KR20070071722A - Liquid crystal display and method for driving thereof - Google Patents

Abstract

A liquid crystal display and a driving method thereof are provided to prevent decrease of luminance when a temperature is lowered and also to improve the degradation of image quality by controlling a data voltage or a dimming control voltage. In a liquid crystal display, there is provided a liquid crystal panel(110) having data lines. A data driving unit(120) supplies data voltages to the data lines. An inverting unit(140) adjusts the luminance of a backlight in accordance with a dimming control voltage. A temperature detecting unit(180) detects the temperature of the liquid crystal display and generates temperature information. A control unit(160) controls one of the data voltage or the dimming control voltage by using the temperature information.

Description

Liquid crystal display and method for driving same

1 is a view for explaining a liquid crystal display according to an exemplary embodiment of the present invention.

2 is a view for explaining the operating characteristics of the control unit according to an embodiment of the present invention.

3 is a view for explaining a data voltage control method according to an embodiment of the present invention.

4 is a diagram for describing an operating characteristic of a controller according to another exemplary embodiment of the present invention.

FIG. 5 is a diagram for describing a relationship between a dimming control voltage and a brightness histogram of an image signal according to an exemplary embodiment.

6 is a view for explaining that the voltage range of the dimming control voltage is controlled according to an embodiment of the present invention.

FIG. 7 is a diagram for explaining that an adjusted weight of a dimming control voltage is controlled according to an embodiment of the present invention.

8 is a view for explaining a method of driving a liquid crystal display according to an exemplary embodiment of the present invention.

***** Explanation of symbols for main parts of drawing *****

110; A liquid crystal display panel 120; Data driver

130; The gate driver 140; Inverter

150; Backlight 160, 200, 400; Control

170; A power generator 180; Temperature detector

210, 410; A temperature information receiver 220; Data voltage change part

420; Dimming Control Voltage Range Control Unit

430; Dimming Control Voltage Adjustable Weight Control Unit

440; Dimming Control Voltage Regulator

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device and a driving method thereof, which are adaptively driven in response to a temperature change.

In recent years, due to the rapid progress of semiconductor technology, the demand for flat panel display devices as an electronic display device suitable for a new environment is rapidly increasing according to the trend of miniaturization, thinning, and lightening of electronic devices along with low voltage and low power of various electronic devices. It is increasing. Accordingly, flat panel display devices such as a liquid crystal display (LCD), a plasma display panel (PDP), an organic EL display (OLED), and the like are being developed. Among flat panel display devices, a liquid crystal display device having a small size, a light weight, and a thin film is easy, and has a low power consumption and a low driving voltage.

The liquid crystal display device includes a liquid crystal display panel displaying an image and a driver for applying a driving signal to the liquid crystal display panel. Here, the liquid crystal display panel is composed of a front substrate and a rear substrate and a liquid crystal layer formed between the front substrate and the rear substrate to be bonded at predetermined intervals.

The front substrate is a color filter substrate, and implements an image with a color filter layer of red, green, and blue to express color color, and a black matrix layer to block light in portions other than the pixel region. A common electrode for forming is formed. The back substrate is a thin film transistor array substrate, and includes a plurality of data lines arranged in a direction crossing the plurality of gate lines and the gate lines, and a plurality of pixel electrodes and data lines formed at each pixel defined by crossing the gate lines and the data lines. A plurality of thin film transistors for transmitting a signal of to each pixel electrode is formed. By applying different potentials to the pixel electrode and the common electrode included in the liquid crystal display panel, the molecular arrangement of the liquid crystal material of the liquid crystal layer is changed. The desired image may be realized by adjusting the amount of light transmitted through the transparent liquid crystal display panel according to the changed molecular arrangement.

Since the liquid crystal display panel does not emit light by itself, the liquid crystal display device requires a light source such as a lamp to visually recognize the display contents. That is, a back light assembly is provided as a light source on the rear surface of the liquid crystal display panel.

On the other hand, the conventional liquid crystal display device adjusts the amount of light transmitted through the liquid crystal display panel according to the changed molecular arrangement of the liquid crystal layer, so that the luminance of the image is reduced as the temperature of the liquid crystal display panel decreases. do. In addition, as the temperature of the data driver decreases, there is a problem in that the image quality of the implemented screen is deteriorated.

