moving image. And a backlight controller 36 for controlling the brightness of the backlight 38 in response to the image quality control signal supplied from the image quality improvement unit 42 when the video is displayed.

The system 40 supplies the synchronization signals and data to the image quality improvement unit 42 and the backlight control unit 36.

The image quality improvement unit 42 determines an image attribute of data supplied from the system 40 and supplies an image quality control signal corresponding to the identified image attribute to the backlight controller 36.

The timing controller 30 rearranges data input from the image quality improvement unit 42 to the resolution of the liquid crystal panel 22 and supplies the data to the data driver 24. The timing controller 30 generates a control signal CS for controlling the gate driver 26 and the data driver 24 using the synchronization signal supplied from the image quality improvement unit 42 or the system 40. .

The gamma voltage supply unit 28 supplies a plurality of gamma voltages to the data driver 24.

The data driver 24 converts the digital video data Ro, Go, Bo into an analog gamma voltage (data signal) corresponding to the gray scale value in response to the control signal CS from the timing controller 30. The gamma voltage is supplied to the data lines D1 to Dm.

The gate driver 26 sequentially supplies scan pulses to the gate lines G1 to Gn in response to the control signal CS from the timing controller 30 to supply a horizontal signal of the liquid crystal panel 22. Select.

The liquid crystal panel 22 includes a plurality of liquid crystal cells Clc disposed in a matrix at the intersections of the data lines D1 to Dm and the gate lines G1 to Gn. Each TFT formed in the liquid crystal cell Clc supplies a data signal supplied from the data lines D1 to Dm to the liquid crystal cell Clc in response to a scan signal supplied from the gate line G. In addition, a storage capacitor Cst is formed in each of the liquid crystal cells Clc. The storage capacitor Cst is formed between the pixel electrode of the liquid crystal cell Clc and the front gate line, or is formed between the pixel electrode of the liquid crystal cell Clc and the common electrode line to maintain a constant voltage of the liquid crystal cell Clc. Let's do it.

The DC / DC converter 34 generates a voltage supplied to the liquid crystal panel 22 by increasing or decreasing the voltage of 3.3V input from the power supply unit 32. The DC / DC converter 34 generates a gamma reference voltage, a gate high voltage VGH, a gate low voltage VGL, a common voltage Vcom, and the like.

The backlight controller 36 determines whether an image displayed on the liquid crystal panel 22 is a still image or a moving image using data input from the system 40. When the video is displayed on the liquid crystal panel 22, the backlight controller 36 controls the brightness of the backlight 38 in response to the image quality control signal supplied from the image quality improvement unit 42. When the still image is displayed on the liquid crystal panel 22, the backlight controller 36 controls the backlight 38 to supply light having a constant luminance regardless of the image quality control signal supplied from the image quality improvement unit 42.

To this end, the backlight controller 36 includes a scaler 50, a high pass filter 52, a storage 54, a comparator 56, a video backlight controller 58, and a still image backlight controller 60 as illustrated in FIG. 3. ).

The scaler 50 supplies only the luminance components of some data of one frame of data supplied from the system 40 to the high pass filter 52, or converts the luminance components of a plurality of preset pixel data into an average value to pass the high pass. It is supplied to the filter 52. In detail, the liquid crystal panel 22 has predetermined pixels corresponding to its resolution, and data is supplied corresponding to the number of pixels. For example, if the liquid crystal panel 22 has a resolution of 1280 × 768 and each data consists of 8 bits, the storage unit 54 stores the luminance component of the data of one frame. As shown in Equation 1, it should have a storage capacity of about 7.7 Mbytes.

1280 × 768 × 8Bit ≒ 7.7Mbyte

Here, since the data is divided into red, green, and blue data, the storage unit 54 should actually have a storage capacity of about 20 Mbytes. However, when the storage unit 54 has 20 Mbytes, the size thereof becomes too large to be mounted inside the backlight control unit 36. Therefore, in the present invention, the scaler 50 is used to reduce the capacity of the storage unit 54 by lowering the resolution of one frame.

