Analysis of multi-phase LLC resonant converters

In this paper a topology for multi-phase interleaved LLC resonant converter is presented. The proposed solution, based on three LLC modules with transformer primary windings star connection allows to drastically reduce the output current ripple and consequently to minimize the output filter capacitor size. Differently from other multi-phase solutions, that are greatly susceptible to resonant component mismatch and consequently can be affected by a considerable current imbalance among modules, the proposed topology exhibits an inherent balancing capability. Small-signal analysis is presented and the possibility to turn-off one or two modules (phase shedding) at reduced output current levels is discussed, highlighting the trade-off between converter efficiency and output capacitor current ripple reduction. Measurements on a prototype will be included in the paper as validation of assertions and proposals.