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Electrolytic caps in LED light bulbs

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eem2am

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I took apart some very expensive LED light bulbs (40W incandescant replacement).

They all had a 450V electrolytic just after the full wave bridge.

The bulbs cost £30.

The marketing goes that its worth paying that as they last for 10 years.

But how will they last for 10 Years with an electrlytic in them?
 

if the electrolytic is within maximum voltage in operating life ,
no possibility of failure(assuming a good manufac company cap).

another fact is that , the 450v types should not be kept idle for months together.
you should use it everyday by having chrge (and dischrge) cycle.

probably your doubt may be due to failed electrolytics in electronic equipments , that you might have seen.

srizbf
11thmay2010
 

Not only max voltage, but also max temperature is important. Not in LED drives, but motor drives I have seen electrolytics dried in several years due to high temperature. I can imagien with LED lighting you are going to be at hot levels., even if you have a good PCB and colling mechanisms.
 

Look at compact fluorescent light bulbs that are supposed to last 7 years to 10 years. Many fail in 1 or 2 years.
Usually the electrolytic capacitor inside dries out due to the heat then the circuit blows up.
 

Hello,

I also have strong doubts about the expected lifetime. LED lamps produce heat that has to be removed by conduction/convection only (so you need temperature difference). Maybe they managed to use a test setup that is far from realistic operating conditions.

When the lamps are in an armature, temperature rise will be significant in many cases. As life expectancy of electrolytic capacitors halves each 8..10 K increase, I don't believe the 7 to 10 Years, because I don't believe they use extra long life 105 or 130 degrees C. capacitors in it.

Experience over the years will tell us….
 

Low power LED lamps use Polyester type capacitors and the failure in such cases is due to other reasons. It is worth finding if it is really electrolytic capacitor rated at 450V or it is some other type where the life expectancy is high and cost too !!
 

Hello,

I saw a (low power) lamp with polyester capacitor also. These types use that capacitor as a current limiting device (instead of an electronic circuit). Of course here the capacitor is no problem, there it was too high temperature of the aluminum cooling frame.
 

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