JPH05344375A - Raster distortion correcting circuit - Google Patents

Abstract

PURPOSE:To provide the raster distortion correcting circuit capable of superimposing the current demodulated according to the input correction waveform on a horizontal deflection coil and parallely correcting the raster shape in a horizontal direction. CONSTITUTION:The current to be superimposed on a horizontal deflection coil 4 by the value of base current Ib1 of a pnp transistor 14 can be adjusted freely in either positive or negative direction with Zero centered. The base of the npn transistor 16 is imparted the proper DC bias from resistances 20 and 21 linked to the non-reverse input terminal of an arithmetic amplifier 19, further, the parabolic wave Vpbo is applied through a capacitor 22 from a potentiometer 23. When the parabolic wave Vpbo is changed by moving the potentiometer 23, the emitter voltage Ve is changed in coincidence with it, and the raster curve distortion or the like can be corrected by changing the base current Ib1 of the pnp transistor 14 and the corrector current Ic1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a raster distortion correction circuit for a television apparatus or the like, which corrects a raster distortion such as a left and right bow-shaped distortion on a picture tube surface which is displaced parallel to the horizontal direction. Regarding

[0002]

2. Description of the Related Art Up to now, when a deflection yoke is attached to a picture tube to deflect a beam and a raster is projected on the surface of the picture tube, the raster may be reflected depending on a mechanical error between the deflection yoke and the tube axis of the picture tube. The shape was not a correct rectangle, and as shown in FIG. 7, there was a phenomenon in which the left and right ends were distorted in an arcuate shape in the same direction.

Conventionally, as a method for correcting this distortion, as shown in FIG. 8, a horizontal AFC (automatic frequency control circuit) is used to move the horizontal phase of the image. That is,
In FIG. 8, 1 is a phase comparison circuit, 2 is a horizontal oscillation circuit, 3 is a horizontal output circuit, and 4 is a horizontal deflection coil in a deflection yoke. Here, the phase comparison circuit 1 compares the horizontal synchronizing signal pulse Ps from the outside with the pulse Ph which matches the phase of the deflection current Iy flowing through the horizontal deflection coil 4, and determines the DC voltage Ed corresponding to the phase difference. Output. The horizontal oscillation circuit 2 has a VFO (variable frequency oscillator) configuration that changes its oscillation frequency according to the value of the voltage Ed, and its output rectangular wave Vd drives the next horizontal output circuit 3. The horizontal output circuit 3 performs a switching operation in accordance with the rectangular wave Vd to flow a sawtooth wave current Iy in the horizontal deflection coil 4 and to generate a small pulse Ph of a horizontal output whose phase matches that of the sawtooth wave. This is the phase comparison circuit 1
Return to.

In this way, the circuit of FIG. 8 functions as an automatic frequency control circuit, and the output Vd of the horizontal oscillation circuit 2 is determined so that the synchronizing signal pulse Ps and the horizontal output pulse Ph have the same frequency and phase.

[0005]

The above is an example of a circuit of an ordinary television receiver or display device. When the parabolic wave Vpb of the vertical cycle shown in FIG. 8 is superimposed on the circuit, a pulse is generated according to this waveform. Ph, ie the phase of the sawtooth current Iy, changes, so that the bow distortion of the entire image can be corrected thereby. However, in this case, the distortion of the image itself can be corrected, but the raster shape cannot be corrected. Therefore, when a lattice fringe signal is received as shown in FIG. 9, the left and right ends of the raster remain curved even if the lattice pattern of the image is formed so that straight lines intersect at a right angle.
This is because when it is desired to minimize the amount of overscan in a display device or the like for displaying graphics, image defects easily occur at the left and right ends.

In order to eliminate this problem, it is necessary to move the horizontal position of the raster itself according to the parabolic wave Vpb instead of moving the horizontal phase of the image as shown in FIGS. However, since the current flowing through the horizontal deflection coil 4 is a large current in the unit of several amperes to several tens of amperes,
It is not easy to correct the raster shape by moving the DC component of the current flowing here. Further, since the horizontal deflection coil 4 normally has a high potential with respect to the ground, it is difficult to move this current by the small-signal parabola wave Vpb from the viewpoint of the circuit configuration also in this respect. The current situation was that there was no simple practical circuit.

