1.3 - 32 V / 5A Power Supply w/ Short Circuit Protection by LM338


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This is a very easy to build power supply that is based on LM338 5A adjustable voltage regulator. I am using the supply for a long time, have no problem yet. Only current adjust is missing but I overcome this situation by using an LCD panel ampermeter.
There is no PCB for the circuit. I took a 3x16 copper plate and strip the unused areas by a knife. If you want you can use analog meters instead of LCD panels.




  • Use thick wires for connections.
  • When connecting the LM338 to the heatsink use thermal paste.
  • Use external supplies for LCD panels. They can be 9V batteries. The panels I use draws 1mA current and the batteries last sufficiently long time. If you have small transformers which can supply regulated 9V, you can use them. You need separate transformers for each panel!
  • The transformer should be 100 Watt but if you don't need high current you can try transformers that you already have. (I can draw 6A from 100Watt transformer.)
  • If you have multi winding transformer you can use the diode connections shown in schematic. Diodes must be 10-15 A.
  • Be careful while connecting LM338. Don't put it inverse.
  • Output of your transformer mustn't exceed 25V AC.


  • 1_to_32V_5A_short_circuit_protection_power_supply_by_LM338.gif
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