looking for a led driver board

[haklesup]

It is surprising how much noise some solid state circuits will make. Changing the PWM base frequency, duty cycle or filtering off the highest frequencies (so you don't have a square wave) can help. If the fundamental frequency is above 20Khz, you won't hear it but your dog might. Lowering the PWM frequency might help too but now you risk seeing flicker to get it lower than your hearing. Conformal coating also sometimes helps

[dyarker]

I'll believe you, but it isn't easy. Pulse frequeny? Peak current?

[haklesup]

Depends on what is making the noise. in a low voltage LED and logic circuit, I would tend to think it is rapid expansion and contraction of the LED as a result of heat generated when current is applied. Other components especially at high voltage may have other modes of making sound for example induced movement of adjacent structures from a changing electric or magnetic field.

Pulse frequency would be easiest to manipulate and you may not need to go to very high frequency, just high enough so that the mechanical resonance is not excited. Similar duty cycle or any pulse frequency will give you approximately the same power to the load. Can't really modulate peak current unless you can change the impedance of the load which is generally not practical, it is what it is based on the operating point of the LED. The Current source I suggested can also vary its frequency as well, although the output is DC, its probably best not to run the PWM at the same frequency as your SMPS to avoid constructive interference.

If you scan faster then you also need to deliver your data faster. That may not be practical either and will set a speed limit of sorts. Parallel is so much easier

[Lenp]

Chime in....
Don't know about noise, except when they are letting out their smoke!

[dacflyer]

well the 10" led displays have 20 leds per segment and 6 7-segment digits.. you can definitely hear it,, it is high frequency.
no electronics on the displays..just the leds.