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0-30V Stabilized Power Supply


redwire
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Okay sir, I will add an external power supply for the meter.

1. I really can't get a hold of these new op amps. I searched online, and found uA741CP Op amps, is it a good sub?

2. Also, I was thinking of connecting the center tap like the attached image, since it's easier to get a hold of a center tap transformer in our area. Would this work? 

3. Did anything change from the original schematic? I am trying to redesign the board to accommodate the updated parts list. 

Thanks. 

CT.JPG

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Motorola/ON Semiconductor and Texas Instruments opamps are available everywhere. I buy them from Digikey and Newark. Newark has recently been bought by Farnell who have warehouses all over the world. Go to their website and click on the flag of your country or a neighbouring country.

 

The very old LM741 is the same as a very old uA741 and they will not work with the updated parts list.

 

if your meter needs a completely separate power supply then your idea using a center tap will not work. 

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  • 3 months later...

I've built a power supply using this circuit. I noticed that it is noisy/oscillating when in constant current mode. When probing the circuit I see this oscillation on the current sense op-amp. Has anyone else seen this? Not a big problem for me as I'll probably only use CC to keep from letting the smoke out while testing a project :) It'd still be nice if I could fix this problem. I've mostly worked with digital electronics & embedded programming. My analog circuit skills are not the best. Any help would be appreciated.

 

Attached are two scope captures of the supply output. One in CC and the other in CV mode.

PS-CC.bmp

PS-CV.bmp

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I've built a power supply using this circuit. I noticed that it is noisy/oscillating when in constant current mode.

It is 60Hz from your electricity supply, not oscillation. Maybe you built the defective original circuit that has errors and many overloaded parts? The fixed and improved version is at the beginning of this thread. Maybe the tiny overloaded rectifier diodes failed or the transformer has burnt. The main filter capacitor has a value much too low. The original project cannot produce regulated 30V at 3A but maybe 25V at 3A instead or 30V at 1.5A. The original opamps are operating at a total supply voltage higher than their maximum allowed voltage and are noisy.  

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It is 60Hz from your electricity supply, not oscillation. Maybe you built the defective original circuit that has errors and many overloaded parts? The fixed and improved version is at the beginning of this thread. Maybe the tiny overloaded rectifier diodes failed or the transformer has burnt. The main filter capacitor has a value much too low. The original project cannot produce regulated 30V at 3A but maybe 25V at 3A instead or 30V at 1.5A. The original opamps are operating at a total supply voltage higher than their maximum allowed voltage and are noisy.  

 

I should have provided more information. I built the revised circuit that uses the TLE2141 op amps.

 

Also, the noise only occurs when in constant current mode. It happens regardless of the voltage or current settings.  I put a 100 ohm load on it with the voltage set to 10V. (100mA load). As I adjust the current set pot the noise increases as soon as it goes into constant current mode. Very similar to the scope traces I posted before. These were with the supply running at almost full load current. Also, I had 24VAC transformers available. With this transformer it will only maintain voltage regulation at full load up to a little more than 24VDC. I don't think this will cause any problem. I just set that maximum voltage adjust pot for 24V. So, I really only have a 0-24V supply. And finally the currennt regulation is working. It will maintain constant current. It's just noisy.

 

It'd be interesting to know if anyone else has scoped the output of their supply. Is there any difference in noise from CC to CV mode. If not then I need to find out what's causing the problem with mine.

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Your interference is 60Hz but the fullwave rectifiers produce 120Hz so maybe your rectifiers are defective?

60Hz hum pickup from the wiring in your home? 60Hz picked up by a see-through diode (like a 1N4148) in the circuit being shined on by an AC light and acting like a photo-diode?

 

You know what? The current regulator opamp is the only one using the -1.3V supply that is half-wave rectified so if C3 is defective or is upside down then it produces 60Hz interference. 'scope the -1.3V supply to see.

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You know what? The current regulator opamp is the only one using the -1.3V supply that is half-wave rectified so if C3 is defective or is upside down then it produces 60Hz interference. 'scope the -1.3V supply to see.

