KR20000014620U - Mute Circuit of High Voltage Separate Monitor - Google Patents

Abstract

The present invention relates to a high voltage separation type monitor in which a high voltage circuit and a horizontal deflection circuit are separated, and the present invention generates a scan B + voltage by switching a constant voltage input from a constant voltage source (SMPS) by a PWM control signal (H.out). In the high-voltage separation monitor equipped with the deflection DC / DC converter 20, the non-inverting (+) input terminal of the internal comparator COM is connected to the deflection DC / DC converter 20 through the first terminal FB. The horizontal IC determines the duty ratio of the PWM control signal H.out supplied to the deflection DC / DC converter 20 by the output signal of the internal comparator COM when the deflection feedback signal FB is supplied. (10) and; RC circuits R11, R12, and C11 provided to adjust the RC time constant value of the output signal of the internal comparator COM inside the horizontal IC 10 through the second terminal COMP; A microcomputer 40 for outputting a high level mute signal for a predetermined time when switching modes; And a high level mute signal connected to the second terminal COMP of the horizontal IC 10 and the RC circuits R11, R12, and C11 to be switched on when the high level mute signal is input from the microcomputer 40. The IC 10 further includes a switching unit 50 which emits an output signal of the internal comparator COM to the ground, and is configured to include a PWM control signal H. By keeping out) at a low level, the effect is to mute the scan B + voltage generated from the deflection DC / DC converter 20.

Description

A muting circuit of a monitor that separating a High-Voltage production circuit from a horizon-deflection circuit

The present invention relates to a high-voltage separation type monitor in which a high voltage circuit and a horizontal deflection circuit are separated, and more particularly, to a mute circuit of a high voltage separation type monitor configured to mute a scan B + voltage for a predetermined time during mode switching.

In general, a color display device (CRT) used in a monitor focuses and accelerates hot electrons emitted from R, G, and B guns and collides with R, G, and B fluorescent surfaces through a point on a shadow mask to form pixels. And a sawtooth current flowing through the horizontal deflection coil to form a two-dimensional screen.

In order to operate the color display device (CRT), a heater voltage of about 6.3V is applied to the heater, and a focus grid voltage, a screen grid voltage, etc. are required for focusing the emitted hot electrons. High pressure of about 25KV is applied.

In the conventional single mode monitor, since there is no horizontal frequency variation, the high voltage circuit and the horizontal deflection circuit are integrally used, but in recent years, the high voltage circuit and the horizontal deflection circuit have been separated as the monitor becomes larger and higher in resolution. In the multi-sync monitor in which the high voltage circuit and the horizontal deflection circuit are integrated, when the horizontal frequency (mode) is changed, the B + voltage used for the horizontal deflection circuit and the high voltage circuit is changed. High pressure is also variable. In this case, when the high voltage is changed, the anode current is changed to affect the size and brightness of the screen.

Here, the multi-sync monitor is a monitor that is compatible with at least two video modes, and changes the size and position of an image according to various horizontal frequencies (about 30 to 75 KHz) output from a video card and horizontal and vertical synchronization And a monitor capable of optimizing the deflection unit and adjusting various deflection correction circuits.

The video mode outputs a horizontal frequency and a vertical frequency differently according to the resolution to be implemented. As the horizontal frequency increases from low frequency to high frequency, screen flicker is prevented, thereby reducing eyestrain of users.

Table 1 categorizes the monitors depending on the video modes.

Video mode Horizontal frequency (KHz) Vertical frequency (Hz) Resolution (H * V) CGA 15.75 60 640 * 200 EGA 21.8 60 640 * 350 VGA 31.5 60/70 720 * 350 640 * 480 SVGA 35 to 37 INTERLACE 1024 * 768 High resolution mode 64 to 75 60 to 70 1024 * 7681280 * 1024

Today, monitors are becoming larger in size, and since high-voltage circuits and deflection circuits are integrally used in large-sized monitors, the high-voltage separate multi-sink monitors in which a high-voltage circuit and a deflection circuit are separated are widely used in large monitors. .

1 is a circuit diagram illustrating a conventional high-voltage separate multi-sink monitor, when an external AC power is input, the constant voltage source (SMPS) outputs a predetermined level of DC voltage, which is a DC-DC converter 20 for deflection and a high voltage. Input to a DC / DC converter (not shown).

In general, when the external AC power source is an AC signal of 220V and 60Hz, a relatively high voltage of 200V is output from the constant voltage source (SMPS), so that the DC-DC converter 20 for deflection is a scan B + voltage of about 80V. After pressing down, it is applied to the horizontal deflection circuit 30.

In addition, the high-voltage DC-DC converter (not shown) boosts 200V to a voltage of about 1500V and then applies it to the anode of the water pipe. As the DC-DC converter 20 for deflection, a buck converter is used. A boost converter is used as the high voltage DC-DC converter (not shown).

At this time, in order for the deflection PWM control signal (H.out) and the high voltage PWM control signal to have the same horizontal frequency, the horizontal IC 10 is the deflection DC-DC converter 20 and the high voltage PWM control unit ( Supply horizontal frequency information).

