KR20110047656A - LCD and its driving method - Google Patents

Abstract

According to an aspect of the present invention, there is provided a control circuit unit which determines whether to perform over-driving by analyzing a gray level of an image signal for each frame, and outputs an RGB signal or a modulated RGB signal according to whether the over-driving is performed; A liquid crystal panel which displays an image corresponding to the image signal by using the RGB signal or the modulated RGB signal of the control circuit unit; It provides a liquid crystal display device including a backlight unit for supplying light to the liquid crystal panel.

Description

Liquid Crystal Display Device And Method Of Driving The Same

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display, and in particular, an over-driving for compensating for response time of a liquid crystal is selectively performed according to a display image, thereby reducing the amount of heat generated in the driving circuit unit and a driving method thereof. It is about.

LCDs have advantages of small size, thinness, and low power consumption, and are being used as notebook computers, office automation devices, and audio / video devices. In particular, an active matrix type liquid crystal display device using a thin film transistor as a switch element is suitable for displaying a dynamic image.

However, unlike the cathode ray tube (CRT), which is an impulsive type, the hold type liquid crystal display has a disadvantage in that the response speed is slow due to the viscosity and elasticity of the liquid crystal itself. That is, there is a disadvantage in that the response time is long, and the disadvantage of the liquid crystal may be caused by deterioration in image quality.

For example, the response time of a liquid crystal in a twisted nematic (TN) mode liquid crystal display device, which has been most widely used, has a rising time and a falling time of 20-80 msec and 20-30 msec, respectively. It is known that the rising time and the falling time of the liquid crystal are longer than one frame (about 16.67 msec) so that the frame elapses before the liquid crystal molecules reach the rearrangement state corresponding to the applied voltage and the next frame proceeds to another voltage. Is applied.

Since the transmittance of the liquid crystal layer and the luminance of the liquid crystal display device are determined according to the rearrangement state of the liquid crystal molecules of the liquid crystal layer, the liquid crystal display device does not display the luminance corresponding to the applied voltage of the current frame and thus corresponds to the applied voltage of the next frame. The luminance is displayed, and a quality deterioration phenomenon such as a motion blur in which a pattern boundary is blurred in a video is displayed.

In order to prevent such deterioration of the image quality of the liquid crystal display, a driving method using an over-driving circuit (ODC) has been proposed.

FIG. 1 is a diagram illustrating a comparison between a general driving method of a conventional liquid crystal display device and a driving method using an over-driving circuit. FIG. 1 is a graph showing pixel applied voltage and luminance of a liquid crystal display device.

As shown in FIG. 1, in the liquid crystal display device, a voltage corresponding to the gray level is applied to each pixel for gray level display, and the liquid crystal molecules are rearranged, whereby the liquid crystal layer has a transmittance corresponding to the voltage. The liquid crystal display displays a desired gray scale with luminance corresponding to a voltage.

However, when driving the liquid crystal display by a general driving method, the applied voltage designed by the response time of the liquid crystal molecules does not display the desired luminance.

For example, referring to the applied voltage graph VN and the luminance graph BN according to a general driving method, the first voltage V1 is applied to display the target luminance Bn of the nth frame, but the liquid crystal Since the nth frame is terminated before reaching the target luminance Bn due to the delay of the response time of the molecule, the first luminance B1 smaller than the target luminance Bn is finally displayed, which is a moving image of the liquid crystal display. It causes image quality deterioration.

Looking at the applied voltage graph (VO) and the luminance graph (BO) according to the driving method using the over-driving circuit to prevent this, the second voltage (V2) greater than the first voltage (V1) designed in the n-th frame By applying, the response time of the liquid crystal molecules can be reduced to reach the target luminance Bn before the nth frame is finished.

In the driving method using the over-driving circuit, the response time of the liquid crystal is shortened as the applied voltage is larger or the applied voltage difference between the frames is larger.

That is, by comparing the image data of two consecutive frames, by using a look up table (LUT) to calculate the applied voltage change corresponding to the degree of change and apply it when displaying the image of the current frame, The response time of the liquid crystal is reduced and the desired luminance is displayed.

Such an over-driving circuit is included in or controlled by a timing controller in the driving circuit portion of the liquid crystal display device. The timing controller is operated and controlled so that the over-driving method is always applied to the entire frame. There is a problem in that the load and the heat generation amount of increase.

