JPH0346616Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a screen distortion correction circuit in a television receiver.

In the conventional screen distortion correction circuit, as shown in FIG. 1, for example, by switching a horizontal output transistor 1 driven by a horizontal deflection drive circuit A, a deflection coil 4 and an S-shaped correction capacitor 5 are caused to have series resonance. Then, an S-shaped corrected deflection current flows through the deflection coil 4. This current value is determined by the amount of charge on the capacitor 5, and the amount of charge on the capacitor 5 is determined by the voltage Vcc supplied to the primary winding of the flyback transformer 6 from the power source. On the other hand, the CRT anode voltage induced in the flyback transformer 6 has a characteristic that it decreases as the load current increases, and in areas where the brightness is high, the CRT anode voltage decreases, the deflection sensitivity increases, and the screen becomes wider. However, the configuration is such that the primary winding of the flyback transformer 6 is supplied with the voltage Vcc via the resistor 8.

Therefore, a current proportional to the brightness flows through the resistor 8,
The amount of charge in the capacitor 5 is modulated by the voltage drop caused by this current. Therefore, as the brightness increases, the amount of charge in the capacitor 5 decreases and the deflection power decreases, so the deflection power decreases as much as the CRT anode voltage decreases, and the horizontal deflection width on the screen is kept constant. In FIG. 1, 2 is a damper diode, 3 is a resonant capacitor, and 7 is a power supply capacitor.

However, with the conventional screen distortion correction circuit as described above, when the brightness is increased, horizontal screen width fluctuations do not occur, but the CRT anode voltage decreases compared to when no compensation is used, resulting in vertical fluctuations. There was a drawback that the screen width fluctuation increased.

The present invention was developed in consideration of the above, and does not correct the screen width fluctuations caused by direct current brightness changes.
It is an object of the present invention to provide a screen distortion correction circuit that can correct only screen distortion caused by alternating current luminance changes and eliminates the above-mentioned drawbacks.

The present invention will be explained below with reference to examples.

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

In one embodiment of the present invention, a transistor ₉ for power supply voltage control is inserted between a resistor 8 and one end of a capacitor 7 in the conventional screen distortion correction circuit shown in FIG. A divided voltage divided by and 11 ₂ is supplied to the base of transistor 9, and a capacitor 10 for AC component filtering is connected between the collector and base of transistor 9.

That is, the resistor 8 serves as a detection circuit that detects the current of the power supply voltage, and the transistor 9 serves as a control circuit that controls the power supply voltage of the horizontal deflection circuit.

In one embodiment of the present invention constructed as described above, the horizontal output transistor 1 is switched by the horizontal deflection drive circuit A, and a deflection current flows through the deflection coil 4 and the capacitor 5 due to this switching. This current value is determined by the amount of charge in the capacitor 5, and this amount of charge is determined by the voltage supplied to the primary side of the flyback transformer 6 via the transistor 9.

However, the divided voltages of the voltage dividing resistors 11 ₁ and 11 ₂ are applied to the base of the transistor 9 as a bias voltage, and the emitter voltage of the transistor 9 is determined by the DC bias voltage of the transistor 9. Now, the CRT anode voltage induced in the flyback transformer 6 drops as the load current increases, such as when the brightness on the CRT increases. As the load current increases, the current flowing through the resistor 8 increases. The current flowing through the resistor 8 is proportional to the brightness, and a voltage drop proportional to the brightness occurs across the resistor 8.
This appears as a voltage change at the collector of transistor 9.

However, since the DC potential of the emitter of the transistor 9 is determined by the DC bias voltage, the DC voltage fluctuation on the collector side does not appear at the emitter of the transistor 9. Therefore, the power supply voltage on the primary side of the flyback transformer 6 does not vary in a DC manner, and the deflection current is also kept constant.

On the other hand, since the capacitor 10 for AC filtering is inserted between the collector and base of the transistor 9, an AC voltage change is applied to the base of the transistor 9. Therefore, the emitter potential of the transistor 9, that is, the power supply voltage supplied to the primary side of the flyback transformer 6, is controlled in response to alternating current changes in the collector potential of the transistor 9, modulating the deflection power, and changing the polarity on the screen. The horizontal deflection width is corrected to remain constant.

In the above embodiments, the case of a television receiver is illustrated, but the same structure can be applied to a horizontally deflecting television camera, and the same effect can be obtained.

As mentioned above, the present invention detects only the alternating current component on the primary side of the flyback transformer to control the power supply voltage of the horizontal deflection circuit. When the overall brightness is increased, such as when controlling the power supply voltage of the horizontal deflection circuit, the deflection does not spread abnormally in the vertical direction. This has the effect of being able to correct screen distortion due to brightness modulation by making constant corrections.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram of a conventional screen distortion correction circuit, Figure 2 is a circuit diagram of a conventional screen distortion correction circuit.
The figure is a circuit diagram of a screen distortion correction circuit according to an embodiment of the present invention. 1... Horizontal output transistor, 2... Damper diode, 3... Resonance capacitor, 4... Deflection coil, 5... S-shaped correction capacitor, 6...
Flyback transformer, 7... Power supply capacitor, 8... Resistor, 9... Transistor, 10
...AC filtering capacitors, 11 ₁ and 11 ₂ ...
...Divisional voltage resistance.

Claims (1)

[Claims for Utility Model Registration] In a horizontal deflection circuit having an output circuit in which a horizontal output transistor, a deflection coil, a resonant capacitor, and a damper diode are connected in parallel, a flyback transformer connected to the output of the output circuit; Power is supplied to the flyback transformer via a control circuit to be described later, and a detection circuit consisting of a resistor detects the power supply current, and only an alternating current component of the power supply current according to the brightness level detected by the detection circuit is provided. A screen distortion correction circuit comprising: a control circuit that extracts the AC component and controls the power supply voltage of the horizontal deflection circuit using an active element according to the level of the AC component.