KR100755560B1 - Reference voltage generator of liquid crystal display - Google Patents

Abstract

The present invention discloses a liquid crystal display device. According to an exemplary embodiment of the present invention, there is provided a liquid crystal display device comprising: a reference voltage compensator configured to control switching so that each reference voltage of a reference voltage divider may be kept the same by receiving a power supply voltage;

A reference voltage divider coupled in series between the reference voltage corrector and a ground voltage to uniformly distribute a plurality of reference voltages according to a voltage applied by the reference voltage corrector; And an output unit configured to transfer the reference voltage output from the reference voltage divider to a source driver, thereby applying the same reference voltage to the liquid crystal.

Description

Reference voltage generator for liquid crystal display device {Referent Voltage Generating Curcuit Of Liquid Crystal Display device}

1 is a block diagram showing a typical chip on glass type liquid crystal display device.

2 is a block diagram illustrating a process of outputting a reference voltage to the liquid crystal panel unit.

3 is a circuit diagram for explaining a conventional reference voltage generator.

4 is a circuit diagram illustrating a reference voltage generator according to the present invention.

5 is a circuit diagram for explaining a method of driving a switching device according to the present invention.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device including a reference voltage distribution unit for applying a reference voltage to a source driver unit when the liquid crystal display device is configured in a chip on glass method.

In general, a liquid crystal display device includes a liquid crystal panel unit which directly displays an image, a timing controller which receives an RGB digital data signal through an external signal, distributes data to a source driver IC, and controls a gate driver IC, and the timing controller A source driver unit converts the applied RGB digital data into analog data and outputs the data to a data line, and a gate driver unit applies a scan signal to drive the source driver unit to open a road.

Hereinafter, a liquid crystal display of a general chip on glass method will be described with reference to the accompanying drawings.

1 is a block diagram showing a general liquid crystal display device. As shown, the liquid crystal display according to the present invention includes a liquid crystal panel unit 100, a gate driver unit (not shown), a source driver unit 110, a reference voltage generator (not shown), and a timing controller 120. do.

The liquid crystal panel unit 100 is formed by injecting RGB liquid crystals between substrates in which a plurality of thin film transistors are vertically and horizontally disposed in a matrix shape, and the thin film transistors disposed on the same horizontal line share the same scan line and are disposed on the same vertical line. The thin film transistors are formed to share the same column line.

The reference voltage generator receives the power supply voltage and distributes the reference voltage of the RGB digital data signal to the reference voltage according to the voltage characteristics to apply the reference voltage to the source driver.

The timing controller 120 receives R, G, and B data signals, a vertical synchronization signal as a frame discrimination signal, a horizontal synchronization signal as a line discrimination signal, and other signals by external signals of the liquid crystal display, respectively. A digital signal for driving the gate driver 110 and an analog voltage AVDD used as a power supply voltage of the reference voltage generator are output.

In addition, the digital signal and the analog reference voltage AVDD generated by the timing controller 120 are connected to a plurality of source driver units 110 by an FPC (130 Flexible Printed Circuit).

The gate driver receives a gate clock signal and a vertical line signal from the timing controller 120 and receives an on / off voltage from a driving voltage generator (not shown) to sequentially sequence each pixel on the liquid crystal panel by one column. Scan.

The source driver 110 includes a plurality of source driver ICs 112 and includes a digital-to-analog converter and an output circuit, according to the RGB digital data signal applied by the timing controller 120. The digital-to-analog converter converts the analog voltage to an analog voltage based on the reference voltage applied from the voltage generator, and applies the output voltage amplified by the buffer amplifier (not shown) of the output circuit to the data line 114.

At this time, as the wiring becomes thinner and aggregated in the process of applying the reference voltage to each source driver IC 112, the wiring resistance increases and the impedance increases, so that the reference voltage applied to each source driver IC 112 becomes the wiring resistance. As a result, a problem occurs that is reduced.

Here, reference numeral AVDD denotes an analog power supply voltage applied by the timing controller 120, AVDD ₁ denotes a reference voltage of the first source driver Icy X1, and AVDD ₂ denotes a reference voltage of the second source driver Icy X2. Is the reference voltage of the nth source driver IC Xn. In addition, r ₁ represents wiring resistance from the timing controller 130 to X1 in the wiring for transmitting the reference voltage to each source driver IC, r ₂ represents wiring resistance from X1 to X2, and r _n represents Xn. Wiring resistance from -1 to Xn is shown.

In the above-described liquid crystal display device, when the reference voltage drop according to the wiring resistance is calculated, it is represented by Equation 1 below.

