JPS597260B2 - 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 generated in the high voltage circuit provided on the secondary side of the flyback transformer is prevented from fluctuating.

Generally, in 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 moving speed of the bright spot increases as it moves away from the center of the fluorescent surface or as the deflection angle increases. As the speed increases, the drawn raster will have its four corners distorted, causing 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, reference numeral 1 denotes a horizontal oscillation circuit. The output of the horizontal oscillation circuit 1 is supplied to the base of a horizontal output NPN transistor 3 via a horizontal drive circuit 2. 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. The collector of this transistor 3 is grounded via a horizontal deflection coil 6, a saturable reactor T, and a capacitor 8, and is connected to the positive terminal of a DC power supply 10 via a primary coil (hereinafter referred to as coil 9a) of a flyback transformer 9. The negative terminal of this DC power supply 10 is grounded. The town saturation reactor T is connected to the terminal γa from the vertical output circuit.
The inductance is changed by the vertical parabolic voltage supplied to the horizontal deflection coil 6, and the magnitude of the horizontal deflection current flowing through the horizontal deflection coil 6 is changed so that the width of the raster increases at the center of the vertical scanning period. However, since the characteristics of the saturable reactor 1 are distorted, it is not possible to change its inductance to a desired shape, and changing the inductance in this way will change the magnitude and pulse width of the flyback pulse generated in the coil 9a. Flyback transformer 9
The drawback was that the output (high voltage) of the high voltage rectifier circuit connected to the secondary side of the converter 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 and the high voltage generation circuit, the output of the horizontal 1 drive circuit 2 is connected to the transistor 3.
The emitter of this transistor 11 is grounded, and the collector thereof is grounded via a parallel circuit consisting of a damper diode 12 and a capacitor 13.

These transistor 11, damper diode 12, capacitor 13, and the aforementioned flyback transformer 9 supply voltage to the Takada rectifier circuit and the low voltage rectifier circuit.
Also, the collector of the transistor 3 is grounded through a series circuit of a coil 30 and a capacitor 31, the emitter of an NPN transistor 14 is connected to the midpoint between the coil 30 and the capacitor 31, and the collector is connected to the city terminal of the DC power supply 10. Connect to. A vertical parabolic voltage synchronized with the vertical period is supplied to the base of the transistor 14 via the terminal 14a. In this way, the power supply voltage of the horizontal deflection circuit 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 raster increases at the center of the vertical scanning period. At this time, the pulse voltages supplied to the high voltage rectifier circuit and the Takada 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 electron beam determined by the horizontal deflection power and high-voltage output changes. The disadvantage is that the size of the image changes, causing screen distortion. In view of the above-mentioned points, the present invention aims to eliminate the disadvantages mentioned above.

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 supplied to the bases of NPN transistors 15 and 16, the emitter of this transistor 15 is connected to the collector of a transistor 16, and the emitter of this transistor 16 is grounded. .

The power source 5 of the damper diode 11 is connected to the collector of the transistor 15 and also grounded via the capacitor 18. The anode of a damper diode 17 is connected to the emitter of this transistor 15. Further, the cathode of a diode 19 is connected to the anode of this diode 1r, and the anode of this diode 19 is grounded. A series circuit of a horizontal deflection coil 20 and a capacitor 21 is connected between the cathode and anode of the diode 1r, and the cathode of the diode 19 is grounded via the capacitor 22 and the coil 23. Also, these capacitors 22
and an NPN transistor 24 at the connection midpoint of the coil 23.
3, the collector of the transistor 24 is connected to the midpoint between the capacitors 21 and 22 via the coil 25, and the tab led out from the coil 25 is connected to the anode of the diode 26.
The cathode of is connected to the midpoint between the horizontal deflection coil 20 and the capacitor 21.

