Advice on a switching power supply - Page 1
Forum section: electronics / beginners

author: fabiodl
author_rank: Frequent Contributor
timestamp: April 13, 2020, 07:50:37 am
content: I have a project where I need a 9V, a 5V and a 3.3v rail, where the last two require quite a lot of current (in the order of 2-3A).I am currently using a 36W, 12V switching power supply, specifically thishttps://www.amazon.com/beioust-Switching-Supply-Module-Circuit/dp/B07Y38LHM5followed by a L7809, a tps54525 and tps563200 converting the 12V to the respective voltagesI know it doesn't make sense economically, but I would like to design my own 110/220V -> 9+V stage.Do you have any suggestion on what IC / transformer I could use?I need to keep the footprint 110x45x30mm so small transfortmers are a must

author: tunk
author_rank: Super Contributor
timestamp: April 13, 2020, 10:22:48 am
content: If U1 is a TL431 voltage reference then you may be ableto modify it to output 9V by changing some resistor(s).

author: fabiodl
author_rank: Frequent Contributor
timestamp: April 13, 2020, 10:48:23 am
content: sorry,maybe I was not clearI'd like to recreate the 110/220v-> 12v part with known parts. I am not interested in modifying the existing module

author: Vovk_Z
author_rank: Super Contributor
timestamp: April 13, 2020, 11:48:34 pm
content: There are a lot of high voltage dc-dc step down regulators. Use one of them.Google for Viper, TinySwitch, LinkSwitch, TopSwitch. Some of them will fit you.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: April 14, 2020, 12:20:20 am
content: Well, basically just copy the circuit. The 6-pin SMT on the bottom will be some kind of flyback controller, you can find brand-name versions from the usual suspects. There's really not much to vary on these things, it's a basic power supply.Now... knowing what to vary, when, and by how much; that, of course, is the trick...If you're just doing it to say you can, it's more or less...whatever. Any risk is your own; it's not UL rated, so if it starts a fire, it's not like you're going to get insurance back, or something. Anyway, as long as you keep the fuse in the design, and put the unit in a metal enclosure, fire should be a very remote possibility. Likewise for EM emissions, at least putting on the filter components is a start, but if you knock out neighboring licensed radio users nearby... that's technically your problem.In a commercial context: expect to spend ca. $20k minimum, or the equivalent amount of time and personal labor, to develop a new from-scratch custom power supply, and get it through regulatory testing for commercial sale. For beginners, some months of concerted study on top of that, bare minimum, including scale model tests, exploratory experiments, that sort of thing, and assuming the test equipment to measure and verify hypotheses. At a more casual rate, expect several years of study, preferably directed by a standard college curriculum. And no, they still won't teach you power supplies specifically, but they'll teach you the tools you need to know to understand them.Or, the forum is always open, of course.But just as a matter of scale, don't expect people to be able to answer every possible question, because -- there are thousands upon thousands of tiny questions, and hundreds of large ones, that this kind of study encompasses. Your best start is to learn how to ask questions in the first place -- learning how to learn. Be curious, pick things apart and understand that there are so many aspects to them and how in turn to figure out about those, etc.Tim

author: Vovk_Z
author_rank: Super Contributor
timestamp: April 14, 2020, 02:26:45 am
content: For low power (<20..50W) there are now integrated (and cheap enought) ac-dc convertors. You have to add only input and output filter circuits.

author: fabiodl
author_rank: Frequent Contributor
timestamp: April 14, 2020, 03:45:14 am
content: the 6 pin chip seems to be something called 63J04a, but I cannot find any datasheet.Here is the schematichttps://cxem.net/pitanie/5-360.phpI am going to do it as a hobbyist, so time/certifications are not a problem.Vovk_z, do you have any links? I looked digikey, but all I find are metal boxes which are way too big