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TL431 linear power supply

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not1xor1:

--- Quote from: imo on December 25, 2018, 09:39:31 am ---With a 6.3mA current source and 2n2 ser 100ohm comp.
3V/5A
25V/5A

--- End quote ---

I confirm the circuit works as showed in your screenshot.
Il looks like the problems arises from the placement of the AC source that yields awful results when placed like I did.

I've to check more carefully the subject to understand what is wrong.
Thanks

P.S.
since I suspected something is wrong in your measurement method I made a quick transient test, switching between 5mA and 1A on 25V output and the output goes awry... huge oscillations... see below

iMo:
Measurement method?? - That is the question! :)

I took the LT/ADI method - see the link above.
You previously did with a simple AC sweep.

Your oscillation - are you using zero ESR output capacitors?

Below with "real capacitors", no oscillation, a small ringing w/ 160mVpp amplitude..

not1xor1:

--- Quote from: imo on December 27, 2018, 02:25:04 pm ---Measurement method?? - That is the question! :)

I took the LT/ADI method - see the link above.
You previously did with a simple AC sweep.

Your oscillation - are you using zero ESR output capacitors?

Below with "real capacitors", no oscillation, a small ringing w/ 160mVpp amplitude..

--- End quote ---

That is a different method but should yield similar results.

I used models of real capacitors too...
I also tried to add a resistor of 0.5 ohm in series to each capacitor with no result.
BTW this is LTspice XVII x64 Jun 15 2018 running in linux.
I tried both alternate and normal solver, 4 threads and single thread.
No matter what I try I always get oscillations.
Might that depend on the TL431 model I'm using here ...?  :-//

in the comment I read:

--- Quote ---** Released by: Analog eLab Design Center, Texas Instruments Inc.
* Part: TL431
* Date: 12/14/2009
* Model Type: Transient and AC 
* Simulator: PSPICE 
* Simulator Version: 16.0.0.p001
* Datasheet: SLVS543J - AUGUST 2004 - REVISED DECEMBER 2005

--- End quote ---

iMo:
Here is the latest LTspiceXVII, and with the latest Bordodynov library (LTspiceXVII_2018Dec21.zip).
Below the TL431s offerings..
PS: tried with several TL431 models and got similar results as above..

And the library is here, for the latest download go to "Additional links :"

xavier60:

--- Quote from: not1xor1 on December 27, 2018, 08:14:20 am ---

P.S.
since I suspected something is wrong in your measurement method I made a quick transient test, switching between 5mA and 1A on 25V output and the output goes awry... huge oscillations... see below


--- End quote ---
I think that C1 and R17 should be made larger, I'd start with 1uF and 1K

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