JPH04321094A - Driving circuit for liquid crystal display element - Google Patents

Abstract

PURPOSE:To allow a liquid crystal display element to display two kinds of images by providing this liquid crystal display element driving circuit with a switching circuit and a shift register circuit and switching the contacts of the switching circuit. CONSTITUTION:The driving circuit for the matrix liquid crystal display element corresponding to a video signal having 525 horizontal scanning lines is provided with the switching circuit 16 and the shift register 17 and the switch circuit 16 is switched. In the case of a video signal having 625 scanning lines, the switch 16 is turned to the (a) side by a switching signal, an output from a shift register 19 is inputted to the shift register 17 and a signal delayed from the output of the register 19 only by one horizontal scanning period is outputted from the register 17 and inputted to a shift register 18. Consequently, an image formed by thinning one of 6 scanning lines can be obtained as the whole image. Thereby the liquid crystal display element corresponding to 525 scanning lines can display both images respectively having 525 scanning lines and 625 scanning lines.

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 matrix type liquid crystal display element, and more particularly to a drive circuit capable of displaying images of two types of horizontal scanning lines with one liquid crystal display element.

0002

[Prior Art] Generally, a matrix type liquid crystal display element requires horizontal scanning electrodes corresponding to a certain number of horizontal scanning lines of a video signal to be displayed. outputs only specific signals. FIG. 2 shows an example of such a conventional drive circuit.
0 and 22 are shift registers, 21 is shift register 20
, 23 is a video signal output from the horizontal drive circuit, 24 is a liquid crystal cell, and 25 is a liquid crystal display element.

0003

[Problems to be Solved by the Invention] With the conventional drive circuit for the liquid crystal display element described above, it is not possible to display video signals with different numbers of horizontal scanning lines, and it is not possible to display video signals with different numbers of horizontal scanning lines. It is necessary to use a liquid crystal display element having horizontal scanning electrodes and a drive circuit corresponding to the liquid crystal display element.

0004

[Means for Solving the Problems] The present invention provides a drive circuit for a matrix type liquid crystal display element that supports a video signal with 525 horizontal scanning lines, by adding a switch circuit and a shift register and switching the switch circuit. It is characterized by being able to display video signals with 625 horizontal scanning lines.

[0005]

[Operation] The present invention enables the necessary video information to be sufficiently recognized even if the video signal is thinned out at a ratio of one in six scanning lines from a video signal having 625 horizontal scanning lines. This is a driving circuit for a liquid crystal display element that takes advantage of this fact. That is, in a drive circuit for a liquid crystal display element that supports 525 horizontal scanning lines, a switch circuit and a shift register circuit are provided for every fifth horizontal scanning signal output, and when displaying a video signal with 525 scanning lines, When performing sequential scanning in accordance with the scanning lines of the video signal and displaying a video signal with 625 scanning lines, input the sixth horizontal scanning signal to a shift register circuit with an additional 6th scanning line. By applying the horizontal scanning signal to the scanning electrode with a delay of In addition to the liquid crystal cell of
A liquid crystal display element that can produce an image with the video signal thinned out at a ratio of one in every six scanning lines, and is compatible with images with 525 scanning lines and images with 625 scanning lines. This is what is displayed.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be explained with reference to the drawings. FIG. 1 is an embodiment of the present invention, and is a block diagram of a driving circuit for a liquid crystal display element compatible with the NTSC signal system having 525 scanning lines. 10 is a shift register that outputs a horizontal scanning signal in response to a start signal and a horizontal synchronization clock. 11 is a horizontal scanning signal output from the shift register 10. A shift register 12 outputs a scanning signal delayed by one horizontal scanning period from the horizontal scanning signal 11 using the output of the shift register 10 and a clock, and all the shift registers have the same circuit configuration. 13 is a video signal output from the horizontal drive circuit. 14 is a liquid crystal cell. 15 is a liquid crystal display element. Reference numeral 16 denotes a switch circuit which selects whether to input the output signal of the shift register 19 to the shift register 17 or to the shift register 18 using a switching signal. 17 to 19 are shift registers similar to the shift register 12.
In the case of an NTSC signal, the switch 16 is turned to the b side by the switching signal, and the output from the shift register 19 is input to the shift register 18, and the output signal y6 of the shift register 18 is input to the shift register 18.
is an output delayed by one horizontal scanning period from the output y5 of the shift register 19, and a normal image is obtained.

[0007] A video signal with 625 scanning lines (for example, P
(AL system), switch 16 is activated by the switching signal.
is turned to side a, the output from the shift register 19 is input to the shift register 17, and a signal delayed by one horizontal scanning period from the output of the shift register 19 is input to the shift register 17.
The signal is output from the shift register 18 and input to the shift register 18. As a result, the output y6 from the shift register 18 becomes a signal delayed by two horizontal scanning periods from the output y5 from the shift register 19. That is, the video signal corresponding to the horizontal scanning signal output from the shift register 17 is not applied to the liquid crystal cell and is not displayed.

By repeating the above series of operations,
An image is obtained in which the entire video is thinned out at a ratio of one scanning line to every six. Therefore, by changing the switching signal in accordance with the number of scanning lines of the video signal, in a liquid crystal display element corresponding to the number of scanning lines of 525, a video with 525 scanning lines and a video with 625 scanning lines can be created. Both images can be displayed.

[0009] It should be noted that the changeover switch section is
The circuit may be changed to automatically discriminate between an image having 25 scanning lines and an image having 625 scanning lines. By using an automatic discrimination circuit as the changeover switch section, there is an advantage that it can be used in applications where both scanning systems coexist.

0010

Effects of the Invention As explained above, the present invention provides a switch circuit and a shift register circuit, whereas conventional liquid crystal display element drive circuits can only display images with one type of scanning line number on one liquid crystal display element. By providing a switch circuit and switching the switch circuit, two types of images can be displayed.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention.

FIG. 2 is a block diagram showing a conventional example.

[Explanation of symbols]

10, 12, 17, 18, 19, 20, 22 Shift register 11, 21 Shift register horizontal scanning signal output 1
3, 23 Video signals output from the horizontal drive circuit 14, 24 Liquid crystal cells 15, 25 Matrix type liquid crystal display element (240 horizontal scanning electrodes) 16 Switch circuit

Claims (1)

[Claims] Claim 1: In a drive circuit for a matrix type liquid crystal display element compatible with a video signal having 525 horizontal scanning lines,
1. A driving circuit for a liquid crystal display element, characterized in that a switch circuit and a shift register are provided, and by switching the switch circuit, it is possible to display a video signal with 625 horizontal scanning lines.