What causes flicker in lighting?

- May 10, 2019-

Flicker can be defined as the perception of visual unsteadiness induced by a light source which fluctuates with time for a static observer in a static environment. LED Flicker is caused by voltage ripple at the output of the AC power supply. Furthermore, a stroboscopic effect is the change in motion perception induced by a light stimulus whose luminance or spectral distribution fluctuates with time for a static observer in a non‐static environment.

The frequency range in which the stroboscopic effect is typically experienced is from 50 Hz up to 3000 Hz. Stroboscopic effect may occur as a result of product properties or system‐level interactions, such as lamp/dimmer interactions and is especially important when considering lighting for industrial markets, where high speed machines are operating or in garages at home as the lighting stroboscopic effect can make high speed moving parts appear static when they are not.

The degree and effects of flicker depend on a number of variables
• Frequency of the voltage change – Hz.
• How much of a voltage change occurs.
• The type of light source (LED, incandescent, fluorescent, HID, etc.)
• The gain factor of the lamp (gain factor is a measure of how much the light intensity changes when the voltage fluctuates – [% relative change in light levels] divided by [% relative fluctuation in voltage]).
• The amount of natural ambient light within the lit area.
• Mains frequency: the frequency of the flicker is typically equal to either the mains frequency or double the mains frequency (in Europe this would mean flicker is seen at 100Hz or 120Hz in the USA).