The method of lowering the resolution of one frame in the scaler 50 may be variously determined. For example, the scaler 50 converts a plurality of preset pixel data (for example, nine pixel data) into luminance components as shown in FIG. 4A and arranges only the luminance components positioned in the middle of the high pass filter. 52 can be supplied.

The scaler 50 converts the luminance components of a plurality of preset pixel data (for example, nine pixel data) into an average value to generate a luminance component having a new gray scale value, as shown in FIG. 4B. The high pass filter 52 can be supplied. Meanwhile, the scaler 50 includes a luminance converter for converting data into luminance components.

The high pass filter 52 extracts a high frequency component from the luminance component supplied from the scaler 50 and supplies the extracted high frequency component to the storage unit 54. When displaying a video, a high frequency component appears at the edge of the video. That is, the high pass filter 52 supplies only the high frequency component included in the luminance component to the storage unit 54.

The storage unit 54 stores the high frequency component supplied from the high pass filter 52. Here, the storage 54 stores a high frequency component corresponding to the luminance component output from the scaler 50, thereby minimizing the storage capacity. At least two frames of high frequency components are stored in the storage unit 54.

The comparator 56 compares the high frequency components of the i (i is a natural number) frame and the i-1 th frame stored in the storage 54 to determine whether the currently displayed image is a still image or a moving image. In other words, the comparator 56 compares the high frequency components of the i frame and the i-1 th frame stored in the storage 54 to determine whether the image displayed on the liquid crystal panel 22 is a still image or a moving image. In fact, the comparator 56 determines that the image currently displayed is a moving image when the high frequency component extracted in the i and i-1th frames is changed, and otherwise, it is a still image.

When a video is displayed on the liquid crystal panel 22, the comparator 56 supplies a control signal to the video backlight controller 58. When the still image is displayed on the liquid crystal panel 22, the comparator 56 supplies a control signal to the still image backlight controller 60.

When the control signal is supplied from the comparator 56, the video backlight controller 58 controls the backlight 38 to supply light having a luminance corresponding to the image quality control signal supplied from the image quality improvement unit 42.

The still image backlight controller 60 controls the backlight 38 to supply light having a predetermined brightness when a control signal is supplied from the comparator 56.

That is, in the present invention, when the still image is displayed on the liquid crystal panel 22, the backlight 38 is controlled to supply light having a predetermined brightness, thereby preventing flickering from occurring in the liquid crystal panel 22. . In the present invention, when the moving image is displayed on the liquid crystal panel 22, the backlight 38 may be controlled to supply the light having the luminance corresponding to the data, thereby displaying a dynamic and lively image.

 In the present invention, since it is determined whether the image displayed on the liquid crystal panel 22 is a still image or a moving image by comparing the high frequency components extracted from the luminance component, the determination time and the like can be drastically reduced. In fact, in order to compare the data and determine whether it is a still image or a video, a lot of time is consumed and a memory, etc., must be added, thereby increasing manufacturing costs.

5 is a diagram illustrating a backlight controller according to another embodiment of the present invention. Referring to FIG. 5, a configuration having the same function as the backlight controller according to the exemplary embodiment of the present invention shown in FIG. 3 will be briefly described.

Referring to FIG. 5, the backlight controller according to another embodiment of the present invention may include a resolution detector 68, a scaler 70, a high pass filter 72, a storage unit 74, a comparator 76, and a video backlight controller. 78 and a still image backlight controller 80.

The resolution detector 68 detects the resolution of the liquid crystal panel 22 by using one frame of data supplied from the system 40. The resolution detector 68, which detects the resolution of the liquid crystal panel 22, supplies data to the scaler 70 when the resolution of the liquid crystal panel 22 is larger than the resolution set in advance. Otherwise, the high resolution filter 72 ) To feed the data.

