JPH04117073A - Deflecting current controller - Google Patents

Abstract

PURPOSE:To keep a deflecting current fast and constant by immediately inputting a change in parabola voltage arising from a change in the frequency of a synchronous signal to a chopper circuit. CONSTITUTION:This controller consists of a deflection current generation circuit l, a transformer 8, a distortion correction circuit 9, a differential amplifier circuit 14, a chopper circuit 18, a reference bias circuit 22 and a operation amplifier 26. When a parabola voltage obtained from the transformer 8 is superimposed on a prescribed reference bias voltage, the parabola voltage superimposed on the reference bias voltage is compared with the parabola voltage obtained from the transformer 8. Accordingly, since comparison is executed between parabola voltages, even a slight change in the parabola voltage can be immediately transmitted to the chopper circuit 18. Thus, the deflection current can be accurately controlled to be kept quickly and constantly.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a deflection current control device for controlling the deflection current of a CRT (cathode ray tube) in a display device using the CRT. [Prior Art] FIG. 2 is a configuration diagram showing a conventional deflection current control device.
In the figure, 1 is a deflection current generation circuit, which includes an input terminal 2 to which a synchronization signal such as a horizontal synchronization signal is applied, an output transistor 3, a damper diode 4, a resonant capacitor 5,
It is constructed in a known manner by a deflection coil 6, a five-figure correction capacitor 7, and the like. 8 is a transformer such as a fly bank transformer to which the output of the deflection current generating circuit 1 is applied; 9 is a distortion correction circuit that supplies a parabolic voltage for distortion correction as the collector voltage of the transistor 3 through the primary coil of the transformer 8; It is composed of a transistor 10 to which a voltage is applied to the base and a bias resistor 11. 12 is a smoothing circuit to which the output of the transformer 8 is applied, and is composed of a resistor 13a and a capacitor 13b. Reference numeral 14 denotes a differential amplifier circuit, which includes an operational amplifier 17 that compares the output of the smoothing circuit 12 with a reference voltage obtained by a resistor 15 and a Zener diode 16. 18 is controlled by the output of the differential amplifier circuit 14, for example, 140.
This chopper circuit switches the voltage of V, and its chopper output is applied to the collector of the transistor 10 of the distortion correction circuit 9. Next, the operation will be explained. The deflection current generating circuit 1 supplies a deflection current to the deflection coil 6 when the transistor 3 is driven by a synchronization signal such as a horizontal synchronization signal applied to the base of the transistor 3 . In addition, a distortion correction circuit 9 is applied to the flyback pulse generated in the transformer 8 by the output of the deflection current generation circuit 1.
The parabolic voltages generated are superimposed and input to the smoothing circuit 12 through the transformer 8. In the smoothing circuit 12, the parabolic voltage is smoothed and shaped into a DC voltage with almost no ripple. Differential amplifier circuit 14
Now, the reference voltage based on the Zener voltage of the Zener diode 16 is compared with the above DC voltage, and the comparison result is inputted to the chopper circuit 18. Now, if the frequency of the manually input synchronization signal becomes higher, the deflection current will become smaller according to the following equation, and the raster size will change, but along with this, the peak value of the flyback pulse will change. will also become smaller. For this reason, the bias of the parabolic voltage applied to the smoothing circuit 12 becomes low, and as a result, the output of the differential amplifier circuit 14 decreases.
The chopper output of the chopper circuit 18 increases. As a result, the collector voltage of the transistor 3 is increased via the transistor 10 of the distortion correction circuit 9, and the deflection current is kept constant. Conversely, when the frequency of the synchronization signal decreases, the peak value of the flyback pulse increases, and as a result, the output of the differential amplifier circuit 14 increases, so the chopper circuit 18 lowers the collector voltage of the transistor 3, and the deflection current decreases. remains constant. 1,=V, ・TS/Ly・・・・・・1

[Question B that the invention attempts to solve]

Since the conventional deflection current control device is configured as described above, as a method for smoothing parabolic voltage to DC voltage,
An integrating circuit including a resistor 13a and a capacitor 13b is used in the smoothing circuit 12, but the resistance value of the resistor 13a and the capacitance of the capacitor 13b must be increased to some extent in order for the ripple to almost disappear. However, increasing the values of resistance and capacitance increases the time constant, which slows down the response to changes in the input parabolic voltage, resulting in problems such as it takes time to maintain the deflection current at a constant value. This invention was made to solve the above problems, and by immediately inputting changes in parabolic voltage due to changes in the frequency of a synchronization signal to a chopper circuit, it is possible to quickly and accurately control the deflection current. The purpose of this invention is to obtain a deflection current control device that can maintain a constant deflection current.

