How to reduce the number of nodes in Pspice model

[Ratna Kumar]

Hi Friends

When I am creating a PI controller for my buck converter,I had a problem when I go for simulation.It shows that "ERROR -- EVALUATION VERSION analog Node Limit (64 Nodes) Exceeded!".
Currently I am using Pspice 9.1

your help will be greatly appreciated

 

[abbeyromy]

@Ratna Kumar
Not able to download your image. Attach as pdf...
Have you tried Orcad+Pspice 16.3 demo version? I think it can support you... Not very sure though...

More the number of nodes means more complexity and the only way to do this is to make circuit less complex. Why dont you divide the circuit in parts and for each stage see how you are getting the output and then make pesudo sources for each stage then

 

[keith1200rs]

You already have good advice from abbeyromy. The problem with the node limit on evaluation versions is that opamp models, particularly modern devices, can have dozens of nodes so you soon run out. You could try something like LTspice which I don't think has a node limit (although it seems to be plagued by convergence issues whenever I have tried it).

SIMetrix demo version has 120 node limit compared to Pspice 64 node, so may be an option:



Keith.

 

[LvW]

Hi Friends
When I am creating a PI controller for my buck converter,I had a problem when I go for simulation.It shows that "ERROR -- EVALUATION VERSION analog Node Limit (64 Nodes) Exceeded!".
Currently I am using Pspice 9.1

your help will be greatly appreciated

Here are two other recommendations:
1.) Use for basic analyses the simplified OPAMP model (PSpice call "opamp").
This model incorporates a single pole response and selectable power rails; input/output impedances are ideal.
2.) Or build your own simplified model and incorporate those parameters which are important for you (VCVS "ELAPLACE" with additional RC elements and buffers "GAIN").

 

[erikl]

I think short-circuiting of 2 amplifier outputs in not ok.

 

[FvM]

I think short-circuiting of 2 amplifier outputs in not ok.

Not at all. When correcting this issue, you may think about reducing the PI design to a one or at maximum two OP circuit,which is possible as well.

 

[neddie]

I'd go for LTSpice.It's unlimited on size of your design.Its FREE :0)
There is a very useful Yahoo group dedicated to this simulator as well. I have had less convergence problems with LTspice , than with other simulators as well.
Just my 2c :0)
Rob