| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a power supply apparatus which includes a plurality of parallel-connected voltage conversion circuits that convert electric power, by switching operation and improves power conversion efficiency to enhance more than the conventional efficiency, over a wide output range. Ž<P>SOLUTION: The power supply apparatus includes a plurality of voltage conversion circuits which receive input of a common voltage to carry out fly-back voltage conversion operation, including switching of the number of operating units, an output synthesizing circuit which synthesizes output currents from the voltage conversion circuits; an input voltage detecting circuit which detects the input voltage to the voltage conversion circuits, at least one input current detecting circuit which detects an input current to at least one voltage conversion circuit; an output voltage detecting circuit which detects the output voltage from the output synthesizing circuit; and a control unit which calculates the power conversion efficiency of at least one voltage conversion circuit, based on at least the result of detection by the above detecting circuits, to control the frequency or duty of a drive signal applied to a switching element of the voltage conversion circuit. Ž<P>COPYRIGHT: (C)2010,JPO&INPIT Ž
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