A New Current-Driven Synchronous Rectifier for Series–Parallel Resonant ( $LLC$ ) DC–DC Converter

A new synchronous rectifier (SR) driving method is proposed using primary current sensing in this paper. 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 directly. A current-compensating winding in current transformer (CT) is used to cancel out the magnetizing current and generate suitable driving signals for SR. Therefore, one CT is used to generate two driving signals for two SRs in LLC converter with a center-tapped rectifier. This current-driven method is simple and low cost for high-output-current dc-dc application. A 150-W dc-dc prototype using LLC half-bridge converter with the proposed SR circuit is built up to verify the theoretical analysis.