JP2001169139A - High-voltage control circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high-voltage control circuit, which performs high voltage control which has no influence on a horizontal deflection amplitude and scarcely has a power loss for high voltage control and effectively corrects picture distortions such as a horizontal pincushion distortion and is realized with a simple constitution. SOLUTION: When a control voltage Ec is raised, an 'on' period ton of a diode 19 in the peak part of a pulse Vp is extended. During this 'on' period, an inductor 18 is equivalent to being connected, in parallel to a tertiary winding 17c with respect to AC. When the 'on' period is extended, a horizontal resonance period is shortened, and the crest value of a collector pulse Vc increases, and the value of a DC high voltage HV increases in proportion to this rise. That is, by changing the value of the control voltage Ec the value of the DC high voltage HV can be adjusted freely.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high voltage control circuit for controlling a high DC voltage supplied to a cathode of a picture tube, and more particularly to a high voltage control circuit capable of efficiently controlling only a DC high voltage with little effect on a horizontal deflection operation. It relates to a control circuit.

[0002]

2. Description of the Related Art FIG. 7 is a circuit diagram showing a conventional horizontal deflection circuit. In FIG. 7, an excitation pulse Vdr from a horizontal excitation circuit (not shown) at a preceding stage is supplied to a primary winding of an excitation transformer 1, and a horizontal output transistor is supplied from a secondary winding thereof.
(Switching element) 2 supplies the base current Ib. In this case, the horizontal output transistor 2 performs a switching operation in cooperation with the damper diode 3 according to a well-known principle. During the off period of the switching operation, a collector pulse Vc of a half sine wave is generated at the collector terminal of the horizontal output transistor 2. The retrace resonance capacitor 4 is for determining the pulse width (return time) of the collector pulse Vc.

[0003] A series circuit of a horizontal deflection coil 5 and an S-shaped correction capacitor 6 is connected between the collector terminal of the horizontal output transistor 2 and the ground, and this series circuit has a sawtooth-shaped deflection having a horizontal deflection cycle. The current Iy flows and deflects the electron beam of the picture tube (not shown) in the horizontal direction.
The collector pulse Vc is supplied to one end of a primary winding 7a of the flyback transformer 7, and a boosted high-voltage pulse Vhv is generated in the secondary winding 7b. The other end of the primary winding 7a is connected to a DC power supply voltage Eb0, from which power is supplied to the circuit. The capacitor 16 is for smoothing the ripple current of the circuit. The high-voltage pulse Vhv is supplied to the high-voltage rectifier diode 8 and rectified to produce a DC high-voltage HV.
And supplied to the anode of a picture tube (not shown).

In FIG. 7, the DC power supply voltage Eb0 is
It is obtained from another DC power supply voltage (first DC voltage) Eb via the voltage control circuit 9. And this voltage control circuit 9
The value of the DC power supply voltage Eb0 which is the output voltage is controlled by the control voltage Ec1. For example, when the value of the DC power supply voltage Eb0 is increased, the value of the DC high voltage HV is also increased in proportion thereto.

FIG. 8 is a circuit diagram showing another conventional example, and FIG. 9 is a waveform diagram for explaining the operation of FIG. 8, which will be described together. 8, the same parts as those in FIG. 7 are denoted by the same reference numerals, and description thereof will be omitted. 8 is different from FIG. 7 in that an intermediate tap p3 is provided in the primary winding 7a1 of the flyback transformer 71, and a retrace time control circuit 10 is connected to the intermediate tap p3. The other end of the primary winding is directly connected to the DC power supply Eb without passing through the voltage control circuit. A flyback time control circuit 10 connected in parallel to a part of the primary winding of the flyback transformer 71 includes a rectifying diode 11 and a capacitor 1.
2, a resistor 13, a transistor 14, a base resistor 15, and a control voltage Ec2.

Here, for example, when the control voltage Ec2 is low and the collector current Ic1 of the transistor 14 hardly flows, the pulse Vp3 generated at the tap p3 is substantially in proportion to the collector pulse Vc of the horizontal output transistor 2. That is, the voltage of the capacitor 12, once charged to the peak value of the pulse Vp3, hardly decreases due to discharging until the next pulse Vp3 comes. Therefore, the subsequent pulse V
Even at the peak of p3, as shown in FIG.
(I.e., the charging period of the capacitor 12) is extremely short, and the pulse shape is almost the same as the collector pulse Vc.

