KR20000009202U - Monitor spot elimination circuit - Google Patents

Abstract

The present invention relates to a spot elimination circuit of the monitor, the circuit of the present invention is a microcomputer 10 for outputting a low level mute signal in normal operation and a high level mute signal in mode switching; In the receiving tube comprising a mute circuit 20 for suppressing the amount of electrons emitted from the cathode to the fluorescent film by boosting the negative voltage applied to the control grid G1 when a high level mute signal is input, A charging capacitor C11 for charging by receiving a predetermined power supply voltage Vcc in normal operation; When the power supply voltage Vcc decreases when the power is turned off and reaches a predetermined level, the switching transistor Q11 is switched on to supply the charging voltage of the charging capacitor C11 as a mute signal of the mute circuit 20. It is further included to reduce the spot by suppressing the amount of electrons emitted from the cathode to the fluorescent film by boosting the negative voltage applied to the control grid G1 by using the mute function when the power is turned off. It works.

Description

An apparatus for deleting a sport in a monitor

The present invention relates to a spot elimination circuit of a monitor, and in particular, by depressing a negative voltage applied to a control grid when the power is turned off, the spot elimination of a monitor designed to weaken spots by suppressing the amount of electrons emitted from the cathode to the fluorescent film. It is about a circuit.

In general, supplying the necessary voltage (rated voltage) to each monitor circuit at the time of monitor mode switching causes an abnormality to each monitor circuit. Therefore, at the beginning of mode switching, each monitor circuit may warm up and then operate normally. It is necessary to supply a ready voltage so that the rated voltage is lower than the rated voltage.

This is called a mute function, and a mute signal for performing the mute function is output from the microcomputer.

The mute signal maintains a low level during normal operation and then transitions to a high level for a while when switching modes. At this moment, the amount of electrons emitted from the cathode to the fluorescent film is suppressed by boosting the control grid voltage supplied to the water pipe.

In general, a spot is a small light point generated when an electron beam collides with a fluorescent film of a cathode ray tube. When a monitor is turned on, the cathode of the electron gun is sufficiently heated to emit electrons. The electrons collide with the fluorescent film to generate spots.

In order for a screen to appear on the receiving tube, one spot must appear on the fluorescent film, and the spot must be deflected from side to side to make a raster, and the brightness of the spot must be changed as an image signal.

This spot can be controlled by the control grid current supplied from the flyback transformer (FBT) to the water tube, which controls the luminance modulation by controlling the amount of electrons emitted from the cathode of the water tube.

At this time, the larger the negative voltage is supplied to the control grid, the greater the power for suppressing the electron emission of the cathode, so that the amount of electrons colliding with the fluorescent film is reduced and the screen is darkened by weakening the spot.

FIG. 1 is a circuit diagram illustrating a mute circuit of a general monitor. As described above, the microcomputer 10 outputs a low level mute signal during normal operation, and then outputs a high level mute signal for a while when switching modes.

First, when the microcomputer 10 outputs a low level mute signal during normal operation, the low level mute signal is input to the base terminal of the PNP type first transistor Q1 through the resistor R1, and thus the first transistor. Since Q1 is turned on and the first transistor Q1 is turned on, the PNP-type second transistor Q2 is turned off, so that a DC voltage of -60V output from the flyback transformer FBT is divided by the distribution resistor R5. R6) drops down to about -40V and is supplied to the control grid G1 of the water pipe.

On the contrary, if the microcomputer 10 outputs a high level mute signal during mode switching, the high level mute signal is inputted to the base terminal of the first transistor Q1 through the resistor R1 and thus the first transistor ( Since Q1 is turned off and the second transistor Q2 is turned on as the first transistor Q1 is turned on, a DC voltage of −60 V output from the flyback transformer FBT is applied to the first transistor (Q1). It is supplied to the control grid G1 of the water pipe as it is through Q1).

That is, while the monitor is normally operated, a DC voltage of about -40V is applied to the control grid G1, but when a mute function is performed, a DC voltage of about -60V is applied to the control grid G1, thereby performing a mute function. At that time, the screen is darkened by suppressing electron emission.

When the power of the conventional monitor is turned off, since the charged cathode of the receiving tube is not yet cooled, the charge charged at a high pressure by the capacitance applied between the inner and outer conductive films of the receiving tube remains for a long time. As a result, the spot absorbs some electrons from the cathode. However, since the deflection circuit is stopped due to the power off, the emitted electrons are not deflected, but are emitted to the center of the water pipe, hitting the fluorescent film, thereby causing a strong spot.

Therefore, the present invention was devised to solve the above problems of the prior art, and by boosting the negative voltage of the control grid by using the mute function when the power is off, the amount of electrons emitted from the cathode to the fluorescent film It is an object of the present invention to provide a spot removing circuit of a monitor which is designed to suppress spots and weaken spots.

Spot removal circuit of the monitor according to the present invention for achieving the above object,

A microcomputer that outputs a low level mute signal when the monitor is in normal operation and a high level mute signal when the mode is switched; In the monitor comprising a mute circuit for suppressing the amount of electrons emitted from the cathode to the fluorescent film by boosting the negative voltage applied to the control grid when a high level mute signal is input,

A charging capacitor charged with a predetermined power supply voltage during normal operation;

When the power supply is turned off when the power supply voltage is reduced to reach a predetermined level, the switching transistor for supplying the charging voltage of the charging capacitor as a mute signal of the mute circuit is characterized in that the configuration further comprises.

1 is a circuit diagram showing a mute circuit of a general monitor;

2 is a circuit diagram illustrating a spot removing circuit of the monitor according to the present invention.

* Names of symbols for main parts of the drawings

10: micom 20: mute circuit

Q11: switching transistor C11; Rechargeable Capacitor

D11: discharge blocking diode FBT: flyback transformer

Q 1,2: first and second transistors D 1,2: first and second diodes

C1: smoothing capacitor R 1,2,3,4,5,6,11: resistor

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

2 is a circuit diagram illustrating a spot removing circuit of the monitor according to the present invention.

The present invention, as shown in Figure 2, the monitor outputs the mute signal of the low level in the normal operation, and the microcomputer 10 for outputting the high level mute signal when switching the mode; A monitor comprising a mute circuit 20 for suppressing an amount of electrons emitted from a cathode to a fluorescent film by boosting a negative voltage applied to a control grid G1 when a mute signal having a high level is input. A charging capacitor C11 connected to a power supply circuit and the other end connected to a ground and charged with a predetermined power supply voltage Vcc during normal operation; The emitter stage is connected in parallel between the power supply circuit and the charging capacitor C11, the collector stage is connected in parallel to the mute signal supply line through the resistor R12, and the base stage is connected to the emitter stage through the bias resistor R11. PNP type switching transistor connected to switch the power supply voltage Vcc when the power supply is turned off when the power supply voltage Vcc is reduced and reaches a predetermined level, thereby supplying the charging voltage of the charging capacitor C11 as a mute signal of the mute circuit 20. (Q11); It is further connected in series between the power supply circuit and the charging capacitor (C11), the discharge blocking diode (D11) for blocking the discharge to the power supply circuit when the charging capacitor (C11) to discharge the charge voltage further includes do.

Looking at the operation and effect of the present invention configured as described above divided into the normal operation and the power off of the monitor as follows.

1. In normal operation

When the monitor operates in a normal state, the charging capacitor C11 is charged by receiving a predetermined power supply voltage Vcc from the power supply circuit.

Therefore, the mute circuit 20 operates by the mute signal supplied from the microcomputer 10.

That is, when the microcomputer 10 outputs a low level mute signal in the normal operation, the low level mute signal is input to the base terminal of the first PNP type transistor Q1 through the resistor R1 and thus the first signal. As the transistor Q1 is turned on and the first transistor Q1 is turned on, the PNP-type second transistor Q2 is turned off, so that a DC voltage of -60 V output from the flyback transformer FBT is divided into a distribution resistor ( R5 and R6 are dropped to about -40V and are supplied to the control grid G1 of the water pipe.

On the contrary, if the microcomputer 10 outputs a high level mute signal during mode switching, the high level mute signal is inputted to the base terminal of the first transistor Q1 through the resistor R1 and thus the first transistor ( Since Q1 is turned off and the second transistor Q2 is turned on as the first transistor Q1 is turned on, a DC voltage of −60 V output from the flyback transformer FBT is applied to the first transistor (Q1). It is supplied to the control grid G1 of the water pipe as it is through Q1).

2. When power off

When the power supply voltage Vcc supplied from the power cycle is reduced and reaches a predetermined level when the power is turned off, the switching transistor Q11 is switched on by the bias resistor R11, and thus the charging capacitor C11 is turned on. Is charged and supplied to the mute circuit 20 through the resistor R12 through the emitter-collector stage of the switching transistor Q11.

The voltage discharged into the mute circuit 20 is used as a high level mute signal to operate the mute circuit 20.

That is, as the high level mute signal is input to the base terminal of the first transistor Q1 through the resistor R1, the first transistor Q1 is turned off and the first transistor Q1 is turned on. Since the second transistor Q2 is turned on, a DC voltage of −60 V output from the flyback transformer FBT is supplied to the control grid G1 of the water pipe as it is through the first transistor Q1.

Therefore, when the power is turned off, the negative voltage applied to the control grid G1 is boosted to suppress the amount of electrons emitted from the cathode to the fluorescent film.

As described above, the present invention has an effect of reducing the spot by suppressing the amount of electrons emitted from the cathode to the fluorescent film by boosting the negative voltage applied to the control grid by using the mute function when the power is turned off. .

Claims (1)

A microcomputer 10 for outputting a low level mute signal when the monitor is in normal operation and a high level mute signal when the mode is switched; In the monitor comprising a mute circuit 20 for suppressing the amount of electrons emitted from the cathode to the fluorescent film by boosting the negative voltage applied to the control grid (G1) when a high level mute signal is input, A charging capacitor C11 for charging by receiving a predetermined power supply voltage Vcc in normal operation; When the power supply voltage Vcc decreases when the power is turned off and reaches a predetermined level, the switching transistor Q11 is switched on to supply the charging voltage of the charging capacitor C11 as a mute signal of the mute circuit 20. Spot removal circuit of the monitor, characterized in that further comprises.