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Is this possible?

I have a 12V regulated supply that I need a 36V and 5v (100W total) supply from to power a peripheral and power the control circuit for said peripheral. This peripheral uses a piezo self resonating oscillator so I need to isolate it from sensitive analog measurements on the CPU that'll be the master of the peripheral. The control circuit will send/receive RS232 commands to/from an isolated RS232 transceiver IC on the CPU.

To repeat me question, is DC-DC galvanic isolation possible without inverting/transforming/rectifying? I want 1:1 isolation for the 12V supply which I'll then buck/boost with a double ended switching converter. I want to avoid creating a flyback converter since that'll destroy my BOM cost and transformers are BIG.

Thanks!

EDIT: I think I am over-complicating things and wasn't completely understanding the task given to me. Even so, I am still curious what the community has to say about DC-DC isolation since it's much more of a rabbit hole than AC isolation.

EDIT2: Closing this question since it is no longer applicable to my work and I believe Bimpelrekkie answered in sufficiently. Thanks Stack Exchange Community!

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  • \$\begingroup\$ I'm not convinced you need galvanic isolation, just supply filtering. \$\endgroup\$ – Finbarr Feb 28 '19 at 12:25
  • \$\begingroup\$ I'm thinking so too, but the need for isolation is coming from "higher ups". I want to explore all my options here in the case that the extreme of galvanic is necessary. \$\endgroup\$ – TammerTheHammer Feb 28 '19 at 12:27
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    \$\begingroup\$ Are the "higher ups" the saftey agency which will certify your product? \$\endgroup\$ – winny Feb 28 '19 at 12:41
  • \$\begingroup\$ A flyback transformer isn't necessarily big and provides natural galvanic isolation. \$\endgroup\$ – Andy aka Feb 28 '19 at 12:42
  • \$\begingroup\$ "higher ups" are the other EEs that created the CPU board. I'm creating the interface between that and a chinese designed piezo module. \$\endgroup\$ – TammerTheHammer Feb 28 '19 at 13:02
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DC-DC galvanic isolation possible without inverting/transforming/rectifying?

For power transfer with isolation we generally use magnetic conversion, by that I mean the electric energy is converted to magnetic energy and back to electrical energy. For that we need a varying magnetic field meaning an AC input signal is needed and rectification is also needed. You cannot transfer energy with a static magnetic field.

The only solution I can think of is optical so a (LED) lamp shining it's light on a solar panel. That will be big, inefficient and somewhat expensive perhaps.

So possible: yes

But practical: no

I agree with Finbarr's comment that you very likely do not need galvanic isolation. What you need to do is take care that you use proper grounding that does not mean a stick in the earth but following good practices like a star ground setup.

Also, current travels in loops. Make sure the loops that the disturbing currents follow are not shared with the loops that the currents in the sensitive circuits follow. Using a start grounding scheme helps with this. To separate the supplies use voltage regulators and plenty of decoupling.

A general tip: try to avoid "fixing" a certain problem (separation of circuits) by introducing something complex and costly (galvanic isolation) without fully understanding if the problem actually is a problem and what the potential solutions are to fix that problem. Only if that proves that there is no other solution that those drastic solutions should you consider those drastic solutions.

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    \$\begingroup\$ I did think of the LED-solar panel route but that would hurt his BOM cost even more and take up way more space than a transformer! \$\endgroup\$ – Finbarr Feb 28 '19 at 13:01
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    \$\begingroup\$ Another "solution" would be DC motor and DC generator, with same problems as LED +some others. \$\endgroup\$ – Rokta Feb 28 '19 at 14:06
  • \$\begingroup\$ There were a few isolation amplifier hybrids that used capacitive power transfer some time in the past. This would eliminate the transformation component for OP. \$\endgroup\$ – KalleMP Mar 4 '19 at 14:12

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