LED Driver Dimming Types


Analog Dimming
Analog dimming is commonly referred to as “0-10V Dimming”. This dimming type uses a linear potentiometer or a wall slide potentiometer like the Leviton IP710 to control the brightness. In a two wire dimming system configuration, one of the driver dimming wires will have a 10 volt output, and the other wire is the return. The potentiometer will vary voltage between the two wires from 0 volts to 10 volts and typically conducts current in the milliamp range. Common potentiometers for these are a 15k ~ 25k ohm such as 987-1726-ND or 987-1302-ND, 5 but please refer to datasheet. If dimming is not needed, these wires are typically left open to produce full brightness, or are tied together if maximum dimming is required.

It is also common for a driver to be dimmed from an external 0-10 volt system without a potentiometer. By applying an external 0-10 volt wire to the return dimming wire (non-10 volt wire) the driver can be dimmed in similar fashion as long as both power grounds are tied together. Some larger lighting applications configure their external dimmer from safety circuits or motion detection systems to help avoid malfunctions or to reduce energy costs.

DALI Dimming
“Digitally Addressable Lighting Interface” type of dimming is addressable lighting. DALI will allow bi-directional communication to multiple devices with just one DALI communication line (two-wire) and is not only used for dimming purposes. This lighting is considered “smart lighting” and allows the user to individually control single lights or groups of lights while also receiving data feedback from each light. DALI lighting is controlled by some type of DALI software and mostly used in manufacturing, but can also be found in commercial and some higher end residential.

TRIAC (Forward Phase) Dimming
TRIAC dimming is sometimes referred to as forward-phase or lead-edge dimming because these chop the leading edge of the positive and negative going AC voltage wave starting from the zero voltage point. These are the “common household dimmers” used for regular incandescent lighting, resistive loads, and the input to TRIAC dimmable LED drivers. These are a development of the SCR or thyristor, but unlike the thyristor, these are a bidirectional device used for AC voltage. These chop the leading edge of the voltage phase instead of the trailing edge as found in ELV reverse phase dimming.

On another note, if you are using a TRIAC dimmer for a medium base or another 120v type LED “bulb” in a household application without a driver, the manufacturing packaging or engraving on the front plate will state if it is rated for LED dimming. A lot of less-expensive TRIAC type dimmers without an LED setting will label them for use with LED bulbs but are nothing more than an incandescent type of TRIAC, and although they will work for dimming LEDs, they will produce excess amounts of noise from the bulbs and decreased LED bulb life. It is important the dimmer is rated for LED lighting and has an adjustment on it of some sort to set it to LED from incandescent. LED drivers with TRIAC dimming input will work just fine on LEDs as this is just for dimming reference, and not responsible for executing the actual dimming.

ELV (Reverse Phase) Dimming
“Electronic Low Voltage” dimming is sometimes referred to as reverse-phase or trailing-edge dimming because these chop the trailing end of the positive and negative going AC voltage wave starting from the voltage peak. Although these will work with resistive loads such as a regular incandescent or halogen bulb, they are designed for capacitive loads such as LED lighting with or without a driver. These provide quiet and more reliable LED lighting. These are similar function to a TRIAC except these chop the trailing edge of the voltage phase instead of the leading edge. These are the dimming type for household LED bulbs that do not use an LED driver and also ELV type dimmable LED drivers.