SMPS difference between 120v and 240 mains? - Page 1
Forum section: electronics / projects

author: iXod
author_rank: Frequent Contributor
timestamp: October 15, 2021, 04:48:19 pm
content: I’m in the US.I want to convert a laser printer from 120v to 240v mains input for someone moving house overseas. Shipping of the household is being paid so it comes down to converting what’s owned vs. buying new/used there. The pandemic has pushed costs (especially SOHO equipment) skyward which makes conversion a consideration.I do see a UK spec ps board for this printer available online, but being the curious type, I want to understand what the design changes are when creating each of these circuits.Is the transformer the significant unique component between these designs?I’ve confirmed that the manufacturer did not make a “universal input voltage” ps for this printer; there are 2 unique markets/models.Thanks.

author: tooki
author_rank: Super Contributor
timestamp: October 15, 2021, 05:22:49 pm
content: They don’t use transformers, they’re switch mode power supplies. Those might be universal-voltage anyway, but I wouldn’t count on it.The part that is always voltage specific is the fuser assembly. It’s a heater that’s run straight from mains voltage.I don’t really think it makes sense to convert it. On a cheap printer the cost would likely exceed the cost of a new printer;on an expensive printer, the risk of goofing it up and ruining it probably isn’t worth it.The other problem, one many people are unaware of, is that on many printers made in the past decade or two, the supplies (ink/toner) are region-locked. There’s a very real chance that it’d be impossible to procure toner for that printer overseas.When I moved back to Switzerland from USA 12 years ago, I brought my practically new (inkjet) printer with me, because it was compatible with world voltages, and Canon did not, at the time, region-lock the inks. But just a few years later they started doing that, so now it’s impossible to buy supplies for a current US-market Canon over here in Europe.Even now, printers are still cheap, all things considered. Maybe tell your friend it’s an opportunity to look into the bulk-ink inkjet printers that are now available: you pay more for the machine up front, but in return, the ink is absurdly cheap, giving page costsfarbelow laser or regular cartridge-based inkjet. (We’re talking 6000-10000 pages from a $15-20 bottle of ink.)

author: magic
author_rank: Super Contributor
timestamp: October 15, 2021, 06:27:16 pm
content: Quote from: tooki on October 15, 2021, 05:22:49 pmOkayNot sure if there is going to be any problem with the transformer; the controller will reduce duty cycle by half to compensate for different input voltage (if the unit doesn't have active PFC, that's another matter).Surely, components like capacitors and transistors may be not up for the task. Even stupid things like the startup resistor or bleeder resistors across caps will run 4x hotter.Not sure about control loop stability? It seems that with higher input voltage, loop gain will increase due to more dI/dteditI think I have heard of people making such mods to power tool battery chargers, but in those cases the PCBs were designed to be universal and they had samples of both the 120V and 230V versions so they knew what to replace.

author: Benta
author_rank: Super Contributor
timestamp: October 15, 2021, 07:32:25 pm
content: All consumer equipment I've seen the last 20+ years (this includes laser printers) has universal switching power supplies and will typically accept 90...240 VAC input.Before that, there was a switch by the power input between 120 and 230 V.Read the sticker on the machine before going on a wild goose chase.

author: magic
author_rank: Super Contributor
timestamp: October 15, 2021, 08:02:10 pm
content: Well, I have seen (and used) a 230V-only ATX PSUThose things exist. You get to save some $$ by using components with less voltage/current capability than required for universal input.OP says this has already been confirmed with this printer PSU.

author: NiHaoMike
author_rank: Super Contributor
timestamp: October 16, 2021, 01:25:17 am
content: Is there one large mains side electrolytic capacitor or two? In the latter case, there's a chance it's a voltage doubler and you just have to convert it to a plain bridge rectifier.For the fuser, an easy solution is to find the triac that controls it, replace it with a higher voltage version if necessary, and add a 300V SIDAC along with a diode in series with the gate. It would trigger near the peak of the AC waveform on one side only, yielding similar power into a resistive load.

author: The Doktor
author_rank: Regular Contributor
timestamp: October 16, 2021, 04:49:16 am
content: I'd say just get a new printer. But there is a fast & easy "conversion" option which is even reusable when the printer dies. Just buy a transformer with appropriate KVA rating and hook the printer to it.

