0-30V Stabilized Power Supply

[bugmenot1]

So, Audioguru I understand that have more to modify in the original project. I only want to save my original project, make the mods to make it more confiable... I'll make the mods sugested from Ivan and change the watts of some resistors too with your guidance  ;D off course, hehehe. The 2N2219 in my project ahs a heatsink appropriate for this package, and I want to put a fan in the PSU, the LCD meter module has a control for a fan with a mosfet, it power the fan when the load is heavy duty, I think...  .
Can you describe, please, the all parts I have to modify? resistors watts, etc...
Here the pictures of my original project and the LCD module... After I post inside pictures of it ok?

View attachment 40916

 

[audioguru2]

Hi Bugmenot,
Why not make the latest circuit? It works very well. It is not changed much from the original, all parts operate within their ratings and the opamps are available nearly everywhere.

Ivan simply reduced the positive supply voltage to the opamps then the max output voltage is low but the heating is still very high.

What about the transformer? The transformer in the original project and the one in Ivan's circuit is overloaded at max output from the project.

 

[bugmenot1]

Hi AudioGuru, it's because the iginal PSU is already assembled and working, with this limitations, off course... And I want to make it more reliable.
I'll build the 5A RedWire version too, I already make the PCB for it and i'm waiting for the parts...
The transformer I use in the original version have a secundary of 26V at about 3-3.5A. In this PSU I don't need the 30V in the output, ok? So I can use this transformer... In really In this PSU I need less than 30V! If it is the case I  can rebuild the secondary, but In this PSU I think i'nst the case because I need less than 30V as I said before...
I Hope you can understand me... and help me! 
I am at your disposal.

 

[audioguru2]

Hi Bugmenot,
Here is a parts list that I made a few years ago using bigger resistors. It uses a BD139 for Q2. It uses high voltage opamps but you can use TL081 opamps from the original project and the voltage reduction circuit used by Ivan.

View attachment 40917

 

[bugmenot1]

For the original PSU I build can I make the Ivan proposal's (2nd 2N3055, bigger capacitor and 27 V for the opamps) and increase the resistor W's? I don't want to make another PCB for this PSU. And how can I effectively know the real PSU output or the Transformer output? How can I make this test? With a car light bulb,  a shower resistence, resistors or other method? Any Tips?
Thank you.

 

[audioguru2]

Use Ivan's proposals if you want.
The transformer has a listed voltage and has a max allowed current. Multiply them to calculate its max allowed power.
The peak voltage of the transformer is multiplied by the max current from the project to calculate the actual power from the transformer. The original project does not have its max current calibrated so it is much too high and is well above 3A.

Don't test with a light bulb because when cool its current is 10 times or more higher than when it is incandescent. Use a heater as a load.

 

[Erivanst]

Here the pictures of my original project and the LCD module... After I post inside pictures of it ok?

Hi everyone!

Bugmenot, could you please post some information about the LCD meter that you cited?
I

 

[bugmenot1]

Hi Erivan!
It's the meter proposed in the main page of the project, but in DIP version.
http://www.electronics-lab.com/projects/power/001/index.html (someone change the link)
Check the page of the author of the LCD meter:
http://www.elfly.pl/multimetr/multimetr_en_DIP.htm

 

[bugmenot1]

http://www.electronics-lab.com/projects/test/022/index.html

 

[Erivanst]

Hi Erivan!
It's the meter proposed in the main page of the project, but in DIP version.
http://www.electronics-lab.com/projects/power/001/index.html (someone change the link)
Check the page of the author of the LCD meter:
http://www.elfly.pl/multimetr/multimetr_en_DIP.htm

Ok, Bugmenot. Thank you. This is one of the eschematics that I was looking. Good to know that you have build it. Didn

 

[PicMaster]

Just a quick question
Is there any reason why you could not use the quad vesrin of the TLE2141 instead of the three op-amps, Or would this have the effect the operation of U3 ?

 

[ELI1]

Hi,
can i use MC33171 instead of 34071? I compared datasheets and i think it is possible, but i rather ask.
For me is much easier to get MC33171 in local store...

