JPH02280587A - Liquid crystal picture display device - Google Patents

Abstract

PURPOSE:To attain long service life of a back light and to reduce useless power consumption by detecting a synchronizing signal of an input video signal and turning off automatically the back light when the synchronizing signal is not detected. CONSTITUTION:When a video tape loaded on a video signal source 4, for example, comes its end and a video signal is not obtained for the reception channel, a luminance chroma separation circuit 16 cannot extract the synchronizing signal and a vertical synchronizing signal V is not fed to a light control circuit 20. Thus, a charge level of a capacitor 22 is lowered, a transistor(TR) 25 is turned off, and its collector level goes to a high level. Thus, a high voltage drive circuit 31 stops the production of a high voltage signal and the back light 32 is turned off. Thus, useless lighting of the back light 32 is prevented, then useless power consumption of a display device is prevented and power consumption is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a liquid crystal image display device called a liquid crystal television or the like using a liquid crystal panel.

[Summary of the invention]

In a liquid crystal image display device using a liquid crystal panel, the present invention detects a synchronization signal of a human-powered video signal and automatically turns off the backlight when the synchronization signal is not detected, thereby extending the life of the backlight. This is designed to reduce energy consumption and wasteful power consumption.

[Conventional technology]

Conventionally, it has been proposed to install a small television receiver near each passenger seat in the passenger cabin of an aircraft, etc., so that each passenger can watch video programs on any channel of their choice (Japanese Patent Application Laid-Open No. (Sho 62-168794, etc.).

In this case, a liquid crystal image display device using a liquid crystal panel is preferable as a television receiver because it is thinner than one using a cathode ray tube.

[Problem to be solved by the invention]

By the way, in a liquid crystal image display device, since the liquid crystal panel itself does not emit light, it is necessary to attach a light emitting device called a backlight to the back of the liquid crystal panel. Fluorescent lamps are normally used for this backlight, but fluorescent lamps have a relatively short lifespan and must be replaced frequently. In this case, it is difficult to detect how much the fluorescent lamp has been used, so it is common to replace it at regular intervals, such as every few months.

On the other hand, when a liquid crystal image display device is installed in each passenger seat of an aircraft as described above, it is conceivable to periodically replace the backlights of each display device all at once. 10) It was very time-consuming and inconvenient to disassemble the display device and replace the fluorescent lamp.

In view of the above, an object of the present invention is to provide a liquid crystal image display device that can substantially extend the life of a bank light.

[Means to solve the problem]

As shown in FIG. 1, for example, the liquid crystal image display device of the present invention detects a synchronization signal of an input video signal with a lighting control circuit (20), and automatically turns on a backlight (32) when this synchronization signal is not detected. This is what I set it to turn off.

[Effect]

According to such a configuration, the backlight (32) is automatically turned off when the video program ends, eliminating unnecessary lighting of the backlight (32) and extending the life of the backlight (32).

〔Example〕

Hereinafter, one embodiment of the liquid crystal image display device of the present invention will be described with reference to the accompanying drawings.

In this example, as shown in FIG. 3, seats (2a), (2b),
(2c) In front of “ ”, there is a liquid crystal image display device (3a
), (3b), (3c)... are placed.

In this case, a video signal source (4) containing a plurality of video tape playback devices, a television broadcast tuner, etc. is installed in the galley (1b) of this aircraft (1), and this video signal source (
4) and each liquid crystal image display device (3a), (3b).

(3c)... are connected by a coaxial cable (5), and a plurality of video programs are modulated into different frequency bands from a video signal source (4) and sent to the coaxial cable (5).

Also, from this video signal source (4), audio signals and data signals of multiple channels are modulated into a predetermined frequency band and sent to the coaxial cable (5).

Next, the liquid crystal image display device (3a) installed in each seat.
, (3b), (3c)'' is shown in Figure 1.The input terminal (1) connected to the coaxial cable (5) is shown in Figure 1.
The signal obtained in step 1) is supplied to a tuner (12) and a data decoder (13), and the tuner (12) demodulates the signal of the channel from which the video signal is obtained and converts it into an intermediate frequency signal. 13) is the control data.

Demodulates the signal of the channel from which various data such as audio data is obtained. And data decoder (13)
The data signal demodulated by the system controller (14
), and this system controller (14) performs various controls indicated by the data signals. Alternatively, it controls the reproduction of audio data (however, the audio signal reproduction circuit is omitted).

In this case, the system controller (14) is connected to the tuner (
12) so that the receiving channel can be controlled by supplying channel selection data to the receiver.

