Regulated 12 Volt Supply
This circuit above uses a 13 volt zener diode, D2 which provides the voltage regulation. Aprroximately 0.7 Volts are dropped across the transistors b-e junction, leaving a higher current 12.3 Volt output supply. This circuit can supply loads of up to 500 mA. This circuit is also known as an amplified zener circuit. Link
Other Link
Simple regulated power supply with overcurrent trip
Flyback Driver Circuit with 2N3055
High Current Regulated Supply by LM317
Dual Rail Power Supply +/- 0 to 15V 1A by LM317,LM337
