Power density and efficiency optimization of resonant and phase-shift telecom DC-DC converters

Power density and efficiency are one of the major driving forces in the development of new power supplies for telecommunication and information industry. The phase-shift PWM and the series-parallel resonant DC-DC converter are promising topologies that can meet these demands at high power rates. Based on conventional criteria such as the number of semiconductors/passive components or voltage/current stress it is not possible to identify the topology that offers a higher power density or efficiency. Therefore, an optimization procedure has been developed, which calculates the optimal converter parameters (e.g. switching frequency or transformer design) with respect to the maximal power density and/or efficiency. This procedure is based on detailed analytical models for the converter, semiconductor losses, HF losses in the magnetic components as well thermal and geometrical models of the transformer. With the procedure a 5 kW series-parallel resonant converter and a phase shift converter with capacitive output and with current doubler have been optimized. With the calculated parameters a resonant converter prototype has been constructed and experimental results are presented.