DC-DC transformer isolated output - Page 1
Forum section: electronics / beginners

author: peps1
author_rank: Regular Contributor
timestamp: August 06, 2014, 08:03:36 pm
content: Hello,I wanted to build a a circuit that will take 9v DC input, convert to AC through a transformer and covert back to DC isolating the output DC from the input DC giving me a floating 9v that can be used with positive and negative ground circuits.Can anyone link me to some example schismatics or reading material that will help!

author: SeanB
author_rank: Super Contributor
timestamp: August 06, 2014, 08:14:26 pm
content: How much power? Look for isolated power modules, a very common one does 5V in and 9V out at around 1W and was used for older networks that ran on coaxial cable.

author: peps1
author_rank: Regular Contributor
timestamp: August 06, 2014, 08:28:01 pm
content: Quote from: SeanB on August 06, 2014, 08:14:26 pmReally low power, sub 250mW.Will have a hunt round google for isolated power modules

author: mariush
author_rank: Super Contributor
timestamp: August 06, 2014, 09:54:01 pm
content: Another option would be to use something likeAdum5000to get 5v @ 100mA (500mW) isolated. Then, use a boost regulator with high efficiency to get 9v.A proper boost regulator should be able to get about 85-90% efficiency, so your 250mW on 9v (or in other words about 30mA) shouldn't be a problem.Probably more expensive compared to a retail isolated power supply but would make for a much thinner power supply, especially if you use a high frequency boost regulator which would allow surface mount capacitors and low profile inductors.ps. do note that this adum5000 has an efficiency of about 34% so to get 5v @ 100mA on the isolated side you would need 5v at about ~ 350mA which may be more than you planned for.ps2. crap. I don't know how i read "5v" input .. Adum5000 being designed for usb isolation is only capable of 5.5v max.Anyway, reading your posts a bit more carefully, I don't see the need for isolation... you can use even something cheap as MC34063 to convert 9v to -9v (use it in inverter mode) and you have the original 9v there. If you need mains isolation then you could still use 5v in -> isolation chip -> 5v out and then 5v -> -9v , 5v ->9v (but the two -9v and +9v won't be independent, not like it matters)

author: peps1
author_rank: Regular Contributor
timestamp: August 06, 2014, 10:13:47 pm
content: Quote from: SeanB on August 06, 2014, 08:14:26 pmOK, found a9v in 9v out isolated moduleany advice on what I should do regards filter capacitors on the input and output of a module like this (assuming it wont have any of its own)?

author: ice595
author_rank: Regular Contributor
timestamp: August 06, 2014, 10:31:36 pm
content: would be nice if the LTC2943 didnt come in such pain-in-the-arse pin package.anyways, is there any popular differential amplifier that comes in through hole or SOIC package?

author: David Hess
author_rank: Super Contributor
timestamp: August 07, 2014, 08:50:35 pm
content: Low power transformer isolated supplies are often used with Ethernet and interfaces like RS-232 to provide galvanic isolation.Coilcraft has a good list to start with that includes part numbers which will lead to typical application examples:http://www.coilcraft.com/prod_isolation.cfmThese types of transformers can be used with simple inverters to generate a regulated or unregulated output.

author: Jeroen3
author_rank: Super Contributor
timestamp: August 08, 2014, 12:00:50 pm
content: Its not that hard if you know what to look for... "transformer driver".http://www.ti.com/lit/ds/symlink/sn6501.pdf