Accordingly, an object of the present invention is to provide a liquid crystal display device which can prevent a decrease in luminance when a temperature is changed.

Another object of the present invention is to provide a liquid crystal display device capable of preventing deterioration of image quality to be implemented.

Another object of the present invention is to provide a driving method of the liquid crystal display device described above.

 Technical problems to be achieved by the present invention are not limited to the above-mentioned technical problems, and other technical problems not mentioned above may be clearly understood by those skilled in the art from the following description. There will be.

According to an aspect of the present invention, a liquid crystal display device includes: a liquid crystal display panel including a data line; A data driver supplying a data voltage to the data line; An inverter unit adjusting brightness of the backlight according to the dimming control voltage; A temperature detector configured to detect a temperature of the liquid crystal display and generate temperature information; And a controller configured to control at least one of the data voltage and the dimming control voltage using the temperature information.

The temperature detector may generate temperature information by leveling the detected temperature in a predetermined step.

The control unit may increase the data voltage as the temperature is low, and decrease the data voltage as the temperature is high.

The controller may preset a range in which at least two data voltages are adjusted according to the temperature information, and select a range in which the data voltages are adjusted when the temperature information changes.

The control unit may adjust the dimming control voltage using a brightness histogram of an image signal.

The controller may increase the dimming control voltage as the image signal is bright, and decrease the dimming control voltage as the image signal is dark.

The controller may control a range of the dimming control voltage according to the temperature information.

The controller may increase the range of the dimming control voltage as the temperature is lower, and decrease the range of the dimming control voltage as the temperature is higher.

The controller may control a weight at which the dimming control voltage is adjusted according to the temperature information.

 The control unit may increase the weight as the temperature is low, and decrease the weight as the temperature is high.

According to an aspect of the present invention, there is provided a method of driving a liquid crystal display, the method comprising: detecting a temperature of the liquid crystal display and generating temperature information; Controlling at least one of a data voltage and a dimming control voltage according to the temperature information; Supplying the data voltage to a data line; And supplying the dimming control voltage to the inverter unit.

The temperature information is generated by leveling the detected temperature in a predetermined step.

The lower the temperature increases the data voltage, and the higher the temperature decreases the data voltage.

A range in which at least two or more data voltages are adjusted according to the temperature information is set in advance, and a range in which the data voltage is adjusted when the temperature information is changed is selected.

The dimming control voltage is adjusted by using a brightness histogram of an image signal.

The dimming control voltage is increased as the image signal is brighter, and the dimming control voltage is decreased as the image signal is darker.

The range of the dimming control voltage is controlled according to the temperature information.

Lower temperature increases the range of the dimming control voltage, and higher temperature decreases the range of the dimming control voltage.

The weight of the dimming control voltage is adjusted according to the temperature information.

 The lower the temperature, the weight is increased, the higher the temperature is characterized in that the weight is reduced.

Specific details of other embodiments are included in the detailed description and the drawings. Advantages and features of the present invention and methods for achieving them will be apparent with reference to the embodiments described below in detail with the accompanying drawings. Like reference numerals refer to like elements throughout.

Hereinafter, with reference to the accompanying drawings, a specific embodiment according to the present invention will be described.

As shown in FIG. 1, in the liquid crystal display according to the exemplary embodiment, a plurality of data lines 111 and a plurality of gate lines 112 cross each other, and a thin film transistor is formed at an intersection thereof. Gate pulses are applied to the panel 110, the data driver 120 for inputting data pulses to the data lines 111 of the liquid crystal display panel 110, and the gate lines 112 of the liquid crystal display panel 110. A gate driver 130 for inputting, a backlight unit 140 for irradiating light to the liquid crystal display panel 110, an inverter unit 140 for driving a lamp of the backlight unit 150, and a liquid crystal display panel A power supply for supplying power required for the control unit 160 for controlling the data driver 120, the gate driver 130, and the inverter unit 140 of the 110, the liquid crystal display panel 110, and the backlight unit 150. Detecting the temperature of the generator 170 and the liquid crystal display And a temperature detector 180.

