> There are two ways to dim LEDs: linear regulation and some sort of pulse modulation. Linear regulation is wasteful and you're pretty unlikely to encounter it.

> There are two ways to dim LEDs: linear regulation and some sort of pulse modulation. Linear regulation is wasteful and you're pretty unlikely to encounter it. Pulse modulation is common. Within the pulse modulation case, though, there are two important subcases. You can PWM a load that consists basically of just the LED itself, which acts as a resistive load, and will flash on and off at high rate (potentially too fast to be noticeable, as you say). But you can also PWM an LED load with an inductor added, converting the system into a (potentially open loop) buck converter. And this allows you to choose both the brightness ripple and the PWM frequency, not just have 100% ripple. Taking ripple down to 5%, or 1%, or less, is perfectly straightforward… but inductors are expensive, and large, so shortcuts are taken.