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MOSFET Power Loss Calculator

Conduction and switching losses for a power MOSFET in a switching converter.

Input
ℹ Conduction = Irms²·Rds(on). Switching ≈ ½·Vds·I·(tr+tf)·fsw.
Results
Conduction Loss—
Switching Loss—
Total Loss—
💡 Usage & Formula

P_cond = Irms² × Rds(on); P_sw ≈ ½ × Vds × I × (tr+tf) × fsw. Total dissipation sets the heatsink/θJA requirement.

When you need it: Budgeting a MOSFET's conduction and switching losses to choose the part and heatsink for a switching converter or a load switch.

Worked example: Rds(on) = 20 mΩ, Irms = 5 A → conduction loss = I²R = 0.5 W. Switching loss ≈ ½ × Vds × Id × (tr + tf) × fsw; at 24 V, 5 A, 50 ns, 100 kHz that's ~0.3 W, so ~0.8 W total.

Tips & gotchas:

  • Conduction loss dominates at low switching frequency; switching loss dominates at high frequency.
  • Rds(on) rises with temperature (~1.4× at 100 °C) — use the hot value, not the 25 °C figure.
  • Gate-drive strength sets tr/tf; a weak driver quietly multiplies switching loss.
  • Add gate-charge loss Qg × Vgs × fsw and the body-diode/reverse-recovery loss in hard-switched legs.
📖 References:Power MOSFET (Wikipedia)