A passive auxiliary circuit for load and line independent zero voltage switching in full bridge converters with reduced conduction losses for transportation applications

A novel auxiliary circuit to guarantee zero-voltage switching (ZVS) of full bridge converters is presented. A generalized time-domain analysis for steady-state behavior of the auxiliary circuit and a complete comparison with a single-inductor auxiliary are provided. For the same auxiliary peak current, a minimum of 20 percent less rms current is achieved to minimize conduction losses. Also in presence of adaptive peak current adjustment via switching frequency variation scheme 65 percent reduction in frequency variation range is obtained, reducing the need for a wide range of switching frequencies and extra gate driver losses. The theoretical results are experimentally verified.