PWMflicker

PWMflicker refers to perceptible light fluctuation caused by pulse-width modulation used to control brightness in electronic lighting and displays. It occurs when the modulation frequency and duty-cycle variations create intensity changes that the eye or camera sensors detect. PWMflicker is most noticeable with high-contrast scenes, slow dimming transitions, or at low PWM frequencies, and can arise in single-LED or multi-LED arrays due to driver electronics, nonlinearity in LED response, or poor ripple filtering.

Mechanism: PWM rapidly switches the supply on and off. The average current is set by the duty cycle; the instantaneous light output follows the drive current, producing a flicker at the modulation frequency and its harmonics. If the modulation frequency is within the eye’s temporal resolution or if there are irregularities in current rise/fall, flicker becomes visible as flicker bands or shimmering.

Perception and health: Some people experience eye strain, headaches, or migraines from PWM flicker. Perception declines as PWM frequency increases. In practice, many lighting products use PWM frequencies in the high hundreds to several kilohertz to reduce visibility. Cameras and smartphones may still show flicker due to aliasing with exposure and rolling shutter.

Measurement and standards: Flicker is assessed with photodiodes and flicker meters, evaluating modulation depth and temporal characteristics. Industry guidance recommends higher PWM frequencies and smoother transitions. Standards for lighting safety and power quality provide methods to quantify flicker impact, though results depend on observer and use case.

Mitigation and design considerations: To reduce PWM flicker, engineers raise PWM frequency, employ constant-current drivers with smoothing, use analog dimming where appropriate, apply ripple filtering, or use multi-channel or pseudo-analog dimming strategies. Selecting flicker-free LED sources and driver electronics with built-in flicker mitigation is common in consumer lighting and displays.