Soft Switching PWM Cascaded Three-Level Combined DC–DC Converters With Reduced Filter Size and Wide ZVS Load Range

Two soft switching cascaded three-level (TL) combined dc-dc converters are proposed in this paper. The first converter is composed of a half-bridge cascaded TL dc-dc converter (CTLC) and a full-bridge (FB) CTLC, and the other one is composed of two FB CTLCs. The presented topologies have following common advantages: off-state voltage on all switches is only half of the input voltage; the structure of the primary circuit is simple and compact; all primary switches are directly clamped by the input capacitors and no added clamping devices are required; and the voltage across the output LC filter is a TL waveform, which results lower output filter volume and faster system dynamic response. In addition, the input filter can also be minimized. All power switches in the proposed converters can obtain zero-voltage switching in wide load range; furthermore, less conduction loss is added. The operation and technical analysis of the proposed converters are given. Experiments are carried out to validate the proposed converters, and efficiency curves are tested and given.