Synchronous Rectification

Synchronous rectification (SR) is the technique of replacing the rectifying diode on a converter's output with an actively gated MOSFET. A Schottky diode drops roughly 0.35V while conducting; a well-chosen MOSFET acting as a synchronous rectifier drops closer to 0.1V. At the low voltages and very high currents that feed a mining ASIC's hashboards, that difference is the dominant efficiency lever, because the rectifier's loss becomes a larger fraction of total load power as output voltage falls.

How it works

In a synchronous buck, the freewheeling diode is replaced by a low-side MOSFET driven in complement to the high-side switch. The two devices must never conduct at once, so the controller inserts a small dead time between them to prevent shoot-through, a destructive condition where both switches short the input rail. Because a MOSFET's on-resistance can be made very low, conduction loss and the resulting heat both drop sharply versus a diode.

Why it matters for high-current rails

The lower the output voltage and the higher the current, the more synchronous rectification pays off, which is precisely the regime of ASIC core supplies and GPU power stages. Beyond raw efficiency, SR improves thermal performance, power density, and reliability, and it is now standard in the secondary side of high-power supplies.

Synchronous rectification is commonly paired with the soft-switching output of an LLC resonant converter, and it sits at the heart of the multiphase buck converter stages that regulate ASIC and GPU core voltage.