stiff region and hanging simulation

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Shriram Sampat Shriram Sampat
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stiff region and hanging simulation

Hello guys,

Thank you all for your wonderful support. I now have a decent
understanding and a basic model. I have attached the experimental model
along with this email (.cos file)

The real R and L value in my circuit are 300 milli Ohms and 112 micro
ohms. Also a 150A / ms climb of Ids is required at the end. When i try
with these values in my model, its impossible to run the simulation.
Either it nothing happens, or lots of stiff region messages or the whole
program hangs, depending on the values used. So i tried with bigger
values for both L and R. Even now, for one specific R and L value, all
Desired Current values does not work. Still the simulation bumps into
sudden hangs when the current nears the desired value.

Can you give me some hints on how to remove these stiff regions and
bring my simulation close to real world values ?

A little explanation of the model (i have also given some comments in
the diagram itself) :
I measure the current through the circuit, calculate error from the
desired current that should be flowing. I multiple this error with Kp.
The result of this, i downscale to voltage values. if 20V at gate is
110A in circuit, voltage required for a particular current value Y is =
Y * 20/110. Also there is a vgate limit that limits gate voltage to a
max 20V.Now i find the difference voltage to be applied to bring the
current to desired value and give it at the gate with VCS.

Thank you very much again for the help.

Ram

--
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Shriram R Sampat
Software Engineer - Embedded Systems

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