WHITE PAPER
A Systems Approach to the Design and Manufacture of
Solid State Lighting Fixtures
TE Connectivity
NEVALO Product Lighting Team
Introduction
Why Solid State Lighting is Important
Welcome to the world of Solid-State Lighting (SSL). Unlike
In 2009, the lighting industry generated sales of $75 billion glob-
the incandescent / fluorescent lamp world of today’s electrical
ally with less than 5% being solid-state lighting. However, more
lighting fixtures, solid-state lighting is in the realm of electron-
efficient solid-state products are poised to grow rapidly. Sales
ics with multiple interdependent ancillary systems. The purpose
of new and retrofit SSL fixtures are projected to increase to over
of this white paper is to provide an informative summary of the
half of the $91 billion in lighting sales in 2014 and further rise
elements that comprise these new electronic systems and to
to 75% market share by 2019. Regulations coupled with higher
introduce a holistic new systems approach to the design and
energy cost and lower SSL costs will dictate the pace of this
manufacturing of SSL fixtures.
change. Governments most aggressively pursuing the elimination of incandescent bulbs include those in the European Union,
1. The Solid State Lighting System
The ability to keep up with the increasing need for electrical
energy is causing a global pull towards more energy-efficient
products. Lighting consumes over 25% of the electricity generated in the United States. Most industrial nations have a similar
high percentage of energy production consumed by lighting.
The most energy-efficient lighting products use light-emitting
diode (LED) technology (Figure 1.1). These solid-state lighting
(SSL) products are more expensive today than the next best
energy efficient alternative. However, ongoing development is
rapidly improving SSL capability and cost-effectiveness. If all
lighting was shifted to SSL, it would reduce the lighting energy
Efficacy in Lumens/Watt
consumption to less than 10% of electricity generated.
Japan, United States, Canada, Australia and the Republic of
China.
In 2009, restrictions on the sale of incandescent bulbs began in
most of Europe based on Directive 2005/32/Ec of The European
Parliament and of the Council of 6 July 2005. Australia was the
first country to announce a ban for incandescent bulbs. The
ban went into effect in 2010. Canada was the second country to
announce an incandescent bulb ban that goes into effect in 2012.
The Japanese government implemented a series of subsidy policies to pursue the commitment it made in the Kyoto Protocol. In
December 2006 the JELMA (Japan Electric Lamp Manufacturers
Association) announced four proposals to substitute less efficient lamps with higher efficiency alternatives. On April 5, 2008,
the Minister of the Ministry of Economy, Trade and Industry
(METI) announced “the replacement policy for Incandescent to
100
90
80
70
60
50
40
30
20
10
0
CFLi by 2012”.
An energy bill passed in 2007 by the U.S. Congress, the Energy
Low
Independence and Security Act of 2007, effectively bans the
High
incandescent light bulb as we know it by 2014. Initially, the conventional 100-watt bulb will be discontinued in 2012. The incandescent light phase-out process ends with the elimination of 40-
Incandescent
CFL
LED
(Cool White)
Figure 1.1 The efficiency of traditional light sources compared to solidstate lighting shows the significant benefit of LED-based SSL. Source:
Department of Energy (DOE) Energy Savers.
watt bulbs in 2014. The actual requirement is for all light bulbs to
consume 25 to 30% less energy by 2014 and 70% less by 2020.
Since incandescent bulbs waste about 90% of their input energy
on heat, this eliminates them as a viable lighting contender after
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2014. High-efficiency incandescent light bulbs are being pursued
as such, create a hazardous waste condition when they are
that may extend a small portion of the incandescent market but
discarded. In contrast, LEDs do not contain hazardous materials
their cost is quite high. California Title 24 has established energy
and products can be disposed of without concern.
standards for residential and nonresidential buildings that are
LED technology is improving rapidly. Haitz’s Law predicts “that
dictating energy standards for the rest of the country.
every decade, the cost per lumen (unit of useful light emitted)
With the world’s supply of non-renewable energy from fossil
falls by a factor of 10 and the amount of light generated per LED
fuels depleting rapidly, the need to reduce energy consumption
package increases by a factor of 20.” The improvements made
is a global imperative. Developing countries want to experience
over the last 30 years of the twentieth century (Figure 1.2) have
the same advantages that developed countries have enjoyed.
continued into the 21st century. (See Section 2 for more details).
However, developed countries have shown that the insatiable de-
As cost-effective lighting evolves, any company or individual
mand for energy-hungry products has exceeded their capacity
with a stake in the future of the lighting industry should be
to generate sufficient energy to support them, especially when
intimately aware of LED-based lighting’s current status and
the energy must come from clean energy sources. China has
progress toward becoming the dominant lighting source for
announced plans to phase out incandescent bulbs that could be
residential, commercial and industrial lighting.
completed by 2017.
Country
The rapid improvements in LED technology that fulfill Haitz’s
Initial Phase-out
Law have generated recent SSL growth that is attributable to
Target Completion
Brazil
2005
2005
Venezuela
2005
2005
European Union
2009
2012
Switzerland
2009
2009
Australia
2009
2009
Argentina
2012
2012
Russia
2012
2012
Canada
2012
2012
United States
2012
2014
India
--
2012
Japan
-- 2012
China
-- 2020
compelling applications that are emerging for solid state lighting
such as commercial refrigeration and street lighting. Commercial
refrigeration lighting is a perfect application for LEDs. This very
cold environment typically has the lighting on continuously. The
longer life of LEDs make them a natural for avoiding frequent
bulb replacement. In addition, LEDs function better at lower
temperatures compared to fluorescent bulbs that have to be
overdriven and start to lose arc requiring an increasing amount
of energy. This requires the refrigeration units to expend even
more energy to overcome the increased heat generated by the
lighting.
For street lighting and in many industrial and consumer applications, the maintenance avoidance issue alone is sufficient to
Table 1.1 The statutory elimination of incandescent bulbs is taking place
on a global basis.
warrant the use of solid state lighting. The cost to replace a bulb
Without the increased implementation of energy efficient
include the disruption (loss of sales) for shoppers in commercial
alternatives, the insatiable demand for more electrical energy
environments or loss of productivity in industrial situations. As
can only be solved by building more electrical power plants.
early adopters take advantage of the unique capabilities of SSLs
Unfortunately, it takes about 10 years to build a plant in the US
and Haitz’s Law continues its downward trend, the technology
to provide additional power generating capacity. In the U.S.,
will expand to broader applications.
in some environments is as high as $200/hour and that does not
the projected increase in demand of 135,000 megawatts versus
the projected additional capacity of 77,000 megawatts results
in a shortfall of 58,000 megawatts. [Data courtesy of NERAC.]
As a result, subsidizing more efficient technology is a preferred
alternative. Prof. Michael Siminovitch, Director of the California
Lighting Technology Center notes that, “Solid state lighting
equipment provides significant long-term energy savings and
is much less costly to buy than the generating facilities used to
provide power for ordinary wasteful lighting fixtures. As a result,
utilities, federal and state governments are providing an ever
widening array of utility incentives for the adoption of solid state
lighting devices.”
Initially, compact fluorescent lighting was the solution to
Figure 1.2 According to Haitz’s Law, the amount of light generated per
LED package will predictably increase and the cost/lumen of light will
predictably decrease each decade. Source: The Case for a National
Research Program on Semiconductor Lighting.
improved efficiency and replacement of incandescent bulbs
because of its lower cost. However, CFLs contain mercury and,
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The Transition to Solid State Lighting
simplified approach. Before discussing the details of the TE
NEVALO SSL system, the changing capabilities, challenges and
As in many other industries, consumers expect the leading tech-
design aspects associated with each of the areas in Figure 1.3 as
nology companies to respond to global imperatives with new
well as other critical solid state lighting issues will be explored.
products that use the latest technologies. Solid state lighting
is and has been promoted as the solution for improved efficiency and leading companies need to deliver on this promise.
