90 Volt SMPS possible? - Page 1
Forum section: electronics / projects

author: ethernet
author_rank: Newbie
timestamp: December 12, 2022, 05:35:50 am
content: Hi,Is it possible to modify a power socket SMPS power supply to lift the voltage to 90-100 volts? Yes, they have a voltage divider and there may be 6 volts of wriggle room. However these chips usually have over voltage protection and the Mosfet switcher tops out at about 48 volts. 60mA for valve HT would be plenty.Secondly it would be really good to have a beefy SMPS at 56V to drive a battery whipper snipper whose batteries cost a packet. Higher voltage SMPS dont seem to be on Baliexpress and the like. A variac and bridge rectfier is not my preferred option as Akiexpress postage shot up to $20 kilo like overnight.

author: Terry Bites
author_rank: Super Contributor
timestamp: December 14, 2022, 01:57:42 pm
content: NoAny direct off mains convetrer is just waiting to kill you when you're not paying attention.Wall chargers are itching to get at you.You need to design or buy a new converter that will run of 5-6VYou can have any output voltage output you like. [not Farringdon's fatal voltages though]I'll mention again this handy resource.www.ti.com/design-resources/design-tools-simulation/webench-power-designer.html#designPlug in 0.1 A out 90V non-isolated low cost and see what pops out.Or take a punt.www.ebay.co.uk/itm/134341489529?hash=item1f47607379:g:CKEAAOSwPoJjgKQW&amdata=enc%3AAQAHAAABICL%2F6h48807RSH%2BrUfxeEbv9HwQWXC5iLQtc3qiLOWa75MUSirEC1whKasJPz%2BHfautyTdTtrB03g0bJaQiuYTG4DQnvLD%2BGurEvibjRaZKL453laqd29OnRDsGBKEemCNqXdsmBsumRdsxDUWaJLe%2FvbfmuAdzJOCNw4oDtndlAOMZP0O5n1qaj8bO2RcRGhAVciMzwichLFjUQEDzoqxeilW%2F86Wjc7yZ3Jj467IdUJFrfywsi2VGMG993J3fGBKfXvFUSudwKj7RakPS7vPQRfWBZFnwVEsKNv58TrnjJtkYnlVXF2geq%2B057llH7Wn4A0s%2FdxQguZ4pu7SSWfi97SWkHhPlpNc0V7ReD6Iviw5S7lYsmc1YoMl72KiqNSQ%3D%3D%7Ctkp%3ABk9SR9Tb4Y6iYQ

author: coppercone2
author_rank: Super Contributor
timestamp: December 14, 2022, 02:23:17 pm
content: UNFORTUNATELY 90V FALLS INTO A NARROW REGION OF ELECTRICAL PHYSICS PARAMETERS (89.71231V - 91.3014V) THAT JUST DO NOT ALLOW COMMUTATION TO OCCUR.

author: TheMG
author_rank: Frequent Contributor
timestamp: December 14, 2022, 08:22:10 pm
content: No, not without re-designing half the power supply (including re-winding the transformer).Would suggest looking for a DC-DC boost converter capable of the voltage you need instead, and run that off your low voltage power supply.

author: Mechatrommer
author_rank: Super Contributor
timestamp: December 15, 2022, 05:51:51 am
content: Quote from: coppercone2 on December 14, 2022, 02:23:17 pmsounds BS to me. any reference?

author: inse
author_rank: Super Contributor
timestamp: December 15, 2022, 06:17:27 am
content: Where’s your joke detector?

author: Zero999
author_rank: Super Contributor
timestamp: December 15, 2022, 08:54:44 am
content: When I needed that voltage range for a project, I bought two 48VDC power supplies and connected them in series. I added a diode in reverse parallel with each output, to protect it against reverse polarity, in case the other one shut down or current limited.

