Coupled inductor implementation improves performance of output feedback ZVT in full bridge inverters

This paper proposes a topology based on output feedback zero-voltage-transition (ZVT) technique with coupled inductor to realize zero-voltage-switching (ZVS) for all the main switches of the full bridge inverters, and inherent zero-current-switching (ZCS) for the auxiliary switches. The advantages of the strategy include the provision to implement zero state modulation schemes such as unipolar or hybrid scheme in the full bridge inverters to decrease the THD significantly, naturally adaptive auxiliary inductor current and without the requirement of large balancing capacitors. The coupled inductor can decrease the core loss compared with the previously reported individual inductor method and can decrease the auxiliary current needed to realized ZVS of the main switches. The modulation scheme and the commutation process are analyzed in detail. Finally a 1 kW, 400 kHz switching frequency inverter of the proposed topology using SiC MOSFETs has been built to validate the theoretical analysis. The proposed ZVT with hybrid modulation technique is implemented in DSP TMS320F28335 resulting in full ZVS for the main switches. Compared with no ZVT case, the proposed method can improve the system CEC efficiency significantly from 95.58% to 97.29% and peak efficiency from 96.29% to 97.86%.