Electronics > Beginners

Choosing off the shelf transformers for flyback converters

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Buriedcode:
For your specific example, these may eb an off-the-shelf solution:
http://www.cooperindustries.com/content/public/en/bussmann/electronics/products/eaton-magnetics/eaton-transformers/eaton-versa-pac-inductorsandtransformers.html

I realize yours was just an example, but for low turns ratios/low voltage the above can be handy - especially handy for creating bipolar supplies with just a boost converter.

T3sl4co1l:
Thing is, if your application needs a standard transformer, you can do everything so many times cheaper with a standard PSU module -- that already carries agency approvals.  |O

Transformers aren't all that cheap from distributors, either:
https://www.digikey.com/products/en/transformers/switching-converter-smps-transformers/168

And obviously(?), nothing is more expensive than the one it takes an hour to wind, by yourself (unless your time is discounted to ~zero).  Designing and winding transformers is a valuable skill, and the two go hand-in-hand for designing manufacturable transformers as well; but winding more than a few for prototypes?  Geez...

Tim

T3sl4co1l:

--- Quote from: blueskull on December 13, 2018, 05:28:43 pm ---I might be biased, but most of the time I mess with flyback, I get some bad losses. Bifilar winding can help, but then you need to trade with EMI and SRF.

--- End quote ---

The last one I did, I wound the transformer as twisted pairs -- following TLT theory.  Damn good performance, the capacitance was low (switch and diodes dominate) and leakage was exactly as expected: low enough to just barely need R+Cs across diodes.

PITA to wind, though.  In a TLT, primary and secondary come out together, on the same side of the bobbin.  Easy to run out of pins, for a multi-winding transformer.  It's also a lot of wires connected in parallel (the primary from every pair gets wired in parallel), loading up the pins a lot.

It was still just a bit more complex than that, because I made a 2:1 (Guanella type) section, because the overall converter was step-down.

So that was fun.  Fun to realize a design of high optimization.  I don't recommend trying to buy them from a coil winder. :P

Tim

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