Light-emitting diodes (LEDs) have come a long way since their introduction as a practical electronic component in 1962. When LEDs first became commercially available, they were primarily used as indicator lights, replacing incandescent and neon lamps.
As LED technology advanced, the brightness and light output improved, widening the range of LED usage to include traffic signals as well as decorative and accent lighting. The advantages of LEDs over incandescent and other forms of traditional lighting were immediately evident, including longer life, smaller size, increased durability and reliability, and greater efficiency thanks to reduced energy consumption.
There’s no doubt, for the near term, that there are specific applications where a fluorescent, halogen, or discharge source is still effective, and it is important to be aware of those options. But because of all the benefits of LEDs, the lighting industry is quickly realizing the technology’s potential for general illumination, and an increasing range of applications is becoming LED compatible. This change, despite an initial slow start, is now accelerating.
Where Are We Today?
The market for LEDs has grown enormously in the past 10 years, and the technology has drastically improved during this time span. While low-brightness LEDs are still being used for instrumentation and other visualization applications, we now see high-brightness LEDs in an increasingly diverse array of applications, including automotive lighting, street and outdoor area lighting, signage, commercial and retail illumination, and large-scale decorative and entertainment installations.
LED usage for projection and electronic backlighting is also growing, and so is the use of LEDs in a number of non-visual purposes. In fact, non-visual applications such as human perception and well-being may be major growth drivers in the future.
LED retrofits for standard incandescent bulbs have emerged in recent years with 40-W and 60-W equivalents currently available and 75-W and 100-W versions following soon. These retrofit products offer a valuable interim solution that leverage the legacy infrastructure while allowing the rapid deployment of energy-saving LED lamps. Eventually, it’s likely that a uniquely LED-oriented infrastructure will emerge.
Why LEDs Are Succeeding
The characteristics of LEDs make them well poised to be the future of lighting. Already one of the most efficient sources of illumination available, LEDs provide significant and progressively more energy savings over most traditional light sources. Their long life is also a significant advantage, reducing maintenance and replacement costs and changing the total cost of ownership argument in their favor.
Another valuable feature for both practical and decorative applications includes the ability to switch on and off quickly without reducing their lifetime or quality of light. This makes LEDs ideal for applications that involve on/off cycles and controls.
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Though the first efficient LEDs available were red, LEDs are now available in multiple colors enabling a full spectrum and high-color-rendering light engines. They are also available as white light sources offering multiple hues of warm and cool white without the use of inefficient color filters, which is a notable benefit over traditional technologies.
Due to their ability to switch rapidly and their wide range of wavelengths, LEDs now are finding use in dynamically tunable, on-the-fly control strategies. Also, their directional nature is yet another advantage over alternate lighting technologies and is a powerful tool for generating application-specific efficiencies in lighting.
By directing light only where needed in street lighting, LEDs minimize light pollution and more efficiently use their light output. Even though a traditional light source may generate more lumens at comparable efficiency, the application efficacy of the LED, i.e., more light on the road, may be superior in some instances.
LEDs Face Design Challenges
Despite all their benefits, LEDs are not without design challenges. As LEDs become more powerful and appear in applications requiring greater light output, there is an increased need for heat management.
LEDs produce very cool light radiation compared to other technologies. But their component parts do produce heat, and LED performance suffers under high-temperature conditions. Therefore, any application using LEDs must provide adequate heat dispersion.
Naturally, given that legacy infrastructure revolves around lamps that radiate heat, there is not much allowance for conductive heat transfer. This is the source of poor quality products that do not live up to laboratory-test claims. Now, some of these issues are the focus of LM80, LM79, and CALiPer testing, as well as Energy Star requirements.
Another design challenge associated with white LEDs for illumination is fine white binning, the process of grouping both the LED chip components as well as finished LED packages by color and brightness to maintain color consistency within the finished product.
We can test individual LEDs for specific characteristics such as luminous intensity, luminous flux, forward voltage, dominant wavelength, and chromaticity, and we can group them with chips and packages that have similar characteristics. Although the process maintains consistency, the process varies between manufacturers. This makes it very difficult to purchase white LEDs from multiple vendors as color temperature and output can differ.
Much work is being done on binning standards today, and the National Electric Manufacturers Association (NEMA) is developing a standard. However, given that the LED business is global, it becomes imperative to have an international and harmonized standard or system of description that applies globally and across all applications.
Binning is not the only factor in the LED market that lacks industry standardization. Because the market has evolved so rapidly in recent years, lamp, fixture, and luminare designs fluctuate from one manufacturer to the next. This not only creates challenging replacement scenarios, it also proves to be a barrier to mass adoption of LED illumination.
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Since the Edison incandescent electric bulb was first introduced to replace gas lamps, an ecosystem of lamps, luminaires, ballasts, and controls has been created with standard sockets and specifications. These standards have helped to significantly encourage the adoption of electrical light throughout all its iterations.
