Flicker in LED light sources

Flicker is the parameter responsible for the flickering of LED light sources. In traditional tungsten incandescent lamps, flicker was not a problem, as the thermal inertia balanced the fluctuations in luminous flux caused by the alternating line voltage. With LEDs, whose inertia is minimal, all changes in the supply voltage translate into fluctuations in luminous flux. In order to minimise the flickering of light sources, high-quality power supplies with stable output voltages should be used. These power supplies not only eliminate the pulsations associated with mains voltage rectification and pulse-width modulation, but also have good dynamics, i.e. stability of the output voltage even with large load changes. When dynamics are insufficient and the voltage drops sharply during load increases, flicker can occur during brightness adjustment.

The flickering effect is also apparent when looking at an LED light source through the viewfinder of a camera or camcorder, or when there are many different lamps with separate power supplies in a room. In these situations, a stroboscopic effect occurs and changes in brightness become noticeable. In 2021, the next revision of the Ecodesign Directive came into force, which makes it mandatory for lighting suppliers to control the flickering phenomenon.

It is important to pay attention to the flicker parameters when choosing LED lighting to ensure not only comfort, but also health protection.