I have a simple circuit that drive a LED:
The input PWM is created as follow:
- base frequency: 200 kHz
- PWM duty-cycle: 0..100% (to change light intensity)
- low freq modulation: 10 Hz..10 kHz
I mean, the low frequency modulation turn on and off the PWM signal. I'm looking for a way to filter out the 200 kHz base frequency, leaving the low frequency modulation there.
In other works, the PWM duty-cycle should be "levelled" ( = filtered) to obtain a constant DC voltage to drive the LED when it's active. I tried to put a capacitor in parallel to the led but I don't know if it's the best place to put it.
Increasing the capacity will filter a bit the 200 kHz but also "levels-out" the low-frequency modulation.
Is that position the best one? Is the x20 PWM base frequency enough to easily filter that and only that?