KR20080024863A - Liquid crystal display and driving circuit thereof - Google Patents

Abstract

An LCD device and a driving circuit thereof are provided to improve display error due to the resistance deviation of a fan out unit by applying compensated driving signals to compensate for the variation amount of a voltage level of the driving signals. An LCD(Liquid Crystal Display) device includes an LCD panel(300) and drivers(400,500). The LCD panel includes a unit pixel, a display unit having signal lines connected to the unit pixel, a pad unit having a signal pad for connecting the drivers to the signal lines, and a fan out unit having a fan out line for connecting the signal lines and signal pad. The drivers include signal generators(410,510) for generating driving signals required for the operation of the unit pixel and signal compensators(420,520) for compensating the driving signals to have a voltage level in proportion to the length of the fan out line.

Description

Liquid crystal display and its driving circuit {LIQUID CRYSTAL DISPLAY AND DRIVING CIRCUIT THEREOF}

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

2 is a plan view illustrating a liquid crystal display panel according to an exemplary embodiment of the present invention.

3 is a layout view illustrating a wiring structure of a fan out part of the liquid crystal display panel according to the present embodiment.

4 is a graph illustrating wiring resistances of a fanout part of the liquid crystal display panel according to the present exemplary embodiment.

5 is a diagram illustrating a gate signal output from a gate signal compensator according to the present embodiment.

6 is a view showing a gate signal output from the fan out section according to the comparative example and the experimental example of the present embodiment.

<Explanation of symbols for the main parts of the drawings>

300: liquid crystal display panel 310: display unit

320: pad portion 330: fan out portion

400: gate driver 500: data driver

600: signal controller 800: drive voltage generator

900: gray voltage generator.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device and a driving circuit thereof, and more particularly, to a liquid crystal display device having a fan out part between a display unit in which a unit pixel is formed and a pad unit in which a driving circuit providing a driving signal to the unit pixel is mounted. And its driving circuit.

The liquid crystal display includes a liquid crystal display panel in which a liquid crystal layer is filled between an upper substrate on which a color filter and a common electrode are formed, and a lower substrate on which a thin film transistor and a pixel electrode are formed, and a backlight, which is a light source, is disposed below. In addition, in order to control the transmittance of light incident from the backlight together with the liquid crystal layer, polarizers are attached to both surfaces of the liquid crystal display panel.

The liquid crystal display panel includes a display unit in which a plurality of unit pixels for displaying an image and a plurality of signal lines connected to the plurality of unit pixels are formed, and a pad unit in which signal pads for connecting a driving circuit to the signal lines are formed. In this case, the signal lines of the display unit are distributed in a relatively wide area according to the distance between the unit pixels, whereas the signal pads of the pad unit are densely arranged in a relatively narrow area according to the distance between the output terminals of the driving circuit. An area in which a distance between wires is gradually increased, that is, a fan-out area, is formed between the display unit and the pad unit.

Due to the fan-out area, the lengths of the wires vary from area to area, and therefore, the resistance of the wires varies from area to area. The difference in the wiring resistance in the fanout area causes various screen defects by distorting the driving signals applied from the driving circuit to the unit pixels.

The present invention is derived to solve the above problems, by applying a drive signal compensated in advance so that the amount of change in the voltage level of the drive signal due to the resistance deviation in consideration of the resistance variation of the fan out portion, It is an object of the present invention to provide a new liquid crystal display device and a driving circuit thereof that solve various screen defects caused by the resistance variation of the fan out part.

The present invention is derived to solve the above problems, by selectively providing a plurality of reference voltages having different voltage levels to change the gray scale voltage, so that the gamma characteristics and the viewing angle of the output image to match the user's preference or usage environment It is an object of the present invention to provide a novel liquid crystal display device and a driving method thereof that can be easily adjusted.

According to an aspect of the present invention, a liquid crystal display device includes: a display unit in which a unit pixel and a signal line connected to the unit pixel are formed; a pad unit in which a signal pad for connecting a driving circuit is formed to the signal line; A liquid crystal display panel having a fanout portion having a fanout wiring connecting the signal line and the signal pad, respectively, and a driving signal required for operation of the unit pixel, and a voltage proportional to a length of the fanout wiring; And a driving circuit for compensating and outputting the level.

The driving circuit receives a signal generator for generating a first driving signal necessary for the operation of the unit pixel and the first driving signal, and compensates the voltage to be a voltage level proportional to the length of the fan-out wiring. It is preferable to include a signal compensator for outputting.

