Single transformer - multiple bridges!

[UV101]

Does this work? I see no reason why not on paper.

What I mean is if we have a transformer winding. Can we run multiple independent rectification (i.e. ac inputs in parallel) to generate multiple isolated dc supplies with a common ground?

Would we see any adverse effects?

[jazz]

Hi,

It's what i use in one of my tube amps and it works fine.

grtz
Joris

[sofaspud]

It can be done, yes, but if they share a common ground are they really isolated?
Coincidentally, I'm currently working with a recycled linear supply whose single transformer provides 25VDC through a full-wave bridge rectifier and 12VDC through a half-wave diode circuit.

[DF96]

You need just one bridge, and then a single diode for each additional supply. However, they won't be fully isolated from each other.

[UV101]

Thanks. With respect to the common ground, even if I use multiple transformers, I'd need to common the ground for rails in the same device.

What I'm looking to achieve is to replace the multiple 5v psu's with individual transformers I run inside my player with a much larger single transformer hence the multiple full wave bridges from a single winding and keep the separation for each supply back to the bridge (common gnds accepted).

I wonder if the multiple transformers is adding anything or if a single higher quality higher va unit will be as good. I'm not looking to reduce the number of rectifiers, smoothers, regs etc.

[AndrewT]

Would it help to have one transformer with multiple windings?
These are then isolated from each other. Can be rectified and smoothed separately. Regulated if need be.

Then each circuit can have only ONE final connection to your common voltage reference.

[Kay Pirinha]

Hi,

if common gnd is acceptable, you don't need a full bridge for each positive line. You'd just feature a bridge capable for the total current amount, plus two diodes, or a double diode with common cathodes from the AC terminals to each pos. rail.

Best regards!

[DF96]

Most of any problems will be with the grounds. Much easier to have either one big PSU to supply the lot, or lots of genuinely separate PSUs driven from separate secondaries - doesn't have to be separate transformers. 'Separate' PSUs driven from one secondary is about the hardest way to do it. My feeling is that if you knew enough about ground wiring to get it right, you would know enough not to attempt it!

[UV101]

What I have is this


And I'm wondering what will happen if I move the this


I am already dealing with multiple grounds so I've no issue there. Obviously I could got for a transformer with multiple secondary windings and keep that side as per the 1st diagram and the mains side as per the second, but I wonder how using an off the shelf large va transformer would effect things.

I treat each supply as being in its own noise domain but I wonder if going all the way back to the secondary windings is really necessary. I'm not just looking for an it will work or wont, I'm interested in opinions on the quality of the supply.....

I appreciate the comments so far, thanks ;-)

[UV101]

Originally Posted by DF96

You need just one bridge, and then a single diode for each additional supply. However, they won't be fully isolated from each other.

Somehow missed this!!!! Same question applies, how will this effect things compared to individual secondary's?