KR102006265B1 - Liquid crystal display device and method for driving the same - Google Patents

Abstract

The present invention relates to a liquid crystal display and a driving method thereof. A liquid crystal display device according to an embodiment of the present invention includes a display panel; A backlight unit including light sources for emitting light to the display panel; A display panel driver converting the digital video data into data voltages and supplying the data voltages to the display panel; A light source driver for supplying a PWM signal to the light sources; And an adjustment unit adjusting the luminance and contrast ratio of the display panel by controlling a duty ratio of the PWM signal according to a background color selected by the user.

Description

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

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

A liquid crystal display device of an active matrix driving type displays a moving picture by using a thin film transistor (hereinafter referred to as "TFT") as a switching element. The liquid crystal display device can be miniaturized as compared with a cathode ray tube (CRT), and can be applied not only to an indicator in a portable display such as a smart phone, a tablet, an office machine, a computer, It is quickly replacing. Particularly, due to the increase in the number of portable displays, the user's viewing time of the display is increasing, and the fatigue of the user's eyes is also increasing.

In order to reduce the visual fatigue of the user, some portable displays provide a function of sensing the illuminance of external light and automatically adjusting the brightness of the liquid crystal display device according to the illuminance. In addition, some monitors and televisions provide a function to adjust the screen to a movie mode or a sports mode depending on the user's selection. However, there is a limitation in reducing the visual fatigue of the user only by adjusting the screen according to contents such as the movie mode and the sports mode, or adjusting the luminance of the liquid crystal display device according to the illuminance.

The present invention provides a liquid crystal display device and a driving method thereof that can further reduce visual fatigue of a user.

A liquid crystal display device according to an embodiment of the present invention includes a display panel; A backlight unit including light sources for emitting light to the display panel; A display panel driver converting the digital video data into data voltages and supplying the data voltages to the display panel; A light source driver for supplying a PWM signal to the light sources; And an adjustment unit adjusting the luminance and contrast ratio of the display panel by controlling a duty ratio of the PWM signal according to a background color selected by the user.

A driving method of a liquid crystal display according to an embodiment of the present invention is a driving method of a liquid crystal display including a display panel and a backlight unit including light sources for emitting light to the display panel, And supplying the converted data to the display panel; Supplying a PWM signal to the light sources; And adjusting a luminance and a contrast ratio of the display panel by controlling a duty ratio of the PWM signal according to a background color selected by a user.

The present invention can optimally adjust the luminance and contrast ratio of the display panel according to the background color selected by the user. In addition, the present invention can optimally adjust the luminance, contrast ratio, and color temperature of a display panel according to the type of external light. As a result, the present invention can minimize visual fatigue of the user.

1 is a block diagram showing a liquid crystal display device according to an embodiment of the present invention;
2 is a block diagram showing the illuminance analyzer of FIG. 1 in detail;
3 is a block diagram showing a detail of an adjusting unit according to the first embodiment of the present invention;
4 is a flow chart illustrating a method of adjusting brightness, contrast, and color temperature according to a first embodiment of the present invention.
5 is an exemplary view showing a PWM signal.
6 is an exemplary view showing optimal luminance, color temperature, and contrast ratio according to the type of external light and background color;
7 is an exemplary view showing a PWM signal in a peak white gradation and a PWM signal in a peak black gradation;
8 is an exemplary view showing a CIE chromaticity diagram;
9 is a block diagram showing the details of the adjustment unit according to the second embodiment of the present invention.
10 is a flow chart showing a method of adjusting brightness, contrast, and color temperature according to a second embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Like reference numerals throughout the specification denote substantially identical components. In the following description, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear. In addition, the component names used in the following description may be selected in consideration of easiness of specification, and may be different from the parts names of actual products.

1 is a block diagram showing a liquid crystal display according to an embodiment of the present invention. 1, a liquid crystal display according to an embodiment of the present invention includes a display panel 10, a backlight unit 40, a display panel driving unit, a light source driving unit 140, a light source control unit 150, an adjusting unit 160, A luminance analysis unit 170, a color temperature analysis unit 180, and the like.

