Mitigation of Dead-Time Voltage Spikes in High-Frequency WPT Inverters: A Comparative Study of GaN HEMT and Si IGBT Technologies

This paper explores methods to eliminate high-voltage spikes during dead time (tdt) in high-frequency inverters for Wireless Power Transfer (WPT) systems, focusing on the transition from traditional Silicon IGBTs to enhancement-mode Gallium Nitride (GaN) HEMTs. At elevated switching frequencies, dead-time parameters strongly govern system efficiency and signal integrity. While IGBTs suffer from reverse-recovery charge (Qrr) in antiparallel freewheeling diodes that generates severe voltage spikes, hard-switching GaN systems require precise dead-time minimization to prevent shoot-through while limiting third-quadrant conduction losses. Unlike prior WPT studies bounded by specific hardware setups, this paper presents a baseline technology benchmark that explicitly decouples intrinsic semiconductor commutation physics, specifically Qrr=0 versus third-quadrant conduction, from macro-system parameters (fsw, power level, and resonant topology). Experimental evaluation of a 130 kHz L-S-tuned GaN full-bridge inverter confirms that primary current commutates via third-quadrant conduction during dead time, completely eliminating reverse-recovery voltage spikes (Irr=0). Ultimately, this work demonstrates that GaN’s spike-free operation is an intrinsic device-level property, reframing the dead-time optimization objective from transient overvoltage suppression to third-quadrant conduction loss minimization in next-generation WPT systems.