The post explains a simple yet very useful 0 to 50V dual power supply circuit which also includes a wide range current control feature right from 0 to 10 amps. The idea was requested by Mr. Tamam.
Technical Specifications
It was my long term dream to build a 2 channel power supply for personal use, I have seen a lot of circuits, but those does not fit my criteria.
However, please take a look at the following requirements and let me know if its possible or not, if possible I will be the happiest person in the world.
1. Output voltage range: -50V to 0V to +50V ( must be adjustable by individual channel )
2. Output Current range: 0A to 10A ( must be adjustable by individual channel )
3. Output would be Duel channel, means total 6 outputs,
Channel 1 (Positive, GND, Negative) Channel 2 (Positive, GND, Negative)
4. Power Supply Unit should contains 2 Voltmeters and 2 Ammeters (Analogue) for 2 individual channel.
5. Power Supply Unit must have short circuit protection and cooling fan featured and extreme heat protection.
6. I don't want to use any PIC or AVR, so please avoid those.
Money is not a matter here, I will spend continuously until above requirement meets.
Even If I need any custom transformer I will order and make it from our local area.
I have seen many ready made power supply in market but I want to make it by own hand. You just show me the way... please bro, I will be pleased to you for lifetime.
Thank you very much !!
Best Regards,
Tamam
Circuit Diagram
The Design
The basic design of the proposed 0 to 50V variable dual power supply circuit with 0 to 10 amp variable current facility is shown in the above figure.
The entire design is transistor (BJT) based and is virtually indestructible. Moreover it's equipped with an over load and over current protection features.
The two section included in the design are exactly similar with their configurations, the only difference being the use of PNP devices in the lower configuration while NPN in the upper configuration.
The upper NPN design is configured to produce a variable response right from 0.6V to 50V positive while the lower PNP section becomes responsible of producing an oppositely identical response from -0.6V to -50V output.
The Transformer Specs
The maximum limit could be suitably changed simply by changing the voltage rating of the transformer. However for higher voltages you may have to appropriately upgrade the BJT voltage ratings accordingly.
In both the designs, P2 executes the function of varying the voltage levels as desired by the user, while P1 functions as the current regulator and is used for adjusting or setting the output anywhere from 0 to 10 amp current. Here too the maximum rating depends on the selection of the transformer amp rating and may be changed as per individual preferences.
T1s in the both the sections become the fundamental part or the heart of the entire voltage control functioning in the circuit, which becomes possible due to the popular common collector configuration of the devices.
The other two active BJTs only help to implement the same just by controlling the base power of the T1s thus making it possible to adjust the thresholds to any desired user defined voltage and current levels, as per the ratings of the transformer or the input supply.
Parts list
R1 = 1K, 5 watt wire wound
R2 = 120 Ohms,
R3 = 330 Ohms,
R4 = to be calculated using Ohms law, R = 0.6/Maximum Current Limit, Wattage = 0.6 x Maximum Current Limit
R5 = 1K5,
R6 = 5K6,
R7 = 56 Ohms,
R8 = 2K2,
P1,P2 = 2k5 presets
T1 = 2N6284 + 2N2222(NPN), 2N6286 + 2N2907(PNP)
T2, T3 = BC547B (NPN) BC557B (PNP),D1, D2, D3, D4 = 6A4,
D5 = 1N4007,C1, C2 = 10000uF/100V,
Tr1 = 0 – 40 Volts, 10 Amp
Sir please suggest and share. volt-amp adjustable circuit for 50v 10-20amp smps
Hi Grtech,
you can probably try this:
https://www.homemade-circuits.com/adjustable-0-100v-50-amp-smps-circuit/
Sir, i have 50v volt 10-20amp smps. Give me only adjustable circuit that i can use it to smps
OK you can try the second last circuit from this article:
You can eliminate the Q4 stage.
https://www.homemade-circuits.com/how-to-make-versatile-variable-voltage/
except R1 ,all resistors are 1/4watts ??
except R1 and R4, all are 1/4 watt
Mr.swagatham Do you have any youtube channel about electronics projects?
Yes, you can see it here:
https://www.youtube.com/user/TheLavina2011/videos?
i m using 48v 10A tranfo. R4 value 0.1ohm and 0.22ohm res. in parallel. voltage pot P2 works good but Amp Pot P1 is no activity. i m work in circuit wizard software.
The voltage across R4 must be high enough to trigger T3 ON when the output current exceeds the maximum limit. You can remove R5 and check in a a practical setup, and also try increasing R4 value appropriately until this triggering occurs.
nice project…..
Hi,Mr Swagatam.I had visited this site long back.I had the desire to build this power supply since then.As per the theory it has nice voltage and current range.More than that there is the voltage and current control feature.I am not able to get hold of power transistors 2N6284 and 2N6286.Can I use TIP35 and TIP36 instead.And for P1 and P1,will normal carbon film potentiometers work or should I use wirewound pots(greater than 3watts).
Absolute maximum ratings
Symbol Parameter Value Unit
NPN TIP35CW
PNP TIP36CW
VCBO Collector-base voltage (IE = 0) 100 V
VCEO Collector-emitter voltage (IB = 0) 100 V
VEBO Emitter-base voltage (IC = 0) 5 V
IC Collector current 25 A
ICM Collector peak current (tP < 5 ms) 50 A
IB Base current 5 A
Ptot Total dissipation at Tcase = 25 °C 125 W
Tstg Storage temperature -65 to 150 °C
TJ Max. operating junction temperature 150 °C
hFE
(1) DC current gain
IC = 15 A __ VCE = 4 V 50(gain)max
Welcome back Vedamurthy,
Yes TIP35 will work with 2N2222 and similarly TIP36 with 2N2907.
The pots can be any ordinary types, wirewound is not required.
Thanks for your reply.I assembled the top part of the circuit for the positive rail on a bredboard.The circuit was powered using another power supply(27volts,2.5 amps) instead of a transformer for the purpose of testing.The voltage control feature works fine,but not the current control potentiometer.The current remains constant.Double checked all the connections.Connection seems OK.All the components do not warm up except for TIP35 as expected.TIP35 heats up considerably at higher side of the load.Can you help trouble shoot the problem.For your ref here are the component values.
R1 = 1K, 5 watt wire wound
R2 = 120 Ohms,
R3 = 330 Ohms,
R4 = 0.1 Ohms
R5 = 1K5,
R6 = 5K6,
R7 = 56 Ohms,
R8 = 2K2,
P1,P2 = 4.7 kilo ohms Pot
T1 = TIP35 + 2N2222(NPN),
T2, T3 = BC547B (NPN) BC557B (PNP)
D5 = 1N4007,C1, C2 = 3300uF/50V,
TEST POWER SUPPLY = 27VOLTS,2.5AMPS
The power transistor and its base resistor will definitely heat up as input/output differential increases, that’s the common issue with all linear power supply designs.
Basically the T3 has to conduct when the maximum desired current is reached. This will happen because at this current the voltage across R4 is supposed to be high enough for this action.
If your T3 is not responding to the specified high current load, you can make T3 more sensitive by upgrading it into a Darlington and check the response.
Hi Swagatam, great job, but what is the value of the unmarked resistor between the wiper of P1 and tr3?
Thanks G Hunt, sorry for not mentioning the T3 base resistor, it’s not critical though, you can use a 1K there.
Many thanks Swagatam, I can now build this unit!
Glenn
Sure Glenn, wish you all the best!!
You say the circuit is short circuit protected but the resistor R2 blew up when the positive rail unfortunately got shorted. Any suggestion?
And I’m sorry for bombarding you with so many questions.😅
And yes, although the positive rails is working good but the 1k/5W wirewound resistor is getting hot quite a bit.
Hi Swagatam.!
I made the whole project as I discussed with you in comments previously, but as I power up the circuit, the positive rail works absolutely fine but the negative rail power transistor is heating up very fast and isn’t giving any output. Which of the parts may have gone wrong? Can you guide me please?? Will be very grateful to you.
For Reference, I’ve used:-
36-0-36V / 300VA Transformer,
50Amp. Bridge rectifier (more than enough),
MJ15024 / MJ15025 Complementary Power Transistors (CE voltage: 200V, Ic: 16A, Power Dissipation: 250W),
R4: 0.1 ohm/5W fusible resistors,
BD139 / BD140 Complementary Transistors in place of BC547 / BC557,
C1: 2x 4700uF i.e, 9400uF/100V Caps on each rail,
C2: 1x 4700uF/63V Caps on each rail.
I hope the information is enough.
Thanks a lot in advance brother.!! 👍👍
Hi EF,
As you will know that the biggest drawback of linear power supplies is that their power devices become hot as the input/output difference increases.
However R2 should not blow at any cost. If R2 blows that means something is not right.
And which resistor did you select for R4? Because the short circuit will work only when when R4 is present and correctly configured
I have tested this design thoroughly but only with 5 amps and only the positive rail. For me it worked perfectly and nothing blew during short circuit conditions. But yes R1 and T1 did get quite hot.
You can refer to the following article, which is the original one and check if you have missed something in the diagram. The negative circuit is shown in the scanned page which was taken from original elektor electronic magazine.
https://www.homemade-circuits.com/how-to-make-versatile-variable-voltage/
You can try building the negative side separately and check how it works.
And I would not recommend MJ5024, instead please try 2N3055, which is better suited for this application due to ideal voltage/current specifications.
I’ll troubleshoot this problem thoroughly now and replace R1 with 10Watts if that solves the problem of excessive heat.
Once again thanks a lot Swagatam! 🙂
Sure, wish you all the best!
Hi Swagatam!
I found this project very useful and i’m making one. I just wanna quickly ask what value potentiometer to use as 2.5k Potentiometer isn’t available in market and I desperately want to add potentiometer in place of presets as I am making this as a benchtop variable power supply. Please help me as soon as you can…!
Thanks in advance!👍👍
Thanks Electronic Freak, you can use a 1K preset/pot also. But please remember that this concept has one drawback, the power transistor may heat up substantially at lower voltages.
Thanks Swagatam!
By the way, here’s an idea.. I’ll try to use 2 pots of 1k in series to make the value close to 2.5k and in that way I may get a new feature of coarse and fine setting of values. Correct me if I’m wrong. 🙂👍
You are welcome EF, Yes that can be definitely done, no problems!
Thanks for guiding me dude. 🙂
Actually I’m also making a project video on this power supply and post it on my YouTube channel. I’ll provide the link as soon as I post. Thank you very much!! 😊
You are welcome!!
I want to send you a 10 sec video demo of the whole circuit test setup to make clear of what’s wrong happening in my project. How can I connect and talk with you?
Hi EF, you can send the video to my email, but sorry it won’t help me, because finding an issue by seeing a video clip can be difficult.
You can explain the problem here I will try to help!
And what happens if I use 5k pot inplace of that???
I’m currently building this.
Thanks in advance.🙏
It will still work, only the range across the whole dial might change. Meaning now you may get the maximum range somewhere around the 60% of the pot
One more question..
As going through all the comments on this page, i found the BC547 and BC557 transistors don’t work well for some readers. I think BD139 and BD140 can be used in that place because of high voltage as well as current rating. Will it practically work?
Thanks in advance!👍
yes, BC547/BC557 are rated to handle maximum 45V so these will blow beyond this range, so you can either go with BC546 BC556 or any other higher rated variant as mentioned by you. MJE340/MJE350 will be also nice.
It works. I used TIP 140,145 instead of darlington couple due to but it’s Vbe takes about 5 volts.so the power supply maximum output reduced about 5 volts.And BC 547 got burned thrice,2n2222 twice and finally it stopped with bc107. It was very hard to find that the transistor got burned at once. it took me three days to debug.Transformer was 18v 5amps.I learned lot of things from this.
Absolutely thank you for schematic and stuffs.
Thank you for the information, I am glad it worked for you!
By the way 2N2222 is more powerful in terms of current than BC107 but its collector/emitter voltage is only 30V perhaps that’s the only reason why it might have got burnt.
Hi . can I used R4 instead of Variable resistor
Hi, R4 is a fixed a resistor…you can use P1 for varying current…
Hi, why you have choosen for C1 50v instead 63V, the output of the diode bridge is around 54v , for a 0-40V sinewave for tr1.
Thanks.
Richard.
Hi thanks, I have changed it to 100V…you can refer to the corrected parts list.
thanks for the data of the potentiometers, that will be helpful for the start up of the power supply at 0v and 0amps, great, hands to work now. thanks again
You are most welcome herr doctor…
and thank you
and can i use a mosfet insted of using npn
not sure how a mosfet would respond because minimum switching voltage of mosfet is 6V while for a BJT it is 0.7V…but there's no harm in trying it.
hi i want to know what happens when replace r4 with wire (short Circuit the r4)
Hi, if you remove R4, it will disable the current control feature, and the T4 section will become ineffective.
…sorry not by removing R4, rather by shorting it, as you mentioned..
thank you for answering but i made the circuit and then i tried to connect something it didn't give me 1 Amp and when i connected +1.5 Amps to circuit something went burn ,the room filled with smoke.but now i noticed something : you can see the +50v out and isn't connected directly to 2N6284(NPN) transistor it is connected to BC547B which is giving only 100mA and some resistors it will not give more than 100mA with 50v (i tried making circuit for 3 times and it is not working correctly) i hope you correct the circuit i need it, it is awesome thing to have 0v – +50v , 0v – -50v , 0a – 10a power supply i wish i can make it and work correctly and thank you
I rechecked the diagram and I could not find anything wrong in it..everything looks absolutely correct.
Make sure that your power transistors are original and duplicate ones, because a few other readers had also failed with this circuit and later they discovered that their main power transistor was faulty originally.
I have already build the above circuit (the NPN section) and used it for more 5 years without any issues…it is virtually indestructible.
the only issue being the power BJT gets significantly hot at full loads.
I think you should go stagewise, first try and build the NPN section successfully, if everything goes correctly after that you can go for the PNP section.
The NPN section is explained exclusively in the following article:
https://homemade-circuits.com/2012/01/how-to-make-versatile-variable-voltage.html
ok i'll try it again and make sure that the transistors are original ones thanks
if you have a few free minutes and you can tell us all about the variable resistors for voltage and current that will be awesome, i mean to which side the pot of voltage will give 0 volts or max volts and the same with the pot of current control, to which side it will give the max current and 0 amps, i hope is not too much to ask, thank you very much.
Downward side for P2, and right side for P1 will produce higher voltage and higher current respectively.
Can I use tip 147?
Where? is it for the PNP power transistor? Darlinton might not work correctly…
Sir my transformer was 48v 3amp. which number for using in r4 resistor
It will depend on how much maximum current you prefer at the output…..if it's full 3 amp then you can simply short circuit R4
Dear Mr. Swagatam!
I made circuits same your schematic. But it isn't stability, when transistor T2 is hot, the voltage will down. I assembled heatsink but always need to blow by fan to trans T2 and cooling it. When i use a load, about 20 Ohm, the voltage is down 7-8V with adjust to 40V. My tranformer is 48V. And how I do for Voltage is not change by T2 and load?
Thank you so much!
Dear Thanh, if your T2 is getting hot, you can try a higher rated transistor in place of T2, you can replace it with a 8050/8550 pair or a 2N2222/2N2907 pair….to increase the output current you can reduce R1 to 470 ohms 5 watts and see the response.
Dear Sir
My transformer is dual 42VAC and I am trying to get dual 50VDC out of this regulator. Is T1 the transistor which needs cooling? What size You suppose the heatsink should be?
Hi Laura, it's possible with proper rectification through a very large C1.
yes definitely T1 will require a large heatsink for optimal functioning. make as large as feasible, or simply by checking how hot it gets…
Dear Sir
help me
(2N6284 and 2N6286)plz tell me the Equivalent transistors,because for schematic circuit in proteus it will creat a problem,both r not in the proteus library
Dear Kaleem, you can make an equivalent by using a 2N3055 and a 2N2222 pair in the Darlington mode for the NPN….
and 2N2955 with 2N2907 for the PNP side
Hello everyone…
I am very anxious to make this beautiful source.
Would anyone have the layout (pcb) to make available?
I still do not have enough skill to do the layout (I still get there).
Thank you very much!!!
sorry PCB layout is not available, however it does not require one since it can be easily built on a general purpose board, with some patience.
WHICH R4 WILL A NEED FOR A 40 VOLTS 3AMPERE OUTPUT???
AND CAN YOU ACTUALLY POST THE ENTIRE FORMULA OF OHMS LAW TO
CALCULATE BOTH THE OHM VALUE OF R4 AND THE WATTS VALUE OF IT
PLEASE I WILL LIKE TO SEE THE FORMULA IF ITS NOT TOO MUCH
TO ASK, WE CAN ALL LEARN MORE IF YOU POST IT, THANK YOU VERY MUCH
I have updated the formula in the parts list
WHICH ONE IS R6 AND WHICH ONE IS R8? PLEASE CLARIFY THESE, THANKS
which one is r6 and which one is r8? please clarify these. thanks
sir may u tell me watt of all resistors and types of capacitors used here??
All are 1/4 watt except R4.
R4 watt = 0.6 x maximum current selected for the output
all caps are electrolytic
Sir may you please tell me the watt of all resistors used here and also types of capacitors ??????
Please help me
I want the maximum current 10A
what r4 must i use?
Thanks
R4 = 0.7/10 = 0.07 ohms, 10 watts
use 0.1 ohms/ 2 watt and 0.22 ohms/2 watt resistors in parallel
Thank you
Many thanks Swagatam. That's a very helpful explanation of what is happening.
Best wishes.
Martyn
You are welcome Martyn!!
Dear sir, Many thanks for this interesting circuit. I see that R4 is to be calculated by ohms law. Could you give me some idea of the calculation here? For example, where is the voltage and current being measured from and this what figures would go into the calculation? Sorry if this is a silly question, but I'm trying to understand how you would determine the value of R4 in any particular case (ie using a variety of transformer voltages).
Many thanks in advance.
Martyn
Thank you Martin, R4 can be calculated in the following manner
R4 = 0.7/max current limit
The value will cause the required triggering voltage at the base of the associated PNP, sufficient to force T1 OFF…this will happen whenever the max current limit is reached or whenever the load tries to draw a current higher than the set limit…it is not dependent on the transformer rather on the load
I WANT MY POWER SUPPLY FIXED THE VOLTAGE AS WELL AS THE CURRENT. MAY I KNOW THE P1 AND P2 VALUE SO THAT I MAKE IT 40v AND 10 A OUTPUT
owh sorry my bad, coz u draw the pot just like regular resistor. ok i get it.
yes the one which are configured with arrows are the pots….
TR1 is the transformer
thank you, but i cant see any pot, trimpot or vr to adjust the voltage and ampere,, how to adjust voltage and ampere on this circuit ?? maybe you can update the circuit coz im still learning how to build adjustable V and A symetrical ps with volt and amp meter. also i cant find where is the Tr1 on this diagram https://homemade-circuits.com/2012/01/how-to-make-versatile-variable-voltage.html as shown on the part list.
Nice diagram… dear swagatam can u please put the diagram which is if i want to put digital volt and amp meter. Thanks before
Thanks GK, you can attach the ammeter in series with the positive output terminal of the circuit and voltmeter right across the +/- terminals of the output
One more question sir, can i use same transistor for both upper and lower circuit?(i use 2n3055 for npn and mj2955 for pnp)thanks sir
yes the mentioned transistors will do.
Hi sir, why there is so many pots in above circuit.Can you tell me the fuction of that 4 pots?, for example (pots 1 for adjusting voltages).And i want to use 24v 10 amp trafo for this, will this work?thanks sir
Hi Raihan, the upper positive section has two pots one for voltage adjustment and the ohter for current adjustment…the same is true for the lower two pots, which are used for the negative section of the power supply.
Hi swagatam sir
I need 12v-3amp power supply for my project
so please help me.
Hi jaydip, you can use an IC LM338 circuit for your requirement.
Dear Swagatam,
I can use SC1815 and SA1015?
Respectfully,
Ramunas
for which transistors do you want to use these?
T3 and T2
If both are NPN and rated at 60V (collector V) then you can use it
Dear Swagatam
MJlorton has added a link of your variable circuit diagram uploaded on brighthubengineering.com in his video series of how to build a variable power supply and i feel proud of looking at it. i am in search of a versatile digital variable power supply diagram with the specifications of 0-30v 0-5amp. i shall be highly obliged if you could provide me the same either existing diagram with required modification or you are requested which decent brand of variable bench power supply should i get for hobby electronics and laptop repairing. Thanks a lot
Dear Gowhar,
you can probably try the following design, this looks exactly suitable as per your required specs:
https://homemade-circuits.com/2016/01/universal-variable-power-supply-circuit.html
Dear Swagatam,
Can you recommend a short-circuit protection for this circuit?
Respectfully,
Ramunas
Dear Ramunas, the above design is already short circuit and overload protected.
Just to add to my question, what pnp transistors should I use to the lower ciruit?
MJ2955 for the PNP and 2N3055 for the NPN
and BC556 for the PNP and BC546 for the NPN
Hi,what rating of transformer did you use here? I mean the voltage and its current rating. Thanks!
It can be a 50-0-50V 10amp trafo.
Will a transformer with a lower current and voltage rating still for this circuit say 24-0-24, 3amp? If so, are there modifications that I have to do like have to change vlaues of some resistors or change a transistor etc? Thanks!
any voltage and current can be used with this design, depending upon the maximum tolerable rating of the transistors…….no modifications would be required
Dear Swagatam,You have connected C3 in reverse order in above circuit.It will charge in reverse polarity which will damage the capacitor.C3 positive terminal should be grounded while the negative terminal should be at negative voltage.Thanks
Dear Muhammad, thanks!
yes the lower caps were wrongly polarized, I have corrected the diagram now, please check it.
If I use a 0-36 V 3 Amp transformer for this circuit will the output still be 0-50 V and 0-10 Amp? I really need your reply sir its for our project thank you
That's impossible, in fact you will find a little less than 36V and less than 3 amp at the output
then what should i do sir to make an output of 0-50V and 0-10Amp? here in our town there is no 0-40V transformer sir.I hope you could help me sir . thank you
sir may i ask . if i use a 33.5V 10amp transformer what should i add to the circuit to make an output off 50V? here in our town we really cant find a 0-40V transformer. I'm hoping for your reply sir thank you
You'll need to connect a boost converter prior to the transformer, that takes the input from the transformer and boosts the voltage for the input of the circuit above.
using a bridge rectifier and a capacitor will step the voltage to above 40V
I can't find R6 in the diagram. Please Help
base of T3
Thankyou
Where did you use D5? Sorry for asking again and again.
beside C2, it's mistakenly printed as D1
If you are having difficulty in understanding these simple things, then I think you must first learn all the basics and only then attempt building any circuit