Leading Edge or Trailing Edge?

Leading edge and trailing edge are two different types of dimmer switch technology. Leading edge contains a triac and a coil which can cause a slight buzzing noise. Trailing edge contains solid state components (IGBT) which provide a silent, smoother operation. The minimum load for leading edge is usually higher at around 40W for halogen whilst trailing edge is lower at 10W. The main advantage of using leading edge is that it is slightly cheaper. A major advantage of using the more expensive trailing edge is for dimming low energy lighting loads such as LEDs.

Both leading edge and trailing edge dimmers use something called phase cutting technology. This works by “cutting off” part of the mains voltage to vary the voltage supplied to the light. The brightness of the light is controlled by increasing or decreasing the voltage and thereby the power supplied to the lamp.

The “cutting off” of the mains voltage can be done in two ways; at the start of the sine wave or near the end of it. Leading edge dimmers have the mains voltage cut off at the start. Trailing edge dimmers have the mains voltage cut off at the end.

Please feel free to contact us for expert advice and up to date information on dimmer switches.