Multi-winding Transformer based CLLC Current Mismatch Mitigation using Inter-bridge phase shift

High current side of resonant DC-DCs utilize multi-winding transformer structure to ease the current stress of semiconductor devices and avoid layout complexity encountered due to parasitic mismatch of multiple parallelled wide-band gap power devices. However, in practice, a slight variation in the leakage inductance values of such a transformer could lead to a notable variation in port current rms values leading to unequal power losses and non-uniform thermal stress, and possible device failures. In this paper, CLLC modeling and analysis is performed to study the impact of inter-bridge phase shift on the alleviation of non-uniform port current distribution. To benchmark the converter performance vis-a-vis the developed analytical model, a wide-bandgap devices-based 600V -28V 1.6 kW CLLC hardware prototype with a three-winding transformer and two paralleled secondary ports is developed for a resonant frequency of 500 kHz.