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Basically my problem is probably simple, but I could not find anything searching google and here - maybe I was looking for the wrong things, but here is the problem:

I work in a Hostel and we bought five 3W LEDs with each having their own PSU. (see Photo 1) After installing them just three weeks ago, one of the LEDs stopped working and we didn't think much of it and my boss replaced it incl. the PSU (because they come hooked up to each other and he didn't know that they are easily disconnected). Then the next another one stopped working today, not even 4 days later so I decided to take a closer look at it. Took it all out, connected a new LED to the old PSU and it didn't work. Must be the PSU, opened that up and it was all burnt and black on the inside, quite obviously at the capacitor. So now I am wondering what can cause this? Kinda important to know as there are 5 of those in a wooden wall in a wooden building and the last thing I would like to do is burn in this place :)

The input of the PSU is (supposedly) rated at 100V - 265V (Photo 2)

Thanks in advance!

Misha

Photo 1:

the LED connected to the PSU which is connected to 220V AC

Photo 2:

info on PSU

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  • \$\begingroup\$ 12 volts times .3 amps equals 4 watts ;) could be over current, test voltage output? \$\endgroup\$ – Alexander M Nov 10 '15 at 23:50
  • \$\begingroup\$ Unfortunately I don't have the tools to check the voltage output for another few weeks (the availability of those tools is very limited in southern patagonia) but that's what I found odd as well that there is no exact number on the output... thought it was something "self-regulating"... kind of considering buying a power supply that delivers 1.2A@12v and hook up the five lights in parallel to see if that problem persists but that seems kind of nooby and unproper. could the capacitor blow from over current? cause the LEDs still work fine \$\endgroup\$ – mish Nov 11 '15 at 1:11
  • \$\begingroup\$ @AlexanderM: The power supply is a constant current supply that puts out 300mA. The output voltage varies between 9 and 12 volts in regulating the current. So, it can't be over current because the powersupply is supposed to be regulating the current - unless of course the regulator isn't working. \$\endgroup\$ – JRE Nov 11 '15 at 11:22
  • \$\begingroup\$ Were the LEDs and the power supplies bought as units, or did you select LEDs and power supplies separately? In other words, are you sure that you have proper supplies for your LEDs? \$\endgroup\$ – JRE Nov 11 '15 at 14:37
  • \$\begingroup\$ they came together in one package - already connected over a generic cylindrical connector. \$\endgroup\$ – mish Nov 12 '15 at 15:43
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It is not a case of overpower. Most probably you have a not so stable AC grid in Patagonia and the drivers are being destroyed by Surge or Burst events on the AC side. Normally in the no-name drivers the protection against such events is not really effective since some money can be saved when not implementing. Question: Is there any construction work, with drill machines for example, around? Is there a motor connected on the same circuit? Such loads are well know to cause surges on the mains damaging sensitive devices.

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  • \$\begingroup\$ yeah the AC grid here is a bit crappy and yes there are being works done but these run over a different circuit (different switches on the house entrance) is there a way to protect the PSUs somehow? I could buy one of those surge protection multi-socket-strips (for lack of the correct word) take it apart and basically wire the PSUs to the LED drivers \$\endgroup\$ – mish Nov 12 '15 at 15:30
  • \$\begingroup\$ *take it apart and basically wire the sockets to the PSUs. Or is there a way to make a protection myself somehow? I'm good with electronics and know how to work with AC mains and all that, just lack the theory. \$\endgroup\$ – mish Nov 12 '15 at 15:42
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2 out of 5 burned out in just a few weeks sounds too much like really bad hardware. I'd replace them with name brand equipment before the next one burns out and takes the Hostel with it, killing people along the way.

There really isn't anyway for any one to tell you what is going wrong without seeing a schematic of the power supply, and maybe a picture of the circuit board before it burns out.

With the schematic, someone here could probably recognise the weak spots in the design. From the photo, someone might be able to recognize an incorrect part (one that isn't up to the job.)

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  • \$\begingroup\$ there are no name brands around here... if you look at the map of south america - I'm at the southernmost tip of the continent. really weird selection we got here. \$\endgroup\$ – mish Nov 11 '15 at 14:17
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The power supply is overloaded or at least out of its specified operating conditions. The specification says

  • Power: 3x 1W
  • Output: DC 9-12V, 300mA

A 3W LED has a forward voltage of roughly 3-4 volts and draws between 700 and 1000 mA. The problem here is that the power supply is made for three 1W LEDs in series (thus the 9-12V output voltage):

schematic

simulate this circuit – Schematic created using CircuitLab

Consequently, one single 3W LED overloads the power supply, as it is not specified to operate on an output voltage lower than 9 Volts.

The solution is to buy another power supply or other LEDs.

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    \$\begingroup\$ Not necessarily true: some of the available high-wattage LEDs are in series internally. I have a "10W" LED with a ~12V forward voltage which is made up of 40 dies in a single package. \$\endgroup\$ – pjc50 Nov 11 '15 at 14:06
  • \$\begingroup\$ Damn it, it seems that I won't be able to find a way around a voltage and current meter and buying the proper power supply... thank you very much for the insight! I wish I could provide more details, but as I didn't buy these, nor does the packaging either the LED provide any explanation to what is going on inside.. \$\endgroup\$ – mish Nov 11 '15 at 14:13

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