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As a follow up to this question I decided that it is time to see how should I utilize failed LED bulbs. There're 5 of them now, however in different condition - one does not start at all, some start flickering 15 times per second, others start flickering 2 times per second. But those flickering, in a minute or two, eventually start lighting continuously. Obviously the issue was overheating, and as people responding to above mentioned question proposed, the cause is dried up caps, however I did not have a chance to test it so far.

Now background. My chandelier has 5 lamps, each looking down without the ventilation holes in their bodies, thus the heat produced by the bulbs is having issues getting out (the cause of the bulb failures I guess). As I have 5 bulbs now, I can try converting whole chandelier to something else than bulbs powered by the power from the mains.

What I want to do. The bulbs are having LED and this board in their assembly. I can not find suitable 2.2 uF/400 V caps to fit into the board (original ones are 6x12 size, and I suspect they are fake because all caps of this specification start with 8x12) and into inside the body of the bulb, thus I have an idea to remove this board out of the bulbs, and put these boards into the location of chandelier where AC wiring is done, and wire lamp sockets with output of these boards rather than mains AC.

Thus these buck converters will be located in some central point, and LEDs will be located in the lamp sockets.

However I see several potential issues here, but can not evaluate them.

  1. As I understand bulb's controller is having thermal protection, and being within same assembly, it can sense temperature of converter/nearby resistors as well as temperature of LEDs. If I separate LEDs and controller, latter will not sense temperature of LEDs any more. Could there be an issue?

  2. Long wires (~50 cm) from buck converter output to the LEDs. I can not find anything in the datasheet for the chip stating that load must be as close to the converter. Can it be the issue in operation of the converter?

Update: I caught another issue with my design. Buck converters used in the Gauss LED bulbs I used output 85 V with no load condition - in my case when bulb with LEDs is removed from the socket - and output capacitor rated 50 V heats up and will most probably explode.

Thus I either find a way to limit voltage with no load to ~40 V, or scrap my design completely :)

Update: here're results of the project

Board from the bottom, power routing

enter image description here

Board from the top

enter image description here

And within chandelier assembly

enter image description here

Bulbs (with LEDs only) are still heating, but I would say they are ~80 C. Central hub heats a little, but still can be touched by the hand.

The design still needs to be tested for durability though.

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  1. No issue. At worse the LEDs will overheat and die prematurely. But it shouldn't happen if proper voltage and current regulation is applied by the converters/supplies.
  2. Long wire: Increase gauge (cross section), e.g. 1mm or 1.5mm. Thin wires will heat. Thicker wire won't. Solder them. HTH
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  1. There could be an issue if the LED's have faulty thermal design but thermal protection regulation at IC=150'C is to prevent failure as they ought to be running <80'C.

  2. There will be more EMI from the larger loop area of hysteric regulated current. If that matters, depends .... AM radio etc. Otherwise not a big deal.

Considering you have 5 out of ? defective drivers, why would you want to repair them? The design has certain weaknesses to stress the cap's ESR and self heating to random high surge currents when turn on occurs at peak Vac.

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  • \$\begingroup\$ What do you think can be the consequence of (1)? I can not identify LEDs on the bulb's board, IMHO the bulb's design is not as bad it could be. Please elaborate on (2), I do not understand. I have 5 out of 6 bulbs in this faulty conditions (almost all are dead in ~3.5 years). I thought it is good idea to keep original electronics design of the bulbs. Plus, it should be cheapest way to fix them - replace caps and remove original issue - caps overheating. \$\endgroup\$ – Anonymous Jan 28 '18 at 19:26
  • \$\begingroup\$ COB's are now <$0.25/W and lamps $1/W how much will you save? \$\endgroup\$ – Sunnyskyguy EE75 Jan 28 '18 at 19:55
  • \$\begingroup\$ Commercial discussion is off topic. \$\endgroup\$ – Anonymous Jan 28 '18 at 20:09
  • \$\begingroup\$ Thank you very much for edits. For (1) it seems chip has several protections thus if LEDs will fail system will just stop working. LEDs are on the big heat sink so should be ok under normal conditions; Re: (2) everything is inside the metallic chassis :) so EMI should really not be a big issue. \$\endgroup\$ – Anonymous Jan 28 '18 at 21:15

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