Such an ecosystem and standard system have yet to be fully established for LEDs. So, designing and specifying lamps and fixtures that are universally applicable remains a critical challenge.
What’s Next For LEDs?
LED technology is still fairly new for many of the applications in which it is used, and there is room for improvement and growth. The lighting industry is beginning to shift its focus heavily toward LEDs, and manufacturers are investing much of their research and development efforts in the technology. In the near future, we can expect to see improved LED performance as well as further innovations in LED products and applications such as integration into architectural materials.
As fast as the LED market is expanding and developing, the industry must focus on five key factors to drive and accelerate adoption: evolution, flexibility, conversion, interoperability, and infrastructure. These factors will be the bridge between where we are in the LED market today and where it is going in the years to come.
Though Edison garners credit for the invention of the incandescent bulb, he was by no means the first to come up with the idea. There was never a finite definition for the ideal light bulb. In fact, 20 different groups spent 40 years working toward incandescent lighting before Edison developed the first commercially viable solution.
The situation is no different with LEDs. They have already come a long way since their first introduction, but there is still room for improvements and we can expect LEDs to continue to advance as the industry evolves.
The key to managing rapid changes in LED technology will be simple, plug-and-play designs. The introduction of flexible solutions that have clear upgrade paths at minimal cost can significantly reduce the disincentive to adopt LED technology. This approach will lead the industry toward modularity, where only rapidly changing components will require replacement.
By creating modular solutions, the investment in LED technology can be future-proofed. One modular, compact, and future-proof solution, Osram Sylvania’s PrevaLED (Fig. 1), offers easy replacement of the light source once it burns out or becomes outdated, or when the application changes.
Two different forms of conversion will be necessary to advance LEDs and accelerate mass adoption. The first is the conversion of lighting components. Electronics are often neglected in considering LED deployment.
Currently, T8 and T5 fluorescent systems are among the most efficient and long-lived systems—especially their electronics. The development of a program for large-scale conversion to LEDs that would involve adapters or converters for existing fluorescent ballasts could be critical to promoting the fast adoption of LEDs and would reduce waste from already installed platforms.
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Osram Sylvania’s LEDStixx(Fig. 2) similarly utilizes a bi-pin design to fit seamlessly into existing fluorescent sockets for specialty applications . Designing retrofits for the existing installed fluorescent base can go a long way in advancing LED technology.
The second conversion necessary is the transition of conventional lighting manufacturing plants to solid-state lighting production. By doing this, manufacturers will maintain jobs for their workforce, minimize additional resources, and ultimately accelerate production toward LEDs. Conversion of existing traditional lighting factories is the fastest way to gain capacity, reduce prices, and drive adoption.
Design standardization of the key elements of LED systems will be a vital enabler of large-scale LED deployment. International groups such as Zhaga are working on a global standard for interfaces.
Such a standard for interoperability will be an important advance in allowing customers to easily switch from one source to another, providing security as well as a viable upgrade path for future improvements. The concept of upgrading versus replacing after product failure is a concept already familiar to electronics consumers and should be replicated for the LED industry.
Infrastructure represents a large opportunity for today’s lighting industry. Roughly half the electronics in use today are designed to convert ac power to dc, and a dc delivery system could work in the local-area network. This could be significant for the future infrastructure of lighting.
For example, the EMerge Alliance is developing standards for a low-voltage dc micro-grid that will enable the availability of low-voltage dc in a room or sub-unit of a building. There are several other independent developments in this area, and ultimately they all will lead to ease of use and flexibility. They also will permit the rapid relocation and changeover of lighting as the needs of the users change.
Another area of infrastructure that still needs to be addressed for the future of lighting is in controls, e.g., wireless protocols, Internet protocol (IP), hardware and software, and human factors, to promote energy-efficient choices.
Remote controls using radio frequencies or Wi-Fi may soon become a possibility for home and building control systems. Some smart phones and other handheld devices are already equipped with control software. The communications, control, security, and other practical aspects of making such a system work and integrate with building controls are yet to be addressed.
Additionally, human factors studies, such as the impact of human behavior, have received little consideration. Color preferences, visual performance, and similar aspects that affect end-user performance can now be indulged, given the incredible flexibility and on-the-fly tuneability of LED lighting systems.
As we look to the future of lighting, LEDs are front and center. A few hurdles must be crossed before mass adoption, but the technology is quickly evolving and the industry is preparing to make the transformation.
The focus must now be on the development of infrastructure, non-traditional formats for lighting in architecture, and other venues. Design also must focus on human factors and behavior surrounding how light is used and lighting decisions are made, along with creating robust interfaces between key components so updates are easy and cost-effective.
Once there is progress in these key areas, combined with education initiatives for consumers, LEDs will begin to truly take their place as the future of lighting. The electronic design community faces an exciting, once in a lifetime opportunity to start building the next lighting ecosystem, limited only by the imagination.