Multiphase FCML Converter with Coupled Inductors for Ripple Reduction and Intrinsic Flying Capacitor Voltage Balancing

Abstract

This paper investigates multiphase flying capacitor multilevel (FCML) converters with coupled inductors for ripple reduction and intrinsic flying capacitor voltage balancing. FCML topologies and coupled inductors are two commonly used techniques to reduce power conversion stress, reduce ripple current, and improve system performance. Combining coupled inductors with multiphase FCML converters opens a wide range of design opportunities. The coupled inductors are shown to intrinsically balance the flying capacitor voltages, granting greater robustness to disturbances compared to uncoupled inductors and natural balancing. The ripple reduction offered by the coupled inductors and FCML structure are derived. The theoretical derivations are experimentally verified using a two-phase, three-level FCML converter. The ripple reduction and voltage balancing are realized as long as the inductors are sufficiently coupled.