KR102418572B1 - Liquid Crystal Display Device and Driving Method thereof - Google Patents

Abstract

According to the present invention, when grayscale aggregation occurs a lot, it is possible to reduce the grayscale aggregation by changing the pixel gain and lowering the compensation rate of the data signal by controlling the target light quantity instead of the dimming value. To this end, in the present invention, when grayscale aggregation occurs, the pixel gain value is varied according to the degree of grayscale aggregation.

Description

Liquid Crystal Display Device and Driving Method thereof

The present invention relates to a liquid crystal display device and a driving method thereof.

With the development of information technology, the market for display devices, which is a connection medium between users and information, is growing. Accordingly, a flat panel display (FPD) such as a liquid crystal display (LCD), an organic light emitting diode display (OLED), and a plasma display panel (PDP), etc. ) is increasing in use.

The liquid crystal display includes a liquid crystal panel, a backlight unit, a driving unit, a timing control unit, and the like. The liquid crystal panel includes a liquid crystal layer positioned between a transistor substrate on which a thin film transistor, a storage capacitor, and a pixel electrode are formed, and a color filter substrate on which a color filter and a black matrix are formed.

The liquid crystal panel operates based on the gate signal supplied from the gate driver and the data voltage supplied from the data driver. The backlight unit provides light to the liquid crystal panel using a light source such as a light emitting diode (LED).

The liquid crystal display uses a dimming method to increase the power efficiency of the liquid crystal panel. In the dimming method, the brightness of the backlight unit is adjusted according to the screen displayed on the liquid crystal panel, and the data voltage is compensated accordingly. The dimming method can reduce power consumption.

However, when the dimming method proposed in the prior art uses a low consumption mode (reducing power consumption a lot), such as a laptop or a mobile phone, the image quality deteriorates due to grayscale saturation and grayscale aggregation, or there is a limit in power consumption reduction. is required

The present invention for solving the problems of the above-mentioned background art is to alleviate grayscale aggregation, improve power consumption efficiency, improve the expressive power of low grayscale and high grayscale, and provide detailed information of high grayscale and low grayscale without problems such as grayscale reversal when grayscale clustering occurs. It is to further improve the expressive power (detail).

As a means for solving the above-mentioned problems, the present invention provides a liquid crystal display device including a liquid crystal panel, a backlight unit, and a dimming control unit. The liquid crystal panel displays an image. The backlight unit provides light to the liquid crystal panel. The dimming controller controls dimming of the backlight unit. The dimming control unit calculates a dimming value by analyzing the input data signal, outputs a dimming signal for varying the brightness of the backlight unit, and outputs a compensation data signal obtained by compensating for the gain of the data signal by the variable brightness of the backlight unit, When grayscale aggregation occurs, the pixel gain value is varied according to the degree of grayscale aggregation.

When grayscale aggregation occurs, the dimming controller may control a light amount target value indicating an amount of light when the entire light emitting surface of the backlight unit is turned on in full white, and may vary a pixel gain value in response to the target light amount.

When grayscale aggregation occurs, the dimming control unit adaptively controls a target light amount indicating the amount of light when the entire light emitting surface of the backlight unit is turned on in full white, and adjusts a pixel gain value in response to the adaptively changed target value. can be variable.

When grayscale aggregation occurs, the dimming control unit adaptively controls the target light amount indicating the amount of light when the entire light emitting surface of the backlight unit is turned on in full white, and in response to the adaptively changed target value of light amount Only the pixel gain value for the grayscale region can be varied.

When grayscale aggregation occurs, the dimming control unit adaptively controls the target light amount indicating the amount of light when the entire light emitting surface of the backlight unit is turned on in full white, and in response to the adaptively changed target value of light amount Only the pixel gain value for the grayscale region is changed, and when the gradient of the target light amount located in the high grayscale region greater than or equal to the threshold reaches the maximum, the gradient of the target light amount may be lowered.

The dimming control unit calculates the degree of grayscale clustering, and when grayscale clustering occurs, adaptively according to the degree of grayscale clustering, the dimming control unit may include a grayscale clustering compensation unit that varies at least one of a light intensity target value, a pixel gain value, and a light intensity target value slope. have.

The grayscale agglomeration compensator includes a dimming value determiner that determines a dimming value for each block based on the block representative value and the overall representative value of the input image, and outputs a dimming signal based on the determined dimming value for each block, and a dimming value preset for each block A light amount calculation unit for each pixel that selects a light profile and calculates the light amount of each pixel in a specific block, and compensates the pixel data signal by calculating a gain for each pixel and multiplying the gain by the original pixel data signal and compensating for the compensation data signal It may further include a gain correction unit for outputting.

In another aspect, the present invention provides a method of driving a liquid crystal display. A method of driving a liquid crystal display includes: calculating a dimming value by analyzing an input data signal; calculating a pixel gain value using the dimming value and the light profile value; generating a compensation data signal to be output by applying a pixel gain value to the input data signal; and determining whether grayscale clustering occurs, and re-calculating a pixel gain value when grayscale clustering occurs.

