JPH04299387A - Liquid crystal driving device - Google Patents

Abstract

PURPOSE:To make an image display of good picture quality for a long period by setting the center level of an input signal to the center of the dynamic range of a liquid crystal driving circuit. CONSTITUTION:A bias adjusting circuit 4 sets the center level of the input signal to the center of the dynamic range of a buffer circuit 5 and a common voltage adjusting circuit 8 sets the mean value of a liquid crystal applied voltage applied to a liquid crystal display panel 10 to the operation center of the liquid crystal display panel 10. The liquid crystal display panel 10 is driven by the liquid crystal driving circuit whose dynamic range is narrower than the range obtained by adding the dynamic range of the input signal to the variable adjustment range of the input signal. Even if the signal enters a saturation state, neither the burning nor white spot generation of the liquid crystal panel 10 is caused the liquid crystal display panel 10 displays an image of good picture quality for a long period.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal drive device for driving a liquid crystal display panel using a liquid crystal drive circuit having a dynamic range narrower than the sum of the variable adjustment range of an input signal and the dynamic range of the input signal.

0002

[Prior Art] Conventionally, thin film transistors (TFTs)
Liquid Crystal D
liquid crystal display panel (TFT-
Flat displays using LCDs have been developed.

[0003] This type of liquid crystal display panel (TFT-LCD)
) is the equivalent circuit for one pixel as shown in Figure 5.
TFT 1 whose drain is connected to the pixel electrode of the liquid crystal 100
01, the gate of the TFT 101 is connected to the scanning electrode, and the source is connected to the signal electrode. Furthermore, as shown in FIG. 6, a storage electrode pattern 103 connected to the counter electrode pattern 102 of the liquid crystal 100 is provided, and a storage capacitor Cs is connected in parallel to the liquid crystal 100, so that the signal during the off period of the TFT 101 is It is designed to improve voltage holding characteristics.

[0004] In general, in liquid crystal panels, even a slight DC shift is applied to the liquid crystal for a long time.
Since burn-in, white spots, etc. occur and the quality of the displayed image deteriorates significantly, for example, as shown in FIG. being driven.

Conventionally, the above-mentioned liquid crystal drive circuit has been provided as an integrated circuit manufactured by an existing semiconductor manufacturing process, but its operating voltage is low and it is not possible to secure a sufficient dynamic range, so it is difficult to use in actual use. In order to prevent the liquid crystal drive voltage from becoming saturated, a common voltage VCOM whose polarity is inverted every field is applied to the counter electrode side.

For example, a liquid crystal display panel was driven by a liquid crystal drive circuit with a dynamic range of 9V by applying a common voltage VCOM of 6VPP with the black level of the signal set to 5VPP and the adjustment range of the brightness level set to 4VPP. .

[0007]

[Problems to be Solved by the Invention] As mentioned above, when even a slight DC shift is applied to a liquid crystal display panel for a long period of time, burn-in, white spots, etc. occur, and the quality of the displayed image deteriorates. There is a problem that there is a significant decrease in

[0008] Conventionally, therefore, in a liquid crystal drive device that AC drives a liquid crystal display panel using a liquid crystal drive circuit with a dynamic range narrower than the dynamic range of the input signal added to the variable adjustment range of the input signal, AC voltage was applied to the common electrode pattern to prevent the liquid crystal voltage applied to the liquid crystal display panel from becoming dull, but in consideration of redundancy for bright spot correction and improvement of the aperture ratio, the above common electrode pattern need to be deleted. However, if the common electrode pattern is deleted, it becomes impossible to apply an alternating current voltage from the opposing electrode side, and the driving voltage must be increased, which requires an integrated circuit with a high withstand voltage process.

The present invention has been proposed in view of the above-mentioned circumstances. The purpose of the LCD drive device, which drives the display panel with alternating current, is to display images with good image quality over a long period of time. An object of the present invention is to provide a liquid crystal driving device that does not generate stains or the like.

0010

[Means for Solving the Problems] In order to achieve the above-mentioned object, the present invention provides a liquid crystal drive circuit that uses a liquid crystal drive circuit having a dynamic range narrower than the sum of the variable adjustment range of an input signal and the dynamic range of the input signal. In a liquid crystal driving device for driving a display panel, a first adjustment means for setting a center level of the input signal to the center of a dynamic range of the liquid crystal driving circuit, and a first adjusting means for setting the center level of the input signal to the center of the dynamic range of the liquid crystal driving circuit, and a first adjusting means for setting the center level of the input signal to the center of the dynamic range of the liquid crystal driving circuit, and applying the input signal to the liquid crystal display panel by the liquid crystal driving circuit. The present invention is characterized in that a second adjustment means is provided for setting the average value of the voltage applied to the liquid crystal at the center of operation of the liquid crystal display panel.

