Optimized Switching Sequence for Multiphase Power Converters Under Inductance Mismatch

Abstract

Multiphase power converters allow to reduce semiconductor stress and to improve total ripple characteristics, when compared to a single-phase converter. Semiconductor stress is reduced by dividing the total current among the N parallel-connected converters or phases. Furthermore, total ripple amplitude is reduced and its frequency increases to N times the switching frequency by interleaving each phase current ripple, which lessens the requirements on the total current filtering. These improvements, however, are detrimented mainly by mismatches among the phase inductors value, leading to different ripple amplitudes among phases. As a consequence, when compared to the ideal case, total ripple amplitude is increased, ripple cancellation points are lost, and switching frequency component and its N-1 harmonics are generated. This letter proposes a method to mitigate this problem by selecting the phase switching sequence, in converters operating in the continuous conduction mode, which minimizes the switching frequency component and its harmonics in the total ripple. The proposed method efficiently finds the proper switching sequence for any number of phases, by using a previously presented current ripple characterization as the objective function for the optimization procedure. Simulations validate the proposal and show the improvement, when compared to another strategy present in the literature, which uses the switching sequence modification principle.