Categories Lighting

Optimizing Lighting Efficiency with Glass

In last month’s blog post, I kicked off a series of about glass in lighting by providing a brief history and mentioned possible ways in which glass could effectively be used to increase lighting performance.  In particular, how it can be modified through glass chemistries (low iron), applied coatings (anti-reflective, conductive, etc.) and surface treatments (acid-etching, patterning, etc.) to optimize optical performance.  In this blog post, I want to continue the series by reviewing and discussing each of these areas in more detail to provide a more comprehensive understanding on how glass can be wisely used to optimize lighting efficiency in lighting applications.

The first major challenge of using glass as a material in lighting is with its inherent material properties.  Glass, as a material, loses 9 to 10 percent of lighting efficiency through reflection and absorption losses as shown in the graphic below.

 

 

Diagram courtesy of Guardian Industries

 

As you can see, 4 percent of light is lost through reflecting off of the first surface, another 2 percent lost through absorption from the FeOx content (0.11 to 0.08 percent) in standard soda lime glass chemistry, and still another 4 percent lost through reflecting off of the second surface.  In today’s world of high-efficiency and high-efficacy luminaire requirements, this is an unacceptable sacrifice and has unfortunately caused glass to be designed out of many lighting fixtures.  However, there are innovative and readily available ways to address this problem with glass and reduce reflection and absorption losses and increase overall light transmission and efficiency. These include using:

  • Low Iron Soda Lime Glass;
  • Anti-Reflective (AR) Coatings; and
  • Surface Treatments and Textures.

The use of low iron soda lime glass attacks the 1 to 2 percent absorption losses mentioned above by reducing the FeOx content of the glass chemistry down to 0.2 to 0.3 percent and all but eliminates absorption losses.  The spectral graph below compares the transmission curves at NADIR (0 degree incident angle) of standard soda lime glass and low iron glass with special attention given to the visible range where luminaires perform in:

 

 

Diagram courtesy of Guardian Industries

 

You can clearly see a boost of 1 to 2 percent of light transmission gained just from the replacement of the substrate material itself with low iron glass.  However, that still leaves 8 percent of lost light transmission due to reflectance losses to recover to gain optimum luminaire efficiency.  How can that be undone?

Anti-Reflective (AR) coatings can be effectively used to reduce reflection losses and increase light transmission in lighting as well as many other commercial applications.  In fact, they are already commonly used in eyeglasses, picture frames, and photovoltaics.  The principle of AR coatings is to minimize the interference of light traveling through a given material’s surface versus that of its immediate surrounding environment (in this case, air).  Therefore, the goal of an AR coating with a glass lens in lighting is to create this interference layer with a refractive index (n) as close as possible to air (n = 1) and the glass surface (n = 1.52) to filter the reflection losses and bridge that optical gap.

Adding a 3-layer AR coating (medium, high, and low index gradient) to a low iron substrate, mentioned above, allows most of the 8 percent reflection losses to be recovered in light transmission and efficiency.  The spectral graph below compares the transmission curves at NADIR (0 degree incident angle) of standard soda lime glass and low iron glass as well as application of an AR coating on one (singled sided or SS AR) and both (double sided or DS AR) sides of the low iron glass (again with special attention given to the visible range where luminaires perform in):

 

Diagram courtesy of Guardian Industries

 

A reduction of reflection losses from 4 percent down to 0.5 percent per surface can clearly be seen and allows a Low Iron substrate with Double-Sided Anti-Reflective coatings to reach 99 percent light transmission (efficiency) in the visible range.  The absorption and refection losses seen earlier with using standard soda lime glass have been all but removed at the 0 degree incident angle.

But what about angular losses in light transmission? Since most LED-based luminaires are dispersing light in very aggressive light distribution patterns there is limited value in maximizing light transmission at a 0 degree incident angle only.

The combination of Low Iron glass and AR coatings also help with the reduction of angular losses as shown in the material output files from LTI Optics of standard soda lime glass, low iron glass, and Single-Sided and Double-Sided AR coatings on low iron glass:

 

Diagram courtesy of Guardian Industries

Where:  τ = Transmission, α = Absorption, and ρ = Reflection

As these plots show, the average light transmission achieved with standard soda lime glass from 0 to 75 degree incident angles is only 86 percent whereas low iron reaches 88 percent, SS AR on low iron 90 percent, and DS AR 94 percent and holds > 90 percent light transmission up to 55 degrees (when standard glass only reaches that at 0 degrees).  Clearly, the combination of low iron glass and AR coatings help reduce angular light losses as well.

Finally, another method of reducing reflection losses with glass is by modifying its surface texture.  There are two commercially ready methods of doing this:

  • Acid-etching the surface to make the glass “frosted” or “diffuse”; and
  • Texturing (or patterning) the surface while the glass is still in its molten form.

Comparing standard clear glass (as a reference) to various acid-etched and textured products combinations (with and without an AR coating), you can clearly see benefits of modifying the glass surface to increase your light capture over angle with all cases providing superior performance versus standard soda lime glass:

 

Chart courtesy of Guardian Industries

In summary, glass indeed has some inherent challenges for effective use in the high-performance and energy-efficient LED luminaires of today.  However, with the use of innovative glass chemistries (low iron), coatings (AR), and surface modifications (acid-etch, texturing) these challenges can not only be removed but also allow for even higher levels of efficiency and efficacy to be achieved.

In my next post, I will provide some case study examples of effectively using these innovative uses of glass lenses, which provide both performance and economic (ROI, TCO, etc.) benefits in selected applications.

Categories Lighting

LED Optics – Beam Angle Counts for Warehouse Aisle Lights Now More than Ever

An ongoing trend for Distribution Centers and Warehouses across the storage market is narrower aisles and higher ceilings.  The driver for the trend is about revenue per square foot. Owners and operators have the ability to store and sell more products if they pack in those products to areas that occupy less of a footprint.

