A high power density power factor correction front end based on a 7-level flying capacitor multilevel converter

This paper presents a power factor correction (PFC) front end based on a 7-level flying capacitor multilevel (FCML) boost converter. The operation of the FCML converter is introduced to illustrate its benefits in terms of efficiency and power density. Compared to conventional 2-level boost converter design, the proposed 7-level FCML converter features the use of low-voltage-rating transistors and a high effective switching frequency. These characteristics of FCML converter lead to drastic reduction in the filter inductor size while maintaining high efficiency and small heat sink volume, and thus significantly improve the power density. On the other hand, the small inductance imposes unique challenges in the implementation of the PFC control. In this work, a digital control implementation is presented to overcome these challenges. A hardware prototype is designed for universal AC input (90 Vac to 265 Vac), 400 V DC output and 1.3 kW power rating, and its performance has been experimentally demonstrated.