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| | Standards group publishes report on flicker and LED lighting
| | 10 Mar 2010 | | An IEEE standards working group has produced a report looking at the health effects of flicker in LED lighting. | | The IEEE Standard P1789 working group has produced a report on flicker in LED lighting.
The report, which is open for public comment, is entitled "A Review of the Literature on Light Flicker: Ergonomics, Biological Attributes, Potential Health Effects, and Methods in Which Some LED Lighting May Introduce Flicker."
Brad Lehman of Northeastern University in Boston, MA, who chairs the working group, says that the document is a survey report and gives no recommended practices or standards. “Its intent is to educate stakeholders on flicker with applications in LED lighting, as per the request of several government agencies,” he says.
The P1789 group goes under the title of "Recommending practices for modulating current in high-brightness LEDs for mitigating health risks to viewers." The group is composed of international research experts in areas such as lighting health, power electronics, photobiology and lamp design.
“The group is assembled to help other standards groups and government labs to understand health effects in light flicker with objective and accurate information. This report is the first step in the process,” says Lehman.
The issue of LED flicker came to the fore recently, after the Energy Star criteria for Integral LED Lamps included a requirement for LED operating frequency to exceed 150 Hz. It is now proposed to change this requirement back to 120 Hz.
The P1789 group is working towards a standard which has the scope to:
- Define the concept of modulation frequencies for LEDs and give discussion on their applications to LED lighting
- Describe LED lighting applications in which modulation frequencies pose possible health risks to users
- Discuss the concept of dimming of LEDs by modulating the frequency of driving currents/voltage
- Present recommendations for modulation frequencies for LED lighting and dimming applications to protect against known adverse health effects.
| | COMMENTS | | Name: geryw Posted: Wed, 17 Mar 2010 21:03 |
| Why the focus on LED lighting? Photons don't come with a label attached. Any light source that flickers, and many do, should be of equal concern. | | Name: kevin willmorth Posted: Fri, 19 Mar 2010 20:03 |
| There are more issues involved in perception and actual reception of flicker than the waveform driving the LED or any other light source. There must be consideration of duty cycle (how long in the on and off periods), latency of phosphors, DC component, contrast between the highest and lowest emission quantity, and illuminated environmental characteristics, such as visual contrast of the light source to background, illuminance ratios within the spaces lighted, movement within the space (speed, distance, duration, viewing angle, etc..) and combination of light sources contributing to the visual task or visible surfaces illuminated. Looking only at this from an overly simplistic perspective and deriving conclusions from it is not an accurate or valid approach. A large number of "DC" drivers use PWM dimming to modulate LED output directly, at 200Hz. When dimmed to 10%, this produces a flicker modulation of 200Hz, with an effective 10% strobe, 90% off. This will be more noticeable than a 120Hz LED operated at 100% duty cycle. Add to this all of the other factors, and one can see this is not an issue that will be resolved easily. Simply blocking all AC LEDs by setting an unrealistic standard now, commits the LED market to be always tied to drivers, and power supplies with their related hazards (failures, fires, etc..). Much more research is needed, and careful consideration of the factors involved must be included to make any valid conclusions or establish realistic standards on this issue. | | Name: mr0791 Posted: Fri, 23 Jul 2010 19:07 |
| Will there be any standards or discussions on the harshness of some LED lighting products currently on the market? Specifically in the comercial settings where motorized equipment and/or machinery is being used. I have heard that this may be an issue to be addressed in the near future. While there are currently no glare or discomfort indexes that I know of available pertaining to LED lighting, that this is being looked at as well. Is there any truth to this, and if so, which agency is handling this? | | Name: ilyafedorov Posted: Thu, 05 Aug 2010 22:08 |
| Do DC Led Lights have the same issue of flickering? |
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