KR101136793B1 - LCD and driving method thereof - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device and a driving method thereof, and more particularly, to an overdriving drive for a high speed response of a liquid crystal and a liquid crystal display device implementing the same.

 The liquid crystal panel includes a plurality of liquid crystal pixels that display an image by forming a thin film transistor and a liquid crystal in an area where a plurality of data lines to which a data signal is applied and a plurality of gate lines to which a gate driving signal is intersected are formed. It is proposed as an impulse driving method for driving a liquid crystal panel by applying an impulse signal to a plurality of data lines and then outputting the data signal. Conventional methods for improving the response speed of liquid crystals are provided in a memory device or a separate device. Unlike the need for a driver IC, no additional device is added, and a simple circuit configuration can provide an over-driving effect.

Description

Liquid crystal display and driving method thereof

1 is a view showing the configuration of a conventional active matrix liquid crystal display device

FIG. 2 is a diagram illustrating a gate driving signal applied to drive the liquid crystal display according to FIG. 1.

3 is a signal diagram showing a relationship between a data signal output from a data driver and a signal applied to a liquid crystal cell of a conventional liquid crystal display device;

4 is a signal diagram illustrating an over-driving driving method for improving a liquid crystal response speed in a conventional driving method of a liquid crystal display device;

5 is a signal diagram illustrating a method of driving a liquid crystal display device according to the present invention.

6 is a signal diagram illustrating an impulse signal applied to the liquid crystal by driving the liquid crystal display device impulse according to the present invention;

7 is a diagram illustrating a configuration of a signal output control circuit unit configured for realizing an impulse driving method according to the present invention.

8 is a view for explaining the operation of the signal output control circuit unit according to the present invention;

<Brief description of the main parts of the drawing>

IS: Impulse Signal DS: Data Signal

VGH, VGL: Gate drive signal Vcom: Common voltage

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display and a driving method thereof, and more particularly, to an overdriving drive for a high speed response of a liquid crystal and a liquid crystal display implementing the same.

A liquid crystal display device applies a voltage to a specific molecular array of a liquid crystal to convert it into another molecular array, and visually changes the optical properties such as birefringence, photoreactivity, dichroism, and light scattering characteristics of the liquid crystal cell that emit light by the molecular array. By converting into a display device using a modulation of light by a liquid crystal cell, a conventional liquid crystal display device displays an image corresponding to a video signal by adjusting the light transmittance of the liquid crystal cells on the liquid crystal panel. In order to drive the liquid crystal cells on the liquid crystal panel, the liquid crystal display device includes a liquid crystal panel driver.

The liquid crystal display generally uses a dot inversion method, which is a driving method for reducing defects caused by flickering or crosstalk by inverting and applying the voltage polarity of the pixel electrode to one pixel period based on the opposite electrode. Doing.

Referring to FIG. 1, a conventional active matrix liquid crystal display includes a liquid crystal panel 3 in which liquid crystal cells are arranged in a matrix form between two transparent substrates, and data lines on the liquid crystal panel 3. And a data driver 1 (Data Driving Integrated Circuit) for supplying data to the DL1 through DLn, and a gate driver 2 (Gate Driving Integrated Circuit) for sequentially driving the gate lines GL1 through GLm. do. The liquid crystal panel 3 includes a plurality of liquid crystal cells and thin film transistors (TFTs) for switching data signals to be supplied to each of the liquid crystal cells.

A plurality of liquid crystal cells are respectively installed at intersections of data lines and gate lines, and thin film transistors are also positioned at the intersections.

The data driver 1 includes a shift register and a latch, shifts data bits in response to a data shift clock, and simultaneously supplies one line of data to the data lines DL1 to DLn in response to a data output enable signal. do.

The gate driver 2 is composed of a shift register including a plurality of stages for driving the respective gate lines to sequentially drive the gate lines in response to the gate start pulse.

When the gate start pulse is supplied to the gate drivers, the gate drivers sequentially drive the m gate lines by sequentially supplying the gate driving signals to the m gate lines on the liquid crystal panel as shown in FIG. 2. Then, the thin film transistors TFT on the liquid crystal panel are sequentially driven by one gate line to sequentially charge data capacitors to the liquid crystal cells of one gate line, thereby charging the storage capacitors C _ST connected to the one gate line.

In this case, referring to FIG. 3, which illustrates a relationship between a data signal output from the data driver 1 and a signal applied to a liquid crystal cell, the signal B applied to the liquid crystal cell compared to the data signal A output. Due to the characteristics of the liquid crystal and the capacitive load present in the signal transmission line, the time required for applying a sufficient signal voltage to reach the target luminance of the liquid crystal cell is delayed by "D", resulting in a slow response time of the liquid crystal. This occurs and appears as an abnormal picture quality.

In order to solve this problem, as shown in FIG. 4, the luminance value of the previous frame is compared with the luminance value of the previous frame by using the principle that the response speed of the liquid crystal is increased by the higher voltage difference as the gray level is higher. The over-driving method of amplifying a signal by applying a preset lookup table (LUT) to improve the response speed of a liquid crystal is used.

However, the above method requires a separate memory device such as an EEPROM to store the lookup table, leading to an increase in manufacturing cost.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and in performing overdriving to increase the liquid crystal response speed, the overdriving operation is performed without adding a memory element, modulating a data signal, and adding a circuit IC for overdriving. It is aimed at realization.

In order to achieve the above object, the present invention provides a liquid crystal for displaying an image by forming a thin film transistor and a liquid crystal in an area where a plurality of data lines to which a data signal is applied and a plurality of gate lines to which a gate driving signal is applied cross each other. In a liquid crystal panel having a plurality of pixels, a method of driving a liquid crystal display device for driving a liquid crystal panel by applying an impulse signal to the plurality of data lines and then outputting the data signals is provided.

The impulse signal may be a voltage higher than the maximum voltage of the data signal or lower than the minimum voltage of the data signal.

The impulse signal is a signal applied using the gate drive signal.

The high level voltage of the gate driving signal is 25 volts and the low level voltage of the gate driving signal is -5 volts.

The application time of the impulse signal may be shorter than one frame driving period of the liquid crystal panel.

The present invention also includes a timing control unit for outputting a first data signal and a plurality of control signals; A data driver which receives the first data signal and converts the first data signal into a second data signal according to the control signal; A gate driver for outputting a gate driving signal according to the control signal; A plurality of data lines to which the second data signal output from the data driver is applied, a plurality of gate lines formed to intersect the plurality of data lines, and to which the gate driving signal is applied, and a plurality of data lines and a plurality of data lines A liquid crystal panel including a plurality of liquid crystal pixels in which thin film transistors and liquid crystals are formed in regions where the gate lines cross each other; In order to apply an impulse signal to the plurality of data lines, a voltage signal input terminal to which the high level voltage signal, the low level voltage signal and the data signal of the gate driving signal are respectively input, and a selection signal input terminal to which the plurality of selection signals are input. And a signal selector for selecting one of a plurality of signals input to the voltage signal input terminal according to the plurality of selection signals, and a voltage signal output terminal for outputting the signal selected by the signal selector to the data line. A liquid crystal display device including a signal output control circuit part is proposed.

The signal selector may be configured as a multiplexer.

The plurality of selection signals include a first selection signal for selecting a voltage magnitude of an impulse signal output to each data line, and a second selection signal for selecting an application time of an impulse signal output to each data line. It is characterized by.

The signal output control circuit part may be a circuit part configured inside the data driver.

The first data signal is a digital signal and the second data signal is an analog signal.

Hereinafter, the present invention will be described with reference to the accompanying drawings.

FIG. 5 is a signal diagram for explaining a method of driving a liquid crystal display according to the present invention, hereinafter referred to as impulse driving.

In brief, the impulse driving, in displaying an image on a liquid crystal display, in particular, a plurality of data lines to which a data signal (DS) is applied and a plurality of gate driving signals VGH and VGL are applied. In order to display an image on a liquid crystal panel having a plurality of liquid crystal pixels displaying an image by forming a thin film transistor and a liquid crystal (LC) in a region where the gate lines cross each other, to improve a slow response speed of the liquid crystal. To this end, the present invention applies a voltage impulse higher than the maximum value of the data signal or a voltage impulse lower than the minimum value before the data signal is applied to the liquid crystal LC, so that the liquid crystal LC has a desired luminance. This method reduces the time required to receive and respond to the signal voltage (V _LC ).

In summary, when the data signal is output from the data driver, an impulse signal (hereinafter referred to as IS) is applied to improve the response speed of the liquid crystal LC even faster.

In this case, the impulse signal IS applied to the liquid crystal LC is a data signal DS inverted for each frame and output from the data driver as shown in the signal comparison diagram of FIG. 6 based on the common voltage Vcom. When the voltage higher than) is the positive data signal DS _H and the voltage lower than the common voltage is the negative data signal DS _L , the positive data signal is generated by the data driver. for each output point of the (DS _H) is applied to the positive (+) data signal a high level of the impulse signal voltage (iS _H) than (DS _H) the negative polarity - for each output point of the data signal (DS _L) () An impulse signal voltage IS _L lower than the negative data signal DS _L is applied. At this time, it is natural that the impulse signals IS _H and IS _L applied for each frame should be applied for a time shorter than one frame driving time of the liquid crystal panel.

In the impulse driving method according to an embodiment of the present invention described below, the gate driving to implement the over-driving driving without adding a separate memory device or IC to each of the applied impulse signals (IS _H , IS _L ) Signals VGH and VGL are used, where the gate driving signals VGH and VGL are typically + 25V (VGH) and -5V (VGL). In addition, the impulse signals (IS _H , IS _L ) is not a voltage signal applied in the gate driver may be provided by configuring other circuit application signal or a separate signal source.

In other words, the impulse driving method according to the embodiment of the present invention, by applying the gate driving signals (VGH, VGL) as an impulse signal source for each positive point of the output of the positive data signal (DS _H ) ( +) A gate driving signal VGH having a level higher than that of the data signal DS _H is applied, and the negative data signal DS _L is output at each output point of the negative data signal DS _L. By applying the gate driving signal VGL having a lower level than), the response speed of the liquid crystal LC is improved.

