Finding an  off-the-shelf inductor for DC/DC - Page 1
Forum section: electronics / projects

author: max_torque
author_rank: Super Contributor
timestamp: January 13, 2018, 08:29:25 pm
content: I'm doing a 5v in, 30V @ 20mA out, isolated step up converter. But what is the correct "search name" for a dual wound, isolated inductor? I can't seem to pin down what i need to search for!! I need some sort of split wound device, ideally with a suitable turns ratio to suit the step up?

author: Paul Price
author_rank: Super Contributor
timestamp: January 13, 2018, 08:42:58 pm
content: An unisolated simple boost converter will do the job with an single-winding ordinary inductor. An isolated converter requires atransformerwith isolated windings.When doing a one-time job, to get the job done quickly and for free cost of parts, I usually wind my own upon a toroid core which can be salvaged for free from many discarded/junk CE devices, especially easy to find several sizes in a PC power supply and smaller toroidial inductors can be found in discarded ADSL modems, etc. Alternatively, 5V to 28V or 48V small convertor modules can be purchased for much more money.Since your requirements are very light, winding your own toroid transformer could be quite easy to accomplish.

author: Paul Price
author_rank: Super Contributor
timestamp: January 13, 2018, 08:56:53 pm
content: If you can locate a small solenoid or toroid-wound inductor, you can unwind the existing winding and rewind a twisted-pair winding on the same core, and bingo, you've converted an inductor to a transformer. If the toroid is big enough you can wind the secondary on the opposite side of the core for much better isolation.This works safely only if your isolation requirements are not trying to isolate from mains voltages, so this is not for very high voltage isolation, and for a project that is not requiring very good capacitive-coupling isolation. Your voltage isolation is only as good as the insulation ratings of the wire you use x 2.

author: Buriedcode
author_rank: Super Contributor
timestamp: January 14, 2018, 03:34:27 am
content: "Coupled Inductor" is what I have used for sepic or isolated boost (flyback).

author: max_torque
author_rank: Super Contributor
timestamp: January 14, 2018, 02:27:54 pm
content: My continuous isolating rating is just a few volts, but in failure state, i need to withstand up to 1.5kV, so the wire insulation and seperators need to be somewhat sturdy. I'm only building a few of these units (maybe 20) so hand wound is possible, but i'd need to validate the isolation rating somehow?(hence i'd rather buy something pre wound with a data sheet!)If i search for transformer, rather than inductor, i get sunk under massive 50Hz stuff of course! Perhaps an AC line protecting common mode choke could be re-purposed?)

author: chris_leyson
author_rank: Super Contributor
timestamp: January 14, 2018, 02:54:47 pm
content: Wurth do a high voltage version of their we-flex transformershttp://katalog.we-online.de/en/pbs/WE-FLEXHVYou might have to go with flyback or isolated boost as the turns ratio is 1:1:1:1:1:1, at best you could get 1:5 with five windings in series for the secondary.

author: max_torque
author_rank: Super Contributor
timestamp: January 14, 2018, 03:49:40 pm
content: Hey thanks! That Wurth part looks promising! I'll go see if i can get any samples etc