The signal compensator includes a plurality of output terminals for outputting the second driving signal, and compensates for the voltage level of the output signal to increase from the center terminal of the plurality of output terminals to both ends of the terminals.

The signal compensator preferably includes a pulse width modulation circuit having a different duty ratio, or a plurality of resistor circuits having different resistance values.

In order to achieve the above object, a driving circuit of a liquid crystal display according to the present invention includes a signal generator for generating a first driving signal required for driving a liquid crystal display panel and a second driving signal by receiving the first driving signal. And a signal compensator for generating the signal compensator, wherein the signal compensator includes a plurality of output terminals for outputting the second driving signal, and the voltage level of the output signal is increased from the center terminal to the both terminals of the plurality of output terminals. Characterized in that.

The first and second driving signals may be at least one driving signal among a gate signal applied to a gate line of the liquid crystal display panel and a data signal applied to a data line of the liquid crystal display panel.

The signal compensator preferably includes a pulse width modulation circuit having a different duty ratio, or a plurality of resistor circuits having different resistance values.

Hereinafter, with reference to the accompanying drawings will be described an embodiment according to the present invention in more detail. However, the present invention is not limited to the embodiments disclosed below, but will be implemented in various forms, and only the embodiments are intended to complete the disclosure of the present invention, and to those skilled in the art to fully understand the scope of the invention. It is provided to inform you. Like reference numerals in the drawings refer to like elements.

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

Referring to FIG. 1, the liquid crystal display includes a liquid crystal display panel 300, a gate driver 400, a data driver 500, a driving voltage generator 800, a gray voltage generator 900, and a signal for controlling the liquid crystal display panel 300. The control unit 600 is included.

The liquid crystal display panel 300 includes a plurality of unit pixels arranged in a matrix form. The unit pixel is defined by a cross region of a plurality of gate lines G1 to Gn and a plurality of data lines D1 to Dm formed in a horizontal and vertical direction, and includes a switching element Q and a liquid crystal capacitor connected thereto. Clc) and a storage capacitor (Cst).

The driving voltage generator 800 includes a plurality of gate voltages including a gate on voltage Von, a gate off voltage Voff, a logic voltage VDD, a reference voltage AVDD, and a common voltage Vcom. A voltage power source is generated, and among them, a gate on voltage Von, a gate off voltage Von, and a logic voltage VDD are output to the gate driver 400, and the reference voltage AVDD and the logic voltage VDD are data. The common voltage Vcom is output to the driver 500, and the common voltage Vcom is provided to a common electrode of the liquid crystal display panel 300. The driving voltage generator 800 may include a DC / DC converter having at least one charge pumping circuit.

The gray voltage generator 900 selects the maximum gray voltage and the lowest gray voltage based on the reference voltage AVDD from the driving voltage generator 800 in response to a luminance selection signal from an external user or an internal system. The plurality of intermediate gray voltages (or gamma voltages) are generated and output by dividing between the highest gray voltage and the lowest gray voltage. The gray voltage generator may include a resistor string circuit having a plurality of output nodes.

The gate driver 400 is connected to each gate line G1 to Gn of the liquid crystal display panel 300 to include a gate on voltage Von and a gate off voltage Voff from the driving voltage generator 800. Analog signals are sequentially applied to the gate lines G1 to Gn as gate signals. The gate driver 400 may include a gate signal generator 410 for outputting a first gate signal and a gate signal compensator for differentially compensating a voltage level of the first gate signal for each output region and outputting the same as a second gate signal. 420. Here, the gate signal compensator 420 is composed of a pulse width modulation (PWM) having a different duty ratio and a plurality of resistor circuits having different resistance values, thereby providing a voltage of the first gate signal. The level is differentially compensated for each output area.

The data driver 500 is connected to each of the data lines D1 to Dm of the liquid crystal display panel 300, and the grayscale voltage applied from the gray voltage generator 900 is converted into the image signals R ', G', and B '. It modulates to suit and apply it sequentially to each data line D1 to Dm as a data signal. The data driver 500 may include a data signal generator 510 for outputting a first data signal and a data signal compensator for differentially compensating a voltage level of the first data signal for each output region and outputting the result as a second data signal. 520). Here, the data signal compensator 520 is composed of a pulse width modulation circuit having a different duty ratio and a plurality of resistor circuits having different resistance values to differentially compensate the voltage level of the first data signal for each output region.

