I'm using a 24 volt constant-voltage power supply from Meanwell (link) and I'm fading a string of LEDs with this IRF520 breakout module (link), driving it with PWM from an Arduino.
I'm hearing the power supply start whining when I fade the LEDs (is that coil whine?). I'm just curious if this whining in any way means that the power supply is being used outside of its intended parameters. Is this harmful? Are there things I should be aware of?
It's usually not a concern apart from that the whining can be annoying. Yes, it's probably mechanical resonance in the inductors. I wouldn't worry about it. I never do, in any case. Sometimes adjusting the PWM frequency alleviates the issue.
Indeed, you can try to change the PWM frequency, this should help.
Or use another dimmable power supply, for example IDLC-25A-1050
You can probably eliminate / reduce the whine by putting a capacitor at the output of the supply somewhere between 100µF and 1000µF. I know its a large range but it is a range you can try if you wish.
You might also test with a different string of LED on the supply where they are constantly ON. This would mean the supply will be going from hi current to low current instead of from hi current to no current.
Thanks for chiming in. I usually also don't care about this noise but for some reason wanted to hear what the community says about it. Will try changing the PWM frequency to see if it matters!
That's a nice model but a constant current driver doesn't fit my situation, thanks for the suggestion though!
Keep in mind that if you change the PWM frequency exactly 2, 3, 4 times, then you can again get into resonance. It makes sense to change the frequency slightly, 1.1, 1.2, 1.3 times to get away from resonance.
I can try a cap on the output. I intuitively had pondered that option too but then again the question "hmm, maybe a cap would help" crosses my mind very often 
Couldn't explain to myself why adding a capacitor might eliminate the coil whine in the power supply. The whine is due to a change in its internal switching frequency (or something in that vein), no?
I think I understand what you mean with your suggestion to add an always-on LED strip but that's not feasible for my situation. Entertaining workaround though
Please IDLV-25-24
Two dimming technology, PWM and 0-10V.
Have you tried to give the power supply a constant load without dimming? Is there a whistle or not?
Haha, thanks for that! Apologies, I should have said that there will be more devices using the output of the power supply, so dimming at the power supply is not an option for me.
The whistle goes away when the load is constant (i.e. no PWM being applied).
Now the power supply itself is supposed to have a large capacitor directly across the output which buffers the output as the PWM switches on and off - the internals of the power supply should not "see" the change in current. This appears to be a rather small power supply though! 
The two aspects here are that the capacitor may not be adequately filtering the PWM impulses from the power supply and it is trying to compensate for them , and/ or that it whines at particular average current demand levels.
Arguably, the first of these is probably mostly the case, in which case the answer is to filter the current demand better. A good 1 mF (you might call it 1000 µF) low ESR capacitor would be a good start, connected as near to the PWM switch as possible rather than near to the power supply, and perhaps a series inductor between the power supply and where the capacitor connects to PWM switch, forming a "Pi filter".
Yes but maybe it is aggrivated by the change in current. Was just something easy to try.
I only suggested an LED strip because I though you might have an extra for testing. Again it would be a test, if the whine was reduced or elimination then it would be time to consider a solution.
Ah, now I understand.
Thanks for expanding on what one should expect from a power supply. I'm inclined to agree that the power supply doesn't inherently whine at particular current demand levels but that it's the PWM impulses. I'll try the 1000µF capacitor at the PWM switch!
It should be read "at the power terminals of the PWM module".
yes yes, I read it as such 
I copied @Paul_B 's wording to remain consistent but you're right: PWM module, not PWM switch!
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