KR101666223B1 - Liquid crystal display and apparatus for driving the same - Google Patents

Abstract

Disclosed is a liquid crystal display device capable of selectively reducing color deviation or power consumption.

The liquid crystal display of the present invention includes a liquid crystal display panel, a backlight unit divided into a plurality of blocks to provide light to the liquid crystal display panel, and image data and illuminance are detected to reduce color deviation between blocks according to image data and illuminance And a backlight driver for correcting the dimming value of the blocks.

Description

Technical Field [0001] The present invention relates to a liquid crystal display (LCD)

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device and a driving method thereof that can selectively reduce color deviation or power consumption.

2. Description of the Related Art In recent years, various flat panel display devices that can reduce weight and volume, which are disadvantages of cathode ray tubes (CRTs), are emerging. Examples of such flat panel display devices include a liquid crystal display device, a field emission display device, a plasma display device, and an organic electro luminescence display device .

Among the display devices, a liquid crystal display device is a device that displays light by generating light from a light source on the rear side, by selectively transmitting each pixel of the liquid crystal display panel on the front side as a kind of optical switch. That is, while a conventional cathode ray tube (CRT) controls brightness by controlling the intensity of an electron beam, a liquid crystal display controls the intensity of light generated from a light source to display a screen.

The liquid crystal display device includes a liquid crystal display panel, a timing controller, and a gate and a data driver for driving the liquid crystal display panel using the timing signal supplied from the timing controller.

A liquid crystal display panel includes a plurality of gate lines for transmitting a scan signal, a plurality of data lines for transmitting image data intersecting the plurality of gate lines, a pixel defined by the gate lines and the data lines, And a thin film transistor formed in a crossing region of the gate lines and the data lines.

Since the liquid crystal display panel is not a self-luminous element, it includes a backlight unit for irradiating light to the liquid crystal display panel.

The image quality of the liquid crystal display device depends on the contrast characteristics. There is a limitation in improving the contrast characteristic only by modulating the light transmittance in the liquid crystal layer of the liquid crystal display panel. In recent years, a backlight dimming control method for adjusting the brightness of a backlight unit according to an image has been proposed in order to improve the contrast characteristic.

In the backlight dimming method, there are a global dimming method (global dimming method) for adjusting the brightness of the entire display surface and a local dimming method for locally adjusting the brightness of the display surface divided into a plurality of blocks.

The local dimming method can improve the static contrast that can not be improved by the global dimming method and can reduce the power consumption of the backlight unit by locally controlling the luminance of the display surface within one frame period I have.

However, the local dimming method has a problem of causing color deviation and flicker due to the luminance difference between a plurality of blocks in the display surface.

An object of the present invention is to provide a liquid crystal display device and a driving method thereof that can selectively reduce color deviation or power consumption.

According to an embodiment of the present invention,

A liquid crystal display panel; A backlight unit divided into a plurality of blocks to provide light to the liquid crystal display panel; And a backlight driver for detecting image data and illuminance and correcting the dimming value of the blocks so as to reduce the color deviation between the blocks according to the image data and the illuminance.

According to another aspect of the present invention, there is provided a method of driving a liquid crystal display device,

Detecting ambient illuminance; Analyzing occurrence of color discrepancy between blocks using the detected illuminance and image data; And correcting the dimming value of the blocks according to whether color discrepancy has occurred or not.

According to the present invention, the dimming value of the blocks is corrected by adjusting the filtering value by filtering the low pass filter according to the ambient illuminance and the image data, thereby selectively reducing the color deviation or reducing the power consumption.

In the present invention, a liquid crystal display device is described as an example in a flat panel display device.

FIG. 1 is a schematic view of a liquid crystal display according to an embodiment of the present invention, and FIG. 2 is a diagram illustrating the configuration of a backlight driver according to an embodiment of the present invention.

1 and 2, a liquid crystal display device according to an embodiment of the present invention includes a liquid crystal display device in which gate lines GL1 to GLn and data lines DL1 to DLm are crossed, A liquid crystal display panel 110 in which a thin film transistor (TFT) for driving the cell Clc is formed and a liquid crystal display panel 110 for supplying a data signal to data lines DL1 to DLm of the liquid crystal display panel 110 A gate driver 130 for supplying a scan signal to the gate lines GL1 to GLn of the liquid crystal display panel 110 and a gate driver 130 and a data driver 120 for controlling the data driver 120, And a timing controller 150 for controlling the timing controller 150.

