(1) comprising a rectifier bridge (2) of SCRs (T1, T2 ) and diodes (D2, D2 ) connected to a single phase AC supply (S2 ) through an input filter inductor (L1) capacitor (C1)configuration and fuse (F). a free wheeling diode (D3) and an output filter inductor (L2) and capacitor (C2) configuration are connected across the rectifier bridge. A load ® is connected across the output filter capacitor. A control circuit 5 comprises a dual output trigger generator (6), a pulse width modulated signal generator (7), a voltage comparator (8), a triangular wave generator (9), a switching frequency controller (10), an error amplifier (11), a turn off trigger generator (12), a transistor Q1, a high frequency voltage transformer (XT), a pair of diodes (D4,D5), a resistance (R1) and diode (D6) configuration and a diode D7. V1 and V2 are single-phase reference AC voltage and reference DC voltage, respectively.