KR20110049529A - Liquid crystal display and driving method of thereof - Google Patents

Abstract

PURPOSE: A liquid crystal display and a driving method of thereof are provided to secure a cross ratio by dividing an image into a predetermined number of block and driving a light source in a corresponding block. CONSTITUTION: In a liquid crystal display and a driving method of thereof, an LCD panel(10) displays image data. A backlight unit(16) includes a plurality of light sources and divides a surface light source projected on the LCD into a matrix blocks. A backlight driving circuit(15) the light sources by a unit block based on the PWM signal at blocks. A back light controls circuit(14) analyzes image data by a unit block. The back light control circuit adjust the dimming duty of the PWM signal in a corresponding block.

Description

Liquid crystal display and its driving method {LIQUID CRYSTAL DISPLAY AND DRIVING METHOD OF THEREOF}

The present invention relates to a liquid crystal display device and a driving method thereof capable of improving the contrast ratio of a display image.

BACKGROUND ART Liquid crystal display devices have tended to be gradually widened due to their light weight, thinness, and low power consumption. The liquid crystal display device is used as a portable computer such as a notebook PC, office automation equipment, audio / video equipment, indoor and outdoor advertising display devices, and the like. The liquid crystal display displays an image by using a thin film transistor (TFT) as a switching element. The transmissive liquid crystal display device, which occupies most of the liquid crystal display device, displays an image by controlling an electric field applied to the liquid crystal layer to modulate the light incident from the backlight unit.

The image quality of the liquid crystal display device depends on the contrast characteristics. Only the method of modulating the light transmittance of the liquid crystal layer by controlling the data voltage applied to the liquid crystal layer has a limitation in improving this contrast characteristic. In order to improve the contrast characteristic, an AFLC (Area Focused Luminance Cortrollable) technique for adjusting the brightness of the backlight unit according to an image has been proposed.

The AFLC technology divides an image displayed on one screen into a predetermined number of logical blocks, and adjusts the luminance of the backlight (light sources) corresponding to the block according to the average luminance value to be displayed by the data signal corresponding to each block. The AFLC technique analyzes an image for one frame in a predetermined number of block units to increase the backlight luminance of the block for a block having a large average luminance value and to decrease the backlight luminance of the block for a block having a small average luminance value. Let's do it. AFLC technology attempts to improve contrast characteristics and reduce power consumption by locally varying luminance according to an input image.

However, since the AFCL technique uses only the average luminance value of the corresponding block when determining the luminance of the backlight of each block, it is difficult to improve the contrast characteristic when there is a dark area and a bright area in the block. For example, when the image shows a star in the night sky, the average luminance value of the image data is set very small when there are some dark areas in the block and a very bright area close to white, so that the brightness of the backlight of the block is lowered. do. As a result, the bright areas are displayed very dark, reducing the contrast ratio of the block.

The backlight of each block not only affects the brightness of the block but also affects the brightness of neighboring blocks by about 20%. AFCL technology is limited in improving the contrast ratio because it determines the brightness of the backlight without considering the effect of light leakage between these neighboring blocks.

Accordingly, it is an object of the present invention to provide a liquid crystal display device and a driving method thereof capable of improving the contrast ratio of a display image.

In order to achieve the above object, a liquid crystal display device according to an embodiment of the present invention comprises a liquid crystal display panel on which image data is displayed; A backlight unit including a plurality of light sources and dividing the surface light source irradiated onto the liquid crystal display panel into blocks in a matrix form; A backlight driving circuit for driving the light sources in units of blocks based on a block-by-block PWM signal for controlling the lighting; And analyzing the image data in units of blocks, and a weight proportional to the maximum luminance value of the image data to be displayed in the block and inversely proportional to the average luminance value of the image data to be displayed in neighboring blocks affecting the brightness of the block. With reference to a constant, a backlight control circuit for independently adjusting the dimming duty of the PWM signal of the corresponding block.

The backlight control circuit adjusts the dimming duty of the PWM signal of the corresponding block by comparing the amount of multiplication by the weighting constant of the corresponding block with the weighting constant of the corresponding block.