Although not shown in the figure, the liquid crystal display device includes a DC-DC converter (not shown) that generates various power supply voltages for driving the liquid crystal display panel 110 using a power supplied from the outside, And a gamma voltage generator (not shown) for supplying the gamma voltage to the data driver 120.

In the liquid crystal display panel 110, a thin film transistor (TFT) is formed as a switching element for each liquid crystal cell. The gate electrode of the thin film transistor TFT is connected to the gate lines GL1 to GLn, the source electrode thereof is connected to the data lines DL1 to DLm, the drain electrode thereof is connected to the pixel electrode of the liquid crystal cell Clc, (Cst). The common voltage Vcom is supplied to the common electrode of the liquid crystal cell Clc and the storage capacitor Cst charges the data voltage supplied from the data lines DL1 to DLm when the thin film transistor TFT is turned on Thereby maintaining the voltage of the liquid crystal cell Clc constant.

When the scan pulse is sequentially supplied to the gate lines GL1 to GLn, the thin film transistor TFT is turned on to form a channel between the source electrode and the drain electrode to supply the voltage on the data lines DL1 to DLm to the liquid crystal cell (Clc). At this time, the liquid crystal molecules of the liquid crystal cell Clc are changed in arrangement by the electric field between the pixel electrode and the common electrode to modulate the incident light.

The data driver 120 supplies a data signal to the data lines DL1 to DLm in response to the data driving control signal DCS supplied from the timing controller 150. [ The data driver 120 samples and latches the image data (R, G, and B Data) input from the timing controller 150 and then latches the image data (R, G, and B Data) by using the gamma reference voltage supplied from the gamma voltage generator ) Into an analog data voltage capable of expressing the gradation in the liquid crystal cell Clc of the liquid crystal cell Clc and supplies it to the data lines DL1 to DLm.

Here, the data driving control signal DCS supplied from the timing controller 150 includes SSP, SSC, SOE, POL, and the like.

The gate driver 130 sequentially generates scan pulses in response to a gate drive control signal GCS supplied from the timing controller 150 and sequentially applies scan pulses to the gate lines GL1 to GLn sequentially .

Here, the gate drive control signal (GCS) supplied from the timing controller 150 includes GSP, GSC, GOE, and the like.

The timing controller 150 receives the vertical / horizontal synchronizing signal Vsync / Hsync, the data enable signal DE, the clock signal Clk and the data signals R, G and B Data supplied from a system And controls the data driver 120, the gate driver 130, and the backlight driver 170 using the data driver 120. [

The backlight driving unit 170 drives the backlight unit 160 into a plurality of blocks by using the backlight control signal BCS and the data signals R, G, and B data from the timing controller 150.

The backlight unit 160 is divided into a plurality of blocks, and a plurality of light emitting diodes (LEDs) are used as a light source.

The backlight driving unit 170 includes a block dividing unit 171 for dividing the backlight unit 160 into a plurality of blocks, a mean value analyzing unit 172 for analyzing the average value of data displayed for each block, A local dimming correction unit 176 for adjusting the dimming of the blocks on the basis of the average value of the blocks from the local dimming correction unit 176 and the LED dimming unit 176 for driving the light emitting diodes of the blocks using the corrected dimming value from the local dimming correction unit 176. [ (177).

The backlight driver 170 further includes an illuminance sensor (not shown) that detects an external illuminance, although not shown in the figure. The illuminance detector 173 detects an external illuminance sensed by the illuminance sensor. The illuminance detector 173, And a Halo analyzer 175 for analyzing the generation of a halo between adjacent blocks using the external illuminance detected from the external controller 150 and the image data 174 input from the timing controller 150. [

Here, the halo can be defined as a color deviation caused by a difference in dimming value between adjacent blocks of the backlight unit 160 when an image of the same gray level is displayed between adjacent blocks.

The halo is easily discernible to the naked eye in a dark environment than in a bright environment, and the gray series contrasted with each other is easily distinguished by the naked eye.

The Halo analyzing unit 175 determines whether a halo is generated according to the image data and the surrounding illuminance in units of one frame inputted from the image data 174 and the illuminance detecting unit 173 and outputs the halo to the local dimming corrector 176. [ .

