KR101920756B1 - Liquid crystal display device and method for driving the same - Google Patents

Abstract

The present invention relates to a liquid crystal display device and a method of driving the same that can reduce the power of expression in a low gradation region while reducing power consumption through dimming value adjustment. And adjusts the dimming value according to the ratio of the calculated high gradation region and the ratio of the low gradation region, and outputs the adjusted dimming value; And an inverter for driving the backlight according to the dimming value provided from the dimming value adjusting unit.

Description

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

The present invention relates to a liquid crystal display device and a driving method thereof that can reduce power consumption in a low gradation region while reducing power consumption through dimming value adjustment.

A liquid crystal display device displays an image using electrical and optical characteristics of a liquid crystal. Liquid crystals can have different anisotropic properties depending on the molecular axis and the direction of the short axis, such as refractive index and dielectric constant, and can easily control the molecular arrangement and optical properties. A liquid crystal display device using the same displays an image by changing the alignment direction of liquid crystal molecules according to the electric field size and adjusting the light transmittance transmitted through the polarizing plate.

A liquid crystal display device includes a liquid crystal panel in which a plurality of pixels are arranged in a matrix form, a driving circuit for driving the liquid crystal panel, and a backlight unit for irradiating the liquid crystal panel with light. The luminance of the liquid crystal display device is determined by the data supplied to the liquid crystal panel and the luminance of the backlight unit. The brightness of the liquid crystal display device is generally adjusted by adjusting the dimming ratio, i.e., the dimming value, according to the user's adjustment, thereby adjusting the brightness of the backlight unit.

In order to reduce the power consumption of the liquid crystal display device, it is effective to reduce the power consumption of the backlight unit which occupies a relatively large proportion. Recently, in order to reduce the power consumption of the liquid crystal display device, a method of adjusting the dimming value through analysis of the input image has been proposed.

The power consumption reduction method using the dimming value adjustment reduces the dimming value of the backlight unit to reduce the brightness of the backlight unit, thereby reducing the power consumption of the backlight unit when an image including a large number of pixels of high gradation is displayed. However, the power consumption reduction method using the dimming value adjustment has a problem in that the display power of the low gradation region is reduced as the brightness of the backlight unit is set too low when displaying an image including a large number of low gradation pixels.

It is an object of the present invention to provide a liquid crystal display device and a driving method thereof that can reduce power consumption in a low gradation region while reducing power consumption through dimming value adjustment.

According to an aspect of the present invention, there is provided a liquid crystal display device including: a liquid crystal display (LCD) device according to an embodiment of the present invention that analyzes input image data to calculate a ratio of a high gray scale area and a low gray scale area, A dimming value adjusting unit for adjusting and outputting a dimming value according to a ratio of the dimming value; And an inverter for driving the backlight according to the dimming value provided from the dimming value adjusting unit.

The dimming value adjusting unit sets a minimum dimming value according to the ratio of the low gradation region and sets a final dimming value according to the ratio of the high gradation region and sets the final dimming value equal to or greater than the minimum dimming value .

Wherein the dimming value adjuster comprises: a histogram analyzer for analyzing the input image data and analyzing and outputting a histogram for each gradation; A high grayscale analysis unit configured to set, as a ratio of the high grayscale area, a ratio of pixels occupying a grayscale range higher than a first reference grayscale in all the pixels using the histogram for each grayscale; A low grayscale analysis unit that sets a ratio of a pixel in a gradation range lower than a second reference gradation in the entire pixels to a ratio of the low gradation range using the histogram for each gradation; A first dimming value is set according to a ratio of the high gradation region, a second dimming value is set according to a ratio of the low gradation region, and a large value among the first and second dimming values is set as a third dimming value And outputting the result; And a second determining unit for setting a smaller value among the third dimming value and the dimming setting value of the user as the final dimming value; And the minimum dimming value is the second dimming value.

The first determining unit sets the first dimming value to a lower value as the ratio of the high gradation region increases and sets the second dimming value higher as the ratio of the low gradation region increases.

The dimming value adjusting unit temporarily sets the dimming value according to the ratio of the high gradation region and raises the dimming value temporarily set according to the ratio of the low gradation region to set the final dimming value.

