KR20140063294A - Liquid crystal display device and method for driving the same - Google Patents

Liquid crystal display device and method for driving the same Download PDF

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KR20140063294A
KR20140063294A KR1020120130492A KR20120130492A KR20140063294A KR 20140063294 A KR20140063294 A KR 20140063294A KR 1020120130492 A KR1020120130492 A KR 1020120130492A KR 20120130492 A KR20120130492 A KR 20120130492A KR 20140063294 A KR20140063294 A KR 20140063294A
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value
unit
saturation
dimming
image data
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KR1020120130492A
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Korean (ko)
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KR102050437B1 (en
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조병철
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엘지디스플레이 주식회사
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    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
    • G09G3/34—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source
    • G09G3/36—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source using liquid crystals
    • G09G3/3611—Control of matrices with row and column drivers
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
    • G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2330/00—Aspects of power supply; Aspects of display protection and defect management
    • G09G2330/02—Details of power systems and of start or stop of display operation
    • G09G2330/021—Power management, e.g. power saving

Abstract

In the present invention, image data is modulated and displayed so that the display luminance is increased, thereby reducing the power consumption of the backlight unit, reducing the display failure due to gray scale accumulation and gray scale saturation, and improving the power consumption reduction rate of the backlight unit The present invention relates to a liquid crystal display device and a method of driving the same, and more particularly, to a liquid crystal display device and a method of driving the same, which includes a liquid crystal panel having a plurality of pixel regions to display an image, a data driver driving data lines of the liquid crystal panel, A timing controller for aligning video data from outside in accordance with the driving of the liquid crystal panel and controlling the data and the gate driver and a controller for modulating the video data so that the brightness of the display video is high, According to the result of comparison between the offset value and the preset offset value, And an image enhancement unit for controlling the degree of modulation of the image data and the driving time of the backlight unit.

Figure P1020120130492

Description

TECHNICAL FIELD [0001] The present invention relates to a liquid crystal display (LCD)

In the present invention, image data is modulated and displayed so that the display luminance is increased, thereby reducing the power consumption of the backlight unit, reducing the display failure due to gray scale accumulation and gray scale saturation, and improving the power consumption reduction rate of the backlight unit To a liquid crystal display device and a driving method thereof.

2. Description of the Related Art In recent years, flat panel display devices that have emerged include liquid crystal display devices, field emission display devices, plasma display panels and organic light emitting diodes (OLEDs) Display Device).

Of the flat panel display devices, the liquid crystal display devices are excellent in resolution, color display, and image quality, and are actively applied to notebook computers, desktop monitors, and mobile terminals.

Such a liquid crystal display device includes a liquid crystal panel for displaying an image with a plurality of liquid crystal cells, a driving circuit for driving the liquid crystal panel, and a backlight unit for irradiating light to the liquid crystal panel.

The liquid crystal panel displays a desired image by adjusting the transmittance of the light emitted from the backlight unit according to the image signal. At this time, the backlight unit drives a plurality of light sources provided in the backlight unit according to the light source driving control signal supplied from the driving circuit to supply light to the liquid crystal panel.

The backlight unit driven as described above has a problem that the power consumption is increased because the light is always generated at a constant brightness irrespective of the video signal of the liquid crystal panel.

Accordingly, a method has been proposed in which power consumption is reduced by modulating image data so as to improve display brightness of an image while reducing driving time of the backlight unit. However, in order to increase the power consumption reduction rate, the display brightness of the image must be modulated as high as possible. As the display brightness is increased, the image quality is deteriorated due to gray scale saturation and gray scale accumulation phenomenon.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide a backlight unit capable of reducing the power consumption of a backlight unit and display failure due to gray scale accumulation and gray scale saturation phenomenon by modulating and displaying image data, And it is an object of the present invention to provide a driving apparatus for a liquid crystal display device and a driving method thereof that can improve the power consumption reduction rate.

According to an exemplary embodiment of the present invention, there is provided a liquid crystal display device including a liquid crystal panel having a plurality of pixel regions to display an image, a data driver driving data lines of the liquid crystal panel, A gate driver for driving lines, a timing controller for aligning video data from outside in accordance with driving of the liquid crystal panel and controlling the data and gate drivers, and a controller for modulating the video data so that the luminance of the display video is high, And an image enhancement unit for controlling the degree to which the image data is modulated and the driving time of the backlight unit according to the comparison result between the gray level saturation of the image data and the preset offset value.