When the image data is a gray series in a dark environment, the Halo analyzing unit 175 determines that a halo is generated, generates a first control signal by generating a halo, And supplies it to the correction unit 176. The local dimming correction unit 176 corrects the dimming value of the blocks by the first control signal to reduce the difference in dimming value between the display block of the bright series image data and the adjacent block.

Here, the local dimming correction unit 176 adjusts the filtering value by filtering the low pass filter according to the first control signal to correct the dimming value of the blocks.

That is, the filtering value of the low pass filter by the first control signal is for minimizing the difference in dimming value between blocks, and the local dimming correction unit 176 corrects the dimming value between the blocks so that the difference in dimming value between the blocks is minimized.

When the image data has a sequence of multiple colors as a whole in an environment in which the ambient illumination is bright, the halo is not easily recognized by the naked eye. Accordingly, the Halo analyzing unit 175 determines that no halo is generated, generates a second control signal due to no halo, and supplies the second control signal to the local dimming correction unit 176.

The local dimming correction unit 176 corrects the dimming value of the blocks by the filtering value by the filtering of the low pass filter preset by the second control signal.

Here, the dimming value of the blocks has a large deviation by the filtering value by the filtering of the predetermined low-pass filter, so that the power consumption can be reduced.

When the image data has a gray series in a bright ambient illumination or in a dark ambient illumination environment, if the image data has a plurality of colors in the whole, the halo is not easily recognized visually. Therefore, the halo analyzing unit 175 determines that no halo is generated, and generates a second control signal to supply it to the local dimming correction unit 176.

As described above, the liquid crystal display of the present invention adjusts the filtering value by filtering the low pass filter according to the ambient illuminance and the image data so that the dimming value of the blocks is corrected, thereby selectively reducing the color deviation, .

FIG. 3 is a diagram illustrating a backlight unit divided into a plurality of blocks, FIG. 4 is a diagram illustrating dimming values between blocks at the time of occurrence of a hayrow according to an embodiment of the present invention, and FIG. Fig. 8 is a diagram showing dimming values between blocks at the time of occurrence of the hayrou according to the example.

As shown in Figs. 3 to 5, the backlight unit 160 of the present invention is divided into a plurality of blocks a1-1 to a4-4.

For example, if image data of the white series and the black series are input to the a3-2 block in an environment where the ambient illumination is dark, and the image data of the black series is input to the remaining blocks, The filtering value of the low pass filter is adjusted by the control signal 1, and the deviation of the dimming value becomes smaller as the distance from the adjacent block of the a3-2 block is minimized.

That is, when the a3-2 block has a dimming value of 90%, a2-2 and a4-2 adjacent to the a3-2 block have a dimming value of 80%, and the a1-2 block has a dimming value of 70% .

Although not shown in the figure, the a2-1, a2-3, a3-1, a3-3, a4-1 and a4-3 blocks are adjacent to the a3-2 block and thus have a dimming value of 80%.

Likewise, the a1-1, a1-3, a1-4, a2-4, a3-4 and a4-4 blocks have the same 70% dimming value as the a1-2 block.

Therefore, when image data of a white-based system and a black-based system are input to the a3-2 block and image data of the black-based system is input to the remaining blocks in an environment of dark ambient illumination, the a3-2- The color difference between the blocks can be improved by correcting the dimming value of the blocks so as to minimize the dimming value deviation from the block to the far block.

On the other hand, when image data of the white series and the black series are input to the a3-2 block and the image data of the black series is input to the remaining blocks in a bright ambient illumination environment, Depending on the filtering value of the low-pass filter, the smaller the distance from the adjacent block in the a3-2 block, the smaller the dimming value becomes.

That is, when the a3-2 block has a dimming value of 90%, a2-2 and a4-2 adjacent to the a3-2 block have a dimming value of 50%, and the a1-2 block has a dimming value of 20% .

Although not shown in the drawing, the a2-1, a2-3, a3-1, a3-3, a4-1 and a4-3 blocks are adjacent to the a3-2 block and thus have a dimming value of 50%.

Likewise, the a1-1, a1-3, a1-4, a2-4, a3-4 and a4-4 blocks have the same dimming value of 20% as the a1-2 block.

Accordingly, when image data of a white series and a black series are input to the a3-2 block and image data of the black series is input to the remaining blocks in an environment with a high ambient illumination, the a3-2 block, The dimming value from the farthest block to the farthest block has a large deviation, and the power consumption can be reduced.

