Planar transformers

Use 'em much? How does your experience compare with regular components, in regards to anything that might've caught your attention: performance, area, effective cost, etc.

Any opinions on design tools for them? I'm guessing most EDA packages don't have this, though many will support the structures (e.g., Altium lets me declare a net bridge and put whatever funky copper I want between pads, which would work well for printed RF components as well).

Anyone tried building them in two-sided PCBs? It occurs to me, to get any isolation clearance, the layout must extend pretty far beyond the core, which is going to do interesting things to leakage and EMI.


Deep Friar: a very philosophical monk.
Reply to
Tim Williams
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I've not used them in my own designs, but I've used plenty of DC/DC converter modules that do, and they all have multi-layer PCBs. Power is in the range 50-200W, PCB thickness is usually 2-3mm (to fill the core), and the layer count is often 10 or more. There are no tracks on outer layers in the vicinity of the core.

I don't think two sided will cut it, because of leakage inductance and clearance. YMMV.

Regards, Allan

Reply to
Allan Herriman

Never.Thought about it though.

The first big question is copper fill factor. One ounce copper is 1.4 mil - 35 micron - thick.You can get thicker copper

Two sided PC is 1.5mm thick. With 2-ounce copper on either side you'd have a maximum fill factor of 9.3%.

With a ten layer board of the same total thickness, you'd be up to

0.7mm, of copper and 0.8mm of board which isn't too far short of what you get with round insulated wire in conventional windings, by the time you've figured in the winding area lost to the former.

IIRR such a board would be made by stacking five double layer boards, each 0.24 mm thick (including the copper) with four very thin resin- loaded interleaving layers.

This article refers to 10 ounce copper used in a big planar transformer -14 mil or 0.35mm.

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Perhaps not. Why not talk to a printed circuit board manufacturer who makes this kind of part? I did that once at a trade show, and got about ten minutes worth of explanation ...

-- Bill Sloman, Nijmegen

Reply to
Bill Sloman

I've never used them, but I can recommend a company in NJ that does a = good=20 job at reasonable cost for EI core transformers, and they seem to have=20 expertise in planar designs. Talk to Simon and tell him I sent you :)

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Reply to
P E Schoen

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