I am working on updating an older flyback design. Part of the update is adding a comparator to control a relay through a MOSFET. It's a quasi-resonant flyback so the operating frequency swings between 30-50 kHz based on load/line.

Board space is fairly limited and we cannot change the board's dimensions, so our layout resource has placed the comparator circuit on the bottom side of our board below the transformer. I have a feeling that it's not a good idea but if we can get away with it, there is a large amount of open space there.

Should these components be moved elsewhere? Or could adding a ground plane between the components and the transformer shield it from any noise from the transformer?

  • \$\begingroup\$ I would worry more about isolation between the pri and the sec because placing a component underneath the transformer will effectively decrease the clearance. \$\endgroup\$ Nov 20 at 22:33
  • \$\begingroup\$ Is this a 4+ layer design, or what? Isolated, if so to what voltage, category etc.? What does the space under the transformer look like, was it placed there because it's "empty" space? Was it empty for a reason? What design is the transformer, is it self-shielded, metal shielded? What signal level is the comparator working with? \$\endgroup\$ Nov 20 at 23:26


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