Study on reducing switching current in dual bridge series resonant DC/DC converter

Dual bridge series resonant DC/DC converter (DBSRC) usually works at continuous current mode (CCM), whose switching frequency is set higher than resonant frequency. Thus, soft switch-on and soft switch-off of power switch cannot be realized simultaneously with no extra snubber circuit connected. And the primary measure to reduce switching losses is to reduce the switching current of power devices. The commutations of DBSRC in different conditions are analyzed in this paper and the values of switch-on and switch-off current are derived from this model. From the view of reducing switching current, this paper gives a guideline to select the parameters of DBSRC correctly, including the voltage conversion ratio (M), the ratio between switching frequency and resonant frequency (F) and the characteristic impedance (Zr). The simulation obtains the switching currents at different F, M and Zr, whose results verify the effectiveness of theoretical analysis. And the experiment results prove a better system efficiency with a better selection of switching frequency.