The Future with Solid State Lighting
However, certain aspects such as cost and complexity have lim-
What can users do with the next generation of solid state light-
ited the industry’s response.
ing? It’s not just cheaper lighting over the life of the bulb. It’s
not just a matter of incrementally greater efficiency. All of the
Lighting suppliers have closely monitored how poorly the tran-
next generation SSL fixtures will take advantage of digital con-
sition from incandescent lighting to the obviously more efficient
trol to enable many more desirable features. For example, the
compact fluorescent lamp (CFL) technology has been handled.
next generation of luminaires made with solid state lighting will
The lessons learned from this process are being applied to solid
be able to provide color mixing within the white spectrum for
state lighting. Among the key observations is the difficulty sup-
warmer light in the morning and cooler lighting in the afternoon
pliers have had in coping with a new technology. SSL is even
or whatever the end user desires. Next-generation SSL-based
more complex than CFL, so a new approach is required.
street lighting will increase in intensity and/or flash when a 911
Complete solid state lighting solutions involve technical exper-
(or police) call is made to brighten the area for first responders.
tise in myriad technologies. As shown in Figure 1.3, several
SSL-fixtures will automatically dim within 15% to save energy
distinct, high-level areas are easily identified. Knowledge in one
and reduce peak energy demand – without occupants even
area can be quite unique and the successful application of that
knowing it happened. These and many other exciting possibili-
know-how must be brought together at the systems level to
ties can and will occur with solid state lighting. And, they are
achieve an optimum lighting solution that takes into account
not possible with existing lighting sources. With SSL technol-
the interaction between the technologies.
ogy, the future is approaching rapidly.
The number of different areas of expertise required and the
interaction between them has been among the factors that
have hindered the development of solid state lighting. With its
broad technical expertise, TE Connectivity (TE) has addressed
the complexity of today’s SSL design process and created a
Figure 1.3. Several essential and interconnected technology areas of
solid state lighting (SSL) must be brought together at the systems
level for a successful SSL solution. (The SSL Orbit: Courtesy of TE
Connectivity).
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2. LEDs – SSL’s Enabling Technology
LED packaging and its semiconductor contents deserve a closer
look. High power LEDs are currently offered in 1 to 5-W encapsu-
Light-emitting diodes (LEDs) have been produced since the
lated packages as well as hybrid or chip-on-board / array pack-
1960’s. Early applications were primarily for indicator lamps,
ages that can exceed 50-W levels. As Figure 2.2 demonstrates,
since the power output was quite low and colors were restricted
this packaging is not standard for high power LEDs.
to red, yellow, orange and green. White LEDs did not appear
until the late 1990s. Recent advancements in much higher output
LEDs have made LEDs useful in illumination. The term high
brightness or HB LED is used frequently to describe these higher
power LEDs however, it is not clearly defined and as such tends
to create more confusion instead of increased clarity. Understanding the different types of LEDs can help to select the right
LED for the application.
Figure 2.1 shows a comparison of an incandescent bulb and compact fluorescent lamp to a lighting-class, multi-chip LED in a surface mount package. The obvious visual distinction is just one of
the major differences between these light sources. In contrast to
the others, LEDs are essentially a point light source that provides
a unidirectional light that serves to put the light where a user
needs it rather than backscattered in a fixture. Further, LEDs are
typically low voltage devices and require only a constant current
source unlike fluorescent and high-intensity discharge (HID)
lamps that require a high-voltage ignition source. As an added
benefit, LEDs do not generate high inductive spikes or surges
like magnetically ballasted HID lamps that often necessitate ad-
Figure 2.2 Available high-power LED packaging is anything but
standardized. The Lumileds Rebel is an example of a discrete LED. The
others shown are examples of LED array packages.
ditional filtering devices to prevent wreaking havoc on AC power
distribution systems.
Figure 2.1 A visual comparison of an incandescent bulb and compact fluorescent lamp to Cree’s XLamp
MC-E single multi-chip LED shows the physical differences between conventional and solid-state
lighting technology. Source: Big Stock Photo and Cree.
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LED packaging has optical, electrical, thermal and mechanical
cent lamp which approximates the ideal black body source and
design considerations. All these elements are accommodated
yields a CRI of 100 against which other light sources are mea-
within the very small space of the LED package. To start, the
sured. This is a somewhat subjective analysis that attempts to
semiconductor chip or die needs to be mounted to a thermally
accommodate the tri-chromic nature of human vision.
conductive surface that allows the generated heat of the die to
A Color Quality Scale is being developed at the National Institute
be efficiently transferred to a separate heat sink. Also within the
of Standards & Technology (NIST) to address the problems of
package, electrical connections between contact pads on the
the CIE Color Rendering Index for solid state light sources and
package to the die are made with small gold wires called bond
to meet the new needs of the lighting industry and consumers
wires that need to be protected from mechanical damage. To
for communicating color quality of lighting products. With the
protect the bond wires, the die and to focus the light, an opti-
advent of LED sources, this new color reference measurement
cal lens or encapsulant is attached to the top side of the LED
technique attempts to correct chromatic saturation deficiencies
assembly.
in the CRI method. As opposed to the single number CRI, the
CQS results in a composite number that more accurately defines
LED Capabilities
a lamp’s ability to render colors in a manner pleasing to most
Key performance metrics for LEDs include luminous efficacy
consumers.
(the amount of light provided in lumens, per watt of electricity
Another important LED parameter is its correlated color tem-
consumed (lm/W), total power consumption, maximum current
perature (CCT) specified in degrees Kelvin. The CCT provides a
capability and the associated luminous output, and Correlated
relative color appearance of a white light source when compared
Color Temperature (CCT), Color Rendering Index (CRI) or Color
to a theoretical black body source. As shown in Figure 2.3, eight
Quality Scale (CQS). In this section, additional details on these
typical color classifications extend from 2,700K to 6,500K with
metrics are provided.
the lower color temperatures often referred to as “warmer”
The CIE (Commission Internationale de l’Eclairage) established
colors and the higher color temperatures referred to as “cooler”
a color rendering index (CRI) that rates how well a light source’s
colors. As a comparison, incandescent bulbs are approximately
illumination of sample patches compares to the illumination from
2,700-3,000K, fluorescent bulbs are typically 2,700-5,500K and
a reference source. The reference source is typically an incandes-
natural daylight often referenced as 5000K. White LEDs are
therefore also identified as warm, neutral and cool based on CCT
rating.
Figure 2.3 The CIE 1931 chromaticity diagram depicts the eight nominal CCT quadrangles. Source: ENERGY STAR
Program Requirements for Solid State Lighting Luminaires, Eligibility Criteria – Version 1.1.
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As noted in Section 1, improvements in these key metrics are oc-
must select the proper mix of LEDs to arrive at a consistent,
curring at a rapid pace. The industry is in a never-ending pursuit
comfortable, color rendition or with a supplier that makes this
of ever-increasing performance requirements, yet one of the
complex issue transparent to them.
most confusing parts of this specsmanship is the broad chasm
Achieving Cost-effective LEDs
that often separates laboratory performance from the practical
performance of available products.
While performance is improving rapidly, the cost of LEDS is
Manufacturers continue to announce ever-increasing perfor-
decreasingly rapidly as well. When will the cost of LED-enabled
mance from their LEDs. In 2010, Cree announced its XLamp® XM
lighting decrease enough for wide-spread general illumination
LED that delivers 160 lumens/watt at 350 mA and 750 lumens at
adoption? Many think the time is imminent.
2 A. The later rating is equivalent to the light output of a 60W in-
According to Strategies Unlimited 2010 report on High Bright-
candescent light bulb but requires less than 7W. Recently, Philips
ness LEDs, the HB LED market is forecast to grow at average of
Lumileds announced a Luxeon Rebel LED that delivers in excess
29.5% per year, reaching over $19 billion by 2014. The highest
of 300 lm with a 1A drive current. Bridgelux RS Array Series
forecast growth rate is 60.6% for signs/displays. Illumination has
deliver between 3400 and 5000 lumens under normal operating
the next-highest growth rate, with a projected CAGR of 45.4%.
conditions (Tc= 25°C). Based on the highly competitive envi-
This growth is based on cost reductions. As shown in Figure 2.4,
ronment and current market status, continued high-power LED
the DOE Report Solid State Lighting Research and Development:
improvements are expected in the future as the industry moves
Manufacturing Roadmap, September 2009, projects packaged
toward the maximum achievable range of 220 to 250 lm/W (ver-
LED cost in 2015 to be almost 10% of 2009 levels.
sus the theoretical limit of 300 lm/w).
