Convert 0-30V 3A PSU to 5A or more

[Kain]

I know that this is a bit out of topic since it is not directly related to the PSU, but can anybody here suggest a good CAD to draw a cover label for the face pannel of the PSU? I finally put it together - now it is going all the way to 30V/6.9A with fan cooling. The ripple problem is solved - audioguru was right about the proper star grounding technique. I shortened all wires as much as possible, and avoided crossing them too to avoid inductive coupling. After I make the label I will post the picture of the final result which I think looks quite nice even now (and works quite nice too

 

[Kain]

Ok, I finally managed to blow this PSU up. I burned Q2 and it was quite obvious since R15 begun to smoke. The output current was 7A at 2V when this happened. Any idea why it burned? I haven't replaced Q2 yet, and I don't wan to if it is going to burn on me again since this is not a fix obviously. I still coldn't figure out how i burned Q2 neither... The datasheet says that the max collector current is 3A. I think I haven't reached this value.

 

[audioguru2]

Ok, I finally managed to blow this PSU up. I burned Q2 and it was quite obvious since R15 begun to smoke. The output current was 7A at 2V when this happened. Any idea why it burned?

Oh, oh. If Q2 has a pretty good heatsink then it should be fine.
If the three 2N3055 transistors have minimum gain of 32 at 7A/3, their total base current is only 219mA. Q2 will have about 39.2V across it when the output voltage is 2V so dissipates only 8.6W. With a "perfect" heatsink a TIP31A is allowed to dissipate 40W.

 

[Kain]

I actually found the problem. As I said I was assembling the PSU and what happened was that one of the 2N3055 was not hooked up correctly. I exchanged the base and the emmiter so when I loaded the PSU on 7A I blew all of the 2N3055 transistos and the TIP31A one (Q2). I think I might have blown something else too. I haven't placed the parts back yet but I am getting maximum output on pin 6 of U2 - no regulation possible. I replaced the chip too and result is still the same. The output on pin 6 U1 is 11.2V so I think this is acceptable. U3 is working fine too. U2 is acting like this even without Q2. Any idea what else might be blown? I was thinking Q1 maybe.

 

[audioguru2]

I actually found the problem. As I said I was assembling the PSU and what happened was that one of the 2N3055 was not hooked up correctly. I exchanged the base and the emitter

A good way to blowup stuff.

I am getting maximum output on pin 6 of U2 - no regulation possible. I replaced the chip too and result is still the same.

Without the transistors then the feedback will normally force the output high.

The output on pin 6 U1 is 11.2V so I think this is acceptable.

That is normal.

Any idea what else might be blown? I was thinking Q1 maybe.

It is probably OK. It is used only for a moment when the power is turned off.

 

[Kain]

Ok, I thought so about the feedback but wasn't sure - no enough time to analyze this circuit anyways, but this is why we have Audioguru here  ;D! I measured the negative input of U2 and it was quite enough to force the output to max so it does make sence. I am about to replace the 3 power BJTs now. Hopefully i won't see the smoke again... :

 

[Kain]

Alrighty, I assembled the machine and it is fully operational now. The unit was tested again 3 days ago in my university and the results were more than satisfying - ripple under 6A load was merely 2mV and I am not sure if that wasn't partually scope noise. On any other working modes the ripple is less than 1mV. The maximum current I got out of it with dead short output was 6.97A. I will take few pics soon and post them too since I put the effort not to only get it to work well but to look well too. People in school nearly freaked out when I got to 6A without problem, and it is not surprise given the fact that the lab PSU's that we use are limited to 1.5A

 

[audioguru2]

6A with hardly any ripple is pretty darn good! ;D

 

[jasssam]

Hi I found The website conver 0-30 V

http://www.elec-micro.com/electronics--circuit--Power%20Supply%2030V%20Converter.html

in this circuit he use IC-CD-1846P

 

[gogo2520]

Hello
      I have been reading this thread for awhile and I just have to ask jassam where can you find the ic CD-1846P. I did a web search and couldn't even find a data sheet on that ic let alone a source to buy one. There are a few sites that show the circuit you posted buts thats about it. Maybe it goes by another name.
                                              Let Me Know
                                              Thanks gogo

 

[audioguru2]

I recognised the broken English accent to this Japanese site:
http://hobby_elec.piclist.com/e_ckt28.htm

The IC is really an obsolete module that was found in a junk shop.

View attachment 38795

 

[cedeal]

hi,
  you are all building this PSU,and you ?

 

[audioguru2]

hi,

 

[Kain]

Ok, here are pictures of the completed PSU. It is now set at 12V on both sides as one can see on the picture. The fan on the top cover is pushing air in the case causing circulation. The air gets out from both sides - left and right as it cools down both h/s. The fan is actually temperature controlled - it senses the temperature of each of the h/s... The PSU also starts up with a delay - I am passing the start up inrush current through a resistor in series to limit it down otherwise the fuses blow up. That is pretty much all. The info about ripple and so on I already posted. I'm happy the project is finally finished

View attachment 38877

View attachment 38878

View attachment 38879

 

[audioguru2]

Hi Kain,
It looks great! ;D

 

[ante1]

Hi Kain!

Holy Cow! 
An outstanding job, you must have put quite a few hours in this one!
I am sure most of our members would like to have one just like it!

 

[Kain]

Thank you both Audioguru and Ante, and Ante you are right - I did put quite some time into it. I love the results though  ;D

 

[ante1]

Thank you both Audioguru and Ante, and Ante you are right - I did put quite some time into it. I love the results though

 

[MP1]

Yes I can really appreciate that, you have every right to be proud!

Yes, you certainly do. It is really nice to see a project come together like this. Congratulations, Kain!

MP

 

[Kain]

Thanks MP