Meanwhile, the deflection DC / DC converter 20 converts 200 V supplied from the constant voltage source SMPS into a scan B + voltage of about 80 V by the deflection PWM control signal H.out output from the horizontal IC 10. After stepping down, the voltage is applied to the horizontal deflection circuit 30, and the pulse wave output from the dummy transformer DT is rectified and supplied to the horizontal IC 10 as a deflection feedback signal FB. By the deflection feedback signal FB, the horizontal IC 10 readjusts the duty ratio of the deflection PWM control signal H.out.

On the other hand, the high-voltage DC / DC converter (not shown) is 200V supplied from the constant voltage source (SMPS) by the high-voltage PWM control signal input from the high-voltage PWM control unit (not shown) through the flyback transformer (FT) After the voltage is increased to about 1500V, the voltage is applied to the anode of the water pipe, and the pulse wave output from the flyback transformer FT is rectified to be supplied as a high voltage feedback signal to the high voltage PWM controller (not shown). The high-pressure PWM control unit (not shown) readjusts the duty ratio of the high-voltage PWM control signal by the high-pressure feedback signal.

Accordingly, when the collector-emitter voltage of the horizontal output transistor is varied by changing the horizontal frequency, the scan B + voltage is varied. When the scan B + voltage is varied, the feedback voltage for deflection is varied to output from the deflection DC-DC converter 20. The scan B + voltage is varied so that the best image is displayed on the monitor's CRT screen.

The high voltage DC / DC converter (not shown) does not change the high voltage applied to the anode of the water pipe even if the horizontal frequency is changed. In addition, when the horizontal frequency is varied, the scan B + voltage output from the deflection DC-DC converter 20 is varied so that the best image is displayed on the CRT screen of the monitor.

On the other hand, if the necessary voltage (rated voltage) is supplied to each monitor circuit at the time of switching the monitor mode, it will cause an abnormality to each monitor circuit. Therefore, it is better than the rated voltage to allow normal operation after each monitor circuit warms up. After supplying a low ready voltage, it is necessary to supply a rated voltage.

Accordingly, an object of the present invention is to provide a mute circuit of a high-voltage separation monitor configured to mute the scan B + voltage for a predetermined time during mode switching.

The circuit of the present invention for achieving the above object,

Deflection DC / DC generating a scan B + voltage by switching a constant voltage input from a constant voltage source by a PWM control signal, converting the scan B + voltage into a pulse wave through a dummy transformer, and then rectifying again to generate a deflection feedback signal. A converter; In the high-voltage separation monitor having a horizontal deflection circuit for supplying the horizontal deflection coil after generating a sawtooth current by switching the scan B + voltage input from the deflection DC / DC converter by a horizontal drive signal,

Duty of the PWM control signal supplied to the deflection DC / DC converter by the output signal of the internal comparator when the non-inverting input terminal of the internal comparator receives the deflection feedback signal from the deflection DC / DC converter through the first terminal A horizontal IC for determining the ratio;

An RC circuit provided to adjust an RC time constant of an output signal of the internal comparator outside the horizontal IC through a second terminal;

A microcomputer that outputs a high level mute signal for a predetermined time when switching modes; And

And a switching unit connected between the second terminal of the horizontal IC and the RC circuit to switch on when a high level mute signal is input from the microcomputer and to release an output signal of the horizontal IC internal comparator to ground. do.

1 is a circuit diagram showing a conventional high pressure detachable monitor,

2 is a circuit diagram illustrating a mute circuit of the high-voltage separation monitor according to the present invention.

* Explanation of symbols for main parts of the drawings

SMPS: Constant Voltage Source 10: Horizontal IC

20: DC-DC converter for deflection 30: horizontal deflection circuit

40: micom 50: switching unit

R11, R12, C11: RC circuit Q11, Q12: First and second transistors

ZD11: Zener Diode C11: Capacitor

R 11,12: Resistor COM: Comparator

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 mute circuit of the high-voltage separation monitor according to the present invention.

As shown in FIG. 2, the device of the present invention generates a scan B + voltage by switching a constant voltage input from the constant voltage source SMPS by a PWM control signal H.out, and converts the scan B + voltage into a dummy transformer ( A deflection DC / DC converter 20 for converting into a pulse wave through DT) and rectifying again to generate a deflection feedback signal FB; A horizontal deflection circuit that generates a sawtooth current by switching the scan B + voltage input from the deflection DC / DC converter 20 by a horizontal drive signal H.out and supplies it to the horizontal deflection coil H.DY. In the high-voltage separation monitor equipped with (30), the non-inverting (+) input terminal of the internal comparator COM has a deflection feedback signal FB from the deflection DC / DC converter 20 through the first terminal FB. A horizontal IC 10 for determining the duty ratio of the PWM control signal H.out supplied to the deflection DC / DC converter 20 by the output signal of the internal comparator COM; RC circuits R11, R12, and C11 provided to adjust the RC time constant value of the output signal of the internal comparator COM inside the horizontal IC 10 through the second terminal COMP; A microcomputer 40 for outputting a high level mute signal for a predetermined time when switching modes; And a high level mute signal connected to the second terminal COMP of the horizontal IC 10 and the RC circuits R11, R12, and C11 to be switched on when the high level mute signal is input from the microcomputer 40. The IC 10 further includes a switching unit 50 which emits an output signal of the internal comparator COM to ground.

