The Novel Synchronous Rectifier Driving Method for LLC Series Resonant Converter

Abstract

This paper proposes a current driving scheme for synchronous rectifier (SR) of the LLC series resonant converter. Because the magnetizing current of transformer is included in the primary winding of transformer, it cannot be used to generate the driving signals of SRs. To cancel the magnetizing current from primary current, the magnetizing current detector circuit is used. With the proposed driving scheme, the SR body diode conduction is reduced to almost zero. Moreover, the driving scheme eliminates the reverse recovery problem of SRs. Therefore, higher efficiency can be achieved. To verify the proposed method, a 300W LLC series resonant converter prototype is made.