author: Nominal Animal
author_rank: Super Contributor
timestamp: December 15, 2022, 01:50:15 pm
content: If you look at e.g. Mean Well AC-DC supplies, they tend to top out at 48V because they tend to be universal (85 - 264 VAC, 120 - 370 VDC). For similar reasons, there does not seem to be too many AC-DC or DC-DC supplies with output in the range 55-100V.I believe (but check with the more experienced members here, I'm just a hobbyist) that using two Class II isolated 48V supplies, like Mean Well HDR-15-48 (DIN rail mountable units that you can buy from e.g. TME for 16€ apiece, or Mouser for 17.25€ apiece) in series would give you 96 VDC. Each can be adjusted between 43.2V and 55.2V, so you should be able to adjust the combination between 87V and 110V.I also asked TI Webench on suggestions for a 5-12VDC to 96VDC 100mA boost converter, and it provided several designs based on chips like LM51561H that would yield better than 85% efficiency at 60mA.Quote from: inse on December 15, 2022, 06:17:27 amI COULDN'T HEAR IT GO OFF BECAUSE OF THE SHOUTING GOING ON.

author: TimNJ
author_rank: Super Contributor
timestamp: December 15, 2022, 02:30:31 pm
content: Most commercial power supplies top out at 48-56VDC due to the 60V SELV requirement. Staying under this voltage makes your system design and regulatory process much easier. You may of course need an internal voltage above 60V for whatever reason. If so, proper precautions need to be taken to prevent user from coming in contact with this potential. That’s the reason most power supplies manufacturers don’t bother above 60V.

author: jonpaul
author_rank: Super Contributor
timestamp: December 16, 2022, 01:04:43 am
content: 48V = std telcom battery plantVery commpon in all sizes, 2X in series.Some can adjust set both at 45VDONE!Jon

author: Zoli
author_rank: Frequent Contributor
timestamp: December 16, 2022, 07:18:14 am
content: You can get 56V POE supplies; quick search gave me 120W brick.90V: fly-back with one of the 1:10-12 small(Pulse or Würth) transformers.

author: Terry Bites
author_rank: Super Contributor
timestamp: December 16, 2022, 08:38:19 pm
content: You have failed to define a temperature at which this band is valid.Clearly it is subject to drift. Imbecile!

author: Zero999
author_rank: Super Contributor
timestamp: December 16, 2022, 09:03:35 pm
content: Quote from: TimNJ on December 15, 2022, 02:30:31 pm120VDC is the actual limit for SELV, but it does require basic insulation, because it still presents a hazard, just less so than the mains.

author: james_s
author_rank: Super Contributor
timestamp: December 16, 2022, 09:29:18 pm
content: That depends on how much engineering work you want to do. Keep in mind that if you modify it for higher voltage, the current it can deliver will fall accordingly.It's relatively easy to find surplus telecom "rectifiers" which are really just 48VDC SMPS's. You could probably tweak one of those up to 56V fairly easily. Or you could do what I've done with obsolete cordless tools and just install XT60 connectors and use cheap LiPo packs meant for model airplanes and drones and such.

author: Zero999
author_rank: Super Contributor
timestamp: December 16, 2022, 09:56:45 pm
content: I used two DIN rail mount power supplies, in series, with anti-parallel diodes, in an enclosure.Here's an example.https://uk.rs-online.com/web/p/din-rail-power-supplies/2358693

author: Someone
author_rank: Super Contributor
timestamp: December 16, 2022, 10:07:50 pm
content: Quote from: Zero999 on December 16, 2022, 09:03:35 pmDepends which standard you refer to, Australian AS3100:SELV "40V between conductors"IEC/EN/AS/etc 6101070V DC dry, 35V DC wet, or current (more complex)Now with more modern IEC/EN/AS/etc 62368:ES1 DC 60V or 0.5mA

author: Zero999
author_rank: Super Contributor
timestamp: December 16, 2022, 10:23:09 pm
content: Quote from: Someone on December 16, 2022, 10:07:50 pmYes I got ELV confused. Extra Low Voltage is always below 120V, or 50VAC, but SELV varies, depending on the standard.

author: langwadt
author_rank: Super Contributor
timestamp: December 16, 2022, 10:28:29 pm
content: Quote from: james_s on December 16, 2022, 09:29:18 pmquite few places that sell stepper motors and drivers have 60V supplies