JP3139530B2 - Horizontal deflection high voltage generation circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a horizontal deflection high-voltage output circuit in a television receiver or the like, and more particularly, to a method in which a horizontal amplitude of an image is kept constant irrespective of a change in a cathode tube anode current. The present invention relates to a horizontal deflection high voltage output circuit in which image distortion is reduced.

[0002]

2. Description of the Related Art FIG. 3 is a block diagram showing an example of a conventional horizontal deflection high voltage output circuit. In FIG. 3, a horizontal deflection output circuit 1 causes a horizontal deflection current Iy, which is a sawtooth current, to flow through a horizontal deflection coil 2 by an excitation pulse Vh of a horizontal deflection cycle from a preceding stage (not shown). As is well known, the horizontal deflection coil 2 is mounted on the neck of the picture tube and deflects the electron beam of the picture tube in the horizontal direction according to the horizontal deflection current Iy. Further, since a horizontal output pulse Vp of a half sine wave is generated at one end of the horizontal deflection coil 2 every horizontal retrace time, this is output to the primary winding 3a of the next flyback transformer 3.
To one end. Note that a DC voltage Ebo is applied to the other end of the primary winding 3a, and this is an operating power supply for the horizontal deflection output circuit 1.

The horizontal output pulse Vp is boosted by the secondary winding 3b of the flyback transformer 3 to generate a high-voltage pulse Vhv
After that, it is rectified by the high-voltage rectifier diode 4 to become a DC high voltage HV, which is applied to the anode a of the picture tube (not shown). The anode a has an anode current I according to the brightness of the picture tube.
a flows to the load of the high-voltage generating circuit 5 composed of the flyback transformer 3, the high-voltage rectifier diode 4, and the like. Further, the high voltage HV is reduced to a small voltage by the high voltage detection circuit 6 and is compared with a reference voltage to generate a control voltage Vr according to the fluctuation of the high voltage HV. This control voltage Vr is applied to the next voltage control circuit 7. The voltage control circuit 7 converts the DC power supply voltage Eb into a DC voltage Ebo according to the control voltage Vr.

Here, if the anode current Ia increases and the high voltage HV decreases due to the internal impedance of the high voltage generating circuit 5, the control voltage Vr is adjusted so that the DC voltage Ebo, which is the output voltage of the voltage control circuit 7, increases. It is assumed that a circuit is configured. Then, as described above, since this voltage Ebo is the power supply voltage of the horizontal deflection output circuit 1, the value of the horizontal output pulse Vp increases, and the high voltage HV obtained by boosting and rectifying this voltage also increases. And the anode current Ia
Can be compensated for a decrease in the high pressure HV due to an increase in the pressure.

However, an increase in the DC voltage Ebo causes an increase in the horizontal deflection current Iy. Therefore, while the high voltage HV is stabilized as it is, the horizontal amplitude of the image fluctuates with the change of the anode current Ia. Therefore, the addition of the circuit with reference numeral 8 and thereafter also prevents the fluctuation of the horizontal deflection current Iy. That is, the horizontal amplitude modulation circuit 8 acts on the horizontal deflection output circuit 1 by a control voltage from another part, and adjusts the value of the horizontal deflection current Iy. In this case, although a detailed circuit is not shown, a well-known diode modulator circuit or a saturable reactor may be used. Further, a parabolic wave voltage Vpc that changes in a vertical cycle is added to the horizontal amplitude modulation circuit 8, and the horizontal deflection current Iy is modulated in accordance therewith to correct the left and right pincushion distortion of the image or to adjust the parabolic wave voltage Vpc. It is common practice to adjust the horizontal deflection amplitude by changing the DC component.

If the control voltage Vr described above is applied to the horizontal amplitude modulation circuit 8 via the buffer 9 as the voltage Vro, even if the voltage Ebo rises with the decrease of the high voltage HV, the horizontal amplitude modulation circuit of the voltage Vro If the action on 8 acts to reduce the horizontal deflection current Iy just to cancel this, it is possible to make the horizontal deflection current Iy constant as a result. Further, as shown by the broken line in FIG. 3, the input of the buffer 9 need not be the control voltage Vr, and the voltage Ebo
Is passed through the voltage shift circuit 10, thereby similarly achieving the purpose of keeping the horizontal deflection current Iy constant. The details of these techniques are described in
-308477 and Japanese Patent Application No. 6-86045.

