KR20110093290A - Liquid crystal display device and method for driving the same - Google Patents

Abstract

PURPOSE: A liquid crystal display device and a method for driving the same are provided to improve power consumption by changing a gamma voltage level. CONSTITUTION: In a liquid crystal display device and a method for driving the same, a liquid crystal panel(1) defines a pixel region by crossing data lines and gate line. Gate and data drivers(2,3) drive a gate and the data line. An illuminance sensing part(8) comprises at least one illuminance sensor The illuminance sensing part generates an illuminance signal. A backlight part(6) varies the brightness of the light. A timing control part(4) generates a gamma voltage control signal. The timing control part generates a pulse-width modulating signal. A gamma voltage generator(7) changes the level of the gamma voltage and supplies it to the data driver.

Description

Liquid crystal display and its driving method {LIQUID CRYSTAL DISPLAY DEVICE AND METHOD FOR DRIVING THE SAME}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display, and more particularly, to a liquid crystal display and a driving method thereof to improve power consumption by changing the gamma voltage level as well as adjusting the brightness of the backlight unit according to the brightness of the outside of the liquid crystal display.

Recently, due to excellent image quality, light weight, thinness, and low power, among display devices, liquid crystal displays are used as display devices for mobile devices (for example, portable computers, personal digital assistants (PDAs), cellular phones, etc.). Devices (Liquid Crystal Display) are the most used.

Meanwhile, currently being developed mobile devices are pursuing light weight and low power consumption. To that end, manufacturers are constantly working to reduce power consumption without compromising the performance of mobile devices. In particular, mobile devices powered by batteries, and display devices used therein, are constantly required to reduce power consumption due to their finite power source.

Accordingly, a method for improving power consumption by sensing the brightness of the outside of the liquid crystal display and corresponding thereto is known. Specifically, the liquid crystal display as described above is characterized by having an illuminance sensor and an illuminance sensing circuit. The liquid crystal display may improve the power consumption of the backlight unit by adjusting the brightness of the backlight unit of the liquid crystal display according to the external illuminance detected using the illumination sensor.

However, in recent years, liquid crystal displays have become larger and have higher resolutions, leading to higher power consumption of the liquid crystal panel. Therefore, efforts to reduce not only the power consumption of the backlight unit but also the power consumption of the liquid crystal panel are required.

The present invention is to solve the above problems, to provide a liquid crystal display and a driving method for improving power consumption by changing the gamma voltage level as well as adjusting the brightness of the backlight according to the brightness of the outside of the liquid crystal display. The purpose is.

According to an exemplary embodiment of the present invention, a liquid crystal display device includes: a liquid crystal panel defining a pixel area at an intersection of a gate line and a data line; Gate and data drivers driving the gate and data lines; An illuminance sensing unit having at least one illuminance sensor to generate an illuminance signal corresponding to an external brightness; A backlight unit configured to vary brightness of light irradiated onto the liquid crystal panel; A timing controller configured to generate a gamma voltage control signal to change the gamma voltage according to the illuminance signal and to generate a pulse width modulation signal to vary the brightness of the backlight unit; And a gamma voltage generation unit for converting a voltage level of the gamma voltage according to the gamma voltage control signal and supplying the data driver to the data driver.

In addition, the driving method of the liquid crystal display device according to an embodiment of the present invention for achieving the above object is to irradiate light to the liquid crystal panel having a pixel region and the liquid crystal panel, it is possible to vary the brightness of the irradiated light A liquid crystal display having a backlight unit, comprising: detecting at least one external brightness with at least one illumination sensor, and generating and outputting an illumination signal according to the detected brightness; Generating and outputting a gamma voltage control signal for changing the gamma voltage according to the analyzed result by analyzing external brightness included in the illuminance signal and a pulse width modulation signal for varying the brightness of the backlight unit Making; And converting the voltage level of the gamma voltage according to the gamma voltage control signal to supply the data driver to the data driver of the liquid crystal panel.

The liquid crystal display and the driving method thereof according to the present invention can improve the power consumption by changing the gamma voltage level as well as adjusting the brightness of the backlight unit according to the brightness of the outside of the liquid crystal display.

1 is a block diagram illustrating a liquid crystal display according to an exemplary embodiment of the present invention.
FIG. 2 is a configuration diagram illustrating a timing controller shown in FIG. 1. FIG.
3 is a graph showing voltage levels of the first and second gamma reference voltages.
4 is a graph showing voltage levels of first and second gamma reference voltages.

