Soft-Switching Operation of the Dual-Interleaved Boost Converter over all Duty Ratios

To extend the operating range of the snubber assisted zero-voltage and zero-current transition (SAZZ) dual-interleaved boost converter beyond its inherent soft-switching limit of D=0.5, a resonant pulse transformer is proposed instead of the resonant inductor. The 1:2 turns ratio of the transformer ensures full discharge of the snubber capacitor at all duty ratio values to facilitate zero-voltage zero-current switching (ZVZCS) at turn on of the main switching devices. The effectiveness of the topology has been confirmed by SPICE simulation and demonstrated by a 20 kW SiC MOSFET converter. The prototype operated at 20 kW, 112 kHz, 320-600V achieving 98.7% efficiency and achieved 98.2% efficiency at 6 kW. Taking the additional losses in the auxiliary circuit into account, the switching losses at 20 kW are reduced by 74% compared with hard-switching operation, representing a 54% reduction in overall losses.