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power supply simulation
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Old 16th July 2018, 06:51 PM   #1
sumotan is offline sumotan  Indonesia
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Default power supply simulation

Hi Guys
Am learning how to use PSUD ll but canít get it to work correctly.
Would appreciate some advice pls.

Thanks
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Old 16th July 2018, 09:27 PM   #2
PRR is offline PRR  United States
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First, check your values.

Do you *really* have "30mF" (30,000uFd!) caps?? That seems totally extreme. Or a mis-type.

Second: there are no true "current sources" in audio amp supplies. In this case, with 30,000uFd and "infinite" resistance on the end, PSUD goes on (after you soothe its error) to show a huge 125Hz oscillation which does indeed swing negative.

The "current source" is never realistic. For one, current must be zero at start up. For another, most tube circuits are more like resistors than constant-current loads. Given about 300V and 6mA, replace the CC load with a 50K resistive load. The resistance will damp the apparent oscillation. The result will be close enough for any tube work.

This still shows that "30mF" (30,000uFd) caps are sledgehammers on fleas. It takes *minutes* for the caps to charge-up to hundreds of Volts.
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Old 17th July 2018, 01:36 AM   #3
sumotan is offline sumotan  Indonesia
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Oopps will retry again. Thks PRR
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Old 17th July 2018, 12:28 PM   #4
merlin el mago is offline merlin el mago
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Rob's PSUDII tutorial.
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Old 17th July 2018, 12:33 PM   #5
sumotan is offline sumotan  Indonesia
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wow thank you kindly Merlin
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Old 17th July 2018, 06:58 PM   #6
DF96 is offline DF96  England
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PSUD2 does not work very well with 'unusual' component values. In some cases this is because it gets confused; in other cases it may be that it believes that the user is confused.
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Old 17th July 2018, 11:17 PM   #7
trobbins is offline trobbins  Australia
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Quote:
Originally Posted by merlin el mago View Post
Rob's PSUDII tutorial.
I'd recommend viewing that tutorial with 'a grain of salt', both for editorial comment about what a 'good' power supply is, and that the text has some significant mistakes (like when stating that stabilising time is in milliseconds rather than seconds for fig 5, 6 and 7). There are a lot of glorified but unsubstantiated comments, like adding a snubber cap across the power transformer secondary, and his discussion about 'ringing' by looking at power on charge up behaviour with a constant current load.
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Old 18th July 2018, 09:51 AM   #8
DF96 is offline DF96  England
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Quote:
Originally Posted by merlin el mago
Rob's PSUDII tutorial.
Some useful info, but some confusion too. Not a good way to start in PSU design.

For example, he claims that the 'high quality cap' at the output supplies power to the audio amp, yet this is part of a filter with a cutoff around 50kHz. The result is that the cap only supplies the amp for frequencies above 50kHz; below this it has to get its power from the previous cap.
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Old 19th July 2018, 07:11 PM   #9
MagicBus is offline MagicBus  Greece
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Quote:
Originally Posted by trobbins View Post
I'd recommend viewing that tutorial with 'a grain of salt', both for editorial comment about what a 'good' power supply is, and that the text has some significant mistakes (like when stating that stabilising time is in milliseconds rather than seconds for fig 5, 6 and 7). There are a lot of glorified but unsubstantiated comments, like adding a snubber cap across the power transformer secondary, and his discussion about 'ringing' by looking at power on charge up behaviour with a constant current load.

I'm wondering if this "overshooting" means anything useful for the simulated psu.
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