Multi-Level Flying Capacitor Buck Converters with Digital-Predictive Current-Mode Control

Abstract

This talk presents the main results of my PhD research on multi-level flying capacitor buck converters with digital predictive current-mode control, focusing on their application in modern automotive electronics. The increasing demand for compact, high-efficiency, and high-performance DC-DC converters in vehicles has driven the exploration of advanced converter topologies. Multi-level flying capacitor architectures offer significant advantages in terms of efficiency, dynamic response, volume, and converter footprint reduction. Unfortunately, their practical deployment is challenged by the need to maintain stable and balanced flying capacitor voltages.

To address this, I developed a unified analytical methodology for the closed-loop stability analysis of flying capacitor voltages under digital predictive current-mode control. This approach fills a gap in the literature, providing closed-form solutions for both three-level and generic n-level converters. The proposed methodology is more general and may be used for a wide range of digital controllers, enabling precise prediction of steady-state and dynamic behavior.

Additionally, I introduced two novel digital corrective controllers that enhance the speed of corrective actions and expand the available control bandwidth without increasing the switching frequency. These controllers, validated through extensive simulation and experimental testing, demonstrate robust self-balancing properties and improved dynamic performance. The experimental results, obtained using custom prototypes, confirm the theoretical predictions and highlight the practical feasibility of the proposed solutions.

In summary, this research delivers new analytical tools and control strategies for multi-level flying capacitor converters, advancing their reliability and performance in automotive and other demanding applications. Given the ongoing trend toward electrification and digitalization in transportation and industrial systems, these innovations have the potential to significantly influence the next generation of power electronic converters, enabling more efficient, compact, and reliable solutions for future smart mobility and energy management platforms.