MOSFET Switching Loss

P = ½ × V × I × (tr + tf) × f

Quick answer

This calculator solves P = 0.5 × V × I × (tr + tf) × f for P. With Drain-Source Voltage 12 V, Drain Current 2 A, Rise Time 10 ns, Fall Time 22 ns, Switching Frequency 100 kHz, the result is 0.0384 W.

Calculator

Result
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Formula

P = 0.5 × V × I × (tr + tf) × f

Description

During each switching transition, the MOSFET passes through its linear region where both significant voltage and current exist simultaneously, causing power dissipation. The energy lost per transition is approximated as a triangle with peak power V × I and duration equal to the rise or fall time. Total switching loss scales linearly with frequency, making it the dominant loss mechanism at high switching frequencies. Gate driver strength and MOSFET gate charge directly determine the transition times and thus the switching losses.

Variables

  • P — Average switching power loss (W)
  • V — Drain-source voltage being switched (V)
  • I — Drain current being switched (A)
  • tr — Turn-on rise time (s)
  • tf — Turn-off fall time (s)
  • f — Switching frequency (Hz)

Practical Notes

This simplified model does not account for reverse recovery of the body diode, output capacitance losses (Coss), or gate charge losses. For hard-switched applications, total MOSFET loss = conduction loss + switching loss + gate drive loss. Soft-switching topologies (ZVS/ZCS) can nearly eliminate switching losses.

Symbols and units

Symbol Meaning Default unit Accepted units
V Drain-Source Voltage V pV, nV, µV, mV, V, kV
I Drain Current A pA, nA, µA, mA, A, kA
tr Rise Time ns ps, ns, µs, ms, s, min, h
tf Fall Time ns ps, ns, µs, ms, s, min, h
f Switching Frequency kHz Hz, kHz, MHz, GHz

Step by step

  1. 1. What you know: Drain-Source Voltage 12 V, Drain Current 2 A, Rise Time 10 ns, Fall Time 22 ns, Switching Frequency 100 kHz
  2. 2. The relation: P = 0.5 × V × I × (tr + tf) × f
  3. 3. Substitute: V = 12 V, I = 2 A, tr = 10 ns, tf = 22 ns, f = 100 kHz
  4. 4. Result: P = 0.0384 W

Related quantities from the same inputs

  • P = V × I = 24 W

Worked examples

Minimum range

Given: Drain-Source Voltage 0.33 V, Drain Current 2 mA, Rise Time 100 ps, Fall Time 0.22 ns, Switching Frequency 100 Hz

Result: P = 1.06 × 10⁻¹¹ W

Low range

Given: Drain-Source Voltage 3.3 V, Drain Current 20 mA, Rise Time 1 ns, Fall Time 2.2 ns, Switching Frequency 1 kHz

Result: P = 1.06 × 10⁻⁷ W

Typical

Given: Drain-Source Voltage 12 V, Drain Current 2 A, Rise Time 10 ns, Fall Time 22 ns, Switching Frequency 100 kHz

Result: P = 0.0384 W

High range

Given: Drain-Source Voltage 0.23 kV, Drain Current 100 A, Rise Time 100 ns, Fall Time 0.22 µs, Switching Frequency 0.5 MHz

Result: P = 1840 W

Maximum range

Given: Drain-Source Voltage 2.3 kV, Drain Current 1 kA, Rise Time 1 µs, Fall Time 2.2 µs, Switching Frequency 5 MHz

Result: P = 1.84 × 10⁷ W

How P changes with Drain-Source Voltage

Drain-Source Voltage (input) P (result)
1.2 V 0.00384 W
3 V 0.0096 W
6 V 0.0192 W
9 V 0.0288 W
12 V 0.0384 W
18 V 0.0576 W
24 V 0.0768 W
48 V 0.1536 W
84 V 0.2688 W
120 V 0.384 W

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Frequently asked questions

How do you calculate MOSFET Switching Loss?

Use P = 0.5 × V × I × (tr + tf) × f. With Drain-Source Voltage 12 V, Drain Current 2 A, Rise Time 10 ns, Fall Time 22 ns, Switching Frequency 100 kHz, P works out to 0.0384 W.

How do you calculate fall time in mosfet?

Rearrange for P: with Drain-Source Voltage 3.3 V, Drain Current 20 mA, Rise Time 1 ns, Fall Time 2.2 ns, Switching Frequency 1 kHz, P is 1.06 × 10⁻⁷ W.

What is the formula for MOSFET Switching Loss?

The formula is P = 0.5 × V × I × (tr + tf) × f. During each switching transition, the MOSFET passes through its linear region where both significant voltage and current exist simultaneously, causing power dissipation.

Related Concepts

All Semiconductors formulas →
MOSFET Conduction Loss MOSFET Switching Loss BJT Total Dissipation Diode Power Loss Zener Regulation Resistor Transistor Current Gain (β) MOSFET Gate Drive Power MOSFET Rds(on) vs Temperature

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