JPH089187A - Correction circuit for horizontal cross distortion - Google Patents

Abstract

PURPOSE:To obtain the correction circuit for horizontal cross distortion in which sure clamping action is obtained with small power without increasing the capacitance of a charge/discharge capacitor. CONSTITUTION:As a charging current Ich is obtained at a portion where a pattern tends to be shifted to the right while a discharging current Ids is obtained at a portion where a pattern tends to be shifted to the left, one terminal of a capacitor 13 is grounded through a clamp diode 14 or a clamp transistor(TR) 15 without failure at the point of time of each of tips of parabolic waves. Thus, a clamp action is always produced for each horizontal blanking time and a parabolic voltage Vs2 across the clamp diode 14 is not floated positively, resulting that a horizontal deflection coil current Iy is made stable thereby suppressing horizontal cross distortion of an image.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a horizontal cross distortion correction circuit for reducing deflection distortion (horizontal cross distortion) caused by the brightness of a screen when horizontal deflection is performed in a television receiver or the like.

[0002]

2. Description of the Related Art Conventionally, when a picture tube is deflected, when the brightness of a part of the screen is high, the horizontal deflection action immediately after that is affected, causing a phenomenon of distortion. For example, as shown in FIG. 6, when a lattice fringe signal is received, the image horizontal amplitude may be affected immediately below the white horizontal line, and the white vertical line, which should be a straight line, may oscillate left and right. . This phenomenon is particularly noticeable in a small-sized picture tube which requires a relatively small horizontal deflection power, and when a large amount of high-voltage load current is passed in order to increase the brightness, the quality of the image is often degraded.

FIG. 7 shows a conventional horizontal cross distortion correction circuit in which measures are taken to reduce the so-called horizontal cross distortion. First, 1 is a horizontal output transistor that performs a switching operation together with the damper diode 2 in accordance with a drive waveform V1 from the preceding stage (not shown). Further, 3 is a return resonance capacitor, 4 is a horizontal deflection coil, 5 is an S-shaped correction capacitor, 6 is a flyback transformer, and 7 is a high-voltage rectifying diode.

In this way, the flyback transformer 6
When a DC power supply voltage Eb is applied to one end of the primary winding 6a of
This circuit applies a sawtooth wave current Iy to the horizontal deflection coil 4 according to a well-known principle to deflect the electron beam of the picture tube in the horizontal direction. At the same time, a half-sine-wave pulse Vc is generated in the collector of the horizontal output transistor 1, which is boosted by the secondary winding 6b of the flyback transformer 6 and then rectified by the high-voltage rectifying diode 7 to generate a DC high voltage HV. Become. This high voltage HV is guided to the anode of a picture tube not shown, and a high voltage current Ihv corresponding to the brightness of the image flows.

The reference numerals 1 to 7 described above are standard horizontal deflection and high voltage output circuits, but this alone tends to cause cross distortion as shown in FIG. Therefore, as a countermeasure, a clamp circuit 8 may be added. In this clamp circuit 8, 9 is a charge / discharge capacitor, 10
Is a clamp diode, and 11 is a discharge resistor.

As described above, the picture tube projects an image such as a lattice-stripe signal, and the high-voltage current Ihv suddenly appears in the white portion.
Is increased. Then, during the blanking period, the corresponding energy is supplemented from the primary side resonance circuit, so the average level of the deflection coil current Iy in the next scanning period moves, and the image shifts to the right. At this time, the parabolic wave voltage Vs across the S-shaped correction capacitor 5 also moves as a result.

Therefore, conversely, this parabolic wave voltage Vs
Is stabilized, the fluctuation of the deflection coil current Iy can be suppressed. For example, after the image has a white peak, the deflection coil current I
As a result of y being shifted in the direction shown by the arrow in FIG. 7, the average value of the parabolic wave voltage Vs generated across the S-shaped correction capacitor 5 tends to decrease. At that time, if the charging current Ich is caused to flow through the diode 10 and the capacitor 9 to replenish the electric charge of the S-shaped correction capacitor 5 to be reduced, the subsequent fluctuation of the voltage is suppressed. When the charging / discharging capacitor 9 is completely charged, the current Ich does not flow from the next cycle onward, so the charge accumulated in the charging / discharging capacitor 9 is discharged through the discharging resistor 11 during the scanning period.

