WEBENCH® Tools/UCC28742: .

Hello Aban,

I am an occasional user of Simplis, no expert, but I see that no one has commented in a while.

I downloaded the UCC28742 simplis zip-file, extracted the folder and files and ran the transient simulation of the circuit without modification.  It produced a simulation of Vout and Iout for 50ms, and took about 5 minutes to run.  So this proves that the Simplis model, as packaged, works.  
Aside from the flyback converter model, there are two external subcircuit models (for the TL431 and for the switching MOSFET).  Make sure that these sub-models are located in the same directory as the main converter model.

That said, if you modify the "stock" model to match your Webench schematic, it may require additional external sub-circuit models or component models that are not present within the directory.  If you have them, I suggest that you put them into the model directory.  If you do not have them, I suggest that you use the subcircuits that are already available and modify them as needed to reflect the parameters of the components that you wish to model.

Before making any changes, always work on a copy of the files, don't modify the master files themselves.  If something goes wrong, you can always make a new copy of the master and start over.  Also, I suggest to make a few changes at a time rather than all changes at once.  Test each change with a few milliseconds of simulation to verify that it works, or to limit the amount of debug necessary from the last model that worked.
Eventually you will have made all of the modifications needed to change the stock design into the Webench design, and you can run full simulations as needed.

Regards,
Ulrich

Hello Aban,

Yes, I believe that the Elements free version cannot support the model.  It seems most software error messages are almost useless to describe what the real problem is.

A look at their website (https://www.simplistechnologies.com/product/elements ) shows that one of the free version restrictions is that it will not support encrypted models. The UCC28742 controller model is encrypted, but even so, additional free-ware restrictions are on the limited number of elements, topologies, and logic gates that can be used in the overall model.  Essentially, the UCC28742 controller and system model is far more complicated than what the freeware will support, encrypted or not.  

I'm sorry but without a full license, you won't be able to model it.  However, a simulation is only as good as the models of the components used.  The controller model is accurate, of course, but all the other components used may not be.  I find that if you follow the datasheet design procedure and use the Excel calculator tool, you should be able to get the correct component values for you application.  Build a prototype of it and it should work well enough to be able to fine tune its performance as needed. Follow good pcb design practices to avoid loop areas and other noise-related problems.  A simulation will not reveal those anyway.  There is nothing like a real board to show what is really happening.

Regards,
Ulrich