A 99.1% efficient, 490 W/in3 power density power factor correction front end based on a 7-level flying capacitor multilevel converter

Abstract

This paper presents a power factor correction (PFC) front end based on a GaN-Based 7-level flying capacitor multilevel (FCML) boost converter. Compared to the conventional 2-level boost converter, the proposed 7-level FCML converter features the use of low-voltage-rated transistors, reduced voltage stress and high effective switching frequency on the filter inductor. These characteristics of the FCML converter lead to drastic reduction in the filter inductor size while maintaining high efficiency, and therefore significantly improve the power density of the PFC frond end compared to conventional solutions. On the other hand, the small inductance imposes challenges for the PFC control. The dynamics of the 7-level FCML converter has been analyzed and a feedforward control has been implemented to overcome these challenges. A hardware prototype is designed for universal AC input (90 VAC to 265 VAC), 400 V DC output at 1.5 kW power rating. The hardware prototype demonstrates improved efficiency and power density as well as power factor and THD performance compared to existing solutions. A peak efficiency of 99.07% and a power density of 490 W/in3 has been experimentally verified.