Dissecting a Cree LED Incandecent Bulb Replacement

[e2matrix]

Sorry, there are many high-power LED chips that use 10-12 volts supply. Yes, it's stupid to put 20 LEDs in series, but we've all seen stupider things from Chinese designers.

http://www.youtube.com/watch?v=BkUGNtYKasU
please read the description on the YT page

http://www.youtube.com/watch?v=j2DFJo90JUA

gahh... where do these people get these musics....

It would be extremely unlikely to have a power supply fault that caused it to produce much higher voltage than normal, rather than simply stopping working at all. I'm not saying it's impossible....

(later)
I found this article which you may find interesting.
http://ledsmagazine.com/features/10/4/1
Turns out the Cree bulb uses a 10series2parallel arrangement, so a single LED failure would knock out half the bulb.

They may use 10-12 volts as a supply but the individual LED's will be a quick blue flash bulb if you put that much across them with any current at all behind it.   Check the spec's on the Cree web site for an individual LED.   Unless it has it's own regulator in front of the LED or is an array of LED's they do not run on 10 or 12 volts.   You will find some that are on a single board under one dome in an array but if they use more than about 4 volts they are individual led's wired in series and you can usually see the separate diodes under the dome.   Most less expensive LED 'bulbs' made for 120 VAC use individual little LED's like mondrasek showed and those are generally less than 4 volts each.    Newer high power LED's putting out the equivalent of a 60 watt bulb or more are often higher voltage only because they are an array on one chip.   So not to confuse or refute anything here I'm just saying a single individual Light Emitting Diode is almost always limited to around 3 to 4 volts or so.   

[Pirate88179]

I run all of my Cree 60 watt equiv. LED bulbs on 350-400 volts (each) with no problems at all.  I have many of them and all are still working just fine.  The best LED bulb out there I have ever used.  I am using a JT circuit and the bulbs are gutted. (Driver board removed)  I have many Youtube videos of this.

Bill

[TinselKoala]

They may use 10-12 volts as a supply but the individual LED's will be a quick blue flash bulb if you put that much across them with any current at all behind it.   Check the spec's on the Cree web site for an individual LED.   Unless it has it's own regulator in front of the LED or is an array of LED's they do not run on 10 or 12 volts.   You will find some that are on a single board under one dome in an array but if they use more than about 4 volts they are individual led's wired in series and you can usually see the separate diodes under the dome.   Most less expensive LED 'bulbs' made for 120 VAC use individual little LED's like mondrasek showed and those are generally less than 4 volts each.    Newer high power LED's putting out the equivalent of a 60 watt bulb or more are often higher voltage only because they are an array on one chip.   So not to confuse or refute anything here I'm just saying a single individual Light Emitting Diode is almost always limited to around 3 to 4 volts or so.

But we aren't talking about "individual LEDs" are we? We (most of us except you) were talking about the LED chips that are in the Cree light bulb. Try to access one of the individual LEDs in such a chip. You cannot... they are all made on a single substrate and the CHIP itself needs 10-12 volts! So to have a power supply that puts out 288 volts _unloaded_  might be perfectly reasonable to power a 10-series 2-parallel array of such CHIPS as appear in the Cree bulb.

http://lighthouseleds.com/downloads/dl/file/id/145/10w_led_cool_white_datasheet.pdf
Note the forward voltage (typical) is given as 10.5 volts @900 mA. You cannot get to the individual LEDs inside that chip!

[e2matrix]

Yep and I was talking about individual LED's because that is what was common in many LED bulbs in the past and it is what appeared to be in the pictures in the OP.   However they could very well be LED array chips and without knowing the model # or having a much closer look it is all speculation.   

[mondrasek]

Houston (or Austin), we have a problem.

A second Cree LED bulb has blown in the same fixture as before.  The fixture holds two bulbs.  The bulb that blew today has been installed in that fixture since the first incident of failure when I started this thread.

When the first LED failed I replaced it with an incandescent.  That bulb is still fine.

New info:  The fixture is in my "mud room" that incudes the clothes washer and dryer.  So there is a 240V outlet in use near by.  The new failure also occurred while I was using the 240V dryer unit.  BUT, the LED bulb went dark for a short time earlier when I stopped the dryer to check on the clothes inside.  It came back on a few seconds later once I restarted the dryer.

When the most recent failure occured I turned off the light fixture with the LED bulb after it did not re-ignite when power was cycled to the dryer (and the fixture) and let it sit idle for about 10 min.  After that it still did not ignite, so it was replaced by another incandescent.

The failed LED's glass dome has obvious residue on the inside now!  Definitely on one side, so I assume one of the multiple LEDs actually exploded.

So I am looking for advise (again).  Is there anything to be learned by dissecting the latest burnt out bulb?  What is the likely root cause of the LED bulb failures?  (I am thinking the fixture is probably on one leg of the 240V circuit in that area and inrush currents are f-ing up the silicon based elements in the LED's circuitry?)

Let me know what you guys think.  Especially if there is anyway to test besides "borrowing" a Power Analyzer from work.

I'd like to know that I don't have a potential fire hazard in the construction of this home's wiring.

M.