4.5 to 25volt 15Amp power supply circuit

[irving2008]

if you have a source of those John... most of us don't... lol

[John S]

I do a lot of work for 3 rewind companies and they save me any dead ones, as do the inverter reps. Problem is now the cheaper versions have pressed steel heat sinks, you need the older ones for the best ones.

[der_fisherman]

Sounds interesting, tho if it was in Elektor its a copyrighted design... but you could post up the gist of it for information.... personally, with the cost of PSUs on eBay in the £20 region its hardly worth building you own in many cases... I have a 0 - 20v bench supply @ 5A I built 20y ago, when I had access to unlimited MIL spec parts lol, but hardly ever use it, since a fixed 5v and 12v supply suffices for most things PIC-based these days. Rarely do any discrete analogue stuff now....

The complete article is attached here. The PCBs are still available via the companies that Elektor uses themselves or you can get one made.
The reason that I build my own is that they are far simpler to repair if need be because I know how it works!!! Not that I have needed to up to now.
Bought Switched Mode Power Supply (ebay for example) examples are seldom supplied with a manual, nor are the parts always easy to find. Plus true SM Power Supplies are simply dangerous for the amateur, whereas the chips used in the Elektor design do all the clever stuff and the only dangerous part is the mains input to the transformer. So its far far safer.......
The supply is actually 2 x 5 amp chips, running in parallel at a high efficiency.
There are two resistors that need to be programmed to set the voltage required, as is, the power supply supplies 17 volts, not a useful voltage!!! One of mine is set for 24 volts another for 36. Both run with no problems at all.....
best wishes
Andy

[irving2008]

Thats a neat design, but its a bit disengenuous to say its not switched mode... it is a switched mode regulator, but I take your point that its not AC line level switching, therefore safer. That chip is good to 60v so a 0 - 50v variable supply at 5A (for a single chip) with low heat output is very possible, and using tapped inductors a 0 - 25v at 10A with a single chip is possible... interesting that the Elektor approach used two chips for 6A when they could have done it in one by winding their own coil instead of buyng off the shelf... think they missed a trick there... the chips are £9.24, the ferrite a lot cheaper...

However, it still doesn't overcome the OP's initial issue - the cost of toroidal transformers...

[der_fisherman]

Thats a neat design, but its a bit disengenuous to say its not switched mode... it is a switched mode regulator, but I take your point that its not AC line level switching, therefore safer. That chip is good to 60v so a 0 - 50v variable supply at 5A (for a single chip) with low heat output is very possible, and using tapped inductors a 0 - 25v at 10A with a single chip is possible... interesting that the Elektor approach used two chips for 6A when they could have done it in one by winding their own coil instead of buyng off the shelf... think they missed a trick there... the chips are £9.24, the ferrite a lot cheaper...

However, it still doesn't overcome the OP's initial issue - the cost of toroidal transformers...

Actually, if you look around a bit, ebay and the like, you can get hold of a transformer for very little money. I paid €20 for a brand new one for my first power supply. The second one I got given!!! He should be a bit patient!! Not in a rush!!
But each to his own....I spent many years in the computer industry and I like REALLY stable regulated and efficient supplies. Ones that I fully understand exactly how to repair......
Also many thanks for your comments about prices and other methods etc....very informative.
Best wishes
Andy