KR20090005500A - Driving apparatus for liquid crystal display device and method for driving the same - Google Patents

Abstract

A driving device of liquid crystal display capable of rapidly removing afterimage of screen and driving method thereof are provided to rapidly increase difference voltage of reference common voltage and data voltage by supplying high or low gate voltage to storage line of liquid crystal panel in power off. A liquid crystal panel(2) includes a thin film transistor(TFT) and a liquid crystal capacitor(Clc) formed on each pixel region. A data driver(4) drives a plurality of data lines(DL1-DLm). A gate driver(6) drives a plurality of gate lines(GL1-GLn). A timing controller(8) arranges an external image data(RGB), supplies an arranged data to the data driver, and controls the data driver and the gate driver. A power supply unit(10) supplies a plurality of driving voltages for driving a liquid display device. A common controller(12) supplies a common voltage(Vcom) to the liquid crystal panel according to a driving voltage supplied from the power supply unit, and supplies a high or low gate voltage to the liquid crystal panel in power off.

Description

Driving apparatus for liquid crystal display device and method for driving the same {Driving apparatus for 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 device, and more particularly, to a driving device of a liquid crystal display device and a method of driving the liquid crystal display device capable of quickly removing an afterimage on a screen when a power is turned off.

In general, a liquid crystal display device displays an image by adjusting the light transmittance of a liquid crystal having dielectric anisotropy using an electric field. To this end, the liquid crystal display includes a liquid crystal panel in which pixel regions are arranged in a matrix, and a driving circuit for driving the liquid crystal panel.

In the liquid crystal panel, a plurality of gate lines and a plurality of data lines are arranged to cross each other, and a liquid crystal cell is positioned in each region where each gate line and the data line are vertically crossed. Here, each of the liquid crystal cells is formed with a pixel electrode and a common electrode for applying an electric field. Each pixel electrode is connected to a thin film transistor (TFT) which is a switching element. The TFT is turned on by the scan pulse of the gate line so that the data signal of the data line is charged to each pixel electrode. Here, a storage capacitor is formed in each of the liquid crystal cells. The storage capacitor is formed between the pixel electrode and the front gate line of the liquid crystal cell, or is formed between the pixel electrode and the storage line of the liquid crystal cell to maintain a constant data signal, that is, the data voltage charged in the liquid crystal cell.

The driving circuit includes a gate driver for driving gate lines, a data driver for driving data lines, a timing controller for supplying control signals for controlling the gate driver and the data driver, and a liquid crystal panel, a gate and data driver, a timing controller, and the like. A power supply unit for supplying a driving voltage is provided.

However, in the conventional liquid crystal display, when the supply of the driving voltage from the power supply is interrupted, for example, when the power is turned off, the afterimage occurs due to the voltage remaining in the liquid crystal panel. Specifically, when the power supply of the liquid crystal display is turned off to stop the supply of the driving voltage, the data voltage charged in the liquid crystal capacitor and the storage capacitor formed in each liquid crystal cell cannot be discharged. Accordingly, there is a problem in that the image data voltages of the previous frame are not discharged and displayed until all remaining voltages disappear.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object thereof is to provide a driving device and a driving method thereof for a liquid crystal display device which can quickly remove an afterimage of a screen when the power is turned off.

A driving device of a liquid crystal display according to an exemplary embodiment of the present invention for achieving the above object is a liquid crystal panel formed with a plurality of pixels; A power supply unit supplying a plurality of driving voltages required for driving the liquid crystal display device including the liquid crystal panel; And a common controller configured to generate a common voltage according to each driving voltage from the power supply unit, supply the common voltage to each pixel, and supply a gate high voltage or a gate low voltage from the power supply unit to each pixel when the power is turned off. It is done.

When the gate high or gate low voltage and the DC driving voltage are supplied from the power supply unit, the common controller supplies the common voltage generated according to the gate high or gate low voltage and the DC driving voltage to the storage line of each pixel. When the supply of the DC driving voltage is stopped, the gate low or gate high voltage is supplied to the storage line.

