JPS5812788B2 - X Senhoushi Yaboushi Cairo - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an X-ray radiation prevention circuit. In a television receiver, X-ray radiation occurs when high-voltage power becomes abnormally large; this is because the anode voltage is high; Moreover, it becomes the largest when the anode current increases.

An object of the present invention is to simultaneously detect an increase in anode voltage and an increase in anode current, stop horizontal oscillation, and prevent the generation of X-ray radiation.

In FIG. 1, a conventional example of an X-ray radiation prevention circuit including a horizontal oscillation output circuit will be described (description of the horizontal deflection circuit will be omitted).

In FIG. 1, numeral 6 denotes a protection circuit, which performs the following operations.

A horizontal pulse is taken out from the tertiary winding 5 of the horizontal output flyback transformer 2, rectified by a diode 17, smoothed by a capacitor 16, and divided by a resistor 15, 13 and a volume 14 for adjusting the operation start voltage to obtain a rectified DC voltage. .

This voltage is applied to the cathode terminal of the Zener diode 12.

It is applied from the anode terminal of the Zener diode 12 to the base terminal of the SCS (a type of thyristor) 7 through the low resistor 9.

When the high-voltage current becomes abnormally high and X-ray radiation is about to occur from the picture tube, the horizontal pulse generated in the tertiary winding 5 of the flyback transformer 2 also increases at the same time.

As a result, the rectified voltage applied to the cathode terminal of the Zener diode 12 increases, and when it exceeds the contact potential between the base and emitter of the SCS 7 and the Zener voltage of the Zener diode 12, the SCS 7 is turned on and becomes active.

Note that the resistor 9 is a protective resistor.

In this state, the power supply voltage of the horizontal oscillation circuit is lowered through the SCS 7 to a level lower than the normal operating potential.

In other words, the voltage applied to terminal 20 is resistor 18KΩ and resistor 1K.
Ω and SCS7, and the potential of the oscillation circuit power supply line 21 is lowered to near zero potential.

As a result, the oscillation stops, the horizontal output also stops, high voltage output is no longer produced, and there is no need to worry about X-ray radiation.

The SCS 7 remains on while the power supply voltage is applied to the terminal 20.

In the figure, 1 is a synchronous pulse input terminal, 3 is a primary winding, 4 is a high voltage winding, 8 is a capacitor for preventing the operation, 10 is a diode, 11 is a protective resistor, and 19 is a diode.

By the way, this circuit normally operates only when the high voltage pulse becomes high, and does not operate when the anode load current increases.

The present invention has been made to address this problem, and the present invention will be explained below based on drawings showing an example of multiple implementation.

Note that parts common to those in FIG. 1 are designated by the same reference numerals.

The anode terminal of the Zener diode 12 is grounded via the light emitting diode 10' and the protective resistor 11.

At the same time, a light emitting diode 18 is connected to the ground side of the flyback transformer 2, and its anode terminal is grounded.

Also, a photothyristor 7' is used as a switching element in place of the SCS 7 in FIG.
Ω, and the emitter of the photothyristor 7' is grounded.

The light emitting diodes 10', 18 and the photothyristor 7
′ constitutes a multi-photocoupler.

With the above configuration, if the high voltage increases abnormally, the horizontal pulse generated in the tertiary winding of the flyback transformer 2 increases, the rectified voltage increases, and the Zener diode 12
, the Zener voltage of the DC circuit of the light emitting diode 10' is exceeded, and a current is emitted in the light emitting diode 10'.

This light is received by the photothyristor 7', which turns on and stops the horizontal oscillation as in the case of FIG. 1.

Also, when the anode load current increases abnormally, the light emitting diode 18 emits light and stops oscillating.

Since the X-ray radiation prevention circuit of the present invention can be implemented as described above, when the increase in the anode voltage and the increase in the anode current become abnormally large, each change can be detected simultaneously and the product of the increase can be detected. (power) activates the protection circuit, stopping oscillation and high voltage output.

Therefore, X-ray radiation can be detected reliably, and the safety of the receiver can be improved.

In addition, in order to perform control by detecting two types of anode voltage and anode current in this way, it is generally necessary to have a mixing and synthesizing circuit for the two detection outputs and a control output from that output. However, according to the present invention, two light emitting diodes and one Since a multi-photocoupler consisting of two photothyristors is used, there is no mutual interference between the light emitting diodes, the operation is accurate, and a mixing/synthesizing circuit is not required, making it possible to simplify the circuit configuration.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing a conventional example, and FIG. 2 is a circuit diagram showing an example of implementation of the present invention. 1... Synchronous pulse input terminal, 2... Flyback transformer, 7' Photothyristor, 10'... Light emitting diode, 11... Protection resistor, 12... Zener diode, 18... Light emitting diode .

Claims (1)

[Claims] 1. The horizontal output pulse voltage taken out from the tertiary winding of the high-voltage generating trackless whose primary winding is connected to the horizontal deflection circuit is rectified by a diode, and sent to the Zener diode, and between the anode of the Zener diode and the ground. A first light emitting diode is connected, a photothyristor is connected between the power line of the horizontal oscillation circuit and the ground, and a second light emitting diode is connected to the ground side terminal of the high voltage winding of the high voltage generating transformer. The second light emitting diode and the photothyristor constitute a multi-photocoupler, and when the anode voltage becomes abnormally high or the anode current increases, the photothyristor receives the light emitted from any of the light emitting diodes. 1. An X-ray radiation prevention circuit characterized in that X-ray radiation is prevented by turning on a photothyristor of a lever, lowering a power supply voltage for a horizontal oscillation circuit, and stopping oscillation.