Having trouble making a Buck converter using two complimentary switches in LTSpice. I've got everything laid out exactly as perscribed, but when I run I get the following error:

enter image description here "Can't find definition of model "SW""

I've put the model for each one right there, so I've got no clue why it wouldn't know what to do with the switches. If anyone has any ideas on how to correct that please let me know, thanks.

  • 1
    \$\begingroup\$ "SW" is a model name. Thus you should modify the "SW" to "Switch1" and" Switch2" and your "Switch1" and "Switch1" are part designator "S1", "S2" \$\endgroup\$
    – G36
    May 2, 2020 at 10:05
  • \$\begingroup\$ Just a minor comment: C2 is completely useless, unless you're adding some sort of series resistance between V1 and C2 (either add a new resistor, or add Rser=<...> to V1). Or add Rser to C1, that will also do, if you can live with that zero. \$\endgroup\$ May 2, 2020 at 10:08

1 Answer 1


You are not assigning a model to your switch, but just renaming it. In order to assign a model, you have to right click on the switch and change its value to the model name you want to use.

enter image description here

  • \$\begingroup\$ Oh, that was pretty simple. Its all working now thank you! \$\endgroup\$
    – JacobEE
    May 2, 2020 at 10:10

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