A Simple Active Balancing Technique for 5-Level Flying Capacitor Converters with Reduced Sensing Requirements

Flying-capacitor multi-level converters invariably require the flying-capacitor voltages to be balanced for optimal operation. Balancing is typically carried out using dedicated controllers that require multiple voltages to be sensed and operate multiple loops in parallel. This paper presents a simple control technique for flying-capacitor 5-level converters in which only one flying-capacitor voltage needs to be sensed, leading to reduced system, design, and hardware complexity. The technique, based on eliminating the main unbalancing mode of the converter using a single balancing loop, is theoretically developed through both steady-state and dynamic considerations, and validated in simulations as well as experimentally on a 12 V - 2.4 V, 200 kHz flying-capacitor 5-level converter prototype.