Affordable high current PSUs? - Page 1
Forum section: electronics / projects

author: KaneTW
author_rank: Frequent Contributor
timestamp: January 25, 2019, 06:11:20 am
content: I'm planning out my physical vapor deposition project and it looks like I need a 1-3V 200-400A supply for most applications (with some edge cases going up to 10V, <100A). Ideally the PSU would have a constant power mode, but not strictly necessary.Most commercial adjustable PSUs with these specs are at least in the 2-4k EUR region, which seems a bit excessive. So I've been looking to do it myself, but can't decide on a good topology.Ideas:1) Multiphase buck converter can give me 400A at 1-3V with enough phases (e.g. based on Renesas ISL68137). Not too expensive, but would have to monitor current draw closely and adjust V_out accordingly since the controller is a constant-voltage device.2) AC power source and a transformer down to the needed region. AC power sources are expensive-ish, and a transformer for those currents is a lot of metal.3) Salvaging a TIG inverter seems tempting, but they don't seem to allow voltages in the single volts (not sure about this).4) Finding a used high-current supply is pretty hard, especially in Europe, but that'd simplify things a lot. Would probably need to use three-phase power if I don't want to swap units around (e.g. Agilent 6681A), but that's not an issue.5) A new, adjustable PSU like a TDK-LAMBDA Gen8-400-1P runs over 3k, which is way out of budget.Any ideas? I'm sure I'm missing something since I don't normally deal with high-current stuff.

author: BravoV
author_rank: Super Contributor
timestamp: January 25, 2019, 06:29:03 am
content: Quote from: KaneTW on January 25, 2019, 06:11:20 amJust sharing my experience, not sure if the situation is similar in Europe.I love to hunt down cool & rare electronics stuffs, and mostly used of course, and usually for high power PSU, 1st, I did few detective work for local cellular tower installation contractors, they practically exist at every big cities since cellular industry explosions decades ago.While ago I made few calls to them, and gathered few local contractors that do towers upgrade/installation and "decommission"... voila ... there you go, made few calls again, I managed to snag few used but working fine TDK-Lambda PSUs, and "other" cool RF gears & stuffs too.Yep, starting from early GSM era and then 2G so forth 4G and upcoming 5G cellular trend, usually these towers produced lots of cool stuffs that probably cost arm & leg when new.An example, these beast can be parallel and series "by design", cost me $20/pcs and managed to get few of them.A TO-220 chip as reference size to show how big the output connectors size.Hope this helps.

author: coromonadalix
author_rank: Super Contributor
timestamp: January 25, 2019, 08:05:38 am
content: Nice findings im jealous loll

author: BravoV
author_rank: Super Contributor
timestamp: January 25, 2019, 09:39:38 am
content: Quote from: coromonadalix on January 25, 2019, 08:05:38 amThanks, yeah, I was lucky. If you think that is just another boring 36 volt PSU, adding insult to injury, just read at the attached fine prints below quoted from the user manual, its basically an "adjustable" PSU starting from 7.2 up to 43.2 Volt with 46.5 Amp capable throughout that range.Also to OP, as the below attachment to give you clue what kind of capabilities of this kind of PSU capable of, especially your demand for high current, you can parallel them and set one as master while others as slave, its worth pursuing imo, if you could get the model that can be adjusted down to the voltage level you want.Fyi, a brand new price of this PSU is about the cost of middle class oscilloscope.

author: Giaime
author_rank: Regular Contributor
timestamp: January 25, 2019, 11:10:47 am
content: Quote from: KaneTW on January 25, 2019, 06:11:20 amA big transformer + big diodes and capacitors, and you do all the regulation with TRIACs on the primary side. This, with some analog circuitry, could be also adopted for CV/CC/CP operation. For example output current can be measured with an Hall sensor.