author: ejeffrey
author_rank: Super Contributor
timestamp: October 16, 2021, 05:41:10 am
content: Quote from: Benta on October 15, 2021, 07:32:25 pmIt's less now, but definitely 10 years ago it was still somewhat common for small wall warts to be 120 V only (with no switch). I learned this when I had one release the magic smoke because I assumed they would all be universal. Really ATX computer power supplies are the only consumer equipment where I have seen the voltage switch, and indeed those haven't been common in ages.I just checked my ~3 year old brother laser printer and it definitely only lists 120 V on the label.So definitely check before assuming something will work.

author: iXod
author_rank: Frequent Contributor
timestamp: October 16, 2021, 05:59:34 am
content: Quote from: Benta on October 15, 2021, 07:32:25 pmHence my statement:QuoteAnd the sticker says “100-120 vac”.

author: iXod
author_rank: Frequent Contributor
timestamp: October 16, 2021, 06:05:28 am
content: QuoteTHANK YOU. This one is also a Brother. ~10 years.

author: iXod
author_rank: Frequent Contributor
timestamp: October 16, 2021, 06:10:13 am
content: QuoteA non-issue. I’ve been using aftermarket toner cartridges with no issues.But thanks for the heads-up for future reference.

author: Zero999
author_rank: Super Contributor
timestamp: October 16, 2021, 01:00:27 pm
content: Quote from: tooki on October 15, 2021, 05:22:49 pmOf course a switched mode power supply uses a transformer to provide isolation from the mains, reduce the voltage and increase the current.What you probably meant was that a switched mode power supply, doesn't use a big, low frequency mains transformer, but a high frequency transformer.Anyway, to answer the original post: it depends. Quite often there's no difference. If the power supply has 400V capacitors, then it's highly likely it will work off 230V. If it has a 200V capacitor, then it's most likely 120V only, in which case is should be powered off a small transformer, rather than a modifying the SMPS.SMPS

author: tooki
author_rank: Super Contributor
timestamp: October 16, 2021, 01:32:17 pm
content: Quote from: Benta on October 15, 2021, 07:32:25 pmCan you give me one concrete example? I have never seen a universal-input laser printer, and I just took a quick look just now.The SMPS modules inside are often universal-input, but the printer as a whole is not, due to the mains-powered fuser assembly.Quote from: iXod on October 16, 2021, 06:05:28 amA 10 year old printer?! It’s not worth the trouble: the parts and effort needed to convert it will exceed the current value of the printer. Just buy a used one in the UK. (Used laser printers are very cheap since people often balk at the price of a toner cartridge and just get a new one instead…)Quote from: iXod on October 16, 2021, 06:10:13 amAftermarket is a separate issue. An aftermarket cartridge also has to be properly region-coded, for printers that are region-locked.Probably doesn’t apply to this Brother, but it’s something toverify(not assume) nonetheless.Quote from: Zero999 on October 16, 2021, 01:00:27 pmYes, you’re exactly right. I meant “transformer” in the sense of mains transformer, as that’s a common everyday usage when contrasting power supplies.(What I really object to is people using the word “transformer” to mean “SMPS”.)

author: Terry Bites
author_rank: Super Contributor
timestamp: October 16, 2021, 04:42:27 pm
content: Its unlikely the printer manufacturer used two different power supplies. An uneccesary cost. So the PSU is probably either universal or switchable.

author: iXod
author_rank: Frequent Contributor
timestamp: October 16, 2021, 05:45:49 pm
content: Quote from: Terry Bites on October 16, 2021, 04:42:27 pmAs stated, printer label says “110v-120v ~ 50/60 Hz”. Not to be believed?EDIT:Ah, a “bulb moment”(credit to tooki) : maybe the ps is universal, but input voltage is specified because of the mains-powered fuser heater?

author: SeanB
author_rank: Super Contributor
timestamp: October 16, 2021, 06:29:47 pm
content: Yes, the power board is universal input voltage, because they cost engineered it down to a single part for world wide use, but the fuser assembly is a thin film resistor, carefully selected that it has a thermal time constant of a half second, so running on double the voltage likely will blow it up in under a quarter second, long before the thermal control loop has time to control it, and probably before the thermal fuse in there has had time to heat up. The ceramic heater is the only thing changed in converting between 120VC and 230VAC versions, the rest of the printer is otherwise identical. Power control for the heater is critical, as it has to come up to the right temperature in the half second it has between the printer accepting a print job, and the printer doing the raster conversion, and the coated paper arriving at the fuser assembly.Older (as in ones that took 40 seconds of warming up before first page) had a single halogen lamp there, and these were often universal voltage, as the controller did phase angle control of the lamp to keep it at a dull heat, and kept it at close to fuse temperature all the time the printer was not in a sleep mode.But yes, either use a autotransformer, not the cheap lightweight lamp dimmer style ones, but proper iron core and copper (or likely now CCA wire) windings, or simply buy a new printer on arrival, it will probably be cheaper than shipping the 120VAC model over.

author: james_s
author_rank: Super Contributor
timestamp: October 16, 2021, 06:52:39 pm
content: Quote from: iXod on October 16, 2021, 05:45:49 pmYes that's exactly what I was going to say. The fuser has a tubular halogen lamp inside a metal roller and this lamp will be specific to the mains voltage. It is possible to get replacement lamps for many printers so it may be possible to convert it but unless there is something really special about this particular printer why would you bother? My HP color laserjet was only about $250 and it's been great, if I were going to move overseas I'd just sell it and buy a new one when I got to my destination.

author: NiHaoMike
author_rank: Super Contributor
timestamp: October 16, 2021, 07:14:29 pm
content: In this case, there are separate part numbers for 120V and 240V power supply boards, so I would be surprised if they were universal.Perhaps check if there are separate part numbers for the fuser? While unlikely, it's possible it's 120V rated in all versions and the 240V version of the power supply has a phase angle control to drop the voltage. (But then why not design it to autodetect voltage and make it all universal?)

author: tooki
author_rank: Super Contributor
timestamp: October 16, 2021, 10:03:49 pm
content: All this discussion over a 10 year old SOHO printer (since Brother doesn’t make any printers for large workgroups)! 😂

author: boB
author_rank: Frequent Contributor
timestamp: October 16, 2021, 10:14:06 pm
content: Could just use a "transformer" or, auto-former to step down the 240 VAC to 120 VAC if the frequency isn't an issue.boB

author: james_s
author_rank: Super Contributor
timestamp: October 16, 2021, 10:16:30 pm
content: That certainly would work, although you'd want something around 1kVA for a laser printer and it's going to add some losses. Just the magnetizing current of the transformer being powered up when the printer is not being used is going to add up to significant energy consumption over the remaining life of the printer.

author: BrokenYugo
author_rank: Super Contributor
timestamp: October 16, 2021, 11:23:54 pm
content: Even a Chinesium house fire grade 1kVA 240-120 converter box costs more than any 10 year old desktop laser printer is worth, and I'll hazard a guess a legit one costs more than comparable new Brother built for 240V.

author: NiHaoMike
author_rank: Super Contributor
timestamp: October 17, 2021, 12:39:09 am
content: Might it be possible to find a construction site transformer for cheap?

author: amyk
author_rank: Super Contributor
timestamp: October 17, 2021, 01:22:24 am
content: Quote from: tooki on October 16, 2021, 10:03:49 pmAdvocating for planned obolescence?Mine is approaching 30 and still works fine. Then again, it's a HP.

author: tooki
author_rank: Super Contributor
timestamp: October 17, 2021, 03:07:42 am
content: Quote from: amyk on October 17, 2021, 01:22:24 amDon’t put words in my mouth.It doesn’t make sense to ship and modify something that cheap and that old. You could give it away, and then get the equivalent UK model on eBay for peanuts. I never said it’s useless or should be thrown away. But that doesn’t change the fact that shipping and modifying an old, not particularly high end printer is lunacy, when you can just get the same thing used over there.I did exactly that with some audio gear when moving from USA, for the same reason: rather than ship it and create workarounds to get it working in Switzerland, I just got the same stuff used here, and either sold or gave away the stuff I didn’t bring.It’s similar with cars: it’s not even thaaaat expensive to ship a car, if you can bring it to the seaport and pick it up on the other end. (You pay a fortune to have it picked up and delivered.) But even so, unless it’s a really special car, it’s rarely worth it to move a car overseas, because the modifications and inspections required to make it street legal, plus the shipping cost, usually make it wiser to just sell the car and then rebuy the same model in the destination.Also, LOL if you think an HP from today would last 30 years! Of course, they also cost dramatically less now. 1991 laser printers were anything but cheap. They also use a lot more power and spew more air contaminants into the room. BTW, Canon made the print engines in most (possibly all) HP LaserJets until HP acquired Samsung’s printer division a few years ago. So Canon is actually the company that deserves the credit. Canon laser printer engines are inside a lot of printers, past and present. (And in some cases, the entire printers are just rebadged Canons. Many current Xerox models are just rebadges, with even the exterior plastics absolutely identical.)