| 摘要 |
PROBLEM TO BE SOLVED: To provide an insulated switching power unit, which can supply an appropriate output voltage at momentary power failure, without providing a switching power unit, which receives the input of a commercial power voltage, with an electrolytic capacitor for a countermeasure to momentary power failure on its primary side. SOLUTION: A circuit 15 to counter momentary power failure is connected between the output lines HLo and CLo of a DC-DC converter 12. The circuit 15 to counter momentary power failure includes a secondary capacitor Cpf, a charge circuit, which is composed of a diode D1 that trickle-charges the secondary capacitor Cpf and a resistor R1, and a switch circuit SW, which outputs the charge voltage of the secondary capacitor Cpf at momentary power failure. A digital signal processing circuit 13 switches on a switch circuit SW when it detects that an AC input power source Vac has stopped, receiving the input of the output signal of an input voltage detecting circuit 10. Hereby, the charge voltage of the secondary capacitor Cpf is outputted. Therefore, it keeps the output voltage at a fixed value even in the power failure. COPYRIGHT: (C)2010,JPO&INPIT
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