JPS5847904B2 - Pincushion distortion correction circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pincushion distortion correction circuit for a television receiver;
In particular, by correcting pincushion distortion, the high voltage applied to the high voltage circuit provided on the secondary side of the flyback transformer is prevented from fluctuating.

In general, for an electron beam deflected by a deflection current with good linearity, the moving speed of the beam at the deflection point is constant, so the farther from the center of the phosphor screen or the larger the deflection angle, the faster the bright spot moves. Therefore, the four corners of the drawn rask will stretch and cause pincushion distortion.

Conventionally, circuits as shown in FIGS. 1 and 2 have been used as circuits for correcting pincushion distortion in the horizontal direction among such pincushion distortions.

That is, in FIG. 1, 1 is a horizontal oscillation circuit, and the output of this horizontal oscillation circuit 1 is passed through a horizontal drive circuit 2 to an NP for horizontal output.
It is supplied to the base of N-type transistor 3.

The emitter of this transistor 3 is grounded, and the collector is grounded via a parallel circuit of a damper diode 4 and a capacitor 5.

Also, the collector of this transistor 3 is a horizontal deflection coil 6,
It is grounded through the saturable reactor 7 and the capacitor 8, and connected to the positive terminal of a DC power supply 10 through the primary coil 9a of the flyback transformer 9, and the negative terminal of the DC power supply 10 is grounded.

The saturable reactor 7 changes its inductance by the vertical parabola voltage supplied to the terminal 7a from the vertical output circuit, and changes the magnitude of the horizontal deflection current flowing through the horizontal deflection coil 6 so that the width of the rask increases at the center of the vertical scanning period. It is something.

However, since the characteristics of the saturable reactor 7 are distorted, it is not possible to change the inductance to a desired shape, and when the inductance is changed in this way, the size and pulse width of the flyback pulse generated in the coil 9a are There was a drawback that the output (high voltage) of the high voltage rectifier circuit connected to the secondary side of the flyback transformer 9 also fluctuated.

However, in FIG. 1, terminal 9b is the input terminal of the high voltage rectifier circuit, and terminal 9c is the input terminal of the low voltage rectifier circuit.

In addition, in FIG. 2, in order to separate the horizontal deflection circuit, the high voltage generation circuit, and the low voltage rectification circuit, the output of the horizontal drive circuit 2 is supplied to the base of the transistor 3 and to the base of the NPN transistor 11. The emitter of this transistor 11 is grounded, and the collector is grounded from a damper diode 12 and a capacitor 13 via a certain parallel circuit.

These transistor 11, damper diode 12, capacitor 13, and the aforementioned flyback transformer 9 supply voltage to the high voltage rectifier circuit and the low voltage rectifier circuit.

Also, the collector of the transistor 3 is grounded through a series circuit of a coil 40 and a capacitor 41, and the emitter of an NPN transistor 14 is connected to the midpoint between the coil 40 and the capacitor 41, and the collector is connected to the positive terminal of the DC power supply 10. Connect to.

A parabolic voltage synchronized with the vertical period is supplied via the base terminal 14a of this transistor 14.

In this way, the voltage between the terminals of the capacitor 8 also changes in a parabolic manner, and the horizontal deflection current flowing through the horizontal deflection coil 6 can be changed so that the width of the lanuta widens at the center of the vertical scanning period.

At this time, the pulse voltages supplied to the high voltage rectifier circuit and the low voltage rectifier circuit do not vary.

However, when the beam current increases and the high-voltage output decreases, the horizontal deflection power value has no relation to the fluctuation of the high-voltage output, so the traveling direction of the electrons determined by the horizontal deflection power and high-voltage output changes, and the screen size changes. It has the disadvantage of causing screen distortion.

In view of the above-mentioned points, the present invention aims to eliminate such drawbacks.

An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 3, the output of the horizontal drive circuit 2 is connected to the base of an NPN transistor 15, and the emitter of the transistor 15 is connected to the anodes of diodes 16 and 17.

The cathode of the diode 16 is grounded, and the anode of the diode 16 is grounded via the capacitor 18.

Also, a damper diode 1 is connected to the collector of the transistor 15.
The cathode of diode 9 is connected, and the anode is connected to the cathode of diode 17.

A capacitor 20 is inserted between the cathode and anode of the diode 17, and the cathode of the diode 17 is connected to the cathode of the damper diode 21.

Also, the anode of this diode 21 is grounded.

A capacitor 22 is connected between the cathode and anode of the diode 19, and a series circuit of a horizontal deflection coil 23 and a capacitor 24 is also connected.

Further, the collector of the transistor 15 is connected to one end of the primary coil 9d of the flyback transformer, and the other end of this coil 9d is connected to the emitter of the NPN transistor 25.

Then, the collector of this transistor 25 is connected to the DC power supply 26.
and to the base of the transistor 25 via a resistor 27.

Further, a parabolic voltage synchronized with the vertical period is supplied to the base of this transistor 25 from a terminal 28 via a capacitor 29.

The negative terminal of the DC power supply 28 is connected to the anode of the damper diode 19 via the coil 30.

This coil 30 is connected to a DC power supply 32 and capacitors 24 and 2.
It has the function of disconnecting from the second class in terms of AC.

Further, one end of this coil 30 that is not connected to the anode of the damper diode 19 is connected to the collector of a PNP type transistor 31, and the emitter of this transistor 31 is connected to the positive terminal of a DC power supply 32.

