MOSFET Switching Loss Calculator

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Estimate MOSFET conduction loss, switching loss, gate-drive loss, total dissipation, and junction temperature for power switching designs.

Input Parameters

Drain-Source Voltage

Drain Current RMS / Effective

RDS(on)

mΩ

Duty Cycle

Switching Frequency

kHz

Rise Time + Fall Time

Total Gate Charge Qg

Gate Drive Voltage

Thermal Resistance Junction-Ambient

°C/W

Ambient Temperature

°C

Results

Conduction Loss

Switching Loss

Gate Drive Loss

Total MOSFET Loss

Estimated Junction Temperature

Design Note

Equations Used

Pcond = I² × RDS(on) × Duty

Psw ≈ 0.5 × VDS × ID × (tr + tf) × fsw

Pgate = Qg × Vgate × fsw

Tj ≈ Ta + Ptotal × RθJA

Frequently Asked Questions (FAQ)

Q1: What does a MOSFET switching loss calculator estimate?
It estimates conduction, switching, gate-drive, total loss, and thermal rise.

Q2: Why is MOSFET switching loss only an estimate?
Real loss depends on gate driver strength, Miller plateau, voltage/current overlap, parasitics, layout, and waveform shape.

Q3: Should I use RMS current or peak current?
Use RMS or application-effective current for conduction loss; use switching-event current for switching loss if known.

Q4: Why include gate drive loss?
At high frequency, charging and discharging MOSFET gate charge can become a meaningful power loss in the driver system.

Q5: Can this replace thermal testing?
No. It is a first-pass estimate and should be verified with datasheets, simulation, and measured temperature.

Disclaimer: This is an engineering estimator, not a complete switching simulation. Verify with device datasheets, actual waveforms, gate-driver design, PCB layout, thermal model, and bench testing.

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