The dimming profile > behavior on a dimmer

The dimming profile describes how the light source behaves when dimming.

In other words:

What is the brightness of the illuminant related to the dimmer position?

For this purpose, Der Lichtpeter has developed the new measure DPA, which expresses the Dimming Profile Deviation in comparison to the incandescent light bulb in percent.
 

At the bottom of this page, there is a list of illuminants tested for dimmability.

The correlation between the applied energy and the brightness of cold lamps (fluorescent tubes, energy saving lamps and LEDs) is determined by the electronic ballast. Since this can look totally different depending on the manufacturer, a cold lamp behaves correspondingly differently.

For this reason, there exists a distinction between dimmable and non-dimmable illuminants in contrast to the incandescent light bulb.
With the so-called dimmable LED lamps, however, the variance of the behavior during dimming as with light flickering has achieved such a degree that they largely do not correspond either to the behavior of a incandescent or to one another.

Or extremely: They call themselves dimmable, but sometimes they are not in practice, they may only survive operated on a dimmer.

In the meantime, it is generally known that a dimmer operated below its minimum load can cause problems, for example the light begins to flare like a candle light with low frequency and irregulary (not to be mixed up with light flicker at double mains frequency).
It is also known that the dimmability for other reasons fails with some dimmers and that there may be incompatibilities between dimmers and lamps.

This has also been stated by the NDR (a German radio broadcast service) in its program "Markt" series on 04-Apr-2016 (even if procedural errors were made, e.g. disregarding the dimmer minimum load).

However, this is not the subject of this page or of the dimming profile. The consideration of the minimum load and the basic compatibility of the dimmer with an LED illuminant is assumed for the following. Here with the dimmig profile it is about the illuminants unfortunate not ideal behaviour with an ideal dimmer, caused by the manufacturer's design of the electronic ballast.

By experience there are two main applications where the dimming behavior plays a role:

In contrast to light flickering, which can be dangerous or unhealthy, the dimming behavior of a luminous means is a pure quality feature and when dimming the illuminant, a lower quality is immediately noticeable to everyone.

This raises two questions about the problem:
1. How bright is the LED bulb in certain dimmer settings compared to an incandescent lamp?
2. How do you express the partial large differences between leading edge and trailing egde?

The consumer would therefore be much clearer if the dimming behavior of an illuminant is measured, set as a measure compared to an incandescent lamp and specified in the technical data.
The Lichtpeter has invested quite a bit of manpower and has now found a solution.

The reference dimmer is a specially developed ideal dimmer:
It is processor-controlled, operates precisely according to the (dimming) educational book, and is independent of the load in its behavior.
This means that the measuring method is independent of dimmers on the market, which in turn behave differently.

The measuring method only reflects the dimming behavior of the illuminant.

The dimming behavior is measured as a dimming profile (relative brightness vs. dim position) in 16 dimpositions (evenly distributed over 360° of a circle, i.e. at distances of 22.5°). By means of the positions 4... 14 used for a real dimmer, the associated dimming profile abberation is determined using the abbreviation DPA as a percentage.

Strictly speaking, two percentages are given because, in contrast to the incandescent bulb, it can make a very large difference whether the light source is dimmed with a classical leading edge or a more trailing edge dimmer. This also clearly indicates at which type of dimming the LED illuminant runs better.

In the following diagrams, the light bulb is designated "Incandescent" as the reference of the dimming profile, for the device unter test it is  "LE" for leading edge and "TE" for trailing edge.

Just as with light flickering: the smaller the deviation, the better.

The two figures as a pair of figures DPA/% = L##T## respectively indicate the percent deviations for leading edge and trailing edge.

It should be made clear that the categorization and evaluation of the dimming properties of a product is not an overall assessment of the product but only the partial aspect of the dimming behavior. Nevertheless, the DPA value to describe the dimming behavior may be considered as a useful quality criterion. Everyone makes their own decision, which criteria he or she uses to evaluate a product in its entirety.

The list on the test page for light flicker has already become very long.

From the presentation similar here the DPA list (updated 03-Sep-2020):

It should be noted that, particularly some filament lamps and all driverless lamps, which each contain only a small amount of electronics, perform relatively well in the dimming behavior, which is similar to the tungsten filament in the nature of the (missing) thing. However, these lamps have very high light flicker values, so a view at the light flicker test page is quite important.