PURPOSE: To obtain a high-efficiency power circuit by connecting a parallel circuit of plural sets of resistances and capacitors in series with a DC power source, deriving a control power source from one of said resistances and connecting other resistance ends with DC/AC converters.

CONSTITUTION: Parallel circuits of resistances R1∼Rn and capacitors C1∼Cn and of a resistance RS and capacitor CS are connected in series with a DC power source E. An alternating current generated by application of the DC voltage at both ends of respective resistances R1∼Rn to DC/AC converters CO1∼COn is inputted to the primary side of transformers T1∼Tn. Synthetic voltage obtained by connection in series of AC outputs on the secondary side is commutated D, smoothed by a reactor L and a capacitor C and supplied to a load. Also, the voltage at both ends of the resistance RS is made a constant voltage by a shunt regulator, a control circuit CC is driven and the DC/AC converters CO1∼COn are controlled by an output of the control circuit CC. In this manner, a voltage divider circuit for the control circuit use becomes unnecessary to permit constituting a high-efficiency power unit.