In addition, in recent years, the timing controller has been miniaturized and its functions have been diversified. Therefore, the heat generation amount of the timing controller has become a more serious problem.

For example, when the over-driving circuit does not operate, the timing controller temperature is about 71 ° C, whereas when the over-driving circuit operates, the temperature of the timing controller reaches 78 ° C, causing problems in its operating characteristics. Sometimes.

The present invention has been made to solve the above problems, and the liquid crystal display device and the drive of the heat generation of the driving circuit portion is reduced by selectively operating the over-driving to compensate for the response time of the liquid crystal according to the display image It is an object to provide a method.

In addition, the present invention provides a liquid crystal display and a driving device having improved operation characteristics and power consumption of the driving circuit unit by selectively performing over-driving and optimal power control according to the gray level and bitmap of the display image. It is another object to provide a method.

In order to achieve the above object, the present invention, by analyzing the gray level of the image signal for each frame to determine whether to perform the over-driving, and outputs an RGB signal or a modulated RGB signal according to whether the over-driving is performed A control circuit unit; A liquid crystal panel which displays an image corresponding to the image signal by using the RGB signal or the modulated RGB signal of the control circuit unit; It provides a liquid crystal display device including a backlight unit for supplying light to the liquid crystal panel.

The liquid crystal display device includes: a system circuit part for supplying the image signal and the first dimming signal to the control circuit part; It may further include an inverter circuit unit for controlling the backlight unit.

The control circuit unit may include: an optimum power control unit configured to output the RGB signal, the second dimming signal, and the bitmap count signal by analyzing the gray level of the video signal for each frame; And an over-driving circuit unit configured to output the RGB signal or the modulated RGB signal according to whether the over-driving is performed using the second dimming signal and the bitmap count signal.

The optimum power controller may include: a histogram analyzer configured to determine whether to perform data conversion and duty ratio conversion by analyzing the gray level of the video signal for each frame; A data converter configured to generate the RGB signal by performing data conversion to increase the gray level of the video signal according to whether to perform the data conversion of the histogram analyzer; A duty ratio converter for generating the second dimming signal by performing a duty ratio conversion to increase the duty ratio of the first dimming signal according to whether the histogram analyzer performs the duty ratio conversion; And a bitmap analyzer configured to generate a bitmap count signal by generating a bitmap of the gray level of the video signal for each frame and calculating a bitmap count.

In this case, the histogram analyzer determines that the data conversion and the duty ratio conversion are not performed when the number of pixels that is greater than or equal to the first reference gray level of the video signal is determined and the number of pixels that is greater than or equal to the first reference gray level of the video signal is determined. When the reference number is greater than or equal to, the data conversion and the duty ratio conversion may be determined to be performed.

The over-driving circuit unit may include: an over-driving controller configured to determine whether to perform the over-driving by analyzing the second dimming signal and the bitmap count signal; A frame memory unit which stores the RGB signal as data of a previous frame and updates each frame; A data modulator for generating the modulated RGB signal by comparing the RGB signal of the current frame with the RGB signal of the previous frame according to whether the over-driving is performed; And a lookup table that stores a value corresponding to a result of comparing the RGB signal of the current frame with the RGB signal of the previous frame.

In this case, the over-driving control unit determines the magnitude of the duty ratio and the reference duty ratio of the second dimming signal and the magnitude of the bitmap count and the reference bitmap count of the bitmap count signal to determine the magnitude of the second dimming signal. When the duty ratio of is less than the reference duty ratio and at the same time the bitmap count of the bitmap count signal is less than the reference bitmap count, it is determined that the over-driving is not performed so that the RGB signal is output. When the duty ratio of the 2 dimming signal is greater than or equal to the reference duty ratio or the bitmap count of the bitmap count signal is greater than or equal to the reference bitmap count, it is determined that the over-driving is performed to output the modulated RGB signal. Can be.

On the other hand, the present invention comprises the steps of analyzing the gray level of the video signal for each frame to generate a dimming signal and a bitmap count signal; Determining whether to perform over-driving using the dimming signal and the bitmap count signal; A method of driving a liquid crystal display device comprising displaying an image corresponding to the image signal using an RGB signal or a modulated RGB signal according to whether the over-driving is performed.

