Many electronics circuits and projects for learning in simple ways.

High Current 12V-13.8V at 30A,25A,20A,15A Power Supply

Essential for those who want to use the radio transmitters from a car to use in your home is you need a ham radio power supply DC-12V or high current 13.8V power supply with enough power out of 5A to 30A. According to size of the a transmitter. I highly recommend this high-current power supply circuit. Because good performance, size of output 13V-14V depending on the load.

And can be choose to create multiple sizes of 5A, 10A, 15A, 20A, 25A, 30A. According to actual usage. So allows to save and easier to build.

Of course you can buy the power supplies of this simple and effective with a variety of sizes.But if you build them with your own or together build in groups of your friends, will be have a great time while creating this project. And when completed. Activated According to its function. It would be very proud.

In addition this power supply circuit is also useful as a wide variety. Such as, A large DC motor. Circuit of car audio and other. Which you may apply. By changing the voltage and current as needed. This circuit is very flexible.

High Current 13.8V 30A,25A,20A,15A Ham Radio Power Supply

Note: If you are beginner this circuit may be hard for you.
You may use LM317 as this circuit : Variable DC Power Supply 1.2V to 30V 1A First projects

Ideas of this circuit.
Tired to find hard and expensive equipment.
if you familiar in the field of electronics, When looking at this circuit be accustomed with the device I choose. It is designed looking easy using a device around the world, Friends would make it easier.
Sorry, friends who are looking for a new technologies that may not be suitable for everyone. But everyone still need a high current power supply that actually works!

But must have the quality.
– The good protection circuit. When the output short circuit or overload.
– In addition, you can also choose to create size circuit in output currents according to the your purpose. by can make the circuit increase the current in step by step with steps of 5 amps. Started minimum currents rate of 5A to additional step . 10A, 15A, 20A, 25A and a maximum to 30A.

The heart of circuit.

I use a regulator IC No.MC7815 or LM7815 or AN7815 is maintain the level as constant voltage 15V. Within this IC have a short circuit protection and prevent overheating. As a result this circuit can be maintain the level output voltage as well. And If there overload or short circuit. It will not damage too.

How currents higher?
At output pin of IC1 will be connected Darlington connected emitter follower With the transistor Q1. And use the Q1 drive to six transistor Q2-Q7 together parallel. To expand the current is increased up. From the original currents maximum output of IC at 1A. When to connect these transistor TIP35 Q1-Q7 to complete 7 pcs. Makes can supplying up to 30A. By parallel with the transistor Q2, from the Q3 onwards there. Each transistor can be expanded current is 5A.

The resistor 0.15 ohm at emitter pin of the each transistor has two act as are:
1. Check the current flowing through the transistor Because there are the voltage drop across them as a ratio of the current flowing through a each transistor.
2. The current through the transistor to equally.

Better protection.
IC-7815 has a wonderful protection system.

1. Short circuit or over current power supply is not broken. IC1 can prevent the overload very well. Even being long short circuit throughout the day. It is still in good condition.

2. Hot does not work. When the temperature its highly unusual. The high temperature protection system will be order it to temporarily stops responding. Until the temperature drops. It is started as usual.

With the advantages of this IC I installed it on a heat sink near the transistor. Which currently active have heat reasonably. But in the load current is too high or too hot.
IC1 has been heating up over defined transistor. It so suspended. Of course, there is no current to the transistor. It thus gradually reduce heat down. IC1, it will return the as it was again.

Overcurrent protection to superior by SCR.
In the short-circuit conditions. or Overload or Using too much currents, the Q2 is pulled by the current estimate 5A Until the voltage size of. 0.75V drop across R5 – 0.15 ohm. (The emitter pin of Q2) and this voltage to the gate pin of SCR1, that it is enough to trigger SCR1 work immediately.
IC1 is temporarily stops responding. Because is overloaded. By earlier, the current of 1A flow through the IC1 and the SCR1 into loaded directly. Not through all transistors.
The SCR1 is working to hold, until the power supply is cut off. Which automatically resets itself in this manner is called a Electronic circuit breaker.

How much the output voltage.

