JPH08202314A - Full color liquid crystal driving device - Google Patents

Abstract

PURPOSE: To easily drive a liquid crystal element having many numbers of pixels of a horizontal direction and a video signal having a high frequency by providing a shift register, a sample-hold circuit and a voltage output circuit in a liquid crystal driving circuit. CONSTITUTION: A liquid crystal driving circuit 7 is constituted of a shift register 1 generating x lines of sampling pulses (SMP1 to SMPx), a sample-hold circuit 2 sampling video signals of respective colors respectively to output them and a voltage output circuit 3 supplying powers for driving respective pixels of a liquid crystal display element 4. Then, voltages of video signals of three colors are sampled simultaneously by the circuit 2 every time when pulses SMP1 to SMPx are inputted and the circuit 2 holds sampled voltages by numbers of sampling pules with respect to respective three colors. Thus, this circuit can be operated equally to the case of using circuit elements having a triple operating speed even though the operating speed of circuit elements consisting of the circuit 2 and the shift register 1 is the same as that of a conventional circuit.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a full color liquid crystal driving device, and more particularly to a full color liquid crystal driving device for driving an active matrix type liquid crystal display element.

[0002]

2. Description of the Related Art Liquid crystal display devices for displaying color images are
It is composed of a plurality of pixels displaying each color of RGB (red green blue), and each pixel is arranged in a grid pattern. In addition, a color image is displayed by supplying a video signal for each color of RGB (red, green, blue) to each pixel in the horizontal direction of the liquid crystal display element and driving each pixel row by row.

FIG. 5 is a block diagram showing the structure of a conventional full-color liquid crystal driving device. In FIG. 5, it is assumed that the number of pixels in the horizontal direction is x, and the video signal for driving the pixels row by row is updated at each time t (hereinafter referred to as update time).

The liquid crystal display element 24 includes the liquid crystal display element 24.
Is connected to a liquid crystal drive circuit 27 for driving each pixel, and the liquid crystal drive circuit 27 is supplied with a timing generation circuit 26 for transmitting a control signal of the liquid crystal drive circuit 27 and a video signal input for inputting video signals of RGB colors. The terminal 25 is connected. The liquid crystal drive circuit 27 also has a shift register 21 that generates 3 × sampling pulses, a sample hold circuit 22 that samples and outputs video signals of each color, and power for driving each pixel of the liquid crystal display element 24. And a voltage output circuit 23 for supplying the voltage.

In such a configuration, when the control signal and the clock synchronized with the video signals of RGB colors are input from the timing generation circuit 26 to the liquid crystal drive circuit 27, the shift register 21 in the liquid crystal drive circuit 27 becomes R
3 × sampling pulses are output to correspond to each color of GB. The sampling pulse is sequentially generated in synchronization with the clock in order to capture the video signal for one row of pixels in the horizontal direction while scanning. Sample hold circuit 22
Has 3x sample and hold means, and R, G1, B1, and R video signals of RGB colors input from the video signal input terminal 25 at the timing of each sampling pulse.
2, G2, B2, ... Rx, Gx, Bx are sampled and held in this order. Further, the sample hold circuit 22 outputs to the voltage output circuit 23 the voltage of the video signal of each color held in synchronization with the H pulse sent from the output of the timing generation circuit 26. The voltage output circuit 23 is a liquid crystal display element 24.
Is a buffer circuit that supplies electric power for driving
Each pixel of the liquid crystal display element 24 is driven based on the video signal of each color output from the sample hold circuit 22. Here, the update time t coincides with the time required to obtain 3x video signals of each color, so the timing generation circuit 26
The frequency of the clock output from is 1 / (t / 3x). Therefore, the shift register 21 and the sample hold circuit 22 operate at a frequency of 1 / (t / 3x).

[0006]

However, in the conventional full-color liquid crystal driving device as described above, when the number of pixels x in the horizontal direction of the liquid crystal display element is increased, or in order to operate with a high frequency video signal, the update time When t becomes short, a shift register or a sample hold circuit that operates at high speed is required.

Obtaining a shift register or a sample hold circuit that operates at high speed may be difficult to achieve due to the limitation of the element capability, and even if it is realized, it causes an increase in cost.