The amount of clipping is obtained by multiplying a histogram value for each gray level of the image data by a clipping error corresponding to a decrease in brightness of light sources due to local dimming in the corresponding block.

The leakage amount is obtained by multiplying a histogram value for each gray level of the image data by a leakage error corresponding to a brightness change of the corresponding block according to the brightness of the neighboring blocks during local dimming.

The backlight control circuit determines the dimming duty of the PWM signal of the corresponding block based on the amount of multiplying the weighting constant of the corresponding block by the weighting constant and the dimming duty when the amount of the storage of the corresponding block is equal to each other.

The backlight control circuit may include: a histogram analyzer configured to calculate the histogram value for each gray level by analyzing the image data; An error calculator configured to calculate a clipping amount and a leakage amount for each block after dimming according to a feedback dimming control signal; A luminance calculator for analyzing the image data to calculate an average luminance value and a maximum luminance value for each block; A weight constant calculator for calculating the weight constant for each block; A dimming control unit configured to adjust the dimming duty of the dimming control signal for each block by comparing the amount of multiplication by the weighting constant with the weighting constant in each block; And a PWM generator configured to generate the PWM signal according to the block-specific optimal dimming duty.

The dimming control unit adjusts a dimming control signal of the corresponding block so that the dimming duty is reduced by a predetermined value when the amount of the leakage in the corresponding block is greater than the multiplied amount, and then the adjusted dimming control signal. Feeds back to the error calculator.

The dimming control unit adjusts a dimming control signal of the corresponding block so that the dimming duty is increased by a predetermined value when the amount of the liquid crystal is smaller than the multiplied amount in the corresponding block, and then the adjusted dimming control. The signal is fed back to the error calculator.

The dimming control unit determines, as the optimal dimming duty, the dimming duty when the leakage amount and the multiplied amount are equal to each other in the corresponding block through the feedback process.

Driving of a liquid crystal display apparatus having a liquid crystal display panel displaying image data and a backlight unit for dividing a surface light source irradiated to the liquid crystal display panel into blocks of matrix form according to an embodiment of the present invention; The method comprises the steps of: driving the light sources in units of blocks based on a block-by-block PWM signal for controlling the flashing light (A1); And analyzing the image data in units of blocks, and a weight proportional to the maximum luminance value of the image data to be displayed in the block and inversely proportional to the average luminance value of the image data to be displayed in neighboring blocks affecting the brightness of the block. Independently adjusting the dimming duty of the PWM signal of the corresponding block with reference to the constant (A2).

According to an exemplary embodiment of the present invention, a liquid crystal display and a driving method thereof divide a display image into a predetermined number of logical blocks, and the amount of clipping and the amount of leakage of each block is proportional to the maximum luminance value of each block and the average luminance value of neighboring blocks. After comparing the weight constants in inverse proportion to each other, the light sources of the blocks are driven by the dimming duty when the amount of multiplication by the weighting constant of the block is equal to the amount of the storage blocks. As a result, the liquid crystal display and the driving method thereof according to the present invention can compensate for the brightness of the high luminance data even in a block having a low average luminance value, thereby ensuring a high contrast ratio.

Hereinafter, exemplary embodiments of the present invention will be described with reference to FIGS. 1 to 7.

1 shows a liquid crystal display according to an embodiment of the present invention.

Referring to FIG. 1, a liquid crystal display according to an exemplary embodiment of the present invention includes a liquid crystal display panel 10, a data driving circuit 12 for driving data lines DL of the liquid crystal display panel 10, and a liquid crystal display. The gate driving circuit 13 for driving the gate lines GL of the panel 10, the timing controller 11 controlling the data driving circuit 12 and the gate driving circuit 13, and the liquid crystal display panel 10. A backlight unit 16 for irradiating light to the backlight unit, a backlight drive circuit 15 for driving the light sources of the backlight unit 16, and a backlight for analyzing the input image and controlling the backlight drive circuit 15 according to the analysis result The control circuit 14 is provided.

