KR100977216B1 - The driving circuit of liquid crystal display device - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving circuit of a liquid crystal display device capable of improving image quality by modulating the brightness of display data and backlight according to the brightness of ambient light. A liquid crystal display comprising a driver and a backlight for providing light to the liquid crystal panel, the liquid crystal display comprising: a sensor unit for sensing a luminance of ambient light and outputting a sensing signal; A backlight control signal for reading the sensing signal and modulating the display data input from the driving system of the liquid crystal panel based on the luminance of the ambient light, and as a result, outputting the corrected display data and controlling the luminance of the backlight; Image quality improvement unit for outputting; And a timing controller configured to receive the corrected display data output from the image quality improving unit and format and output the corrected display data to the data driver at an appropriate timing.

LCD, driving circuit, backlight, luminance

Description

The driving circuit of liquid crystal display device

1 is a block diagram of a driving circuit of a general liquid crystal display device

2 is a block diagram of a driving circuit of a liquid crystal display according to an exemplary embodiment of the present invention.

3 is a waveform diagram of a gamma curve in normal mode, bright mode and dark mode.

* Explanation of symbols on the main parts of the drawings

11: liquid crystal panel 11a: gate driver

11b: data driver 13: timing controller

17 drive system 18 backlight

19: inverter 20: luminance control unit

30: image quality improvement unit 30a: control unit

30b: image correction unit 40: sensor unit

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device. In particular, a driving circuit of a liquid crystal display device capable of improving image quality by sensing brightness of ambient light and controlling brightness of backlight and display data according to the sensed brightness of ambient light. It is about.

As the information society develops, the demand for display devices is increasing in various forms, and in recent years, the LCD (Lipuid Crystal Display Device), PDP (Plasma Display Panel), ELD (Electro Luminescent Display), and VFD (Vacuum Fluorescent) Various flat panel display devices such as displays have been studied, and some of them are already used as display devices in various devices.

Among them, LCD is the most widely used as the substitute for CRT (Cathode Ray Tube) for mobile image display because of its excellent image quality, light weight, thinness, and low power consumption. In addition to the use of the present invention, a variety of applications such as a television, a computer monitor, and the like for receiving and displaying broadcast signals have been developed.

Such a liquid crystal display may be classified into a liquid crystal panel displaying a video signal and a driving circuit applying a driving signal to the liquid crystal panel from the outside.

Although not shown in the drawing, the liquid crystal panel is a display device in which liquid crystal is injected between two transparent substrates (glass substrates) bonded to each other with a predetermined space, and a plurality of liquid crystal panels arranged at regular intervals on one of the two transparent substrates. A gate line, a plurality of data lines arranged at regular intervals in a direction perpendicular to the gate line, a plurality of pixel electrodes formed in each pixel region having a matrix defined by the gate lines and the data lines, A plurality of thin film transistors for applying the signal of the data line to each pixel electrode in accordance with the signal of the gate line is formed at a portion where the gate line and the data line cross each other. A color filter layer, a common electrode, and a black matrix layer are formed on the remaining substrates.

Therefore, when the turn-on signal is sequentially applied to the gate line, an image is displayed because the data signal is applied to the pixel electrode of the corresponding line.

In addition, a backlight is provided on the back surface of the two substrates thus bonded to provide a uniform light source. CCFL (Cold Cathode Fluorescent Lamp), which is used as a light source of the backlight, has an inverse relationship in brightness and lifetime in terms of its characteristics. That is, when driving at a high current to increase the brightness, the life is reduced, while to increase the life, it is difficult to achieve high luminance because it must be driven at a low current. In practice, however, in most cases, high brightness and long life are required simultaneously.

To meet these demands, while driving a screen with a certain brightness in a screen state of a general liquid crystal display device, when driving a screen where a high brightness is required, a high current is temporarily applied to a backlight lamp to temporarily It is applying technology to widen the active area.

In addition, in the case of the liquid crystal display device, the amount of current used varies depending on the image displayed on the screen. For example, in the normally white mode, in which liquid crystal molecules are rearranged in the direction of an electric field with the application of a voltage to block incident light, the panel consumes more power as the number of bright pixels on the screen increases. On the other hand, as the number of dark pixels increases, the power consumed by the panel tends to increase.