This trend creates opportunities for the LED market to support the storage businesses at new levels. Old technology like metal halide fixtures distribute light to the sides as well as down. Fluorescent tube fixtures typically do the same. These “WIDE” beam angle fixtures waste a lot of the light in areas where it is not needed. Reflector kits on multi-tube T8 or T5 fixtures help reduce the wasted light going up and to the sides but they largely still deliver “WIDE” output.

Optics help LED high bay fixtures deliver “NARROW” beam angles. Look for LED high bay fixtures that maximize the light output with optics to direct the light where you need it most.  Save money by wasting less energy and review fixture costs relative to useable output.

 

High Bay Performance: Watts, Lumens, and Foot Candles
A Metal Halide High Bay with a 400 watt bulb (up to 450 watts with the ballast factor) may deliver 36,000 lumens of which only 24,000 are directional. The foot candles on a ceiling with 25’ x 25’ grid may come in at about 30 fc.

A Fluorescent High Bay with 6 Tube High Output (HO) T5 tubes at 54 watts each (total 324 watts) and a reflector kit may deliver 24,000 directional lumens and the 30 fc to replace the Metal Halide High Bays.

An LED High Bay without reflectors or optics at 216 watts may deliver the 24,000 directional lumens and the 30 fc to replace the Metal Halide and the Fluorescent High Bays.

An LED High Bay with reflectors may only needs 162 watts to deliver 18,000 “narrow focused” directional lumens to achieve the same 30 fc.

An LED High Bay with optics may only needs to draw 108 watts to deliver 12,000 “ultra-narrow focused” directional lumens to achieve the same 30 fc.

The key here is for buyers to understand that they should not just shop for high bays based on lumens. Buyers should definitely not disqualify LED high bays that have less lumens without looking into the reflectors and optics. The economic impact is significant as the wattage consumption decreases with more advanced technology:

  • 450 watt Metal Halide
  • 324 watt Fluorescent
  • 216 watt LED
  • 162 watt LED with Reflectors
  • 108 watt LED with Optics

 

The level of optics is determined by the ceiling height, the width of the aisles, and the foot candle needs at the floor and at the racks.

 

Understanding the loading process for fork lifts helps provide perspective on the width of the aisles:

  • Wide Aisle (WA) lift trucks operate in aisles that are 12’ on average. They are the standard counterbalanced lift trucks that have become synonymous with the term “fork lift”. Wide aisle trucks generally operate in aisles greater than 11’ for handling 48” deep loads.
  • Narrow Aisle (NA) lift trucks operate in aisles 8’ to 10’ across. This is primarily the domain of the stand-up reach and double-deep reach trucks.
  • Very Narrow Aisle (VNA) trucks generally operate in aisles of less than 6’ and often use guidance systems (wire, rail, optical) to travel within the aisles. Standardized VNA vehicles consist of man-up order selectors used to manually handle less-than-pallet-load quantities and man-up turret trucks used to handle unit loads.

Top Tip on LED Light Matching with Photometrics:
Choose a commercial LED lighting manufacturer or solutions provider that has high bay and /or aisle light fixtures with options for optics to focus the light down to where you need it most. Check the foot candle output at the horizontal work surface and on the vertical storage racks so that lift operators can see the products clearly. Overall, go beyond selecting a short list of fixtures by lumens or lumens per watt and look into the foot candles per watt and also the foot candles per dollar for the fixture cost.

Categories Lighting

Smart Lighting – Removing the Power Burden

Smart Lighting – One of the major benefits of solid-state lighting (SSL) is that it is very controllable. The advent of highly responsive LED lamps and an increasing ability to control brightness and color are giving rise to an imaginative new era in lighting design. The spectrum of innovation today includes context-aware lighting, lighting that reacts to user activity, and smart lighting systems that adjust to human requirements. The aim of these new lighting regimes is to increase productivity. But before implementing such a system, productivity benefits must be weighed against the cost of complex control systems and computing engines as well as the ability to manage power. SSL was first introduced with the goal of reducing power consumption and this remains central to the realization of the concept. Unless designers adeptly manage the power budget, any gains of these new systems could be wiped out.

Context-Aware Lighting – One type of leading-edge lighting system today takes account of user activity within a room and is known as context-aware lighting. Room occupancy sensing is not a new idea, but the increase in sophistication has taken the concept way beyond a motion-activated, on-off switch. With today’s technology, a lighting system can detect the presence of multiple occupants in a room and use their relative positions to deduce what the group is doing (eg., watching a presentation, drawing on a white-board, or simply working on a computer). The lighting system then provides lighting appropriate for that activity. This is certainly impressive, but does require significant computing power and numerous sensors that track the positions of multiple occupants continuously, and then infer their actions from their location and motion.

For this system to work acceptably for the room user(s), each of the sensor and lighting nodes must always be ready and react quickly to data inputs and commands and to provide data to the system – a delay of more than 500 ms is generally considered unacceptable for a lighting system to respond. Typically, a fast-wake from standby requires power to be continuously delivered to each node in the system. Therefore, controlling the amount of power consumed by smart lighting devices while they are inactive is very important if smart lighting is to deliver the power savings partly necessary to justify its expense.

 

 

Simple single-stage bulb driver

 

 

Simplified view of a multi-output-stage LED driver

Powering Smart Lighting Systems in Standby- SSL systems are typically powered by AC mains (either 115 VAC or 230 VAC) or, in some cases, using Power over Ethernet (PoE – IEEE802.3at and later derivatives under development).

