A Five-Level Flying Capacitor Multilevel Converter with Integrated Auxiliary Power Supply and Start-Up

Andrew Stillwell, Robert Carl Nikolai Pilawa-Podgurski

Research output: Contribution to journalArticlepeer-review


This paper presents a five-level flying capacitor multilevel (FCML) converter with an integrated auxiliary power converter to supply power to the controller and gate drive circuitry. The auxiliary power converter is sourced from within the FCML converter at a naturally occurring low-voltage node, reducing the voltage rating requirements by 75% and thus the size of the auxiliary converter. The auxiliary load current drawn from the FCML converter induces an imbalance in the flying capacitors, which is detrimental to the capacitor and switch ratings if left unchecked. To compensate for this imbalance, an active-balancing method is proposed that adjusts the phase and duty cycle of the traditional phase-shifted pulsewidth modulated control signals. The active balancing requires only a single capacitor voltage measurement and proportional control with no additional hardware components. A start-up circuit is proposed to power the auxiliary power supply and soft-start the FCML converter. Experimental results have been demonstrated with an experimental prototype resulting in an excellent flying capacitor balancing and FCML start-up.

Original languageEnglish (US)
Article number8371641
Pages (from-to)2900-2913
Number of pages14
JournalIEEE Transactions on Power Electronics
Issue number3
StatePublished - Mar 2019


  • Active balancing
  • auxiliary power
  • flying capacitor
  • flying capacitor multilevel (FCML)
  • GaN
  • multilevel

ASJC Scopus subject areas

  • Electrical and Electronic Engineering


Dive into the research topics of 'A Five-Level Flying Capacitor Multilevel Converter with Integrated Auxiliary Power Supply and Start-Up'. Together they form a unique fingerprint.

Cite this