JPH07104705A - Driving circuit for liquid crystal device - Google Patents

Abstract

PURPOSE:To provide a driving circuit capable of using even with a combination in which the output level of a gamma correction and polarity inverter circuit 1 does not match with the input level of a source driver IC 2 and using by combining the best ICs in reference to the performance and the price. CONSTITUTION:In the driving circuit of a liquid crystal device inputting a picture signal being inverted in the polarity for every 1H to a source driver IC 2 through a gamma correction and polarity inverter circuit 1 and outputting it to the picture signal wiring of the liquid crystal device from the source driver IC 2, a level converting circuit 12 using a clamp circuit 7 for clamping the picture signal to be a constant level for every 1H is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive circuit for a liquid crystal device, and more particularly to a drive circuit for a liquid crystal device used in an active matrix type liquid crystal device or the like.

[0002]

2. Description of the Related Art As shown in FIG. 3, a drive circuit of a conventional liquid crystal device outputs an image signal R (red) output from an image signal generation circuit 41 in an image signal generation source 49 such as a personal computer.
The gamma correction / polarity inversion circuit 42 of the liquid crystal device 50 performs processing such as gamma correction to invert every 1H, and then the voltage level and the input level of the image signal output from the gamma correction / polarity inversion circuit 42 match. Source driver IC4
3 and the source driver IC 43 samples the image signal R at the timing of the three-phase clock B and outputs L
It was outputting to the CD module 44. The polarity inversion signal is supplied to the gamma correction / polarity inversion circuit 42 via the controller 46 to which the vertical synchronization signal and the horizontal synchronization signal are input, and the three-phase clock B is horizontally synchronized from the dot clock generation / phase alignment circuit 47. The clock B having the same phase as the signal is supplied to the source driver IC 43 via the controller 46.

On the other hand, the controller IC 46 outputs the vertical synchronizing signal and the horizontal synchronizing signal output from the image signal generating circuit 41.
Then, the controller IC 46 converts the serial data and the shift clock for scanning to the gate driver IC 48 and outputs the scanning signal to the LCD module 44 from the gate driver IC 48.

The drive circuit of the liquid crystal device shown in FIG.
For example, a drive circuit of a projector type liquid crystal device,
The image signal G (green) and the image signal B (blue) are sent to the liquid crystal devices for green and blue, respectively.

[0005]

However, in the drive circuit of the conventional liquid crystal device, the voltage level of the image signal R generated by the image signal generation circuit 41 is the same as that of the image signal generation circuit 4.
1 and the input level of the source driver 43 is determined by the source driver 43. Therefore, there is a problem that the source driver IC 43 having an input level that matches the output level of the gamma correction / polarity inversion circuit 42 must be selected. It was Therefore, when a commercially available general-purpose IC is used, the selection range of the gamma correction / polarity inversion circuit 42 and the source driver IC 43 is narrowed, and the best IC is selected and used in terms of frequency characteristics, other performance and price. There was a problem that I could not.

Further, in order to match the output level of the gamma correction / polarity inversion circuit 42 and the input level of the source driver IC 43, either one of the ICs may be customized, but if a custom IC is used, it is very high. It comes at a cost.

[0007]

The drive circuit for a liquid crystal device according to the present invention has been invented in view of the above problems of the prior art, and is characterized by gamma correction and polarity inversion. In the drive circuit of the liquid crystal device, in which the polarity-reversed image signal is input to the source driver IC through the circuit and is output from the source driver IC to the image signal wiring of the liquid crystal device, the gamma correction / polarity inversion circuit The point is that a level conversion circuit that converts a voltage level is provided between the source driver IC and the source driver IC by using a clamp circuit that clamps an image signal for each 1H.

[0008]

With the above-described structure, the output level of the gamma correction / polarity inversion circuit can be matched with the input level of the source driver IC in the level conversion circuit, and the input levels of the gamma correction / polarity inversion circuit and the source driver IC can be obtained. It is also possible to use a combination that does not match, and in terms of performance and price, the best IC can be selected and used in combination.