Further, the base of the transistor 24 is connected to the emitter of the transistor 24 via the secondary winding of the transformer 27. This transformer 2r is for supplying the output from the pulse width modulator 28 to the base of the transistor 24. Here, the pulse width modulator 28 is supplied with a parabolic voltage synchronized with the vertical period from the terminal 28a, and pulse width modulates the horizontal period pulse from the horizontal oscillation circuit 1. In order to facilitate understanding of the present invention configured as described above, first consider a circuit excluding the transistor 24, coil 25, diode 26, transformer 21, pulse width modulator 28, etc.

First, before transistors 15 and 16 are turned on, capacitor 18 is connected to power supply voltage E. The capacitors 21 and 22 are each charged to a predetermined voltage, which will be described later. In other words, are capacitors 21 and 22 charged? The inductance of the horizontal deflection coil 20 is assumed to be El and E2, respectively, and the inductance of the horizontal deflection coil 20 is
Let the inductance Lx be as follows. As shown by the solid line in FIG. 4A, the capacitance of the capacitor 21, the inductance of the horizontal deflection coil 20, and the electric current Ff are
．． A current determined by El flows, and the coil 23 and capacitor 22! and the coil 23 through the transistor 16
A current flows that is determined by the inductance of the capacitor 22, the capacitance of the capacitor 22, and the voltage E2.

Further, as shown by the broken line in FIG. 4A, capacitor 18 discharges through transistors 15 and 16, and DC power supply 10 discharges through coil 9a with a current magnitude determined by coil 9a and voltage E. Next, transistor 1
5 and 16 are turned off, the magnetic energy i stored in the coils 20, 23, and 9a causes a current to flow to the capacitor 18 as shown in FIG. When the accumulated charge is discharged, resonance occurs. The local phase of this resonance is determined by the capacitance of capacitors 18, 20 and 22 and the horizontal deflection coil 2 of coil 9a5.
0 and the inductance of the coil 23. After this resonance ends, the inductance of the coil 20, the capacitance of the capacitor 21, and the electric current 8E1 pass through the coil 20, capacitor 21, and Tasopa diode 17 as shown in the solid line in FIG. 4C, as in FIG. 4A. A determined damper current flows, and a damper current determined by the inductance of the coil 22, the capacitance of the capacitor 23, and the voltage E2 flows through the coil 22, the capacitor 23, and the damper diode 19.

At this time, a current flows through the diodes 1r and 19, the coil 9a, and the DC power supply 10 as shown by the broken line in FIG. 4C. The current flowing through each element in FIG. 4 as described above is illustrated in FIG. 5.

In this Figure 5, TA. T.B. TC is shown in Figure 4A, respectively.
Compatible with sBsC. Here, the magnitude of the horizontal deflection current flowing through the horizontal deflection coil 20 depends on the electric field E1 between the terminals of the capacitor 21, and the magnitude of the b1 flyback pulse depends on the power supply voltage E. It will be according to. In this example, the voltage E1 between the terminals of the capacitor 21 is changed to a parabolic shape synchronized with the vertical period to change the magnitude of the horizontal deflection current.
is changed to a parabolic shape with the same level and opposite polarity as the terminal voltage E1 of the capacitor 21, and the power supply voltage across the series circuit of the horizontal deflection coil 20, capacitors 21, 22, and coil 23 is kept constant, and the fly generated in the coil 9a is The pulse width and peak value of the back pulse are made constant.

That is, assume that charges are stored in the capacitors 21 and 22 as shown in FIG.

Here, when the transistor 24 turns on, the capacitor 22
produces a discharge as shown by the solid line in Figure 6, and therefore the coil 25
A voltage is generated at the tapped tap, and the capacitor 21 is charged as shown by the broken line in FIG. In this example, the pulse width of the horizontal frequency from the horizontal oscillation circuit 1 is pulse width modulated by a parabolic wave synchronized with the vertical period as shown in FIG. It is supplied between the base and emitter of 24. Therefore, the voltage between the terminals of the capacitor 21 changes in a parabolic manner as shown in FIG. 7B, and the voltage between the terminals of the capacitor 22 changes as shown in FIG.
As shown in , a parabolic voltage of the same level and opposite polarity as the voltage between the terminals of the capacitor 21 is obtained. Therefore, the amplitude of the horizontal deflection current is modulated by the parabolic voltage of the vertical period, as shown in FIG. r DVc. This horizontal deflection current can correct pincushion distortion in the left and right directions. In the present invention, since there is no change in the pulse width and peak value of the flyback pulse generated by the coil 9a during pincushion distortion correction, there is no change in the high output or low voltage output.

