A three-level GaN-based gate driver with reduced loss by stepwise charging

Abstract:
This work presents a GaN-based gate driver with three levels, where stepwise capacitor charging theoretically enables a 50% loss reduction compared to conventional two-level drivers. A discrete n-type GaN-based driver final stage with Si- CMOS pre-driver and bootstrap supply is built. Experimentally, a gate drive loss reduction by 35% is measured while driving a GaN power transistor with 3 nF input capacitance at 500 kHz. This work beneficially uses the gate-source voltage dependent reverse blocking behavior of GaN HEMTs such that only one GaN HEMT with only one additional gate is needed to implement the middle level, instead of a conventional bidirectional blocking GaN HEMT, which would require two additional gates even in the case of monolithic bidirectional blocking GaN HEMT. While wide-bandgap semiconductors enable increased switching frequencies, this also increases the gate driving losses. Thus, especially for high power applications, this work contributes to more efficient energy conversion.