JPS58127473A - Horizontal deflecting circuit containing high voltage protecting circuit - Google Patents

Abstract

PURPOSE:To prevent the destruction of a horizontal output transistor, by detecting the presence of an input to a horizontal driving circuit, and actuating a high voltage protecting circuit while a horizontal driving transistor is turned off. CONSTITUTION:For a horizontal deflecting circuit of a TV picture receiver, the output terminal of a horizontal oscillating circuit 13 is connected to the base terminal of a horizontal driving transistor TR16 via a current limiting resistance 15 as well as to the base terminal of a timing TR32 via a resistance 31. The emitter of the TR32 is grounded with its emitter connected to the gate of an SCR28. When the TR16 is turned on, the TR32 is also turned on. Then the abnormal voltage pulse flows to the TR32 from the tertiary coil of a flyback transformer via a diode 26 and a Zener diode 27. Thus the operation of the SCR28 is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a horizontal deflection circuit, and more particularly to an improvement in a horizontal deflection circuit equipped with a high voltage protection circuit for detecting and preventing an abnormal rise in voltage applied to a cathode ray tube anode terminal.

The high voltage protection circuit in the conventional horizontal deflection circuit rectifies and detects the voltage generated in the tertiary coil of the flyback transformer in the high voltage generation circuit using, for example, a diode.If the detected voltage abnormally rises above a certain value, it immediately shuts down the voltage. It was configured to stop the operation of the horizontal drive circuit and continue to do so to stop the operation of the horizontal output circuit.

Incidentally, the horizontal drive circuit is mainly composed of a horizontal drive transistor and a horizontal drive transformer, and the secondary terminal of the horizontal drive transformer is configured to be connected to the horizontal output transistor of the horizontal output circuit. The horizontal drive transistor operates as a switching element in the same way as the horizontal output transistor, and when the horizontal output circuit is on, the horizontal drive circuit is off, and when the horizontal output circuit is off, the horizontal drive circuit is on. A circuit in which the transistor always acts as a load for the horizontal drive transformer is common.

Then, when the high voltage protection circuit detects an abnormal voltage and stops the operation of the horizontal drive transistor, if the horizontal drive transistor is in the on state, the transistor is switched from on to off.

This means that the horizontal drive transistor operates to turn on the horizontal output transistor, and if an abnormal voltage pulse is generated at the collector of the horizontal output transistor at this time, the horizontal output transistor will consume a large amount of power and be destroyed. was there. In other words, despite having a high voltage protection circuit, the horizontal output transistor was sometimes destroyed.

Therefore, the main object of the present invention is to provide a horizontal deflection circuit which eliminates the above-mentioned drawbacks and allows the high voltage protection circuit to operate more appropriately.

To summarize this invention, the presence or absence of input to the horizontal drive circuit is detected, and the operation timing is adjusted so that the high voltage protection circuit is activated when the horizontal drive transistor is in the OFF state, thereby preventing destruction of the horizontal output transistor. This is a horizontal deflection circuit.

The above-mentioned objects, configurations, and effects of the present invention will become clearer from the description made with reference to the following drawings.

FIG. 1 shows a block diagram of a horizontal deflection circuit of a television receiver as an embodiment of the present invention.

In FIG. 1, oscillation circuit 1. A feature of the present invention is that an operable circuit 5 is added to the conventional horizontal deflection circuit consisting of a drive circuit 2, an output circuit 3, and a high voltage protection circuit 4.

FIG. 2 shows a circuit diagram of a horizontal deflection circuit of a television receiver as an embodiment of the present invention. The configuration of the circuit diagram will be explained. DC electricity! 11 is connected to a horizontal oscillation circuit 13 via a voltage drop resistor 12. Further, a voltage drop capacitor 14 is connected in parallel with the horizontal oscillation circuit 13. One end of the horizontal oscillation circuit is grounded, and the output end is connected to the base terminal of a horizontal drive transistor 16 via a current limiting resistor 15. The horizontal drive transistor 16 is a transistor used with a common emitter, and its collector terminal is connected to one of the primary terminals of the horizontal drive transformer 17. The other terminal on the primary side of the horizontal drive transformer 17 receives power from the DC power supply 11. Further, one of the secondary side terminals of the transformer is grounded, and the other side is connected to the base terminal of the horizontal output transistor 18. The horizontal output transistor 18 is used with its emitter grounded, and its collector terminal is connected to one terminal on the primary side of the flyback transformer 19. The other terminal on the primary side of the flyback transformer 19 is connected to the DC power supply 11 similarly to the horizontal drive transformer 17 .

Also, a damper diode 20. is connected in parallel between the horizontal output transistor and the flyback transformer. Resonant capacitor 2
1. A series connection of horizontal deflection coil 22 and correction capacitor 23 is connected. One of the secondary terminals of the flyback transformer 19 is connected to the cathode ray tube 2 via a high voltage rectifier diode 24.
5, and the other one is grounded.

