LpR Articles

LED professional Review (LpR) - Articles

Resources | LpR Article | Feb 20, 2021

Reader's Question About "Short-Pulse Testing"

In reference to the article "Short-Pulse Testing Eliminates Self-Heating Errors to Produce True L-I Graphs" in issue LpR#83, a reader has asked why one measures with these short pulses, since this differs very much to the conditions in real application. Read the author's answer below. Read more »

Resources | LpR Article | Technologies | LED Drivers | Jan 13, 2021

How to Increase the Efficiency of Two-Stage Drivers

In this article, Dr. Weirich from Infineon Technologies, describes a simple method for increasing the efficiency of drivers that can operate with LED engines with a wide range of current and power levels, at virtually no effort. In addition, the method allows for using smaller inductors in the buck stage, leading to lower cost and potentially, smaller size. Read more »

Discomfort Caused by Glare from Luminaires with a Non-Uniform Source Luminance

Glare and the resulting discomfort are a persistent issue in lighting that became even bigger with the introduction with LEDs as a light source. While the UGR method is well established, it is sometimes heavily discussed if it is appropriate for SSL. The limitations of the UGR method need to be understood. Peter Thorns BSc(Hons), CEng, FCIBSE, FSLL, explains these limitations and consequently describes the research and how to apply correction measures. Read more »

Adopting an LED More Suited to Circadian Entrainment

Since the introduction of LED lights, a lot has been said about risks of blue light for ocular health on the one hand, and the opportunity of circadian entrainment, on the other hand. While a controversial discussion on the first topic is ongoing, the second topic is well accepted. To solve both issues, Bill Chan, President of LiteController Inc. proposes the application of 465-470nm pumped phosphor converted white LEDs with a content of 86% - 92% blue-turquoise light and 8% - 14% blue-violet light. In the article he concentrates on the second topic and proves the benefit of regulating the circadian entrainment more efficiently, maintaining a high typical efficacy of 150 lm/W and good color rendering of CRI 80+ ideally supporting the WELL Building Standard. Read more »

Offline Lighting Voice Controller — An Alternative to Voice Assistants

The historical evolution of light control by users started with a mechanical switch followed by potentiometer and dimming, touch panels and touch screens, gesture and movement detection control, and ending with voice. Voice control are mostly online speaker independent like Alexa, Google Home and Siri. But there are privacy and security concerns. Filip Michalski, Electronic Engineer, and Cezary Skotak, CEO, from Cezos describe a speaker independent offline voice controls system, explain the technology and discuss the pros and cons. Read more »

A New LED Controller Technology to Expedite the Next Level of Smart Lighting

Lighting installations that use artificial lighting and often deemed more comfortable and energy efficient are generally referred to as "Smart Lighting". While no clear definition exists "Smart Lighting" has become a common catch phrase. Kurt Marquardt, Senior Director LED Lighting Systems and Product Marketing, Infineon Technologies has a more accurate definition. For him, the term "smart lighting" describes the capability of the lighting system to adapt automatically to the needs of the users and the room. He presents an alternative way to implement smart lighting systems, using the new XDPL8221 digital LED-driver IC [1]. Read more »

LpR Article | Research | Health + Environment | Environment | Jul 30, 2020

The Adverse Ecological Impacts of Light Pollution: LEDs' Role in Mitigation

With the negative effects of artificial light at night on ecosystems increasingly well-understood, attention is now turning to the ways in which these impacts can be mitigated through uptake of novel technology and lighting strategies. Dr. Callum J. Macgregor, post-doctoral research associate at the Department of Biology of the University of York, and Dr. Darren M. Evans from the School of Natural and Environmental Sciences of the Newcastle University, discuss the current evidence for costs and opportunities associated with uptake of LED lighting and highlight important directions for future investigation. Read more »

Temperature Profiling of Secondary LED Optics by Infrared Thermography

Over the last few years, the power density of white LEDs has increased dramatically. Whilst there are large efforts to optimize the thermal management and thus the temperature stability of the LEDs, less attention is paid to the temperature of the secondary optic. Peter W. Nolte, Franziska Steudel, Bernd Ahrens, Nils J. Ziegeler, Frank Drees, Horst Rudolph, and Stefan Schweizer from the Fraunhofer Application Center for Inorganic Phosphors, the South Westphalia University of Applied Sciences, and the Innovations-and Technologycenter GmbH, TRILUX Group respectively, have approached this issue. They investigated the temperature profiles of polymethyl methacrylate (PMMA) and polycarbonate (PC) secondary optics and they discuss the results. Read more »

On Life Cycle Assessment to Quantify the Environmental Impact of Lighting Products

