A soft switching four-phase converter with ultra-high step down conversion ratio and automatic uniform current sharing

This paper introduces a new high step down four-phase converter with soft switching and automatic uniform current sharing. The phase number of the introduced topology can be expanded. In this converter, the main switches are turned on under zero voltage zero current switching condition and turned off under zero voltage switching. Also, the auxiliary switches and diodes operate respectively under zero voltage switching and zero current switching conditions. In the proposed architecture, the duty cycle is extended and the semiconductors voltage stress is reduced by applying series capacitors and coupled inductors. The leakage energy associated with the coupled inductors is absorbed and the reverse recovery losses of diodes are eliminated. Uniform current sharing between four phases is achieved without any extra current sharing control circuit. Furthermore, by utilizing the interleaved method, the current stress and the output current ripple are reduced. This converter provides above advantages while its input and output grounds are connected. As a result, the introduced topology can provide high step down conversions at high frequencies. The converter operation and its characteristics are analysed in detail. The accuracy of the theoretical analysis is verified by a laboratory prototype.