JPS6231278A - Liquid crystal display - Google Patents

Abstract

PURPOSE:To enjoy a satisfactory picture by comparing a signal received by an antenna with a reference level in a level comparison circuit and by opening a switch when this signal goes below the reference level to prevent an output of a timing pulse generating circuit from being supplied to an X drive circuit and to a Y drive circuit. CONSTITUTION:A signal 10 and a signal 12 are outputted to a switch 21, and respective outputs are inputted to an X drive circuit 9 and a Y drive circuit 11. By the X drive circuit 9 and the Y drive circuit 11, a liquid crystal display 13 is operated. A video siganl 22 converted into an intermediate frequency by a tuner 2 is converted into a signal 24 proportional to an input electric wave by a detecting circuit 23. This signal 24 is compared with a reference level by a level comparison circuit 25 and when it is judged that it is below the reference level, namely, the condition of the electric wave is bad, a signal 26 for opening the switch 21 is outputted and in the case of other than that, the signal 26 for closing the switch 21 is outputted. Accordingly, on the liquid crystal display, a picture immediately before the condition of the electric wave becomes bad is successively displayed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a liquid crystal display device that can display a good screen even when radio wave conditions deteriorate.

[Technical background of the invention]

A conventional liquid crystal display device has an antenna 1 as shown in FIG.
The tuner 2 tunes the received radio waves, and the video detection circuit 3 separates them into a video signal 4 and a synchronization signal 5.
is decomposed into R-G-B signals by a signal processing circuit 6 and further shaped into a signal 7 suitable for driving a liquid crystal, while a synchronizing signal 5 is processed by a timing pulse generation circuit 8 suitable for operating an X drive circuit. The signal IO and the signal I2 suitable for operating the Y drive circuit II are converted into the signal I2 suitable for operating the X drive circuit 9 and the Y drive circuit II.
The liquid crystal display 13 was operated by the drive circuit IO.

[Problems with background technology]

However, in such conventional liquid crystal display devices, if the microwave condition temporarily worsens due to the movement of the receiver, the image may become distorted, colors may no longer be reproduced, or in the worst case, the image may not be displayed at all. It is not visible and is actually eye straining and very uncomfortable.

[Purpose of the invention]

This invention was made in order to eliminate the above-mentioned drawbacks of the conventional technology, and the present invention is a liquid crystal display that can maintain an image immediately before the radio wave condition deteriorates and not display a distorted image even when the radio wave condition deteriorates for a short period of time. The purpose is to provide equipment.

[Summary of the invention]

In the liquid crystal display device of the present invention, a signal received by an antenna is detected by a video detection circuit and separated into a video signal and a synchronization signal. The generation circuit operates the X drive circuit and the Y drive circuit, which drive the X and Y side electrodes of the liquid crystal display, and the level comparison circuit compares the signal received by the antenna with the reference level. When this signal becomes below the reference level, the switch is opened to prevent the output of the timing pulse generation circuit from being supplied to the X drive circuit and Y drive circuit. The video signal immediately before the operation stops is continuously displayed.

[Embodiments of the invention]

Embodiments of the liquid crystal display device of the present invention will be described below based on the drawings. FIG. 1 is a block diagram showing the configuration of one embodiment. In FIG. 1, the same parts as in FIG. 3 are given the same reference numerals and will be explained.

In FIG. 1, radio waves received by an antenna I are tuned by a tuner 2, and separated into a video signal 4 and a synchronization signal 5 by a video detection circuit 3.

The video signal 4 is separated into R, G, and B signals by a signal processing circuit 6, and further shaped into a signal 7 suitable for driving a liquid crystal.

On the other hand, the synchronizing signal 5 is converted by the timing pulse generating circuit 8 into a signal 10 suitable for operating the X drive circuit 9 and a signal I2 suitable for operating the Y drive circuit 11.

The points up to this point are the same as those in FIG. 3, but the parts described below are different from those in FIG. 3 and are the features of the present invention.

