JPH0831963B2 - Horizontal deflection output circuit - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a horizontal deflection output circuit suitable for a horizontal deflection circuit in which an electron beam scans a fluorescent screen at a constant speed for an arbitrary horizontal deflection frequency. It is about.

[Background of the Invention]

In a television or display device,
The curvature of the display surface of the cathode ray tube (fluorescent surface curvature) is larger than the curvature of the deflecting surface that deflects the electron beam, and the ratio increases as the deflection angle increases.

When the display surface curvature is larger than the deflection surface curvature as described in JP-A-59-165570, when a sawtooth wave current that linearly increases during the display period is applied to the deflection coil, the raster displayed on the cathode ray tube is displayed. Has a shape that extends at both ends of the display screen and contracts at the center. To correct this, a sawtooth wave current distorted into an S shape during the display period may be applied.

In order to realize this, conventionally, a capacitor is connected in series with the horizontal deflection coil, and an S-shaped sawtooth wave current is caused to flow by series resonance between the horizontal deflection coil and the capacitor (referred to as an S-shaped capacitor). This means that the driving voltage of the horizontal deflection coil (the voltage of the S-shaped capacitor) is modulated into a parabola shape of the horizontal deflection cycle to realize the S-shaped correction. The P-P value V _PP of this horizontal parabolic voltage is obtained by integrating the horizontal sawtooth wave current. Is represented by However, I _P is the PP value of the horizontal deflection current,
T _H is the horizontal deflection period, C is the capacitance of the S-shaped capacitor, and τ is the scanning rate (horizontal scanning period / horizontal deflection period). The S-shaped correction amount, which indicates how much the horizontal deflection current is S-shaped, is the P-P value of this parabola voltage and the power supply voltage of the horizontal deflection output circuit.
It is expressed as a ratio with E _B.

The diversification of information media and the progress of the OA industry in recent years have brought about a wide variety of horizontal deflection frequencies for displays. On the other hand, a display for multi-horizontal deflection frequencies corresponding to several horizontal deflection frequencies as shown in FIG. 1 has been considered. In FIG. 1, 1 is a video signal processing circuit, 2 is a video output circuit, 3 is a deflection yoke, 4 is a cathode ray tube, 5 is a sync separation circuit, 6 is a vertical deflection circuit, 7 is a frequency discrimination circuit, and 8 is a horizontal oscillation circuit. Reference numerals 9 denote horizontal deflection output circuits, and 10 a power supply circuit.

The outline of the multi-horizontal deflection frequency compatible display of FIG. 1 will be described. The composite video signal input to the A terminal is input to the video signal processing circuit 1 and the sync separation circuit 5. The horizontal sync signal separated by the sync separation circuit 5 is input to the horizontal oscillation circuit 8 and the frequency discrimination circuit 7. Here, the frequency discriminating circuit is an fV converter that generates a voltage corresponding to the cycle of the horizontal synchronizing signal. The voltage corresponding to the horizontal period controls the output voltage of the power supply circuit 10 to keep the PP value of the horizontal deflection current of the horizontal deflection output circuit constant with respect to the horizontal deflection frequency.

Where the horizontal deflection current I _P is Is represented by However, E _B is the power supply voltage, L is the inductance of the horizontal deflection coil, and T _S is the horizontal scanning period. That is, in order to keep the horizontal deflection size constant with respect to the frequency, if the cathode voltage of the cathode ray tube and the inductance of the horizontal deflection coil are constant, the voltage inversely proportional to the horizontal scanning period may be used as the power supply voltage of the horizontal deflection output circuit. . Since the horizontal scanning period is almost equal to the horizontal deflection period, the power supply voltage E _{B is changed} to E _B ∝1 /
In terms of T _H , the horizontal deflection size is constant.

