5.5kW Buck/Boost Power Supply 48V in 12-150V Out - Page 1
Forum section: electronics / projects

author: offbyfour
author_rank: Contributor
timestamp: December 13, 2023, 07:22:53 am
content: Hello, does anyone have any reference designs or documentation for the design of a 5.5kW Buck/Boost Supply?The specs I'm trying to hit:Vin = 42VDC-58VDCVout = 12VDC-150VDCIout = 250A maxPout = 5.5kW max

author: PSR B1257
author_rank: Frequent Contributor
timestamp: December 13, 2023, 02:22:41 pm
content: Only 5,5kW - peace of cakeWhat kind of experience do you have in that field?I'm not even sure, if such a wide range is even possible.

author: johansen
author_rank: Super Contributor
timestamp: December 13, 2023, 06:19:12 pm
content: Do you need 5.5kw at both 12v and 150v out?From the same circuit with no transitions between topologies?Because you could design an isolated boost converter to produce 0 to 110v out, place it on top of a buck converter designed to produce 12 to 40 volts out, so they add together. Use a few dozen relays to short the output of the boost converter when it is not needed.5.5kw is 460 amps at 12v.

author: offbyfour
author_rank: Contributor
timestamp: December 13, 2023, 06:24:51 pm
content: To be honest, my knowledge of buck/boost converters barely covers the basics, and I’ve done a little work with high voltage circuits but I’m much more comfortable with the digital side of things. I know I’m looking at a pretty steep (and probably expensive) learning curve but i’m willing to put the time in for it as I would like to make this part of an open source project.I have done some initial digging and found a chip that may be able to do some of what I want but it’s clearly not designed for my power target. According to the datasheet the output current is scalable depending on the external fets you choose (I’m thinking paralleled GaNs are the way to go) but there are still a lot of details that don’t account for the large currents I’m trying to hit (like the Rsense resistors).https://www.mouser.com/datasheet/2/609/LTC3777-3125324.pdf

author: offbyfour
author_rank: Contributor
timestamp: December 13, 2023, 06:34:25 pm
content: Not quite for 12V, I’d like to cap the current to 250A as that is the most my application would need. So it would be something like12-22V @ 250A22-30V @ 180A30-60V @ (no specific requirement)60V-120V @ 45A120-150V @ 36A250A still seems tough to hit though.

author: PSR B1257
author_rank: Frequent Contributor
timestamp: December 13, 2023, 08:03:06 pm
content: QuoteWhat project?QuoteThen this (part of the) project is basicly doomed to fail. Even experienced engineers for SMPS would have a hard time designing such a converter, I would imagine.That's why a power supply with a similar power has a 5 digit price tag:https://www.keysight.com/us/en/product/N8754A/power-supply-20v-250a-5000w.htmlQuoteYa thinkQuoteResistors would be least concern in this case.

author: coromonadalix
author_rank: Super Contributor
timestamp: December 13, 2023, 08:17:04 pm
content: even known products doesn't have a third of theses specs, if it was easily doable we would have heard of ...your only option at the moment are psu's on a AC 3 phase system, going onto the 5-6 kw range(s) you're askingand did you see their sizes ?and yes your requirements are undefinedbattery charger ?? = server psu's can do that, add come bms on top of them ... doneother ?yes the Keysight is a good one, 10K$ usd easy loll see the 3 phases inlet lollthey have a broad range of psu'shttps://www.heliosps.com/smart-variable-dc-power-supply-6kw-36kw/https://www.heliosps.com/wp-content/uploads/sites/5/2020/09/GEN-GSP-Variable-Lab-Bench-DC-Power-Supply.pdf

author: Slh
author_rank: Regular Contributor
timestamp: December 13, 2023, 10:14:46 pm
content: You don't want to be playing with GaN as a inexperienced player. Paralleling silicon MOSFETs for high current is a pain and single GaN devices have so many headaches that putting them in parallel will guarantee that this project will cost a lot and not go anywhere.Heavy copper boards aren't cheap either. I've done 300A in a 8 layers, 4 ounce board but it needed cooling. It's also a pain to solder (I didn't do it , we've got competent technicians for that).What's the purpose of the project? It's a rather strange set of inputs and outputs. There's a few vehicles with 48V buses, otherwise I guess it's using data centre or telecoms PSUs? Maybe some DIY solar thing?Less that 60V puts you in the SELV region where you don't have to do anything for safety. Above that, various standards start to think that you need galvanic isolation from anything that someone may touch. You may need isolation to protect the 48V side from the 150V output. Depends on your application.

