r/AskElectronics • u/Toaster910 • 1d ago

Why is copper strap used in SMPS transformers?

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20 Upvotes

89% Upvoted

13 comments sorted by

56

u/Array2D 1d ago

Low resistance, low profile, good high frequency performance, easy to wind.

13

u/nixiebunny 1d ago

Solid round wire of that cross section is difficult to use. Another common solution is multifilar windings with 3 or 4 conductors next to each other in parallel. 

11

u/SyrupStraight7182 22h ago

If this was placed between two windings, this is a shield.

Typically it's used to reduce common mode noise due to switching on the secondary by providing a low impedance path to dc common or a dc voltage.

4

u/zifzif Mixed Signal Circuit Design, SiPi, EMC 13h ago

And if it's the outermost layer, it's a flux band to contain emissions radiating from an air gap in the core.

4

u/Toaster910 1d ago

I have a feeling it has to do with the skin effect, but what about the proximity effect?

7

u/2748seiceps 23h ago

It's more to do with the fact that it's easier to wrap this than it is big fat round wire of the same cross sectional area. 60Hz power transformers also start doing this when you get bigger than the size of consumer electronics.

3

u/jeweliegb hobbyist 20h ago

Presumably it also wraps fairly flat and close this way, making it closer to ideal?

10

u/toxicatedscientist 1d ago

Power. When you don’t need many turns but do want all the watts

0

u/k-mcm 22h ago

Capacitance?  It's more, but only across one winding instead of many.

1

u/Baselet 17h ago

Because it's a good conductor and reasonably cheap and easy to form.