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0-30V Stabilized Power Supply


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audioguru, I have an other question: does C1 have to be exactly 12000uF? I've found only 10000uF. Do I have to add two more 1000uF in parallel (or one 2200uF [?]) or the circuit will work without problems only with the 10000uF capacitor?

I selected 12000uF because it works best and is a common value. 10000uF will be almost the same.

How many uF is in your "10000uf" capacitor when its tolerance is plus or minus 20%? It might be as low as only 8000uF which might cause ripple when the output is 30V at 3A.
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It's because I already have all the parts, but the capacitor. Also in the country I live 12000uF capacitors are a bit hard to get. I could order one from Farnell, UK, but the delivery would cost me as much as the capacitor and it's not worth it.
Thank you for your replies, I will try with the one I can get. I hope it will be ok.

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hello. i am new in forum. i checked yesterday almost all 118 pages and i have to admit that you are all amazing. Audioguru you are doing really good job. I already built today 3A version (will upload pictures after testing it). I found also picmaster's Schematic and i am interested to build 5A version also. Can u point me where to find picmaster posts and part list. is there any forum where can i read about 5A project?

thanks alot for answers

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Hello Gentlemen,
good night in the first place!
I am writing this post because I'm riding the circuit posted by PicMaster (30V and 5A) and would like to know one thing, it would be possible to change the tle2141 by the TL081, because it is easier to find here in Brazil.
I appreciate everyone's attention.

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I am writing this post because I'm riding the circuit posted by PicMaster (30V and 5A) and would like to know one thing, it would be possible to change the tle2141 by the TL081, because it is easier to find here in Brazil.

No, because it is completely different.
The TLE2141 and MC34071 opamps were selected because:
1) Their max allowed supply voltage is 44V and they do not need a negative supply voltage. The TL081 max allowed supply voltage is only 36V and they need a huge negative supply voltage.
2) The inputs of a TLE2141 and MC34071 work at 0V when there is no negative supply. The inputs of a TL081 do not work if they are within 3V from the negative supply which is +3V with no negative supply.
3) The output of a TL081 has a problem called "Opamp Phase Inversion" where the output suddenly goes high if the input voltage is too close to 0V with no negative supply.
4) The TLE2141 and MC34071 are inexpensive and are available anywhere in North America.
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I copied your schematic from PhotoBucket because it is too small here.
Even at PhotoBucket it is too small because its parts are spread apart too much.
I tried to enlarge it but then it was too blurry.
Its very low contrast makes everything look faint. I increased the contrast and it looks much better but it is still too small to read.


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sorry but i CAN NOT attach any image or anything on this forum

It is simple to attach a schematic to your post:
1) During your reply, click on Additional Options.
2) Click on browse and locate the schematic's file on your hard drive.
3) Click on the file then click Open and it will be placed in the Attach box.
4) Post your reply then your schematic will be attached here.

Can't you increase the contrast since now it is pastel and pastel and is hard to see?
Can't you place parts closer together on the schematic so that all parts will look bigger?

Your new image that was linked looks better but it still lacks contrast.
Its parts are still far apart so it is huge which makes the parts too small. When enlarged it bigger as my neighbourhood since the parts are blocks apart.

Sorry but I can't spend hours scrolling through your huge schematic.

Here is the difference between its original image and the same image with contrast added:


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I can't read his schematic because it is fuzzy and has no contrast. If he draws the parts closer together then the schematic can have larger parts which will look clearer. Then he should increase the contrast.

I guess that RV3 is a variable resistance trimpot in series with the current pot.
Maybe you also cannot read his schematic then you have a resistor value wrong.

The current sense resistor is 0.47 ohms for the 3A power supply and is 0.27 ohms for the 5A power supply. 3A x 0.47 ohms produces 1.41V and 5A x 0.27 ohms produces 1.35V.

Adjust RV3 so that the slider of the current pot is 1.41V at a load of 3A or is 1.35V with a load of 5A. Then any more current will cause opamp U3 to reduce the output voltage which will regulate the current.

Maybe your opamps have different part numbers than the two that the revised circuit uses?
The negative supply for U3 is only -1.3V. Many opamps will not work with a negative supply that is so low. If you increase the negative supply voltage then opamp U2 will have too much total supply voltage which will cause it to fail.

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I built it, it works, but it doesn't work correctly. Input voltage on C1 rises up to 57V!!! And I don't know why. Is it because R1 has 22k instead of 2.2k? The lady from the electronics shop messed up the values.
Output voltage varies from 0-30V, though. Should I be worried about the input voltage?

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