[0007]

As described above, in the conventional example shown in FIG. 3, the control voltage Vr or the voltage E
The modulation gain of the horizontal amplitude modulation circuit 8 with respect to bo is determined only under static conditions. That is, when the anode current Ia changes slowly, the high voltage HV also changes the horizontal deflection current Iy.
Also, the voltage is stabilized by changing the voltage Ebo and the voltage Vro so as to cancel the change, and the image is stabilized. However, when receiving an image in which the anode current Ia greatly changes in a relatively short period of time, for example, a window pattern as shown in FIG. 4, the high voltage HV and the horizontal amplitude are not always kept constant. . The main reason is that there is a frequency limit in the response characteristic of the high voltage stabilizing operation by the loop of the high voltage generating circuit 5, the high voltage detecting circuit 6, and the voltage control circuit 7.

This will be described with reference to the waveform diagram of FIG. Anode current Ia by window signal of vertical period tv
5 (A), the high pressure HV is originally shown in FIG.
As shown by the dashed line in (B), it is ideal that it is fixed at HVO, but in practice it fluctuates as shown by the solid line. Accordingly, the image is swollen as shown by the broken line in FIG. 4 due to the decrease in the high voltage HV in the window portion, so that a correct rectangular window cannot be displayed.

This characteristic is also affected by the high voltage capacitor 11 between the high voltage HV and the ground in FIG. This high-voltage capacitor 11 serving as a smoothing capacitor for the high-voltage rectifier diode 4 is usually not provided, and is often replaced by a duck capacitance formed on the glass tube wall of the picture tube. If a dedicated high-voltage capacitor 11 is newly provided to increase the capacity of the entire smoothing capacitor, a short-term change in the anode current Ia is covered by the charging / discharging current of this capacitor. Small changes are absorbed and the image is hardly affected.

However, in the case of a change over a relatively long time such as the above-mentioned window signal, on the contrary, the time until the time constant when charging the capacitor 11 from the high voltage generation circuit 5 becomes longer and reaches a steady value is reached. There is a delay. Then, the response characteristics of the control loop for stabilizing the high voltage described above deteriorate, and the image distortion often becomes rather large. Therefore, this is not a problem solved by increasing the capacitance value of the capacitor 11. Further, in a case where a plurality of horizontal deflection frequencies are supported, the response of the high voltage generation circuit 5 becomes slower as the horizontal deflection frequency becomes lower. Generally, the time width for charging the high-voltage capacitor 11 from the high-voltage rectifier diode 4 is equal to the high-voltage pulse V
Only a short period at the tip of hv is required, and a certain number of pulses or more are required to recover the high-pressure HV that has once dropped. However, when the horizontal deflection frequency is low, the number of scanning lines existing in the vertical direction of the same window signal is small as compared with the case where the horizontal deflection frequency is high, resulting in a delay in response, and as a result, the broken line in FIG. The image distortion as shown by becomes large.

When the horizontal deflection time is reduced while the horizontal blanking time width is the same, in order to maintain the same horizontal amplitude and high voltage HV, the value of the voltage Ebo which is the power supply voltage of the substantial circuit is changed to the original DC power supply voltage. It must be greatly reduced compared to the voltage Eb. Although it depends on the type of the voltage control circuit 7, if the difference between the output voltage Ebo and the DC power supply voltage Eb is large, this also causes a response delay, which is also a factor causing a lower horizontal deflection frequency. This will increase the image distortion. As described above, in the case where a plurality of horizontal deflection frequencies are supported, there is a tendency that the image distortion is larger when the horizontal deflection frequency is lower, which has been a problem.

The present invention has been made in view of such a problem, and does not cause image distortion even if the picture tube anode current changes, and does not affect the image distortion even if the horizontal deflection frequency changes. It is an object of the present invention to provide a horizontal deflection high voltage output circuit which does not provide the output.

