Does Photometric Flicker caused by poor quality LED drives affect human health?
Human beings receive information around them with their senses. And when it comes to light, we undoubtedly perceive its existence with our eyes. It is known that we perceive 80% of the ambient information with our eyes based on scientific studies. Especially in light sensitive people , Photometric Flicker is known to affect our health and affect visual performance and comfort in its long-term effects, trigger migraines, cause headaches, dizziness and nausea. (1) In its lighting book, IES (Society of Lighting Engineers) describes photometric Flicker as an instantaneous light intensity change in the light source. (2) The reason for the change in this light source is undoubtedly the driver of the lighting fixture.
Flicker (instant light intensity change) was a common problem in magnetic ballast flöresans and gas discharge lamps. With the development of technology, this perception gradually disappeared with electronic ballast drivers. With the proliferation of LED technology, different quality fixtures were introduced to the market, and this Flicker effect reappeared. When we examine the lighting fixtures currently used, we can say that almost the vast majority of them form high Flickers, as in fluoresan fixtures with magnetic ballast. Despite this, it is produced by domestic and foreign companies in fixtures that produce almost nonexistent Flicker, as in electronic ballast flöresans.
When all the products sold in the lighting market are examined; proportionally, we can see that there are more products with high percentage of Plicker.This value is not included in the query list because there is no standard or test routine determined by what the max percentage of the Lightflicker value shared with the public in this regard should be and how much is harmful. However, flicker value is as important and remarkable as the energy-saving lighting fixture. This Flicker, which originates from the driver of lighting fixtures, has become an increasingly popular topic for IEEE (International Society of Electrical and Electronics Engineers) and leading lighting designers.
The Flicker value of the lighting fixture can be easily measured with handheld spectrum and luxury meter devices (ColorMeter) and Flicker data as well as Lux, CCT, CRI data, and it is possible to compare these values with flickerin dex or Percentage Flicker data in the IES lighting book. Quality lighting is undoubtedly products that provide comfortable lighting according to the relevant standard (EN 12464-1), light color is selected correctly and instant light change (LightFlicker) is low.
- What is Flicker?
While photometric Flicker is a serious subject of research, there is no official limitation or standard yet. However, studies show that frequencies below 100Hz are detected and completely disappear above 500Hz.
The Society of Lighting Engineers (IES) has a standard called RP-16-10; while naming percentageflicker as a periodic change in the amplitude of the light source, it considers flickerindex as the waveform of periodic light amplitude change and defines the ratio of average light intensity to total light intensity. (2,3) Both values are calculated according to the standard as follows.
The graph of the relationship between Percentage Flicker and Flickerin dex is shown as follows.
ASSIST Solid state lighting systems and technologies association states that at 100Hz frequency it should be 8% below the acceptable percentage flicker and at 120Hz it should be below 10%. (5)
2.Examining the effect of instantaneous change of output current (Outputcurrentripple) on Flicker
When we examine the catalog information of LED drives, we see that output current sudden changes (outputripple) range from 10% to 30%, while voltage changes range from 5% to 15%. For example, if the instantaneous current change of a 700mA drive is 20%; the output current value (700 x 0.20 = 140mA) varies between 560mA and 840mA based on the drive's technology. Since this instantaneous current change directly affects the resulting light, the smaller this value, the fewer Flickers are generated.
- Calculations and studies on Flicker's Measurement
All lighting products that work with mains voltage are Flicker in encandesen, flöresan and gas discharge lamps. In fact, some traditional sources of lighting, such as compact flöresan, begin to make a high degree of Flicker as soon as the energy is first given or towards the end of their life, and it increases so much that it informs us that we need to change it.
The following table shows flickerindex and percentage Flicker, which are created by traditional lighting sources.
Flicker values can be measured with handheld light meters available on the market. With devices such as uprtek MK350D, Gigahertz Optical Light-Meter, EverfineLightFlicker Analyzer, you can make these measurements in a practical way.
- Acceptable limit of Flicker value and apps where it matters
Restrictions should be imposed on the use of all lighting fixtures that can cause flicker in office areas, hospitals, schools, industrial areas and general lighting areas. Since the mains voltage is 50HZ in our country, fixtures with flicker frequency below 100Hz should not be preferred and the acceptable percentage flicker value should not be more than 8%. In the treatment centers of patients such as epilepsy, this value should be below 3.3%. (6)
Flicker is an extremely important and remarkable topic, especially in TV studios and live venues, conference call halls.
All lighting sources (including LED technology) that work with mains voltage have Flicker, and this is inevitable. However, while the percentage Flicker can be improved as with electronic ballast fliers, it can be improved by being drawn within acceptable limits if quality LED drives are used.
Based on the standards prepared in the world (IES RP-16-10 and Energy Star requirements), the mains voltage frequency in our country is 50Hz and the Flicker Frequency of the lighting source we choose or use should not be below 100Hz. The percentage flicker network frequency we measure with handheld devices should not exceed 8% if it is 50Hz and the mains voltage should not exceed 10% if it is 60Hz. In addition, this value should not exceed 3.33% in epilepsy treatment centers. (6)
Since the Flicker source is the LED driver of the lighting fixture, the luminaire manufacturers must pay attention to the instantaneous changes of the output current (outputripple) of the LED drives available in the market. In applications where Flicker is important, values with outputripple, i.e. instantaneous change of the output current of the LED drive above 10%, should not be accepted and should not be used in applications where Flicker is important.
Lighting designers and end users should question this value and avoid applications that will affect human physiology and health. Lighting should also warn fixture manufacturers to include a percentage Flicker or flickerindex (PercentageFlicker&Flicker Index) on driver tags. At TSE, it should do its part, set standard values and force lighting fixture manufacturers to do so.
US Department of Energy http://apps1.eere.energy.gov/buildings/publications/pdfs/ssl/flicker_fact-sheet.pdf
US Department of Energy -CharacterizingPhometricFlicker http://energy.gov/sites/prod/files/2016/03/f30/characterizing-photometric-flicker.pdf
ENERGY STAR® Program Requirements Product Specificationfor Lamps (Light Bulbs) Eligibility Criteria Version 1.0 energystar.gov/products/specs/sites/products/files/ENERGY%20STAR%20Lamps%20V1%200%20Final%20Specification.pdf
ASSIT Alliancefor Solid StateIlluminationSystems ad Technologies http://www.lrc.rpi.edu/programs/solidstate/assist/
IEEE 1789-2015 – IEEE RecommendedPracticesforModulatingCurrent in High-BrightnessLEDsforMitigatingHealthRiskstoViewers http://grouper.ieee.org/groups/1789/