Synchronous rectification replaces diodes with MOSFETs switched ON when the diode would conduct. MOSFET $V_{DS(on)} = I_D \times R_{DS(on)}$ (typically 5–20 mΩ) produces far lower conduction losses than even Schottky diodes at high currents and frequencies. At 400 kHz and 48 V output, synchronous rectifiers are essential to achieve >95% efficiency in modern power supplies.