Diode Reverse-Recovery Loss

Formula

Description

When a diode (or a MOSFET’s body diode) is forced off, the stored minority-charge Qrr must be swept out, briefly shorting the supply through the opposing switch. The energy lost each cycle is roughly the recovery charge times the voltage, and it scales with frequency. In hard-switched synchronous and bridge converters this can be one of the largest loss terms.

Variables

• P — Reverse-recovery loss (W)
• Qrr — Reverse-recovery charge (C)
• Vin — Voltage across the diode when it recovers (V)
• fsw — Switching frequency (Hz)

Practical Notes

Use fast/soft-recovery or Schottky diodes (near-zero Qrr) to cut this loss. It is why GaN and SiC devices, with little or no reverse recovery, excel at high-frequency hard switching.