Advantage of GaN in Phase Shift Full Bridges

GaN FET and Si MOSFET have very different voltage dependence of output capacitance (Coss). Due to the difference, GaN FET offers low C
_oss
stored charge (Q
_oss
) while Si MOSFET gives low Coss stored energy (E
_oss
). As low Q
_oss
benefits reduction of resonant energy and time, GaN FET is ideal for resonant type of half or full bridges requiring low resonant energy and short resonant time. And, low Eoss makes Si MOSFET a good candidate for single switch hard switching applications. In this paper, detailed comparative analysis between GaN FET and Si MOSFETs is conducted for resonance in Phase Shift Full Bridge converters (PSFB). Following the analysis, a 200 kHz 3.3 kW PSFB for on-board charger application is built and evaluated in order to demonstrate the advantages of GaN FETs.