Abstract: A rectifier 4 develops a rectified voltage between output terminals thereof. Capacitors 6a and 6b are connected in series between the output terminals of the rectifier. Inverters 8a and 8b convert DC voltages across the associated ones of the capacitors 6a and 6b into high-frequency voltages, which are, then, voltage transformed. The transformed voltages are rectified by diodes 24a and 24b for application to an arc-utilizing apparatus. Inverter control circuits 38a and 38b control the inverters 8a and 8b, respectively, in such a manner as to make current-representative signals from current detectors 50a and 50b equal to a reference signal, respectively. A voltage divider 54 is connected in parallel with the series combination of the capacitors 6a and 6b. Voltage detectors 62a and 62b connected between the junction A of the capacitors 6a and 6b and the junction B of resistors of the voltage-divider 54 develop a voltage representative signal representative of the voltage between the junctions A and B.