 Determining whether or not the over-driving is performed, determining the magnitude of the duty ratio and the reference duty ratio of the dimming signal; And determining the magnitude of the bitmap count and the reference bitmap count of the bitmap count signal, wherein the duty ratio of the dimming signal is less than the reference duty ratio and at the same time the bitmap count of the bitmap count signal is Outputting the RGB signal by determining that the over-driving is not performed when the reference bit map count is less than the reference bit map count; When the duty ratio of the second dimming signal is greater than or equal to the reference duty ratio or the bitmap count of the bitmap count signal is greater than or equal to the reference bitmap count, determining that the over-driving is performed to output the modulated RGB signal. It may further comprise the step of.

According to the present invention, the over-driving is stopped for a display image in which relatively dark and bright portions are not dense, and the over-driving is selectively performed only for the other display images, thereby reducing the amount of heat generated by the driving circuit unit, especially the timing controller. The operation characteristics can be improved.

At the same time, power consumption can be reduced by performing optimum power control driving on a relatively dark display image.

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

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

As shown in FIG. 2, the liquid crystal display device 110 according to an exemplary embodiment of the present invention includes a liquid crystal panel 120 for displaying an image, a backlight unit 130 for supplying light to the liquid crystal panel 120, and a liquid crystal. Control circuit unit 140 for supplying a control signal, a gate signal and a data signal to the panel, the inverter circuit unit 150 for controlling the power supply of the backlight unit 130, the control circuit unit 140 and the inverter circuit unit 150 for controlling System circuitry 160 is included.

Specifically, the liquid crystal panel 120 includes first and second substrates (not shown) spaced apart from each other and a liquid crystal layer (not shown) formed between the first and second substrates. One substrate includes a plurality of gate lines 122 and a plurality of data lines 124 that cross each other to define a plurality of pixels P, a thin film transistor Tr formed in each pixel P, and a thin film transistor. The liquid crystal capacitor Clc and the storage capacitor Cst connected to the stir Tr are formed.

Although not shown, the liquid crystal panel 120 is a form of a driving integrated circuit (D-IC) for generating gate signals and data signals applied to the plurality of gate lines 122 and the data lines 124, respectively. The gate driver may include a data driver. When the thin film transistor Tr is turned on according to the gate signal, the data signal is supplied to the liquid crystal capacitor Clc and the storage capacitor Cst to display an image. Display.

In addition, the backlight unit 130 may include a cold cathode fluorescent lamp (CCFL), an external electrode fluorescent lamp (EEFL), and a light emitting diode (LED) to supply light to the liquid crystal panel 120. diode: LED) lamps and other lighting devices.

The control circuit 140 may be configured in the form of a printed circuit board (PCB) including a timing controller, and the like. The image circuit and the data enable signal DE may be provided from the system circuit 160. The horizontal synchronization signal HSY, the vertical synchronization signal VSY, the clock signal CLK, and the like are generated, and a plurality of control signals and RGB signals are generated and supplied to the gate driver and the data driver of the liquid crystal panel 120.

In particular, the control circuit unit 140 analyzes the gradation distribution and the position distribution of the error gradation of the video signal supplied from the system circuit unit 160 for each frame, and over-corresponds only to the video signal of the frame in which relatively dark and bright parts are not concentrated. The driving circuit (over-driving circuit) is controlled to operate to generate a plurality of control signals and modulated RGB data to the liquid crystal panel 120.

In addition, the control circuit unit 140 generates an RGB signal by supplying the RGB signal to the liquid crystal panel 120 by converting the image signal such that the gray level of the frame is variable according to the gray scale distribution analysis result, and changing the luminance of the backlight unit 130. The second dimming signal is generated by supplying the first dimming signal supplied from the system circuit unit 160 to the inverter circuit unit 150.

The inverter circuit unit 150 controls the light emission of the backlight unit 130, and receives the second and third dimming signals for controlling the backlight unit 130 from the control circuit unit 140 and the system circuit unit 160, respectively.

In addition, the system circuit unit 160 is an external interface circuit such as a TV system or a graphics card, and includes a video signal, a data enable signal DE, a horizontal synchronization signal HSY, a vertical synchronization signal VSY, and a clock for displaying an image. The signal CLK is supplied to the control circuit unit 140, and the first and third dimming signals for controlling the backlight unit 130 are supplied to the control circuit unit 140 and the inverter circuit unit 150, respectively.

Here, the first to third dimming signals are supplied, such as a VBR-A method that provides only an analog voltage and a VBR-B method that selects and provides a PWM signal and an analog voltage.