author: jbb
author_rank: Super Contributor
timestamp: December 13, 2023, 10:16:06 pm
content: Quote from: PSR B1257 on December 13, 2023, 08:03:06 pmAgreed. This is ahardtarget to hit.If you were to proceed with a straightforward buck-boost, you would need to build a converter which can handle both 150 V and 250 A (yes, not at the same time but still need switch voltage rating and current rating); that’s 37.5 kVA, ie 6.8 times the actual power. Way overbuilt!If at all possible, I suggest you cut back the requirements. You seemed to indicate earlier that you were mostly interested in 12 - 30 V and 60 - 150 V.Why not build a buck converter for 12 - 30 V and a separate boost converter for 60 - 150 V? It’ll be much easier.I’ve worked in power electronics in the past and I can see two ways to accomplish the original rating concept: a) overwhelming force and b) reconfigurable topologyOverwhelming force: just splat out a great big buck-boost converter using integrated power modules and a HUGE inductor. It’ll be big and expensive and not very efficient, but that could be OK. I smashed out one like this a few years ago (800V DC -> 200 V, 200 A) with an inductor from the basement which weighed about a ton.Reconfigurable topology: 4 isolated DC-DC converters with approx. 1:1 voltage ratio. The input sides all connect in parallel to the 48 V DC supply. The DC output sides go through a set of switches so they can be coupled in various ways. For outputs < 40 V, use all 4 in parallel. For outputs between 40 and 80 V, use 2-parallel 2-series. For outputs > 80 V, use 4 in series. Your control scheme would need to consider voltage balancing and current sharing.

author: Smokey
author_rank: Super Contributor
timestamp: December 13, 2023, 10:35:26 pm
content: Power stage in a box. Maybe not these particular devices, but something like that:https://www.infineon.com/cms/en/product/power/igbt/automotive-qualified-igbts/automotive-igbt-coolsic-mosfet-modules/hybridpack-drive/.... not that that will help much here....

