AN1547

Synchronous Rectification is possible with all commonly used converter topologies. It is achieved by simply replacing the freewheeling diode with a MOSFET utilizing an additional gate drive circuit. As a result of this replacement, the efficiency will improve significantly.

Efficiency of 92% and higher can be achieved by using very low onresistance MOSFETs at a lower frequency if size is not a constraint to the design. At a higher switching frequency, a fast switching gate drive and low gate charge MOSFET is required to reduce losses. To further increase the efficiency, use a low ESR capacitor for input and output filtering. In addition, reduce I²R losses by using a low dc losses inductor and increasing the PCB copper track width on the high current path.