Computer and telecom rack systems have standby power consumption in the order of 180 – 250 mW but are “network aware” with approximately 3 W of consumption. There will not be very many control hubs in the system so their power drain in quiet mode can typically be ignored.

Sensors and luminaires are another matter. A context-aware lighting system in an average sized conference room may use 20 motion sensors and 20 adjustable light sources. Even with a standby power consumption of 1 W per device this equipment will consume power equivalent to an incandescent bulb left permanently on – far from ideal if you are aiming to save power and reduce waste heat.

Therefore, deep sleep modes and power supplies that can efficiently deliver very low power will be necessary. The drive towards low power consumption in power adapters for cell phone chargers (currently less than 30 mW in no-load) means that it is now possible to keep power consumption low with existing low power drivers. LCD monitors in sleep mode consume approximately 100 mW while delivering 25-30 mW to control circuits that are able to monitor the PC interface looking for a wake-up signal.

Drivers that use less than 10 mW in standby mode are achievable (some are already in use in the TV and appliance market). Managing even the 40 nodes described above could therefore consume less than 0.5 W if the sensors can run in a zero-load mode.

 

Ultra-low, no-load/standby power supply

 

The LED lighting market has always had separate commercial/industrial and consumer requirements. Consumers need low cost and fast payback from LED bulbs and small luminaries. Commercial customers can take a longer term view, trading increased fixture cost for large luminaires against increased efficiency and reduced maintenance cost. It is therefore not hard to see that smart lighting will first see significant deployment in commercial applications where the increased infrastructure cost can be more easily accepted.  Care must be taken to limit standby power consumption in each power stage, lest the advantages of high efficiency are allowed to literally leak-away via many devices and sensors waiting in standby mode.

Categories Lighting

Smarter LED Street Lighting Applications

LED Street Lighting is a technology and infrastructure with evolving demands. It is not only about bringing light to an area anymore, it is about anticipating tomorrow’s needs for value added services. Until recently, designers have mostly only been able to select ANSI/NEMA standard product lines, simply because no specific alternative – or even European – standard existed. Now, working with leading industry partners, TE Connectivity has developed a new connectivity solution for LED street lighting, while at the same time creating a standard for European outdoor luminaires.

Over the past few years, engineers and system architects at TE Connectivity have applied their specific industry knowledge and expertise to gain input from leading suppliers and partners to create a vision of a new street lighting architecture. A key consideration was the potential of new architecture and new functionalities to help create value for developers, installers and users of outdoor lighting, whilst making the move from individually programmed street lighting to Central Management Systems (CMS).

The result is LUMAWISE Endurance S modules, a compact connectivity solution for street lighting with LED light sources. The system offers greater flexibility in luminaire design and street lighting architecture. A key benefit is that it is field upgradeable, which makes it possible to simply and quickly upgrade existing luminaires.

Today streetlights are viewed as an underutilized asset. In the coming years, street lighting poles will be seen as more than fixtures for luminaires, but as outlets for electrical energy and be used for other purposes such as charging electric vehicles, operating WLAN routers and video cameras, as well as hosting sensors. Which is the application space for the LUMAWISE Endurance S connectivity platform. Providing manufacturers with a standard mechanical base to build electronics on to, coupled with a new DALI based architecture this new technology allows for an endless list of connected sensors to be developed. Already entering the market are the more traditional sensors such as photocells and central management systems. This is shortly followed by motion detection, but why stop there? Exchangeable modules could be developed for traffic counting, incident detection, pollution monitoring and for identifying free or occupied parking spaces.

Move Towards Central Management Systems
With an increased use of LED in outdoor applications, local authorities, councils and utility companies will have already reduced their energy consumption. To realize further savings comes a growing need for control of the LED. As a consequence, many luminaire operators are considering moving from streetlights with basic functionalities (photocells) to more flexible Central Management Systems (CMS) that offer more control, better programming, and higher efficiencies. However, this decision to move to a CMS does not need to be made on day one. As LUMAWISE Endurance S modules is a pluggable system, a luminaire can be installed with a simple photocell or even with no control and later extra functionality can be added or replaced. Giving a streetlight a truly 20 years of useable life.

The LUMAWISE Endurance S modules consists of a standardized interface between the receptacle and module base or sealing cap. This uses an integrated single gasket that can accommodate and seal both luminaire and module using the same connection interface for either 40mm or 80mm diameter central management systems. This allows different modules to be exchanged and upgraded in only a few seconds, without having to electrically isolate the lighting pole.

Designed specifically for outdoor LED light sources and drivers, LUMAWISE Endurance S modules has been created as a standalone system and can be used in a complementary function as an auxiliary sensor module when additional functionality is required in ANSI/NEMA based fixtures.

Installation is easy thanks to its simple push-and-twist lock feature which does not require any tools and can be completed using one hand. The LUMAWISE Endurance S modules can be mounted in any direction and offers improved sealing when compared to other systems. Modules can be exchanged and upgraded in only a few seconds without having to electrically isolate the lighting pole.

LUMAWISE Endurance S modules was developed with several partners to ensure a complete system is available, including application specific drivers and control nodes. The partners also collaborated with the Zhaga Consortium. This is a global lighting-industry organization that is standardising components of LED luminaires, including LED light engines, LED modules, LED arrays, holders, and electronic control gear (LED drivers) and connectivity fit systems. Having these standardized components helps to simplify LED luminaire design and manufacturing, and to accelerate the adoption of LED lighting solutions.

Zhaga describes a connectivity fit system for smart outdoor luminaires in what is called Book 18. This is Zhaga’s most recent contribution to the rapidly-emerging world of smart lighting. Book 18 defines a standardized interface between an outdoor LED luminaire and a sensing/communication module that sits on the outside of the luminaire. The module connects to the LED driver and control system, and typically can provide sensory inputs while also communicating with other luminaires in a network.

