Traditional Rectification: Diodes (such as Schottky diodes) are used for rectification. Diodes feature unidirectional conductivity, but they have a fixed forward voltage drop (usually ranging from 0.3V to 0.7V). When large current flows through, the conduction loss (P_loss = Vf * I) is considerable, leading to reduced efficiency and severe heat generation.

Synchronous Rectification: Power MOSFETs with extremely low on-resistance (Rds(on)) are used to replace diodes. Through a dedicated control circuit, the MOSFET is precisely turned on when conduction is required and turned off when cut-off is needed, achieving the function of unidirectional conductivity. Since the on-voltage drop of MOSFET (Vds = I * Rds(on)) can be made extremely small (at millivolt level), it can significantly reduce conduction loss and improve efficiency.

Synchronous rectification technology can be applied in various switching power supply topologies:

Flyback Synchronous Rectification: This is the most common and widely used application, especially in low-power adapters and chargers. It replaces the secondary-side rectifier diode of the transformer with an SR MOSFET, resulting in a remarkable improvement in efficiency. Most applications adopt the integrated package of Controller + MOSFET, while the combination of controller + External MOSFET is used to expand output power.

Mainstream package types: ◇ SOP8 Package ◇ SM7 Package ◇ TO252 Package ◇ TO220F Package ◇ Synchronous Rectification Controller ◇ SM10 Package ◇ PDFN5*6 Package

Forward Synchronous Rectification: Including active-clamp forward converters, the secondary side uses SR MOSFETs to replace freewheeling diodes and rectifier diodes.

For low-voltage and high-current scenarios, the combination of Controller + External MOSFET is preferred.

LLC Resonant Half-Bridge/Full-Bridge Synchronous Rectification: On the secondary side of LLC resonant converters, full-wave rectification or full-bridge rectification is usually adopted. The application of synchronous rectification here (using two or four MOSFETs) can greatly reduce rectification loss during high-current output, which is a key technology for high-end power supplies to achieve high efficiency (such as Titanium-level efficiency).

Synchronous Rectification in Buck Converters: In synchronous buck circuits, the lower switch tube (replacing the freewheeling diode) is a typical application of synchronous rectification. This has become the standard configuration for power supply of modern CPUs and GPUs.