In the liquid crystal display panel 110, liquid crystal is injected between the front substrate and the rear substrate. The thin film transistor TFT formed at the intersection of the data lines 111 and the gate lines 112 of the liquid crystal display panel 110 may be disposed on the data lines 111 in response to a gate pulse from the gate driver 130. Data is input to the liquid crystal cell. The source electrode of the thin film transistor is connected to the data line 111, and the drain electrode is connected to the pixel electrode of the liquid crystal cell. The gate electrode of the thin film transistor is connected to the gate line 112.

After the data driver 120 samples the data according to the data control signal DCS from the controller 160, the data driver 120 latches the sampled data by one line for each horizontal period, and then latches the latched data to the data lines 111. Supply. In addition, the digital pixel data R, G, and B from the controller 160 are converted into analog pixel signals by using the data voltages GMA1 to 6 input from the power generator 170 to the data lines 111. To feed. The data driver 120 according to an embodiment of the present invention supplies a data voltage controlled according to temperature to the data lines 111.

The gate driver 130 may include a shift register that sequentially generates gate pulses in response to the gate control signal GCS from the controller 160, and a level for shifting the voltage of the gate pulses to a voltage level suitable for driving the liquid crystal cell. It includes a shifter. The gate driver 130 sequentially supplies a gate high voltage to the gate lines 112 in response to the gate control signal GCS.

The inverter unit 140 converts an AC voltage for supplying a DC voltage to the backlight unit 150 under the control of the controller 160. The inverter unit 140 according to an embodiment of the present invention outputs a voltage for adjusting the brightness of the backlight unit 150 according to the dimming control voltage input from the controller 160. At this time, the dimming control voltage is controlled according to the temperature. Here, the dimming control voltage is a voltage related to the dimming frequency of the inverter unit 140, and the magnitude of the voltage has a relationship proportional to the brightness of the backlight unit.

The backlight unit 150 includes a lamp (not shown) for irradiating light onto the liquid crystal display panel 110. The backlight 150 receives the lamp driving voltage Vinv from the power generator 170 to drive the lamp.

The controller 160 rearranges the digital video data input from the digital video card (not shown) for each of red (R), green (G), and blue (B). The data rearranged by the controller 160 is stored for each of red, green, and blue data in a line memory formed in the controller 160. Red data is stored in the first line memory, green data is stored in the second line memory, and blue data is stored in the third line memory. Each of the red, green, and blue data stored in each of the line memories is input to the data driver 120.

In addition, the controller 160 generates a data control signal (DCS) using the horizontal and vertical synchronization signals H and V and the main clock signal MCLK, which are input to the data driver 120. The gate control signal (GCS) is generated and supplied to the gate driver 130. The data control signal DCS includes a dot clock signal Dclk, a source shift clock signal SSC, a source output enable signal SOE, and a polarity inversion signal POL. Is input to 120. The gate control signal GCS is input to the gate driver 130 including a gate shift clock signal GSC and a gate out enable signal.

The controller 160 controls at least one of a data voltage and a dimming control voltage according to the temperature information detected by the temperature detector 180. A more detailed description thereof will be described with reference to FIGS. 2 to 7.

The power generator 170 supplies the common electrode voltage Vcom to the liquid crystal display panel 110, the gamma voltages GMA1 to 6 to the data driver 220, and the lamp driving voltage Vinv to the lamp inverter.

The temperature detector 180 detects a temperature of the liquid crystal display device, for example, the liquid crystal display panel 110 or the driving units 120 and 130, and generates temperature information. The temperature detector 180 generates the temperature information by leveling the detected temperature in a predetermined step. Here, the leveling step can be arbitrarily changed as necessary.

2 is a view for explaining the operating characteristics of the control unit according to an embodiment of the present invention.

As shown in FIG. 2, the control unit 200 according to an embodiment of the present invention includes a temperature information receiving unit 210 and a data voltage changing unit 220.

The temperature information receiver 210 receives temperature information input from the temperature detector 180. The data voltage changing unit 220 controls the data voltage supplied to the data line of the liquid crystal display panel according to the temperature information input from the temperature information receiving unit 210. Preferably, the lower the temperature is to increase the data voltage, the higher the temperature is to decrease the data voltage. Thereby, when a temperature falls, it can suppress that brightness falls.

