JPH06284307A - Cathode ray tube display device with stray emission preventing function - Google Patents

Abstract

PURPOSE:To prevent the generation of stray emission without applying a sense of uneasiness or the like to a viewer when the off operation of a power source is performed, and to prevent the generation of the stray emission even when an input power source is interrupted due to interruption or the like. CONSTITUTION:A microcomputer 11 receives the command of a power source off from a remote controller or the like, and transmits a signal to a video chroma junction(VCJ) IC 2. The VCJIC 2 transmits an on-screen display(OSD) signal constituted of characters, patterns, or chrominance signals for making the surface of a CRT 5 uniformly bright to the CRT 5. Afterwards, the microcomputer 11 turns off a switch 18 of a main power source 17. Also, at the time of interruption, an interruption detecting circuit 21 detects the trailing of the output of a stand-by power source 20, and outputs an interruption detection signal to the microcomputer 11. Then, the microcomputer 11 transmits the signal to the VCJIC 2, and the VCJIC 2 transmits the OSD signal for making the display surface uniformly bright.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display device using a cathode ray tube having a stray emission preventing function.

[0002]

BACKGROUND OF THE INVENTION In stray emission, when the power is turned off, even if no electric potential is applied to the heater or cathode of the cathode ray tube, the stray electrons in the tube of the cathode ray tube are generated by the high voltage charged in the capacity of the cathode ray tube. This is a phenomenon in which it is attracted and collides with the fluorescent screen to cause it to shine, which causes anxiety to the viewer and is therefore prevented.

FIG. 4 is a block diagram of a main part of a color cathode ray tube display device having a conventional spot killer circuit for preventing stray emission. 1 is a spot killer circuit, 2 is a video chroma junction IC (hereinafter referred to as " V
CJIC ”), 3 is its CLAMP signal input terminal, 4 is RGB signal output terminal, 5 is a color cathode ray tube (hereinafter referred to as“ CRT ”), 6 is a capacitance between the anode of the CRT 5 and ground, and 7 is a flyback transformer. (Hereafter, "FB
8) is a high-voltage discharge resistance.

Next, the operation of this conventional example will be described. The spot killer circuit 1 is provided to prevent the generation of stray emission when the high-voltage discharge resistor 8 is not provided, and the input voltage V1 falls as the power supply (not shown) is turned off. Then, the transistor Q1 is turned on, and a signal for raising the potential is transmitted to the CLAMP signal input terminal 3 through D1, so that the output level of the RGB output terminal becomes high, and the charge of the capacitor 6 is released by forcibly lighting the CRT5. To prevent stray emissions.

[0005]

The conventional stray emission prevention device using the spot killer circuit raises the black level of the operating signal of the CRT irrespective of the input signal when the power is turned off, so that the screen is disturbed. There was a problem that it disappeared.

Japanese Patent Laid-Open No. 61-23768 discloses a stray emission preventing device which solves such a problem and in which the screen shines white for a moment when the power is turned off. However, in this apparatus, a reset pulse is applied to the character generator IC at the same time when the power is turned off, and the R
Since all the GB output terminals are set to the high level and applied to the CRT, the floating electrons are not always absorbed when the application time is short, and the screen may continue to be bright and bright for a while.

Further, stray emission cannot be prevented when a power failure occurs or the plug is pulled out.

The present invention has been made for the purpose of solving the above problems, and it is an object of the present invention to obtain a stray emission prevention device capable of preventing the occurrence of the stray emission phenomenon without giving the viewer anxiety. To aim.

[0009]

A cathode ray tube display device with a stray emission prevention function according to the present invention is a cathode ray tube for a predetermined time after receiving a power off command signal by means for transmitting a power on / off command signal. Is operated by a predetermined signal, and then the cathode ray tube is turned off.

Further, when the input power source is turned off, this is detected, and the cathode ray tube is operated by a predetermined signal for a predetermined time after the detection signal is output.

[0011]

According to the present invention, when a power-off command is received, a predetermined color signal, character signal, or pattern signal is input to the CRT instead of or superposed on the input video signal, and the entire screen is illuminated. Stray emissions do not occur because the power is turned off after the power is turned on.

When the input power is interrupted or the power plug is pulled out, the on-screen display signal is input by this detection signal to illuminate the entire screen, so that stray emission does not occur.

