Fully soft-switched three-stage AC-DC converter

The paper presents a fully soft-switched three-stage AC-DC power supply for server applications. In this three-stage architecture, the front-end boost PFC is followed by a dc-dc boost converter that serves as a preregulator to the isolated dc-dc output stage. Through magnetic integration, softs witching of all semiconductor switches in the PFC boost converter and dc-dc boost preregulator is achieved in addition to a reduced number of magnetic components. Generally, the output dc-dc stage can be implemented with any isolated topology. In this development, zero-voltage-switching half-bridge dc-dc converter is employed for the third stage. The performance of the proposed three-stage approach was evaluated on a 700-W / 12-V, universal-line-range ac-dc prototype.