JPS6150427B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION As is well known, in color television receivers, unless a special correction circuit is provided, so-called left-right pincushion distortion occurs in which the width at the top and bottom of the screen is larger than that at the center. A method for removing this pincushion distortion is described in "Funkschau Magazine, 1966, No. 22, 689.
690, in which the amplitude of the horizontal deflection current is modulated by a vertical frequency correction voltage,
The amplitude is made to decrease at the upper and lower edges of the screen. In this case, the modulation of the horizontal deflection current can be carried out by passive elements, for example transductors, or by additional other modulators. In this case, the sawtooth wave vertical frequency correction voltage derived from the vertical deflection circuit needs to be shaped. This voltage must first be converted into a parabolic correction voltage, then made adjustable for amplitude adjustment of the correction voltage, and then amplified to have the amplitude and power required for modulator control.

For this purpose, in the case of the known circuit (Telefunken television receiver with type 712 chassis) a pincushion distortion correction amplifier is provided with a total of four transistors. In this amplifier, the amplitude of the correction voltage, that is, the amount of correction for pincushion distortion, is adjusted by a potentiometer provided between two transistor stages of the amplifier.
A further potentiometer adjusts the operating point of the transistor stage. This shifts the DC voltage level of the correction voltage. This adjustment effect is used to adjust the amplitude of the horizontal deflection current.
Since these adjustments need to be made independently of each other, many circuit elements are required.

It is an object of the invention to reduce the outlay for a circuit of this type for shaping the correction voltage for left-right pincushion correction.

This problem is solved by the structure described in claim 1 of the present invention.

The circuit of the invention offers many advantages. First, in order to solve the above problem, many circuit elements, for example, 1
One transistor, six resistors, and two capacitors are saved. Furthermore, the available operating voltages can be better utilized. In the known circuit, the correction voltages at the first two transistor stages of the amplifier are set to a fixed value and can each have only one predetermined amplitude, taking into account deviations. In a range exceeding this amplitude, therefore, no adjustment can be made any longer in the subsequent circuit with the adjustable potentiometer. In contrast, in the circuit according to the invention, both adjustments take place in a circuit upstream of the one-stage amplifier and in cooperation with this amplifier stage. This amplifier stage is directly powered by a correction voltage derived and shaped from the vertical deflection circuit. This makes it possible to better utilize the amplitude range for the correction voltage, which is predetermined by the operating voltage. This is because the previous adjustment makes it possible to compensate for the narrowness of the permissible operating range of the component. A second advantage is that the adjustment of the AC voltage negative feedback path simultaneously changes the waveform of the correction voltage at the output side of the amplifier. It is precisely this variation of the correction voltage that matches the actual requirements for correction. This will be explained next.

Circuits for pincushion distortion correction are usually constructed as modules. In order to be able to use this module as widely as possible, it is desirable to be able to use the same module to correct the left-right pincushion distortion not only of the known AX device, but also of other deflection devices. For example, Japanese deflectors have substantially different pincushion distortions. For example, in the case of a 20AX-device, if distortion is corrected using a parabolic correction voltage, residual distortion persists in the form of a narrow portion at the center of the screen. This narrow portion corresponds to a 100Hz vibration, the zero-crossing points of this vibration correspond to the top and bottom edges of the screen, and the maximum values correspond to the top and bottom thirds of the screen and the center of the screen. . For the removal of this residual strain, a parabolic current with a high order index is therefore required for the AX-device. By the way, when a deflection device made in Japan, for example, is controlled by this circuit, a residual distortion whose phase is inverted from that of the residual distortion of the 20AX-device remains. Therefore, on the image-receiving surface, a bulge appears at the center of the screen and points at the top and bottom corners of the screen. This distortion itself is eliminated by increasing or decreasing the amplitude value within a predetermined range using a diode (German Published Patent Application No. 2424174). However, this solution requires an optionally insertable matching circuit, which limits the compatibility of the correction device. However, the circuit of the invention automatically adapts to changing conditions in the case of said residual distortions in the case of amplitude adjustment of the correction voltage. In this case it is advantageous that the Japanese deflection device requires only one-third the amplitude of its correction voltage compared to the 20AX device.

In the case of the circuit of the present invention, since the amplitude of the correction voltage for left and right pincushion distortion is changed by changing the amount of negative feedback, the exponent of the parabolic function can also be changed, so that it depends on the amplitude in order to remove the aforementioned residual distortion. You will be able to respond by doing so.

