Routing a hi side gate drive: NOT over a ground plane?

[cupoftea]

Hi,

We are Routing a hi side gate drive in a Half bridge LLC converter with Vin = 390VDC.

Obviously you wouldn’t route a high voltage switching node over the lo side gate drive tracking….so the reverse must also apply…that is, you should never route the hi side gate drive tracks over the ground plane (since the hi side gate drive tracking is indeed a switching node as its referenced to the switching node).

…As such, I just had to put a gap in the ground planes of a four layer PCB as attached….you can see the secondary pins of the gate drive transformer, and the hi side gate drive tracking going to the FET, in the “clearing”, now cleared of ground plane…..clearing such a ground plane area, on three layers, took over an hour. Is there any quicker way to do this? (in Eagle Pro), and do you agree that it needs doing?

 

[FvM]

I'd expect that Eagle has a keep-out polygon (also called plane obstruct) feature like most CAD tools.

--- Updated Jun 16, 2022 ---

In switcher PCB we often have splitted rather than continuous planes, with plane areas assigned to the switching node(s). Gate driver circuits would be placed above a respective plane area.

 

[cupoftea]

Thanks, yes Eagle Pro 7.4.0 has keepout for top and bottom layers (tkeepout, bkeepout)...but not for those inbetween unfortunately

 

[KlausST]

Hi,

you may use an auxiliary line with the width of the isolation, then align the pologon to the auxilairy line.
After that you may delete the auxiliary line.

Klaus