The Flying Capacitor LLC Converter: A Hybrid Switched Capacitor Converter with Galvanic Isolation for Large Step-Down Applications

Abstract

In this work, we combine two popular power conversion topologies, the flying capacitor multilevel (FCML) converter and the LLC converter, to arrive at the proposed flying capacitor LLC (FCLLC) solution with advantages of each. The FCLLC comprises a stepdown resonant switched-capacitor (ReSC) stage followed by a resonant transformer-based stage which provides soft charging of the flying capacitors, galvanic isolation, and an additional step-down through the transformer. These conversion ratios are multiplied, making the FCLLC especially suited for extreme conversion ratios. An FCLLC prototype capable of direct 400 V to 1 V conversion is fabricated, which demonstrates the potential this topology has for future datacenter applications.