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Oscillation in PSU simulation
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ElectronSurf:
Yeah I have to build it on breadboard and test it out. the problem is I don't have a decent oscilloscope to analyze it in depth. just a cheap chinese one, that's why I was trying to use a simulator...
Zero999:

--- Quote from: ElectronSurf on April 17, 2020, 10:36:22 am ---That's what I wanted to know, is it the simulator or there's really oscillation.

Max scale zooms in to the signal.

I have to learn to use ltspice, this isn't working...

--- End quote ---

--- Quote from: ElectronSurf on April 17, 2020, 10:49:43 am ---Yeah I have to build it on breadboard and test it out. the problem is I don't have a decent oscilloscope to analyze it in depth. just a cheap chinese one, that's why I was trying to use a simulator...

--- End quote ---
Yes, I noticed the link could easily be missed, so I went back and enlarged it. In that case, it's just noise i.e. rounding errors in the simulation. You'll often see similar things in real life, when zooming in on a signal very closely, especially with a digital oscilloscope. What oscilloscope do you have? Some of the cheap Chinese ones are perfectly decent.

The circuit you originally attached appears to oscillate and experience tells me it's likely to do so, because it has two amplifiers in each loop, especially as one of them is open-loop. Sometimes this is a necessary evil, or it's is just easier to design that way, but in this case it isn't: you've already got a current source going to the base of the Darlington pair and ORing diodes, so you might as well connect the output of each amplifier to each of them.

Why is LTSpice not working? I know it depends on what one is familiar with, but I find it infinity easier to use than that falstad simulator, which made me curse and swear after a few minutes of editing your schematic. If it was in LTSpice, I would have been able to mirror it, with the input to output going left to right, but there doesn't seem to be a way to do that with falstad, without redrawing it. :palm:
ElectronSurf:
The scope is DSO138, it's a toy. I didn't say ltspice isn't working, I meant the falstad isn't working and I have to learn ltspice.

For current sensing I ordered INA128 in-amp so I thought it's better to simulate it as a simple differential amplifier for now. and to be able to measure the voltage remotely I'm going to need another in-amp which I'm planning to home-brew it with three OP07. do you think having two in-amp and two op amp is going to oscillate because of the loop you mentioned? (the keyword is "hobbyist", this guy (me) don't know anything about electronics)
xavier60:
If a loop oscillates, add a compensating capacitor as already shown. The more stages there are in a loop, the more likely it will be unstable.
You can experiment with the value to see what works ok. Too large a value for the CV loop wont matter much because the output stage is naturally voltage sourcing.
You don't want the capacitor to be too large for the CC loop because the PSU will be too slow too respond to large overloads.
Many designs have extra circuitry for fast current limiting.
ElectronSurf:

--- Quote from: xavier60 on April 17, 2020, 11:38:07 am ---Many designs have extra circuitry for fast current limiting.

--- End quote ---

Isn't what I implanted fast? can you please show me an example?
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