The display panel 10 includes two substrates and a liquid crystal layer formed therebetween. A plurality of data lines (D) and a plurality of gate lines (G) cross each other on the lower substrate of the display panel (10). In the display panel 10, the liquid crystal cells Clc are arranged in a matrix by the intersection structure of the data lines D and the gate lines G. [ Each of the liquid crystal cells Clc includes a thin film transistor (TFT), a pixel electrode 1 connected to a TFT, and a storage capacitor Cst. On the upper substrate of the display panel 10, a black matrix, a color filter, and the like are formed. The common electrode 2 is formed on an upper glass substrate in a vertical electric field driving method such as TN (Twisted Nematic) mode and VA (Vertical Alignment) mode. And is formed on the lower substrate together with the pixel electrode 1 in the horizontal electric field driving system. Each of the liquid crystal cells Clc is driven by an electric field between the pixel electrode 1 and the common electrode 2. On the upper substrate and the lower substrate of the display panel 10, a polarizing plate having an optical axis orthogonal to each other is attached, and an alignment film for setting a pre-tilt angle of liquid crystal on the inner surface in contact with the liquid crystal is formed.

The backlight unit 40 includes a plurality of light sources for irradiating the display panel 10 with light. The backlight unit 40 may be implemented as either a direct type or an edge type. The direct-type backlight unit has a structure in which a plurality of optical sheets and a diffusion plate are stacked under the display panel 10 and a plurality of light sources are disposed under the diffusion plate. The edge type backlight unit has a structure in which a plurality of optical sheets and a light guide plate are stacked under the display panel 10 and a plurality of light sources are disposed on a side surface of the light guide plate. The light sources may be realized by point light sources such as a light emitting diode (LED).

The display panel driving unit includes a gate driving unit 110, a data driving unit 120, and a timing control unit 130. The gate driver 110 includes a plurality of gate drive integrated circuits. The gate drive integrated circuit includes a shift register, a level shifter for converting an output signal of the shift register into a swing width suitable for driving a TFT of a liquid crystal cell, an output buffer, and the like. The gate driver 110 sequentially outputs gate pulses (or scan pulses) to the gate lines GL under the control of the timing controller 130, thereby selecting a horizontal line to which the data voltage is to be applied.

The data driver 120 includes a plurality of data drive integrated circuits. The data drive integrated circuit receives the digital video conversion data RGB 'from the timing controller 150. The data drive integrated circuit converts the digital video conversion data RGB 'into a positive / negative analog data voltage using a positive / negative gamma compensation voltage supplied from a gamma voltage generator (not shown). The data drive integrated circuit supplies the positive / negative analog data voltages to the data lines (D) of the display panel (10).

The timing controller 130 receives digital video data RGB and timing signals from a host system (not shown). The timing signals may include a vertical synchronization signal, a horizontal synchronization signal, a data enable signal, a clock signal, and the like. The timing controller 130 generates a gate control signal GCS for controlling the gate driver 110 based on the timing signals and generates a data control signal DCS for controlling the data driver 120. The timing controller 130 supplies the gate control signal GCS to the gate driver 110 and supplies the digital conversion data RGB 'and the data control signal DCS to the data driver 120.

The light source driver 140 receives the pulse width control data Dpwm from the light source controller 150 and generates a pulse width modulation signal PWM Quot;). The light source driving unit 140 supplies the PWM signals PWM to the light sources of the backlight unit 40. Since the lighting time of the light sources is determined by the duty ratio of the PWM signal PWM, the luminance and contrast ratio of the display panel 10 can be adjusted by adjusting the duty ratio of the PWM signal PWM. A detailed description thereof will be given later in conjunction with FIG. 5 and FIG.

The light source control unit 150 receives the light source control data Dlc from the adjustment unit 160. The light source control data Dlc includes pulse width modulation information for adjusting luminance and contrast ratio. Therefore, the light source control unit 150 can generate the pulse width control data Dpwm based on the light source control data Dlc. The light source control unit 150 supplies the pulse width control data Dpwm to the light source driving unit 140. The light source control unit 150 may be included in the adjustment unit 160.

