Regenerative Passive Snubber Circuit for High-Frequency Link Converters

Abstract

This letter presents a passive snubber circuit for high-frequency link cycloconverters, which typically suffer from voltage oscillations across matrix-stage semiconductor devices. The proposed passive snubber allows for effective damping of the oscillations and reduction of the peak voltage stress. It is based on an auxiliary transformer and a diode bridge rectifier, which are rated only for a fraction of total converter power regenerated back to the input DC source. The performance of the circuit was verified with 350 VDC/230 VAC, 1 kW SiC MOSFET-based experimental prototype and a reduction of the peak voltage overshoot from 2.24 to 1.55 times the nominal was achieved, without negative impact on the converter overall efficiency. As a result, the blocking voltage rating of the matrix-stage semiconductors can be reduced from 900 to 650 V.