JPH0411408Y2 - - Google Patents

Description

[Detailed explanation of the idea] The present invention relates to a deflection circuit for a television receiver.

With the implementation of stereo broadcasting using so-called audio multiplexing, television receivers are being required to function as audio equipment, and for example, it is required to be able to connect the audio output of the television receiver to another power amplifier or the like. In this case, it is necessary to use an insulated power source for the audio system of the television receiver.

That is, FIG. 1 shows an example of a circuit configured in this manner.

In the figure, voltage from a commercial power source is supplied to a primary coil 2a of a power transformer 2 through a terminal 1, and is switched on and off by a switching element 3. A detection coil 2b is also provided to detect the state of the load on the secondary side of the transformer 2, and a signal from this coil 2b is supplied to the control circuit 4 of the element 3 for stabilization.

Further, the voltage obtained at the first secondary coil 2c of the transformer 2 is supplied through the rectifying element 5 and the smoothing capacitor 6 to the resistor 7 and capacitor 8 that constitute a ripple filter, and the voltage from this ripple filter is It is supplied to the primary coil 9a of the back transformer 9 and the switching element 10. Furthermore, a series circuit including a damper diode 11, a resonance capacitor 12, a horizontal deflection coil 13, and an S-shaped correction capacitor 14 is provided in parallel with the switching element 10. and switching element 1
A sawtooth deflection current is caused to flow through the horizontal deflection coil 13 by intermittent zero in the control circuit 15 according to the horizontal synchronizing pulse. Also, high voltage is taken out from the secondary coil 9b of the flyback transformer 9 through the rectifying element 16.

Furthermore, the voltage obtained at the second secondary coil 2d of the transformer 2 is applied to the rectifying element 17 and the smoothing capacitor 1.
Resistor 1 forming a ripple filter through 8
9 and a capacitor 20, and a low voltage is extracted from this ripple filter to be supplied to audio system circuits and the like.

However, in this circuit, if the load of the audio circuit connected to the secondary coil 2d changes, for example, the output voltage of the secondary coil 2c will change because the detection coil 2b is separate from the secondary coil 2c. It is not possible to provide complete feedback, and the output voltage of the secondary coil 2c is slightly affected by variations in the load on the secondary coil 2d. Such voltage fluctuations affect the current flowing through the deflection coil 13, resulting in a change in screen size.

That is, in this circuit, when the load of the audio circuit changes, the screen size changes, resulting in screen fluctuations called so-called sound fluctuations.

For this reason, in the past, a transformer 2 with a special structure was used to reduce crosstalk between the secondary coils 2c and 2d, the capacity of the smoothing capacitor 6 of the secondary coil 2c was increased, a resistor 7, A ripple filter for capacitor 8 is provided. However, such measures have drawbacks such as an increase in the number of circuit elements and a decrease in efficiency. Furthermore, even with this method, fluctuations could not be completely eliminated.

In view of these points, the present invention is designed to effectively eliminate the above-mentioned screen fluctuations with a simple configuration.

By the way, in the horizontal deflection circuit, the following circuit has been proposed as a circuit for correcting the so-called pink distortion (pin distortion) of the screen.

In FIG. 2, a damper diode 11,
A diode 21, a capacitor 22, and a coil 23 are provided in series with the series circuit of the resonance capacitor 12, the horizontal deflection coil 13, and the S-shaped correction capacitor 14, respectively. Further, the collector of the transistor 24 is connected to the midpoint between the diodes 11 and 12 and the capacitors 12 and 22. This transistor 24 is controlled by a signal from a control circuit 25 that corresponds to, for example, a parabolic wave with a vertical period. Furthermore, the connection midpoint between the diodes 11 and 21 and the connection midpoint between the capacitor 14 and the coil 23 are connected via a capacitor 26. Note that 9' is a DC power source equivalent to the flyback transformer 9.

In this circuit, in the latter half of the horizontal deflection trace period, the switching element 10 is turned on, and current flows as indicated by the solid arrow a in the figure.

