KR900000776Y1 - Speed up devices of beam current auto-control circuits - Google Patents

Abstract

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Description

Speed up device of automatic current control circuit for beam

1 is a conventional circuit diagram.

2 is a circuit diagram of the present invention.

The present invention is a circuit that automatically controls the beam current when the screen becomes bright or dark due to the high or low beam current flowing in the cathode ray tube of the monitor or television receiver, and maintains the screen brightness constant. The present invention relates to a speed up device circuit configuration of a beam current automatic control circuit that changes the image signal level at an early stage and stabilizes the screen brightness.

Conventionally, referring to the circuit illustrated in FIG. 1, the high voltage (HV) is applied to the output terminal 3.4 of the secondary coil by the voltage applied to the input terminals 1 and 2 which are the flyback transformer (FBT) primary coils. The transistor TR21 and the peripheral circuits are induced to flow, and the automatic circuit current control circuit is an automatic beam current control circuit. When the beam current increases (A) and the point potential decreases, the transistor voltage of the transistor TR21 decreases and the emitter potential also decreases. CNT) and Bright (BRT) potentials are also lowered, thereby lowering the video signal level of the video output width, thereby darkening the screen and controlling the flow of a large amount of beam current. On the contrary, the beam current is applied to the flyback transformer (FBT) output terminal. If it decreases, it works contrary to the description above.

At this time, the diode D21 serves to set the level so that the A point suppression is not higher than the B voltage of the diode D21.

However, such a conventional circuit does not control normally at a very short time when the beam current decreases or increases, and is slowly controlled by the capacitor C21 and other time constant circuits. The speed slowed down.

Therefore, since the beam current change is not properly controlled, the reliability of the device is lowered and the screen brightness becomes unstable.

The present invention solves this problem by speeding up the initial control operation of the beam current automatic control circuit, thereby preventing the change of screen brightness, watching a stable screen, and improving the reliability of the device. The purpose of the present invention to provide a speed-up device of the present invention will be described in detail below with reference to the accompanying drawings.

First, referring to Figure 2 the configuration of the present invention. Between the one end of the secondary coil of the flyback transformer (FBT) and the contrast terminal (CNT) and the try terminal (BRT) of the image output circuit (A), the resistors (C1) and diodes (R1-R5, VR1, VR2) Connect a beam current automatic control circuit consisting of DI) and a transistor (TRl), and one end of the flyback transformer (FBT) secondary coil to a collector of the base-grounded transistor (TR2) through a resistor (R1). The emitters of the transistor TR2 are diodes D2 connected in parallel, respectively. It is connected to one end of the flyback transformer (FBT) secondary coil through the capacitor (C2) at the same time as the ground through the resistor (R7) and capacitor (C3).

As shown in FIG. 2, the effect of the present invention is that the beam current control action by the automatic beam current control circuit (b) is the same as that of the conventional FIG. Speed of beam current controller. The following describes the up action.

In other words. In the automatic beam current control circuit, the beam current flows in a constant state while the brightness of the screen does not change. Therefore, the A point voltage is constant and the screen becomes bright while maintaining a constant potential of "+" potential at both ends of the capacitor C2. When the (A) point potential suddenly decreases due to an increase in the beam current at the backtrans (FBT) output terminal 3.4, the voltage on the "+" side of the capacitor C2 abruptly decreases, and the voltage is momentarily on the "_" side of the capacitor C2. A negative voltage (negative voltage) is applied.

Therefore, the transistor TR2 emitter potential becomes lower than the base potential and becomes a forward bias, so that the transistor TR2 is operated (on), and a closed circuit is formed in which the voltage charged in the capacitor C1 discharges instantaneously.

Therefore, at this moment, the collector potential of transistor TR2 is lowered, thereby lowering the (.A) point potential at a short moment when transistor TR2 is operated and thus lowering the transistor (TR,) base potential. By lowering the contrast (CNT) and bright (BRT) voltages, the beam current is quickly restored to normal operation.

After that, when the beam current becomes constant and the point voltage is constant, the capacitor C2 is fully charged and the reverse bias is applied to the transistor TR2 emitter. There should be no bustling in.

On the other hand, when the screen is dark and the beam current decreases, the potential before (A) becomes high and becomes a higher "+" potential across the capacitor (C2), so that a greater reverse bias is applied to the transistor (TR2) emitter, resulting in a collector potential. Since there is no change (A), it does not affect the point potential.

As described above, the screen becomes bright and the transistor TR2 is operated at the initial moment when the beam current increases, so that the potential of the point (A) is lowered so that the automatic beam current control circuit can be operated at an early stage. ) Is off and does not affect the screen.

At this time, the diode D2 prevents the reverse bias from being applied to the transistor TR2 emitter.

As described above, according to the present invention, when the screen of a monitor or television receiver becomes brighter and the beam current increases, the control speed of the beam current is initially increased, and thus the surface can be stabilized quickly, thereby improving the reliability of the device. It is.

Claims (1)

A resistor and a capacitor between one end of the secondary coil of the flyback transformer and the gonast and bright terminals of the video output circuit. In connection with a beam current automatic control circuit consisting of a diode and a transistor. One end of the flyback transformer (FBT) secondary coil 3 is connected to the collector of the base-grounded transistor TR2 via a resistor R6, and the emitter of the transistor TR2 is a diode D2. The speed-up of the beam and current automatic control circuit is made by grounding through the parallel connection of the resistor R7 and the capacitor C3 and connecting to one end of the flyback transformer (FRT) secondary coil 3 via the capacitor C2. Device.