IEEE Std 1789-2015 pdf download – IEEE Recommended Practices for Modulating Current in High-Brightness LEDs for Mitigating Health Risks to Viewers

02-25-2022 comment

IEEE Std 1789-2015 pdf download – IEEE Recommended Practices for Modulating Current in High-Brightness LEDs for Mitigating Health Risks to Viewers.
In LED power electronic drivers, typical design specifications in application notes might include specifications on peak-to-peak LED ripple current% or root-mean-square (rms) LED ripple current. Peak- to-peak LED current% = 100 × (ILEDmax – ILEDmin)/ILEDavg, where ILED represents the current through the LED. For the special symmetric cases when ILEDavg = 0.5 × (ILEDmax + ILEDmin), then the peak-to-peak LED ripple current% is equal to twice the Modulation (%). This may be typical of triangular wave periodic flicker or sinusoidal wave flicker in LED currents that are commonly produced in LED drivers. Relating rms of the ripple current to Modulation (%), however, is more complicated. This depends on the shape of the LED current, even if it is symmetric. Examples of flicker in lighting can be seen in Figure 2 for incandescent bulbs and in Figure 3 for LED lighting. The luminous flux is normalized on the vertical axis so that the maximum value equals 1. Therefore, the percent flicker simplifies to 100 × (1 – Min)/(1 + Min), where the minimum value is specified in each figure. Figure 2 and Figure 3 represent only sample flickering outputs in luminaires. Extensive testing and measurements of flicker in LED and other lamps can be found in Lehman et al. [B72] and in several U.S. Department of Energy (DOE) and Pacific Northwest National Laboratory (PNNL) publications (Poplawski et al. [B84], Poplawski and Miller [B83], Poplawski [B85], and Miller et al. [B77]).
Among the performance issues that contributed to slow CFL uptake was the perception that fluorescent lighting can cause adverse health effects. Flicker had long been among the complaints made about fluorescent lighting (Stone [B103]), when Beckstead and Boyce [B4] found that the belief that fluorescent lighting could cause negative effects on people predicted the likelihood that people would use fluorescent lighting at home. As the lighting industry strives not to repeat the CFL experience, these findings underpin the need for recommended practices concerning LED flicker. Other clauses of this document summarize what is known concerning the effects of flicker on human health and well-being (see Clause 6) and the variety of flicker rates that LED lighting systems can exhibit (see Clause 5). Possible adverse health effects can occur under flicker conditions that lie outside the visible range (see Clause 7); the nervous system can detect and respond to these conditions without their being accessible to conscious reports of the perception. This sets the stage for learned associations between LED lighting and potential adverse health effects from the specific product to the general class of LED products. Given the wide variety of flicker patterns detected in LED products already on the market (Poplawski et al. [B84]), some of which may lie in the region where potential health risks exist, it is possible that the public will associate this new technology with negative health outcomes. However, the lighting industry has the opportunity through product design to reduce the occurrence of flicker conditions that could cause potential adverse health and well-being effects and thereby help avoid a future in which the public associates LEDs with these outcomes. A recommended practice for LED lighting flicker can make a valuable contribution to the speedy adoption of LED technology and the achievement of energy efficiency targets by defining, based on science and consensus, the flicker conditions that may best be avoided.

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