Power semiconductor loss calculator (MOSFET, IGBT)
Power devices and thermal design. Everything is calculated in your browser; nothing you enter is sent to a server.
KEY POINTS
Power semiconductor losses split into conduction loss from current while on (Irms² × Rds(on) for a MOSFET) and switching loss where voltage and current overlap at each transition ((Eon + Eoff) × fsw). Conduction loss does not depend on frequency while switching loss is proportional to it, so SiC and GaN, with small switching losses, pull ahead at higher frequencies.
Inputs
A first-order approximation in which Eon and Eoff scale in proportion to the test conditions (voltage and current; gate resistance and temperature are taken as matching). If the gate resistance differs or the device is nonlinear with current, enter values read from the datasheet's Eon/Eoff–Ic curves.
Switching frequency and loss
Conduction loss and switching loss
Power semiconductor losses split into conduction loss, caused by current flowing while the device is on, and switching loss, caused by voltage and current overlapping in the instant the device turns on or off. Conduction loss does not depend on frequency, while switching loss is proportional to it, so switching loss quickly dominates at higher frequencies.
IGBTs operate bipolar and keep conduction loss low at high currents, but a tail current at turn-off makes Eoff large, limiting practical frequencies to tens of kHz. SiC MOSFETs have no tail current and cut switching loss sharply, so at the same loss they can run several times faster, shrinking inductors and capacitors. Use the resulting loss for heat sink design (junction temperature calculation).
FAQ
Why do IGBTs have high turn-off loss?
IGBTs conduct as bipolar devices, and stored minority carriers produce a tail current at turn-off, which makes Eoff large and limits practical frequencies to tens of kHz.
How do I scale datasheet Eon and Eoff?
This calculator scales them in proportion to voltage and current relative to the test conditions. For different gate resistance or nonlinear devices, read values from the datasheet's Eon/Eoff–Ic curves.
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Last updated: October 23, 2026