The post explains a simple yet very useful 0 to 50V dual power supply circuit which will enable a full 0 to maximum dual voltage +/- control of the input power supply DC. It 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
For calculating the part values accurately, you can refer to this bench power supply article
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.
You may also like this LM317 based Dual Power Supply Circuit
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 + BD139(NPN), 2N6286 + BD140(PNP)
- T2, T3 = BC546 (NPN) BC556B (PNP)
- D1, D2, D3, D4 = 6A4,
- D5 = 1N4007,C1, C2 = 10000uF/100V,
- Tr1 = 0 – 40 Volts, 10 Amp
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Hi all,
I’ve built Swagatams power supply and want to contribute with this description of my approach. If I point out some issues this does by no means mean me criticizing Swagatam. I have all respect for people publishing something for free and even more when they support their project as thoroughly as Swagatam does. It’s my experience with my setup.
Now, I had a very nice bench power supply that is exactly adjustable down to mV and mA. Problem was, it has only +-15V at 3A, and I had several occasions where I needed more than that, +-30V at 1-2A would be nice. Overcurrent protection was another main requirement. In comes Swagatams design.
As built, it does what is to be expected. I run it with +-42V at 3A. The voltage and current regulation is a bit crude, but that doesn’t matter, as this is the ‘grunt’ unit.
What parts did I use? It may be a well know trick, but I actually gutted an old Denon AV 5.1 receiver. The old ones without HDMI get tossed out, and when you’re lucky you can get one very cheap. Mine was $10, albeit with burnt outputs.
What do you get out of it? A powerful transformer, a heatsink able to handle a lot. And 2, maybe 4 filter capacitors rated for the voltage coming from the transformer. Those are by far the most expensive parts of our project. If you’re lucky you get fans, feet, pots, silicone thermal pads and lot’s of other useful parts out of it.
I designed a PCB with KiCad to match the case I had from another abandoned project. It fitted the mounting perfectly and was very cheaply made by JLCPCB.
It could be done on a protoboard, but I like honing my skills with KiCad.
On the PCB I added a small 12 volt regulated power supply from another secondary winding of the AV transformer, again using sockets, rectifier, caps and regulator taken from the Denon.
I also added a small circuit using a 4013 flipflop, that toggles on and off on a push button press to switch a relay and activating a LED. This is to have a means of disconnecting the load easily.
A fan controller board was mounted in the case to have a temperature controlled fan. Those are available on eBay for cheap and I had several laying around. I used an 8cm PWM fan from an old PC for that. It too gets it’s power from the small 12V supply.
Then I added two volt/amp meters. Again, those panel mount style meters are cheap on eBay. They are not very accurate, but good enough for my needs. They got their supply from the 12 volts, too
Now, I found out that those cheap meters measure positive voltage only. And they get their reference from the amp meter ground. That worked fine for the positive part of the project, but when connecting it in reverse to the negative side, things didn’t work or shorted. The solution was to give the negative meter it’s own 12 volt supply, so that it was decoupled from the rest and could establish it’s own ground. So I threw in a small regulated 12 volt supply from the standby transformer of the Denon built on a proto board. The meter only takes 15mA.
With all that in place, the supply worked, but I had troubles with the current limiting pot P1 of the design. It did nothing. The lone R4 does the job fine, though. After some fruitless tries I gave up on it, removed the pot and implemented a 6 way 2 pole selector to switch 6 different R4s in, giving me 0.1, 0.2, 0.5, 1, 3 and 5 amp current limiting. Notice that my switch has a 5 amp rating, but only 150mA when switching. The load needs to be disabled when changing the current protection setting.
Tests on the positive side proceeded. The rectified voltage without load is 48 volts, 42 with load. Btw, the big manufacturers are not as generous with their cap voltage as Svagatam, saving some pennies there. The filter caps in the Denon had 10000uF at 50V. Close, but works. When I tested the full 42 volts with about 3 amps the magic smoke escaped and the fuse blew.
Investigation revealed that it was R2 that burned. It did it, because the BC546 T3 could not handle the load and shorted. It took T1 (I’m using a TIP142 here) with it, also shorting, causing the fuse to blow.
The issue that T3 is perhaps underrated is mentioned in the comments. So I replaced the parts, upped R2 to 1/2 watt and changed T3 to a BD139. That worked fine and the BD139 can handle the load. I modified the negative side accordingly with a BD140.
The supply works fine now and I’m very happy with it. I also learned a lot, and that is what DIY is all about, right?
Thanks again to Swagatam for the nice project.
Regards
Thank You Rytikar for your detailed analysis and the related suggestions!
Initially your comment was sent to the spam folder due to the external link which you had included in the comment. It is an automated process.
The above power supply is a basic cheap linear power supply concept which is not among the most efficient power supply designs.
The current and voltage handling capacity are directly associated with the power ratings of the various components used in the circuit which will need to be upgraded accordingly.
I may not have calculated the part values very accurately, since I knew it is just about upgrading them appropriately which could be done by the user while experimenting, just as you did, and I appreciate it very much.
The current is not properly regulated by T3, since T3 switching is also linear and sluggish, so the effect is not sharp and unidentifiable quickly.
Instead if an op amp based sensing is incorporated then the current control could be more effective using a pot.
You can even try a MOSFET for T1 and see how it responds, although the highest voltage will be 7 to 8V less than the input supply with a MOSFET.
A big drawback with this supply is the heat dissipation, which could be improved by using a tapped transformer, at 9, 18, 24, 40V, which could be selected depending on the output requirements, and this would hugely help to save power by eliminating large dissipation from the transistors.
Anyway thanks again for your helpful tips, I am sure the users will find them very helpful
Hi all,
two findings to add to the above.
The BD139/BD140 T3 still gets over 100 degrees C warm and needs to be mounted on a heatsink.
I started to use a 1 watt 1K for R1, but that is not enough, it needs to be 5 watts.
Regards
Hi Swagatam,
I built the PS and it works, sort of. 🙂
The voltage regulation works as designed, but the current regulation does nothing. Always the full current is allowed.
I have a hard time understanding the setup, though.
If I measure voltage over R4 (0.22 ohm in my case for 3A), I get corresponding voltage drop depending on load, say 114mv at 0.5A. Not the 0.6V needed to trigger overcurrent protection, but generally this seems to work.
But looking at the circuit, R5 and P1 are parallel to R4, so the same voltage is dropping. As you increase R5/P1 the overall resistance can only go down, increasing the maximum current allowed.
So how is this supposed to work? I’m missing something here.
Can you please explain a bit more in detail how the current regulation is supposed to do it’s job?
Thanks for your help
Regards
Hi Rytikar, Actually R5 is not required, it can be removed, so only the P1 pot becomes in parallel to R4. Compared to R4 P1 will have a high value so it won’t have any effect on the overall output current set through R4. P1 adjustment only helps to divide the 0.6 V developed across R4 to the base of T3. At the extreme right side the T4 base/emitter shorts so it disables and unable to detect any current, while on the left side extreme, it becomes maximum sensitive to the 0.6V across R4….other intermediate detection values become accessible as the pot is moved across the extremes.
You can get a detailed information regarding the same in the following article:
How to Design a Stabilized Bench Power Supply Circuit
Thanks for the reply. I get the idea of the regulation from your link, and I think it will work with the R4 to R7 selector for different R4 values of appropriate wattage
I removed R5 and see more movement in the dropped voltage now.
I’m aware I need 600mV drop to trigger T3 to enable the current regulation.
With a 0.22 ohm R4 (for 3A max) and the pot though, I get 228mv drop for 1 A load when at max extreme as expected, as the 1k5 in parallel does not make a big difference to the 0.22. But the mV value gets LOWER ending at 0mV when turning the pot to the low extreme. I actually would expect this, as the pot going to 0 will change R4 to a LOWER resistance shorting in the end, upping the max A and thus lowering the dropped mV.
Sorry, still not getting how the pot should work together with a fixed R4. 🙂
I may add the resistor selector as shown in link, as it would fit my needs.
Regards
The pot works like a voltage divider. The center pin of the pot will have a potential which will depend on the ratio of the resistance on either side of the center pin.
Hello again sir,
Regarding potentiometers P1 and P2, if I’m doing my math right, does P2 need to have higher power rating (roughly 1 watt if output is 50V)? Alternately, what is the overall effect if I use a 3kohm or 5kohm pot for voltage control P2 instead?
Thank you,
Paul
Hello Paul, the resistance value won’t have much effect on the range, since there’s no high value resistor in series to form any significant resistive divider with the pot resistance. 1 watt is fine for the P2
Hi Swagatam,
thanks for the project, exactly what I need, a robust ps for the heavy duty tasks.
I understand the circuit and I’ve read through all the comments twice, as there is a lot of information to get there. I still have two questions, if I may.
I get that R4 takes the load and needs to be calculated, 5 watts for me.
But what with R1? In the parts list you say 5 watt, wirewound. In the comments you say 1 watt in one place, ‘all 1/4 watt but R4’ in another.
I care a bit because of space issues, fitting the pcb in an existing cabinett, else I would go with 5 watts without asking.
And then T1. The schematic shows a darlington ‘drawn simple’ out of two transistors, I guess for ease of drawing.
But the 2N6284 IS a darlington. Driven by the BD139?
Then, in the comments, you say ‘If you do not want T1, you can replace the T1 pair with a single TIP122, for the NPN side’. So both transistors that make the T1 in the schematic can be replaced by one TIP122?
Also, later, you say ‘TIP142 TIP147? -> Yes can be used…’, but then ‘Can I use tip 147? -> Where? is it for the PNP power transistor? Darlinton might not work correctly…’
Can the TIP142/TIP147 be used? Do I still need the BD139/BD140?
Again, I can get the 2N6284 + BD139(NPN), 2N6286 + BD140(PNP) parts, but would very much prefer the TIP142/TIP147 for ease of mounting on the heatsink.
Thanks a lot in advance.
BTW, I admire your patience.
Hi Rytikar, thanks for analyzing the circuit.
Actually, initially the T1 was not meant to be a Darlington, however, since a high current is expected,later on the T1 was recommended to be a Darlington.
A single Darlington or a triple Darlington can be also used to enhance the current, however a single Darlington looks more reasonable, so a TIP142/TIP147 is what I would suggest, but then the current may not be as high as 10 amps, raher just around 3 amps.
For 10 amps I would rather recommend a MOSFET here, or a combination of TIP122/TIP35 and TIP127/TIP36, with huge heatsinks.
For T1 as MOSFET the input/output supply differential will need to be a minimum of 7 V.
For a MOSFET or a Darlington T1, the R1 wattage may be simply a 1/4 watt.
Thanks Swagatam,
3 amps is fine, I’m more interested in the voltage. So, a pair of TIP142/147 with a 1 watt R1 it will be. I’ll report back how that worked. 🙂
Rytikar
No problem Rytikar, wish you all the best.
Hello, this might have an obvious answer, regarding the cascaded transistors of each T1, which part number is which transistor? For example, looking at the top T1, which transistor is 2N6284 and which is BD139?
Thank you!
Hi, the transistor with higher power rating goes in series with the power line, and the smaller one becomes its complementary Darlington pair….so the 2N6284 connects in series with the power line, and the BD139 attaches as the Darlington pair with the base resistor.
Great, thank you for the reply and info!
You are welcome!
Sir, I like your webpage, It is very useful for me. I want little help for you. Can you please send me Circuit diagram and components list for 48v 20amp Battery charger?
Thank you,
Thanks Ruturaj, please use the search box and type “48 V battery”, you will be able to find the required circuit.
Sir,
After constructing and testing your design without the current control( R4,R5,P1,T3 have been removed) there is an approximately 10 volts drop at the output. I use a 35V/5A secondary and my output is about +-25,5VDC with or without load. Plus the BC546 and BC556 are extremely hot with or without load!2N6284 and 2N6287 (not 6286) are hot too only under load which is normal.BD139 and BD140 are in normal conditions. My goal is an output of 30VDC with load for supplying a class A amplifier.Do I need a 30volts zener instead of 1N4007?Please advice. Thanks
Spyridon, It seems there’s some serious issue with your parts, because this circuit cannot drop more than 2V at the output. Also, the smaller transistors can never heat up because they have no significant loads across their base or collector.
I have tested this circuit with up to 24 V and it worked perfectly. The power transistor can heat up a lot depending on the input output differential and the load current….without load nothing heats up at all.
The circuit is so simple that I can’t realise which part is responsible for this strange behaviour. Both rails(+-) behave the same way, so what do you suppose? Shall I replace BC546-556 with new ones? A 27volts zener is out of the question?I need +- 30volts for my amplifier, not a variable power supply!When I changed the 2.5K pot to a 10K the output goes up to 42VDC but after 27 volts the adjustment jumps to 33vdc, 38vdc and finally 42volts at maximum.My next tests will be replacing the pot with a 5K and finally replacing the 1N4007 with a zener. If you have tested the circuit up to 24 volts you don’t know the circuit behaviour with higher output. I think that the BC546,556 are heated up because of the current (100mA max.) which flowing through them not the voltage(80v max.).Please advise.Thanks a lot.
Using Ohm’s law for the collector current of the BC546 gives
I = V / R = 40 / 1000 = 40 mA, which should not make the transistor hot, rather just warm. You can increase R1 to 4k7 and check if the BC546 stays cooler.
The zener diode will fix the minimum voltage achievable, not the maximum voltage. The 1N4007 in place of the zener fixes the minimum voltage to 0.6V + Darlington drop of 1.5 V = 2.1V
Whether it is 24V, or 44V volt the behavior of the power supply will remain the same provided the parts are correctly rated and are not faulty. The Darlington will drop not more than 2V.
Try the following concept and check the response to confirm how Darlington transistor work:
100 amp Variable Voltage Power Supply Circuit
Use only one transistor for testing purpose, not all.
After replacing the 1K to a 3K6, the transistor temperature fell to normal. Using my simulator, I remarked that replacing the Bc546/556 with BD139/140 the circuit works fine( with a 27 volts zener) and if there is any overheating I can put a heat sink on the BD139 ( A 2K to 3K instead of the 1K resistors seems to work OK). All these because I don’t want to change the original circuit configuration. The Elektor configuration works fine too ( 100R instead of 120R, 470 for the 330R, 1K for the 2K2 and 47 for the 56R)! I will definitely replace the 1N4007 with a 27 volts zener because I want a stable +-30 volts DC for my amplifier. The current control parts have been removed( R4,R5,P1,T3). Using a zener the voltage drop using an 8Ohm /150Watts load is just some hundreds of millivolts( 600 -800) I would appreciate your comment. Thanks a lot
The D1 drop fixes the minimum voltage of the power supply which cannot be reduced below that value. The maximum output voltage value is determined by the pot adjustment.
I cannot comment because the circuit is simple, linear and perfect without any issues, it should work immediately once built.
Hi Swagatam,sorry for the last question, i don’t saw you’ve respond the same question about R6 location.
Today i just want to know if you have some ideas about Am and Volt meter i can add in the circuit for monitoring the load .
Thanks.
Richard
Hi Richard, making digital ammeter/voltmeter can be quite complex, I would recommend using moving coil type meter which can be installed directly without any concerns.
Hi Swagatam, in the parts list, they mentioned R6=5K6, sorry but i can’t found R6 in the schematics.
regards,
Richard
Hi Richard, it is at the base of T3, but it is not required, you can replace it with a link
good morning. sorry if I write here but I didn’t know how to post a comment directly. I wanted to create this variable power supply and your scheme was the only one that I found that meets my needs. meanwhile I would like to ask you what value to use in R4 (considering that if you do the calculation I get 0.06 ohms, which I can’t find anywhere). Surely I will be wrong in the calculations and therefore I wanted to ask for your opinion as a creator. thank you for your time
Output ELKO is maybe higher value(10.000 microfarad).Are you sure that is correct value?
Hi, my transformer is not dual voltage and i only need upper part of this circuit but i don’t know how to make it and what changes it needs .
Hi, you can try this.
https://www.homemade-circuits.com/how-to-make-versatile-variable-voltage/
thanks, my transformer is 48 volt 8amp and i need a circuit which works with 50-60 volt input and give 50-60 volt 8-10 amp variable output (i only want to control output voltage and don’t need current control ) there is three diagrams in the link you posted which one will do it for me ? sorry for my poor english btw .
You can try this diagram:
https://homemade-circuits.com/wp-content/uploads/2012/01/power-supply.png
Remove Q4, Q5, R5, R2, D1
thanks again . i have a few more questions what is the wattage of resistors in circuit modified by Mr. Nuno ? and since i want to remove Q4 Q5 R5 R2 D1 , do i need change value of other resistors ? last question is can i use 1n4007 instead of 1n4001 ?
Use 1 watt 5% for R1, rest all can be 1/4 watt 5%
Hi TIP142 TIP147 kulanabilrmiyi
yes can be used…
Mr. Swagatam:
I have just left you a comment in your “Adjustable 0 – 40V 10A Power-Supply” article and my reply (also shown down below) of the type of power-supply that I am looking for. Then, I came across this other article of yours which details a “0 to 50V, 0 to 10amp Variable Dual Power Supply Circuit”, that is more closely what I am looking for. Can you relate to me how much will this circuit of yours need to be modified in order to meet, or at least be very closely similar to, the type of power-supply that I am looking for? Any help, ideas and/or suggestions of yours will be highly appreciative!!! THANKS!!!
Hi Jerry,
I have answered to your comment in the other post, here’s the link:
https://www.homemade-circuits.com/0-40v-power-supply-circuit-construction/#comment-70744
Hi Swagatam,
Nice design and I would like very much to build this! I have a transformer on hand I would like to use but it is not labeled except for numbers stamped on it that I cannot find any specs online to match. I was hoping you may have knowledge on tracking down transformer specs? I measured the output at 57VAC but the current rating is unknown. There is no MFG name I can ID but it does have those numbers… I assume one of which is the real part number but again Googeling them came up empty. Here are the numbers stamped into the casing:
199-40020
SP-66-0001
491-8746
Thanks for any light you can shed!
Thanks Mike, the easiest and the legit way to verify current is by connecting your DMM ammetere range with the output of the transformer momentarily.
You will have to set the DMM at the 20 amp range (AC) and then connect the prods just for a second across the transformer wires, and quickly record the results. This will give you the required current capacity of the transformer.
Dear Swatagam,
We have a project dual power supply 30 0 – 30 4A. We used a transformer 30 0 30 4A and we use a TIP 41 and TIP 42 transistor but it keep exploding when its turning on. We are planning to make another circuit diagram. Do you have any references that we can use?
Dear Krad, the above circuit is the safest design and is tested, it can never explode. Please check your circuit connections again. Or you can build the NPN side first and confirm, and then go for the PNP side.
An alternative design is given here:
https://www.homemade-circuits.com/dual-power-supply-3v5v6v9v1215v-with/
Dear Sir,
Good day.
I want to make a simple project Dual Complementary Power Supply. I shall be highly obliged if you could provide me some circuits. I don’t know how to send pictures here. I initially used the common transistors for the two rails. Also, I want to increase current output to the requirement.
Output: about 5 Amperes to 10 Amperes
+/- 15 V above (preferably adjustable)
preferably two transistors
(No ICs should be used like LM317 and LM7918 pair)
Thanks.
Dear Ronaldo, you can try this concept:
https://www.homemade-circuits.com/0-to-50v-0-to10amp-variable-dual-power/
Thanks. I send another one. Thanks again in advance.
Sorry Jose, I missed that the comment was posted under the same article.
If you don’t want the current control system you can remove the T3, R3, R5, P1 stage, to make the circuit smaller and easier!
Sir,
I have designed your circuit and build a pcb with sprint layout 6.0. I used a toroidal transformer with 2 X 35volt AC/ 5A secondary which produced +- 47,5vdc after the 2 main capacitors (40.000uF/63volts). I excluded R3,R5,T1,P1 for simplicity. The maximum output voltage was not more than 28 volts in both channels and finally was dropped to 23 volts after a couple of minutes. In 5 minutes the 2N2222A got burnt (no smoke) and the output voltage went to +1,5 volts. The negative channel still works but the maximum voltage is 23 volts DC( P2 is fully open). Any suggestions?? No spare part is hot or smokie. The transistor connections have been made due to the factory recommendations. I am an experienced technician electronic, working in military radars! Thanks a lot.
Spyridon, the 2N2222 could have been destroyed due to over voltage. In the parts list I have replaced it with BD139/BD140, and also have replaced BC547/BC557 with BC546/BC556, which are all rated to handle up to 80 V. Please make the necessary changes and it should work OK.
R3 and T1 must be included.
If you do not want T1, you can replace the T1 pair with a single TIP122, for the NPN side
Excuse my mistake, i have removed the current circuit parts T3, R3, R6, R5, P1 as you have already mentioned in previous posts. Shall I keep R3(330R) or not?Do you believe that if i change the transistors to more powerful ones the circuit will work up to +- 45 volts??? My negative channel works perfectly but until -28 volts maximum!!! I think that the 2,5K pot must be replaced with a 10K as i have tested in the simulator.
R3 must be included since it forms a voltage divider with R2.
The previously mentioned transistors must be changed otherwise the circuit can malfunction
yes 10k can be tried for the pot
Dear Sir,
I have constructed your circuit in real world as you have said! Unfortunately it doesn’t work after 31VDC. While you adjust the pot, when the voltage reaches the value 31volts, the next reading is 41volts.I used a 10K pot because the 2,5K adjust up to 26volts. I have seen all these problem in NI simulator 12.0 and you suggested I would test it in “real world”!! Photos of the project are available. I am an experienced technician and I have done no mistake at set up. Please advise! I use a transformer with secondaries 2 X 35 vac / 5A and I intended to get a +- 39vdc . If I wanted a +- voltage up to 30 volts, your circuit would be great!! Thanks
Dear Spyridon,
In my testing I could not find any issues with the voltage drop?
You can see the single positive stage circuit and testing proof here:
https://www.homemade-circuits.com/how-to-make-versatile-variable-voltage/
There will be a some drop since a Darlington emitter-follower regulator is used, which can be around 3 V, but a 10V drop looks problematic.
Sir,
The problem of the circuit is the linearity. A zener diode might be the solution. The Darlington configuration is quite different to a single 2N3055 one. The elektor magazine project(you have posted as a sample reference) uses a 22 volts zener in place of D5.Elektor uses the 22volts zener for a regulation up to 33 vdc!!So you could try a 35volts zener for up to 45vdc regulation. Check it out. This is probably the solution. Please advice. Thanks a lot
Spyridon, The 22V zener in the elektor had been used to suit a specific application, it is no way related to linearity, the circuit is perfectly linear because it is a simple emitter follower configuration.
By the way I am referring to my design not the elektor one, although it was a 15 V design, it worked perfectly linearly, an so should a 35V circuit also.
How a Darlington will be quite different to a single transistor in this configuration? Even if it is a Darlington BJT it is a still an emitter follower. The only difference being the excess drop of 0.6V, due to addition of an extra transistor. So a Darlington may drop around 1.5 V at the output without load. With load it may drop even more as it gets heated up.
Please check your PNP and NPN circuits separately to confirm the results…I hope you have changed the 2N2222/2N2907 as advised previously.
Please study how an emitter follower works to get an exact detail about the linearity of the circuit
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.
I’m using the same voltage and current he’s using. And I haven’t understood what is the value of R4 I have to use. Please help me. If you send me your email I may tell you via email
The voltage across R4 will develop when the output is suitably loaded. You can initially keep the T3 base disconnected and connect meter probes across R3, and check at how much output load the voltage across R4 becomes around 0.6 V. This will determine the maximum current capacity of the circuit. You can increase this cut off threshold by reducing the R4 value and vice versa. Once this is fixed you can connect T3 base back with the P1.
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
Dear Sir,
I have run the circuit under National instrument simulator 12.0 and it works funny when I try to adjust the voltage. At the 100 % pot P1 adjust, the voltage is 5 volts, at 5% is 15 and at 0% 34,5 volts. I use 35 volts secondary voltage X 1,41- 49 volts DC. Please advise. Thank you
Dear Spyridon, Please Build it practically and test it, then I can guide you if you have any problems, I cannot troubleshoot a simulator result.
I want to use this circuit to supply +- 39 volts to a mosfet class A power amplifier ( Elektor AXL amplifier)2 x 16 watts. The current requirement of the amplifier is around 8A. The current adjustment is not necessary to my project as I want a 10 A current flow at all time of the amplifier operation and I will eliminate it from the circuit(T3,R3,R6,R5,P1). The 2n2222 must be replaced with a more powerful transistor because the Emitter Collector voltage must be more than its 40volts available.I will make a pcb with sprint layout 6 and I will give it a try.Any suggestions will be appreciated! Thank you in advance.
No problem, you can go ahead and make it. The single supply version for the same circuit can be seen in the following article:
Variable Voltage, Current Power Supply Circuit Using Transistor 2N3055
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.
Wandows:
GREETINGS!!! I am a long-time PCB Designer and if you still need to have a PCB designed for this circuit, just send me the version of the schematic you have used, along with a complete Parts List (including manufacturers Part Numbers) of all of the parts you are using and I could design a PCB for you to use. As an example, I once designed a PCB for a U.S. defense contractor that was capable of carrying 600-Amperes of current!!! WOW!!!
Here is my e-mail address: midnight_blue_designs@yahoo.com
Let me know if you receive this message and if you would like to have a PCB designed.
Regards,
Jerry B. Williams
Senior Electronics Mechanical Packaging Designer
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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
0.1R/2w and 0.22R/2w in parallel is 4w not 10. It needs 5w + 5w in parallel
yes, it should be 5 + 5 watts…
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.
Multiply every transformer ac secondary voltage X 1,41 – 2volts about and you will have the dc output of the power supply. In your case 33,5 X 1,41 = 47,23 volts – 2 volts = 45,5 volts
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
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