MOSFET synchronous rectifiers for isolated, board-mounted DC-DC converters

Board-mounted isolated DC-DC converters are being rapidly deployed in telecom and electronic data processing applications. In order to achieve required efficiency, power density, manufacturability and cost, a great majority of new low-voltage designs are utilizing power MOSFETs not only for the primary control switching, but also for the secondary synchronous rectification. However, requirements for MOSFETs used as secondary synchronous rectifiers can differ significantly from requirements of primary control MOSFETs, or even from MOSFETs used in nonisolated synchronous buck converters. Identifying these differences and specific circuit requirements is a prerequisite to specifying power MOSFETs suitable for a broad range of applications. This paper provides comprehensive analysis of circuit-level and MOSFET-level parameters and determines their significance for efficient synchronous rectification.