The focus of developing this new Book 18 specification was to demonstrate the potential of new architecture and new functionalities which can create value for developers, installers and users of outdoor lighting. The standardized interface defined in Zhaga Book 18 enables the installation of future-proofed outdoor LED luminaires, which can be easily upgraded with smart communication and sensing capabilities. Zhaga member companies are already using the specification to develop products that will stimulate the market for smart outdoor LED luminaires.

The development process was relatively short: TE first started work on this in early 2016. Throughout the process, the product developers worked closely with the Zhaga Consortium, which is responsible for developing specifications that enable the interchangeability of LED light sources made by multiple different manufacturers. As a result, the new module now sets a new standard for European outdoor luminaires, providing an alternative or complementary solution to existing ANSI/NEMA product lines.

Categories Lighting

Flicker, Shimmer and Ripple – Lessons in Light Quality

Lighting oscillation characterized by flickering and sometimes shimmering between on and off is universally a bad experience – to consumers, lights should be either on or off. The human eye easily detects low-frequency oscillation in output light amplitude (intensity). Therefore, lighting designers must attempt to minimize any periodic disturbances below 2x the line frequency (< 100 Hz) to avoid unacceptable (detectable) variations in light output.  

There is some confusion in the market over terms used to describe variations in light intensity, possibly not an entirely accidental state of affairs, so let’s look at what is acceptable and what is not.

Flicker is Not Acceptable – Flicker is a rapid light-dark oscillation of the light source at low frequency. In solid-state (LED) lighting, flicker is typically associated with the misfiring of a TRIAC dimmer when presented with a high-impedance LED driver (dimming will be described in another article). A consumer confronted with a flickering light source, will change that light source.

Shimmer is Sometimes Acceptable – Shimmer is a variation of the light output from a light source. It is also low frequency and varies between almost imperceptible and extremely obvious. Depending on the application and the proximity of other light sources, a certain amount of shimmer may be acceptable to the user.

Low Frequency Components Cause Shimmer and Flicker – All power supplies for solid-state lighting have a ripple component in the output current they deliver to drive the LEDs. Depending on the topology selected, this can be in the order of 1 percent to 100 percent (how ripple is measured will be described shortly). The frequency of the ripple typically comprises 120 Hz or 100 Hz (for 50 Hz AC line voltage regions) and a higher frequency component typically in the 30 kHz to 100 kHz region. It is worth noting that 100 percent ripple is not new in lighting. Low-pressure-sodium streetlights (the yellow ones) typically exhibit 100 percent output ripple as do several types of compact fluorescent tube lamps. Single-stage bulb drivers are by far the most widely used LED bulb drivers in the market today and typically have output ripple current in the order of 30 to 100 percent.

 

Figure 1. Typical output current and voltage waveforms for an LED driver

The Role of Frequency in Determining the Impact of Output Ripple – In describing flicker, shimmer and ripple, both amplitude and frequency were described. The frequency of the variation in light intensity is critical because the human eye is extremely sensitive to low frequency variations but quickly becomes insensitive to variations above 100 Hz. LED drivers are designed to eliminate very low frequency ripple, in the sub 100 Hz range. Asymmetric TRIAC operation in deep dimming is one example of a condition that can cause obvious shimmer when TRIAC dimming – it is readily noticeable because of its 50 or 60 Hz operating frequency.

100 Hz and 120 Hz ripple is not easily seen by most observers. Even so, various lighting standards and guidelines regulate output ripple in order to limit secondary (stroboscopic) effects and to further reduce the likelihood of noticeable shimmer. In addition, some LED manufacturers are reluctant to publish limits in the amplitude of the ripple current that their LEDs will tolerate. Very high ripple values can reduce the average current that an LED string can pass without exceeding maximum current limits – reducing the effectiveness of the LEDs and increasing cost.

How Ripple Current is Measured and Specified – While it is not a perfect match, the variation in light intensity provided by LEDs in a light source closely follows that of the current used to drive them.

LED-driver specifications typically describe the acceptable ripple as the ratio of peak-to-peak current as a percentage of the average current. Energy Star has opted to prescribe Flicker Index in its guidelines.  Flicker Index is the ratio of the light output above and below the average in one cycle. Japan also has a limit for output ripple (the Denki-Youhin-Anzenhou – Safety requirement for Electrical equipment) that requires the minimum output current to be more than 5 percent from maximum output current; frequency of ripple must be ≥100 Hz. Japanese customers often opt for very low ripple current designs to meet the required specifications of local LED manufacturers.

How to Reduce Ripple Current – Increasing output capacitance will reduce ripple current but space is often limited and additional capacitance is expensive.  Another alternative is to use a linear regulator that can smooth out the peaks in the ripple current. While this is extremely effective, the linear regulator components do add a cost burden and reduce the driver efficiency by up to 6 percent (see Table 1). Figure 2 shows an Active Ripple Current Filter (ARF).

 

 

Table 1. Active Ripple Current Filter (ARF) efficiency

 

 

Figure 2. ARF diagram

Active ripple reduction circuits can also be used – the LED driver detects and compensates for the reduction in output current associated with the rectified AC line cycle. These circuits can reduce ripple by a small amount without the bulk of electrolytic capacitors, but they significantly reduce power factor.

Wonderful Technicolor – Once the designer has managed to keep the lights on without variations in intensity, they next have to focus on the quality of the illumination provided. Features such as color temperature have some regional variability (Northern climates tend to prefer cooler colors), and the Color Rendering Index (CRI) becomes important, especially when the lighting environment is to be used to view something. We will look at the meaning of terms including Color temperature, CRI and MacAdam ellipsis next month in the second half of this article.

