Balancing Multiphase FCML Converters With Coupled Inductors: Modeling, Analysis, Limitations

Daniel H. Zhou, Janko Celikovic, Dragan Maksimovic, Minjie Chen

Research output: Contribution to journalArticlepeer-review


This article investigates the modeling, analysis, and design methods for passively balancing flying capacitor multilevel (FCML) converters using coupled inductors. Coupled inductors synergize with FCML converters by reducing inductor current ripple, reducing switch stress, and, as proven in this article, by providing flying capacitor voltage balancing. This enables FCML topologies to be scaled well to larger systems. This article proves that coupled inductors can solve the unbalancing problem in many FCML converters. Moreover, tools are developed to thoroughly explain and quantify coupled inductor balancing, allowing general design guidelines to be offered for robust coupled inductor FCML converters. Finally, this article derives the limitations of coupled inductor balancing with respect to the number of phases, levels, and the required coupling ratio. The key principles of coupled inductor FCML balancing in steady state are demonstrated with a systematic theoretical framework and extensive experimental and simulation results.

Original languageEnglish (US)
Pages (from-to)9268-9291
Number of pages24
JournalIEEE Transactions on Power Electronics
Issue number8
StateAccepted/In press - 2024

All Science Journal Classification (ASJC) codes

  • Electrical and Electronic Engineering


  • Charge balancing
  • coupled inductors
  • feedback mechanism
  • flying capacitor multilevel (FCML) converter
  • natural balancing
  • passive voltage balancing


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