The present invention has been made in order to solve the problems of the above-mentioned conventional techniques, and facilitates liquid crystal display devices having a large number of pixels in the horizontal direction and video signals of high frequency. An object is to provide a full-color liquid crystal driving device that can be driven.

[0009]

To achieve the above object, a full-color liquid crystal driving device of the present invention comprises a liquid crystal display element for displaying a color image, a liquid crystal driving circuit for driving the liquid crystal display element, and the color image. In a full-color liquid crystal driving device having a timing generation circuit for outputting a clock and a control signal synchronized with video signals of three colors of red, green, and blue for displaying, to the liquid crystal driving circuit, the liquid crystal driving circuit is configured to control the control signal. And a shift register that sequentially outputs sampling pulses synchronized with the clock by the number of pixels in the horizontal direction of the liquid crystal display element,
With the sampling pulse as an input, the voltages of the video signals of the three colors are simultaneously sampled each time the sampling pulse is input, and the sampled voltage is obtained for each of the video signals of the three colors.
A sample hold circuit for holding the number of the sampling pulses, and a voltage output circuit for supplying an electric power for driving the liquid crystal display element with an output of the sample hold circuit as an input are provided. At this time,
At least two liquid crystal drive circuits may be provided, and the liquid crystal display element may be driven in parallel by the at least two liquid crystal drive circuits.

[0010]

In the full-color liquid crystal driving device of the present invention configured as described above, the sample and hold circuit in the liquid crystal driving circuit simultaneously samples the voltages of the video signals of three colors each time a sampling pulse is input. Therefore, it is possible to sample a video signal for one row of pixels in the horizontal direction in 1/3 of the time required in the conventional art.

[0011]

Next, an embodiment of the present invention will be described with reference to the drawings.

(First Embodiment) FIG. 1 is a block diagram showing a configuration of a first embodiment of a full-color liquid crystal driving device of the present invention, and FIG. 2 is a timing showing an operation of the full-color liquid crystal driving device shown in FIG. It is a chart.

In FIG. 1, it is assumed that the number of pixels in the horizontal direction is x and that the video signals for driving the pixels row by row are updated every time t.

A liquid crystal drive circuit 7 for driving each pixel of the liquid crystal display element 4 is connected to the liquid crystal display element 4, and a timing generation circuit 6 for sending a control signal of the liquid crystal drive circuit to the liquid crystal drive circuit 7. And a video signal input terminal 5 to which a video signal of each color of RGB is input. Further, the liquid crystal drive circuit 7 has x sampling pulses (SMP1 to SMP1).
SMPx), a shift register 1, a sample hold circuit 2 for sampling and outputting video signals of respective colors, and a voltage output circuit 3 for supplying electric power to drive each pixel of the liquid crystal display element 4. Has been done.

Here, the sample and hold circuit 2 is divided into three sample and hold means groups each having x sample and hold means, and each sample and hold means group has a one-to-one correspondence with video signals of RGB colors. And work. In addition, each sampling pulse (SMP1 to
SMPx) is sent in common to each of the three sample and hold means groups, and each sample and hold means group performs sampling in synchronization with the sampling pulse for each of the video signals of RGB colors.

In such a structure, the operation will be described below with reference to FIG. 1 and FIG.

The control signal output from the timing generation circuit 6 resets the shift register 1.
It is composed of a SET signal, an SP signal which gives a timing for outputting a sampling pulse from the shift register 1, and an H pulse signal which gives a timing for outputting a video signal held by the sample hold circuit 2.

First, the shift register 1 and the sample hold circuit 2 are initialized by the RESET signal in the control signal and the H pulse signal.

Next, when the shift register 1 receives the SP signal from the timing generating circuit 6, it scans and fetches the video signal for one row of pixels in the horizontal direction, so that x sampling pulses are sequentially output in synchronization with the clock. To do. The output interval of the SP signal coincides with the update time t, and x sampling pulses are output during the time t.

The video signals of RGB colors are respectively input to the sample hold circuit 2 via the video signal input terminal 5, and the sample hold circuit 2 samples the voltages of the video signals of RGB colors simultaneously in synchronization with each sampling pulse. To do. At this time, the sample hold circuit 2 holds x pieces of voltages (sample data) of the video signals of RGB colors.