In FIG. 2, the first dimming signal is directly supplied from the system circuit unit 160 to the control circuit unit 140. However, in another embodiment, the first dimming signal is input to the inverter circuit unit 150 in consideration of a pin-map of a connector. It may be supplied to the control circuit unit 140 by bypass.

The control circuit part of the liquid crystal display according to the exemplary embodiment of the present invention will be described in detail with reference to the drawings.

3 is a block diagram illustrating a control circuit of the liquid crystal display according to the exemplary embodiment of the present invention.

As shown in FIG. 3, the control circuit unit 140 largely includes an optimal power control (OPC) unit 142 and an over-driving circuit (ODC) unit 144.

The optimum power controller 142 includes a histogram analyzer 182, a data converter 184, a duty ratio converter 186, and a bitmap analyzer 188, and over- The driving circuit unit 144 includes an over-driving control unit 192, a frame memory unit 194, a data modulator 196, and a look up table 198.

The histogram analyzer 182 analyzes the gray level of the video signal supplied from the system circuit unit 160 of each frame to determine whether to perform data conversion and duty ratio conversion on the video signal of the corresponding frame.

That is, when the number of pixels that are equal to or greater than the first reference gray level preset in the video signal of the frame is less than the preset reference number, the histogram analyzer 182 determines to perform data conversion and duty ratio conversion, and is equal to or greater than the first reference gray level. If the number of pixels is greater than or equal to the reference number, the histogram analyzer 182 determines not to perform data conversion and duty ratio conversion.

In detail, the histogram analyzer 182 may increase the gray level of a relatively dark video signal when the number of pixels of the first frame or more is less than the reference number in the image signal of a specific frame, thereby increasing the gray level of the backlight unit 130. It is determined that data conversion and duty ratio conversion to reduce the duty ratio are performed.

The histogram analyzer 182 saturates and loses the pixels by increasing the gray level when the video signal of the specific frame includes the number of pixels equal to or greater than the first reference gray level, that is, a relatively bright image. In order to prevent this, it is determined that data conversion and duty conversion are not performed.

The data converter 184 generates an RGB signal by performing data conversion such that the gray level is increased for an image signal of a frame determined by the histogram analyzer 182 to perform data conversion and duty ratio conversion. 144 and a liquid crystal panel (120 in FIG. 2).

The duty ratio converter 186 is supplied from the system circuit unit 160 to reduce the duty ratio of the backlight unit 130 with respect to the frame determined by the histogram analyzer 182 to perform data conversion and duty ratio conversion. The first dimming signal is converted to generate a second dimming signal, and is supplied to the over-driving circuit unit 144 and the inverter circuit unit 150 (refer to FIG. 2).

In this case, the duty ratio converter 148 may have a duty ratio smaller than that of the first dimming signal to reduce light emission time of the backlight unit 130 to supply light of lower illuminance (or luminance) to the liquid crystal panel 120. The second dimming signal may be generated.

Meanwhile, the bitmap analyzer 188 calculates the bitmap count of the video signal of the frame by analyzing the gray level of the video signal supplied from the system circuit unit 160 for each frame.

That is, the bitmap analyzer 188 creates a bitmap using an error pixel that may be defined as a pixel that is greater than or equal to the second reference gray scale, and scans the bitmap with a window including a specific number of pixels. A bitmap count indicating a position distribution of error pixels of the video signal of the frame is calculated and supplied to the over-driving circuit unit 144 as a bitmap count signal.

Meanwhile, the over-driving controller 192 analyzes the second dimming signal transmitted from the duty ratio converter 186 and the bitmap count signal received from the bitmap analyzer 188 to determine whether to perform over-driving. Decide

If the duty ratio of the second dimming signal is greater than or equal to a preset reference duty ratio, that is, the over-driving control unit 192 determines to perform over-driving for a relatively bright image, and the duty ratio of the second dimming signal is the reference duty ratio. If less, that is, do not over-driving for a relatively dark image.

Specifically, the over-driving control unit 192 determines that over-driving is performed in order to prevent a deterioration of image quality of a video such as motion blur in the case of a relatively bright image, and over in the case of a relatively dark image. Since deterioration of image quality such as motion blur is hardly observed even if driving is not performed, it is determined that over-driving is not performed in order to reduce heat load by reducing the load of the timing controller of the control circuit unit 184. do.

