Buzzing LED lights

[youmanskids]

Just started using some comercial LED lights, found a 45 watt equiv for $10 at LOWEs,  but notice they buzz loudly when on my inverter power-  I have a modified sine wave inverter from china-  Is this normal or is there a way to quiet them down without buying a new true sine wave inverter?  I love the low 7 watt power use but the sound is maddening.      Roger

[joestue]

They probably have a 10 or 22uf 200 volt cap inside the cfl, replace it with 47uf or so, whatever you can fit in there. they keep the value low to keep power factor high, but the reduced peak value means the inverter circuitry falls out of regulation and may actually be restarting oscillation 120 times a second. (this might cause early failures, but thats just speculation)

[ghurd]

How many watts does it take?
How many LEDs, and what is the watt per LED?

I don't suppose you are willing to take it apart far enough to see what makes it tick?
Some open up pretty easy.

If it has a stepdown transformer, it will be heavy.  They can buzz on grid power, and can buzz louder on MSW.

Switching regulator will feel like the inside is hollow.  The newer ones don't usually buzz in the ones I played with.

Will need to know what is in it to quiet it down, and will need to open it to add parts anyway.
G-

[Rover]

Will need to know what is in it to quiet it down, and will need to open it to add parts anyway.
G-

I think that is why I Love this board, if it don't work we can just take it part and fix iit the way it should have ben done in the first place

[David HK]

This website may be of some interest to you and other readers.

http://www.pavouk.org/hw/lamp/en_index.html

David in HK

[TomW]

They probably have a 10 or 22uf 200 volt cap inside the cfl, replace it with 47uf or so, whatever you can fit in there. they keep the value low to keep power factor high, but the reduced peak value means the inverter circuitry falls out of regulation and may actually be restarting oscillation 120 times a second. (this might cause early failures, but thats just speculation)

Joe;

Uh, you seem to have slipped a gear or something here? You are talking about CFL, NOT LED lights!

The thread is about a noisy LED light.

You are just confusing people if the recent contents of my my private messages folder is any indication.

 

Tom

[joestue]

heh. yeah, i read that as cfl

still applies though, except its probably a buck regulator instead.

another source of the noise is di/dt, it don't take much of an inductor to fix that..

or you could just fill it with silicon.

[OperaHouse]

I doubt that a $10 LED light has anything more than a capacitor and a low ohm (10-22) resistor that acts as a fuse in case anything goes bad.  That capacitor doesn't act the same with a square wave as it does with a sine wave.   I would try a 100 ohm resistor in series and see if that cures it.   

In a simplistic sense an inductor would smooth things out.  However, an inductor in series would greatly increase the current if the LC combination is anywhere near resonance.  Example, I use a capacitor in series with 220V muffin fans to create 190V from 120V.

[joestue]

the only purpose of an inductor is to slow di/dt to something less than 100 times the average current, not smooth it out. if this cures the noise than its safe to say the noise was caused by the current spike making something vibrate.
I would not be supprised if some new regulation comes up in 2011 that says all cfls will have to have 95% power factor by 2013. some of them are really bad, and the fast rise time of the MSW inverters only complicates things.