The image enhancement unit is built in the timing controller, analyzes the average brightness of the image data input from the outside, extracts a gain value for modulating the image data and a dimming value of the backlight unit according to the analyzed average brightness And controls the driving time of the backlight unit using the extracted dimming value while modulating the image data so that the brightness of the display image is increased using the extracted gain value, By detecting the gray level saturation of the data by at least one frame and varying the gain value and the dimming value by increasing or decreasing the gain value and the dimming value, respectively, in the opposite tendency according to the comparison result between the detected gray level saturation amount and the preset offset value, The degree to which data is modulated and the driving time of the backlight unit are half Characterized in that the adjusted to increase or decrease each of the inclination.

The image enhancement unit includes a maximum / average value extraction unit for detecting the maximum gray level value or the average gray level value for each unit pixel of the image data arranged from the timing controller or the image data supplied from the outside, (Dimming Control Signal) according to the ratio of the average gradation level of the detected at least one frame to the preset maximum gradation level, A gain value extracting unit for extracting a gain value by dividing the maximum gradation level by the average gradation level of the detected at least one frame unit and a gain value extracting unit for extracting image data sorted from the timing controller, Modulates data according to the gain value in at least one frame unit A saturation improving unit for outputting the modulated image data of at least one frame by further modulating the saturation gray level values of the compensation data by setting a gray level compensation inflexion point according to the gain value, A PWM generator for generating a PWM signal such that a duty ratio is converted according to the dimming value extracted in units of a unit of the modulation image data and a driving time of the backlight unit, And a dimming compensation unit for modulating the dimming value of the dimming extraction unit and the gain value of the gain value extraction unit by increasing or decreasing the gain value of the dimming extraction unit, respectively, do.

Wherein the dimming extraction unit sets a dimming value at a ratio of an average gray-scale level to a preset maximum gray-scale level, and then outputs the calculated saturation compensation amount to the set dimming value according to a result of the comparison between the gray- The value is added / subtracted so that the dimming value is modulated.

And the gain value extractor may modulate the gain value as opposed to the dimming value according to a saturation compensation value according to a result of the comparison between the tone saturation amount and the offset value.

According to another aspect of the present invention, there is provided a method of driving a liquid crystal display, including: driving gate and data lines defining pixel regions of a liquid crystal panel; Modulates the image data so that the luminance of the display image is increased by using the image enhancement unit, adjusts the degree to which the image data is modulated in accordance with the comparison result between the gray level saturation of the modulated image data and a predetermined offset value, And a control unit for controlling the control unit.

The modulation degree of the image data and the driving time control step of the backlight unit may include analyzing an average luminance of the image data input from the outside, calculating a gain value for modulating the image data according to the analyzed average luminance, Controlling the driving time of the backlight unit using the extracted dimming value while modulating the image data so that the brightness of the display image is high using the extracted gain value A step of detecting the gray level saturation of the image data modulated so as to increase the brightness by at least one frame, and a step of comparing the gain value and the dimming value with each other in accordance with a result of comparison between the detected gray level saturation amount and a predetermined offset value The image data is modulated by increasing or decreasing the image data, respectively, And a step of controlling so as to raise or lower each of the opposite tendency driving time of the backlight unit characterized by including more.

Wherein the modulation degree of the image data and the driving time control step of the backlight unit are controlled by using a maximum / average value extraction unit to calculate a maximum gray scale value or an average gray scale value of unit pixels of the image data sorted from the timing controller, Detecting an average gradation level of at least one frame by sequentially receiving a maximum gradation value or an average gradation value for each unit pixel by using an average analyzing unit, Setting and outputting a dimming control signal in accordance with a ratio of the detected average gray level of the at least one frame unit to the average gray level of the detected at least one frame using the gain value extracting unit, Dividing the gradation level into a plurality of gradation levels, Generating compensated data by modulating the image data aligned from the timing controller or the image data supplied from the outside by using the upper portion in accordance with the gain value in at least one frame unit; Outputting the modulated image data of at least one frame unit by further modulating the saturation gray level values of the compensation data by setting a compensation inflection point, outputting the modulated image data of at least one frame unit by using the duty ratio Duty Generating a PWM signal so as to convert a gray level of the modulated image data into a gray level and controlling a driving time of the backlight unit, and generating a saturation compensation value according to a gray level saturation amount of the modulated image data and a comparison result of the offset value using a dimming compensation unit The saturation compensation value and the dimming value of the dimming extraction unit And modulating the gain value of the gain value extractor by increasing or decreasing the gain value of the gain value extractor, respectively.