The liquid crystal display panel 10 includes two glass substrates and a liquid crystal layer formed therebetween. A plurality of data lines DL and a plurality of gate lines GL cross on the lower glass substrate of the liquid crystal display panel 10. The liquid crystal cells Clc are arranged in a matrix form on the liquid crystal display panel 10 due to the cross structure of the data lines DL and the gate lines GL. In the lower glass substrate of the liquid crystal display panel 10, TFTs, pixel electrodes 1 of liquid crystal cells Clc connected to TFTs, storage capacitors Cst, and the like are formed.

The black matrix, the color filter, and the common electrode 2 are formed on the upper glass substrate of the liquid crystal display panel 10. The common electrode 2 is formed on the upper glass substrate in a vertical electric field driving method such as twisted nematic (TN) mode and vertical alignment (VA) mode, and has an in plane switching (IPS) mode and a fringe field switching (FFS) mode. In the same horizontal electric field driving method, the pixel electrode 1 is formed on the lower glass substrate. A polarizing plate is attached to each of the upper glass substrate and the lower glass substrate of the liquid crystal display panel 10, and an alignment layer for setting a pretilt angle of the liquid crystal is formed on an inner surface of the liquid crystal display panel 10 in contact with the liquid crystal.

The data driver circuit 12 includes a plurality of data drive integrated circuits. The data drive integrated circuit stores a shift line for sampling a clock signal, a register for temporarily storing digital image data (RGB), a line of data in response to a clock signal from the shift register, and stores one line of data. A latch for outputting at the same time, a digital / analog converter for selecting a positive / negative gamma voltage under reference to a gamma reference voltage corresponding to a digital data value from the latch, and an analog converted by a positive / negative gamma voltage And a multiplexer for selecting a data line DL to which data is supplied, and an output buffer connected between the multiplexer and the data line DL. The data driving circuit 12 latches the digital image data RGB under the control of the timing controller 11 and uses the positive / negative gamma compensation voltage to latch the latched digital image data RGB. The polarity is converted into an analog data voltage and then supplied to the data lines DL.

The gate driving circuit 13 includes a plurality of gate drive integrated circuits. The gate drive integrated circuit includes a shift register, a level shifter for converting an output signal of the shift register into a swing width suitable for driving a TFT of a liquid crystal cell, an output buffer, and the like. The gate driving circuit 13 sequentially outputs scan pulses (or gate pulses) to the gate lines GL under the control of the timing controller 11, thereby selecting a horizontal line to which a data voltage is applied.

The timing controller 11 rearranges the digital image data RGB input from the system board on which the external video source is mounted, to the backlight control circuit 14 by rearranging the digital image data RGB to match the resolution of the liquid crystal display panel 10. The digital image data RGB fed back from the backlight control circuit 14 is supplied to the data driving circuit 12.

The timing controller 11 includes timing control signals for controlling the operation timing of the data driving circuit 12 and the gate driving circuit 13 based on the timing signals Vsync, Hsync, DE, and DCLK from the system board. DDC, GDC). The timing controller 11 inserts an interpolation frame between frames of an input video signal input at a frame frequency of 60 Hz, multiplies the data timing control signal DDC and the gate timing control signal GDC, and 60 × N The operation of the data driving circuit 12 and the gate driving circuit 13 can be controlled at a frame frequency of two or more positive integers Hz.

The backlight unit 16 includes a plurality of light sources and divides the surface light source irradiated to the liquid crystal display panel 10 into blocks in a matrix form. The backlight unit 16 may be implemented as one of a direct type and an edge type. Although the backlight unit illustrated in FIG. 1 exemplifies a direct backlight unit, the backlight unit of the present invention is not limited to the direct backlight unit but may include a backlight unit having any known structure. The direct type backlight unit 16 has a structure in which a plurality of optical sheets and a diffusion plate are stacked below the liquid crystal display panel 10 and a plurality of light sources are disposed below the diffusion plate. The light sources may be implemented as point light sources such as light emitting diodes (LEDs). The optical sheets may include at least one prism sheet and at least one diffusion sheet to diffuse light incident from the diffusion plate and to deflect the traveling path of the light at an angle substantially perpendicular to the light incident surface of the liquid crystal display panel. The optical sheets may comprise a dual brightness enhancement film (DBEF).

