JP2002236476A - Liquid crystal driving device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal display device in which the image persistence of a liquid crystal display panel and luminous dot stains or the like are not generated even when a signal jam is generated in the device. SOLUTION: In this liquid crystal display device, the center levels of input signals are set at the center of the dynamic range of a buffer circuit 5 by using a bias adjusting circuit 4, and the average value of the voltage to be applied to the liquid crystal display panel 10 is set at the center of the operation of the panel 10 by using a common voltage adjusting circuit 8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal driving circuit having a dynamic range narrower than a range obtained by adding a dynamic range of a video signal to a variable adjustment range of the video signal. The present invention relates to a liquid crystal display device that displays an image by driving a liquid crystal panel having electrodes.

[0002]

2. Description of the Related Art Conventionally, a thin film transistor (TFT:
Active matrix type liquid crystal display device (LCD: Liq) using Thin Film Transistor as a switching element
A flat display using a liquid crystal display panel (TFT-LCD) formed by a uid crystal device has been developed.

[0003] This type of liquid crystal display panel (TFT-LC
D) is a TF in which the pixel electrode of the liquid crystal 100 is connected to the drain as shown in FIG.
T101 is provided. The gate of the TFT 101 is connected to the scanning electrode, and the source is connected to the signal electrode. Also,
Also, 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, thereby holding the signal voltage during the OFF period of the TFT 101. The characteristics are improved.

In general, when a liquid crystal panel is applied to liquid crystal for a long time even with a slight DC shift,
Since the image quality of the displayed image is remarkably deteriorated due to the occurrence of burn-in, white spots, etc., for example, as shown in FIG. Being driven.

Conventionally, the above-mentioned liquid crystal driving circuit has been provided as an integrated circuit manufactured by an existing semiconductor manufacturing process. However, since the operating voltage is low and a sufficient dynamic range cannot be ensured, the liquid crystal driving circuit is actually used. In order to prevent the liquid crystal driving voltage from being saturated, a common voltage _VCOM whose polarity is inverted every field is applied to the counter electrode side. For example, the signal of deep black level _{5V PP,} the adjustment range of the luminance level as _{4V PP,} so as to apply a common voltage _{V COM} of _{6V PP,} not drive the liquid crystal display panel dynamic range by the liquid crystal drive circuit 9V Was.

[0006]

As described above, when a liquid crystal display panel is applied for a long period of time even with a slight DC shift, the liquid crystal display panel generates image sticking, white spots, etc. Is significantly reduced.

Therefore, conventionally, in a liquid crystal display device in which a liquid crystal display panel is AC-driven by a liquid crystal driving circuit having a dynamic range narrower than a range obtained by adding the dynamic range of the input signal to the variable adjustment range of the input signal, the common electrode side common electrode An AC voltage was applied to the electrode pattern so that the liquid crystal applied voltage applied to the liquid crystal display panel did not become dull.However, considering the redundancy and aperture ratio improvement for bright spot correction measures, the above common voltage pattern Need to be removed. However, if the common electrode pattern is deleted, the AC voltage cannot be applied from the counter electrode side, and the driving voltage must be increased, and an integrated circuit with a high withstand voltage process is required.

The present invention has been proposed in view of such a situation, and a liquid crystal drive circuit having a dynamic range narrower than a range obtained by adding a dynamic range of the input signal to a variable adjustment range of the input signal. An object of the present invention is to provide a liquid crystal display device that drives a display panel with alternating current so that an image with good image quality can be displayed over a long period of time. An object of the present invention is to provide a liquid crystal display device that does not cause spots or the like.

[0009]

In order to achieve the above object, the present invention provides a liquid crystal driving circuit having a dynamic range narrower than a range obtained by adding a dynamic range of a video signal to a variable adjustment range of the video signal. In a liquid crystal display device that displays a video by driving a liquid crystal panel having a counter electrode provided to face a pixel electrode, the liquid crystal drive circuit inverts the video signal at a predetermined cycle around a predetermined potential. A signal inverting circuit for converting the signal into an inverted AC signal,
A first adjusting unit that adjusts a DC level of the inverted AC signal output from the signal inverting circuit; and a second adjusting unit that adjusts a potential of the counter electrode of the liquid crystal panel. The center level of the inverted AC signal is set at the center of the dynamic range of the liquid crystal drive circuit by the adjusting means, and the potential of the counter electrode is adjusted by the first adjusting means by the second adjusting means. The average value of the liquid crystal applied voltage applied to the liquid crystal panel based on the inverted AC signal is adjusted.

[0010] In the liquid crystal display device according to the present invention, the liquid crystal drive circuit further includes an amplifier circuit for amplifying the inverted AC signal adjusted by the first adjusting means to apply power to the liquid crystal panel. The dynamic range of the liquid crystal drive circuit can be the dynamic range of the amplifier circuit.

[0011]

Embodiments of the present invention will be described below in detail with reference to the drawings.

The liquid crystal display device according to the present invention is, for example, shown in FIG.
It is configured as shown in FIG.

The liquid crystal display device shown in FIG. 1 is one in which the present invention is applied to a flat display for performing color display by a liquid crystal panel 10, and includes a video signal processing circuit 1, a timing controller 2, an inversion driver 3, and a bias adjustment circuit 4. , Buffer circuit 5, X (horizontal) driver 6, Y
(Vertical direction) It comprises a driver 7, a common voltage adjusting circuit 8, and the like.

The video signal processing circuit 1 separates a synchronizing signal Sync of an input video signal (composite color video signal) and converts the input video signal into component video signals R, G, and B. This video signal processing circuit 1
Is supplied to the timing controller 2. The component video signals R, G, and B are output from the inversion driver 3
Supplied to The 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. Further, the timing controller 2
Inversion control pulse FRP synchronized with the synchronization signal Sync
And supplies it to the inversion driver 3.

The inversion driver 3 performs a polarity inversion operation according to the inversion control pulse FRP, and outputs the component video signals R and R supplied from the video signal processing circuit 1.
For G and B, the polarity is reversed for each line,
Inverted video signal R / I whose polarity is inverted for each field
R, G / IG and B / IB are formed. Inverted video signals R / IR, G / IG,
B / IB is supplied from the bias adjustment circuit 4 to the X driver 6 via the buffer circuit 5.

The bias adjustment circuit 4 includes inverted video signals R / IR and G / I supplied from the inversion driver 3.
Level setting units 41 and 4 for G and B / IB, respectively.
Each DC biasing voltage _V DCR set by _2,43, V _DCG, the _{V DCB} adder 44,45,4
Add by 6. Then, each of the adders 44, 45,
The added output signals R ′ / IR ′, G ′ /
IG ′, B ′ / IB ′ are supplied to the X driver 6 via the buffer circuit 5.

In the bias adjustment circuit 4, each of the DC bias voltages V _DCR , V _DCG , V set by the level setting units 41, 42, 43, respectively.
_DCB is the sum output signal R '/ IR', G '/ IG',
The center level of B '/ IB' is set to coincide with the center of the dynamic range of the buffer circuit 5.

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

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

The Y driver 7 is provided with a horizontal driving clock YC supplied from the timing controller 2.
It operates based on L and the start pulse STY, and outputs a drive pulse for scanning the liquid crystal display panel 10 line-sequentially to the scan electrode terminals Y _{1 to} Y _n of the liquid crystal display panel 10 in parallel.

[0022] The liquid crystal display panel 10 includes a thin film transistor (TFT: Thin Film Transistor) liquid crystal display device of the active matrix system using a switching element: is formed by (LCD Liquid Crystal Device), the signal electrode terminal X ₁ X driver 6 to _Xn
There are connected, also, the Y driver 7 is connected to the scanning electrode terminals Y ₁ to Y _n, Furthermore, the counter electrode terminal Z
Is connected to the common voltage adjusting circuit 8.

The common voltage adjusting circuit 8 is connected to the liquid crystal display.
Voltage V applied to the counter electrode terminal Z of the display panel 10
_COMThe voltage setting device 80 adjusts Above common
Voltage V_COMIs the liquid crystal display by the X driver 6.
Signal electrode terminal X of panel 10 ₁~ X_nThrough TFT
The average value of the liquid crystal applied voltage applied to the LCD is
The common voltage is set so as to be the operation center of the display panel 10.
It is set by the adjustment circuit 8.

The liquid crystal display panel 10 has a structure shown in FIG.
As shown in (1), the aperture ratio is improved by connecting the Cs electrode 11 to the gate line, and the bright spot correction is performed by cutting the bridge portion 12 of the Cs electrode 11 for the pixel where the Cs leak failure has occurred. It has a structure that allows it to be performed. The liquid crystal display panel 10 is illuminated by a fluorescent tube 14 driven by a backlight power supply 13.

