Ripple-based approach for predicting fast-scale instability in multi-level converters

Multilevel (multicell) converters are candidates of interest for power management applications requiring miniaturization -onchip integration- and/or bandwidth extension - wideband tracking -. This paper proposes a design-oriented model for predicting fast-scale instability occurrence in a 3-level (2-cells) converter, based on extending a ripple-based index previously validated for predicting fast-scale instability in a simple two-level buck converter, thereby demonstrating the general applicability of such instability index. The paper first characterizes fast-scale period-doubling instabilities in the multilevel converter, and afterwards presents a discrete-time map for predicting their occurrence as a reference analytical method for instability characterization. The paper finally explores the design-oriented fast-scale instability boundary prediction capability through the ripple-based index. It is shown how the multilevel converter, due to its inherent capability to reduce output voltage ripples, is less prone to exhibit chaos-resulting fast-scale instabilities.