Wherein the dimming value adjuster comprises: a histogram analyzer for analyzing the input image data and analyzing and outputting a histogram for each gradation; A high grayscale analysis unit configured to set, as a ratio of the high grayscale area, a ratio of pixels occupying a grayscale range higher than a first reference grayscale in all the pixels using the histogram for each grayscale; A low grayscale analysis unit that sets a ratio of a pixel in a gradation range lower than a second reference gradation in the entire pixels to a ratio of the low gradation range using the histogram for each gradation; A first gain value is set according to the ratio of the high gradation region, a second gain value is set according to the ratio of the low gradation region, the dimming setup value of the user is multiplied by the first gain value, And calculating a final dimming value by multiplying the first gain value by the second gain value.

Wherein the first determination unit sets the first gain value to be lower as the ratio of the high gradation region is higher and sets the second gain value to be higher as the ratio of the low gradation region becomes higher.

According to another aspect of the present invention, there is provided a method of driving a liquid crystal display (LCD) device, the method comprising: calculating a ratio of a high gray scale area and a low gray scale area by analyzing input image data; Adjusting and outputting the dimming value according to the ratio of the calculated high gradation region and the ratio of the low gradation region; And driving the backlight according to the dimming value.

The adjusting and outputting the dimming value may include: setting a minimum dimming value according to the ratio of the low gradation region; Setting a final dimming value according to a ratio of the high gradation region and setting the final dimming value equal to or greater than the minimum dimming value.

Wherein the step of adjusting and outputting the dimming value comprises: analyzing the input image data and analyzing and outputting a histogram for each gradation; Setting a ratio of a pixel corresponding to a gradation range higher than a first reference gradation in all the pixels to a ratio of the high gradation range using the histogram for each gradation; Setting a ratio of the pixels corresponding to the gradation range lower than the second reference gradation in all of the pixels to a ratio of the low gradation range using the histogram for each gradation; A first dimming value is set according to a ratio of the high gradation region, a second dimming value is set according to a ratio of the low gradation region, and a large value among the first and second dimming values is set as a third dimming value ; Setting a third value of the third dimming value and a user's dimming setting value to the final dimming value; And the minimum dimming value is the second dimming value.

The step of adjusting and outputting the dimming value may include: temporarily setting a dimming value according to the ratio of the high gradation region; And increasing the dimming value temporarily set according to the ratio of the low gradation region to set the final dimming value.

Wherein the step of adjusting and outputting the dimming value comprises: analyzing the input image data and analyzing and outputting a histogram for each gradation; Setting a ratio of a pixel corresponding to a gradation range higher than a first reference gradation in all the pixels to a ratio of the high gradation range using the histogram for each gradation; Setting a ratio of the pixels corresponding to the gradation range lower than the second reference gradation in all of the pixels to a ratio of the low gradation range using the histogram for each gradation; Setting a first gain value according to a ratio of the high gradation region and setting a second gain value according to a ratio of the low gradation region; And calculating the final dimming value by multiplying the dimming setting value of the user by the first gain value and then multiplying the multiplied value by the second gain value.

In the present invention, the dimming value dim is set according to the ratio of the high gradation region, and the dimming value dim is also adjusted in consideration of the ratio of the low gradation region, thereby reducing power consumption of the backlight unit, Can be prevented.

1 is a configuration diagram of a liquid crystal display device according to an embodiment of the present invention.
2 is a configuration diagram of the dimming value adjusting unit 10 according to the first embodiment.
3 is a flowchart of the operation of the dimming value adjusting unit 10 according to the first embodiment.
Fig. 4 shows an example of a histogram for each gradation.
5 is a configuration diagram of the dimming value adjusting unit 10 according to the second embodiment.
6 is a flowchart of the operation of the dimming value adjuster 10 according to the second embodiment.

