A Novel Soft-Switching Secondary-Side Modulated Multioutput DC–DC Converter With Extended ZVS Range

In this paper, a novel soft-switching secondary-side modulated dc-dc structure with extended zero voltage switching (ZVS) range is proposed. In a simple manner, this structure can be extended to provide isolated multioutputs with independent voltage regulation capability. Besides, the secondary side can be bidirectional to interface with energy storage elements such as batteries and ultracapacitors. The proposed topology is suitable for high voltage gain or high output dc-link voltage, low-power, and multioutput applications. The primary-side full-bridge switches operate complementarily to generate a two-level square wave. Therefore, the circulating energy is significantly smaller than conventional phase-modulated full-bridge converters. The output voltage is regulated by controlling the duty cycle of the auxiliary mosfet on the active/semiactive rectifier, which offers a simple control. Moreover, the ZVS operation range of full-bridge mosfets is enhanced due to the volt-second balance of magnetizing inductance and the secondary-side control. All the secondary-side rectifying diodes turn off with limited di/dt. A 1-kW prototype generating two 390 V, 330-400 V outputs from a 130-180 V dc link is designed to serve as a proof of concept. The full-load efficiency is 95.6% at 100 kHz switching frequency.