[0007]

In order to solve the above-mentioned problems of the prior art, the present invention provides (1) a sawtooth saw in a series circuit of a horizontal deflection coil and an S-shaped correction capacitor by a switching operation of a horizontal deflection cycle. A horizontal output circuit for flowing a wave current, a flyback transformer having one end connected to one end on the hot side of the horizontal deflection coil and the other end connected to a DC power supply voltage, or a primary winding of the horizontal output transformer,
A series circuit of a choke coil and a current modulation element connected between the DC power supply voltage, the horizontal deflection coil and the S-shaped correction capacitor, and one end of the output connected to the DC power supply voltage One end of the DC voltage generating circuit for generating a DC voltage in the direction opposite to that of the DC power supply voltage, the other end of the output of the DC voltage generating circuit, and the connection between the choke coil and the current modulation element. A resistor connected between the point and a point, and by modulating the current value flowing in the current modulation element with a correction waveform of a vertical cycle, it is possible to correct the distortion that is parallelly displaced in the horizontal direction of the raster. Providing a raster distortion correction circuit characterized by (2)
The correction waveform is parabolic or similar waveform,
A raster distortion correction circuit according to claim 1, which corrects the left and right bow distortion of the raster, and (3) the correction waveform is a sawtooth wave to correct the XY orthogonal distortion of the raster. The raster distortion correction circuit according to claim 1, wherein a constant current circuit is provided in place of (4) the resistor. 4. The raster distortion according to any one of claims 1 to 3, wherein: A correction circuit is provided.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A raster distortion correction circuit of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a circuit diagram showing an embodiment of the present invention. Here, the horizontal output circuit 3 and the horizontal deflection coil 4 operate in the same manner as in the conventional example shown in FIG. 8, and the elements of other numbers in FIG.

Reference numeral 5 is a linearity coil connected in series with the horizontal deflection coil 4, and reference numeral 6 is an S-shaped correction capacitor. By doing so, the sawtooth wave current Iy of the horizontal deflection period flows in the series circuit due to the switching operation of the horizontal output circuit 3 to perform the horizontal deflection operation of the picture tube electron beam. At the same time when the sawtooth wave current Iy flows through the horizontal deflection coil 4, a horizontal pulse Vc is generated at one end on the hot side thereof.
Of the horizontal output circuit 3 from which the power supply voltage Eb is connected to the other end of the primary winding 7a.
Supply operating power. It should be noted that during the period of the horizontal pulse Vc, a sinusoidal resonance current flows through the horizontal deflection coil 4, but most of this current flows toward the horizontal output circuit 3 and is shunted toward the primary winding 7a. Also, since the value of the resistor 9 is very small, such as several ohms, here, the horizontal pulse V
The voltage drop of c can be ignored, and the horizontal pulse Vc is applied to the primary winding 7a in almost the same form.

The horizontal pulse Vc applied to the primary winding 7a is boosted by the secondary winding 7b to become a high voltage pulse Vhv, and then becomes a direct current high voltage HV in the high voltage rectifier circuit 8 and is applied to the anode of a picture tube not shown. To be done. In addition, the primary winding 7
A tap a is provided at a, and a positive small pulse Va generated by stepping down the horizontal pulse Vc is generated there. Further, a diode 10 (DC voltage generating circuit) is connected to the tap a to rectify the base side of the pulse Va, and a DC voltage is applied to both ends of the smoothing capacitor 11 (DC voltage generating circuit) as shown in the figure. Give rise to Ea. This voltage Ea is led from one end on the negative side, through the resistor 12 and the choke coil 13, to the connection point between the linearity coil 5 and the S-shaped correction capacitor 6,
A direct current for adjusting the left and right positions of the raster flows through the choke coil 13.

A pnp transistor 1 is connected between the connection point between the resistor 12 and the choke coil 13 and the power supply voltage Eb.
4 is connected between the collector and emitter, and is connected from the base to the collector of the npn transistor 16 via the resistor 15. The emitter of the npn transistor 16 is grounded by the resistor 17, and the base is connected to the output terminal of the operational amplifier 19 through the resistor 18. The inverting input terminal of the operational amplifier 19 is connected to the emitter of the npn transistor 16, and the non-inverting input terminal thereof is supplied with a DC voltage divided by the resistors 20 and 21 extending between the second power source E and the ground. At the same time, the coupling capacitor 22 is connected to the movable piece of the potentiometer 23 from this non-inverting input terminal. Then, both ends of the potentiometer 23 are applied with parabolic waves Vpb1 and Vpb2 having vertical periods whose polarities are opposite to each other.

