Quote Originally Posted by efficient View Post
Well, I am no expert either to these stuff so I can't give any extra comment on the very issue. But if it really is the PFC Mosfet that is causing this problem it doesn't make any sense to me. The MOSFETs are actually commonly used in other mid to high end PSUs, an example would be the GPU based DQ-M (v1), so maybe it's something else.
Be my guest to watch this slow video with patience up to 50% of total duration.
This helped also my understanding at large scale DC to DC converter the ones at computer PSU.

https://www.youtube.com/watch?v=xFyPj9YnZx8