[sdiy] Using switching power supplies in series to get bipolar outputs?

[Guy McCusker]

That sort of issue definitely happens if you try to use a positive
regulator on a negative supply, e.g. attempting to regulate +/-15V to
+/-12V by using a 12V regulator on the positive supply and a 3V
regulator on the negative supply. The lower rail's regulator cannot
sink current on its regulated output so if the +12V is sourcing more
than the -12V is sinking then we have a problem.

With two separate 12V supplies in series this is not an issue and I
haven't been able to cook up a scenario where it becomes a problem.
It's also not a problem to hook up in series two 15V supplies each
regulated to 12V by a positive regulator. And actually that tends to
be how dual-output lab supplies work, if I am not mistaken.

On Mon, Nov 20, 2023 at 3:24 PM Mattias Rickardsson <mr at analogue.org> wrote:
>
> Wasn't there something with the sinking/sourcing of current that introduced some potential (no pun intended) problem when using two positive supplies as a bipolar supply?
>
> Can't seem to remember the details or where I heard it right now.
>
> /mr
>
>
>
> Den mån 20 nov. 2023 13:43Roman Sowa <modular at go2.pl> skrev:
>>
>> But hooking them up in series to get higher voltage actually IS making a
>> bipolar supply. It only depends which node you decide is the 0V. The
>> outputs are isolated from AC inpt so you can do whatever you want with
>> multiple outputs up to the isolation limit which is if I'm not mistaken
>> up to 3kV
>>
>> Roman
>>
>> W dniu 2023-11-18 o 15:08, Scott Bernardi via Synth-diy pisze:
>> > I've noticed that most switching power supplies that offer bipolar
>> > outputs(i.e., to get +/-12v) have less current capability on the
>> > negative supply than the positive.  For example, the Meanwell 65B which
>> > has +/-12v and +5v, great for Eurorack, has
>> > +5v max 8 amps
>> > +12v max 3.5 amps
>> > -12v max 1 amp
>> > What about buying two +12v supplies, or maybe one that has +12v and +5v
>> > with another with just +12v, and hooking them in series with a center
>> > tap to get +/- 12v?
>> >
>> > This article
>> > https://www.mouser.com/pdfDocs/blog_how-to-operate-parallel-and-series-connection.pdf <https://www.mouser.com/pdfDocs/blog_how-to-operate-parallel-and-series-connection.pdf> looks like it's possible, although they only talk about hooking them up in series to increase the output voltage rather than bipolar.
>> > Has anybody done this?
>> >
>> >
>> > _______________________________________________
>> > Synth-diy mailing list
>> > Synth-diy at synth-diy.org
>> > http://synth-diy.org/mailman/listinfo/synth-diy
>> > Selling or trading? Use marketplace at synth-diy.org
>> _______________________________________________
>> Synth-diy mailing list
>> Synth-diy at synth-diy.org
>> http://synth-diy.org/mailman/listinfo/synth-diy
>> Selling or trading? Use marketplace at synth-diy.org
>
> _______________________________________________
> Synth-diy mailing list
> Synth-diy at synth-diy.org
> http://synth-diy.org/mailman/listinfo/synth-diy
> Selling or trading? Use marketplace at synth-diy.org