Great job! I'd checked the positive supply and it's ripple was low. I forgot to check the negative supply. The negative supply has a lot of ripple. Now to troubleshoot that problem & get it fixed.

 

Thanks a bunch!

 

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  • 1 month later...

Hi there. I assembled a kit of the v1 of this power supply and did a stupid mistake: I wasn't paying attention and I powered the board through the output, so 24VAC went trough the protection diode and smoke came out, I disconnected as fast as I could but damage was done. First I thought that only the diode broke so I replaced it and powered it properly but it doesn't work properly.

The voltage adjust works fine all  the way from 0 to the top range. The problem arises when I connect a load to the output. then the voltage drops to under 2V

I started troubleshooting the circuit with U1 and I get the output voltage of 2x5V1 which is  the zenner diode used by this kit. Also on the negative rail uses the same zenner diode and the voltage is 5V1. Then I removed U3 and disconnected the reverse series diode D9 that makes the connection from the current regulator side to the voltage regulator side so that only voltage regulation is active. The problem remains the same, loading the output with significant load (1R / 10R) makes i drop to under 1V. I then proceed to replace the transistors and even let only one of them, the 2N30055 in place to eliminate more components.

I have gotten to no result. I can't think of anything else that the op-amps to be damaged.

Any thoughts? Thanks

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The voltage regulation is provided by the reference voltage of 10.2V from U1, opamp U2, a driver transistor and an output transistor. The transistors are simple emitter-followers. then a few quick voltage measurements of the output with the malfunctioning occurring will show you what has failed.

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Yes indeed, I fixed the V pot to ~2V (at pin 3 of U2) which gives me an output of 6V (at pin 6 and main output), when I'm connecting the load the output drops to near 0V, and the output of U2 goes high (~9V from 12V supply) while the input voltage stays the same.

I removed everything although I can't seem to find it easy to figure out because the U2 op-amp has a feedback loop and while I suspect that the op-amp is broken and i have to replace that next, I'm also thinking of some adjacent components like the small capacitors.

EDIT: I discovered that I had the diode D9 damaged, acting like a short. Removed it and the output now drops only a few volts when connecting the load.

FInal EDIT: I've put everything back on and it works ok. The problem was that shorted diode. Thank you for helping me.

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  • 1 month later...
On 10/20/2015 at 6:46 PM, liquibyte said:

Many, many questions keep getting asked about this thing and people keep attempting to build it without even knowing the basics, why I don't know.  The power supply suffers from a couple of issues that have never really been adequately addressed so this is going to be my attempt at bringing this thing into the modern age.  What follows is just preliminary work to right several wrongs I've noticed with the design.  It's not complete but I'm posting it to get opinions and suggestions.

This paragraph is for the newbies:  DO NOT ATTEMPT TO BUILD THIS YET.  If you don't know what you're doing, do not even try and breadboard this.  Once I have a final design, I promise that I'll post it.

Now, onward.  I'm posting my spice simulation for anyone that wants to try and give this a go.  One of the things that concerns me is the power dissipation in the op amps but I'm not sure how to get this down to a more acceptable level because I don't think 150mW at load is very good so suggestions are most welcome.

First, the voltage reference in the old version was an extremely odd thing to me so what I wanted to do was get a precision reference in there to work with.  10V seemed like a nice round number so that's what I went with and I actually have one on hand to use.

Second, the sense resistor.  0.47 ohms?  Once again, odd.  Plus, it suffers from extreme power dissipation as well.  My idea is to have a nice 0.1 ohm 3W 4 wire resistor in there to hook a meter to so I adjusted things around the reference to get me to where I wanted to be and I also have some of these.

What I'd like to eventually do is design the meters along with the supply so that what we end up with is a relatively complete project with all the nice bits people seem to be after.  No one, I repeat, no one ever offers a suggestion as to what to build to replace this, not one single engineer.  They will, however, be the first people to tell you how bad the design is but never offer any sort of advice as to why.  I know, I've asked and so have many other people.

