0-30V Stabilized Power Supply

[lighty]

Since your current regulator does not work then U3 or D9 are not working. Maybe D9 is open or is disconnected.
Maybe you messed up the connections to the current-setting pot or VR3.

Sorry Audioguru, I think I wasn't clear, the current limiting function is working when adjusting on the POT, but the VR3 "MAX" limit doesn't seem to be working. Since my transformer is only 125va, I need to limit the maximum at 3A prevent any damage.

 

[audioguru2]

Sorry Audioguru, I think I wasn't clear, the current limiting function is working when adjusting on the POT, but the VR3 "MAX" limit doesn't seem to be working. Since my transformer is only 125va, I need to limit the maximum at 3A prevent any damage.

VR3 is in series with R18 and the current-setting pot so it sets the max current before the current-regulation reduces the output voltage. The max resistance of RV3 is 100k and it is in series with R18 which is 20k so their total is 120k ohms. The original project used a total of only 56k so its max current was about 4.1A. With RV3 at 100k plus 20k in series for R18 your max current should be 2.06A.
If your RV3 is set at halfway to 50k then in series with R18 the total is 70k then the max current should be 3.35A. The current-setting pot should be 10k ohms. R17 should be 33 ohms. R7 should be 0.47 ohms.

 

[PicMaster]

You missed the second output transistor, the emittrer resistors for both output transistors and the emitter resistor for the driver transistor.

Thanks for that, I did for get to add the resistor to the BD139, The reason is I had the idea of having the BD139 and the ouput transistors and the emitteres resistors on a seperate board so they can bolt direct to the main heathisnk rather than have 2 heatsinks for them. I wll sort that out either add them to the main board or go back to the first idea,

 

[audioguru2]

Thanks for that, I did forget to add the resistor to the BD139, The reason is I had the idea of having the BD139 and the ouput transistors and the emitteres resistors on a seperate board so they can bolt direct to the main heathisnk rather than have 2 heatsinks for them. I wll sort that out either add them to the main board or go back to the first idea,

Then your schematic is confusing like Redwire's since parts not on the pcb are not shown.

 

[lighty]

The current-setting pot should be 10k ohms. 

:-[ Damn, I messed up again, I've used 100K on for the POTs and not 10K.....

Thanks Audioguru.....

 

[PicMaster]

Then your schematic is confusing like Redwire's since parts not on the pcb are not shown.

This is only the schematic I have a drawing explaining all the connections in detail, I t will be simple to follow, I'll upload the details in a short while

Picmaster

 

[lighty]

Ok, the POTs are working fine, just that when the current is turned down to 0, the limiting LED turns on, could this be because C7 is an electrolytic type?

 

[audioguru2]

Ok, the POTs are working fine, just that when the current is turned down to 0, the limiting LED turns on, could this be because C7 is an electrolytic type?

With the current-setting pot at minimum, a load of 12mA or more will cause current regulation.
Maybe C7 leaks as much as 12mA or more because it is connected backwards or because it is defective?

Opamp U3 is a TLE2141 with a max input offset voltage that is much too low to cause your problem. Maybe U3 is a counterfeit one or is defective?

 

[lighty]

With the current-setting pot at minimum, a load of 12mA or more will cause current regulation.
Maybe C7 leaks as much as 12mA or more because it is connected backwards or because it is defective?

Opamp U3 is a TLE2141 with a max input offset voltage that is much too low to cause your problem. Maybe U3 is a counterfeit one or is defective?

Cool, I'll try replacing it. I did notice when I was fiddling with the setting that the output dropped to about -0.3 V.

I think I will try replace C7 1st then test it again, perhaps the offset is way off?

 

[PicMaster]

This is the connections drawing for my version of the power supply and updated schematic, To me it looks quite simple
This is the actual size of the PCB and what the layout looks like.
The next thing is to update the component values on the schematic and create BOM
Hopefully over the weekend I shall get PCB made and assembled

POWER_SUPPLY_V2.pdf

power_supply.pdf

 

[PicMaster]

I've got it 3/4 built, I missed some parts off and by the time I thought about it Maplins was closed.

will try and get them tomorrow (Monday) then I will be ready for testing and if all goes well I will upload  the pcb

picmaster

 

[Scooter_3D]

Hi all, here is a rendering of the board im going to be making.
It is a similar in design to the original....

 

[PicMaster]

Here is the working version on my PSU, There is just just a couple of minor things I have got to look into and clarify. Yes the connecting wires may look a little on the light side but this is for testing only Has I only took to 3amps and calibrated max current for a few seconds to try.

These are the minor things that I have got to look into.
1. Because I'm using a 30V transformer the voltage is slightly to high feeding the op-amps has the TLE2141 is only rated at 44V I got 48V.
2. With the current pot set to Min the limit LED comes and and this restricts the voltage I have to turn it up slightly(not sure what the voltage is at the center of the pot has it is getting late.)

Aslo I'm not sure if this is normal if the limit LED should light up with the pot to min, I did disconnect C10 has if I remember lighty  had the same trouble but it is still the same

I get full control over the current range min current is about 40ma, I did see that is should only be 12ma, I will have to make sure that I've got all the correct components in place first and I will read through the older posts.

View attachment 41183

 

[audioguru2]

These are the minor things that I have got to look into.
1. Because I'm using a 30V transformer the voltage is slightly to high feeding the op-amps has the TLE2141 is only rated at 44V I got 48V.

A half-decent 30V/127VA transformer is 31V with no load which produces a positive unregulated supply of 42.6V. Since your unregulated supply is very high at 48V then either your transformer is poor or your mains voltage is too high.

 

[ultima2009]

Picmaster, can you upload the pcb and BoM?

 

[PicMaster]

Here is my vesrion of the power supply comlete.
PDF file is a new BOM(for this project only),PCB copper side, PCB overlay, assembly drawings

Please let me know if you find any errors or suggestions

Picmaster

 

[PicMaster]

I forgot to add the latest schematic to the PDF file

Picmaster

Schematic_Prints.pdf

 

[Skleb]

PDF file is a new BOM(for this project only),PCB copper side, PCB overlay, assembly drawings

I don't see any of these.
Please, can you upload PCB copper side?
Thanks

 

[mauriciovargas]

Hello guys. Firstly I have to say how you've helped me with this project. I've built the original project and it was such a fail...

So, I have a doubt: If I use a  24VAC/435 mA transformer on the audioguru's project (3A), it will work? It's all I have here

Brazil regards!

 

[audioguru2]

For 30V output, the transformer must be at least 28V.
For 3A output, the transformer must be 4.2A.
The power from the transformer is 28V x 4.2A= 188W.

The power from your tiny little transformer is 24V x 0.435A= only 10.4W which is 14 times too small.
Your transformer will power a project that goes to 25VDC at 300mA. If you do not change the value of R7 to prevent it from trying to go to 3A then either the transformer will get extremely hot then burn out or it might catch on fire.