Flicker (or light ripple), along with spectral distribution and illuminance, is one of the biggest factors affecting visual comfort while working, studying, or performing daily tasks. Dynamic changes in brightness can be triggered by factors such as:
Network voltage fluctuations
Power supply
Lamp design defects
Or the use of low-quality components.
In most cases, the human eye cannot perceive the ripple frequency. However, increased brightness amplitude and intensity can cause fatigue, tearing, headaches, and eye pain. Even exposure to light for just a few seconds can produce the first symptoms of a faulty light source.
In addition to light pulsation, varying light frequencies can cause changes in visual perception, known as the stroboscopic effect. This creates a perception of stopping or slowing down, posing a threat to human health and life.
New EU Regulations on Light Ripple Limits
In early September 2021, the European Commission's new regulation, under the motto "Ecodesign," came into effect. Requirements for electrical equipment, including LED light sources, are changing. Furthermore, new energy efficiency classes and new minimum requirements for flicker and stroboscopic effects have been introduced.
PstLM is a flicker metric, where "Pst" (Short-Term Flicker Severity Value) indicates short periods, and "LM" refers to the measurement method defined in the standard. A PstLM = 1 indicates a 50% probability of flicker being noticeable to an average observer. The regulation stipulates that the required PstLM level should be ≤ 1 at full lighting load.
SVM is a metric that measures the flicker effect (a measure of flicker visibility). The new parameter used to specify the probability of a flicker effect requires SVM ≥ 1. If the SVM value is below 1, the observer will not be able to observe the flicker effect. Assuming an SVM value of ≤ 0.4 significantly reduces the likelihood of this phenomenon.
LED Light Sources and Flicker Effects
Compared to traditional light sources, light-emitting diodes are more sensitive to voltage spikes in the line. Therefore, when designing new systems, we must consider not only the electrical aspects but also the optical parameters of the LEDs. To prevent flicker effects, protection filters are used in power supplies, and their rating directly affects the lighting quality.