That is, the signals 10 and 12 are connected to the switch 2I.
The respective outputs are input to the X drive circuit 9 and the Y drive circuit II.The X drive circuit 9 and the Y drive circuit 11 operate the liquid crystal display I3.
--Furthermore, the video signal 22 converted into an intermediate frequency by the tuner 2 is converted by the detection circuit 23 into a signal 24 proportional to the input radio wave. This signal 24 is compared with a reference level by a level comparison circuit 25, and if it is determined that it is below the reference level, that is, the radio wave condition is poor, it outputs a signal 26 that opens the switch 21. Otherwise, it outputs a signal 26 that opens the switch 21. Outputs signal 2-6 to close. 'Figure 2 shows the operating principle of an active matrix drive liquid crystal display = In this drive system, scanning electrodes 3Ia to 3Ic
and signal electrodes 32a to 32c are arranged in a matrix, and transistors 33a to 33f for driving the liquid crystal layers 34h to 34f are connected to the intersections thereof.

Transistors 33a to 33cm are turned on by applying a scan pulse to the darts of transistors 33h to 33c connected to a selected scan electrode (for example, JIm).

'A signal whose amplitude is modulated by a video signal synchronized with the scanning pulse is applied from the signal electrodes 32a to 32a to the drains of the transistors 33a to 33c, and further passes from the drain to the source of the transistor to the liquid crystal layer 34&
34c, and charges are accumulated in the liquid crystal layers 34a to 34c.

When the scan electrode is no longer selected, the transistors 33h~
33e is a time constant determined by the off resistance of the transistor when it is in the off state and the capacitance of the liquid crystal layer 341Q-U4c, and the liquid crystal layers 348 to 348 remain in the off state until the accumulated charge is completely discharged. A voltage continues to be applied to 34c.

``-'' When displaying a television signal, these two time constants are chosen to accumulate charge until the next scan is applied (usually one frame per input synchronization).

In this invention, the signal 24 detected from the video signal 22 by the detection circuit 23 is compared with the reference level in the level comparison circuit 25, and when this signal 24 becomes below the reference level, it is determined that the radio wave condition has deteriorated. When the level comparison circuit 25
The switch 2I is opened by the signal 26 outputted from the
All transistors are turned off by stopping the operation of the Y drive circuit II and making the scanning electrodes non-selected.

As mentioned above, in this state, the psychic charges accumulated in the liquid crystal layer are held for a time constant determined by the off-resistance of the transistor and the capacitance of the liquid crystal layer. The image that was displayed continues to be displayed.

In addition, as another application example of the present invention, it is possible to temporarily record an image by operating the signal 26 for operating the switch from the outside even when the radio wave condition is good.

By doing this, you can temporarily stop viewing the image you want to view at any time, and it becomes easy to take notes from the image.

〔Effect of the invention〕

As explained above, since the liquid crystal display device of the present invention applies the principle of the active polymer (IJ) drive system, it requires few additional circuits and can be changed relatively easily.
Even if the radio wave condition temporarily deteriorates, you can enjoy a good image without seeing a distorted screen.

In addition, even when radio wave conditions are good, images can be temporarily stopped and notes can be taken from the images, making it possible to use them as inexpensive memory devices.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the liquid crystal display device of the present invention, and FIG. 2 is a diagram showing the operating principle of an active matrix drive liquid crystal display used as a liquid crystal display in the liquid crystal display device of the present invention. FIG. 3 is a block diagram showing the configuration of a conventional liquid crystal display device. ! ...Antenna, 2...Tuner, 3...Video detection circuit, 6...Signal processing circuit, 8...Timing noise generation circuit, 9...X drive circuit, 11... Y
Drive circuit, I3...Liquid crystal display, 21...Switch, 23...Detection circuit, 25...Level comparison circuit. - Applicant's agent Patent attorney Suzue Takehiko 2nd WJ 3rd cause

Claims (1)

[Claims] a video detection circuit that detects the signal received by the antenna, separates it into a video signal and a synchronization signal, and outputs the same; an X drive circuit that drives the X side electrode of the liquid crystal video display using the video signal; a timing pulse generation circuit that outputs a signal to drive the drive circuit and the Y drive circuit that drives the Y-side electrode of the liquid crystal video display; a level comparison circuit that compares the signal received by the antenna with a reference level; The timing pulse generation circuit is configured to continuously display the video signal immediately before the operation of the X drive circuit and the Y drive circuit stops on the liquid crystal display when the signal received by the antenna is below the reference level as a result of comparison by the comparison circuit. A liquid crystal display device comprising a switch for blocking the supply of output to the X drive circuit and the Y drive circuit.