The over-driving control unit 192 determines that the bitmap count of the bitmap count signal is greater than or equal to a preset reference bitmap count, that is, to perform over-driving on an image in which relatively bright portions are concentrated. When the bitmap count of the bitmap count signal is less than the reference bitmap count, that is, over-driving is not performed on an image in which a relatively bright portion is not dense and is spread.

Specifically, the over-driving control unit 192 determines that the over-driving is performed in order to prevent deterioration of the quality of a video such as a motion blur in a case where an image having a relatively bright portion is dense, and is relatively bright. In the case of an image having a diffused portion, even if over-driving is not performed, image quality deterioration such as motion blur is hardly observed. Therefore, the amount of heat generated is reduced by reducing the load of the timing controller of the control circuit unit 184. In order to prevent over-driving.

In conclusion, the over-driving control unit 192 determines that over-driving is performed when the image of the frame is relatively bright and when the dark portion of the frame is relatively dark, but the image of the frame is relatively dark. It is determined that over-driving is not performed only if the bright part is not dense but diffused.

The frame memory unit 194 stores the RGB signal received from the data converter 184 as data of a previous frame and updates each frame.

The data modulator 196 may determine the RGB signal of the current frame received from the data converter 184 and the previous frame received from the frame memory 194 according to the over-driving performance of the over-driving controller 192. By comparing the RGB signals and modulating the RGB signals of the current frame using a lookup table 198 that stores the values corresponding to the comparison results, the response time of the liquid crystals is provided by supplying the modulated RGB signals to the liquid crystal panel 120. It shortens and prevents video quality deterioration such as motion blur.

In addition, the data modulator 196 may perform the operation on the liquid crystal panel 120 without changing the RGB signal of the current frame received from the data converter 184 according to the over-driving non-driving decision of the over-driving controller 192. To feed.

In this case, since the relatively dark and bright portions of the frame are diffused without being dense, video quality deterioration such as motion blur is not observed even if over-driving is not performed, but rather by not performing over-driving. The load of the timing controller of the control circuit unit 140 can be reduced and the amount of heat generated can be reduced.

For example, when the timing controller selectively overdrives in this manner, the temperature of the timing controller is about 73 ° C, which is about 78 ° C when the timing controller continuously performs overdriving. Compared with this, it can be seen that the calorific value is drastically reduced.

The first and second reference gradations, reference counts, reference duty ratios, and reference bitmap counts may be variously set in consideration of characteristics of the liquid crystal display and may be stored in the control circuit unit 140 or the like.

2 and 3, the gray level of the frame of the video signal is determined using the duty ratio of the dimming signal, and whether or not to perform over-driving according to the determination result is determined. The non-conversion unit may be omitted, and the gray level of the frame of the image signal may be determined using the result of the histogram analyzer as it is, and whether to perform over-driving according to the determination result.

On the other hand, the operation principle of the optimum power control unit will be described in more detail with reference to the drawings.

4A, 4B, and 4C are diagrams for describing gray level increase, data conversion, and duty ratio conversion in the optimum power control unit of the liquid crystal display according to the exemplary embodiment of the present invention, respectively.

As shown in FIG. 4A, the optimum power controller 142 converts an image signal such that the gray level is increased for an image of a frame satisfying a specific condition. For example, the gray scale value 200, which is the first reference gray level, is maximized. The gray scale value is increased to 255, and gray scales below it may be converted by multiplying a gain defined as a ratio of the first reference gray scale to the maximum gray scale. In this case, even if the illuminance of the backlight unit 130 is reduced, the liquid crystal display 110 may display an image having the same luminance.

This conversion is applied to each frame and each pixel of the video signal. For example, as illustrated in FIG. 4B, each of the first histogram h1 of the video signal of the corresponding frame supplied from the system circuit unit 160 is provided. The second histogram h2 is obtained by multiplying the gray level by about 0.78 (˜200 / 255), thereby performing data conversion.

At the same time, the dimming signal is converted so that the duty ratio is increased so as to correspond to the data conversion. For example, as illustrated in FIG. 4C, the first dimming signal of the first duty ratio supplied from the system circuit unit 160 is converted into a first dimming signal. The duty ratio conversion is performed by generating a second dimming signal having a second duty ratio smaller than one duty ratio.

