Switchinhg power supplies is something anyone can design and only few can make work. I had an engineer trying to design some for us (we pay $20.000+ monthly for power supplies) after 6 months I told him to give up and we had to replace all "his" power supplies with purchased units. examples of problems:
One of 1000 would mysteriously pop every week.
A customer could not use his walkie-talkie because of EMF radiations.

Go ahead, give it a try, should you so desire, but do not make it "I'll throw one together this afternoon".

Erik