Variable voltage regulator using LM317 ( 5V to 30V,1A )

Design Challenge:

Designing linear variable regulated power supply for 5 to 30 Volt, 1 Ampere consider 230V,50Hz Main Supply.

Theory:

1.National Semiconductors' LM317 is a three-terminal voltage regulator IC.
2.The IC has a maximum output current of 1A.
3.The output voltage can be changed from 1.2V to 37V and the input voltage can be up to 40V. 

4.Pin 3 (v in) of the IC receives the input voltage, whereas pin 2 ( V out) provides a regulated output voltage.
5.To set the output voltage, a resistor network with R1 and R2 connected in series with pin1 (adj) is utilized.
6.The input filter capacitor C1 is the input filter capacitor, while the output filter capacitor C2 is the output filter capacitor.

Calculation:

The equation 

Vout = 1.25V (1 + (R2/R1)) + I adj.R2 

determines the regulator circuit's output voltage.

 

Circuit:

 

 

PCB Layout: