residual norm and unconverged equation error

hi. i use a simulink and simscape model to buildd an aplifier for audio use. class d.

when i start simulation I get this error:

_Steady state solve failed to converge. ...Nonlinear solver: failed to converge, residual norm too large. ......Here is the set of components with unconverged equations:

'mosfet_driver/N-Channel MOSFET' 'mosfet_driver/gate driver 2/NPN Bipolar Transistor'_

the strange about this error is that i did not change actually anything on my model since the previous time, that the simulation worked! so strange and wuote annoying I'd say. I suppose it is some kind of numerical linear algebra error inside the simulink computation engine.. but i cannot tell what the problem exactly is! so any help!?

thanx. andreas

Answer 1

[Guy Rouleau]

Here are a few tips to make your model more robust to this error:

- Try increasing the Consistency tolerance in the Solver Configuration block. The default is 1e-9. Try something like 1e-6.

- Some components in your circuit probably have parameters like snubbers or "Open resistance" or "Closed Conductance". Those are there for numerical reasons. Making them less ideal should help.

[Andreas]

reduced the solver tolerence but did not help. actually it showed another error when setting it too low (e.g. 1e-3) as expected.

-when talking about resistence and conductunce do you mean those of a capacitor (which has parallel conductance)? also the ohmic resistence inside a mosfet of npn has to play some role i suppose. note that for my n channel power mosfet i use irf 6665 and i cannot find the correct ohmic resistance info inside the datasheet...

[Andreas]

well... it seems i had made a mistake. i had set in the n channel mosfet ids=20 uA instead of 19A (due to a misunderstanding of the datasheet). it performs the simulation now( 5 minutes or more for 0.004seconds for the whole system on a i3 2.2Ghz system!!!)

i wonder if the error i got sufficiently described the (obviously) extremely low value in the ids current, which caused the error to show. i believe that it could be more implicit on what to do.

anyway Mr.Rouleau thank you for helping me.. again!

Andreas

Answer 2

[PENG SHI]

I have encountered this problem as well. It is resolved by reducing min time step in my case.