| 摘要 |
PURPOSE: A circuit for sensing an AC input line at the power failure is provided to store data and prevent error of external devices during a predetermined time by sensing an inputted power source when the inputted power source is turned off. CONSTITUTION: A power source inputting unit(1) comprises a rectifier(1-1) rectifying an AC power source inputted at primary and a resistance(R1) and a condenser(C1) coupling the rectified power source. A power source sensing unit(2) is connected to a Zener diode(ZD1) the other side thereof is grounded to the condenser(C1) of the power source inputting unit(1). A diode(D1) and a resistance(R3) are connected between the Zener diode(ZD1) and the condenser(C1). A condenser(C2) one side thereof is grounded and a resistance(R2) are connected between the diode(D1) and the resistance(R3) for charging/discharging by a coupling signal of the resistance(R1) and the condenser(C2). A primary photocoupler(PC1) is connected to one side of the resistance(R3) for being tuned on/off by charging/discharging of the condenser(C2). A pulse generating unit(3) comprises secondary photocoupler(PC2) being tuned on/off by the primary photocoupler(PC1), a resistance(R4) being connected between one side of the secondary photocoupler(PC2) and a 5V power inputting unit, a resistance(R5) being connected among the resistance(R4), the secondary photocoupler(PC2) and a transistor(Q1), a resistance(R6) being connected between the transistor(Q1) and the resistance(R5), a resistance(R7) being connected between a collector of the transistor(Q1) and the 5V power inputting unit, and the transistor(Q1) being turned on/off and outputting a high/low signal to a computer through the collector by the 5V power source being inputted through the resistances(R4)(R5).
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