Zero Voltage Switching for Flying Capacitor Multilevel Converters at Nominal Conversion Ratios

In Hybrid Switched Capacitor topologies, zero voltage switching (ZVS) has recently gained attention as a key method to reduce switching losses. However, recent literature has identified certain conditions (particularly light-load), and conversion ratios where ZVS is challenging or impossible. Specifically, in Flying Capacitor Multilevel (FCML) converters, there are certain nominal conversion ratios (at integer fractions of the input voltage) where a first-order model predicts zero current ripple -preventing effective ZVS for low-high transitions. This paper will show that through the introduction of additional switching states and operating near the resonant frequency, ZVS can indeed be achieved in these scenarios. We discuss the additional switching states and analytically determine their time durations to achieve ZVS operation. The theory is verified with a 3:1 and 2:1 converter prototype, showing that the proposed method can significantly reduce power loss and dv/dt noise.