I've been in this business a long time. When someone asks me if I can design a power supply for them, my first question is usually "have you tried to buy one of these?"
Why would you design your own power supply?
Developing power supplies is expensive, time-consuming, difficult and frustrating, yet the custom power business is alive and well.
Given the modern environment of high performance power, digital control needs, efficiency, etc., why are you contemplating or already designing your own power system?