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

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

As shown in FIG. 1, the liquid crystal display device according to the present invention includes a liquid crystal panel 1, a gate driver 2, a data driver 3, an illuminance sensing unit 8, a timing controller 4, and a gamma voltage. The generation part 7 and the backlight part 6 are provided.

The liquid crystal panel 1 defines each pixel area by a plurality of gate lines GL1 through GLn and a plurality of data lines DL1 through DLm. Each pixel area includes a thin film transistor (hereinafter referred to as TFT), a liquid crystal capacitor Clc and a storage capacitor Cst connected to the TFT. The liquid crystal capacitor Clc is composed of a pixel electrode connected to a TFT and a common electrode facing each other with the pixel electrode and the liquid crystal interposed therebetween. The TFT supplies analog image data from the respective data lines DL1 to DLm to the pixel electrode in response to the scan pulses from the respective gate lines GL1 to GLn. The liquid crystal capacitor Clc charges the difference voltage between the analog image data supplied to the pixel electrode and the common voltage supplied to the common electrode, and adjusts the light transmittance by varying the arrangement of liquid crystal molecules according to the difference voltage. . The storage capacitor Cst is connected to the liquid crystal capacitor Clc in parallel so that the voltage charged in the liquid crystal capacitor Clc is maintained until the next analog image data is supplied.

The gate driver 2 sequentially supplies scan pulses to the gate lines GL1 to GLn in response to a gate control signal GDC from the timing controller 4 to be described later.

The data driver 3 converts the RGB data Data inputted from the timing controller 4 into analog image data according to the data control signal DDC from the timing controller 4 to be described later, and converts the gate lines GL1 to G1 through the gate lines GL1 through. The analog image data for one horizontal line is supplied to the data lines DL1 to DLm every one horizontal period in which the scan pulse is supplied to GLn). Specifically, the data driver 3 uses the source start pulse (SSP) and the source shift clock (SSC) among the supplied data control signals DDC to input RGB data (Data). ) Is converted into analog image data, and the analog image data corresponding to one horizontal line is supplied to each data line DL1 through each horizontal period in which the gate-on signal (or scan pulse) is supplied to the gate lines GL1 through GLn. DLm). In this case, the data driver 3 supplies analog image data to each of the data lines DL1 to DLm in response to a source output enable (SOE) signal.

More specifically, the data driver 3 latches the RGB data inputted according to the SSC in every horizontal line unit, and then latches the latched RGB data in a plurality of positive and negative polarities. The gamma voltage (GV) is used to convert analog image data. At this time, the data driver 3 has at least one polarity of the analog image data according to the polarity control signal from the timing controller 4 and the gamma voltages GV from the positive and negative polarity from the gamma voltage generator 7. It is converted to be inverted in units of horizontal lines. The converted positive or negative analog image data is supplied to each data line DL1 to DLm by one horizontal line for each horizontal period in which the gate-on signal is supplied to each gate line GL1 to GLn.

The illuminance sensing unit 8 has at least one illuminance sensor. The illuminance sensor detects external light and changes the detected light into a signal in the form of voltage or current. The illuminance sensing unit 8 may further include a low pass filter and an analog to digital converter (ADC).

The low pass filter performs low pass filtering (LPF) on a signal in the form of voltage or current detected by the illuminance sensor. The reason for using LPF is to not reflect the change in illuminance due to instantaneous sensor error.

The ADC generates and outputs an illuminance signal lx by converting the LPF voltage or current signal into a digital signal so that the timing controller 4 can recognize the signal.

FIG. 2 is a diagram illustrating the timing controller illustrated in FIG. 1.

As shown in FIG. 2, the timing controller 4 according to the present invention includes an image aligner 10, an illuminance analyzer 11, a PWM generator 12, a data controller 13, and a gate controller ( 14).

The image aligner 10 receives image data RGB in at least one frame unit. The image aligning unit 10 outputs RGB data by aligning the input image data RGB with the resolution of the display panel 1.

The illuminance analyzer 11 outputs a gamma voltage control signal GVC according to the illuminance signal lx of the illuminance sensing unit 8, thereby allowing the gamma voltage generation unit 7 to be described later to generate a voltage of the gamma reference voltage GV_ref. Try to change the level. In addition, the illuminance analyzer 11 outputs the duty signal DS according to the illuminance signal lx and supplies it to the PWM generator 12.

The process of outputting the gamma voltage control signal GVC in the illuminance analyzer 11 will now be described in detail.

