Adaptive driving of synchronous rectifier for LLC converter without signal sensing

Abstract

This paper presents the novel driving technique of synchronous rectifier (SR) for the LLC converter. The unique characteristic of “Vo*D=constant” of LLC converter is utilized to predict optimal duty ratio D, where D is the conduction period of secondary diode. This technique does not need the sensing of SR current neither SR voltage. Additionally, the auto tuning technique is implemented to adjust the duty ratio precisely as well by digital control using TI's DSP of Piccolo TMS320F28027. The technique is confirmed by experimentally..