Wherein the step of setting and outputting the dimming value sets the dimming value at a ratio of the average gradation level to a preset maximum gradation level and then outputs the set dimming value to the dimming compensation unit according to a result of the comparison between the tone saturation amount and the offset value And the dimming value is modulated by adding / subtracting the input saturation compensation value.

Wherein the gain value extraction step modifies the gain value in a manner opposite to the dimming value according to a saturation compensation value according to a result of comparison between the gray level saturation value and the offset value.

According to the liquid crystal display device and the driving method thereof according to the embodiment of the present invention, the power consumption of the backlight unit can be reduced by modulating and displaying the image data so that the luminance of the display image is high.

Particularly, the power consumption reduction rate of the backlight unit can be further improved by reducing display defects due to gray scale accumulation and gray scale saturation, while modulating and displaying the image data so that the brightness of the display image is high.

1 is a configuration diagram illustrating a liquid crystal display device according to an embodiment of the present invention;
FIG. 2 is a block diagram specifically illustrating the image enhancement unit shown in FIG. 1. FIG.
3 is a graph showing a driving dimming value calculating method of the backlight unit.
4 is a graph for explaining a compensation data generating method of the data compensator shown in FIG.
5 is a graph for explaining a saturation tone value modulation method of the saturation improving unit shown in Fig.
FIG. 6 is a configuration diagram specifically showing the dimming compensation unit shown in FIG. 2. FIG.
Figs. 7A and 7B are experimental views showing a display screen of an image in which a large number of tone saturation are generated. Fig.
8 is a graph showing a display screen of an image in which grayscale saturation has not occurred.

Hereinafter, a liquid crystal display device and a driving method thereof according to embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a configuration diagram illustrating a liquid crystal display device according to an embodiment of the present invention.

1 includes a liquid crystal panel 2 having a plurality of pixel regions for displaying an image, a data driver 4 for driving the data lines DL1 to DLm of the liquid crystal panel 2, The gate driver 6 for driving the gate lines GL1 to GLn of the panel 2 and the image data RGB from the outside are arranged in accordance with the driving of the liquid crystal panel 2 and the data driver 4 and the gate driver The timing controller 8 controls the timing controller 8 to control the image data RGB so that the brightness of the display image is high and compares the gray level saturation of the modulated image data MData with a predetermined offset value Offset An image enhancement unit 10 for controlling the degree of modulation (or modulation size) of the image data according to the result and the driving time of the backlight unit 18; And a backlight unit 18 which emits light to the liquid crystal panel 2 in response to the driving signal PWM from the image improving unit 10. [

The liquid crystal panel 2 includes a thin film transistor (TFT) formed in each pixel region defined by a plurality of gate lines GL1 to GLn and data lines DL1 to DLm and a liquid crystal capacitor Clc . The liquid crystal capacitor Clc is composed of a pixel electrode connected to the TFT, and a common electrode facing the pixel electrode and the liquid crystal. The TFT supplies a video signal from each of the data lines DL1 to DLm to the pixel electrode in response to a scan pulse from each of the gate lines GL1 to GLn. The liquid crystal capacitor Clc charges the difference voltage between the video signal supplied to the pixel electrode and the common voltage supplied to the common electrode, and adjusts the light transmittance by varying the arrangement of the liquid crystal molecules according to the difference voltage. The storage capacitor Cst is connected in parallel to the liquid crystal capacitor Clc so that the voltage charged in the liquid crystal capacitor Clc is maintained until the next data signal is supplied.

The data driver 4 receives the data control signal DCS from the timing controller 8 using the source start pulse SSP and the source shift clock SSC, ) Into analog image data, that is, a video signal. Then, a video signal for one horizontal line is supplied to each of the data lines DL1 to DLm for every one horizontal period in which scan pulses are supplied to the gate lines GL1 to GLn. At this time, the data driver 4 supplies a video signal to each data line DL1 to DLm in response to a source output enable (SOE) signal.

The gate driver 6 is responsive to a gate control signal GCS from the timing controller 8, for example, a gate start pulse (GSP) and a gate shift clock (GSC) And controls the pulse width of the gate-on signal in accordance with a gate output enable (GOE) signal. Then, the gate-on signals are sequentially supplied to the gate lines GL1 to GLn. Here, the gate-off voltage is supplied during a period in which the gate-on voltage is not supplied to the gate lines GL1 to GLn.

The timing controller 8 arranges image data RGB input from the outside in a manner suitable for driving the liquid crystal panel 2 and supplies the image data to the image improving unit 10. The timing controller 8 uses at least one of a synchronizing signal supplied from the outside, that is, a dot clock DCLK, a data enable signal DE, and horizontal and vertical synchronizing signals Hsync and Vsync, (GCS, DCS) for controlling each of the data lines (4, 6).

The image enhancement unit 10 may be incorporated in the timing controller 8 or may be formed separately from the timing controller 8. The image enhancement unit 10 analyzes the average luminance of the image data RGB input from the outside or the data Data aligned from the timing controller 8 in at least one frame unit. Then, the gain value for modulating the image data (Data or RGB) and the dimming value of the backlight unit are extracted according to the analyzed average brightness.

The image improving unit 10 modulates the image data (Data or RGB) so that the brightness of the display image is increased by using the extracted gain value, while controlling the driving time of the backlight unit 18, that is, (Dimming Control). In particular, the image improving section 10 detects the gray level saturation amount of the image data (MData) modulated so that the display brightness is high at least in units of one frame, and outputs the comparison result of the detected gray level saturation amount and the preset offset value The gain value and the dimming value are varied.

At this time, the image enhancement unit 10 increases or decreases the gain value and the dimming value, respectively, according to the result of the comparison of the gray-scale saturation amount and the offset value, thereby varying the degree of modulation Or the modulation size) and the driving time of the backlight unit 18 can be adjusted so as to be raised or lowered, respectively, have. For example, if the gray level saturation amount is larger than the offset value (Offset), the image enhancement unit 10 determines that the gray level saturation amount is larger and drives the backlight driving dimming value to be brighter. However, I will. On the other hand, when the gray level saturation amount is smaller than the offset value (Offset), the image improving unit 10 determines that the gray level saturation amount is small, thereby reducing the backlight driving dimming value to reduce power consumption. I will.

The image enhancement unit 10 of the present invention will be described later in more detail with reference to the accompanying drawings. In the present invention, only when the image conversion unit 10 is separately provided outside the timing controller 8 Will be described.

The backlight unit 18 includes a backlight 12 having a plurality of light sources for generating light in the liquid crystal panel 2 and an optical unit for improving the efficiency of light incident from the respective light sources, And an inverter 16 for supplying a driving voltage ADS to each of the plurality of light sources in response to a control signal (e.g., PWM (Pulse Width Modulation) signal).

The light sources of the backlight 12 are driven by the driving voltage ADS from the inverter 16 to generate light, and the optical unit diffuses and condenses the incident light from the light source to improve the light efficiency. The inverter 16 is driven in a burst mode in which the driving voltage ADS is supplied or cut off according to the PWM signal PWM from the image improving unit 10 to turn on / off each light source.

FIG. 2 is a block diagram specifically illustrating the image enhancement unit shown in FIG. 1. FIG.