In detail, since the backlight controller according to the exemplary embodiment of the present invention shown in FIG. 3 supplies data input from the outside to the scaler 70 unconditionally, only a part of data actually input to the high pass filter 72 is provided. Will be supplied. However, in the exemplary embodiment of the present invention illustrated in FIG. 5, when the resolution of the liquid crystal panel 22 is low, data input from the outside is supplied to the high pass filter 72 without adding or subtracting to provide a moving image and a still image with higher accuracy. You will be judged. That is, in another exemplary embodiment of the present invention, when the resolution of the liquid crystal panel 22 is low, the moving image and the still image are determined with higher accuracy, and when the resolution of the liquid crystal panel 22 is high, the resolution is lowered. It is possible to prevent the dose of) from increasing.

On the other hand, the resolution detector 68 converts the data into a luminance component and supplies it to the high pass filter 72 when the data supplied thereto is lower than the preset resolution. Here, the preset resolution is experimentally set in a range in which the capacity of the storage unit 74 is not increased.

The scaler 70 supplies only a luminance component of some data of one frame of data supplied from the resolution detector 68 as shown in FIG. 4A to the high pass filter 72, or as shown in FIG. 4B. The luminance component is converted into an average value and supplied to the high pass filter 72.

The high pass filter 72 extracts a high frequency component from the luminance component supplied from the scaler 70 or the resolution detector 68 and supplies the extracted high frequency component to the storage 74.

The storage unit 74 stores the high frequency component supplied from the high pass filter 72. At this time, the storage unit 74 stores at least two frames of high frequency components. For example, the storage unit 74 stores high frequency components of the current frame and high frequency components of the previous frame.

The comparator 76 compares the high frequency components of the two frames stored in the storage 74 to determine whether the currently displayed image is a still image or a moving image. The comparator 76 supplies a control signal to the moving image backlight controller 78 when it is determined that the currently displayed image is a moving image, and supplies the control signal to the still image backlight controller 80 in other cases.

When the control signal is supplied from the comparator 76, the video backlight controller 78 controls the backlight 38 to supply light having a luminance corresponding to the image quality control signal supplied from the image quality improvement unit 42.

The still image backlight controller 80 controls the backlight 38 to supply light having a predetermined brightness when a control signal is supplied from the comparator 76.

That is, when the still image is displayed on the liquid crystal panel 22, the backlight controller 36 controls the backlight 38 to supply light having a predetermined brightness. Flickering can be prevented from occurring. In addition, the backlight control unit 36 according to another embodiment of the present invention controls the backlight 38 to supply light of luminance corresponding to data when a moving image is displayed on the liquid crystal panel 22 to generate a dynamic and lively image. I can display it.

As described above, according to the driving method and driving apparatus of the liquid crystal display according to the present invention, it is determined whether the image displayed on the liquid crystal panel is a still image or a moving image, and the luminance of the backlight is controlled in response to the determined result. This deterioration can be prevented. That is, in the present invention, when the still image is displayed, the backlight is controlled to supply light having a predetermined brightness, and when the video is displayed, the backlight is controlled to supply light corresponding to data. Therefore, in the present invention, it is possible to prevent the flicker phenomenon from occurring when displaying a still image while displaying a live image when displaying a moving image.

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 view showing a driving device of a conventional liquid crystal display device.

2 is a view showing a driving device of a liquid crystal display device according to an embodiment of the present invention;

3 is a block diagram illustrating a first embodiment of the backlight controller illustrated in FIG. 2.

4A and 4B illustrate an operation process of the scaler shown in FIG. 3.

FIG. 5 is a block diagram illustrating a second embodiment of the backlight controller illustrated in FIG. 2. FIG.