Furthermore, since the inductance values of the flyback transformer 9 and the coils 20 and 23 and the capacitance of the capacitor 18 remain unchanged, the size and pulse width of the flyback pulse do not change as in the pincushion distortion correction circuit shown in FIG. do not have. 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, and the pincushion distortion correction circuit shown in FIG. There is no screen distortion like that seen in . Incidentally, instead of the capacitor 18 in FIG. 3, capacitors 32 and 33 may be connected in parallel to the diode 1r and the diode 19, respectively, as shown in FIG.

Further, in the above embodiment, the capacitor 22 was discharged and the capacitor 21 was charged by the transistor 24 and the pulse width modulator 28, but conversely, as shown in FIG.
1 may be discharged and the capacitor 22 may be charged.

At this time, it is sufficient to supply the base of the transistor 24 with a pulse signal whose pulse width is small at the center of the screen, contrary to the case of the circuit shown in FIG. Alternatively, as shown in FIG. 10, the transistor 16 is not used, but the anodes of diodes 29a and 29b are connected to the emitter of the transistor 15, the cathode of the diode 29a is grounded, and the cathode of the diode 29b is connected to the cathode of the diode 19. You may. In this case, when the transistor 15 is turned on, the capacitor 21, the horizontal deflection coil 20, the transistor 15 and the diode 29b form a closed circuit, and the coil 23,
It is easy to understand that the capacitor 22, damper diode 17, transistor 15, and diode 29a form a closed circuit, and that the circuit shown in FIG. 10 operates similarly to the circuit shown in FIG. 3.

[Brief explanation of drawings]

1 and 2 are conventional pincushion distortion correction circuits, FIG. 3 is a connection diagram showing one embodiment of the pincushion distortion correction circuit of the present invention, and FIGS. 4 and 5 are explanations of one embodiment of the present invention. 6 and 6 are connection diagrams and waveform diagrams of various parts thereof, and FIGS.
0 are connection diagrams of other embodiments of the present invention. 9 is a flyback transformer, 10 is a DC power supply, 15 and 16 are transistors for the first and second switching elements, respectively, 20 is a horizontal deflection coil, 21 is a first capacitor, 22 is a second capacitor, 23 is the first coil, . 24 is a transistor constituting a third switching element, 25 is a second coil, and 28 is a pulse width modulator.

Claims (1)

[Claims] 1. A series circuit of a horizontal deflection coil and a first capacitor is connected in series with a series circuit of a second capacitor and a first coil, and a primary coil of a high voltage generation transformer and a DC power supply are connected to both ends of this entire series circuit. A first switching element is inserted in parallel with the series circuit of the horizontal deflection coil and the first capacitor, and a first switching element is inserted in parallel with the series circuit of the horizontal deflection coil and the second capacitor. A second switching element that is switched in the same phase as the element is inserted, and the second switching element and the first switching element are connected to each other.
a series circuit of a third switching element and a second coil between the connection midpoint of the coil or the connection midpoint of the horizontal deflection coil and the first capacitor and the connection midpoint of the first and second capacitors; and connect the tap derived from the second coil to the connection midpoint between the horizontal deflection coil and the first capacitor or the connection midpoint between the second capacitor and the first coil, and The first or second capacitor is charged or discharged in accordance with the parabolic voltage by supplying a horizontal period pulse modulated with a parabolic voltage synchronized with the vertical period through a switching element of the spool. Distortion correction circuit.