,

,

Wherein D ₁ is the reference voltage drop by r _1, D ₂ is r _1, the reference voltage drop by r _2, D _n is r _1, r _2, ... indicate the reference voltage drop by r _n.

As described above, the difference between the power supply voltage AVDD output from the timing controller 120 and the power supply voltage AVDD of the n-th source driver Icy Xn may indicate a difference in D_n due to the wiring resistance.

Referring to the drawings to describe in detail the effect of the reference voltage drop on the output voltage of the source driver unit 110 as follows.

2 is a block diagram illustrating a connection relationship between a reference voltage generator and the source driver unit 110. As illustrated, the source driver 110 may include a reference voltage generator 202 for generating a plurality of reference voltages based on the power voltage AVDD applied by the timing controller 120, and the reference voltage generator 202. The analog-to-analog converter 204 converts the digital data of the reference voltage and RGB applied to the analog voltage into an analog voltage, and the analog voltages OUT1 to OUT2 converted by the digital / analog converter 204 into data lines. It consists of an output circuit part 206 to apply.

Here, the reference voltage generator 202 related to the voltage drop will be described in more detail.

3 is a circuit diagram illustrating a conventional reference voltage generator 202.

As illustrated, the reference voltage generator 202 has a plurality of split resistance circuits R1 to R8 connected in series between the power voltage AVDD applied by the timing controller 120 and the ground terminal GND. The reference voltages GAMMA1 to GAMMA10 are generated between the resistors and the resistors.

The reference voltages GAMMA1 to GAMMA10 are determined according to the ratio of the plurality of resistors R1 to R8.

Here, since the plurality of resistors R1 to R8 are the same for each source driver IC, the difference in the reference voltages GAMMA1 to GAMMA10 is different depending on the difference in the reference voltage drops D_1 to D_n according to the wiring resistance in Equation 1. You lose.

That is, even though the same RGB digital data is input to the source driver IC 112, the source drive IC 112 is applied to the source drive IC 112 according to the reference voltage drop amounts D_1 to D_n corresponding to the wiring resistances r_1 to r_n. Since the reference voltage is changed, a difference occurs in the analog voltage value output to the liquid crystal.

The first reference voltage GAMMA1 of each source driver IC 112 according to the reference voltage drop amount is calculated as shown in Equation 2 below.

As shown in the above equation, a difference occurs in the first reference voltage GAMMA1 value corresponding to the reference voltage drop amounts D_1 to D_n according to the wiring resistances r_1 to r_n for each source driver IC 112, respectively. When the respective reference voltages are calculated in the above manner, the same ratio difference occurs in the remaining reference voltages GAMMA2 to GAMMA10. As a result, this phenomenon appears as a block phenomenon of the source driver eye time in the LCD.

In particular, in the chip on glass method in which the source driver IC 112 is mounted on the liquid crystal panel unit 100, since the application signal and the power line must be installed together with the liquid crystal panel unit, the power supply voltage AVDD. ), The wiring width increases, resulting in an increase in wiring resistance, which in turn causes a drop in the reference voltage.

That is, the reference voltage is not applied to the data line at regular intervals due to the difference in the voltage drop supplied to the source driver IC, which causes difficulty in displaying a delicate image.

Accordingly, the present invention has been made to solve the above-mentioned conventional problems, and includes a reference voltage compensator between the first reference voltage of the reference voltage generator and the power supply voltage AVDD, thereby providing the same reference voltage at each source driver IC. It is to provide a liquid crystal display device to be supplied.

In order to achieve the above object, the present invention provides a reference voltage generator for supplying a reference voltage, which is a reference for an RGB digital data signal, to a plurality of source drivers by receiving a power supply voltage. A reference voltage corrector for outputting a switching voltage adjusted to maintain the same voltage; A reference voltage divider coupled in series between the reference voltage corrector and a ground voltage to uniformly distribute the correction voltage to a reference voltage; And an output unit configured to transfer the reference voltage output from the reference voltage divider to the source driver, wherein the reference voltage corrector is disposed between the power supply voltage and the reference voltage divider, and a plurality of resistors are connected in parallel. Each of the plurality of resistors is characterized in that the switching element for controlling the on / off is coupled in series.

Hereinafter, described in detail with reference to the accompanying drawings.

4 is a circuit diagram illustrating a reference voltage generator according to the present invention. As shown, the reference voltage generator includes a reference voltage corrector 420 and a reference voltage divider 440.

The reference voltage corrector 420 is connected between the power supply voltage and the first reference voltage, and a plurality of resistors R0, Ra, Rb, Rc..Rn are connected in parallel, except for the first resistor R0. Switching elements SW1 to SWn connected in series to a plurality of resistors Ra, Rb, and Rc..Rn are respectively connected.

