Isolated Voltage Regulator Circuit

Thread Starter

dlad87

Joined Nov 9, 2020
20
Hello,

I'm looking to do a project where I need multiple isolated regulated outputs. I understand how to wire the regulator but am unsure how to isolate them from each other. They need to be isolated for groundloops. I've attached a portion of a schematic for illustration of what I think may work. Am I on the right track with the diodes? Or should I do something different?

I've searched for similar circuits with "isolation" but all I get is simple wiring circuits of the V reg's.

Thanks
 

Attachments

ericgibbs

Joined Jan 29, 2010
12,258
hi dlad,
Welcome to AAC.
That method will not give isolation from each other or ground.
How many outputs do you require and is it complete isolation from ground and the other Vouts.?
E
 

Thread Starter

dlad87

Joined Nov 9, 2020
20
Thank you.

I need (8) outs and yes complete isolation from ground and each of the other regulator out's.

Thank you!
 

Thread Starter

dlad87

Joined Nov 9, 2020
20
The 12V would be a linear supply. A transformer into a bridge rectifier.

I wonder to get the isolation I need if i would need a transformer with several secondaries? Or could this be accomplished with discrete components?

Thanks
 

ericgibbs

Joined Jan 29, 2010
12,258
hi 87,
You could use transformer with 8 off windings , say 8v output, you would need a rectifier, smoothing and 7805 for each winding.
Can you tell us what it will be used for.?

E
 

ericgibbs

Joined Jan 29, 2010
12,258
hi,
OK, for a 7809, ie: 9Vout you will need about 12Vdc in from the rect and smoothing.
What are the current loads on the 9Vouts.?
E
 

ericgibbs

Joined Jan 29, 2010
12,258
hi,
One option would be to strip the secondary windings from an old transformer and rewind on 8 secondaries,
So a transformer capable of 8 * 0.5A say would be required.
You may have to use a higher VA rated transformer that has enough clearance for 8 secondaries

E
 

Attachments

Last edited:

Thread Starter

dlad87

Joined Nov 9, 2020
20
Another thought I just had is to use these Meanwell SPBW06F-12 isolated dc-dc converters ahead of the regulators. I would use one of these converters to supply each regulator. The converters would be powered by the transformer secondary after the rectifier and filter. I think it would allow me to use a transformer with one secondary and still maintain isolation of each regulator output from each other. Is my understanding correct? https://www.digikey.com/en/products/detail/mean-well-usa-inc/SPBW06F-12/7707012

Thanks
 

ericgibbs

Joined Jan 29, 2010
12,258
hi,
These are the type as I suggested in post #4.

The type you have posted are +12Vout , so a single 9V thru 36Vdc input would be OK.
E
 

AnalogKid

Joined Aug 1, 2013
9,058
If you need complete galvanic isolation among all outputs, then your options are capacitive coupling or transformers. One primary and multiple secondaries will work fine, but I doubt there is an off-the-shelf transformer that meets your requirements.

One option is several dual-secondary transformers, but the size, weight, and cost might be too much. Another is small isolated DC/DC converters, each with one output. For ausio applications you probably will need to add extra filtering to each output.

https://www.ebay.com/sch/i.html?_from=R40&_nkw=isolated+dc-dc+converter&_sacat=0&_sop=15

ak
 

Thread Starter

dlad87

Joined Nov 9, 2020
20
Multiple secondaries are my preference but I can’t find a transformer that is 8x12V for secondary taps. I could run multiple dual secondary transformers such as ones from Antek but that takes a lot of space. Cost of the smaller Antek transformers are about the same as one of the Meanwell dc-dc converters so it is likely cheaper going with multiple toroids but the enclosure will have to be bigger.
 

ericgibbs

Joined Jan 29, 2010
12,258
I can’t find a transformer that is 8x12V for secondary taps.
hi dlad,
If you decide on a transformer solution, you do not want a tapped transformer secondary, it must be 8 independent secondary windings.
E
 
Top