Design of GaN FET-Based Multilevel Three-Phase Inverter for High Voltage Automotive Applications

In the ongoing growth of electrical mobility, there is much interest in new technologies for traction inverters. While silicon carbide (SiC) is already widespread in commercial products, gallium nitride (GaN) is still in the exploration phase. However, GaN FETs' low output capacitance and no reverse recovery when in reverse conduction, GaN transistors are more suitable than MOSFETs in several topologies and offer a significant reduction in PCB dimensions, enabling higher power density and efficiency. Therefore, this paper deals with designing, laying out, and prototyping a four-level flying-capacitor multilevel (FCML) three-phase 400 V DC, 50 Arms traction inverter for automotive applications. This inverter is intended both as a demonstrator and a fundamental building brick for a modular solution at higher power. In this paper, the design is described in both the electrical, thermal and control aspects highlighting the difficulties that may rise in a product. Finally, the experimental results of the prototype working at full current are presented.