Standard LED PWM Frequency?

Thread Starter

tvist21

Joined Jun 11, 2021
20
I'm trying to determine a standard PWM frequency output for RGBW controllers.
I see a lot of constant current LED chips call out a maximum PWM frequency input between 300 and 500 Hz.
1. I assume this indicates that 300 to 500 Hz is standard?


I've seen a 12 Vdc 385 Hz RGBW controller pass FCC Class B testing without any filters on the input.
 

crutschow

Joined Mar 14, 2008
29,792
I don't think there is a standard frequency.
You just want a frequency that is above the flicker frequency the human eye can detect which is usually above 100Hz.
 

ElectricSpidey

Joined Dec 2, 2017
2,146
Normally you can't see flicker at 100Hz if you are looking directly at the light source, but if the light source is moving relative to your eye position or you scan your eyes across the light source you will see a flicker.

And the faster the motion, the more the effect.

I use 3k Hz for my LED PWM.
 

Papabravo

Joined Feb 24, 2006
18,422
I have never heard of a standard frequency for PWM of anything. Like in baseball it is a fielder's choice. There may be other reasons to choose different frequencies, duty cycles, maximum current, minimum current, and so forth to enhance either visibility, LED life expectancy, or power consumption. There is no single set of circumstances that apply to all situations.
 

Ya’akov

Joined Jan 27, 2019
5,660
I have never heard of a standard frequency for PWM of anything. Like in baseball it is a fielder's choice. There may be other reasons to choose different frequencies, duty cycles, maximum current, minimum current, and so forth to enhance either visibility, LED life expectancy, or power consumption. There is no single set of circumstances that apply to all situations.
Unless hr is somehow talking about addressable LEDs like the WS8212 or the APA102 in which case it is data not PWM. Even in that case it is the timing rather than the frequency that is critical as long as it lies inside the operating range.

The only reason I even bring it up is because he mentioned RGBW LEDs and that could be an addressable string—he didn't specify the part.
 

DickCappels

Joined Aug 21, 2008
8,710
As @crutschow intoned, there is no such thing. Generally speaking, just make the refresh rate as high as you can until you run into problems switching fast enough, which would usually appear as reduced light output.
 

ErnieM

Joined Apr 24, 2011
8,294
There is an issue if you go too low as some people can perceive what seems to be a high PWM rate. I can see 100Hz easily even on a stationary LED. Put them on a moving vehicle and I'm constantly looking at the flashy things thinking something unexpected is moving.

I've used 500 to 5000 Hz in my designs. Higher is better!
 
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