The adjustment unit 160 receives background color data Dbgd and digital video data RGB including the background color information selected by the user from a host system (not shown). The adjusting unit 160 receives the illuminance data Di including external illuminance information from the illuminance analyzer 170 and receives the color temperature data Dct including the color temperature information of the external light from the color temperature analyzer 170 . The adjustment unit 160 may supply the light source control data Dlc including the pulse width modulation information for adjusting the brightness and the contrast ratio to the light source control unit 150 in order to control the duty ratio of the PWM signal PWM according to the background color, . The adjustment unit 160 converts the digital video data RGB according to the color temperature and supplies the digital video data RGB to the timing control unit 130. A detailed description of the adjustment unit 160 will be given later with reference to FIGS. 3, 4, 9, and 10. FIG.

The illuminance analyzer 170 includes an illuminance sensor circuit 171 including an illuminance sensor and a first analog-to-digital converter 172 as shown in FIG. The illuminance of the external light measured by the illuminance sensor of the illuminance sensor circuit 171 is converted into illuminance data Di which is digital data by the first analog-to-digital converter 172. The illuminance analyzing unit 170 transmits the illuminance data Di to the adjusting unit 160.

The color temperature analyzer 180 may analyze the photographed image using the image sensor to calculate the color temperature of the external light. In this case, the image sensor may be implemented by a CMOS sensor, and the method of calculating the color temperature of the external light by analyzing the photographed image using the image sensor may be implemented using any known method. Alternatively, the color temperature analyzer 180 may calculate the color temperature by analyzing the wavelength information of the external light obtained by using a photo diode. In this case, the photodiode may include a red photodiode for measuring the red wavelength, a green photodiode for measuring the green wavelength, and a blue photodiode for measuring the blue wavelength. In addition, the method of calculating the color temperature by analyzing the wavelength information of the external light obtained using the photodiode can be implemented using any of known methods known in the art. The color temperature analyzer 180 transmits the color temperature data Dct including the color temperature information to the adjusting unit 160.

FIG. 3 is a block diagram showing an adjustment unit according to the first embodiment of the present invention in detail. Referring to FIG. 3, the adjusting unit 160 according to the first embodiment of the present invention includes a luminance and contrast ratio adjusting unit 161, a color temperature adjusting unit 162, a plurality of look-up tables 163 and 164 ).

4 is a flowchart illustrating a method of adjusting brightness, contrast, and color temperature according to the first embodiment of the present invention. The luminance and contrast ratio adjustment method of the luminance and contrast ratio adjustment unit 161 and the color temperature adjustment method of the color temperature adjustment unit 162 according to the first embodiment of the present invention will be described in detail with reference to FIGS.

First, the luminance and contrast ratio adjustment unit 161 receives illumination data Di from the illumination intensity analysis unit 170 and receives background color data Dbgd from the host system. The illuminance data Di includes external illuminance information. The brightness and contrast ratio adjustment unit 161 can determine the background color selected by the user from the background color data Dbgd. The background color selected by the user may be the color of the background of the image displayed on the display panel 10. [ For example, if the liquid crystal display device is implemented as a monitor connected to a computer, the background color may be a background color of the desktop. In addition, when the liquid crystal display device displays text, images, and the like, the background color may be a background color such as text, images, and the like.

The luminance and contrast ratio adjustment unit 161 adjusts the brightness of the display panel 10 higher than when the user selects the first background color. The brightness of the display panel 10 can be adjusted by controlling the duty ratio of the light sources of the backlight unit 40. [ Accordingly, the luminance and contrast ratio adjustment unit 161 outputs the light source control data Dlc so that the duty ratio of the PWM signal PWM becomes larger than when the user selects the first background color, The brightness of the display panel 10 can be adjusted to a high level.

5 is an exemplary diagram showing a PWM signal. Referring to FIG. 5, the PWM signal PWM is repeated at a predetermined period tp, and one period tp of the PWM signal PWM is divided into a duty-on time ton and a duty-off time toff Respectively. The duty-on time (ton) means a period during which the light sources are lit, and the duty-off time (toff) means a period during which the light sources are turned off. The duty ratio DR of the PWM signal PWM can be calculated as shown in Equation (1).

The duty ratio DR of the PWM signal PWM is equal to the duty ratio DR of the PWM signal PWM because the sum of the duty-on time ton and the duty- It is proportional to the time (ton). Therefore, when the duty ratio DR of the PWM signal PWM becomes large, the brightness of the display panel 10 becomes high.

The brightness and contrast ratio adjustment unit 161 can adjust the brightness of the display panel 10 using a first look-up table 163 prepared in advance through a preliminary experiment. In this case, the first look-up table 163 receives the background color data Dbdg as the input address, and outputs the duty ratio information Ddr of the PWM signal PWM stored at the input address. The first look-up table 163 may be included in the luminance and contrast ratio adjuster 161.

On the other hand, the reason why the brightness of the display panel 10 is adjusted according to the background color selected by the user is that the optimal brightness which causes the user to feel less visual fatigue varies depending on the background color. Hereinafter, this will be described in detail with reference to FIG.

FIG. 6 is an exemplary diagram showing optimal luminance, color temperature, and contrast ratio according to the type of external light and the background color. In FIG. 6, the first background color is white and the second background color is white. However, it should be noted that the present invention is not limited thereto. Referring to FIG. 6, when the same external light is irradiated, the optimum luminance range of the off-white is higher than the optimal luminance range of white. Therefore, the present invention controls the brightness of the display panel 10 higher than when the user selects white as the background color. That is, the brightness and contrast ratio adjustment unit 161 outputs the light source control data Dlc so that the duty ratio of the PWM signal PWM becomes larger than when white is selected when the user selects the white color as the background color, The luminance of the display device 10 can be controlled to be higher. As described above, according to the present invention, since the optimum luminance which causes the user to feel less visual fatigue is changed according to the background color, the present invention optimally adjusts the luminance of the display panel 10 according to the background color selected by the user, thereby minimizing the visual fatigue of the user . (S101)

Secondly, the luminance and contrast ratio adjustment unit 161 adjusts the luminance of the display panel 10 to a maximum value within a set range regardless of the background color selected by the user when the illuminance of the external light is equal to or higher than the first threshold value. More specifically, the luminance and contrast ratio adjuster 161 adjusts the light source control data Dlc so that the duty ratio of the PWM signal PWM has a maximum value within a set range when the illuminance of the external light is equal to or greater than the first threshold value Output. The present invention reduces the visibility of the image displayed on the display panel due to external light when the illuminance of the external light is equal to or greater than the first threshold value. Therefore, in order to improve the illuminance, if the illuminance of the external light is equal to or greater than the first threshold, The luminance of the display panel 10 is adjusted to the maximum value within the set range. (S102, S103)

Thirdly, the luminance and contrast ratio adjuster 161 adjusts the contrast ratio of the display panel 10 higher than when the user selects the second background color when the user selects the first background color. The contrast ratio means the difference in brightness between the peak white gradation (full white) and the peak black gradation (full black). The contrast ratio can be adjusted by controlling the duty ratio of the light sources of the backlight unit 40 in the peak black gradation.

7 is an exemplary diagram showing the PWM signal in the peak white gradation and the PWM signal in the peak black gradation. 7, the duty-on time (ton) of the PWM signal PWM (b) in the peak black gradation corresponds to the duty-on time ton of the PWM signal PWM (w) in the peak white gradation It is shorter than that. The shorter the duty-on time (ton) of the PWM signal PWM (b) in the peak black gradation, the higher the contrast ratio can be. Accordingly, the luminance and contrast ratio adjuster 161 adjusts the light source control data Dlc (Dlc) so that the duty ratio of the PWM signal PWM at the peak black gradation becomes smaller than the case where the second background color is selected when the user selects the first background color So that the contrast ratio of the display panel 10 can be adjusted to a high level.

The brightness and contrast ratio adjustment unit 161 can adjust the contrast ratio as well as the brightness of the display panel 10 using the first look-up table 163. [ In this case, the first look-up table 163 receives the background color data Dbdg as an input address and stores the duty ratio information Ddr (b) of the PWM signal PWM in the black gradation stored at the input address as Can be output. The luminance and contrast ratio adjustment unit 161 generates the light source control data Dlc from the duty ratio information Ddr of the PWM signal PWM and the duty ratio information Ddr (b) of the PWM signal PWM in the black gradation And outputs it to the post-light source control unit 150.