In the step of re-calculating the pixel gain value, when grayscale aggregation occurs, the target light amount indicating the amount of light when the entire light emitting surface of the backlight unit is turned on in full white is adaptively controlled, and the target light amount is adjusted to the adaptively changed target value Correspondingly, the pixel gain value may be recalculated, and the pixel gain value may be varied.

In the step of re-calculating the pixel gain value, when grayscale aggregation occurs, the target light amount indicating the amount of light when the entire light emitting surface of the backlight unit is turned on in full white is adaptively controlled, and the target light amount is adjusted to the adaptively changed target value Correspondingly, only the pixel gain value for the high grayscale region equal to or greater than the threshold value is varied, and when the gradient of the target light quantity target value located in the high grayscale region equal to or greater than the threshold value reaches a maximum, the gradient of the light quantity target value may be lowered.

According to the present invention, when grayscale aggregation occurs a lot, it is possible to reduce the grayscale aggregation by changing the pixel gain and lowering the compensation rate of the data signal by controlling the target light quantity instead of the dimming value. In addition, the present invention has effects of alleviating grayscale aggregation, improving power consumption efficiency, and improving the expressive power of low grayscale and high grayscale. In addition, the present invention has the effect of further improving the detail of high grayscale and low grayscale without problems such as grayscale reversal when grayscale aggregation occurs.

1 is a block diagram schematically showing a liquid crystal display device;
FIG. 2 is a circuit diagram schematically illustrating the sub-pixel shown in FIG. 1;
3 is an exemplary diagram in which light emitting surfaces of a display panel and a backlight unit are divided into blocks;
4 and 5 are exemplary diagrams of a dimming curve.
6 is an exemplary configuration diagram of a dimming control unit;
7 is a view for schematically explaining a problem of a dimming method according to an experimental example.
8 is a diagram schematically illustrating a dimming method according to a first embodiment of the present invention.
9 is a diagram schematically illustrating a dimming method according to a second embodiment of the present invention.
10 is a diagram schematically illustrating a dimming method according to a third embodiment of the present invention.
11 is a diagram schematically illustrating a dimming method according to a fourth embodiment of the present invention;
12 is a view for explaining variations of a target light amount, a compensation rate of a data signal, and a slope of a target light amount by a dimming method according to embodiments of the present invention;
13 is a diagram illustrating a variable example of a light quantity target value and a slope of the light quantity target value;
14 is a view for explaining the difference between the experimental example and the present invention.

Hereinafter, specific details for carrying out the present invention will be described with reference to the accompanying drawings.

1 is a block diagram schematically showing a liquid crystal display device, FIG. 2 is a circuit diagram schematically illustrating a sub-pixel shown in FIG. 1, and FIG. 3 is an exemplary diagram in which the light emitting surfaces of the display panel and the backlight unit are divided into blocks. , 4 and 5 are exemplary diagrams of a dimming curve, and FIG. 6 is an exemplary configuration diagram of a dimming control unit.

1 and 2 , the liquid crystal display includes an image supply unit 110 , a timing control unit 130 , a gate driver 140 , a data driver 150 , a liquid crystal panel 160 , a backlight unit 170 and A dimming control unit 180 is included.

The image supply unit 110 outputs various driving signals together with a data signal supplied from the outside or a data signal DATA stored in an internal memory. The image supply unit 110 supplies the data signal DATA and various driving signals to the timing control unit 130 . The image supply unit 110 may output the data signal DATA in units of frames. The data signal DATA output from the image supply unit 110 includes R (red), G (green), and B (blue) data signals.

The timing controller 130 outputs a gate timing control signal GDC for controlling the operation timing of the gate driver 140 and a data timing control signal DDC for controlling the operation timing of the data driver 150 . The timing controller 130 supplies the data signal DATA supplied from the image processor 110 together with the data timing control signal DDC to the data driver 150 .

The gate driver 140 outputs a gate signal while shifting the level of the gate voltage in response to the gate timing control signal GDC supplied from the timing controller 130 . The gate driver 140 supplies a gate signal to the sub-pixels SP included in the liquid crystal panel 160 through the gate lines GL. The gate driver 140 is formed in the form of an IC (Integrated Circuit) or is formed in the liquid crystal panel 160 in the form of a Gate In Panel.

The data driver 150 samples and latches the data signal DATA in response to the data timing control signal DDC supplied from the timing controller 130 , and converts the digital signal into an analog signal form in response to the gamma reference voltage and outputs it do. The data driver 150 supplies a data signal (or data voltage) DATA to the sub-pixels SP included in the liquid crystal panel 160 through the data lines DL. The data driver 150 is formed in the form of an integrated circuit (IC).

The liquid crystal panel 160 displays an image in response to the gate signal supplied from the gate driver 140 , the data signal DATA supplied from the data driver 150 , and the common voltage VCOM. The liquid crystal panel 160 includes sub-pixels SP that control the light provided through the backlight unit 170 .

One sub-pixel includes a switching transistor SW, a storage capacitor Cst, and a liquid crystal layer Clc. The gate electrode of the switching transistor SW is connected to the gate line GL1 , and the source electrode is connected to the data line DL1 . One end of the storage capacitor Cst is connected to the drain electrode of the switching transistor SW and the other end is connected to the common voltage line Vcom. The liquid crystal layer Clc is formed between the pixel electrode 1 connected to the drain electrode of the switching transistor SW and the common electrode 2 connected to the common voltage line Vcom.

The liquid crystal panel 160 has a TN (Twisted Nematic) mode, VA (Vertical Alignment) mode, IPS (In Plane Switching) mode, FFS (Fringe Field Switching) mode depending on the structure of the pixel electrode 1 and the common electrode 2 . Alternatively, it is implemented in an Electrically Controlled Birefringence (ECB) mode.

The backlight unit 170 provides light to the liquid crystal panel 160 using a light source that emits light. The backlight unit 170 includes a light source (eg, a light emitting diode), an LED driver for driving a light emitting diode (hereinafter, LED), an LED board on which the LED is mounted, a light guide plate for converting light emitted from the LED into a planar light source, and from the lower part of the light guide plate A reflective plate for reflecting light, optical sheets for condensing and diffusing the light emitted from the light guide plate, and the like are included.

The dimming controller 180 analyzes the data signal DATA, calculates a dimming value, and outputs a dimming signal DIM for varying the luminance of the backlight unit 170 . In addition, the dimming control unit 180 outputs a compensation data signal DATA′ obtained by compensating (adjusting) the gain of the data signal DATA by a variable amount of the luminance of the backlight unit 170 .

The dimming signal DIM output from the dimming controller 180 is supplied to the backlight unit 170 , and the compensation data signal DATA′ is supplied to the timing controller 130 . The dimming controller 180 varies the backlight unit 170 using a global dimming method or a local dimming method. The dimming controller 180 may be included in the timing controller 130 .

3 to 5 , the dimming control unit 180 divides the light emitting surfaces of the display panel and the backlight unit for each block, derives a representative value for each block, and maps the representative value for each block to a dimming curve. You can select the dimming value (%) for each block.

For example, during local dimming, a curve having a shape as shown in FIG. 4 or a curve having a shape as shown in FIG. 5 may be selected. 4 and 5 , the X-axis is a representative value for each block, and the Y-axis is a dimming value (%). In the dimming curve of FIG. 4 , the dimming value (%) increases exponentially as the gray level increases, whereas in the dimming curve of FIG. 5 , the dimming value (%) increases linearly in proportion to the gray level. According to the dimming curve of the above type, the backlight unit 170 can change the ratio or luminance of turning on and off.

The dimming control unit 180 calculates an average picture level (APL) for each block, increases the weight of the global dimming value when the luminance difference between adjacent blocks at the average picture level is large, and increases the weight of the global dimming value between adjacent blocks at the calculated average picture level. If the luminance difference is small, the weight of the local dimming value may be increased.

As shown in FIG. 6 , the dimming control unit 180 includes a first representative value calculation unit 181 , a second representative value calculation unit 182 , a dimming value determination unit 185 , and a light amount calculation unit 186 for each pixel. , a gain corrector 187 , a grayscale blur prediction unit 188 , and a grayscale blur compensation unit 189 .

The first representative value calculator 181 calculates a representative block value of the input image. The second representative value calculator 182 calculates a total representative value of the input image of one frame. The block representative value and the total representative value are calculated as the average value or average picture level (APL).

The dimming value determiner 185 determines a dimming value for each block based on the block representative value and the overall representative value, and outputs a dimming signal DIM based on the determined dimming value for each block. The dimming value determiner 185 may select a dimming value for each block using a lookup table.

The light amount calculation unit 186 for each pixel selects a preset light profile as a dimming value for each block and calculates the light amount of each of the pixels in a specific block. The light profile may be calculated as the sum of the amount of light of a specific pixel and the amount of light reaching the specific pixel from neighboring pixels of the specific pixel during local dimming. In addition, the light profile may be determined through a pre-experiment in which luminance is measured for each pixel by performing local dimming with a dimming value for each block.

The gain compensator 187 calculates a gain for each pixel, compensates the pixel data signal by multiplying the gain by the original pixel data signal, and outputs the compensation data signal DATA'. The gain is calculated as the ratio of the pixel light amount when all the light sources of the backlight unit are turned on to full white (full white or maximum brightness) (non-local dimming) and the pixel light amount calculated through the light profile during local dimming. That is, the gain G is calculated as G = Knormal/Klocal. Here, Knormal is a target light amount (constant value) indicating the amount of light when the entire light emitting surface of the backlight unit is turned on in full white in a state where local dimming is not performed, and Klocal is a block when local dimming is performed. It is a light amount local value (variable value) indicating the light amount of a specific block according to the dimming value of each star.

The grayscale clustering prediction unit 188 calculates the grayscale clustering degree by analyzing compensation values of the pixel data signal of a specific block input from the gain correcting unit 187 and predicts the grayscale clustering. The grayscale aggregation predictor 188 calculates the number of white grayscale data from among pixel data compensation values of a specific block. The gray level of the pixel data may be determined as a Most Significant Bit (MSB). For example, if the MSB is "11", it may be determined as white grayscale data, if the MSB is '00', it may be determined as black grayscale pixel data, and if the MSB is '01', it may be determined as intermediate grayscale data.

The grayscale aggregation prediction unit 188 determines that grayscale aggregation will appear in a specific block when the number of white grayscale data is greater than a predetermined reference value and calculates the degree of grayscale aggregation. It may be judged that there is no such thing and the extent may not be calculated. The grayscale clustering prediction unit 188 determines the grayscale clustering degree and, when grayscale clustering occurs, outputs a signal for adaptively varying the target light amount Knormal and/or the pixel gain value according to the grayscale clustering degree. .

In response to the signal output from the grayscale clustering prediction unit 188, the grayscale clustering compensator 189 alleviates grayscale clustering without changing the device's power consumption efficiency and grayscale reversal and compensates for preventing luminance drop. do. The grayscale agglomeration compensator 189 alleviates the grayscale agglomeration in various ways as follows.

According to the first embodiment of the present invention, the grayscale blur compensation unit 189 alleviates the grayscale blur by changing a pixel gain rather than a dimming value for each block. To this end, the grayscale aggregation compensator 189 recalculates a pixel gain and outputs a signal for changing the pixel gain when grayscale aggregation occurs.

According to the second exemplary embodiment of the present invention, the grayscale blur compensation unit 189 reduces grayscale blur by changing the target light amount. To this end, the grayscale blur compensator 189 outputs a signal for adaptively varying the target light amount in response to the degree of grayscale aggregation.

According to the third exemplary embodiment of the present invention, the grayscale blur compensation unit 189 reduces grayscale blur by changing the target light amount and changing a pixel gain in response thereto. To this end, the grayscale blur compensator 189 outputs a signal for adaptively varying the target light amount and the pixel gain value.

According to the fourth embodiment of the present invention, the grayscale agglomeration compensator 189 varies the target light quantity, changes a pixel gain, and varies the slope of the target light quantity for a specific grayscale region (grayscale aggregation). Increase or decrease the angle so that the change of angle appears gradually or radically depending on the degree of gradation). To this end, the grayscale aggregation compensator 189 outputs a signal for adaptively varying the light intensity target value, the pixel gain value, and the light intensity target value slope in response to the degree of grayscale aggregation.

Meanwhile, as in the embodiments of the present invention, in order to adaptively vary the light quantity target value (Knormal), the pixel gain, etc., a standard is prepared based on the pre-experimental result, and when grayscale aggregation occurs, it is Correspondingly, change the value. For example, it is preferable to prepare the adaptive light amount target value Knormal through calculation based on a dimming value for each block, a light amount target value, a pixel gain value, a data signal compensation value, and the like to improve accuracy. However, if it is desired to vary the adaptive light quantity target value Knormal within an appropriate level range, other means such as a lookup table may be used.

Hereinafter, the problems of the experimental examples will be considered and examples that can improve them will be described.

[Experimental example]

7 is a diagram for schematically explaining a problem of a dimming method according to an experimental example.

7, the dimming method according to the experimental example is a dimming value operation (S10), a pixel gain operation (S20), a pixel gain is applied to a pixel (S30), a grayscale clustering determination (S40), a dimming value increase ( S50).

The dimming method according to the experimental example calculates a dimming value by analyzing the input data signal (S10). Then, a pixel gain value is calculated using the dimming value and the light profile value. (S20) Then, a compensation data signal to be output is generated by applying a pixel gain to the input data signal. (S30) And if it is determined that grayscale aggregation occurs in the compensation data signal to be output (S40), increase the dimming value Alleviates clumping. (S50)

In the experimental example, when the dimming value is increased due to the occurrence of grayscale aggregation, all pixel gains corresponding to the dimming block are decreased. Therefore, it was found that the gain of the low gray scale part, which is not related to the actual gray scale aggregation, is also decreased, and the detail of the low gray scale is deteriorated.

In addition, since the experimental example has a relational expression of pixel gain = constant value/dimming value, it was found that when the dimming value was increased to alleviate grayscale aggregation, power consumption increased correspondingly. In addition, although the experimental example is intended to alleviate grayscale aggregation, it has been shown that the grayscale aggregation may become severe because the data signal is stretched to the maximum value (max) (compensation range saturation).

In addition, in the experimental example, in order to increase the efficiency of power consumption of the liquid crystal panel (reduction of power consumption) by a dimming method, particularly a local dimming method, when the dimming value is lowered, the compensation value (compensation rate) of the data signal is increased conversely. However, as in the experimental example, if the data signal is compensated a lot, it was found that aggregation of the upper grayscale may occur depending on the image.

[Example]

8 is a diagram schematically illustrating a dimming method according to a first embodiment of the present invention.

