JPS6047569A - X-rays protecting circuit - Google Patents

Abstract

PURPOSE:To prevent malfunction due to a short-time single output such as click sound and stabilize the operation of a circuit by utilizing variation in the output voltage of an abnormal high voltage detecting circuit, and turning on and off a Zener diode connected in series with the gate of a silicon controlled rectifying element. CONSTITUTION:The series circuit of a resistance 20 and a capacitor 21 whose values are so set that a time constant is sufficiently long is connected to the output terminal 14 of the abnormal high voltage detecting circuit 1 of a color TV receiver. The cathode of the Zenor diode 22 is connected to the intersection of the resistance 20 and capacitor 21, and the anode of the diode 22 is connected to the gate of th silicon controlled rectifying element 15. This element 15 is connected between a power source +B and the ground through a resistance 16, and the gate of a transistor TR18 connected to a horizontal deflecting circuit 19 is connected to the connection point of the resistance 16 and element 15. Then, if the power source or circuit 12 is failed and an abnormal voltage is outputted to the circuit 1, the element 15 is turned on while not turned on with a single output, stabilizing the operation of the circuit.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is applicable to
This relates to line protection circuits.

Conventional configuration and its problems A typical example of an X-ray protection circuit for a conventional color television receiver is shown in FIG. In the figure, 1 is a high-voltage abnormal voltage detection circuit section, and 2 is connected to the winding of a fly bank transformer. The winding terminal of the flyback transformer 2 is connected to the anode of the diode 3, and the
The cathode of is grounded via a capacitor 4.

A connection point between the diode 3 and the capacitor 4 is grounded via a resistor 5 and a resistor 6. The connection point between the resistor 5 and the resistor 6 is connected to the base of the transistor 7, the resistor 8 is connected to the emitter of the transistor 7, and the cathode of the Zener diode 9 is connected to the connection point between the emitter of the transistor 7 and the resistor 8. The anode of the connected Zener diode 9 is grounded. Still transistor 7
The collector of transistor 7 is connected to transistor 10B through resistor 10, and the connection point between the condenser of transistor 7 and resistor 10 is transistor 3.
1, --- Connected to the base of Sister 11. The emitter of the transistor 11 is connected to 10B through a resistor 12, and the collector of the transistor 11 is similarly grounded through a resistor 13. 1. The connection point 14 between the collector of the run sister 11 and the resistor 13 is the output terminal of the high voltage abnormal voltage detection circuit section.

The output terminal 14 is connected to the gate of a silicon-controlled rectifier 15, and the anode of the silicon-controlled rectifier 15 is connected to 10B. On the other hand, the cathode of the silicon-controlled rectifying element 15 is grounded through a resistor 16. A connection point between the cathode of the silicon-controlled rectifying element 15 and the resistor 16 is connected to the base of the transistor 18 via a resistor 17.

The emitter of transistor 18 is grounded, while the collector is connected to horizontal deflection circuit 19.

Next, the operation of this circuit will be explained.

In a normal image receiving state, the high voltage abnormal voltage detection circuit section 1
Since it is configured so that it does not operate, no output is output from the output terminal 14. Therefore, silicon controlled rectifier 15
does not operate, and similarly, transistor 18 also does not operate.

As a result, there is no influence on the horizontal deflection circuit 19.

Next, a case will be described in which the high voltage increases due to various abnormalities occurring in the receiver. An increase in high voltage means that the pulse generated in the flybank transformer increases, so the voltage at the winding terminals of the flyback transformer 2 increases, and the transistor 7 obtained by rectifying the voltage increases.
The base potential of is lowered and the transistor 7U is turned on.

When the transistor 7 is turned on, the transistor 11, which had been off, is turned on and a gate current flows into the silicon-controlled rectifying element 15, so that the silicon-controlled rectifying element 15 is also turned on. When the silicon-controlled rectifying element 15 turns on, the transistor 18, which had been off until then, turns on. transistor 18
When the horizontal deflection circuit 19 turns on, the operation of the horizontal deflection circuit 19 stops and high voltage is no longer output. This circuit is widely used as an X-ray protection circuit because no high voltage is generated, which means there is no risk of X-rays being generated.

However, with this circuit, even when it is not supposed to work, such as when the power supply circuit or horizontal deflection circuit breaks down, for example, a crackling sound occurs, or when the horizontal frequency suddenly shifts to a lower side when using TR. Even in such a case, the winding terminal voltage of the flyback transformer 2 in FIG. 1 increases, and as a result, the X-ray protection circuit is activated. As described above, the conventional circuit (FIG. 1) has the disadvantage of being prone to malfunction.

OBJECTS OF THE INVENTION The present invention aims to eliminate the above-mentioned drawbacks and provide a stable X-ray protection circuit for color television receivers that does not malfunction due to short single outputs due to putty sounds, etc. .

