September 2020 – LED Journal

LED

2021- New Year, New Possibilities for LEDs

Fardin Posted on September 25, 2020January 18, 2021

How are LEDs evolving and impacting businesses? With the New Year comes new opportunities and this is certainly true with LEDs. There are now high quality LED luminaires for street, area and landscape lighting; down lighting; track lighting; shelf and display lighting; decorative fixtures; 2X2 and 2X4 recessed luminaires for general ambient light; even high brightness high bay luminaires. The directional nature of LED sources allows for more of the lumens generated to be emitted from the luminaire compared to traditional light sources making these luminaires extremely efficient. The advancements in LED technology has lead to higher efficacy and higher lumen LED chips, as well as chip on board technology minimizing or eliminating heating sinking requirements, enabling the development of luminaires for general ambient lighting that deliver more than 100 lumens per watt. Most indoor luminaires typically have a rated life of 50,000 hours (L₇₀), but there are many street and area lighting luminaires with life ratings in the 70,000 to 100,000 hours range. Color consistency fixture-to-fixture and color stability over life is being address with “hot binning” of LED chips or the incorporation of intelligent active color control into the LED system to maintain the color within a two-step or three-step Macadam color ellipse minimizing perceptual color differences. There are also a variety of phase cut, 0-10 V, DALI and wireless lighting controls that have been developed for dimming of LED lamps and luminaires down to 5 to 20 percent.

Boston Interiors Photo Credit: Shannon Creeden

One example of LED technology making a difference for businesses is Boston Interiors, a family owned and operated furniture retailer with seven locations throughout Massachusetts that sought to reduce operating costs at its retail locations. Having identified lighting as an area that could offer significant savings, it was also critical to Boston Interiors that its lighting provided excellent color rendering to highlight its quality furniture and catch customers’ eyes. Boston Interiors selected its retail store in Stoughton, Mass. as the pilot location for upgrading the lighting to LEDs. Having selected OSRAM SYLVANIA’s ULTRA High Performance series PAR38 LED retrofit lamps to replace the existing 60-watt halogen lamps throughout the store, Boston Interior was very satisfied with the quality of light and color rendering of the ULTRA High Performance Series LEDs.

As a result of the retrofit to LED lighting, Boston Interiors will save more than $8,000 annually in energy and maintenance costs at its Stoughton store. Over the lifetime of the lamps, the savings will total nearly $100,000 over approximately 12 years. In addition to the energy and maintenance savings, Boston Interiors has also noticed savings in cooling the Stoughton store. Because OSRAM SYLVANIA’s LED lamps produce far less heat than halogen lamps, Boston Interiors has not needed to rely on its HVAC system quite as much since the LED lighting was installed.

In addition to cost savings, the LED lighting has enabled Boston Interiors to reduce its carbon footprint, as the company is committed to green initiatives. The retrofit is a major contributor in helping reduce the store’s energy consumption by 48,315 kWh, the equivalent of 74,163 pounds of carbon dioxide.

The advancements in LED technology and more reasonable price points for LED luminaires definitely makes LED lighting solutions worth looking at. Remember, not all LED solutions are alike and requires doing your homework. Before deciding on an LED solution, it is best to install a few luminaires and evaluate its performance before making a final decision.

LED

LEDs Cook Eggs

Fardin Posted on September 25, 2020January 19, 2021

LEDs are very good at producing light and heat. Unfortunately they are slightly better at the latter than the former and as each generation improves, more Lumens for every Watt of electrical energy are produced.

Indeed, LEDs have now become so good at producing light that they are rapidly replacing other types of light source for a wide range of applications including automotive lighting, domestic “light bulbs” and industrial luminaires (e.g. ‘high bays’). The one thing these applications have in common is that it is the manufacturer’s responsibility to prove the product is safe and performs as advertised. Both are accomplished through testing. Often these tests are defined by standards.

While passing a test is highly desirable, it does not guarantee that an LED light is suitable for an application or will survive long in service. There are two reasons for this:

The manufacturer often has little control as to how or where the LED lights are installed
There is Mother Nature to contend with.

Consider, for example, the thermal management of LEDs. Due to the production of heat (alongside photons) LEDs must be cooled to keep the junction temperature within safe limits. Ideally LEDs will run at the lowest practicable temperature since virtually every performance metric of LEDs efficiency, stability of hue and lifetime all decline as the temperature increases. LEDs are cooled by conduction so it is important to use circuit boards with very low thermal resistance between the semiconductors and the heat sink. It is for this reason that high brightness and high intensity LED light sources use various forms of metal-back PCBs on which to mount the LEDs. A metal board is able to spread the heat and conduct it through to a heat sink that dissipates it to ambient air.