The illuminance analyzer 11 compares the first reference illuminance preset by participating in a memory and an external brightness included in the illuminance signal lx. The illuminance analyzer 11 does not output the gamma voltage control signal GVC when the external brightness included in the illuminance signal lx is brighter than the first reference illuminance. When the illuminance analyzer 11 does not output the gamma voltage control signal GVC, the gamma voltage generator 7 outputs a gamma reference voltage GV_ref having a maximum or minimum voltage level. On the other hand, the illuminance analyzer 11 outputs a gamma voltage control signal GVC when the external brightness included in the illuminance signal lx is darker than the first reference illuminance. The gamma voltage control signal GVC is a signal which causes the voltage level of the gamma reference voltage GV_ref output by the gamma voltage generation unit 7 to be reduced or increased. The gamma reference voltage GV_ref will be described in detail later. The gamma voltage control signal GVC is output differently according to the brightness of the external brightness included in the illuminance signal lx. In detail, the illuminance analyzer 11 adjusts the gamma voltage control signal GVC to change the voltage level of the gamma reference voltage GV_ref more as the external brightness included in the illuminance signal lx is darker than the first reference illuminance. Output The second reference illuminance is preset and stored in the memory. The second reference illuminance is set lower than the first reference illuminance and serves as a reference for limiting the change of the voltage level of the gamma reference voltage GV_ref. That is, by setting the second reference illuminance, the voltage level of the gamma reference voltage GV_ref does not change more than a specific level.

The operation of the illuminance analysis unit 11 will be described with reference to Table 1 as an example.

It is assumed that the first reference illuminance stored in the memory is set to 10000 lux. The second reference illuminance stored in the memory is assumed to be set to 300 lux.

The illuminance analyzer 11 does not output the gamma voltage control signal GVC when the detected illuminance (illuminance signal lx) is equal to or greater than the first reference illuminance when the illuminance signal lx is 15000 to 10000 lux. The illuminance analyzer 11 determines that a compensation voltage is required when the detected illuminance is darker than the first reference illuminance when the detected illuminance is 8000 lux, and gamma compensates the voltage level of the gamma reference voltage GV_ref 100 mV corresponding to 8000 lux. Output the voltage control signal GVC. The illuminance analyzer 11 compensates for the voltage level of the gamma reference voltage GV_ref more when the detected illuminance is darker than 8000 lux. For example, the illuminance analyzer 11 compensates the voltage level of the gamma reference voltage GV_ref by 400 mV, more than 100 mV corresponding to the detected illuminance of 8000 lux when the detection illuminance is 1000 lux. On the other hand, the illuminance analyzer 11 refers to the second reference illuminance set in the memory, and when the detected illuminance is darker than the second reference illuminance, the voltage of the gamma reference voltage GV_ref corresponds to the compensation voltage value corresponding to the second reference illuminance. Let's compensate the level. That is, the illuminance analyzer 11 outputs a gamma voltage control signal GVC to compensate for 500 mV corresponding to 300 lux even when the detected illuminance falls below 300 lux of the second reference illuminance. For example, when the detection illuminance is 100 lux, the second reference illuminance is darker than 300 lux, but the voltage level of the gamma reference voltage GV_ref is compensated by 500 mV corresponding to 300 lux.

The expression 'compensation' is an expression of decompressing or boosting the gamma reference voltage GV_ref having the maximum or minimum voltage level generated by the gamma voltage generator 7 to be described later, and the detailed description thereof will be described later. do.

Meanwhile, the process of outputting the duty signal DS according to the illuminance signal lx from the illuminance analyzer 11 and supplying the duty signal DS to the PWM generator 12 will be described in detail as follows.

The illuminance analyzer 11 outputs a duty signal DS having a predetermined duty set value according to the illuminance signal lx and supplies it to the PWM generator 12. The duty setting value is a value for setting the duty ratio of the pulse width modulation signal PWM output from the PWM generator 12 to be described later.

The third and fourth reference illuminance are additionally preset and stored in the memory. The third reference illuminance serves as a reference for outputting the maximum value of the duty setting value to be described later. The fourth reference illuminance is set lower than the third reference illuminance and serves as a criterion for limiting the size of the duty setting value. That is, by setting the fourth reference illuminance, the magnitude of the duty setting value does not fall below a specific value.