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

1 includes a liquid crystal panel 2 for displaying an image, a data driver 6 for driving a data line DL of the liquid crystal panel 2, a gate line (not shown) for the liquid crystal panel 2, A timing controller 8 for supplying input data to the data driver 6 and for controlling the gate driver 4, and a timing controller 8 for analyzing the input image data, A dimming value adjusting unit 10 for calculating the ratio of the area and the low gradation area and adjusting and outputting the dimming value dim according to the ratio of the calculated high gradation area and the ratio of the low gradation area, And an inverter 12 for driving the backlight 14 in accordance with the dimming value dim provided from the dimming value dim.

The liquid crystal panel 2 displays an image through a pixel matrix in which a plurality of pixels are arranged. Each pixel implements a desired color by a combination of red, green, and blue sub-pixels that adjust the light transmittance by varying the liquid crystal array according to the data signal. Each sub pixel includes a thin film transistor TFT connected to the gate line GL and the data line DL, a liquid crystal capacitor Clc connected in parallel with the thin film transistor TFT, and a storage capacitor Cst. The liquid crystal capacitor Clc charges the difference voltage between the data signal supplied to the pixel electrode through the thin film transistor TFT and the common voltage Vcom supplied to the common electrode, drives the liquid crystal according to the charged voltage, . The storage capacitor Cst stably maintains the voltage charged in the liquid crystal capacitor Clc.

The data driver 6 converts the digital image data from the timing controller 8 into an analog data signal (pixel voltage signal) using a gamma voltage in response to the data control signal from the timing controller 8, To the data line DL.

The gate driver 4 sequentially drives the gate line GL of the liquid crystal panel 2 in response to the gate control signal of the timing controller 8. [

The timing controller 8 arranges the input image data and outputs it to the data driver 6. The timing controller 8 controls the timing of driving the data driver 6 using a plurality of input synchronous signals, that is, a dot clock, a data enable signal, a horizontal synchronizing signal, and a vertical synchronizing signal, And generates and outputs a gate control signal for controlling the driving timing of the gate driver 4.

The dimming value adjusting unit 10 analyzes the input image data and adjusts the dimming value dim to output it. The dimming value adjusting unit 10 calculates the ratio of the high gradation region from the input image data and outputs the dimming value dim as the higher the ratio of the calculated high gradation region is. However, if the dimming value dim is decreased in proportion to the ratio of the high gradation region, the brightness of the backlight 14 becomes excessively low, so that the expression power in the low gradation region can be reduced.

In order to prevent this, the dimming value adjusting section 10 calculates the ratio of the high gradation region and also calculates the ratio of the low gradation region. The dimming value dim is set according to the ratio of the high gradation region, and the dimming value dim is set in consideration of the ratio of the low gradation region. For example, the dimming value adjusting unit 10 may set the minimum dimming value according to the ratio of the low gradation region and set the dimming value dim according to the ratio of the high gradation region to be equal to or greater than the minimum dimming value. As another example, the dimming value adjusting unit 10 temporarily sets the dimming value dim according to the ratio of the high gradation region and performs correction to raise the dimming value dim temporarily set according to the ratio of the low gradation region . The dimming value adjusting unit 10 will be described later in detail.

The inverter 12 drives the backlight 14 according to the dimming value dim from the dimming value adjusting unit 10 to adjust the brightness of the backlight 14. [ The inverter 12 generates a PWM signal corresponding to the dimming value and supplies a backlight 16 driving signal corresponding to the pulse width of the PWM signal to the backlight 14. [ Specifically, the inverter 12 adjusts the pulse width of the PWM signal according to the dimming value, and adjusts the brightness of the backlight 14 by adjusting the on / off period of the backlight driving signal according to the pulse width.

Hereinafter, the dimming value adjuster 10 of the present invention will be described in detail with reference to embodiments.

2 is a configuration diagram of the dimming value adjusting unit 10 according to the first embodiment. And FIG. 3 is a flowchart of the operation of the dimming value adjuster 10 according to the first embodiment.

2 includes a histogram analyzing unit 16, a high tone analyzing unit 18, a low tone analyzing unit 20, a first determining unit 22, a second determining unit (24).

