Synchronous Rectification (SR) in a power supply is a technique used to improve the efficiency of the rectification by replacing diodes with an active controlled switch. The voltage drop of a standard diode is typically too high and causes significant power losses. These losses in the rectifying diode can be significantly reduced when it is replaced by a switch, typically a MOSFET. The Rds(on) resistance of the switch can be chosen to match the needed power and to result in low conduction losses. NXP’s GreenChip SR is a control IC which operates at the secondary side of the transformer in a flyback converter where the IC drives a synchronous rectification switch for optimal efficiency and performance of the power supply. NXP also has GreenChip SR versions available that, in addition to the SR function measure the output voltage, control the feedback loop, and offer protection against high output currents.