Power supplies to build yourself
There are many types of power supplies.
Most are designed to convert AC line supply to an appropriate value for low-voltage circuits and other electronic devices, maintain and stabilize DC output. Power Supply, supplies electric power to an electrical load.
All PS obtain energy from a source which supply to load and, all consume some amount of energy to work.
Depending of its type, a power supply obtain energy from:
Some Power Supplies Diagrams: