What would you use for isolated DC-DC? - Page 1
Forum section: electronics / projects

author: Juha
author_rank: Contributor
timestamp: January 08, 2022, 04:26:20 pm
content: Hello All,I have been trying to decide how to do an isolated DC-Dc converter, rough specs:package pcb mount/soldered12- ~30 VDC input5V 3A outputLow bom count / smallish foot printCost max target around 10-15$, low volumeParts availableIm having a real hard time deciding what to use and the availability of parts doesnt make it any easier. I first thought I would do it in an easy way by buing a PoL (like flexpower PNA) and then use a transformer driver (like max258) to isolate it, but I wasnt able to find drivers that can drive 3A...Then I thought if I could find flybacks without the need of an opto (example LT8302), but you cant really get them...Is the "only" option to go with example some uc384, these are available from multiple vendors but requires much more parts?Would be nice to find something quite easy and generic that could be slapped to "any pcb".Edit: Added "package" and low volume to specs

author: Benta
author_rank: Super Contributor
timestamp: January 08, 2022, 04:35:40 pm
content: For your cost point, look at DC/DC modules, you'll get them ready-made. As an example, from Traco Power. This is so trivial, no need to reinvent the wheel.

author: nctnico
author_rank: Super Contributor
timestamp: January 08, 2022, 05:41:56 pm
content: Quote from: Benta on January 08, 2022, 04:35:40 pmIndeed. DC-DC converter modules are a dime a dozen. Not worth it to design yourself.

author: Terry Bites
author_rank: Super Contributor
timestamp: January 08, 2022, 06:03:38 pm
content: So many choices. So 15-20W and what level of isolation do you need. 100s of volts or kV isolation?DIY is a waste of effort and cash.Have a look at a meanwell PSD-15B-05 about $10. But be careful, withstand voltage and working voltage are not the same thing.

author: Juha
author_rank: Contributor
timestamp: January 08, 2022, 06:07:06 pm
content: Quote from: Benta on January 08, 2022, 04:35:40 pmQuote from: nctnico on January 08, 2022, 05:41:56 pmYeah thats what I also thought and should of said that this was my first idea. I typically use digikey to find parts as the filters are quite nice and you get a rough idea of the price. I should of added (will edit) that cost traget in low volume.Cheapest with above specs is a module from Meanwell NSD15-12S5 16.77, cheapest example from is THL 15-2411WI at 30$/pc.

author: Juha
author_rank: Contributor
timestamp: January 08, 2022, 06:11:04 pm
content: Sorry did not put it to specs but I am looking for something mounted to a pcb. 100s of V is enough.

author: SiliconWizard
author_rank: Super Contributor
timestamp: January 08, 2022, 06:36:37 pm
content: Quote from: nctnico on January 08, 2022, 05:41:56 pmYep, although the OP said ISOLATED. There are still many available, but of course not quite as many as just "DC/DC converter modules".Now I still agree, no need to reinvent the weel here.RECOM Power, and a lot of other vendors have them.You'll also find "medical" DC/DC isolated converters, if that's what you are after, compliant with IEC60601 or equivalent.Another point: if you want *isolated* then surely you have some requirements in terms of isolation. And if you want to test that your design complies with what you claim, you'll need specific equipment for that. And, if, on top of that, you actually want the whole thing to be compliant with some standard, then you definitely don't want to do it yourself, unless you have ample cash, some experience and a very good reason for doing so.

author: nctnico
author_rank: Super Contributor
timestamp: January 08, 2022, 07:18:21 pm
content: Quote from: Juha on January 08, 2022, 06:07:06 pmAnother option is this manufacturer:https://www.mornsun-power.com/This one for example:https://www.mornsun-power.com/index/sitesearch/partlink/keyword/URB2405YMD-15WR3.htmlhttps://store.nacsemi.com/Products/Detail?part=URB2405YMD-10WR3&stock=MS0000000006536Farnell / Newark is selling some of Mornsun's products under their Multicomp brand.

author: Juha
author_rank: Contributor
timestamp: January 08, 2022, 08:53:14 pm
content: Quote from: nctnico on January 08, 2022, 07:18:21 pmGreat stuff, thanks for this.This just about what I was looking for, seems to be in the price range and do exactly what I was wanting. Your nac store link goes to the 10W one but they also have the 15W.Huge thanks for letting me know about this one.