In this case, the gray level of the first reference gray level or more becomes a gray level value of 255 due to data conversion (saturation), so that the pixels cannot be distinguished from each other, which acts as data loss in data conversion.

Therefore, when the number of pixels above the first reference gray level is equal to or greater than the first reference number, that is, when the data loss is so large that it adversely affects the image quality, the data conversion is not performed and the duty ratio conversion is not performed accordingly.

In addition, the second duty ratio may be supplied to the over-driving control unit 192 and used as a criterion for determining whether to perform over-driving.

5 is a diagram for describing bitmap analysis in an optimum power control unit of a liquid crystal display according to an exemplary embodiment of the present invention.

As shown in Fig. 5, in a video signal of one frame, the case where the gradation of each pixel is equal to or greater than the second reference gradation is defined as an error pixel, and is displayed as "1", and the gradation of each pixel is less than the second reference gradation. In the case of "0", a bitmap is created.

For example, the maximum gray level of the video signal of the previous frame may be set as the second reference gray level.

Since the smallest size at which gradation saturation can be seen visually is 16 square pixels, the window defined by 4 X 4 pixels is scanned as "1" inside the window while scanning from the upper left to the lower right of the image. If the number of displayed pixels is equal to or greater than the second reference number, it is determined that the bright parts are concentrated and count is performed.

For example, the second reference count may be “14”, and the bitmap count may be supplied to the over-driving control unit 192 to be used as a criterion for over-driving.

6 is a flowchart illustrating a method of driving a liquid crystal display according to an exemplary embodiment of the present invention, which will be described with reference to FIGS. 2 and 3.

The control circuit unit 140 of the liquid crystal display 110 receives the image signal and the first dimming signal from the system circuit unit 160 (st10).

The histogram analyzer 182 of the control circuit 140 analyzes the gradation histogram of the image signal for each frame (st12), and generates an RGB signal and a second dimming signal for the frame according to the analysis result (st14).

The bitmap analyzer 188 of the control circuit 140 analyzes the grayscale bitmap of the image signal for each frame (st16), and generates a bitmap count signal for the corresponding frame according to the analysis result.

The second dimming signal and the bitmap count signal are transmitted to the over-driving control unit 192 of the control circuit unit 140, and the over-driving control unit 192 compares the duty ratio of the second dimming signal with a preset reference duty ratio. To determine the magnitude (st20).

As a result of the determination, when the duty ratio for the frame is less than the reference duty ratio, the over-driving control unit 192 compares the bitmap count of the bitmap count signal with a preset reference bitmap count to determine the magnitude (st22).

As a result of determination, when the bitmap count for the frame is less than the reference bitmap count, the over-driving control unit 192 determines that over-driving is not performed (st24), and the data conversion unit 184 of the control circuit unit 140. RGB signal for the corresponding frame is output as is (st26).

On the other hand, when the over-driving control unit 192 determines that the duty ratio for the frame is greater than or equal to the reference duty ratio, or if the bitmap count for the frame is greater than or equal to the reference bitmap count, the over-driving control unit 192 is over- It is determined that driving is performed (st28), and the modulated RGB signal of the corresponding frame of the data converter 184 of the control circuit 140 outputs the modulated RGB signal (st30).

Accordingly, the liquid crystal panel 120 displays an image of a corresponding frame by using an RGB signal without over-driving or a modulated RGB signal with over-driving applied (st32).

As described above, in the liquid crystal display according to the exemplary embodiment of the present invention, when the video signal is relatively dark and the bright parts are not relatively dense, the over-driving is stopped, so that the load of the timing controller or the like is reduced. It reduces and heat quantity is reduced.

Therefore, it is possible to prevent deterioration of characteristics such as a timing controller due to overheating and to reduce power consumption.

The present invention is not limited to the above embodiments, and various modifications can be made without departing from the spirit of the present invention.

1 is a view for comparing a general driving method of a conventional liquid crystal display device and a driving method using an over-driving circuit.

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

3 is a block diagram showing a control circuit of the liquid crystal display according to the embodiment of the present invention.

4A, 4B, and 4C are diagrams for describing gray level increase, data conversion, and duty ratio conversion in the optimum power control unit of the liquid crystal display according to the exemplary embodiment of the present invention, respectively.

5 is a diagram for describing bitmap analysis in an optimum power control unit of a liquid crystal display according to an exemplary embodiment of the present invention.

6 is a flowchart illustrating a method of driving a liquid crystal display device according to an embodiment of the present invention.

Claims (10)

A control circuit unit for determining whether to perform over-driving by analyzing a gray level of an image signal for each frame and outputting an RGB signal or a modulated RGB signal according to whether the over-driving is performed; A liquid crystal panel which displays an image corresponding to the image signal by using the RGB signal or the modulated RGB signal of the control circuit unit; A backlight unit for supplying light to the liquid crystal panel Liquid crystal display comprising a. The method of claim 1, A system circuit part which supplies the video signal and the first dimming signal to the control circuit part; Inverter circuit unit for controlling the backlight unit Liquid crystal display further comprising. The method of claim 2, The control circuit unit, An optimum power control unit for analyzing the gray level of the video signal for each frame and outputting the RGB signal, the second dimming signal, and the bitmap count signal; An over-driving circuit unit for outputting the RGB signal or the modulated RGB signal according to whether the over-driving is performed using the second dimming signal and the bitmap count signal Liquid crystal display comprising a. The method of claim 3, wherein The optimum power control unit, A histogram analyzer to determine whether to perform data conversion and duty ratio conversion by analyzing the gray level of the video signal for each frame; A data converter configured to generate the RGB signal by performing data conversion to increase the gray level of the video signal according to whether to perform the data conversion of the histogram analyzer; A duty ratio converter for generating the second dimming signal by performing a duty ratio conversion to increase the duty ratio of the first dimming signal according to whether the histogram analyzer performs the duty ratio conversion; A bitmap analyzer for generating a bitmap count signal by generating a bitmap of the gray level of the video signal for each frame and calculating a bitmap count Liquid crystal display comprising a. The method of claim 4, wherein The histogram analysis unit, If the number of pixels that is greater than or equal to the first reference gray level of the video signal is less than the reference number, the data conversion and the duty ratio conversion are determined not to be performed. And determining that the data conversion and the duty ratio conversion are performed when the number of pixels equal to or greater than the first reference gray level of the image signal is equal to or greater than the reference number. The method of claim 3, wherein The over-driving circuit unit, An over-driving controller configured to determine whether to perform the over-driving by analyzing the second dimming signal and the bitmap count signal; A frame memory unit which stores the RGB signal as data of a previous frame and updates each frame; A data modulator for generating the modulated RGB signal by comparing the RGB signal of the current frame with the RGB signal of the previous frame according to whether the over-driving is performed; A lookup table that stores a value corresponding to a result of comparing the RGB signal of the current frame with the RGB signal of the previous frame Liquid crystal display comprising a. The method of claim 6, The over-driving control unit, Determining the magnitude of the duty ratio and the reference duty ratio of the second dimming signal and the magnitude of the bitmap count and the reference bitmap count of the bitmap count signal, If the duty ratio of the second dimming signal is less than the reference duty ratio and at the same time the bitmap count of the bitmap count signal is less than the reference bitmap count, it is determined that the over-driving is not performed so that the RGB signal is output. and, If the duty ratio of the second dimming signal is greater than or equal to the reference duty ratio or if the bitmap count of the bitmap count signal is greater than or equal to the reference bitmap count, it is determined that the over-driving is performed to output the modulated RGB signal. Liquid crystal display device. Analyzing a gray level of an image signal for each frame to generate a dimming signal and a bitmap count signal; Determining whether to perform over-driving using the dimming signal and the bitmap count signal; Displaying an image corresponding to the image signal using an RGB signal or a modulated RGB signal according to whether the over-driving is performed; Method of driving a liquid crystal display device comprising a. The method of claim 8, Determining whether or not the over-driving is performed, Determining the magnitude of the duty ratio and the reference duty ratio of the dimming signal; Determining the magnitude of the bitmap count and the reference bitmap count of the bitmap count signal; Method of driving a liquid crystal display device comprising a. The method of claim 9, Determining whether or not the over-driving is performed, Outputting the RGB signal by determining that the over-driving is not performed when the duty ratio of the dimming signal is less than the reference duty ratio and at the same time the bitmap count of the bitmap count signal is less than the reference bitmap count; ; When the duty ratio of the second dimming signal is greater than or equal to the reference duty ratio or the bitmap count of the bitmap count signal is greater than or equal to the reference bitmap count, determining that the over-driving is performed to output the modulated RGB signal. Steps to Driving method of the liquid crystal display device further comprising.

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