0-30V Stabilized Power Supply

[audioguru2]

just replaced R2 with higher watt, 5W and C2 with branded one still -2.1V with full load. output still stuck at 28.5V.

The opamps should draw only a small amount of current from the negative supply. Your U2 or U3 opamp draws too much. Find it and look at how it is connected wrongly.

R7 because i have difficulties to find one so i use 4 1Ω parallel is it problem?

R7 should be 1.92V/3A= 0.64 ohms. The original project had a max putput current of 1.92V/0.47 ohms= 4.1A which is too high.
We use 0.47 ohms then calibrate for a max current of 3A.
With 0.25 ohms then your max current is 1.92V/0.25 ohms= 7.68A which is much too high.

 

[audioguru2]

Why do not use cheap LF356? I have one channel power supply made with those OPAMPs and works great. I think, that those are good alternative for MC34071 and TLE2141

The MC34071 or TLE2141 opamps are used in the latest version because their max allowed supply is 44V and their inputs work at their negative supply voltage which is 0V for U2. these opamps do not need q1 to short their output when the mains power is turned off.

the TL081 opamp in the original project and the LF356 that you are talking about have a max allowed supply of only 36v and they need a -5.6V supply because their inputs do not work if their voltage is close to the negative supply voltage. They need Q1 because they have the Opamp Phase Inversion problem.View attachment 40897

 

[audioguru2]

What's conclusion is about this modification:

Received the following email from Ivan on 02/2010

Maybe Ivan did not see our modified circuit.
The original project has many problems. It does not produce 30V at 3A (its max is 25V at 3A) and many of its parts get too hot so it is unreliable. Its little transformer is overloaded.

Ivan's modification is not needed because the transformer voltage could be reduced to do the same thing. The driver and output transistors are emitter-followers so with Ivan's 27V positive supply the max output from his project is only about 20V or less.

 

[halentech]

The MC34071 or TLE2141 opamps are used in the latest version because their max allowed supply is 44V and their inputs work at their negative supply voltage which is 0V for U2. these opamps do not need q1 to short their output when the mains power is turned off.

the TL081 opamp in the original project and the LF356 that you are talking about have a max allowed supply of only 36v and they need a -5.6V supply because their inputs do not work if their voltage is close to the negative supply voltage. They need Q1 because they have the Opamp Phase Inversion problem.

But LF356 has 44V power supply, so it is usable for this project. As I say, I used those opamps in this psu before and withouth problem at all.

 

[audioguru2]

The datasheet from the inventor, National Semiconductor shows the expensive LF156 with a max supply of 44V and the cheap LF356 with a max supply of only 36V.

View attachment 40900

 

[GabrielRR]

Hi audioguru,

After this suggestions made by you and the others, what's the best and final circuit. By the way and what about tesseract's circuit, it seems quite simple...

Thank's in advance

 

[audioguru2]

Hi audioguru,

After this suggestions made by you and the others, what's the best and final circuit. By the way and what about tesseract's circuit, it seems quite simple...

Thank's in advance

The best and final circuit has been posted here many times. It uses MC34071 or TLE2141 single-supply opamps.

Tesseract never said which version he used. He said he used three high dissipation output transistors for an output up to 5A.

 

[akademiker]

works awesome, thank you very much!

Next on my list: Upgrade to 8A version  ;D

P.S. use PTC! They limit the output current in case of a transistor melt down

 

[redwire]

Nice Job, Congratulations.

 

[bugmenot1]

Hi RedWire, this is your double sided PCB made with the toner transfer method. Soon I will make your 5A PSU version. I build the original before I see this forum... Now I will upgrade to the 5A version with samples of TI. I'll post the progress...

View attachment 40906

View attachment 40907

 

[bugmenot1]

Again...

View attachment 40908

View attachment 40909

 

[bugmenot1]

Hi, Can Audioguru comment the modifications suggested from Ivan in the main page os the original project? I would know if I can upgrade my original project and and make it great without change the PCB. I'll change some resistors Watts too.
Please help here AudioGuru. Thanks a lot. Best Regards.

 

[Hero999]

I like the way you've done the silk screen - I use the same method.

I notice there's a track that doesn't go anywhere and another track is broken; is that deliberate or a mistake?

 

[audioguru2]

Hi, Can Audioguru comment the modifications suggested from Ivan in the main page os the original project? I would know if I can upgrade my original project and and make it great without change the PCB. I'll change some resistors Watts too.
Please help here AudioGuru. Thanks a lot. Best Regards.

Where is "the main page of the original project"? please provide a link.
The original project had many overloaded parts including its little transformer. Its opamps operated at a total supply voltage that are higher than their max allowed supply voltage and even then the project did not have enough voltage to produce 30VDC at 3A. The main filter capacitor value is much too small.

 

[bugmenot1]

http://www.electronics-lab.com/projects/power/003/index.html

 

[bugmenot1]

Gi Hero999, Hehehe, there are 2 break tracks... one top and one bottom... ;D it's anxiety, but its fixed. I thought that nobody will notice... The tracks without a destination you have to ask to RedWire... I only change the bottom area for the ground... Thanks for comment.

Audioguru, the Ivan comment are in the bottom of the link of the project... Do you see?

 

[bugmenot1]

Ah I have to say this is my first double side PCB I made, so forgive any faults...

 

[bugmenot1]

...

View attachment 40914

View attachment 40915

 

[audioguru2]

Hi, Can Audioguru comment the modifications suggested from Ivan in the main page os the original project? I would know if I can upgrade my original project and and make it great without change the PCB. I'll change some resistors Watts too.
Please help here AudioGuru. Thanks a lot. Best Regards.

Ivan reduced the positive supply to the TL081 opamps to only 27V so they do not have a total supply that is higher than their 36V max allowed supply. Then his project will have a max output voltage of only about 22V or less.
His little 24V/3A transformer and many other parts including Q2 are still overloaded.

 

[bugmenot1]

I am also a little confused with some connections points in the RedWire PCB...connection point 4B, 4B1, 4, 4A...etc. Can redwire give some help?  ???