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0-30V 0-3A Latest Data

Guest liquibyte

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I will explain to you in English,
Hello dear developers of the scheme, I ask you to solve the problem, why I collected the circuit did not work on the IC mc34071, on the input circuit 25.5v, on the C1 39.8v, on the Ic3 4-foot -1.5v, on the output circuit -5v, help please what is the problem, why does not it work? I have no experience with electronics, help please?R1 2.2k 2w ,R3 230R 0.5w ,R2 83R 1w ,R7 0.11R 15w ,Q4 2sc5200 1,Q1 bc139 ,Q2 s9014 ,Q3 s9015 ,R22 1.2k 1w ,D1 10v0.5w ,D8 5.1v1w!

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On 2017-02-27 at 12:46 AM, repairman2be said:

Hi all,

Finally after some months have gone by, my build of the Power Supply is done.

I have used liquibyte schematic Rev. 8 and had made the cirquit board according to the Gerber.zip file he posted here:

0-30V Stabilized Power Supply

Page 88 posted October 6, 2014


I left out D10 and R15 as per his description.

I have plenty of boards leftover if someone has a need for it. There was only one mistake liquibyte made which have outlined in one of the pictures uploaded here.

I was fortunate enough to get a big case with a Toroidal transformer from the scrapyard. Also many parts are recycled from various sources.

Regards, William










I also made this project after your example (however i had to etch the boards my self, little bit hard from these gerbers but any way:-))

It worked nice but after a little longer session with a 12v 25w lamp the current control started to oscilate and be unreliable when i was testing.

Any ideas about where to start. I am not an expert so thats why I am asking.

The only thig i have tried so far is ro replace the tle op amp but same result.


Attaching some pictures of my project as well.....


And yes i realise that a cooling fan is needed:-)



Regards Niklas


Ok so now solved:-)


Now it works like a charm again and the problem was that due to a tight layout i had a small pice of aluminium on the backside of the board between two thin lines. (it did not burn anything so lucky i guess).

Just have to find a good way for the cooling fan.




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I am another one who has set out to build this supply and discovered the endless possibilities of revisions and possible enhancements to this design. Thank you for this post. The original links on pg 1 need to be revised to point to the relevant posts as I currently end up on the community index page. The links to all the pdf and other files work fine.

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Hello. The first thing is to introduce myself and say thank you.
I started with the original version and researching I have come here and I have to say that I have seen beautiful versions derived from v1. 0.
I would like to keep the original project (the TL081, the toroidal transformer of 24v. . . etc), but I've already seen so many projects that I'm a mess. What I'm looking for is simplicity and I don't mind staying at 27 or 28.maximum volts. . . but toroids are not cheap here and I want to take advantage of the one I bought from 24 which one do you advise me for that 24AC transformer?

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The 24VAC transformer probably produces 25VAC with a light load on the project. Then its rectified and filtered output is +34V and -5.6V which power the opamps. At times the voltages are higher. Your transformer will be overloaded if its power rating is 105VA or less (24V at 4.4A)..

The old TL081 opamps have an absolute maximum allowed supply of a total of only 36V so they will not last long. Replace the opamps with TLE2141 opamps that have a maximum allowed supply of 44V.

Many of the resistors and the driver transistor in the original project are overloaded. Upgrade them. The main filter capacitor C1 value is much too low, upgrade it.

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Hola, ante todo me llaman José Silva, (FRISIL). Me acabo de registrar en Comunidad Electronics-Lab.com.

no soy profesional en la electrónica, apenas estoy comenzando y con avanzada edad (55 años).

E estado observando el desarrollo de esta fuente y me ha despertado un gran interés en armarla.

Yo la estoy simulando en proteus con el TL081, tengo una duda sobre SetOFF NULL en el U2. ¿Este potenciómetro va entre pin 1 y 5?

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From above:

Hello, first of all they call me José Silva, (FRISIL). I just registered at Comunidad Electronics-Lab.com.

I am not a professional in electronics, I am just beginning and with advanced age (55 years).

I have been watching the development of this source and it has aroused great interest in putting it together.

I am simulating it in proteus with TL081, I have a question about SetOFF NULL in U2. Does this potentiometer go between pin 1 and 5?


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I found this description of our PSU by Rod Elliott on www.sound-au.com and he also introduces some improvements and shows how to use this power supply as bipolar unit. The schematic below is an example, and although simulated it's not been tested on the bench. Copying description:


A single supply might be attractive for some people, and it's certainly simpler than a dual tracking version.  Of course, if you only have one polarity that limits your options as to what you can test, but they are commonly available from any number of suppliers.  The circuit shown below is adapted from one that's shown on a number of different websites [2, 3, 4].  As such, it's difficult to know which one was 'first', and there have been many improvements (or at least changes, which aren't always the same thing!) made to it over the years.  The basics haven't changed much, and the one shown below dispenses with one voltage regulator in favour of a simple diode regulated negative supply.  Because I used LM358 opamps, the negative supply only needs to be around -1.2V at fairly low current.

When the supply is in current limit mode, the LED will come on, indicating 'constant current' operation.  It's normally off, so you can tell at a glance if the load is drawing the preset current with a reduced output voltage.  Constant current operation is particularly useful for testing high power LEDs or LED arrays, as that's the way they are meant to be driven.  You also need an 'on/ off' switch, which reduces the output voltage to zero when in the 'off' position.  This is an essential feature (IMO) as it lets you make changes without having to disconnect the supply.  The best arrangement is to provide the switching at the output of the supply, as that lets you set the voltage while the DC is turned off.  Consider using a relay (or two) for the switching, otherwise you need a heavy duty switch.  Wile the voltage can be reduced to (near) zero by pulling the non-inverting input of U1B to ground, there may be 'disturbances' when AC power is first applied.  This is avoided by switching the output.

The supply shown below is fairly basic, and you'd need to add meters for voltage and current, and thermal management (a fan and over-temperature cutoff) at the very least.  There are countless improvements that can be made, but they would make the circuit more complex, more expensive, and provide more 'exciting' ways to make a seemingly minor error and cause the supply to blow up the first time it's switched on.

U1 is a 7815 regulator, but with a 15V zener from the 'ground' pin to raise the voltage to 30V.  Additional zener current is provided by R3 to ensure a stable output.  U2A is the current regulator.  When the voltage at the inverting input (U2A, Pin 2) is greater than that on the non-inverting input (Pin 3), the output goes low, pulling down the reference voltage provided to U2B (the voltage regulator).  The voltage is reduced by just the amount required to ensure that the preset current is provided to the load.

The current limit is variable from (theoretically) zero to 2.5A.  VR4 allows adjustment to ensure the reference voltage for U2A (TP2) is as close as possible to 825mV (825mV across R18 (0.33Ω) is 2.5A output current).  It may be possible to increase the output current to 3A (990mV reference voltage), but you would need to add another series pass transistor to keep the transistors within their SOA at minimum voltage and maximum current.  Some ripple breakthrough at maximum output (voltage and current) is likely unless you add more capacitance (C1).

When in voltage mode, U2B compares the reference voltage from VR2 with the voltage at the output, reduced by R16, R11 and VR3 (voltage preset).  If the output falls due to loading, U2B increases the drive to the output series-pass combination (Q3, Q4 and Q5) to maintain the desired voltage.  The upper output voltage limit is imposed by the opamp (U2), which can't force its output to much above 25V with the typical output current of around 2mA (this depends on the gain of the output section, Q3, Q4 & Q5).  Note that the reference voltage is itself referred to the negative output terminal - this ensures that the regulator will correct for any voltage drop across R18.  If it were otherwise, regulation would be badly affected, especially at maximum current.

Note that the heavy tracks are critical, and any significant resistance in these sections will upset the current sensing.  Also, be aware that the points indicated with a 'ground' symbol are marked 'Com' (Common).  They are not connected to chassis or any other ground.  The 'Com' designation means only that all points so marked are joined together.  Also note the diodes with an asterisk (*), which must be 1N5404 (3A continuous) or better.  All other diodes are 1N4004 or equivalent (other than the 25A bridge rectifier of course).  Bench power supplies often get connected to 'hostile' loads, and the high current diodes (D8 and D9) are to protect the supply.

The supply uses 'low side' current sensing, so it needs some tricks to use it as a dual tracking supply with both positive and negative outputs.  The current sense resistor (R18) is a compromise between voltage drop and dissipation.  At maximum current (2.5A), R18 will dissipate a little over 2 watts, which is easily manageable using a 5W wirewound resistor.  Both voltage and current regulation are very good (at least according to the simulator), and there's no sign of instability.  In theory (always a wonderful thing), the current can be regulated down to a couple of milliamps, but in reality it will not get that low.  Expect around 50mA or so, but it might be a bit lower than that (depending on the opamp's own DC offset).  Another trimpot can be added to correct for opamp DC offset, but it shouldn't be necessary (and adds something else that needs adjustment).

All of the alternative versions specify a single 2N3055 for the output, but with a shorted output and maximum current, the dissipation will be about 80W, and maintaining the series pass transistor(s) at 25°C will be impossible.  The TIP35 devices have a higher power rating (125W) and a good SOA (safe operating area), but there is still a case to be made for using three, rather than the two shown.  The BD139 also needs a heatsink, but a simple 'flag' type will normally suffice.  In common with any transistor that dissipates significant power, excellent thermal bonding to the heatsink is essential, and you will need to use a fan.  This can be thermostatically controlled, and can use PWM (pulse width modulation) for speed control, or it can just turn on and off.  Figure 8.1 shows a suitable circuit for both operating the fan and shutting down the supply if it gets too hot (which in this context is no more than 50°C heatsink temperature).

The original article has many more information and useful add-ons. Read more here: https://sound-au.com/articles/bench-supply.htm

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There are others who are more qualified than I on this circuit but not letting ignorance stand in my way I will continue anyway.

In the various schematics U2 is connected to a transistor base through a 0, 22, or 1k ohm resistor. So it makes a difference which schematics you are referring to. At 1k the current from Q2 would be limited to 33v/1k or 33ma well within the 88ma max. of U2. Else for the 0 or 22 ohms I would wonder about diode D10 if it is shorted or not.

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Hi all,ive built this but have issues with current regulation,ive added another led as well fed frompin 6 of u3,its a dual colour led,fed fromq3 its red indicating cc and from u3 pin 6 its green indicating cv,when i load the output and turn my current pot ccw untill the led turns red,ie cc,i can still increase the voltage using p1,im using MC34071AP opamps,d9 is fitted good and works,any ideas?,also when in cc mode if i wind p2 ccw(its a 10k 10 turn pot,about 1/4 turn from the end the voltage suddenly jumps up by about 3 volts,thanks in advance.

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