High Current Adjustable Power Supply Circuit using LM317

Variable power supplies are available in different ranges but they provide very low current of one or two amperes, they can’t drive high power devices like motor or high power lamps.So to get through such problems I introduce a high current variable voltage power supply circuit which can drive 10A of load, the current handling capacity can be increased simply by connecting 2N3055 power transistors in parallel.

I happened to design variable power supply schematic diagram for my inverter battery for safe and quick charging. My 30Ah lead acid inverter battery takes more time for constant voltage charging when I use a LM317 variable voltage regulator. This is due to its lower output current.

So I connected a power transistor which helps to increase the current without varying the voltage. 2N3055 can handle 15A, so by connecting parallel make add the individual current.

This can be used as a regulated 48V DC power supply or 24 V DC power supply. The maximum input to this DC variable power supply is 37 volts.

High Current Variable Power Supply Circuit Diagram

High+current+variable+power+supply+circuit High Current Adjustable Power Supply Circuit using LM317

Components Required

  1. IC LM317
  2. Transistor 2N3055 X 3
  3. Diode 6A4
  4. Resistor (220 ohm, 4.7K(POT))

Working

  • As you know LM317 is a variable voltage regulator IC. Output voltage of this IC can be varied between 1.25V and 37V.! Yes, this is the best choice of variable power supply circuits.
  • Output of LM317 variable voltage regulator in connected to the base of 2N3055 power transistor. We have already discussed LM 317 Variable DC Power supply, but it was low current.
  • Here the first section of circuit is same as before but in order to boost current we are using 2N3055 transistor.
  • 2N3055 power transistor can handle a maximum of 115 watts and the maximum collector current is 15A.
  • In this circuit the output from LM317 directed to parallel combination of 2N3055 power transistors which will increase the output current hence the power also.
  • Collector of 2N3055 connected to Vcc and Emitter of each transistor are looped together to get  output terminal.
  • By varying the resistance of potentiometer output voltage of LM317 IC can be varied. Correspondingly the emitter voltage of power transistor 2N3055 is varied.
  • Proper heat sink must be provided for the power transistors.

I used these to charge my 30Ah lead acid inverter battery. This circuit is tested under i-St@r labs.
 
Adjustable+Power+Supply+Circuit+diagram High Current Adjustable Power Supply Circuit using LM317
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Pinout

 High Current Adjustable Power Supply Circuit using LM317LM+317+Voltage+regulator+Pinout High Current Adjustable Power Supply Circuit using LM317
Diode 64A                                    LM 317
2N3055+Pinout High Current Adjustable Power Supply Circuit using LM317
2N3055

9 thoughts on “High Current Adjustable Power Supply Circuit using LM317

  1. There are no required caps in this schematic? How would you go about adding a power indicator led to this?

  2. Whenever i connect load at output the output voltage (at emitter) reduces while the current increases.
    I regulate a 3.3V at output of lm317 but when i connect a load the emitter voltage drops.
    I require a constant voltage of 3.3V and able to draw 3A current for my circuit as m connecting it to a motor.
    its URGENT !
    thanks

  3. what if I replace the 2N3055 with TIP35, will it make a change in current and when the input is around 15V-20V,what will be the current output?

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