Wide Load Range ZVZCS Three-Level DC-DC Converter With Compact Structure

To fit the requirements of high input dc-dc power conversion, a novel zero-voltage and zero-current switching (ZVZCS) three-level dc-dc converter is proposed. Some advantages of the proposed converter are concluded as follows. The OFF voltages on the primary switches are clamped around V-in/2 by the input capacitors and the blocking capacitor. A total of two MOSFETs with low VA rating are added to provide ZVZCS for the main switches in a wide load range. The switching loss of themain switches can be optimized because the soft-switching conditions of the turn-ON and turn-OFF instants are well decoupled. The primary components can achieve reduced current stress and even current distribution because the primary current is zero during the free-wheeling stages. As the current of the auxiliary MOSFETs is zero during most operation stages, the added conduction loss can be neglected. Furthermore, the added switching loss can also be neglected because these MOSFETs can achieve zero-voltage turn-OFF and zero-current turn-ON. The circuit, operation principles, and some technical analyses are discussed in this letter, and experimental results are also provided to evaluate the proposed converter.