This 13V/5A power supply is based on the famous LM338 IC from the ST Microelectronics. The IC has time dependent current limiting, thermal regulation and is available in 3 lead transistor package. The IC can easily supply well over 5A at an output voltage range between 1.2V and 30V.
In this circuit the output voltage is determined by the two resistors R1 and R2.The output voltage can be varied by adjusting the R2.Diodes D2 and D3 are protection diodes. Capacitors C1 and C5 are filter capacitors while C2 and C3 are decoupling capacitors.

Circuit diagram.



  • Transformer T1 can be a 230V primary; 15V,8A secondary step down transformer.
  • If 5A bridge is not available, make one using diodes likes SR520.
  • IC1 must be fitted with a heat sink.
  • An optional 6A fuse can be connected in series with the positive output terminal.
  • Switch S1 can be used as an ON/OFF switch.
  • 8A transformer and 5A diodes make this circuit a bit costly. So assemble this circuit only if you have real need.
  • Many low cost/low current adjustable regulators for beginners are there in the power supply section.


  1. Hi…. I want to build a 16.8 V/1A & 16.8V/3A power supply circuit. Please help me.

  2. hello…. i want to make a 12v 5a supply for that what transformer rating shpuld i use 230/15v or 230/12v

  3. seetharaman

    Hi Joshi it is 5 amps 200PIV bridge rectifier. you can use 5amp 200PIV rectifiers 4nos in bridge form. BY299 or similar. readily available 6amps rectifier diodes 4nos in bridge form can also be used.

  4. kamal joshi

    i am not getting diodes SR520 can you tell me proper alternate for these diodes.

  5. rabee salman

    thank you for this circuit , can we use it to charging a car battery (12v,60amp)
    and can this circuit behave as auto charging .can you describe the schematic for auto car charger with variable input voltage.