Stability Properties of Digital Predictive Current-Mode Controllers for Three-level Flying Capacitor Converters

This paper investigates the stability properties of digital predictive current-mode control (DPCMC) of three-level flying capacitor Buck converters (3LFC) operated in single-sampling and multi-sampling mode. While DPCMC has been extensively studied for basic dc-dc topologies, a dedicated analysis is required when it comes to multi-level converters due to the interaction between the predictive control law and the flying-capacitors (FC) voltage dynamics. This work clarifies the operating point-dependent and load-dependent stability properties of average and valley DPCMC and combines them with recently published results for peak DPCMC in order to provide a comprehensive picture for these types of digital controllers. The developed analysis is validated through simulations and experimentally on a low-voltage 500 kHz, 12V-to-1.5V, 500mA 3LFC-Buck prototype.