Will Philips Master LED lamps work on all Dimmer Switches?

Last year, when the Philips Master MR16 LED was still quite new, Philips released some information about their dimmable LED's.

Even today very few LED retro-fit lamps are actually dimmable. One of the distinct benefits of this product is that it can work on existing dimmer switches.

Not surprisingly, Philips received quite a few questions about this. Now, I have too, so I dug up some information from Philips and have shared the key points here.

'Phase cut' dimmers

Most mainstream dimmers employ phase cutting technology to achieve dimming. This works by cutting off part of the mains voltage to vary the average (or 'RMS') voltage fed to the lamp.

The brightness of the lamp can therefore be controlled by increasing or decreasing the RMS voltage.

There are two ways to cut off the mains voltage: either at the beginning of the sine wave or towards the end of it. A dimmer where such 'cutting off' is done at the beginning is called a leading edge dimmer and a dimmer where the 'cutting off' is done towards the end of the sine wave is called a trailing edge dimmer.

Dimmer switch classifications

There are three popular types of traditional lighting loads that dimmers are designed to be compatible with:

  • R type load: for GLS (General Lighting Service, incandescent) and HV (High Voltage) Halogen
  • L type load: LV (Low Voltage) Halogen with magnetic transformer
  • C type load: LV Halogen with electronic transformer

Using this classification, we have the following dimmer types:

  • R - which can be compatible with R type load (leading edge dimmer)
  • RC - which can be compatible with R type and C type load (trailing edge dimmer)
  • RL - which can be compatible with R type and L type load (leading edge dimmer)
  • RLC - which can be compatible with all three types load

Philips Master LED compatibility

Philips offers a range of dimmer-compatible LED lamps, with specially designed electronics so that the lamp works on most common dimmers.

But, given the vast diversity in dimmer types and quality, they do not guarantee 100% compatibility. Some compatibility issues include flickering lamps at certain dim level or an audible noise (hum).

Philips reports that their LED lamps are tested on more than 30 reference dimmers, and they perform well with most of them. The lamps work well with most R and RL dimmers, but not RC and RLC units, nor any dimmers with neon/LED light indicator.


The vast majority of halogen downlights in Australia are "L type." As a result, most dimmers employed are "RL" units which (luckily) work very well with the new range of LED downlights (click to see Philips MR16 LED installation photos).

- Ryan McCarthy

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