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Drive circuit for driving an image display unit

a drive circuit and image display technology, applied in the direction of television systems, instruments, static indicating devices, etc., can solve the problems of increasing the area, increasing the size of the chip, etc., and reducing the circuit scale, die area, and cost of testing the drive circuit

Inactive Publication Date: 2009-06-23
RENESAS ELECTRONICS CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0016]It is therefore an object of the present invention to provide a drive circuit for driving an image display unit, such as a TFT (Thin Film Transistor) LCD unit, to display thereon multi-level gray-scale digital video data, especially such as having gray-scale levels of digital video data higher than eight bits per pixel, to realize reduction of the circuit scale, the die area, and the cost for testing the drive circuit.
[0018]In accordance with the drive circuit of the present invention, use of the intermediate voltage between adjacent two of the gray-scale voltages in the linear region reduces the number of gray-scale voltages to be generated substantially without degrading the image quality of the image display unit to be drive by the drive circuit, and reduces the circuit scale of the drive unit and reduces the test procedures for the drive circuit. The intermediate voltage may be preferably obtained by interpolation of the adjacent two of the gray-scale voltages.

Problems solved by technology

In the conventional resistor string method described above, although a 6-bit (64-level gray scale) drive circuit can be implemented without a significant problem, an attempt to realize gray-scale levels higher than 64 levels may cause the following problems.
A first problem is that employing a semiconductor integrated circuit implementing the drive circuit may cause the chip to significantly increase in size.
This causes the die area to increase, leading to an increased in its size.
A second problem is that longer time may be required for testing the semiconductor integrated circuit after it is fabricated.
This may cause the testing time to increase four times, leading to an increase in testing cost.

Method used

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  • Drive circuit for driving an image display unit
  • Drive circuit for driving an image display unit
  • Drive circuit for driving an image display unit

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Experimental program
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first embodiment

[First Embodiment]

[0036]FIG. 6 illustrates the configuration of a drive circuit according to the first embodiment of the present invention. The drive circuit of the present embodiment includes an 80-bit shift register 901, a data register block 902, and a data latch block 903, which are similar to those in the conventional drive circuit of FIG. 1. The drive circuit also includes a gray-scale voltage generator 101A, a gray-scale voltage selector block 102A, and an output stage circuit 105A. The gray-scale voltage generator 101A has a circuit configuration which is similar to the circuit configuration of the gray-scale voltage generator 906 shown in FIG. 2. The gray-scale voltage selector block 102A includes a group of 240 gray-scale voltage selectors each having a configuration similar to that shown in FIG. 4.

[0037]The output stage circuit 105A includes an amplifier block 104A and a least-significant-bit (LSB) controller 103A, as shown in FIG. 7. The least-significant-bit controller ...

second embodiment

[Second Embodiment]

[0048]Referring to FIG. 11, there is shown the configuration of the main portion of a drive circuit according to a second embodiment of the present invention. The overall configuration is similar to that shown in FIG. 6. A gray-scale voltage generator 101B is similar to the gray-scale voltage generator 906. A group of 240 gray-scale voltage selectors 102B constitutes the gray-scale voltage selector block. A least-significant-bit controller 103B is included in the second embodiment. A group of 240 output stage amplifiers constituents the output stage amplifier block 104B. The output stage amplifier block 104B has a configuration similar to that the output amplifier block 905 shown in FIG. 1 added by resistors and switches.

[0049]The gray-scale voltage generator 101B is configured similarly to that shown in FIG. 2 and divides input gray-scale reference voltages (VG0 to VGn). In general, to display 64 levels of gray scale data solely by means of the gray-scale voltage...

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PUM

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Abstract

A drive circuit has a judgement circuit for judging whether the magnitude of the input video data resides in a linear region or the non-linear region of characteristic of liquid crystal transmittance. When the vide data resides within the linear region, some of the output gray-scale voltage for the LCD are generated by interpolation of adjacent two of the gray-scale voltages generated by a voltage generator. The reduced gray-scale voltage taps reduces the circuit scale and the test procedures for the drive circuit.

Description

BACKGROUND OF THE INVENTION[0001](a) Field of the Invention[0002]The present invention relates to a drive circuit for an image display unit and, more particularly, to a drive circuit for driving an image display unit to display thereon multi-level gray-scale digital video data. The present invention also relates to a method for operating such a drive circuit.[0003](b) Description of the Prior Art[0004]FIG. 1 illustrates the configuration of a conventional drive circuit for use in an image display unit such as a liquid crystal display (LCD) unit. This drive circuit is used for displaying digital video data of 240 pixels each having six bits, or data of 240 pixels by 6 bits / pixel.[0005]The drive circuit of FIG. 1 includes an 80-bit shift register 901, a data register block 902, a data latch block 903, a gray-scale voltage selector block 904, an output amplifier block 905, and a gray-scale voltage generator 906. Power source voltages VDD1 and VSS1 are supplied to the 80-bit shift regis...

Claims

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Application Information

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IPC IPC(8): G09G5/00G02F1/133G09G3/20G09G3/36H04N5/66
CPCG09G3/3688G09G2310/027G09G2310/0291G09G3/36
Inventor HASHIMOTO, YOSHIHARU
Owner RENESAS ELECTRONICS CORP