Busbar S-Parameter Modeling to Simulate MOSFET Current Sharing


In this article, we'll go through the process of generating S-Parameters from a busbar and placing them onto a power converter simulation using HyperSpice inside PSIM.

The workflow has two main components on two different environments with two different solvers:

From the S-parameter extraction we'll be able to get an ".s#p" (where # is the number of ports) file which can be read by the "S-Parameter" Block on PSIM which then can be solved with HyperSpice inside PSIM.

 

1. SimLab | S-Parameter Extraction Workflow

For this part of the workflow, SimLab 2024 is used. The first step is to create a "Parasitics Extraction" Solution:

Here, it's important to setup the Simulation Type as "S-Parameter Extraction" and the Port type as "Differential".

For frequency definition the following conditions apply:

With the Parasitics Extraction solution created, the PE Workflow ribbon is going to appear with all of the steps and tools required for this workflow. These steps should be followed from left to right starting with the import of the CAD file.

The attached ".xmt_txt" parasolid file is imported with the default settings and then a material needs to be applied:

Then, a quick Tet mesh is created with a 0.5 mm element size and default settings (for other CAD models, this might change):

Then the ports need to be created and assigned. Two ports were created for this extraction and the setup is as follows:


Considerations for Solver Settings

Enable the "Use Model Order Reduction" feature on the Solver Settings. Capacitance effects can also be disabled if not used, this will make calculation faster. Use the default "Stopping Criterion Tolerance" value for better results (1e-07).

The solution then can be solved and an the ".s#p" parameter file will be created, this can be found on the results folder [Right Click on Results > Open Results Folder]

 

2. PSIM | Converter Simulation with Busbar S-Parameter

About the S-Parameter Block in PSIM

The ".s#p" file is handled by the "S-Parameter" Block on PSIM. This block only works with the HyperSpice solver    and is only available on PSIM 2024.

The ports of the S-Parameter are arranged as follows, with the circle marking the Input nodes:

The attached simulation (BoostWSparams.psimsch) is a boost converter with two parallel MOSFET ideal models. The simulation already includes the S-Parameter Block and the only setup is to select the ".s#p" file (double click on the S-Parameter block to open attributes).

Running the simulation at different switching frequencies show the behavior of the S-Parameters affecting the current sharing of the MOSFETs.

MOSFET currents at 12.5 kHz

MOSFET currents at 25 kHz

MOSFET currents at 50 kHz

MOSFET currents at 100 kHz

Questions about this workflow? Feel free to contact us for further support!