[0013]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems of the prior art, the present invention provides a plurality of horizontal deflection frequencies.
A corresponding horizontal deflection high voltage generation circuit, a horizontal deflection output circuit for supplying a horizontal deflection current to a horizontal deflection coil, and a DC high voltage obtained by boosting and rectifying a pulse voltage generated in the horizontal deflection coil, an anode voltage of a picture tube. A high-voltage generation circuit, a high-voltage detection circuit that detects a change in the DC high voltage, and a DC power supply that supplies the horizontal deflection output circuit according to the output of the high-voltage detection circuit so as to suppress the fluctuation of the DC high voltage A voltage control circuit for controlling a voltage value, and a horizontal amplitude that acts on the horizontal deflection output circuit according to a control state of the voltage control circuit, and reduces the amplitude of the horizontal deflection current when the DC power supply voltage increases. A horizontal deflection high-voltage generation circuit comprising: a modulation circuit; and an AC gain of the horizontal amplitude modulation circuit with respect to the change of the DC power supply voltage. Larger than the DC gain, the
Change AC gain according to horizontal deflection frequency
If the horizontal deflection frequency is low,
Make the AC gain larger than when the
There is provided a horizontal deflection high voltage generating circuit, characterized in that the way.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A horizontal deflection high voltage output circuit according to the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a block diagram showing an embodiment of a horizontal deflection high voltage output circuit of the present invention, and FIG. 2 is a waveform diagram for explaining the operation of the horizontal deflection high voltage output circuit of the present invention. In FIG. 1, the same parts as those in FIG. 3 are denoted by the same reference numerals.

In FIG. 1, a horizontal deflection output circuit 1 supplies a horizontal deflection current Iy, which is a sawtooth current, to a horizontal deflection coil 2 by an excitation pulse Vh of a horizontal deflection cycle from a preceding stage (not shown). As is well known, the horizontal deflection coil 2 is mounted on the neck of the picture tube and deflects the electron beam of the picture tube in the horizontal direction according to the horizontal deflection current Iy. Further, a half-sine wave horizontal output pulse Vp is generated at one end of the horizontal deflection coil 2 every horizontal retrace time, and is applied to one end of the primary winding 3a of the next flyback transformer 3. Note that a DC voltage Ebo is applied to the other end of the primary winding 3a, and this is an operating power supply for the horizontal deflection output circuit 1.

The horizontal output pulse Vp is stepped up by the secondary winding 3b of the flyback transformer 3 to generate a high voltage pulse Vhv
After that, it is rectified by the high-voltage rectifier diode 4 to become a DC high voltage HV, which is applied to the anode a of the picture tube (not shown). The anode a has an anode current I according to the brightness of the picture tube.
a flows to the load of the high-voltage generating circuit 5 composed of the flyback transformer 3 and the high-voltage rectifier diode 4.

Further, the high voltage HV is reduced to a small voltage by the high voltage detection circuit 6 and is compared with a reference voltage.
A control voltage Vr corresponding to the fluctuation of the high voltage HV is generated. This control voltage Vr is applied to the next voltage control circuit 7. The voltage control circuit 7 converts the DC power supply voltage Eb into a DC voltage Ebo according to the control voltage Vr. Here, an example in which a chopper type regulator is used as the voltage control circuit 7 is shown. Therefore, the control voltage Vr for controlling this is a square wave pulse as shown in the figure. The value of the output voltage Ebo is controlled by changing the duty cycle of the square wave pulse of the control voltage Vr.

Here, if the anode current Ia increases and the high voltage HV decreases due to the internal impedance of the high voltage generating circuit 5, the control voltage Vr is adjusted so that the DC voltage Ebo, which is the output voltage of the voltage control circuit 7, increases. It is assumed that a circuit is configured. Then, as described above, since this voltage Ebo is the power supply voltage of the horizontal deflection output circuit 1, the value of the horizontal output pulse Vp increases, and the high voltage HV obtained by boosting and rectifying this voltage also increases. And the anode current Ia
Can be compensated for a decrease in the high pressure HV due to an increase in the pressure.

However, an increase in the DC voltage Ebo causes an increase in the horizontal deflection current Iy. Therefore, while the high voltage HV is stabilized as it is, the horizontal amplitude of the image fluctuates with the change of the anode current Ia. Therefore, the horizontal amplitude modulation circuit 8 also prevents the fluctuation of the horizontal deflection current Iy. That is, the horizontal amplitude modulation circuit 8 acts on the horizontal deflection output circuit 1 by a control voltage from another part, and adjusts the value of the horizontal deflection current Iy. In this case, although a detailed circuit is not shown, a well-known diode modulator circuit or a saturable reactor may be used. Further, a parabolic wave Vpc that changes in a vertical cycle is added to the horizontal amplitude modulation circuit 8, and the horizontal deflection current Iy is modulated in accordance therewith to correct left and right pincushion distortions of the image or to reduce the DC voltage of the parabolic wave Vpc. Adjusting the horizontal deflection amplitude by changing the minute has conventionally been performed well.

