CALCULATORS / POWER CONVERSION AND SWITCHING

MOSFET conduction and switching losses calculator

RMS conduction plus linear overlap switching loss; no capacitance/recovery losses.

power-electronics-mosfet-loss.napkin / editable

SCENARIO COMPARISON

Compare the numbers.

This source describes an analytical model. Its quantities and checks are the view.

Scenario	conductionW	switchingW	totalW
	0.5	0.072	0.572
	0.32	0.0576	0.3776

All calculated quantities are listed with the inputs. Switch to Source to inspect the equations.

SCENARIOS / CALCULATED VALUESSAME SOURCE

Change an input to see the consequences.

loss budget0.57 W✓ passes

BASELINE INPUTS

current5 Aresistance0.02 ohmvoltage24 Vrise30 nsfall30 nsfrequency20000 Hz

CALCULATED

conduction0.5 W

switching0.072 W

total0.572 W

Edits change the baseline source.

THE SOURCE

Edits below update the same model.

# MOSFET conduction and switching losses
# Scope: RMS conduction plus linear overlap switching loss; no capacitance/recovery losses.
# Status: illustrative worked example; engineering review pending.
# Inputs are example values. Checks are editable example requirements, not standards.

current = 5 A
resistance = 0.02 ohm
voltage = 24 V
rise = 30 ns
fall = 30 ns
frequency = 20000 Hz

conduction := current^2*resistance [W]
switching := voltage*current*(rise+fall)*frequency/2 [W]
total := conduction+switching [W]

check loss budget: total <= 1 W

scenario alternative: current = 4 A

Calculated from your source · not saved

Baseline · Baseline

loss budget0.57 W ✓ passes

alternative · alternative

loss budget0.38 W ✓ passes

Illustrative first-order example. Checks are editable requirements, not design standards. The broader topic may require additional equations, data, and validation.

Formula and units

This example uses the following equations. Input names and units match the editable source above.

conduction: conduction = current^2*resistance [W]
switching: switching = voltage*current*(rise+fall)*frequency/2 [W]
total: total = conduction+switching [W]

Original worked example

These are the baseline values in the downloadable source. Edits above let you test your own values.

Given

current: 5 A
resistance: 0.02 ohm
voltage: 24 V
rise: 30 ns
fall: 30 ns
frequency: 20000 Hz

Calculated

conduction: 0.5 W
switching: 0.072 W
total: 0.572 W

Assumptions and limits

RMS conduction plus linear overlap switching loss; no capacitance/recovery losses.

The requirement checks use the limits written in this example. Passing a check does not establish that the model covers every load, material behavior, or operating condition in a real design.

Download this .napkin example ↓

Take it further with your agent

Napkin keeps the inputs, equations, checks and assumptions together in one study. Your agent sets it up; you change the numbers.

Try with Claude ↗

codex 'Use Napkin (https://napkin.engineering/mcp, or the local Napkin plugin) to build a study: MOSFET conduction and switching losses. Inputs: current waveform; Rds(on); switching times; voltage; frequency. Outputs: conduction, switching and gate-drive losses. Model scope: First-order switching models and explicit nonidealities. Read napkin_capabilities and the current snapshot. Ask me for the values that matter, label assumptions with units, author .napkin source, validate it and apply it with napkin_source using the current revision, then open the study. Add checks for the limits I supply. Keep unsupported analyses explicit.'

Claude needs the Napkin connector; Codex needs the Napkin plugin. Set up your agent ↗

The broader study

The topic brief below describes the broader scope. The worked example above states the particular calculation it implements.

Inputs: current waveform, Rds(on), switching times, voltage, frequency
Outputs: conduction, switching and gate-drive losses
Modes: calculate, compare, sweep
Drawing: Switching waveforms and loss plots

EXECUTABLE WORKED EXAMPLE · FIRST-ORDER MODEL · CHECK THE SCOPE & ASSUMPTIONS