Flicker, or light ripple, together with spectrum distribution and illuminance, is one of the factors that have the greatest impact on visual comfort at work, study, or everyday duties. Dynamic changes in intensity can be triggered by:
- voltage fluctuations in the network
- power supply
- faulty luminaire design
- or the use of low-quality components.
In most cases, the human eye cannot perceive the ripple frequency. Nevertheless, an increase in the amplitude and amount of luminance causes fatigue, tearing, headaches, and eye aches. Even after a few seconds of exposure to light, we may experience the first symptoms of using a faulty source.
In addition to the pulsation of light, there may also be change in the perception of visual perception of different frequencies of the light source, the so-called strobe effect. It creates the impression of stopping, slowing down, and poses a threat to human health and life.
New EU regulations on the scope of light ripple
At the beginning of September 2021, new regulations of the EU Commission entered into force, with the slogan Ecodesign. Requirements for electrical equipment are changing , including LED light sources. In addition, new energy efficiency classes and new minimum requirements have been introduced for flicker and strobe effect.
PstLM is the flicker indicator, where "Pst" (short-term flicker severity value) is the short period and "LM" is the measurement method as defined in the standards. PstLM = 1 means that the average observer has a 50% probability of noticing the flicker. The regulation specifies the required PstLM level ≤ 1 at full lighting load.
SVM is a measure of the apparent strobe effect (Stroboscopic Visibility Measure). The new parameter specifying the probability of a strobe effect must be SVM ≥ 1. With a value below 1, the strobe effect will not be visible to the observer. It is assumed that the SVM value of ≤ 0.4 significantly reduces the possibility of this phenomenon occurring.
LED light sources and the flickering effect
Light emitting diodes are much more sensitive to voltage spikes in the line than a traditional light source. In this case, when designing a new system, we must take into account not only electrical issues, but also the optical parameters of the LEDs. To prevent the flickering effect, protective filters are used in power supplies, and their class has a direct impact on the quality of lighting.