author: johansen
author_rank: Super Contributor
timestamp: December 14, 2023, 07:03:25 am
content: this isn't even that hard.. its just hard to make it small or reasonably low noise, or fast.A 4 switch buck boost converter, designed to handle 50 amps is not all that difficult. what might be difficult is to parallel 5 of them.No need for expensive mosfets, 200 volt rated mosfets that can handle 15 amps continuous (parallel 4 of them, so that's 16 total per converter) aren't particularly expensive. you could do this with 16, irfp 260 mosfets per converter, parallel 5 converters.. so 80 mosfets, or 80$ each time it blows up.i built an induction heater using the irs2453 self oscillating full bridge driver. i used 1/4 watt 10 ohm gate resistors.. and i protected the driver with some SOT123 sized TVS diodes rated for 12 volts.one time the fets blew up. so did the gate drive resistors. 30 amps into those gate resistors did not fry the irs2435 chip and i just replaced the mosfets and the gate resistor, the redundant npn/pnp drive transistors.. the tvs diode survived. since then i've never understood since then why people say this stuff is so hard. yes its hard, when you're too cheap to use gate resistors as fuses and put extra redundant capacitors, diodes, and tvs or other surge protection on the gate drivers to protect them from worst case scenario failures.you can even use optically coupled, completely independant gate drive circuitry, and then do all your testing with lower powered mosfets so they blow up when you exceed your intended parameters. then once you get the bugs out, put the expensive low loss mosfets or igbt switches in.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: December 14, 2023, 08:16:03 am
content: Given OP's previous threadhttps://www.eevblog.com/forum/projects/inverter-welder-design-using-r48-3000e3/msg5217144/#msg5217144I'm guessing it's a portable welder sort of application. Which is pretty cool that batteries are that powerful these days, and yeah, they exist, these are real products already. Not sure about this power level, but, just a matter of scale if nothing else.The question is, how much are you willing to spend on it?- If entirely amateur, are you deeply, well and truly committed to working on this project? Foryears?This is a comprehensive project. It requires knowledge of everything from basic circuit operation, deep down into control theory, and wide across EM design: not just component placement and PCB layout, but transformer winding as well. It will take a long time to develop all of these skills.I speak from personal experience -- in high school, I had it in mind that I could build an induction furnace to further my metal shop projects. Given my relatively strong electronics knowledge at the time (I had made a couple crude switching regulators), I started doing more targeted experiments, and scaling up in power. I did some basic oscillator things up to a few hundred watts, enough to, you know, melt solder, make small bits of steel glow red hot, but nothing with control -- mind, this is a bit more complex to solve than for a regular SMPS as frequency control is required, instead of just PWM (or perhaps both at once). Eventually, by mid college I had a working, reliable design, good for a kW or so, and was working on a 5kW model in my parent's basement when I was home from school. I managed to get 5kW out of it, though never melted steel (aside from brutalizing some tubing and plate); I did get a slug of steel rather toasty at least (yellow-white hot). By end of college I had something pretty promising, but then I started work, and had no time (or place) to work on it anymore, also, then I was making a design professionally, so, what would I want/care anymore...I don't know what your capability is, I don't know if you have any idea what mine was like; or, needless to say it took aneventual-engineersome concerted effort, on and off over many years, to pull it off. I wouldguessmost will take longer than this, and still not come up with something as comprehensive; a more evolved rather than synthesized design, fewer control/protection features, etc.; seriously, it takes a lot of experience to come up with or implement these things. (Mind, some of the features I used, were suggested by much more experienced engineers than I; you'll never invent the whole world from scratch, and cribbing from known good designs is a great idea. Just take the time to understand them first.)- If built in part or whole, what is your budget?Even if it takes years to gather parts, it must be something. I mean, it will even if -- nay especially if made from scratch, as without experience you're likely to burn a lot of transistors (and other things) in the process. (With a couple early design tricks, I managed to avoid the most destructive events; my record to this day, is I've burned enough transistors that would just fit on both hands. Mainly because two were hand-sized modules, and the rest stack on top neatly enough. Some people seemingly brag about having whole buckets worth on their scoreboard, which, doesn't really sound like something to brag about to me. Make of that what you will.)A tip: semiconductors are one of the smallest costs in such a project. Big power components -- inductors, transformers, bypass capacitors (or resonant ones for that matter), heatsinks, and brackets, plates, terminals, etc. as applicable, and assemblies most of all, are where all the cost is concentrated. Transistors are useless without all the support components around them, and transformers are only good for what they're wound for (they're very often custom, and certainly so at this power level). Inductors and capacitors are a bit more general-purpose, but still limited on power handling in a given size, and the value determines impedance (and impedance and power are equivalent to voltage and current, thus you'll use components of some certain size and value range for a converter of given ratings). And assemblies are expensive even if you order with commodity parts from China, or in terms of your time doing it by hand (plus gaining soldering skill, if applicable).