Self-Driven Synchronous Rectification System With Input Voltage Tracking for Converters With a Symmetrically Driven Transformer

Synchronous rectification (SR) is mandatory to achieve good efficiencies with low output voltages. If a transformer is driven asymmetrically without dead times, the self-driven SR (SDSR) is a very interesting solution. However, if the transformer is driven symmetrically, the synchronous rectifiers are off during the dead times, and as a consequence, the efficiency is lowered. This paper deals with the optimization of an SDSR system that keeps the rectifiers on even during the dead times. The input voltage is tracked, and the information is used to adapt the gate to the source voltage of the synchronous rectifiers and improve the efficiency. The system has been implemented in a prototype, and the results have been compared with the ones obtained in the same prototype without SDSR.