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

From the state (A in FIG. 3) of the image quality optimum operating point with respect to the voltage-light transmission characteristic of the liquid crystal display panel 10 as shown in FIG. FIG. 3B shows that when the luminance level is lowered, the saturation of the inverted video signals R / IR, G / IG, and B / IB becomes asymmetric due to the shortage of the dynamic range D of the buffer circuit 5. Although the DC shift ΔV is generated as described above, the bias adjustment in the bias adjustment circuit 4 causes the saturated states of the inverted video signals R / IR, G / IG, and B / IB to be symmetrical as shown in FIG. As a state, the DC shift ΔV can be made zero.

Then, in this state, the average value of the liquid crystal applied voltage applied to the LCD from the signal electrode terminals X _{1 to Xn of the} liquid crystal display panel 10 via the TFT by the X driver 6 is calculated. By setting the common voltage adjustment circuit 8 so that it becomes the operation center,
Due to the shortage of the dynamic range D of the buffer circuit 5, the inverted video signals R / IR, G / IG, B / IB
Even when is saturated, the liquid crystal display panel 10 can display an image with good image quality over a long period of time without causing the liquid crystal display panel 10 to burn or white spots.

Here, in the above-described embodiment, the bias adjustment circuit 4 provided before the buffer circuit 5 for driving the liquid crystal is provided.
, The inverted video signals R / IR, G / IG, B / I
The center level of B is set to match the center of the dynamic range of the buffer circuit 5 for adjusting the center level.
The voltage regulator 5 is connected to the power supply line of the buffer amplifier 51 (52, 53) constituting the buffer circuit 5 as shown in FIG.
4, 55 may be provided to adjust the dynamic range, that is, the saturation level. In this case, by adjusting the voltage regulator 54 of the power supply line having the margin of the dynamic range, as shown in FIG.
The center of the dynamic range of the buffer circuit 5 can be set to match the center level of the inverted video signals R / IR, G / IG, B / IB.

[0029]

As described above, in the liquid crystal driving device according to the present invention, a signal inverting circuit that inverts the video signal at a predetermined cycle around a predetermined potential to obtain an inverted AC signal;
A liquid crystal drive circuit comprising: first adjusting means for adjusting the DC level of the inverted AC signal output from the signal inverting circuit; and second adjusting means for adjusting the potential of the counter electrode of the liquid crystal panel. The first adjusting means sets the center level of the inverted AC signal to the center of the dynamic range of the liquid crystal driving circuit, and the second adjusting means sets the potential of the counter electrode to the first level.
Is adjusted to the average value of the liquid crystal applied voltage applied to the liquid crystal panel based on the inverted AC signal adjusted by the adjusting means, so that it is narrower than the range obtained by adding the dynamic range of the video signal to the variable adjustment range of the video signal. By using a liquid crystal drive circuit with a dynamic range, even if the signal is saturated, the liquid crystal display panel does not suffer from burning, white spots, and the like. Image display can be performed.

[Brief description of the drawings]

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

FIG. 2 is a diagram for explaining a structure of a liquid crystal display panel in the liquid crystal display device shown in FIG.

FIG. 3 is a diagram provided for describing an operation of the liquid crystal display device illustrated in FIG. 1;

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

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

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

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

[Explanation of symbols]

1 video signal processing circuit, 2 timing controller,
3 inversion 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

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G09G 3/20 670 G09G 3/20 670K

Claims (2)

[Claims] 1. A liquid crystal panel having a counter electrode provided to face a pixel electrode by a liquid crystal drive circuit having a dynamic range narrower than a range obtained by adding a dynamic range of the video signal to a variable adjustment range of the video signal. In a liquid crystal display device that drives and displays an image, the liquid crystal drive circuit includes: a signal inversion circuit that inverts the video signal at a predetermined cycle around a predetermined potential to generate an inverted AC signal; A first adjusting unit that adjusts a DC level of the output inverted AC signal; and a second adjusting unit that adjusts a potential of the counter electrode of the liquid crystal panel. The center level of the inverted AC signal is set at the center of the dynamic range of the liquid crystal drive circuit, and the potential of the counter electrode is adjusted by the second adjusting means. The liquid crystal display device, characterized in that to match the average value of the liquid crystal application voltage to be applied to the liquid crystal panel based on the inverted AC signal adjusted by the first adjusting means. 2. The liquid crystal drive circuit further includes an amplifier circuit for amplifying the inverted AC signal adjusted by the first adjustment means and for applying the inverted AC signal to the liquid crystal panel. The dynamic range of the liquid crystal drive circuit is 2. The liquid crystal display device according to claim 1, wherein the dynamic range is the dynamic range of the amplifier circuit.