FIG. 6 is a diagram showing an image according to local dimming driving of a general liquid crystal display device, and FIG. 7 is a diagram showing an image according to local dimming driving of the liquid crystal display of the present invention.

As shown in FIG. 6, in an image in which a white ball is displayed on a black background in a dark environment, the black of the block in which the white ball is displayed and the black of the other blocks have different color deviations from each other. The color deviation is generated in an image displaying the same gradation because the dimming value of the block in which the white ball is displayed differs from that of the other blocks.

As shown in FIG. 7, in an image in which a white ball is displayed on a black background in a dark environment, according to the present invention, a filtering value of a low pass filter is controlled by a first control signal of a Halo analyzing unit, And the deviation of the dimming value from the adjacent block to the block away from the adjacent block is minimized, so that the color deviation can be improved.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the 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 schematic view illustrating a liquid crystal display according to an embodiment of the present invention.

2 is a diagram illustrating a configuration of a backlight driver according to an exemplary embodiment of the present invention.

3 is a view showing a backlight unit divided into a plurality of blocks.

4 is a diagram illustrating dimming values between blocks at the time of occurrence of a hayrow according to an embodiment of the present invention.

FIG. 5 is a diagram illustrating dimming values between blocks at the time of occurrence of a haylobe according to an embodiment of the present invention.

6 is a diagram showing an image according to local dimming driving of a general liquid crystal display device.

7 is a diagram showing an image according to the local dimming driving of the liquid crystal display of the present invention.

Claims (11)

A liquid crystal display panel provided with image data; A backlight unit divided into a plurality of blocks to provide light to the liquid crystal display panel; And And a backlight driver for detecting the image data and the external illuminance of the liquid crystal display panel and correcting the dimming value of the blocks so as to reduce the color deviation between the blocks according to the image data and the external illuminance, Wherein the backlight driving unit detects a dark environment of the external illuminance and reduces a deviation of a dimming value between blocks when the image data is a gray series, When the external illuminance is detected in a bright environment and the image data is a gray series and the external illuminance is detected in a dark environment or a bright environment and the image data has a plurality of colors, Liquid crystal display device. The method according to claim 1, The backlight driver includes: A block dividing unit dividing the backlight unit into a plurality of blocks; An average value analyzer for analyzing the average value of the image data of the plurality of blocks; An illuminance detector for detecting the external illuminance; A halo analyzer for analyzing the occurrence of color deviation using the external illuminance and the image data detected from the illuminance detector; And And a local dimming correction unit for correcting the dimming value of the blocks in accordance with the control signal from the lowrow analyzing unit. 3. The method of claim 2, Wherein the local dimming correction unit adjusts the filtering value of the low pass filter to correct the dimming value. 3. The method of claim 2, The gray-level analyzing unit generates a first control signal when the image data is gray-based in a dark environment and supplies the first control signal to the local dimming correction unit, and in a bright environment of the external illumination, And generates a second control signal and supplies the second control signal to the local dimming correction unit when image data having a plurality of colors are inputted regardless of the external illuminance. delete 5. The method of claim 4, Wherein the local dimming correction unit corrects the dimming value of the blocks so that the dimming value between the blocks has a large deviation by the second control signal. Detecting external illuminance; Analyzing the occurrence of color discrepancy between blocks using the image data and the detected external illuminance; And And correcting the dimming value of the blocks depending on whether color discrepancy has occurred or not, The external illuminance is detected in a dark environment, and when the image data is a gray series, the dimming value deviation between the blocks is minimized, When image data of a gray series is inputted in the bright environment of the external illuminance or image data having a plurality of colors are input irrespective of illuminance, the dimming value of the blocks is corrected so that the dimming value between the blocks has a large deviation. A method of driving a device. 8. The method of claim 7, Dividing the backlight unit into a plurality of blocks; And And analyzing the average value of the image data of the plurality of blocks. 8. The method of claim 7, Wherein the dimming value is corrected by adjusting a filtering value of a low pass filter. delete 8. The method of claim 7, When image data of a gray series is inputted in the bright environment of the external illuminance or image data having a plurality of colors are inputted regardless of the external illuminance, the dimming value of the blocks is corrected so that the dimming value between the blocks has a large deviation And a driving method of the liquid crystal display device.

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