The signal controller 600 may include image signals R, G, and B and control signals thereof input from an external graphic controller (not shown), for example, a vertical synchronization signal Vsync, a horizontal synchronization signal Hsync, and a main clock. The image signal and the control signal are processed in accordance with the operating conditions of the liquid crystal display panel 300 in response to the signal MCLK, the data enable signal DE, and the like, and then the gate control signal CONT1 and the data control signal CONT2. ) And the voltage part control signal CONT3.

2 is a plan view illustrating a liquid crystal display panel according to an exemplary embodiment of the present invention.

Referring to FIG. 2, the liquid crystal display panel 300 includes a display unit 310 having a plurality of unit pixels, a gate line G and a data line D connected to the unit pixels, the gate line G, and Pad portions 321 and 322 having gate pads (not shown) and data pads (not shown) on which a driving circuit for applying a driving signal to a data line D is mounted, the gate line G, and the gate pads; And fanout parts 331 and 332 having fanout wirings therebetween and connecting the data line D and the data pad therebetween.

The above-described gate driver 400 and data driver 500 are mounted on the pads 321 and 322 to provide respective driving signals to the plurality of unit pixels. In this embodiment, the gate driver 400 and the data driver 500 are made of a plurality of driving chips 401-403, 501-504, and each of the driving chips 401-403, 501-505 is COG (Choip). On Glass) was mounted on the lower substrate. Of course, the gate driver 400 and the data driver 500 may be manufactured by a single driving chip, and may be mounted by other methods such as a tape carrier package (TAP) method or a chip on film (COF) method.

The fan-out parts 321 and 332 are pad parts 331 and 332 which are densely arranged in a relatively narrow area of the gate line G and the data line D of the display part 310 that are distributed in a relatively wide area. To the gate pad and data pad.

3 illustrates a wiring structure of the fanout part of the liquid crystal display panel according to the present exemplary embodiment, and illustrates a wiring structure of the fanout part 331 connected to the gate driving chip 101.

Referring to FIG. 3, output terminals of the gate driving chip 401 mounted in the gate pad part (not shown) are electrically connected to the fanout wiring 331a, respectively, and the length of the fanout wiring 331a is a gate. It becomes longer from the center output terminal of the driving chip 401 to both ends of the output terminal. That is, the fanout wire 331a connected to the center output terminal of the gate driving chip 401 has the shortest length, and the fanout wire 331a connected to the output terminal of both ends of the gate driving chip 401 has the shortest length. long.

FIG. 4 illustrates wiring resistances of the fanout part of the liquid crystal display panel according to the present exemplary embodiment, and illustrates wiring resistances of the fanout part corresponding to area A-A 'of FIG. 3.

Referring to FIG. 4, since the length of the fan-out wiring 331a varies depending on the position of the output terminal of the gate driving chip 401 connected thereto, the fan depends on the position of the output terminal of the gate driving chip 401. The resistance of the out wiring 331a also varies. That is, the resistance of the fan-out wiring 331a connected to the center output terminal of the gate driving chip 401 is the lowest, and the resistance of the fan-out wiring 331a connected to the output terminal of both ends of the gate driving chip 401 is the lowest. The resistance graph of the entire fan-out wiring 331a as a cursor is drawn in an inverse parabolic form.

Due to the difference in resistance of each region of the fanout wiring 331a, the driving signals having the same voltage level applied from the driving circuit, that is, the gate driving chip 401, have different voltage levels while passing through the fanout part 331. By changing to a drive signal to be applied to the unit pixel, different display images are output for the same image signal in the unit pixel. Therefore, the liquid crystal display according to the present exemplary embodiment prevents signal distortion in the fanout part 331 by applying a drive signal corrected in advance in consideration of the wiring resistance of the fanout part 331. The explanation is as follows.

The gate signal generator 410 receiving the gate control signal CONT1 from the signal controller 600 includes a gate on voltage Von and a gate off voltage Voff applied from the driving voltage generator 800. The one gate signal is output to the gate signal compensator 420. In this case, the first gate signal is a signal that does not take the wiring resistance characteristic of the fan out part 331 into consideration and has the same voltage level.

5 illustrates a gate signal output from the gate signal compensator according to the present embodiment.

The gate signal compensator 420 compensates for the first gate signal to generate a second gate signal as shown in FIG. 5, and sequentially applies the gate signal to each gate line G1 to Gn. In this case, the second gate signal is a signal compensated in consideration of the difference in wiring resistance for each region of the fanout unit 331. The second gate signal has a relatively high voltage level as it moves away from the center output terminal of the gate signal compensator 420. For example, the present embodiment has a voltage level of 23V at the center output terminal of the gate signal compensator 420 and a voltage level of 25V at both ends of the output terminal.

