MOSFET Switching Losses - A Deep Dive - Part I


Previously Held on Thu, September 27th, 2018 from 1:00 - 2:00 PM EDT

The MOSFET switching losses for a typical synchronous buck converter were described in a previous webinar which also covered efficiency of the power train in general: 

Modeling Switching Losses and Efficiency

In this one-hour webinar, we focus on the losses of a MOSFET switching a clamped inductive load. A dual simulator mode test bench will be presented which helps compare and contrast how MOSFETs are modeled in both SIMPLIS and SPICE. Losses due to turn-on, turn-off, and conduction are quantified using both SIMPLIS and SIMetrix SPICE. All losses will be presented in both terms of energy as well as power dissipation, and these energy curves provide helpful insight into which part of a switching transition dominates the loss. Finally, we end the webinar discussing the difficulties in finding a true, periodic steady-state operating point which is crucial to measuring efficiency in a power converter.


  1. How MOSFETs are Modeled in SIMPLIS and in SPICE
  2. Open Loop Clamped Inductive Load Testbench
    • Comparison of Losses (SPICE vs. SIMPLIS)
    • Discussion of Internal Inductance
    • Results from Several MOSFETs
  3. Measuring Energy From Switching Transitions
  4. The Elephant in the Room: How to Get to Steady-State

Link to Webinar Recording

The webinar recording can be viewed at this link: MOSFET Switching Losses - A Deep Dive - Part I (1:00:6)

Reference Materials

Schematics and presentation slides for the webinar can be downloaded here:


Towards the end of the video the presenter meant to show the last schematic, which has the file name of FDD8882_3.sxsch. The correct file is included in the above zip archive and this example matches loss within 1%. This schematic will be covered in the next webinar.