| Electronics > Beginners |
| Power over Ethernet - How to find a proper Transformer |
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| Ranayna:
Hi, as already alluded in a couple of other threads, I am planning to build a Power over Ethernet supply. I have looked at a lot of datasheets, checked availability of reference designs, overall complexity of those designs, and finally took solderability into account. Now a new problem has me stumped... For example, take the PM8803 from ST. Datasheet: https://www.st.com/resource/en/datasheet/pm8803.pdf Design Example: https://www.st.com/content/ccc/resource/technical/document/application_note/aa/00/34/1b/19/82/4a/da/DM00113368.pdf/files/DM00113368.pdf/jcr:content/translations/en.DM00113368.pdf (reference design) From the datasheet alone, how would I be able to find what transformer I need? Have I missed something in the datasheet, or would that be obvious for someone who is proficient in designing switch mode supplies? Additionally, how would I find alternatives to the transformers used in those designs? For most designs that I have looked at, the transformers that have been used are difficult or impossible to find. Often I cannot even find a datasheet for the correct part. This ST design is an exception, the HA3691AL is available, but expensive. Maybe I have to admit to myself that I do not know enough (yet) about designing such a supply. At the moment I feel like I'm searching for "Lego Bricks" in the huge bin labeled "Internet", without understanding enough of the basics... |
| madires:
I assume that you're talking about the flyback transformer. The type of the transformer core is selected based on several parameters like the switching frequency for example. And you might need several windings for different power rails. Therefore you won't find many off-the-shelf flyback transformers, they are customized for specific designs. For prototyping you could use the flyback from a cheap SMPSU and re-wind it for your purposes. |
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