JPH06332418A - Luminant screen protection circuit for display device - Google Patents

Abstract

PURPOSE:To protect a luminant screen by preventing the luminant screen from being burnt when a still picture is continued for a longe time in the luminant screen of a display device such as a cathod-ray or a PDP(plasma display panel). CONSTITUTION:A video circuit provided with a movement adaptive circuit 1 outputting detection signals on whether video signals are of a moving picture or a still picture, is provided with a counter 2 counting the continuation time of the detection signal when the detection signal is the still picture and outputting a prescribed signal when the continuation time exceeds a prescribed reference time, and a control part 4 controlling a power source on-off relay 6 so as to be made 'OFF' via a transistor 5 when the counter 2 outputs a prescribed signal.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a cathode ray tube or PDP.
The present invention relates to a light emitting surface protection circuit which prevents burn-in of a light emitting surface of a display device such as a (plasma display panel) when a still image is continued for a long time.

[0002]

2. Description of the Related Art Conventionally, in a display device operated by a keyboard, it is conventionally monitored whether or not the keyboard is operated, and when no operation is performed for a certain period of time, the power is turned off and the same image (still image) is displayed. The method of preventing the burn-in of the light emitting surface due to the continuation of) has been implemented. However, this method presupposes the presence of a keyboard, and therefore cannot be applied to a display device that does not use a keyboard.

[0003]

SUMMARY OF THE INVENTION In the present invention, regardless of the presence of a keyboard, it is detected from the contents of a video signal whether it is a moving image or a still image, and if the still image continues for a certain time, the power is turned off. It is an object of the present invention to provide a light emitting surface protection circuit for a display device.

[0004]

According to the present invention, there is provided a motion adaptive circuit for outputting a detection signal indicating whether a video signal is a moving image or a still image,
A counter that counts the duration of the detection signal when the detection signal is a still image and outputs a predetermined signal when the duration exceeds a predetermined reference time; and the counter outputs the predetermined signal In this case, a light emitting surface protection circuit for a display device is provided which is provided with a control unit for controlling the power on / off relay to be turned off.

[0005]

[Action]

(1) As one method, when a detection signal indicating that the video signal is a still image is output from the motion adaptation circuit, the duration is counted. When this time exceeds a predetermined reference time, the control unit turns off the power on / off relay. Whether to operate the above function can be selected by turning on / off the switching circuit. (2) As another method, the digital video signal is once latched by the latch circuit and is output at every predetermined timing. The output of the latch circuit and the digital video signal are subtracted. The NOR or OR of the upper n bits of this subtraction data is taken, and when the former is "high level" and the latter is "low level", the duration is counted. When this time exceeds a predetermined reference time, the control unit turns off the power on / off relay.
The switching circuit can also be applied to this method.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A light emitting surface protection circuit for a display device according to the present invention will be described below with reference to the drawings. 1 is a block diagram of an essential part showing an embodiment of a light emitting surface protection circuit of a display device according to the present invention, FIG. 2 is a block diagram of an essential part showing another embodiment, and FIG. 3 is a subtraction for explaining FIG. It is an input / output relationship diagram of a container. In FIG. 1, 1 is a motion adaptive circuit,
Reference numeral 2 is a counter, 3 is a switching circuit, 4 is a control unit, 5 is a transistor (TR) for driving a power on / off relay, and 6 is a power on / off relay (hereinafter referred to as "power relay").
In FIG. 2, 21 is an A / D converter for converting the analog video signal S1 into a digital video signal, 22 is a latch circuit, 23 is ROM, 24 is a subtractor, 25 is a NOR gate, 26 is a counter, 27 is a It is a control unit. The switching circuit 3, the relay driving transistor 5, and the power supply relay 6 are the same as those in FIG.

Next, the operation of the present invention will be described with reference to the drawings. (1) Description of Operation in FIG. 1 A motion adaptation circuit is provided in a video circuit that digitally processes a video signal. Then, this motion adaptation circuit outputs a detection signal indicating whether the video signal is a moving image or a still image. The present invention presupposes the existence of this detection signal and utilizes it. The counter 2 measures the duration of the detection signal from the motion adaptation circuit 1, but when the detection signal indicating a still image exceeds a predetermined reference time, it is “high level” (hereinafter, “H output”). Is output). That is, the counter 2 has a function of comparing with the reference time. The H output is input to the control unit 4 through the switching circuit 3, and when the H output is input, the TR drive TR
Turn 5 from on to off. With this off, the SW of relay 6
1 is turned off and the power is turned off. The switching circuit 3 makes it possible to select whether the above function is operated or not operated, and the user selectively switches the function.

(2) Description of FIG. 2 The video signal D1 digitized by the A / D converter 21 is sent to the latch circuit 22 and the subtractor 24. Latch circuit 22 is a ROM
The latch operation of the input video signal D1 and the output of the latched signal are repeated according to the timing data written in 23. The output signal D2 of the latch circuit 22 and the video signal D1 are subtracted by a subtractor. For example, as shown in FIG. 3, signals D1 and D2
If and are 8-bit signals (N = 8),
The output of 24 is D3. NO for the upper n bits of D3
Take R. For example, in FIG. 3, when n = 5,
The output of the NOR gate 25 becomes "H". In the present invention, this state is determined as a still image. In FIG. 3, the lower 3 bits of D3 are not "0", but such a variation is regarded as a still image.

If D1 = D2, all bits of D3 are "0", which means a complete still image. The output of the NOR gate 25 is sent to the counter 26, its duration is counted as in the case of FIG. 1, and when the above "H" level becomes equal to or more than a predetermined reference time, "H" is output, It is sent to the control unit 27 via the switching circuit 3. When the H output is input, the control unit 27 turns the relay driving TR5 from on to off. By this turning off, SW1 of the relay 6 is turned off and the power is turned off. The switching circuit 3 is similar to that described with reference to FIG.
In FIG. 2, the same operation can be performed by using an OR gate instead of the NOR gate 25. However, the NOR gate outputs "H" when the still image continues for a predetermined time.
On the other hand, the OR gate is different in that it becomes “low (L). Therefore, in the case of the OR gate, the control unit 27 is turned off when the“ L ”is input.

[0010]

As described above, according to the present invention, it is discriminated from the video signal itself whether it is a moving image or a still image, and when the state of the still image continues for a predetermined reference time or longer, the power is automatically turned on. Can be turned off. Therefore, it becomes possible to prevent light emission deterioration of the light emitting surface that occurs when this still image is displayed for a long time, which contributes to prevention of deterioration of the PDP, the cathode ray tube display device and the like.

[Brief description of drawings]

FIG. 1 is a principal block diagram showing an embodiment of a light emitting surface protection circuit of a display device according to the present invention.

FIG. 2 is a block diagram of an essential part showing another embodiment of the light emitting surface protection circuit of the display device according to the present invention.

3 is a relationship diagram of input / output levels of a subtractor 24 in FIG.

[Explanation of symbols]

 1 Motion adaptation circuit 2 Counter 3 Switching circuit 4 Control unit 5 Transistor (TR) 6 Power on / off relay 21 A / D converter 22 Latch circuit 23 ROM 24 Subtractor 25 OR gate 26 Counter 27 Control unit

Claims (3)

[Claims] 1. A motion adaptive circuit that outputs a detection signal indicating whether a video signal is a moving image or a still image, and the duration of the detection signal is counted when the detection signal is a still image, and the duration is predetermined. A display for displaying a display, comprising: a counter that outputs a predetermined signal when the reference time is exceeded; and a control unit that controls the power on / off relay to turn off when the counter outputs the predetermined signal. Device light emitting surface protection circuit. 2. A N-bit digital video signal obtained by A / D converting an analog video signal, a latch circuit for latching the digital video signal and outputting the digital video signal at predetermined time intervals, and the predetermined time being written as timing data. , A ROM for sending the timing data to the latch circuit, and subtracting the data relating to the digital video signal and the data relating to the output video signal of the latch circuit,
A subtractor that outputs N-bit subtraction data, a NOR gate that takes the NOR of the upper n bits of the N-bit subtraction data, and a continuation time of the data for each output data of the NOR gate, high level"
A counter is provided which outputs a predetermined signal when the data duration exceeds a predetermined reference time, and a control unit which controls to turn off the power-on / off relay when the counter outputs the predetermined signal. A light emitting surface protection circuit for a display device, characterized in that. 3. A latch circuit for latching the digital video signal in the N-bit digital video signal and outputting the digital video signal at predetermined time intervals, and the predetermined time is written as timing data, and the timing data is written in the latch circuit. To the ROM, a subtractor for subtracting the data relating to the digital video signal and the data relating to the output video signal of the latch circuit, and outputting subtraction data consisting of N bits, and the subtraction data consisting of N bits. An OR gate that ORs the upper n bits and the duration of the data for each output data of the OR gate is counted, and a predetermined signal is output when the duration of the "low level" data exceeds a predetermined reference time. And a power on / off relay that is turned off when the counter outputs the predetermined signal. A light emitting surface protection circuit of a display device, comprising: