Influence of Reverse Conduction on Dead Time Selection in GaN-Based Inverters for AC Motor Drives

Although Gallium Nitride (GaN) Field Effect Transistor (FET) devices have found extensive application in DC-DC converters, their utilization in inverter motor drives remains an evolving area of study. In particular, the intricacies of reverse conduction operation during the dead time, specific to GaN FETs, require in-depth exploration for inverters supplying AC currents to electrical motors. Therefore, this paper undertakes an assessment of reverse conduction during the dead time intervals in low-voltage GaN FETs employed in motor drives applications. This analysis provides correlations between device technology attributes and the variations in AC phase current. To facilitate this investigation, a dedicated numerical tool is developed to evaluate the reverse conduction characteristics of GaN FET and associated power losses. Furthermore, this study includes a comparative analysis of the reverse conduction behavior of GaN FET devices with their low-voltage MOSFET counterparts, taking into account their differing static and dynamic characteristics. As a result, the main contribution of this work is to provide to the inverter designers a comprehensive understanding of dead-time effects in GaN-based inverters, along with guidance on selecting and optimizing dead time intervals within inverter legs for motor control applications employing the latest generation of GaN FET devices.