In this way, the parabolic wave voltage Vs1 across the diode 10 is clamped to 0 V at the tip of the parabolic wave, that is, the portion corresponding to the horizontal retrace time, as shown in FIG. Does not fluctuate. Then, the level of the parabolic wave voltage Vs at both ends of the S-shaped correction capacitor 5 is kept unchanged by the difference between this Vs1 and the power supply voltage Eb, and the deflection coil current I
y is stabilized, and image distortion is suppressed. The polarity of the clamp diode does not have to be as shown in this figure, and even if it is reversed, the upper part of the parabola wave is clamped and the image is similarly stabilized.

[0009]

However, as can be seen from FIG. 6, the phenomenon of the horizontal shift of the image due to the influence of the high-voltage load current is oscillatory, and after shifting to the right once, the normal position is reversed. Move more to the left. The average level of the parabola voltage Vs at the time of this left shift tends to rise.

Consider this in correspondence with the video signal Vk in which the white signal continues for one horizontal period from time T0 to T1 and becomes black thereafter, as shown in FIG. 9 (A). Then, as shown in FIG. 9B, immediately after the white signal, the time T
At 2 and T3, a large clamp current Ich flows in the direction in which the charge / discharge capacitor 9 is charged, and a reliable clamp action is performed. That is, the clamp diode 10 at this time
The parabola voltage Vs1 is as shown in FIG. 9C, and the tip of the parabola wave voltage Vs1 is fixed at 0 V at least until around time T5.

However, from time T6 to T8, the parabolic wave voltage V is generated in the portion where the vertical line in FIG.
Since the entire waveform of s1 floats in the positive direction, the current does not flow in view of the polarity of the diode 10, and the clamp action does not work. Therefore, the average level of the parabolic wave voltage Vs at this time also fluctuates, and there is almost no effect of distortion correction.

To improve this, the value of the discharge resistor 11 may be reduced so that the charge of the charge / discharge capacitor 9 is sufficiently discharged in each horizontal period. However, if such an improvement is attempted, the power consumption in the discharge resistor 11 increases, the efficiency of the entire circuit deteriorates, and the peak value of the current flowing through the clamp diode 10 increases, which makes the diode large and expensive. It's not a good idea because things are needed.

Further, if the capacitance value of the capacitor 9 is increased, a large charging current for correcting the voltage of the S-shaped correction capacitor 5 can be obtained, so that the effect of distortion correction is increased.
However, since the time constant of the response also becomes long, the period of vibration on the left and right of the vertical line in FIG. 6 becomes long, which may make it unsightly, and there is a limit to improvement by this capacitance value.

[0014]

In order to solve the above-mentioned problems of the prior art, the present invention provides a horizontal deflection coil for flowing a sawtooth wave current of a horizontal deflection period for performing horizontal deflection of a picture tube and an S-shaped correction. A series circuit with a capacitor, a series circuit with a charging / discharging capacitor and a clamp diode connected in parallel with the S-shaped correction capacitor, and a series circuit with the clamp diode are connected in parallel and conduct during a part of the horizontal blanking period. A horizontal cross distortion correction circuit including an electronic switch controlled as described above, wherein the clamp diode has a polarity that makes a part of the horizontal retrace period conductive, and the electronic switch has a current flowing when the clamp diode is made conductive. The present invention provides a horizontal cross distortion correction circuit characterized in that it flows in the direction opposite to that of a diode.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A horizontal cross distortion correction circuit according to the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a circuit diagram showing an embodiment of a horizontal cross distortion correction circuit of the present invention, FIGS.
5 is a waveform diagram for explaining the operation of the circuit shown in FIG.
FIG. 6 is a circuit diagram showing another embodiment of the horizontal cross distortion correction circuit of the present invention. 1 and 5, the same parts as those in FIG. 7 are designated by the same reference numerals, and detailed description thereof will be omitted. That is, the portions 1 to 7 operate as a horizontal deflection output circuit and a high voltage output circuit.

In FIG. 1, reference numeral 12 is a clamp circuit for distortion correction according to the present invention. Here, 13 is a charge / discharge capacitor, 14 is a clamp diode, 15 is a clamp transistor, 16 and 17 are base resistors thereof, 18 is a differential capacitor, and 6c is a tertiary winding of the flyback transformer 6. Here again, as in FIG. 7, a sawtooth wave current Iy flows through the horizontal deflection coil 4 and a pulse Vc is generated at the collector of the horizontal output transistor 1. As a result, a high voltage HV is generated at the cathode of the high voltage rectifier diode 7, and a parabolic wave voltage Vs is generated at both ends of the S-shaped correction capacitor 5.

The parabolic wave voltage Vs is clamped at 0 V by the clamp circuit 12 according to the present invention. In the clamp circuit 12, the diode 14 becomes conductive near the tip of the parabola wave, that is, near the center of the horizontal blanking period, and the charging current Ich is supplied to the S-shaped correction capacitor 5 through the charging / discharging capacitor 13.

On the other hand, the flyback transformer 6 is newly provided with a tertiary winding 6c, and the pulse V2 obtained there passes through the differential capacitor 18 and the clamp transistor 15c.
Added to the base of. Then, the collector and the emitter are conducted mainly in a part of the first half of the blanking period, and the S-shaped correction capacitor 5 through the charge / discharge capacitor 13
Discharge the discharge current Ids. The pulse V2 obtained from the tertiary winding 6c can be used in common with the pulse supplied to other circuits in the receiver.

FIG. 2 shows the waveform of each part in FIG. 1 as in the case of FIG. Here, as before, when the video signal Vk as shown in FIG. 2A is added to the picture tube, a white horizontal line appears from time T0 to T1 and then black is displayed for a while until the next white horizontal signal. Shall continue. At this time, the clamp diode 14 detects the parabola voltage Vs.
As shown in FIG. 2 (B), the charging current Ich that conducts near the center of the horizontal retrace time, that is, the charging current Ich that charges the S-shaped correction capacitor 5 and the charging / discharging capacitor 13, is Flow to. The amount of current for each cycle is the same as in the case of FIG. 9, and is large for a few cycles immediately after the white signal, then decreases once and then approaches a steady value while oscillating.

The discharge current Ids of the capacitors 5 and 13 flowing in the clamp transistor 15 flows in the direction opposite to Ich, as shown in FIG. 2 (C). Then, immediately after the white signal, the amount of current is small near T2 and T3,
The image becomes large in the vicinity of T5 to T7 where the image tends to shift to the left, and then becomes a steady value while vibrating slightly.

Therefore, the current Ich is in the portion where the screen tends to shift to the right, and the current Ids in the portion where the screen tends to shift to the left.
Therefore, one end of the capacitor 13 is always grounded by a diode or a transistor at each tip of the parabolic wave. As a result, the clamp action always occurs at each horizontal retrace time, and the parabolic voltage Vs2 across the clamp diode 14 becomes as shown in FIG. 2 (D), as shown in FIG. 9 (C) of the related art. The waveform does not float in the positive direction, and as a result, the horizontal deflection coil current Iy is stabilized and the image cross distortion is suppressed.

Here, an example in which a bipolar transistor is used as an element for flowing the discharge current Ids is shown, but any other element may be used as long as it operates as an electronic switch, and for example, an FET or the like can be used. .

FIG. 3 shows the charging current Ich and the discharging current Ids.
2 is an enlarged view of the time axis from FIG. 2, showing a state in which a certain amount of time has passed from the white signal and the value has reached a substantially steady value. That is, FIG. 3A shows the flyback transformer 6
Shows the pulse V2 appearing on the third winding 6c of the. When this pulse V2 is differentiated by the differentiation capacitor 18 and the resistance 16,
The shape is as shown by the broken line dV2 in FIG. However,
Voltage waveform Vb actually applied to the base of the transistor 15
Is sliced when the on-voltage between the base and emitter of the transistor exceeds about 0.7 V, and the collector-emitter conducts in this flat portion.