The intermediate frequency signal output from the tuner (12) is then supplied to an intermediate frequency circuit (15) to perform predetermined signal processing for image reception. Then, the video signal output from the intermediate frequency circuit (15) is supplied to the luminance/chroma separation circuit (16), and is separated into a luminance signal Y and color difference signals B-Y and RY,
The separated luminance signal Y and color difference signals B-Y and RY are supplied to a liquid crystal panel drive circuit (17). In addition, a brightness/chroma separation circuit (16) extracts a horizontal synchronization signal H and a vertical synchronization signal ■ from the video signal, and converts the extracted horizontal synchronization signal H and vertical synchronization signal ■ into a phase-locked loop circuit (hereinafter referred to as a PLL circuit). ) (18), and also supplies a vertical synchronizing signal V to a lighting control circuit (20), which will be described later.

Then, the PLL circuit (18) creates a synchronization signal for image reception from the horizontal and vertical synchronization signals H and V of the supplied input video signal, and supplies the created synchronization signal to the liquid crystal panel drive circuit (17). . In addition, the system controller (14) and the lighting control circuit (2) transmit the vertical period synchronization signal created by the PLL circuit (18) based on the vertical synchronization signal (■).
0).

The liquid crystal panel drive circuit (17) includes a PLL circuit (
18), the luminance signal Y is synchronized with the synchronization signal supplied from
and color difference signals B-Y, R, , -Y, the liquid crystal panel (1
9) to display an image on the liquid crystal panel (19).

In this example, when displaying an image on the liquid crystal panel (19), the system controller (14) controls the backlight (32) to turn on.

That is, the system controller (14) controls the liquid crystal panel (1
9), when the system controller (14) controls the display of an image, the lighting control circuit (20
) supplies a lighting control signal to turn on the backlight. This lighting control signal is a low level signal "0" when the backlight is turned on, and a high level signal "l II" when the backlight is not turned on.
) is supplied to one input terminal of the OR gate circuit (29).

Further, the vertical synchronization signal V of the input video signal supplied from the brightness/chroma separation circuit (16) to the lighting control circuit (20) is supplied to the anode of the diode (21), and the cathode of this diode (21) is Connect to one end of the capacitor (22), and ground the other end of the capacitor (22).

With this configuration, the diode (21) prevents reverse current, and the capacitor (22) is charged by the vertical synchronization signal V, thereby functioning as an integrating circuit.

Then, connect one end of the capacitor (22) to a resistor (23).
It is connected to the base of an npn type transistor (25) through a parallel circuit consisting of a capacitor (24) and a capacitor (24), and the emitter of this transistor (25) is grounded. In this case, the capacitor (24) functions as a speed-up capacitor. Further, the power supply terminal (26) is connected to the collector of the transistor (25) via the resistor (27), and this collector is connected to the D input terminal of the D flip-flop (28). Then, the vertical period synchronization signal output from the PLL circuit (18) is supplied to the clock signal input terminal of this D flip-flop (28). Then, the signal obtained at the Q output terminal of this D flip-flop (28) is
It is supplied to the other input terminal of the R gate circuit (29).

The signal obtained at the output terminal of this OR gate circuit (29) is then supplied to the high voltage drive circuit (31) as the output signal of this lighting control circuit (20).

This high voltage drive circuit (31) generates a high voltage signal when the low level signal "θ" is supplied from the lighting control circuit (20), and supplies this high voltage signal to the backlight (32) consisting of a fluorescent lamp. , this backlight (32) is turned on. In addition, the lighting control circuit (20) is connected to the high voltage drive circuit (
When a high level signal “1” is supplied to 31),
A high voltage signal is not supplied to the backlight (32), and the backlight (32) is not turned on.

Next, using the liquid crystal image display device of this example, the coaxial cable (
To explain the operation when receiving the video signal supplied from the video signal source (4) to the terminal (5) via the tuner (12), the tuner (12) connects the system controller (1
4) Demodulates the video signal of the designated channel. At this time, when a video signal is obtained on this reception channel, that is, when the video program of this channel is being sent from the video signal source (4), the horizontal synchronization signal H and a vertical synchronization signal V, and an image is displayed on the liquid crystal panel (19) at a timing based on the synchronization signals H and V. At this time, the vertical synchronization signal (2) extracted by the luminance/chroma separation circuit (16) is charged in a capacitor (22) forming an integrating circuit in the lighting control circuit (20). That is, when a vertical synchronizing signal is obtained as shown in FIG. 2A, the potential at one end of the capacitor (22) maintains a predetermined high level as shown in FIG. 2C. Therefore, the transistor (25) is turned on, and the collector potential of this transistor (25) becomes a low level as shown in the second diagram.