The second gate signal may be generated by adjusting the pulse width of the first gate signal by applying the first gate signal to a pulse width modulation circuit having a different duty ratio, or to a plurality of resistor circuits having different resistance values. It can be generated by applying a voltage drop of the first gate signal.

6 illustrates a gate signal output from the fanout unit according to the comparative example and the experimental example of the present embodiment, and (a) shows the voltage level of the gate signal output from the fanout unit according to the comparative example of the present embodiment. (B) shows the voltage level of the gate signal output from the fanout section according to the experimental example of this embodiment.

First, in FIG. 6A, gate signals V1 having horizontal lines having the same voltage level are output from the output terminal of the gate driver 400, and the gate signals V1 are inverse parabolic resistors. Distorted while passing through the fanout part 331 having a distribution, the final output gate signals V2 are output in a parabolic form with different voltage levels. In the conventional liquid crystal display, since the gate signal V2 for the same image signal is applied differently according to the position of the unit pixel, various screen defects may occur due to the difference in resistance of the fanout part 331.

On the other hand, in FIG. 6B, gate signals V1 having a voltage level compensated in an inverse parabolic form are output from an output terminal of the gate driver 400, and the gate signals V1 are inverse parabolic form. The compensated portion is canceled while passing through the fanout part 331 having a resistance distribution, so that the final output gate signals V2 are output in the form of a horizontal line having the same voltage level. In the liquid crystal display of the present exemplary embodiment, since the gate signal V2 is applied to the same image signal regardless of the position of the unit pixel, various screen defects are not generated due to the difference in resistance of the fanout part 331.

On the other hand, in the present embodiment has been described to solve the resistance deviation generated in the fan-out portion around the gate-side fan-out portion, it is possible to solve the resistance deviation generated in the data-side fan-out portion in this way, Its configuration and effects are the same, so it is omitted.

As mentioned above, although this invention was demonstrated with reference to the above-mentioned Example and an accompanying drawing, this invention is not limited to this, It is limited by the following claims. Therefore, it will be apparent to those skilled in the art that the present invention may be variously modified and modified without departing from the technical spirit of the following claims.

As described above, the present invention provides a resistance deviation of the fan-out part by applying a pre-compensated driving signal to offset the amount of change in the voltage level of the driving signal due to the resistance deviation in consideration of the resistance deviation of the fan-out part. Various screen defects caused due to this can be solved.

Claims (9)

A fan having a display unit having a unit pixel and a signal line connected to the unit pixel, a pad unit having a signal pad for connecting a driving circuit to the signal line, and a fan-out wiring connecting the signal line and the signal pad, respectively A liquid crystal display panel having an out portion; And a driving circuit for generating a driving signal necessary for the operation of the unit pixel and compensating the driving signal to have a voltage level proportional to the length of the fan-out wiring. The method according to claim 1, The drive circuit, A signal generator for generating a first driving signal required for the operation of the unit pixel and a signal for receiving the first driving signal and compensating to have a voltage level proportional to the length of the fan-out wiring and outputting it as a second driving signal. Liquid crystal display comprising a compensation unit. The method according to claim 2, The signal compensator, And a plurality of output terminals for outputting the second driving signal, and compensating for the voltage level of the output signal to increase from the center terminal to the both terminals of the plurality of output terminals. The method according to claim 3, And the signal compensator comprises a pulse width modulation circuit having a different duty ratio. The method according to claim 3, And the signal compensator comprises a plurality of resistor circuits having different resistance values. A signal generator which generates a first driving signal required for driving the liquid crystal display panel; A signal compensator configured to receive the first driving signal and generate a second driving signal; The signal compensator includes a plurality of output terminals for outputting the second driving signal, and compensates for the voltage level of the output signal to increase from the center terminal to the both terminals of the plurality of output terminals. Driving circuit. The method according to claim 6, And the first and second driving signals are at least one driving signal among a gate signal applied to a gate line of the liquid crystal display panel and a data signal applied to a data line of the liquid crystal display panel. The method according to claim 6, And the signal compensator comprises a pulse width modulation circuit having a different duty ratio. The method according to claim 6, And the signal compensator comprises a plurality of resistor circuits having different resistance values.

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