JPH05183770A - Circuit for generating high voltage - Google Patents

Abstract

PURPOSE:To improve the stability degree of a high voltage by reducing an inner impedance in a high voltage generating circuit. CONSTITUTION:A horizontal synchronizing signal Ps is supplied to a horizontal deflection circuit 1 so as to obtain a fly-back pulse Vr1. The pulse Vr1 is adopted as a high voltage pulse Vhv1 by a fly-back transformer 12 so as to be supplied to a high voltage rectifier circuit 13. the horizontal synchronizing signal Ps is adopted as a pseudo synchronizing signal Psd by a phase shift circuit 11 and supplied to a high voltage output circuit 5 so as to obtain the fly-back pulse Vr2. The pulse Vr2 is adopted as the high voltage pulse Vhv2 by the fly-back transformer 13 so as to be supplied to the high voltage rectifier circuit 7. The outputs of the high voltage rectifier circuits 13 and 7 are connected in common and a DC voltage HV obtained at the connecting point is supplied to the possitive electrode of a picture tube.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high voltage generating circuit for generating a DC high voltage applied to the anode of a picture tube in a television receiver or the like.

[0002]

2. Description of the Related Art In a television receiver, the means for generating a DC high voltage applied to the anode of a picture tube is usually obtained by boosting and rectifying a horizontal deflection pulse generated in the receiver. FIG. 5 is a circuit diagram showing an example of a conventional high voltage generating circuit. In FIG. 5, the horizontal deflection circuit 1 includes
A horizontal synchronizing signal Ps is supplied from a preceding stage (not shown) in the receiver, and a series circuit of the horizontal deflection coil 2 and the S-shaped correction capacitor 3 connected to the output thereof is provided with a saw having a horizontal deflection cycle synchronized with the horizontal synchronizing signal Ps. The wave current Iy flows. Further, the output of the horizontal deflection circuit 1 is also connected to the primary winding 4a of the horizontal output transformer 4, one end of which is connected to the DC power source Eb. In this way, the first retrace pulse Vr1 is generated in the primary winding 4a, which is transformed into an appropriate peak value Vo by the secondary winding 4b, and then the horizontal AFC in the horizontal deflection circuit 1 is changed.
In addition to being added as a comparison signal for the circuit, it is supplied to the necessary circuits in each unit in the receiver.

Further, the horizontal synchronizing signal Ps is supplied to the high voltage output circuit 5
Is supplied to. One end of the primary winding 6a of the flyback transformer 6 is connected to the output of the high voltage output circuit 5, and the controlled DC power supply voltage Eb1 is connected to the other end of the primary winding 6a. In this way, the secondary winding 6a has a second
, A high voltage pulse Vhv is obtained by boosting the voltage by the secondary winding 6b, and the high voltage pulse Vhv is further converted to a DC high voltage HV by the rectifier circuit 7 and then applied to the anode of a picture tube not shown. The other end of the secondary winding 6b is grounded, or the value of the anode current Ia is detected and the video circuit is controlled according to the detected value to prevent excessive anode current Ia from flowing.
Connect to a so-called ABL circuit.

A high voltage detection resistor 8 is connected to the output of the rectifier circuit 7, and a reference voltage Erf proportional to the high voltage HV is generated at the intermediate tap p point. The reference voltage Erf is compared with the reference voltage Es by the comparison circuit 9, and its output voltage Eo is supplied to the voltage control circuit 10. The voltage control circuit 10 converts the DC power supply voltage Eb into a substantial DC power supply voltage Eb1 of the circuit according to the value of the output voltage Eo of the comparison circuit 9. The condenser 14 is a condenser formed on the tube wall of the picture tube and plays a role of smoothing.

In the circuit of FIG. 5, a high voltage detecting resistor 8
Consider a case where there is no circuit element up to the voltage control circuit 10 and the DC power supply voltage Eb is directly connected to one end of the primary winding 6a of the flyback transformer 6. In general, if the anode current Ia increases due to the increase in picture tube brightness, the value of the high voltage HV decreases due to the internal impedance of the flyback transformer 6 and the rectifier circuit 7. Since this adversely affects the brightness, deflection amplitude, focus quality, etc. of the picture tube, it is desirable that the value of the high voltage HV be constant regardless of the value of the anode current Ia of the load. Therefore, the reference voltage Erf obtained by the high voltage detection resistor 8 is added to the comparison circuit 9 and compared with the reference voltage Es. If this high voltage HV
Is decreased, the reference voltage Erf is also decreased at the same time. Therefore, at this time, the circuit is determined so that the output Eo of the comparison circuit 9 increases the DC voltage Eb1. Then, the increase of the DC voltage Eb1 raises the high voltage HV, and therefore the high voltage HV is stabilized without being affected by the value of the anode current Ia.

[0006]

However, the above-mentioned conventional high voltage generating circuit also has a problem. One of them is that the difference between the DC voltages Eb and Eb1 becomes large when it is necessary to increase the correction amount of the high voltage drop. If this voltage difference is large, if an ordinary transistor series regulator or the like is used for the voltage control circuit 10, power loss will increase in this part. For this reason, it is necessary to reduce the decrease in the high voltage HV due to the anode current Ia from the beginning to reduce the load on the voltage control circuit 10.
Another problem is that the response of the feedback circuit composed of the circuit elements from the high voltage detection resistor 8 to the voltage control circuit 10 is inevitably slow. Therefore, when the anode current Ia suddenly changes, the above-described stabilizing effect of high voltage cannot catch up, and when there is a white peak portion on an image receiving screen such as a so-called window screen, the image may be distorted at this portion. The only way to prevent this is to reduce the amount of reduction of the original high voltage HV due to the anode current Ia and reduce the contribution of the high voltage stabilizing circuit composed of the high voltage detection resistor 8 to the voltage control circuit 10.

However, it is difficult to reduce the amount of decrease in the above-mentioned original high voltage HV. This is because the pulse width tp of the high voltage pulse Vhv is narrow and the conduction period to of the high voltage rectifier diode in the rectifier circuit 7 is narrow accordingly, as shown in FIG. This pulse width tp substantially coincides with the second retrace pulse Vr2, which is a value similar to the pulse width of the retrace pulse Vr1 on the primary side of the horizontal output transformer 4 by design. Therefore, the width tp of the high-voltage pulse Vhv, and hence the conduction period to of the high-voltage rectifier diode, cannot be sufficiently wide in a receiver such as a high-definition display or an HDTV which has a high horizontal deflection frequency and a small retrace time ratio. At present, the amount of decrease in the high voltage HV becomes large. The problem to be solved by the present invention is to increase the conduction period of the high-voltage rectifier diode, reduce the internal impedance of the high-voltage power supply, and reduce the high-voltage by any means, without impairing the operation of the circuit as a whole. The point is whether it is possible to reduce power increase and response delay during stabilization.

[0008]

In order to solve the above-mentioned problems of the prior art, the present invention provides (1) a first horizontal deflection cycle.
A horizontal deflection circuit which is supplied with the synchronization signal of 1 to output a first retrace pulse, a horizontal deflection coil which is supplied with the first retrace pulse and through which a sawtooth wave current having a horizontal deflection cycle flows, and A first flyback transformer to which a retrace pulse is supplied to the primary winding, a first high-voltage rectifier circuit connected to the secondary winding of the first flyback transformer, and the first synchronization A high-voltage output circuit which is supplied with a second synchronizing signal having a phase different from that of the signal and outputs a second retrace pulse; and a second fly in which the second retrace pulse is supplied to the primary winding. An output of the first high-voltage rectifier circuit and an output of the second high-voltage rectifier circuit, which is composed of a back transformer and a second high-voltage rectifier circuit connected to the secondary winding of the second flyback transformer. Are connected in common, and the DC voltage obtained at this connection point is received by the picture tube. (2) The phase difference between the first synchronizing signal and the second synchronizing signal is the voltage of the high voltage rectifying diode in the second high voltage rectifying circuit. The high-voltage generating circuit according to (1), characterized in that the conduction period is set to be located in the pulse period of the first retrace pulse or in the vicinity thereof.
(3) A detection circuit that detects a change in the DC voltage, and a voltage control circuit that controls an output value of the second flyback transformer according to an output of the detection circuit (1) Alternatively, the high voltage generating circuit described in (2) is provided.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The high voltage generating circuit of the present invention will be described below with reference to the accompanying drawings. 1 is a circuit diagram showing a first embodiment of a high voltage generating circuit of the present invention, FIG. 2 is a waveform diagram for explaining the operation of the first embodiment, and FIG. 3 is a circuit showing a second embodiment of the high voltage generating circuit of the present invention. 4 and 5 are waveform diagrams for explaining the operation of the second embodiment. 1 and 3, the same parts as those of FIG. 5 are designated by the same reference numerals, and detailed description thereof will be omitted.

