Isolated flyback converter - secondary grounding

Thread Starter


Joined Jan 9, 2009
Hi All,

I've been beating my head around this topic for a while now so why not through it at the community.

I have a flyback converter design which generates two isolated voltage rails, each completely isolated from each other.

Both of the grounds from both of these isolated rails eventually go outside the design for use in external referencing. Therefore, it appears to me that both of these should be tied to EARTH (your thoughts?) for safety, as the secondaries on an isolated transformer may float to who knows where (your thoughts?)

'If' I earth these two isolated grounds, they are in essence connected externally, so why would I not just create two voltage rails which 'share' the isolated ground and therefore helps to reduce further ground loops.

It starts to get pretty ground loopy and I'm concerned so hoping someone can just inform me of the industrial practice so I don't need to keep running in circles trying to think of the best way to go about this.

Thanks in advance,



Joined Apr 2, 2009
Well!! This ground loop thingy kind of gets me irritating at times, so I just ground the whole thing at let it do all the worrying :D
In practice that is.

But to lighten you up all I can say through years of experience in PSU repair, is that grounding is rather for protection through earthing.
But sometimes a circuit needs to be grounded for proper operation from all sorts of nasty interference generated from it self and all the surrounding that it is in.
And also grounding provides a more common reference point for all the electrical currents that is looping here and there in a circuit.
Isolated ground is needed to separate high voltage areas and low voltage areas mainly to protect the user from coming in contact with live circuits.