Categories Lighting

Global LED Lighting Trends Reveal Significant Growth and Product Development

The outlook for the LED lighting market remains very bright. Despite fluctuations in the economy and the general lighting industry, LED lighting continues to occupy a significant portion of the overall lighting market. In fact, a November 2014 article in LEDinside, a research division of TrendForce, has projected that LED lighting market penetration will reach 31 percent of the $82.1 billion global lighting market in 2015. LEDinside also reported that Europe is the largest geographic market segment—accounting for 23 percent of the global lighting market share, followed by China at 21 percent and the US at 19 percent. Industry analysts predict significant growth over the next decade.

Product development managers and electronics engineers in the LED lighting market strive to continue growing right along with the industry trends. To succeed in developing LED designs that flourish in the current market, however, they must incorporate reliable circuit protection technologies that deliver a strong return on investment (ROI).

This LED market report reveals the present state of the market, trends for several LED segments and projections for global growth. It highlights the need for industry-leading circuit protection solutions from a reliable manufacturer and specifies the ideal protection devices for several LED applications.

Present State: LED Market is Shining Bright
Recent statistical data supports the pivotal position of LED technology in the global lighting market. Global LED lighting market penetration is expected to reach 31 percent in 2015, according to a recent article from LEDinside. In addition, LEDinside has reported that the global commercial LED lighting sector will reach $26.7 billion in 2015.

Some of the most common applications for LED lighting are outdoor, residential and architectural. Outdoor LED lighting is quickly gaining popularity for tunnels, roadways, traffic lights, parking lots and garages. According to Strategies Unlimited, 2013 revenues for outdoor LED lighting were $0.7 billion. The firm also reported that nearly two million LED luminaires were installed in tunnels and roadways in 2012. IHS Technology stated that out of the 140 million streetlights installed worldwide in 2013, 19 million of them were LEDs (Source: Forbes).

Residential applications for LEDs include lighting in kitchens, hallways, dining rooms and bathrooms. When compared with other lighting technologies, only LED lighting can be used as a comprehensive replacement for fluorescent lighting (Source: LEDinside). LEDs can be used in multiple rooms throughout the home, are available in several varieties and offer a technology that is relatively easy for consumers to learn. McKinsey’s 2012 lighting market report revealed that residential is the largest general application segment for LED lighting. In 2011, it represented almost 40 percent of the general lighting market.

According to MarketWatch, the architectural segment is the second-largest end-user segment for LED lighting. For architectural applications, LEDs are used in both decorative and functional lighting. Decorative LEDs are used to illuminate fountains, pools, gardens and statues. For functional applications, including building facades and landscaping, LEDs provide visibility and enhance safety on residential and commercial properties.

In response to the current LED market trends, manufacturers are making significant changes in their operations. IHS reported that manufacturers are placing a greater emphasis on vertical integration, focusing on chip-on-board modules and light engines in 2015. Moving down the supply value chain to products that form the intermediate steps between LED components and lamps/luminaires may be an attractive strategy due to the low-profit margins for LED components. Both Phillips and Siemens, top players in the LED lighting market, have separated their lighting work from their core business to enable faster response-to-market dynamics and to achieve higher profitability. In addition, GE has taken steps to start producing its own LED circuit boards and may spin off its lighting business in the future.

Future Promise: LEDs Light the Way to Outstanding Growth
Forbes has predicted that the LED market will continue to grow throughout the next decade, with the global LED market share reaching about 70 percent by 2020. According to McKinsey, Asia will occupy about 45 percent of the global general lighting market by 2020. The report indicated that rapid penetration in Japan and China is driving Asia’s market-leading position for transitioning to LEDs in general lighting. In Europe, the current LED value-based market share is approximately 9 percent, McKinsey reported. By 2020, the share is expected to rise to over 70 percent.

 

Figure 1. The global growth of the outdoor LED market is self-evident as cities around the world adopt LED lighting. London (pictured above) announced the largest street modernization project with plans to replace 350,000 of the 520,000 city streetlights with LED lights by 2016.

Outstanding growth is projected across various LED market segments, including residential and architectural. Forecasts for LED growth in the residential segment are almost 50 percent for 2016 and over 70 percent for 2020, according to McKinsey. For architectural lighting, MarketWatch revealed that Japan and Europe are the fastest-growing regions. McKinsey has predicted that architectural lighting will remain the early adopter for LED lighting, with its market share reaching almost 90 percent by 2020.

The outdoor lighting industry is also expected to grow at a rapid rate. Strategies Unlimited has forecast that the global outdoor LED lighting market will reach $1.9 billion by 2017. The organization has also predicted that LED street light installations will grow by 400 percent over the next five years. According to Semiconductor Today, the market share of LEDs in street lighting worldwide will grow from 53.3 percent in 2014 to 93.8 percent in 2023.

Safeguard ROI: Circuit Protection for LED Lighting Innovation
Electronics engineers and product development managers are continually innovating LED designs to keep pace with the latest market trends. Creating designs for LED lighting applications presents several challenges, including the need to protect the LEDs’ electronics and circuits from lightning, transient surges and electrostatic discharge (ESD). These electrical threats may jeopardize the safety of personnel and endanger the consumer’s ROI. Failure to use proper safeguards could also lead to compliance issues with regulatory and safety standards related to overvoltage transients.

 

Figure 2. Outdoor lighting applications have a much better chance of delivering their full ROI with the proper implementation of surge protection devices (SPD) such as the LSP05-LSP10 Series from Littelfuse.

Circuit protection technologies are vital for safeguarding the vulnerable electronics and circuits within LEDs. To prevent LED lighting from experiencing failures within an investment payback period of about five years, high durability and reliability are essential. Before selecting a compatible circuit protection device, it is important to find a manufacturer who understands LED lighting industry standards and the safety issues associated with designing LED retrofit lamps and outdoor luminaires.

