Dead Time Losses Comparison of GaN FET Versus Si MOSFET in Inverter Switching Leg

Optimal dead-time selection in switching converters is a critical design consideration for minimizing reverse conduction losses and enhancing output current quality. The minimum achievable dead time strongly depends on the device technology. In recent years, low-voltage AC motor drive applications, such as those in light e-mobility and humanoid robotics, have grown rapidly. While traditional Silicon (Si) MOSFETs remain widely used, they are increasingly being complemented or replaced by Gallium Nitride (GaN) devices, which continue to improve in performance and cost competitiveness. This paper deals with the comparison of the dead time requirements for GaN devices and Si MOSFETs used in inverter switching leg applications. The study focuses on low-voltage enhancement-mode GaN FETs and Si MOSFETs with similar current ratings, emphasizing the different reverse conduction mechanisms exhibited during dead time. The influence of dead time at different load currents, which are typical in inverter operation, is investigated through both simulations and experimental measurements. Additionally, device temperature measurements are used to assess the impact of dead time on the losses, further highlighting the differences between Si MOSFETs and GaN FETs from a thermal point of view. Based on the results, a methodology is proposed to select the optimal dead time duration to prevent cross-conduction, minimize power losses, and improve output current waveform quality.