JPH09266541A - Television receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the television receiver which is enable to remove the rest of a high voltage with simple constitution without providing a circuit for high-voltage removal. SOLUTION: When the power source is turned off, the output of a character output signal generated by a microcomputer 1 is controlled so that the entire screen from the microcomputer 1 becomes white, a signal of white is outputted from a video chroma IC 2, and a beam current is supplied to a CRT 4. Consequently, the high voltage remaining in the CRT 4 is applied from a transistor TR3 to the ground through a, CRT driving circuit 3 and discharged.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to prevention of residual high voltage in a cathode ray tube of a television receiver, and more particularly to a technique for discharging the high voltage of the cathode ray tube when the power is turned off.

[0002]

2. Description of the Related Art Conventionally, in a cathode ray tube, a spot killer circuit has been conventionally used because a spot occurs when the power is turned off. As this spot killer circuit, a discharge type is well known in which a beam current is caused to flow when the power is turned off to discharge the high voltage of the cathode ray tube. An example of such a discharge type is disclosed in, for example, JP-A-60-143066 (H04).
N3 / 20) and is a well-known technique.

Here, an example of a conventional discharge type is shown in FIG. In FIG. 3, reference numeral 1 denotes a channel selection microcomputer (hereinafter, referred to as a microcomputer) that performs various controls of the television receiver, and generates a power on / off generator 11 that generates a signal for turning on / off the power and an on-screen character signal. The character signal output signal generator 12 is provided for the purpose. Further, 2 is a video chroma IC for processing a video signal and a chroma signal, 3 is a CRT (cathode ray tube) drive circuit, 4 is a CRT, and 6 is a relay circuit for turning on / off a relay of a power supply circuit of a television receiver not shown. Is.

Further, 5 is a high voltage removing circuit, which is a resistor R1,
It is composed of R2, R3, R4, a capacitor C, a diode D, and transistors TR1, TR2, TR3.

The operation of the television receiver configured as described above will be described. First, the case where the power of the television receiver is turned on will be described. A desired channel is selected and a television signal of a channel selected by a tuner (not shown) is received. Then, the received television signal is processed by the video chroma IC 2 to output a luminance signal and a color difference signal. The signal, for example the luminance signal, is output to the transistor TR3 via the transistor TR3. Although such a transistor is also configured to output a color difference signal, an example of a luminance signal will be shown here.

This brightness signal is input to the CRT drive circuit 3 through the transistor TR3 and drives the CRT4. From the microcomputer 1, by the operation of the operator, for example,
When the channel display is instructed, a character output signal corresponding to the channel number is generated from the character output signal generator 12 and input to the video chroma IC 2 and mixed with the television signal. Then, as described above, it is output to the CRT 4 via the CRT drive circuit 3.

On the other hand, the power-on signal is output from the power-on / off signal generator 11 from the microcomputer 1. The relay circuit 6 is turned on by the power-on signal and power is supplied. In addition, the high-voltage removal circuit 5 also receives a power-on signal (HIGH
Signal is supplied to turn on the transistor TR1 and turn off the transistor TR2. Therefore, the high voltage removing circuit 5 does not operate.

Next, when the power is turned off, the power on / off signal generator 11 generates a power off signal to turn off the relay circuit 6. As a result, the video chroma IC 2 also stops operating, and no signal is supplied to the CRT 4.

The power-off signal is also supplied to the high-voltage removing circuit 5, and the transistor TR1 is supplied with the power-off signal (LO
When the signal (W signal) is supplied, the transistor TR1 is turned off. Then, by turning on the transistor TR2,
The rest of the high voltage of CRT4 forms a discharge loop of resistor R4 and transistor TR2 ground through CRT drive circuit 2. As described above, the remaining high pressure can be removed.

By the way, as a countermeasure against such a high voltage remaining, it is necessary to separately form the above-mentioned high voltage removing circuit.

[0011]

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and is a television image receiving apparatus capable of removing high voltage with a simple structure without providing the high voltage removing circuit as described above. The purpose is to provide a machine.

[0012]

According to the present invention, a cathode ray tube for displaying an image on a tube surface by flowing an electron beam to cause a fluorescent screen to emit light, and a power supply circuit for supplying a power supply voltage to each circuit are turned off. A power-off detection means for detecting such a situation, a luminance signal processing means for supplying an image luminance signal to the cathode ray tube, a color signal processing means for supplying an image color signal to the cathode ray tube, and the cathode line A character signal generating means for supplying a character signal to the tube; a character signal adding means for adding a character signal to the video signal to the cathode ray tube; and a character signal generating means for turning off the power source by the power-off detecting means. A television receiver comprising: a control means for controlling to add to the cathode ray tube for a predetermined period so that the entire screen becomes a white signal.

Further, in the television receiver, the entire screen becomes white by the control means for 80 milliseconds after the power is turned off.

Further, according to the present invention, a cathode ray tube for flowing an electron beam to cause the fluorescent screen to emit light and displaying an image on the tube surface, and a power-off means for designating OFF of a power supply circuit for supplying a power supply voltage to each circuit. A luminance signal processing means for supplying an image luminance signal to the cathode ray tube; a color signal processing means for supplying an image color signal to the cathode ray tube; and a character for supplying a character signal to the cathode ray tube. A signal generating means and a character signal adding means for adding a character signal to a video signal to the cathode ray tube. When the power-off means is instructed to turn off the power, the entire screen from the character signal generating means is white. A television receiver comprising a control means for controlling the signal to be added to the cathode ray tube for a predetermined period so as to become a signal.

Further, the present invention is the television receiver characterized in that the entire screen becomes white by the control means 20 milliseconds before the power is turned off.