However, when the control voltage Ec2 increases and a large amount of the collector current Ic1 of the transistor 14 flows, the voltage stored in the capacitor 12 discharges through the resistor 13 and the transistor 14 until the next pulse and drops. . Therefore, as shown in FIG. 9B, in order to compensate for this discharge, the conduction period ton2 of the diode 11 becomes longer than that in FIG. 9A. During this conduction period, the capacitor 12
Charging period. Therefore, during this conduction period ton, the capacitor 12 is connected in parallel between a part p3 and q of the primary winding 7a1 of the flyback transformer 7, which is equivalently impedance-converted and the capacitor 12 This means that the flyback resonance capacitor 4 is connected in parallel.
As a result, during the conduction period ton, the resonance period of the collector pulse Vc becomes longer, so that the branch height value decreases.

From the above, when the collector voltage Ic1 of the transistor 14 increases by increasing the control voltage Ec2 and the conduction period ton becomes longer, the peak value of the collector pulse Vc of the horizontal output transistor 2 decreases. The value of the DC high voltage HV obtained by boosting and rectifying this decreases. That is, the DC high voltage value can be freely adjusted by the value of the control voltage Ec2. As the ton period becomes longer, the length of the pulse width (retrace time) tr of the collector pulse Vc becomes longer. That is, the circuit shown in FIG. 8 is a circuit that changes the high voltage by adjusting the length of the retrace time tr. On the other hand, the circuit shown in FIG. 7 described above can be said to be a circuit that changes the high voltage by adjusting the power supply voltage Eb0.

[0009]

In the case of the conventional circuit shown in FIG. 7, when the DC power supply voltage Eb0 is changed to change the DC high voltage HV, the deflection current Iy flowing through the horizontal deflection coil 5 also changes. There is a problem of doing it. Therefore, when trying to adjust the DC high voltage HV, the horizontal amplitude of the raster on the picture tube changes. In order to avoid this problem, the horizontal deflection coil 5 of FIG. 7 is not used for horizontal deflection as a mere dummy coil, but another set of similar circuits is provided for horizontal deflection. It is conceivable to use a horizontal deflection coil. However, in this case, there is a problem that the circuit scale increases and the cost increases.

It is also possible to incorporate a dedicated horizontal deflection amplitude control circuit, for example, a known saturable reactor or a diode modulator, and to control the deflection current Iy so as to cancel the change in the DC power supply voltage Eb0. . But,
This also has a problem that it is quite difficult to accurately keep the horizontal amplitude constant irrespective of the value of the DC power supply voltage Eb0 as the circuit scale increases.

In the case of the conventional circuit shown in FIG. 8, since the DC power supply voltage Eb does not change and the retrace time tr changes when adjusting the high voltage, the value of the deflection current Iy flowing through the horizontal deflection coil 5 becomes Hardly change. However, in order to adjust the DC high voltage HV, a large current Ic1 must be passed, so that the power loss in the resistor 13 and the transistor 14 in this portion becomes extremely large. Since this is heat generation, the reliability of peripheral circuit elements may be impaired,
Further, since the current consumption Ib of the circuit from the DC power supply voltage Eb also increases, there is a problem that the power efficiency of the entire circuit also deteriorates. The present invention has been made to solve the above-described problems, and can perform high-pressure control without affecting the horizontal deflection amplitude, has almost no power loss during high-pressure control, and has image distortion such as left and right pincushion distortion correction. It is an object of the present invention to provide a high-voltage control circuit that can perform correction effectively and can be realized with a very simple configuration.

[0012]

In order to achieve the above object, a switching element for performing an on / off operation in a horizontal deflection cycle, and a series circuit of a horizontal deflection coil and an S-shaped correction capacitor connected in parallel to the switching element. A flyback transformer having one end of a primary winding connected to one end of the switching element and the other end connected to a first DC voltage. A high-voltage rectifier diode connected to one end of a secondary winding of the flyback transformer and outputting a DC high voltage, a tertiary winding of the flyback transformer having one end connected to a second DC voltage, A series circuit of an inductor and a diode connected between the other end of the tertiary winding of the flyback transformer and the first DC voltage. By changing the value of said second DC voltage, to change the conduction period of the diode,
Another object of the present invention is to provide a high-voltage control circuit that controls the value of the DC high voltage.

[0013]

FIG. 1 is a circuit diagram showing a first embodiment of the present invention, FIG. 2 is a waveform diagram for explaining the operation of FIG.
FIG. 3 is a characteristic diagram for explaining the operation of FIG. 1 and will be described together. In FIG. 1, the same parts as those in FIGS. 7 and 8 of the conventional example are denoted by the same reference numerals, and description thereof will be omitted. In FIG. 1, a main difference from FIGS. 7 and 8 of the conventional example is that a tertiary winding 17c is provided in the flyback transformer 17 and one end of the tertiary winding 17c has a DC control voltage (the second control voltage). DC voltage) Ec is supplied, a small pulse Vp in which the collector pulse Vc is transformed is generated at the other end p of the tertiary winding 17c, and the load inductor 18 and the charging diode
(First diode) 19 and a series circuit of the inductor 18 and the diode 19 is connected between the point p of the tertiary winding and the DC power supply voltage (first DC voltage) Eb. That is the point.

At this time, the peak value of the pulse Vp is slightly smaller (lower) than the value of the DC power supply voltage Eb as shown in FIG.
Set. The control voltage Ec is superimposed on the pulse Vp. If the control voltage Ec is zero, the peak value of the pulse Vp does not reach the DC power supply voltage Eb.
Does not flow in the off state. Next, as shown in FIG. 2 (B), when the control voltage Ec has a positive voltage value, the voltage level of the entire pulse Vp rises, so that the top of the pulse Vp temporarily exceeds the DC power supply voltage Eb. Will do. Then, during that period, the diode 19 conducts, and the current Id flows to charge the capacitor 16 connected to the DC power supply voltage Eb. And the inductor 18 and the diode 19 at that time
The waveform Vp1 at the point of connection with is such that the top is sliced during the conduction period ton1 of the diode 19.

This is equivalent to the fact that the inductor 18 is connected in parallel to the tertiary winding 17c during the conduction period ton1. The inductor is converted to the primary side and a new inductor is added in parallel to the resonance capacitor 4. As a result, the resonance period becomes shorter correspondingly. In other words, by shortening the resonance cycle,
The retrace time tr1 in FIG. 2B is shorter than the retrace time tr in FIG. 2A, which is the original retrace time. As a result, the peak value of the collector pulse Vc increases, and in proportion thereto, the value of the DC high voltage HV also becomes higher than the state shown in FIG. When the control voltage Ec further rises as shown in FIG. 2C, the conduction period of the diode 19 further increases to ton2, and the retrace time shortens to tr2. As a result, the DC high voltage HV further rises on the same principle.

As described above, the circuit shown in FIG. 1 changes the value of the control voltage Ec so that the DC high voltage HV
Can be freely adjusted. At this time, since the value of the DC power supply voltage Eb does not change, the value of the deflection current Iy flowing through the horizontal deflection coil 5 hardly changes. Therefore, FIG.
As in the circuit of the prior art shown in FIG. 1, there is no adverse effect that the deflection current Iy is simultaneously changed by adjusting the DC high voltage HV. Another feature of the circuit of FIG. 1 is that there is no power consumption associated with high-voltage control, unlike the circuit of the conventional example shown in FIG. That is, the current Id flowing through the diode 19 charges the capacitor 16 of the DC power supply voltage Eb, and the energy is used for the operation of the circuit through the primary winding 17a of the flyback transformer.

Therefore, when the control voltage Ec is increased in order to increase the DC high voltage HV, the circuit consumption current Ib from the power supply voltage Eb tends to decrease as shown in FIG. This is significantly different from the conventional example shown in FIG. 8 in that when the DC high voltage HV is changed (in this case, the voltage is reduced), the circuit power consumption is significantly increased. However, in the case of the present invention shown in FIG. 1, as shown in FIG. 3, the inflow current from the control voltage Ec, that is, the current Id flowing through the diode 19 increases with the increase of the control voltage Ec. The overall power consumption of the device remains almost unchanged. However, unlike the retrace time control circuit 10 of the conventional example shown in FIG.

FIG. 4 is a circuit diagram showing a second embodiment of the present invention. In FIG. 4, the main differences from FIG. 1 are the resistors 20 and 21 for high voltage division, the comparator 22, the voltage control circuit 2
3 and an amplitude modulation circuit 24 are added. In FIG. 4, the DC high voltage HV is divided by the resistors 20 and 21, and a small voltage Ehv proportional to the DC high voltage HV is obtained. The small voltage Ehv is supplied to the comparator 22 together with the DC reference voltage Es. The voltage Erf of the comparison result is output from the comparator 22,
It is supplied to the voltage control circuit 23. The voltage control circuit 23
The voltage of the DC power supply voltage (third DC voltage) Ec0 is converted according to the value of the voltage Erf to obtain the control voltage Ec, and the pulse Vp
To raise or lower the voltage level of the entire pulse.

