New driving scheme for self driven synchronous rectifiers

Abstract

Self-driven synchronous rectification (SDSR) is a very good technique to improve efficiency and thermal management in low output voltage converters. In this paper, a new scheme to drive the synchronous rectifiers (SRs) is proposed. It allows for maintaining the SRs on even when the voltage in the transformer is zero, which is impossible to do in traditional self-driven approaches. It also makes possible to drive properly the SRs even for applications where output voltage is lower than 3.3 V, namely 1.5 V. Furthermore, driving losses are very low, since the discharge of one MOSFET is used to charge the other and vice versa. This scheme has been validated in two prototypes.