3 is a view for explaining a data voltage control method according to an embodiment of the present invention.

As shown in FIG. 3, the data voltage changer according to an embodiment of the present invention presets a range in which at least two data voltages are adjusted according to temperature information, and selects a range in which the data voltage is adjusted when temperature information changes. do. For example, in the table of FIG. 3, when the temperature is the lowest first temperature, the table is set to the first power mode that increases the data voltage the most. When the temperature is the next higher second temperature, the data voltage is set to a second power mode lower than the first power mode. Further, when the temperature is the next highest third temperature, the data voltage is set to the third power mode lower than the second power mode. When the temperature is the highest fourth temperature, the fourth power mode is set to be lower than the third power mode that lowers the data voltage. Thus, since it selects in the preset range, it is possible to adjust adaptively according to temperature.

4 is a diagram for describing an operating characteristic of a controller according to another exemplary embodiment of the present invention.

As shown in FIG. 4, the controller 400 according to another embodiment of the present invention includes a temperature information receiver 410, a dimming control voltage range controller 420, a dimming control voltage adjustment weight controller 430, and a dimming control voltage. It includes an adjusting unit 440.

The temperature information receiver 410 receives temperature information input from the temperature detector 180.

The dimming control voltage range controller 420 controls the range of the dimming control voltage according to the temperature information. A more detailed description thereof will be described with reference to FIG. 6.

The dimming control voltage adjustment weight controller 430 controls the weight at which the dimming control voltage is adjusted according to the temperature information. The dimming control voltage controlled by either the range of the dimming control voltage or the adjusted weight of the dimming control voltage is input to the dimming control voltage adjusting unit 440.

The dimming control voltage controller 440 adjusts the dimming control voltage by using the brightness histogram of the image signal. The adjusted dimming control voltage is supplied to the inverter unit.

FIG. 5 is a diagram for describing a relationship between a dimming control voltage and a brightness histogram of an image signal according to an exemplary embodiment.

As shown in FIG. 5, the dimming control voltage is adjusted according to the brightness histogram of the image signal. Preferably, the brighter the video signal, the higher the dimming control voltage, and the darker the video signal, the lower the dimming control voltage. As a result, as the bright screen becomes brighter and the dark screen becomes darker, contrast of a screen implemented may be improved.

6 is a view for explaining that the voltage range of the dimming control voltage is controlled according to an embodiment of the present invention.

As shown in Figure 6, (a) is a case of low temperature, (b) is a case of room temperature, (c) is a case of high temperature. In an embodiment of the present invention, a lower temperature increases the range of the dimming control voltage, and a higher temperature decreases the range of the dimming control voltage. As described above, the lower the temperature, the greater the range of the dimming control voltage, so that luminance compensation can be performed when the temperature decreases.

FIG. 7 is a diagram for explaining that an adjusted weight of a dimming control voltage is controlled according to an embodiment of the present invention.

As shown in Figure 7, (a) is a case of low temperature, (b) is a case of room temperature, (c) is a case of high temperature. In one embodiment of the present invention, the lower the temperature is to increase the adjusted weight of the dimming control voltage, the higher the temperature is to reduce the adjusted weight of the dimming control voltage. As such, the lower the temperature, the greater the adjusted weight of the dimming control voltage, thereby making it possible to compensate for luminance when the temperature decreases.

As such, in another embodiment of the present invention, unlike in the embodiment of the present invention of FIG. 3, the dimming control voltage is controlled. Here, although the configuration for controlling each of the data voltage and the dimming control voltage is shown, the controller according to an embodiment of the present invention can control the data voltage and the dimming control voltage, respectively, and simultaneously control the data voltage and the dimming control voltage. It is also possible to control. As a result, it is possible to improve the problem that the brightness is reduced when the temperature is lowered, and also to deteriorate the image quality.

8 is a view for explaining a method of driving a liquid crystal display according to an exemplary embodiment of the present invention.

As shown in FIG. 8, the driving method of the liquid crystal display according to the exemplary embodiment of the present invention first detects a temperature of the liquid crystal display (S801).