As the global leader in circuit protection, Littelfuse recommends protection devices for LED driver and power converter circuits used in a variety of lighting applications. Littelfuse manufactures a variety of fuses, varistors, surge protection modules (combination of varistors) and TVS diodes for LED lighting applications. To ensure compliance with industry standards and reliability, the company performs extensive product testing.

The following table indicates the ideal circuit protection device for several applications:

 

Table 1. Circuit protection solutions for LED lighting applications.

Conclusion
According to industry experts, the global LED market is experiencing rapid growth across several applications and will continue to grow throughout the next decade. In response to this growth, the demand for high-reliability circuit protection technologies will continue to increase. Circuit protection is needed to safeguard sensitive LED electronics and circuits from electrical threats and meet industry standards for safety and reliability. This technology also prevents LED lighting from experiencing failures within an investment payback period of five years. Fuses, varistors, surge protection modules and TVS diodes are designed to protect LED applications and maximize the lighting investment.

Categories Lighting

LED Light Reparability

Think back some months, and picture the following scenario: ‘twas the night before Christmas, and suddenly an overhead LED light in the household went out. And so began a tale from the modern age…

The LED light in question illuminated the kitchen. No replacement was immediately available, as there is clearly no need to carry spares for a LED light that should last 50,000 hours (according to the marketing information on the box). And being after dusk on Christmas Eve the shops were shut so there was no hope of buying a replacement.

While some might consider stuffing a turkey by candlelight a romantic way to commence the festive season, reception of this suggestion matched the outside temperature in its ability to freeze mercury.  This called for drastic action…

LED lights are not generally sold on the basis of their reparability. But in this aspect some designs do have advantages over incandescent and florescent bulbs. With the old technology if a filament blew or the emissions mix became denuded, there was no hope of repair, at least not in your garage on a cold Christmas Eve. But some LED lights are constructed from packaged LEDs that are soldered to a printed circuit board. Usually the LEDs are wired in a string. This raises the driving voltage and increases the system efficiency. But if one LED fails then the entire lamp goes out. So, in theory, by identifying and replacing the defective LED, repair of the lamp should be possible.

Finding an open circuit LED in a string is easily accomplished, especially when the manufacturer has kindly provided a silkscreen marking on the PCB that indicates the polarity of each device. A replacement LED was fortunately to hand so the soldering iron was duly warmed and in a state of euphoria over the prospect of a turkey dinner and world peace, an attempt was made to de-solder the defective LED. Herein a minor difficulty was encountered. The solder refused to melt.

LEDs, for all their merits, are not as efficient as one might like in converting electrons into photons. The balance of the energy is liberated as heat. This heat has to be removed by conduction to keep the LED temperature within safe limits. FR4 is not up to the job so LED light manufacturers solder the LEDs to metal-in-board printed circuit boards. As the name suggests these have a metal core, which does the heavy lifting in terms or removing the heat and a dielectric skin that stops the copper tracks shorting to the metal core. The very best metal-in-board PCBs use a thin layer of nanoceramic for the insulator as this provides high dielectric potential while ensuring good transport of heat from the LED to the metal core of the PCB. So good are these materials at cooling the LEDs that a 15 Watt soldering iron is seriously underpowered for the task of de-soldering an LED.

Desperate times call for desperate measures. It can be officially confirmed that a Crème Brulee torch has just sufficient oomph to desolder a defective LED on a metal in board PCB, restoring light to the World, marital relations and the schedule for turkey dinner.

Could this be the start of a whole new industry with an LED light repair shop in every town?

Categories Lighting

Lighting Controls: Decisions, Decisions

So we’ve made the decision…..we’re converting the parking deck to LED lighting.  Considering the money saved on the energy bill, along with the lower maintenance costs accompanied with not putting someone on a bucket truck for the next 10 years to swap out a bulb, it was an easy call.  Now the difficult question; do we also add controls to optimize the lighting system?  And if we do want controls, where do we begin? What will work for our parking deck?                   

Do We Need Controls?
The first question might not be whether or not we want to implement lighting controls, but whether or not we need to implement them.  Depending on the location, the state or municipality may very well require basic lighting controls to meet ASHRAE 90.1 requirements (or Title 24 compliance in California).  The overall intent of these standards is to ensure that, as a society, we are minimizing unnecessary energy expenditures, as determined by these governing bodies.  The goal is to reduce energy consumption per capita, which is often achieved through regulation.  The first step is to know whether we’re actually required to have a control system.  Keep in mind, this broad range of standards covers retrofits as well as new construction.

Do We Want Controls?
The next thing we have to ask ourselves is whether we want controls to manage our lighting system and to what degree.  In our world of high technology, embedded systems, and mobile devices, we have a plethora of choices to make when deciding exactly how we want our lights controlled.  When evaluating lighting control systems, they fall into two categories: Sensor Networks and Services.

Sensor Networks
Sensor networks deploy strategies for minimizing our energy bill, namely occupancy detection and daylight harvesting.  Nothing new here, but the decision-making comes into play in how sophisticated or intelligent we want that sensor network to be. Basically, our options are as follows:

System A: One-Way Communication

  1. A car enters the parking lot, tripping an occupancy sensor
  2. Sensor sends a control signal to a group of luminaires, declaring occupancy in the space
  3. Luminaires increase light output to safely illuminate the occupant’s path
  4. Occupant exits the area, causing the sensor to enter a state of non-occupancy, dimming the lights accordingly

In this scenario, the only system feedback we receive is a reduction in our energy bill.  But if our budget is tight, and we simply want to enjoy enhanced energy savings while complying with regulations, this approach will do.  If we desire more information from our system, then we’ll want System B.

