JP3313181B2 - High voltage output stop circuit - Google Patents

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 a CRT display device has been improved, the convergence accuracy of a CRT including a deflection yoke has been required to be improved. Therefore, deflection amplifiers suitable for various deflection yokes have been designed. Used in various deflection yokes, it can handle a wide range of inductance,
As an example of a deflection amplifier capable of generating a wide range of high voltage output, there is a type in which a horizontal deflection circuit and a high voltage generation circuit are separated. In such a type of deflection amplifier, the high-voltage generation circuit continues to operate even when the operation of the horizontal deflection circuit is stopped.

[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, the high-voltage generation circuit is activated. Subsequently, a high voltage is supplied to the anode of the CRT.
There is a problem that the RT is damaged. Also, when the horizontal deflection circuit breaks down and the CRT display is to be repaired as it is, the repairer has a concern that it may come into contact with the high voltage system output by the high voltage circuit and cause electric shock.

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

[0005]

According to the present invention, 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 are provided. 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 the deflection amplifiers independent of each other, and connected to the horizontal deflection circuit and induced by the horizontal deflection current of the horizontal deflection coil. A horizontal deflection transformer having a tertiary winding for outputting a voltage, a rectifying / smoothing circuit for rectifying a voltage induced in the tertiary winding of the horizontal deflection transformer, and when a DC voltage of a predetermined value or more is input from the rectifying / smoothing circuit. The reference voltage generation circuit outputs the stabilized reference voltage to the high voltage generation circuit, and lowers the reference voltage when the input voltage from the rectifying / smoothing circuit falls below a predetermined value. If, comprising a reference voltage was reduced
In this case, the generation of the high voltage by the high voltage generation circuit is stopped .

[0006]

According to the present invention having the above features, when the horizontal deflection circuit operates and supplies a deflection current to the horizontal deflection coil, the rectifying / smoothing circuit induces the tertiary winding of the horizontal deflection transformer. Is input. The reference voltage generation circuit rectifies this voltage and outputs a stabilized reference voltage. The high-voltage generation circuit has the reference voltage of the reference voltage generation circuit,
The high voltage output is compared with a divided voltage, and the high voltage is stabilized using the difference value as a control input. 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 generating high voltage and lowers the voltage of the electrode of the CRT. Then C
The phosphor of the RT is prevented from being damaged.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A high voltage output stop circuit according to one 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 stop circuit according to the present embodiment. In this figure, the deflection amplifier is a horizontal deflection circuit A,
It comprises a reference voltage generation circuit B and a high voltage generation circuit C.

In a horizontal deflection circuit A shown by a broken line, a horizontal deflection control circuit 1 receives a horizontal synchronization signal from an input terminal 1a and generates a horizontal synchronization pulse based on a phase control pulse supplied to an input terminal 1b. And its output is provided to the base of transistor 2. Transistor 2
Is a switching transistor that amplifies the horizontal synchronization pulse and generates 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 deflects an electron beam emitted from an electron gun of a CRT in a horizontal direction.

The diode 4 is a diode for a damper that 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 corrects a part of the deflection current waveform of the sawtooth wave in an S-shape.

[0010] Horizontal deflection transformer 7, a transformer having a primary winding 7a wound in a core, the secondary winding 7b, the tertiary winding 7c, one end of the primary winding 7a is connected to a power supply V _B,
The other end is connected to the collector of transistor 2. One end of the secondary winding 7b is connected to the input terminal 1b of the horizontal deflection control circuit 1, and the other end is grounded. Further, one end of the tertiary winding 7c is connected to the reference voltage generating circuit B via the diode 8, and the other end is grounded. A capacitor 9 is connected to an 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 indicated 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 supplies a reference voltage to a comparison circuit 11.
The shunt regulator 10 is a temperature-compensated variable three-terminal regulator. The gate of the shunt regulator 10 is commonly connected to the cathode, and is connected to one input terminal of the comparison circuit 11.

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

The operation of the deflection amplifier including the high-voltage output stop circuit configured as described above will be described. When a horizontal synchronization signal is input to the horizontal deflection control circuit 1, the transistor 2
Is supplied with a horizontal synchronization pulse. The transistor 2 performs a switching operation to generate a sawtooth-shaped horizontal deflection current in the horizontal deflection coil 3. At this time, current also flows through 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.

A DC voltage generated by the operation of the horizontal deflection circuit A is supplied to a shunt regulator 10 via a resistor R. If the applied voltage is equal to or higher than the operating voltage, the shunt regulator 10 conducts, and the reference voltage generation circuit B supplies a constant reference voltage to the comparison circuit 11. Next, the high pressure generator 1
2 operates and outputs a predetermined high voltage to the CRT 13. While the horizontal deflection circuit A is operating normally,
Assuming that 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
Performs control to increase the generated voltage, and performs feedback control until the voltages at the two input terminals of the comparison circuit 11 become equal. In this case, a stable high voltage is always supplied to the CRT 13.

Next, it is assumed that the operation of the horizontal deflection circuit A has become abnormal and its output has dropped. Therefore, the horizontal deflection of the electron beam is stopped, and the same vertical line is repeatedly scanned. Also, no current flows to 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, when the high voltage output stop circuit is provided in the deflection amplifier, an abnormality occurs in the horizontal deflection circuit, and when the output of the horizontal deflection circuit decreases, the output is reduced in conjunction with this. The operation of the high voltage generation circuit can be stopped.
Therefore, an effect is obtained that damage to the phosphor of the CRT can be prevented.

[Brief description of the drawings]

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

[Description of sign]

 DESCRIPTION OF SYMBOLS 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 dividing resistor A Horizontal deflection circuit B Reference voltage generating circuit C High voltage generating circuit R Resistance

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H04N 3/185 H04N 3/20

Claims (1)

(57) [Claims] A horizontal deflection circuit including a horizontal deflection coil;
A high-voltage generation circuit that stabilizes a high-voltage generation output by comparing a reference voltage and a feedback voltage obtained by dividing the output voltage,
A high-voltage output stop circuit for stopping the operation of the high-voltage generating circuit when the operation of the horizontal deflection circuit is abnormal in a deflection amplifier that is independent of each other, and is connected to the horizontal deflection circuit and has a horizontal deflection current of the horizontal deflection coil. A horizontal deflection transformer having a tertiary winding that outputs a voltage induced in the rectifying / smoothing circuit; a rectifying / smoothing circuit for rectifying a voltage induced in the tertiary winding of the horizontal deflection transformer; together but outputs the stabilized reference voltage when the input to the high voltage generating circuit, and a reference voltage generating circuit to lower the reference voltage when the input voltage from the rectifying smoothing circuit becomes the predetermined value or less If the reference voltage drops
A high-voltage output stop circuit for stopping generation of a high voltage by the high-voltage generation circuit.