JPS6031298B2 - High voltage control circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a high voltage generating circuit that controls the high voltage generated in a high voltage generating circuit coupled to a horizontal deflection output circuit of a television receiver.

Second, if constant voltage control of high voltage (cathode ray tube anode voltage) is not possible due to high-order tuning of the flyback transformer,
As shown in the figure, a constant voltage element 20 was inserted between the anode of the cathode ray tube 5 and the ground to control the high voltage.

In the figure, 1 is a horizontal output transistor, 2 is a damper diode, 3 is a resonant capacitor, and 4 is a flyback transformer. This constant voltage element 20 is expensive and consumes several watts of power because current is constantly flowing through it. Further, since the voltage-current characteristics of the constant voltage element 20 were not ideal, there were some high voltage fluctuations. SUMMARY OF THE INVENTION An object of the present invention is to eliminate the drawbacks of the prior art described above and to provide a high voltage control circuit that can control high voltage at low cost.

The present invention equivalently changes the capacitance of the resonant capacitor of the horizontal deflection output circuit by controlling the charging current, and changes the pulse width of the flyback pulse, making it possible to freely control high voltage fluctuations due to beam current changes. It is something.

The present invention will be explained below with reference to FIGS. 2 and 3.

FIG. 2 is a circuit diagram showing one embodiment of the present invention.

6 is a circuit for controlling the charging current of the resonant capacitor 3, and is connected in series with the resonant capacitor 3.

The resonant capacitor charging current control circuit 6 is connected to the low voltage side connection point 8 of the secondary winding of the flyback transformer 4 . Since the voltage at the connection point 8 corresponds to the beam current, the control circuit 6 controls the charging current of the resonant capacitor 3 according to this voltage. The larger the beam current flows, that is, the lower the high voltage, the greater the voltage drop across the resistor 7 and the lower the voltage at the connection point 8. The control circuit 6 reduces the charging current of the resonant capacitor 6 as the voltage at the connection point 8 is lower, equivalently reducing the capacitance of the resonant capacitor 6, increasing the height of the flyback pulse, and reducing the high voltage generated by the flyback transformer. raise. Conversely, when the beam current decreases, the circuit operation described above is reversed and the control circuit 6 lowers the high voltage. FIG. 3 is a circuit diagram specifically showing the control circuit 6. As shown in FIG.

A parallel circuit consisting of a diode 9 and a transistor 10 is connected in series to the resonant capacitor 3, and the transistor 10
The base bias of is controlled by the voltage at node 8. Now, consider a situation where the beam current flows and the high voltage drops. When the beam current flows, the voltage at the connection point 8 decreases, and the control section 11 increases the operating resistance of the transistor 10. As a result, the charging current of the resonant capacitor 3 decreases, and the high voltage increases as the circuit operates as explained in FIG. When the beam current decreases, the opposite operation is performed. In this way, by controlling the operating resistance of the transistor 10 connected in series with the resonant capacitor 6 along with changes in the beam current, high voltage fluctuations caused by changes in the beam current can be freely controlled, and changes in the screen size of the television receiver can be kept approximately constant. I can do it. As described above, according to the present invention, a high voltage control circuit that is inexpensive and consumes little power can be obtained. Also, high pressure fluctuations can be freely controlled.

[Brief explanation of the drawing]

FIG. 1 is a conventional high voltage control circuit, FIG. 2 is a circuit diagram showing an embodiment of the high voltage control circuit according to the present invention, and FIG. 3 is a specific circuit diagram of FIG. 2. 3... Resonance capacitor, 7... Resistor, 9.
...Diode, 10...Transistor, 11...
...control section. Diagram O, Diagram O, Diagram 2, Diagram 3

Claims (1)

[Scope of Claims] 1. In an image display device comprising a cathode ray tube, a horizontal deflection output circuit, and high voltage generation means for generating high voltage for the anode of the cathode ray tube from flyback pulses generated in the horizontal deflection output circuit, A high voltage control circuit characterized in that a variable resistance means is provided in series with a resonant capacitor of an output circuit, and the resistance value of the variable resistance means is changed in accordance with a beam radio wave of a cathode ray tube. 2. The variable resistance means includes a transistor having a collector-emitter path connected in series to the resonant capacitor, and a transistor connected in parallel to the collector-emitter path so that the conduction direction is opposite to that of the transistor. 2. The high-voltage control circuit according to claim 1, characterized in that the conductivity of the transistor changes in accordance with the beam radio wave.