The image enhancement unit 10 shown in FIG. 2 includes a maximum gray scale value (R, G, B) of unit pixels (R, G, B) of image data (Data) A maximum / average value extracting unit 21 for calculating a maximum gray value PM or an average gray level value for each unit pixel R, G and B by sequentially receiving a maximum gray level value PM or an average gray level value for each unit pixel R, A dimming control signal (Dim) is set and output according to the ratio of the average gradation level (APL) of at least one frame detected relative to the preset maximum gradation level to the average analyzing unit (22) A gain value extracting section 25 for dividing the maximum gradation level by the detected average gradation level APL in units of frames and extracting a gain value gs from the timing controller 8; (RGB) supplied from the outside or at least the image data A data compensator 26 for modulating the gain data gs in units of frames to generate compensation data PData, a gain compensator 26 for compensating for saturation gradation values of the compensation data PData by setting a gradation compensation inflection point in accordance with the gain value gs A saturation improving section 27 for outputting the modulated image data MData of at least one frame unit by further modulating the PWM signal Dm so that the duty ratio is converted in accordance with the dimming value Dim extracted in units of at least one frame, (24) for generating a PWM (PWM) signal and controlling a driving time of the backlight unit (10), and a saturation signal generating unit for generating a saturation signal according to a result of comparison between the gray level saturation amount of the modulated image data A dimming compensation unit 28 that generates a compensation value MAS and modulates the dimming value Dim of the dimming extraction unit 23 and the gain value gs of the gain value extraction unit 25 to the saturation compensation value MAS, Respectively.

The maximum / average value extracting unit 21 sequentially extracts the maximum gradation value PM or the average gradation value for each pixel of red, green, and blue (R, G, B) pixels of the aligned image data Data from the timing controller 8 In real time. The detected maximum gradation value PM or average gradation value for each unit pixel is sequentially supplied to the average analyzer 22.

The average analyzer 22 sequentially receives the maximum gradation value PM or the average gradation value for each of the unit pixels R, G, and B and detects an average gradation level APL that is an average value in at least one frame unit.

3 is a graph showing a driving dimming value calculating method of the backlight unit.

As shown in FIG. 3, the dimming value is extracted as 100% or less according to the ratio of the average gradation level of the current frame to a predetermined maximum gradation level. In particular, the dimming extraction unit 23 detects a backlight dimming value corresponding to the average gradation level APL in accordance with a preset dimming curve, and then calculates a saturation compensation value MAS, which is input from the dimming compensation unit 28, And then modulates and outputs the detected dimming value Dim.

Specifically, the dimming extraction unit 23 extracts a dimming value for the average gradation level APL detected by the average analyzing unit 22 using a dimming curve, adds the saturation compensation value MAS to the extracted dimming value And dimming the dimming value (Dim).

The saturation compensation value MAS from the dimming extractor 23 is set according to the result of comparison between the saturation gradation number (saturation saturation amount) of the saturation region and the preset offset (Offset), and the difference value. Accordingly, if the number of saturation gradations in the saturation region is larger than the offset, the saturation compensation value (MAS) corresponding to the difference value is added to the dimming value extracted by the dimming curve. On the other hand, if the saturation gradation number of the saturation region is smaller than the offset, the saturation compensation value (MAS) corresponding to the difference value is subtracted from the extracted dimming value. Thus, the larger the saturation gradation of the saturation region, the higher the dimming value, and the smaller the saturation gradation of the saturation region, the lower the dimming value.

When the dimming value (Dim) becomes high, the gain value (gs) becomes low and the modified saturation area becomes small when the saturation saturation of the next frame is improved. Therefore, by calculating the gray-scale saturation amount in the smaller gray-scale saturation area, the gray-scale saturation amount of the next frame data can be made smaller than the offset (Offset). If the gray level saturation amount is larger than the offset value even in the smaller gray level saturation region, the driving dimming value Dim of the backlight unit continues to increase until it becomes smaller. Thus, even when the saturated gradation is displayed, the image display quality is improved.

Conversely, when the amount of grayscale saturation is smaller than the offset, the dimming value Dim is continuously lowered so that the gain value gs is increased. When the gain value gs is increased, the gray level saturation amount is found in the further increased gray level saturation period, so that the gray level saturation amount can be larger than the offset Offset. If this process is continuously repeated until the saturation saturation amount is greater than or equal to the offset, the dimming value Dim is continuously lowered and the power consumption reduction effect is increased.

The gain value extracting section 25 receives the average gradation level from the dimming extracting section 23 and divides the maximum gradation level (for example, 8 bits and 255 gradations) by the average gradation level to extract the gain value gs . The gain value gs from the gain value extracting section 25 is changed inversely to the dimming value Dim. That is, when the dimming value Dim rises, the gain value gs decreases. Conversely, when the dimming value Dim decreases, the gain value gs is varied to increase.