Several factors are in the LED’s favor to offset the initial cost difference when compared to other light sources. LEDs:
LED Binning Issues
•Are inherently compliant to Restriction of Hazardous
Substances (RoHS) as opposed to CFLs which have
compliancy issues due to mercury content
White LEDs actually use phosphor to create white light from a
blue LED. The color and output variations of both the die and
the phosphors that occur during manufacturing cause suppliers
•Provide significantly longer life (50,000 full-power hours or
about 11 years @ 12 hours/day to 70% of rated lumens) than
CFLs
to sell products using a binning approach. According to the DOE
Report Solid State Lighting Research and Development: Manufacturing Roadmap, September 2009, “Understanding issues
•Operate at high efficacies (70-120 lumens/watt) rather than
10 lm/W or less exhibited by incandescent lights
such as how much performance variability can be tolerated and
which performance parameters are critical for the development
•Are available in broader ranges of warm and cool white than
CFLs
of luminaires of consistent performance is crucial. Color consistency of the LEDs to be used in the luminaires was seen as the
most important binning issue.” The National Electrical Manufac-
•Are easier to control than CFLs with better dimming
performance and no flicker
turers Association (NEMA) recently published High-Power White
LED Binning for General Illumination that provides standardized
•Start without the delay associated with CFLs
categorization areas (bins) for the colors of “white” LEDs used
for general lighting.
Even though solid state lighting is produced in very sophisticated processing facilities there are many variations between the
LEDs produced, even during the same run. Variations in forward
voltage occur throughout the production simply due to normal
statistical distributions inherent in all products. To provide repeatable and dependable systems, the LEDs must be electrically
sorted based on this forward voltage. A similar sorting is done to
accommodate variations in the color of the blue LED chips and
phosphor chemistry and density. This sorting results in the “bins”
in which all LEDs are offered.
The quality producer of LED systems will take all of these differences into account as the LEDs are matched for consistent color
and performance. While the current ANSI binning standards
allow variation of up to seven Macadam ellipses, most viewers
Figure 2.4: Packaged LED costs are projected to continue to decrease
rapidly. Source: Solid State Lighting Research and Development:
Manufacturing Roadmap, September 2009.
are bothered by variation of more than four. A system producer
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Some of these differences are subtle but extremely significant.
bodies. In contrast, LEDs are mounted on a flat surface and emit
Because LEDs are so much different than traditional incandes-
light from the top and sides in a hemispherical pattern. In many
cents or fluorescent bulbs, light fixtures can now be designed
applications, the LED’s inherent directional light pattern adds to
with a “clean sheet of paper” approach. This will provide a lot
its lighting efficiency.
more design freedom for new form factors and thinner designs
In addition to the primary optics that protects the LED chip in its
and should result in a considerable cost saving at the fixture
device-level package, secondary optics provide greater func-
level.
tionality at the system level. Without secondary optics, the LED’s
Lambertian and other light distributions (Figure 3.1) make them
The Heat is On
less useful for lighting applications. Secondary optics optimize
Increasingly higher output LEDs mean increasingly higher power
the distribution of the LED light for specific applications such
densities and tougher thermal challenges. In addition to de-
as down lighting, broadly disbursed or focused lighting. Some
creased life with increasing LED temperature, LED light output
system manufacturers offer easily interchanged optics to achieve
decreases, dominant and peak wavelengths increase and color
different distributions within the same package that allow the
temperature shifts. Addressing the system issues of thermal
user to adjust the system for the specific application.
R E L AT I V E I N T E N S I T Y %
where TE plans on making a significant difference by introducing innovative tools to aid in fixture design. Section 8 will delve
into more details regarding the thermal aspects of LEDs and SSL
systems.
3. Optics
Optics is the science of controlling and redistributing light. Tradi-
BATWING
RADIATION PATTERN (WITHOUT OPTICS)
100
60
20
-100
0
100
ANGULAR DISPLACEMENT (DEGREES)
R E L AT I V E I N T E N S I T Y %
challenges is of critical importance. This is specifically an area
LAMBERTIAN
RADIATION PATTERN (WITHOUT OPTICS)
100
60
20
-100
0
100
ANGULAR DISPLACEMENT (DEGREES)
tional light sources emit light in all directions. As a result, optical
systems for these sources are typically less efficient because
Figure 3.1: LEDs batwing (a) or Lambertian (b) distribution requires
secondary optics to provide the required light distribution. Source:
Lumileds presentation at the Institute for Energy Efficiency FastTracking Widespread Adoption of LED Lighting, Feb 2010.
some light bounces within the optics components or luminaires’
Figure 3.2 LED lamp products for different levels of power dissipation and lumen output require different optics
designs. Source: 2009, NEMA published Solid State Lighting—The Need for a New Generation of Sockets
and Interconnects.
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Challenges of Secondary Optics
supply and the driver converts this AC input into a controlled DC
current or voltage for most applications. Since the driver’s power
Secondary optics has a direct impact on several performance as-
requirements detract from the overall efficiency of the SSL
pects of the SSL product. Improperly designed secondary optics
system, very low power consumption drivers must be used for
can significantly reduce the light efficiency of the LED and lead
the most efficient lighting. (Note: luminous efficacy published by
to inferior performance. However, light efficiencies within the tar-
LED manufacturers typically refers only to the LED and does not
geted illumination area can exceed 90% or better with properly
include driver or optical losses.)
designed optics.
Figure 4.1 shows an example of the functions provided by a
There are several designs of corrective optics for LEDs. They
typical LED driver module. The capabilities include protection
range from reflectors to TIR (Total Internal Reflection) polymeric optics and to free-form polymeric optics. The selection of
the correct optic is based on efficiency, color shift, application
requirements and cost. Free-form optics for large array LEDs are
difficult to create. The size and volume of such an optic requires
a lot of material and a substantial time for it to set up in the
mold. Even though a free-form optic may give superior beam
control, cost, weight and stability, applications often require the
selection of an alternate optic. Reflectors show high efficiency in
conventional tests. However, because the light is often bounced
several times within the reflector, the edges of the beam may
Figure 4.1: The driver module provides several system-level functions.
lack definition and accuracy. The selection of optics must be
made by considering all of these factors.
features such as temperature protection, current detection and
In addition to the specific angle and lighting efficiency, other
power factor correction (PFC), as well as several system level
system design considerations for the secondary optics include,
functions. Input control/communications provides the ability
diffusers, lenses, prisms, multiple LEDs and the ability to ac-
to interface with AC line or 0-10VDC dimmers as well as facility
commodate unusual footprint LEDs as well as form factor. Since
management systems (FMS) and other emerging electronic con-
optics are the corrective lenses for LEDs, these different aspects
trols such as daylight harvesting, occupancy detection, ambient
all become an important part of the SSL design process for the
light sensing and more.
supplier and decision process for the fixture designer. Figure 3.2
LED driver module design must handle design challenges and
shows three different optics designs.
tradeoffs such as efficiency and life expectancy as part of its
performance criteria. All of these design aspects are handled
4.0 Driving LEDs
in a driver module assembly to avoid burdening lighting fixture
With semiconductor technology at its core, SSL transitions light-
companies with electronic circuit design and system concerns.
ing from an electrical to electronics-based industry. In contrast
While there are several off-the-shelf driver modules available
to fluorescent lighting with simple ballast control, solid-state
to address some of the design requirements, lighting fixture
lighting is a true power electronics system with extensive ca-
companies certainly need to be comfortable with and verify how
pabilities. As a result, lighting system manufacturers have an
well all of these concerns are addressed at the system level. This
additional electronics component to consider – the LED driver
includes matching the driver module with the interface require-
module. Replacing the basic electrical circuit for incandescent
ments of the LED module and the appropriate thermal response,
and fluorescent light sources in solid-state lighting fixtures in-
overvoltage, over temperature, overcurrent and surge protection.
volves a sophisticated electronic design.
The driver module has two additional criteria: it must be small
and easily integrate into SSL fixtures to simplify the entire light-
Since they are semiconductor devices, LEDs require additional
ing design process. As in most electronic power systems design,
circuitry to make them useful. The primary function of the driver
smaller form factors and higher power density are part of the
module is supplying a controlled power level over the operating
ongoing improvements. Projected and expected improvements
temperature range for the LED or LEDs in order to maintain a
are essential aspects of the extended capabilities that semicon-
consistent light output. Power for the driver comes from the AC
ductor technology provides to lighting.
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5. Solid State Lighting Controls
DALI (Digital Adressable Lighting Interface), other digital controls and pulse-width modulation (PWM) can also dim LEDs. For
In lighting, control ultimately results in some level of dimmabil-
solid state lighting, the right driver technology makes dimming
ity. There can be control at the local level, the light fixture itself,
easy. SSLs can provide a profiled dim to avoid lighting problems,
as well as at the building level. The control can be based on
especially in automated lighting situations. With LEDs, color
occupancy, existing light level, safety, comfort and many other
mixing can be performed for lighting that mimics the natural
factors. LEDs work extremely well with these types of controls
changes in coloration of sunlight during the day, providing en-
and enable improved functionality well beyond improved energy
hanced productivity and health benefits.
efficiency. Building controls at the light level including Facil-
FMS provide computer-based automated technologies to moni-
ity Management Systems and an increasing number of wireless
tor and control the operation of a building’s lighting, heating
control options are among the control techniques being applied
ventilating and air conditioning, safety and security systems.
to solid state lighting.
Lighting obviously has a critical role in occupancy as well as the
In fact, controllability is one of the attributes of solid state light-
safety and security aspects. Certain drivers can interoperate with
ing that distinguishes it from all other light sources. LEDs are
existing facility management systems.
instantaneously and broadly controllable.
For increased lighting efficiency, sensing techniques are used.
Incandescent light dimmers can produce audible hum. Fluores-
These include daylight sensing to reduce or turn off unnecessary
cent and discharge lights are difficult to control. As a result dim-
lighting in bright sunlit environments and occupant detection
ming systems are complex, very expensive and have a limited
that turns off lighting when no motion is detected in the room or
dimming range. In addition, color consistency (shifting to blue)
automatically turns on the lighting if motion is detected. In some
within the dimming range is poor. The ability to easily dim SSLs
cases, the sunlight entering a room can even power the ambient
provides advantages to Smart Grid and Facility Management
light sensing technologies that monitor the indoor light level.
Systems (FMS) and an enabling technology for several unique
Other advanced sensing methods such as near-field or local oc-
lighting situations. For example, human eyesight, especially in
cupancy sensing can detect an individual in a smaller area such
the elderly, become less efficient and requires higher levels of
as a single cubicle and control only the lighting for that specific
light. Also, many situations, such as presentations in a work
area. Light sensing and control is becoming increasing sophisti-
environment benefit from reduced lighting levels in certain areas.
cated to provide optimized, energy-efficient lighting.
User-controlled solid state lighting can allow lower levels of
light for user comfort as well as energy savings. Color tempera-
Digital Control Aspects
ture control, i.e., the dynamic adjustment of the hue of the light
source, is a unique aspect of some advanced solid state lighting
For solid state lighting to replace incandescent and fluorescent
systems.
lighting in networks, SSL products must be compatible with all
existing and emerging network controls. Fortunately, SSL lends
Traditional lighting control has been restricted to dimming using
itself ideally to these communication techniques and, in fact may
AC line dimming (TRIACs) and other techniques to reduce the
be used to establish a new wireless communication technique
current to the bulb. For retrofit applications, SSLs need to be
similar to infrared (IR) technology commonly used for remote
controlled by TRIACs as well. Specially designed LED drivers
controls. Table 5.1 shows a summary of the controls that impact
enable LED control from TRIACs. Besides reducing power con-
today’s solid state lighting systems. SSL technology works ex-
sumption, dimming of LEDs can extend the lifetime. In addition
tremely well with advanced sensing control and the various com-
to TRIACs, control technologies such as 0-10V analog,
Control Standard
munication systems.
Function
Control Standard
Function
TRIAC
dimming
Ethernet
networking
0-10V
dimming
BACnet
networking
FMS
dimming/switching
Modbus
networking
Demand
dimming/switching
PLC
networking with existing wiring
Daylight sensing
dimming/switching
LonWorks
networking with existing wiring/wireless
Occupancy sensing
dimming/switching
ZigBee
wireless networking
DALI
lighting-specific network
Z-Wave
wireless networking
DMX
lighting-specific network
X10
wireless networking
Enocean
wireless networking
6LoWPAN
wireless networking
Table 5.1 SSL lighting controls address a variety of functions and network communications techniques.
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Advanced lighting systems are part of the digital age. Unlike
in a consumer electronics product compared to an industrial
their 20th Century predecessors, today’s lighting systems can be
product or a personal computer. The wiring and connectors
networked together. Digital electronics such as microcontrollers,
have a significant impact on the cost, manufacturability, opera-
the brains inside any digital product including computers, cell
tion and overall reliability of the system. Early versions of solid
phones and automotive controls, provide the intelligence. As
state lighting use solder connections but they cause several
part of a network, today’s lighting systems communicate with
problems including limiting the flexibility of the design for future
standard digital communication languages that can include
upgradability. Interconnects have system design implications and
DALI, DMX512 and others.
complexity well beyond the traditional lamp holder and lighting
socket.
DALI is a protocol defined in IEC 62386 for lighting control systems. It allows the mix and match of components from different
Unlike traditional lighting systems that are basically non polar-
suppliers. DMX 512 was initially developed as a standard means
ized AC electrical products, a solid state luminaire is a highly
for controlling light dimmers in stage lighting. Today, it handles
electronic product. Some of the common problems of electronic
digital data transmission between controllers and lighting equip-
systems that system-level connectors can avoid are the mis-
ment and accessories.
connection of components as well as grounding, electrostatic
discharge (ESD) and polarity issues. For example, a first-make
Unlike the lighting-specific protocols, Ethernet is a communica-
last-break for the ground connection is necessary to achieve a
tion network commonly used in factory automation and comput-
continuous path for static discharge to protect static sensitive
er applications, standardized as IEEE 802.3. However, it is also
semiconductor junctions. A properly designed interconnect sys-
used to control lighting. Communication with building lighting is
tem can avoid ESD problems and bring together all the protec-
an integral part of several industry network control systems such
tion aspects of the system as well.
as BACnet, ASHRAE’s data communication protocol for building
Even though several subassemblies need to be interconnected
automation and control networks.
in an SSL fixture, solid state lighting does not have standards
Increasingly, communications with external systems are per-
for wiring or connectors. However, in 2009, NEMA published
formed using wireless techniques including control standard
Solid State Lighting—The Need for a New Generation of Sockets
ZigBee, Z-Wave, X10, Enocean and more. Besides wireless
and Interconnects. One of the more complex systems that uses
techniques, power-line communication (PLC) uses the existing
numerous connectors and sizes of wire, the computer, demon-
wiring to transmit data. PLC is also being applied to lighting. For
strates an excellent example of the benefits of standardization.
example, Echelon’s LonWorks protocol is used for power line
A standardized approach to connectors and wiring not only pro-
network control.
vides a cost-effective solution, it can prevent assembly problems
As smart grid and smart metering systems are implemented for
of inadequately mated connectors, and readily identify/avoid
more effective control of the power generation, distribution and
mistakes through color coding and keyed design features. (See
use of electricity, the ability to communicate through a variety of
Figure 6.1). With a system level approach to SSL interconnects,
networks with the lighting system will be critical. This communi-
more than two wires are required, since more than power must
cation will allow the control of lighting and other loads to reduce
be connected throughout the fixture.
electricity consumption and cost, especially as utility rates vary
based on peak load demands. SSL has the ability to respond
to demand emergencies with energy reductions of 15 to 20%
without perception by lighting system users.Properly designed
SSL technology can readily accommodate both the control in
digital networks as well as modern sensing techniques for improved lighting efficiency. In fact, SSL designed with a systems
approach can provide a finer granularity of control for building
lighting designers.
6. Interconnects in the SSL System
For the most part, the interconnects (cables and connectors)
have been a critical but unaddressed challenge for solid state
Figure 6.1: Connector designs for SSL must address inadequately mated
connectors with a snap design or detent latch and have keyed design
features.
lighting systems. As system designers have found in electronic
systems of all types, the wiring and connections are quite unique
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7. SSL Protection
As noted in Solid State Lighting—The Need for a New Generation of Sockets and Interconnects, new generation interconnects
Fault protection is a requirement for successful implementa-
must provide:
tion and problem avoidance for any electronic circuitry and
– Improved efficacy over traditional bases
solid state lighting is no exception. As noted previously, since an
– Replacement capability
SSL fixture is an electronic and not an electrical assembly, the
– Upgrade path in performance
protection requirements are much more sophisticated. The SSL
– Optimized performance
orbit first described in Section 1 of this paper, identified the need
for this protection.
– New lighting options
Typically, an LED driver module includes some level of protective
– Prevent substitution of low efficacy lamp sources
circuitry to handle common faults that can occur in electronic
– Communications and network potential for integrated
energy systems
systems such as short circuits, overvoltage, reverse polarity in
DC circuits and overtemperature. (Note: Common LEDs are a po-
Reducing cost is a major challenge for solid state lighting in all
larity-sensitive device that requires a DC and not an AC voltage
areas. The connectors can do their part by avoiding costly as-
source. However, even AC LEDs require much greater protection
sembly procedures that require special tooling and stripping and
than ordinary electrical devices.)
cutting assembly techniques. Insulation displacement connec-
In addition to standard electronic circuit protection, an SSL can
tors (IDC) are a proven technique for quality low-cost reliable
be exposed to extreme surge conditions including lightning.
connections in many applications.
Any power-line coupled transients can reduce LED lifetimes,
The new ENERGY STAR standards differentiate between fixtures
and, in the worst case, result in immediate failure. As a result, a
where the source and the systems are the separable or integral.
variety of overvoltage-protection devices, such as MOVs (metal-
There are different levels of performance associated with each.
oxide varistors), ESD surge-protection devices, resettable PPTC
Integral designs cannot be upgraded or replaced. As a result,
(polymeric-positive-temperature-coefficient) circuit-protection
integral designs have to perform 20 to 30% better than other
devices like TE’s PolySwitch device and integrated overcurrent/
systems. Avoiding solder interfaces in the connectors is one
overvoltage devices, such as PolyZen devices are frequently
means of achieving interchangeability, increased reliability and
incorporated into the circuit design.
future upgradeability.
Adequate thermal protection for temperature-sensitive LEDs
Moreover, reliable connections are essential to assure that the in-
requires localized temperature measurements to provide a suf-
terconnect system is as robust as the solid state lighting sources.
ficiently quick response to limit excessive temperature and shut
A properly made interconnect system allows the LED light
down if necessary to avoid stressing LEDs or contributing to
module (LLM) to be easily installed, exchanged, upgraded and
early-life failure. In systems with several LED sub-assemblies,
replaced if necessary. It can be dependably installed by typi-
each LED sub assembly must be accounted for as a single point
cal assemblers with a minimum of training. A properly designed
of potential failure if its localized temperature exceeds the maxi-
interconnect system can last through more than one LED life
mum safe operating level. As a result, temperature detection at a
cycle securing the investment of the buyer. It maintains a quality
centralized location is insufficient to protect an overheating LED
connection through thermal changes and power cycles that can
module. An alternate temperature sensing approach is required.
be expected during the life of a lighting fixture.
Section 8 will delve deeper into the temperature issues associated with solid state lighting.
SSL connectors add a design problem that is common in portable consumer electronic products – the connectors must be
8. Temperature - The Ultimate SSL
Challenge
small and unobtrusive. However, the connectors and wiring are in
close proximity to heat-generating LEDs so their operating temperature environment more closely resembles industrial applica-
As pointed out in several of the previous sections, excessive
tions. Interconnects must solve the mechanical, electrical, ther-
temperature is detrimental to the performance, lifetime and
mal and optics issues that arise in an SSL system. Consequently,
reliability of LEDs. It also affects nearby circuitry and connectors.
interconnects certainly represent an opportunity for improving
To keep LED temperatures within safe operating limits, large
solid state lighting and if properly designed can result in:
heat sinks are often required to remove the heat generated.
–Rapid growth and adoption of SSL
Advanced SSL lighting designs incorporate a comprehensive
–Modular approach economics
thermal management system to provide monitoring, detection
–Rapid fixture and luminaire innovation
and protection for the light source. The critical LED temperature
–Innovative product platform designs
is called the junction temperature and it is deep within the
package — far from the surface of the chip. Since this is not eas-
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ily measured, a package (or case) temperature is normally read
and the actual junction temperature is calculated. The maximum
junction temperature, for some LEDs, can be up to 150°C and
the normal operating case temperature is between -40 to 135°C
( Source: Philips Lumileds). Each LED manufacturer determines
the maximum junction temperature for their LEDs with the value
growing on newly introduced devices.
Figure 8.1 shows that with the proper design considerations,
LEDs can last well over 50,000 hours. The projected lifetimes are
based on B50, L70 data. This means that 50% of the products
will have at least 70% of the lumen output for the projected
number of operating hours. At 350 mA, at least 70% of initial lumens are expected for 60,000 hours if the junction temperature
is maintained at about 160°C or lower. With a higher operating
Figure 8.2 The relative light output decreases with increasing thermal
pad (case) temperature. Data is from Philips Lumileds Luxeon Rebel ES
DS61. Source: Philips Lumileds.
current of 700 mA, the temperature would have to be reduced
to about 140°C. Note: As LED efficacy increases in the future,
thermal requirements will diminish for equivalent lumen output.
In Recommendations for Solid State Lighting Sub-Assembly
Interfaces for Luminaires, the NEMA authors provide detailed
recommendations for temperature test points for LEDs. Figure
8.3 shows the acceptable location for temperature sensors in
multiple LED design. With properly located temperature sensors,
the temperature must be measured, monitored and controlled by
additional circuitry. The added circuitry increases the complexity
of the SSL design but it also adds to the performance, reliability
and lifetime of the luminaire. With the importance of temperature to the overall system design and complexity of making accurate temperature measurements, specially-designed test tools
that accurately record temperatures can simplify the task of
verifying that the temperature design has been done correctly.
While thermal management is essential for the electronics portion of SSLs, thermal design is one of the key factors that im-
Figure 8.1 Increasing current requires lower junction temperatures to
achieve extended operating life. Source: LED Device Lifetime.
pacts fixture aesthetics. The challenge for luminaire designers is
making a piece of aluminum aesthetically pleasing. In combination, the thermal management and a slick heat sink provide the
In addition to reducing the operating life, increasing temperature
performance and long term reliability that make SSLs the ideal
reduces the performance of LEDs. Figure 8.2 shows the reduc-
technology for energy-efficient lighting.
tion of relative luminous flux (light output) with increasing temperature. At a case temperature of 130°C, the output is reduced
about 80% or more depending on the color temperature rating.
Increased temperature causes other performance changes
including increases in dominant and peak wavelengths and color
temperature shifts.
Temperature Measurements/Thermal
Management
In LED Luminaire Reliability, the authors point out that LED luminaire life is not identical to estimated LED life. As a result, they
stress the need to understand how temperature was measured
and how it relates to the expected life of the system. Centrally
Figure 8.3 For multiple LED assemblies, multiple test points provide
a more thorough means of verifying proper system operating
temperatures. Image source: TE Connectivity’s thermal evaluation tool.
located temperatures are not sufficient to monitor, detect and
protect multiple LED designs.
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9. Lighting Fixtures / Luminaires
organization for standardization, has previously established
lighting requirements for luminaires. Other regulatory and stan-
Historically, lighting fixture design has essentially involved
dards organizations that impact solid state lighting include:
mechanical and industrial design expertise. To create a success-
•American National Standards Institute (ANSI) / National
Electrical Manufacturers Association (NEMA) efforts include
industry norms, guidelines and standards for SSL products.
ful light fixture, the lighting designer had to consider color, light
output, controls, aesthetics (including the environment) and
manufacturability aspects. In contrast, solid state light fixtures
•Illuminating Engineering Society of North (IESNA) is
the recognized North American technical authority on
illumination and currently publishes LM-79 and LM-80 SSL
standards. IESNA is developing a specification (EN 21) for
long term reliability of fixtures.
require the addition of electronics technology. However, this is
just the beginning of the totally different design approach that is
required for successful SSL products.
In addition to the electronics, the LED, driver module and control, all of the issues discussed in earlier sections, the thermal
•IESNA has partnered with American Society of Heating,
Refrigerating and Air-Conditioning Engineers (ASHRAE)
to develop efficient lighting for buildings. ASHRAE has a
lighting subcommittee that generates standards.
aspects including heatsinks, interconnects, optics and protection need be addressed in the design. The complexity of these
various areas and broad range of expertise required to address
each of them has been a barrier to entry, especially for smaller to
•International Commission on Illumination (CIE) has several
standards for lighting performance including SSL.
medium-sized lighting fixture suppliers.
•Federal Communications Commission (FCC) is involved with
radio frequency aspects of SSL.
Simplifying the design process for light fixture/luminaire manufacturers requires an integrated approach for solid state lighting systems. The ideal systems design approach should provide
•Federal Trade Commission (FTC) is pursuing more accurate
labeling for light bulbs.
manufacturers of lighting fixtures with a plug-and-play solution
including all the components required to convert from incandes-
•Department of Energy (DOE) Commercially Available LED
Product Evaluation and Reporting (CALiPER) program tests
and reports on available SSL products.
cent or fluorescent lighting to solid state lighting design. A systems design solution enhances the lighting designer’s capability
with a flexible light output and color and the ability to focus and
•Environmental Protection Agency (EPA) has the ENERGY
STAR qualified LED lighting.
distribute light in different places. In addition to the components
and design methodology, a complete systems approach should
This is actually a rather short (and by no means complete)
include a toolbox to allow lighting fixture suppliers of any size
summary of what is occurring today in the area of SSL regula-
to easily design the latest, high-efficiency solid state lighting
tions and standards. In a few years, the list will be completely
fixtures with confidence and bridge the technology gap.
different. While light fixture suppliers may be well aware of and
With the appropriate overall systems design methodology,
readily capable of dealing with traditional and even fluorescent
luminaire manufacturers can avoid the extensive engineering
lighting regulations, meeting any one of these and other orga-
and qualification involved to embrace this new technology. This
nizations’ new requirements for solid state lighting can prove
includes addressing the global differences in light fixtures and
to be a challenge. Complying with all of them, especially in a
requirements. Instead, manufacturers can focus on the esthetics
coordinated, harmonized manner could be a daunting task and
and performance of the lighting fixture with the confidence that
provide a considerable delay to market entry. For example, the
the technology inside their fixtures works and meets industry
ENERGY STAR Solid State Lighting (SSL) Luminaire program
regulations.
went into effect on September 30, 2008. Warranty is one of the
requirements for ENERGY STAR conformance. Unlike conven-
10. Regulatory Issues
tional lighting that has a typical 90-day warranty, ENERGY STAR
requires a three year warranty that is expected to increase to
In addition to existing lighting standards and regulatory issues,
five years in the near future. An enhanced and expanded version
solid state lighting represents a dynamic area where standards
is in the final comment phase before its publication.
are changing and new standards are being issued on a continuous basis. Several regulatory agencies have already modified or
In addition to lighting-specific changes, the difference in lighting
established requirements for solid state lighting.
design requirements for SSLs (DC instead of AC) may eventu-
These standards address performance, radio frequency emis-
ally change the way that buildings are wired. For example, 24
sion/interference, testing, safety and other issues. For example,
VDC could become a standard for distributed lighting within
Underwriters Laboratories Inc. (UL) Class 2 Power Units (UL
buildings. For this to happen, significant changes and modifica-
1310) and Light-Emitting Diode (LED) Light Sources for Use in
tions to building codes will have to occur. Leading LED and SSL
Lighting Products (UL 8750) have recently been issued. The
suppliers will be intimately involved in and well aware of the
International Electrotechnical Commission (IEC), a worldwide
changes that could occur long before they are implemented.
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11. The NEVALO SSL System
System Applications
The NEVALO SSL system from TE addresses the challenges fac-
The NEVALO SSL system allows flexibility of system design and
ing SSL manufacturers with a new, holistic and simple approach
optimization by application. A few examples of the NEVALO
that delivers application flexibility, speed (time to market), and
system in some common applications are shown in Figure 11.2,
confidence to SSL design (Figure 12.1). The NEVALO SSL sys-
11.3 and 11.4.
tem is the product of TE’s extensive experience in electronics,
electro-mechanical design and manufacturing. With the NEVALO
SSL system, manufacturers have the tools and components
needed to respond quickly and competitively to market demand
for innovative lighting solutions.
Figure 11.2 Down light and typical NEVALO CN88 socket shown.
Application Flexibility
•Simplify SSL system integration with a menu of state-of-theart plug & play components
– System configurations are optimized by application
• down lights
• wall mounted fixtures (sconces)
• track lights
• others to follow
Figure 11.3 Wall Sconce and typical
NEVALO LN24x100 system shown.
– Configurations are almost limitless
Speed
•Define a complete system in minutes with the web-based
NEVALO system configurator
•Configure a system in a matter of hours with off-the-shelf components
Figure 11.4 Track Light and NEVALO CN58 socket shown.
•Eliminate painstaking thermal testing and validation with the
NEVALO thermal test system product
NEVALO System Components
•Facilitate luminaire safety agency approval with agencyapproved NEVALO product components
A solid state lighting fixture can be designed and built with the
NEVALO SSL system product set as shown in Figure 11.5 starting
•Speed production with NEVALO product components that
with:
are designed to eliminate improper assembly
(1) LED Light Boards (LLBs) which are printed circuit subas-
Confidence
semblies that combine LEDs and thermal monitoring.
•Back your product designs with warranted TE’s NEVALO
SSL System components
(2) Sockets for circular assemblies
(3) Optics that can be selected specifically for the application
•Expect long life with NEVALO system components designed
for 50,000+ hours of operation
(4) Drivers that power one or more LLM(s) and provide interface to control electronics
(5) An intuitive wiring system ties it all together, and finally
(6) Heat sinks matched to the LLM(s) designed to provide appropriate thermal performance.
The NEVALO SSL system toolbox includes thermal evaluation
tools and an SSL system budget calculation that makes designing easy.
LED Light Module
TE defines the LLM in the NEVALO System as a subassembly
Figure 11.1 The NEVALO System simplifies and speeds the design and
production of SSL fixtures.
that includes the LED Light Board (PCB with LEDs mounted),
thermal interface material, a socket (for circular
NEVALO product) and matching optics as depicted in Figure 11.6.
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Optic
LLM
LED Board
Socket
Wiring
Thermal
Driver
Control
Figure 11.5 The key elements of solid-state lighting come together as a
system in the NEVALO SSL system approach.
TE has designed several standard form factors of LLM which are
Figure 11.7 NEVALO CN58 socket (L) Finished assembly and (R) the
components of the assembly (Base, LLM, Thermal Gap Pad, Attachment
Screws, Optic, Outer Ring, Thermal Protective Device and Polarity
Protection Device.
each optimized for certain applications, such as down lights, wall
sconces, and track lights. TE has selected LEDs for each light
module that reflect the latest in commercially available LEDs.
Recognizing the rapid advances in LED technology, future proofing of NEVALO LLMs will assure the ability to incorporate next
generation LEDs into the LLMs as they become available, thus
providing state of the art lumen output, color and CRI, efficiency
(L/W) and cost. It is our objective to always maintain leadership
in performance, efficiency and cost.
Figure 11.8 NEVALO CN88 socket (L) Finished assembly and (R) the
components of the assembly (Base, LLM, Thermal Gap Pad, Attachment
Screws, Optic, Outer Ring, Thermal Protective Device and Polarity
Protection Device.
Figure 11.6 A typical NEVALO circular LED light board contains LEDs,
thermal monitoring, protection circuitry and special connectors.
Optics
Sockets
The NEVALO circular modules are sold with optics included.
Sockets have been designed for use with the NEVALO LLMs.
There are several optics available for each LLM style. Optional
Sockets provide a mechanical holder for the LLM or LED, inter-
optics can be purchased to swap out in the modules. They are
changeable optics and attachment to a heat sink. There are two
available in a variety of beam angles to best suit the application.
types of sockets:
TE conforms to de facto beam angle designations for its optics
(1) For use with TE LLMs
families, as depicted in Figure 11.9.
(2) Designed for use with Off the Shelf LED packages
The socket provides optic alignment and mechanical attachment
to the LLM/LED to confirm optimal optics performance. De-
The first type, as typified by the NEVALO CN58 socket, works
pending on the application, TE provides Total Internal Reflective
with the TE LLM and comes in three easily assembled pieces
(TIR) or Reflector based optics. A variety of standard optics
as shown in Figure11.7. The base assembly is preassembled and
styles and patterns are available for each LLM/LED.
includes the base, the LLM, thermal pad and attachment screws.
Optics are simply added and the outer ring brings the assembly
Beam Angle
(FWHM)
Degrees
together.
The second type, as typified by the NEVALO CN88 socket
<10
10 - 20
20 - 30
30 - 40
40+
design, brings the system value of the NEVALO product to a
standard LED package-in this case, the Bridgelux RS. The NEVALO CN88 socket brings interconnectivity to the LED, as well
as thermal monitoring, interchangeable optics, thermal interface material, making the LED an integral part of the system.
Category
Narrow Spot
Spot
Narrow Flood
Flood
Wide Flood
Abbreviation
NS
SP
NF
FL
WF
Figure 11.9 Optics with popular full width at half-maximum (FWHM)
beam angles are offered with NEVALO circular modules.
Additional form factors will soon be available to address other
industry leading LED packages.
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phase dimming). Future drivers will accommodate 0-10V dimming, fixed systems (on/off only) and digital technologies.
TE has incorporated circuitry to address issues related to AC
line dimming, such as low power flicker, low power drop out, and
low power system turn on. The NEVALO system has been tested
against all industry standard AC dimmers. Performance specs
are included in the datasheet.
Figure 11.10 Optics available for NEVALO circular LLMs include TIR and
reflector based optics.
With these three control interfaces, the NEVALO system can
interface with industry control systems such as FMS, Demand,
Driver Modules
Daylight Sensing, Occupancy Sensing and more.
The driver modules in the NEVALO system have a compact,
Wiring System
thin form factor for easy mounting and they contain several
important features. The main purpose of the driver module is to
As in any electronic system, the interconnections and wiring pro-
convert the AC power from the utility company to the DC power
vide the critical connectivity. In the NEVALO SSL System, these
required by the LEDs and the electronic circuitry. The driver’s
components have additional system functionality. Not only does
features include a design life matched to the LEDs for optimum
the wiring provide power to the LLMs, the system has a thermal
luminaire design life, the ability to achieve flickerless and quiet
monitoring circuit, as shown in Figure 11.12.
operation and a smart/resettable thermal management scheme.
The SSL System Budget is clearly identified on the driver.
In the NEVALO wiring system, a low-profile, four–wire, 24 AWG
(2.5mm centerline) stranded ribbon cable simplifies the connectivity of LLMs to each other and the driver module. All interconnects employ Insulation Displacement Crimp (IDC) technology
and are connected with simple tooling.
Driver
Figure 11.11 The NEVALO driver,
with system budget identification.
The initial NEVALO system offering (see Table 11.1) includes six
LED
LED
TEMP
TEMP
drivers, but more are planned to address international voltages
and additional control schemes.
Figure 11.12 The NEVALO system bus structure structure has an integrated thermal monitoring circuit connected by orange and green wires.
The heart of the wiring system is keying. The system is keyed
physically and also visually (color coded). Physical keying enables the plug and play aspects of the NEVALO system. The connectors are keyed to specific current ratings. For example, if a
350mA keying option is selected, it will only mate with a 350mA
driver and a 350mA LLM. Systems are designed to operate at
specific currents…any mismatching of driver and LLMs could
shorten the system life, or create an energy inefficient system.
Table 11.1 Six driver modules have been defined for NEVALO systems to
satisfy a range of luminaire requirements.
The NEVALO system’s physical keying prevents this.
The NEVALO system’s color coding is tied to the physical key,
Control
but has several other advantages (refer to Figure 11.13 and 11.14).
•System design/SSL budget
The NEVALO drivers are configured to address most of the common control schemes. The initial driver offering is designed for
•System manufacturing
AC line dimming (most often referred to as TRIAC dimming or
•Inspection on the cable assembly
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The NEVALO system has four keying options (Figure 11.13) with
one example shown in Figure 11.14. Keys are selected to match
the ideal driver to the ideal LLM for the application.
System Key to Drive Current (mA)
350
700
1000
2100
orange
red
green
blue
Figure 11.13 NEVALO keying options
Figure 11.16. For build-it-yourself
assemblies a simple “flat rock” tool is used
to attach NEVALO connectors to the cable.
hole. Appendix A has more information on the interconnect
design.
All of the NEVALO connector design attributes meet NEMA’s
requirements in the recently proposed Solid State Lighting—The
Need for a New Generation of Sockets and Interconnects. In fact,
Figure 11.14 A drive current key prevents connecting a LLM board to
an inappropriately rated driver module. The detent confirms that the
connection is made properly during the assembly.
NEVALO connectors go well beyond the proposal to set the
stage for a new standard for SSL connectivity.
Thermal Management
In addition to the thermal monitoring built into the NEVALO
system, TE offers heat sinks matched to the various offered LLM
form factors as shown in Figure 11.17. The TE heat sinks have
been designed to provide heat sinking for worst case conditions.
All components are tested and rated to 50,000 hours of operating life with mean time between failure (MTBF) curves included
in the product specifications. To complete the thermal design
Figure 11.15 Color coding facilitates manufacturing by identifying
compatible elements.
process, a test & validation tool confirms operation within design
limits based on temperature measurements in a variety of operating modes.
The NEVALO system allows you to pick a standard cable assembly for your application. If your system design requires a new
Thermal Monitoring
cable configuration, it is simple to design and build. TE offers
an expert system tool for rapidly designing a custom cable as-
The NEVALO system is designed with a thermal monitoring
sembly, called the NEVALO cable configurator. TE can build that
circuit. As shown in Figure 11.18, the circuit accommodates up
assembly for you, or you may build it yourself from the discrete
to seven LLMs and the thermal device on the LLM determines
components. Numerous connectors are available to allow the
the shutoff temperature of the system. TE has engineered the
creation of many different wiring harnesses.
system to shut off before any LLM exceeds the LEDs maximum
junction temperature.
Additional design goals of the NEVALO SSL system interconnects include:
Thermal Evaluation Tool
• A 3-mm maximum height above the pc board for compact
design
The NEVALO system’s thermal evaluation tool is a microprocessor-based system that includes three components:
• First-Make/Last-Break of the LED ground for safety
1) Thermal test LLM,
• Metal-clad pc-board capable attachment for flexibility
2) Thermal test instrument and cabling, and
One very unique interconnect allows the NEVALO product wiring
3) Test software with Graphical User Interface (GUI) that is run
to be invisible to the LLM. The connector is designed to accom-
on a PC.
modate 0.4 to 0.8-mm thick sheet metal and fit into a round
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Figure 11.17 Heat sinks are designed to match the footprint and heat dissipating requirements of different
light engines in the linear NEVALO family of products. The heat sink design for circular products
accommodates cable routing.
With this tool, users confirm the thermal performance of each
LLM in the lighting fixture. The tool allows the user to monitor
the junction temperature of the LEDs under different operating
and environmental conditions. In addition, the tool assists in:
•Analyzing LLM design and correlating the design to the LED
junction temperature;
•Optimizing LLM reliability testing; and
(a)
(b)
Figure 11.19 A seven-LED board (a) and its thermal test board (b)
counterpart. The special connector on the right-hand side of the test
board provides connectivity to a PC through the USB port.
•Optimizing the size of the heat sink required for keeping the
LED in safe operating temperature.
The thermal test LLM (Figure 11.19) is identical to the production
LLM but includes a thermal test circuit (thermistors) and an interconnect for attachment to the thermal test instrument shown
in Figure 11.20.
As shown in Figure 11.21, the GUI allows the tool to display,
record and log the LLM temperature on a PC screen similar to
chart recorders. Temperature readings are made either in °C or
°F with the accuracy of ±0.1°C. In addition to a programmable
temperature range, there are multiple temperature reading devices for better accuracy. While the tool provides rather detailed
information, it also has a simple Go/No Go indication of an
Figure 11.20 The NEVALO thermal test instrument operates to the
thermal test LLM and provides interface to the PC .
aceptable thermal design.
Driver
LED
LED
LED
LED
TEMP
TEMP
TEMP
TEMP
Figure 11.18 The NEVALO SSL’s thermal management system can detect
a problem based on an excessive temperature at one of the LLMs and
responds with power shutdown.
With the data obtained from the thermal evaluation tool, a
complete SSL system can be tested and results documented
that the system performs well enough to meet TE’s warranty
Figure 11.21 The PC GUI display of Thermal Test Tool data provides a
record and log of the LLM temperature.
requirements. The data not only validates the warranty but also
determines the safety factor in the fixture’s design.
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Industry Standards, Regulations & Compliance
With all of the components colored orange in this design, the
final system budget check is a total of the orange values on the
When the SSL assembly meets the NEVALO system standard,
LLMs to confirm they are at or below the maximum value of the
the process of obtaining safety agency certification for the light-
driver. Now look at a real example:
ing fixture is greatly simplified :
•Underwriters Laboratories
UL1977, UL8750 (for use in UL1598 devices)
•Electrical Appliance and Material Safety Law of Japan
J60838-2-1, J60998-1, J60998-2-2
•International Electrotechnical Commission
IEC 61984, 60838-1 &-2, 60838-2-2, 60998-1, 61995-1,
60352, 61347-2-13, 61347-1
In addition, the NEVALO system facilitates U.S. Environmental
Protection Agency (EPA) ENERGY STAR compliance.
With all of these certifications, NEVALO system customers
have avoided the time-consuming certification processes of all
Figure 11.23 Example of NEVALO SSL system budget demonstrates the
ease in verifying an acceptable design.
of these agencies, reducing the time-to-market for the newest
energy-saving lighting fixtures. This is just one more vital piece
of the NEVALO systems approach to solid-state lighting. The
Summary
combined package simplifies the path from today’s to tomor-
The rapid growth of SSL offers exciting opportunities for lighting
row’s lighting technology.
fixture manufacturers. But with these opportunities come the
realities of the complex nature of solid state electronics design.
SSL System Budget
Competent SSL design has many considerations, as depicted in
The SSL system budget is yet another aspect of the NEVALO
the TE Orbit in Figure 11.24. SSL applications demand that each
system that simplifies fixture design and decreases the opportu-
of the planets of the orbit be optimized. The NEVALO System
nities for errors. As shown in Figure 11.22, color coding indicates
provides application flexibility, fast time-to-market implementa-
that the right subassemblies have been selected. Since the drive
tion and the confidence backed by TE Connectivity.
module can handle 33 to 59 (Volts), as long as the total of the
LLMs color-coded values do not exceed 59, the system is within
safe operating limits to Underwriters Laboratories (UL) Class II
lighting.
Figure 11.24 The NEVALO
system brings the critical
pieces together at the
systems level for a successful
SSL solution.
Figure 11.22 Color coding simplifies the NEVALO SSL system budget
tool.
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12. The Future of SSL: Futureproofing
with conventional sources that were hard to start and maintain
in cold temperatures. They often found it best just to leave them
It is clear that the demise of incandescent bulbs and the continu-
on which had the side effect of wasted power and additional
ing environmental and operational concerns surrounding CCFLs
heat to remove from the coolers. LEDs function well in such an
are driving the adoption of SSL solutions. On the basis of simple
environment and can turn on instantly as they are needed for
replacement, the advances in solid-state lighting technology in
workers and equipment.
performance and energy efficiency are compelling. Solid-state
lighting offers dramatic improvements in energy efficiency, in
Task lighting
lighting comfort and in utility. Yet, it is just the beginning. With
Conventional lighting design attempts to provide even illumina-
solid-state lighting, several changes will occur in how lighting is
tion across the lit space. When activity is carried out in only a
specified for new construction and for renovation projects. Users
small part of that space, the remaining lighting becomes waste-
will become increasingly aware of the power of SSL technology
ful. Lighting professionals are moving to a task/ambient lighting
and will increasingly demand new capabilities. Manufacturers
model. Low levels of light are provided in the walkway areas and
will need to adapt their designs to quickly respond to consumer
high levels of light are provided directly on the tasks in the work
demand for new features and advanced functions.
space. Because LEDs are small sources, their light can be better
Future-proofing will require lighting manufacturers to be part
controlled and targeted by secondary optics. Because LEDs are
of the digital revolution and embrace lighting’s exciting solid-
so controllable, the various fixtures can be coupled to occupan-
state future. In this section, several examples of the promising
cy detectors, daylight harvesting sensors and facility manage-
new features possible with SSL technology are described. This is
ment systems further minimizing their energy use.
hardly a comprehensive review. Rather, it is offered as anecdotal
Proximity
evidence of the exciting future SSL offers to the lighting industry.
Coordination with sensors allows solid-state lighting to function
Public Safety
well outdoors in the area lighting and security sectors. Proximity
For increased public safety, demonstration projects are under-
detection devices make it possible to operate at a minimal level
way to connect streetlights to the 911 emergency telephone
until someone enters the space. At that point, light levels can
network. In these tests, the light over the house making the
be increased both providing visibility for the user, if authorized,
emergency call flashes to help guide emergency responders. Si-
and a clear indication that someone is in the area if he is not
multaneously, streetlights in the immediate area increase to 150%
authorized.
of normal illumination to help officials locate fleeing criminals.
Dimming
Adapting to Natural Conditions
LEDs maintain color as they are dimmed. This makes them most
Many studies indicate that lighting systems which mimic the
appropriate for use in buildings where free light from outside is
natural changes in coloration of sunlight during the day provide
used to reduce light generated by the interior light fixtures. Day-
enhanced productivity and health benefits. Solid-state lighting
light Harvesting can save energy while at the same time main-
can provide this adaptability using existing technologies. No
taining consistent light levels for building occupants.
ordinary lighting systems can perform as well.
Light Trespass
Refrigerated Grocery Display Case
The great opportunities for precision beam control in solid-state
Lighting used in retail refrigerated displays consumes energy
lighting provide fixture manufacturers an excellent way to com-
in two ways. Energy is used both to light the fixtures and to
ply with ever-tightening standards for light trespass/intrusion.
remove the heat generated from them as they create light. Tra-
Efficiently targeting the beams of the exterior fixtures keeps the
ditional fluorescent lighting used in these systems requires even
light within the confines of the property owner’s premises.
greater power as the lamps become increasingly less efficient at
Building Construction
the low temperatures in refrigeration and freezer cases and ad-
Since LEDs have a smaller source length than CFLs or incandes-
ditional drive is required to maintain the arc stream. LEDs, on the
cent lamps, less building headroom is required. Today, down-
other hand, provide even higher efficiency at low temperatures
lights typically require a minimum of one foot headroom. With
meaning that much less energy is needed both to power them
SSL technology and effective, well designed thermal manage-
and to remove any residual heat. The extreme longevity of these
ment, the headroom could be reduced to four inches. As a result,
fixtures also provides significant reductions in maintenance ex-
in new buildings, the distance between floors could be reduced
penses associated with these displays.
by up to eight inches and a multi-story building could have a
Food Storage Facilities
substantial material savings. Accordingly, it can thus be readily
Extremely cold temperatures in food storage facilities also favor
seen that some of the economies of solid-state lighting are seen
solid-state lighting. Previously, food processors had to contend
not just in the direct energy savings.
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its licensors. Other logos, products and company names mentioned herein may be trademarks of their
respective owners. All information, including illustrations, is believed to be reliable. Users, however, should
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Buyer—to materials or processing that do not affect compliance with any applicable specification.
© 2011 Tyco Electronics Corporation, a TE Connectivity Ltd. Company. All rights reserved. Printed in USA.