On the other hand, the reason why the contrast ratio of the display panel 10 is adjusted according to the background color selected by the user is that the optimal contrast ratio that causes the user to feel less visual fatigue varies depending on the background color. Referring to FIG. 6, when the same external light is irradiated, the optimum contrast ratio of the off-white is higher than the optimal contrast ratio of white. Therefore, the present invention controls the contrast ratio of the display panel 10 higher than when the user selects white as the background color. That is, the brightness and contrast ratio adjuster 161 adjusts the brightness and contrast ratio of the light source control data (e.g., the brightness level and the contrast ratio) so that the duty ratio of the PWM signal PWM (b) in the peak black gradation becomes smaller than when white is selected when the user selects the off- The contrast ratio of the display panel 10 can be controlled to be higher. As described above, since the optimum contrast ratio that causes the user to feel less visual fatigue depending on the background color is changed, the present invention minimizes the visual fatigue of the user by optimally adjusting the contrast ratio of the display panel 10 according to the background color selected by the user . (S104)

Fourth, the color temperature adjustment unit 162 receives the color temperature data Dct from the color temperature analysis unit 180 and receives digital video data RGB and background color data Dbgd from the host system. The color temperature adjustment unit 162 can determine the background color selected by the user from the background color data Dbgd. The color temperature adjustment unit 162 converts the digital video data RGB into digital conversion data RGB 'according to the background color. Specifically, the color temperature can be adjusted by changing Wx and Wy in the CIE chromaticity diagram as shown in Fig. Wx can be expressed as shown in Equation (2), and Wy can be expressed as in Equation (3).

In Equations (2) and (3), X, Y, and Z indicate tristimulus values. The tristimulus value refers to the amount of red, green, and blue contained in the color of any light source or object color. Therefore, when X is large, it means that there is a large amount of red. When Y is large, it means that there is a large amount of green. When Z is large, it means that there is a large amount of blue. Particularly, in the embodiment of the present invention, the color temperature can be adjusted by changing Z among X, Y and Z. It is known that blue has a short wavelength and strong energy, so it is not absorbed by the cornea or lens of the user but reaches the retina. Therefore, if the value of Z is changed to a smaller value, the user will feel less visual fatigue. As shown in FIG. 8 and Equations 2 and 3, when Z is changed to a smaller value, Wx and Wy are increased, so that the color temperature is lowered.

The color temperature adjustment unit 162 can convert the digital video data RGB by using the second look-up table 164 created in advance through a preliminary experiment. In this case, the second look-up table 164 receives the background color data Dbdg and the digital video data RGB as input addresses and outputs the digital conversion data RGB 'stored at the input addresses. The second look-up table 164 may be included in the luminance and contrast ratio adjuster 161. For example, if the digital video data (RGB) is 8-bit data and there are two user-selectable background colors, then there will be 256 x 2 = 512 input addresses and thus the second look- Stores 512 digital converted data (RGB '). The color temperature adjustment unit 162 outputs the digital conversion data RGB 'to the timing control unit 130.

On the other hand, the reason why the user adjusts the color temperature according to the background color selected by the user is that the optimal color temperature which causes the user to feel less visual fatigue varies depending on the background color. Referring to FIG. 6, when the same external light is irradiated, the optimum color temperature range of the off-white is lower than the optimum color temperature range of white. Thus, the present invention controls the color temperature to be lower than when the user selects white as the background color. As described above, since the optimal color temperature at which the user feels less visual fatigue depends on the background color, the present invention can minimize the visual fatigue of the user by optimally adjusting the color temperature according to the background color selected by the user. (S107)

As described above, the first embodiment of the present invention can optimally adjust the luminance, contrast ratio, and color temperature of the display panel 10 according to the background color selected by the user. As a result, the first embodiment of the present invention can minimize the visual fatigue of the user. In the first embodiment of the present invention, the user selects one of the first background color and the second background color. However, the present invention is not limited thereto. That is, the first embodiment of the present invention may be implemented so as to select any one of three or more background colors. It should be noted that the color temperature analyzer 180 and the color temperature controller 162 may be omitted in the first embodiment of the present invention. In this case, the first embodiment of the present invention can optimally adjust only the luminance and contrast ratio of the display panel 10 according to the background color selected by the user.

