shout out to Kristof_2649 for responding to my earlier post about having trouble finding a flyback transformer for my USB-C 65W power supply design, after changing the ic to more easily findable transformer i now find myself in the exact same problem I’m working on a 65 W isolated USB-C PD wall adapter and I’ve hit a practical roadblock on the magnetics side.
The design is based around TI’s UCG28826 offline quasi-resonant flyback controller, with a USB-C PD controller on the secondary side for voltage selection. Target input is 90–265 VAC, and the main output target is 20 V at 3.25 A.
From going through the datasheet and reference design flow, I’ve narrowed the flyback transformer target to roughly:
Primary inductance: about 200–220 µH
Turns ratio: about 6:1
No auxiliary winding
Reinforced isolation
Low leakage inductance for a compact 65 W QR flyback design
The closest reference part I’ve been able to identify is the Renco RLTI-1464, which appears in TI’s UCG28826EVM-093 documentation. From what I found, it’s around:
200 µH
6:1 turns ratio
low leakage
intended for this exact 65 W UCG28826 USB-C PD flyback platform
So electrically, it seems like I’ve deduced the right class of transformer.
The problem is that when I try to move from theory to actual implementation, the part is basically nowhere to be found through normal distribution. I’m also running into the usual follow-on issues:
no easy sourcing path
limited practical documentation outside the reference design
no straightforward symbol/footprint workflow
uncertainty on whether I should design around this exact transformer or treat it as a semi-custom magnetic from the beginning
At this point I know pretty well what transformer I need, but I’m less sure about the best engineering path forward.
For people who’ve built offline flyback adapters before, what would you do here?
Contact the transformer vendor directly and treat the reference transformer as a custom / RFQ part
Find the closest available off-the-shelf flyback transformer and redesign around it
Switch to a different controller/reference design with easier magnetics sourcing
Something else
Also, if anyone has experience sourcing parts like the RLTI-1464 or finding realistic alternatives in the 65 W, 6:1, ~200–220 µH, no-aux-winding range, I’d appreciate any pointers.
I’m trying to handle this like a real product-design problem, not just a schematic exercise, so I’d value practical advice from people who’ve dealt with magnetics sourcing in low-volume or prototype builds.
