LM317 / Adjustable Power Supply

LM317 / Small Linear Power Supply
4.5 5 4 Product

LM317 is perhaps the most popular linear regulator for low-power supply applications. The circuit which is presented here is a compact power supply unit based on this popular linear regulator. It is an adjustable power supply unit and it is able to supply up to 2A at 1.3 to 25V where the desired output voltage approaches the source voltage (the voltage at regulator’s input). Otherwise, expect about 1.5A. As in any linear regulator, the heat losses increase when the output voltage decreases.  In fact, the power loss due to heating is the current times the voltage dropped across the regulator. Besides heating losses, a linear regulator is often preferred over a switching one because it does not require any inductors which can be relatively expensive or bulky. 

If you decide to build this circuit, remember to use a large heat sink for the LM317 regulator and use a transformer which has a slightly higher output voltage than the maximum required one at regulator’s output.

LM317 / Adjustable Power Supply Electronic Schematic

The electronic schematic is quite simple. It contains a transformer which is the main power source, a diodes bridge for the rectifier, some capacitors for filtering, one resistor and two potentiometers. R4 is used for voltage adjustment and R3 trimmer is used for adjustable voltage limiting.

Artwork by: A.G

Click here to view PCB Artwork and Assemply details


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