Each pixel converts a charged data voltage level to the gate low or high voltage level when the gate low or gate high voltage is supplied to the storage line, thereby increasing the difference voltage between the reference common voltage and the data voltage of the common electrode. It is characterized by ignition.

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 a plurality of driving required for driving the liquid crystal panel formed with a plurality of pixels and the liquid crystal display device having the liquid crystal panel. A driving method of a liquid crystal display device having a power supply unit for supplying a voltage, the method comprising: generating a common voltage according to each driving voltage and supplying the common voltage to each pixel; And supplying a gate high voltage or a gate low voltage from the power supply unit to the pixels when the power is turned off.

The common voltage supplying may include generating the common voltage by using the gate high or gate low voltage and the DC driving voltage when the gate high or gate low voltage and the DC driving voltage are supplied from the power supply unit. And supplying a voltage to the storage line of each pixel. The supplying of the gate low or gate high voltage may include supplying the gate low or gate high voltage input from the power supply unit to the storage line when the supply of the DC driving voltage is stopped.

The driving device of the liquid crystal display according to the present invention supplies a gate high or low voltage to the storage line of the liquid crystal panel when the power is turned off, thereby rapidly increasing the difference voltage between the reference common voltage and the data voltage to rapidly darken the plurality of pixels. Can be. That is, when the power is turned off, each pixel of the liquid crystal panel is rapidly darkened to quickly remove an afterimage on the screen.

A driving device and a driving method thereof of a liquid crystal display according to an exemplary embodiment of the present invention having the above characteristics will be described in detail with reference to the accompanying drawings.

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

1 illustrates a liquid crystal panel 2 including a plurality of pixels, a data driver 4 driving a plurality of data lines DL1 to DLm, and a plurality of gate lines GL1 to GLn. A timing controller 8 and a liquid crystal that align the driving gate driver 6, the image data RGB input from the outside, supply the data data to the data driver 4, and control the data driver 4 and the gate driver 6. The power supply unit 10 supplies a plurality of driving voltages required for driving the display device, and the common voltage Vcom is supplied to the liquid crystal panel 2 according to the driving voltage supplied from the power supply unit 10. A common control unit 12 for supplying a high voltage or a gate low voltage to the liquid crystal panel is provided.

The liquid crystal panel 2 includes a thin film transistor (TFT) formed in each pixel area defined by a plurality of gate lines GL1 through GLn and a plurality of data lines DL1 through DLm, and a liquid crystal capacitor connected to a TFT. (Clc). 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 the data signals from the respective data lines DL1 to DLm to the pixel electrodes 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 data signal supplied to the pixel electrode and the reference 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 data signal is supplied. The storage capacitor Cst may be formed by overlapping the pixel electrode with the previous gate line and the insulating layer interposed therebetween, or may form the pixel electrode with the storage line and the insulating layer interposed therebetween. Hereinafter, the storage capacitor Cst formed in parallel with the liquid crystal capacitor Clc, that is, the liquid crystal panel 2 having a storage on command structure in which the storage capacitor Cst is formed between the pixel electrode and the storage line will be described as an example. Shall be.

The data driver 4 converts the digital image data Data from the timing controller 8 into analog image data in accordance with the data control signal DCS. The analog image data for one horizontal line is supplied to the data lines DL1 to DLm every horizontal period in which scan pulses are supplied to the gate lines GL1 to GLn. That is, the data driver 4 selects a gamma voltage having a predetermined level according to the gray value of the analog image data, and supplies the selected gamma voltage to each data line DL1 to DLm as a data signal.

The gate driver 6 includes a shift register that sequentially generates scan pulses, that is, gate high pulses, in response to the gate control signal GCS from the timing controller 8. It also includes a level shifter for shifting the gate high pulse to a voltage level suitable for driving the TFT. Therefore, the gate driver 6 supplies a scan pulse to the gate lines GL1 to GLn in response to the gate control signal GCS.

