Phase / Trailing-edge Dimming Explained

Dimming is the process of reducing the output level of a light source. There are various dimming methods used in LED lighting, but two of the most common ones are phase dimming and trailing-edge dimming.

Phase dimming, also known as leading-edge dimming, works by cutting off a portion of the input voltage waveform to the LED driver. The dimmer switch turns off the voltage at a certain point in the AC cycle, which reduces the power supplied to the LED and dims the light. This method of dimming is cost-effective and easy to use, making it a popular choice for residential and commercial lighting. However, it has some limitations and may cause flicker or buzzing if used with certain types of LED drivers or dimmer switches.

Trailing-edge dimming, on the other hand, works by cutting off the trailing edge of the input voltage waveform to the LED driver. In other words, it turns off the voltage as the waveform approaches zero, rather than at the peak of the waveform as in phase dimming. This method of dimming is typically more compatible with LED lights and has fewer issues with flicker or buzzing. However, it is generally more expensive than phase dimming and may require specialized dimmer switches.

Some examples of phase dimming and trailing-edge dimming in action include:

• In a residential setting, a homeowner may use a phase dimmer switch to adjust the brightness of their LED bulbs in the living room, creating a more comfortable and relaxing atmosphere for watching TV or spending time with family. Alternatively, they may use a trailing-edge dimmer switch to achieve similar results.
• In a commercial setting, a restaurant may use phase dimming to adjust the lighting levels in their dining area throughout the day, from bright and energetic during lunch service to warm and inviting during dinner service. Alternatively, they may use a trailing-edge dimmer switch for more precise control over the intensity of the light.
• In a museum or gallery, phase dimming or trailing-edge dimming can be used to create a dramatic and impactful lighting display for exhibits or artwork, allowing for precise control over the intensity and direction of the light.

Trailing edge dimming is considered better than phase dimming in electronic drivers for several reasons. Firstly, trailing edge dimming causes less stress on electronic components compared to phase dimming. This is because phase dimming switches the circuit off abruptly, creating a high voltage spike that can damage electronic components. In contrast, trailing edge dimming smoothly reduces the voltage and current supplied to the electronic driver, resulting in less stress on the components.

Secondly, trailing edge dimming produces less audible noise than phase dimming. Phase dimming can cause an audible humming noise in electronic drivers, particularly when the light is dimmed to lower levels. Trailing edge dimming, on the other hand, reduces the noise produced by the electronic driver, making it a more attractive option in environments where noise is a concern.

Finally, trailing edge dimming is more compatible with a wider range of electronic drivers than phase dimming. This is because electronic drivers have different dimming compatibility profiles, and trailing edge dimming is more widely supported than phase dimming.

It's worth noting that trailing edge dimming is not always better than phase dimming in all situations. The choice of dimming method depends on several factors, including the type of lighting fixture, the electronic driver used, and the environment in which the lighting will be installed.