Parasitics Assisted Soft-switching and Naturally Commutated Current-fed Bidirectional Push-pull Voltage Doubler

A snubberless current-fed push-pull dc/dc voltage doubler is proposed with zero voltage switching (ZVS) turn-on of low voltage current-fed devices by using the parasitic resonance between the drain-source capacitance of MOSFETs and the leakage inductance of the high frequency transformer. Secondary modulation helps reduce switching losses further by obtaining zero current switching (ZCS) turn-off of primary devices and ZVS turn-on of secondary devices. Realizing ZCS of current-fed devices introduces natural zero current commutation and eliminates the traditional requirement of active-clamp or passive snubbers in current-fed topologies. Push-pull topology has low device and driver requirement. Voltage doubler offers 2x voltage gain reducing the device count by half on secondary that simplifies the transformer and control design and efficiently reduce the low frequency dc current harmonics. The proposed topology with novel modulation is suitable for interfacing energy storage and/or fuel cell stack with dc bus in FCVs or as frontend dc/dc converter in fuel cell inverters or connecting fuel cells to dc grid. Steady-state operation and analysis of proposed topology with proposed modulation has been studied. Design of a 1kW prototype is explained. Simulation results using PSIM 9.3 and experimental results of a 1 kW prototype have been demonstrated to verify the operation, proposed mathematical analysis, design, and the proposed claims.