Voltage Clamping Circuits for Large Voltage Step-Down Coupled Inductor Converters

Abstract

Water desalination processes require power converters with large voltage step-down ratios and high efficiencies.  Coupled‑inductor (tapped-inductor) circuits can achieve this where the whole inductor carries current during one switch state but only part of the inductor carries current during the second switch state. The switch state change results in excessive switch voltages due coupling leakage. To protect the switching device, a novel voltage clamp is presented which improves the overall efficiency of the switching circuit and recovers otherwise wasted energy. It requires no closed-loop control. For higher power levels, an asymmetric half-bridge coupled-inductor buck converter circuit, which offers switch protection without a snubber, is presented. The circuit is shown to offer reduced switching losses despite having two switching components in the high-voltage forward conduction path.