The backlight driving circuit 15 drives the light sources in units of blocks based on a pulse width modulation (PWM) signal for each block for controlling the lighting. The digital image data RGB displayed on one screen may be divided into a predetermined number of logical units according to the number of divisions of the surface light source. For example, the digital image data RGB for one frame may be divided into a plurality of blocks BLK [1,1] to BLK [n, m] as shown in FIG. 2.

The backlight control circuit 14 analyzes the input image data RGB in units of blocks under the control of the timing controller 11, and adjusts the duty of the PWM signal in units of blocks according to the analysis result. The backlight control circuit 14 may enlarge the dynamic range of the input image data RGB to compensate for the reduced brightness due to the dimming duty adjustment. The backlight control circuit 14 considers the maximum luminance value of the image data to be displayed in each block and the average luminance value of the image data to be displayed in neighboring blocks affecting the brightness of the block. We derive the dimming duty and use it to locally adjust the brightness of the light sources.

3 shows the backlight control circuit 14 in detail.

Referring to FIG. 3, the backlight control circuit 14 includes a histogram analyzer 141, an error calculator 142, a luminance calculator 143, an upper weight calculator 144, a dimming controller 145, and The PWM generator 146 is provided.

The histogram analyzer 141 receives the image data RGB in one frame unit, calculates a histogram for each gray level of the image data RGB corresponding to each block, and supplies the histogram value for each gray level to the error calculator.

The error calculator 142 dims according to the dimming control signal fed back from the dimming controller 145 and calculates a clipping amount and a leakage amount in each corresponding block.

To this end, the error calculator 142 previously stores a target luminance value (see “Yideal” in FIG. 4) to be output according to the gray level of the image data RGB as shown in FIG. 4, and dimming according to the feedback dimming control signal. Afterwards, the clipping error caused by the reduction of the maximum brightness and the leakage error caused by the light leakage phenomenon are calculated.

When the brightness of the light sources is reduced due to local dimming (see “After Dimming” in FIG. 4), the brightness of the light that can be maximized in the corresponding block is reduced. In this case, in order to compensate for the reduced brightness to match the target luminance value, the error calculator 142 may enlarge the dynamic range of the image data RGB through data modulation. However, even if the image data RGB is modulated, the brightness of the light in the block is difficult to achieve the targeted brightness due to the aggregation of the gray levels at a relatively high gray level. In other words, in FIG. 4, the target luminance value is clipped (indicated by a solid line) to a predetermined value lower than the maximum luminance value in the high gray scale interval. The clipping error e _c (g, d _{i , j} ) for each block due to the clipping phenomenon is obtained through Equation 1 below.

In Equation 1, "g" represents a gradation level, "d _{i , j} " represents a dimming value of the (i, j) th block, and "γ" represents a gamma value (e.g., 2.2).

On the other hand, in the local dimming of the light sources, at a relatively low gray scale, as shown in FIG. 4, the brightness higher than the luminance targeted by the corresponding block is shown. This is because the liquid crystal layer does not completely block the light so that the brightness of the block is affected by the brightness of neighboring blocks. This light leakage phenomenon is called light leakage, and the block error of each block is obtained through Equation 2 below.

In Equation 2, "g" represents a gradation level, "d _{i , j} " represents a dimming value of the (i, j) th block, and "γ" represents a gamma value (e.g., 2.2).

In that block, reducing the brightness of the light sources improves light leakage but makes the clipping prominent. On the other hand, increasing the brightness of the light source improves the clipping phenomenon, but the light leakage phenomenon is prominent. Therefore, it is important to find a dimming duty that can properly adjust the amount of clipping and the amount of leakage in the block.

To this end, the error calculator 142 calculates the clipping amount D _c (i, j) for each block by multiplying the clipping error by the histogram value for each gray level from the histogram analyzer 141 as shown in Equation 3 below.

In Equation 3, n (g) is a histogram analysis value for each gray level, and represents the number of pixels having a gray level g.

