What is Phase-Cut Dimming?

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James Prietzel, Product Manager at Intelligent LED Solutions (ILS)

James is the ILS Product Manager for everything related to LEDs and has been with ILS since 2012. He is dedicated to understanding the latest technologies and innovations from leading suppliers in the OptoElectronics world, from optics, to LEDs and to Intelligent LED Drivers.

The phase-cut dimming functionality, also referred to as phase-control (PC), is a form of power control through pulse-with modulation (PWM). It operates by turning the AC mains power supply to the LED light on and off twice in every mains cycle. In doing so, the flow of electrical energy to the LED is reduced. This has the effect of decreasing the light output, thus enabling dimming of the luminous flux from 3-5 % to even 100 % (exact values depends on the corresponding dimmer type, driver, and LED used). 

What Are the Different Types of Phase-Cut Dimming? 

Within phase-cut dimming, there are two variations. These are distinguished by how the mains voltage is cut off: 

  • Leading-edge dimming – this variation is most commonly applied to halogen lights that are powered via electromagnetic transformers. This technology cuts off the wave of the AC mains voltage on the leading edge, from the beginning.  
  • Trailing edge dimming – whereas in trailing edge dimming, the wave of the AC mains voltage is cut off on the trailing edge, backwards from the end. This can be preferable as it means that there is less interference than can be seen with leading-edge dimming.  

What Are the Benefits of Phase-Cut Dimming? 

Phase-cut dimming technology allows for precise and responsive control of the luminous flux of the connected LED light(s), even when operating at low dimming levels.  

Phase-cut dimming is a simpler system to implement and set up than some DALI dimming systems. Utilising a phase-cut driver reduces the need for extra wiring via a rotary switch, often installed on the wall.  

Provides high efficiency and high-quality dimming of 1-100 percent by amplitude dimming. Phase-cut technology is suitable for implementation with spotlights, downlights, LED panels, use in luminaires with flexible current setting, and indoor SELV installations. 

OSRAM phase-cut drivers are cost-effective and compatible with both types of dimming.  

OPTOTRONIC Phase-cut OTE-13/220-240/350-PC are ideal for phase-cut dimming control. Perfectly suited for indoor applications, the phase-cut constant current dimmable LED driver comes in a very compact housing, making it ideal for applications where space is limited. It can be applied to SELV installations and optional cable clamps enables independent installations.

OT FIT 24V Phase-Cut LED drivers are also ideal for leading and trailing edge dimming. With 24 V DC constant voltage, they are simply perfect for the phase-cut dimming control of 24 V constant-voltage solutions. Available for different wattage requirements.  

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