JP2003230021A - Vertical deflection circuit and video display apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vertical deflection circuit and capable of accurately collimating scanning lines of a forward path with scanning lines of a return path and to provide a video display apparatus provided therewith. <P>SOLUTION: An amplifier 2 supplies a first sawtooth wave current I1 to a secondary winding 32 of a transformer 3 on the basis of a vertical deflection voltage VA. A second sawtooth wave current I2 is supplied to a primary winding 31 of a transformer 1. A modulation waveform generating circuit 8 generates a modulation waveform signal MD. A power supply modulation circuit 7 modulates a power supply voltage with a modulation waveform signal MD2 and applies a modulation voltage VP to one terminal of the primary winding 31 of the transformer 1. The amplitude of the envelope of the second sawtooth wave current I2 is gradually increased from a start point of vertical scanning and reaches a maximum amplitude in the vicinity of an end point, and the amplitude of the envelope at the end point of vertical scanning is increased more than the amplitude of the envelope at the start point. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reciprocal deflection type vertical deflection circuit for reciprocally scanning an electron beam and an image display device including the same.

[0002]

2. Description of the Related Art In a CRT (cathode ray tube), an image is displayed on a screen by deflecting an electron beam by a deflection magnetic field and irradiating it on a fluorescent screen. In a general CRT,
An internal magnetic shield is provided to reduce the influence of the deflection magnetic field from the earth's magnetism.

In recent years, a reciprocating deflection system has been proposed in order to improve the image quality of image display devices such as television receivers and monitor devices for personal computers.

FIG. 12 is a diagram showing a reciprocal deflection system. In FIG. 12, the forward scanning line is shown by a solid line, and the backward scanning line is shown by a broken line. The electron beam is scanned from the left side to the right side of the screen during the forward scanning, and the electron beam is scanned from the right side to the left side of the screen during the backward scanning.

When vertical deflection is performed by using a sawtooth-shaped vertical deflection current synchronized with the vertical synchronization signal, FIG.
As shown in (a), the forward scan line is formed slightly obliquely downward from the left side to the right side of the screen, and the forward scan line is formed slightly obliquely downward from the right side to the left side of the screen. In this case, in order to improve the image quality, FIG.
As shown in (b), it is necessary to make the forward scanning line and the backward scanning line parallel to each other.

Japanese Unexamined Patent Publication (Kokai) No. 3-145378 discloses a method of parallelizing a forward scan line and a backward scan line in a reciprocating deflection method.

FIG. 13 is a waveform diagram for explaining a vertical deflection current for parallelizing the forward scan line and the backward scan line. FIG. 13A is a first sawtooth wave current that changes in the vertical scan cycle. (B) shows the second sawtooth wave current changing in the horizontal scanning period, and (c) shows the vertical deflection current. In FIG. 13, 1V indicates 1 vertical scanning period, and 1H indicates 1
The horizontal scanning period is shown.

The first sawtooth current of FIG. 13A which changes in the vertical scanning period and the first sawtooth current of FIG. 13A which changes in the horizontal scanning period.
The vertical deflection current shown in FIG. 13C is obtained by combining the second sawtooth wave current shown in FIG. Figure 1
The vertical deflection current of 3 (c) changes stepwise in the horizontal scanning period.

As described above, by superimposing the second sawtooth wave current shown in FIG. 13B on the first sawtooth wave current shown in FIG. 13A, the forward scan line shown in FIG. The scanning line on the return path is horizontally corrected as shown in FIG.

On the other hand, in recent years, a plane CR having a flat screen
Video display devices using T have been developed. Since the radius of the phosphor screen of the CRT is larger than the radius from the deflection center point of the electron beam to the phosphor screen, the movement amount of the electron beam in the peripheral portion of the screen for the same deflection amount is the same as that of the electron beam in the center portion of the screen. It becomes larger than the amount of movement. As a result, distortion appears in the image. Therefore, the distortion of the image is corrected by correcting the deflection current into an S shape so that the deflection amount in the peripheral portion of the screen becomes small.

Japanese Unexamined Patent Publication No. 5-336389 discloses a method of performing reciprocal deflection in an image display device using a flat CRT.

FIG. 14 is a waveform diagram for explaining a vertical deflection current for parallelizing the forward scan line and the backward scan line in the plane CRT. FIG. 14A is a first diagram that changes in the vertical scan cycle. Shows a sawtooth wave current, (b) shows a second sawtooth wave current that changes in the horizontal scanning period, and (c) shows a vertical deflection current. In FIG. 14, 1V indicates one vertical scanning period and 1H indicates one horizontal scanning period.

The first sawtooth current shown in FIG. 14A changes into an S-shape in the vertical scanning period. Further, the second sawtooth wave current in FIG. 14B changes into a sawtooth wave shape in the horizontal scanning period, and the envelope changes into a parabola shape.
By combining the first sawtooth current of FIG. 14 (a) and the second sawtooth current of FIG. 14 (b), FIG.
The vertical deflection current shown in (c) is obtained.

By performing vertical deflection using the vertical deflection current shown in FIG. 14C, theoretically, in the plane CRT, the forward scan line and the backward scan line shown in FIG. 12A are shown in FIG. 12B. It can be corrected horizontally as shown in.

[0015]

However, in the actual CRT, when vertical deflection is performed using the vertical deflection current shown in FIG. 14C, the forward scan line and the backward scan line are accurately Cannot be parallelized.