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows a deflection circuit for a color television receiver. The figure shows a picture tube 1, a horizontal deflection circuit 3 synchronized with a horizontal synchronization pulse 2, a horizontal deflection coil 4, a vertical deflection circuit 6 synchronized with a vertical synchronization pulse 5, and a vertical deflection coil 7. . A modulator 8 is inserted and connected to the current path of the horizontal deflection current. This modulator modulates the amplitude of the horizontal deflection current to correct left-right pincushion distortion. The correction circuit 8 is controlled by a vertical frequency parabolic correction voltage 30 from the output terminal 9 of the amplifier 10. A vertical frequency sawtooth voltage 12 is applied to an input terminal 11 of the amplifier 10 from the vertical deflection circuit 6 . 1
The stage amplifier 10 has an adjustable AC voltage negative feedback path. With this AC voltage negative feedback path, only the amplification degree of the AC voltage can be adjusted without shifting the level of the DC voltage of the signal at the terminal 9. Through this adjustment, desired pincushion distortion can be corrected. Furthermore, the operating point of amplifier 10 and thus the DC voltage level of the signal at terminal 9 can be adjusted. The adjustable DC voltage superimposed on the AC voltage also acts as a modulating voltage for the modulator 8, i.e. for the amplitude of the horizontal deflection current.
act.

Therefore, the amplitude of the horizontal deflection current can be adjusted independently of the amount of pincushion distortion correction. The function of the modulator 8 for controlling the amplitude of the horizontal deflection current is therefore also used in this case to set the operating point for the adjustment of the amplitude of the horizontal deflection current.

FIG. 2 shows the circuit configuration of the amplifier 10. Capacitor 13 and diode 14 adjust the sawtooth voltage so that its positive peak is the voltage across the potentiometer. By adjusting this voltage with the potentiometer 15, the voltage 1
2 DC levels can be shifted. Since the base of the transistor 27 is connected to the base of the transistor 27 via the resistors 17 and 21, this shift causes the operating point of the transistor 27 to change, and thus the terminal 9
The level of the DC voltage of the correction voltage 30 at is also shifted. In this case the amplitude of voltage 30 is not changed. Thus, the amplitude of the horizontal deflection current can be adjusted by the potentiometer. Resistor 16 is used as a series resistor. The amplifier having the transistor 27 as an amplifying element further includes resistors 20,1
It has a DC voltage negative return path consisting of 9 and 21. This negative feedback path also performs a phase rotation effect using capacitors 18 and 22. Resistor 23 is used to correct trapezoidal distortion.

Adjustable AC voltage negative feedback path is capacitor 24
and is adjusted by a potentiometer 26. This potentiometer together with resistor 25 forms the operating resistance of transistor 27.
Moving the sliding tap of potentiometer 26 toward the collector of transistor 27 increases the amount of negative feedback, thereby decreasing the amplitude of the correction voltage at terminal 9. In this case, due to the phase rotation effect of the negative feedback path, the waveform of the parabolic correction voltage 30 is also changed as desired, as described above. Sawtooth voltage 12
The transformation from to parabolic voltage 30 is carried out by means of an integrating network provided in the signal path. In this case, capacitor 24 is also used for integrating this voltage as a Miller integrating capacitor with a capacitance enlarged by the value of the amplification of transistor 27.

In the actual prototype embodiment, the elements of the circuit of FIG. 2 have the following values.

R15=2.5KΩ R16=10KΩ R17=33KΩ R19=8.2KΩ R20=120KΩ R21=68KΩ R23=25KΩ R25=2.7KΩ R26=10KΩ C13=1μF C18=1.15μF C22=0.22μF C24=0.033μF Diode 14 = 1N4148 type Transistor 27 = BC2378 type

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a deflection circuit having an amplifier according to the present invention, and FIG. 2 shows an example of an actual prototype amplifier according to the present invention. 1... picture tube, 3... horizontal deflection circuit, 4... horizontal deflection coil, 6... vertical deflection circuit, 7... vertical deflection coil, 10... amplifier.

Claims (1)

[Claims] 1. A vertical frequency voltage that modulates the amplitude of the horizontal deflection current is supplied via an amplifier, the AC voltage amplification degree of the amplifier is adjustable in order to change the amplitude of the correction voltage, and the amplitude of the horizontal deflection current is adjusted. In a left/right pincushion distortion correction circuit in a color television receiver in which the operating point of the amplifier can be adjusted in order to change the amplitude of It consists of a one-stage DC and AC voltage amplifier having a DC voltage negative feedback path and an adjustable operating point. A right and left pincushion distortion correction circuit for a color television receiver, characterized in that the waveform of the left and right pincushion is selected so as to change the waveform of the signal. 2. The left and right circuits according to claim 1, in which an AC voltage negative feedback path is formed from a capacitor 24, and the capacitor is connected between the adjustment tap of the collector resistor 26 and the base of the transistor 27 constituting the amplifier 10. Pincushion distortion correction circuit. 3. The left-right pincushion distortion correction circuit according to claim 1, wherein the operating point of the amplifier is adjusted by changing the clamp potential of the clamp circuits 13-15 with respect to the vertical frequency voltage 12 guided to the amplifier 10.