PURPOSE: To make constitution simple and pulsation rate small by connecting two rectifier elements between both ends of an interphase reactor and the other side of an output terminal and providing the substantial capacity at which DC current is smoothed to the interphase reactor.

CONSTITUTION: The respective anodes of two rectifier elements 51', 52' for improving pulsation rate are connected to both terminals of an interphase reactor 3, and the respective cathodes are connected, as a common cathode, to the plus side of an output terminal. The DC current I0 in this case flows in the route of the secondary side of a welding transformer-load-interphase reactor-control rectifier element-secondary side of the welding transformer. The pulsation rate is improved by the interphase reactor having substantial smoothing capacity during this time. The electromagnetic energy accumulated in the interphase reactor is further made into DC currents IL1, IL2 by the elements 51', 52' and is supplied to the load.