FIG. 9 is a block diagram showing an adjustment unit according to a second embodiment of the present invention in detail. 9, the adjusting unit 160 according to the second exemplary embodiment of the present invention includes a luminance and contrast ratio adjusting unit 161, a color temperature adjusting unit 162, a plurality of look-up tables 165 and 166 ).

10 is a flowchart illustrating a method of adjusting brightness, contrast, and color temperature according to a second embodiment of the present invention. The luminance and contrast ratio adjustment method of the luminance and contrast ratio adjustment unit 161 and the color temperature adjustment method of the color temperature adjustment unit 162 according to the second embodiment of the present invention will be described in detail with reference to FIGS.

First, the luminance and contrast ratio adjusting unit 161 receives the luminance data Di from the luminance analyzer 170 and receives the color temperature data Dct from the color temperature analyzer 180. The illuminance data Di includes illuminance information of external light, and the color temperature data Dct includes color temperature information of external light. The luminance and contrast ratio adjustment unit 161 adjusts the luminance of the display panel 10 according to the color temperature of the external light. The brightness of the display panel 10 can be adjusted by controlling the duty ratio of the light sources of the backlight unit 40. [ Specifically, the luminance and contrast ratio adjustment unit 161 adjusts the brightness of the display panel 10 to be higher than when the color temperature of the external light is equal to or higher than the second threshold value. The luminance and contrast ratio adjustment unit 161 outputs the light source control data Dlc so that the duty ratio of the PWM signal PWM becomes larger than when the color temperature of the external light is equal to or higher than the second threshold value, Can be adjusted to a high level. The duty ratio of the PWM signal PWM has already been described in detail with reference to FIG. 5 and Equation (1).

The brightness and contrast ratio adjustment unit 161 can adjust the brightness of the display panel 10 using a third look-up table 165 that is prepared in advance through a preliminary experiment. In this case, the third look-up table 165 receives the color temperature data Dct as an input address and outputs the duty ratio information Ddr of the PWM signal PWM stored at the input address. The third look-up table 165 may be included in the luminance and contrast ratio adjuster 161.

On the other hand, when the color temperature of the external light is equal to or higher than the second threshold value, the luminance of the display panel 10 is adjusted to be lower than the second threshold value because the optimal luminance at which the user feels less visual fatigue It is because. The color temperature of the external light depends on the type of external light. For example, as shown in FIG. 6, the color temperature of a fluorescent lamp is 6500K, while the color temperature of an LED bulb is 5000K. In the same background color, the optimal luminance range of the fluorescent lamp is higher than the optimal luminance range of the LED bulb. Therefore, the present invention controls the luminance of the display panel 10 to be higher than the case where the color temperature of the external light is equal to or greater than the second threshold value, which is smaller than the second threshold value. That is, the luminance and contrast ratio adjusting unit 161 adjusts the light source control data Dlc so that the duty ratio of the PWM signal PWM becomes larger than the case where the color temperature of the external light is equal to or greater than the second threshold value The brightness of the display panel 10 can be controlled to be higher. As described above, according to the present invention, the brightness of the display panel 10 is optimally adjusted according to the color temperature of the external light, thereby minimizing the visual fatigue of the user can do. (S201)

Secondly, the luminance and contrast ratio adjustment unit 161 adjusts the luminance of the display panel 10 to a maximum value within a set range, regardless of the color temperature of the external light, when the illuminance of the external light is equal to or higher than the first threshold value. More specifically, the luminance and contrast ratio adjuster 161 adjusts the light source control data Dlc so that the duty ratio of the PWM signal PWM has a maximum value within a set range when the illuminance of the external light is equal to or greater than the first threshold value Output. The present invention reduces the visibility of the image displayed on the display panel due to external light when the illuminance of the external light is equal to or greater than the first threshold value. Therefore, in order to improve the illuminance, if the illuminance of the external light is equal to or greater than the first threshold, The luminance of the display panel 10 is adjusted to the maximum value within the set range. (S202, S203)

Thirdly, the brightness and contrast ratio adjustment unit 161 adjusts the contrast ratio of the display panel 10 higher than when the color temperature of the external light is equal to or higher than the second threshold value. The contrast ratio means the difference in brightness between the peak white gradation (full white) and the peak black gradation (full black). The contrast ratio can be adjusted by controlling the duty ratio of the light sources of the backlight unit 40 in the peak black gradation. The method of controlling the duty ratio of the light sources in the peak black gradation has already been described in detail with reference to FIG.