In detail, the illuminance analyzer 11 compares the external brightness included in the illuminance signal lx with the third and fourth reference illuminance preset in the memory. The illuminance analyzer 11 outputs a duty signal DS having a maximum duty setting value when the external brightness included in the illuminance signal lx is equal to or brighter than the third reference illuminance. The illuminance analyzer 11 outputs a duty signal DS having a duty set value lower than the maximum duty set value when the external brightness included in the illuminance signal lx becomes darker than the third reference illuminance. The illuminance analyzer 11 outputs a duty signal DS having a lower duty setting value as the external brightness included in the illuminance signal lx is darker than the third reference illuminance. For example, the illuminance analyzer 11 outputs a duty signal DS having a lower duty setting value when the external brightness included in the illuminance signal lx is 300 lux than when the luminance is 5000 lux.

The illuminance analyzer 11 may output a duty signal DS having a duty setting value corresponding to the fourth reference illuminance when the external brightness included in the illuminance signal lx becomes darker than a fourth reference illuminance preset in the memory. Output For example, assuming that the fourth reference illuminance is 200 lux, the illuminance analysis unit 11 has a duty signal having a duty setting value corresponding to 200 lux when the external brightness included in the illuminance signal lx is 100 lux. Output (DS) That is, even if the external brightness becomes darker than the fourth reference illuminance, the duty set value of the duty signal DS does not fall below the duty set value corresponding to the fourth reference illuminance.

Meanwhile, the memory may be built in the timing controller 4 and may be an external memory in some cases.

The PWM generator 12 generates a pulse width modulation signal PWM for controlling the brightness of the backlight unit 6 according to the duty signal DS of the illuminance analyzer 11. Here, the pulse width modulation signal adjusts the brightness of the backlight unit 6 by varying its duty ratio.

The data control unit 13 supplies the data control signal DDC to the data driver 3 according to the synchronization signals HSync, VSync, DCLK, and DE input from the outside.

The gate controller 14 supplies a gate control signal GDC to the gate driver 2 using synchronization signals HSync, VSync, DCLK, and DE input from the outside.

The gamma voltage generator 7 receives positive and negative driving voltages, that is, first and second driving voltages VDD and VSS, from a power supply (not shown). Here, the first driving voltage VDD may be a high potential DC driving voltage, and the second driving voltage VSS may be a ground voltage or a low potential DC driving voltage.

The gamma voltage generator 7 changes the voltage levels of the first and second driving voltages VDD and VSS according to the gamma voltage control signal GVC to have first and second gamma references having the highest or lowest voltage level. The voltages GV_ref1 and GV_ref2 are generated.

The gamma reference voltage GV_ref is the sum of the first and second gamma reference voltages GV_ref1 and GV_ref2. The gamma voltage generator 7 divides the first and second gamma reference voltages GV_ref1 and GV_ref2 by using a plurality of resistors connected in series and in parallel to generate a plurality of positive and negative gamma voltages GV. do. The gamma voltage generator 7 switches a plurality of generated positive and negative gamma voltages GV and supplies them to the data driver 3.

Meanwhile, as described above, the gamma voltage generator 7 compensates the voltage level of the gamma reference voltage GV_ref according to the gamma voltage control signal GVC. The gamma voltage generator 7 generates first and second gamma reference voltages GV_ref1 and GV_ref2 having a maximum or minimum voltage level when the gamma voltage control signal GVC is not supplied. When the gamma voltage control signal GVC is supplied, the gamma voltage generator 7 may supply voltage levels of the first and second gamma reference voltages GV_ref1 and GV_ref2 according to the compensation voltage values included in the gamma voltage control signal GVC. And depressurize and respectively. As the voltage levels of the first and second gamma reference voltages GV_ref1 and GV_ref2 are changed, the voltage levels of the positive and negative gamma voltages GV generated by dividing them are also changed.

3 and 4 are graphs showing voltage levels of the first and second gamma reference voltages.

As described above, the compensation voltage value included in the gamma voltage control signal GVC depends on the external brightness. Accordingly, as shown in FIG. 3, the gamma voltage control signal GVC having a larger compensation voltage value when the external brightness is 1000 lux is supplied to the gamma voltage generator 7. That is, at 1000 lux than at 5000 lux, the voltage levels of the first and second gamma reference voltages GV_ref1 and GV_ref2 are further decompressed and boosted, respectively.

The horizontal axis of the graph shown in FIG. 4 represents an external brightness, that is, illuminance (lux), and the vertical axis represents a voltage level.

Referring to FIG. 4, if the external brightness is brighter than the first reference illuminance, the gamma voltage control signal GVC is not supplied to the gamma voltage generator 7, whereby the first and second gamma reference voltages GV_ref1. , GV_ref2) is maintained at the maximum or minimum voltage level.