In this way, for example, when the high voltage load current Ihv flowing through the picture tube anode increases and the DC high voltage HV attempts to decrease, the control voltage Ec increases to compensate for this and the width of the collector pulse Vc ( Return time tr) is shortened,
An operation of increasing the value of the DC high voltage HV is performed. As a result, the feedback circuit operates so that the voltage Ehv obtained by dividing the DC high voltage HV always matches the reference voltage Es, and the DC high voltage HV
Will be stabilized.

The feature of the present invention shown in FIG. 4 is that the result of the high-pressure adjustment does not affect the horizontal deflection. But,
In the conventional example, on the contrary, there is a problem that the adjustment of the horizontal deflection affects the high voltage value. For example, the deflection current Iy of the deflection coil 5 may be modulated by the amplitude modulation circuit 24 of FIG. More specifically, it is common practice to modulate the envelope of the deflection current Iy with a parabolic waveform Vpb having a vertical deflection period by using a saturable reactor, a diode modulator, or the like, so as to correct the so-called left and right pincushion distortion of the image receiving screen. At this time, not only the deflection current Iy but also the DC high voltage HV is modulated, so that the distortion correction effect may be reduced or the correction may not be performed accurately.

If the capacitor 25 shown by a broken line in FIG. 4 is added to the high voltage portion, this phenomenon is reduced. However, since a capacitor that can withstand this type of high voltage is large and extremely expensive, the present invention requires the capacitor as shown in FIG. Instead of adding the capacitor 25, a waveform Vc1 is applied to the voltage control circuit 23 so as to cancel the high voltage fluctuation caused by the amplitude modulation circuit 24. Then, the control voltage Ec, which is the output of the voltage control circuit 23, is similarly modulated, and the DC high voltage HV changes accordingly. As a result, both operations are canceled and the DC high voltage HV is stabilized. Of course, at this time, the operation of the voltage control circuit 23 does not affect the modulation operation of the deflection current Iy by the amplitude modulation circuit 24.

In the embodiment of the present invention shown in FIGS. 1 and 4 described above, the tertiary winding 17 of the flyback transformer 17 is used.
One end of c is not grounded but is connected to the control power supply voltage Ec. In this case, the tertiary winding 17c is a dedicated winding for high voltage control, and it is difficult to share this winding as a winding for supplying pulses to other circuits in the television receiver. ing. If one end of the tertiary winding 17c can be grounded (connected to a fixed potential point), a small pulse Vp without DC superposition is obtained at the other end, and this pulse is supplied to another circuit in the television receiver. It is convenient because it can be used.

FIG. 5 is a circuit diagram showing a third embodiment of the present invention, and FIG. 6 is a waveform diagram for explaining the operation of FIG.
Also described. 5, the main difference from FIG. 1 is that a capacitor 26 for blocking direct current and a diode (second diode) 27 for clamping are added.
In this manner, the waveform Vp2 generated at the connection point between the capacitor 26 and the diode 27 has a pulse base whose control voltage E
clamped at c. Therefore, when the control voltage Ec is zero, the base of the pulse becomes zero as shown in FIG.
Since the pulse peak is set so as not to slightly reach the DC power supply voltage Eb, the diode 19 does not turn on.

Next, when the control voltage Ec rises, the voltage level of the entire pulse rises because the base of the pulse is still clamped to the control voltage Ec. Then, as shown in FIGS. 6 (B) and 6 (C), the time length at which the diode 19 conducts beyond the power supply voltage Eb at the top of the pulse Vp2 becomes longer, ton1 and ton2, as described in FIG. According to the same principle as described above, the retrace time becomes shorter and the DC high voltage HV rises. However, in this case, the capacitance value of the capacitor 26 is assumed to be sufficiently large so that the load on the tertiary winding 17c becomes inductive overall. The embodiment shown in FIG. 5 requires an extra capacitor 26 and a diode 27 as compared with the embodiment shown in FIGS.
Is grounded (connected to a fixed potential point), the pulse Vp can be supplied from the other end p of the tertiary winding 17c to other circuits in the television receiver, and the number of turns of the flyback transformer is reduced. You can save money.