Then, the sample hold circuit 2 holds the sample data of each color held in synchronization with the H pulse sent from the output of the timing generation circuit 6 in the voltage output circuit 3.
Output to. The voltage output circuit 3 is the sample hold circuit 2
The respective pixels of the liquid crystal display element 4 are driven from the respective output voltages HO (1 to x).

Since the update time t matches the time required for the sample hold circuit 2 to obtain x pieces of sample data, the frequency of the clock used in this embodiment is 1 / (t / x). Become. Further, the operating frequency of the shift register 1 and the sample and hold circuit 2 is 1 / (t / x), and the frequency required for the shift register 1 and the sample and hold circuit 2 to operate is 1/3 as compared with the conventional one. I understand.

Therefore, even if the circuit elements constituting the shift register 1 and the sample and hold circuit 2 have the same operating speed capability as in the conventional case, it is equivalent to the case of using a circuit element having a triple operating speed capability. Since the liquid crystal display device can be operated, the liquid crystal display device can be easily driven even when driving a liquid crystal display device having a large number of pixels in the horizontal direction or when driving with a video signal of a high frequency.

In this embodiment, the sample and hold circuit 2 is divided into three sample and hold means groups each having x inputs and outputs, but three sample and hold circuits each having x sample and hold means are used. The configuration may be provided.

(Second Embodiment) FIG. 3 is a block diagram showing the configuration of a second embodiment of the full-color liquid crystal driving device of the present invention, and FIG. 4 is a timing showing the operation of the full-color liquid crystal driving device shown in FIG. It is a chart.

In this embodiment, a first liquid crystal drive circuit 17a and a second liquid crystal drive circuit 17b having the same structure as the liquid crystal drive circuit shown in the first embodiment are provided.

The liquid crystal display element 14 is driven in parallel by the first liquid crystal drive circuit 17a and the second liquid crystal drive circuit 17b, and the output of the timing generation circuit 16 is the first liquid crystal drive circuit 17a and the second liquid crystal. And the drive circuit 17b.

In such a structure, the operation will be described next with reference to FIG. 3 and FIG. In the following description, the case where the number of pixels x in the horizontal direction of the liquid crystal display element 14 is 640 will be described as an example.

First, when the control signal synchronized with the video signal and the first clock are input to the first liquid crystal drive circuit 17a from the timing generation circuit 16, the first shift register 11a causes 320 sampling pulses ( S
MP1, SMP3 ... SMP637, SMP639) are sequentially output. The first sample-hold circuit 12a is composed of three sample-hold means groups each having 320 sample-hold means, and each of the RGB color image signals input from the video signal input terminal 15 is the same as in the first embodiment. Sampling is performed in synchronization with the sampling pulse, and 320 pieces of sample data are held for each of the RGB colors. Next, the first sample hold circuit 1
2a outputs the video signal of each color held in synchronization with the H pulse signal sent from the timing generation circuit 16 to the first voltage output circuit 13a, and the liquid crystal display element 14 is driven by the first voltage output circuit 13a. To be done.

Similarly, when the timing generation circuit 16 inputs the control signal synchronized with the video signal and the second clock to the second liquid crystal drive circuit 17b, the second
The shift register 11b has 320 sampling pulses (SMP2, SMP4 ... SMP638, SMP64).
0) are sequentially output. Second sample and hold circuit 12
b is composed of three sample and hold means groups each having 320 sample and hold means, and RGB input from the video signal input terminal 15 as in the first embodiment.
The video signals of the respective colors are sampled in synchronization with the sampling pulse, and 320 pieces of sample data are held for each of the RGB colors. Next, the second sample hold circuit 12b outputs the H signal sent from the timing generation circuit 16.
The held video signals of respective colors are output to the second voltage output circuit 13b in synchronization with the pulse signal, and the liquid crystal display element 14 is driven by the second voltage output circuit 13b.

At this time, the second clock sent from the timing generation circuit 16 to the second liquid crystal drive circuit 17b is an inverted clock of the first clock sent to the first liquid crystal drive circuit 17a, and the second clock. The sampling pulse output from the shift register 11b is a signal delayed from the sampling pulse output from the first shift register 11a by a time corresponding to 1/2 cycle of the first clock.

