i know what you mean but i dont know why that circuit configuration didnt work with a PMOS.... ive built it on a breadboard it didnt work however, in simulation it worked quite well. the problem back then was that when the gate was driven to mebe +15V +0V the drain voltage of the PMOS only outputs 0.5Vpeak to peak. so it couldnt switch on/off. I really dont know the reason why... i then cahnge it to a NMOS with a source follower circuit then my buck converter works.... lol....