Further, in FIG. 1, the buffer 12 applies the control voltage Vr from the high voltage detection circuit 6 to the horizontal amplitude modulation circuit 8 as the average voltage Vro. High pressure HV
Even if the voltage Ebo rises due to the decrease in the horizontal deflection current Iy, if the action of the voltage Vro on the horizontal amplitude modulation circuit 8 acts to reduce the horizontal deflection current Iy just to cancel the voltage Ebo, the horizontal deflection current Iy will be constant as a result. It is possible to
The specific configuration and operation of the buffer 12 is a feature of the present invention, and will be described in detail below.

The resistor 13 and the capacitor 14 form a filter, generate an average DC voltage Er of the control voltage Vr which is a pulse voltage, and apply it to the next non-inverting terminal of the operational amplifier 15. A resistor 16 is connected between the inverting terminal and the output terminal of the operational amplifier 15. Here, if there is no portion after code 17 in the buffer 12,
The operational amplifier 15 simply functions as a voltage follower, and the DC voltage Er becomes almost equal to the voltage Vro and is applied to the horizontal amplitude modulation circuit 8. However, in this state, when the anode current Ia changes slowly and averagely, the horizontal deflection current Iy is constant and the image amplitude can be kept constant. However, when the anode current Ia changes rapidly according to the image content, as described above. High-pressure stabilization control operation cannot follow
V fluctuates. Therefore, in such a case, if the horizontal deflection current Iy is kept constant, the image amplitude will change.

Therefore, the DC amplification factor of the operational amplifier 15 is kept as it is, and when the DC voltage Er fluctuates, the amplification factor is increased only for the fluctuating component, and the horizontal deflection current Iy is not constant and the fluctuation of the high voltage high HV is compensated. In such a case, the image amplitude becomes constant, and the distortion decreases. For this purpose, a series circuit of the capacitor 17 and the resistor 18 may be inserted between the inverting terminal of the operational amplifier 15 and the ground to increase the amplification factor (gain) for the AC. In this way, the DC amplification factor (gain)
Is unchanged at 1, but the AC amplification factor is
The AC gain of the horizontal amplitude modulation circuit 8 with respect to a change in the DC power supply voltage Eb ₀ can be made larger than the DC gain of the horizontal amplitude modulation circuit 8. It should be noted that from what AC frequency the amplification factor is increased is determined by the time constant of the capacitor 17 and these resistors. Type of image of interest in practice, it determined considering the vertical frequency, etc., of the order of 10 to 100 Hz is practical.

The switch 19 and the resistor 20 are for changing the AC amplification factor of the operational amplifier 15 when the horizontal deflection frequency is switched as described above.
That is, as described above, the horizontal deflection frequency decreases and the high pressure H
When the variation of V becomes large, the switch 19 is turned on to connect the resistor 20 in parallel with the resistor 18 to increase the AC gain (AC gain) of this circuit. Although the switch 19 may be manually operated, it is more convenient to use an electronic switch that can be electrically switched by an external signal. Automation can be performed by switching with a frequency signal Ef whose value changes according to the horizontal deflection frequency.

As described above, according to the horizontal deflection high voltage generating circuit of the present invention shown in FIG. 1, the control voltage Vro applied to the horizontal amplitude modulating circuit 8 is not necessarily a direct current but has a waveform component that changes depending on the image content. . For example, first, FIGS.
The operation in the case where the window signal is projected as described above will be described with reference to FIG. As shown in FIG. 2A, the anode current Ia of the picture tube depends on the vertical period of the window signal.
Flows, the response of the automatic control of the high voltage HV cannot catch up as described above, and the high voltage HV vibrates as shown by a solid line in FIG. 2 (B).

On the other hand, by increasing the AC amplification factor of the operational amplifier 15, the pp value of the horizontal deflection current Iy flowing through the horizontal deflection coil 2 becomes higher as shown by the solid line in FIG. It is forcibly modulated in accordance with the fluctuation of HV. Therefore, although a change in the high voltage HV can be compensated for a slow change in the anode current Ia in the past, a change in the high voltage HV remains in the case of a rapid change. There was a drawback that the horizontal amplitude fluctuated, but this was corrected by positively moving the amplitude of the horizontal deflection current Iy to a larger extent, thereby preventing unnecessary movement and distortion on the screen. .