Output voltage of the power circuit is equal to the voltage output of IC1 (15V) minus the voltage drop across the leg base (B) – E emitter (E) of the transistor driver (Q1) and the transistor through (. Q2) and the voltage drop across R5 E pin of Q2.

However, since the voltage drop across R5 for this. Changed by the current flowing through it. Thus making voltage output of this circuit is slightly changed switch from 14V. Under no load is 13V. In fully loaded conditions (regulation).

At this level, it will be maintained pressure succinctly is better than on the electric car. The output voltage can be changed from 11V to 16V. And the transmitter is normally used in the car with 12V battery is designed to be compatible with existing 13-14V voltage.


Because equipment used in this circuit there is not much. And most of them are large. Which must be installed on a cooling pad(heat sink). The operation this project, thus no need to use a PCB. May use point Connect the power cord,, tighten the nut onto the heat sink. Then Connect the wires to the other equipment. Onto the heat sink.

Select the value device.

I used to build this project to my friend,when about 10 years ago. With the output voltage of 13.8V, current is about 15A. You may be required by your application, be detailed as follows.
1. The C1 and F1 using this table.

The current outputC1F1
5 Amps10,000uF2A
10 Amps15,000uF4A
15 Amps22,000uF6A
20 Amps33,000 uF8A
25 Amps47,000uF10A
30 Amps68,000uF12A

– I chose the C1-22,000 uF 25V. But not for sale, have to use five 4,700uF 25V capacitors to parallel these. Thus has a total capacity of 4,700 uF x 5 = 23,500 uF enough to use.
– Use size of 5A fuse is a slow, or Slow blow fuse.
2. Choose a bridge diode rectifier And the transformer T1 according to usage.
Because IC-7815 requires a low input voltage to 17V. Therefore the input DC voltage to non regulator to output drop across C1 should be between 18V to 20V. If less than 17V may not be enough to use the circuit. and, If more than 20V over 20%, will result in the loss of many transistors and the ICs. Making must use a larger heat sink is too consumes more energy than necessary.
I choose the size of the transformer 15A. My friends go to the core steel EI at antique store, then go hire made new transformer. Output voltage of 15VAC to this durable and inexpensive.
I have Choose a bridge diode value 20A 200V big size there are heat sink hold.
I used transistor TIP3055 which easier to buy, cheaper and the easier to install than a 2N3055 or used TIP35 which performs better.
You can select any number SCR1 is 200V 5A such as C122,C106 etc.


If you not like this circuit you can look others circuit more below.

  1. High power supply regulater 0-30V 20A by LM338
  2. High Current Variable Voltage Regulator 2-36V 10A
  3. Amplifier power supply using High Current Transformer
  4. 10A DC Supply FIX Regulated by IC 78XX and MJ15004
  5. 1-20V 10A adjustable dc power supply by LM338

This Post Has 57 Comments

  1. Saludos cordiales.
    Muy importente esta fuente de poder y de gran utilidad en todo circuito.
    Quisiera que incluyan circuitos para disparar IGBT.

  2. I think there is an error in that diagram! in the 30 A section, the collector and base of Q7 is shorted rendering the whole regulator circuit
    as useless seeing that all bases are in parallel…
    that wold leave someone wanting to know, who let the smoke out?

  3. Dear sam, you are right.

  4. sir,
    reg ic 7815 is much over heated when i short the out put supply. kindly let me know what should i do. another thing, in put voltage to ic 7815 is about 24 vdc, is this high voltage is the matter.
    thanks and regards.

  5. if one of transistor or LM will bow up or LM will lost it’s ground you’ll get high voltage in output.
    Got it twice under developing conditions, I will add overvoltage protection in output side.

  6. If I were to use 2N3055 transistors for Q2 -Q7, would the values for the base and emitter resistors be the same?

  7. please tell me that is this work or not.

  8. Is This Work Or Not?????

  9. Plz Tell Me .

  10. What diode model you use in the bridge ? bdi 25A 100V , i cant found this diode…?

  11. BD1 I am sure he is referring Bridge Diode number 1 BD1 not bdi which is a full wave bridge rectifier at 25 amps.

    Correction with the trace from Q6 base to Q7 collector ommited in the link below.


