Traditional dead-time selection methods developed for kHz-range LLC converters are inadequate for MHz, kW scale designs employing GaN devices. This paper presents a closed-form time-domain equation for dead-time determination based on the nonlinear output charge of GaN switches. Because GaN devices lack a body diode, incorrect dead-time selection can increase third-quadrant conduction losses and compromise zerovoltage switching (ZVS). The proposed formulation accurately predicts the minimum dead time required to fully discharge the device output capacitance with the resonant current, thereby ensuring robust ZVS and reducing switching and conduction losses. The method is validated through detailed circuit simulations and experimentally demonstrated on a 1-MHz, 5-kW LLC resonant converter, confirming its suitability for high-frequency, wide-bandgap-based resonant power stages.
