Fig. 1
From: Overlapping PPM for band-limited visible light communication and dimming
AM/CCR vs. PWM. (Left) In AM/CCR, the LED current flows continuously at a set amount for a given LED brightness (Lumens output). (Right) In PWM, the current is switched between recommended minimum LED current and the rated LED current (IF). The ratio of high to low times determines the average current (blue line) and the corresponding LED brightness (Lumens output)