Lets make a High Current power supply with LM317 Voltage Regulator which can supply upto 5 Amp. LM317 is one of the oldest, most used and wonderful linear voltage regulators. I personally love this IC (yes, it’s not a transistor) a lot, not because it server it purpose well, but because it’s cheap, easy and never disappoints you while making a regulated DC power supply. In this blog we will make a High Current power supply with LM317 Voltage Regulator and a couple of Power Transistors
I am an IT guy, as you know. Electronics is my hobby, and as a hobbyist I need custom made power supplies more often than others. It’s because, I can’t afford a lab bench power supply worth several hundred dollars. So I prefer to make my own power supply as and when required. And that’s where the problem started appearing. Yes, surprisingly enough, Electronics experts prefer to buy a DC Power supply module than making your own. Trust me, that’s what I gathered as experience while knocking the door of several Electronics forums and Bulletin Boards. By then I was already upset by the callousness of the Electronics Blogs for their several hundred pages of untested, not working and intentionally mis-made circuits. NONE of them works seamlessly – sorry to say!
And suddenly you ask your a question on how to make a simple high current power supply with LM317 on StackExchange, and they come up with bagful of suggestions to use a Switch Mode Regulator. Yaak! I hate it. It’s complex, you often need inductors, high power rated ones are rarely available, Ferrite Transformers – virtually impossible to find one in local market (unlike from Chinese sellers on Ebay or AliExpress). Remember, Switch Mode Power Supply is NEVER your first choice when working on a hobby project or college project. It you take half of your entire project’s time to make the power supply itself. You need a quick, easy and cheap solution. And LM317 serves the purpose more perfectly than anyone else. I will tell you why experts on the Electronics forum always recommends using SMPS. They are not geeks, they are agent of Industries. And SMPS is the only solution if you are making a commercial product in the Electronics Industry. They are no-doubt power efficient. But who cares about power efficiency for a College project. It’s overestimation, mate!
Ok, that’s enough of the introduction. Let’s come to point. In this blog post I am going to share a FULLY WORKING, TESTED High Current DC Power Supply Circuit. I have created the circuit on a Bread Board today and tested. It worked just perfectly. Since my 2N3055 Transistor was hanging on the wires without proper heatsink, I couldn’t test it with 5 amp current. However, given the ratings of 2N3055 is well above 5 Amp, this circuit should work just fine at 5 Amps. I have tested upto 2.5 Amps and everything was perfect; I didn’t notice severe voltage drop at 2.5 Amp load which is awesome.
This circuit is not original, it’s copied from the Datasheet of LM317 (Section 8.3.12 High-Current Adjustable Regulator Circuit). However, I have done little adjustments to the circuit to make sure that you do not get stuck with unavailability of components. For example, it uses a 500 Ohm resistor. Do not worry, 500 Ohm is not mandatory, you can simply use a 470 Ohm in its place. When 470 Ohm is really easy to find, 500 Ohm is very very hard to find. If you are a hobbyist and do not have much knowledge on each and every components of a circuit and their functions, these values will often bother you. Any author, not intended to confuse the reader should NEVER use such components. I wonder why the datasheet of LM317 is not as perfect as the IC itself 🙂 !
LM317 based Regulated High Current DC Power Supply Circuit Diagram
Let’s see the Circuit Diagram first. To see a larger version of the image click on the circuit diagram below.
Nothing hectic here, a small explanation of the working principle of the circuit. LM317 does its usual job here. With the help of voltage divider created by the resistor R5 and series resistors R4, R7 voltage at the Adj pin of LM317 is controlled. This helps LM317 regulate the output voltage and keep it constant at the desired level. R4 is a potentiometer (preset if on board) which helps you to adjust the output voltage. The 2N3055 transistor (Q1) along with TIP2955 (Q2) in the schematic allow higher currents to flow at the output which is beyond the capability of LM317 (1.5 Amps). In combination, LM317 controls the output voltage and the NPN-PNP Transistor pair allows most of the current to flow from Input to Output. Makes sense? Let me know in comments.
