JPH06284305A - High voltage output stopping circuit - Google Patents

Abstract

PURPOSE:To prevent the damage of the phosphor of a CRT by stopping the operation of a high voltage generating circuit when the deflection currents of a deflection amplifier are not generated in a CRT display device. CONSTITUTION:In the deflection amplifier in which a horizontal deflection circuit A is operated independently of a high voltage generating circuit C, a horizontal deflection transformer 7 is equipped with a tertiary coil 7c, and the output voltage is rectified, and applied to a reference voltage generating circuit B. When a fault occurs at the horizontal deflection circuit A, and the output is decreased, a comparator circuit 11 applies a control signal to a high voltage generating part 12, and the generation of the high voltage is stopped. When the horizontal deflection circuit A is normally operated, the high voltage generating circuit C supplies the stable high voltage to a CRT 13.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high voltage output stop circuit provided in a deflection amplifier of a CRT display device.

[0002]

2. Description of the Related Art In recent years, as the definition of CRT display devices has become higher, it is required to improve the convergence accuracy of CRTs including deflection yokes. Therefore, deflection amplifiers suitable for various deflection yokes have been designed. It is used for various deflection yokes and can handle a wide range of inductances.
In addition, as an example of a deflection amplifier capable of generating a high voltage output in a wide range, there is a type in which a horizontal deflection circuit and a high voltage generation circuit are separated. In the deflection amplifier of this type, the high voltage generation circuit continues to operate even if the horizontal deflection circuit stops operating.

[0003]

When such a conventional deflection amplifier is used in a CRT display device, if a failure occurs in the horizontal deflection circuit and the vertical deflection circuit stops operating at the same time, the high voltage generation circuit Since a high voltage is continuously supplied to the anode of the CRT, spot burning occurs on the fluorescent surface of the CRT.
There was a problem that the RT was damaged. Further, when the horizontal deflection circuit fails, if the CRT display device is to be repaired as it is, the repairer may come into contact with the high-voltage system output by the high-voltage circuit, which may cause electric shock.

The present invention has been made in view of the above conventional problems, and in a CRT display device in which a horizontal deflection circuit and a high voltage generation circuit are separated, a high voltage is generated when the horizontal deflection circuit stops operating. It is an object to realize a high voltage output stop circuit that automatically stops the operation of the circuit.

[0005]

The present invention comprises a horizontal deflection circuit including a horizontal deflection coil, and a high voltage generation circuit for stabilizing a high voltage generation output by comparing a reference voltage and a feedback voltage obtained by dividing an output voltage. In a separate deflection amplifier, a high voltage output stop circuit that stops the operation of the high voltage generation circuit when the operation of the horizontal deflection circuit is abnormal, is connected to the horizontal deflection circuit, and is induced by the horizontal deflection current of the horizontal deflection coil. A horizontal deflection transformer having a tertiary winding that outputs a voltage, a rectifying and smoothing circuit that rectifies the voltage induced in the tertiary winding of the horizontal deflection transformer, and a DC voltage of a predetermined value or more input from the rectifying and smoothing circuit. The stabilized reference voltage is output to the high voltage generation circuit, and when the input voltage from the rectifying / smoothing circuit falls below a specified value, the reference voltage is reduced. When, it is characterized in that it comprises a.

[0006]

According to the present invention having such characteristics, when the horizontal deflection circuit operates and supplies the deflection current to the horizontal deflection coil, the rectification smoothing circuit induces in the tertiary winding of the horizontal deflection transformer. Voltage is input. The reference voltage generating circuit rectifies this voltage and outputs a stabilized reference voltage. The high voltage generation circuit is the reference voltage of the reference voltage generation circuit,
The high voltage output is compared with a divided voltage, and the difference value is used as a control input to stabilize the high voltage. Therefore, in a normal state, the high voltage generating circuit generates a constant high voltage. If the operation of the horizontal deflection circuit is hindered and its output drops, the reference voltage drops, so that the high voltage generation circuit stops the generation of the high voltage and drops the voltage of the electrode of the CRT. This way C
Damage to the RT phosphor is prevented in advance.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A high voltage output stopping circuit according to an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a circuit diagram showing a configuration of a deflection amplifier including a high voltage output stopping circuit according to this embodiment. In this figure, the deflection amplifier is a horizontal deflection circuit A,
It is composed of a reference voltage generating circuit B and a high voltage generating circuit C.

In the horizontal deflection circuit A shown by a broken line, the horizontal deflection control circuit 1 is a circuit which receives a horizontal synchronizing signal from an input end 1a and generates a horizontal synchronizing pulse based on a phase control pulse given to the input end 1b. Yes, its output is provided to the base of transistor 2. Transistor 2
Is a switching transistor for power-amplifying the horizontal synchronizing pulse to generate a horizontal deflection current in the horizontal deflection coil 3. A diode 4 and a capacitor 5 are connected between the collector and the emitter of the transistor 2, and a horizontal deflection coil 3 and a capacitor 6 are connected in series. The horizontal deflection coil 3 is a coil that horizontally deflects an electron beam emitted from an electron gun of a CRT.

The diode 4 is a diode for a damper which causes a deflection current to flow through the horizontal deflection coil 3 when a reverse voltage is applied to the transistor 2. The capacitor 5 is a resonance capacitor that forms a resonance circuit with the horizontal deflection coil 3. The capacitor 6 is a capacitor that corrects a part of the sawtooth-shaped deflection current waveform in an S shape.