The clock signal input terminal of the D flip-flop (28) is supplied with a vertical period synchronization signal (Fig. 2B) from the PLL circuit (18), and at the timing when this synchronization signal rises, the clock signal input terminal of the D flip-flop (28) receives The signal that is applied is latched.

In this case, when the video signal is being received, the transistor (25) is on as described above, so a low level signal based on the collector potential is latched and sent from the Q output terminal of the D flip-flop (28) as shown in FIG. As shown in the figure, a low level signal “0” is output, and the OR gate circuit (2
This low level signal "0" is supplied to the other input terminal of 9). At the time of image reception, a low level signal "0'" is supplied as a lighting control signal to one input terminal of the OR gate circuit (29) of the system controller (14). A signal "'0" is output, and this low level signal "0P" is supplied to the high voltage drive circuit (31). By supplying this low level signal II OII to the high voltage drive circuit (31),
A high voltage drive circuit (31) generates a high voltage signal to light up the butterfly (32).

For example, when the video tape loaded in the video signal source (4) reaches the end of the tape and no video signal can be obtained on this receiving channel, the luminance/chroma separation circuit (16) can extract the synchronization signal. As a result, the vertical synchronizing signal (2) is no longer supplied to the lighting control circuit (20) as shown in FIG. 2A. Therefore, the charging potential of the capacitor (22) decreases as shown in FIG.
) is turned off. When this transistor (25) is turned off,
As shown in the second diagram, at the timing when the collector potential of this transistor (25) becomes high level and the synchronization signal output from the PLL circuit (18) becomes high level, this high level signal is sent to the D flip-flop (28). is latched, and a high level signal "1" is output from the Q output terminal of the D flip-flop (28) as shown in FIG. This high level signal “I II is OR
When supplied to the lighting control circuit (29), even if the low level signal "0" is supplied as the lighting control signal from the system controller (14), the high level signal "1" is supplied to the lighting control circuit (29). ) begins to output, the high voltage drive circuit (31) stops generating high voltage signals, and the backlight (
32) is turned off.

As described above, according to the liquid crystal image display device of this example, when a video signal is not obtained on the channel received by the tuner (12), the lighting control circuit (20) sends a signal to the high voltage drive circuit (3).
1) The backlight l-(32) does not light up because the low level signal "0" for lighting is not supplied, so when the video program ends or when switching from the video channel to the audio channel, etc. When there is no longer a need for image reception as in
This means that the fluorescent lamps that make up the backlight have a substantially longer lifespan, and the fluorescent lamp replacement cycle becomes longer. In this case, in this example, each passenger seat (2a), (2b), (2c),
A large number of liquid crystal image display devices (3a), (3b
), (3c)..., the replacement cycle for fluorescent lights will be longer, which will greatly reduce the effort required for maintenance. Further, since unnecessary lighting of the backlight (32) can be prevented, unnecessary power consumption of the display device can be prevented, leading to a reduction in power consumption.

Note that when connected to the video signal source (4) via the coaxial cable (5) as in this example, the receiving strength of the video signal at the tuner (12) is approximately constant, so the yJ image program is transmitted. A synchronization signal is reliably detected inside. Therefore, there is little possibility that the lighting control circuit (20) will malfunction.
It is suitable for such a video transmission system in a vehicle or a cable television system (CATV) on a ship.

In the above-described embodiment, the backlight is made of a fluorescent lamp, but the backlight may be made of other light-emitting bodies. Furthermore, it goes without saying that the present invention is not limited to the above-described embodiments, and can take various other configurations without departing from the gist of the present invention.

〔Effect of the invention〕

According to the liquid crystal image display device of the present invention, unnecessary lighting of the backlight can be prevented, and the life of the backlight can be extended and unnecessary power consumption can be reduced.

[Brief explanation of drawings]

FIG. 1 is a circuit configuration diagram showing one embodiment of the liquid crystal image display device of the present invention, FIG. 2 is a waveform diagram for explaining the example in FIG. 1, and FIG. 3 is an example of application of the display device of this example. This is a route map. (3a), (3b), (3c) "" is a liquid crystal image display device, (14) is a system controller, (1
9) is a liquid crystal panel, (20) is a lighting control circuit, (31)
(32) is a high voltage drive circuit, and (32) is a backlight.

Claims (1)

[Claims] A liquid crystal image display device characterized in that a synchronization signal of an input video signal is detected, and a backlight is automatically turned off when the synchronization signal is not detected.