The timing controller 8 arranges the image data RGB from the outside to be suitable for driving the liquid crystal panel 2 and supplies the image data RGB to the data driver 4. The data driver 4 and the gate driver 6 are controlled by generating the gate control signal GCS and the data control signal DCS using the external synchronization signals DCLK, DE, Hsync, and Vsync.

The power supply unit 10 generates and supplies a plurality of driving voltages VGH, VGL, Vin, RVcom, and AVin required for driving the liquid crystal display using the input voltage VCC. In detail, the power supply unit 10 includes a DC / DC converter and the like to convert the input voltage VCC into a DC driving voltage Vin. The converted DC driving voltage Vin is supplied to the gate and data drivers 4 and 6, the timing controller 8, and the common controller 12. Here, the input voltage VCC may be used as the DC driving voltage Vin. In addition, the power supply unit 10 generates the gate low voltage VGL and the gate high voltage VGH using the input voltage VCC and supplies them to the gate driver 6 and the common controller 12, respectively. In addition, the power supply unit 10 generates a reference common voltage RVcom and supplies it to the common electrode of the liquid crystal panel 2, and generates an AC driving voltage AVin to generate the data driver 4 and a gamma voltage generator not shown. To feed.

The common controller 12 generates a common voltage Vcom using the DC driving voltage Vin when the DC driving voltage Vin is supplied from the power supply unit 10, and supplies the same to the storage line of the liquid crystal panel 2. Done. When the liquid crystal display is powered off, that is, when the supply of the DC driving voltage Vin is stopped from the power supply unit 10, the gate low voltage VGH or the gate high voltage VGH from the power supply unit 10 is supplied to the storage line. do. The configuration and operation method of the common control unit 12 will be described in detail with reference to the accompanying drawings.

FIG. 2 is a diagram illustrating the common control unit illustrated in FIG. 1.

The common control unit 12 shown in FIG. 2 is provided between the first and second resistors R1 and R2 and the first and second resistors R1 and R2 connected in series between the DC driving voltage Vin input terminal and the ground. A transistor Tr1 connected to a gate terminal and turned on or off depending on whether a DC driving voltage Vin is supplied; a third resistor R3 and a transistor connected between the drain terminal of the transistor Tr1 and ground; An output terminal connected from the source terminal of Tr1 to the storage line, fourth and fifth resistors R4 and R5 connected in series between the source terminal of the transistor Tr1 and the gate low or gate high voltage input terminal, and the fourth and fifth resistors First and second capacitors C1 and C2 connected in parallel between R4 and R5 and the second resistor R2 and ground are provided. Here, if the transistor Tr1 can be used an NMOS or PMOS transistor, only the NMOS transistor Tr1 will be described below.

When the DC driving voltage Vin and the gate high or low voltages VGH and VGL are input from the power supply unit 10, the common controller 12 may include the first to fifth resistors R1 to R5 and the first and second resistors. The common voltage Vcom is generated by the capacitors C1 and C2. Then, the generated common voltage Vcom is supplied to the storage line. However, when the supply of the DC driving voltage Vin is stopped, the gate high or low voltages VGH and VGL are output to the output terminal through the fourth and fifth resistors R4 and R5 and are supplied to the storage line.

In detail, when the DC driving voltage Vin is input to the common controller 12, the transistor Tr1 is turned on according to the voltage divided by the first and second resistors R1 and R2. Then, the common voltage Vcom of a predetermined level is supplied to the storage line through the output terminal according to the third to fifth resistors R3 to R5 and the first and second capacitors C1 and C2. Therefore, the level of the common voltage Vcom may be generated differently according to the levels of the DC driving voltage Vin and the gate high or low voltages VGH and VGL from the power supply unit 10. In addition, the level of the common voltage Vcom may be generated differently according to the capacitance of the first to fifth resistors R1 to R5 and the first and second capacitors C1 and C2.

