This Power supply circuit is based on lm317 IC circuit . This LM317 power supply can deliver high current (around 5 amps) and variable output voltage . The led D3 mounted on pin 6 at lm301 lights in constant current mode . Current limit can be adjusted using R2 potentiometer and the output voltage can be adjusted from 1.2 volts to 30 volts using R8 potentiometer . Input voltage for this LM317 variable power supply must be around 35 volts .
For this variable power supply circuit you need to use LM317K circuit (in to3 package ) which must be mounted on a heatsink .