There are, however, two diodes connecting the switching side of the primary coil with Vin which are puzzling me.
The input is 5-15V but the Zener chosen is 22V. The schottky is rated 60V. I really don't understand their purpose. It seems like they are just going to introduce noise in Vin with voltage spikes generated at the end of the primary coil.
Could someone more enlightened than me take the time to have a look at it?