If the gray level saturation amount is larger than the offset value in accordance with the inverse proportional modulation process of the dimming value Dim and the gain value gs according to the saturation compensation value MAS, the gain value gs is lowered and the data modulation amount is reduced and the dimming value Dim ) Is increased to improve the image quality of the saturation region. If the saturation saturation amount is smaller than the offset, the gain value gs becomes higher, the data modulation amount is increased, and the dimming value Dim becomes lower, and the power consumption reduction rate can be increased.

The PWM generator 24 generates the PWM signal PWM so that the duty ratio is converted in response to the dimming control signal Dim extracted at least one frame unit and supplies the generated PWM signal PWM to the inverter 16 Supply. Here, the plurality of inverters 16 may be provided in accordance with the number of the light sources of the backlight 12, so that the PWM signal PWM may be supplied to each of the plurality of inverters 16 sequentially or simultaneously. The duty ratio of the PWM signal PWM is varied according to the converted dimming value, so that the on / off period of the light sources is varied and driven.

4 is a graph for explaining a compensation data generation method of the data compensation unit shown in FIG.

4, the data compensating unit 26 modulates the aligned image data Data from the timing controller 8 according to the gain value gs extracted from the gain value extracting unit 25, PData). 4, when the gain value gs extracted from the gain value extracting unit 25 is 1, the input image data Data and the compensation data PData may be the same. However, when the gain value gs is set larger than 1, the gradation level of the compensation data PData can be modulated high. Thus, the larger the gain value gs is, the more all the gradation levels in a specific section are modulated to the maximum level, and the gray-scale saturation amount can be increased.

5 is a graph for explaining a saturation tone value modulation method of the saturation improving unit shown in FIG.

5, the saturation improving unit 27 of the saturation gray level value of the gain (gs) tone after setting the compensation inflection point, compensation data (PData) by applying x 2 curve at the inflection point or more legs in accordance with the Further modulation. Accordingly, the saturation tone values are partially compensated to generate and output the modulated image data (MData).

FIG. 6 is a configuration diagram specifically showing the dimming compensation unit shown in FIG. 2. FIG.

The dimming compensation unit 28 of FIG. 6 includes a saturated region extracting unit 31 for setting a saturated region up to the maximum gradation level according to the inflection point (the minimum gradation level at which the modulation gradation value is saturated) set by the saturation improving unit 27, A saturation amount analyzing section 32 for counting the gray level saturation amount (the number of gray levels equal to or larger than the gray level level of the inflection point) of the modulated image data MData included in the saturation area and outputting the count signal CS, A counting signal CS is supplied in frame units and the offset value Offset is divided by the number of saturation gradients corresponding to the count signal CS to generate a saturation compensation value MAS and a saturation compensation value MAS is supplied to the dimming extraction unit 23 so as to modulate the dimming value Dim and the gain value gs of the gain value extracting unit 25. [

As described above, if the number of saturation gradations in the saturation region is larger than the offset Offset, the saturation compensation value MAS corresponding to the difference value is added to the dimming value. On the other hand, if the number of saturation gradations in the saturation region is smaller than the offset, the saturation compensation value (MAS) corresponding to the difference value is subtracted from the dimming value. Thus, the larger the saturation gradation of the saturation region, the higher the dimming value Dim, and the smaller the saturation gradation of the saturation region, the lower the dimming value.

When the dimming value Dim becomes high, the gain value gs becomes low, and when the gray level saturation of the next frame is improved, the modified saturated area becomes small. Therefore, by calculating the gray-scale saturation amount in the smaller gray-scale saturation area, the gray-scale saturation amount of the next frame data can be made smaller than the offset (Offset). If the gray level saturation amount is larger than the offset value even in the smaller gray level saturation region, the driving dimming value Dim of the backlight unit continues to increase until it becomes smaller.