Component List
Following is the list of components. Almost none of the Electronic Blogger care to write component alternatives while publishing a schematic. That seemed the most fishy part. I am not doing that mistake 🙂
| Component ID | Part Number | Alternatives |
|---|---|---|
| IC U1 | LM317 TO-220 Package | LM338 will work too (not verified) |
| Transistor Q1 | 2N3055 Metallic TO-3 Package | TIP3055, TIP41 (Large Heatsink), TIP73 |
| Transistor Q1 | TIP2955 TO-247 Package | MJE2955, TIP42, BD140 |
| Resistor R1 | 4.7K Ohm 0.5 Watt | 5K Ohm |
| Resistor R2 | 22 Ohm 1 Watt | 18 Ohm |
| Resistor R3 | 470 Ohm 0.5 Watt | 500 Ohm |
| Resistor R4 | 4.7K Ohm Potentiometer | 5K Potentiometer, 4.7K Preset |
| Resistor R5 | 120 Ohm 0.5 Watt | 150 Ohm, 220 Ohm will work too, regulated voltage range will vary |
| Resistor R7 | 2.2K Ohm 0.5 Watt | 1.8K Ohm |
| Capacitor C1 | 4700uF, 50V Electrolytic | 2 x 2200uF, 50V parallel will work too |
| Capacitor C2 | 10uF, 50V Electrolytic | 22uF, 50V |
| Capacitor C3 | 47uF, 50V Electrolytic | 100uF, 50V |
| Rectifier BR1 | GBU808 | GBPC606 or any 6 Amp Bridge Rectifier |
| Diode D1 | 1N4007 | 1N4001, 1N4002 or 1N5402 |
| Transformer | 12-0-12 Center Tapped 5 Amp Step Down Transformer. Leave center tap unused, use the 2 end terminals | 0-18 or 0-24 Transformer of 5 Amp or smaller current limit (120 or less VA Trafo) |
| Heatsinks | Large TO-3 Heatsink + LM317 Heatsink |
Buy these components online
- LM317 with Heat Sink (5 pairs)
- 2N3055 Transistor (2pcs)
- MJE2955
- 6 Amp Bridge Rectifier
- 12-0-12 5 Amp Transformer
- Buy Resistances (in bunch)
- Buy Diodes (in bunch)
- Buy Capacitors (in bunch)
- Buy TO-3 Heat Sink
You can buy power supply components online from shop.sribasu.com or Ebay.in.
Assembling the Circuit
I must say, it’s not safe to test the circuit on a breadboard at higher current. Breadboard connectors and jumper wires are not adequate for 5 Ampere current. So, assemble the circuit on a Dot Vero or Transistor Vero Board. Optionally, if you are familiar with the process of PCB Fabrication you can use the following PCB Layout for printing the circuit on a Copper Clad board and assemble the circuit on PCB.
LM317 Based High Current Power Supply PCB Layout
Click on the image below to download the PCB Layout in printable PDF format (A4 Page). You can also download the doc file of the power supply layout.
- JP1: Solder a thick wire between the 2 holes of JP1.
- 2N3055: Solder 3 thick wires on the holes designated for 2N3055. Solder the Transistor to the end of the 3 wires off the PCB. 2N3055 must be mounted on a large TO-3 compatible Heat Sink and can’t be soldered on the PCB. So, it has to be connected to the PCB using wires.
- 4.7K POT: Solder 3 wires on the holes designated for 4.7K Pot. Solder the Potentiometer to the end of the 3 wires off the PCB. It is connected to the PCB using wires, which allows you to attach the potentiometer on the front panel of power supply cabinet.
- I/P and OP: Use 2 screw terminals or solder thick wire on holes designated for AC input and regulated DC output. The I/P is directly connected to the 2 end terminals of CT Transformer.
Testing the Regulated Power Supply
Ideally in order to test such a voltage regulated high current power supply you must attach a load to the output. However, keeping the output terminals open, doesn’t harm the circuit itself. However, if you try to measure output voltage with a Multimeter, you might get undesired results. Output of the circuit is across C3 Capacitor. Attach a 2.2K Ohm 1 Watt resistor across the capacitor and measure voltage or current of the output. The lesser the load resistance is, the higher the current reading would be. This circuit is not well protected from short circuit. Hence measuring current on close circuit without a suitable load is never recommended. It will take the circuit current to absolute maximum limit of the transformer (often above 5 Amp for a 5 Amp Trafo) and would damage several parts of the circuit.
I am very keen to see your responses and suggestions. Please let me know if you need help to make this High Current Power Supply. I will be glad to help.
Credits: Thanks for help www.electronicspoint.com
Pingback: LM317 Based High Current Compatible Voltage Regulator Circuit PCB Layout | prithwirajbose
I have saw and study many schematics of same PSU’s and I believe yours is absolute CORRECT AT ALL at transistors diagram. Some improvements/modifications you can add as larger capacitance at C1= 10.000μF, LM338 instead of LM317, a capacitor of 100nF paraller to C3, a capacitor of 100nF paraller to C1 and one more Diode 1N4007 backwards from the output to input of LM317. 5KΩ pot, R5= 220 Ohm , R7 no needing.. I shall build your project with the mods/improvements which I mentioned before and also I shall adding a same second pairs of transistors paraller (as indepented stage) Cheers and all the best.
I think theres is a mismatch between the diagram and the components layout on the PCB. According to the schematic diagram, Q1 has the emitter connected to the OUT of the LM337. According to the components layout Q1 has the emitter connected to the….emitter of Q2 ?
thank you for the circuit , what max voltage does this circuit give you ?
Practically you can expect as high as 35-36 volts, since the used regulator is LM317.
this is what i was looking for 5amps 0-24v variable dc power supply.many suggested lm196 but its not available in my area ty.
Thanks you very much! i think that i am going to try your schematics, and report back 😀
Did you try? The readers would love to see some pics here.
I want to build it . Is there any short circuit protection in this circuit ?
Or any one made this .
Thanks ahead
Please go ahead and give it a try. Unfortunately there is no short circuit protection in this circuit. You have to attach an additional module at the output of this circuit to protect from short circuit.
Finally!! I found it I’m seeking for this in long time I hope this will work well BTW I’m hobbiest I try to make this great part list thank you so much for the circuit and info. It helps well
I want to use IRFZ44 instead of the 2N3055, as I need minimum 8 amps; how do I modify your circuit so that I can use these FETs that I have in my workshop. All my 2N3055 are finished!!
Thanks,
IRFZ44 is a MOSFET not BJT. They have certain differences. You can’t replace them keeping the remaining part of the circuit unchanged.
So, IRFZ44 won’t work in place of 2N3055 here.
Try TIP3055 with a large heat sink or 2N6284 instead.
Can we use D1047 transistor in place of 2n3055
Yes, but it’s overkilling. And the circuit may not work well on the lower voltage range
How can I use this circuit for regulated votlage of 29V and high regulated current of 250 A
This circuit is not perfect for drawing current as high as 250 amps. Even if you change transistors, the circuit may not behave the same way, it behaves here at 5 amp. You can test it, but there is no guarantee that it would work. Definitely use a suitable transistor.
Does someone make this? I love to read and see the picture
Cause I want to make this if this working at 5amp
sir can i use higher amp bridge diode in my area they have minimum of 25amp bridge diode max 35amp can i use 25amp bridge diode?
or i will just use rectifier diodes 4pcs 6amp diode? it doesnt affect the calculation of it?
i will make this circuit
plsss help me
looking forward of it
Any bridge rectifier rated higher than the amount of current which you are going to draw from the circuit would work. If you are about to draw 5 amp, bridge rectifiers rated 6amp and 25 amp both would work.
I have made this circuit but one issue is giving minimum 6.3 Volt, so please Solve my problem.
Should be a problem with the POT. Check if its resistance is anywhere close to 1 Ohm (not in hundred’s range), when at the lowest position.
if you are aching to get a 500 ohm resistor, try connecting 2 1k resistors in parallel in its place
Hello,
Your design is simple and easy to build.I’m impressed and interested.
To increase it’s current to 10A what else I have to change instead of C1 (I’m planning to use 2x 10000uf parallel)
Parallel transistors or using transistors with more current tolerance should work.
Hi, I make the circuit and it doesn’t work. All part are connected correctly, I check them with attention.
With an input voltage of 20v DC and current above 10A.
My problem is this:
The voltage without any load goes from 1.6v to 17v;
But with a small load (5w lamp) o even with 21w lamp, the voltage don’t go higher than 10.35v (5w) and 9.70v (21w).
If I crack up the input voltage, the voltage above the output goes up but i have always 10-11v above the collector and the emitter of the transistor 2n3055.
Anyone can help me??
Thanks
Why did you add the 2.2k resister parallel to the 4.7k potentiometer ?
Also I would include a 1n5404 diode reverse bias at emitter/collector of the 2n3055 to divert reverse current upon power off of supply. If any need more current from this, just add another 2n3055 parallel to the one in this design, but also add a .05 ohm 5 watt power resistor on the emitter of the 2n3055 to voltage out on each 2n3055
Why did you add the 2.2k resister parallel to the 4.7k potentiometer ?
Because I am expecting the resistor network to impose a cumulative resistance not exceeding approx 2.4K Ohms. And usually 2.2K Variable resistance is often not so easy to collect.
Tow questions: (1) how can I add current limit (2) I’d like to connect it to arduino instead the potentiometer, for feedback in case of load change. can you help me?
Thanks
1. The current limiter should be added just after C1, before the main circuit starts… That’s an idea on where to use the current limiter. Search Google and you will find plenty of simple current limiter circuits (just need a power transistor and a power resistor).
2. You have to use a voltage divider at the output and take input from the voltage divider junction(< =5V point) to Arduino. Then you have to analog write to the Adj pin of LM317 from one of the Arduino Analog pins based on the input and load. I believe you can't reach an output voltage > 6.25 volts if using Arduino. It would be an altogether different project and may be I will research on it a little and try to make one and publish a blog on it.
Thanks. You are a teacher. To accommodate 20 amps I may need qty 4 2N3055. Would values for R1, R2 and R3 not affected?
Nice to finally find someone trying to answer what must be quite a common problem for many!
You have Q1 and Q2 reversed in comparison to the TI datasheet schematic – is this a mistake or deliberate?
And does this circuit introduce more noise onto the power rails? I’m looking to power a few microphone amplifiers this way..
Thanks!
Nope, I don’t believe it’s reversed. They have just shown using a pair of different transistors.
Hi Sir,
I have a electical load(a water electrolysis unit) which is to be supplied from an array of solar PV modules. The problem is that the output voltage of the modules array(in parallel) is 17.5 volts and the current is 51.3Amps.
but the load is to be operated at an adjustable voltage(0-8volts DC) and an adjustable current(0-45 A)(Any rotary control)
Is there any method by which I can do this…?
Plz. suggest
This circuit is not suitable for loads, as high as 45 AMPs. You need an appropriate SOLAR Panel Charge Controller (long with a High Power Buck Converter) which will perform the task much efficiently.
This is a simple take on creating PSU for personal use.
I am planning to use this for my setup which includes driving some microcontrollers, solenoids, fans and LED lights. I require a setup which can supply both 12V and 5V and i estimate the overall requirement to be about 20A. What are the changes that you suggest i make to the design to get the required output?
Thanks in advance!
This circuit is not suitable for 20 AMP load. Even if you choose transistors capable of this current load, it may not work as efficiently as expected. You need an SMPS power supply instead.
Thank you very much. This one is exactly what I looking for. I just a hobbiest and dont have much knowledge in electronic. Just know some parts and their works but I’m going to do this and if I found problem, I’m going to ask you. Thank you.
What modifications would need to be made for a 120VAC mains supply?
A Proper transformer.
You need a step down center tapped transformer rated for 120VAC input – that’s it.
Hi sir, i run this ckt output across 47 uF capacitor is 13-14 v but its heated after 2-3 sec what should i do
This circuit requires multiple heat sinks – on the transistors and LM317 ICs based on ho much current you draw. For low current draw it should not heat up. Let me know what are the input and output parameters.
Hi Prithwiraj. I Have been using the LM 317 for low voltage low amp circuits. I have an old laptop that requires 19.5v DC @ around 5 amps and found your circuit using the LM 317 to supply both the voltage and amperage. If I use a 20v DC input I just need to reduce the output to 19.5v DC and at 5 amps. Will this work?
Nope. In order to get 19.5V DC output, the input has to be higher than 20V. Should be atleast ~ 22 volts
I want to use it, with input 24 volts to convert 18.5 volts for my laptop, can I avoid to use without filtering components…
If it’s a laptop, it’s better to use the output filter.
Hello,
Nice looking schematic. I have a question however, as I am new to this – after C3 (which I assume is a non-polar cap) things seem to merge together – both + and -, how? Is there a ground line which was not drawn?
Many thanks!,
Donovan.
The output is (+ve and -ve) across the capacitor. It’s a polar one.
ooh, one thing though, IF I wanted to put a smoothing non-polar cap after the final 47uf, what value would it/they be?
Kindest regards,
Donovan.
0.1uF
recently my lm338 based variable dc power supply not working .because of my wrong operation by mistake both outputs are shorted and metal package lm338 damaged.
and unfortunately this power regulator no more available in local market {Jamshedpur}
Your circuit looks very good , simple and can be assembled at home.
1. does it short circuit protection
2. does it over heat protection.
3. can you show how it is assembled.
4. how to make 5 amp 0 to 30 volt dc smps type variable post supply . any idea or suggestion.?
me also a hobbyist and like to work with microcontroller and enjoy the excitement of inventing new application for any small requirement .
till now no website …
1. No
2. You need het sinks
3. I do no have a video
4. Will try to explain in a separate blog post
I’m building a ham radio antenna rotor controller and need 5v at 3-4 amps. I built the circuit and it gives 5v after adjusting the variable resistor. I only added 4 relays to the PSU load, and when they’re activated, the LM317 IC gets really hot. Is this normal? Do I need to put a heat sink on it? I’m using these transistors: Q1=NPN=2N6388; Q2=PNP=2N6667. Most of the resistors are the same values, except I used 4 100 ohm resistors in parallel for R2 and 2 1K ohm resistors in parallel for R3. The ohm meter says 26 ohms for R2 and 499 ohms for R3. Link to relay board: https://smile.amazon.com/dp/B00LW2G7V6/
Yes the LM317 would require a heat sink
Added product list, now you can purchase all the components online
Hi , What a great design you have offered. I to are fed up with power supply circuits that don’t work anf Pc designs where chips are drawn with their leads around the w rong way. Now with your circuit can you parallel 2n3055 to raise the current say to 10 amps? I assume all collectors would be connected together, all base connected together to out put of pnp transistor and all emitters connected to the out put via say .22 ohm 5 watt resitors.
I am about to etch a Pcb.
Many thanks Valve 3
lm317 heats up first, transistors ice cold, did not blow 3A output fuse, but blew 1A input fuse, why doesnt it let current throu the easiest path, the transistors and it flows trhu lm317?
You must have done some mistake. If the circuit is built properly it should not heat up LM317 and most of the current will flow through the transistors. This is a rigorously tested circuit taken from the datasheet of LM317 and slightly modified.
Hi! Thanks for sharing to us your practical ideas. Can I use a 6 (six) ampere transformer instead of your recommended 5 (five) amps?
Yes