The brightness and contrast ratio adjustment unit 161 can adjust the contrast ratio as well as the brightness of the display panel 10 using the third look-up table 165. [ In this case, the third look-up table 165 receives the color temperature data Dct as an input address and stores the duty ratio information Ddr (b) of the PWM signal PWM in the black gradation stored at the input address as Can be output. The luminance and contrast ratio adjustment unit 161 generates the light source control data Dlc from the duty ratio information Ddr of the PWM signal PWM and the duty ratio information Ddr (b) of the PWM signal PWM in the black gradation And outputs it to the post-light source control unit 150.

On the other hand, when the color temperature of the external light is equal to or higher than the second threshold value, the contrast ratio of the display panel 10 is adjusted to be lower than the second threshold value because the optimal contrast ratio at which the user feels less visual fatigue It is because. The optimal contrast ratio of a fluorescent lamp in the same background color is higher than the optimum contrast ratio of the LED bulb. Therefore, the present invention controls the contrast ratio of the display panel 10 to be higher than the case where the color temperature of the external light is equal to or higher than the second threshold value, which is smaller than the second threshold value. That is, the luminance and contrast ratio adjustment unit 161 adjusts the duty ratio of the PWM signal PWM (b) in the peak black gradation to be smaller than that in the case where the color temperature of the external light is equal to or higher than the second threshold value The contrast ratio of the display panel 10 can be controlled to be higher by outputting the light source control data Dlc. As described above, since the optimum contrast ratio at which the user feels less visual fatigue is changed depending on the type of external light, the present invention can optimize the contrast ratio of the display panel 10 as the color temperature of the external light is higher, Can be minimized. (S204)

Fourth, the color temperature adjustment unit 162 receives the color temperature data Dct from the color temperature analysis unit 180 and receives digital video data RGB from the host system. The color temperature adjusting unit 162 converts the digital video data RGB into digital converted data RGB 'according to the color temperature of the external light. The method of adjusting the color temperature of the color temperature adjusting unit 162 has already been described in detail with reference to FIG.

The color temperature adjustment unit 162 can convert the digital video data RGB by using the fourth look-up table 166 created in advance through a preliminary experiment. In this case, the fourth look-up table 166 receives the color temperature data Dct and the digital video data RGB as input addresses and outputs the digital converted data RGB 'stored at the input addresses. The fourth look-up table 166 may be included in the luminance and contrast ratio adjuster 161. The color temperature adjustment unit 162 outputs the digital conversion data RGB 'to the timing control unit 130.

On the other hand, the reason why the color temperature is adjusted according to the color temperature of the external light is that the optimum color temperature that the user feels less visual fatigue depending on the type of external light changes. Referring to Fig. 6, the optimum color temperature range of the fluorescent lamp is higher than the optimal color temperature range of the LED bulb in the same background color. Therefore, the present invention controls the color temperature of the display panel 10 to be higher than when the color temperature of the external light is equal to or higher than the second threshold value. As described above, according to the present invention, when the color temperature of the external light is equal to or higher than the second threshold value, the contrast ratio of the display panel 10 is lower than that of the display panel 10 when the color temperature of the external light is lower than the second threshold value. By optimally adjusting the color temperature, the visual fatigue of the user can be minimized. (S205)

As described above, the second embodiment of the present invention can optimally adjust the luminance, contrast ratio, and color temperature of the display panel 10 according to the type of external light. As a result, the second embodiment of the present invention can minimize the visual fatigue of the user. Although the second embodiment of the present invention has been described mainly with respect to two types of external light, it should be noted that the present invention is not limited thereto. That is, the second embodiment of the present invention may be implemented to select any one of three or more external lights. In the second embodiment of the present invention, the external light is not limited to fluorescent lamps and LED bulbs, and may include solar light, incandescent lamps, and the like. It should be noted that the color temperature adjustment unit 162 may be omitted in the second embodiment of the present invention. In this case, the first embodiment of the present invention can optimally adjust only the luminance and contrast ratio of the display panel 10 according to the type of external light.