Structure of the Invention The X-ray protection circuit according to the present invention connects a series circuit of a resistor and a capacitor whose values are selected so as to have a sufficiently long time constant to the output section of a high-voltage abnormal voltage detection circuit. The cathode of a Zener diode is connected to the intersection, and the anode of this Zener diode is connected to the gate of a silicon-controlled rectifying element. Therefore, a short single output due to crackling noise etc. can be used as an abnormal voltage detection circuit. Even if it is led out to the output section of the silicon-controlled rectifying element, it is possible to maintain the OFF state of the silicon-controlled rectifying element and prevent malfunction.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 2 shows a circuit diagram of an X-ray protection circuit according to an embodiment of the present invention, and the same numbers as in FIG. 1 indicate the same elements.

Output terminal 14 of high voltage abnormal voltage detection circuit section 1 and resistor 2
0 and a capacitor 21 are connected, and the other end of the capacitor 21 is grounded. Still 20 resistors and 2 capacitors
The cathode of the Zener diode 22 is connected to the connection point 1, and the anode of the other end is connected to the gate of the silicon-controlled rectifier 15.

The charging time constant of the series circuit 7bag consisting of resistor 20 and capacitor 21 is chosen to be sufficiently long as shown in FIG.

Next, the operation of this circuit will be explained.

In a normal state, since no output is output to the output terminal 14, the potential at the connection point 23 between the resistor 2o and the capacitor 21 is zero. Therefore, the contact control rectifying element 16 maintains an OFF state.

Next, we will explain the case where some kind of abnormality occurs in the receiver and the high voltage rises.0 When a crackling sound occurs and the abnormal voltage detection circuit 1 operates and an output comes out to the output terminal 14, the resistor 2o and capacitor 2
The potential at the connection point 23 of No. 1 increases as shown in FIG. However, if the crackling sound stops before the Zener diode 22 is charged to the Zener voltage VZ22, the output from the output terminal 14 will stop coming out, so the potential at the connection point 23 will not rise any further, and the Zener The diode 22 is not conductive and the silicon-controlled rectifier 15 maintains the same off state as before the crackling.

JP-A-47569 (3) When the abnormal voltage detection circuit section 1 operates due to a failure in the power supply circuit or the horizontal deflection circuit, and an output appears at the output terminal 14, the potential at the connection point 23 will be as shown in FIG. It continues to rise as shown in the characteristic shown, and eventually tries to rise above the Zener voltage VZ22 of the Zener diode 22. Then, the Zener diode 22 becomes conductive and the silicon-controlled rectifier 1
5 is in the on state.

Effects of the Invention As described above, according to the present invention, a Zener diode connected in series to the gate of a silicon-controlled rectifying element is made conductive by utilizing changes in the output voltage of a high-voltage abnormal voltage detection circuit.
By making it non-conductive, the X-ray protection circuit will be activated in the event of a failure in the power supply circuit or horizontal deflection circuit, and will be activated if there is a crackling sound or if the horizontal frequency suddenly shifts to a lower side for a short period of time in a VTR, etc. In such cases, it is possible to obtain a stable XX-ray protection circuit that does not operate or malfunction.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram of a conventional X-ray protection circuit, Figure 2 is a circuit diagram of an X-ray protection circuit according to an embodiment of the present invention, and Figure 3 is a circuit diagram of the circuit of Figure 2. It is a waveform diagram of the main part. 1... High voltage abnormal voltage detection circuit section, 2...
...Flyback transformer winding terminal, 14...
・Output terminal of high voltage abnormal voltage detection circuit section 1, 15...
...Silicon controlled rectifier, 16...Resistor,
17...Resistor, 18...NPN) Runsistor, 19...Horizontal deflection circuit, 20...
...Resistor, 21...Charging capacitor, 2
2...Zener diode. Name of agent: Patent attorney Toshio Nakao and 1 other person 1st
Figure IQ Figure 2 I f9+B ・-------7'-1ko■ 喀1 1 1 JP-A-Sho GO-47569 (4) Figure 3 1 . 1. ,, Momme 2 - Yako Award Poetry En

Claims (1)

[Claims] A series circuit of a resistor and a capacitor whose value is selected to have a sufficiently long duty cycle is connected to the output part of the abnormal voltage detection circuit that detects high abnormal voltage, and a Zener diode is connected to the intersection of the resistor and the capacitor. and connect the anode of the Zener diode to the gate of the silicon-controlled rectifier, so that when a short-time single output is output to the output section of the high-voltage abnormal voltage detection circuit, the silicon-controlled rectifier The element is maintained in the off state, and when an output due to a failure of the power supply circuit or the horizontal deflection circuit, etc. is output to the output section of the high voltage abnormal voltage detection circuit, the silicon controlled rectifier element is switched to the on state. An X-ray protection circuit characterized by comprising: