High-Efficiency Impedance Control Network Resonant DC-DC Converter With Optimized Startup Control

This paper presents an improved efficiency impedance control network (ICN) resonant dc-dc converter that maintains zero-voltage switching (ZVS) and near-zero-current switching (ZCS) across wide ranges in input and output voltages and output power. The improvement in efficiency in this burst mode operated converter is achieved through an optimized startup control that minimizes its startup transient and helps the converter maintain ZVS and near-ZCS operation, even during the startup for each burst cycle. This optimization of startup is made possible by a new accurate time domain model for the ICN converter waveforms that helps reduce the number of non-ZVS transitions by 75%. A prototype 200 W, 500 kHz ICN resonant converter designed to operate over an input voltage range of 25-40 V and output voltage range of 250-400 V is built and tested. The prototype ICN converter achieves a peak efficiency of 97.2% and maintains greater than 96.2% full power efficiency at 250 V output voltage across the nearly 2: 1 input voltage range, and maintains full power efficiency above 94.6% across its full input and output voltage range. The converter also maintains efficiency above 93.6% over a 10: 1 output power range across its full input and output voltage range.