Switching Power Supply Problem?

Hello!

I'm trying to build a switching power supply but the schematic doesn't seem to do the work, at the output I got the same voltage as at the input.
The 5K trimmer doesn't have any effect, for D1 I use UF5408 and for D2 1N5819.
R1 is 0,22 Ohm.

I've uploaded the schematic. Could you tell me if is something wrong with the circuit?

Check this out.......
https://www.ti.com/lit/an/slva252b/slva252b.pdf

D2 should be a 13V zener according to the schematic; not a 40V Schottky.