Efficient LLC Resonant Converter With a Simple Hold-Up Time Compensation in Voltage Doubler Rectifier

LLC resonant converter is one of the promising converter topologies due to its simple structure and high efficiency. However, when LLC resonant converter is designed considering a hold-up time requirement, it has definite drawbacks such as large conduction and turn-off losses due to large circulating current. To solve this problem, various resonant converters with boost capability have been investigated. Although these methods improved overall performance, they still suffer from a large number of switching components. In this paper, a new LLC resonant converter with boost capability is introduced and verified. The advantage of the proposed converter is a small number of components while achieving the hold-up time capability. Furthermore, it achieves zero average transformer current despite its asymmetric operation. A prototype has been built and tested with 400–250-V input and 200-V/200-W output specification.