The switching unit 50 may include: an NPN type first transistor Q11 having a base end receiving a mute signal from the micom 40 and an emitter end being grounded; A zener diode ZD11 having an anode terminal connected to a collector terminal of the first transistor Q11 through a resistor R11 and a capacitor C11; And a base terminal connected to the cathode terminal of the zener diode ZD11 and an emitter terminal connected in parallel between the second terminal COMP of the horizontal IC 10 and the RC circuits R11, R12, and C11 through a resistor R12. And a PNP type second transistor Q12 connected to the ground terminal and grounded at the collector end.

The operation and effects of the apparatus according to the present invention configured as described above will be described in detail by dividing into normal operation and mute operation with reference to FIG. 1.

1. In normal operation

The horizontal IC 10 receives the deflection feedback signal FB from the deflection DC / DC converter 20 and adjusts the duty ratio of the deflection PWM control signal H.out.

That is, the horizontal IC 10 receives the deflection feedback signal FB from the deflection DC / DC converter 20 through the first terminal FB, so that the non-inverting (+) of the internal comparator COM is performed. Supply to the input terminal. Accordingly, the internal comparator COM compares and outputs the deflection feedback signal FB and a reference voltage. The PWM is supplied to the deflection DC / DC converter 20 by the output signal of the internal comparator COM. The duty ratio of the control signal H.out is determined.

At this time, the RC circuits R11, R12, and C11 adjust the RC time constant of the output signal of the internal comparator COM inside the horizontal IC 10 through the second terminal COMP. It is prepared.

The switching element Q21 of the deflection DC / DC converter 20 switches on / off the constant voltage input from the constant voltage source SMPS by the PWM control signal H.out input from the horizontal IC 10. The scan B + voltage is generated, and the scan B + voltage is converted into a pulse wave through the dummy transformer DT, and then rectified again and supplied as a deflection feedback signal FB of the horizontal IC 10.

In addition, the horizontal output transistor Q32 of the horizontal deflection circuit 30 switches on / off the scan B + voltage input from the deflection DC / DC converter 20 by the horizontal drive signal input from the horizontal IC 10. Off to generate a sawtooth current and supply it to the horizontal deflection coil (H.DY).

(2) In mute operation

Since the microcomputer 40 outputs a high level mute signal (mute) for a predetermined time, the high level mute signal (mute) is input to the base terminal of the NPN type first transistor Q11 and the NPN type first transistor. As the QN is turned on and the NPN type first transistor Q11 is turned on, the PNP type second transistor Q12 is turned on.

As the PNP-type second transistor Q12 is turned on, the output signal of the internal comparator COM of the horizontal IC 10 is emitted to the ground through the PNP-type second transistor Q12, so that the horizontal IC 10 is The low level PWM control signal (H.out) is output.

Since the switching element Q21 of the deflection DC / DC converter 20 is switched off by the low level PWM control signal H.out input from the horizontal IC 10, the scan B + for a predetermined time during mode switching. No voltage is generated.

Since the scan B + voltage is not generated from the deflection DC / DC converter 20, the sawtooth wave current is not generated in the horizontal deflection circuit 30 so that the horizontal deflection operation is stopped for a predetermined time.

As described above, the device of the present invention maintains the PWM control signal H.out output from the horizontal IC 10 at a low level for a predetermined time during mode switching, thereby deflecting the DC / DC converter 20. There is an effect that the operation of the horizontal deflection circuit 30 is stopped by muting the scan B + voltage generated from the circuit.

Claims (1)

Generates a scan B + voltage by switching the constant voltage input from the constant voltage source SMPS by the PWM control signal H.out, while converting the scan B + voltage into a pulse wave through the dummy transformer DT and rectifying it again to deflect. A deflection DC / DC converter 20 for generating a feedback signal FB; A horizontal deflection circuit that generates a sawtooth current by switching the scan B + voltage input from the deflection DC / DC converter 20 by a horizontal drive signal H.out and supplies it to the horizontal deflection coil H.DY. In the high-pressure separation monitor equipped with (30), When the non-inverting (+) input terminal of the internal comparator COM receives the deflection feedback signal FB from the deflection DC / DC converter 20 through the first terminal FB, the output of the internal comparator COM is output. A horizontal IC (10) for determining the duty ratio of the PWM control signal (H.out) supplied to the deflection DC / DC converter (20) by a signal; RC circuits R11, R12, and C11 provided to adjust the RC time constant value of the output signal of the internal comparator COM inside the horizontal IC 10 through the second terminal COMP; A microcomputer 40 for outputting a high level mute signal for a predetermined time when switching modes; And It is connected between the second terminal COMP of the horizontal IC 10 and the RC circuits R11, R12, and C11 and is switched on when a high level mute signal is input from the micom 40. (10) The mute circuit of the high-voltage separate monitor, characterized in that further comprising and configured a switching unit (50) for emitting the output signal of the internal comparator (COM) to ground.