State-Space Modeling and Control of Flying-Capacitor Multilevel DC–DC Converters

Hybrid and resonant switched-capacitor converters show promise in a number of power management applications, but are subject to a range of challenges in control and implementation. In particular, hybrid topologies use a network of switched flying capacitors to reduce voltage stress on switching devices and energy storage requirements of inductor(s). However, the increased order of system dynamics can lead to problems with voltage balance and regulation of the unique flying-capacitor voltage states, leading to higher voltage stress and other undesirable effects. This article presents a simple yet comprehensive state-space analysis of hybrid topologies, which can be used to predict and control system dynamics including voltage imbalance phenomena. The model affords new perspectives on modern control metrics through a condition-number-based treatment, providing relative quantification of observability and controllability. Expanded opportunities such as a state observer and discrete-time eigenvalues that govern natural balance are presented. The model is exemplified and validated using flying-capacitor multilevel converter hardware prototypes.