Control technique for reliable operation of the synchronous series capacitor tapped inductor converter

In the context of reducing total CO₂ emissions as well as reducing the total copper cable length and weight on cars, automotive manufacturers propose to derive all the supply voltages from a single 48 V bus through high step-down ratio dc-dc converters. The series capacitor tapped inductor (SCTI) converter is a promising topology for efficient single-stage step-down conversion from the 48 V bus. In the synchronous version of the SCTI, however, turn-off of the synchronous rectifier at positive drain-to-source current leads to a voltage spike and to a potential catastrophic failure of the converter. In this paper a simple control technique is proposed which prevents the foregoing condition to occur. The approach enables a reliable operation of the synchronous SCTI topology without disrupting its main features and advantages, and eliminating the need for additional snubbers, voltage clamps or auxiliary windings. The approach is validated via computer simulations and experimental tests on a 48 V-to-1.5 V, 4 A SCTI converter prototype.