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This is a very simple and adjustable voltage power supply. Max input voltage is 37V and output adjustable between 1.2 to (vcc - 3) volts.
Q1 is a power PNP Darlington transistor and is used to boost current of LM317. It's the most useful adjustable regulator and for this circuit you can also use LM317L thats can give 100mA, thats enough for transistor bias.
D1 and D2 are protection diodes because when you turn the circuit off the output capacitors discharing and can damage the transistor or regulator.
R1 is 2W and other resistors are 0.25W
R1 is LM317 current limiting resistor and R2 is Q1 bias resistor all capacitors are 50V RV1 is 5k multi turn volume pot.
100nf capacitors are in parallel with electrolytic capacitors to remove high frequency noise because large value electrolytic have large ESR and ESL and cant remove high frequency noise.
I will design a pcb for this circuit and add to project .
Q1 need heatsink and small fan.
Circuit maximum output is 125W
source : http://www.electronics-lab.com/projects/power/021/index.html
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