The histogram analyzing unit 16 detects the number of pixels of each gradation from the inputted image data of at least one frame, and generates and analyzes histograms for each gradation as shown in FIG. 4 and outputs the histograms (FIG. 3, step S1)

The high tone analyzer 18 calculates the ratio of the high tone area, i.e., the high tone ratio, from the input image data using the histogram for each table provided from the histogram analyzer 16, and outputs the ratio. To this end, the high tone analyzer 18 sets the first reference tone corresponding to the high tone range and calculates the ratio of the number of pixels in the tone range higher than the first reference tone to the total number of pixels. At this time, the calculated ratio becomes the high gradation ratio. (Step S2 in Fig. 3)

The low-gray-level analysis unit 20 calculates the ratio of the low gray-scale region, that is, the low gray-scale ratio, from the input image data using the histogram for each gray-scale provided from the histogram analyzing unit 16, and outputs the ratio. To this end, the low-tone analyzer 20 sets the second reference tone corresponding to the low tone range and calculates the ratio of the number of pixels in the range lower than the second reference tone to the total number of pixels. At this time, the calculated ratio becomes the low gradation ratio. The second reference gradation corresponds to a gradation range lower than the first reference gradation (step S2 in Fig. 3)

The first determination unit 22 adjusts the dimming value dim by analyzing the high gradation ratio provided from the high gradation analysis unit 18 and the low gradation ratio provided from the low gradation analysis unit 20. [ Specifically, the first determination unit 22 sets the first dimming value according to the high gradation ratio and sets the second dimming value according to the low gradation ratio. When the first dimming value is set, the first determining unit 22 sets the first dimming value to a lower value as the high gradation ratio is higher. When the second dimming value is set, the first determining unit 22 sets the second dimming value higher as the low gradation ratio is higher (step S3 in FIG. 3)

The first determiner 22 compares the set first and second dimming values and sets a larger value among the first and second dimming values as a third dimming value and outputs the resultant value (step S4 in FIG. 3)

The first determiner 22 may refer to a lookup table (not shown) when setting the first and second dimming values. The lookup table includes a plurality of first dimming Values are stored, and a plurality of second dimming values corresponding to the low gradation ratios are stored as shown in Table 2.

High gradation ratio (%) Dimming value (0 to 100) More than 50% 70 More than 40% 75 More than 30% 80 20% or more 85

Low gradation ratio (%) Dimming value (0 to 100) 15-20% 85 10 to 15% 80 5 to 10% 75

A method of setting the first to third dimming values in the first determiner 22 will be described with reference to Tables 1 and 2, for example. Hereinafter, the setting range of the dimming value is assumed to be 0 to 100. Of course, as the dimming value goes from 0 to 100, the brightness of the backlight 14 becomes brighter.

For example, assume that the input image data has a high gradation ratio of 52% and a low gradation ratio of 7%. Then, the first determination unit 22 sets the first dimming value to 70 in accordance with the high gradation ratio of 52%, and sets the second dimming value to 75 according to the low gradation ratio of 7%. The first determination unit sets 75, which is the larger of the first dimming value of 70 and the second dimming value of 75, to the third dimming value.

As another example, assume that the high gradation ratio of the input image data is 22% and the low gradation ratio is 7%. The first determination unit 22 sets the first dimming value to 85 according to the 22% high gradation ratio and sets the second dimming value to 75 according to the low gradation ratio of 7%. The first determination unit sets 85, which is the larger of the first dimming value of 85 and the second dimming value of 75, to the third dimming value.

In this way, even if the first determination unit 22 analyzes the high gradation ratio and the low gradation ratio to adjust the third dimming value, it can not be set as the final dimming value if it is larger than the dimming setting value set by the user. To this end, the embodiment includes a second determiner 24.

The second determination unit 24 compares the third dimming value provided from the first determination unit 22 with the dimming setting value of the user to calculate a final dimming value. Specifically, the second determiner 24 sets a smaller value among the third dimming value and the dimming setting value of the user as a final dimming value dim and outputs the result (step S5 in FIG. 3). For example, If the third dimming value provided to the determination unit 24 is 80 and the dimming setting value of the user is 85, the second determination unit 24 sets 80 to the final dimming value dim and outputs the final dimming value dim. As another example, if the third dimming value provided to the second determiner 24 is 85 and the dimming set value of the user is 70, the second determiner 24 sets 70 to the final dimming value dim and outputs the final dimming value dim.

