This thesis presents a control technique to improve power density and efficiency of a specific power converter topology, the flying capacitor multi-level (FCML) topology. Controlling these converters in such a way to achieve zero-voltage switching (ZVS) across the full range of duty cycles, reduces switching losses and therefore can be used to allow for more dense designs, or more efficient operation. Previous works have used variable frequency control to enable ZVS at specific duty cycles in FCML converters, but have not been able to use these methods to enable ZVS across the full range. This work uses dynamic level selection and variable frequency control to increase inductor current ripple at duty cycle ranges for which ZVS was previously unattainable. Furthermore, a mathematical analysis to determine parameters for active voltage balancing of the flying capacitors during a dynamic level transition is presented. An experimental 5-level FCML prototype was built using GaN devices on a single-sided printed circuit board (PCB) to demonstrate this control technique. We demonstrate 4-level and 5-level operation with ZVS at duty cycles that are not possible with 5-level operation alone, as well as dynamic level transitioning with active flying capacitor voltage balancing.




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