[0011]

[Operation] In the liquid crystal driving device according to the present invention, the first adjusting means sets the center level of the input signal to the center of the dynamic range of the liquid crystal driving circuit, and also adjusts the average value of the liquid crystal applied voltage applied to the liquid crystal display panel. A second adjustment means sets the operation center of the liquid crystal display panel, and the liquid crystal display panel is controlled by a liquid crystal drive circuit having a dynamic range narrower than the variable adjustment range of the input signal plus the dynamic range of the input signal. drive

0012

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a liquid crystal driving device according to the present invention will be described in detail below with reference to the drawings.

The liquid crystal driving device according to the present invention is illustrated in FIG. 1, for example.
It is configured as shown in . The liquid crystal drive device shown in FIG. 1 is one in which the present invention is applied to a flat display that displays color using a liquid crystal display panel 10, and includes a video signal processing circuit 1, a timing control controller 2, and an inversion driver 3.
, a bias adjustment circuit 4, a buffer circuit 5, an X (horizontal direction) driver 6, a Y (vertical direction) driver 7, a common voltage adjustment circuit 8, and the like.

The video signal processing circuit 1 separates a synchronization signal Sync from an input video signal (composite color video signal) and converts the input video signal into component video signals R, G, B. This video signal processing circuit 1
The synchronization signal Sync obtained is supplied to the timing control controller 2. Further, the component video signals R, G, B are transmitted to the inverting driver 3.
supplied to Note that this video signal processing circuit 1 is provided with a brightness level adjuster 9.

The timing controller 2 forms a horizontal drive clock XCL and a start pulse STX synchronized with the synchronization signal Sync and supplies them to the X driver 6. Further, the timing controller 2 forms a vertical drive clock YCL and a start pulse STY synchronized with the synchronization signal Sync, and supplies them to the Y driver 7. Furthermore, this timing controller 2
Inversion control pulse FRP synchronized with the above synchronization signal Sync
is formed and supplied to the inversion driver 3.

The inversion driver 3 performs a polarity inversion operation according to the inversion control pulse FRP, and converts the component video signals R,
For G and B, the polarity is reversed for each line, and
Inverted video signal R/IR whose polarity is inverted every field
, G/IG, B/IB. This reversing driver 3
Inverted video signals R/IR, G/IG, B obtained by
/IB is from the bias adjustment circuit 4 to the buffer circuit 5.
The signal is supplied to the X driver 6 via.

The bias adjustment circuit 4 receives inverted video signals R/IR and G/I supplied from the inverted driver 3.
Level setters 41 and 4 for G and B/IB, respectively.
Each DC bias voltage VDCR set by 2 and 43
, VDCG, VDCB to adders 44, 45, 46
Add by. And each addition adder 44, 45, 4
The addition output signals R'/IR', G'/I obtained by 6
G', B'/IB' are supplied to the X driver 6 via the buffer circuit 5.

In the bias adjustment circuit 4, each DC bias voltage VDCR, VDCG, VDCB set by the level setters 41, 42, 43
are the addition output signals R'/IR', G'/IG', B'
The center level of /IB' is set to match the center of the dynamic range of the buffer circuit 5.

The buffer circuit 5 includes buffer amplifiers 51, 52, and 53 for driving a liquid crystal with a dynamic range of, for example, 9V.

The X driver 6 operates based on the horizontal drive clock XCL and start pulse STX supplied from the timing controller 2, and receives the inverted video signals R/IR, G/ IG, B/IB, that is, the addition output signals R'/IR', G'/IG', B'/IB' are applied to the signal electrode terminals X1 of the liquid crystal display panel 10 one line at a time.
~Xn is output in parallel.

The Y driver 7 also receives a horizontal drive clock YC supplied from the timing controller 2.
It operates based on L and start pulse STY, and outputs driving pulses for scanning the liquid crystal display panel 10 line-sequentially to the scanning electrode terminals Y1 to Yn of the liquid crystal display panel 10 in parallel.

The liquid crystal display panel 10 includes a thin film transistor (TFT).
An active matrix type liquid crystal display element (LCD: Liquid C
crystal device),
The X driver 6 is connected to the signal electrode terminals X1 to Xn, the Y driver 7 is connected to the scanning electrode terminals Y1 to Yn, and the common voltage adjustment circuit 8 is connected to the counter electrode terminal Z. has been done.

The common voltage adjustment circuit 8 adjusts the common voltage V applied to the counter electrode terminal Z of the liquid crystal display panel 10.
It consists of a voltage setting device 80 that adjusts COM. The common voltage VCOM is applied from the signal electrode terminals X1 to Xn of the liquid crystal display panel 10 by the X driver 6 to TF
The common voltage adjustment circuit 8 sets the average value of the liquid crystal applied voltage applied to the LCD via T to be the center of operation of the liquid crystal display panel 10.

