JPS6034864B2 - Television receiver protection circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a protection circuit for a television receiver, and an object of the present invention is to provide a circuit that is inexpensive, safer, and has good serviceability.

An example of a conventional circuit of this type is shown in FIG. 1 and will be described. 1st
In the figure, 1 is a horizontal oscillation circuit, 2 is a horizontal drive circuit,
3 is a horizontal output circuit, 4 is a flyback transformer,
The flyback transformer 4 has a high voltage output winding 4a for supplying high voltage from a cathode ray tube, a power supply winding 4b for supplying power to other circuits, and a protection circuit supply winding 4c as secondary windings. 6 represents a rectifier circuit connected to the power supply winding 4b, 8 represents loads such as a video output circuit and an audio output circuit,
The rectifier circuit 6 is composed of a protective resistor 6c, a rectifier diode 6a, and a smoothing capacitor 6b for eliminating the risk of fire or the like when an abnormality occurs in the rectifier circuit 6 and the load 8.

5 is a protection circuit having a comparison circuit 5a, and its output controls the horizontal oscillation circuit 1.

A power supply voltage is supplied from the 10B terminal 7 as a reference voltage to the comparison circuit 5a, and the comparison circuit 5a compares this reference voltage with the voltage from the protection circuit supply winding 4c. Therefore, when the high voltage output becomes abnormally high and the X-ray leakage exceeds the standard value, the high voltage of the high voltage output winding 4a increases and the pulse voltage supplied from the winding 4c increases almost proportionally. As a result, the protection circuit 5 which is compared with the reference voltage is activated to stop the horizontal oscillation circuit 1, thereby stopping X-ray leakage. On the other hand, when the transistors constituting the video output circuit, audio output circuit, etc., which are the load 8, are short-circuited, or when the diode 6a and the capacitor 6b are short-circuited, a large current flows through the resistor 6c, which causes this resistor, which is a metal film resistor, to short-circuit. 6c (for example, 1/2W, 10) was disconnected to cut off the current.

However, when the resistor 6c is disconnected in this way, it is necessary to replace the resistor 6c as well as the component that caused the failure, resulting in poor serviceability during repair. The present invention eliminates the need for this resistor and provides a circuit that is inexpensive, has good serviceability, and operates more safely.One embodiment of the present invention will be described below with reference to the drawings. In FIG. 2, the same parts as in FIG. 1 are given the same numbers and will be explained. This circuit is characterized by eliminating the conventional resistor 6c and using the output of the 1B rectifier circuit 6 instead of using the 1B voltage as the reference voltage for the comparator circuit 5a. When an abnormally high voltage occurs here and the output of the winding 4a increases, the output voltage of the winding ja also increases almost in proportion to this, while the output of the rectifier circuit 6 is connected to the zener diode provided in the comparator circuit 5a. Since the voltage is kept almost constant by the stabilizing circuit, the output voltage of the winding 4c becomes larger than the reference voltage which is the output of the rectifier circuit 6, and detecting this difference, the protection circuit 5 starts horizontal oscillation. It outputs an output to stop the circuit 1.

Therefore, it is possible to prevent X-rays from leaking due to abnormally high pressure. Also, if the load 8 and the elements of the rectifier circuit 6 are short-circuited, the output of the rectifier circuit 6 will decrease, so while the output of the winding 4c is normal, the output of the rectifier circuit 6 will be low, and this difference will be compensated for. The protection circuit 5 outputs an output to cause the horizontal oscillation circuit 1 to operate upon detection by the comparison circuit 5a.

Therefore, current is prevented from flowing into the rectifier circuit 6 and the load 8. Note that the output of the winding 4c is rectified and smoothed in the comparator circuit 5a and converted into direct current. As described above, according to the present invention, even if the high voltage becomes abnormal, the rectifier circuit or the load becomes abnormal, the single protection circuit 5 can be used to stop the horizontal oscillation.

Further, since a protective resistor is not required, the cost is reduced, and serviceability is improved since there is no need to replace a broken protective resistor during repair.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a protection circuit for a conventional television receiver, and FIG. 2 is a block diagram of a protection circuit for a television receiver according to an embodiment of the present invention. 1...Horizontal oscillation circuit, 2...Horizontal drive circuit, 3...Horizontal output circuit, 4...Flyback transformer, 4c...Protection circuit for connection winding wire,
5... Protection circuit, 5a... Comparison circuit, 6a
...... Rectifier diode, 8... Load. Figure 1 Figure 2

Claims (1)

[Claims] 1 High voltage output winding on the secondary side of the flyback transformer,
A power supply winding for supplying power supply voltage and a protection circuit winding for supplying voltage to the protection circuit are provided, a rectifier circuit is connected to the power supply winding, and the output of the rectifier circuit is connected to a constant voltage element. A comparator circuit is provided to compare the reference voltage created in addition to the rectified voltage of the output of the protection circuit winding, and a horizontal oscillation circuit that supplies a signal to the primary side of the flyback transformer is connected to the comparator circuit. A protection circuit for a television receiver characterized by output control.