Adjustable Symmetrical Power Supply ± 125 until ±30V 1A


This is the voltage converter to get the voltage of ±1,25-30V from the input voltage of ±35V. I am using the 3 terminal voltage regulator for the voltage to be changed in this unit. As the regulator, LM317 is used for the positive voltage and LM337 is used for the negative voltage. The output current can make output in 1 A.The point of this unit making is the radiator (the heatsink) of the regulator. The regulator becomes hot when outputting the 1 A electric current and when there is not a heatsink, the regulator breaks.The merit of the regulator of this type is what little noise occurs and is cheap and there are few use parts. The demerit is the thing with the conversion efficiency which isn't good. When outputting from 35 V to 5 V, the efficiency (the output power/input power) is < 42%. Recently, the switching regulator became cheap. The number of parts increases little but in case of more than 1 A for >15V and 0,4 A for <15V out power supply, you had better use the switching regulator with the good efficiency. With RV1-2 adj. each Regulator for single out +V or -V out and RV3 adj. for dual out, with S1. With S2 select for monitor at voltmeter V1.

Circuit diagram

Circuit diagram

Part List

  • R1-2=270ohms
  • R3-4=2.2Kohms
  • R5-6=10Kohms
  • C1-5=100uF/63V
  • C2-4=100nF/100V
  • C3-8=10uF/25V
  • C6-10=100uF/63V
  • C7-9=100nF/100V
  • RV1-2=10Kohms Lin.
  • RV3=2X10Kohms Lin.
  • IC 1=LM 317T
  • IC 2=LM 337T
  • D1-2=1N4001
  • D3-4=1N4001
  • L1-2=LED 3mm
  • F1-2=1A slow Blow Fuse
  • S1-2=2X ON-ON SW
  • V1=0-30V DC Voltmeter