When the horizontal deflection frequency is changed,
Until now, there was a tendency that the distortion remaining after the high voltage correction tended to increase at the lower frequency, but this problem can also be solved by switching the AC amplification factor of the buffer 12 which is the horizontal deflection current correction circuit according to the present invention. Can be. That is, since the horizontal deflection frequency has been lowered, FIG.
2B, the AC amplification factor of the buffer 12 is further increased in response to the increase in the fluctuation of the high voltage HV as indicated by the broken line, and the horizontal deflection current Iy is increased as indicated by the broken line in FIG. What is necessary is just to make a pp value move.

[0027]

As described above in detail, the horizontal deflection high voltage generating circuit of the present invention has a larger AC gain for a change in the DC power supply voltage of the horizontal amplitude modulation circuit than a DC gain for a change in the DC power supply voltage. Therefore, not only the high voltage stability and the horizontal deflection amplitude can be stabilized, but also the image is not distorted even if there is a sudden change in the image content like a window signal. In addition, in the case where the horizontal deflection frequency is supported, the AC gain is switched according to the horizontal deflection frequency. When the horizontal deflection frequency is low, the AC gain is increased as compared with the case where the horizontal deflection frequency is high. As a result, even when the horizontal deflection frequency is switched, there is an extremely excellent feature that image distortion is not affected.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention.

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

FIG. 3 is a block diagram showing a conventional example.

FIG. 4 is a diagram for explaining a problem of a conventional example.

FIG. 5 is a waveform chart for explaining the operation of the conventional example.

[Description of Signs] 1 horizontal deflection output circuit 2 horizontal deflection coil 3 flyback transformer 4 high voltage rectifier diode 5 high voltage generation circuit 6 high voltage detection circuit 7 voltage control circuit 8 horizontal amplitude modulation circuit 12 buffer (horizontal deflection current correction circuit) 13, 16, 18, 20 Resistance 14, 17 Capacitor 15 Operational amplifier 19 Electronic switch Eb DC power supply voltage Ebo DC voltage (operating power supply voltage) Ef Frequency signal Ia Anode current Iy Horizontal deflection current Vh Horizontal excitation pulse Vhv High voltage pulse Vp Horizontal output pulse Vpc Parabolic wave voltage Vr control voltage

Continuation of the front page (56) References JP-A-63-308477 (JP, A) JP-A-5-297816 (JP, A) JP-A-6-54219 (JP, A) JP-A-58-13879 (JP) JP-A-1-3161071 (JP, A) JP-A-55-61172 (JP, A) JP-A-61-142869 (JP, A) JP-A-3-102971 (JP, A) 6-13269 (JP, U) JP-A 63-49868 (JP, U) JP-A 63-97962 (JP, U) JP-A 6-34371 (JP, U) (58) Fields surveyed (Int. Cl. ^7, DB name) H04N 3/223 H04N 3/185 H04N 3/27

Claims (1)

(57) [Claims] 1. Horizontal deflection corresponding to a plurality of horizontal deflection frequencies
A high voltage generating circuit, a horizontal deflection output circuit for supplying a horizontal deflection current to a horizontal deflection coil, and a high voltage for supplying a DC high voltage obtained by boosting and rectifying a pulse voltage generated in the horizontal deflection coil as an anode voltage of a picture tube. A generating circuit, a high-voltage detecting circuit that detects a change in the DC high voltage, and a value of a DC power supply voltage supplied to the horizontal deflection output circuit so as to suppress the fluctuation of the DC high voltage in accordance with an output of the high-voltage detecting circuit. A voltage control circuit for controlling, and a horizontal amplitude modulation circuit that acts on the horizontal deflection output circuit according to the control state of the voltage control circuit and reduces the amplitude of the horizontal deflection current when the DC power supply voltage increases. In the horizontal deflection high voltage generation circuit provided, an AC gain of the horizontal amplitude modulation circuit with respect to a change of the DC power supply voltage is converted into a DC gain with respect to a change of the DC power supply voltage. Base Increase, switched in accordance with the AC gain in the horizontal deflection frequency
If the horizontal deflection frequency is low, the horizontal deflection
The AC gain is increased as compared with the case where the wave number is high.
A horizontal deflection high voltage generation circuit characterized in that: