I have an ultra cheap PWM LED setup which makes a very loud humming/buzzing/etc noise when not at 100% light output. I read somewhere that I need to add capacitors because the issue is caused by the PSU not being designed for massive frequent fluctuations in power pulled from it.

What capacitors do I need? Where in the circuit do I need to add them? I would guess electrolytic capacitors in parallel between the PSU and LED Controller, with the negative side of the capacitor on the negative output of the PSU, and the positive side of the capacitor on the positive output of the PSU. Is this right? I have no idea what size capacitors I would need.

I have this PSU (DC24V 15A 360W):
https://www.aliexpress.com/item/Hot...32667656950.html?spm=2114.13010608.0.0.tlxYU8
this LED controller (DC12-24V 288W (if at 24V)):
https://www.aliexpress.com/item/DC1.../1923984213.html?spm=2114.13010608.0.0.EBix1s
and 8 of these LEDs (10-30V 27W each):
http://www.tuffplus.cn/content/?43.html

Thanks for any help!

 

I have doubts about the selected LED modules at all is suitable for dimming?

 

I understand your concern as the listed LED fixtures already have their own drivers. The only reason I "picked" these LED fixtures is because they were free to me.

They do appear to be dimmable via PWM with my current setup. I have tested it which is how I know there is a buzzing. They do not get as dim as I would like them to but assumed that had more to do with the limited PWM frequency of the controller.

I had read elsewhere and/or here in other threads that the issue is the PSU and capacitors. I'm not just blindly copying the other threads advice primarily because I don't know what size capacitors I need since my power specific numbers are different.

 

Okay I'm necroing my own post. Sorry I still don't have an answer though and can't seem to find one.

I've tried 2 different possible fixes I came across online.

• The first is to use a range of uF electrolytic capacitors on the +/- output of PSU: I used 4.7 10 22 33 47 100 all at 25V. This made no difference in sound produced by PSU.

• The second is to use a few thousand farads to help the PSU. I recall they were suppose to be a specific type that would dissipate and recharge quickly. I don't have that specific type and just tried with "normal electrolytics." I also did not have enough caps to get to 3k uF. I used the caps I already had hooked up from my first test plus 8 more 100 uF caps. So I was a bit over 950 uF. The sound was exactly the same as before.

Is there a specific style of large capacitor I can buy that would work? Am I going about this completely wrong?

I just re-read my previous posts and thought I should mention the noise only comes from the PSU.