SMPS High Inrush rocker switch - Page 1
Forum section: electronics / general

author: Coordonnée_chromatique
author_rank: Frequent Contributor
timestamp: March 21, 2025, 08:14:05 am
content: Hello,I'm using a rocker switch (ARCOLECTRIC 1350 High Inrush) designed to resist to my 400W SMPS ignition (MEAN WELL EPP-400-24), but it arcs and the lugs of the rocker starts to exhibits some traces of over heating.I don't see any others product on the market, can i use a delayed relay and a resistor to limit the inrush current please ?

author: Coordonnée_chromatique
author_rank: Frequent Contributor
timestamp: March 21, 2025, 09:25:25 am
content: I've opened the switch the contatcs are clean...There is a design flaw, the lack of a separator between the faston connectors, have a nice dayI will print and glue a separator.

author: Gyro
author_rank: Super Contributor
timestamp: March 21, 2025, 01:55:51 pm
content: Quote from: Coordonnée_chromatique on March 21, 2025, 08:14:05 amPlease see my reply to your previous question...https://www.eevblog.com/forum/testgear/simple-method-to-measure-inrush-current-of-power-supplies-of-computers-etc/msg5853439/#msg5853439

author: Coordonnée_chromatique
author_rank: Frequent Contributor
timestamp: March 26, 2025, 07:33:27 pm
content: Quote from: Gyro on March 21, 2025, 01:55:51 pmThanks the problem is solved, the swicth is designed to handle 30A 10K, i've isolated the lugs now.

author: coppercone2
author_rank: Super Contributor
timestamp: March 31, 2025, 07:39:58 am
content: I had a rocker switch overrated for the current (10 or 12A mains rocker switch) on a little DC supply and I saw a spark shoot out the side loland yes, its on the main side, for a 3A input supply (300W total output 20A 15V loaded at ~15A and set to 12.5V)I guess that's what 96%? efficiency looks like. I have been meaning to look at inrush current. It's about the size of a deck of cards so you wonder if it needs a 20A or 30A switch?

author: Coordonnée_chromatique
author_rank: Frequent Contributor
timestamp: March 31, 2025, 08:42:02 am
content: Engineers don't say all they know hereI was dubitative with the high thickness of the isolant and the tons of glue on the switch lugs that i've found on some high end computer SMPS, so i've choosen a switch for it ability to prevent arcing thanks to an internal screen.A competent EE probably knows how to prevent arcing on powerfull SMPS but it seems that those ones d'ont write it in forums IMO.

author: coppercone2
author_rank: Super Contributor
timestamp: March 31, 2025, 08:47:09 am
content: I am just saying you would think with a ~330% over rating on the switch for rated voltage AC (I am not using it on DC) it would be OK. I think its more of a consequence of the power supply designer skimping, because if you bought that little highly engineered ultra compact power supply, for a space constrained application, you would not think it needs inrush current limiting added unless you are trying to get by with barely rated parts, like a $2 5 amp rated china switch.Its not one of those problems where you don't have a exact figure for derating a switch to DC. The supply just has a bananas inrush current. A 'nice' inrush control that won't break from momentary interruptions (more complicated then a NTC) would add like 30% to the size, basically ruining the 'marketing' they have for that supply being something you can slip into some chic product with little worries other then price.I could probobly get a bigger supply that does not have this problem and ends up being cheaper, easier to install (1 module, instead of 2 modules + wiring and extra mounting hardware and probably engineering on a ICL board) and possibly equal size or even smaller then the super miniaturized supply if it is properly 'protected'.There is plenty of circuits and discussions on this forum for inrush current limiting, but you will find that its rather a significant pain in the ass to implement one more advanced then a thermistor... and even adding a thermistor to a 'tight' chassis ends up being a substantial effort, if you don't want a total hackjob.... which usually disappoints people that had a project figured out. I.e. you need a screw terminal block, a good adapter for the thermistor or a PCB and the associated mounting hardware + the space to put it in (they get hot and fail real hot so you should separate it from stuff). if you repair stuff, depending on the grid where you are, you might find that the inrush current limiter is a pretty big failure point for circuits. In another area I used to live in I found tons of inrush thermistor disks that simply disintegrated when you touched them, like burned wood in stuff that people left on the curb. That grid had a big load (science/industrial surge load) and it frequently dropped out for a split second (enough to turn off a PC and blink the lights). I think the proliferation of laptops over desktops lead to people ignoring the power grid issue (it stopped eating documents since the laptop has a internal battery).. so without complaints the power company don't do shit to 'buffer' the grid. Anyway if the power comes back on too fast, a thermistor will still be hot and won't offer much protection...