A High-Performance Isolated Bridgeless Resonant SEPIC PFC Converter at Medium Line Frequencies

Due to the characteristics of high power factor and low total harmonic distortion in discontinuous conduction mode, the power factor correction (PFC) converter based on isolated single-ended primary-inductor converter (SEPIC) is more suitable for medium-line-frequency avionics applications. However, the inherent defects of isolated SEPIC PFC converter, such as the voltage-spike issue and the hard-switching operations of semiconductor components, severely limit the utilization of such topologies. In this article, a high-performance isolated bridgeless resonant SEPIC PFC converter is proposed. Instead of typical SEPIC-type operational mode, the proposed converter operates in resonant mode, and hence, all switches and diodes in this topology can achieve soft switching and the voltage-spike issue is effectively solved. Moreover, different from the existing isolated SEPIC PFC converters, the transformer in this topology can transfer energy through the whole switching cycle, which greatly improves the core utilization. The overall performance of the proposed topology is illustrated in terms of its working principles, control scheme, and the parameter design considerations. Finally, the analysis is validated by a 400-Hz experimental prototype with soft-switching capability.