According to notebookcheck only about half the devices they tested use PWM: https://www.notebookcheck.net/Why-Pulse-Width-Modulation-PWM-is-such-a-headache.270

According to notebookcheck only about half the devices they tested use PWM: https://www.notebookcheck.net/Why-Pulse-Width-Modulation-PWM-is-such-a-headache.270240.0.html https://www.notebookcheck.net/Why-Pulse-Width-Modulation-PWM... It seems to be well known that it for low frequency PWM it causes headaches for some people, so I would expect that there is at least some research in that direction. That said, it seems to only be a problem for few people and only for very low frequencies.