Monolithic Integration of the Synchronous Rectifier in Isolated Forward DC-DC Converters

摘要

The synchronous rectifier in isolated forward DC-DC converters is traditionally built with discrete DMOS power transistors driven directly from the secondary winding of the pulse transformer. Unfortunately, this technique induces very high switching losses, especially at high switching frequency. This paper presents a new synchronous rectifier topology that drives the DMOS devices in a much more power-efficient manner, employing an additional DC-DC buck converter, and that allows monolithic integration of the whole synchronous rectifier electronics in a suitable high-voltage smart-power IC technology. Special circuitry for suppressing sub-threshold conduction of the DMOS transistors is also provided on the chip.