KR20000009176U - Monitor grid voltage stabilization circuit - Google Patents

Abstract

The present invention relates to the control grid voltage stabilization circuit of the monitor, the circuit of the present invention is the collector stage receives the -DC voltage from the high voltage circuit 10, the emitter stage is connected to the control grid (G1) of the water pipe and the base stage A PNP type first transistor Q11 connected to the collector terminal through the first resistor R11 and turned on by the first resistor R11; The collector terminal is connected to the base terminal of the first transistor Q11, the emitter terminal is grounded through the zener diode ZD11, and the base terminal is connected to the first transistor Q11 through the second and third resistors R12 and 13. A PNP type second transistor Q12 connected in parallel between control grids G1 and turned on by the second and third resistors R12 and R13; And one end connected in parallel between the first transistor Q11 and the control grid G1 and the other end connected in parallel between the second transistor Q12 and the zener diode ZD11. When the transistors Q11 and Q12 are turned on, the fourth resistor R14 for clamping the -DC voltage output from the high voltage circuit 10 to the constant voltage by the zener diode ZD11 and supplying it to the control grid G1. Since the control grid (G1) voltage is always kept constant even if the amount of beam current flowing through the water pipe changes, the effect of the control grid (G1) voltage on the screen brightness is minimized. .

Description

A circuit for stabilizing a G1 of a monitor

The present invention relates to a control grid voltage stabilization circuit of a monitor, and more particularly, to a control grid voltage stabilization circuit of a monitor that is designed to maintain a constant control grid voltage at all times even when the amount of beam current flowing through the receiving pipe is changed.

Referring to Figure 1 looks at the high-voltage circuit and the peripheral circuit of the general monitor as follows.

The high voltage circuit 2 stabilizes the power supply voltage supplied through the switching power supply circuit SMPS to the voltage B + through the DC / DC converter 3 and then boosts the voltage through the flyback transformer FBT of the high voltage circuit 2. Let's do it.

Accordingly, when power is supplied to the monitor and the horizontal deflection circuit starts operation, the high voltage circuit 2 generates a high pressure required in the water pipe and supplies it to the control grid, the focus grid, the screen grid, and the like.

At this time, about -120 output from the flyback transformer (FBT) of the high-voltage circuit (2) V _pp The voltage of the degree is negative (-) rectified through the diode (D1) and capacitor (C1) and then supplied to the control grid (G1) of the water pipe, and controls the amount of electrons emitted from the cathode of the water pipe to modulate the luminance ( Brightness modulation).

The control grid (G1) is generally made of stainless steel cylindrical, the hole surrounding the cathode is drilled by a small hole of about 0.6mm to make a thin electron beam and to control the amount of electrons generated in the cathode.

At this time, the larger the negative (-) voltage is supplied to the control grid (G1), the greater the power for suppressing the electron emission of the cathode, so the amount of electrons colliding with the fluorescent film is reduced and the screen becomes dark.

Meanwhile, the DC / DC converter 3 changes the magnitude of the input power voltage according to the horizontal frequency by using the power supply voltage output from the switching power supply circuit SMPS (these voltages are referred to as B + voltages). It serves to supply the circuit 2 or the horizontal deflection circuit.

At this time, since the flyback transformer (FBT) is connected to the load of the water pipe (CRT), the DC / DC converter (3) as the number of beam current (Beam Current) less and less (in accordance with the change in brightness of the screen) ) It is designed to regulate B + voltage. In other words, after sensing the voltage output from the secondary side of the flyback transformer (FBT) and properly signal processing, the feedback voltage (PWM) to the PWM controller 1 V _fb ), You can adjust B +.

For example, when the beam current increases and the anode voltage (high voltage) falls, the feedback voltage ( V _fb ) Decreases, thereby increasing the B + voltage, thereby increasing the high pressure generated from the flyback transformer (FBT). On the contrary, when the beam current decreases and the anode voltage (high voltage) increases, the feedback voltage ( V _fb ) Rises, thereby lowering the B + voltage, thereby lowering the high pressure generated from the flyback transformer (FBT), thereby keeping the high pressure constant.

