In FIG. 2, the same reference numerals are used to denote the same elements as those used in FIG. 1. In the FIG. 2 embodiment, the AC voltage obtained in secondary coil n2 is rectified by diodes D1,D2 and is smoothed by a smoothing coil or chokes L1 and a capacitor C1, thus obtaining an output voltage V01. On the other hand, the AC voltage produced in secondary coil n3 is rectified by diodes D3,D4 and smoothed by a coil L2 and capacitor C2. The output terminals are con nected, as depicted, so that the output voltage V; formed across smoothing capacitor C2 is added to out put voltage V0], and is available between terminals 10 and 12, which terminals constitute second output terminals, as an output voltage V02 which is greater than output voltage V01.