Digital Predictive Current-Mode Control of Three-Level Flying Capacitor Buck Converters

Abstract

This article investigates the use of digital predictive current-mode control (DPCMC) in dc-dc three-level flying capacitor (3LFC) buck converters. In particular, stability and flying capacitor (FC) balancing properties of predictive peak, average, and valley current-mode controllers are studied when operated in single- and multisampled modes. A variant of the multisampled DPCMC obtained through a fast-update of the duty cycle command is also disclosed and analyzed. Results indicate that single-sampled DPCMC is always stable, and that fast-update approaches can strongly improve the converter dynamic response. Multisampled controllers are also shown to be inherently more robust than single-sampled ones against timing mismatches in the control signals, resulting in a smaller FC voltage imbalance. The analysis is validated in simulation and experimentally on a 500 kHz, 12-1.5 V, 500 mA 3LFC buck case study.