ELV Power Supply[Schematic Check] - Page 1
Forum section: electronics / general

author: pi11235
author_rank: Newbie
timestamp: May 06, 2012, 08:35:48 pm
content: EDIT: Schematic is in the last post, this was preliminary.What do you guys think of the 5A Constant Current/Voltage PSU schematic in the LM350 datasheet:http://www.ti.com/lit/ds/symlink/lm150.pdfI'm thinking about adding a power factor controllerI saw a German one, but I'm an American, and I'm not sure what will happen with 120V input.http://www.elv.de/output/controller.aspx?cid=74&detail=10&detail2=1931&flv=&bereich=&markeI'm guessing I can use transformers rated for the outputs listed, I already have one that will do 30V. Is there anyway to increase the amperage on the board?There's this design here:http://www.microsyl.com/index.php/2010/03/31/bench-power-supply-0-25v-0-5amp/I don't know what to make of it.If either of those don't work, I've read a few threads below:https://www.eevblog.com/forum/projects-designs-and-technical-stuff/general-purpose-power-supply-design-7488/https://www.eevblog.com/forum/general-chat/diy-power-supply/I'd prefer a transformer based supply if possible. What would you guys recommend for 5A and 0-30V with current and voltage limiting? Thanks

author: Unknown
author_rank: Unknown
timestamp: May 06, 2012, 09:10:05 pm
content: Why would you worry about power factor compensation? The power draw would be fairly modest, something like 150-200 W at full load.I'm not a big fan of these complex three terminal regulator based solutions. In my opinion the advantage of monolithic regulators is their simplicity. Once you throw that out of the window, you might as well skip the three terminal regulator, unless you work in the applications department of a semi vendor selling these. I don't really understand why you would use a relatively expensive 3A regulator if you still need an external pass transistor. I would rather use an LM317, I believe there is a similar schematic in its datasheet.The ELV design would work fine. You would obviously pick transformers designed for 120 V input. These designs are quite scalable. You can easily parallel multiple pass transistors and emitter resistors. It may need some minor modifications to increase the base current. If you use the original PCB, make sure you don't run the high current through the PCB traces. This means that the connections to the main rectifier, filter cap, Darlington transistor, emitter resistors and output terminals should be separate wires rated for 5A. If you design your own PCB, than just make the traces wider.I believe I've commented on the third design before. The schematic does not look very professional to, minor things like putting positive rails on the bottom and negative on top. I don't understand the 'trarlington' just for the base current of those pass transistors. I don't understand why he puts the second '4Vac/250mA' transformer winding essentially in parallel with the first, instead of grounding it at the positive output terminal like you see in the ELV design and many HP/Agilent designs. This would make life easier for the op-amps.Any mains power supply for these power levels is going to be transformer based, but I guess you mean you prefer a linear design to a switch-mode design, which is probably not a bad idea if this is your first power supply.

author: pi11235
author_rank: Newbie
timestamp: May 06, 2012, 10:24:50 pm
content: I thought that was the best one. You wouldn't happen to happen to have an English version around would you? I've so far been unsuccessful extracting the text to run through google translate.I've got a few questions so far.1. What does ST signify, a connector type?2. Sounds like I'll have to parallelize T1-3, and either rewire or widen anything connected to the 15V/30V transformer3. I assume the resistors in the middle[R12,13,14,30,31,15,16,17(maybe R2 or R3] are the emitter resistors, and either have to be increased in rating or parallelized.4. Why is there an LM324 sitting out in the middle right of the schematic seemingly connected to nothing?5. Anything else needs to be changed?6.I'll certainly be putting this in to either altium or kicad, and perhaps into make:projects, as I figure this out.Definitely in english though. Maybe my bosses will eventually kit it up in the MakerShed. No promises there though. This sounds fun, I'll have to ask a couple friends who are a little farther along in their engineering degree to help as well.

author: Unknown
author_rank: Unknown
timestamp: May 07, 2012, 12:04:17 am
content: 1. ST stands for solder terminal, something likethis. Nothing critical about this component, just a convenient point to solder a wire to.2. T2 and T3 are in parallel, T1 provides the base current. You may need to add more transistors (with emitter resistors) in parallel to T2/T3, but T1 should be fine.3. All the 1 ohm resistors (R12-17) are emitter resistors. Each transistor has its own emitter resistors, so no need to increase their rating if you're adding more pass transistors. You may also increase the rating of the emitter resistors and put more current through each transistor, but watch their SOA. R30 is a sense connection for IC3B (current regulator) and R2/R3 is just a voltage divider to bias T1.4. The LM324 is a quad op-amp, but they only needed three. They could either buy a dual and a single op-amp, or a quad (which is cheaper). You could also leave out D17 and everything downstream from it if you don't need the temperature protection, that would save another op-amp.5. You might have to increase the base current, although the op-amps can only sink a limited amount, so they may also need replacement (or another transistor to drive the base of T2/T3). I think you should probably be ok at 5A.I believe Elektor described a similar design in their December 1982 issue, not sure if there's an English version of this article available. I have not yet found something similar to the ELV design described in English, though I expect there to be several. I suspect that ELV would not be happy with an English translation, since they are in the business of selling magazines and kits. They took down most schematics from their site, this is one of the few that remains.ELV also a publisheda very similar design for 30V / 10A. It uses essentially the same design, but with more pass transistors and some extra complexity for a tap switching relay and variable speed fan. I'm surprised they still use the same 8mA of base current, since the guaranteed minimum gain of the TIP142 is specified as 1000 (at 5A), but I guess that means it should be plenty at 5A.

author: david77
author_rank: Frequent Contributor
timestamp: May 07, 2012, 01:03:43 am
content: This supply is very similar to the one Elektor published in 1982, it's German again, sorry. The theory of operation was described in detail in a HP app note:http://www.wfp76364.w1.com/HP-AN90B.pdfhttp://hpm-elektronik.de/ng30-4-netzteil.htmI've built a dual supply using the Elektor circuit some years ago, works fine. Some care must be taken that the whole thing doesn't start to oscillate. I had to add/change some caps around the op amps to get it stable in all situatiuons.

author: pi11235
author_rank: Newbie
timestamp: May 10, 2012, 05:20:23 am
content: With this configuration:REV 2https://docs.google.com/open?id=0B5Ycq8DppRJaaGxQR2I4RGhYTUEREV 3https://docs.google.com/open?id=0B5Ycq8DppRJab19YbnJ1RTVoMUkI'm aiming for 30V and 4A, but I think I need to add another transistor to feed the base current on the Darlingtons[Q1-Q4 ] Already doubled the darlingtons. Anyone see anything else?Original:http://www.elv-downloads.de/Assets/Produkte/2/225/22532/Downloads/22532_Universelle_Netzteilplatine_um.pdf