JPH06268880A - Protecting circuit - Google Patents

Abstract

PURPOSE:To avoid burning of a CRT phosphor or the operation in the blackout state by operating a power source turning-off circuit through an operating circuit in the case of abnormal stop of a resonance type horizontal output circuit or a resonance type high voltage generating circuit. CONSTITUTION:When a resonance type horizontal output circuit 17 and a resonance type high voltage generating circuit 18 are normally operated together, a flyback pulse voltage is generated between the collector and the emitter of an output transistor TR. Consequently, the same pulse voltage appears across a resistor 12 and is rectified through a buffer 13 by a diode 14 and a capacitor 19, and a positive DC voltage is generated in the cathode of the diode 14. If the circuit 17 or 18 is abnormally stopped, the positive DC voltage is not generated in the cathode of the diode 14 because the flyback pulse voltage is generated in the output TR of the stopped circuit. Then, a diode 20 is made conductive, and an abnormal mode discriminating circuit 15 is operated, and a control signal operates a power shut-down circuit 16 to stop the power supply. Thus, burning of the CRT phosphor or the operation in the blackout state is avoided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a television receiver,
The present invention relates to a protection circuit for the purpose of preventing burning of a CRT (cathode ray tube) phosphor of a monitor television or the like.

[0002]

2. Description of the Related Art In recent years, in television receivers, monitor televisions, etc., the number of horizontal output colors and the high-voltage generating circuit are designed independently of each other. Along with this, a protection circuit especially for preventing the CRT phosphor from burning has become necessary.

A conventional resonance type horizontal output / high voltage generating circuit will be described below. FIG. 2 shows a conventional resonance type horizontal output / high voltage generating circuit. In FIG. 2, 1 is an output transistor, 3 is a resonance capacitor, 4 is a damper diode, 5 is a deflection yoke, 6 is an S-shaped capacitor, 8 is a power supply, 9 is a flyback transformer, 10 is a rectifying diode, and 11 is a CRT. . In the resonance type horizontal output / high voltage generating circuit configured as described above, a flyback pulse voltage as shown in FIG. 3 is generated between the collector emitters of the output transistor 1. This voltage is boosted by the flyback lens 9 and used as the anode voltage of the CRT 11. Therefore, if the operation of the horizontal output circuit is stopped and the flyback pulse disappears, the boost pulse cannot be output from the output of the flyback transformer.

[0004]

However, in recent years,
In a television receiver, a monitor TV, etc., in which a horizontal output circuit and a high voltage generation circuit as shown in FIG. 4 are used independently, a resonance type high voltage generation is generated during operation even if the resonance type horizontal output circuit is stopped. Since the circuit is operating, the beam concentrates in one direction vertically on the center of the CRT screen, burning the phosphor, and even if the resonant high-voltage generating circuit stops during operation, the resonant horizontal output circuit and , And other circuits are operating, so there was a problem in that they were set to blackout on the screen and continued to operate.

The present invention solves the above problems,
The purpose is to stop the power supply to prevent the CRT phosphor burning and the blackout operation even if either the resonance horizontal output circuit or the resonance high voltage generating circuit is stopped.

[0006]

In order to achieve this object, the protection circuit of the present invention has a resonance horizontal output circuit and a resonance high voltage generating circuit having the same structure, and each output voltage pulse is capacitively divided. An abnormal condition that is taken out by two detection circuits that rectify and output it, and an OR circuit that uses a diode, and that operates when either the resonance type horizontal output circuit or the resonance type high voltage generation circuit stops abnormally A protection circuit that activates the power shutdown circuit through the mode determination circuit.

[0007]

With this configuration, the resonant horizontal output circuit or
The power supply is automatically stopped when either of the operations of the resonance type high voltage generation circuit stops abnormally.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, reference numeral 17 is a resonant horizontal output circuit, and 18 is a resonant high voltage generating circuit. During normal operation, a flyback pulse voltage as shown in FIG. 3 is generated between the collector and emitter of the output transistor in both circuits.
Therefore, a pulse voltage appears also across the resistor 12, passes through the buffer 13, is rectified by the diode 14 and the capacitor 19, and a positive DC voltage is generated at the cathode of the diode 14. If either the resonance-type horizontal output circuit 17 or the resonance-type high-voltage generation circuit 18 is abnormally stopped, the flyback pulse voltage is not generated in the output transistor of the stopped circuit, so that a positive DC voltage is also applied to the cathode of the diode 14. It will not occur. Then, the diode 20 becomes conductive, the abnormal mode determination circuit 15 operates, the control signal is sent to the power supply shutdown circuit 16, and the power supply as a set is stopped.

[0010]

EFFECT OF THE INVENTION In the resonance type horizontal output circuit and the resonance type high voltage generating circuit having the same structure, two detection circuits for extracting each output voltage pulse by capacity division, rectifying and outputting it, and a diode are used. By providing a protection circuit that activates the power supply shutdown circuit through an abnormal mode determination circuit that is continued by the OR circuit and operates when either the resonance type horizontal output circuit or the resonance type high voltage generation circuit stops abnormally, the CRT fluorescence is provided. You can avoid burning your body and avoiding blackouts.

[Brief description of drawings]

FIG. 1 is a protection circuit according to an embodiment of the present invention.

[Figure 2] Conventional resonant horizontal output / high voltage generation circuit diagram

FIG. 3 Flyback pulse voltage waveform diagram

[Fig. 4] Independent resonant horizontal output circuit and resonant high voltage generation circuit diagram

[Explanation of symbols]

 1 output transistor 2 capacitor 3 resonance capacitor 4 damper diode 5 deflection yoke 6 S-shaped capacitor 7 choke coil 8 power supply 9 flyback transformer 10 rectifier diode 11 CRT 12 resistor 13 buffer (emitter follower) 14 diode 15 abnormal mode determination circuit 16 power supply shutdown Circuit 17 Resonant horizontal output circuit 18 Resonant high voltage generating circuit 19 Capacitor 20 Diode

Claims (1)

[Claims] 1. A horizontal output circuit and a resonant high-voltage generating circuit, each output voltage pulse is extracted by capacitance division,
Abnormal mode determination that is connected by two detection circuits that rectify and output it and an OR circuit that uses a diode, and operates when either the resonance horizontal output circuit or the resonance high voltage generation circuit stops abnormally C and a power supply shutdown circuit for stopping the power supply based on the judgment output from the abnormal mode judgment circuit.
RT protection circuit.