The lighting industry has made great efforts to increase energy efficiency around the world with a strong participation from governmental organizations, multilateral organizations and agencies. However, energy consumption is not the only aspect that needs to be considered for transforming the lighting industry. Víctor Ferreira, Deidre Wolff, and Cristina Corchero from Catalonia Institute for Energy Research (IREC) will explore relevant environmental metrics to help inform the reader about circular economy and Industry 4.0 strategies to achieve a sustainable lighting product. Read more »

LED Driver for High Power Machine Vision Flash

Automation is nothing new and its demands are rapidly increasing, either in production or inspection. More sensors are used and many are based on direct or reflected light detection. Some work in the visible range and others work in the non-visible spectrum of light. LED lighting has become the standard in most applications as the solid-state light source offers numerous advantages over other lighting technologies. However, the LED lighting system is only as good as the peripheral components and LED drivers are one key element in many applications. Keith Szolusha, LED driver applications manager and Kyle Lawrence, associate applications engineer, identified the challenges for machine vision flash applications and propose a solution example with Analog Devices' LT3932 high speed LED driver. Read more »

Transparent Material Considerations for UV Optics in Horticultural Lighting Applications

Advancements in UV LED technology have begun changing the horticultural lighting landscape. Research is still ongoing to discover the extent of benefits and best practices of using UV light in horticulture. Using optics in tandem with UV LED light systems can help reach performance goals and optimize growing. Although there are several UV- transmitting materials available, not all are equivalent or able to meet the requirements for UV applications. Justine Galbraith, glass engineer, and Sharayah Follett, market development manager at Kopp Glass, Inc. discuss the performance considerations of various UV-transmitting materials and how application challenges are addressed by integrating optical elements. Read more »

Hermetic Polymer-Free White LEDs for Harsh Environments

AlGaInN-based white LED can easily achieve lifetimes of up to 100,000 h depending on junction temperature and current density. However, state of the art silicone encapsulated LEDs with powder-based phosphors reveal a strong dependence of field lifetimes on environmental conditions such as humidity, corrosive gas and air pollutant exposure. Dr. Michael Kunzer, Group Leader LED Modules at Fraunhofer Institute for Applied Solid State Physics and his colleagues, Ralf Schmidt, Andreas Zibold, Vasileios Georgiou-Sarlikiotis, Michael Arnold and Isabel Kinski propose luminescent ceramics as an interesting alternative to polymer-dispersed phosphors. This provides entirely new opportunities for the manufacturing of white LEDs. The authors explain the properties and advantage of this hermetic, light converting cap material and how to completely avoid polymers. Read more »

A New Approach for Fast and Accurate Measurement of Light Emitting Diodes Junction Temperatures

LpR 73 Article, page 48: Junction temperature of LEDs is one crucial parameter to being thoroughly observed. In this paper, Ahmet Mete Muslu, Onuralp Isil and Prof. Mehmet Arik from the Energy Efficient Electronics and Lighting Technologies Center (EVATEG), Department of Mechanical Engineering at the College of Engineering Ozyegin Universitywill at first describe the importance of Tj for LED systems including RGB and white LEDs. Then they will present techniques from literature and recently in-house developed novel methods and a new Junction Temperature Measurement Device (EVAtherm). Results in selected general lighting and automotive lighting applications will be demonstrated. Read more »

Resources | LpR Article | Special Applications | Artificial Intelligence | Dec 16, 2019

AI & Lighting

LpR 73 Article, page 62: Recently, Artificial Intelligence has emerged as an evolutionary force in almost every industry, demonstrating its potential to radically change existing processes. In common literature, AI is interchangeably used with Machine Learning for which various tools have already become commonplace. Henri Juslén, D.Sc (tech.), Chief Future Illuminator, Omar Nasir, M.Sc (tech.), Data Scientist, and Javad Nouri, M.Sc, Data Scientist at Helvar Oy Ab discuss AI on the context of the lighting industry where the scope of applications of AI is similarly quite broad, impacting the various stages involved in the lighting life-cycle such as design, installation, commissioning and configuration. Read more »

Resources | LpR Article | Special Topics | LiFi | Dec 16, 2019

LiFi as a Paradigm-Shifting 5G Technology

LpR 73 Articles, page 54: There are many misconceptions about LiFi, a wireless communication technology that uses the infrared and visible light spectrum for high speed data communication. Prof. Harald Haas, Professor of Mobile Communications at the Institute for Digital Communications from the University of Edinburgh, will explain what Light-Fidelity (LiFi) is and argue why it is a 5th Generation (5G) technology. Peak transmission speeds of 8 Gbps from a single light source have been demonstrated, and complete cellular networks based on LiFi have been created. Besides discussing numerous misconceptions, the potential impact this technology can have across a number of existing and emerging industries will be explained as well as new applications that LiFi can unlock in the future. Read more »