The dimming value adjusting unit 10 according to the second embodiment will be described below.

5 is a configuration diagram of the dimming value adjusting unit 10 according to the second embodiment. And FIG. 6 is an operational flowchart of the dimming value adjusting unit 10 according to the second embodiment.

5 includes a histogram analyzing section 16, a high tone analyzing section 18, a low tone analyzing section 20 and a first determining section 26. The histogram analyzing section 16,

In the second embodiment, the histogram analyzing unit 16, the high tone analyzing unit 18, and the low tone analyzing unit 20 have substantially the same functions as those of the first embodiment, (Steps S6 and S7 are omitted in Fig. 6). In the second embodiment, only the first determination unit 26 will be described.

The first determination unit 26 adjusts the dimming value by analyzing the high gradation ratio provided from the high gradation analysis unit 18 and the low gradation ratio provided from the low gradation analysis unit 20. [ Specifically, the first determination unit 26 sets the first gain value in accordance with the high gradation ratio and sets the second gain value in accordance with the low gradation ratio. (Fig. 6, Step S8) The first determination unit 26 Sets the first gain value to a lower value as the higher gradation ratio is higher when the first gain value is set. When the second gain value is set, the first determination unit 26 sets the second gain value higher as the low gradation ratio is higher.

In this case, the first gain value is a value for lowering the user's dimming setting value in proportion to the high gray-scale ratio, and the second gain value is a value for raising a dimming setting value set low in proportion to the low gray-scale ratio. Therefore, the first gain value is set to a range smaller than 1, and the second gain value is set to a range larger than 1.

After setting the first and second gain values, the first determination unit 26 multiplies the dimming setting value of the user by the first gain value, multiplies the multiplied value by the second gain value to obtain the final dimming value dim (Step S9 in Fig. 6)

Of course, it is preferable that the user's dimming setting value is multiplied by the first and second gain values so that the set final dimming value dim is less than or equal to the dimming setting value of the user.

As described above, according to the present invention, the dimming value dim is set according to the ratio of the high gradation region, and the dimming value dim is also adjusted in consideration of the ratio of the low gradation region to the power saving effect of the backlight unit It is possible to prevent the reduction of the expressive power in the low gradation region.

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 general inventive concept as defined by the appended claims and their equivalents. Will be clear to those who have knowledge of.

2: liquid crystal panel 4: gate driver
6: Data driver 8: Timing controller
10: dimming value adjustment unit 12: inverter
14: Backlight

Claims (12)

