Author Topic: TL431 linear power supply  (Read 9689 times)

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Offline Kleinstein

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Re: TL431 linear power supply
« Reply #150 on: December 28, 2018, 09:16:10 am »
A larger value for R17 is likely a good idea. About half the values of R8 (feedback from the input) could be a good start.
1 µF for C1 would be really slow and only a start. The shown 2.2 nF seem to be in a reasonable range, when looking at simulations from IMO.

One should also keep in mind that the loop gain would change with the feedback divider.
 

Offline not1xor1

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Re: TL431 linear power supply
« Reply #151 on: December 28, 2018, 10:05:21 am »
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 :"

OK, but what really matters is to know which kind of TL431 library you got.
The one I'm using clearly states: Model Type: Transient and AC.
The one you're using might be a coarser model... might it not?  :wtf:

(OK... I'm downloading the huge zip and will check that myself later  :D )
 

Online imo

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Re: TL431 linear power supply
« Reply #152 on: December 28, 2018, 10:14:11 am »
Here with the 2n2 (C4 in my simulation) and R4 from 100-16k.
For 25V/5A pulses and 3V/5A pulses.

For 3V the R4s>=1k in order the simulation works "reasonably fast" (PS:With Behavioral model TL431A it simulates fine from 100ohm up).

With 25V the R4s>400ohm make more ringing.
« Last Edit: December 28, 2018, 10:32:42 am by imo »
 

Online imo

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Re: TL431 linear power supply
« Reply #153 on: December 28, 2018, 10:40:34 am »
(OK... I'm downloading the huge zip and will check that myself later  :D )
A good move  :-+

Be careful with the installation of the Library.

You have to replace the 2 folders (examples, lib) in:
C:\Users\..user..\Documents\LTspiceXVII\
PS: make backup of your own models/parts.

Do not touch folders in:
C:\Program Files\LTC\LTspiceXVII\

After the start LTspice will reindex the new Library.
« Last Edit: December 28, 2018, 10:56:40 am by imo »
 

Offline not1xor1

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Re: TL431 linear power supply
« Reply #154 on: December 28, 2018, 04:49:13 pm »
(OK... I'm downloading the huge zip and will check that myself later  :D )
A good move  :-+

Be careful with the installation of the Library.

You have to replace the 2 folders (examples, lib) in:
C:\Users\..user..\Documents\LTspiceXVII\
PS: make backup of your own models/parts.

Do not touch folders in:
C:\Program Files\LTC\LTspiceXVII\

After the start LTspice will reindex the new Library.

I already did that in past, but I prefer to add just the models I need.
BTW I use my own paths and just add them to the search path in LTspice settings.

In any case I see that there are 4 different TL431 models which added to the one I've been using so far are 5.
No wonder the same circuit may produce so different results... ;D

I guess the only way to know which one works better is to build a few different real circuits and compare the results.
 

Offline not1xor1

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Re: TL431 linear power supply
« Reply #155 on: December 31, 2018, 08:01:13 am »
I unsuccessfully tried to use the other TL431 models (LTspice reported some error messages). Probably the problem was due to the symbols (.asy files) I used.

I did not investigate further for lack of time, but I tend to trust the model I used previously much more than the others as it was provided by TI.

This last simple schematic seems to work under a range of loads and feedback resistors. If I had to build a TL431 variable voltage PSU (I wouldn't call that a bench PSU), I would start from this circuit.

 


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