Further, as the external brightness becomes darker than the first reference illuminance, the voltage levels of the first and second gamma reference voltages GV_ref1 and GV_ref2 are also decompressed and boosted, respectively.

On the other hand, when the external brightness is less than or equal to the second reference illuminance, the voltage levels of the first and second gamma reference voltages GV_ref1 and GV_ref2 generated by the gamma voltage generator 7 are the first and the second when the second reference illuminance is used. 2 The voltage level of the gamma reference voltages GV_ref1 and GV_ref2 is no longer reduced or increased.

The backlight unit 6 includes a plurality of backlight units to irradiate the liquid crystal panel 1 with light emitted from the backlight unit. The backlight unit 6 adjusts the brightness according to the pulse width modulation signal PWM of the timing controller 4. Here, the pulse width modulation signal PWM adjusts the brightness of the backlight unit by controlling the power supplied to the backlight unit according to the duty ratio.

As described above, the liquid crystal display and the driving method thereof according to the present invention can improve the power consumption by changing the voltage level of the gamma voltage as well as adjusting the brightness of the backlight unit according to the brightness of the outside of the liquid crystal display.

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.

1: display panel 2: gate driver
3: data driver 4: timing controller
6: Backlight part 7: Gamma voltage generation part
8: illuminance sensing unit 12: illuminance analysis unit

Claims (8)

A liquid crystal panel defining a pixel area at the intersection of the gate line and the data line;
Gate and data drivers driving the gate and data lines;
An illuminance sensing unit having at least one illuminance sensor to generate an illuminance signal corresponding to an external brightness;
A backlight unit configured to vary brightness of light irradiated onto the liquid crystal panel;
A timing controller configured to generate a gamma voltage control signal to change the gamma voltage according to the illuminance signal and to generate a pulse width modulation signal to vary the brightness of the backlight unit; And
And a gamma voltage generator for converting a voltage level of the gamma voltage according to the gamma voltage control signal and supplying the gamma voltage to the data driver. The method of claim 1,
The timing controller
The detection illuminance included in the illuminance signal is compared with a first reference illuminance preset by the user, and when the detection illuminance is darker than the first reference illuminance, the gamma voltage control signal is output and a duty corresponding to the detection illuminance is obtained. An illuminance analyzer for outputting a duty signal having a set value;
And a PWM generator for converting and outputting a duty ratio of the pulse width modulated signal according to the duty signal. The method of claim 2,
The roughness analysis unit
And outputting a gamma voltage control signal for reducing the voltage level of the gamma voltage as the detection illuminance becomes darker than the first reference illuminance when the gamma voltage control signal is output. The method of claim 3, wherein
The gamma voltage generation unit
Generate a gamma reference voltage having the highest voltage level,
And a plurality of gamma voltages having different voltage levels using the plurality of resistors connected in series and in parallel with the gamma reference voltage. The method of claim 4, wherein
The gamma voltage generation unit
And depressurizing the voltage level of the gamma reference voltage according to the gamma voltage control signal. In the liquid crystal display device having a liquid crystal panel having a pixel region and a backlight unit for irradiating light to the liquid crystal panel and varying the brightness of the irradiated light,
Sensing the external brightness with at least one illumination sensor and generating and outputting an illumination signal according to the detected brightness;
Generating and outputting a gamma voltage control signal for changing the gamma voltage according to the analyzed result by analyzing external brightness included in the illuminance signal and a pulse width modulation signal for varying the brightness of the backlight unit Doing; And
And converting the voltage level of the gamma voltage according to the gamma voltage control signal to supply the data driver to the data driver of the liquid crystal panel. The method of claim 6
Generating and outputting the gamma voltage control signal
The detection illuminance is set according to the external brightness included in the illuminance signal, and the gamma voltage control is performed when the detection illuminance is darker than the first reference illuminance by comparing a first reference illuminance preset by a user with the detection illuminance. Outputting a signal,
Generating and outputting the pulse width modulated signal
Outputting a duty signal having a duty setting value corresponding to the detection illuminance; And
And converting a duty ratio of a pulse width modulated signal according to the duty signal and supplying the duty ratio to the backlight unit. The method of claim 7,
Generating and outputting the gamma voltage control signal
And outputting a gamma voltage control signal for reducing the voltage level of the gamma voltage as the detection illuminance becomes darker than the first reference illuminance.

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