The charging current Ich flowing through the diode 14 is
Since it flows at the tip of the parabola voltage Vs, FIG.
As shown in (C), the flow just flows around the center of the retrace time tr. On the other hand, the discharge current Ids flows in the portion before the charging current Ich as shown in FIG. 3D, because the transistor 15 becomes conductive in the first half of the retrace time tr as described above.

At this time, the current I in FIGS. 3 (C) and 3 (D)
The areas of the pulse portions of ch and Ids, in other words, the charge amounts of charge and discharge are almost equal in the steady state. During this charging / discharging, the resistance component of the current path is so small that it can be almost ignored, so that there is no occurrence of power loss in the discharging resistance as in the conventional circuit shown in FIG. Then, as is apparent from the above description, immediately after the horizontal white line, the charging current Ich decreases and the discharging current Ids increases for several cycles, and thereafter, this movement converges to a steady value. In this case, charging current Ich,
One of the discharge currents Ids flows during each retrace time, and the clamp action is maintained.

In FIG. 1, it has been described that the transistor 15 is mainly conductive in the first half of the flyback time tr. But,
It is also possible to stop the differentiation by the differentiation capacitor 18 and add the waveform of the pulse V2 to the base of the transistor 15 as it is. Then, the collector-emitter of the transistor 15 becomes conductive over the entire blanking time tr.

FIG. 4A shows the discharge current Ids at this time. First, since the parabolic wave voltage Vs2 applied to the collector is positive at the beginning of the retrace time, Ids is used as the collector current.
Flows. Next, the diode 14 becomes conductive at the tip of the parabolic wave voltage Vs2, and the charging current Ich is turned on as shown in FIG.
Discharge current Ids once disappears. And I
When ch disappears, Ids flow out again and continue for the retrace time tr.

The current value of the discharge current Ids is determined by the deflection coil current Iy and the impedance of the discharge path. The total charge amount, that is, the sum of the pulse partial areas in FIG. 4A is shown in FIG. 4B. Is equal to the area of the pulse portion of the charging current Ich. Therefore, as compared with the case of FIG. 3, the charging current Ich of FIG.

This has the drawback that the peak value of the current flowing through the diode 14 becomes large while the clamping action is ensured, and that an object having a large current rating must be used here. From the point of view of preventing image distortion, it does not matter that the current value is Ich or Ids as long as the current value does not become zero even during the transient vibration with remarkable distortion.
It is more advantageous to form the discharge current Ids as shown in FIG. 3D by differentiating and adding.

Next, another embodiment of the present invention will be described with reference to FIG. The horizontal output high voltage generating circuit shown here is known as a diode modulator. In FIG. 5, the damper diodes are 19 and 20.
A series circuit of a return resonance capacitor 21 and a voltage dividing capacitor 22 is connected to the first damper diode 19, and another resonance capacitor 23 is connected in parallel to the second damper diode 20. . Further, one end of the series circuit of the deflection coil 4 and the S-shaped correction capacitor 5 is connected to the point A which is the connection point of the two damper diodes 19 and 20, unlike the conventional grounding.

If, in FIG. 5, there is no clamp circuit 12, the voltage dividing capacitor 2 which is a part of the resonance capacitor is used.
If 2 were shorted, this would be a normal diode modulator circuit. This diode modulator circuit, depending on the state of the high voltage load Ihv, the deflection coil current Iy
And the image brightness greatly changes, the apparent image amplitude does not change. Further, since the amplitude of the current Iy of the deflection coil 4 can be changed by the amount of the current Iw drawn from the point A in the figure, the horizontal amplitude is adjusted by this, or this current Iw is modulated by the parabolic wave of the vertical cycle. , It is possible to correct the pincushion distortion of the image.

In this circuit, as in FIG. 1, the parabolic wave voltage Vs generated across the S-shaped correction capacitor 5 is clamped by the clamp circuit 12. Since the configuration and operation of the clamp circuit 12 are exactly the same as those in the case of FIG. 1, the circuit elements 13 to 18 are designated by the same reference numerals as the corresponding portions of FIG. 1, and the operation will not be particularly described. As shown in FIG. 5, when the clamp circuit 12 is applied to the diode modulator circuit, one problem is that one end of the S-shaped correction capacitor 5 is not grounded but two damper diodes 1 are connected.
That is, it is connected to a point A which is a connection point of 9 and 20. A small pulse V3 having a horizontal cycle is generated at point A, and if pincushion distortion correction is performed as described above, this small pulse V3 is modulated by a parabolic wave having a vertical cycle.