[0013]

EXAMPLES Example 1. FIG. 1 is a block circuit diagram of an embodiment of the present invention. The same reference numerals as those in FIG. 4 denote the same parts, and 9 denotes a remote control transmitter (hereinafter,
“Remote control transmitter”), 10 is a remote control receiving unit (hereinafter, “remote control receiving unit”), 11
Is a control unit (hereinafter,
"Microcomputer"), 12 is a remote control signal input terminal (IN
T) and 13 are R'G 'for sending an on-screen display (OSD) signal from the microcomputer 11 to the R'G'B' signal input terminal 14 of the video chroma junction IC 2.
B'signal output terminal, 15 is a plug connected to a commercial power supply, 16 is a power switch of the display device, 17 is a main power supply device, 18 is its power switch, 19 is an on / off control signal of the power switch 18 of the microcomputer 11. An output terminal, 20 is a standby power supply device, and 21 is a power failure detection circuit that detects when the power input to the display device is turned off.

Next, the operation will be described with reference to the flowchart of FIG. When the power-off instruction signal is sent from the remote controller 9, the power-off instruction signal is input from the remote controller receiver 10 to the remote control signal input terminal 12 of the microcomputer 11.
When the power-off command signal is input in step 1 (hereinafter abbreviated as "S1"), the microcomputer 11 proceeds to step S2, and outputs a predetermined color signal and character from the R'G'B 'signal output terminal 13. A signal, a pattern signal, or an OSD signal that combines these signals and that brightens the entire display surface of the CRT is sent to the R′G′B ′ signal input terminal 14 of the video chroma junction IC 2. Video Chroma Junction I
When C2 receives this OSD signal, R2 according to its contents
The GB signal is output from the RGB signal output terminal 4 to the cathode of the CRT 5 to display an image by the OSD signal on the display surface of the CRT 5. The microcomputer 11 proceeds to S3,
The main power supply off signal is sent out from the terminal 19 at a timing delayed by a predetermined time after the OSD signal is sent out to turn off the on / off switch 18 of the main power supply device 17.

When the drive input signal of the CRT 5 and the OFF operation of the switch of the main power supply device are controlled in this manner, the entire display surface of the CRT becomes bright when the main power supply device is turned off, so that the capacity 6 of the CRT is reduced. The charge is discharged quickly,
Stray emissions will not occur.

Next, the operation when the input power is interrupted, the power switch 16 of the display device is turned off, or the plug 15 is unplugged during operation will be described with reference to the flowchart of FIG.

In the above case, the input power of both the main power supply device 17 and the standby power supply device 20 is turned off, and the output potential V2 of the standby power supply device 20.
Falls. Then, the transistor Q2 of the power failure detection circuit 21 is turned on, and the microcomputer 1 is connected via the diode D2.
The “H” signal is input to the power failure detection signal input terminal 22 of No. 1. When the "H" signal is input in S4, the microcomputer 11 performs S
5 and proceed to the above OSD from the R'G'B 'signal output terminal.
The signal is sent and the video chroma junction IC2
The above OSD signal is output from the RGB signal output terminal 4 to the CRT 5
To display the image by the OSD signal on the display surface of the CRT 5.

When the drive input signal of the CRT is controlled in this manner, the entire display surface of the CRT is momentarily brightly lit upon power failure, and the electric charge of the CRT capacitor 6 is quickly discharged, so that no stray emission occurs.

[0019]

According to the present invention, when the power-off command signal is received, the CRT is operated by a predetermined signal, and then the switch of the main power supply device is turned off at an appropriate timing. A desired color, character, pattern, etc. can be displayed on the surface, and the effect of reliably preventing stray emission can be obtained.

Since a means for detecting a power failure is provided and the CRT is operated by a predetermined signal when a power failure is detected, the same effect can be obtained.

[Brief description of drawings]

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

FIG. 2 is a flow chart when the switch of the main power supply device of this embodiment is turned off.

FIG. 3 is a flow chart when the input power supply of this embodiment fails.

FIG. 4 is a block circuit diagram of a conventional cathode ray tube display device with a stray emission prevention function of this kind.

[Explanation of symbols]

 2 Video Chroma Junction (VCJ) IC 5 Color Cathode Ray Tube (CRT) 6 CRT Capacity 11 Microcomputer 17 Main Power Supply 20 Standby Power Supply 21 Power Failure Detection Circuit

Claims (2)

[Claims] 1. A means for transmitting a power-on / off command signal, a cathode-ray tube being powered off after a predetermined signal is operated for a predetermined time after receiving the power-off command signal by this means. A cathode ray tube display device with a stray emission prevention function, which is provided with a control means for setting the state. 2. A stray emission prevention function having means for detecting that the input power source is turned off, and control means for operating the cathode ray tube with a predetermined signal for a predetermined time after the input power source off detection signal is output. Cathode ray tube display device.