In addition, the error calculator 142 multiplies the error of the histogram by the gray level from the histogram analyzer 141 to obtain a blockage amount D _j (i, j) as shown in Equation 4 below. .

In Equation 4, n (g) is a histogram analysis value for each gray level, and represents the number of pixels having a gray level g.

The luminance calculator 143 receives the image data RGB in one frame unit, calculates the average luminance value and the maximum luminance value of the image data RGB corresponding to each block, and calculates the average luminance value and the maximum luminance value for each block. The value is supplied to the weighted upper calculator 144.

The weighted upper calculator 144 calculates, by block, a weight constant determined by a function proportional to the maximum luminance value of the block and inversely proportional to the average luminance value of neighboring blocks. The weight constant α _{i, j} of the (i, j) th block is obtained through Equation 5 below.

In Equation 5, "MAX (i, j)" denotes the maximum luminance value of the (i, j) th block, and "APL (i, j)" denotes the luminance of the pixels included in the ((i, j) th block. Sum) / total number of pixels included in the (i, j) th block), and the average luminance value of the (i, j) th block, and “M” is a macro including the (i, j) th block and neighboring blocks. Represent the horizontal and vertical size of the block, respectively. Here, the size "M" of the macro block may be predetermined to a predetermined value according to the number (a, b) of neighboring blocks affecting the brightness of the (i, j) -th block as shown in FIG. In Equation 5, the denominator represents an average luminance value of neighboring blocks.

As can be clearly seen in FIG. 5, the weight constant of the block is determined to be proportional to the maximum luminance value of the block and inversely proportional to the average luminance value of neighboring blocks. Even if the average luminance value of the block is very low, such as a star shining in a dark night sky, there may be a very bright area therein. In this case, when the brightness of the light sources of the corresponding block is reduced according to the average luminance value as in the related art, a star disappears. Therefore, the weight constant of the block is determined as a value proportional to the maximum luminance value of the block, thereby compensating for the brightness of the high luminance data in a block having a low average luminance value.

In addition, when the neighboring blocks are bright due to the influence of light leakage by the neighboring blocks, the corresponding blocks are also brightened by a certain ratio. Therefore, the weight constant of the block is determined to be inversely proportional to the average luminance value of the neighboring blocks, thereby reducing the degree of light leakage by the neighboring blocks.

The dimming control unit 145 controls the dimming duty of the dimming control signal by using the amount of clipping and liquidity for each block from the error calculator 142 and the weight constant for each block from the weighted upper calculator 144. . The dimming control unit 145 compares the amount of multiplication of the block by the weighting constant of the block with the amount of the storage of the block. If the comparison amount is greater than the multiplied amount, the dimming control unit 145 adjusts the dimming control signal of the corresponding block so that the dimming duty is reduced by a predetermined value, and then calculates an error of the adjusted dimming control signal. Feedback to unit 142. On the other hand, if the amount of leakage is less than the multiplied amount, the dimming control unit 145 adjusts the dimming control signal of the corresponding block so that the dimming duty is increased by a predetermined value, and then the error is adjusted. The feedback to the calculation unit 142. When the multiplied amount and the leakage amount are equal to each other through this feedback process, the dimming control unit 145 determines the dimming duty at that time as an optimal dimming duty, and outputs a dimming control signal including the optimal dimming duty to a PWM generator ( 146).

The PWM generator 146 generates a PWM signal having an optimal dimming duty in response to the dimming control signal from the dimming control unit 145.

6 is an experimental result comparing the effects of the present invention with the prior art.

FIG. 6A is a display image when all the light sources of the backlight unit are turned on regardless of the image data, and light contrast is severe in all areas of the screen, resulting in very poor contrast characteristics of the display image. FIG. 6 (b) shows a display image when the luminance of the light sources are adjusted according to the average luminance value of each block by applying the conventional AFLC technique. As a result, clipping is hardly caused by stars, which makes it difficult to express a detailed image. FIG. 6C is a display image when the brightness of the light sources is adjusted according to the maximum luminance value of each block, and light contrast is still generated in the portion where the stars are displayed, resulting in poor contrast characteristics.

On the other hand, Figure 6 (d) is a display image according to the present invention, the luminance of the light sources of each block is adjusted by using a weight constant that is proportional to the maximum luminance value of the block and inversely proportional to the average luminance value of the neighboring blocks. As a result, as compared with FIGS. 6C and 6D, light images are hardly generated, that is, detailed image expression is possible while having high contrast characteristics.

7 illustrates a method of driving a liquid crystal display according to an exemplary embodiment of the present invention.

Referring to FIG. 7, when the image data RGB is input (S1), the histogram value of each gray level of the image data RGB corresponding to each block is analyzed by analyzing the input image data RGB by one frame unit. To calculate (S2).

This driving method calculates the amount of clapping and the amount of leakage in the block after dimming according to the feedback dimming control signal (S3). Here, the amount of clipping is obtained by multiplying the histogram value for each gray level by a clipping error corresponding to a decrease in brightness of light sources due to dimming in the block. The amount of liquidity is obtained by multiplying a histogram value of each gray level by a liquidity error corresponding to a brightness change of a corresponding block according to the brightness of neighboring blocks when dimming.

The driving method receives the image data RGB in one frame unit and calculates an average luminance value and a maximum luminance value of the image data RGB corresponding to each block (S4).

This driving method calculates a weight constant for each block, which is determined by a function proportional to the maximum luminance value of the block and inversely proportional to the average luminance value of neighboring blocks (S5).

This driving method compares the amount of clipping of the block with the weight constant of the block and the amount of leakage of the block (S6). If the comparison result is greater than the multiplied amount (NO in S6 and Y in S7), the driving method adjusts the dimming control signal so that the dimming duty is reduced by a predetermined value (S8). The adjusted dimming control signal is fed back to the step S3. On the other hand, if the leakage amount is smaller than the multiplied amount (NO in S6 and NO in S7), the driving method adjusts the dimming control signal so that the dimming duty is increased by a predetermined value (S9). The adjusted dimming control signal is fed back to the step S3.

After the feedback process, if the multiplied amount and the leakage amount are equal to each other (YES in S6), the driving method determines the dimming duty at that time as an optimal dimming duty, and then adjusts the duty of the PWM signal according to the optimum dimming duty. (S10). The brightness of the light sources is locally controlled by the duty adjustment of the PWM signal.

As described above, the liquid crystal display device and the driving method thereof according to the present invention divide a display image into a predetermined number of logical blocks, and the amount of clapping and the amount of leakage of each block is proportional to the maximum luminance value of each block and is neighboring. After considering the weight constants inversely proportional to the average luminance value of the blocks, the dimming duty is obtained when the amount of clipping of the block is multiplied by the weight constant and the dimming duty of the block is equal to each other. Drive. As a result, the liquid crystal display and the driving method thereof according to the present invention can compensate for the brightness of the high luminance data even in a block having a low average luminance value, thereby ensuring a high contrast ratio.

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

2 is a diagram illustrating an example in which image data of one frame is divided into a predetermined number according to the number of divisions of the surface light source.

3 is a block diagram illustrating a backlight control circuit in detail.

4 is a diagram illustrating a clipping error and a leakage error generated during local dimming.

5 illustrates a macroblock including the block and neighboring blocks.

Figure 6 shows the results of experiments comparing the effects of the present invention with the prior art.

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

<Description of Symbols for Main Parts of Drawings>

10 liquid crystal display panel 11 timing controller

12: data driving circuit 13: gate driving circuit

14 light source control circuit 15 light source driving circuit

16: backlight unit 141: histogram analysis unit

142: error calculator 143: luminance calculator

144: weight upper part calculation unit 145: dimming control unit

146: PWM generator

Claims (14)

A liquid crystal display panel on which image data is displayed; A backlight unit including a plurality of light sources and dividing the surface light source irradiated onto the liquid crystal display panel into blocks in a matrix form; A backlight driving circuit for driving the light sources in units of blocks based on a block-by-block PWM signal for controlling the lighting; And Analyzing the image data in units of blocks, a weight constant proportional to the maximum luminance value of the image data to be displayed in the block and inversely proportional to the average luminance value of the image data to be displayed in neighboring blocks affecting the brightness of the block. And a backlight control circuit for independently adjusting the dimming duty of the PWM signal of the corresponding block. The method of claim 1, And the backlight control circuit adjusts the dimming duty of the PWM signal of the corresponding block by comparing the amount of the clipping of the corresponding block with the weighting constant and the amount of leakage of the corresponding block. Device. The method of claim 2, Wherein the amount of clipping is obtained by multiplying a histogram value of each gray level of the image data by a clipping error corresponding to a decrease in brightness of light sources due to local dimming in the corresponding block. The method of claim 2, And the liquidity amount is obtained by multiplying a histogram value for each gray level of the image data by a leakage error corresponding to a brightness change of the corresponding block according to the brightness of the neighboring blocks during local dimming. The method of claim 2, The backlight control circuit may determine the dimming duty of the PWM signal of the corresponding block based on the amount of multiplying the weighting constant of the corresponding block by the weighting constant and the dimming duty when the amount of the storage of the corresponding block is equal to each other. A liquid crystal display device. The method of claim 1, The backlight control circuit, A histogram analyzer for analyzing the image data and calculating a histogram value for each gray level; An error calculator configured to calculate a clipping amount and a leakage amount for each block after dimming according to a feedback dimming control signal; A luminance calculator for analyzing the image data to calculate an average luminance value and a maximum luminance value for each block; A weight constant calculator for calculating the weight constant for each block; A dimming control unit configured to adjust the dimming duty of the dimming control signal for each block by comparing the amount of multiplication by the weighting constant with the weighting constant in each block; And And a PWM generator for generating the PWM signal according to the optimum dimming duty for each block. The method of claim 6, The dimming control unit, In the corresponding block, if the leakage amount is greater than the multiplied amount, the dimming control signal of the corresponding block is adjusted so that the dimming duty is reduced by a predetermined value, and then the adjusted dimming control signal is sent to the error calculator. A liquid crystal display device characterized by feeding back. The method of claim 6, The dimming control unit, In the corresponding block, if the leakage amount is smaller than the multiplied amount, after adjusting the dimming control signal of the corresponding block so that the dimming duty is increased by a predetermined value, the adjusted dimming control signal is calculated based on the error. Liquid crystal display device characterized in that the negative feedback. 9. The method according to claim 7 or 8, The dimming control unit, And in the corresponding block through the feedback process, dimming duty when the amount of liquidity and the multiplied product are equal to each other is determined as the optimum dimming duty. A driving method of a liquid crystal display apparatus having a liquid crystal display panel displaying image data and a backlight unit including a plurality of light sources and dividing a surface light source irradiated onto the liquid crystal display panel into matrix blocks. Driving the light sources in units of blocks based on a block-by-block PWM signal for controlling the lighting; And Analyzing the image data in units of blocks, a weight constant proportional to the maximum luminance value of the image data to be displayed in the block and inversely proportional to the average luminance value of the image data to be displayed in neighboring blocks affecting the brightness of the block. A method of driving a liquid crystal display device, comprising the step of independently adjusting the dimming duty of the PWM signal of the corresponding block. 11. The method of claim 10, In the step (A2), the dimming duty of the PWM signal of the block is adjusted by comparing the amount of multiplication by the weighting constant with the amount of clipping of the block and the amount of liquidity of the block. Method of driving display device. The method of claim 11, Wherein the amount of clipping is obtained by multiplying a histogram value of each gray level of the image data by a clipping error corresponding to a decrease in brightness of light sources due to local dimming in the corresponding block. The method of claim 11, The liquid crystal amount is obtained by multiplying a histogram value for each gray level of the image data by a leakage error corresponding to a change in brightness of the corresponding block according to the brightness of the neighboring blocks during local dimming. Driving method. The method of claim 11, In step A2, the dimming duty of the PWM signal of the corresponding block is determined based on the amount of multiplying the weighting constant of the corresponding block by the weighting constant and the dimming duty when the amount of the corresponding block is equal to each other. A method of driving a liquid crystal display device.

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