On the other hand, the switching element 10 is turned off during the retrace period and the first half of the trace period. First, in the first half of the retrace period, the currents in the coils 13 and 23 tend to continue flowing as indicated by the broken line arrow b, and energy is accumulated in the capacitors 12 and 22. Next, in the latter half of the retrace period, the energy stored in the capacitors 12 and 22 is returned to the coils 13 and 23, and a current flows in the direction opposite to the broken line arrow b. Furthermore, in the first half of the trace period, the energy of coils 13 and 23 is transferred to diode 1.
1 and 21 to the power source 9', and a current as indicated by the dashed-dotted arrow c is caused to flow.

In this way, a sawtooth horizontal deflection current is passed through the coil 13.

In this circuit, when the impedance of transistor 24 is changed, transistor 2
The DC component of the current flowing through 4 (dotted chain arrow d) changes. For example, if the DC component is controlled to increase, the collector-emitter voltage of the transistor 24 decreases. This means that the voltage across the capacitor 26 is reduced in terms of DC component. Furthermore, this means that capacitor 26 and coil 2
This will reduce the energy given to 3. Note that the energy of the capacitor 26 is smaller than that of the coil 23. On the other hand, the energy of the entire circuit is almost constant. Therefore, if the energy given to the coil 23 is reduced in the above-described circuit, the energy of the coil 13 will be increased.

Based on this principle, by reducing the current flowing through the transistor 24 at the top and bottom of the screen and increasing it at the center, it is possible to change the current flowing through the coil 13 and correct pin distortion.

Therefore, if we further consider the effect on the screen size of the fluctuation in the output voltage of the secondary coil 2c mentioned above,
The effect of horizontal deflection variation is greater than the effect of high voltage variation, and as the output voltage increases, the screen size increases.

The present invention has been developed with attention to these points. In other words, the present invention obtains a voltage serving as a deflection current from the secondary side of a transformer whose primary side is stabilized, and a deflection distortion correction circuit is provided in this deflection current path, and a dependent circuit is provided from the secondary side. In a deflection circuit that obtains a power source, voltage changes due to variations in dependent circuits are detected, and this detection signal is supplied to a correction circuit to compensate for changes in deflection due to variations in dependent circuits. It is. An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 3, a case will be described in which the pin distortion correction circuit of FIG. 2 is used. In this figure, the output voltage of the secondary coil 2c is supplied to the control circuit 25 through a capacitor 27 and a resistor 28. The rest of the structure is the same as in FIGS. 1 and 2. Note that the resistor 7 constituting the ripple filter,
19 and capacitors 8, 20 are removed.

Further, in the control circuit 25, the transistor 24 is controlled so that the variation in the output voltage is superimposed on the above-mentioned pin distortion correction, and the change in screen size due to the variation in the output voltage is reversely corrected.

Therefore, in this circuit, even if the output voltage of the secondary coil 2c fluctuates due to a change in the load of the audio system circuit, for example, the transistor 24 is controlled so that the change in screen size due to this fluctuation is reversely corrected. Therefore, the screen size is kept constant and fluctuations such as so-called sound fluctuations do not occur.

In this way, variations in screen size are corrected, and according to the present invention, correction is performed by controlling the existing pin distortion correction circuit in the deflection circuit, which reduces ripple filters and crosstalk. There is no need to use a transformer with a special structure, the number of circuit elements can be reduced, and efficiency does not deteriorate. Furthermore, since the circuit response is extremely fast, fluctuations can be almost completely eliminated.

Thus, according to the present invention, screen fluctuations can be effectively removed with a simple configuration.

Note that the present invention is not limited to the case where the above-mentioned pin distortion correction circuit is used, but can also be applied to a deflection circuit that performs pin distortion correction using a supersaturated reactor.

[Brief explanation of drawings]

FIG. 1 is a connection diagram of a conventional circuit, FIG. 2 is a diagram for explaining pin distortion correction, and FIG. 3 is a connection diagram of an example of the present invention. 1 is a power supply terminal, 2 is a power transformer, 9 is a flyback transformer, 13 is a horizontal deflection coil, 24 is a pin distortion correction transistor, and 25 is a control circuit.

Claims (1)

[Scope of utility model registration request] a transformer having a primary winding, a secondary winding and a detection winding; switching means controlled by a signal obtained from the detection winding of the transformer and connected to the primary winding; has a rectifying means connected to the secondary winding of the rectifying means, an output control section controlled by the output of the rectifying means, and a deflection output section compensated by the output control section; A deflection circuit configured to compensate for changes in the deflection output section according to changes in output voltage.