 

[audioguru2]

Just a quick question
Is there any reason why you could not use the quad vesrin of the TLE2141 instead of the three op-amps, Or would this have the effect the operation of U3 ?

The opamps will not affect each other in a quad package but it might overheat.

 

[audioguru2]

Hi,
can i use MC33171 instead of 34071? I compared datasheets and i think it is possible, but i rather ask.
For me is much easier to get MC33171 in local store...

The MC33171 is low power like an old LM324 but is improved.
Therefore its output current is too low, its bandwidth is too low and its slew rate is also too low.

 

[PicMaster]

The opamps will not affect each other in a quad package but it might overheat.

But looking at the schematic U3 if feed by +10V -1.3V supply if I'm looking at correct and U1,U3 are fed form the high plus side of power supply(41V), I was not sure if this would affect the operation of it if it all was in one chip which would maje a smaller neater design well I think so any way

 

[audioguru2]

The output of U3 must go up to at least 11.9V so its positive supply must be at least 13.1V.
U1 needs a positive supply of at least 12.4V.
U2 needs the full positive supply of about 41V. 

 

[ferespo1]

Hi

My name is Fernando and I'm from Argentina.

First I would like to thank you all for the quality of the discussions and specially to Audioguru and RedWire  for the excellent job regarding the new PS design.

I have built the new version and I'm very pleased with it (btw, I built the old version too, but I use it nowadays as spare one for low power circuits only).

Some thing that I'm concerned about is power dissipation. I use one heat sink of 12 x 5 x 3 cm (about 5 x 2 x 2 1/2 inches) for each Tr  plus a salvaged fan from a PC PSU. So far all is well (despite the death of a power transistor and consequently the death of a power led during testing) but I'm worried about delivering 3 amps at say, 5 volt.

So here is my question.

I've read in this forum (I think it was Hero999) about tap changing as a way to reduce heat.

In fact, the transformer that I got has two secondaries: one at 30V and the other at 9V (it used to power a huge dot matrix printer).

I tried to google a tap changer circuit but to no avail.

Does anyone know how to do it? I thought about using a SCR but sadly, at least for now, I lack the knowledge to face such a task.

Thank you all

Fernando

 

[noworries2004]

HI
I am currently constructing the updated version of this power supply,
I have a fwe questions about this power supply.
Q1 ; What happens when current limiting kicks in, does the output voltage drop or does it stay steady. If current limiting is then does this mean that the power supply is a constant current source rather than power supply.

Q2 ; What is the output regualation of my power supply. Input transformer is 31.6 V AC.

Also what is the rated load of this power supply.

Thanks for your time especially redwire and audioguru.

Cheers

 

[audioguru2]

Q1 ; What happens when current limiting kicks in, does the output voltage drop or does it stay steady? If current limiting is then does this mean that the power supply is a constant current source rather than power supply?

It doesn't have current limiting. Instead it has current regulation (constant current source) which is more exact.
Ohm's Law says that the voltage must be reduced for the current to be regulated when the load resistance is reduced. For example if the voltage is set to 30V and the current is set to 1A and the load is 15 ohms then the output voltage becomes 15.0V because the current is still regulated at 1.0A.
The LED lights to warn that current regulation is reducing the output voltage.

Q2 ; What is the output regulation of my power supply? Input transformer is 31.6 V AC.

Its error amplifier consists of U2, Q2 and Q4. Its open loop gain at DC is about 200,000 so the output voltage drop from no load to 3A is a few milli-volts depending on the resistance of the output wiring.
At high frequencies then the circuit gain drops but the smoothing effect of C7 produces good voltage regulation.

What is the rated load of this power supply?

3A or less at 30V or less. The heatsink must be pretty big or have a fan because if the output voltage is low or shorted and the current is set to 3A then the output transistors will have about 38V across them x 3A= 114W of heat that must be dissipated.

 

[noworries2004]

Thanks Audio guru,
With regards Q1 from last comment would this graph be a fair reflection of what happens when current regulation kicks in?

View attachment 40937