LED lighting systems using Power-over-Ethernet (PoE) technology have been introduced to the lighting market in recent years as a network-connected lighting solution. PoE technology can provide low-voltage direct current (dc) power and control information to LED lighting over a standard Ethernet cable. One of the commonly claimed benefits of the PoEbased lighting system is higher system efficiency compared to traditional line voltage alternating current (ac) systems. This is due to the fact that in the case of PoE systems, the ac-dc power conversion losses are minimized because the acdc power conversion takes place at the PoE switch rather than at all the LED drivers within the lighting fixtures. However, it is well known that power losses can occur as a result of increased voltage drop along the low-voltage cables. The objective of this study was to characterize a PoE lighting system and identify the power losses at the different parts of the system. Based on the findings, we developed a methodology for characterizing the electrical efficiency of a PoEbased LED lighting system and then used this methodology to characterize commercially available PoE-based LED lighting systems and compare their performance. The electrical efficiency characterization included both the system as a whole and each individual component in the systems, such as the power sourcing equipment, powered device, Ethernet cables, and LED driver. The study results also investigated the discrepancy between the measured and reported energy use of the system components.
LED A-lamps are used in many types of lighting fixtures; however, these lamps can experience different thermal environments and use patterns (on-off switching), resulting in system life that varies in different applications. A recent study showed that on-off switching negatively affects LED system lifetime, and solder joint failure was the main reason. The goal of this study was to investigate and identify a theoretical model that can be used to predict LED A-lamp failure, when the failure is mainly due to solder joint failure. Although several models for solder joint fatigue failure exist in the electronics industry, the Engelmaier model is the most commonly used in industry standards. The study presented here showed that the Engelmaier model with modified fatigue ductility exponents provided a better fit to the experimental lifetime data for LED A-lamps. This paper describes the Engelmaier model prediction method for LED A-lamp failure.
Proc. SPIE. 10378, Sixteenth International Conference on Solid State Lighting and LED-based Illumination Systems
KEYWORDS: Optical components, Light emitting diodes, LED lighting, Solid state lighting, Manufacturing, 3D printing, Additive manufacturing, Printing, Light sources and illumination, Solid state electronics
Low energy use and reduced maintenance have made the LED, a solid-state light (SSL) source, the preferred technology for many lighting applications. With the explosion of products in the marketplace and subsequent price erosion, manufacturers are looking for lower cost materials and manufacturing methods. 3-D printing, also known as additive manufacturing, could be a potential solution. Recently, manufacturers in the automotive, aerospace, and medical industries have embraced 3-D printing for manufacturing parts and systems. This could pave the way for the lighting industry to produce lower cost, custom lighting systems that are 3-D printed on-site to achieve on-time and on-demand manufacturing. One unique aspect of LED fixture manufacturing is that it requires thermo-mechanical, electrical, and optical components. The goal of our investigation was to understand if current 3-D printing technologies and materials can be used to manufacture functional thermo-mechanical, electrical, and optical components for SSL fixtures. We printed heat sink components and electrical traces using an FFF-type 3-D printer with different filaments. The results showed that the printed heat sinks achieved higher thermal conductivity values compared to components made with plastic materials. For electrical traces, graphene-infused PLA showed low resistivity but it is much higher than bulk copper resistivity. For optics, SLA-printed optical components showed that print resolution, print orientation, and postprocessing affect light transmission and light scatter properties. Overall, 3-D printing offers an opportunity for mass customization of SSL fixtures and changing architectural lighting practice, but several challenges in terms of process and materials still have to be overcome.
LED products have started to displace traditional light sources in many lighting applications. One of the commonly
claimed benefits for LED lighting products is their long useful lifetime in applications. Today there are many
replacement lamp products using LEDs in the marketplace. Typically, lifetime claims of these replacement lamps are in
the 25,000-hour range. According to current industry practice, the time for the LED light output to reach the 70% value
is estimated according to IESNA LM-80 and TM-21 procedures and the resulting value is reported as the whole system
life. LED products generally experience different thermal environments and switching (on-off cycling) patterns when
used in applications. Current industry test methods often do not produce accurate lifetime estimates for LED systems
because only one component of the system, namely the LED, is tested under a continuous-on burning condition without
switching on and off, and because they estimate for only one failure type, lumen depreciation. The objective of the study
presented in this manuscript was to develop a test method that could help predict LED system life in any application by
testing the whole LED system, including on-off power cycling with sufficient dwell time, and considering both failure
types, catastrophic and parametric.
The study results showed for the LED A-lamps tested in this study, both failure types, catastrophic and parametric, exist.
The on-off cycling encourages catastrophic failure, and maximum operating temperature influences the lumen
depreciation rate and parametric failure time. It was also clear that LED system life is negatively affected by on-off
switching, contrary to commonly held belief. In addition, the study results showed that most of the LED systems failed
catastrophically much ahead of the LED light output reaching the 70% value. This emphasizes the fact that life testing of
LED systems must consider catastrophic failure in addition to lumen depreciation, and the shorter of the two failure
modes must be selected as the system life. The results of this study show a shorter time test procedure can be developed
to accurately predict LED system life in any application by knowing the LED temperature and the switching cycle.
The concept of connected lighting systems using LED lighting for the creation of intelligent buildings is becoming
attractive to building owners and managers. In this application, the two most important parameters include power
demand and the remaining useful life of the LED fixtures. The first enables energy-efficient buildings and the second
helps building managers schedule maintenance services. The failure of an LED lighting system can be parametric (such
as lumen depreciation) or catastrophic (such as complete cessation of light). Catastrophic failures in LED lighting
systems can create serious consequences in safety critical and emergency applications. Therefore, both failure
mechanisms must be considered and the shorter of the two must be used as the failure time. Furthermore, because of
significant variation between the useful lives of similar products, it is difficult to accurately predict the life of LED
systems. Real-time data gathering and analysis of key operating parameters of LED systems can enable the accurate
estimation of the useful life of a lighting system. This paper demonstrates the use of a data-driven method (Euclidean
distance) to monitor the performance of an LED lighting system and predict its time to failure.