Design of a 9-Level Flying Capacitor Inverter with Very Fast Response of the Controller

With the increasing utilization of wide bandgap materials in power electronics such as silicon carbide (SiC) and gallium nitride (GaN), high voltage GaN transistors step into focus. However, low voltage GaN transistors have been on the market much longer and offer several advantages. The flying-capacitor multilevel converter topology enables these advantages and therefore makes system designs with highest power density and low volume possible. These characteristics are key-factors for penetration of products with wide bandgap materials into industrial electronics markets. This work presents a 9-level flying capacitor DC-AC inverter. Zero voltage switching (ZVS) greatly reduces switching losses, thereby enables high frequency operation of the inverter and consequently enhances efficiency. The implemented hardware is designed for an output power of 200Watt and the prototype is built on a modular platform around an FPGA based control system. The modulation scheme and control system allow for extremely high effective switching frequencies and very fast response. Experimental results demonstrate a peak efficiency above 99.0% and an effective switching frequency of up to 4MHz.