 The switching elements SW1 to SWn are configured to be controlled on / off from the outside. Here, reference numeral I is a total current flowing through the reference voltage generating circuit when the power supply voltage AVDD is applied, and reference numeral Va is a voltage flowing through the reference voltage corrector 420.

이고, 이때 제1감마전압은

이므로, 상기 전압강하량을 보상하기 위해선 결국, 제 1기준전압(GAMMA1)에 흐르는 전압은

이 되어야 한다.When the method according to the present invention is described in comparison with Equation 1 and Equation 2, the analog voltage drop amount of the Xn-th source driver Icy when the reference voltage corrector 420 is not present

Where the first gamma voltage is

In order to compensate for the voltage drop, the voltage flowing in the first reference voltage GAMMA1 is eventually

Should be

Therefore, in order to eliminate the voltage drop amount D_n flowing in the first gamma voltage GAMMA1, the value of Va of the reference voltage corrector 420 is equal to the value of D_n and the sign is reversed. At this time, the switching elements other than R0 are turned off.

Since Va = R0 * I, adjustment can be made by appropriately setting the resistor R0.

이므로, 이때 제1 기준전압은

이므로 ,

이 되어 회로의 제 1기준전압에 흐르는 전압강하량 D_2를 없애기 위해서는 결국 D_2=Va가 되어야 한다. 그러므로 상기 기준 전압 보정부(420)의 Ra저항을 온(ON)시킨후 Ra값을 조절한다. 이때 상기 기준 전압 보정부(420)에 흐르는 전압은Va=(R0*Ra)/(R0+Ra))*I가된다. 상기 식에서 R0저항 값은 앞서 계산한 상기 X_n번째 소오스 드라이브 아이시에서 정해진 저항값이다.Next, for the source driver IC of X2, the reference voltage drop is

In this case, the first reference voltage is

Because of ,

Thus, in order to eliminate the voltage drop amount D_2 flowing to the first reference voltage of the circuit, it should be D_2 = Va. Therefore, after the Ra resistance of the reference voltage corrector 420 is turned on, the Ra value is adjusted. At this time, the voltage flowing through the reference voltage corrector 420 becomes Va = (R0 * Ra) / (R0 + Ra)) * I. In the above formula, the R0 resistance value is a resistance value determined in the X_n-th source drive IC.

As described above, the reference voltage value can be configured to be constant by sequentially turning on / off the switching element for each source driver IC. At this time, the on / off control of the switching element is configured to be selected from the outside.

5 is a circuit diagram for explaining the switching circuit. As shown in the drawing, when three switching circuits are installed to turn on / off one by one, two input signal terminals A and B are used to control SW1 with one OR gate OR1 and one AND gate. The AND1 and one OR gate OR2 are connected in parallel with the input signal to adjust the SW2 signal, and similarly, the one AND gate AND2 is connected in parallel with the input signal to adjust the SW3 signal. As described above, if the input signal of A and B is applied according to the input signal after connecting the circuit, the truth table shown in Table 1 can be obtained.

Table 1

On the other hand, when the switching element is further extended according to the number of source driver ICs, the ora and end gates of FIG. 5 may be appropriately increased.

As described above, according to the reference voltage generator of the liquid crystal display device according to the present invention, when the liquid crystal display device is configured as a chip on glass type, the source voltage drop due to the wiring resistance causes a difference in source. When a difference in the reference voltage level input to the driver is generated, the reference voltage compensator provided in the reference voltage generator can output the same level of the reference voltage to the liquid crystal cell, so that a smooth image can be displayed and a clean image can be obtained. It can be effective.

On the other hand, the present invention is not limited to the above-described specific preferred embodiment, and any person having ordinary skill in the art to which the invention pertains can make various changes without departing from the gist of the invention claimed in the claims. something to do.

Claims (3)

delete In a reference voltage generator for supplying a reference voltage, which is a reference of an RGB digital data signal, to a plurality of source drivers by receiving a power supply voltage: A reference voltage corrector configured to receive a power supply voltage and output a correction voltage that is switched and adjusted so that the reference voltage supplied to the source driver is maintained the same; A reference voltage divider coupled in series between the reference voltage corrector and a ground voltage to uniformly distribute the correction voltage to a reference voltage; And An output unit which transfers the reference voltage output from the reference voltage divider to the source driver, The reference voltage corrector is disposed between the power supply voltage and the reference voltage divider, a plurality of resistors are connected in parallel, and each of the plurality of resistors has a switching element for controlling on / off in series. Reference voltage generator of the liquid crystal display device characterized in that. The method of claim 1, And the reference voltage divider comprises a plurality of split resistor circuits and is connected between the reference voltage corrector and a ground terminal.

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