However, as described above, the conventional monitor is controlled according to the beam current change because the magnitude of the B + voltage changes as the beam current flowing through the water pipe changes and the magnitude of the secondary output voltage of the flyback transformer (FBT) changes. There was a problem that the grid G1 voltage was also sensitively changed.

Accordingly, the present invention has been made to solve the problems of the prior art as described above, the control grid voltage of the monitor to always maintain a constant control grid (G1) voltage even if the amount of beam current flowing through the water pipe is changed. The purpose is to provide a stable circuit.

The control grid voltage stabilization circuit of the monitor according to the present invention for achieving the above object,

In the high-voltage circuit for negative rectifying the AC voltage output from the flyback transformer through a diode and a capacitor to supply to the control grid of the water pipe,

A PNP type first transistor in which a collector terminal receives a -DC voltage from the high voltage circuit, an emitter terminal is connected to the control grid, and a base terminal is connected to the collector terminal through a first resistor, and turned on by the first resistor;

The collector terminal is connected to the base terminal of the first transistor, the emitter terminal is grounded through a zener diode, and the base terminal is connected in parallel between the first transistor and the control grid through the second and third resistors. A PNP type second transistor turned on by the second transistor; And

One end is connected in parallel between the first transistor and the control grid and the other end is connected in parallel between the second transistor and the zener diode, and when the first and second transistors are turned on, the -DC voltage output from the high voltage circuit is turned on. And a fourth resistor for clamping the zener diode at a constant voltage to supply it to the control grid.

1 is a circuit diagram showing a high voltage circuit and a peripheral circuit of a general monitor;

2 is a circuit diagram showing a control grid voltage stabilization circuit of the monitor according to the present invention.

* Explanation of symbols for main parts of the drawings

10: high voltage circuit 20: voltage compensation unit

Q 11,12: first and second transistor ZD11: zener diode

R 11,12,13,14: 1,2,3,4 resistors

Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

2 is a circuit diagram showing a control grid voltage stabilization circuit of the monitor according to the present invention.

As shown in FIG. 2, the circuit of the present invention includes a high voltage circuit 10 which rectifies an AC voltage output from a flyback transformer FBT by a diode D1 and a capacitor C1; The control grid voltage supply unit 20 supplies the control grid voltage G1 to the control grid G1 of the water pipe by subtracting the correction voltage by the amount of change of the -DC voltage from the -DC voltage input from the high voltage circuit 10.

In the control grid voltage supply unit 20, the collector terminal receives the -DC voltage from the high voltage circuit 10, the emitter terminal is connected to the control grid (G1) and the base terminal through the first resistor (R11). A PNP type first transistor Q11 connected to a stage and turned on by the first resistor R11; The collector terminal is connected to the base terminal of the first transistor Q11, the emitter terminal is grounded through the zener diode ZD11, and the base terminal is connected to the first transistor Q11 through the second and third resistors R12 and 13. A PNP type second transistor Q12 connected in parallel between control grids G1 and turned on by the second and third resistors R12 and R13; And one end connected in parallel between the first transistor Q11 and the control grid G1, and the other end connected in parallel between the second transistor Q12 and the zener diode ZD11. When the transistors Q11 and Q12 are turned on, the fourth resistor R14 for clamping the -DC voltage output from the high voltage circuit 10 to the constant voltage by the zener diode ZD11 and supplying it to the control grid G1. It consists of.

Next, the operation and effects of the circuit according to the present invention configured as described above will be described in detail.

1. Initial operation

When the flyback transformer FBT operates and the (A) point voltage gradually drops from 0 V to the negative (-) voltage, the base voltage of the first transistor Q11 changes with the (A) point voltage, and the control grid G1 The voltage is maintained at 0 V until the first transistor Q11 is turned on.

(A) When the point voltage reaches a negative (-) voltage enough to turn on the first transistor Q11, the control grid G1 voltage is the first resistor R11, the second resistor R12, and the third resistor. (R13) and have a voltage formed by the difference between the emitter voltage and the base voltage of the first transistor Q11.

At this time, as the voltage of the control grid G1 falls negatively, the fourth resistor R14 forms a path of the emitter current of the second transistor Q12 so that the zener diode ZD11 can maintain a constant voltage.

2. -DC voltage decreases

When the -DC voltage output from the high voltage circuit 10 decreases, that is, when the (A) point voltage is lowered, the base voltage of the first transistor Q11, that is, the (C) point voltage is lowered, so that the first transistor Q11 is reduced. As the current flowing from the emitter stage to the collector stage increases, the emitter voltage of the first transistor Q11, that is, the (D) point voltage, decreases, and thus the base voltage of the second transistor Q12, that is, the (B) point voltage. Is lowered.

At this time, the difference between the emitter voltage and the base voltage of the second transistor Q2 increases, and as the current flowing from the emitter end of the second transistor Q12 to the base end increases, the base voltage of the first transistor Q11, i.e. Since the (C) point voltage increases, the emitter voltage of the first transistor Q11, that is, the (D) point voltage increases.

Accordingly, when the -DC voltage output from the high voltage circuit 10 decreases, the control grid voltage supply unit 10 corrects the amount of the reduction through the control grid voltage supply unit 10 and supplies the correction amount to the control grid G1 of the water pipe.

2. -DC voltage increases

When the -DC voltage output from the high voltage circuit 10 increases, that is, when the (A) point voltage increases, the base voltage of the first transistor Q11, that is, the (C) point voltage increases, and thus the first transistor Q11 As the current flowing from the emitter stage to the collector stage decreases, the emitter voltage of the first transistor Q11, that is, the (D) point voltage increases, so that the base voltage of the second transistor Q12, that is, the (B) point voltage, increases. Increases.

At this time, the difference between the emitter voltage and the base voltage of the second transistor Q12 decreases, and as the current flowing from the emitter end of the second transistor Q12 to the base end decreases, the base voltage of the first transistor Q11 is decreased. That is, since the (C) point voltage is decreased, the emitter voltage of the first transistor Q11, that is, the (D) point voltage is reduced.

Accordingly, when the -DC voltage output from the high voltage circuit 10 is increased, the amount is corrected by the increase amount through the control grid voltage supply unit 10 and then supplied to the control grid G1 of the water pipe.

As described above, the circuit according to the present invention maintains the control grid voltage G1 constantly even when the amount of beam current flowing through the water pipe changes, thereby controlling the effect of the control grid voltage on the screen brightness. Minimize the effect.

Claims (1)

In the high voltage circuit 10, the AC voltage outputted from the flyback transformer FBT is rectified negatively through the diode D1 and the capacitor C1 and supplied to the control grid G1 of the water pipe CRT. , The collector terminal receives the -DC voltage from the high voltage circuit 10, the emitter terminal is connected to the control grid G1, and the base terminal is connected to the collector terminal through the first resistor R11, thereby the first resistor R11. PNP type first transistor Q11 turned on by < RTI ID = 0.0 > The collector terminal is connected to the base terminal of the first transistor Q11, the emitter terminal is grounded through the zener diode ZD11, and the base terminal is connected to the first transistor Q11 through the second and third resistors R12 and 13. A PNP type second transistor Q12 connected in parallel between control grids G1 and turned on by the second and third resistors R12 and R13; And One end is connected in parallel between the first transistor Q11 and the control grid G1, and the other end is connected in parallel between the second transistor Q12 and the zener diode ZD11, and the first and second transistors are connected. When Q11 and Q12 are turned on, the -DC voltage output from the high voltage circuit 10 is clamped by the zener diode ZD11 to a constant voltage to the fourth resistor R14 for supplying to the control grid G1. A control grid voltage stabilization circuit of a monitor, characterized in that it is configured.