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Old 24th January 2002, 11:23 PM   #1
diyAudio Member
Join Date: Nov 2001
Location: Massachusetts
Default Anyone have experience using PSUD2?

I've been using PSUD2 to design a power supply for a project amp and have run into a problem.This is a full wave type with a tube rectifier, pi filter, and 3 current taps. Peak current draw should be about 175ma and is reasonable for the design. It SHOULD work,but I keep getting an error message saying that "A current sink has pulled the voltage below zero for more than 5 mains cycles". I've tried dropping the current and still get the same message. Is there a bug in this program or what?
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Old 26th January 2002, 09:22 PM   #2
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Join Date: Jan 2001
Location: Scandinavia
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You are probably getting this warning because you are using constant current source draw. The analogy goes like this:

1. The current source is perfect and starts immediately at full current.
2. The power supply takes some time to charge up, particularly when using inductors.
3. The current source makes the voltage across it negative which would not happen in real life.

I suggest you change into a resistive load, or set up stepping, say value 1: 0, value 2 to what current you want, time: 2 seconds (or any other value). Unless you have something really radical to confuse PSUD2 (I have done it), you should still end up with correct levels. I also suggest you turn on the soft start option as well to reduce the risk of confusing the simulator.

I did a lot of beta testing on PSUD2, and find it most useful. Quick, accurate enough etc. If nothing else, it is great value (being free )

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Old 26th January 2002, 09:41 PM   #3
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Join Date: Nov 2001
Location: Massachusetts
That sounds like what's going on. I figured that using constant current would probably model better in places where class A stages were tied to the supply. I wish there was some documentation to go with this program. I find help menus annoying with complex programs, especially CAD stuff. I want a manual, so I can read as I go along. The help menus put you on pause. I'm probably not the only one that feels this way. I DO admire the fact that Mr. Munro has put it out here for free. Can't imagine how much work went into it. Thanks for the reply and I'll give it a try.
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Old 26th January 2002, 11:31 PM   #4
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Join Date: Nov 2001
Location: Massachusetts
I seem to have better results with the constant current loads and setting them up as stepped,rather than use the resistive loads. I tried modelling a couple of known power supplies and have a little better grasp of what's going on here. Now if I can just figure out the ESR on caps and the source impedance, I'll be in decent shape.
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