stiff region and hanging simulation

[Shriram Sampat]

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

  EK Tronic Ing. R. Nitz        
  Tel.: + 49/(0)7154/8311-12
  FAX : + 49/(0)7154/70449
  email: s.sampat at ektronic.de
  www.ektronic.de
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  EK Tronic  Ing. R.Nitz       
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