After that, when the power supply of the liquid crystal display is turned off, that is, when the supply of the DC driving voltage Vin is stopped from the power supply unit 10, the transistor Tr1 is turned off. Then, the gate high or low voltages VGH and VGL from the power supply unit 10 are output to the output terminal through the fourth and fifth resistors R4 and R5 and supplied to the storage line. In general, when the supply of the input voltage VCC from the outside is stopped, the power supply unit 10 stops outputting the DC driving voltage Vin at the same timing. However, since the gate high voltage VGH and the gate low voltage VGL are output through the gate high and low voltage generators (not shown) included in the power supply unit 10, the gate high voltage VGH and the gate low voltage VGL are output for a predetermined period even after the liquid crystal display is turned off. . Accordingly, the common controller 12 may supply the gate high or low voltages VGH and VGL to the storage line of the liquid crystal panel 2 even after the liquid crystal display is turned off.

For example, the capacitances of the first and second resistors R1 and R2 are 3.3 mA and 1 mA, the third resistor R3 is 39 mA, and the fourth and fifth resistors R4 and R5 are respectively It may be formed of 5.1 GHz and 1.2 GHz, respectively. In addition, the capacitance of each of the first and second capacitors C1 and C2 may be 10 kV, the level of the input DC driving voltage Vin may be set to 15V, and the level of the gate high voltage VGH may be set to 31V. . In this case, the common controller 12 generates a common voltage Vcom having a level of about 5V when the DC driving voltage Vin is input, and supplies the generated common voltage Vcom to the storage line. Meanwhile, when the supply of the DC driving voltage Vin is stopped, the common controller 12 supplies the gate high voltage VGH converted to a level of about 30V to the storage line.

The common control unit 12 of the present invention may convert the level of the common voltage Vcom and the gate high voltage VGH by outputting only the capacitance of the fourth resistor R4 in the above-described state. For example, when the capacitance of the fourth resistor R4 is set to 51 mA, the level of the common voltage Vcom when supplying the DC driving voltage Vin is 6.6 V and the gate when supply of the DC driving voltage Vin is interrupted. The level of the high voltage VGH may be output at 31V. When the capacitance of the fourth resistor R4 is set to 2.2 mA, the level of the common voltage Vcom when the DC driving voltage Vin is supplied is 15 V and the gate high voltage when the supply of the DC driving voltage Vin is stopped. The level of VGH) can be output at 29V. In addition, when the capacity of the fourth resistor R4 is set to 11 kV, the level of the common voltage Vcom when the DC driving voltage Vin is supplied is 11V, and the gate high voltage (when the supply of the DC driving voltage Vin is stopped). The level of VGH) can be output to 30.6V and supplied to the storage line.

3 is a waveform diagram illustrating a voltage change of a liquid crystal capacitor and a storage capacitor when a power supply is on or off.

As shown in FIG. 3, when the reference common voltage RVcom is applied to the common electrode of the liquid crystal panel 2 and the data voltage Vp is applied to each pixel electrode in the ON period of the power supply, the storage capacitor Cst The difference voltage between the reference common voltage RVcom and the data voltage Vp is charged. Then, the charged voltage is maintained until the next data voltage Vp is supplied. In addition, the common voltage Vcom from the common controller 12 is supplied to the storage line at a predetermined level. The common voltage Vcom level supplied to the storage line may be maintained at the same level as the reference common voltage RVcom level supplied to the common electrode.

Thereafter, the gate low voltage VGL from the common controller 12 is applied to the storage line in the OFF period of the power supply. Accordingly, the voltage level of the storage capacitor Cst suddenly drops to the gate low voltage VGL level, and the charged data voltage Vp level also drops rapidly to the gate low voltage VGL level. That is, when the power is turned off, the level of the charged data voltage Vp is rapidly lowered to the gate low voltage VGL level, thereby increasing the difference voltage between the reference common voltage Vcom and the data voltage Vp. Quickly darken a plurality of pixels.