Further, although the first embodiment and the second embodiment of the present invention are separately described, the first embodiment and the second embodiment of the present invention can be combined. Accordingly, the present invention can optimally adjust the luminance, contrast ratio, and color temperature of the display panel 10 in consideration of both the background color and the type of external light selected by the user.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. Therefore, the present invention should not be limited to the details described in the detailed description, but should be defined by the claims.

10: display panel 40: backlight unit
110: gate driver 120: data driver
130: timing controller 140: light source driver
150: light source control unit 160:
161: Brightness and contrast ratio adjustment unit 162: Color temperature adjustment unit
163: first look-up table 164: second look-up table
165: third look-up table 166: fourth look-up table
170: illuminance analyzing unit 180: color temperature analyzing unit

Claims (13)

Display panel;
A backlight unit including light sources for emitting light to the display panel;
A display panel driver converting the digital video data into data voltages and supplying the data voltages to the display panel;
A light source driver for supplying a PWM signal to the light sources; And
A liquid crystal having an adjustment unit for controlling the duty ratio of the PWM signal in order to control the luminance of the display panel according to a background color selected by a user and separately controlling the duty ratio of the PWM signal in black gray to adjust the contrast ratio according to the background color Display. The method of claim 1,
Wherein,
When the user selects the first background color among the first background color and the second background color having the optimum luminance range and the optimal contrast ratio lower than the first background color, the second background color is selected to adjust the luminance of the display panel higher. A luminance adjusting unit controlling a duty ratio of the PWM signal to be larger than that of the case; And
In order to adjust the contrast ratio of the display panel higher when the user selects the first background color, the contrast ratio adjusting unit controls the duty ratio of the PWM signal in the black gray to be smaller than when selecting the second background color. A liquid crystal display device. 3. The method of claim 2,
The brightness adjusting unit may include:
Wherein the brightness of the display panel is adjusted to the maximum by controlling the duty ratio of the PWM signal to a maximum value within a set range when the external light illuminance is equal to or greater than a first threshold value. 3. The method of claim 2,
Wherein,
And a color temperature adjusting unit for adjusting the color temperature of the display panel by converting the digital video data according to the background color. The method of claim 1,
And a color temperature analyzer for analyzing the color temperature of the external light. The method of claim 5, wherein
Wherein the color temperature analyzer comprises:
Wherein the color temperature is calculated by analyzing a photographed image using an image sensor or analyzing wavelength information of the external light obtained using a photodiode. The method of claim 5, wherein
Wherein,
And adjusts the luminance and contrast ratio of the display panel by controlling the duty ratio of the PWM signal according to the color temperature. The method of claim 7, wherein
Wherein,
A brightness controller configured to control the duty ratio of the PWM signal to be larger than a case where the color temperature is greater than or equal to a second threshold value, in order to adjust the brightness of the display panel higher than the second threshold value; And
And a contrast ratio adjusting unit configured to control a duty ratio of the PWM signal at a black gray level smaller than a case where the color temperature is greater than or equal to the second threshold value in order to adjust the contrast ratio of the display panel higher than the second threshold value. A liquid crystal display device. The method of claim 8,
The brightness adjusting unit may include:
Wherein the brightness of the display panel is adjusted to the maximum by controlling the duty ratio of the PWM signal to a maximum value within a set range regardless of the color temperature when the illuminance of the external light is equal to or greater than a first threshold value . The method of claim 9,
Wherein,
And a color temperature adjusting unit for adjusting the color temperature of the display panel by converting the digital video data according to the color temperature. 11. The method of claim 10,
Wherein the color temperature adjustment unit comprises:
And adjusts the color temperature of the display panel to be higher than when the color temperature is lower than the second threshold value when the color temperature is higher than or equal to the second threshold value. The method of claim 1,
And a roughness analyzer for analyzing the roughness of the external light measured using the roughness sensor circuit. A method of driving a liquid crystal display including a display panel and a backlight unit including light sources for emitting light to the display panel,
Converting the digital video data into data voltages and supplying the data voltages to the display panel;
Supplying a PWM signal to the light sources;
Controlling the duty ratio of the PWM signal to control the brightness of the display panel according to a background color selected by a user; And
And controlling the duty ratio of the PWM signal in the black gray level to adjust the contrast ratio according to the background color.

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