author: KaneTW
author_rank: Frequent Contributor
timestamp: January 25, 2019, 04:36:41 pm
content: Thanks for the replies.BravoV: that are some really nice PSUs. I'm not too sure where to even start looking for contractors that might want to get rid of this kind of stuff, though. And, yeah, they suffer from the "companies buy this, so we can jack up the price" syndrome.Giaime: Good idea. So basically just a dimmer on the primary with feedback from a suitable current sensor. Still would need to make a transformer, but much less of a headache.

author: coromonadalix
author_rank: Super Contributor
timestamp: January 26, 2019, 04:13:22 am
content: Quote from: Giaime on January 25, 2019, 11:10:47 amA big waste of time and ressources, thoses psu are very well designed, sometimes they have pfc correction, very good line and load reglation etc ... the list goes on.The only way to have a good regulation basis is to use toroid x-former, the bigger they get the more stable they are, for an 1.2kw toroid you can have under 4% of drop.With huge power smps based ones, it will be better. We could debate a very long time over this and that ...I used 900 to 1.2 kw servers psu's, with good active coling they where incredible. Had one at 5vdc 120 amps loll oh i have paid 254 usd for each of them. Ebay has lots of them in many wattage and currents, you have some websites (dont recall) who tells how to mod them to suit your needs.

author: KaneTW
author_rank: Frequent Contributor
timestamp: January 26, 2019, 04:42:34 am
content: I'm basically driving a resistive heater. The requirements aren't particularly high.

author: mariush
author_rank: Super Contributor
timestamp: January 26, 2019, 05:12:39 am
content: Sounds like the VRM of a processor or video card.Processors these days are running at 1v..1.5v and 100A+ ... video cards use even more current.You could get a 8 phase controller and use 8 doublers to get 16 phases and that should give you what you need.For example, this EVGA Power V vrm for video card overclockers costs $250 :https://www.evga.com/articles/01140/evga-epower-v/or product page link:https://www.evga.com/products/product.aspx?pn=100-UV-0600-BRSPECIFICATIONS12 phase main output (0.6 - 2.0V, 600A)2 phase secondary output (0.6 - 2.3V, 80A)IR latest generation digital PWMRemote sense option support for vdroop compensationIntegrated voltage monitor LED displayOnboard EVbot MKII controls allow you to adjust voltages on the fly!Update your EVbot firmware and connect it via the EVbot port!Control your EPOWER via software by connecting a USB Type-C connector to your PCDual 3-pin +12V Fan header1 Year, DOA Warranty (no exceptions)It may be possible to tweak it to get more than 2v on the main output.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: January 26, 2019, 06:41:01 am
content: A TIG welder seems like a logical choice to me.Tig Welders have an ouput of usually between 20V and 30V (Max ratings probably betweeen 15 to 40?)These will not work unmodified, but they will contain almost all the hardware you need. They have a powerfull SMPS with isolation between primary and secundary, Power electronics for switching, auxilary power supply for the electronics / displays, a case to contain everything, Cables & connectors etc. And you can get such a thing for < EUR 100.When you open such a thing It could even be that you find something like a TL494 or other commonly uses SMPS chip inside.It seems unlikely that 2kW of power is switched by a single chip design. A regulator chip with external power switches is far more likely, especially by the cheap brands.With expensive brands you might find fully potted PCB's or module's.There must be plenty of tearowns of these on Youtube. It could be worth to watch some to find a model that is easy to modify.Also:You have to be aware that these welders are never capable of delivering the full current continuously.They always have an ED rating, and this can be as low as 20% for the full current.ED of 20% means you can only use it 20% of the time (at that specified current) during a 15 minutes (or half an hour?) period.So when modding, you might consider adding bigger heat sinks, fans and temperature sensors / cutoff's.Even skottky diodes easily go over 1V @400A, so that is already over 400W you have to dissipate ( Unless you have a synchronous rectifier).Make sure that the versions you get are capable of outputting DC. Some may only do AC.But doing such a mod can easily consume a few day's worth of time, with no guaranteed result.