KR19990007328U - X-ray protection circuit of monitor - Google Patents

Abstract

The present invention relates to an X-ray protection circuit for preventing the emission of harmful X-rays from the cathode ray tube (CRT) in the case of abnormally high pressure in the monitor, the circuit of the present invention is a power supply 110, the DC-DC converter 120, the FBT (130), the horizontal oscillator 140, the horizontal drive unit 150, the horizontal output unit 160 in the monitor equipped with the third winding of the FBT (130) Diode D1 for rectifying the rectified voltage, smoothing capacitor C1 for removing ripple of the voltage rectified in the diode D1, split resistors R1, R2 for reducing the output voltage of the diode, and ply When the level of the back pulse is higher than or equal to a predetermined level, the zener diode ZD1 conducts, the microcomputer 20 outputs a high level mute signal while the monitor switches modes, and the microcomputer mute has a high level mute. Turn on while the signal is Group comprises a transistor (Q2) to induce a flyback pulse to ground.

Therefore, the present invention has a high level mute signal is output from the microcomputer while the video mode is converted, and by using the mute signal to induce a high level flyback pulse to the ground, it is possible to perform a more stable X-ray protection function There is.

Description

A X-RAY Protection circuit of a monitor

The present invention relates to an X-ray protection circuit for preventing the harmful X-rays (X-RAY) emitted from the cathode ray tube (CRT) in the case of abnormally high pressure in the monitor.

In general, a cathode ray tube (CRT) focuses and accelerates hot electrons emitted from R, G, and B electron guns, and then collides with R, G, and B fluorescent surfaces through a point on a shadow mask to form pixels. Sawtooth current flows to form a two-dimensional screen.

In order to operate the cathode ray tube (CRT), a heater voltage of about 6.3 V is applied to the heater, and a focus grid voltage, a screen grid voltage, etc. are required to focus the emitted hot electrons, and the anode is accelerated to the anode. High pressure of about 25KV is applied.

However, when the high pressure applied to the anode is normal in the cathode ray tube, electrons collide with the fluorescent surface to emit light in the visible region, but when an abnormally high pressure is applied to the anode, the electrons collide more strongly on the fluorescent surface. In some cases, an X-ray having a shorter wavelength than visible light may be generated.

Most human monitors monitor the high pressure applied to the anode when the human body is exposed to the X-ray, and when the high pressure is abnormally high, the driving of the horizontal drive signal is stopped to prevent the high pressure from being generated. It is equipped with X-ray protection circuit.

1 is a circuit diagram illustrating a conventional X-ray protection circuit in a monitor, in which horizontal oscillation is integrated when a high voltage is abnormally increased by monitoring a high voltage (HV) induced in a secondary winding of a high voltage generator (FBT) 130. The X.RAY terminal of the circuit 140 is set to 'high' to prevent the generation of the H.drive signal.

That is, the voltage induced in the cubic coil of the FBT 130 is rectified in the diode D1 and smoothed in the electrolytic capacitor C1, and then divided into the zener diode ZD1 through the split resistors R1 and R2. It is applied to the cathode side. The anode side of the zener diode ZD1 is connected to the X-RAY protection terminal of the oscillator 140.

At this time, when the high voltage (H.V) of the FBT 130 is normal, a low voltage (ie, below the rated voltage of the zener diode) is applied to the zener diode ZD1 to maintain the zener diode ZD1 in the off state.

However, when the high voltage HV induced in the secondary winding of the FBT 130 and applied to the anode of the CRT becomes high, the flyback pulse FBP induced in the tertiary winding of the FBT 130 also increases accordingly. .

As the flyback pulse FBP becomes large, the voltage applied to the cathode of the zener diode ZD1 increases and rectifies and smoothes. The 'high' level is applied to the X.RAY terminal of the oscillator 140.

When the current flows through the X-RAY terminal, the oscillator 140 blocks the horizontal drive signal (H.drive) oscillated from the internal oscillation circuit, and accordingly, to the horizontal output unit 160 through the horizontal drive unit 150. Since there is no horizontal driving signal applied, the horizontal output transistor of the horizontal output unit 160 maintains the turn-off state.

If the horizontal output transistor is continuously turned off, the voltage is not induced in the secondary winding of the FBT 130 so that a high voltage is not generated. Therefore, the high voltage rises to prevent the CRT from generating X-rays. have.

In the X-ray protection circuit, the reference voltage of the zener diode ZD1 for starting the oscillator 140 to start the X-ray protection operation plays an important role. That is, the voltage of the FBP for starting the X-RAY protection operation is determined according to the reference voltage of the zener diode and the values of the resistor elements R1 and R2 constituting the circuit.

However, the conventional X-ray protection circuit has a problem in that when the mode is switched in the multi-mode monitor, the screen is held down while the X-ray protection function is operated even if the flyback pulse FBP increases momentarily.

Accordingly, the present invention has been devised to solve the above problems, and provides an X-ray protection circuit in a monitor that performs a more precise X-ray protection function by using a mute signal output from a microcomputer when switching modes. There is this.

In order to achieve the above object, the circuit of the present invention receives a synchronization signal (H.sync, V.sync) during normal operation, generates a horizontal drive signal, and has a high level through an X-ray terminal. When the signal is input, the horizontal oscillation means to block the output of the horizontal drive signal, the FBT generating a high voltage through the secondary winding when the horizontal output transistor switches the B + voltage in accordance with the horizontal drive signal, and in the tertiary winding of the FBT In the monitor consisting of an X-ray protection circuit for outputting a high level signal to the X-ray terminal when the output flyback pulse increases above a certain level,

The X-ray protection circuit includes a microcomputer that outputs a high level mute signal while the monitor switches modes;

And a transistor which is turned on while a high level mute signal is output from the microcomputer and guides the flyback pulse to the ground.

1 is a circuit diagram showing a conventional X-ray protection circuit in the monitor,

2 is a circuit diagram illustrating an X-ray protection circuit according to the present invention in a monitor.

* Explanation of symbols for main parts of the drawings

110: power supply 120: DC-DC converter

130: high pressure generator (FBT) 140: oscillation unit

150: horizontal drive unit 160: horizontal output unit

170: X-ray protection circuit 20: Micom

Q2: transistor

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

As shown in FIG. 2, the X-ray protection circuit according to the present invention includes a power supply 110, a DC-DC converter 120, an FBT 130, a horizontal oscillator 140, a horizontal driver 150, and a horizontal output unit. A diode D1 for rectifying the voltage induced in the tertiary winding of the FBT 130 in the monitor equipped with the 160, and a smoothing capacitor C1 for removing ripple of the voltage rectified in the diode D1. When the level of the division resistors R1 and R2 for reducing the output voltage of the diode D1 and the flyback pulse level is higher than or equal to a predetermined level, the zener diode ZD1 that is turned on and the high level while the monitor switches modes, The microcomputer 20 outputs a mute signal and a transistor Q2 which is turned on while the high level mute signal is output from the microcomputer 20 to guide the flyback pulse to the ground.

The operation and effects of the present invention configured as described above are as follows.

The power supply 110 receives the AC power AC and outputs predetermined DC voltages to each part of the monitor. The DC-DC converter 120 is a boost or buck type converter and receives a DC voltage and applies a predetermined B + voltage to the primary winding of the FBT 130.

The FBT 130 includes a primary winding to which the B + voltage is applied, a secondary winding to which a high voltage is induced, a tertiary winding to induce a low voltage induced voltage, and a rectifying unit to rectify the voltage induced in the secondary winding. Is configured to generate a high pressure in accordance with the operation of the horizontal output unit 160. The FBT used in the embodiment of the present invention is a laminated type, and the laminated type FBT has an advantage of reducing reliability of the short layer of the secondary winding.

