An Active Split-Phase Control Technique for Hybrid Switched-Capacitor Converters Using Capacitor Voltage Discontinuity Detection

Abstract

Hybrid switched-capacitor (SC) converters have gained popularity due to their efficient switch utilization and use of energy-dense capacitors, which allows them to achieve high efficiency and power density even at large conversion ratios. The Dickson converter is one such popular hybrid SC converter, as it can achieve the theoretical minimum switch stress rating for a given operating condition. However, unlike other hybrid SC topologies that can automatically achieve full soft-charging through the addition of one or more augmenting inductors, certain Dickson variants also require the use of special switching schemes to fully soft-charge all flying capacitors. This technique, denoted as split-phase switching, inserts extra sub-phases into the control scheme so that flying capacitors are disconnected or connected at staggered times. Traditionally, split-phase timing has been calculated analytically, sometimes using imprecise models. This paper instead proposes an active control technique for detecting hard-charging events on the flying capacitors, such that the split-phase timing automatically converges on soft-charging operation. The technique is validated on an 8-to-1 resonant single-inductor Dickson hardware prototype. While this method is demonstrated on a resonant fixed-ratio converter in this work, the technique can also be applied to regulating split-phase applications, as well as used to detect hard-charging events in general.