Hi Seungyeon.won,
We recommend using the MP8007 part, it has both non-isolated and isolated applications. The reference for non-isolated layout can be found in the MPSmart Model. Attaching capture below.
Here is the link: MP8007 | Fully-Integrated 802.3af-Compatible PoE PD Interface with 13W Primary-side Regulated Flyback or Buck Converter | MPS (monolithicpower.com)
Thanks,
Nouman
