| 摘要 |
PROBLEM TO BE SOLVED: To improve apparatus efficiency during the backup operation without increase of capacity of a capacitor which forms a half-bridge converter. SOLUTION: An output terminal of a voltage boosting chopper 20 is connected to one capacitor of a serial circuit of a couple of capacitors forming a half-bridge converter 10. A first switch 31 is turned off when a single phase AC power supply 1 fails to isolate the converter 10 from the single phase AC power supply 1, and then a second switch 32 is turned on to terminate the coupling point of the switching circuits of converter 10 and the coupling point of the capacitors via a filter reactor. As a result, the voltage boosting chopper 20 is operated and one switching circuit is also turned on and off. Otherwise, a voltage boosting chopper 40 provided with a 2-wiring reactor including a first wiring 42 and a second wiring 43 which are magnetically coupled is used in place of the voltage boosting chopper 20, and this second wiring 43 is connected to the other capacitor via the second impeding diode 44.
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