As shown in FIG. 8, the dimming method according to the first embodiment includes a dimming value operation (S110), a pixel gain value operation (S120), a pixel gain value applied to a pixel (S130), a grayscale cluster determination (S140), The pixel gain value re-calculation ( S120 ) is performed in the order of operation.

In the dimming method according to the first embodiment, a dimming value is calculated by analyzing an input data signal (S110). And a pixel gain value is calculated using the dimming value and the light profile value. (S120) and a compensation data signal to be output is generated by applying the pixel gain value to the input data signal (S130). If it is determined that grayscale aggregation occurs in the compensation data signal to be output (S140), the pixel gain Recompute the values to alleviate grayscale agglomeration. (S120)

According to the experimental examples, when the dimming value is increased due to the occurrence of grayscale aggregation, power consumption increases correspondingly, and when the dimming value is decreased, the compensation value of the data signal increases.

In the first embodiment, the pixel gain value is recalculated and the pixel gain value is varied without raising or lowering the dimming value in order to simply alleviate grayscale agglomeration. For example, if a large amount of grayscale aggregation occurs, the target light quantity Knormal, not the dimming value, is controlled, and the pixel gain value is lowered accordingly.

As a result of the experiment based on the first embodiment, the first embodiment controls the light amount target value (Knormal) and lowers the pixel gain value, so that all pixel gains do not decrease, so the low grayscale details are maintained. or could be improved. In addition, in the first embodiment, since the target light amount Knormal is controlled and the pixel gain value is lowered, all pixel gains do not go down, but only the pixel gains of the portion where grayscale aggregation occurs. appeared to be able to lower it. In addition, since there is no substantial change in the dimming value in the first embodiment, it was found that grayscale agglomeration can be alleviated while maintaining power consumption efficiency.

The above first embodiment improves grayscale aggregation, power consumption efficiency, and expressive power of low and high grayscales by controlling the target light quantity (Knormal) and varying other parameters (eg, variable pixel gain) with the concept of +α. can do.

9 is a diagram schematically illustrating a dimming method according to a second embodiment of the present invention.

As shown in FIG. 9, the dimming method according to the second embodiment includes a dimming value operation (S210), a pixel gain value operation (S220), applying a pixel gain value to a pixel (S230), grayscale clustering determination (S240), The target light amount is adaptively controlled in the order of S250.

The dimming method according to the second embodiment calculates a dimming value by analyzing an input data signal (S210). Then, a pixel gain value is calculated using the dimming value and the light profile value. (S220) and a compensation data signal to be output is generated by applying the pixel gain value to the input data signal (S230). If it is determined that grayscale aggregation occurs in the compensation data signal to be output (S240), the grayscale aggregation By adaptively controlling the target light amount according to the degree (Adaptive Knormal control), grayscale blur is alleviated (S250).

According to the experimental examples, when the dimming value is increased due to the occurrence of grayscale aggregation, power consumption increases correspondingly, and when the dimming value is decreased, the compensation value of the data signal increases.

In the second embodiment, the target light amount Knormal is adaptively controlled without raising or lowering the dimming value in order to simply alleviate grayscale agglomeration. For example, when a large amount of grayscale aggregation occurs, the target light amount Knormal is adaptively controlled according to the degree of grayscale aggregation rather than the dimming value, and the pixel gain value is recalculated in response thereto, and the pixel gain value is varied.

As a result of an experiment based on the second embodiment, in the second embodiment, the target light amount (Knormal) is adaptively controlled according to the degree of grayscale aggregation, and all pixel gains do not decrease because the pixel gain value is lowered. It has been shown that it is possible to maintain or improve the fine expressiveness (detail) of Also, since the second embodiment adaptively controls the light amount target value (Knormal) and lowers the pixel gain value, all pixel gains do not decrease, but only the pixel gain values of the portion where the grayscale clustering occurs, so grayscale clustering may occur. appeared to reduce the probability. In addition, since the second embodiment does not substantially change the dimming value, it was found that grayscale agglomeration can be alleviated while maintaining power consumption efficiency.

The second embodiment adaptively controls the light quantity target value (Knormal) and improves grayscale aggregation, power consumption efficiency, and low grayscale expression by varying other parameters (eg, variable pixel gain) with the concept of +α. can do. In particular, since the second embodiment has an original light quantity target value only for an image without grayscale clustering, a luminance drop phenomenon in an image without grayscale clustering can also be eliminated.

10 is a diagram schematically illustrating a dimming method according to a third embodiment of the present invention.

As shown in Fig. 10, the dimming method according to the third embodiment includes a dimming value operation (S310), a pixel gain value operation (S320), a pixel gain value applied to a pixel (S330), a grayscale clustering determination (S340), A target light amount is adaptively controlled ( S350 ), a pixel gain value is adaptively controlled according to the degree of grayscale aggregation and a compensation rate of the data signal ( S360 ), and the pixel gain value re-calculation ( S320 ) is performed in the order of adaptively controlling the target value.

The dimming method according to the third embodiment calculates a dimming value by analyzing an input data signal (S310). Then, a pixel gain value is calculated using the dimming value and the light profile value. (S320) and a pixel gain is applied to the input data signal to generate a compensation data signal to be output. Accordingly, the target light amount is adaptively controlled (Adaptive Knormal control) (S350). Then, the grayscale aggregation is alleviated by adaptively controlling the pixel gain value according to the degree of grayscale aggregation and the compensation rate of the data signal. (S360)

According to the experimental examples, when the dimming value is increased due to the occurrence of grayscale aggregation, power consumption increases correspondingly, and when the dimming value is decreased, the compensation value of the data signal increases.

The third embodiment adaptively controls the light quantity target value (Knormal) according to the degree of grayscale aggregation without raising or lowering the dimming value to simply alleviate the grayscale clustering, and adaptively according to the grayscale clustering degree and the compensation rate of the data signal. A pixel gain value is controlled, and the pixel gain value is recalculated correspondingly. That is, when a lot of grayscale aggregation occurs, the target light amount Knormal is adaptively controlled according to the degree of grayscale aggregation rather than the dimming value, and the pixel gain value is controlled according to the grayscale clustering degree and the compensation rate of the data signal. Correspondingly, the pixel gain value is recalculated.

As a result of experiments based on the third embodiment, the third embodiment recalculates the target light amount Knormal and the pixel gain value according to the grayscale aggregation degree and the compensation rate of the data signal, and the pixel gain value for the high grayscale pixel Since all pixel gains are not lowered by decreasing In addition, in the third embodiment, since the target light amount (Knormal) is controlled and the pixel gain value is lowered, all pixel gains do not go down, but only the pixel gains of the portion where grayscale aggregation occurs, so the probability of occurrence of high grayscale clustering is reduced. appeared to be able to lower it. In addition, since the third embodiment does not substantially change the dimming value, it was found that grayscale agglomeration can be alleviated while maintaining power consumption efficiency.

In the third embodiment, grayscale aggregation in a way that adaptively controls the target light quantity (Knormal) and varies other parameters (eg, variable pixel gain according to the degree of grayscale aggregation and the compensation rate of the data signal) with the concept of +α; It is possible to improve power consumption efficiency and expressive power of low and high grayscales. In particular, in the third embodiment, since the pixel gain value for the high grayscale pixel is lowered based on the target light amount, the probability of occurrence of high grayscale clustering can be reduced.

11 is a diagram schematically illustrating a dimming method according to a fourth embodiment of the present invention.

11, the dimming method according to the fourth embodiment includes a dimming value operation (S410), a pixel gain value operation (S420), applying a pixel gain value to a pixel (S430), grayscale clustering determination (S440), Adaptively control the target light quantity (S450), adaptively control the pixel gain according to the degree of grayscale aggregation and the compensation rate of the data signal (S460), control the slope of the target light quantity (S470), and recalculate the pixel gain (S420) ) in the order of

The dimming method according to the fourth embodiment calculates a dimming value by analyzing an input data signal (S410). Then, a pixel gain value is calculated using the dimming value and the light profile value. (S420) and a pixel gain value is applied to the input data signal to generate a compensation data signal to be output. According to the degree, the target light amount is adaptively controlled (Adaptive Knormal control) (S450). Then, the pixel gain value is adaptively controlled according to the degree of grayscale aggregation and the compensation rate of the data signal. (S460) Then, when the slope of the target light intensity reaches the maximum slope, the grayscale is controlled so that the slope of the target value is lowered. Relieves lumpiness. (S470)

According to the experimental examples, when the dimming value is increased due to the occurrence of grayscale aggregation, power consumption increases correspondingly, and when the dimming value is decreased, the compensation value of the data signal increases.

The fourth embodiment adaptively controls the light amount target value (Knormal) according to the degree of grayscale aggregation without raising or lowering the dimming value to simply alleviate the grayscale clustering, and adaptively according to the grayscale clustering degree and the compensation rate of the data signal. Controls the pixel gain value. And, if the slope of the target light quantity reaches a maximum (Max slope), the control is controlled to decrease the slope of the target light quantity, and the pixel gain value is re-calculated in response thereto. That is, if a lot of grayscale aggregation occurs, the target light amount Knormal is adaptively controlled according to the degree of grayscale aggregation rather than the dimming value, and the pixel gain value is controlled according to the grayscale clustering degree and the compensation rate of the data signal, and the amount of light The slope of the target value is controlled and the pixel gain value is recalculated in response thereto.

As a result of an experiment based on the fourth embodiment, the fourth embodiment controls the light intensity target value (Knormal), the pixel gain value, and the gradient of the light intensity target value according to the degree of grayscale aggregation and the compensation rate of the data signal, and the high grayscale pixel Since all pixel gains are not lowered by lowering the pixel gain value, it has been shown that the details of low grayscale can be further improved. In addition, in the fourth embodiment, since the target light amount Knormal is controlled and the pixel gain value is lowered, all pixel gain values do not go down, only the pixel gain values of the portion where grayscale aggregation occurs, so high grayscale aggregation may occur. appeared to reduce the probability. In addition, since the fourth embodiment does not substantially change the dimming value, it was found that grayscale agglomeration can be alleviated while maintaining power consumption efficiency.

The fourth embodiment adaptively controls the light quantity target value (Knormal) and other parameters (eg, variable pixel gain according to the degree of grayscale aggregation and the compensation rate of the data signal, control of the slope of the target light quantity value) with the concept of +α. It is possible to improve grayscale aggregation, power consumption efficiency, and expressive power of low grayscale and high grayscale in a variable manner. In particular, since the fourth embodiment controls the slope of the target light amount and the target light amount, it is possible to further improve the detail of high grayscale and low grayscale without problems such as grayscale reversal.

Hereinafter, changes in the light intensity target value, the compensation rate of the data signal, and the gradient of the light intensity target value by the dimming method according to embodiments of the present invention will be described.

12 is a diagram for explaining a change in a target light amount, a compensation rate of a data signal, and a slope of a target light amount by a dimming method according to embodiments of the present invention, and FIG. 13 is a light amount target value and a target light amount target value It is an example diagram of variable inclination of .

As shown in FIGS. 12 and 13 , in the embodiments of the present invention, in order to solve the problem of the experimental example, the light intensity target value (KNOR), the compensation rate of the data signal (data), and the slope of the light intensity target value according to the degree of grayscale aggregation The brightness (B/L) of the backlight unit and the pixel data signal (Pixel data) are controlled by varying one or more of (θ) and a pixel gain value. A variation range of the compensation rate (data) of the data signal or the luminance (B/L) of the backlight unit (B/L) varies according to the target light amount KNOR.

In at least one of the embodiments of the present invention, a grayscale region with a high probability of occurrence of grayscale clustering is set as a threshold value, and at least one of a light intensity target value and a gradient of the light intensity target value is adaptively applied to a region above the threshold value and a pixel Change the gain value at the same time. The threshold value may be determined through a prior experiment, and is usually determined in a high grayscale region or a region close to the high grayscale region.

According to the above explanation, in the grayscale region that does not exceed the threshold, the target light intensity (KNOR) changes linearly like K1, K2, or K3, but the grayscale region exceeding the threshold has a gradient depending on the degree of grayscale aggregation. Therefore, it becomes non-linear. And when the slope of the target light intensity reaches the maximum (refer to “Max slope” in FIG. 13 ), the target light intensity KNOR in the grayscale region that does not exceed the threshold is lowered (refer to “B” in FIG. 13 ). Threshold If the target light quantity KNOR in the grayscale region that does not exceed the value is lowered, the slope of the target light quantity target value is decreased (refer to θ1 > θ2 in FIG. 13).

In some cases, there is a need for a liquid crystal display to maximize a reduction in power consumption. This is especially true for display devices that need to use a low consumption mode, such as a mobile device or a notebook computer. In the experimental example, when the power consumption reduction rate is maximized, the dimming value is lowered by that amount, and the compensation value (compensation rate) of the data signal is increased. As a result, the probability of occurrence of grayscale aggregation increases dramatically. In this case, the target light amount is reduced through the target light amount control, and a grayscale reversal phenomenon may occur in the high grayscale region.

It is confirmed that the same problem as in the experimental example occurs because the slope (θ) of the target value of the light quantity in the region A, which is an adaptively operated region, is too steep. As described above with reference to FIGS. 12 and 13 , in the present invention, in preparation for a problem that may occur in the experimental example, the "B" area, which is the basic area of the target light amount KNOR, is controlled together. As a result, the present invention can limit (variably lower) the light quantity target value KNOR to have the maximum slope θ at which the grayscale reversal does not occur, thereby solving the problem of the grayscale reversal in the high grayscale region. be able to do

Hereinafter, a degree of relaxation of grayscale aggregation according to an embodiment of the present invention will be described through differences between the experimental example and the embodiment of the present invention.

14 is a diagram for explaining the difference between an experimental example and the present invention. For reference, regions indicated by dotted lines in FIGS. 14A and 14B are regions in which grayscale aggregation occurs intensively because full white is the background.

As shown in FIG. 14 (a), in the experimental example, a high gray level clock image cannot be properly recognized due to gray level aggregation. On the other hand, as shown in FIG. 14(b), in the embodiment of the present invention, even the fine expressive power (Detail) of the image is saved by alleviating grayscale agglomeration, so that a high grayscale clock image can be recognized more clearly. In addition, as in the embodiment of the present invention, if grayscale agglomeration can be effectively alleviated, power consumption can be reduced, image quality can be improved, and luminance deterioration can be minimized.

As described above, in the present invention, when grayscale aggregation occurs a lot, it is possible to reduce the grayscale aggregation by varying the pixel gain and lowering the compensation rate of the data signal by controlling the target light quantity instead of the dimming value. In addition, the present invention has effects of alleviating grayscale aggregation, improving power consumption efficiency, and improving the expressive power of low grayscale and high grayscale. In addition, the present invention has the effect of further improving the detail of high grayscale and low grayscale without problems such as grayscale reversal when grayscale aggregation occurs. In addition, the present invention can be stably applied to hardware, and there is no restriction according to the structure or shape of the backlight unit.

Although the embodiments of the present invention have been described above with reference to the accompanying drawings, the technical configuration of the present invention can be changed to other specific forms by those skilled in the art to which the present invention pertains without changing the technical spirit or essential features of the present invention. It will be appreciated that this may be practiced. Therefore, it should be understood that the embodiments described above are illustrative in all respects and not restrictive. In addition, the scope of the present invention is indicated by the claims to be described later rather than the above detailed description. In addition, all changes or modifications derived from the meaning and scope of the claims and their equivalents should be construed as being included in the scope of the present invention.

110: image supply unit 130: timing control unit
140: gate driver 150: data driver
160: liquid crystal panel 170: backlight unit
180: dimming control unit 186: light amount calculation unit for each pixel
187: gain correction unit 188: grayscale cluster prediction unit
189: gradation aggregation compensation unit

Claims (10)

a liquid crystal panel for displaying an image;
a backlight unit providing light to the liquid crystal panel; and
a dimming control unit for controlling dimming of the backlight unit;
The dimming control unit calculates a dimming value by analyzing an input data signal, outputs a dimming signal for varying the luminance of the backlight unit, and compensates a gain of the data signal by the luminance variable amount of the backlight unit. output, but if grayscale aggregation occurs, the pixel gain value is varied according to the degree of grayscale aggregation,
The dimming control unit calculates the degree of grayscale aggregation, and when the grayscale clustering occurs, adaptively according to the degree of grayscale aggregation, the dimming control unit includes a grayscale clustering compensator that varies at least one of a target light intensity value, a pixel gain value, and a light intensity target value slope. do,
and a dimming value determiner configured to determine a dimming value for each block based on the block representative value and the overall representative value of the input image and output the dimming signal based on the determined dimming value for each block;
a light amount calculation unit for each pixel that selects a preset light profile value as the dimming value for each block and calculates the light amount of each pixel in a specific block;
The liquid crystal display device further comprising: a gain correction unit for calculating a gain for each pixel, compensating the pixel data signal by multiplying the gain by the original pixel data signal, and outputting the compensation data signal. According to claim 1,
The dimming control unit
When the grayscale aggregation occurs, the liquid crystal display device controls the target light amount indicating the amount of light when the entire light emitting surface of the backlight unit is turned on in full white, and varies the pixel gain value in response to the target light amount. According to claim 1,
The dimming control unit
When the grayscale aggregation occurs, the target light amount indicating the amount of light when the entire light emitting surface of the backlight unit is turned on in full white is adaptively controlled, and the pixel gain value corresponds to the adaptively changed target value. A liquid crystal display that changes the According to claim 1,
The dimming control unit
When the grayscale aggregation occurs, the target light amount, which represents the amount of light when the entire light emitting surface of the backlight unit is turned on in full white, is adaptively controlled, and in response to the adaptively changed target value, the light intensity is higher than or equal to the threshold. A liquid crystal display that varies only a pixel gain value for a grayscale region. According to claim 1,
The dimming control unit
When the grayscale aggregation occurs, the target light amount, which represents the amount of light when the entire light emitting surface of the backlight unit is turned on in full white, is adaptively controlled, and in response to the adaptively changed target value, the light intensity is higher than or equal to the threshold. Only the pixel gain value for the grayscale region is varied,
A liquid crystal display for lowering the slope of the target light quantity when the slope of the target light quantity located in the high grayscale region greater than or equal to the threshold value reaches a maximum. delete delete In the driving method of the liquid crystal display device manufactured according to claim 1,
calculating the dimming value by analyzing the input data signal;
calculating the pixel gain value using the dimming value and the optical profile value;
generating the compensation data signal by applying the pixel gain value to the input data signal; and
and determining whether the grayscale clustering occurs, and re-calculating the pixel gain value when the grayscale clustering occurs. 9. The method of claim 8,
The step of re-calculating the pixel gain value
When the grayscale aggregation occurs, the target light amount indicating the amount of light when the entire light emitting surface of the backlight unit is turned on in full white is adaptively controlled, and the pixel gain value corresponds to the adaptively changed target value. A method of driving a liquid crystal display device by re-calculating , and varying the pixel gain value. 9. The method of claim 8,
The step of re-calculating the pixel gain value
When the grayscale aggregation occurs, the target light amount, which represents the amount of light when the entire light emitting surface of the backlight unit is turned on in full white, is adaptively controlled, and in response to the adaptively changed target value, the light intensity is higher than or equal to the threshold. Only the pixel gain value for the grayscale region is varied,
A method of driving a liquid crystal display device for lowering the slope of the target light quantity when the slope of the target value of the light quantity located in the high grayscale region equal to or greater than the threshold value reaches a maximum.

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