Objective
Replace a drawer of wall-warts with one adjustable 0–18 V, 2 A linear supply with a proper current limit - and learn analog power design by building it.
Requirements
Output ripple under 5 mV at full load, current limit adjustable from 50 mA to 2 A, and no magic smoke when the output is shorted.
Design
A toroidal transformer feeds a bridge and reservoir caps; an LM317-based pre-regulator drops the bulk of the voltage before a discrete pass stage handles the fine regulation. Current sensing is a low-side shunt into a comparator that folds back the drive.
Build
Rev P0.1 was point-to-point on perfboard; P0.3 is the first custom PCB.
Problems Encountered
What I Learned
Stability is a property of the whole system including the leads - not of the schematic. The next revision gets designed with the output network first, not last.