Robust ZAD sliding mode control for an 8-phase step-down converter

This paper describes the design, robustness analysis, and implementation of a zero average dynamics sliding mode control (ZAD–SMC) for a multiphase step-down converter. The ZAD–SMC operates at fixed switching frequency and allows to implement an interleaving technique providing current-ripple cancellation at the converter output. Moreover, the proposed control structure, which is based on a master–slave strategy, includes an equalization technique guaranteeing current sharing among the phases and avoiding undesirable power unbalance. Additionally, a stability analysis considering unmatched losses in the converter phases shows that the design provides asymptotic stability for the overall load range. The controllers are implemented in an FPGA, and all the expected features, such as fast transient response, robustness, fixed switching frequency, interleaving, and current equalization are sustained by the experimental results obtained from using a 1.5-kW prototype.