KR950010190Y1 - Output control circuit of image signal - Google Patents

Abstract

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Description

Video signal output control circuit

1 is a circuit diagram showing a conventional output control circuit of a video signal.

2 is a circuit diagram showing an output control circuit of an image signal according to the present invention.

* Explanation of symbols for main parts of the drawings

10: main power circuit 100: first signal detection circuit

110, 210: first and second DC 120, 220: first and second detection

200: second signal detection circuit 300: logic sum circuit

400: switching circuit

C1, C2, C101, C201, C401: Capacitor

D1, D101, D121, D201, D202, D301, D302: Diode

FBT: Flyback Trans MICOM: Micom

Q121, q401, q402: transistor

R1, R2, R121 ~ R124, R221 ~ R223, R401, R402: Resistance

SMPS: Power Supply Units ZD1, ZD121, ZD221: Zener Diodes

The present invention relates to an image signal output control circuit, and more particularly, to an output control circuit of a Youngsan signal that detects a voltage induced from a flyback transformer (FBT) and approves power supply according to the magnitude of the induced voltage. It is about.

The electromagnetic wave generated by the recent use of electricity is very harmful to the human body, so all electronic products should be equipped with a device that blocks the electromagnetic wave.

For example, in the case of a television, a voltage induced by a flyback transformer (FBT) is applied to the CRT. When the voltage applied to the CRT is a high voltage above the normal voltage, electromagnetic waves harmful to the human body are emitted from the CRT.

In a conventional television, the AC voltage induced through the flyback transformer (FBT) is rectified and smoothed by the diode D1 and the capacitor C1, and the rectified and smoothed voltage is the capacitor C2 and the resistor R1. ) Is detected.

When the detected voltage is greater than or equal to a predetermined voltage of the zener diode ZD1, the zener diode ZD1 is turned on and a voltage induced from the flyback transformer FBT is applied to the integrated device IC in which the output of the image signal is controlled. do.

At this time, in the integrated device IC, the output of the horizontal synchronization signal HS is cut off, so that the screen output of the image signal is stopped, thereby preventing overexposure of electromagnetic waves.

In the control circuit of the video signal produced as described above, even if the output of the video signal is blocked when the electromagnetic wave is overexposed, there is a problem that the power supply is continued to consume unnecessary power.

The object of the present invention is to provide an output control circuit of an image signal in which the supply of power is automatically cut off when the voltage induced from the flyback transformer is higher than a specific voltage.

The video signal output control circuit for achieving the above object is the output control of the video signal, the output of the horizontal synchronous signal is cut off when the voltage induced by the flyback transformer (FBT) is more than a specific voltage, the screen output of the video signal is controlled In the circuit,

Main power circuit 10 for converting AC power (AC) into the main power (B2) required for the system according to the control signal (S1) output from the microcomputer:

The first signal detection circuit 100 and the second signal detection circuit 200 for detecting whether the voltage induced from the flyback transformer FBT is greater than or equal to a specific voltage:

A logic sum circuit 300 for performing an OR operation on the signals output from the first signal detection circuit 100 and the second signal detection circuit 200; and

And a switching circuit 400 for supplying or cutting off AC power to the power supply device SMPS according to the output signal of the logic sum circuit 300.

In the output control circuit of the video signal, the logic sum circuit 300 is preferably composed of diodes D301 and D302, and the switching circuit 400 is preferably comprised of transistors Q401 and 402.

In addition, the first signal detection circuit 100 is input from the first direct current unit 110 and the first direct current unit 110 for rectifying the voltage induced by the secondary coil L2 of the flyback transformer FBT. When the voltage is greater than or equal to a specific voltage, the first detection unit 120 may pass the input voltage. The second signal detection circuit 200 may be a voltage induced by the secondary coil L3 of the flyback transformer FBT. Preferably, the rectifier includes a second direct current unit 210 for rectifying and a second detector 220 for passing the input voltage when the voltage input from the second direct current unit 210 is greater than or equal to a specific voltage.

In the first signal detection circuit 100, the first detector 120 includes a diode D121 in which the voltage output from the first DC unit 110 is rectified, and a resistor in which the voltage input from the diode D121 is distributed. (R121), (R122), a diode (D122) for rectifying the voltage output from the second DC unit 210, resistors (R123), (R124) for distributing the voltage input from the diode (D122), A transistor Q121 connected to the input side of the resistor R124 and 'turned on / turned off' by a potential difference between the zener diode ZD121 and the resistors R121, R122, and the zener diode ZD212 set to a constant voltage. Is preferred.

In the second signal detection circuit 200, the second detector 220 includes resistors R221, R222, and R221, R222 to which a voltage induced from the second DC unit 210 is divided. When the input voltage is greater than or equal to the set specific voltage, the zener diode ZD221 that is turned on and the resistor R223 that is connected to the output side of the zener diode ZD221 are biased.

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

2 is a circuit diagram showing an embodiment according to the present invention, which converts an AC power input AC according to a control signal S1 output from a microcomputer (not shown) into a main power supply B2 required for a system. A flyback transformer (FBT) for supplying power required for the system by inducing a voltage according to the turns ratio, the main power supply circuit 10, and detecting whether the voltage induced in the flyback transformer (FBT) is greater than or equal to a predetermined voltage. A second signal detection circuit 100 for detecting whether the voltage induced by the first signal detection circuit 100 and the flyback transformer FBT is equal to or greater than a predetermined voltage and providing a reference voltage of the first signal detection circuit 100 ( 200, a logic sum circuit 300 for performing an OR operation on the signals output from the first signal detection circuit 100 and the second signal detection circuit 200, and an AC power source according to the output signal of the logic sum circuit 300. ) To the power supply (SMPS) It consists of a switching circuit 400.

Here, the control signal S1 for converting and outputting the main power supply B2 required for the system is configured in the same manner as before. In other words, the control signal S1 is a signal output from the microcomputer of the television. When the power source is normally applied to the television, the control signal S1 has a logic level of 'H'.

The first signal detection circuit 100 includes a first direct current unit 110 composed of a diode D101 and a capacitor C101, diodes D121, D122, resistors R121 to R124, and a zener diode ( ZD121 and a first detector 120 formed of a transistor Q121, the second DC portion 210 of the second signal detection circuit 200 is the first DC portion of the first signal detection circuit 100 ( It is configured in the same manner as 110, the second DC portion 210 and the second detection unit 220 is connected.

In this case, the winding ratio of the secondary side first coil L2 of the flyback transformer FBT is higher than the winding ratio of the secondary side second coil L3 of the flyback transformer FBT. Therefore, a high voltage (about 180V) is induced by the first coil L2 and a low voltage 12V is induced by the second coil L3.

That is, the first direct current unit 110 is configured such that the high voltage induced by the secondary coil L2 of the flyback transformer FBT is rectified and smoothed, and the first detection unit 120 receives the high voltage input to the zener. When the voltage is equal to or higher than the specific voltage set by the diode ZD121, the transistor Q121 is configured to conduct.

In addition, the second direct current view 210 configured to smooth the low voltage induced by the second coil L3 of the secondary side of the flyback transformer FBT is smoothed by a diode D201 and a capacitor C201. The second detector 220 includes resistors R221 to R223 and a zener diode ZD221. Therefore, when the induced low voltage is higher than or equal to a specific voltage set in the zener diode ZD221, the low voltage is configured to be conducted.

Meanwhile, the logic sum circuit 300 includes diodes D301 and D302, and the diodes D301 and D302 are turned on / turned in response to a signal output from the first detector 120 or the second detector 220. Is off.

In addition, the switching circuit 400 includes transistors Q401, Q402, resistors R401, 402, and capacitors C401, and the transistors Q401 by signals output from the logic sum circuit 300. Is conducted, and transistor Q402 is configured to continue to conduct after the transistor Q401 is turned on.

The case where a high voltage is applied to the flyback transformer FBT in the power cutoff control circuit configured as described above will be described.

The diode is applied to the diode D201 and the capacitor C201 of the second DC unit 210, rectified, and smoothed. The low voltage is applied to the diode D122 of the first detector 110. The low voltage applied to the diode D122 is distributed by the resistors R123 and R124 of the first detector 110. In this case, the divided voltages of the resistors R123 and R124 are applied to the zener diode ZD121 of the first detector 120, and the applied voltages are divided by the resistors R121 and R122. If it is less than 0.7 V, the transistor Q121 of the first detection unit 110 is turned on.

That is, when the transistor Q121 is turned on, the high voltage output from the first DC view 110 is applied to the diode D301 of the logic circuit 300, and the voltage passing through the diode D301 is applied to the switching circuit 400. Applied to transistor Q401.

As described above, the signal S1 input to the main power supply circuit 10 is applied to the ground connected to the emitter side of the transistor Q401 due to the transistor Q401, so that the relay switch RSW of the main power supply circuit 10 is turned off. Therefore, the supply of AC power source AC is cut off. At this time, the transistor Q402 of the switching circuit 400 is turned on to maintain the conduction state of the transistor Q401.

On the other hand, the low voltage DC-flowed through the second DC unit 210 is distributed by the resistors R221 and R222 of the second detector 220, and the divided voltage is applied to the Zener of the second detector 220. When the voltage is greater than or equal to the specific voltage set by the diode ZD221, the output voltage of the second DC unit 210 is applied to the diode D302 of the logic circuit 300. At this time, the voltage passed through the diode D302 is applied to the transistor Q401 of the switching circuit 400 to conduct the transistor Q401.

Accordingly, the signal SI input to the main power supply circuit 10 is applied to the emitter side of the transistor Q401 so that the relay switch RSW is turned off, the input of the AC power supply AC is cut off, and the transistor Q402 is simultaneously applied. Is conducted so that the conduction state of the transistor Q401 is maintained.

Hereinafter, an embodiment of the above-described video signal output control circuit will be described in more detail with reference to the input / output level.

When the normal voltage AC is applied to the primary coil LI of the flyback transformer FBT, the control signal SI output from the microcomputer is 'H', and the secondary side first of the flyback transformer FBT is applied. The voltage 180V induced in the coil L2 and the voltage 12V induced in the second coil L3 of the secondary side of the flyback transformer FBT are determined by the first signal detection circuit 100 and the second signal detection circuit ( 200) respectively.

The voltage 180V input to the first signal detection circuit 100 is half-wave rectified by the first direct current unit 110 and output to the first detection unit 120. The diode D101 of the first detection unit 120 is' Turn on, and the voltage divided by the resistors R121 and R122 becomes 6V. (C point)

At this time, since the 6V zener diode ZD121 is used, the transistor Q121, the diode C301, the transistors Q401, and Q402 maintain 'turn off', and accordingly, the control signal SI is the relay RL. The relay switch RSW is turned on to supply AC power to the power supply device SMPS.

Hereinafter, a case in which a high voltage is induced in the flyback transformer FBT will be described.

The high voltage induced through the first coil L1 of the secondary side of the flyback transformer FBT is applied to the diode D101 and the capacitor C101 of the first direct current unit 110 to be half-wave rectified and smoothed (point A). The smoothed voltage is applied to the diode D121 of the first detector 120 to rectify the rectified voltage. The rectified voltage is applied to the resistors R121 and R122 and distributed.

On the other hand, the low voltage induced through the second coil L3 of the secondary side of the flyback transformer FBT is applied to the diode D201 and the capacitor C201 of the second DC unit 210 to be half-wave rectified and smoothed. (B) The smoothed voltage is applied to the resistors R221 and R222 of the second detector 220 and divided (E point), and the voltage divided by the resistors R123 and R124 is the first detector. The transistor 120 is applied to the base terminal of the transistor Q121 to supply a reference voltage.