At this point A, the clamp transistor 15
Since the emitter of is also connected, it is difficult to differentiate and add the horizontal retrace pulse V2 between the base and the emitter. At least as shown in FIG. 1, the pulse V2 obtained from the tertiary winding 6c whose one end is grounded cannot be used while being shared with other circuits. In order to create this differential waveform with the pulse from the flyback transformer 6, a dedicated winding with one end connected to the point A is required.

Therefore, in FIG. 5, the pulse Vc1 generated at both ends of the first damper diode 19 is applied to the resonance capacitor 2
The voltage is divided by 1 and 22 to obtain the pulse V4, which is differentiated by the capacitor 18. Unlike the pulse V3 side, this pulse Vc1 is a sine wave that is relatively unaffected by changes in the high voltage load Ihv and the like, and the pulse V4 obtained by dividing the voltage Vc1 also has a beautiful waveform with few harmonics, and the clamping operation of the transistor 15 is performed. Definitely done. Further, since the pulse V4 is generated with reference to the point A, the transistor 15 can be comfortably operated.
The differential waveform can be applied between the base and emitter of the.

As a result, the transistor 15 and the diode 1 are also used in FIG. 5 using the diode modulator.
4, the parabolic voltage Vs generated across the S-shaped correction capacitor 5 is reliably clamped, and horizontal cross distortion as shown in FIG. 6 is improved.

[0036]

As described in detail above, the horizontal cross distortion correction circuit of the present invention is effective because a reliable clamping action can be obtained with a small amount of power without increasing the capacity of the charge / discharge capacitor. Horizontal cross distortion can be corrected.
In addition, it has an extremely excellent practical effect that it can be easily applied to a diode modulator circuit.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a horizontal cross distortion correction circuit of the present invention.

FIG. 2 is a waveform diagram for explaining the operation of the circuit shown in FIG.

FIG. 3 is a waveform diagram for explaining the operation of the circuit shown in FIG.

FIG. 4 is a waveform diagram for explaining the operation of the circuit shown in FIG.

FIG. 5 is a circuit diagram showing another embodiment of the horizontal cross distortion correction circuit of the present invention.

FIG. 6 is a diagram showing horizontal cross distortion.

FIG. 7 is a circuit diagram showing an example of a conventional horizontal cross distortion correction circuit.

FIG. 8 is a waveform chart for explaining the operation of the circuit shown in FIG.

9 is a waveform diagram for explaining the operation of the circuit shown in FIG.

[Explanation of symbols]

 1 horizontal output transistor 2 damper diode 3 return resonance capacitor 4 horizontal deflection coil 5 S-shaped correction capacitor 6 flyback transformer 7 high voltage rectifier diode 12 clamp circuit 13 charge / discharge capacitor 14 clamp diode 15 clamp transistor 18 differential capacitor 19, 20 damper diode 21,23 Retrace resonance capacitor 22 Capacitor for voltage division Iy Horizontal deflection current (sawtooth wave current) Ich Charging current Ids Discharging current

Claims (2)

[Claims] 1. A series circuit of a horizontal deflection coil for flowing a sawtooth wave current having a horizontal deflection period for horizontally deflecting a picture tube and an S-shaped correction capacitor, and a charging circuit connected in parallel to the S-shaped correction capacitor. A horizontal cross distortion correction circuit comprising a series circuit of a discharge capacitor and a clamp diode, and an electronic switch connected in parallel with the clamp diode and controlled so as to conduct in a part of a horizontal retrace period, wherein: The horizontal cross distortion correction circuit is characterized in that the clamp diode has a polarity that makes it conductive during a part of a horizontal blanking period, and the electronic switch causes a current flowing when made conductive to flow in a direction opposite to that of the clamp diode. 2. A pulse obtained by transforming and differentiating a horizontal retrace pulse generated in the horizontal deflection coil is used to control the electronic switch so as to be conductive. Horizontal cross distortion correction circuit.