Difference between synchronous and conventional dc-dc boost converter?
Synchronous rectification refers to the practice of using an active element such as a MOSFET switched at the appropriate instants in place of a diode. Here's a simplified example of a boost converter:







simulate this circuit &ndash; Schematic created using CircuitLab

Not shown here is the logic to switch the transistors. In the synchronous case it's important that M2 and M3 are never both on at the same time, as this would short C2 to ground, possibly damaging the transistors, and severely decreasing efficiency.

The advantage is the conduction losses through a MOSFET (M3) may be less than through a diode (D1). Consider the voltage across D1 will be about 0.6V, or perhaps 0.2V if current is low enough that a Schottky diode is feasible. However, a properly selected MOSFET in many circumstances may have a VDS even lower, and thus lower losses.

The disadvantage is higher complexity and cost.