Flicker and Perceived Brightness in PWM-Dimmed LEDs: A Simulation Study of Driver Filtering and Gamma-Corrected Duty Mapping

Pulse-width modulation (PWM) is the usual way to dim LEDs in lighting and displays, but it produces temporal light modulation (flicker) and, with a linear code-to-duty mapping, uneven perceived brightness steps. This paper uses numerical simulation to examine both effects. A first-order driver filter (time constant 100 µs) leaves the flicker of a 50 % duty PWM at 100 % at 500 Hz, 46 % at 5 kHz and 12 % at 20 kHz. For brightness, a linear 8-bit code-to-duty mapping gives a maximum lightness step of 3.5 units of CIE L* between adjacent codes, whereas a gamma-2.2 mapping reduces it to 0.59. Realising a gamma-2.2 mapping without visible quantisation steps needs at least 10 bits of PWM duty resolution in the simulation. The study is a simulation with an idealised optical model. This is a simulation study; all results are outputs of the deposited Python code with assumed parameters. Source code is attached.