It is an object of the present invention to provide a vertical deflection circuit capable of accurately parallelizing a forward scan line and a backward scan line, and an image display device including the same.

[0017]

As a result of studies and experiments for parallelizing scanning lines in reciprocal scanning, the present inventor found that the deflection magnetic field was disturbed by the influence of the internal magnetic shield, and the vertical deflection was performed. The inventors have found that the influence of the internal magnetic shield is corrected by modulating the magnetic field in a predetermined method, and have devised the following invention.

(1) First Invention A vertical deflection circuit according to the first invention is for vertically deflecting an electron beam in a cathode ray tube having an internal magnetic shield for reducing the influence of the geomagnetism on the electron beam. It is a vertical deflection circuit, and S changes when it changes in the vertical scanning cycle.
A first sawtooth wave current generating means for generating a first sawtooth wave current having a letter correction, and a second sawtooth wave current changing means in a horizontal scanning cycle.
The amplitude of the second sawtooth current generating means for generating the sawtooth current and the envelope of the second sawtooth current generated by the second sawtooth current gradually increases from the starting point of vertical scanning. In addition, the modulating means for modulating the second sawtooth wave current so as to be maximum at the end point side from the intermediate point of the vertical scanning, and the first sawtooth wave current and modulating means generated by the first sawtooth wave current generating means. And a vertical deflection magnetic field generating means for generating a vertical deflection magnetic field that changes stepwise based on the second sawtooth wave current modulated by.

In the vertical deflection circuit according to the present invention, the first sawtooth wave current generating means generates the first sawtooth wave current that changes in the vertical scanning period, and the second sawtooth wave current is generated.
The sawtooth current generator generates a second sawtooth current varying in the horizontal scanning period, the amplitude of the envelope of the second sawtooth current gradually increases from the start point of the vertical scan, and the midpoint of the vertical scan. The second sawtooth wave current is modulated by the modulating means so as to be maximized on the side of the end point. Further, the vertical deflection magnetic field generating means generates a vertical deflection magnetic field that changes stepwise based on the first sawtooth wave current and the modulated second sawtooth wave current.

As a result, the disturbance of the vertical deflection magnetic field due to the internal magnetic shield can be corrected, and the forward scan line and the backward scan line can be accurately parallelized.

(2) Second Invention In the vertical deflection circuit according to the second invention, in the structure of the vertical deflection circuit according to the first invention, the modulation means has the level gradually increasing from the starting point of vertical scanning. A modulation waveform generation circuit that generates a modulation waveform that changes so as to become maximum on the end point side from the midpoint of vertical scanning, and modulates the second sawtooth wave current in response to the modulation waveform generated by the modulation waveform generation circuit. And a sawtooth current modulation circuit.

In this case, the modulation waveform generating circuit generates a modulation waveform in which the level gradually increases from the starting point of vertical scanning and changes so as to become maximum at the end point side from the intermediate point of vertical scanning, and the sawtooth current modulation is performed. The circuit modulates the second sawtooth current in response to the modulating waveform. As a result, the amplitude of the envelope of the second sawtooth wave current gradually increases from the starting point of vertical scanning and changes so as to become maximum at the end point side from the intermediate point of vertical scanning.

(3) Third Aspect of the Invention A vertical deflection circuit according to a third aspect of the present invention is the configuration of the vertical deflection circuit according to the first or second aspect of the invention, in which the modulation waveform generating circuit is a saw that changes in a vertical scanning cycle. Wave generation circuit that generates a wave signal, a parabolic wave generation circuit that generates a parabolic wave signal that changes in the vertical scanning period, a sawtooth wave signal that is generated by the sawtooth wave generation circuit, and a parabola that is generated by the parabolic wave generation circuit And a synthesizing circuit that outputs a modulated waveform by synthesizing the wave signal.

In this case, the sawtooth wave generation circuit generates a sawtooth wave signal that changes in the vertical scanning period, and the parabolic wave generation circuit generates a parabolic wave signal that changes in the vertical scanning period. The sawtooth wave signal and the parabolic wave signal are combined by a combining circuit to output a modulated waveform. As a result, the level of the modulation waveform gradually increases from the starting point of the vertical scanning and changes so as to become maximum on the end point side of the intermediate point of the vertical scanning.

(4) Fourth Invention In the vertical deflection circuit according to the fourth invention, in the configuration of the vertical deflection circuit according to the third invention, the modulation waveform generating circuit is a sawtooth wave generated by the sawtooth wave generating circuit. The first amplifier that amplifies the signal, the second amplifier that amplifies the parabolic wave signal generated by the parabolic wave generation circuit, and the sawtooth wave signal that is amplified by the first amplifier are set to a predetermined potential at predetermined timing. The first to clamp and give to the synthesis circuit
Clamp circuit, a second clamp circuit that clamps the parabolic wave signal amplified by the second amplifier to a predetermined potential at a predetermined timing and gives the combined circuit, and the DC level of the modulation waveform output by the combination circuit. And a DC level adjusting circuit for adjusting.

In this case, the sawtooth wave signal generated by the sawtooth wave generation circuit is amplified by the first amplifier,
The amplified sawtooth wave signal is clamped to a predetermined potential at a predetermined timing by the first clamp circuit. In addition, the parabolic wave voltage generated by the parabolic wave generation circuit is amplified by the second amplifier, and the amplified parabolic wave signal is clamped to a predetermined potential at a predetermined timing by the second clamp circuit. Further, a sawtooth wave signal clamped to a predetermined potential and a parabolic wave signal clamped to a predetermined potential are combined by a combining circuit and output as a modulation waveform, and the DC level of the output modulation waveform is adjusted by a DC level adjusting circuit. Adjusted.

In this way, a modulation waveform is generated in which the level gradually increases from the starting point of vertical scanning and changes so as to become maximum at the end point side from the intermediate point of vertical scanning.

(5) Fifth Invention In the vertical deflection circuit according to the fifth invention, in the configuration of the vertical deflection circuit according to any one of the first to fourth inventions, the first sawtooth current generating means is: It may include a sawtooth voltage generation circuit that generates a sawtooth voltage in synchronization with the vertical synchronization signal, and a voltage-current conversion circuit that converts the sawtooth voltage generated by the sawtooth voltage generation circuit into a first sawtooth current. Good.

In this case, the sawtooth voltage generating circuit generates a sawtooth voltage in synchronism with the vertical synchronizing signal, and the voltage / current conversion circuit converts the sawtooth voltage into a first sawtooth current. As a result, the first sawtooth wave current that changes in the vertical scanning period is obtained.

(6) Sixth Invention In a vertical deflection circuit according to a sixth invention, in the configuration of the vertical deflection circuit according to any one of the first to fifth inventions, the vertical deflection magnetic field generating means is a modulation means. Superimposing means for generating a vertical deflection current that changes stepwise by superimposing the modulated second sawtooth current on the first sawtooth current generated by the first sawtooth current generating means, and a superimposing means. And a vertical deflection coil that generates a vertical deflection magnetic field based on the vertical deflection current generated by.

In this case, the modulated second sawtooth wave current is superposed on the first sawtooth wave current by the superposing means, whereby a vertical deflection current which changes stepwise is generated and supplied to the vertical deflection coil. It This produces a vertical deflection field with the effects of the internal magnetic shield corrected.

(7) Seventh Invention In the vertical deflection circuit according to the seventh invention, in the configuration of the vertical deflection circuit according to the sixth invention, the superposing means is generated by the second sawtooth current generating means. A secondary winding supplied with a second sawtooth current and a secondary winding supplied with the first sawtooth current generated by the first sawtooth current generating means and connected in series to the vertical deflection coil. It includes a transformer having a wire.

In this case, the second sawtooth current generated by the second sawtooth current generating means is the transformer 1
The first sawtooth current supplied to the secondary winding and generated by the first sawtooth current generating means is supplied to the secondary winding of the transformer. As a result, the second sawtooth current is superimposed on the first sawtooth current in the transformer.

(8) Eighth Invention A vertical deflection circuit according to an eighth invention is the configuration of the vertical deflection circuit according to any one of the first to fifth inventions, wherein the vertical deflection magnetic field generating means is the first invention. Based on a first vertical deflection coil that generates a first vertical deflection magnetic field based on the first sawtooth current generated by the sawtooth current generation means, and a second sawtooth current modulated by the modulation means. Second
And a second vertical deflection coil for generating the vertical deflection magnetic field of the above.

In this case, the first vertical deflection coil generates the first vertical deflection magnetic field on the basis of the first sawtooth wave current, and the second vertical deflection coil on the basis of the modulated second sawtooth wave current. Generates a second vertical deflection magnetic field. By combining the first vertical deflection magnetic field and the second vertical deflection magnetic field, a vertical deflection magnetic field in which the influence of the internal magnetic shield is corrected is generated.

(9) Ninth Invention An image display apparatus according to a ninth invention is a cathode ray tube, an internal magnetic shield provided in the cathode ray tube for reducing the influence of geomagnetism on an electron beam, and an electron in the cathode ray tube. The vertical deflection circuit includes a vertical deflection circuit that generates a vertical deflection magnetic field for vertically deflecting the beam, and a horizontal deflection circuit that generates a horizontal deflection magnetic field for horizontally reciprocally deflecting the electron beam in the cathode ray tube. Is a first sawtooth wave current generating unit that generates a first sawtooth wave current that changes in the vertical scanning period and is S-corrected, and a second sawtooth wave current that changes in the horizontal scanning period. With the sawtooth current generating means and the amplitude of the envelope of the second sawtooth current generated by the second sawtooth current generating means, the amplitude gradually increases from the start point of vertical scanning. By the modulation means for modulating the second sawtooth wave current so that it becomes maximum on the end point side from the intermediate point of the vertical scanning, and the first sawtooth wave current and the modulation means generated by the first sawtooth wave current generating means. And a vertical deflection magnetic field generating means for generating a vertical deflection magnetic field that changes stepwise on the basis of the modulated second sawtooth wave current.

In the image display device according to the present invention, the electron beam is vertically reciprocally deflected by the horizontal deflection magnetic field by the horizontal deflection circuit in the cathode ray tube, and the electron beam is vertically deflected by the vertical deflection magnetic field by the vertical deflection circuit. Biased. As a result, the forward and backward scanning lines are formed on the fluorescent screen of the cathode ray tube.

In this case, the first sawtooth wave current generating means generates the first sawtooth wave current which changes in the vertical scanning cycle, and the second sawtooth current current generating means changes the first sawtooth wave current in the horizontal scanning cycle. The second sawtooth wave current is generated, and the amplitude of the envelope of the second sawtooth wave current is gradually increased from the start point of vertical scanning and is maximized by the modulation means so that it becomes maximum on the end point side from the midpoint of vertical scanning. Two sawtooth currents are modulated. Further, a vertical deflection magnetic field that changes stepwise is generated based on the first sawtooth wave current and the modulated second sawtooth wave current.

As a result, the disturbance of the vertical deflection magnetic field due to the influence of the internal magnetic shield is corrected, and the forward scan line and the backward scan line are made parallel.

(10) Tenth Invention A video display device according to a tenth invention is the video display device according to the ninth invention, wherein the vertical deflection magnetic field generating means is the second video signal modulated by the modulation means. Superimposing means for generating a vertical deflection current that changes stepwise by superimposing the sawtooth current on the first sawtooth current generated by the first sawtooth current generating means, and vertical deflection generated by the superimposing means. And a vertical deflection coil that generates a vertical deflection magnetic field based on an electric current.

In this case, the modulated second sawtooth wave current is superimposed on the first sawtooth wave current by the superimposing means, whereby a vertical deflection current which changes stepwise is generated and supplied to the vertical deflection coil. It This produces a vertical deflection field with the effects of the internal magnetic shield corrected.

(11) Eleventh Invention In the image display device according to the eleventh invention, in the configuration of the image display device according to the ninth invention, the vertical deflection magnetic field generating means is constituted by the first sawtooth current generating means. A first vertical deflection coil for generating a first vertical deflection magnetic field based on the generated first sawtooth current, and a second vertical deflection magnetic field based on the second sawtooth current modulated by the modulation means. And a second vertical deflection coil for generating.

In this case, the first vertical deflection coil generates the first vertical deflection magnetic field on the basis of the first sawtooth wave current, and the second vertical deflection coil on the basis of the modulated second sawtooth wave current. Generates a second vertical deflection magnetic field. By combining the first vertical deflection magnetic field and the second vertical deflection magnetic field, a vertical deflection magnetic field in which the influence of the internal magnetic shield is corrected is generated.

[0044]

1 is a block diagram showing the structure of a video display device according to a first embodiment of the present invention.

The video display device of FIG. 1 includes a video signal processing circuit 100, a horizontal deflection circuit 200, a vertical deflection circuit 300 and a CRT (cathode ray tube) 400. The horizontal deflection coil 14 and the vertical deflection coil 4 are attached to the CRT 400.

The video signal processing circuit 100 uses the video signal VD
The display signal CS is applied to the CRT 400 on the basis of
00, and the vertical synchronizing signal VS to the vertical deflection circuit 300.

The horizontal deflection circuit 200 synchronizes with the horizontal synchronizing signal HS supplied from the video signal processing circuit 100, and outputs the C signal.
A horizontal deflection current is supplied to the horizontal deflection coil 14 for horizontally reciprocally deflecting the electron beam at the RT 400.

The vertical deflection circuit 300 vertically synchronizes a vertical deflection current, which will be described later, in order to vertically deflect the electron beam in the CRT 400 in synchronization with the horizontal synchronization signal HS and the vertical synchronization signal VS provided from the video signal processing circuit 100. Supply to the deflection coil 4.

FIG. 2 is a schematic sectional view showing the structure of the CRT 400. FIG. 3 is a schematic perspective view of the internal magnetic shield attached to the CRT 400 of FIG.

As shown in FIG. 2, the glass bulb 401 of the CRT 400 has a cylindrical neck portion 401a and a bulged cone portion 401b. A deflection yoke 408 is arranged outside the glass bulb 401 at a position including a boundary portion between the neck portion 401a and the cone portion 401b. The deflection yoke 408 is the horizontal deflection coil 1 of FIG.
4 and a vertical deflection coil 4.

An electron gun 402 is arranged in the neck portion 401a of the glass bulb 401. A fluorescent screen 403 is formed inside the front surface of the cone portion 401b. On this phosphor screen 403, a plurality of phosphors emitting red, green and blue light are arranged. A shadow mask 404 is attached to the frame 410 along the phosphor screen 403. An internal magnetic shield 405 is arranged inside the rear surface of the cone portion 401b. As shown in FIG. 3, an opening 406 is provided at the center of the inner magnetic shield 405.

The three electron beams 407 emitted from the electron gun 402 are opened by the opening 406 of the internal magnetic shield 405.
Through, and enters the shadow mask 404 at slightly different angles, and emits red, green, and blue light on the phosphor screen 403.

These electron beams 407 receive the Lorentz force due to the earth's magnetism on the earth, and are irradiated to the position deviated from the center of a predetermined phosphor. Internal magnetic shield 405
Are provided to prevent the position shift of the electron beam 407 due to the geomagnetism.

FIG. 4 is a circuit diagram showing the configuration of the vertical deflection circuit 300 of the image display device of FIG. FIG. 5 is a waveform diagram of each part showing the operation of the vertical deflection circuit 300 of FIG.
In FIG. 5, 1V represents one vertical scanning period, and 1H represents a horizontal scanning period.

As shown in FIG. 4, a vertical deflection circuit 300 is provided.
Is a vertical deflection voltage generating circuit 1, an amplifier 2, a transformer 3,
Vertical deflection coil 4, feedback circuit 5, resistor 6, power supply modulation circuit 7, modulation waveform generation circuit 8, DC power supply 9, resonance capacitance 10,
Damper diode 11 and drive transistor 12
It is composed of

The vertical deflection voltage generation circuit 1 generates a sawtooth-shaped vertical deflection voltage VA in synchronization with the vertical synchronization signal VS shown in FIG. 5, and supplies the vertical deflection voltage VA to one input terminal of the amplifier 2. The amplifier 2 supplies the first sawtooth wave current I1 shown in FIG. 5 to the secondary winding 32 of the transformer 3 based on the vertical deflection voltage VA. The first sawtooth wave current I1 is S-shaped corrected, and changes to a positive or negative S shape with 0 as the center in the vertical scanning period.

On the other hand, the drive transistor 12 turns on and off in response to the drive pulse HD of FIG. 5 synchronized with the horizontal synchronizing signal HS. The drive pulse HD changes in the horizontal scanning cycle. Thereby, the primary winding 3 of the transformer 3
The second sawtooth current I2 that changes to 1 in the horizontal scanning period
Flows.

The modulation waveform generating circuit 8 generates a modulation waveform signal MD2 described later and supplies the modulation waveform signal MD2 to the power supply modulation circuit 7. The power supply modulation circuit 7 modulates the power supply voltage Vcc of the DC power supply 9 with the modulation waveform signal MD2 provided from the modulation waveform generation circuit 8, and applies the modulation voltage VP of FIG. 5 to one end of the primary winding 31 of the transformer 3. . Modulation voltage V
The level of P gradually increases from the start point to the end point of the vertical scanning, reaches the maximum near the end point, and the level at the end point of the vertical scanning becomes higher than the level at the start point of the vertical scanning. As a result, as shown in FIG. 5, the amplitude of the envelope of the second sawtooth current I2 is gradually increased from the start point of vertical scanning by the modulation voltage VP, and is maximized in the vicinity of the end point of vertical scanning. Is modulated to.

In the transformer 3, by superimposing the second sawtooth current I2 on the first sawtooth current I1, the vertical deflection current ID of FIG. 5 which changes stepwise in the horizontal scanning period is obtained, and the vertical deflection current ID is obtained. It is supplied to the deflection coil 4. As a result, a vertical deflection magnetic field that changes stepwise in the horizontal scanning period according to the vertical deflection current ID is generated.

The feedback circuit 5 includes a vertical deflection coil 4 and a resistor 6.
The voltage at the connection point with is fed back to the other input terminal of the amplifier 2.

In the present embodiment, the vertical deflection voltage generating circuit 1 and the amplifier 2 constitute a first sawtooth wave current generating means, and in particular, the vertical deflection voltage generating circuit 1 corresponds to the sawtooth wave voltage generating circuit, and the amplifier 2 corresponds to a voltage-current conversion circuit. Further, the DC power supply 9, the resonance capacitor 10, the damper diode 11 and the drive transistor 12 form a second sawtooth wave current generating means. The power supply modulation circuit 7 and the modulation waveform generation circuit 8 constitute modulation means, and particularly the power supply modulation circuit 7 corresponds to a sawtooth wave current modulation circuit. The transformer 3 and the vertical deflection coil 4 constitute a vertical deflection magnetic field generating means.

FIG. 6 is a circuit diagram showing an example of the configuration of the power supply modulation circuit 7 of FIG. The power supply modulation circuit 7 is composed of a transistor 71 and a resistor 72. Transistor 7
The collector of 1 is connected to the power supply terminal for receiving the power supply voltage Vcc, the base receives the modulation waveform signal MD2, and the emitter outputs the modulation voltage VP. Transistor 7
The modulation voltage VP changes in response to the voltage change of the modulation waveform signal MD2 given to the base of 1.

FIG. 7 is a block diagram showing the structure of the modulation waveform generating circuit 8 of FIG. FIG. 8 is a waveform chart of each part showing the operation of the modulation waveform generating circuit 8 of FIG.

The modulation waveform generating circuit 8 includes a sawtooth wave generating circuit 81, a parabolic wave generating circuit 82, amplifiers 83 and 84,
Clamp circuits 85, 86, adder 87, DC level adjusting circuit 88, D / A converter (digital / analog converter)
91, 92, 93 and memories 94, 95, 96 are included.

Data indicating the gain of the amplifier 83 is stored in the memory 94. The D / A converter 91 converts the data read from the memory 94 into an analog signal,
The analog signal is used as the gain control signal GA1 and the amplifier 8
Give to 3. The memory 95 stores data indicating the gain of the amplifier 84. The D / A converter 92 converts the data read from the memory 95 into an analog signal,
The analog signal is used as the gain control signal GA2 and the amplifier 8
Give to 4.

The memory 96 stores data indicating the DC level. The D / A converter 93 converts the data read from the memory 96 into an analog signal, and supplies the analog signal to the DC level adjusting circuit 88 as the DC level control signal GA3.

The sawtooth wave generating circuit 81 and the parabolic wave generating circuit 82 are supplied with the vertical synchronizing signal VS shown in FIG. The sawtooth wave generation circuit 81 uses the vertical synchronization signal VS.
Sawtooth voltage SA that changes in the vertical scanning cycle in synchronization with
1 is generated. The amplifier 83 is a sawtooth wave generation circuit 81.
The sawtooth wave voltage SA1 generated by the amplifier is amplified based on the gain control signal GA1, and the amplified sawtooth wave voltage S1 is amplified.
Output A2. The clamp circuit 85 clamps the sawtooth wave voltage SA2 output from the amplifier 83 to the ground level at the start point of the vertical scanning period, and outputs the clamped sawtooth wave voltage SA3.

The parabolic wave generation circuit 82 generates a parabolic wave voltage PA1 which changes in the vertical scanning period in synchronization with the vertical synchronizing signal VS. The amplifier 84 amplifies the parabolic wave voltage PA1 generated by the parabolic wave generation circuit 82 based on the gain control signal GA2, and outputs the amplified parabolic wave voltage PA2. The clamp circuit 86 includes an amplifier 84
The parabolic wave voltage PA2 output from is clamped to the ground level at the start point of the vertical scanning period, and the clamped parabolic wave voltage PA3 is output.

The adder 87 adds the sawtooth wave voltage SA3 output from the clamp circuit 85 and the parabolic wave voltage PA3 output from the clamp circuit 86, and outputs the addition result as a modulated waveform signal MD1. Modulation waveform signal MD
The level of 1 gradually increases from the start point of the vertical scanning and changes so as to become maximum near the end point of the vertical scanning.

The DC level adjusting circuit 88 adjusts the DC level of the modulated waveform signal MD1 output from the adder 87 based on the DC level control signal GA3, and outputs the adjusted modulated waveform signal MD2.

In this way, the modulated waveform signal MD2 which changes in the vertical scanning period is obtained. The level of the modulation waveform signal MD2 gradually increases from the start point of vertical scanning, reaches the maximum near the end point of vertical scanning, and the level at the end point of vertical scanning becomes higher than the level at the start point.

In this example, the amplifier 83 corresponds to the first amplifier, the amplifier 84 corresponds to the second amplifier, the clamp circuit 85 corresponds to the first clamp circuit, and the clamp circuit 8
6 corresponds to the second clamp circuit, and the adder 87 corresponds to the combining circuit.

Now, the influence of the internal magnetic shield 405 on the deflection magnetic field will be considered. The following two mechanisms can be considered as the mechanism of the influence of the internal magnetic shield 405 on the vertical deflection.

First, as the influence of the horizontal deflection magnetic field, a change in the horizontal deflection magnetic field causes an eddy current in the internal magnetic shield 405, and a new magnetic field is generated by the eddy current. The trajectory of the scan line changes. As the influence of the vertical deflection magnetic field, a change in the blanking period of the vertical deflection magnetic field causes an eddy current in the internal magnetic shield 405, a new magnetic field is generated by the eddy current, and the influence of the newly generated magnetic field is caused. The trajectory of the scan line changes. Also,
The extra energy consumed to generate the eddy current changes the vertical deflection magnetic field itself, affecting the scan line.

FIG. 9 compares the scanning line when the electron beam is deflected using the vertical deflection current of FIG. 14C with the scanning line when the electron beam is deflected using the vertical deflection current ID of FIG. FIG. FIG. 9A shows scanning lines at the upper part of the screen when the vertical deflection current of FIG. 14C is used, and FIG. 9B shows the screen when the vertical deflection current of FIG. 14C is used. The lower scanning lines are shown, and FIG. 9C shows the scanning lines over the entire screen when the vertical deflection current ID of FIG. 5 is used.

When the vertical deflection current shown in FIG. 14C is used, as shown in FIG. 9A, the scanning line shown by the broken line is excessively corrected as shown by the solid line in the upper portion of the screen, as shown in FIG. As shown in FIG. 9B, the scanning line indicated by the broken line is undercorrected as indicated by the solid line in the lower part of the screen. As described above, when the vertical deflection current of FIG. 14C is used, the scanning lines are not parallelized.

On the other hand, the vertical deflection current I shown in FIG.
When D is used, as shown in FIG. 9C, the scanning line indicated by the broken line is parallelized as indicated by the solid line over the entire screen.

As described above, in the vertical deflection circuit 300 of the present embodiment, the vertical deflection current ID shown in FIG. 5 is used to vertically deflect the electron beam to correct the disturbance of the magnetic field due to the internal magnetic shield 405. Thus, it becomes possible to obtain parallel scanning lines.

FIG. 10 is a block diagram showing the structure of a video display device according to the second embodiment of the present invention.

The image display device of FIG. 10 differs from the image display device of FIG. 1 in that a vertical deflection circuit 300a is provided instead of the vertical deflection circuit 300, and the first vertical deflection coil 4a is provided instead of the vertical deflection coil 4. And that the second vertical deflection coil 4b is provided.

The vertical deflection circuit 300a includes a first vertical deflection coil for vertically deflecting the electron beam in the CRT 400 in synchronization with the horizontal synchronizing signal HS and the vertical synchronizing signal VS supplied from the video signal processing circuit 100. The first vertical deflection current is supplied to 4a, and the second vertical deflection current is supplied to the second vertical deflection coil 4b.

FIG. 11 is a circuit diagram showing the configuration of the vertical deflection circuit 300a of the image display device of FIG.

The vertical deflection circuit 300a of FIG. 11 is different from the vertical deflection circuit 300 of FIG. 4 in that the transformer 3 is not provided, and instead of the vertical deflection coil 4, the first vertical deflection coil 4a and the second vertical deflection circuit 4a are provided. The point is that the deflection coil 4b is provided.

In this embodiment, the first vertical deflection coil 4a and the second vertical deflection coil 4b constitute the vertical deflection magnetic field generating means.