Conversely, even when the amount of grayscale saturation is smaller than the offset Offset, the dimming value Dim is continuously lowered so that the gain value gs is increased. When the gain value gs is increased, the gray level saturation amount is found in the further increased gray level saturation period, so that the gray level saturation amount can be larger than the offset Offset. This process is repeated to set the optimum dimming value Dim and the gain value gs.

Figs. 7A and 7B are views showing a display screen of an image in which a large number of tone saturation are generated. 8 is a graph showing an experimentally displayed display screen of an image in which gray scale saturation has not occurred.

As shown in FIG. 7A, there is a limitation in modulating image data so that images having a large number of gradation saturation have a high brightness. Therefore, it is necessary to reduce the image quality due to gray level saturation and increase the power consumption reduction rate of the backlight unit 18 I could not. However, as shown in FIG. 7B, when a large number of gray-scale saturation quantities are generated, the gain value gs is lowered to reduce the data modulation amount, and when the dimming value Dim is increased, the image quality of the tone saturation region (circular dotted line region) is improved.

On the other hand, as shown in FIG. 8, images in which grayscale saturation does not occur or images in which the grayscale saturation amount is less than the offset are modulated such that the gain value gs is increased, thereby increasing the image data luminance modulation amount, Dim) can be lowered and the power consumption reduction rate can be increased.

As described above, in the liquid crystal display device and the driving method thereof according to the present invention, the power consumption of the backlight unit 18 is reduced by modulating and displaying the image data Data so that the display brightness is high, The degree of modulation of the image data Data and the driving time of the backlight unit 18 can be adjusted according to the degree of aggregation and gradation saturation. Accordingly, the present invention can reduce the display failure due to the gray-scale saturation phenomenon and improve the power consumption reduction rate of the backlight unit 18. [

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. Will be clear to those who have knowledge of.

2: liquid crystal panel 4: data driver
6: Gate driver 8: Timing controller
10: Image enhancement unit 12: Backlight
16: inverter 18: backlight unit
21: maximum / average value extracting unit 22: average analyzing unit
23: dimming extracting unit 24: PWM generating unit
25: gain value extracting unit 26: data compensating unit
27: saturation improvement unit 28: dimming compensation unit

Claims (10)