  12. The transistor Q7 base and collector are in short.
    To fix that,the wire going truth colector must finish Q6 collector?
    Thanks for your attention.
    I believe is going to be a very good project.
    Thanks again.

  13. For the 30 amp. Circuit where go the 12 amp. Fuse.

  14. As I can see from datasheets, I can use 2n3055 transistors instead TIP3055 without any other changes. Am I right?
    Thanks for circuit!

  15. is the above correct or the one given by ECStrat correct????
    plz help….

  16. is the above circuit diagram correct or the one given by ECStrat correct????
    plz help….

  17. I am in need of a scumadic for a 110V AC, 13.8V 100A DC power supply. I will now tell you what I have and what has been done so far. I have a 3 stage 110V 13.8, 14.6 and 17.5V output transformer capable of 100A. I am using 2N3002 pass transistors X 12! 2 driving 10. I have 2 100V 1000A Stock Astron bridge rectifiers, a 723 complete board, 63V 180000uf cap etc. I am wiring up the pass transistors 2 driving 10 using the crow bar wiring! 0,1 10W ceramic resistors! I already have the pass transistor mounted in 2 6 bay TO2 heat sinks. I am in need of a complete wiring diagram if you could showing me how to wire this thing. You wouldn’t believe how hard its been to find any info on crow bar wiring let alone find someone who can tell me any info on how to wire this thing. I am not new to electronics but this is my first power supply build of this size! Please Help. THX Billy

  18. please tell me which diode used, the rectifier circuit.

  19. First off, the schematic diagram is complete unreadable, appears to have errors and is pretty much worthless circuit. I would suggest finding a more detailed power supply somewhere else.

  20. Dear Sr

    i am really happy to ready all over your project. please sr i wont 5vols out voltage and remain all the how
    could i do, or i could change ic1 to (7805). thank you .

  21. i have one faulty 24volt /10 amps SMPS.
    If i on the powersupply the output LED flickering and the voltages also varying,i want to rectify the SMPS.Kindly give your valuable tips.

  22. Hello Mom

    Nice circuit and works wonderfull. Gutted out an old 1400 watt UPS and the transformer filled the bill perfectly for a 25 amp supply, the parts were cheap and the whole project went without a hitch. Took a little time doing the artwork for the PC board. At 18 amps it drops down to 12.6 volts and at idle with a 1.7 amp load it’s 13.9 colts which is acceptable and will try it with a receiver in the morning and hopefully I will have no chirp on the transmitter. Needed a supply for the bench and it will work perfectly.

    Nice design and nothing heats up except the bleeder resistor which I might change out but everything else is cool as a cucumber at a few amps and of corse heats up when loaded.

    Thanks for the wisdom
    Pat KD4OBQ


  23. pls what value of bridge rectifier can handle up to 30amps?

  24. is it right that basis Q7 connecting to collector? i thing its not common.imho

  25. I’m looking for a manual or circuit of a Sharp CD-C25x(bk) on pdf or doc please help


  27. Hello, but you can have the pattern of the PCB. thanks

  28. hi there man i just build this sweet power supply at first i thought it wasnt working so i rechecked and tested every part of the circuit but i figured its because i powered it up when the transformer was already on so the capacitor must of needed to charge and the scr may have tripped took me 6 hrs from scratch to build i got some old power supplies from computers that were blown out and used the heat sinks i bought all the parts it came up to approx 350 TT dollars i would say around 60 us or so i havnt loaded the circuit fully jus yet but i see the potential in it i also used a multitap transformer from a computer grade power supply from the 1980’s and i used tip 35c transistors and a bt151-500r SCR but i used a 150uf capacitor on it i also installed a led light for the output and im gettin a constant no load voltage of 13.52 v boss of a circuit cheers!

  29. dont know the rating of my transformer per say but the output im using read 20.5 v it may be a 30va not sure but it works!

  30. Momename, it would help immensely if you could get someone to proofread and edit your description of this power supply circuit because it is very difficult at times to fully understand exactly what you are trying to describe.

    For example: ” – I chose the C1-22,00uF 25V. But not for sale, have to use five 4,700 25V capacitors to parallel these.”

