A high-density 1 kW resonant power converter with a transient boost function

A series/parallel resonant DC-DC converter with secondary-side resonance and a novel input boosting feature is described. In order to greatly reduce the conduction loss (factor of 4) due to circulating currents in the resonant components, the boost circuit, which requires no additional active switches, operates only when needed during transient input voltage dips. This reduces the effective input voltage range over which the converter must operate and allows optimization at the steady-state input voltage. The converter employs highly efficient resonant inductors and novel z-folded thin flex circuit transformer windings in order to meet a density of 60 W/in³ with an efficiency approaching 95%. The DC-DC converter is being developed for use as a 270 V to 50 V line converter for distributed power applications