System B: Two-Way Communication

  1. A car enters the parking lot, tripping an occupancy sensor
    – Sensor records and timestamps the event
  2. Sensor sends a control signal to a group of luminaires, declaring occupancy in the space
    – Luminaire(s) sends acknowledgement to the sensor that the message was received
  3. Luminaires increase light output to safely illuminate the occupant’s path
    – Light output measured and recorded
  4. Occupant exits the area, causing the sensor to enter a state of non-occupancy, dimming the lights accordingly
    – Sensor records and timestamps when system moved back into non-occupancy state
    – Occupancy events, power consumption, occupancy duration, etc. tracked and sent to central control unit for data processing

From the occupant’s perspective, System B’s functionality is identical to that of System A.  The value of the data is to us, as the owner, because we now have metrics telling us whether our investment is operating as intended.  We can also determine traffic patterns from the system data, including when the parking lot is being used, and how much energy the lights are consuming.  Using this basic information, we can further configure our system to minimize energy consumption, while ensuring the space is safely and securely illuminated for our patrons.

Whether we choose a one-way or two-way (data feedback) communication network, we need to consider the protocol.  Essentially, the protocol a system utilizes is the language executed to communicate between devices (sensors, controllers, light fixtures, etc.).  We have two protocol choices; 1) an open protocol (e.g. DALI, ZigBee, etc.), which allows devices from multiple manufacturers to communicate on the same network, or 2) a proprietary protocol, which is typically exclusive to a single manufacturer.  A network using an open-protocol is attractive from a competitive price standpoint because we have multiple controls vendors from which to choose.  The advantage of a proprietary protocol is that each device on the network was designed and tested to be compatible, so we can be confident in the communication and performance of the system.  Since a proprietary system is from a single manufacturer, we only have one phone call to make if we experience a system malfunction.

Services
This is where lighting gets fun.  The lighting industry is experiencing a renaissance as it comes to grips with a convergence of technologies beginning with the LED.  LED luminaires present two distinct advantages over traditional lamp options:  1) the light source is a semiconductor, which provides for easier integration into embedded systems, and 2) its location. Since data can now be provided by the sensor network, we can take that information and send text or email alerts to maintenance personnel, notifying them of a system disruption.  Once that email alert is received, maintenance can locate the specific luminaire on a virtual lighting layout via their internet browser.  And speaking of location, luminaires can also provide application-specific services to parking patrons.  With intelligent lighting (located everywhere) we can track available parking spaces in a structure or lot, creating efficient notifications to inbound customers looking for an open spot.  But why stop there?  Once parked, why not deploy a mobile app that guides patrons from their car into the facility and back again once their visit has concluded?  In essence, our lighting system can act as a local satellite network, providing services unique to a particular application.

Conclusion
The lighting landscape has changed, there’s no longer a simple answer as to whether we want lighting controls.  We now have to ask ourselves a series of questions:

  1. Do regulations require I purchase lighting controls?
  2. Do I want my system to provide data?
  3. Are email and text alerts important to my operation?
  4. Are there other services I can provide with my lighting system?
  5. What support or warranty does the lighting control manufacturer provide?

The last question is critical.  As the industry grapples with the technology shift, an unprecedented number of start-ups are jumping into the fray with warranties longer than the lifespan of the company.  Remaining diligent in vendor selection and asking a few probing questions can lead to a beneficial controls solution that will positively impact our monthly cash flow—saving energy while providing a unique experience for the customer.  When we show a friend our new smartphone, we delightfully talk about its apps, camera quality, user interface, and so on. The conversation then ends with, “and by the way, it makes pretty good calls too”.  We’ll soon talk about our lighting features in a similar manner…and by the way, the quality of light is pretty good too!

Categories Lighting

Dimming Control Solutions for LED Lighting Systems Using CCRs

The migration from incandescent and fluorescent lighting to the lower power, longer lifespan alternatives offered by modern LED technology continues at a frantic pace. Research firm Strategies Unlimited predicts that, due to the greater energy efficiency and extended operation of LED emitters, the solid-state retrofit lamp market will be worth more than $3.7 billion by the year 2016. The possibilities are not just limited to general illumination – as more sophisticated digital signage and decorative lighting systems are now seeing widespread deployment, taking advantage of the high degree of versatility that LED based lighting can provide. However, if this huge market growth is to continue and new application areas are to be exploited, engineers must be totally assured that the LEDs specified into their lighting system designs can cope with the harsh environmental or operational conditions they could potentially be exposed to.

The incandescent lamp, with its resistive light element, masks changes in power. Power spikes and surges will often have no immediate effect, as the slow response of the element absorbs the spike, with little or no change in light output. However, the life of the element is decreased due to the extra power being absorbed. Solid state lighting tends to respond immediately to any small change in power and thus spikes or surges will be seen as a higher pulse or flash of light. The LED driver circuit must thus be designed to handle these changes in power, so that they do not impact the light output or the life of the circuit. In addition, engineers need to be able to specify component parts that will not impinge on the systems economic viability in an increasingly price-sensitive market.

A vast number of different lighting dimmers are now found on the market, and there is a great deal of difficulty creating a power control solution that will work with all of them. Normally the control systems needed for this task rely on the use of cumbersome discrete and passive components. There are a number of major drawbacks with this approach though, namely:

  1. The components involved will exhibit relatively high power consumption.
  2. They take up considerable board space and impinge on the form factor of the system.
  3. The total bill of materials resulting from their use can be high and potentially prohibitive.
  4. The development of such systems can often be complex and time consuming.

These issues are causing lighting design engineers to explore highly integrated solutions, based on more sophisticated power semiconductor technology. Advanced linear constant current regulator (CCR) devices can present engineers with a more reliable and cost-effective method for regulating the level of current passing through LEDs than is possible via conventional methodologies.

