[sdiy] +/-12v from a single +12v psu - possible?

[R. D. Davis]

Quothe Julian, from writings of Wed, Aug 25, 2004 at 02:55:20AM +0100:
> I want a +/- 12v supply, which can happily be some ammount under the 3.4A.
[...]
> In short, is there a simple way to get a negative rail from this supply?

Well, I can think of one way that involves doing some switching and
some capacitors of a suitable capacity... could be as simple a
solution as an oscillator switching a relay on and off, so that
polarity is switched while alternately sending the juice to two
different capacitors, alternating the charging of them.  Haven't had a
chance to try this or to give it much thought, but it seems like the
following might possibly work, with some modifications.

1  +  >---------+-------> +
               === C1
2  -/+ >--------+-------> Gnd for output, separate from PSU gnd.
               === C2   
3  -  >---------+-------> -     


In the above circuit C1's negative terminal would be connected to C2's
positive terminal.  During alternate cycles, +V would be applied to 1
and -V would be applied to 2, then, switcheroo and +V would be applied
to 2 and -V would be applied to 3, ad infinitum... well, until power
is turned off.  Well, something like that.  As I said, I've not tried
this or had time to give it much thought.  You might want to have a
second relay, or switch, so that the load isn't applied until after
the caps charge up... may need to add a few more components, like some
resistors for current limiting.  

Any thoughts?  

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