Making transformers

[Rulycat]

During lockdown I decided to do more research on power supply theory, take this image for example:

http://www.pavouk.org/hw/en_atxps.html

This is the DTK 200w schematic that seems common on the web... I would like to build a clone of an old design such as this to understand better how it works (we learn by doing, after all) I don't fully understand why everything is the way it is, but that would be the fun of building a copy... the only thing I can't get my head around is, how do forum users on here go about building a transformer? Parts are easy to get but a transformer I would presumably have to wind myself?

Side questions:
Safety-wise, this is fucking with 230V AC, so I was planning safety glasses, and presumably plugging the thing into an RCD plug in the wall - what do you use to minimize the risk of high voltage?

[budm]

Re: Making transformers

Not simple: Examples
https://talema.com/smps-transformer-design
https://www.wcmagnetics.com/resources/
https://circuitdigest.com/tutorial/h...upply-circuits
https://cdn.badcaps-static.com/pdfs/...49659ecc97.pdf

Or learn about SMPS design: Example
https://www.smps.us/smpsdesign.html
https://www.smps.us/

[Per Hansson]

Re: Making transformers

As a coincidence I just watched these two videos, they have useful theory:

Is it easy to create your own Transformer? Everything you need to know about Transformers! || EB#42
Can you 3D print a Transformer? (Experiment) || How to make a mains Transformer!

[Rulycat]

Re: Making transformers

Looks good, I was struggling with where to get materials for a transformer as well like the core... as I don't have any PSUs lying around to cannibalise...

[Th3_uN1Qu3]

Re: Making transformers

I've made a bunch of them years ago, they're still chugging just fine. I have a spreadsheet posted around this forum somewhere that can help you. It's called the "Mega SMPS Cheat Sheet", use that search term and you'll find it.

It's not as hard as you may think. There are some parameters that you must take into account, these will be provided in the core datasheet. Transformer cores are standard and you'll be able to find these parameters for all of them based on their physical dimensions.

You're going to need to know the core parameters, the operating voltage and the frequency your controller will be running at (that would be full load frequency if your controller uses variable frequency, like modern resonant mode controllers do). Plug those numbers into my magical spreadsheet, number of turns comes out as a result. Tada. Click here.

Or if you like the hard way, the books I've based my calculations on are all mentioned in there, have a read. No safety glasses required - but if you want to be sure your creations will be electrically safe you may want to invest in a hipot tester. Or just overdo the insulation between primary and secondary, it is a critical safety aspect. More insulation will bite into your efficiency a little, but better safe than sorry.

Side note: You'll be shocked (pun very much intended) on how much of a joke "insulation" is in some of the Chinese knockoff chargers... Any homemade transformers built with the tiniest bit of common sense will be much safer than those piles of junk.

[Rulycat]

Re: Making transformers

Th3_uN1Qu3, that's a fantastic document. I must have read on here years ago, but it was so long ago, it slipped my mind.

I'm not professionally educated in this field at all so some of the information goes over my head but I do have a copy of Power Supplies A to Z (Although, a large amount of that goes over my head as well!)

[Th3_uN1Qu3]

Re: Making transformers

Everything in that spreadsheet has been checked by building power supplies that actually worked (and still do!), you're welcome.

Out of all the SMPS books I read that are mentioned in there, the easiest to understand by far is Switching Power Supply Design, 3rd edition (A. Pressman). I remember Power Supplies A to Z going over my head, too.

[Rulycat]

Re: Making transformers

That's a good recommendation, I have bought a used copy online, and have downloaded a hookie copy until the doorstopper comes.

Doing a quick scan through and it seems already more digestible than A-Z.

Thanks for the heads up.