4 is another waveform diagram illustrating voltage changes of the liquid crystal capacitor and the storage capacitor when the power supply is turned on or off.

As shown in FIG. 4, when the reference common voltage RVcom is applied to the common electrode and the data voltage Vp is applied to each pixel electrode in the ON period of the power supply, the storage capacitor Cst is the reference common voltage RVcom. The voltage difference between the data voltage Vp and the battery is charged. Then, the charged voltage is maintained until the next data voltage Vp is supplied. In addition, the common voltage Vcom from the common controller 12 is supplied to the storage line at a predetermined level. The common voltage Vcom level supplied to the storage line may be maintained at the same level as the reference common voltage RVcom level supplied to the common electrode.

After that, the gate high voltage VGH from the common controller 12 is applied to the storage line in the OFF period of the power supply. Accordingly, the voltage level of the storage capacitor Cst rapidly rises to the gate high voltage VGH level, and the charged data voltage Vp level also rapidly rises according to the gate high voltage VGH level. That is, when the power is turned off, the level of the charged data voltage Vp is quickly increased to the gate high voltage VGH level, thereby increasing the difference voltage between the reference common voltage Vcom and the data voltage Vp. Quickly darken a plurality of pixels.

5 is another configuration diagram illustrating the common control unit illustrated in FIG. 1.

The common control unit 12 illustrated in FIG. 5 includes a transistor Tr1 and a transistor whose gate terminal is connected to a DC driving voltage Vin input and turned on or off depending on whether the DC driving voltage Vin is supplied. A first resistor R1 connected between the drain terminal of Tr1 and ground, an output terminal connected to the storage line from the source terminal of transistor Tr1, and a series between the source terminal of transistor Tr1 and the gate low or gate high voltage input terminal; It has a second resistor (R2) connected.

When the DC driving voltage Vin and the gate high or low voltages VGH and VGL are input from the power supply unit 10, the common control unit 12 receives the transistors Tr1 and the first and second resistors R1 and R2. As a result, a common voltage Vcom having a predetermined level is generated. However, when the supply of the DC driving voltage Vin is stopped, the gate high or low voltages VGH and VGL are output to the output terminal through the second resistor R2 and supplied to the storage line.

In detail, when the DC driving voltage Vin is input to the common controller 12, the transistor Tr1 is turned on. Then, the common voltage Vcom of a predetermined level is supplied to the storage line through the output terminal by the transistor Tr1 and the first and second resistors R1 and R2. Therefore, the level of the common voltage Vcom may be generated differently according to the levels of the DC driving voltage Vin and the gate high or low voltages VGH and VGL from the power supply unit 10. The level of the common voltage Vcom may be generated differently according to the capacitance of the transistor Tr1 and the first and second resistors R1 and R2.

After that, when the power of the liquid crystal display is turned off, that is, when the supply of the DC driving voltage Vin is stopped from the power supply unit 10, the transistor Tr1 is turned off. Then, the gate high or low voltages VGH and VGL from the power supply unit 10 are output to the output terminal through the second resistor R2 and supplied to the storage line.

In general, when the supply of the input voltage VCC from the outside is stopped, the power supply unit 10 stops outputting the DC driving voltage Vin at the same timing. However, since the gate high and low voltages VGH and VGL and the reference common voltage RVcom are output through the gate high and low voltage generators and the reference common voltage generator, which are not provided in the power supply unit 10, It is output for a certain period even after the power is turned off.

Therefore, the common controller 12 supplies the gate high or low voltages VGH and VGL to the storage lines of the liquid crystal panel 2 after the liquid crystal display is turned off, thereby providing the reference common voltage Vcom and the data voltage Vp. By rapidly increasing the difference voltage with), a plurality of pixels can be rapidly darkened.

The present invention described above is not limited to the above-described embodiments and the accompanying drawings, and 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.

