A Power Supply Circuit for Gate Driver of GaN-based Flying Capacitor Multi-level Converters

Recently, flying capacitor multi-level (FCML) converters with GaN power switches have received increased attention due to their potential to achieve high efficiency and high power density. However, one of the major challenges is providing power to the gate drive circuits, most of which are not ground referenced. The most common existing method utilizes isolated DC/DC converters, which are bulky, expensive and energy inefficient. This work introduces two new techniques that leverage inherent properties of the FCML topology and the GaN switches to provide gate drive power to the floating switches with minimum hardware requirements. The two methods, termed cascaded bootstrap and gate driven charge pump, are analyzed in details and their performance evaluated. A new power supply circuit combining the two techniques can help shrink the size of the converter, and further increase the converter's power density. Experimental results show that the proposed circuit is up to 5x more power efficient than conventional solutions, at 1/10 of the cost.