Key Aspects of CCR-Based Lighting Control
Engineers developing solid-state lighting control systems need to consider how to keep the power factor (PF) as high as possible, while trying to ensure the total harmonic dispersion (THD) is kept low. In addition, so that economies of scale can be satisfied, the voltage range should be broad so the design can be applied across multiple geographic regions, while not having to sacrifice either the THD or PF too significantly. This is a very difficult balancing act – as design teams have to take into account the price points and the efficiency levels that will be acceptable in different parts of the world. In developing countries, the priority will be keeping the cost low, while elsewhere (such as in Europe or North America) compliance with environmental legislation will mean that efficiency levels are critical to the overall design.

The LED dimming circuit described in Figure 1, which is based on CCR operation, enables a marked increase in power efficiency levels and lowers the overall bill of materials. It is capable of working with a wide variety of different dimmers. The circuit makes use of three CCRs from ON Semiconductor based on proprietary self-biased transistor technology. Two NSIC2050 120 V rated devices which can deliver a steady-state current of 100 mA, and  a single NSI5010 CCR to limit the power consumption of the triac dimmer.

 

Figure 1. Low Cost Lighting Circuit based on CCRs with Dimmable Interface

 

The circuit can be broken up into two separate sections:

  1. LED management – This takes the AC and converts it, by charging the output capacitor, to produce a DC state.
  2. Dimmer Management – This provides loading current for the silicon controlled rectifier (SCR) within the dimmer and delivers a gate voltage to the series pass MOSFET. The gate drive of the series MOSFET pulse width modulates the LEDs at their peak current rating. The two NSIC2050 CCRs provide over-current and over-voltage protection to the LED emitters, while the NSI5010 CCR limits the power consumption of the dimmer management circuit. It synchronises the operation of the led to the signal coming off the TRIAC.

For optimal performance, the gate voltage of the MOSFET (driven by the voltage divider of the 11 kΩ and 1.5 kΩ resistances shown in Figure 1) needs to correspond to the threshold voltage when the input voltage to the circuit is at the minimum conduction angle.

The self-biased transistor found within each of these CCRs is preset by design for a suitable current in the fixed current devices, or a small current range in the adjustable devices (the current being selected through the use of an external resistor). These devices have built-in voltage surge suppression and negative temperature coefficients. They are capable of providing full over-current and over-voltage protection to the LED emitters while only requiring inclusion of a minimal number of external components.

The CCR’s temperature sensing ability allows it to make use of a negative temperature coefficient to automatically stabilize the current as it warms up due to power dissipation. The CCR turns on immediately and is able to provide 25 percent of the set current with a voltage of only 0.5 V across it. This allows the LEDs to be activated virtually as soon as power is applied. Regulation begins at about 1.8 V and remains stable up to the maximum voltage of the device.

By utilizing advanced CCRs like the ones discussed here, based on innovative self-biased transistor technology with a high degree of functionality integrated onto the chip, it is possible to support vulnerable solid-state lighting systems design against extreme levels of ambient heat and high voltage spikes as well as deal with the key ‘board level’ issues effecting the design. The system design elements will include enhanced system performance, ensuring long-term operation, lowering the total bill of materials, reducing board space utilization and shortening the overall development time.

Categories Lighting

Lighting Must Continue to Lead…

Two years ago, I closed a guest blog post in this very space with the following: “….exciting times and opportunities lie ahead for lighting that leads…” (see “Tipping Points, Toothaches and LEDs” published on 4/9/2013).  That two-year old blog post hinted of evolutionary opportunities available to/for “lighting,” something I referred to as “lighting that leads.”  Some likely thought my speculations/thinking were too far afield for “lighting,” but clearly there were/are those who thought/think similarly.  Recently, numerous lighting companies, including OSRAM SYLVANIA with our new LIGHTIFY portfolio, have made announcements about connected lighting.  Recognizing that sockets compatible with connecting lighting heretofore only served to hold and power a source of illumination, it is remarkable to realize that those same sockets are also now physically and technically positioned to enable intelligent receiving and transmitting nodes in a “connected world,” indeed to become an integral part of the coming Internet of Things/Everything.  Remarkable!

Knowing that light and lighting are ubiquitous and a mainstay in our 24/7 culture, one should not be too surprised to discover products and technologies which facilitate the production and delivery of light might also be an important part of the “connected world’s” infrastructure.  Said differently, I believe products and technologies which facilitate the production and delivery of light will have the first right of refusal in becoming a critically important part of the coming “connected world,” particularly in ways which are very visible to the average consumer.  To me, this is both obvious and concerning.  Done correctly, I believe this will provide service, application and business opportunities for companies who have long-served consumers of light and lighting products.  I expect said companies will have opportunities to participate in new growth and profitable business areas which have been difficult to find and take benefit of in recent years.  In addition to the growth and profitability opportunities, I do have concerns related to the challenges the former “lighting companies” have in accommodating the dramatic change in expertise and competence required to design, develop and support  “connected” products, technologies and services.  Having said that, lighting companies, once known only as experts in traditional light sources and/or drivers/controls, are embracing the opportunity to change their technological core, to evolve and reinvent themselves toward connected technologies, products and service, while maintaining their competence and expertise in providing light and illumination.  I believe the trend and direction of the players, and the industry, is favorable.

Although I view the current situation as favorable, I believe many challenges remain.  Despite those challenges, I stand by my closing comment of nearly two years ago – – – – The work will be challenging, but interesting. The benefits will initially be difficult to document with numbers, but nonetheless evident. Patience (by all) will be required but exciting times and opportunities lie ahead for lighting that leads!