A well-designed LED luminaire will keep the LEDs comfortably warm at around 70-90°C and the heat sink at a pleasant 30°C or thereabouts. However that very design assumes the luminaire will be used in a temperate climate where the ambient air is around 20°C. More importantly, LED lights are often tested in just that sort of environment. In some parts of the world, night time minimum temperatures can be as high as 40°C – and that is outside in a nice “cool” breeze. Typically luminaires are installed on or in ceilings. Now given hot air rises and the ceiling air is relatively stagnant (particularly if the LED light is installed in a closed void) the operating environment can easily reach 50°C or more.

Traditional metal finned heat sinks that transfer thermal energy to air function by having lots of surface area. As such the LED luminaire sent for testing will, in all probability, have a pristine heat sink that will function at maximum efficiency. Now fast-forward five years and some heat sinks will be covered in a thick layer of dust and cobwebs (when did you last clean your light fittings?). Indeed, it is not uncommon for larger high bay lights to be used as nesting sites by a variety of lesser and more endangered bird species! Cutting the efficiency of the heat sink has only one outcome, which is to raise the operating temperature of the LEDs and inevitably shorten their lifespan.

While the construction of a birds nest on an LED heat sink is not part of standard tests, some allowance for product aging should be included in the thermal design.

Blog

An Evolutionary Overview of SSL Connectors

Fardin Posted on September 24, 2020

Connectors for SSL applications continue to evolve as engineers push manufacturers for more unique and innovative solutions specifically designed to suit emerging lighting designs. Looking back over the past five years, one can see just how far SSL connector technology has progressed since the first solid-state lights started to appear in the market.

Early SSL engineers were limited to finding an existing connector that looked similar to what he needed and then drilling down to identify those that met performance requirements. Since connectors had yet to be specifically designed for SSL applications, however, the selection was extremely limited. Typically, if a connector met the high current or voltage requirements, it was too big for the design; and, similarly, if a connector was small enough, it was often not surface mountable (SMT) or robust enough. In fact, even finding a white connector was nearly impossible.

In the years since, we have moved past that “mission impossible” era. Now, there are multiple solutions available for most board-to-board (BTB) or wire-to-board (WTB) applications that emerge. However, these often appear as niche or individual product offerings with a limited range of options; so, engineers frequently still need to mix-and-match connectors from different vendors to meet the pin count or configuration requirements of SSL designs.

Based on a highly reliable gold-plated, beryllium copper contact system designed to match the 20+ year life spans of SSL products, the 9159 series of two-piece connectors from AVX Interconnect stands out as one of the few exceptions to this rule. The first connector in this series – the 9159 horizontal plug and socket (pictured in Figure 1) – was designed in response to a customer’s request for a coplanar, two-position, SMT, white, connector system that was 50 percent smaller than what was currently available on the market and capable of handling between four and five amps of current. Once that was achieved, the series was extended to include connectors featuring two to six positions to accommodate additional power or mixed power and signal lines and a greater breadth of SSL designs.

Figure 1. AVX’s 9159 series two-piece, coplanar BTB connectors

Over the next couple of years, as customer requests kept rolling in, connector engineers grew more accustomed to accommodating SSL-specific design requirements, and the initial 9159 products began to accumulate years of proven performance, the series continued to expand. First, a straight-cabled plug with an integral latching mechanism that maintains the connection integrity during handling and installation was developed in response to a request for a WTB solution that allowed engineers to build a common board layout with a plug on one end and a socket on the other. Capable of serving either a WTB or BTB function, this plug and socket connector enabled the development of a single board capable of achieving volume economies with almost unlimited expansion based on the required light output.

Figure 2. AVX’s current 9159 Series product offering

Next, a top load socket was developed in response to several customer complaints about board level failures in linear strings, which required technicians to disassemble the light out in the field until the defective board was reached. This solution features a slide-top design that acts a zero insertion force (ZIF) connector and allows one end of an interior board to be quickly and easily lifted up, removed, and replaced in the field, saving both time and money.

Figure 3. AVX’s 9159 series IDC cabled plug and socket connectors and cable assemblies

Later, a vertical connector capable of perpendicular mating was introduced to accommodate linear edge lighting applications while maintaining a common PCB footprint pattern, as with the cabled plug. And, most recently, right angle WTB options in both a plug and socket configuration were introduced to continue the theme of building a single board with a plug on one end and a socket on the other. These two new connectors (Figure 3) allowed for wires to be connected from either side of the board, which effectively simplified applications in which multiple lights needed to be connected end-to-end to cover a specific distance using standard length lights.

The evolutionary development of the 9159 Series is exemplary of the challenges and innovative solutions that continue to be brought to market by connector manufacturers with the express purpose of satisfying the unique requirements of the rapidly expanding SSL market. Now that a small array of SSL connectors developed by several manufacturers exist, the pace of innovation may not match that of these first few years; however, the continually evolving nature of the SSL industry will surely continue to require novel solutions for new designs.

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The Importance of Fixture Design, Engineering and Thermal Management

Fardin Posted on September 24, 2020

According to a recent US Department of Energy (DOE) report, nearly half of all commercial lamps and luminaires sold will be LED-based by 2020.[1] Additionally, Navigant Research recently released a report stating global unit shipments of LED lamps and luminaires are expected to total 10.7 billion from 2014 through 2023.

While this is excellent news for reducing energy costs and consumption, how does the architectural and engineering community view this technology shift? Are LED luminaire manufacturers able to combine form and function to meet lumen requirements, esthetic specifications, and engineers’ and facility managers’ concerns? The answer is yes if careful analysis and comparison is conducted on the various LED luminaires on the market.

LED Luminaire Form
Often, maximizing lumens per watt takes precedence with manufacturers over luminaires’ complementing architectural schemes. Additionally, meeting the needs of facility managers’ concerns about energy consumption also drives how products are designed and engineered. But, do these have to be mutually exclusive or can manufacturers achieve it all?

Lighting design necessitates an integrated approach—taking into account the exterior conditions, such as exposure to weather and pollution. Both in the dense urban spaces of the cities and in the surroundings of private buildings, the requirements are growing for precision lighting, energy efficiency, and visual comfort.[1]

However, with quality and performance improving, and cost decreasing by about 18 percent each year, LED technology is well positioned for further adoption by the design community for general lighting.

Function and Thermal Management
Are all LED luminaires created equal? Manufacturers have different opinions on how luminaires should be engineered and designed to meet esthetics and function requirements, which involves the overarching issue of thermal management.

Let’s start with a brief overview. LEDs generate heat, but unlike traditional light sources they transmit heat instead of radiating it. This means most of the heat from an LED goes upward into the fixture housing. This heat, coupled with heat generated by the power supply, must somehow exit the system through conduction, convection or a combination of both. Since LEDs are sensitive to heat they must be kept below their rated maximum temperature. Consequently, luminaire manufacturers need to be conscious of these heat dissipation challenges in order to design effective thermal management systems that support LED performance and longevity. Inadequate thermal management can lead to a shift in color, lower light output, and dramatically shortened life.

Time and market demand have a way of advancing technology to the point where thermal management may soon be just an afterthought rather than an obstacle in luminaire design. With each generation of LEDs, efficacy continues to rise exponentially; LEDs today are more than 50 per cent efficient—that is, they convert more energy into light than they do into heat.[2]

However, thermal management involves more than just evacuating heat from the fixture; it includes using the best LED and being able to operate at a low drive-current while still providing high lumens per watt. A lower drive-current means less heat, which allows the fixture to manage heat better.

In evaluating manufacturers’ LED luminaires for both form and function, another important issue is the power supply. The type of power supply selected for a lighting application will be based on several factors. First, the environment where the application will be operating in must be considered. For example, is the application for indoor or outdoor use? Does the power supply need to be waterproof or have any special ingress protection (IP) rating? Will the power supply be able to use conduction cooling or only convection cooling?[3]

According to the DOE’s Office of Energy Efficiency and Renewable Energy, the temperature at the junction of the diode determines performance, so heat sinking and air flow must be designed to maintain an acceptable range of operating temperature for both the LEDs and the electronic power supply. Luminaire manufacturers can be asked to provide operating temperature data at a verifiable temperature measurement point on the luminaire, and data explaining how temperature relates to expected light output and lumen maintenance for the specific LEDs used.

Regardless of how efficient LED fixtures are at dissipating heat, ambient operating temperatures still play a major role in a product’s life cycle. Naturally, warmer climates make it harder to maintain the lowest possible operating temperatures during peak summer months. However, cooler geographical areas such as the northern US and Canada have lower temperatures, therefore ensuring a longer LED life: the cooler the climate the more ideal it is for LED luminaires.

Retrofit Considerations
Many LED retrofit lamps do not retain the exact form factor of their non-LED counterparts. This can lead to challenges with fit, function, and/or thermal management when installed in standard luminaires. Additionally, some LED retrofit lamps’ packaging indicates the lamps are not designed for use in enclosed luminaires such as recessed downlights. If LED retrofit lamps require access to ambient air for thermal management, installing the glass lenses often used with standard luminaires can damage or severely affect the lamp’s performance and life cycle. Also, LED sources can appear extremely bright and/or pixilated and require appropriate shielding and/or cut-off for comfortable application. Unless a manufacturer has optimized the luminaire to account for a specific lamp, performance and appearance may be compromised when LED retrofit lamps are installed.[4]

Conclusion
With the dramatic proliferation of LED luminaire in full force, SSL technology will dominate general illumination going forward. That being said, there are hurdles manufacturers and those specifying LED luminaires must overcome. Specifiers must conduct due diligence on products, particularly because since 2006 there have been 600 new lighting manufacturers in the LED industry.

