A resonant DC-DC transformer

The characteristics of a push-pull parallel resonant converter (PPRC) when operated as a DC-DC transformer were investigated theoretically and experimentally. In the DC-DC transformer region, the voltage transfer ratio of the PPRC was found to be practically constant and independent of the input voltage and load. In this mode, all the switching elements operate in the zero voltage switching (ZVS) condition. Another important feature of the proposed DC-DC transformer is the ability to drive it by an arbitrary switching frequency, provided that the latter is lower than the self-oscillating frequency. This permits the synchronization of the converter to a master clock. The analytical expressions for voltage and current stresses, as well as the other key parameters derived, are applied to develop design guidelines for the DC-DC transformer. The proposed topology was tested experimentally on a 100-W unit which was run in the 200-kHz frequency region