The vertical deflection voltage generation circuit 1 generates a sawtooth-shaped vertical deflection voltage VA in synchronization with the vertical synchronization signal VS shown in FIG. 5, and supplies the vertical deflection voltage VA to one input terminal of the amplifier 2. . The amplifier 2 supplies the first sawtooth wave current I1 shown in FIG. 5 to the first vertical deflection coil 4a based on the vertical deflection voltage VA generated by the vertical deflection voltage generation circuit 1. The first vertical deflection coil 4a generates a first vertical deflection magnetic field based on the first sawtooth wave current I1. The feedback circuit 5 feeds back the voltage at the connection point between the first vertical deflection coil 4a and the resistor 6 to the other input terminal of the amplifier 2.

On the other hand, drive transistor 12 is turned on and off in response to drive pulse HD shown in FIG. 5 which is synchronized with horizontal synchronization signal HS. The drive pulse HD changes in the horizontal scanning cycle. Thereby, the second vertical deflection coil 4
The second sawtooth wave current I2 that changes in the horizontal scanning period in b
Flows.

The modulation waveform generation circuit 8 generates the modulation waveform signal MD2 of FIG. 8 and supplies the modulation waveform signal MD2 to the power supply modulation circuit 7. The power supply modulation circuit 7 modulates the power supply voltage Vcc of the DC power supply 9 with the modulation waveform signal VD2 provided from the modulation waveform generation circuit 8, and the modulation voltage VP shown in FIG.
Is applied to one end of the second vertical deflection coil 4b.

As shown in FIG. 5, in the second sawtooth current I2, the amplitude of the envelope gradually increases from the starting point of vertical scanning due to the modulation voltage VP, and becomes maximum near the ending point of vertical scanning. The amplitude of the envelope at the end point of vertical scanning is modulated so as to be larger than the amplitude of the envelope at the start point. The second vertical deflection coil 4b generates a second vertical deflection magnetic field based on the second sawtooth current I2.

The first vertical deflection coil 4a generates the first vertical deflection magnetic field and the second vertical deflection coil 4b.
By synthesizing the second vertical deflection magnetic field generated by, the vertical deflection magnetic field that changes stepwise in the horizontal scanning period is obtained.

As described above, also in the vertical deflection circuit 300a of the present embodiment, the magnetic field disturbance due to the internal magnetic shield 405 is corrected by the combination of the first vertical deflection magnetic field and the second vertical deflection magnetic field, and the parallelism is achieved. It becomes possible to obtain a scan line.

[0091]

According to the first sawtooth wave current and the modulated second sawtooth wave current, the vertical deflection magnetic field generating means generates the vertical deflection magnetic field which changes stepwise, whereby the vertical magnetic field generated by the internal magnetic shield is increased. It is possible to correct the disturbance of the deflection magnetic field and accurately parallelize the forward scanning line and the backward scanning line.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a video display device according to a first embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view showing the structure of a CRT.

FIG. 3 is a schematic perspective view of an internal magnetic shield attached to the CRT of FIG.

4 is a circuit diagram showing a configuration of a vertical deflection circuit of the video display device of FIG.

5 is a waveform chart of each part showing the operation of the vertical deflection circuit of FIG.

6 is a circuit diagram showing an example of the configuration of the power supply modulation circuit of FIG.

7 is a block diagram showing the configuration of the modulation waveform generation circuit of FIG.

8 is a waveform chart of each part showing the operation of the modulation waveform generation circuit of FIG. 7.

9 is a diagram showing a comparison between the scanning line when the vertical deflection current of FIG. 14C is used and the scanning line when the vertical deflection current of FIG. 5 is used.

FIG. 10 is a block diagram showing a configuration of a video signal processing circuit according to a second embodiment of the present invention.

11 is a circuit diagram showing a configuration of a vertical deflection circuit of the video display device of FIG.

FIG. 12 is a diagram showing a reciprocal deflection method.

FIG. 13 is a waveform diagram for explaining a vertical deflection current for parallelizing the forward scan line and the backward scan line.

FIG. 14 is a waveform diagram for explaining a vertical deflection current for parallelizing a forward scan line and a backward scan line on a plane CRT.

[Explanation of symbols]

1 Vertical deflection voltage generation circuit 2,83,84 Amplifier 3 transformers 4 Vertical deflection coil 4a First vertical deflection coil 4b Second vertical deflection coil 5 Feedback circuit 6 resistance 7 Power supply modulation circuit 8 Modulation waveform generation circuit 9 DC power supply 10 Resonance capacity 11 Damper diode 12 drive transistor 14 Horizontal deflection coil 31 Primary winding 32 secondary winding 81 sawtooth wave generation circuit 82 Parabolic wave generation circuit 85,86 Clamp circuit 87 adder 88 DC level adjustment circuit 91, 92, 93 D / A converter 94, 95, 96 memory 100 video signal processing circuit 200 Horizontal deflection circuit 300,300a Vertical deflection circuit 400 CRT 405 Internal magnetic shield

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Hiroka Shimosaka             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. (72) Inventor Toshiaki Kitahara             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. F-term (reference) 5C068 AA17 BA02 BA12 HB04 JA07                       JB03 LA20

Claims (11)

[Claims] 1. A vertical deflection circuit for vertically deflecting an electron beam in a cathode ray tube having an internal magnetic shield for reducing the influence of geomagnetism on the electron beam, the circuit comprising an S-shaped vertical deflection circuit. First sawtooth current generating means for generating a corrected first sawtooth current, second sawtooth current generating means for generating a second sawtooth current changing in a horizontal scanning cycle, and the second The amplitude of the envelope of the second sawtooth wave current generated by the sawtooth wave current generating means gradually increases from the start point of vertical scanning and becomes maximum at the end point side from the intermediate point of vertical scanning. 2 modulating means for modulating the sawtooth current, and the first sawtooth current generated by the first sawtooth current generating means and the modulating means by the modulating means. A vertical deflection circuit, characterized in that a vertical deflection magnetic field generating means for generating a vertical deflection magnetic field changes stepwise on the basis of the second sawtooth wave current was. 2. A modulation waveform generating circuit for generating a modulation waveform, the level of which gradually increases from a starting point of vertical scanning and is maximized at an end point side of an intermediate point of vertical scanning. 2. The vertical deflection circuit according to claim 1, further comprising a sawtooth current modulation circuit that modulates the second sawtooth current in response to the modulation waveform generated by the modulation waveform generation circuit. 3. The sawtooth wave generation circuit, wherein the modulation waveform generation circuit generates a sawtooth wave signal that changes in a vertical scanning cycle, a parabolic wave generation circuit that generates a parabolic wave signal that changes in a vertical scanning cycle, and the sawtooth. 3. A combining circuit for outputting the modulated waveform by combining a sawtooth wave signal generated by a wave generating circuit and a parabolic wave signal generated by the parabolic wave generating circuit. Vertical deflection circuit. 4. The modulation waveform generating circuit includes a first amplifier that amplifies the sawtooth wave signal generated by the sawtooth wave generating circuit, and a second amplifier that amplifies the parabolic wave signal generated by the parabolic wave generating circuit. Amplifier, a first clamp circuit that clamps the sawtooth wave signal amplified by the first amplifier to a predetermined potential at a predetermined timing, and applies the clamp circuit to the combining circuit; and a parabola amplified by the second amplifier. It further includes a second clamp circuit that clamps the wave signal to a predetermined potential at a predetermined timing and applies it to the combining circuit, and a DC level adjusting circuit that adjusts the DC level of the modulated waveform output by the combining circuit. 4. The vertical deflection circuit according to claim 3, wherein: 5. A sawtooth voltage generating circuit that generates a sawtooth voltage in synchronism with a vertical synchronizing signal, and a sawtooth voltage generated by the sawtooth voltage generating circuit. The vertical deflection circuit according to claim 1, further comprising a voltage-current conversion circuit that converts the first sawtooth wave current. 6. The vertical deflection magnetic field generating means superimposes the second sawtooth wave current modulated by the modulating means on the first sawtooth wave current generated by the first sawtooth wave current generating means. And a vertical deflection coil for generating the vertical deflection magnetic field based on the vertical deflection current generated by the superimposing means. The vertical deflection circuit according to any one of Items 1 to 5. 7. The primary superimposing means is provided with a primary winding to which the second sawtooth wave current generated by the second sawtooth wave current generating means is supplied, and the first sawtooth wave current generating means. 7. The vertical deflection circuit according to claim 6, further comprising a transformer having a secondary winding which is supplied with the generated first sawtooth wave current and is connected in series to the vertical deflection coil. 8. The first vertical deflection magnetic field generating means generates a first vertical deflection magnetic field based on the first sawtooth wave current generated by the first sawtooth wave current generating means. 6. A coil, and a second vertical deflection coil that generates a second vertical deflection magnetic field based on the second sawtooth current modulated by the modulation means. The vertical deflection circuit according to claim 1. 9. A cathode ray tube, an internal magnetic shield provided in the cathode ray tube for reducing the influence of geomagnetism on the electron beam, and a vertical deflection magnetic field for vertically deflecting the electron beam in the cathode ray tube. And a horizontal deflection circuit that generates a horizontal deflection magnetic field for horizontally reciprocally deflecting the electron beam in the cathode ray tube. The vertical deflection circuit changes in a vertical scanning cycle and S-shaped correction is performed. Sawtooth current generating means for generating a first sawtooth current, and second sawtooth current generating means for generating a second sawtooth current changing in a horizontal scanning cycle; and the second sawtooth current generating means. The amplitude of the envelope of the second sawtooth current generated by the sawtooth current generating means gradually increases from the starting point of vertical scanning, and A modulation means for modulating the second sawtooth current so as to be maximum on the end point side from the point, and the first sawtooth current generated by the first sawtooth current generating means and the modulation means. A vertical deflection magnetic field generating means for generating a vertical deflection magnetic field that changes stepwise based on the modulated second sawtooth wave current, and a video display device. 10. The vertical deflection magnetic field generating means superimposes the second sawtooth wave current modulated by the modulating means on the first sawtooth wave current generated by the first sawtooth wave current generating means. And a vertical deflection coil for generating the vertical deflection magnetic field based on the vertical deflection current generated by the superimposing means. The video display device according to claim 9. 11. The first vertical deflection magnetic field generating means generates a first vertical deflection magnetic field based on the first sawtooth wave current generated by the first sawtooth wave current generating means. 10. The image display according to claim 9, further comprising a coil and a second vertical deflection coil that generates a second vertical deflection magnetic field based on the second sawtooth wave current modulated by the modulation means. apparatus.