Quote Originally Posted by Ioannis View Post
...The modules are just bad copies of western know chips with too cheap inductors and capacitors....
A lot of those converter circuits look like they were done in some cave. This one looks surprisingly well done:

https://www.aliexpress.com/item/1005001629723875.html


The 5V pro variety comes down to $0.69ea in packs of 20.

I'm going to look for those app notes.