1 is a configuration diagram showing a driving device of a liquid crystal display according to an exemplary embodiment of the present invention.

FIG. 2 is a diagram illustrating a common control unit illustrated in FIG. 1.

Figure 3 is a waveform diagram showing the voltage change of the liquid crystal capacitor and the storage capacitor when the power supply on / off.

Figure 4 is another waveform diagram showing the voltage change of the liquid crystal capacitor and the storage capacitor when the power supply on / off.

5 is another configuration diagram illustrating the common controller illustrated in FIG. 1.

* Brief description of symbols for the main parts of the drawings.

2: liquid crystal panel 4: data driver

6: gate driver 8: timing controller

10: power supply unit 12: common control unit

Cst: Storage Capacitor Tr: Transistor

R1 to R5: first to fifth resistors

C1 and C2: first and second capacitor

Claims (9)

A liquid crystal panel formed with a plurality of pixels; A power supply unit supplying a plurality of driving voltages required for driving the liquid crystal display device including the liquid crystal panel; And And a common controller configured to generate a common voltage according to each driving voltage from the power supply unit and supply the common voltage to the pixels, and to supply the gate high voltage or the gate low voltage from the power supply unit to each pixel when the power is turned off. A drive device for a liquid crystal display device. The method of claim 1, The common control unit When the gate high or gate low voltage and the DC driving voltage are supplied from the power supply unit, the common voltage generated according to the gate high or gate low voltage and the DC driving voltage is supplied to the storage lines of the pixels, and the DC driving voltage And supplying the gate low or gate high voltage to the storage line when the supply of the power supply is stopped. The method of claim 2, The common control unit First and second resistors connected in series between the DC driving voltage input terminal and ground; A transistor connected with a gate terminal between the first and second resistors and turned on or off depending on whether a DC driving voltage is supplied; A third resistor connected between the drain terminal of the transistor and ground, An output terminal connected to the storage line from a source terminal of the transistor, Fourth and fifth resistors connected in series between a source terminal of the transistor and the gate low or gate high voltage input terminal, and And first and second capacitors connected in parallel between the fourth and fifth resistors, the second resistor, and the ground. The method of claim 2, The common control unit A gate terminal connected to the DC driving voltage input terminal and turned on or off depending on whether the DC driving voltage is supplied; A first resistor connected between the drain terminal of the transistor and ground, An output terminal connected to the storage line from a source terminal of the transistor, and And a second resistor connected in series between the source terminal of the transistor and the gate low or gate high voltage input terminal. The method of claim 2, Each pixel is When the gate low or gate high voltage is supplied to the storage line, the charged data voltage level is converted into the gate low or high voltage level to increase the difference voltage between the reference common voltage and the data voltage of the common electrode, thereby darkening. A drive device for a liquid crystal display device. In the driving method of a liquid crystal display device having a liquid crystal panel formed with a plurality of pixels and a power supply unit for supplying a plurality of driving voltages to the liquid crystal display device having the liquid crystal panel, Generating a common voltage according to the plurality of driving voltages and supplying the common voltages to the pixels; And And supplying a gate high voltage or a gate low voltage from the power supply unit to the pixels when the power is turned off. The method of claim 6, The common voltage supply step Generating the common voltage by using the gate high or gate low voltage and the DC driving voltage when a gate high or gate low voltage and a DC driving voltage are supplied from the power supply unit, and And supplying the common voltage to the storage line of each pixel. The method of claim 7, wherein The gate low or gate high voltage supplying step And supplying the gate low or gate high voltage input from the power supply unit to the storage line when the supply of the DC driving voltage is stopped. The method of claim 8, Each pixel is When the gate low or gate high voltage is supplied to the storage line, the charged data voltage level is converted into the gate low or high voltage level to increase the difference voltage between the reference common voltage and the data voltage of the common electrode, thereby darkening. A method of driving a liquid crystal display device.

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