The high voltage HV induced in the secondary winding of the FBT 130 is applied to the anode of the CRT, and the focus voltage and the screen voltage divided by the resistors are respectively applied to the focus grid and the screen grid of the CRT. Is approved. In addition, when the ABL circuit is connected to one end of the secondary winding and the anode current increases, the contrast of the video preamplifier (not shown) is reduced.

The oscillator 140 receives the synchronization signals H.sync and V.sync and generates a H.drive signal locked thereto, and the horizontal driver 150 outputs the horizontal drive output from the oscillator 140. H.drive) signal is sufficiently amplified and output to the horizontal output unit 160. The horizontal output unit 160 allows the sawtooth current to flow through the horizontal deflection coil H.DY by turning on / off an internal horizontal output transistor according to the horizontal drive signal input through the horizontal driver 150.

At this time, when the horizontal output transistor is turned off, the energy accumulated in the primary winding of the FBT 130 is guided to the secondary winding and the tertiary winding of the FBT 130. That is, the horizontal output transistor also serves as a switching element of the power supply circuit so that a high voltage is generated in the secondary winding of the FBT.

On the other hand, if the high pressure induced in the secondary winding of the FBT 130 in the above monitor rises above the normal voltage, there is a risk that the X-rays may occur in the CRT. Suppresses the occurrence of

That is, when the voltage induced in the secondary winding increases, the voltage induced in the third winding also increases. The voltage induced in the tertiary winding is rectified in the diode D1 and then smoothed in the electrolytic capacitor C1.

The detection voltage smoothed in this manner is appropriately divided according to the sizes of the division resistors R1 and R2. When the voltage divided by the division resistors R1 and R2 becomes larger than the rated voltage of the zener diode ZD1, the zener diode As ZD1 is turned on, a high level is applied to the X.RAY terminal of the oscillator 140.

That is, since the low level is applied to the X.RAY terminal of the oscillator 140 in the normal state, the oscillator 140 outputs a normal horizontal driving signal, and if the high voltage is excessively increased, the X.RAY terminal of the oscillator 140 As the high level is applied, the oscillator 140 blocks the output of the horizontal drive signal, thereby preventing the image from being displayed on the CRT screen.

In this case, while the mode is switched in the multi-mode monitor, the high voltage may increase for a while. At this time, the microcomputer 20 outputs a high level mute signal through the mute terminal.

When the high level mute signal is applied to the base terminal of the transistor Q2, the transistor Q2 is turned on to ground the X.RAY terminal of the oscillator 140. The high voltage rises so that the control diode ZD1 Even when turned on, since the flyback pulse FBP is induced to the ground, a low level is applied to the X.RAY terminal of the oscillator 140.

In other words, while the video mode is changed in the multi-mode monitor, the X-ray function is not driven even if the high-pressure rises and the flyback pulse rises, thereby preventing the holddown of the screen.

As described above, the X-ray protection circuit according to the present invention outputs a high level mute signal from the microcomputer while the video mode is converted, and is more stable by inducing a high level flyback pulse to ground by the mute signal. It has the effect of performing X-ray protection.

Claims (1)

Horizontal operation signal is generated by receiving synchronization signals (H.sync, V.sync) during normal operation, and when high level signal is input through X-ray terminal, horizontal output signal is cut off The X-rays when the FBT generates a high voltage through the secondary winding when the horizontal output transistor switches the B + voltage according to the oscillation means and the horizontal drive signal, and the flyback pulse output from the tertiary winding of the FBT increases by a predetermined level or more. In the monitor consisting of an X-ray protection circuit for outputting a high level signal to the terminal, The X-ray protection circuit includes a microcomputer that outputs a high level mute signal while the monitor switches modes; And a transistor which is turned on while a high level mute signal is output from the microcomputer and guides the flyback pulse to the ground.