SV: Re: [sdiy] LM723 synth power supply issues!

[karl dalen]

--- Harry Bissell Jr <harrybissell at prodigy.net> skrev:

> Hi Karl
>   
>   woah I'm not sure what you are saying.
Im not shure either! I had to rewrite it 
because when rereading my first proposal
of the issue i couldent undersand it either! :)

   
>   Two secondary windings - total four wires ???
>   (ie they are not center tapped)

Not center tapped, four wires yes.

>   If so you could make two serarate supplies... then
>   you could put those two in series to make a bipolar
>   supply.

My start point is just that, two separate floating
supplies, just like a bench supply are done using LM723
as regulators, no tracking regulators, separate bridges
bypass and regulators.

No forget about serializing regulators, bad idea.
   
>   I don't like that method, because it pust one of the pass transistors
>   in the 'center tap' or 'ground'... but it would work.  I like
>   complimentary supplies better (one NPN, one PNP)

You cant serialize one regulated + supply into one + and 
one - supply you need a separate winding or halfbridge with
one end of the winding to GND.

>   If you connect them, they become a bipolar supply and they are no longer
>   independant.

If i connect (bridge in bench supply language) one floating
- supply to the other floating + supply i create a virtual GND
and the supply becomes bipolar, but isint the supply still
floating?? Because i can futher cascade supplies like this 
to create higher voltages!
   
> If you add a second bridge to each one... they will still
> be tied together through the bridge diodes and won't be 
> independant, either.

I dont agree, you can paralellize diode bridges bypass 
and regulators in large numbers and all can have independant voltages as long
as they use same GND point (ie the - side of
the bridges) so if you tie all GND (minuses)together you have 
separate voltages with a common GND point in the 4 way supply.

The issue here is that its very difficult to come by a ring
transformer that has many secondary windings, allmost all are
sold as one winding or two windings however i can easily
purchase a 100A 250V unit if i want to, so having plenty
of current (no im not using 100A im using 4x2A)i would be 
able to feed many voltages of less currents ie 4x1A +15-15 +5-5.

>   Most of the ways of doing what you are suggesting (that I know of) involve
>   having to use HALF wave rectifiers.  Then the diodes can isolate you...
>   but that has its own troubles...

Yes thats another way of doing it.

KD