The flickering of (LED)lampsPeter’s parameter is about to change this situation. He has analyzed many investigations about this subject and created a parameter that seems to be complete. He calls it the Compact Flicker Degree (in German: Kompaktflimmergrad) or in short CFD. The CFD is a single number that indicates whether the flickering is imperceptible, acceptable, moderate, strongly affected or heavily affected (and the last two often are not acceptable). He also uses a color-coding like a traffic light, to make clear in a visual way how heavily the LED lamp flickers. OliNo will report this parameter also in the chapter about flickering. A number of examples of how the parameter will be visualized are given at the end of this article. Also the results reported already since a long time (flicker frequency, modulation depts and index) are given for those examples, so that these can be compared. The CFD is the only parameter that gives a final verdict.Background about Der Lichtpeter and the CFDFor example: when the total flicker signal would consist of a set of 4 sinusoidal frequencies of 10, 30 100 and 200 Hz, then these four frequencies should be weighted with respectively the following factors: 157, 53, 1.05, 0.66.
This shows that a flicker frequency of 10 Hz is weighted much more than a frequency of 100 Hz (the human is more sensible to 10 than to 100 Hz). And that the effect of a 200 Hz flicker frequency signal with equal amplitude as an 100 Hz signal, is still 2/3rds of that of 100 Hz.When all single sinusoidal components are weighted, then all these components are squared, summed and then the square root is taken of this total sum. This is finally the CFD result which is expressed in %.
The equation is given here:where A0 is the DC component of the signal, Ak is the amplitude of each found harmonic, MW(f) is the weighing function and 100 is used to make the result in %. All components are squared, summed and over the result the root square is taken. The CFDFB means CFD Frequency Based which is also abbreviated to CFD.
0-1 %: flicker free; deep green
12-25 %: acceptable flicker level; yellow green. Maybe not suitable for work environments, where (for this flickering sensitive) people work (more than) 8 hours and especially where this light is the only light the people has.
50-75%: strong flicker level (strongly affected); orange
75-100%: extreme flicker level (extremely affected); red
100% +: extreme flicker level (extremely affected); redInterpretation of the CFDIt is of importance that this parameter is provided for all lamps so that buyers are well informed about flickering.DimmingThere are other ways that LED lamps can be dimmed, where the feeding voltage is not chopped. These lamps have drivers with separate dimming inputs on which a voltage, signal or resistance is connected to indicate the driver to what level the lamp should be dimmed. It is to be expected that these dimming methods do not necessarily lead to a higher flicker level of the lamp.Examples of flicker results
43 %, moderate flicker level.
26 %, moderate flicker level.
16 %, acceptable flicker level.
1 %, flicker free or imperceptible flicker level.LinksWant to know more about relevant parameters of led lamps? See the explanatory articles here.