JPH05260334A - Deflection amplitude correcting circuit - Google Patents

Abstract

PURPOSE:To automatically correct the fluctuations of the vertical and horizontal amplitudes caused by the high voltage fluctuations only in a small area of an anode current for a CRT deflection circuit of a TV receiver, etc. CONSTITUTION:When the ABL voltage which varies in response to an anode current is kept in a prescribed small current area, anode current detecting circuit 4 outputs the correction voltage accordand with the ABL voltage. The correction voltage is inputted to each minus terminal of the 1st and 2nd operational amplifiers 5 and 6. At these minus terminals, the voltage is kept at a fixed level in a large current area and then starts to rise by an extent equal to the correction voltage with the start of output of this correction voltage. Meanwhile the present amplitude control voltage is supplied to each plus terminal of both amplifiers 5 and 6 from the vertical and horizontal deflection circuits 8 and 9 respectively. Therefore the voltage is kept at a fixed level between the input terminals of both amplifiers in a large current area and the amplitude is set based on the voltage. When the correction voltage is outputted in the small current area, the voltage is compressed between the input terminals of both amplifiers and therefore the output voltage levels of both amplifiers are reduced. As a result, both vertical and horizontal amplitudes are increased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention, in a cathode ray tube deflection circuit such as a television receiver or a display monitor, automatically changes the vertical and horizontal amplitudes due to variations in the cathode ray tube anode voltage (high voltage) only in a small current area of the cathode ray tube anode current. The present invention relates to a deflection amplitude correction circuit configured to correct.

[0002]

2. Description of the Related Art In deflection in a cathode ray tube, both horizontal deflection and vertical deflection vary in amplitude due to variations in cathode ray tube anode voltage. The fluctuation has a smaller amplitude both horizontally and vertically as the anode voltage increases. This is because the magnitudes of the vertical and horizontal deflection currents are constant regardless of variations in the anode voltage. Further, the anode voltage fluctuates mainly because the anode current changes depending on the video signal. As a conventional general improvement measure for preventing this amplitude fluctuation, improvement of the high-voltage regulation characteristic of the flyback transformer itself or stabilization of the high voltage has been the main. Since then, the technology for stabilizing high voltage has further advanced, and the amplitude fluctuations of television receivers and the like in recent years have been considerably improved.

However, high pressure fluctuations have not disappeared at all. FIG. 2 (A) shows an example of high voltage fluctuations with respect to the average anode current (Ia). In the figure, if I2 is the maximum current (bright image) and I1 is an arbitrary current in the small current region (dark image), Ia is a high-voltage fluctuation between 0 and I1, and ΔV1 is a high-voltage fluctuation between I1 and I2. Greater than ΔV2.
Generally, the high voltage fluctuation in the small current region is larger than that in the large current region, and thus the amplitude fluctuation is also large. This is largely due to the characteristics of the flyback transformer itself.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a deflection amplitude correction circuit which automatically corrects fluctuations in vertical and horizontal deflection amplitudes in the small current region.

[0005]

The present invention is a so-called AB generated on the low potential side of a high voltage winding of a flyback transformer.
Utilizing the L voltage, an anode current detecting means for outputting a correction voltage according to the cathode current of the cathode ray tube only in a range where the anode current is a fixed value or less, and the correction voltage is supplied to an input terminal forming an inverted output, and an in-phase output is provided. A first vertical feedback circuit supplies a vertical amplitude adjustment voltage from a vertical deflection circuit to the input terminal forming the input signal and feeds back the output from the output terminal to the vertical deflection circuit as a vertical amplitude setting voltage.
The correction voltage is supplied to the operational amplifier and the input terminal that forms an inverted output, the horizontal amplitude adjustment voltage from the horizontal deflection circuit is supplied to the input terminal that forms an in-phase output, and the output of the output terminal is used as the horizontal amplitude setting voltage. And a second operational amplifier that feeds back to the horizontal deflection circuit, and provides a deflection amplitude correction circuit that automatically corrects the vertical and horizontal amplitudes in a range in which the anode current is a fixed value or less. is there.

[0006]

When the ABL voltage that changes according to the anode current is in a predetermined small current region, a correction voltage corresponding to the ABL voltage is output, and inverted outputs of the first operational amplifier and the second operational amplifier are output. Input to the eggplant input terminal. The voltage of the input terminal forming the inverted output is constant in the large current region, and starts to rise by the correction voltage when the correction voltage output starts. On the other hand, the current amplitude adjusting voltage is supplied from the vertical deflection circuit and the horizontal deflection circuit to the input terminals forming the in-phase output of the first operational amplifier and the second operational amplifier. Therefore, in the large current region, the voltage between both input terminals maintains a constant value and is set to an amplitude based on the voltage. When the correction voltage is output in the small current region, the voltage between both inputs decreases, and the output voltage of each operational amplifier decreases. As a result, the vertical and horizontal amplitudes increase.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A deflection amplitude correction circuit according to the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram of an essential part showing an embodiment of a deflection amplitude correction circuit according to the present invention, FIG. 2 is a relation (A) of ABL voltage with respect to a cathode ray tube anode current, and others (B to D). It is the figure which showed various characteristic charts. In FIG. 1, 1 is a flyback transformer provided in a horizontal output circuit, N2 is a high voltage winding of the flyback transformer 1, 2 is a low potential side of the high voltage winding N2, 3 is a low potential side of the high voltage winding ABL voltage generated at 2, 4 is an anode current detection circuit, 5 is a first operational amplifier, 6 is a second operational amplifier, 7 is a cathode ray tube (hereinafter referred to as "CRT"), 8 is a vertical deflection circuit, 9 is a horizontal deflection circuit, TR1 is a first transistor (hereinafter referred to as "TR1"), TR2 is a second transistor (hereinafter referred to as "TR2"), R1 is a first resistor, R2 is a second resistor, D1 is a diode.

Next, the operation of the present invention will be described. The high-voltage pulse generated in the high-voltage winding N2 is the high-voltage rectifier diode D2.
Rectified by CRT 7 (hereinafter referred to as "CRT")
Applied to the anode of the anode current Ia (hereinafter “Ia”
Said). The path of Ia flows from the cathode of the CRT 7 through a video circuit or the like (not shown) and returns to the low potential side 2 of the high voltage winding N2 via the resistors R3 and R4. Therefore,
The voltage generated in the resistors R3 and R4 is proportional to the Ia. The ABL voltage 3 means this voltage, and in this embodiment, as shown in the figure, it is the voltage between the intersection of the resistors R3 and R4 and the ground. The relationship between the ABL voltage 3 and Ia is shown in FIG. I1 and I2 of FIG. 2 (A) are made to correspond to (B) of FIG. To have this area, TR2
A predetermined bias voltage obtained by dividing the power source (B3) by R5 and R6 is applied to the emitter of the diode through the diode D1. As a result, TR2 turns on when its base voltage is above a certain level,
It turns off at a voltage lower than that. Therefore, the emitter voltage when TR2 is off is held at a constant voltage determined by the power source (B3) and R5 to R10. And, the ON start point of TR2
Define each constant so as to correspond to I1.

On the other hand, since TR1 and TR2 form an emitter follower circuit, when the base of TR1 changes as shown in FIG. 2B, the emitter of TR2 also tries to change in the same manner. However, since the bias voltage from the diode D1 is applied to the TR2 emitter, AB
The TR2 emitter output with respect to the L voltage is as shown in FIG. That is, the ABL voltage 3 for the anode current I1 is set to V1
Then, if the ABL voltage 3 is V1 or higher, it becomes a constant voltage, and if it is V1 or lower, it follows the ABL voltage 3. In addition, Va, Vb
Is a voltage obtained by dividing the emitter output. The former is for vertical amplitude correction, and the latter is for horizontal amplitude correction. As shown in the figure, the TR2 emitter is provided with a series circuit of two systems, and the Va and Vb
Is obtained by simply dividing the voltage by one series circuit.
You may get Va and Vb. Va and Vb are as shown
It is added to the “−input end” of each of the first operational amplifier 5 and the second operational amplifier 6. Here, “-input end” shown in the figure
Is an input terminal at which the output of the operational amplifier is inverted, and "+ input terminal" is an input terminal at which the output of the operational amplifier is in phase. Hereinafter, the “−input end” is referred to as an “inverting input end”, and the “+ input end” is referred to as an “in-phase input end”.

A vertical amplitude adjusting voltage is applied from the vertical deflection circuit 8 to the in-phase input terminal of the first operational amplifier 5. The vertical amplitude adjusting voltage is a voltage when the vertical amplitude is adjusted to an appropriate amplitude by a vertical amplitude adjusting volume or the like. Similarly, the horizontal deflection circuit 9 is applied to the in-phase input terminal of the second operational amplifier 6.
The horizontal amplitude adjustment voltage is applied. Here, each amplitude is adjusted in a large current region where the anode current Ia is I1 or more (region where ABL voltage is V1 or more). From the above, each amplitude is set by the voltage of each operational amplifier output. Further, each deflection circuit has such a characteristic that vertical and horizontal amplitudes become smaller as the voltages (Vc and Vd) of the operational amplifier output become larger. FIG. 2D shows this relationship.

In the region where the ABL voltage is V1 or higher, the voltage between the input terminals of each operational amplifier does not change, and therefore the amplitude at the time of the above adjustment remains (vertical and horizontal). However, when the ABL voltage is V1 or less, that is, when the anode current Ia is in the small current region of I1 or less, the emitter voltage of TR1 rises from the above description, TR2 turns on, and Va and Vb start to increase. Figure 2
As shown in (C), Va and Vb increase as the ABL voltage decreases. At this time, since the voltage at each in-phase input terminal is constant as described above, the increase in Va and Vb decreases the outputs Vc and Vd due to the differential amplification effect of the operational amplifier. Vc and
The decrease in Vd acts to increase each amplitude from FIG. 2 (D). By this action, the vertical and horizontal amplitudes are automatically corrected by following the anode current.

[0012]

As described above, according to the present invention, the fluctuation of the deflection amplitude due to the high voltage fluctuation of the cathode ray tube anode is automatically corrected only in the small current region of the anode current. The stability of each horizontal amplitude is further improved.

[Brief description of drawings]

FIG. 1 is a block diagram of a main part of an embodiment of a deflection amplitude correction circuit according to the present invention.

2A and 2B are conceptual characteristic diagrams for explaining the present invention, in which FIG. 2A is a high voltage fluctuation characteristic diagram with respect to an anode current;
(B) is an ABL voltage characteristic diagram with respect to the anode current,
(C) is an emitter output characteristic diagram of the second transistor with respect to the ABL voltage, and (D) is a vertical and horizontal amplitude characteristic diagram with respect to the output of the operational amplifier.

[Explanation of symbols]

 1 Flyback transformer N2 High voltage winding of flyback transformer 1 Low potential side of high voltage winding N2 3 ABL voltage 4 Anode current detection circuit 5 First operational amplifier 6 Second operational amplifier 7 Braun tube (CRT) 8 Vertical deflection Circuit 9 Horizontal deflection circuit TR1 1st transistor TR2 2nd transistor R1 1st resistance R2 2nd resistance D1 Diode

Claims (2)

[Claims] 1. In a cathode ray tube deflection circuit, a so-called ABL voltage generated on a low potential side of a high voltage winding of a flyback transformer is used to adjust a correction voltage corresponding to an anode current of a cathode ray tube so that the anode current is below a certain value. The correction voltage is supplied to the anode current detection means that outputs only in the range and the input terminal that forms the inverted output, and the vertical amplitude adjustment voltage from the vertical deflection circuit is supplied to the input terminal that forms the in-phase output, and the output of the output terminal A first operational amplifier that feeds back to the vertical deflection circuit as a set voltage of the vertical amplitude, and the correction voltage is supplied to an input terminal that makes an inverting output, and a horizontal amplitude adjustment voltage from the horizontal deflection circuit to an input terminal that makes an in-phase output. And a second operational amplifier which feeds back the output of the output terminal to the horizontal deflection circuit as a set voltage of horizontal amplitude. A deflection amplitude correction circuit, which automatically corrects each amplitude so that the amplitude is constant. 2. A first PNP type of the anode current detecting means, wherein the ABL voltage is supplied to the base, the collector is grounded, and the emitter is connected to a power source through a first resistor.
And a base connected to the emitter of the first transistor, a collector connected to a power supply through a second resistor, and an NPN-type first transistor in which a series circuit including a plurality of resistors is provided between the emitter and ground. 2 transistors and a diode whose cathode end is connected to the emitter of the second transistor and whose anode end is supplied with a predetermined voltage,
The deflection amplitude correction circuit according to claim 1, wherein a division voltage in the series circuit provided at the emitter of the second transistor is used as a correction voltage.