A New Voltage-Doubler Rectifier for High-Efficiency LLC Resonant Converters

The LLC resonant converter is widely recognized as an effective solution for achieving high efficiency in high-frequency operations. This is primarily due to its ability to perform zero-voltage switching (ZVS) on primary switches and zero-current switching (ZCS) on secondary rectifier switches. However, implementing the secondary rectifier of an LLC resonant converter often requires the use of jumpers on the PCB to construct circuit topologies such as the center-tap rectifier (CTR), full-bridge rectifier, and voltage-doubler rectifier (VDR). In conventional VDR configurations, the source voltage of the high-side FET fluctuates according to the switching operation of the primary switch. This fluctuation necessitates auxiliary windings or bootstrap circuits to provide a floating voltage source, adding significant complexity to gate drive circuits in high-power-density applications. This complexity poses a major barrier to the practical adoption of VDRs. To address these challenges, this paper proposes a novel rectification circuit based on the VDR topology, specifically designed for LLC resonant converters, offering simplified gate drive circuitry and improved suitability for high-power-density applications.