A novel adaptive synchronous rectification method for digitally controlled LLC converters

In this paper, a novel adaptive synchronous rectification method for digitally controlled LLC converters is proposed. By sensing the synchronous rectifier (SR) body diode forward drop, both the SR turn-on and turn-off edges are optimized for efficiency. Negative current prevention is utilized to improve the system robustness and is enhanced by simple digital control capabilities. Compared with a conventional analog SR control approach, this method achieves higher system efficiency and flexibility. This control method has been implemented in a Texas Instruments digital power controller UCD3138A and a companion gate driver UCD7138.