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Modeling >> Behavioral Models >> Simulation & Modeling of non linear magnetics
https://designers-guide.org/forum/YaBB.pl?num=1341565979

Message started by jerome_ams on Jul 6^th, 2012, 2:12am

Title: Simulation & Modeling of non linear magnetics
Post by jerome_ams on Jul 6^th, 2012, 2:12am

Hi there,
I am using the core and winding verilog-a models provided on www.designers-guide.org as a starting point to model and simulate a flyback transformer topology.
Here the circuit:

Here are the waveforms I would expect:

But I do not get these waveforms out of the simulation. Indeed as soon as the current is turned off at the primary side the flux collapses very quickly and no current is available at the secondary side.
The model does not seem to feature any magnetic energy storage.

Has anyone some more experience simulating this model/application?
Great thx!

Title: Re: Simulation & Modeling of non linear magnetics
Post by jerome_ams on Jul 6^th, 2012, 2:14am

here the circuit (new try):

Title: Re: Simulation & Modeling of non linear magnetics
Post by Geoffrey_Coram on Jul 6^th, 2012, 12:36pm

jerome_ams wrote on Jul 6^th, 2012, 2:12am:

Hi there,
I am using the core and winding verilog-a models provided on www.designers-guide.org as a starting point to model and simulate a flyback transformer topology.

It took me a few clicks to find these models:

http://www.designers-guide.org/Modeling/jilath.va

Are these what you are using?

Title: Re: Simulation & Modeling of non linear magnetics
Post by jerome_ams on Jul 10^th, 2012, 1:07am

Yes, exactly

Title: Re: Simulation & Modeling of non linear magnetics
Post by jerome_ams on Jul 23^rd, 2012, 2:26am

so nobody has ever tried these models in a flyback converter topology?

Title: Re: Simulation & Modeling of non linear magnetics
Post by Geoffrey_Coram on Jul 23^rd, 2012, 6:39am

I haven't tried these models (in any simulation).

Did you try the netlist in the associated whitepaper?
http://www.designers-guide.org/Modeling/mag.pdf

Title: Re: Simulation & Modeling of non linear magnetics
Post by jerome_ams on Aug 3^rd, 2012, 5:45am

We finally got the expected simulation results. Let me emphasize on it, to close this post:
Actually, while connecting properly the windings, the gap and the core and using a diode on the secondary side to block this side when the primary is energized, the expected simulation results were obtained.
Real problems started when the testbench was slightly changed to fit to our very application: no diode is used on the secondary side, but an analogue switch. When switching the primaty OFF and the secondary ON, a peak current was observed on the secondary current instead of the expected "triangle". Replacing the switch by a trivial Dmos VHDL-AMS model solved this issue!

At a first glance it feels like changing the resistance of the switch from Roff to Ron using a digital signal as a trigger did not give the same results as changing the resistance of the diode fom Roff to Ron using the voltage drop at the diode as a trigger... Timig issue? => we are still investigating this testcase...

Cheers,
J

Title: Re: Simulation & Modeling of non linear magnetics
Post by Geoffrey_Coram on Aug 13^th, 2012, 5:46am

Thanks for letting us know how you got success.