JPH01173976A - Vertical deflection circuit - Google Patents

Abstract

PURPOSE:To correct vertical linearity even when the title device is used for an FS tube by equipping the device with a waveform shaping circuit composed of an element on an output edge of a constant current circuit to execute a switching with a driving pulse synchronized with a vertical synchronizing signal, a capacitor for integrating a current, and a variable resistor connected to the capacitor in parallel. CONSTITUTION:The device is equipped with a waveform shaping circuit 200 composed of a constant current circuit 150 to output a constant current waveform modulated by a sawtooth signal, an element 29 connected to the output edge of this constant current circuit 150 and to execute the switching with the driving pulse synchronized with the vertical synchronizing signal, and a variable resistor 30 for a diverting connected to a capacitor 28 for integrating the current in parallel, which is connected to the output edge of the constant current circuit 150 and connected with the element 29 in parallel. Consequently, not only an approximately complete sigmoidal correction can be executed but also the linearity of a picture upper part and that of a picture lower part can be adjusted independently. Thus, the device can obtain enough linearity even when the FS tube is used.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention relates to a vertical deflection circuit that significantly improves vertical linearity.

[Conventional technology]

Conventionally, CRTs with relatively round tube surfaces have been exclusively used, but recently, FS tubes have been increasingly used to improve the visibility of the screen.

However, in the case of an FS tube, for example, the radius of curvature of the tube surface is 21 mm, which is R = 850 mm in a conventional round 20-inch CRT.
For an inch CRT, R = approximately 1730 mm, which is large, and the difference in distance between the center and the periphery from the virtual center when the electron beam emitted from the electron gun is deflected within the deflection coil, the so-called deflection center, to the phosphor screen. As the screen became significantly larger, the vertical linearity of the screen deteriorated.

As a conventional vertical deflection circuit that performs correction to improve the vertical linearity of the screen, so-called vertical linearity correction, for example, Japanese Patent Application Laid-Open No. 1179-1983
In addition to the one shown in Publication No. 77, various other ones have been proposed.

FIG. 3 is a diagram showing a conventional vertical deflection circuit described in Japanese Patent Application Laid-open No. 117977/1983.

In this figure, 1 is a vertical oscillation stage, 2 is a vertical drive and output stage, 3 is a vertical deflection coil, 4 is a DC blocking capacitor, 5 is a sweeping resistor, and 6 to 8 are first to third variable resistors. 9 is a series resistor, 1o and 11 are first and second coupling capacitors, 12 is a load resistor, 13 is an oscillation output transistor, 14.15 is a DC source, 16 is a DC power supply terminal,
17 is an inverting amplifier. In this vertical deflection circuit, a DC blocking capacitor 4 is connected in series to a vertical deflection coil 3.
A sawtooth wave current as shown in FIG. 4(a) and a sawtooth wave current as shown in FIG. 4(b) are generated from the one end and the third variable resistor 8 through the first feedback loop and the second feedback loop, respectively. After extracting the inverted parabolic current as shown in FIG. 4(C), the vertical drive and output stage 2
Three-character correction is performed by feeding back to the input terminal of. Further, by adjusting the first to third variable resistors 6 to 8, the correction amount and correction range can be adjusted.

[Problem that the invention seeks to solve]

However, in the conventional vertical deflection circuit as described above, the parabolic waveform generated across the DC blocking capacitor 4 when a sawtooth wave current is passed through the vertical deflection coil 3 is fed back and used. When vertical linearity correction (three-character correction) is performed on the image, the generated parabolic waveform changes and there is a problem in that sufficient correction cannot be performed.

In addition to the above vertical deflection circuit, there is also a
No. 3, No. 60-127877, No. 62-26978, Japanese Utility Model Application Publication No. 145165/1987, etc. also mention correction of vertical linearity, but none of them apply to FS tubes with a large radius of curvature. Since this method is not taken into account, there is a problem in that sufficient effects cannot be obtained even when applied to FS pipes.

The present invention was made in order to solve such problems, and an object of the present invention is to obtain a vertical deflection circuit that can sufficiently correct vertical linearity even when applied to an FS tube.

[Means for solving problems]

The vertical deflection circuit according to the present invention includes a constant current circuit that outputs a constant current waveform modulated by a sawtooth wave signal, and a constant current circuit that is connected to the output end of the constant current circuit and performs switching by a drive pulse synchronized with a vertical synchronization signal. A waveform shaping circuit consisting of a current integration element connected to the output end of a constant current circuit and in parallel with the element, and a shunt variable resistor connected in parallel with this capacitor. It is equipped with the following.

(Function) In the present invention, the current flowing through the constant current circuit mainly flows through the current integrating capacitor in the first half of the cycle, and the voltage across the capacitor increases in an upward parabolic manner. In addition, in the latter half of the cycle, the current mainly flows through the shunt variable resistor, and the voltage across the current integration capacitor increases in a downward parabolic manner.

〔Example〕

FIG. 1 is a diagram showing an embodiment of the vertical deflection circuit of the present invention.

In this figure, 21 is a transistor that performs switching by a drive pulse synchronized with a vertical synchronization signal, 22.2
8 is a capacitor for current integration, 23 is a DC constant current source whose current value can be varied, 24 is a DC voltage source, and amplifier 25.
A constant current driving transistor 26 modulated by a sawtooth wave signal. The minimum current value of the constant current circuit 150 constituted by the resistor 27 that detects the emitter power supply is determined. 29
3 is a transistor that performs switching by a drive pulse synchronized with a vertical synchronization signal; 30 is a variable resistor for shunting; 3
1.34 is an amplifier, 32 is a variable resistor, 33 is a DC voltage source that determines the position of the screen, 35 is a vertical deflection coil, 36
100 is a sawtooth wave signal generating circuit, 200 is a waveform shaping circuit, and 300 is a vertical deflection coil driving circuit.

2(a) to 2(d) are waveform diagrams of main signals in the vertical deflection circuit shown in FIG. 1.

Next, the operation will be explained.

The transistors 21 and 29 are turned "on" during the vertical retrace period by a drive pulse synchronized with a vertical synchronizing signal as shown in FIG. 2(a) inputted from the base. The capacitor 22, which has been charged in advance by the constant current source 23, is discharged when the transistor 21 is turned on and then charged again when it is turned off, so the change in voltage across it is as shown in Figure 2(b). It comes to show. That is, a sawtooth wave signal is generated, and the amplifier 25 modulates the transistor 26 in response to a change in the voltage of the sawtooth signal input to the inverting input terminal. As a result, the emitter-collector current of the transistor 26 changes as shown in FIG. 2(b).

Now, assuming that the variable resistor 30 is not connected in parallel with the capacitor 28, the transistor 29 is "off".
During this period, the capacitor 28 is charged with the current waveform shown in Fig. 2(b), and the capacitor 28
The change in voltage across both ends is as shown in FIG. 2(C), but since the variable resistor 30 is actually connected, the current will be shunted. If the resistance value of the variable resistor 30 is small, the higher the voltage across the capacitor 28, the easier the current will flow toward the variable resistor 30, and the voltage across the capacitor 28 will be as shown in FIG. 2(d). It changes into a sawtooth shape with complete three-character correction.

Therefore, if this signal is buffered by the amplifier 31 and the vertical deflection coil 35 is driven at a constant current by the amplifier 34, the FS
A screen with good vertical linearity can be obtained even with respect to the tube.

In the vertical deflection circuit of this embodiment, the vertical dimension of the screen is determined by the resistance ratio of the variable resistor 32 and the resistor 36, and the vertical position of the screen is determined by the voltage of the DC voltage source 33.

In addition, the vertical linearity can be adjusted independently at the top and bottom of the screen, and by adjusting the current value of the constant current source 23, the first half of the waveform in Fig. 2(d), that is, the vertical linearity at the top of the screen, can be adjusted independently. By adjusting the linearity and the resistance value of the variable resistor 30, the linearity of the latter half of the waveform shown in FIG. 2(d), that is, the lower part of the screen, can be adjusted. For example, if the current value of the constant current source 23 is increased, the amount of 3-character correction in the first half of the waveform will be increased, and if the resistance value of the variable resistor 30 is decreased, the amount of 3-character correction in the latter half of the waveform will be increased.

In addition, since there is no need to separate the feedback from the vertical deflection coil drive circuit 300 into DC components, parabolic components, etc., it can be realized with a simpler circuit than conventional ones, and an output stage with flat frequency characteristics up to DC can be realized. Easy to configure;
It is possible to realize a vertical deflection circuit that has poor direct current characteristics when operating in an interlaced manner, and has excellent characteristics in which so-called bearings, such as the rask spacing between even and odd fields are not the same, are less likely to occur.

In particular, as the sawtooth wave signal generation circuit 100, the I
Since components built in C can be used, the circuit configuration can be further simplified.

Further, in the above embodiment, the circuit was constructed using bipolar transistors, but the present invention is not limited to this, and may be constructed using FETs or the like.

Furthermore, it goes without saying that it is applicable not only to FS tubes but also to CRTs with a wide-angle deflection equivalent to 110° deflection, and high linearity can be obtained.

〔Effect of the invention〕

As explained above, this invention includes a constant current circuit that outputs a constant current waveform modulated by a sawtooth wave signal, and a constant current circuit that is connected to the output end of this constant current circuit and performs switching using a drive pulse synchronized with a vertical synchronization signal. A waveform shaping circuit consisting of an element, a current integration capacitor connected to the output end of a constant current circuit and in parallel with the element, and a shunt variable resistor connected in parallel with this capacitor. With this feature, not only can a complete three-character correction be performed, but also the linearity at the top and bottom of the screen can be adjusted independently, allowing for sufficient linearity to be obtained even when used for FSS tubes.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an embodiment of the vertical deflection circuit of the present invention;
FIGS. 2(a) to (d) are diagrams for explaining the operation of the vertical deflection circuit of the present invention, FIG. 3 is a diagram showing a conventional vertical deflection circuit, and FIGS. 4(a) to (C) are diagrams for explaining the operation of the vertical deflection circuit of the present invention. FIG. 3 is a diagram for explaining the operation of a conventional vertical deflection circuit. In the figure, 21, 26, 29 are transistors, 22, 28 are capacitors, 23 is a constant current source, 24° 33 is a DC voltage source, 25, 31, 34 is an amplifier, 30, 32 is a variable resistor, and 35 is a vertical Deflection coil, 100 a sawtooth signal generation circuit, 150 a constant current circuit, 200 a waveform shaping circuit, 30
0 is a vertical deflection coil drive circuit. Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] a constant current circuit that outputs a constant current waveform modulated by a sawtooth wave signal; an element connected to the output end of the constant current circuit that performs switching using a drive pulse synchronized with a vertical synchronization signal; The device is characterized by comprising a waveform shaping circuit connected to the output end and consisting of a current integration capacitor connected in parallel with the element, and a shunting variable resistor connected in parallel with this capacitor. vertical deflection circuit.