Should I rather use a leading or trailing edge dimmer?

The classical dimming principles are leading and trailing edge. Depending on which kind of light source needs to be dimmed, the one or the other dimming principle is best used. In general, the leading edge principle is more common. The current flow is controlled by a triac and is being switched on retarded after the zero crossing of the alternating voltage (white triangle in figure 1). Then the current continues to flow to the next zero crossing, and is being “cut” again. This is how the desired dimming performance is being achieved and the brightness of the lamp being regulated.

The trailing edge principle works the opposite way. In zero crossing, the current is being switched on directly and being “cut” in the further process of the sine wave.

In general, LEDs can be dimmed with both principles. The electronic inside the LED is a main factor of a good dimming performance and also how well the dimmer can handle this electronic. For many LEDs the trailing edge principle has proven itself to be the better opportunity. Especially LEDs working with drivers seem to better be handled with the trailing edge dimmer. Unfortunately, most of the times one needs to test the combination of dimmer and LED personally.

A universal dimmer can make life easier for you: a universal dimmer can combine both, leading and trailing edge principle, and you can test on one dimmer, which works best with your LED.

For halogen lamps with magnetic transformers you should use a dimmer with leading edge control, for halogen lamps with electronic transformer a trailing edge dimmer.