Understanding Flicker and the New IEEE 1789-2015 Standard
Wednesday, March 01, 2017: 2:15 PM - 2:45 PM
Amplitude, pulse frequency and/or pulse width modulation are the most common methods used to dim LED light sources, introducing a risk of unhealthy flicker. While amplitude (“constant current”) dimming can be flicker-free down to about 20% intensity, this is not low enough for most applications because the eye perceives light levels to be higher than the measured dimmed level, especially at low dim levels. Thus, some kind of modulation is required for deep dimming. Modulation itself is not an issue if modulation frequency is kept sufficiently high, but high frequency is difficult to maintain at meaningfully deep dimming levels. And some drivers flicker even at maximum output.
Until 2015, there were ideas but no solid standard for the understanding and specification of flicker as it pertains in particular to LED lighting. In 2015, the IEEE released standard 1789, which defines the various parameters of flicker, describes the kind of effects seen with different degrees of flicker, and sets research-based thresholds for flicker frequency and modulation depth, while accounting for other attributes such as field of view. The goal of this session is to frame the problem, present the standard in clear, concise language, and provide guidance to manufacturers, lighting designers, specifiers, and end users as to how to select components and systems that avoid the negative health effects of flicker.
As part of this session, Jay and Naomi will provide a framework for understanding deep dimming and how it is achieved, demonstrate the flicker, stroboscopic, and phantom array effects (or lack thereof) from multiple LED drivers, and pass out flicker wheels that will allow attendees to do informal testing of lighting systems.