The present invention is the television receiver characterized in that the entire screen becomes white by the control means for 80 milliseconds after the power is turned off.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a block diagram of the present invention, and FIG. 2 shows a flow chart showing the operation of the present invention.

In FIG. 1, the same functions as those in the prior art shown in FIG. 3 perform the same functions, and the description thereof will be omitted. The difference in FIG. 3 is that the high voltage removing circuit 5 is deleted. The relay circuit 6 and the power supply ON / OFF signal generation circuit 11 are not shown in this block diagram, and are present as a configuration.

Next, the operation will be described. First, when the power is on, the television signal of the selected channel is received and supplied to the video chroma IC 2. Then, the luminance signal and the color difference signal are output, and the transistor T
It is output to the CRT drive circuit 3 and CRT4 via R3.

The character output signal is generated from the character output signal generator 11 of the microcomputer 1, and the character signal is supplied to the video chroma IC 2. The character output signal is RGB
The primary color signal of
The Y, G-Y, and B-Y color difference signals and outputs are switched. Further, the luminance signal is switched so as to have a fixed level instead of the luminance signal of the television signal.

In this way, the character output signal is output to the CRT drives 3 and CRT4 via the transistor TR3, and the character output signal is displayed.

On the other hand, FIG. 2 shows the operation when the power is turned off.
This will be described with reference to the flowchart of FIG. First, when the power source is turned off by a remote controller or a key (not shown), the microcomputer 1 detects this (S1). Then, the character output signal generation unit 12 outputs a white signal (a state in which all RGB are output) (S2). It outputs a white signal over the entire screen. This state is continued for 20 mm (S3).

When this white signal is output, the output of the video chroma IC 2 works so as to pass a beam current to the CRT 4, so that the transistor TR3 is controlled to be turned on. Then, since a current flows from the transistor TR3 to the ground through the CRT 4 and the CRT drive 3, the electric charge remaining in the CRT disappears as the current flows.

This is because if a white signal is output 20 milliseconds before the power is turned off, the remaining high voltage can be discharged more efficiently than after the power is turned off.

After a lapse of 20 milliseconds, the power supply circuit is turned off (S4), and the white signal continues to be output, which is maintained for another 80 milliseconds (S5). This causes the rest of the high voltage to be discharged.

The definition of 80 milliseconds is because the high voltage remains in the state where the current of the CRT does not flow for 80 milliseconds after the power is turned off and the high voltage does not effectively decrease. Further, if the microcomputer continues to output a white signal for 80 milliseconds or more, an overcurrent will flow from the terminal of the microcomputer that outputs the character output signal, and the microcomputer IC will be damaged. As described above, it is defined as 80 milliseconds.

Next, when 80 milliseconds have elapsed, the character output signal from the character output signal generator 12 of the microcomputer 1 is stopped to stop the high voltage discharge operation (S6).

As described above, if a high voltage remains in the CRT when the power is turned off, it is possible to prevent the current from flowing between the high voltage electrode inside the CRT and the focus electrode and the screen of the CRT from emitting light.

[0029]

As described above, according to the present invention, when the power source is turned off by the program of the microcomputer, the character output signal generated from the microcomputer causes the screen to be entirely white to cause the CRT to emit light, thereby causing the beam current of the CRT to flow and the high voltage. Since the CRT is discharged, it is possible to eliminate the residual high voltage remaining in the CRT with a simple configuration without separately providing a circuit therefor.

[Brief description of drawings]

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

FIG. 2 is a flowchart showing the operation of the embodiment of the present invention.

FIG. 3 is a diagram showing a conventional technique.

[Explanation of symbols]

 1 Microcomputer 2 Video chroma IC 3 CRT drive circuit 4 CRT 12 Character output signal generator

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Satoshi Shigemura 2-5-5 Keihan Hondori, Moriguchi City, Osaka Sanyo Electric Co., Ltd.

Claims (5)

[Claims] 1. A cathode ray tube for causing an electron beam to flow to cause a fluorescent screen to emit light to display an image on a tube surface, and a power-off detection means for detecting that a power supply circuit for supplying a power supply voltage to each circuit is turned off. A luminance signal processing means for supplying an image luminance signal to the cathode ray tube, a color signal processing means for supplying an image color signal to the cathode ray tube, and a character supplying a character signal to the cathode ray tube A signal generating means and a character signal adding means for adding a character signal to the video signal to the cathode ray tube so that the entire screen becomes a white signal from the character signal generating means when the power is turned off by the power off detection means. A television receiver comprising a control means for controlling the addition to the cathode ray tube for a predetermined period. 2. The television receiver according to claim 1, wherein the control means causes the entire screen to be white during 80 milliseconds after the power is turned off. 3. A cathode ray tube for flowing an electron beam to cause a fluorescent screen to emit light to display an image on a tube surface, a power-off means for designating off of a power supply circuit for supplying a power supply voltage to each circuit, and the cathode line. A luminance signal processing means for supplying an image luminance signal to the tube; a color signal processing means for supplying an image color signal to the cathode ray tube; and a character signal generating means for supplying a character signal to the cathode ray tube. A character signal adding means for adding a character signal to the video signal to the cathode ray tube, so that when the power-off means is instructed to turn off the power, the entire screen from the character signal generating means becomes a white signal before the instruction. A television receiver comprising a control means for controlling the addition to the cathode ray tube for a predetermined period. 4. The television receiver according to claim 3, wherein the control means causes the entire screen to become white 20 milliseconds before the power is turned off. 5. The television receiver according to claim 4, wherein the control unit causes the entire screen to be white during 80 milliseconds after the power is turned off.