Understanding LED Flicker: How Drivers Impact Lighting Quality and Health
A major challenge in the LED lighting industry today is flicker, defined as rapid variations in light output over time. While flicker can be inherent to the design of a luminaire, it is often introduced when a luminaire is dimmed. Unlike flicker from line noise or power transients, dimming-related flicker can be controlled with the right LED driver.
Choosing the correct driver not only improves lighting quality, but also reduces potential health risks associated with undesirable flicker.
What is LED Flicker?
There are two types of flicker:
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Visible Flicker, consciously perceived by humans, often considered annoying or distracting (except in special applications like strobe lights)
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Invisible Flicker, not consciously observed, but can still have biological or health impacts, including:
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Neurological issues, including epileptic seizures
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Headaches, fatigue, blurred vision, eyestrain, and migraines
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Increased autistic behaviors in children
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Flicker can also cause non-health-related issues, such as:
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Reduced visual performance
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Apparent slowing or stopping of motion, known as the stroboscopic effect
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Distracting or unstable lighting for video applications
Why LEDs Are More Prone to Flicker
Unlike fluorescent or incandescent lights, which naturally fade out when turned off, LEDs respond instantly to current changes. This fast response means any fluctuations in the driver’s current or dimming method can directly translate to flicker.
Pulse Width Modulation (PWM), a common LED dimming method, switches current on and off at high frequency. While effective for dimming, it can introduce invisible flicker depending on the modulation frequency and driver quality.
Flicker Percentage and Frequency
%Flicker measures the intensity of light variation at a given frequency. A lower %flicker means less flicker and better lighting quality.
Flicker frequency, the rate at which light output fluctuates, also matters. Higher frequencies reduce perceptible flicker and potential health effects, even if %flicker is similar.
IEEE P1789 Standard for Safe Flicker Levels
The IEEE P1789 standard provides recommended practices for modulating current in high-brightness LEDs to mitigate health risks.
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LED drivers should conform to IEEE P1789 or demonstrate equivalent performance through testing
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Flicker measurements, including %flicker and modulation frequency, are essential metrics for quality LED drivers
For example, the eldoLED SOLOdrive 360/A measures light output across different dimming levels. All tested components fell within the “green zone,” indicating no observable effect from flicker.
Choosing the Right LED Driver for Flicker-Free Lighting
An LED system consists of three components: dimmer/controller, LED driver, and the luminaire. Compatibility is key to avoiding flicker.
Three common dimming methods include:
| Dimming Method | How It Works | Benefits & Limitations |
|---|---|---|
| Pulse Width Modulation (PWM) | Switches LEDs on/off at high frequency | May introduce flicker if frequency is low |
| Constant Current Reduction (CCR) | Reduces current to dim LEDs | No flicker, but poor regulation at deep dimming |
| Hybrid HydraDrive (eldoLED) | Combines reduced current with variable frequency | Smooth dim to dark, minimal flicker, compatible with multiple controls (0–10V, DALI, DMX/RDM) |
Key Takeaways:
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Drivers control dimming, so choosing the right driver is critical for natural light and minimal flicker
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PWM alone can introduce undesirable flicker, while hybrid or current-reduction methods are safer for deep dimming
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Always evaluate drivers for flicker metrics and ensure IEEE P1789 compliance
Recommendations for Specifiers and Manufacturers
Specifiers:
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Test products in person to evaluate flicker
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Choose drivers that comply with IEEE P1789 or provide equivalent documentation
Manufacturers:
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Test drivers across the full dimming range in 1% increments
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Use high-frequency modulation to minimize flicker
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Avoid PWM as the sole dimming method
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Publish flicker metrics including %flicker, modulation frequencies, and IEEE P1789 graphs
Final Thoughts
Flicker is a critical factor in LED lighting performance, safety, and comfort. Selecting the right LED driver and dimming method not only improves lighting quality, but also reduces potential health risks associated with LED dimming.
For LED lighting systems, especially in professional or high-traffic applications, driver selection is just as important as the LEDs themselves. Choosing high-quality, flicker-tested drivers ensures safe, comfortable, and reliable lighting for any environment.
