JPH0748803B2 - Distortion correction circuit - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a distortion correction circuit of a television receiver, and more particularly to correction of distortion due to a change in screen brightness.

[Conventional technology]

FIG. 3 shows a distorted shape in the case where a bright screen is partially present in the black screen. In the figure, the solid line shows the distorted shape, and the dotted line shows the distorted shape. The cause of this distortion is
While the cathode ray tube anode voltage is high when the screen is dark,
This is because when the bright screen comes, the cathode ray tube anode voltage becomes low. The CRT anode ripple voltage is shown at the right end of FIG. A related circuit for correcting such distortion is disclosed in Japanese Patent Application Laid-Open No. 49-111542.

This conventional circuit not only corrects the left and right pincushion distortions but also corrects the distortions as shown in FIG. 4, so that the distortion correction effect as shown in FIG. 3 is small.

[Problems to be solved by the invention]

The above-mentioned related art cannot sufficiently obtain the effect of correcting the screen distortion that occurs when the screen is dark and there is a partially bright screen.

SUMMARY OF THE INVENTION An object of the present invention is to, in a left and right pincushion distortion correction circuit composed of transistors, to almost completely correct distortion that occurs when a dark screen has a partially bright screen in an inexpensive part.

[Means for solving problems]

The above object is achieved by superimposing a signal according to the brightness of the screen on a vertical period parabolic signal for left and right pincushion distortion correction.

[Action]

A signal corresponding to the content of the screen brightness is superimposed on the parabolic signal for left and right pincushion distortion correction. Thus, when a dark screen has a partially bright screen, it is possible to almost completely correct the distortion that spreads in a trapezoidal shape toward the lower side of the screen.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2. The present invention relates to a distortion correction circuit of a television receiver, and in particular, for the purpose of realizing a correction means for correcting the problem that the horizontal amplitude of the screen increases when the screen becomes bright, a damper is provided. Positive side of the power supply via the primary coil of the flyback transformer to the high voltage side of the three-way parallel connection circuit of the series circuit of the horizontal output transistor in which the diode is connected in parallel, the horizontal deflection coil, the S-shaped correction capacitor, and the resonance capacitor. Is connected, and a series circuit of a capacitor, a transistor, a diode, an inductance and a capacitor is connected in parallel between the negative side of the power source and the low-voltage side of the circuit, and this transistor and the horizontal output transistor have the same polarity voltage. When it is turned off, the transistor is turned off before the horizontal output transistor when turned off. The voltage of the capacitor connected in series to the serial inductance, a configuration in which parabolic voltage and the screen brightness voltage of the vertical synchronization is to perform the modulation to distortion correction in superimposed signal voltage.

With such a configuration, in the present invention, the horizontal output transistor 4 and the switching transistor 5 are simultaneously turned on by the secondary winding of the horizontal drive transformer 1 by the ON signal from the horizontal oscillator. As a result, the primary side current of the flyback transformer 10 flows from the positive electrode side of the power supply through the horizontal output transistor 4 and the switching transistor 5. In addition, the horizontal deflection current also applies to the S-shaped correction capacitor 10
Then, the current flows back through the horizontal deflection coil 9 and the turned-on horizontal output transistor 4 to return to the S-shaped correction capacitor. A current also flows from the capacitor 13 through the inductance 12 and the switching transistor 5 which is turned on. The horizontal output transistor 4 and the switching transistor 5 are turned off by an off signal from the next drive transformer. By setting the base current of the switching transistor 5 at the time of ON to be smaller than that of the horizontal output transistor, the accumulated charge becomes small, and when it is switched to the OFF signal, it is turned off earlier than the horizontal output transistor. The current flowing from the primary winding of the flyback transformer through the horizontal output transistor which is still on charges the capacitor 11. Then enter the resonance period,
A current returns from the capacitor 11 to the inductance 12 and causes the inductance 12 to generate a resonance pulse. At the same time, the voltage charged in the resonance capacitor 8 also returns to the horizontal deflection coil 9 to generate a resonance pulse in this horizontal deflection coil. Further, a return resonance current flows through the large-capacity S-shaped correction capacitors 10 and 13 to generate a DC voltage, and the total value of these two voltages becomes the power supply voltage value. Here, if the values of the capacitor 11 and the inductance 12, the value of the resonance capacitor 8 and the value of the horizontal deflection coil 9 are selected so that the pulse widths of the two resonance pulses are almost equal, the total of the two resonance pulses is selected. The peak value of is a constant value determined by the power supply voltage.

In the present invention, in order to perform distortion correction by modulating the charging voltage of the capacitor 13 with a distortion correction signal, a discharging transistor is connected in parallel to the capacitor 13, and the base of this transistor is connected to the vertical parabola for left and right pin distortion correction. The voltage of the capacitor 13 is modulated by applying a superimposed signal voltage of the signal and the screen brightness signal to control the discharge amount. The brightness signal according to the screen brightness is a resistor inserted in the low-voltage side of the flyback transformer through which the CRT beam current directly flows.
It is obtained by detecting the voltage drop of 20. When the screen becomes bright, the beam current increases, the voltage drop of the resistor 20 increases, and the brightness signal voltage decreases. This brightness signal voltage is guided by the resistor 18 and the capacitor 19 and superposed on the parabolic signal. In the bright part of the screen, the discharge transistor 14
The base voltage of the battery decreases and the discharge amount decreases. The voltage of the capacitor 13 also rises. Since the total value of the voltage of the capacitor 13 and the voltage of the S-shaped correction capacitor 10 is determined by the power supply voltage, the voltage of the S-shaped correction capacitor 10 decreases by the amount of increase in the voltage of the capacitor 13. Since the amplitude of the horizontal deflection current is determined by the voltage of the S-shaped correction capacitor 10, the horizontal amplitude is reduced by the amount by which the voltage of the S-shaped correction capacitor 10 is lowered, and the horizontal amplitude of the screen is widened when the screen becomes bright. The distortion can be corrected. In the present invention, the increase in horizontal amplitude when the screen becomes bright can be corrected in this way while the effect of correcting left and right pin distortion is maintained.

〔The invention's effect〕

According to the present invention, the voltage due to the screen brightness of the same period is superimposed on the vertical period parabolic voltage for correcting the left and right pincushion distortion. Can be completely corrected.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an embodiment of the present invention, and FIG. 2- (a).
Is a voltage waveform diagram at point a without the present invention, FIG.
(B) is a voltage waveform diagram of point b in the case of the present invention,
Fig .- (c) is a voltage waveform diagram of point C in the case of the present invention,
FIG. 3 is a waveform diagram showing the shape of screen distortion. 1 …… Horizontal drive transformer, 4 …… Horizontal output transistor, 5 …… Transistor that switches in synchronization with horizontal output transistor 4, 2.3 …… 4.5 Resistance that controls the base current of each transistor, 6,7 …… Damper diode, 8.11 …… Resonance capacitor, 9 …… Horizontal deflection coil, 10 …… S-shaped correction capacitor, 12 …… Resonance coil, 13
...... Capacitor 11 Capacitor that becomes the battery of the resonance circuit consisting of coil 12, 14 ...... Transistor that modulates the voltage across capacitor 13, 15 ...... Flyback transformer, 16 ...... CRT, 18 ...... For adjusting ripple voltage amplitude Resistance, 19
...... Capacitor for AC coupling, 20 ...... Automatic brightness control detection resistor.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-59-186470 (JP, A) JP-A-55-61172 (JP, A) JP-A-59-160378 (JP, A)

Claims (1)

[Claims] 1. A primary output coil of a flyback transformer on the high voltage side of a parallel circuit of a horizontal output transistor having a damper diode connected in parallel, a series circuit of a horizontal deflection coil and an S-shaped correction capacitor, and a resonance capacitor. The positive side of the power source is connected via the, and the third capacitor, the transistor, the diode, the series circuit of the inductance and the fourth capacitor is connected between the negative side of the power source and the low voltage side of the circuit. The transistors and the horizontal output transistor are connected in parallel to be turned on by a voltage of the same polarity, and when turned off, the transistor is turned off before the horizontal output transistor, and the NPN is placed across the fourth capacitor. Type transistor is connected in parallel, and the base electrode of the transistor is connected according to the vertical synchronizing parabola voltage and the cathode ray tube current. Distortion correcting circuit, characterized in configuration so as to drive the signal obtained by superimposing the voltage generated.