0-30V-0-3A-redesign.zip

0-30V-0-3A-redesign.png

Hi liquibyte,

Did you ever progress this project? Did you solve/test the power on transient issue that is mentioned elsewhere in this thread?

Thanks for your help

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  • 4 months later...

I finally have my power supply finished! It's on the shelf! I'm doing some full power tests.

I Started with a pair of the Chinese circuit board kits.  Lucky that I found this thread. I made the mods to the boards and added higher power components and  PWM fan control.

My transformers have multiple primary voltage taps. I Used a comparator to select a higher transformer input voltage tap when the power supply  output voltage is low. This greatly lowered the power Dissipation. With commercial power supplies this transformer voltage selection is done on the secondary of the transformer.  With the transformers that I got for free, I could only switch primary winding taps. This required triac switching circuits.

Pictures are attached.

 

PS4 001s.jpg

PS4 002s.jpg

PS4 004s.jpg

PS4 006s.jpg

PS4 007s.jpg

PS4 009s.jpg

PS4 010s.jpg

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  • 3 weeks later...

Hello all,

A lot of reading here and much more to learn. Also have the Banggood power supply board, still in the bag though - will likely stay there.

Have ordered PCB's at Elecrow from Gerber files provided by Liquibyte. So, thank you very much Liquibyte.

10PCB + shipping = US$ 18.50 that is about AUS$ 25.00

Since I have a 24V Toroidal already I will have to settle for a 25V 3A power supply. That is fine for me as it is more important

to build it.

Thanks to all here.

Regards, William

 

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  • 4 months later...
On 06.09.2015 at 8:27 PM, James Bond said:

Hi everyone

Sorry my bad.

There go the schematic and the error. 

I joined the Proteus file too, so you can test it if you have Proteus. 

Best regards 

 

P.S::

Can i change TLE2141 by MC34071 without any problem?

My goal is controll the PSU using arduino, but need put its to work first :)

Final.pdsprj

erro1.jpg

Schematic.jpg

 

On 06.09.2015 at 8:27 PM, James Bond said:

Hi everyone

Sorry my bad.

There go the schematic and the error. 

I joined the Proteus file too, so you can test it if you have Proteus. 

Best regards 

 

P.S::

Can i change TLE2141 by MC34071 without any problem?

My goal is controll the PSU using arduino, but need put its to work first :)

Final.pdsprj

erro1.jpg

Schematic.jpg

 

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  • 2 months later...
  • 1 month later...

@mars

Hi there,

Look at Page 87 and 88 posts from Liquibyte and you will find PCB, schematic and gerber files to make a nice power supply that will work.

How would I know you might ask. Glad you asked. I have had PCB's made from those gerber files and built a power supply. And it works well.

Look here for my post:

"electronics-lab.com/community/index.php?/topic/40835-0-30v-0-3a-latest-data/&page=2"

All credit goes to member Liquibyte. Thanks a lot Liquibyte for making all files available.

Many thanks also to those who were actively involved in this thread and helped improve the original design.

Hope that will answer your question.

PS. I f you want to built one like I just mentioned, I still have some PCB's left. I only ask AU$2.50 per PCB plus shipping to your country in an envelope.

 

Cheers, William

Edited by repairman2be
Added more info.
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  • 2 weeks later...

Hi Liquibyte,

I have bought two of your PCBs from repairman2be (rev. 8.), awaiting them any day now. I have studied the schematic pretty thoroughly and tried to read up on the threads.
Very interesting, and good to have something educating to do with my time :-). So far I have one question that I can't find a comment on in the forums.

First, let me introduce myself. I'm a Swedish 30 year old mmWave/μWave/RF engineer (read: allergic to noise) and I just had a second son so I had to find something to do all the nights I stay up taking care of him. Designing a PSU seems like a good choice!
It started with me realizing that I today financially can handle some of the ideas I had when I was 20, now time is more of an issue instead. But hey, it doesn't matter if it takes time to reach the finish line.

I always wanted to build a boombox. I thought a good place to start was to design a PSU (to not waste battery when a socket is available) and a relay-circuit. I read up a lot on audio PSUs and actually designed a linear 10-18V, 10A supply, and hand drew the breadboard and everything. When I saw the end-price I reconsidered. This PSU is kinda useless for anything but the amplifer, it's better to have a 0-30V supply I can use for lots of things. Especially considering I have no use for or place to store a boombox. The reason I'm saying this is that I might be tainted by audiophiles in my way of thinking :-). That I'm tainted by my RF-world at work I don't see as a problem, RF is probably what I'm going to use it for.

Then I found this design and got interested. But I still wanted it to be able to run the amplifier I had in mind for the boombox, which is something like 14V/6A. I considered paralleling two of these or use a LM723 regulator. I ended up with the idea of two 0-15V LM723 PSUs which I can parallel connect for  0-15V/0-10A or series connect for 0-30V/0-5A. I was pretty happy with this idea and started designing. However, I couldn't get the current limit to work as nicely as I desired for a bench PSU.
Then I came back to this design, and here I am now.

I'll start with building your 3A design pretty much identical to yours. To be able to do some measurements and see how it behaves before I try to improve it :-). After that I will start designing my own board. I'll probably stick to 3A or 5A for a while, if I need an amplifier PSU I'll design it for that purpose. 
My ideas for improvements is to reduce the voltage drop a little, have a look at the negative supply (it hurts my eyes that it doesn't load both lines symmetrically). If I reduce the voltage drop and feel that I can't find an optimal transformer I might reduce the output voltage a little. I feel 30VAC is a little too high and 24VAC apparently is not enough so there is some unused power wasted there. We will see how it goes.

For later I might also take up the idea of LT1236 as reference. We will see. First I believe I have some startup transients to deal with!

So, now to my question:
Your R9 (original R17), is 68 Ohm. The original design says 33 Ohm but you changed it to 68 Ohm. Why did you change that? Have you found some issues with stability if it is too small? The reason I'm asking is that if I lower the current sense resistor I might want to increase this. Maybe I'm doing this wrong. I calculate the original design to give a minimum current limit of 10mA (while it says 2mA in the description), and your gives 20 mA.

Edit: I found the change, it was just to get the voltage divider to give the correct minimum voltage. However I'm still confused, but this can probably anyone answer. It should be simple. I don't get the formula for the current limit.
If we have a minimum of 5mV at the non inverting U3 input, that should allow for a 5mV drop over the current sense resistor right? That's 10 mA... Not 2..

Edit2: LTSpice seem to agree with me...

 

I might have more questions but I'll search and think a little more before I speak :-)

 

Best Regards

Björn

Ps. Thanks for the pdf with QA and other useful info. Would have saved me some time if I read that before I started study the circuit. But imI might learn it better by figuring things out on my own.

 

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Audio amplifiers do not need a voltage regulator or a current regulator. A car radio amplifier is powered directly from the car battery with no voltage regulator but the low current radio parts might use a simple little voltage regulator.

14V at 6A is 84W!  One amplifier produces a maximum output of 16W into a 4 ohm speaker then 4 channels make 64W. If all 4 amplifiers are producing 64W then if they are linear they heat with an additional 36W and the current is 7.14W but it does not need to be regulated.

 

 

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Yeah but it's a lot cheaper to use a regulator rather than quality caps to get rid of the 100 hz ripple :-)

Plus I could make sure it runs on 14 V regardless of load (volume, usb charger etc) and temperature!

The two amplifiers I had in mind were 45W and 50W into two channels, with losses and other functionality I estimated 6A.

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I could add that when I was looking for a suitable amplifier I didn't know electronics-lab even existed. So I just browsed for the most suitable class d chip and went on from there :-)

It was when I gave up on the 14V PSU idea because of a stronger need for a lab PSU that I found this design and this place!

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Hi  Repairman

I am interested in Liquibyte Rev-8 PCB.  Do u have any left?

How to go ahead about ordering from u?  Any idea on the shipping costs from ur location to India (Kerala\Trivandrum )?

I understand u are charging 2.5 AUS$ per PCB. I want to know total costs before commiing.

rgds

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