Resources | LpR Article | Research | Thermal Management | Sep 17, 2019

Thermal and Optical Challenges for SSL in Automotive Applications

LpR 72 Article, page 50: Solid State Lighting changed the lighting environment in automotive lighting almost more than in the field of general lighting. While efficiency of the devices increased and every few weeks new improvements are reported, thermal management remains crucial and a critical part of the system. Umut Zeynep Uras, Ahmet Mete Muslu and Mehmet Arik, from the Energy Efficient Electronics and Lighting Technologies Center (EVATEG), Department of Mechanical Engineering, College of Engineering at Ozyegin University, and Fatih Goren from the FARBA Corporation, explain the dependencies between photometric, electrical and thermal parameters of an automotive lighting application. Read more »

Resources | LpR Article | Technologies | DC-Grids | Sep 17, 2019

LED Lighting Systems in Smart Buildings with DC Microgrids

LpR 72 Article, page 60: While electric motors for ventilation and air-conditioning systems were already DC-based in the past, powerful IT systems, LED lighting systems, photovoltaic systems with batteries and charging systems for electro mobility are now increasingly being used in modern building environments. They all need direct current (DC). Therefore, an obvious step is to equip modern buildings with DC grids. Carsten Moellers from Abalight discusses a number of unresolved questions and presents possible solutions in this article. Read more »

Resources | LpR Article | Research | Micro-Optics | Aug 13, 2019

Semi-Empirical Characterization of Freeform Microlens Arrays

LpR 72 Article - page 42: Microlens arrays (MLA) have been used for imaging and non-imaging applications for a long time as cost-effective solutions. Non-symmetrical beam shapes require more advanced non-symmetrical freeform microlens arrays (FMLA). The required FMLA molding tools convey a high cost and an iteration process is required for the final design. Oscar Fernández, Tamara Aderneuer, Rolando Ferrini from the Centre Suisse d'Electronique et de Microtechnique, CSEM, and Julien Duchene from ANSYS proposed a method to overcome these limitations based on 3D surface sampling, computer generation of a ray-traceable model and ray-tracing performance simulation and demonstrate feasibility for several commercially available freeform asymmetric thin-film diffusers. Read more »

Applications | Smart Lighting + IoT | Resources | LpR Article | Aug 13, 2019

Technologies for Shared Office Space

LpR 72 Article, page 66: Shared office spaces are gaining popularity as a flexible, resource-efficient and creativity-inspiring way to work. The dynamic nature of such office spaces requires building automation and lighting control solutions that can quickly be deployed and easily be adapted to new office layouts. Matthias Kassner, Vice President Product Marketing at EnOcean GmbH, takes a look at different connectivity architectures (wired, wireless, hybrid) and protocols (Bluetooth, ZigBee, EnOcean, PoE) to assess their usability and show how minimizing the need for maintenance is a key for increasing profitability of service-based offerings. Read more »

Circadian-Friendly Light Emitters: From CCT-Tuning to Blue-Free Technology

Common levels of blue radiation are sufficient to disrupt the circadian cycle, calling for blue-depleted emitters in the evening. Most current solutions employ low-CCT and suffer from poor light quality. Aurelien David, chief scientist at Soraa explains the melanopic lumen and its possible sources of inaccuracy related to the uncertainty in assessing the circadian action spectrum. In addition, he also discusses the concept of a blue-free emitter with minimal melanopic lumen at very low CCT and how such a spectrum providing a good light quality can be optimized. Read more »

Flex LED Based Smart Light System for Healing of Chronic Wounds

LpR 71 Article - page 48: Chronic wounds are notoriously challenging to treat, because they do not follow the typical healing process or time-frame. The resulting burden is significant, affecting over 40 million patients. Blue light is known for its anti-microbial and anti-inflammatory effects in the initial stages of the healing process. David Kallweit, researcher at CSEM, reports about the joint development of a chronic wound treatment device with their MEDILIGHT partners, URGO RID, University of Heidelberg, SignalGenerix, Microsemi, Technical University of Berlin, and Amires. He furthermore shows how it works and discusses future prospects. Read more »

Technologies | Smart Lighting + IoT | Resources | LpR Article | Jul 29, 2019

Voice Controlled Lighting that Protects Privacy and Data

LpR 71 Article - page 54: Intelligent lighting systems undoubtedly offer high comfort and energy efficiency. But especially conventional voice control systems like Amazon Alexa, Apple Siri or OK Google, with connected lamps and lighting fixtures are also becoming targets for uninvited guests. The benefits and technology of a new approach offering local voice control and artificial intelligence will be explained by Genia Shipova, Director Global Communications at Snips. Read more »

Healthy Light - LED Technology for Health and Care Applications

The right light, at any time during the day or night, is absolutely essential for health and well-being especially in health and care applications. Peter Haumer, Head of Technical Sales at Lumitech/Kiteo reveals why, besides full spectrum and high color rendering, mimicking real daylight conditions with extended daylight curves, a direct and an indirect component (CCT 1.800–16.000 K), are essential. The article discusses the benefits that can be derived from special colors for medical staff, patients and residents. Read more »

Implications for Human-Centric Lighting Design in Tropical Nursing Homes: A Pilot Study

Light synchronizes our physiological and psychological rhythms to the 24-hour rhythm of the ambient changes. For the elderly, adequate environments to compensate for increasing frailty and sensory loss are crucial. Dr. Szu-Cheng Chien, Assistant Professor at the Singapore Institute of Technology reports from a pilot study that aimed to explore HCL design strategies in nursing homes in Singapore. Pre-/post implementation user surveys and quantitative evaluations were conducted. Read more »

Melanopic Green - The Other Side of Blue

LpR 71 Article - page 74: For years now, there has been a controversial discussion about the amount of blue light in LEDs. Medical studies have shown that, depending on the amount, blue light at night disrupts the circadian rhythm. As a result, warm white (<3000 K) light sources are often touted as a solution for street lighting as well. Ian Ashdown, P. Eng. (Ret.), FIES Senior Scientist at SunTracker Technologies discusses whether or not it is sufficient to only look at the CDT or if other wavelengths and aspects should be considered. Numerous medical studies have shown that exposure to blue light at night suppresses the production of melatonin by the pineal gland in our brains and so disrupts our circadian rhythms. As a result, we may have difficulty sleeping. It is therefore only common sense that we should specify warm white (3000 K) light sources wherever possible, especially for street lighting. - True or false? Read more »

User Evaluation of the OpenAIS Pilot Installation

The OpenAIS project (2015-2018) has developed an open IoT lighting solution to enable a wider community to deliver the smartness of light, allowing easy adaptability to cater for the diversity of people and demands. The project is a cooperation between seven leading companies in the European industry and two academic partners: Signify, Zumtobel, Tridonic, Johnson Controls, Dynniq Belgium, NXP, ARM, Eindhoven University of Technology. Thomas van de Werff, Harm van Essen and Berry Eggen from the Eindhoven University of Technology describe the evaluation results of the pilot installation in a real office building in Eindhoven (The Netherlands), a former Philips factory. Read more »

Resources | LpR Article | Horticulture | Applications | Mar 28, 2019

Enriching Horticultural Lighting for Faster Growth and Better Crops

Horticulture lighting is no new lighting application, but it gained momentum with the introduction and evolution of LED lighting, and it is meanwhile one of the fastest growing markets in lighting. Dr. Richard Blakey, Application Engineer at Würth Elektronik eiSos, explains how LED-based horticultural lighting can deliver even bigger advantages for commercial growers by introducing additional wavelengths that increase photosynthetic response - like Würth Elektronik's new members of the WL-SMDC SMD Mono-Color Ceramic LED Waterclear family that is used as a reference in the article. Read more »

48 VDC Integrated Drivers Offer New Options

LpR 70 Article, page 102: In the telecommunication and IT businesses, especially, 48 VDC grids have become quite popular. This growing global trend to facilitate direct current (DC) power supply in building "microgrids" presents new opportunities for solid state lighting designers. TE's Lighting Industry Manager, Ron Weber, and Global Product Manager, Scott Hamilton, describe how LED lighting fixture designers can now design luminaires around a 48 VDC constant voltage input, available to take advantage of the benefits of a low voltage DC distribution grid in a building. Read more »

Standardized Programming of Lighting Components Using NFC Technology

LpR 70 Article, page 88: NFC programming of LED drivers is rapidly gaining popularity as a fast, feature-rich, flexible and easy method to set the operating characteristics of LED drivers inside luminaires. Arnulf Rupp, Chair of MD-SIG, describes how the MD-SIG specification for NFC programming of lighting components makes it easy for luminaire manufacturers to use NFC programming in a production line where multiple brand drivers are used one after the other. Read more »

Bluetooth Mesh Protocol as Applied to Lighting

Little more than one year ago, Bluetooth SIG released the Bluetooth Mesh standardization. Meanwhile, it has become widely adopted and is also one of the favorite systems for lighting controls. Russ Sharer, Vice President of Global Marketing and Business Development for Fulham, starts with an explanation of the Bluetooth Mesh protocol as applied to lighting control and defining its key elements. In a second portion of the article, he answers questions that lighting control evaluators could be asking their vendor. Read more »