First, a first embodiment of the high voltage generating circuit of the present invention will be described with reference to FIG. In FIG. 1, a horizontal synchronizing signal Ps is supplied to the horizontal deflection circuit 1, and a sawtooth current Iy synchronized with this phase flows in the horizontal deflection coil 2. First retrace pulse Vr1 generated at the output of the horizontal deflection circuit 1
Is applied to one end of the primary winding 12a of the first flyback transformer 12 newly provided by the present invention, and the DC power supply voltage Eb is connected to the other end of the primary winding 12a. Then, a first high-voltage pulse Vhv1 is generated in the secondary winding 12b, and this pulse Vhv1 is supplied to the first high-voltage rectifying circuit 13 to become a direct-current high-voltage HV and added to the anode of the picture tube. The flyback transformer 12 has 3
The secondary winding 12c is provided, and the pulse Vo generated here is supplied to the horizontal deflection circuit 1 for performing the horizontal AFC operation as in the conventional case, and is also supplied to the circuits of the respective units in the receiver. The capacitor 14 is a capacitor formed on the wall of the picture tube or a high voltage capacitor additionally provided, and also functions as a smoothing capacitor of the high voltage rectifier circuit 13.

The horizontal synchronizing signal Ps is also supplied to the phase shift circuit 11 newly provided according to the present invention, delayed by a predetermined time td to become the pseudo synchronizing signal Psd, and supplied to the high voltage output circuit 5. The high voltage output circuit 5 generates a second retrace pulse Vr2 synchronized with the pseudo synchronization signal Psd and supplies it to one end of the primary winding 6a of the flyback transformer 6.
Here, the flyback transformer 6 is substantially the same as the flyback transformer 6 of FIG. 5, but is referred to as a second flyback transformer 6 in correspondence with the first flyback transformer 12. This second flyback transformer 6
A second high voltage pulse Vhv2 is generated in the secondary winding 6b of
This pulse Vhv2 is supplied to the second high voltage rectifier circuit 7. DC high voltage is still generated at the output of the high-voltage rectifier circuit 7, and is connected to the output of the first high-voltage rectifier circuit 13 in common here, and the first and second high-voltage rectifier circuits 7 and 13 work together. Then, the high voltage HV is supplied to the anode of the picture tube.

Further, in FIG. 1, the high-voltage detection resistor 8, the comparison circuit 9, and the voltage control circuit 10 are substantially the same as the power-supply voltage of the high-voltage output circuit 5 according to the value of the high-voltage HV, as in the case of FIG. Move the value of Eb1. That is, if the high voltage HV rises and the value of the reference voltage Erf exceeds the reference voltage Es, the output voltage Eo of the comparison circuit 9 changes so as to act on the voltage control circuit 10 in the direction of lowering the voltage Eb1. On the contrary, when the high voltage HV is lowered, the voltage Eb1 is increased, and serves to suppress the change of the high voltage HV as a whole.

FIG. 2 is a waveform diagram showing the relationship between the first and second high voltage pulses Vhv1 and Vhv2 in FIG. In FIG. 2A, the second high-voltage pulse Vhv2 is delayed from the first high-voltage pulse Vhv1 by a delay time amount td due to the phase shift circuit 11 at the pulse peak. Here, the broken line Ehv shows the actual movement of the high voltage HV. This voltage Ehv becomes the charge / discharge curve of the high voltage capacitor 14,
Once charged with high voltage pulse Vhv1 or Vhv2,
After that, the cathode ray tube anode current Ia discharges and the value gradually decreases. As shown, the first high voltage pulse Vhv
When the high voltage pulse becomes higher than the value of the voltage Ehv in the high voltage pulse period by the second high voltage pulse Vhv2 after being charged by 1, the high voltage capacitor 14 is charged and the voltage Ehv becomes Rises like.

In FIG. 2 (A), unlike the case of FIG. 6, even if the charging by the first high voltage pulse Vhv1 ends within the time to1, the charging by the second high voltage pulse Vhv2 immediately starts and the time It lasts only for to2. And this to2
As the charging continues further in the section of, the potential of the high voltage capacitor 14, that is, the voltage Ehv rises more than in the case of FIG. That is, even if the potential of the voltage Ehv drops due to discharge during the period between the pulses, the recovery is large, and the drop of the average potential of the voltage Ehv with respect to the anode current Ia that is a constant current is small accordingly. In other words, the internal impedance of this high-voltage power supply has become low. This is because the conduction period of the high voltage rectifier diode is from to to t as compared with the conventional FIG.
It can be said that it is due to the spread to o1 + to2. Therefore, in the case where the width of the high voltage pulse Vhv is narrow in the related art and the internal impedance of the high voltage power source is increased, the present invention can be effectively used.

The phase shift amount td of the phase shift circuit 11 is arbitrary, and may be any value as long as the sum to1 + to2 of the conduction periods of the high-voltage rectifier diodes is larger than in the conventional case. However, noise is often generated at the front end and the rear end of the conduction period of this high-voltage rectifier diode. In order to prevent this from appearing on the screen, the second conduction period to2 is set within the horizontal deflection retrace time tr1. It is desirable that the scanning period ts is not reached. When the conduction period to2 further extends beyond this, it is advantageous that the screen noise is less likely to occur at least within the time tos corresponding to the screen overscan and not to the substantial scanning period tsa.

Furthermore, in FIG. 1, the output voltage Eb1 of the voltage control circuit 10 is moved by the voltage Eo obtained by comparing the output Erf of the high voltage detection resistor 8 with the reference voltage Es by the comparison circuit 9 to stabilize the high voltage HV. Consider the operation. If the value of the anode current Ia is small and the voltage Ehv, which is the potential of the high voltage capacitor 14 between the high voltage pulses, does not decrease significantly,
The value of the actual power supply voltage Eb1, and thus the second high voltage pulse Vhv
The peak value of 2 is lowered. As a result, as shown in FIG. 2 (B), the second conduction time to21 becomes short and the rise of the voltage Ehv is suppressed. On the contrary, when the value of the anode current Ia is large and the decrease in the voltage Ehv due to the discharge is large, the actual power supply voltage Eb1
The second high voltage pulse Vhv is increased by increasing the value of
The peak value of 2 rises, and the second conduction period to22 is as shown in FIG.
As shown in (C), it becomes longer. As a result, the amount of increase in the voltage Ehv during the second conduction period to22 increases,
Even if the voltage Ehv greatly decreases during the high voltage pulse due to the anode current Ia, the average value of the voltage Ehv can be fixed.

As can be seen from the above description, in the circuit of FIG. 1, the peak value and the value of the conduction period of the high-voltage rectifier diode change according to the change of the anode current Ia mainly due to the second high-voltage pulse Vhv2. .. Since the first high-voltage pulse Vhv1 of the output of the flyback transformer 12 to which the horizontal deflection coil 2 is connected to the primary side does not move, the horizontal deflection is affected in the white portion of the screen where the anode current Ia sharply increases. White peak distortion is rare. Further, FIGS. 1 and 2B and 2C show an example in which the second high voltage pulse Vhv2 for moving the peak value is positioned immediately after the first high voltage pulse Vhv1 for keeping the peak value constant. However, the positional relationship between the first and second high voltage pulses Vhv1 and Vhv2 may be reversed. For example, as shown in FIG. 3, the horizontal synchronizing signal Ps is added to the horizontal deflection circuit 1 as the pseudo synchronizing signal Psd through the phase shift circuit 15, and the synchronizing signal Ps is added to the high-voltage output circuit 5 as it is and synchronized with this. Good.

Next, a second embodiment of the high voltage generating circuit of the present invention will be described with reference to FIG. In FIG. 3, the parts denoted by the same reference numerals as those in FIG. 1 perform the same operations, and thus detailed description thereof will be omitted. In FIG. 3, the first high-voltage pulse Vhv1 is positioned after the second high-voltage pulse Vhv2 in which the peak value changes, as shown in FIGS. 4A and 4B. The average value of the voltage Ehv can be controlled. That is, when the anode current Ia is small, the decrease in the voltage Ehv between the high voltage pulses is small as described above.
Accordingly, as shown in FIG. 4 (A), the peak value of the second high-voltage pulse Vhv2 is lowered, and as a result, the conduction period to23 of the high-voltage rectifier diode is shortened and the increase of the average value of the voltage Ehv is suppressed. Be done.

