JPH0223777A - Television receiver - Google Patents

Abstract

PURPOSE:To surely discharge high voltage remaining in a Braun tube at the time power supply is turned off regardless of the load situation of a circuit by providing a means to make a video output circuit generate an output forcedly at the time the power supply is turned off. CONSTITUTION:When the power supply is turned off by a remote controller, the output of a control circuit 11 changes into H-level from L level rapidly, and a switching circuit 12 is inverted into a conductive state. Therefore, the emitters of the amplifying transistors 2a to 4a of respective primary color signal amplifiers 2 to 4 are turned into a grounded state by the switching circuit 12. At that time, since a chroma video processing circuit 1 or the amplifiers 2 to 4 stay at a state capable of operating by each remaining bias voltage, consequently, the amplifiers 2 to 4 come to be operated forcedly toward a white direction, and the picture of the Braun tube 9 turns into a shining state for a moment, and the high voltage remaining at the anode side of the Braun tube 9 comes to be discharged rapidly.

Description

[Detailed Description of the Invention] The present invention provides a television receiver that prevents high voltage from remaining on the anode side of a cathode ray tube when the power is turned off, particularly a television receiver with a remote control. It is related to.

Traditionally, television receivers with remote controls have been powered on or off by control signals from a remote control transmitter while the main power switch remains on.
For example, turning off the power was done by turning off the oscillation of the horizontal circuit inside the television receiver.

However, when the power is turned off in such a television receiver with a remote control, the off operation of the circuit is first caused by the oscillation off of the horizontal circuit - the flyback transformer supplied from the flyback transformer. Since each bias voltage is turned off in the order in which each bias voltage is turned off, it takes some time for each bias voltage to actually turn off after the remote control is turned off. The falling time was different. Therefore, when the power is turned off by remote control, each bias voltage remains, and as a result, the high voltage applied to the cathode ray tube sometimes remains, causing a problem called stray emissions. was occurring.

The present invention has been made in view of the above points, and an object of the present invention is to provide a television receiver that can reliably discharge the high voltage remaining in the cathode ray tube when the power is turned off, regardless of the load condition of the circuit. purpose.

In order to achieve the above-mentioned object of reducing the noise, the present invention provides a television equipped with means for applying a high voltage to the anode side of a cathode ray tube and a video output circuit for supplying a drive signal to the cathode side of the cathode ray tube. The receiver is provided with means for forcibly producing an output from the video output circuit when the power is turned off.

Effect: According to this configuration, when the power is turned off, the screen of the cathode ray tube is made to shine (that is, brightened) momentarily, and the high voltage remaining on the anode side of the cathode ray tube is discharged.

implementation - second doctor An embodiment of the present invention will be described below with reference to the drawings.

That is, (1) in the figure is the intermediate frequency amplification from the tuner,
Chroma/video processing circuit (2) that processes the signal sent out after video detection and outputs three color difference signals (R-Y, G-Y, B-Y) and a luminance signal (-Y). )
(3) (4) is a primary color signal amplifier that outputs three primary color signals (-R, -G, -B) with three color difference signals and a luminance signal, and each primary color signal amplifier (2) (3) (4) Each color difference signal is supplied to the base of the amplification transistors (2a), (3a), and (4a) that constitute the , and the luminance signal amplified by the video amplifier (5) is supplied to each emitter of the resistor (6).
(7) Supplied via (8). (9) has its cathode supplied with the three primary color signals from the respective primary color signal amplifiers (2), (3), and (4), and its anode applied with a high voltage from a high voltage circuit (10) consisting of a flyback transformer, etc. (11) is a control circuit (microcomputer) that rapidly switches the output from its output end to L level/H level when the power is turned on and off by remote control, (12) is a control circuit (11)
When the power is turned off by remote control, the video output circuit (i.e.,
A switching circuit that forcibly generates the output of primary color signal amplifiers (2) (3) (4), video amplifier (5), etc., and the switching circuit (12) includes a switching transistor (13) and a resistor (14) ( 15) and a diode 16).

Therefore, in the above configuration, when the power is turned off by remote control, the output terminal (
The output from lla) quickly changes from the L level to the H level, and the base of the switching transistor (13) is biased to the H level via the resistors (14) and (15), and is inverted to a conductive state. Therefore, the amplification transistor (2) of each primary color signal amplifier (2) (3) (4)
a) The emitter of (3a) (4a) is a resistor (6) (
7) It becomes grounded by the switching transistor (13) via (8) and the diode (16). At this time, the chroma video processing circuit (1) and each primary color signal amplifier (2), (3), and (4) are still operable due to the remaining bias voltages, so as a result, each primary color signal amplifier ( 2) (3) (4) are forced to move towards white, and the CRT (9)
The screen becomes bright for a moment (that is, the electron beam is emitted from the cathode side to the anode side),
The high voltage remaining on the anode side of the cathode ray tube (9) is rapidly discharged.

Note that when the power is turned on by remote control, the output from the output terminal (lla) of the control circuit (11) is at L level, so the chroma/video processing circuit (1) and each primary color signal amplifier (2) (3) (4) ) is the switching circuit (
12), normal operation will be performed using the primary color drive method without being affected by the above.

Mitsugai: As previously mentioned, according to the television receiver of the present invention, the high voltage remaining on the anode side of the cathode ray tube when the power is turned off is reliably discharged regardless of the various elements on the circuit. , it is possible to eliminate the adverse effects on the circuit caused by high voltage remaining in the cathode ray tube, and the circuit design becomes easier.

[Brief explanation of the drawing]

The figure is a block diagram of a television receiver that is an embodiment of the present invention. (1)-1-Chroma video processing circuit. Primary color signal amplifier. Braun tube. switching circuit. Applicant Sharp Corporation Agent

Claims (1)

[Claims] (1) A television receiver comprising means for applying a high voltage to the anode side of a cathode ray tube and a video output circuit for supplying a drive signal to the cathode side of the cathode ray tube, wherein the video output circuit is activated when the power is turned off. A television receiver characterized by being provided with means for forcibly producing an output.