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

[karl dalen]

--- Harry Bissell Jr <harrybissell at prodigy.net> skrev:
> 
> 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 are crazy enough, you could AC couple the windings and do  strange
> things... or also, make a center tap using large capacitors....

Ah, yes you can sort of make a GND point of AC them by place 
two resistors from each wire and pick a GND in between the resistors. No i dont
want to do that, thats wired! :)
>     
>   I don't suggest it :^P

Im not that crazy!

> >   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!
>     
>   Yes you can do that !

Yes but is it still floating?

Isnt all supplies actually floating?
    
> > 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 50V 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.
>     
>   Yes. The 'outside' of the rails is +/-15V... and the +/-5 can >   be
contained  within there (sharing the center tap...)
>     
>   like
>     
>   +15
>   +5
>   COM
>   -5
>   -15
>     
>   but you cannot put them like
>     
>   +5
>   (separate com)
>   -5
>   +15V
>   (separate com)
>   -15V

Yes thats right but what happends when:
+5 (minus side of separate +5V bridge not tied to com)
+15
com
-15
-5 (plus side of separate -5V bridge not tied to com)

>   Like you could if they were REALLY independant....

Like as in "separate windings".

KD