Multi-Mode Rectifier-Based LLC Resonant Converter for Wide Input Voltage Range Applications

A Photovoltaics system needs to be conditioned by a wide voltage gain converter to achieve high efficiency under a wide voltage range. The LLC resonant converter is a common solution in such applications, owing to its zero-voltage switching and zero-current switching capabilities. However, the frequency modulation in the LLC converter requires operating at a significantly different frequency from the resonant converter to cover the PV’s wide voltage, sacrificing efficiency. In this paper, an LLC resonant converter using a novel rectifier structure is proposed to achieve high efficiency under wide PV voltage. The novel rectifier structure can operate in three modes of operation— voltage-tripler rectifier, voltage-quadrupler rectifier, and voltage fifthfolder rectifier. In addition to the LLC converter’s soft-switching capability, this rectifier can narrow the switching frequency range and provide high voltage gain with a moderate transformer size. Finally, a 250-W experimental prototype with a high output voltage of 500 V was built and validated the proposed converter’s effectiveness.