Next, in order to make the S-curve correction amount constant regardless of the horizontal deflection frequency, if the display surface curvature and the deflection curvature are constant (1)
S, which is the ratio of the parabola voltage V _PP and the power supply voltage E _B obtained by the equation
The character correction amount may be constant. Further, the power supply voltage E _B in order to maintain the horizontal deflection size constant as described above is in relation E _B α1 / T _H, the V _PP is the relationship between V _PP .alpha.T _H from (1) Therefore, in order to keep V _PP / E _B = constant, S in equation (1)
The value of the letter capacitor must be changed by 1 / T _H ² . In the case of a TV, the S-capacitor is about 0.2 to 0.4 μF, and it is very difficult to adapt the variable capacitance element because a deflection current of several amperes peak flows, and the S-capacitor shown in FIG. A method of switching by the output of the frequency discriminating circuit 7 is general. However, in the S-shaped capacitor switching method of FIG. 2, since the capacitance change of the capacitor is discrete, a horizontal deflection frequency range with a large correction error occurs. In order to reduce this error, the number of S-shaped capacitors and the number of switch contacts are increased.

In addition to the above, as patent applications relating to S-shaped correction, there are JP-A-57-107676 and JP-A-57-203374.

[Object of the Invention]

The object of the present invention is to eliminate the above-mentioned drawbacks of the prior art,
An object of the present invention is to provide a horizontal deflection output circuit that performs optimum S-shaped correction for any continuous horizontal deflection frequency.

[Outline of Invention]

The present invention is characterized by the following points. First, when the S-shaped correction capacitor is set to a constant value, the peak value of the parabolic voltage generated in the capacitor is inversely proportional to the horizontal deflection frequency according to the equation (1), but the S-shaped correction amount depends on the horizontal deflection frequency. Considering that the required parabolic voltage for maintaining a constant value increases in direct proportion to the horizontal deflection frequency, the S-shaped capacitor is determined so as to achieve the optimum S-shaped correction at any specific horizontal deflection frequency, and other horizontal deflection frequencies are determined. In terms of frequency, an S-correction signal generation circuit provided at the connection point between the horizontal deflection coil and the S-shaped capacitor has an amplitude proportional to the horizontal deflection frequency in order to accurately correct the excessive or insufficient S-curve correction amount. To generate a horizontal parabolic voltage.

Example of Invention

An embodiment of the present invention will be described with reference to FIGS.
FIG. 3 is a diagram showing a specific circuit and configuration of the multi-horizontal frequency-compatible S-shaped correction circuit according to the present invention. The output transistor 13, the damper diode 14, the resonance capacitor 15, the deflection coil 3 ', the choke (FBT; fly). The back transformer) 16 and the S-shaped correction capacitor 12 'are components that constitute a generally known deflection output circuit.

In the display for multi-horizontal frequency shown in Fig. 1,
The maximum horizontal deflection frequency is _fHmax , and the minimum is _fHmin .
As described above, the value of the S-shaped correction capacitor 12 'is set to f
Optimally chosen in _hmin, if constant, the amplitude of horizontal parabola voltage generated in the S-shaped capacitor in f _Hmax is inversely proportional to the horizontal deflection frequency becomes smaller than the amplitude required, S
Character correction is insufficient.

Therefore, in order to make up for the insufficient S-shaped correction, the S-shaped correction power sources 18 and 19 and the S-shaped correction output transistor 2 shown in FIG.
An S-shaped correction signal generation circuit composed of 0, 21, an S-shaped correction drive transistor 24, resistors 22, 23, a transformer 25, and an amplifier (hereinafter referred to as a variable gain amplifier) 26 whose gain changes according to the control voltage V _cont The deflection coil 3'is used so that it can be supplied to the deflection coil 3 '. The voltage V _cont (the output of the frequency discriminating circuit 7 in FIG. 1) corresponding to the horizontal deflection frequency has the relationship shown in FIG.
The above S-curve correction shortage is between the points A and B in FIG.
This is supplemented by applying a parabolic voltage having the same polarity as that of the parabolic voltage generated at the point C and adding a shortage to the parabolic voltage generated at the point C. If a parabolic voltage of opposite polarity is applied to the transformer 25, it will be inverted by the transistor 24, and the transistor 2 connected in push-pull
By amplifying at 0 and 21, a parabolic voltage can be generated between the points A and B. Here, the P-P value V _SP of the parabolic voltage applied between points A and B is f _Hmin , and if the voltage at the point C of the S-shaped capacitor at 0 and f _Hmin is V _PBO , the horizontal parabolic voltage V _PP = V _{From SP} + V _PBO V _{SP for} horizontal deflection frequency f _H is Becomes That is, V _SP may be increased in proportion to the horizontal deflection frequency based on f _Hmin .

The variable gain amplifier 26 uses the parabolic voltage V _PB obtained at the point C of the S-shaped correction capacitor as the voltage V corresponding to the horizontal deflection frequency.
_{In cont} , the gain is changed as shown in equation (3).

Since the parabolic voltage is inversely proportional to the horizontal deflection frequency, the gain of the variable gain amplifier needs to change in proportion to the square of the horizontal deflection frequency.

A first concrete example of the variable gain amplifier is shown in FIG. The variable gain amplifier 26 is realized by changing the resistance value of the resistance of the cds photocoupler 262 with the control voltage V _cont . cds Photocoupler 262 resistance R262, resistance 263 resistance R2
If it is 63, the gain of the amplifier 261 is represented by R262 / R263.
The resistance value of the resistance of the cds photocoupler 262 changes depending on the current passed through the light emitting diode. The current sent to the light emitting diode of the cds photo coupler is the detection winding provided in the transformer 25.
The voltage generated in 274 is converted to DC by diode 272, resistor 271, and capacitor 270, and V _cont is multiplied by 2 in multiplier 273.
The gain of the amplifier 261 changes in proportion to the square of the horizontal deflection frequency, which is controlled by a differential amplifier composed of transistors 266, 267 and resistors 264, 265, 268 so as to be equal to the multiplied voltage.

A second specific example of the variable gain amplifier is shown in FIG. Seventh
In the figure, 29 and 30 are multipliers. As shown in the equation (1), the _PP value of the voltage V _PB generated at the point C of the S-shaped capacitor V _PP
Is inversely proportional to the horizontal deflection frequency. Therefore, as described in the first example of the variable gain amplifier, the voltage V _cont proportional to the horizontal deflection frequency is added to the V _PB and the multipliers 29 and 30 are used.
By multiplying by 2 (by applying V _cont to the A and B terminals in FIG. 7), the same effect as the first specific example can be obtained.

In the above description, the correction amount of the S-shaped correction current is always positive with reference to f _Hmin . However, a variable gain amplifier shown in FIG. 7, FIG. 6, the voltage V _cont corresponding to the horizontal deflection frequency shown in FIG. 8, the V _cont 1, the center f _HCENT the horizontal deflection frequency that can correspond ((f _{Hmax
-F Hmin} ) / 2), the value of the S-shaped capacitor is selected so that the S-shaped correction amount is optimal, and at this horizontal deflection frequency, S
Insufficient character correction is set to 0. Here, one and the other of V _cont and V _cont 1 shown in FIG. 6 or 8 are connected to terminals A and B in FIG. 7, respectively. Further, V _cont 1 may be a value obtained by applying a DC level shift to V _cont . As a result, when the horizontal deflection frequency is lower than f _HCENT , the excess S-shaped correction amount is
When the horizontal deflection frequency is higher than f _HCENT , the parabolic voltage in the direction opposite to the point C is generated and canceled between points A and B in Fig. 3 by the letter correction circuit. Correction is performed according to the same principle as that of the embodiment.

The variable gain amplifier may be of any other type as long as the above-described S-shaped correction waveform is obtained on the secondary side of the transformer 25.

Further, in the above example, the positive relative to the positive direction or f _HCENT, S-deficiency in f _Hmin reference has been described in the negative direction, if different principle, based on an arbitrary f _H over You may correct the shortfall.

A concrete example of the power supplies 18 and 19 of the S-shaped correction output section shown in FIG. 3 is shown in FIG. Fig. 5 shows that choke transformer 16 'is provided with windings, and diodes 181, 191, capacitors 182, 192,
It is to obtain the power supplies 18 and 19.

〔The invention's effect〕

By using the horizontal deflection output circuit of the present invention, the S-shaped correction of the display corresponding to the multi-horizontal deflection frequency can be continuously and appropriately varied with respect to the horizontal deflection frequency, and the optimum S-shaped correction can always be performed.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing the overall configuration of a multi-deflection frequency compatible display. FIG. 2 is a block diagram showing a conventional S-shaped correction switching circuit for a multi-deflection frequency compatible display. FIG. 3 is a circuit diagram showing a horizontal deflection output circuit for a multi-deflection frequency compatible display of the present invention. the 4th,
FIG. 7 is a circuit diagram showing a specific example of the variable gain amplifier.
FIG. 5 is a circuit diagram showing a specific example of the S-shaped correction power source. 6 and 8 are characteristic diagrams showing the output characteristics of the frequency discrimination circuit. 1 ... Video signal processing circuit, 2 ... Video output circuit, 3,
3 '... deflection yoke, 4 ... cathode ray tube, 5 ... sync separation circuit, 6 ... vertical deflection circuit, 7 ... frequency discrimination circuit,
8 ... Horizontal oscillation circuit, 9 ... Horizontal deflection output circuit, 10 ...
Power supply, 11 ... S-shaped capacitor selector switch, 12 ', 1
21,122,123,124 …… S-correction capacitor, 13 …… Horizontal output transistor, 14 …… Damper diode, 15 …… Resonance capacitance, 16 …… Choke transformer (flyback transformer), 18,19 …… Power supply, 20,21,24 ...... Transistor, 22,
23 …… resistor, 25 …… transformer, 26 …… variable gain amplifier,
261 ... Amplifier, 262 ... Photo coupler, 263,264,265,26
8,269,271 …… Resistance, 266,267 …… Transistor, 272…
… Diode, 270… Capacitor, 273, 29, 30… Multiplier.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masafumi Oki 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Inside the Home Appliances Research Laboratory, Hitachi, Ltd. (56) Reference JP-A-53-74833 (JP, A)

Claims (2)

[Claims] 1. A horizontal parabolic voltage is supplied in a horizontal deflection output circuit having a horizontal output transistor, a horizontal deflection coil connected to the horizontal output transistor, and an S-shaped capacitor connected in series with the horizontal deflection coil. S-shape having a first input terminal that is provided, a second input terminal to which a signal corresponding to the horizontal deflection frequency is supplied, and an output terminal that outputs a horizontal parabolic voltage having an amplitude corresponding to the horizontal deflection frequency. A horizontal deflection output circuit, wherein a correction signal generating circuit is provided, and an output terminal of the S-shaped correction signal generating circuit is connected to a connection point between the horizontal deflection coil and the S-shaped capacitor. 2. The horizontal deflection output circuit according to claim 1, wherein the S-shaped correction signal generation circuit includes a first multiplication circuit and a second multiplication circuit, and the first multiplication circuit. A horizontal parabolic voltage generated in the S-shaped capacitor is supplied from the first input terminal to one input terminal of the circuit, and the second input terminal is connected to the other input terminal of the first multiplication circuit. Is supplied with a voltage corresponding to the horizontal deflection frequency, the output voltage of the first multiplication circuit is supplied to one input terminal of the second multiplication circuit, and the other input of the second multiplication circuit is supplied. A horizontal deflection output circuit, characterized in that a voltage corresponding to the horizontal deflection frequency is supplied from the second input terminal to the end, and the output voltage of the second multiplication circuit is supplied to the output terminal.