Two Trends to Watch in LED Light Sources

LED lighting has become a mainstream, accepted light source – within commercial lighting markets – in an incredibly short period of time. LED prices continue to drop while output-per-LED continues to rise roughly every six months. Odds are good that you are beginning to see LED luminaires and lamps creep into decorative, and even residential, markets. I’m not one of those people who thinks LED is the best light source for every application, but it is starting to be utilized in decorative and residential luminaires at an increasing rate.

As a major supplier of advanced light sources to the decorative luminaire industry, I have no choice but to track how the technology is evolving and engage in the tricky business of making predictions on technology winners. Here are two trends in LED light sources that I think you’ll be seeing a lot more of over the next two years:

HIGHLY INTEGRATED LED LIGHT ENGINES

When members of the semi-conductor industry first came knocking on the lighting industry’s door, they only had bags of parts to offer. Luminaire makers had to struggle with pairing this LED with that driver, and often had to figure out the heat sinking and optics on their own. The early results ranged from merely okay to outright disastrous depending on the capabilities of the luminaire maker.

Today, there is a new breed of “integrator” that takes care of all of the engineering required to properly integrate LEDs, the driver, heat sink, optics, and even the mechanical mounting. The integrated assembly is known in the industry as an “LED light engine,” and it can even resemble a traditional lamp (bulb). These light engines are typically hard-wired and are offered in either line-voltage or low-voltage options. This new availability of highly integrated LED engines will allow more decorative luminaire makers and those with little in-house engineering capabilities to create high-performing and high-quality LED luminaires. Of course, it is still up to the luminaire makers to choose their light engine suppliers with care. After all, it is the engine that “drives” the luminaire. One of the key things to remember is that there is a lot of time, testing, and research that needs to go into the development of an LED source. Not all luminaire makers have the time or resources to do that and stay competitive, so why reinvent the wheel if there is an integrated source available?

KEY ADVANTAGES OF HIGHLY INTEGRATED LED ENGINES:
•   Avoids LED / driver compatibility issues
•   Provides proper thermal management (when used according to the light engine thermal and electrical requirements). Some engines include internal thermal regulators to actively protect against overheating (a great question to ask about your prospective LED purchase!)
•   No need to hide a remote driver
•   Avoids costly integration mistakes
•   Greater speed to market for an LED fixture design, and a shorter product development cycle
•   Greater accountability if there is ever a problem. The LED chip maker can’t blame the driver maker, and vice versa. The buck stops with the engine integr ator and the luminaire maker.
•   Some of the best engines feature field-interchangeable optics to change the beam angle and internal constant current drivers to avoid voltage drops when multiple luminaires are on one circuit.

DISADVANTAGES:
•   It is a larger light source when the heat sink and driver are integrated into the engine. This can be problematic at very high outputs.
•   The integrated engine can lull a careless luminaire maker into believing all thermal, electrical, optical, and chemical issues are solved for all applications. Due diligence is still required – especially on thermal requirements.
•   The weakest link in most LED installations is the driver, so anyone assembling an LED engine or other LED source needs to make sure the driver spec matches the published lifetime of the product. LEDs may be able to last 50K-100K hours, but the driver also needs to keep up.
•   There are certain factors such as in-rush, voltage spikes (dirty power), dimmer incompatibility, transformer incompatibility, etc., that need to be considered and discussed.
•   There is no replacing a subcomponent – such as an LED or driver – only. If an integrated engine were to fail, the entire engine or luminaire would typically need to be replaced.

TYPICAL APPLICATIONS:
• There is a very wide range of applications for decorative and commercial fixtures in both directional and omni-directional versions.

HIGH-WATTAGE CHIP-ON-BOARD (COB):
High-wattage Chip-on-Board (COB) needs to be viewed as an alternative way to package LEDs. In the right application, it’s excellent. However, and it’s a big caveat, it’s not the optimal solution in all applications.

COB refers to a method of semiconductor assembly in which the LED die is directly mounted on and electrically interconnected to its circuit board. The elimination of conventional device packaging from COB assemblies simplifies the overall process of designing and manufacturing the final product. Shorter interconnection paths also improve COB performance.

The COB process consists of just three major steps: 1.) die attachment 2.) wirebonding, and 3.) encapsulation of the die and wires. I’ve personally seen demonstrations using COBs up to 20 watts. It created the equivalent light output of a 100-watt incandescent lamp from a single LED that is only about one square inch. Needless to say, it was a very intense light source!

Like other LED technologies, it is paramount to find a reliable partner that understands the technology, utilizes proper design, and understands the intended applications. However, designing luminaries from the ground up using this technology shows a lot of promise!

KEY ADVANTAGES OF HIGH-WATTAGE COB:
•   Very high COB power density can significantly reduce space requirements
•   Reduced cost
•   Better performance due to decreased interconnection lengths and resistance
•   Higher reliability at the chip level, due to better heat distribution and a lower number of solder joints
•   Shorter time-to-market
•   Can protect against reverse-engineering and aid in differentiation
•   Allows remoting of the driver
•   More even light distribution and consistency compared to high-power surface-mounted LEDs (SMD).

DISADVANTAGES:
•   The high power density comes with more concentrated heat. This is not as big a deal with low-wattage COBs, but it becomes a larger challenge with high-wattage COB.
•   Heat sink geometries and requirements can be large, so this technology is not ideal for retrofitting many existing luminaires.
•   This is not an integrated engine technology, so more technical expertise is required to design the full light engine system, including the heat sink and optics.
•   There are limitations on the optical control for narrow beams. Beam spread is typically controlled with a secondary optic, such as a reflector, which results in limits on the narrowness of the beam angle.

TYPICAL APPLICATIONS:
• Very wide range of applications, both decorative and commercial fixtures, directional.

The lighting industry has never had a technology evolve as fast as solid-state lighting. This article has only addressed two emerging trends in LED technology. There are, however, other significant trends, such as remote phosphors and AC-LEDs. Stay tuned for additional articles in enLIGHTenment magazine covering tech trends that will impact the showroom industry.

About the Author: David Shiller is President of Lighting Solution Development (LSD); a national, OEM rep agency specializing in advanced light sources, including: LED, fluorescent, and induction. LSD clients include: Progress, Kichler, Generation Brands, Juno, Pacific Coast Lighting, Minka, Maxim, Uttermost, and 100+ other leading luminaire makers. LSD’s line card includes: MaxLite, American Illumination, Advanced Optoelectronics, CFS, and Buhl Electric. Shiller can be contacted at: http://www.lightingsold.com/contact.php .