The horizontal deflection transformer 7 is a transformer having a primary winding 7a, a secondary winding 7b, and a tertiary winding 7c wound around a core. One end of the primary winding 7a is connected to a power source V _B ,
The other end is connected to the collector of the transistor 2. The secondary winding 7b has one end connected to the input end 1b of the horizontal deflection control circuit 1 and the other end grounded. Further, the tertiary winding 7c has one end connected to the reference voltage generating circuit B via the diode 8 and the other end grounded. A capacitor 9 is connected to the output terminal (cathode) of the diode 8 to form a rectifying / smoothing circuit.

Both ends of the capacitor 9 are connected to a reference voltage generating circuit B shown by a broken line. The reference voltage generation circuit B is a circuit in which a resistor R and a shunt regulator 10 are connected in series, and is a circuit that supplies a reference voltage to the comparison circuit 11.
The shunt regulator 10 is a temperature-compensated variable three-terminal regulator, the gate of which is commonly connected to the cathode and is connected to one input terminal of the comparison circuit 11.

The high voltage generation circuit C is a circuit which includes a comparison circuit 11 and a high voltage generation unit 12 and supplies a high voltage to the anode electrode of the CRT 13. The comparison circuit 11 is a circuit that outputs the difference value of the voltages applied to the two input terminals. The voltage generated by the high voltage generator 12 is controlled by the output signal of the comparison circuit 11, and details thereof are omitted here. The voltage dividing resistor 14 is connected to the output terminal of the high voltage generating circuit C, and its tap output is given to the other input terminal of the comparison circuit 11. Here, the tertiary winding 7c of the horizontal deflection transformer 7, the rectifying circuit by the diode 8 and the capacitor 9, and the reference voltage generating circuit B are CRTs when the horizontal deflection circuit A is abnormal.
A high voltage output stop circuit for stopping the supply of high voltage to the high voltage electrodes of 13 is configured.

The operation of the deflection amplifier including the high voltage output stopping circuit configured as described above will be described. When the horizontal synchronizing signal is input to the horizontal deflection control circuit 1, the transistor 2
Is supplied with a horizontal sync pulse. The transistor 2 performs a switching operation and causes the horizontal deflection coil 3 to generate a sawtooth horizontal deflection current. At this time, a current also flows in the horizontal deflection transformer 7, and an induced voltage is generated in the secondary winding 7b and the tertiary winding 7c. The voltage of the tertiary winding 7c is rectified by the diode 8 and a smoothed DC voltage is generated across the capacitor 9.

The DC voltage generated by the operation of the horizontal deflection circuit A is applied to the shunt regulator 10 via the resistor R. If the applied voltage is equal to or higher than the operating voltage, the shunt regulator 10 becomes conductive, and the reference voltage generation circuit B gives a constant reference voltage to the comparison circuit 11. Next, the high voltage generator 1
2 operates and outputs a predetermined high voltage to the CRT 13. With the horizontal deflection circuit A operating normally,
If the output voltage of the high voltage generator 12 decreases, the voltage output from the voltage dividing resistor 14 also decreases, and the control voltage output from the comparison circuit 11 increases. Therefore, the high voltage generation circuit C
Controls to raise the generated voltage, and performs feedback control until the voltages at the two input terminals of the comparison circuit 11 become equal. In this way, a stable high voltage is always supplied to the CRT 13.

Next, it is assumed that the operation of the horizontal deflection circuit A becomes abnormal and its output is lowered. Therefore, the horizontal deflection of the electron beam is stopped and the same vertical line is repeatedly scanned. Also, no current flows through the shunt regulator 10 of the high voltage output stop circuit, and the voltage at one input terminal of the comparison circuit 11 becomes zero. At this time, the output of the comparison circuit 11 also suddenly drops, and the high voltage generation circuit C does not generate a high voltage. Therefore, no voltage is applied to the anode of the CRT 13, the irradiation of the electron beam is stopped, and damage to the phosphor is prevented.

[0016]

As described above, according to the present invention, by providing the high voltage output stop circuit in the deflection amplifier, when the horizontal deflection circuit becomes abnormal and its output is lowered, it is interlocked with this. The operation of the high voltage generation circuit can be stopped.
Therefore, the effect of preventing damage to the phosphor of the CRT can be obtained.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a configuration of a deflection amplifier including a high voltage output stopping circuit according to an embodiment of the present invention.

[Explanation of sign]

 1 Horizontal Deflection Control Circuit 2 Transistor 3 Horizontal Deflection Coil 4,8 Diode 5,6,9 Capacitor 7 Horizontal Deflection Transformer 7a Primary Winding 7b Secondary Winding 7c Tertiary Winding 10 Shunt Regulator 11 Comparison Circuit 12 High Voltage Generator 13 CRT 14 Voltage division resistance A Horizontal deflection circuit B Reference voltage generation circuit C High voltage generation circuit R Resistance

Claims (1)

[Claims] 1. A horizontal deflection circuit including a horizontal deflection coil,
A high voltage generation circuit that stabilizes the high voltage generation output by comparing the reference voltage and the feedback voltage obtained by dividing the output voltage,
A high-voltage output stop circuit for stopping the operation of the high-voltage generation circuit when the operation of the horizontal deflection circuit is abnormal in a mutually independent deflection amplifier, the horizontal deflection current of the horizontal deflection coil being connected to the horizontal deflection circuit. A horizontal deflection transformer having a tertiary winding that outputs a voltage induced in the horizontal deflection transformer, a rectifying and smoothing circuit that rectifies the voltage induced in the tertiary winding of the horizontal deflection transformer, and a DC voltage that is a predetermined value or more from the rectifying and smoothing circuit. And a reference voltage generating circuit that outputs a stabilized reference voltage to the high-voltage generating circuit and that lowers the reference voltage when the input voltage from the rectifying and smoothing circuit becomes a predetermined value or less. A high voltage output stop circuit characterized by: