Where to buy 125VDC SMPS 0,5A? - Page 1
Forum section: electronics / general

author: Kjelt
author_rank: Super Contributor
timestamp: December 21, 2013, 04:23:41 pm
content: I usually buy TDK-Lambda SMPS for my projects but that series stop at 48VDC.I need a few for Led lighting, about 120/125VDV and 400/500mA.Anyone any idea where to get these and brand? A dedicated led driver with that voltage would also be ok but those are usually current limited instead of steady output voltage. Price should be around $30.- since it is for lighting. Thanks!PS: 230VAC 50Hz input voltage

author: Kjelt
author_rank: Super Contributor
timestamp: December 21, 2013, 11:56:24 pm
content: Quote from: AcHmed99 on December 21, 2013, 05:17:56 pmThanks but they are current limited and too high current for my target devices, thanks anyway.

author: IanB
author_rank: Super Contributor
timestamp: December 22, 2013, 02:11:29 am
content: What devices need 120 V DC to operate?

author: Kjelt
author_rank: Super Contributor
timestamp: December 22, 2013, 01:28:03 pm
content: Quote from: IanB on December 22, 2013, 02:11:29 amLED modules, 40 leds in series are rated at max 140VDC but I measured them at 117VDC. So I wanted to have a 120VDC PSU followed by a LM317 as current limiter, should work fine.

author: nctnico
author_rank: Super Contributor
timestamp: December 22, 2013, 02:10:29 pm
content: Meanwell has a range of constant current PSUs for led lighting. This one may be an option:http://www.meanwell.com/search/HVGC-100/default.htm

author: Kjelt
author_rank: Super Contributor
timestamp: December 22, 2013, 04:16:48 pm
content: Yes those kind of specialized drivers are all in the $70+ rangeI only need a couple of 125VDC SMPS for around half that price, i need about 5 pieces so price is an issue.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: December 22, 2013, 04:35:54 pm
content: Best bet is probably to use two 48V units ( trimmed up to ~60V) in series.Do the LEDs really need to be in series?

author: Kjelt
author_rank: Super Contributor
timestamp: December 22, 2013, 04:52:44 pm
content: Quote from: mikeselectricstuff on December 22, 2013, 04:35:54 pmThe modules were a gift, they are already assembled in a series of 40 leds. I could desolder one or two in the middle or actually more short it ( desoldering is an impossible task on an 8mm thick alumium pcb)which would result in two strings of 19 leds, then 60Vwould be sufficient. I think I rather keep them as they are. What would you do?

author: nctnico
author_rank: Super Contributor
timestamp: December 22, 2013, 05:18:04 pm
content: Slap myself on the head for accepting such a present...If it has to be cheap and it is a one-off project I'd go for a linear solution (transformer), rectifier and a series resistor. Otherwise get a few PSU modules from Ebay.

author: Kjelt
author_rank: Super Contributor
timestamp: December 22, 2013, 05:38:24 pm
content: Quote from: nctnico on December 22, 2013, 05:18:04 pmI have been thinking about a linear solution, the problem of finding the right SMPS would then be shifted to finding the exact correct transformerIf I want 120-125VDC the transformer should have aprox. an output of 84-88 VAC which is also a pretty difficult valueQuoteCan't find 120VDC's if you can please give me a linkI am getting more and more the idea of breaking up the single string of leds into multiple strings.

author: tom66
author_rank: Super Contributor
timestamp: December 22, 2013, 08:29:15 pm
content: Samsung LED TV backlights operate around 120V, 400mA for 40", 46" panels. Take 24VDC to work the driver. Could try harvesting one from a cracked/wrecked TV.

author: nctnico
author_rank: Super Contributor
timestamp: December 22, 2013, 09:37:32 pm
content: Quote from: Kjelt on December 22, 2013, 05:38:24 pmYou could combine the Ebay PSU (put several in series) but you'd still have to deal with the current regulation bit. About the transformer: you can regulate it using a small micro (seehttps://www.eevblog.com/forum/testgear/hp6024a-psu-restoration-project/msg325567/#msg325567for a starting point of such a circuit).Another option is to use a 220V to 110V transformer and use a half or full wave rectifier. By choosing a large ripple (small capacitor) you can make 120Vdc on average.

author: Kjelt
author_rank: Super Contributor
timestamp: December 22, 2013, 09:50:27 pm
content: Quote from: tom66 on December 22, 2013, 08:29:15 pmThanks for the tip, will ask a friend who is in the repair business to look out for me.Quote from: nctnico on December 22, 2013, 09:37:32 pmCurrent regulation is a simple LM317, five components <$2.-QuoteInteresting ideas will have a deeper look into them and experiment some. Thanks

author: MarkL
author_rank: Unknown
timestamp: December 23, 2013, 02:34:32 am
content: Quote from: Kjelt on December 22, 2013, 01:28:03 pmIf you're thinking of a simple series limiter with the LM317, be aware that it has a max input-output differential of 40V. A short on your output could place 120V across the 317 and fry it.And because your proposed power supply can source 60W of power, it would be wise to consider how that power would be dissipated during shorts and other possible failure scenarios, or how you could safely shut down.The simplest solution is to find a supply that already has, or can be set to, the current limit you want.

author: Kjelt
author_rank: Super Contributor
timestamp: December 23, 2013, 01:42:18 pm
content: Quote from: MarkL on December 23, 2013, 02:34:32 amYeah thought about that as well but thanks for thinking with me. I always use a fuse in all supplies I build, in this case I will probably use multiple fuses, one for the output of the supply (which should already have an fuse on the mains input itself) and one before each LM317 current limiter. And yes probably when something will fail the LM317 will be blown, but at $1 a piece I can live with thatI also would like to have at least three powerlevels (0ff, 100mA, 300mA or something like), so a very crude way of dimming.QuoteAgree, the most simple solution was to buy the driver that matches the module, but it costs >$120.- which times 5 runs up to $600which I don't want to spent on my garage lighting system .The proposed drivers above also run around $80 a piece.The TDK-Lambda PSU's have a lot of protections built in, I am thinking of shorting some leds and use a 48V PSU for two strings in one module (so from 40 leds go back to about 2 times 15 or 16 leds). Think I am going to the shack and see if that is easily modified on that thick alu pcb. Very nice for heat distribution but a PITA to solder on.

author: Towger
author_rank: Super Contributor
timestamp: December 23, 2013, 01:50:12 pm
content: These have appeared on eBay UK :The description is not very clear, but looks like 220-240 in and 98-132V out?http://www.ebay.co.uk/itm/Weir-SMS-300-5-SMS3005-110-120V-6A-220-240VAC-3-0A-45-63Hz-U-AC-DC-Switching-PSU-/181287129925?On second thoughts, it looks as if the seller just lists the input voltages...

author: Kjelt
author_rank: Super Contributor
timestamp: December 23, 2013, 02:18:27 pm
content: Quote from: Towger on December 23, 2013, 01:50:12 pmThanks anyway, amazing that some one can sell a PSU without specifying the output voltage / current

author: Kjelt
author_rank: Super Contributor
timestamp: December 24, 2013, 12:50:32 pm
content: Quote from: Kjelt on December 22, 2013, 09:50:27 pmI heard today from my friend. Unfortunately these 24V drivers are only used in the first two generations and seem to be quite rare, nowadays they use the Bus voltage to drive the leds (400+V). Oh well I postpone this project for now, probably find something in the coming year that will be suitable.Thanks all for looking and the advice.

author: tom66
author_rank: Super Contributor
timestamp: December 25, 2013, 06:26:45 pm
content: Well I just fixed a 2012 Toshiba Smart LED TV which had that driver for 24V... 32 inch screen.I do have one from a 2011 TV too, also 24V in.I think most Samsung now use bus voltage but the OEM ones using Samsung panels will still take 24V.