By using this tendency, a method of controlling a current value of a lamp interlocked with the panel according to power consumed is mainly used.

The application of this technique requires the implementation of additional circuitry such as detecting the current consumed by the panel and modifying it to fit the variable range of the luminance control signal of the inverter driving the backlight.

A general liquid crystal display having a driving circuit will be described with reference to the accompanying drawings.

1 is a block diagram of a driving circuit of a general liquid crystal display device.

That is, as described above, the driving circuit of the liquid crystal display device includes a liquid crystal panel 1 having a plurality of gate lines G and data lines D arranged in a direction perpendicular to each other and having a pixel region in a matrix form; The driving circuit unit 2 supplies a driving signal and a data signal to the liquid crystal panel 1, and a backlight 8 providing a constant light source to the liquid crystal panel 1.

In this case, the driving circuit unit 2 may include a data driver 1b for inputting a data signal to each data line D of the liquid crystal panel 1 and a gate at each gate line G of the liquid crystal panel 1. The gate driver 1a applying the driving pulse, the display data R, G, and B input from the driving system 7 of the liquid crystal panel, the vertical and horizontal synchronization signals Vsync, Hsync, the clock signal DCLK, and the like. Each of the display data R, G, and B and the clock signal at a timing suitable for the data driver 1b and the gate driver 1a of the liquid crystal panel 1 to reproduce the screen by receiving the control signal DTEN. A timing controller 3 for formatting and outputting a DCLK) and a control signal DTEN, a power supply unit 4 for supplying a voltage required to the liquid crystal panel 1 and each unit, and power supply from the power supply unit 4; Digital data input by the data driver 1b after being authorized A gamma reference voltage section 5 for supplying a reference voltage necessary for converting the data into analog data, and a constant voltage VDD and a gate used in the liquid crystal panel 1 using the voltage output from the power supply section 4. DC / DC converter 6 for outputting high voltage VGH, gate low voltage VGL, reference voltage Vref and common voltage Vcom, and inverter 9 for driving the backlight 8 It is provided.

The operation of the driving circuit of the conventional liquid crystal display device configured as described above is as follows.

That is, the timing controller 3 controls the display data R, G, and B inputted from the driving system 7 of the liquid crystal panel, the control signals DTEN such as the vertical and horizontal synchronization signals Vsync and Hsync, and the clock signal DCLK. ) And the display data (R, G, B) and the clock signal (DCLK) and control at the timing suitable for each data driver (1b) and the gate driver (1a) of the liquid crystal panel 1 to reproduce the screen Since the signal DTEN is provided, the gate driver 1a applies a gate driving pulse to each gate line G of the liquid crystal panel 1, and in synchronization therewith, the data driver 1b causes the liquid crystal panel 1 to operate. A data signal is input to each data line (D) to display the input video signal.

At this time, the backlight 8 provides a backlight having a constant brightness regardless of the brightness of the input video signal.

However, the driving circuit of the conventional liquid crystal display device has the following problems.

That is, in the driving circuit of the conventional liquid crystal display device, since the backlight always emits light at a constant brightness regardless of the brightness of the ambient light, when the ambient light is displayed in a bright place, the image of the liquid crystal display device is not clear. When the ambient light is displayed in a dark place, there is a problem that the image of the liquid crystal display is irritating to the viewer's eyes.

The present invention is to solve the above problems, and provides a driving circuit of the liquid crystal display device that can sense the brightness of the ambient light to improve the image quality by changing the brightness of the backlight and the brightness of the display data according to the brightness of the ambient light Its purpose is to.

The driving circuit of the liquid crystal display device according to the present invention for achieving the above object is a gate driver and data driver for driving the gate line and data line of the liquid crystal panel, and a backlight for providing light to the liquid crystal panel A liquid crystal display comprising: a sensor unit for sensing a luminance of ambient light and outputting a sensing signal; A backlight control signal for reading the sensing signal and modulating the display data input from the driving system of the liquid crystal panel based on the luminance of the ambient light, and as a result, outputting the corrected display data and controlling the luminance of the backlight; An image quality improvement unit for outputting a; And a timing controller that receives the corrected display data output from the image quality improving unit and formats and outputs the corrected display data to the data driver at an appropriate timing.