A liquid crystal panel having a plurality of pixel regions and displaying an image,
A data driver for driving the data lines of the liquid crystal panel,
A gate driver for driving the gate lines of the liquid crystal panel,
A timing controller for aligning video data from outside in accordance with driving of the liquid crystal panel and controlling the data and gate drivers,
Modulates the image data so that the brightness of the display image is high and controls the degree to which the image data is modulated and the driving time of the backlight unit according to the result of comparison between the gray level saturation of the modulated image data and a preset offset value And an image enhancement unit. The method according to claim 1,
The image enhancement unit
A gain controller for generating a gain value for modulating the image data and a dimming value of the backlight unit in accordance with the analyzed average brightness,
Controls the driving time of the backlight unit using the extracted dimming value while modulating the image data so that the brightness of the display image is increased using the extracted gain value,
The gray level saturation of the image data modulated so as to increase the luminance is detected in units of at least one frame and the gain value and the dimming value are reversed in accordance with the comparison result between the detected gray level saturation value and the predetermined offset value Wherein the control unit adjusts the degree of modulation of the image data and the driving time of the backlight unit such that the degree of modulation of the image data and the driving time of the backlight unit are respectively increased or decreased in opposite directions. The method according to claim 1,
The image enhancement unit
A maximum / average value extracting unit for detecting a maximum gradation value or an average gradation value for each unit pixel of the image data arranged from the timing controller or the image data supplied from the outside,
An average analyzing unit for sequentially receiving the maximum gradation value or the average gradation value for each unit pixel and detecting an average gradation level of at least one frame,
A dimming extracting unit for setting and outputting a dimming control signal in accordance with a ratio of the average gradation level of at least one frame to the preset maximum gradation level,
A gain value extracting unit for dividing the maximum gradation level by the average gradation level of the detected at least one frame unit to extract a gain value,
A data compensator for generating compensation data by modulating image data aligned from the timing controller or image data supplied from the outside according to the gain value in at least one frame unit,
A saturation improving unit for outputting the modulated image data of at least one frame unit by further modulating the saturation gray level values of the compensation data by setting the grayscale compensation inflexion point according to the gain value,
A PWM generator for generating a PWM signal such that a duty ratio is converted according to the dimming value extracted in at least one frame unit and controlling a driving time of the backlight unit;
A saturation compensation value according to a result of the comparison between the gray level saturation of the modulated image data and the offset value is generated and the gain value of the gain value extracting unit and the dimming value of the dimming extracting unit are respectively set to a height And a dimming compensating unit for modulating the modulated light by the modulation unit. The method of claim 3,
The dimming extraction unit
Wherein the controller sets the dimming value at a ratio of the average gradation level to a preset maximum gradation level and then sets the saturation compensation value input from the dimming compensation unit to the set dimming value according to the comparison result of the saturation saturation amount and the offset value, So that the dimming value is modulated. 5. The method of claim 4,
The gain value extractor
And modulates the gain value as opposed to the dimming value according to a saturation compensation value according to a result of comparison between the saturation saturation amount and the offset value. Driving gate and data lines defining pixel regions of a liquid crystal panel;
Modulates the image data so that the luminance of the display image is increased by using the image enhancement unit, adjusts the degree to which the image data is modulated in accordance with the comparison result between the gray level saturation of the modulated image data and a predetermined offset value, And controlling the driving of the liquid crystal display device. The method according to claim 6,
Wherein the degree of modulation of the image data and the driving time control step of the backlight unit
Analyzing an average luminance of the image data input from the outside, extracting a gain value for modulating the image data according to the analyzed average luminance and a dimming value of the backlight unit,
Controlling the driving time of the backlight unit using the extracted dimming value while modulating the image data so that the luminance of the display image is increased using the extracted gain value,
Detecting a gray-scale saturation amount of the image data modulated so as to increase the luminance by at least one frame,
The gain value and the dimming value are increased or decreased in opposite tendencies according to a result of comparison between the detected saturation saturation amount and a preset offset value, thereby changing the degree of modulation of the image data and the driving time of the backlight unit And adjusting the driving voltage to be increased or decreased in opposite directions, respectively. The method according to claim 6,
Wherein the degree of modulation of the image data and the driving time control step of the backlight unit
Detecting a maximum gradation value or an average gradation value for each unit pixel of the image data sorted from the timing controller or the image data supplied from the outside using a maximum / average value extracting unit,
A step of sequentially receiving a maximum gradation value or an average gradation value for each unit pixel by using an average analyzing unit to detect an average gradation level of at least one frame,
Setting and outputting a dimming control signal in accordance with a ratio of the detected average gradation level of at least one frame to a preset maximum gradation level using a dimming extracting unit,
Extracting a gain value by dividing the maximum gradation level by the average gradation level of the detected at least one frame using a gain value extracting unit,
Generating compensated data by modulating image data aligned from the timing controller or image data supplied from the outside using the data compensating unit in accordance with the gain value in at least one frame unit;
Outputting the modulated image data of at least one frame unit by further modulating the saturation gradation values of the compensation data by setting a gradation compensation inflexion point according to the gain value using a saturation improving unit,
Controlling a driving time of the backlight unit by generating a PWM signal so that a duty ratio is converted according to the dimming value extracted at least one frame by using a PWM generator,
And a controller for generating a saturation compensation value according to a result of the comparison between the saturation saturation amount of the modulated image data and the offset value using the dimming compensation unit and setting the dimming value of the dimming extraction unit and the gain value of the gain value extraction unit And modulating the signals by increasing or decreasing the amplitudes of the amplitudes of the amplitudes and amplitudes of the amplitudes of the amplitudes of the amplitudes of the amplitudes. 9. The method of claim 8,
The dimming value setting and outputting step
Wherein the controller sets the dimming value at a ratio of the average gradation level to a preset maximum gradation level and then sets the saturation compensation value input from the dimming compensation unit to the set dimming value according to the comparison result of the saturation saturation amount and the offset value, So that the dimming value is modulated. 10. The method of claim 9,
The gain value extraction step
And the gain value is modulated inversely to the dimming value according to a saturation compensation value according to a result of comparison between the saturation saturation amount and the offset value.
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KR20200110542A (en) * 2019-03-14 2020-09-24 삼성디스플레이 주식회사 Display device

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