The ratio of the high gradation area and the low gradation area is calculated by analyzing the input image data and the ratio of the calculated high gradation area and the ratio of the low gradation area is analyzed to reflect the dimming value preset by the user in the adjusted dimming value A dimming value adjusting unit for outputting the calculated dimming value;
And an inverter for driving the backlight according to the dimming value provided from the dimming value adjusting unit,
The dimming value adjusting unit
A minimum dimming value is set according to the ratio of the low gradation region,
Wherein a final dimming value is set according to a ratio of the high gradation region, and the final dimming value is set to be equal to or greater than the minimum dimming value. delete The method according to claim 1,
The dimming value adjusting unit
A histogram analyzer for analyzing the input image data and analyzing and outputting a histogram for each histogram;
A high grayscale analysis unit configured to set, as a ratio of the high grayscale area, a ratio of pixels occupying a grayscale range higher than a first reference grayscale in all the pixels using the histogram for each grayscale;
A low grayscale analysis unit that sets a ratio of a pixel in a gradation range lower than a second reference gradation in the entire pixels to a ratio of the low gradation range using the histogram for each gradation;
A first dimming value is set according to a ratio of the high gradation region, a second dimming value is set according to a ratio of the low gradation region, and a large value among the first and second dimming values is set as a third dimming value And outputting the result;
And a second determining unit for setting a smaller value among the third dimming value and the dimming setting value of the user as the final dimming value;
And the minimum dimming value is the second dimming value. The method of claim 3,
The first determination unit
The first dimming value is set to be lower as the ratio of the high gradation region is higher,
And the second dimming value is set higher as the ratio of the low gradation region is higher. The ratio of the high gradation area and the low gradation area is calculated by analyzing the input image data and the ratio of the calculated high gradation area and the ratio of the low gradation area is analyzed to reflect the dimming value preset by the user in the adjusted dimming value A dimming value adjusting unit for outputting the calculated dimming value;
And an inverter for driving the backlight according to the dimming value provided from the dimming value adjusting unit,
The dimming value adjusting unit
The dimming value is temporarily set according to the ratio of the high gradation region,
And the final dimming value is set by raising the dimming value temporarily set according to the ratio of the low gradation region. 6. The method of claim 5,
The dimming value adjusting unit
A histogram analyzer for analyzing the input image data and analyzing and outputting a histogram for each histogram;
A high grayscale analysis unit configured to set, as a ratio of the high grayscale area, a ratio of pixels occupying a grayscale range higher than a first reference grayscale in all the pixels using the histogram for each grayscale;
A low grayscale analysis unit that sets a ratio of a pixel in a gradation range lower than a second reference gradation in the entire pixels to a ratio of the low gradation range using the histogram for each gradation;
A first gain value is set according to the ratio of the high gradation region, a second gain value is set according to the ratio of the low gradation region, the dimming setup value of the user is multiplied by the first gain value, And a first determining unit for calculating the final dimming value by multiplying the first gain value by the second gain value. The method according to claim 6,
The first determination unit
The first gain value is set to be lower as the ratio of the high gradation region is higher,
And the second gain value is set to be higher as the ratio of the low gradation region is higher. Analyzing input image data to calculate a ratio of a high gradation area and a low gradation area;
Analyzing a ratio of the calculated high gradation region and a ratio of the low gradation region, and outputting the calculated dimming value by reflecting the adjusted dimming value by the user;
And driving the backlight according to the dimming value. The driving method of a liquid crystal display device according to claim 1,
The step of outputting the dimming value
Setting a minimum dimming value according to the ratio of the low gradation region;
And setting a final dimming value according to a ratio of the high gradation region, wherein the final dimming value is set to be equal to or greater than the minimum dimming value. delete 9. The method of claim 8,
The step of adjusting and outputting the dimming value
Analyzing the input image data and analyzing and outputting a histogram according to the gradation;
Setting a ratio of a pixel corresponding to a gradation range higher than a first reference gradation in all the pixels to a ratio of the high gradation range using the histogram for each gradation;
Setting a ratio of the pixels corresponding to the gradation range lower than the second reference gradation in all of the pixels to a ratio of the low gradation range using the histogram for each gradation;
A first dimming value is set according to a ratio of the high gradation region, a second dimming value is set according to a ratio of the low gradation region, and a large value among the first and second dimming values is set as a third dimming value ;
Setting a third value of the third dimming value and a user's dimming setting value to the final dimming value;
And the minimum dimming value is the second dimming value. Analyzing input image data to calculate a ratio of a high gradation area and a low gradation area;
Analyzing a ratio of the calculated high gradation region and a ratio of the low gradation region, and outputting the calculated dimming value by reflecting the adjusted dimming value by the user;
And driving the backlight according to the dimming value. The driving method of a liquid crystal display device according to claim 1,
The step of outputting the dimming value
Temporarily setting a dimming value according to a ratio of the high gradation region;
And increasing the dimming value temporarily set according to the ratio of the low gradation region to set the final dimming value. 12. The method of claim 11,
The step of outputting the dimming value
Analyzing the input image data and analyzing and outputting a histogram according to the gradation;
Setting a ratio of a pixel corresponding to a gradation range higher than a first reference gradation in all the pixels to a ratio of the high gradation range using the histogram for each gradation;
Setting a ratio of the pixels corresponding to the gradation range lower than the second reference gradation in all of the pixels to a ratio of the low gradation range using the histogram for each gradation;
Setting a first gain value according to a ratio of the high gradation region and setting a second gain value according to a ratio of the low gradation region;
And multiplying the multiplied value by the first gain value and the final gain value by multiplying the multiplied value by the second gain value.

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