The base of this transistor 31 is connected to the collector via a resistor 33 and to the emitter of the transistor 25 via a capacitor 34.

Further, the negative terminal of the DC power supply 32 is grounded via the coil 9e.6 To facilitate understanding of the operation of the present invention configured as described above, FIG. 4 will be explained.

FIG. 4 is a diagram in which the transistors 25, 31, etc. are omitted from FIG. 3.

Here, when the transistor 15 is turned on, the coil 23,
A current flows in the direction shown by the solid line in FIG. 4A through a closed circuit formed by the DC power supply 26, the transistor 15, and the diode 17.

Also, along with this, a DC power supply 32, a coil 9e, a DC power supply 26
and coil 9d1 transistor 15 and diode 1
Current flows through the closed circuit created by 6 in the direction shown by the dashed line in FIG. 4A.

When the transistor 15 is turned off, the current flowing in the direction of the solid line and the broken line in FIG. 4A flows into the capacitor 22 as shown in the solid line and the broken line in FIG. 4B, and after a while, it flows out from the capacitor 22. Causes resonance.

After such resonance, the horizontal deflection coil 23 and the capacitor 24
A damper current flows through the diode 19 as shown by the solid line in FIG. 4C, and the coil 9d, DC power supply 26, DC power supply 32, coil 9e,
A damper current flows through diodes 21 and 19.

The relationship between the current flowing through the horizontal deflection coil and the primary coil of the flyback transformer, the flyback pulse, and the on/off of the transistor 15 as described above is shown in the figure.
It will look like the figure.

Here, the voltage between the terminals of the capacitor 24 is equal to the voltage of the DC power supply 26, and the magnitude of the horizontal deflection current flowing through the horizontal deflection coil as shown in FIG. 5B is determined by the magnitude of the voltage between the terminals of the capacitor 24. The magnitude of the horizontal deflection current is determined by the voltage of the DC power supply 26.

On the other hand, the magnitude of the current flowing through the coils 9d and 9e as shown in FIG. Since the magnitude and pulse width of the flyback pulse do not change as long as the sum of the voltages of the DC power supplies 26 and 32 is constant, the magnitude and pulse width of the flyback pulse do not change.

The present invention changes the magnitude of the voltage between the terminals of the DC power supplies 26 and 32 in a parabolic manner synchronized with the vertical period, and makes the sum of the voltages of the DC power supplies 26 and 32 constant.

That is, in FIG. 3, when a parabolic voltage synchronized with the vertical period is applied to the base of transistor 25, transistor 2
A voltage of the same polarity as this parabolic voltage is generated at the emitter of transistor 31, and a voltage of opposite polarity to this parabolic voltage is generated at the collector of transistor 31.

Therefore, the magnitude of the voltage between the terminals of the capacitor 24 can be changed in a parabolic manner synchronized with the vertical period, and the sum of the voltages between the terminals of the DC power supplies 26 and 32 can be kept constant.

Therefore, there is no change in the magnitude of the current flowing through the coils 9d and 9e.

According to the present invention, the magnitude and pulse width of the flyback pulse do not change during pincushion distortion correction, so there is no variation in the high voltage output and the low voltage output.

Furthermore, since the inductance value of the flyback transformer 9 and the coil 23 and the capacitance value of the capacitor 24 remain unchanged, the size and pulse width of the flyback pulse do not change as in the pincushion distortion correction circuit shown in FIG. .

When the high voltage output decreases due to an increase in beam current, the horizontal deflection current also decreases because the primary and secondary sides of the flyback transformer 9 are coupled in an alternating current manner.The pincushion distortion correction circuit shown in FIG. There is no screen distortion like that seen in .

Furthermore, in the above embodiment, the diodes 16 and 17 were used as switching elements, but as shown in FIG.
Even if the collector of the transistor 35 is connected to the emitter of the transistor 35 and the anode of the damper diode 19 is connected, the pace of this transistor 35 is connected to the base of the transistor 15, and the emitter of this transistor 35 is grounded, the circuit shown in FIG. It is easy to understand that it operates in a similar way.

[Brief explanation of the drawing]

1 and 2 are conventional pincushion distortion correction circuits, FIG. 3 is a connection diagram showing an embodiment of the pincushion distortion correction circuit of the present invention, and FIGS. 4 and 5 are connections for explaining FIG. 3. The diagram, waveform diagram, and FIG. 6 are connection diagrams showing another embodiment of the present invention. 15. 27 and 31 are transistors, 16 and 17 are diodes, 23 is a horizontal deflection coil, 24 is a capacitor,
9d and 9e are the primary coils of the flyback transformer,
26 and 32 are DC power supplies.

Claims (1)

[Claims] 1. First and second switching elements that operate in the same phase are provided in series, and a series circuit of a horizontal deflection coil and a capacitor is inserted in parallel with the first switching element, and a series circuit of a horizontal deflection coil and a capacitor is inserted in parallel with the first switching element. A series circuit of the first voltage source whose power supply voltage changes in a synchronized parabolic manner is inserted, and the second
a second coil connected in series to the first coil in parallel with the switching element of the first voltage source; A pincushion distortion correction circuit characterized in that a circuit is inserted to supply a flyback pulse voltage generated across the first and second coils connected in series to a high voltage rectifier circuit.