When a high voltage is applied to the flyback transformer (FBT), for example, assuming that the voltage at point A is 220V (point A), the diode D121 is 'on' and divided in the resistors R121 and R122. The voltage (C point) becomes 7V, so that the transistor Q121 and the diode D301 are 'turned on' (G point).

On the other hand, assuming that the voltage induced in the second direct current unit 210 by the secondary side second coil L2 of the flyback transformer FBT is 13 V (point B), the resistance R221 of the second detection unit 220 is determined. , The voltage divided by (R222) (E, F) is 6.5V, the diode D302 of the logic circuit 300 is 'on'. (G point)

That is, when a voltage higher than the normal voltage is applied to the flyback transformer FBT, the diodes D301 and D302 of the logic sum circuit 300 are 'on', and accordingly, the transistors Q401, ( Q402) is 'turned on' so that the voltage at point H becomes OV. Accordingly, the transistor Q1 and the relay switch RSW are 'turned off', and the AC power AC applied to the power supply SMPS is cut off.

In the video signal output control circuit as described above, when an overvoltage is applied to the flyback transformer FBT, the first and second signal detection units 100 and 200 detect a high voltage to turn off the switching circuit 400. Cut off AC power supplied to main power.

Therefore, there is an advantage that can prevent unnecessary loss of power and can block harmful components of the human body due to overexposure of electromagnetic waves.

Claims (7)

When the voltage induced by the flyback transformer (FBT) is higher than or equal to a specific voltage, an output control circuit of a video signal in which the screen output of the video signal is controlled by blocking the power supply, according to the control signal (SI) output from the microcomputer Main power supply circuit 10 for inputting power supply AC to the main power supply B2 required for the system: First detection circuit 100 for detecting whether the voltage induced from the flyback transformer FBT is above a specific voltage. And a second signal detection circuit 200: a logic sum circuit 300 for performing an OR operation on the signals output from the first signal detection circuit 100 and the second signal detection circuit 200: and the logic sum circuit ( And a switching circuit 400 for supplying or cutting off AC power to the power supply device SMPS according to the output signal of 300. The output control circuit according to claim 1, wherein the logic sum circuit (300) comprises diodes (D301) and (D302). The output control circuit of claim 1, wherein the switching circuit (400) comprises transistors (Q401) and (Q402). The first signal detecting circuit 100 of claim 1, further comprising: a first direct current unit 110 for rectifying a voltage induced by the secondary coil L2 of the flyback transformer FBT; The output control circuit of an image signal, characterized in that the first detection unit 120 for passing the input voltage when the voltage input from the 110 is greater than a specific voltage. The method of claim 1, wherein the second signal detection circuit 200 is a second direct current unit 210 for rectifying the voltage induced in the secondary coil (L3) of the flyback transformer (FBT) and the second direct current unit And a second detector 220 for passing the input voltage when the voltage inputted from the 210 is greater than or equal to a specific voltage. 5. The resistor D121 of claim 4, wherein the first detector 120 rectifies the diode D121 from which the voltage output from the first DC unit 110 is rectified, and the resistor R121 divides the voltage input from the diode D121. , R122, a diode D122 in which the voltage output from the second DC unit 210 is rectified, resistors R123 and R124 in which the voltage input from the diode D122 is distributed, and A transistor Q121 connected to an input side of the resistor R124 and turned on / off by a potential difference between the zener diode ZD121 and the resistors R121, R122, and the zener diode ZD212. Output control circuit of the video signal, characterized in that consisting of. The second detector 220 is input from the resistors R221 and R222 to which the voltage induced by the second DC unit 210 is distributed, and the resistors R221 and R222. The output control circuit of the video signal comprising a zener diode (ZD221) which is turned on when the set voltage is above a predetermined voltage, and a resistor (R223) which is connected to an output side of the zener diode (ZD221) and biases an input voltage. .