An Expandable ZVZCS High Step-Down Interleaved DC–DC Converter

This article introduces a new expandable multiphase interleaved converter. The presented idea can be applied to
K
phases, where
K
is an even number (2, 4, 6,…). In this converter, zero voltage zero current switching (ZVZCS) and zero voltage switching (ZVS) conditions are achieved for the main switches at turn-
on
and turn-
off
instants, respectively. The synchronous rectifiers (SRs) and auxiliary switches operate under ZVS conditions. Moreover, the body diodes of SRs turn
off
under zero current switching (ZCS) conditions. This topology employs the series capacitors to improve the voltage gain and clamp the voltage stress of switches. Furthermore, ultrahigh step-down conversions can be achieved by adjusting the turns ratio of coupled windings. In the proposed converter, by utilizing one auxiliary four-quadrant switch for each pair of phases and a new switching algorithm, ZVS and phase interleaving are simultaneously provided, regardless of the number of phases. Although the leakage energy of coupled inductors is used to provide soft switching, the current ripple of the leakage inductor is not reflected in the output current, and uniform current sharing between modules is fully automatic. In addition, by increasing the number of phases, the duty cycle range in which the current sharing is uniform does not shrink. Continuous output current with low ripple and common input and output ground are other important strengths of this converter. The above-mentioned merits are achieved all together without using any extra magnetic core or current sharing control circuit. Also, the number of blocking capacitors is low and equal to the number of phases minus one. The operation principles of the introduced topology are presented and the theoretical analysis is confirmed by two laboratory prototypes.