The image quality improving unit may include: a luminance determining unit configured to read the sensing signal output from the sensor unit and output a luminance signal by dividing the sensing signal into a normal mode, a bright mode, and a dark mode according to the luminance of the ambient light; Receives the luminance signal output from the luminance determination unit and the display data output from the driving system, separates the display data into a luminance component and a chrominance component, modulates the luminance component based on the luminance signal, and corrects the result. A gamma correction unit configured to output the displayed display data; A backlight controller which receives a luminance signal output from the luminance determiner and outputs a backlight control signal; Receiving a first control signal, a first clock signal, a first vertical and horizontal synchronization signal from the driving system, and a second control signal, a second clock signal synchronized with a time point at which the display data corrected by the gamma correction unit is output; And a control unit for outputting second vertical and horizontal synchronization signals.

And an inverter for driving the backlight to receive the backlight control signal output from the image quality improving unit so that the brightness of the backlight is varied.

The image quality improving unit may be built in the timing controller.

When the sensing signal input to the image quality improving unit is determined as the bright mode, the image quality improving unit transmits a backlight control signal to the backlight to drive the luminance of the backlight by 50 nits higher than the normal mode. .

When the sensing signal input to the image quality improving unit is determined to be a dark mode, the image quality improving unit transmits a backlight control signal to the backlight, and drives the luminance of the backlight by 50 nits lower than the normal mode.

When the sensing signal input to the image quality improvement unit is determined to be a bright mode, the image quality improvement unit modulates the gamma curve of the display data input from the driving system to have a higher luminance than the gamma curve of the normal mode. .

When the sensing signal input to the image quality improvement unit is determined to be a dark mode, the image quality improvement unit modulates the gamma curve of the display data input from the driving system to have a lower luminance than the gamma curve of the normal mode. .

The driving circuit of the liquid crystal display according to the present invention having the above characteristics will be described in more detail with reference to the accompanying drawings.

2 is a block diagram of a driving circuit of a liquid crystal display according to an exemplary embodiment of the present invention.

In the liquid crystal display according to the present invention, as shown in FIG. 2, a plurality of gate lines G and data lines D are arranged in a direction perpendicular to each other, and have a liquid crystal panel 11 having matrix pixel areas. and; A backlight 18 for providing light to the liquid crystal panel 11; A gate driver 11a and a data driver 11b for applying a gate signal and a data signal to the gate line G and the data line D of the liquid crystal panel 11; A sensor unit 40 for sensing a luminance of ambient light and outputting a sensing signal including information on the brightness of the ambient light; Receives a sensing signal output from the sensor unit 40 and modulates the display data (R, G, B) input from the driving system 17 of the liquid crystal panel 11 based on the luminance of the ambient light. A quality improvement unit 30 for outputting the corrected display data R ′, G ′, and B ′ and outputting a backlight control signal for controlling the luminance of the backlight 18; And a timing controller 13 which receives the corrected display data R`, G`, B` outputted from the image quality improvement unit 30, and formats and outputs the corrected display data to the data driver 11b at an appropriate timing. .

The driving circuit of the liquid crystal display device configured as described above further includes an inverter 19 for outputting a driving signal for driving the backlight 18 so that the brightness of the backlight 18 is variable.

Here, the image quality improvement unit 30 receives the sensing signal output from the sensor unit 40, reads the sensing signal, and divides the ambient light information into a normal mode, a bright mode, and a dark mode according to the brightness of the light. A luminance determining unit 30a for outputting a luminance signal; The luminance signal output from the luminance determiner 30a and the display data R, G, and B output from the driving system 17 are input, and the display data R, G, and B are converted into luminance components Y. ) And a gamma correction unit for outputting display data (R`, G`, B`), which are separated into the color difference component (U, V) and modulated the luminance of the luminance component (Y) according to the mode of the luminance signal. 30b; A backlight controller (30c) which receives a luminance signal output from the luminance determiner (30a) and outputs a backlight control signal for controlling the luminance of the backlight (18) according to the mode of the luminance signal; The display corrected by the gamma correction unit 30b by receiving the first control signal DE1, the first clock signal DCLK1, and the first vertical and horizontal synchronization signals VSTNC1 and HSYNC1 from the driving system 17. Control unit for outputting the second control signal DE2, the second clock signal DCLK2, and the second vertical and horizontal synchronization signals VSTNC2 and HSYNC2 synchronized at the time when the data R`, G`, and B` are output. It consists of 30d.

In this case, in order to simplify the driving circuit of the liquid crystal display, the image quality improving unit 30 may be built in the timing controller 13.

The operation of the driving circuit of the liquid crystal display according to the exemplary embodiment of the present invention configured as described above will be described in detail as follows.

First, the sensor unit 40 measures the luminance of the ambient light, digitizes information about the luminance of the ambient light, and outputs a sensing signal. Subsequently, the sensing signal output from the sensor unit 40 is outputted by the image quality improvement unit 30. It is input to the brightness determining part 30a.

Then, the luminance determiner 30a reads the input sensing signal and determines three kinds of luminance of ambient light.

That is, the luminance determiner 30a determines the luminance of the ambient light as one of a normal mode, a bright mode, and a dark mode based on the sensing signal, and outputs a luminance signal, and then outputs the luminance signal from the luminance determiner 30a. The luminance signal is input to the gamma correction unit 30b and the backlight control unit 30c, respectively.

First, the luminance signal input to the gamma correction unit 30b is used to correct the display (R, G, B) data.                     

That is, the gamma correction unit 30b separates the display data R, G, and B inputted from the driving system 17 into the luminance component Y and the color difference component U and V, and the mode of the luminance signal. The luminance component Y is modulated accordingly.

Specifically, the gamma correction unit 30b does not modulate the luminance component Y when the luminance signal is in the normal mode, and sets the luminance component Y more than the normal mode when the luminance signal is in the bright mode. When the luminance signal is in the dark mode, the luminance component Y is modulated to a darker color than the normal mode.

Here, the luminance component (Y) and the color difference components (U, V) are obtained by the following equation.

Y = 0.299 * R + 0.587 * G + 0.144 * B

U = 0.493 * (B-Y)

V = 0.877 * (R-Y)

In order to modulate the luminance component Y, it is possible to modulate a gamma curve with respect to the luminance component Y.

3 is a waveform diagram of gamma curves in the normal mode, the bright mode, and the dark mode.

That is, as shown in FIG. 3, in general, the gamma curve of the normal mode gamma curve is 2.2, and the luminance component Y may be modulated by adjusting the gamma value.

Specifically, when the brightness signal is in the bright mode, the gamma curve 50b in the normal mode is moved to the left to modulate the gamma curve 50a having a higher brightness for the same gray level, and the brightness signal is dark. In the case of the mode, the gamma curve 50b of the normal mode may be moved to the right to be modulated by the gamma curve 50a having lower luminance with respect to the same gray level.

In this way, the gamma correction unit 30b modulates the luminance component Y of the display data R, G, and B, and outputs the corrected display data R ′, G ′, and B ′. The displayed display data R`, G`, and B` are inputted to the timing controller 13 to be formatted at a timing suitable for the gate driver 11a and the data driver 11b to reproduce the screen, and thus the data driver 11b. Will be displayed.

Meanwhile, the backlight controller 30c changes the luminance of the backlight 18 by using the input luminance signal.

That is, when the brightness signal mode is the bright mode, the control value is increased, and in the dark mode, the control value is decreased to output the backlight control signal.

Then, the backlight control signal is output to the inverter 19, the inverter 19 outputs a drive signal for changing the brightness of the backlight 18 in accordance with the backlight control signal.

That is, when the brightness signal is in the bright mode, a higher driving signal is output than in the normal mode, so that the brightness of the backlight 18 is higher, and when the brightness signal is in the dark mode, the driving signal is lower than in the normal mode. The luminance of the backlight 18 is further lowered by outputting.

In the bright mode, the brightness of the backlight 18 is about 50 nit higher than in the normal mode, and the brightness of the backlight 18 is about 50 nit lower in the dark mode than in the normal mode.

The controller 30d receives the first control signal DE1, the first clock signal DCLK1, and the first vertical and horizontal synchronization signals VSTNC1 and HSYNC1 from the driving system 17 of the liquid crystal panel 11. The second control signal DE2 and the second clock signal synchronized with the input time when the display data R`, G`, B` corrected by the gamma correction unit 30b of the image quality improvement unit 30 is output. (DCLK2) and the second vertical and horizontal synchronization signals VSTNC2 and HSYNC2 are outputted so that the liquid crystal display device is driven.

As described above, when the ambient light is bright, the gamma correction unit 30b of the image quality improvement unit 30 corrects the display data R, G, and B to have a high luminance component Y, and the image quality is improved. In the backlight controller 30c of the improvement unit 30, the backlight 18 emits light having a high luminance, so that an image displayed on the liquid crystal panel 11 is displayed more clearly and brightly.

In contrast, when the ambient light is dark, the display data R, G, and B have a low luminance component Y in the gamma correction unit 30b of the image quality improvement unit 30. The backlight controller 30c of the image quality improving unit 30 causes the backlight 18 to emit light of low luminance, so that the image displayed on the liquid crystal panel 11 is darker.

The present invention described above is not limited to the above-described embodiment and the accompanying drawings, and it is common in the art that various substitutions, modifications, and changes can be made without departing from the technical spirit of the present invention. It will be evident to those who have knowledge of.

The driving circuit of the liquid crystal display device according to the present invention described above has the following effects.

The driving circuit of the liquid crystal display according to the present invention senses ambient light to brightly modulate the luminance component of the display data when the ambient light is bright and increases the brightness of the backlight, and when the ambient light is dark, the luminance component of the display data. By darkly modulating and lowering the brightness of the backlight, it shows less irritating images while maintaining sharpness regardless of ambient light.

Claims (8)

A liquid crystal display device comprising: a gate driver and a data driver for driving gate lines and data lines of a liquid crystal panel; and a backlight for providing light to the liquid crystal panel. A sensor unit for sensing a luminance of ambient light and outputting a sensing signal; A backlight control signal for reading the sensing signal and modulating the display data input from the driving system of the liquid crystal panel based on the luminance of the ambient light, and as a result, outputting the corrected display data and controlling the luminance of the backlight; Image quality improvement unit for outputting; A timing controller which receives the corrected display data output from the image quality improving unit and supplies the corrected display data to the data driver; The image quality improvement unit, 1) a luminance determiner for reading a sensing signal output from the sensor unit and outputting a luminance signal by dividing the sensing signal into a normal mode, a bright mode and a dark mode according to the luminance of the ambient light; 2) receiving the luminance signal outputted from the luminance determining unit and the display data outputted from the driving system, separating the display data into a luminance component and a chrominance component, and modulating the luminance component based on the luminance signal; A gamma correction unit for outputting the corrected display data; 3) a backlight controller for receiving a luminance signal output from the luminance determiner and outputting a backlight control signal; 4) a second control signal and a second clock synchronized with a time point at which the first control signal, the first clock signal, the first vertical and horizontal synchronization signals are input from the driving system, and the display data corrected by the gamma correction unit is output; And a control unit for outputting a signal and a second vertical and horizontal synchronous signal. delete The method of claim 1, And an inverter for driving the backlight to receive a backlight control signal output from the image quality improving unit so that the brightness of the backlight is varied. The method of claim 1, And the image quality improving unit is built in the timing controller. The method of claim 1, When the sensing signal input to the image quality improvement unit is determined to be a bright mode, the image quality improvement unit transmits a backlight control signal to the backlight to drive the luminance of the backlight by 50 nits higher than the normal mode. Driving circuit of liquid crystal display device. The method of claim 1, When the sensing signal input to the image quality improving unit is determined to be in the dark mode, the image quality improving unit transmits a backlight control signal to the backlight to drive the luminance of the backlight by 50 nits lower than the normal mode. Drive circuit for display device. The method of claim 1, When the sensing signal input to the image quality improvement unit is determined to be a bright mode, the image quality improvement unit modulates the gamma curve of the display data input from the driving system to have a higher luminance than the gamma curve of the normal mode. Driving circuit of liquid crystal display device. The method of claim 1, When the sensing signal input to the image quality improvement unit is determined to be a dark mode, the image quality improvement unit modulates the gamma curve of the display data input from the driving system to have a lower luminance than the gamma curve of the normal mode. Driving circuit of liquid crystal display device.

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