The replacement of a diode in a power electronic converters with a MOSFET is called synchronous rectification (SR) and that particular switch is called SR MOSFET.
Basically, this helps in increasing the overall efficiency by reducing the conduction losses in circuit.
Uses:
Reduce the conduction losses —> Converter efficiency increases
Let’s explore practically where it helps and how it beneficial in reducing loss.
Example-1: Half-bridge rectifier
Let’s assume current flowing through the device is “20 A” when it is conducting.
| Diode | MOSFET |
|---|---|
| In general, diodes have the fixed forward voltage drop in range of 0.3 to 0.7 V. | MOSFETs have the low drain-to-source on resistance in range of milli ohms |
| Assume, VF= 0.5 V | Assume, Rds(on) = 10 m ohm |
| Diode conduction loss = VF . I | MOSFET conduction loss = I2 Rds(on) |
| 0.5 * 20 = 10 W | 202 * 10.10-3 = 4 W |
It is observed that, 2.5 times of power loss is less with SR MOSFET at 20 A of flowing current. If it is 40 A means 5 times less power loss.
Assume 100 W converter,
Efficiency with diode = 100/110 = 90.9 %
Efficiency with MOSFET = 100/104 = 96.15 %
Example-2: Full-bridge rectifier
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