Why do LED light bulbs sometimes flicker when dimmed?

Flickering in LED bulbs when they are dimmed is usually caused by compatibility issues between the bulb, dimmer switch and the electrical system.  

The most frequent cause of this problem is the use of an incompatible dimmer switch.  Many older dimmer switches were designed for use with incandescent bulbs.  Incandescent bulbs operate differently from LEDs in the way that they create light.  LEDs require more precise dimming control and using an incompatible dimmer can cause an unstable delivery of power which leads to flickering.

There are two main types of dimmers:

• Leading-edge (triac) dimmers – These are older types of dimmers and they are often incompatible with LEDs
• Trailing-edge dimmers – These are a modern design of dimmer and they are designed for LED compatibility

If you use a trailing-edge dimmer for your LED lighting system this typically resolves most flickering issues.

Another factor to consider is the minimum wattage load requirement of the dimmer.  LEDs use very little power and if the total load is too low the dimmer may not function correctly. This can cause LED bulbs to flicker, especially when the bulbs are dimmed to lower brightness levels.

The quality of the LED driver may also contribute to a LED bulb flickering.  Lower-quality drivers may not be able to handle dimming smoothly which leads to inconsistent performance from the LED bulb.  

In some cases it may become necessary to switch to a different dimmer model but you should check for the above variables first.

A brief summary of what you should try to fix flickering:

• Use LED-compatible dimmers and drivers
• Ensure bulbs are labelled as dimmable
• Avoid mixing different brands or types of bulbs on the same circuit
• Choose high-quality LED products