- If using off-the-shelf parts, what will you use?There are some eval boards at pretty high power levels, but not quite this high I don't think. Will you stitch a few together? How to make them track? (It's an interesting control question, depending on if the controllers can be tweaked in the right way.) Beware also that some high-power eval boards are targeted at DSP control, which is a whole pile of additional stuff to study (I think DSP isn't that bad, pretty easy even, at least if you have a background of AC analysis, Fourier and Laplace transforms, differential equations; but those are pretty heady topics if you don't have some of that curriculum already; but not to mention just the whole toolchain and programming overhead, and the responsibilities of hard-real-time controls). Cutting those out, you have fewer options to choose from. Many of them are also quite expensive (which hardly matters for engineering, I'll easily spend ten times the cost just pondering the thing, but for a project, that's a different matter).There are some ready-made modules, affordable, in various ratings. But beware the build quality is generally piss-poor. Don't expect protective features like current or temperature limiting, and expect noise levels high enough you'll have trouble making them behave together (again, if you can make them cooperate at all, depends on the controller). You may waste a whole lot of time, or money, or burned parts (both), trying to figure it out, only to solve all the other issues, and finally discover it simply can't work.- If using custom design, how much will you use volunteer versus other sources?Could be contract design, but I'm lumping in tutoring here as well. Make it an investment in a product? Make it an investment in your education? Either one works!For my part, if I were tasked with designing such a thing:I'd want the better part of a year to work on it, low five-digits USD budget, and I would probably do something like a three-phase interleaved SEPIC converter as the basic design, or maybe more phases given just the sheer amount of current capacity.I would choose Si MOSFET technology, unless a very compact form factor is required, in which case GaN is an option, but that will raise timeline and budget as they are harder to use, more of them will be required, more magnetics optimization, more placement and assembly optimization, etc. It can take over a year to optimize a high-density converter; there's a lot of parts involved, and no basic principles to organize them on (lots of freedom to place things, the optimization space is huge, and rough with lots of local minima).If the full V/I has to be available from a single range, parts cost and build size rise significantly -- everything has to be rated for maximum current and maximum voltage, at all times, while only the heatsinking (and input DC related stuff) has to deal with the power rating. Covering it in a single range isn't at all intractable, but it is a challenge.If ranges are acceptable, then I suppose a series-parallel contactor switching arrangement would do, thus a pair of 75V 125A modules can be wired in parallel for 12-75V 0-250A or 24-150V 0-125A, which again will be more-or-less a rectangular operating area based on component ratings, with the power limit taking a hyperbolic chunk out of the corner.A more simplified or budget-minded build (in terms of NRE, not production cost) might opt for fewer phases (or even a single phase), and SEPIC, buck-boost, Cuk or push-pull forward (probably not flyback, but even that can be done given enough materials) might be considerations. Efficiency will also be poorer, and, maybe you settle for big bulky but readily available components -- IGBT bricks instead of optimally sized MOSFETs for example, and you just ignore the 2V forward drop or whatever. This will still take mid to high four-digits budget to design, assuming there's no re-design or additional time spent identifying and substituting poorly-suited components -- the kind of thing you'd do yourself perusing the junkyard for industrial kit, but I can't very well do that remotely.(For the record, not that I would recommend contracting with such an awkward process -- it'll save money overall for the engineer to have complete control over the design, and do it right the first time, than to have to make compromises to force-fit parts into the design, especially if the parts selection is changing constantly. More to say: if you were that engineer, you could make those changes on the fly as you see spare parts and good deals, and maybe you would be willing to sacrifice parameters like efficiency and overall size in favor of such options.)---My assumption, from the limited context of a few posts, is that you don't have much experience in this space, and have a desire for something, but not a way to achieve it; or even the ability to specify it in much detail. So, I hope I'm not being too patronizing here, but the setup sounds generally familiar, and so I chose this direction to write in. Assumptions being what they are of course -- it doesn't mean a thing, it's just an assumption, which might be wildly wrong, it happens. But in that case -- do please give us the good faith and the benefit of a doubt, and tell us about your needs and desires (heh, with regards to this, not in general), your capabilities, and where you really want to go with this thing, because, yeah, it really isn't a simple thing to put together.Tim

author: coromonadalix
author_rank: Super Contributor
timestamp: December 14, 2023, 03:15:08 pm
content: for a portable welder, i saw 2x Dewalt inverters in parallel with 4 battery pack in each of them ...for usable length / time period of use, i dont know the details, for the welder model i dont knowit was all fitted in a 2 wheel buggyonly thing i know it was for very specials occurrences, where portability was primordial, the service truck could not reach ...in the end, this thread seems a variation of the other thread ... waste of time for all of us

author: offbyfour
author_rank: Contributor
timestamp: December 15, 2023, 04:18:44 am
content: Thanks y'all, I appreciate all the responses and feedback. I've been tied up with work so I have not had the chance to respond.[Project origin]The project started with designing a power supply for a welder but the more I think about it, I want to evolve it into something of a universal power supply. Some of the uses for it would be:- 12-42V: Welder- 42-58: Battery Charger- 58-150V: Plasma Cutter- 12-60V: Low resistance/High Power for heating elements (kiln or home-foundry)Right now these are mostly what ifs for down the road, at the end of the day I want to do this 5.5kW building block right.[Power source for DC/DC]Since I have even less knowledge about AC rectification than I do DC/DC conversion I thought I would just buy something off the shelf. There are 3kW telecom rectifiers for $100-$200 that I thought would be an easy start. Specially since they have a parallel feature for greater output.https://www.vertiv.com/globalassets/products/critical-power/dc-power-systems/netsure-731-a412/r48-3000e3-datasheet.pdfEventually though I would like for this part to be open source as well. As a slight tangent, I did find this link during one of my searches which seemed like an instersting start but again I feel like that is wayyy down the road:https://www.arrow.com/en/research-and-events/articles/new-4kw-gan-power-supply-reference-design-by-arrow-nexperia-and-yageoI also had not considered using batteries to power the converter for portable welding, but that seems like that would be a really neat feature as well.[Single over-engineered supply vs multiple stages]I had not thought of approaching it like this but I think multiple stages are a very valid option. It certainly seems like that it may be the cheaper and more reasonable option, but it does have the downside of size/power density.While looking into this stuff I ran into this app note that is sort of putting me into the single supply camp.https://gansystems.com/wp-content/uploads/2020/09/GN004-Design-Considerations-of-Paralleled-GaN-HEMTs_200910.pdfIt does not cover the entire DC/DC converter but its pretty crazy that they hit 650V/240A specs by paralleling 4 GaNs (8 total, granted continuous use is probably current lower than that over temperature). Also their chips are hella expensive haha.But along those lines I also found these integrated GaNs that seem would decrease the chances of me blowing things up and possibly simplifying the design:https://www.ti.com/lit/ds/symlink/lmg3526r030.pdf?ts=1702534620837&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FLMG3526R030Some of the features that may be useful:-Overcurrent and Overtemperature protection-Zero-voltage detection-Integrated GaN driver-650V/55A rated (38A recommended)Only question now is if they can be effectively paralleled. I'm thinking at least groups of 6-8 for this design.[Design Topology]I'm still looking into this as well, but from the info that Tim provided and this document, I'm liking the SEPIC or if its not too expensive the Cascaded buck-boost for the efficiency.https://journals.pan.pl/dlibra/publication/135986/edition/118907/content/international-journal-of-electronics-and-telecommunications-2021-vol-67-no-3-design-analysis-and-comparison-of-si-and-gan-based-dc-dc-wide-input-voltage-rangebuck-boost-converters-br-koszel-mikolaj-grzejszczak-piotr-nowatkiewicz-bartosz-wolski-kornel?language=enAs far as the controller, I thought I would go with an FPGA/CPLD as that would give me the most control and flexibility.[Mosfets vs GaN]The benefits that you seem to get from GaN like efficiency, density and high switching speeds really have me interested in learning to use them. Its not set in stone, but I think that's where I am leaning right now. It will make things more difficult and may end up being an expensive lesson but I think I want to go through with it.[Personal Experience & Budget]I did not mean to give off the idea that I'm brand new to electronics. I work designing datacenter type equipment but its mostly on low voltage high speed design stuff like processors and things like that. Definitely not on the power supply side as I have very little experience with them, but I'm hoping this project will help me get better at it.In terms of budget, I'm hoping it doesnt take many years to gather parts but it definitely will take some time. I'm wanting to simulate as much as I can, and break it into as many independent modules as possible to break up the cost.I very much appreciate the in-depth response and the detail provided. It certainly has given me a lot of information to look into. That kind of experience is what I am hoping to learn from a project like this. I dont think I would hand this off to a contractor, but I can still use all the wisdom I can get so I'll make sure to keep posting updates along the way for anyone that may be interested. Once I get a good block diagram of what I plan to do, I'll post it to github and get things started with KiCad.

author: PSR B1257
author_rank: Frequent Contributor
timestamp: December 15, 2023, 05:54:06 am
content: QuoteThat's makes it way easierQuoteThe power and energy demand makes this battery quit hefty, I supposeQuoteSorry, that's the most stupid idea one can think of. On top of the ludicrously high currents you have to deal with, the converter is generating tons of power losses.A kiln, powered directly from mains voltage is obviously the most efficient way of heating.

author: offbyfour
author_rank: Contributor
timestamp: December 20, 2023, 05:33:17 am
content: I completely agree that this supply would not be the most efficient way of heating a kiln. But I'm thinking if I already have a power supply on the 12-60V range that can do 5.5kW I might as well use it.The currents would be massive, but they are basically the same currents that are needed for the welder so it would not require any additional design changes (the kiln would need to be designed with heating elements that are in the 0.5 to 1-Ohm range). It would also have the added benefit of being a little more DIY friendly since it would not require exposure to a high working voltage.The efficiency loss is significant but I dont think its unmanageable. The first stage of this design would be using the telecom rectifiers that are almost 96% efficient by design. Just using those for the heating element would be 275W(5.5kW *95%) of losses which the supplies are designed to handle. 300W in the grand scheme of 5.5kW seems like a worthwhile trade off for a safer operating voltage.

author: PSR B1257
author_rank: Frequent Contributor
timestamp: December 20, 2023, 08:28:48 am
content: QuoteYour not supposed to touch live wires anyway, so not really a benefit. Managing the wiring and switching for 100A (at DC) is also much harder, than say 20A (at AC).QuoteSure, and the DC supply voltage comes free of losses, eh

author: coromonadalix
author_rank: Super Contributor
timestamp: December 20, 2023, 06:23:53 pm
content: one of the most forgotten thingyou elevate 12vdc 180 amp into 24 vdc you'll get 90 ampif not you'll need to double the amps at 12vdcmeaning 360 amp at 12vdc to get your 24vdc at 180 amphonestly stop this thread it's becoming ridiculous