On the contrary, when the anode current Ia is large, the voltage Ehv is greatly reduced between the high voltage pulses. In this case, as shown in FIG.
As shown in (B), the peak value of the second high voltage pulse Vhv2 is increased. Then, the period to24 during which the rectifying diode is turned on by the second high-voltage pulse Vhv2 becomes long, and the voltage Ehv rises during this period, so that the potential drop between the high-voltage pulses is compensated and the average value thereof, that is, the high-voltage HV is prevented from decreasing. .. In the case of FIG. 3 as well, similar to FIG. 1, the change of the peak value of the high-voltage pulse is taken care of by the second high-voltage pulse Vhv2.
The pulse Vo used for other purposes such as the horizontal AFC obtained by the flyback transformer 12 of FIG.

In FIGS. 1, 3 and 5, the power supply voltage Eb is converted into the voltage Eb1 by the voltage control circuit 10 as a method of controlling the peak value of the high voltage pulse, and this is used as the substantial power supply voltage of the circuit. 1 of the second flyback transformer 6
A circuit added to one end of the next winding 6a is shown. However, the high-voltage pulse control method applied to the present invention is not limited to the above-mentioned method, and various conventionally known methods can be applied.

[0021]

As described in detail above, since the high-voltage generating circuit of the present invention is configured as described above, the conduction period of the high-voltage rectifier diode can be set to be long, and thus the high-voltage having a sufficiently low internal impedance. Power is formed,
It is possible to obtain a high-stability high-voltage output without adding a high-voltage stabilizing circuit. In addition, even when a high-voltage stabilization circuit is added to obtain more complete high-voltage stability, responsiveness is fast,
And it consumes less power. Further, according to the present invention, the noise of the high-voltage rectifier diode is less likely to appear on the image surface of the picture tube, and the effective high-voltage stabilization is achieved without affecting the pulse waveform extracted from the horizontal deflection circuit. You can

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a first embodiment.

FIG. 2 is a waveform diagram for explaining the operation of the first embodiment.

FIG. 3 is a circuit diagram showing a second embodiment.

FIG. 4 is a waveform diagram for explaining the operation of the second embodiment.

FIG. 5 is a circuit diagram showing a conventional example.

FIG. 6 is a waveform diagram for explaining the operation of a conventional example.

[Explanation of symbols]

 1 horizontal deflection circuit 2 horizontal deflection coil 5 high voltage output circuit 6 second flyback transformer 7 second high voltage rectifier circuit 9 comparison circuit (detection circuit) 10 voltage control circuit 11 phase shift circuit 12 first flyback transformer 13th 1 high-voltage rectifier circuit 15 phase shift circuit Iy sawtooth wave current Ps horizontal sync signal Psd pseudo sync signal Vr1 first retrace pulse Vr2 second retrace pulse

Claims (3)

[Claims] 1. A horizontal deflection circuit which is supplied with a first synchronizing signal of a horizontal deflection cycle and outputs a first retrace pulse, and a sawtooth wave of the horizontal deflection cycle which is supplied with the first retrace pulse. A horizontal deflection coil through which a current flows, a first flyback transformer to which the first retrace pulse is supplied to a primary winding, and a first flyback transformer connected to a secondary winding of the first flyback transformer. High-voltage rectifier circuit, a high-voltage output circuit that is supplied with a second synchronization signal having a phase different from that of the first synchronization signal, and outputs a second retrace pulse, and the second retrace pulse is 1 A second flyback transformer supplied to the secondary winding; and a second high-voltage rectifier circuit connected to the secondary winding of the second flyback transformer. Connect the output and the output of the second high-voltage rectifier circuit in common, A high-voltage generation circuit characterized in that the DC voltage obtained at the connection point of is supplied to the anode of the picture tube. 2. The phase difference between the first synchronizing signal and the second synchronizing signal is such that the conduction period of a high voltage rectifying diode in the second high voltage rectifying circuit is the pulse period of the first retrace pulse. Alternatively, the high-voltage generating circuit according to claim 1, wherein the high-voltage generating circuit is defined so as to be located in the vicinity thereof. 3. A detection circuit for detecting a change in the DC voltage, and a voltage control circuit for controlling an output value of the second flyback transformer according to an output of the detection circuit. The high voltage generating circuit according to item 1 or 2.