<Description of Symbols for Main Parts of Drawings>

2,22 LCD panel 4,24 Data driver

6,26: gate driver 8,28: gamma voltage supply

10,30: timing controller 12,32: power supply

14,34: DC / DC converter 16: inverter

18,38: backlight 20,40: system

36: backlight control unit 42: image quality improvement unit

50,70 Scaler 52,72 High Pass Filter

54, 74 storage unit 56, 76 comparison unit

58,78: Video backlight controller 60,80: Still image backlight controller

68: resolution detector

Claims (14)

A liquid crystal panel; A backlight for supplying light to the liquid crystal panel; An image quality improving unit for identifying an image attribute of data supplied from the outside and generating an image quality control signal corresponding to the identified image attribute; Determining whether an image displayed on the liquid crystal panel is a moving image or a still image by using the data; and when the still image is displayed, a backlight control unit for controlling the luminance of the backlight regardless of the image quality control signal. A drive device for a liquid crystal display device. The method of claim 1, And the backlight controller controls the brightness of the backlight in response to the image quality control signal when the video is displayed. The method of claim 1, And the backlight control unit controls to generate light having a predetermined luminance in the backlight regardless of the image quality control signal when the still image is displayed. The method of claim 1, The backlight control unit A scaler for extracting only luminance components of some data from one frame of data input to the self; A high pass filter for extracting high frequency components from luminance components supplied from the scaler; A storage unit for storing high frequency components for at least two frames supplied from the high pass filter; A comparison unit for determining whether an image displayed on the liquid crystal panel is a moving picture or a still image by comparing the high frequency components of the at least two frames stored in the storage unit; A video backlight controller which controls the backlight to supply light having a luminance corresponding to the image quality control signal when a control signal is input from the comparator; And a still image backlight controller configured to control the backlight to supply light having a predetermined brightness when the control signal is input from the comparator. The method of claim 4, wherein The comparing unit supplies the control signal to the moving image backlight control unit when the image displayed on the liquid crystal panel is determined to be the moving image; and otherwise supplies the control signal to the still image backlight control unit. Drive. The method of claim 4, wherein The scaler converts a plurality of preset pixel data of one frame of data input to the luminance component into a luminance component, and supplies only the luminance component having an intermediate gray level to the high pass filter. Drive system. The method of claim 4, wherein And the scaler converts the luminance components of a plurality of preset pixel data among the data for one frame inputted to the average into an average value and supplies the converted average values to the high pass filter. The method of claim 4, wherein The backlight controller detects a resolution of data input from the outside and supplies the data to the scaler when the detected resolution is larger than a preset resolution and converts the data into a luminance component to the high pass filter. And a resolution detecting section for supplying the liquid crystal display device. Identifying image attributes of data supplied from the outside; Determining whether an image displayed on the liquid crystal panel is a moving image or a still image using the data; Controlling the luminance of the backlight regardless of the image attribute of the data when the still image is displayed on the liquid crystal panel; And controlling brightness of the backlight in response to an image attribute of the data when the video is displayed on the liquid crystal panel. The method of claim 9, And controlling to supply light having a predetermined brightness in the backlight when the still image is displayed on the liquid crystal panel. The method of claim 9, Identifying whether the video or still image is A first step of extracting only a luminance component of some data from one frame of data input to the user; A second step of extracting a high frequency component from the luminance component; A third step of storing the high frequency component of at least two frames extracted in the second step; And a fourth step of determining whether an image displayed on the liquid crystal panel is a moving picture or a still image using the high frequency component of at least two frames stored in the third step. The method of claim 11, And in the first step, a plurality of preset pixel data of one frame of data input to the user is converted into a luminance component, and only the luminance component of an intermediate gray level is extracted therefrom. The method of claim 11, And in the first step, convert the luminance components of a plurality of preset pixel data among the data for one frame inputted to the average into an average value and supply the converted luminance component to the average value. The method of claim 11, Identifying whether the video or still image is Detecting a resolution of data input from the outside; And supplying the data to the first step if the detected resolution is larger than a preset resolution, and otherwise converting the data into a luminance component and supplying the data to the second step. A method of driving a liquid crystal display device.