Therefore, the video signals of the RGB colors are the first
The sample and hold circuit 12a and the second sample and hold circuit 12b are repeatedly sampled in this order, and 640 drive signals can be obtained for each of the RGB colors.

If the update time t is 25 μs,
Shift register 11a, shift register 11b, sample hold circuit 12a, and sample hold circuit 1
The operating frequency of 2b is 1 / (t / x / 2),
(25 × 10 ⁻⁶ / 640/2) = 13 MHz.

Therefore, as compared with the first embodiment, the liquid crystal display device having a larger number of pixels in the horizontal direction can be driven because it can be operated in the same manner as when the circuit device having an operating frequency twice as high as that of the first embodiment is used. In this case, the liquid crystal display element can be easily driven even when the liquid crystal display element is driven by a video signal having a higher frequency.

In this embodiment, the liquid crystal display element 14 is driven in parallel by two liquid crystal drive circuits, but the number of liquid crystal drive circuits need not be two, and more liquid crystal drive circuits can be used. 14 may be driven in parallel.

[0036]

Since the present invention is constructed as described above, it has the following effects.

Each time a sampling pulse is input, the sample and hold circuit in the liquid crystal drive circuit simultaneously samples the voltages of the video signals of the three colors, and the sampled voltage is equal to the number of sampling pulses for each of the three colors. By holding the circuit, even if the operating speed of the circuit elements constituting the shift register or the sample and hold circuit is the same as the conventional one, the circuit elements having the triple operating frequency can be operated at the same speed. The liquid crystal display element can be easily driven even when driving a liquid crystal display element having a large number of pixels in the horizontal direction or when driving with a high-frequency video signal.

Further, since at least two liquid crystal drive circuits are provided and the liquid crystal display element is driven in parallel by at least two liquid crystal drive circuits, a circuit element having an operating frequency several times that of the liquid crystal drive circuit is used. Since they can be operated in the same manner, the liquid crystal display element can be easily driven even when driving a liquid crystal display element having a larger number of pixels in the horizontal direction or when driving with a video signal of a higher frequency.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of a first embodiment of a full-color liquid crystal driving device of the present invention.

FIG. 2 is a timing chart showing an operation of the full-color liquid crystal drive device shown in FIG.

FIG. 3 is a block diagram showing a configuration of a second embodiment of a full-color liquid crystal driving device of the present invention.

FIG. 4 is a timing chart showing the operation of the full-color liquid crystal driving device shown in FIG.

FIG. 5 is a block diagram showing a configuration of a conventional full-color liquid crystal driving device.

[Explanation of Codes] 1 shift register 2 sample hold circuit 3 voltage output circuit 4, 14 liquid crystal display element 5, 15 video signal input terminal 6, 16 timing generation circuit 7 liquid crystal drive circuit 11a first shift register 11b second shift Register 12a 1st sample hold circuit 12b 2nd sample hold circuit 13a 1st voltage output circuit 13b 2nd voltage output circuit 17a 1st liquid crystal drive circuit 17b 2nd liquid crystal drive circuit

Claims (2)

[Claims] 1. A liquid crystal display device for displaying a color image, a liquid crystal drive circuit for driving the liquid crystal display device, a clock and a control synchronized with video signals of three colors of red, green and blue for displaying the color image. In a full-color liquid crystal driving device having a timing generation circuit that outputs a signal to the liquid crystal driving circuit, the liquid crystal driving circuit generates a sampling pulse synchronized with the control signal and the clock in the horizontal direction of the liquid crystal display element. A shift register for sequentially outputting the number of pixels, the sampling pulse as an input, each time the sampling pulse is input, the voltages of the video signals of the three colors are simultaneously sampled, and the sampled voltage is converted into the three voltages. For each color video signal,
A full-color liquid crystal drive comprising: a sample hold circuit for holding the number of the sampling pulses; and a voltage output circuit which receives an output of the sample hold circuit and supplies power for driving the liquid crystal display element. apparatus. 2. The full-color liquid crystal driving device according to claim 1, wherein at least two liquid crystal driving circuits are provided, and the liquid crystal display element is driven in parallel by the at least two liquid crystal driving circuits. Liquid crystal drive device.