A multi-level, multi-phase buck converter with shared flying capacitor for VRM applications

This paper introduces a multiphase high step-down DC-DC converter that is suitable for voltage regulator module (VRM) applications. In particular, this converter is derived from the conventional flying capacitor multilevel converter. Despite being a multiphase topology, the converter contains just a single flying capacitor that reduces voltage swing at the inductor switching nodes. Furthermore, all switches experience a maximum voltage stress of half the input voltage providing benefits such as the use of transistors with better figures of merit (FOM), as well as reduced switching losses. The converter is well suited for high conversion ratios and high load output required by VRMs as the freewheeling path of each phase contains only one switch. The effectiveness of this topology is verified with an experimental prototype with wide input voltage 12V/24V, and load V_out = 1.2 V, I_out ≤ 40 A operating at 500 kHz switching frequency. Peak efficiencies of 93.2% at 16A, and 89.4% at 28A, are attained with inputs at 12 V and 24V, respectively.