Abstract: In addition to a conventional rectifier responsive to an input AC voltage, another or second rectifier is employed such that the input AC voltage is first reduced to be applied to the second rectifier. To reduce the input AC voltage a transformer or one or more capacitors may be used. Furthermore, when one or more capacitors are used, the input AC voltage may be once boosted by way of a boosting transformer. A capacitor is connected across output terminals of the second rectifier to be charged with a rectified current therefrom. The output terminals of the first rectifier are respectively connected to output terminals of the first rectifier so that two different DC voltages are combined or superposed one on another. A diode is employed to prevent the capacitor from being charged with a current from the first rectifier.