In explaining the operation of FIG. 1, first, how the current flowing through the horizontal deflection coil 4 changes when the collector current Ic1 of the pnp transistor 14 as a current modulation element is changed. 2 is pnp
The case where the transistor 14 is in the cutoff state and the collector current Ic1 thereof is zero is shown. At this time, originally p
This is equivalent to disconnection between points c and e where the collector and emitter of the np transistor 14 were connected. Then, the DC voltage Ea is equivalent to the shape in which the DC voltage Ea is inserted in the loop formed by the primary winding 7a, the resistor 9, the horizontal deflection coil 4, the linearity coil 5, the choke coil 13 and the resistor 12 in FIG. Therefore, the DC component I1 flowing in the horizontal deflection coil 4 flows through the path shown by the loop of the arrow in the figure, which shifts the horizontal position of the image to the left.

Next, let us consider a case where the pnp transistor 14 is saturated, as shown in FIG. In this case, the collector-emitter, that is, the two points c and e, is equivalent to a short circuit. In FIG. 1, the DC current Ih flows from the DC power source Eb as the current consumption of the horizontal output circuit 3. FIG. 3 illustrates how the route reaches the horizontal output circuit 3 when a short circuit occurs between c and e. That is, this direct current Ih is applied to the flyback transformer 7
The It component that flows into the horizontal output circuit 3 through the primary winding 7a and the resistor 9 and the I2 component that also flows into the horizontal output circuit 3 through the choke coil 13, the linearity coil 5 and the horizontal deflection coil 4. Divide. The I2 shunted to the horizontal deflection coil 4 is
It acts to shift the horizontal position of the raster to the right, which is the opposite of I1 in FIG.

The amount of the current I2 is short-circuited between c and e,
That is, it becomes maximum when the pnp transistor 14 of FIG. 1 is in a saturated state. Then, as the base current Ib1 decreases, the base current Ib1 gradually decreases and finally becomes zero. Further, as the value of the base current Ib1 of the pnp transistor 14 is reduced, the component of the current I1 in FIG. 2 becomes larger, and the direction of the current flowing through the horizontal deflection coil 4 is reversed to move the raster horizontally. Since the action is in the opposite direction and the base current Ib1 becomes zero, the amount of the current I1 becomes maximum as described above. The resistor 9 is not particularly indispensable, and is inserted when the current I2 is still insufficient even if the pnp transistor 14 is completely saturated. The resistance 9 decreases the ratio of the current It and increases I2 by that amount, but if the current I2 proportionally divided by the DC resistance values of the primary winding 7a, the choke coil 13, the horizontal deflection coil 4 and the like is sufficient, it is deleted. It doesn't matter.

As is clear from the above description, the value of the base current Ib1 allows the current superimposed on the horizontal deflection coil 4 to be adjusted freely in either the positive or negative direction with respect to zero. Therefore, this base current I
By modulating b1 with a parabolic wave having a vertical period, the raster shown in FIG. 7 can be easily corrected. That is, the current I2 flows in the upper and lower parts of the screen, and the current I1 flows in the central part in reverse, in other words, the pnp transistor 1
The value of the collector current Ic1 or the base current Ib1 of No. 4 may be maximized near the starting point and the ending point of the vertical cycle, and the parabolic wave may be minimized near the center. Then, the raster position shifts to the right in the upper and lower parts of the screen, and to the left near the center, so that the bow distortion as shown in FIG. 7 is effectively corrected. Of course, in the case of a distortion in which the direction of the arc shape is opposite to that in FIG. 7, it suffices that the collector current Ic1 becomes a parabolic wave of the opposite polarity such that the collector current Ic1 is minimum at both ends of the vertical period and maximum at the center.

An example of a circuit for modulating the collector current Ic1 as described above will be described below again with reference to FIG. That is, p
A resistor 15 for flowing a base current Ib1 of the np transistor 14
Is also the collector current of the npn transistor 16,
It is also approximately equal to the emitter current. Therefore, the waveform of the voltage Ve generated across the emitter resistor 17 is pn
The waveforms of the base current Ib1 and the collector current Ic1 of the p-transistor 14 are the same, and this is the correction amount of the bow distortion of the raster itself as described above. Further, the base of the npn transistor 16 passes through the resistor 18 and the operational amplifier 19
Connected to the output of. An appropriate DC bias is applied by the resistors 20 and 21 connected to the non-inverting input terminal of the operational amplifier 19, and the parabola wave Vpbo is applied from the potentiometer 23 through the capacitor 22.