FIG. 7 is a view illustrating a specific method for implementing an embodiment of an impulse driving method according to the present invention, and as described above, a signal output control circuit unit configured to apply the gate driving signals VGH and VGL as an impulse signal source. 100) configured and provided.

The signal output control circuit unit 100 for applying an impulse signal to a plurality of data lines formed in the liquid crystal panel includes a high level voltage signal VGH, a low level voltage signal VGL, and a data signal DS of a gate driving signal. Are respectively input to the voltage signal input terminal 110, the selection signal input terminal 120 to which the plurality of selection signals op1 and op2 are input, and the voltage signal input terminal 110 according to the plurality of selection signals op1 and op2. A signal selector 130 for selecting one of a plurality of signals (VGH, VGL, DS) input as a signal and a signal VSout selected by the signal selector 130 are outputted to the plurality of data lines. The voltage signal output terminal 140 is provided.

In this case, the signal selector 130 is specifically a multiplexer, and the selection signal input terminal 120 may change the number of input terminals in various ways as necessary. In the present invention, an impulse signal output to a plurality of data lines is provided. second selection to set the application time of the first selection signal (op1) and the impulse signal (iS _H, iS _L) outputted the to the plurality of data lines to select a voltage level of (iS _H, iS _L) Only the signal op2 is configured to receive an example. In addition, the signal output control circuit unit 100 exemplified above may be included in the liquid crystal display device data driver in consideration of the type of application element (ie, MUX) having a very narrow configuration area.

The operation of the signal output control circuit unit 100 constructed in accordance with the present invention as described above will be described with reference to FIG.

The illustrated figure briefly describes an internal operation of the signal selection unit 130 of the signal output control circuit unit 100. The data output from the liquid crystal display data driver is a positive data signal DS _H. In this case, the gate driving signal VGH having a high level is output through the switching operation for a time shorter than one frame period time, and then switching is again performed to output the data signal DS. In addition, when the data output from the liquid crystal display data driver is a negative data signal DS _L , the low-level gate drive signal VGL is output for a time shorter than one frame period through a switching operation. Switching is again performed to output the data signal DS. As described above, an appropriate impulse signal IS _H , IS _L and a data signal DS _H , DS _L are sequentially output VSout, and the liquid crystal has a faster response speed by the impulse signal. Image quality can be realized for gray levels.

In the liquid crystal display and the driving method thereof according to the present invention described above, an additional element is not added, unlike conventional methods for improving the response speed of the liquid crystal require a memory element or a separate driving IC. A simple circuit configuration has the advantage of providing an over-driving effect.

Claims (10)

A liquid crystal panel having a plurality of liquid crystal pixels for displaying an image by forming a thin film transistor and a liquid crystal in an area where a plurality of data lines to which a data signal is applied and a plurality of gate lines to which a gate driving signal is crossed are formed. After applying an impulse signal to the plurality of data lines and outputs the data signal to drive the liquid crystal panel, The impulse signal is a signal applied to the liquid crystal display device driving method using the gate driving signal. The method according to claim 1, Wherein the impulse signal is a voltage higher than the maximum voltage of the data signal or lower than the minimum voltage of the data signal. delete The method according to claim 1, The high level voltage of the gate driving signal is 25 volts and the low level voltage of the gate driving signal is -5 volts. The method according to claim 1, The application time of the impulse signal is a liquid crystal display device driving method characterized in that the time shorter than one frame driving period of the liquid crystal panel. A timing controller which outputs a first data signal and a plurality of control signals; A data driver which receives the first data signal and converts the first data signal into a second data signal according to the control signal; A gate driver for outputting a gate driving signal according to the control signal; A plurality of data lines to which the second data signal output from the data driver is applied, a plurality of gate lines formed to intersect the plurality of data lines, and to which the gate driving signal is applied, and a plurality of data lines and a plurality of data lines A liquid crystal panel including a plurality of liquid crystal pixels in which thin film transistors and liquid crystals are formed in regions where the gate lines cross each other; In order to apply an impulse signal to the plurality of data lines, a voltage signal input terminal to which a high level voltage signal, a low level voltage signal, and the second data signal of the gate driving signal are respectively input, and a plurality of selection signals are input. A signal selector for selecting one of a plurality of selection signals inputted to the voltage signal inputter according to the plurality of selection signals, and a voltage signal outputter for outputting the signal selected by the signal selector to the data line Signal output control circuit section with Liquid crystal display comprising a The method of claim 6, And the signal selector comprises a multiplexer. The method of claim 6, The plurality of selection signals include a first selection signal for selecting a voltage magnitude of an impulse signal output to each data line, and a second selection signal for selecting an application time of an impulse signal output to each data line. Liquid crystal display device characterized in that The method of claim 6, And the signal output control circuit part is a circuit part configured inside the data driver. The method of claim 6, Wherein the first data signal is a digital signal and the second data signal is an analog signal.

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