Furthermore, the other one of the tertiary terminals of the flyback transformer, one of which is grounded, is connected to the anode terminal of a rectifier diode 26, the cathode terminal of which is connected to the cathode terminal of a Zener diode 27, and the anode terminal is connected to the gate terminal of the thyristor 28. connected to. This thyristor 28 has its 7-node terminal connected to the DC current mii via a resistor 29, and its cathode terminal connected to the base terminal of a detection transistor 30 whose emitter is grounded. The collector terminal of the detection transistor 3° is connected to the contact between the current limiting resistor 15 and the horizontal drive transistor 16. In addition, the contact point between the horizontal oscillation circuit 13 and the resistor 15 is connected via a resistor 31 to the base terminal of a transistor 32 for synchronizing the operation timing, and the collector terminal of this transistor is connected to the gate terminal of the Zener diode 27 and the 5CR28. connected to the contact point.

Note that the transistor 32 is used with its emitter grounded. A rectifying capacitor 33 and a rectifying resistor 34 are connected in parallel to the ground between the diode 26 and the Zener diode 27, and the gate terminal of the 5CR28 and the transistor 3 are connected in the same way.
Between the collector connection point of 2 is a resistor 35, and a transistor 3o
The base of is grounded through a resistor 36.

In addition, in the circuit diagram, the resistor 31. Two new parts, the transistor 32, are required compared to the conventional circuit, but there are currently many ICs with built-in high voltage protection circuits, and this circuit is also configured inside the IC, which increases the number of parts and costs. No problem arises.

Next, the operation of this circuit will be explained with reference to FIG.

The voltage generated in the flyback transformer tertiary coil is rectified by the diode 26 to provide a detection voltage, and an increase in high voltage can be detected by increasing this voltage.

Therefore, when this voltage rises and exceeds the Zener voltage of the Zener diode 27, a voltage is applied to the gate of the 5CR28, the 5C828 is turned on, and the transistor 30 is turned on, so that the horizontal drive transistor 16 is no longer biased and is turned off.

However, if the horizontal drive transistor 16 is in the on state at the time when the horizontal drive transistor 16 is turned off by this action of the transistor 30, the operation from on to off of the horizontal drive transistor 16 is controlled by the horizontal output transistor as described above. operates to turn on 18,
A collector current of the horizontal output transistor 18 flows. This will become even clearer when looking at FIGS. 3A to 3B.

In this case, if five high-voltage pulses are generated at the collector of this transistor, the horizontal output transistor 18 will consume a large amount of power, and the horizontal output transistor 18 may be destroyed.

Incidentally, in this circuit, when the horizontal drive transistor 16 is on, the transistor 32 is also on, and conversely, when one is off, the other is also off. Now, when the horizontal drive transistor 16 is on, if the detection voltage increases abnormally and exceeds the Zener voltage, the diode 26. zener diode 2
The current flowing through the horizontal drive transistor 1
Similarly to 6, it is grounded through the transistor 32 which is on. Therefore, 5CR28 is not turned on. Conversely, when the transistor 32 is off, the detection voltage turns on the 5CR28 and turns off the horizontal drive transistor 16 by the transistor 30, but since the horizontal drive transistor 16 is off at this time, the horizontal output transistor 18
The problem of turning on does not arise. If the horizontal drive transistor 16 is kept off, the horizontal output transistor 18 is also turned off and the generation of high voltage is stopped.

As described above, according to the present invention, the high voltage protection circuit operates only when the horizontal drive transistor is in the off state.
Therefore, the horizontal output transistor will not be destroyed,
It is possible to create a horizontal deflection circuit in which the high voltage protection circuit operates more appropriately.

[Brief explanation of drawings]

FIG. 1 shows a block diagram of the invention, FIG. 2 shows a circuit diagram of an embodiment of the invention, and FIG. 3 shows a waveform diagram of an embodiment of the invention. In the figure, 5 is an operable circuit, 16 is a horizontal drive transistor, 17 is a horizontal drive transformer, 18 is a horizontal output transistor, 19 is a flyback transformer, 26
27 is a rectifier diode, 27 is a Zener diode, 28 is an SCR, 30 is a detection transistor, and 32 is an operation timing transistor. Agent Shin Kuzuno - (1 other person)
Figure 1, Figure 3

Claims (1)

[Scope of Claims] A horizontal oscillation circuit, a horizontal drive circuit that operates upon receiving the output from the horizontal oscillation circuit, a horizontal output circuit that operates based on the output of the horizontal drive circuit, and an output voltage of the horizontal output circuit. In a horizontal deflection circuit consisting of a high voltage generation circuit that boosts the voltage and supplies it to the 7 node terminals of the cathode ray tube, and a high voltage protection circuit that detects abnormal voltage generated in the high voltage generation circuit and stops the operation of the horizontal output circuit, detects the presence or absence of input of the horizontal drive circuit, and detects the presence or absence of the input