Since the vertical period parabolic waves Vpb1 and Vpb2 having opposite polarities are applied to both ends of the potentiometer 23, the wave of the parabolic wave Vpbo applied to the non-inverting input terminal of the operational amplifier 19 depends on the position of the movable piece. High value and polarity can be set arbitrarily. Since the above-mentioned emitter voltage Ve is applied to this inverting input terminal, n is set so that this voltage Ve matches the parabola wave Vpbo.
The operational amplifier 19 works so as to flow the base current Ib2 of the pn transistor 16. Therefore, when the potentiometer 23 is moved to move the parabolic wave Vpbo, the emitter voltage Ve changes correspondingly, and the base current Ib1 and collector current Ic1 of the pnp transistor 14 change accordingly.
From this, according to the principle described in detail above, by adjusting the potentiometer 23, the arc shape distortion as shown in FIG. 7 is correctly corrected in the raster shape itself including the image.
As shown in FIG. 4, both the checkered image and the left and right ends of the raster become original straight lines. It is clear from the above description that the horizontal position of the entire raster, that is, the horizontal centering can be adjusted by changing the DC level of the non-inverting input terminal of the operational amplifier 19 by moving the values of the resistors 20 and 21.

By the way, in FIG. 1, the high voltage rectifier circuit 8 connected to the secondary winding 7b of the flyback transformer 7 obtains a high voltage HV and applies it to the anode of the picture tube. However, in this case, it is desirable that the change in the high-voltage load current Ia is as small as possible. This is because the DC consumption current Ih of the horizontal output circuit 3 changes according to the change of this load current, that is, the anode current Ia of the picture tube.
This is because the current I2 of the raster changes, which affects the horizontal movement amount of the raster. Therefore, this FIG. 1 is applied only to a small-sized receiver or a monochrome receiver in which the amount of change in the high-voltage current Ia is small. If the circuit shown in FIG. 1 is used for a normal color image receiver or display, 7 is operated as a horizontal output transformer instead of a flyback transformer for supplying high voltage, and the high voltage applied to the cathode of the picture tube is It must be a deflection high voltage separation type circuit which is supplied from a part different from this circuit.

FIG. 5 shows another example of the circuit according to the present invention, in which the value of the current I2 superimposed on the horizontal deflection coil 4, that is, the correction amount of the raster distortion influences the change of the high voltage current Ia. It is configured not to be performed. Here, the numbers up to the number 23 have almost the same functions as the same numbers in FIGS. 1, 2, 3, and 8 described above, and thus detailed description thereof will be omitted. The difference between FIG. 5 and FIG. 1 is that the resistor 12 of FIG.
That is, the p-transistor 24 (constant current circuit) is replaced between the collector and the emitter. The base terminal of the pnp transistor 24 is grounded via the base resistor 25. In this case, the emitter potential of the pnp transistor 24 changes slightly depending on the value of the current Ih and the value of the current I2, but the change is small compared to the value of the voltage Eb, and is almost constant. Therefore, it can be considered that the base potential is almost constant, and from this fact, the base current Ib3 flowing through the base resistor 25 is also constant. Then, it means that it was replaced with a constant current circuit using transistors.

In the case of FIG. 1, the pnp transistor 14 also forms a constant current circuit, but in such a configuration, when the current Ih actually changes, the potential at the point c changes slightly, which is a relatively small value. Since the value is not negligible with respect to the voltage Ea, the value of the current flowing through the resistor 12 also changes due to the influence. As a result, even if the current Ic1 flowing through the pnp transistor 14 is constant, the current Ic for flowing distortion flowing through the horizontal deflection coil 4 through the choke coil 13 is corrected.
The value of 2 also changes depending on the value of the current Ih or the high voltage current Ia. Therefore, as shown in FIG. 5, in FIG.
The part that was 2 is also a constant current circuit using the second pnp transistor 24. By doing so, the current flowing through this part is also made constant, so that even if the current Ih or Ia changes, it becomes horizontal. The current value for distortion correction flowing through the deflection coil 4 does not change. Therefore, there is no problem in using the circuit of FIG. 5 in a large-sized color image receiver in which the value of the high-voltage current Ia changes greatly depending on the brightness of the picture tube.

Incidentally, as the constant current circuit up to now, the one in which the base current of the transistor is made constant has been taken as an example, but of course, other constant current circuits known in the related art may be used. Absent. Also, as an example of the present invention, the correction of the arcuate distortion in which the raster is corrected by the parabolic waveform has been described so far, but the object of correction is not limited to this arcuate distortion, and the raster is biased parallel to the horizontal direction. The present invention can be applied to any distortion that has been transferred.
For example, when the deflection directions of the deflection yoke in both the horizontal and vertical directions are not right angles, parallelogram raster distortion called XY orthogonal distortion as shown in FIG. 6 may occur. This can also be easily corrected by using the present invention, and by using a sawtooth wave having a vertical cycle as a correction waveform in place of the parabola waves Vpb1 and Vpb2 in FIG. 1 or 5, a correct raster shape as shown in FIG. 4 can be obtained. Be done.

