100-200V adjustable, isolated 1A power Supply with 24VDCin - Page 1
Forum section: electronics / projects

author: luky315
author_rank: Regular Contributor
timestamp: November 06, 2012, 10:53:40 am
content: I search for a circuit or a project idea for a power pupply with special requirements for experiments at the University.I need a galvanic isolated adjustable output voltage from 100V to 200V with <= 1A peak Current and <15mA continuous load. The accuracy is not important, +-5% should be ok. My second problem is that the input voltage must be DC, so i can't use a "classic" AC/DC power supply topology.My problem is that I need a starting pont ( Topology IC etc.). Any Ideas would help...

author: penfold
author_rank: Frequent Contributor
timestamp: November 06, 2012, 11:05:20 am
content: What input voltage range are you looking at? What is the isolated side going to be attached to (will it be a rapidly changing voltage)?And what kind of isolation withstand voltage do you need?

author: penfold
author_rank: Frequent Contributor
timestamp: November 06, 2012, 11:14:51 am
content: Sorry, I didn't read the thread subject to the end!My personal opinion would lead me to look at a push-pull topology for that kind of low voltage input. They're *generally* a nicely behaved converter.Since you're not too worried about accuracy you can probably get away by generating feedback either from an auxiliary winding on the transformer and rectify that to produce a feedback signal, or use the input line (primary side feedback), if you can get away without using isolated feedback from your secondary it'll make things a lot easier. The SG3524 Push-pull control chip should serve you well, there are also some good unitrode (part of texas instruments now) application notes based around that chip.

author: brainwash
author_rank: Frequent Contributor
timestamp: November 06, 2012, 10:27:57 pm
content: Not sure about the feasibility of this but if you need a one-off cheap project you can modify an existing 24V DC->110/220V AC car converters that are floating around. Truck systems use 24V so you can probably find these boxes easily. Usually rated for 200-500W nominal, 1000-2000W peak, prices arond 30-150$, quality and real specs vary wildly from advertised. But you do get a complete SMPS working circuit, power stage with beefy MOSFETs and a nice aluminium box. Just the FET's alone cost more than the complete box.Usually they use TL494 or derivatives so they are pretty easy to modify. Result is usually a modified sine-wave, in worst-case they provide square-wave. Switching frequency is obviously low, 50/60Hz.

author: penfold
author_rank: Frequent Contributor
timestamp: November 07, 2012, 08:13:39 am
content: That's a good point by brainwash. If it is a one off, then your best bet would be to do some reverse engineering.Just to throw in another idea to the mix, coilcraft make a nice 'solar micro inverter' flyback transformer for 36V input and 220v output,http://www.coilcraft.com/ja4635.cfmwhich are rather nice and would work on your 24V input bearing in mind it would be ever so slightly tickling the limits to get 200V but should be fine.I know a million people will argue with the statement that push-pull type circuits are generally lower noise than flybacks, so i'll rephrase and say in my experience, I have had more problems caused by improperly designed flybacks than with equally improperly designed push-pull converters.So that kind of brings in the issue of just what you're doing with the supply, if you're doing some particularly sensitive measurements on the system to which they're attached, I'd advise more towards the push-pull rather than the flyback,

author: luky315
author_rank: Regular Contributor
timestamp: November 08, 2012, 01:51:20 pm
content: The Problem is solved. There are a few Lab power supplies with universal input. Not cheap, but it works.