Good intentions yield flicker standard, but questions remain (MAGAZINE)

The Institute of Electrical and Electronic Engineers (IEEE) has published a new LED standard that addresses flicker in solid-state ighting - defining safe levels of flicker by percentage relative to the operating frequency of a light source powered by the AC line.

The Institute of Electrical and Electronic Engineers (IEEE) has published a new standard that addresses flicker in LED-based lighting - defining safe levels of flicker by percentage relative to the operating frequency of a light source powered by the AC line. Presumably, IEEE Std 1789-2015, "Recommended Practice for Modulating Current in High-Brightness LEDs for Mitigating Health Risks to Viewers," was developed with good intentions to guide developers of solid-state lighting (SSL) in delivering products that are safe for consumers. But again we are reminded that nothing about SSL is simple, and there are strong opinions that the standard is overly strict.

The National Electrical Manufacturers Association (NEMA) has issued a press release questioning the IEEE recommendations. NEMA previously published a position paper on what it calls temporal lighting artifacts (TLAs) that addresses what are more typically called flicker and stroboscopic effects. The paper calls for better metrics to quantify TLAs and states that current work, including the IEEE standard, does not account for the fact that human impact depends on both frequency and the wave shape of a light source.

What would be wrong with an LED standard that is perhaps overly strict and possibly cushioned with margins that ensure no impact of SSL on humans? NEMA and others believe that the IEEE standard will result in unnecessary costs being added into LED driver electronics. And upfront cost remains the biggest roadblock to broad uptake of SSL and global energy savings.

Zdenko Grajcar, CTO of Once Innovations and a former executive with AC-LED advocate Seoul Semiconductor, said the IEEE standard fails to address AC-LED technology proven in the field and even would eliminate legacy lighting as safe for humans. Grajcar said incandescent and high-pressure sodium lighting would not qualify as safe under the IEEE guidelines. NEMA concurs on the point about incandescent lighting. Many AC-LED products would also fail to meet the guidelines.

There are fundamental differences between incandescent and other legacy sources and LEDs. LEDs have no persistence when there is no power and quit producing light instantly. Incandescent and other legacy sources produce light through the zero crossing of the AC input. And the new standard was intended to apply to LED-based lighting.

Still, should the authors of the IEEE standard have been less conservative? Should they have directly addressed AC-LED technology? Grajcar said he has seen no credible evidence that any danger exists for flicker above 75 Hz. He further has accused the IEEE 1789 committee of bias against AC-LED technology and is attempting to organize a legal challenge to the conclusions reached in the standard.

We fully support the concept of standards as a vehicle that allows for profitable deployment of LED-based lighting and related technologies such as networks and controls. And an LED standard that defines the flicker risk is a good thing because it can be a serious problem. However, such standards must be accurate and defined without bias to specific technologies. It's not clear that a bias existed in the IEEE committee and the guidelines may truly be focused on conservative bounds to ensure health. But the subject will require more work.

Maury Wright,

Editor

[email protected]