[0022]

As described in detail above, the raster distortion correction circuit of the present invention superimposes the current modulated according to an arbitrary input correction waveform on the horizontal deflection coil to make the shape of the raster horizontal. Since the correction can be performed in parallel, there is an extremely excellent practical effect that, for example, the bow distortion of the raster, the XY orthogonal distortion, and the like are effectively corrected.

[Brief description of drawings]

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

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

FIG. 3 is a diagram for explaining the operation of the first embodiment.

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

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

FIG. 6 is a diagram showing an example of distortion targeted by the present invention.

FIG. 7 is a diagram showing an example of distortion targeted by the present invention.

FIG. 8 is a circuit diagram showing an example of a conventional distortion correction circuit.

FIG. 9 is a diagram for explaining the operation of the conventional example.

[Explanation of symbols]

 3 Horizontal output circuit 4 Horizontal deflection coil 5 Linearity coil 6 S-shaped correction capacitor 7 Flyback transformer 8 High voltage rectifier circuit 10 Diode (DC voltage generation circuit) 11 Smoothing capacitor (DC voltage generation circuit) 13 Choke coil 14 pnp transistor (current modulation) Element) 16 npn transistor 19 operational amplifier 23 potentiometer 24 second pnp transistor (constant current circuit)

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[Procedure amendment]

[Submission date] April 1, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0007

[Correction method] Change

[Correction content]

[0007]

In order to solve the above-mentioned problems of the prior art, the present invention (1) saws a series circuit of a horizontal deflection coil and an S-shaped correction capacitor by a switching operation of a horizontal deflection cycle. A horizontal output circuit for passing a wave current, a flyback transformer having one end connected to one end of the horizontal deflection coil on the hot side and the other end connected to a DC power supply voltage, or a primary winding of the horizontal output transformer, A DC power supply voltage, a series circuit of a choke coil and a current modulation element connected between the horizontal deflection coil and the S-shaped correction capacitor, and one end of the output connected to the DC power supply voltage One end has a DC voltage generating circuit for generating a DC voltage in a direction opposite to the DC power supply voltage, the other end of the output of the DC voltage generating circuit, and the choke coil. And a resistance connected between the current modulation element and a connection point between the current modulation element and the current value flowing through the current modulation element is modulated by the correction waveform of the vertical cycle to shift the current parallel to the horizontal direction of the raster. A raster distortion correction circuit characterized by correcting the above distortion is provided. (2) The correction waveform is a parabolic shape or a waveform similar to the parabolic shape, and the right and left bow distortion of the raster is corrected ( 1) The raster distortion correction circuit described above is provided,
(3) The correction waveform is a sawtooth wave, and the raster X-
A raster distortion correction circuit according to (1), which corrects Y orthogonal distortion, is provided, and (4) a constant current circuit is provided in place of the resistor (1) to (3). The raster distortion correction circuit according to any one of 1) to 3) is provided.

Claims (4)

[Claims] 1. A horizontal deflection cycle switching operation,
A horizontal output circuit that causes a sawtooth wave current to flow in a series circuit of a horizontal deflection coil and an S-shaped correction capacitor, and a fly with one end connected to the hot end of the horizontal deflection coil and the other end connected to a DC power supply voltage. A primary winding of a back transformer or a horizontal output transformer, the DC power supply voltage, and a series circuit of a choke coil and a current modulation element connected between the horizontal deflection coil and an S-shaped correction capacitor; One end of the output is connected to the power supply voltage, and the other end of the output is a DC voltage generating circuit that generates a DC voltage in a direction that is applied in a direction opposite to the DC power supply voltage, and another output of the DC voltage generating circuit. One end and a resistor connected between the choke coil and the connection point of the current modulation element are provided, and the value of the current flowing through the current modulation element is modulated with a correction waveform of a vertical cycle. And the raster distortion correction circuit is characterized in that the manner of correcting the distortion which is shifted parallel to the horizontal direction of the raster. 2. The raster distortion correction circuit according to claim 1, wherein the correction waveform has a parabolic shape or a waveform similar to the parabolic shape to correct left and right bow distortion of a raster. 3. The raster distortion correction circuit according to claim 1, wherein the correction waveform is a sawtooth wave, and the XY orthogonal distortion of the raster is corrected. 4. The raster distortion correction circuit according to claim 1, further comprising a constant current circuit in place of the resistor.