KR920004810Y1 - High voltage stabilization circuit having op amplifier - Google Patents

Abstract

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Description

High Voltage Stable Circuit Using OP Amplifier

1 is a conventional circuit diagram.

2 is a circuit diagram of an embodiment according to the present invention.

* Explanation of symbols for main parts of the drawings

5: OP amplifier 10: voltage control circuit

20: voltage stabilization circuit FBT: flyback transformer

The present invention relates to a high voltage stabilization circuit of a color television, and particularly to a high voltage stabilization circuit using an OP amplifier that can maintain a constant screen size by reducing a high pressure change rate in a television composed of a double scan and a large CRT. It is about.

In general, the CRT of a color television has a large beam current and direct current reproduction, so the beam current varies greatly depending on the brightness of the screen. Therefore, if the high pressure is not stabilized, the size of the screen changes due to the voltage change.

In other words, when the high pressure is lowered, the deflection intensity is increased, the screen is increased, and when the high pressure is lowered, the deflection sensitivity is lowered and the screen is smaller.

1 is a conventional circuit diagram for solving the above problems, and includes a flyback transformer (FBT), transistors (Q1) to (Q5), resistors (R1-R8), variable resistors (VR1) (VR2), and capacitor ( C1)-(C8), coils L1- (L3), horizontal deflection coil DY, and diodes D1- (D5).

The operation of the circuit will be described. The circuit detects a change in the amount of beam current and stabilizes the high voltage. For example, when the screen is dark, the beam current flows less and the high voltage, which is the anode voltage of the CRT, increases. When the high voltage rises, the ABL (Auto Brightness Limitting) output of the flyback transformer FBT also increases, so that a "high" voltage is applied to the base of the transistor Q5, and the transistor Q5 is "on". When the transistor Q5 is "on", the emitter bias of the transistor Q4 rises through the zener diode ZD2 and the variable resistor VR1, so that the transistor Q4 is "off". Therefore, since the bias of the "high" state is applied to the base of the transistor Q3 through the zener diode ZD1, it is "on", and the transistor Q2 is also "on". Therefore, the size of the screen operates in the reduced direction.

However, when the screen is bright, the CRT high voltage drops because the beam current flows a lot. When the high voltage drops, the ABL output of the flyback transformer FBT also drops. Therefore, the operations of the transistors Q1 to Q5 operate in the opposite direction to when the screen is dark, and thus operate in the direction in which the size of the screen is enlarged.

Therefore, the conventional circuit as described above has a problem in that the rate of change of the size of the screen is large because the high voltage fluctuation rate is large according to the brightness of the screen.

Accordingly, an object of the present invention is to provide a high voltage stabilization circuit using an OP amplifier that can maintain a constant size of the screen regardless of the brightness of the screen in view of the conventional problems as described above.

According to the present invention for achieving the above object, in the high-voltage stabilization circuit having a flyback transformer (FBT) for inputting a horizontal output signal and flowing a beam current to the anode of the CRT, corresponding to the screen brightness of the CRT A voltage regulating circuit 10 for detecting a difference between a predetermined voltage and a predetermined voltage by using an OP amplifier so that the size of the screen is constant regardless of the brightness of the screen, the voltage regulating circuit 10 and the flyback transformer ( A high voltage stabilization circuit 20 which is connected between the FBT and regulates the power supply voltage applied to the flyback transformer FBT in response to the detection output of the voltage regulating circuit 10 so as to make the anode voltage of the CRT always constant. It is prepared.

According to the above configuration, the size of the screen will be maintained at a constant size regardless of the brightness of the screen.

Hereinafter, the configuration and operation will be described in detail with reference to the accompanying drawings.

2 is a circuit diagram of an embodiment according to the present invention, in which a low voltage (+ B1) is connected to a resistor (R1), a low voltage (+ B2) is connected to a resistor (R2), and the resistor (R2) is connected to a resistor (R3). The resistor R1 is connected to the (−) input terminal of the OP amplifier 5, and the resistor R3 is connected to the (+) input terminal of the OP amplifier 5, and the An output terminal is connected to an input terminal with a resistor R4 therebetween (+), a zener diode ZD having a cathode connected between the resistors R2 and R3 and an anode grounded, and the zener diode ZD. The capacitor C1 is connected to the capacitor C1 in parallel to the voltage regulating circuit 10, and a resistor R5 connected to the output of the OP amplifier 5 of the voltage regulating circuit 10 at the base of the transistor Q1. ) Is connected, resistor R8 is connected to the collector, resistor R7 is connected to the emitter, and between the emitter and resistor R7 of the transistor Q1 and between the low voltage (+ B2) R6 is connected, a collector of the transistor Q1 is connected to the base of the transistor Q2, a resistor R9 is connected to the collector, a base of the transistor Q3 is connected to the emitter, and a capacitor C2) is connected, the power supply voltage (+ B3) is commonly connected to the capacitor (C3) and the collector of the resistors (R8), (R9) and the transistor (Q3) and between the collector and emitter of the transistor (Q3) It can be seen that the configuration in which the resistor R10 is connected and the resistor R11 is connected to the emitter of the transistor Q3 corresponds to the high voltage stabilization circuit 20.

In addition, a flyback transformer FBT is connected to a primary side of the emitter of the transistor Q3 of the stabilization circuit 20.

Therefore, the circuit operation of FIG. 2 will be described in detail based on the above-described configuration.

First, when a horizontal output signal applied from the horizontal output terminal is input through the primary side of the flyback transformer FBT, a corresponding beam current flows to the secondary side.

Here, when the screen is bright, a large amount of beam current flows to the secondary side of the flyback transformer FBT, so that the anode high voltage of the CRT is lowered, and thus the ABL output of the flyback transformer FBT is also lowered.

At that time, the low voltage (+ B1) is input to the negative input terminal of the OP amplifier (5) via a resistor (R1) at a voltage corresponding to that when the screen is bright. In addition, when the low voltage (+ B2) is input through the resistor (R2), the reference voltage is set by the zener diode (ZD) and is input to the (+) input terminal of the OP amplifier 5 through the resistor (R3). That is, in this case, the voltages input to the (+) and (-) input terminals are almost the same. Accordingly, the output terminal of the OP amplifier 5 is applied to the base of the transistor Q1 through the resistor R5 to output a low voltage. In addition, the output voltage is fed back to the (+) input terminal through the resistor (R4), the input low voltage (+ B2) is divided by the resistors (R6) and (R7) to the transistor (Q) through the resistor (R6) Is applied to the emitter. Thus, transistor Q1 is " off " so that power supply voltage + B3 is applied to collector through resistor R8, and power supply voltage + B2 is applied to base of transistor Q2. The transistor Q2 is " on " because the voltage applied to the base is high, so the transistor Q3 is also " on " so that the emitter's potential becomes the power supply voltage (+ B3).

Therefore, by increasing the voltage applied to the flyback transformer (FBT) to maintain a high pressure to maintain a constant size of the screen.

However, in contrast to the above case, when the screen is dark, the beam current flows less and the anode voltage of the CRT is increased.

Therefore, the ABL output of the flyback transformer (FBT) is also increased.

At that time, the same voltage is applied to the negative terminal of the OP amplifier 5 as when the screen is dark. However, at the positive input terminal, the reference voltage set by the zener diode ZD and the voltage fed back are input together. Therefore, the output of the OP amplifier 5 becomes larger than when the screen is bright, and therefore, a high voltage is applied to the base of the transistor Q1 through the resistor R5. When the bass voltage becomes lower than the voltage divided by the resistors R6 and R7 when the low voltage + B2 becomes greater than the voltage Q1, the transistor Q1 is turned on so that a low voltage is applied to the base of the transistor Q2. . Therefore, the transistors Q2 and Q3 are " off " and the supply voltage + B3, which is dropped by the resistor R10, lowers the voltage applied to the flyback transformer FBT so that a constant high voltage is always applied to the anode of the CRT. As you feed, the size of the screen is always constant.

As described above, the present invention has an advantage that the size of the screen can be kept constant even if the brightness of the screen changes.

Claims (1)

In a high voltage stabilization circuit having a flyback transformer (FBT) for inputting a horizontal output signal and flowing a beam current to an anode of a CRT, the op amp uses a difference between a voltage corresponding to the screen brightness of the CRT and a predetermined voltage. It is connected between the voltage regulating circuit 10 and the voltage regulating circuit 10 and the flyback transformer (FBT) to detect and uniform the size of the screen irrespective of the brightness of the screen so that the anode voltage of the CRT is always constant. A high voltage stabilization circuit using an OP amplifier, characterized in that the high voltage stabilization circuit 20 for intermittent the power supply voltage applied to the flyback transformer (FBT) in response to the detection output of the voltage regulation circuit (10).