A Universal Adaptive Driving Scheme for Synchronous Rectification in LLC Resonant Converters

In this paper, a universal adaptive driving scheme for synchronous rectification (SR) is proposed. The drain to source voltage of the synchronous rectifier is sensed so that the paralleled body diode conduction is detected. Using the proposed SR driving scheme, the SR turn-OFF time is tuned to eliminate the body diode conduction. The SR gate driving signal can be tuned within all operating frequency regions. Moreover, a simple digital implementation is introduced. Compared with analog ones, it enables more intelligent and precise SR control, improving converter efficiency. For rapid prototyping purposes, the digital SR tuning system is realized in Cyclone III field-programmable gate array (FPGA).