[Means to solve the problem]

A deflection current control device according to the present invention superimposes a parabolic voltage obtained from a transformer on a predetermined reference bias voltage, and compares the parabolic voltage superimposed on this reference bias voltage with the parabolic voltage obtained from the transformer. This is what I did.

[For use]

Since the deflection current control device according to the present invention compares the parabolic voltages, even a slight change in the parabolic voltage is immediately transmitted to the chopper circuit.

【Example】

An embodiment of the present invention will be described below with reference to the drawings. 1st
In the figure, parts corresponding to those in FIG. 2 are denoted by the same reference numerals, and explanations thereof will be omitted. In FIG. 1, 19 is a differential amplifier circuit to which the parabolic voltage obtained from the transformer 8 is applied. In this differential amplifier circuit 19, 20 is a guide for smoothing pulse components, 2 is a capacitor, 22 is a reference bias generation circuit, resistors 23, 24, and a capacitor 2.
5. 26 is a first comparator;
In this embodiment, an operational amplifier 26 is used. 27 and 28 are bias resistors provided between the differential amplifier circuits 19 and 14. Note that the differential amplifier circuit 14 constitutes a second comparator. Next, the operation will be explained. The parabolic voltage from the distortion correction circuit 9 is superimposed on the flyback pulse generated by the transformer 8 by the output of the deflection current generating circuit 1, and the parabolic voltage from the distortion correction circuit 9 is superimposed on the flyback pulse generated by the transformer 8 by the output of the deflection current generating circuit 1.
is input to. In the differential amplifier circuit 19, first, the diode 20 and the capacitor 21 generate a parabolic voltage from which the pulse component of the flyback pulse has been removed. The above parabolic voltage is input to the non-inverting input terminal of the operational amplifier 26. Further, the parabolic voltage is input to the reference bias circuit 22 and is superimposed on the reference bias voltage created by the capacitor 25 and resistors 23 and 24. The parabolic voltage provided with this reference bias voltage is applied to the inverting input terminal of the operational amplifier 26. As a result, the difference between these inputs is output from the operational amplifier 26, and a DC voltage with the parabola component canceled out is obtained. This DC voltage is compared with a reference voltage by the differential amplifier circuit 14. In response to this comparison result, the chopper circuit 1 controls the collector voltage of transistor 3 via transistor 10 to keep the deflection current constant.

【Effect of the invention】

As described above, according to the present invention, since the parabolic voltage obtained from the transformer and the voltage obtained by applying a predetermined reference bias voltage to this parabolic voltage are compared to obtain the DC voltage, the frequency of the synchronizing signal changes. Changes in the parabolic voltage caused by the change can be immediately input to the chopper circuit, and as a result, it is possible to quickly and precisely control the deflection current to a constant value.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a deflection current control device according to an embodiment of the present invention, and FIG. 2 is a block diagram showing a conventional deflection current control device. 1 is a deflection current generating circuit, 8 is a transformer, 9 is a distortion correction circuit, 14 is a differential amplifier circuit, 18 is a chopper circuit, 22 is a reference bias circuit, and 26 is an operational amplifier. In addition, in the figures, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] a deflection current generation circuit configured to supply a deflection current to the deflection coil by being driven by a synchronous signal; a transformer to which the output of the deflection current generation circuit is applied; and a parabolic voltage applied to the deflection coil through the transformer. a distortion correction circuit that applies a predetermined reference bias voltage to the parabolic voltage obtained from the transformer; and a reference bias circuit that applies a predetermined reference bias voltage to the parabolic voltage obtained from the transformer; a first comparator that compares the output of the first comparator with a reference voltage; and a second comparator that compares the output of the first comparator with a reference voltage.
and a chopper circuit configured to be controlled by the output of the second comparator and to control the distortion correction circuit by the chopper output.