• Skip to main content
  • Skip to primary sidebar

Making Easy Circuits

Learn and build electronic circuits

You are here: Home / Voltage Regulators / High Current LM317 Variable Power Supply Circuit

High Current LM317 Variable Power Supply Circuit

Last Updated on January 10, 2018 by Admin 12 Comments

You you are looking for a high current LM317 variable power supply circuit version then you have probably landed on the right post. Here you will find how an ordinary LM317 circuit could be converted into a high current 20 amp variable power supply circuit using just a few 2n3055 power transistors in conjunction with a standard LM317 voltage regulator circuit stage.

high current LM317 variable power supply circuit

 

Looking at the proposed high current LM317 regulator circuit design we can see how the basic LM317 variable power supply design which is normally rated to deliver just  1 amp current is cleverly upgraded to a high current version using a few 2N 3055 transistors.

All the 2N3055 transistor are configured in their individual emitter follower mode, which implies that all these will follow and produce voltage output at their emitters that may be exactly equal to the LM317 output, meaning when the LM317 pot is adjusted for a particular output voltage, the emitters of the power transistors would exactly replicate and produce the same amount of voltage at their emitters, but since he collectors of these devices are connected with the high current supply rail would transform the LM317 voltage into a high current capacity that may be equal to the maximum current carrying capability of the transistors as well as the power supply specification.

Thus this simple tweak using a few 2N3055 transistor transforms a ordinary LM317 variable regulated power supply into an awesome high current LM317 regulated variable power supply unit.

However make sure that all the 2N3055 are mounted over a large common heatsink, using a generous amount of heatsink compound paste but without mica isolators.

The 0.47 ohm resistors limit the current to the devices maximum current specs, if some other transistor such TIP35C are used this may be changed to obtain current as high as 100 amps

You'll also like:

  • 1.  Simple Adjustable Constant Current Circuit
  • 2.  High End Bench Power Supply with Variable Voltage/Current
  • 3.  DC to DC Converter Circuit
  • 4.  Build this One Transistor Regulated Power Supply Circuit
  • 5.  Simplest Variable 0-100V Power Supply Circuit
  • 6.  Make these Low Dropout Regulator Circuits at Home

About Admin

Hey friends, Thanks a bunch for stopping by this site! I am an engineer with a Bachelor of Engineering in Electronics and Telecommunication. One of my passions is gathering information from all sorts of electronics books and tutorials. I then take that information and compile it into a language that is super easy to understand. My goal is to make those complex electronics circuit concepts and technical terms much more accessible for all the new and budding electronics engineers out there. I can also design customized circuit diagrams as required by the users.
If you have any questions related to this field, please do not hesitate to drop a comment! I am always here and ready to help you out with any queries you might have. I cannot wait to hear from you!

Reader Interactions

Comments

  1. drjackool says

    January 22, 2025 at 1:25 am

    Hi
    Why the output of LM317 is directly connected to 3055 base without a resistor! Base voltage of BJTs must be about 0.7 volt! unless transistor will damage! How this possible?

    Reply
    • admin says

      January 25, 2025 at 9:07 am

      Hey, you are right, each transistor must have an individual base series resistor, otherwise it can burn due to over-current.
      Kindly make the changes accordingly.

      Reply
  2. Владимир says

    September 1, 2023 at 4:30 am

    5 штук 3055 тянут 10а упр. Через оптопару, ответь что я делаю не так

    Reply
    • admin says

      September 7, 2023 at 12:13 pm

      Yes 5nos of 2N3055 in parallel can handle 10 amp current

      Reply
  3. Richard says

    June 6, 2023 at 6:50 pm

    Wouldn’t moving the 270 ohm resistor from pin 2 of the LM317 to the emitters of the the 2N3055? Wouldn’t this help keep the output more constant for the loss of the transistors and the .47 ohm resistors?

    Reply
    • admin says

      June 17, 2023 at 11:52 am

      The 270 ohm resistor is the part of the LM317 circuit, without this resistor the LM317 would cease to work…

      Reply
    • ericalanrawson@aol. com says

      August 24, 2024 at 2:30 pm

      Exactly what I thought. I have ordered parts and will try it out using BD911 instead of 2N3055.

      Reply
      • admin says

        August 27, 2024 at 1:18 pm

        Sure, no problem, BD139 can handle at the most 300 mA without heatsink and maybe 700mA with heatsink…which the IC can do without the need of any external transistor…

        Reply
  4. JD says

    February 22, 2023 at 10:58 pm

    wouldn’t just 2 of the 2N3055 transistors suffice? Why 6?

    Reply
    • admin says

      March 6, 2023 at 11:28 am

      You can use 1, 2, 3, or as many as you want depending on how much output current you need.

      Reply
  5. Mark G. Cooper Sr. says

    May 3, 2020 at 5:49 pm

    Exactly what I’ve been looking for ! Thank you for the great information !

    Reply
    • admin says

      May 4, 2020 at 11:07 am

      thanks and glad you found it useful

      Reply

Leave a Reply Cancel reply

Your email address will not be published. Required fields are marked *

Primary Sidebar

Categories

  • 3 Phase (4)
  • 8051 Microcontroller (1)
  • Arduino (11)
  • Audio and Amplifier (102)
  • Automation (8)
  • Battery Chargers (64)
  • Bicycle Projects (4)
  • Car and Motorcycle Projects (39)
  • Datasheets (10)
  • DIY Projects (5)
  • Electrical (15)
  • Free Energy (6)
  • Games Projects (2)
  • High Voltage (14)
  • Hobby Projects (30)
  • Household Circuits (2)
  • IC 555 Circuits (4)
  • Ignition Circuits (2)
  • Indicators (50)
  • Infrared (6)
  • Inverter Circuits (29)
  • Lights and Lamps (97)
  • Medical (8)
  • Meter and Tester Circuits (38)
  • Motor Driver (17)
  • New Circuits (56)
  • Oscillators (30)
  • Pets and Pests (5)
  • Power supply (81)
  • Protection Circuits (25)
  • PWM (8)
  • Remote Control (20)
  • Security and Alarm Circuit (48)
  • Sensors and Detectors (66)
  • Signal Processor (23)
  • Solar Controller Circuits (61)
  • SSR (3)
  • Temperature Controller (20)
  • Timer (25)
  • Transformerless (7)
  • Transmitters (12)
  • Tutorials (45)
  • UPS (2)
  • Voltage Regulators (57)
  • Water Sensor and Controller (29)
  • Home
  • Privacy Policy
  • Contact
  • Disclaimer
  • Copyright

© 2025 · Making Easy Circuits