[0025]

The high voltage control circuit according to the first aspect of the present invention can perform high voltage control without affecting the horizontal deflection amplitude.
There is almost no power loss during high-voltage control, and image distortion correction such as right and left pincushion distortion correction can be performed effectively. The high voltage control circuit according to claim 2 of the present invention has an extremely excellent effect that the number of windings of the flyback transformer can be further reduced in addition to the effect of claim 1.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a first embodiment of the present invention.

FIG. 2 is a waveform chart for explaining the operation of FIG.

FIG. 3 is a characteristic diagram for explaining the operation of FIG. 1;

FIG. 4 is a circuit diagram showing a second embodiment of the present invention.

FIG. 5 is a circuit diagram showing a third embodiment of the present invention.

FIG. 6 is a waveform chart for explaining the operation of FIG. 5;

FIG. 7 is a circuit diagram showing a conventional horizontal deflection circuit.

FIG. 8 is a circuit diagram showing another conventional horizontal deflection circuit.

FIG. 9 is a waveform chart for explaining the operation of FIG.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 horizontal excitation transformer 2 horizontal output transistor (switching element) 3 damper diode 4 retrace resonance capacitor 5 horizontal deflection coil 6 S-shaped correction capacitor 7,17 flyback transformer 8 high voltage rectifier diode 9,23 voltage control circuit 16,25,26 Capacitor 18 Inductor 19 Diode (first diode) 20, 21 Resistance 22 Comparator 24 Amplitude modulation circuit 27 Diode (second diode) Vc Collector pulse Vp, Vp1, Vp1, Vp2, Vp3 pulse Vpb Distortion correction waveform Eb DC power supply voltage ( Ec control voltage (second DC voltage) Ec0 DC power supply voltage (third DC voltage) Ehv, Erf voltage Es DC reference voltage Iy deflection current Ib DC power supply current Id current HV DC high voltage tr, tr1 , tr2 Return time ton, ton1, ton2 Diode conduction period

Claims (4)

[Claims] 1. A switching element for performing an on / off operation in a horizontal deflection cycle, a series circuit of a horizontal deflection coil and an S-shaped correction capacitor connected in parallel to the switching element, and a flyback connected in parallel to the switching element. A resonance capacitor, a flyback transformer having one end of a primary winding connected to one end of the switching element, and the other end connected to a first DC voltage; and one end of a secondary winding of the flyback transformer. A high voltage rectifier diode connected to output a DC high voltage, a tertiary winding of the flyback transformer having one end connected to a second DC voltage, the other end of the tertiary winding of the flyback transformer, First
And a series circuit of a first diode and an inductor connected between the first and second DC voltages, and by changing the value of the second DC voltage, the conduction period of the first diode is reduced. A high-voltage control circuit that changes the value of the DC high voltage. 2. A switching element for performing an on / off operation at a horizontal deflection cycle, a series circuit of a horizontal deflection coil and an S-shaped correction capacitor connected in parallel to the switching element, and a return wire connected in parallel to the switching element. A resonance capacitor, a flyback transformer having one end of a primary winding connected to one end of the switching element, and the other end connected to a first DC voltage; and one end of a secondary winding of the flyback transformer. A high voltage rectifier diode connected to output a DC high voltage, a tertiary winding of the flyback transformer having one end connected to a fixed potential point, the other end of the tertiary winding of the flyback transformer and the first
And a series circuit of an inductor, a capacitor, and a first diode connected between the second DC voltage and a connection point between the capacitor and the first diode and the second DC voltage. A second diode, and the value of the second DC voltage is changed to change the conduction period of the first diode, thereby controlling the value of the DC high voltage. Control circuit. 3. A comparator for comparing a voltage proportional to the DC high voltage with a DC reference voltage and a third DC voltage, and the output of the comparator determines the value of the second DC voltage to be output. 3. The high-voltage control circuit according to claim 1, further comprising a voltage control circuit that controls and operates so that the DC high voltage is constant. 4. An amplitude modulation circuit for modulating a deflection current flowing through the horizontal deflection coil, and a modulation waveform for canceling the DC high voltage modulation effect generated by the amplitude modulation circuit, thereby providing the second The high-voltage control circuit according to claim 3, further comprising the voltage control circuit that controls a value of a DC voltage.