Designers and specifiers need to play an active role in the development of standards and code requirements to ensure quality lighting is maintained. Beyond important lighting metrics such as efficacy, lumen output, and luminous distribution, designers and specifiers are needed to define the essential attributes of lighting as it becomes integrated with building automation systems, energy management systems, and security systems.[5]

LED

All LED Luminaires Are Not Created Equal

Fardin Posted on September 5, 2020

As readers of LED Journal you know that both interior and exterior conventional lighting is rapidly being replaced by LEDs with intelligent lighting management. End-users are reaping the myriad benefits of this technology in reduced energy consumption and costs, and the virtual elimination of lighting maintenance. These benefits provide an incentive to help vigorously drive the ongoing development and implementation of LED technology. However, when considering this technology, it’s important to assess factors that contribute to the lifetime of an LED luminaire.

Kenall's TekDek engineered with a systems-approach. Photo courtesy of Kenall Lighting

Given that the LED luminaire is a system, it is vital to recognize all aspects [of the system] and not just individual components that can affect or limit lifetime. Luminaire manufacturers are learning how to better account for the lifetime behavior of the many components that are used when designing an LED fixture, including drivers, optics, mechanical fixings and housings. Each of these is a factor in determining the lifetime of a luminaire. The primary factors in the lifetime of a LED luminaire are the LED source selection and the durability of the power electronics.

An effective, long-lasting luminaire design combines the most advanced LED sources, driver technologies, optics and form into each product. Let’s examine a few of these components to really get a feel for what engineers need to consider in designing an LED luminaire. The entire luminaire must be built to last for the lifetime of the application.

In the Lighting Industry Liaison Group’s 2011 Guidelines for Specification of LED Lighting, the following criteria provide excellent considerations when determining what factors should be considered for the length of an LED luminaire.

LED Source Selection – When selecting LEDs, it’s important to consider the color, color temperature (if selecting white LEDs), the viewing angle and CRI. But one of the most important factors is the application: what is the area to be illuminated – spot or area? Optics – diffuser, reflector, lens? Thermal density and heat removal? Size and lit appearance? Also, does the manufacturer’s LM-80 test data support the lumen depreciation requirement?

Power Electronics’ Durability – The electronics affects almost every performance aspect of an LED design. High quality components – not using electrolytic components when possible and not running at maximum capacity or temperature– help to ensure the luminaire’s reliability and lifetime.

Optical Performance – LEDs are directional light sources, giving the lamp or luminaire designer new challenges when compared to existing lamp technology. The use of reflectors, lenses and diffusers, or a combination thereof, allows a designer to direct light in many different ways. The efficiency of the optical system must be considered and factored into the overall efficiency value of the lamp or luminaire.

PCB – A PCB is the electrical carrier as well as the interface between the LED and heat-sink that carries with it a thermal resistance value. The higher the resistance, the less efficient the system is at wicking away heat from the LED, this may well impact the LED lumen output performance and, ultimately, the life, lumen maintenance and/or catastrophic failure of the LED.

Finish – The paint finish/color may affect the heat dissipation from the luminaire, but more importantly, plays a significant role in the long-term integrity of the luminaire enclosure. As the finish degrades, the base material of the enclosure may become susceptible to corrosion. Different applications require different levels of corrosion protection. Tunnel lighting, for instance, requires one of the highest levels of protection while indoor office lighting, the one of the lowest.

Mechanical – The mechanical integrity of a luminaire is important in several different areas, including: ingress protection ratings suited to the application, gasketing that will not become compromised with time and/or lack of maintenance, chemical compatibility with all materials used within the luminaire, UV resistance of polymeric materials when used outdoors and vibration resistance. While solid state lighting sources are inherently vibration resistant, that in itself is not enough to ensure the long term integrity of the remainder of the luminaire, in an application such as street lighting or parking structures, where constant vibration is commonplace.

Thermal Management – The performance of an LED is dependent on its temperature during operation. The design of the luminaire will influence its operating temperature. Heat management is a critical factor that affects LED luminaire performance and the LED lifetime.

Housing – LEDs allow new luminaire design freedom to lighting manufacturers and engineers. Innovative form factors not possible with incumbent lamp sources can be used both for styling and function. Even though it should be infrequent, design consideration should be given to the maintenance of the LED light source and all power electronics, because even the most well-designed luminaire will eventually no longer meet its expectation of light production.

All LED Luminaires are Not Created Equal – While it’s easy to get caught up in the LED revolution, it’s critical to understand the application as well as manufacturers’ luminaires’ designs. Does screwing in a replacement LED bulb provide the same quality illumination as a well-engineered, from-the-ground-up fixture? As we head into one of the industry’s largest tradeshows, LightFair, take the time to consider the system components I’ve briefly addressed above; these provide metrics for the quality and lifetime of an LED luminaire.