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duncanamps 16th February 2017 09:57 AM

PSUD (Power Supply Unit Designer)
Hello there, I'm the author of a freeware package called PSUD2, a simple application for designing linear power supplies.

It's been around since 1998 and has been received a fair amount of use from the DIY audio and ham radio community, amongst others. I'm planning a PSUD3 which will have a new file format and allow some enhancements to be made, some of which I've had to hold back on due to the fixed file format.

Here's some of the ideas that are brewing the lab right now:

  • Integrated diode modeling tool - add points from the data sheet to get the correct parameters
  • Rectifiers as separate files rather than a single rectifier.txt so you don't get a wipeout every time the software is updated
  • Diode parameters stored in the PSU file, makes things easier to share
  • Chart preferences (line colour, width, style) stored in the PSU file so you can have a consistent look that works for you
  • R type block before load (current limit)
  • Stepped resistance load in addition to stepped current source
  • Support for mercury rectifiers

Anything else?

Regards / 73,

AndrewT 16th February 2017 10:16 AM

Can you make the transformer settings easier to make and understand?
Maybe a few more paragraphs in a .txt Help file?

DF96 16th February 2017 10:34 AM

This might not be very helpful, but sometimes I have had reason to doubt the RMS current figures. I can't remember when or where I saw this (which is why this remark is unhelpful to a software developer!). Could you cast your eye over the code for this calculation, just in case you spot something?

Things to think about:
1. NTC thermistor in primary circuit for soft-start
2. Output impedance as a function of frequency (I'm going to guess that this would not be easy, as PSUD works in the time domain)
3. Plot something (e.g. mean output voltage, ripple) vs. something else (e.g. cap value) - would presumably mean repeating several runs while varying something

PSUD2 is extremely useful so we are very grateful to you for developing it and making it available to us.

mcandmar 16th February 2017 10:44 AM

First off, i want to say a big thank you for creating PSUD, words cannot explain how invaluable a tool it has been over the years :up:

I have a request for two changes i would really like to see..

1) Allow split path power supplies. Say you have a CRC filter section, then branch off with two separate RC supplies for the left and right channel. Currently PSUD has no mechanism to allow for this, other than adding in a current tap which does not fully simulate the startup load from the capacitance on each section.

2) Remove the limitation preventing you from putting two capacitors after one another. Currently the system will only except an RC or LC layout after a capacitor. Reason being is some amplifiers have bulk filtering in a CRC layout, then another capacitor locally at the tube. PSUD will not accept this layout as there is no cap or choke between each capacitor.

RajkoM 16th February 2017 11:40 AM


Originally Posted by DF96 (

2. Output impedance as a function of frequency (I'm going to guess that this would not be easy, as PSUD works in the time domain).


Thanks for PSUD2.

trobbins 16th February 2017 11:42 AM

I'll add my grateful appreciation to Duncan's efforts. :up::up::up:

In PSUD2, I've assessed the influence of an NTC by just running a 'cold' sim and then a 'hot' sim, where the NTC resistance at hot and cold is fairly well identifiable, and it just adds to the primary winding resistance if used on the AC side. From a worst-case design perspective that seems to be reasonable.

In PSUD2, I've just added another RC stage, where R is very low resistance, to model two capacitors that are effectively in parallel. The R value can go down to pretty low values without too much sim hassle. Similarly, if I've wanted to add a series resistance value only, then I'll add an RC stage where C is very small.

Perhaps there is some value in whether real power dissipation in a part could be worth adding as a result parameter. That could then be used to assess transient power dissipation from t=0 in say a diode/bridge or resistor, compared to a steady-state value taken from a later simmed time slice.

Would it be 'relatively' easy to add a diode in as a series element after the normal location of the rectifier diodes. A number of enthusiasts seem to want to use a ss rectifier, but then insert a damper valve diode in the DC path so as to allow some time-delayed B+ rise and possibly other reasons.

PS. and some use a hybrid valve and ss bridge, where a common dual diode valve is used for the 'positive' arms of the bridge.

jazbo8 16th February 2017 02:17 PM

:cop: OT Posts removed.

MagicBus 16th February 2017 05:06 PM

I' m grateful to you for this tool!

Originally Posted by DF96 (
2. Output impedance as a function of frequency

This would be very nice!
And please keep it running on windowsXP.

dearchap 16th February 2017 07:58 PM

Duncan can you make it web based ?

Lingwendil 16th February 2017 11:33 PM


Originally Posted by dearchap (
Duncan can you make it web based ?


Android programs that are actually worth using aren't terribly common for such things

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