    It’s better written thusly: “Because a 22,000uF 25V capacitor was unavailable at the time, I just paralleled five 4,700 25V capacitors instead, which provides the slightly greater capacitance of 23,500uF.”

  31. There’s a really good 13.8 Volt, 30 Amp power supply circuit diagram in the ARRL handbook with clear instructions on how to build it. The voltage is adjustable and it even has remote voltage sensing which automatically compensates for any voltage drop that occurs between the power supply and the load [transceiver]. It uses a very large capacitor of ~500,000uF which allows each of the five 2N3055 pass transistors to run quite cool because they only have about 2-3 Volts maximum dropped across them. If each 2N3055 [or TIP35] pass transistor drops only 3Volts at 6Amps then it will only be dissipating 18Watts [3×6=18] which is quite cool, especially if the pass transistors are mounted on a large heatsink. The main transformer supplies only 12.6Volts AC which when rectified provides ~17.8Volts for the pass transistors and a much smaller transformer provides 15Volts AC for the voltage regulator, which is a LM723 integrated circuit. It also uses an SCR for over-voltage protection and when the SCR is triggered it causes a relay to quickly open instead of blowing a fuse. The relay breaks the circuit faster than a fuse can blow and it’s a lot cheaper too than having to replace a fu$e.

  32. Hello, I would like to make this circuit but I need variable power supply. Could I add resistor and pot to lm317 and that way change output voltage?

  33. pls dis circuit is not giving me good output current i use 0.22ohm 5wat and bt151 as the scr but am having a droping current of 1amp any help?

  34. Hello sam, but you can have the pattern of the PCB? and can i use 18vdc transfomer on this circuit..? thanks & regards

  35. Please give more details about all Q1,Q2,Q3,Q4,Q5,Q6 & Q7 like volt, power etc and where I can bought all parts from. I m from Raipur chhattishgarh.
    I also want to know that how can I blow 2
    12 volts 55 watt lamps in my bike discover 100 cc 4g with magnet coil or battery when I connect these with magnet it burns like candle a and when connect with battery it discharge my battery in 15 minutes please tell can I increase its ampiers upto 10 amp or more by little change please give me proper solution ..

  36. Greetings, Friend

    You have this already drawn design in Proteus, for I am wanting to set up this project but the biggest problem and draw it if possible if you have the project designed to make the gentiliza send to my email [email protected]

    Thank you.

  37. Can I use this circuit to power the car amplifier which require around 25amp constant current…

  38. Sir,
    My Question is
    If i want to amplify it more than 30A if near 100A so then what should be need to do changes in circuit

  39. Sir I have 220v ac 18watt input can i output about 30amp using this circuit ?

  40. What would be appropriate transformer power for the product? I guess 15V 30W transformer is too small?

  41. If I just need 10 Ampere, R16 C4 C5 I must use it too?

  42. Who ever writes these electronic articles should read the work before posting it because none of these articles make any sense. ????????????????????

  43. dear sir, i have do it, i note that error on schematic ,becouse last tip 35 , the collector is cc with base.
    It is OK! Very power, very good,but i’have a problem when i ON. I’think the scr current is very sensible, and a simple car lamp 12v 3A make protection. If i use 1A and following 10A =11A that is OK. The resistor of 100 OHM will upgrade to 120 or 150 OHM???
    Thank for your reply.
    Best regards…Mike

  44. or R16 < 470 Ohm????

  45. a nice circuit.
    thank u

  46. Good circuit. I have built it, worked ok

  47. Buen día tengo un pequeño problema se protege con mucha facilidad y la resistencia de 470 se quema me ayudas ?? Por favor

  48. Want to make dual output 24vdc to 12vdc converter for VHF radio and GPS.
    For VHF 13.8vdc, 15A & for GPS 13.8vdc, 10A. Please advice which IC should I use. And other important details.

  49. Can you please suggest equivalent model to c122b. It is no available here in my place.

  50. I used TYN612. And it works. Thanks for the circuit.

  51. Same here C122 is not available..

  52. Can you add a parts list and this schematic is so flue. I can not see any of them

  53. Is there any way possible to simply make this a variable current circuit, for instance changing the current through 5A to 30A

  54. Is the connection above Q7 from its base to the collector, joining the two, a mistake or correct? Thanks

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