[0024] This liquid crystal display panel 10 is shown in FIG.
As shown in FIG. 2, the aperture ratio is improved by connecting the Cs electrode 11 to the gate line, and bright spot correction is achieved by cutting the bridge portion 12 of the Cs electrode 11 in pixels where a Cs leakage defect has occurred. A structure that allows this to be carried out is used. Further, the liquid crystal display panel 10 is illuminated by fluorescent tubes 14 driven by a backlight power source 13.

In the liquid crystal drive device having such a configuration, each pixel of the liquid crystal display panel 10 is scanned line-by-line by the Y driver 7. Then, the inverted video signals R/IR, G whose polarity is inverted every line formed by the inversion driver 3 and whose polarity is inverted every field.
/IG, B/IB, each pixel of the liquid crystal display panel 10 is AC driven by the X driver 6, and an image is displayed according to the input video signal VIN.

From the image quality optimum operating point state (A in FIG. 3) for the voltage-light transmission characteristics of the liquid crystal display panel 10 as shown in FIG. When the brightness level is lowered, the saturation states of the inverted video signals R/IR, G/IG, and B/IB become asymmetrical due to the insufficient dynamic range D of the buffer circuit 5, as shown in FIG. 3B. However, as shown in FIG. As a state, the DC shift ΔV can be made zero.

In this state, the signal electrode terminals X1 to Xn of the liquid crystal display panel 10 are connected by the X driver 6.
By setting the common voltage adjustment circuit 8 so that the average value of the liquid crystal applied voltage applied to the LCD via the TFT becomes the center of operation of the liquid crystal display panel 10, the dynamic range D of the buffer circuit 5 can be adjusted. Due to the shortage, the above inverted video signals R/IR, G/IG, B/
Even when the IB reaches a saturated state, the liquid crystal display panel 10 does not suffer from burn-in, white spots, etc., and the liquid crystal display panel 10 can display images with good image quality for a long period of time. .

In the above embodiment, the center level of the inverted video signals R/IR, G/IG, and B/IB is adjusted by the bias adjustment circuit 4 provided before the liquid crystal buffer circuit 5. The buffer amplifier 5 configuring the buffer circuit 5 is set to coincide with the center of the dynamic range of the buffer circuit 5, as shown in FIG.
1 (52, 53) power supply line with voltage regulators 54, 55
may be provided to adjust the dynamic range, that is, the saturation level. In this case, as shown in FIG. It can be set to match the center level of /IR, G/IG, and B/IB.

[0029]

As described above, in the liquid crystal driving device according to the present invention, the center level of the input signal is set at the center of the dynamic range of the liquid crystal driving circuit by the first adjusting means, and the input signal is applied to the liquid crystal display panel. The average value of the voltage applied to the liquid crystal is set as the center of operation of the liquid crystal display panel by a second adjustment means, and the liquid crystal is driven with a dynamic range narrower than the range obtained by adding the dynamic range of the input signal to the variable adjustment range of the input signal. The circuit drives the LCD panel with AC, so even if the signal reaches saturation, there will be no burn-in or white spots on the LCD panel.
The liquid crystal display panel can display images with good quality over a long period of time.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a liquid crystal driving device according to the present invention.

FIG. 2 is a diagram illustrating the structure of a liquid crystal display panel driven by the liquid crystal driving device shown in FIG. 1;

FIG. 3 is a diagram for explaining the operation of the liquid crystal driving device shown in FIG. 1;

FIG. 4 is a main circuit diagram showing the configuration of another embodiment of the liquid crystal driving device according to the present invention.

FIG. 5 is an equivalent circuit diagram showing the configuration of one pixel of an active matrix liquid crystal display panel.

FIG. 6 is a diagram for explaining a storage electrode pattern in a conventional active matrix liquid crystal display panel.

FIG. 7 is a diagram for explaining AC drive operation in a conventional active matrix liquid crystal display panel.

[Explanation of symbols]

1...Video signal processing circuit 2...Timing controller 3...
Inverting driver 4...Bias adjustment circuit 5...Buffer circuit 6...X driver 7...Y driver 8...Common voltage adjustment circuit 10...Liquid crystal display panel 54, 55...Voltage regulator

Claims (1)

[Claims] 1. A liquid crystal drive device that AC drives a liquid crystal display panel by a liquid crystal drive circuit with a dynamic range narrower than the sum of the variable adjustment range of the input signal and the dynamic range of the input signal, wherein the center level of the input signal is a first adjusting means for setting the voltage at the center of the dynamic range of the liquid crystal drive circuit; and a first adjusting means for setting the average value of the liquid crystal applied voltage applied to the liquid crystal display panel by the liquid crystal drive circuit to the center of the operation of the liquid crystal display panel. A liquid crystal driving device characterized in that it is provided with a second adjusting means for adjusting the amount of the liquid crystal.