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Hi. I've been poking around trying to explain a 10volt difference between PSUD2 and LTSpice results for an EZ81 based power supply. It's not a big deal (the amp's been working for years) - I'm just trying to understand the use of both tools for Power Supply design. I've been assuming that the difference is in the models of the EZ81. I kept trimming the design down until I reached the attached configuration. The Transformer current matches the Diode current, but the Resistor current (Mean) is 7mA less. What am I missing?
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Hi John,
This is a PSUD2 problem rather than a mismatch in setups. Kirchoffs first law is quite clear, the currents going into a node should equal the currents coming out. To speed up and simplify simulations, PSUD2 breaks Kirchoff's laws and, as such, has been broken as designed for over 20 years. Most of the time it's reasonably close, and can get away with it but there are times when something comes up that diverges to a really whacky result. Wasn't really expecting it on such as simple example as the one you've illustrated. For your example above, all three currents should be identical at all times. Therefore, the mean/min/max should all be the same too. The problem stems from the way PSUD2 tries to balance the network of components, so it's not fixable without a total rewrite, which is why I started on PSUD3. This uses a matrix solver which is similar to the SPICE family and will respect both of Mr Kirchoff's pearls of wisdom. Unfortunately PSUD3 has taken a pause right now, I recently put out a beta to a half dozen participants to try it out. It needs more work in the way the user interface operates, and was messing up their installations in some instances which isn't acceptable. I'll get more time to work on it during the Christmas break so should be able to incorporate their feedback and introduce it to a wider audience. Will post on here when it's good to go. Regards, Duncan |
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Just a word of thanks, Duncan for making such a useful piece of software available gratis. I've used it as necessary for many years; it beats faffing around finding suitable models for Spice, and for sure beats using Schade's paper and his graphical method. Actually back in the day Schade was how I used to do this stuff before free versions of Spice were available, and long before your software was available. Cheers! Craig (in the UK)
------ Original Message ------
From "Duncan Munro" <duncan@...>
Date 17/11/2023 08:47:40
Subject Re: [duncanampspsud] Where did the current go? Hi John, |
