Availability of recommended flyback transformer cores and equivalence of vendor materials

Hi dch53,

Good day. Thank you for using Power Integrations solutions.

Other core types of PQ25/20 should work, as long as their parameters are within each specification and similar to the parameters considered in the design, such as the core cross-sectional area (Ae), core magnetic path length (Le), and core volume (Ve).

Regarding the sourcing of magnetic wires, we do not have a directory for distributors. Therefore, we’re unable to provide suggestions in this regard. Thank you for your understanding.

I hope this resolves your inquiry. Thank you for reaching out to us.

Thanks!

Small quantities of cores and bobbins are available from Digi-Key and Mouser. I checked, and the PQ26/20  size is definitely available. Bobbins are also available. Magnet wire is available from MWS Wire Services in Chatsworth, California, though you might have to buy a pound or two to meet their minimum requirement. Triple insulated wire is available from Rubadue Wire at rubadue.com. If you ask them nicely, you may be able to get a sufficient sample quantity from them to meet your needs.

Thanks for the reply. 

The issue was the core material rather than the core size and shape. I ended up getting a TDK N97 core.

Thanks also for the wire recommendations. I was able to purchase what I needed from aliexpress and an online hobby store.

All that said, I haven't set up a winder yet. Hoping to get to that soon. The PCBs for my prototype flyback converter arrived yesterday.

How will you grind the gap for the transformers? You will need a gap to get any significant power output, otherwise the transformer core will saturate like mad. What software are you using for the transformer design? What is your proposed controller/mosfet combination?

None of the available gapped cores met my requirements so my plan is to add paper "spacers" to create the gap required while doing repeated inductance measurements to find the correct gap.

I'm planning on using the transformer design specified by the PI tool.

The actual flyback converter design is based on an MPS MPX2002  evaluation board.

Can you share a PDF of the transformer design output by the PI tool?

Sure. Pages 10 and 11 of the attached pdf.

You have three outputs with separate grounds. There will definitely be issues with cross regulation with wide load variations.

Yeah. Fortunately, all outputs are pretty much constant current so I'm hoping that won't be an issue.