[0009]

Embodiments of the present invention will now be described in detail with reference to the accompanying drawings. FIG. 1 is a diagram showing an embodiment of a drive circuit according to the present invention. In the drive circuit of the present invention, the level conversion circuit 12 is provided between the gamma correction / polarity inversion circuit 1 and the source driver IC 2. This level conversion circuit 12
Is mainly composed of a DC cut capacitor 3, a buffer amplifier 4, and a clamp circuit 7. That is, the level conversion circuit 12 is a level conversion circuit using the clamp circuit 7.

The DC cut capacitor 3 is provided to extract only the amplitude of the video signal, that is, the AC component.

The buffer amplifier 4 is provided to prevent the output amplitude of the video signal from being attenuated. A noise-cutting capacitor 6 is placed in front of the buffer amplifier 4.
Is branched from the video signal line 5.

The clamp circuit 7 is mainly composed of an analog switch 8 and an amplifier circuit 9. Analog switch 8
Switches at a timing at which the video signal from which only the AC component is extracted should be clamped. The timing to be clamped is the blanking period of the video signal, which will be described later. The amplifier circuit 9 is configured so that the gain and the offset can be arbitrarily adjusted when the level signal is input. At that time, the video signal from which only the AC component is extracted is
A signal input from the amplifier circuit 9 to the analog switch 8 is converted to an arbitrary level and output to the source driver IC 2.

The operation of the drive circuit will be described with reference to the waveform chart shown in FIG. FIG. 2A shows the level conversion circuit 12
Video signal input to the, (b) clamp timing signal,
(C) is a level signal, and (d) is a video signal output from the level conversion circuit 12. The polarity of the video signal input is alternately inverted with blanking periods ab, cd, ef, gh, and ij sandwiched therebetween. That is, the blanking period a-
Based on b, ef, and ij, the blanking periods cd and gh are inversion.

A clamp timing signal is input to the analog switch 8 of FIG. 1 so that the switch 8 is turned on when the video signal input is in the blanking period. When the analog switch 8 is turned on, the potential of the blanking period of the video signal input via the analog switch 8 becomes the potential of the level signal input at that time. The level signal includes
A polarity reversal signal was used. The analog switch 8 is turned on so that the blanking period of the video signal is clamped every 1H by the clamp timing signal. Note that 1H is
Blanking start time (eg, c) at which polarity reverses from blanking start time (eg, a) of video signal input
Up to. Then, the potential of the clamped video signal in the blanking period is converted into the potential of the level signal. By changing the gain and offset of this level signal, the video signal output can be made to match the input level of the source driver IC2 regardless of the potential of the video signal input or the level of the video signal input inverted every 1H. You can For example, when it is desired to set the video signal output level to 1V-6V in FIG. 2, the level signal may be set to 1V-6V. However, although the polarity inversion signal is used as the level signal here, it is not necessary to use the polarity inversion signal, and any signal may be used as long as the signal can be converted to an arbitrary level.

[0015]

As described above, according to the drive circuit of the liquid crystal device of the present invention, the clamp circuit that clamps the image signal every 1H is used between the gamma correction / polarity inversion circuit and the source driver IC. Since a level conversion circuit for converting the voltage level is provided by using the combination, it is possible to use a combination in which the output level of the gamma correction / polarity inversion circuit does not match the input level of the source driver IC. The best IC can be selected and used in combination.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of a drive circuit of a liquid crystal device according to the present invention.

FIG. 2 is a waveform diagram of signals in a drive circuit of a liquid crystal device according to the present invention.

FIG. 3 is a drive circuit of a conventional liquid crystal device.

[Explanation of symbols]

1 ... Gamma correction / polarity inversion circuit, 2 ... Source driver IC, 3 ... DC cut capacitor, 4 ...
Buffer amplifier, 6 ... Noise cut capacitor, 7
... Clamp circuit, 8 ... Analog switch, 9 ...
..Amplification circuits, 12 ... Level conversion circuits

Claims (1)

[Claims] 1. A source driver IC which inputs an image signal whose polarity is inverted every 1H from an image signal generation circuit through a gamma correction / polarity inversion circuit, and the source driver I.
In the drive circuit of the liquid crystal device for outputting from C to the image signal wiring of the liquid crystal device, the voltage level is converted between the gamma correction / polarity inversion circuit and the source driver IC by using a clamp circuit for clamping the image signal every 1H. A drive circuit for a liquid crystal device, which is provided with a level conversion circuit for controlling.