LAUSR

LLC resonant converter is a soft switching frequency modulated dc–dc topology with its switching frequency near the resonant frequency. However, in applications where a wide output voltage is desired, it is extremely difficult to tune its operation close to the resonant frequency. In this paper, a novel pulsewidth modulated LLC type resonant converter based on voltage quadrupler rectifier is proposed. The proposed converter always operates at the resonant frequency and is able to achieve a wide output voltage range by modulating the duty cycle of the secondary side auxiliary mosfet. This brings the benefits of the decreased circulating current and corresponding conduction loss, as well as the simplification of the parameters selection and magnetic component design. Zero-voltage-switching and zero-current-switching are realized among all power mosfets and all power diodes, respectively. Detailed circuit operation principles and modeling method are presented. A 1.3-kW converter prototype, generating 250–420 V output from 390-V dc-link is designed. Both the circuit functionality and the theoretical analysis are verified in the experimental results.