Thereafter, the data voltage is changed according to the temperature (S802). At this time, as the temperature is lowered, the data voltage is increased to suppress the decrease in luminance.

Thereafter, the data voltage is supplied to the data line (S803).

After the temperature detection, the voltage range of the dimming control voltage is controlled according to the detected temperature (S804). At the same time, it is also possible to control the adjusted weight of the dimming control voltage according to the detected temperature (S805).

Thereafter, the dimming control voltage is adjusted according to the brightness histogram of the image signal (S806).

Thereafter, the dimming control voltage is supplied to the inverter unit (S807).

A detailed description of the driving method of the liquid crystal display according to the exemplary embodiment of the present invention has been described in detail through the configuration and operating characteristics of the liquid crystal display according to the exemplary embodiment of FIGS. 1 to 7. do.

As such, the technical configuration of the present invention described above can be understood by those skilled in the art that the present invention can be implemented in other specific forms without changing the technical spirit or essential features of the present invention.

Therefore, the exemplary embodiments described above are to be understood as illustrative and not restrictive in all aspects, and the scope of the present invention is indicated by the following claims rather than the detailed description, and the meaning and scope of the claims and All changes or modifications derived from the equivalent concept should be interpreted as being included in the scope of the present invention.

As described above, the present invention improves the driving method of the liquid crystal display device and the liquid crystal display device, and thus, there is an effect of preventing a decrease in luminance upon temperature change.

In addition, the present invention has the effect of suppressing the deterioration of the image quality of the implemented image by improving the liquid crystal display and the driving method of the liquid crystal display.

Claims (20)

A liquid crystal display panel including data lines; A data driver supplying a data voltage to the data line; An inverter unit adjusting brightness of the backlight according to the dimming control voltage; A temperature detector configured to detect a temperature of the liquid crystal display and generate temperature information; And And a controller configured to control at least one of the data voltage and the dimming control voltage using the temperature information. The method of claim 1, And the temperature detector generates temperature information by leveling the detected temperature in a predetermined step. The method of claim 1, The control unit increases the data voltage as the temperature is lowered, and decreases the data voltage as the temperature is higher. The method according to claim 1 or 3, The controller may preset a range in which at least two data voltages are adjusted according to the temperature information, and select a range in which the data voltages are adjusted when the temperature information changes. The method of claim 1, And the controller is configured to adjust the dimming control voltage using a brightness histogram of an image signal. The method of claim 1, The control unit may increase the dimming control voltage as the image signal is brighter, and decrease the dimming control voltage as the image signal is dark. The method according to claim 1 or 5, And the control unit controls the range of the dimming control voltage according to the temperature information. The method of claim 7, wherein The control unit increases the range of the dimming control voltage as the temperature is lowered, and decreases the range of the dimming control voltage as the temperature is higher. The method according to claim 1 or 5, And the control unit controls a weight at which the dimming control voltage is adjusted according to the temperature information. The method of claim 9,  The control unit increases the weight as the temperature is lower, and decreases the weight as the temperature is higher. Detecting a temperature of the liquid crystal display and generating temperature information; Controlling at least one of a data voltage and a dimming control voltage according to the temperature information; Supplying the data voltage to a data line; And And supplying the dimming control voltage to an inverter unit. The method of claim 11, And generating temperature information by leveling the detected temperature in a predetermined step. The method of claim 11, The lower the temperature increases the data voltage, and the higher the temperature decreases the data voltage. The method according to claim 11 or 13, And setting a range in which at least two data voltages are adjusted according to the temperature information, and selecting a range in which the data voltages are adjusted when the temperature information changes. The method of claim 11, And adjusting the dimming control voltage using a brightness histogram of an image signal. The method of claim 11, The dimming control voltage is increased as the image signal is brighter, and the dimming control voltage is decreased as the image signal is darker. The method of claim 11 or 15, And controlling the range of the dimming control voltage according to the temperature information. The method of claim 17, The lower the temperature is, the range of the dimming control voltage is increased, and the higher is the temperature, the range of the dimming control voltage is decreased. The method of claim 11 or 15, And controlling a weight to which the dimming control voltage is adjusted according to the temperature information. The method of claim 19,  And the weight is increased as the temperature is lower, and the weight is decreased as the temperature is higher.

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