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PSUD (Power Supply Unit Designer)
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Old 29th June 2019, 10:23 AM   #91
DF96 is offline DF96  England
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Quote:
Originally Posted by eduard
Because usually you will see people adding a small bypass capacitor on a big power supply capacitor. Sometimes adding a low esr capacitor at the output of a regulator can have bad effects. Could something similar happen to a simple power supply? And that is the reason why would use an RC instead of only a capacitor.
A snubber is not a bypass. Most bypass caps do nothing useful; some do harm; a few do some good.

The idea of the snubber is to damp the LC resonance formed by the choke and the capacitors, if necessary. It has some similarity to the problem at the output of a regulator, because there you have a virtual inductor (the regulator output impedance) so a capacitor (which people love to add) can resonate.

Quote:
In my audio documents i have an article written by Morgan Jones where he has done some test with snubbers or just caps positioned across the secondary windings on or across the diodes. HIS conclusion in most cases a 1 nF cap in series with a 1000 ohm resister across the transformers secundary is all you need.
Different snubber in a different position for a different purpose.
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Old 6th October 2019, 05:36 PM   #92
R Kneck is offline R Kneck  United States
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First, many thanks to duncanamps for this invaluable tool.

I have a question about entering values for a center tapped full wave rectifier.
For entering off load voltage, the help file is quite clear that you should enter one half of the total end to end voltage.
I am unclear about the impedance for the transformer secondary.
Bringing up the source impedance calculator help file states that "Winding resistance: The measured resistance of the secondary winding." Would this be the resistance from the center tap to one end just like the off load voltage or the resistance across the entire secondary?

Again, this is a great resource for the diy community!
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Old 6th October 2019, 05:53 PM   #93
trobbins is offline trobbins  Australia
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yes
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Old 6th October 2019, 05:57 PM   #94
R Kneck is offline R Kneck  United States
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Should I measure the resistance
a) from the center tap to either end
b) across the entire secondary winding
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Old 6th October 2019, 06:07 PM   #95
RickRay is offline RickRay  United States
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PSUD (Power Supply Unit Designer)
Any movement on the 3rd version. I struggle with trying to model rectifiers not listed. The rectifier modeling feature would be a godsend.
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Old 6th October 2019, 06:49 PM   #96
duncanamps is offline duncanamps  United Kingdom
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Quote:
Originally Posted by R Kneck View Post
First, many thanks to duncanamps for this invaluable tool.

I have a question about entering values for a center tapped full wave rectifier.
For entering off load voltage, the help file is quite clear that you should enter one half of the total end to end voltage.
I am unclear about the impedance for the transformer secondary.
Bringing up the source impedance calculator help file states that "Winding resistance: The measured resistance of the secondary winding." Would this be the resistance from the center tap to one end just like the off load voltage or the resistance across the entire secondary?

Again, this is a great resource for the diy community!

Take the impedance from the centre to one leg. In reality, your transformer is likely to be wound with two different winding resistances as the one towards the outside uses more copper for the same turns. Take the end to end and divide by 2 if you really want to get a good result.


The help file offers no guidance on that, an omission that will be fixed in PSUD 3.
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Old 6th October 2019, 06:54 PM   #97
duncanamps is offline duncanamps  United Kingdom
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Join Date: Apr 2013
Quote:
Originally Posted by RickRay View Post
Any movement on the 3rd version. I struggle with trying to model rectifiers not listed. The rectifier modeling feature would be a godsend.

Yes, things are happening, just very slowly. It's a whole ground up rewrite, the simulation engine is complete and is extremely accurate, unlike PSUD2.


The user interface is being sorted out at the moment, and I continue to spend time here and there when other demands permit. It's not likely I will get anything out on the streets until the Christmas break, but that's the one time of the year when I get an opportunity to do stuff like this
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Old 6th October 2019, 09:22 PM   #98
PRR is offline PRR  United States
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PSUD (Power Supply Unit Designer)
Thank you very much. I turn to PSUD almost daily.
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Old 6th October 2019, 09:37 PM   #99
JeffYoung is offline JeffYoung  Ireland
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Indeed. A great tool. Thanks for your efforts.
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Old 7th October 2019, 11:14 AM   #100
merlin el mago is offline merlin el mago  Catalonia
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Your effort is really appreciated.
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