From Two to Seven Level GaN π-Type Converter Operation for Increased Efficiency of Capacitive-Load Charging

This work experimentally investigates the effect of increasing number of levels on the measured converter system efficiency, using a seven-level $\pi$-type GaN power converter for cyclic capacitive load charging/discharging. The work provides insight into the partial power processing mechanism, and estimates further expected efficiency improvement from GaN-based monolithic bidirectional switches (MBDS). This work uses two common-drain connected HEMTs as discrete bidirectional switches (DBDS). Increasing the operation mode from two to seven levels increased the charging power by $600 \%$, but the measured losses only increased by $75 \%$, which improved the $\mathbf{9 9 . 0 \%}$ half-bridge efficiency to over $\mathbf{9 9 . 7 \%}$ multilevel charging efficiency (reducing the relative losses over 4 times).