Combined Multilevel and Two-Phase Interleaved LLC Converter with Enhanced Power Processing Characteristics and Natural Current Sharing

This paper introduces a new two-phase interleaved flying-capacitor LLC converter topology with high output current applications. Compared to a conventional two-phase LLC converter, the new converter adds a single capacitor that contributes to lower voltage stress on the primary side's switches, automatically balances the current distribution between the phases, and enhances the power processing capabilities. All the attractive features of LLC converters are preserved, such as zero-voltage switching on the primary side's mosfets, zero-current switching on the secondary side's power devices, narrow switching frequency range, and simple design. Full principle of operation and analysis of the converter are described, as well as the converter's primary characteristics and the impact of nonideal components on the current sharing behavior. A 600 W, 400 V-to-12 V experimental prototype is used as a showcase of the attractive features of the new converter, demonstrating excellent current sharing, simple implementation, and high efficiency of up to 97.3%.