A Novel ZVZCS L2C-Type Parallel Resonant Converter with A Separated Resonant Tank

A novel ZVZCS L²C-Type parallel resonant converter is presented in this paper. This converter, compared with the Type-4 LLC converter, narrows the switching frequency deviation under wide input voltage range applications, while maintaining all soft-switching advantages as ZVS for primary switches and ZCS for output rectifiers, both of which eases design for input EMI filter. In addition, the proposed converter features in high-order resonance which not only improves the voltage conversion gain shown in curves under heavy load but also clamps short-circuit current to some level. Besides, the resonant tank is unique that one of the resonant inductor locates after the output stage rectifiers and whose energy flow keeps uni-directional, which is very different from the conventional bi-directional resonant tank concept. The detail operation principles, as well as the design considerations, were presented. A prototype aiming at network and telecom system of 200 V-400 V input, 54 V/10 A output, whose highest conversion efficiency is 95.2%, was developed to verify the validity and applicability of this topology.