JPS6114221Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a circuit improvement for preventing abnormally high voltage generation in a television receiver.

In television receivers, if a component of the power supply circuit fails or the AC input voltage changes, the high voltage applied to the anode of the picture tube increases abnormally, causing X-ray radiation. For this purpose, conventionally,
A flyback pulse is derived from the secondary winding provided in the flyback transformer of the horizontal deflection circuit, and this pulse is rectified to obtain a DC voltage.The DC voltage is rectified with respect to the voltage value set by the reference voltage source. A switch circuit is prepared that turns on when the voltage becomes large, and the turn-on operation of this switch circuit cuts off the B voltage supplied to the horizontal oscillation circuit and stops the oscillation, thereby stopping the generation of high voltage. A circuit is used. however,
In this type of circuit arrangement, when the voltage of the reference voltage source changes, the ON operation start voltage of the switch circuit also changes proportionally, causing malfunction. Furthermore, when a constant voltage diode is used as the reference voltage source, the on-operation start voltage of the switch circuit differs from receiver to receiver due to variations between devices during mass production. Therefore, it is necessary to preset using a variable resistor.

This proposal was proposed to improve the conventional circuit as described above, and is a circuit arrangement that operates so that the on-operation start voltage of the switch circuit is substantially stabilized against variations in the reference voltage source. It is something that gives. Therefore, according to the present invention, it is possible to obtain an abnormally high voltage generation prevention device that does not require a variable resistor to preset the ON operation start voltage and does not require an adjustment process.

FIG. 1 is a circuit configuration diagram according to an embodiment of the present invention. Reference numeral 1 denotes a flyback transformer of the horizontal deflection circuit, in which a horizontally periodic flyback pulse is boosted and applied as a high voltage to the anode of the picture tube. A flyback pulse is derived from one end of a secondary winding _L1 appropriately provided in this transformer and applied to the rectifier circuit 2. The rectified DC voltage is passed through a voltage divider 3 and supplied to a switch circuit 4 as an appropriate voltage value. The switch circuit 4 is also supplied with a reference voltage from a reference voltage source, and the circuit 4 compares the value of the rectified and divided DC voltage with the reference voltage.

Here, if the DC voltage is lower than the reference voltage, the switch circuit 4 remains off, and the B voltage supply from the horizontal oscillation circuit 7 is maintained. Next, when the high voltage starts to rise, the rectified and divided DC voltage also rises. When the DC voltage reaches the reference voltage, the switch circuit 4 is turned on, grounding the B voltage supply path to the horizontal oscillation circuit 7, cutting off the oscillation, and stopping high voltage generation.

The features of the present invention in _the circuit shown in FIG. This is what is happening. That is, the output voltage of the reference voltage source 5 is also superimposed on the flyback pulse voltage taken out from the secondary winding _L1 . The DC voltage obtained by rectifying this superimposed voltage is divided into appropriate values, but variations in the reference voltage also exist in these divided components. When this divided voltage and the reference voltage are compared using a switch circuit, the variation component between the two can be ignored because the difference is taken.

FIG. 2 shows a specific circuit diagram of the circuit configuration of FIG. 1. D ₁ is a rectifier, and C ₁ is a smoothing capacitor. Resistors R ₂ and R ₃ are for dividing the rectified output voltage. constant voltage diode
ZD ₁ and capacitor C ₂ form a reference voltage source. _D2 is a reverse current blocking diode, which is normally non-conducting because the cathode side is set to a higher voltage than the anode side by the reference voltage. P ₁ is a programmable union transistor (PUT), in which the reference voltage applied to the gate, which is the first detection terminal, and the rectified divided voltage applied to the anode, which is the second detection terminal, are compared. However, it functions as a switch that turns on when the anode voltage rises above the reference voltage. Since the gate electrode is grounded when _P1 is turned on, the terminal 6 connected to the B voltage supply path of the oscillation circuit is substantially grounded by _P1 via the diode _D2 . As can be seen from this figure, since the reference voltage is superimposed on the flyback pulse, the above-mentioned problem with variations is eliminated.

As described above, according to the present invention, the reference voltage of the reference voltage source connected to the first detection terminal of the switch circuit is applied to the flyback pulse rectifier circuit connected to the second detection terminal of the switch circuit. Since it is superimposed on the DC voltage, it has the effect of substantially stabilizing the ON operation start voltage of the switch circuit against variations in the reference voltage source.

[Brief explanation of the drawing]

Figure 1 is a circuit configuration diagram according to an embodiment of the present invention, Figure 2
The figure is an actual circuit connection diagram of the configuration shown in FIG. L ₁ ... Secondary winding of flyback transformer, 2
... Rectifier circuit, 3 ... Voltage division circuit, 4 ... Switch circuit, 5 ... Reference voltage source, 7 ... Horizontal oscillation circuit.

Claims (1)

[Scope of utility model registration request] A secondary winding installed in the flyback transformer of the horizontal deflection circuit that extracts the high voltage applied to the anode of the picture tube, and a rectifier circuit that rectifies the flyback pulse derived from one end of this secondary winding to obtain a DC voltage. and a reference voltage source, a first detection terminal connected to the reference voltage source, and a second detection terminal connected to the rectifier circuit, the first detection terminal being set by the reference voltage source. Turns on when the DC voltage applied from the rectifier circuit to the second detection terminal becomes larger than the voltage value applied to the first detection terminal, and this on operation stops the operation of the horizontal oscillation circuit. In a television receiver equipped with a switch circuit, by connecting the reference voltage source to the other end of the secondary winding of the flyback transformer, the DC voltage rectified by the rectifier circuit is connected to the reference voltage source. Superimpose the reference voltage to obtain the superimposed voltage,
and the second of the rectifier circuit and the switch circuit.
Abnormal high voltage generation characterized in that a voltage dividing circuit is inserted between the detection terminal of the switch circuit to divide the superimposed voltage, and the divided DC voltage is applied to the second detection terminal of the switch circuit. Prevention device.