Categories Lamp

Is the Future Bright for the California Quality Lamp?

The California Energy Commission (CEC) in conjunction with the California Public Utilities Commission (CPUC) drafted and adopted a document for a new California Quality Lamp, which is currently voluntary. However, beginning in 2014, only LED replacement lamps that meet this new specification will be eligible for rebates in the state. The rationale and drive behind the new specification is to promote quality of light over cheaper, poorer LED replacement lamps that may negatively impact consumer adoption of high efficiency LED light sources.

Development of the new spec was fueled by the historic low adoption rate of poor quality CFL bulbs, which began flooding the market in the 90s when China ramped up mass production of the helical CFL design. Utilities, wanting to reduce energy consumption due to rising oil costs and global warming, encouraged residential consumers to swap out incandescent lamps for CFLs through rebates and buy-downs. Unfortunately, the ultimate market penetration of the CFL was extremely low (roughly 11 percent nationally and 20 percent in California) due to the performance and perceived value of the CFL. Noticeable flaws in CFLs were poor quality of light, the inability to dim, the short life, the flicker, the buzz, the shape, the slow start up in cold weather and the mercury content. This overall lack in comparable product performance drove the consumer back to incandescent bulbs as the primary choice on the basis of both price and quality.

In a nutshell, the perfect storm of events occurred in the US lighting industry demonstrating the importance of all Four P’s of the ‘marketing mix’ – product, price, promotion and place. The results have created a long lasting negative view of CFLs despite significant product improvements in almost all attributes.

The introduction of the California Quality Lamp is positioned by the CEC and CPUC to be the game changer in product performance for energy efficient replacement lamps. Key lessons were learned from the failed CFL marketing approach and, as a result, the voluntary CEC spec focuses primarily on LED light quality, dimmability and longevity while adopting Energy Star performance criteria in other areas such as efficacy. The CEC allows only omnidirectional, floodlamps and spotlights to be qualified as California Quality (refer to summary table of select criteria below).

Product performance is but one of the Four P’s of the traditional marketing mix and understandably, the CEC cannot alone significantly impact the other three factors of price, promotion or the place of sale/method of distribution. So how will the California Quality Lamp succeed and what is the broader plan?

The white paper, “Relighting American Homes with LEDs”, and the DOE study on ‘Lessons Learned’ as cited in Appendix D of the Voluntary California Quality LED Lamp Specification, certainly seem to point toward a more consumer-oriented niche marketing program, collectively known as the Four C’s.

  • Understand and focus on what the Consumer needs rather than the product alone
  • Shift from price to Cost of ownership, i.e. long term value
  • Replace promotion with Communication which includes emphasis on education, environmental impact, advertising and incorporate use of social networks
  • The place and method of distribution should offer Convenience utilizing channels such as the internet and other trends in purchasing

You have the hindsight and the foresight to make the light right! Good luck California, and as always, you lead the way.

Summary of Select Residential California Quality Lamp requirements vs. Energy Star Requirements

Performance Criteria California Quality Lamp Energy Star Lamps
Lamp base and Lamp Shape Limited to Omnidirectional, spotlight and newly defined flood lamps Open to more bases, shapes and decorative lamps
Efficacy Not required Between 40 – 50 lumens/Watt depending on lamp type
Light Output at Elevated Temps Not Required 90% or greater output at elevated temperature
Correlated Color Temp – CCT Only 2700K and 3000K 2700K, 3000K, 3500K, 4000/4100K and 5000K
Color Rendering Index – CRI CRI ≥90 and R9=.50 CRI≥80 and R9=0
Dimming, noise, flicker 100% – 10%, free of noise and flicker No established criteria
Lumen Maintenance Not Required Shall maintain ≥80% of output at 40% of rated life
Rated Life Same as Energy Star Not less than 25,000 hours for residential lamps
Power Factor Pf ≥.9 Pf ≥.7
Electrical Safety Not Required Must Comply with UL1993 and UL8750
Warranty Minimum 5 year Warranty Provide a Warranty period (not specified) and contact information for manufacturer
Categories Lighting

Connect, Protect and Control Your LED Lighting

Thus far in this SSL Blog series, we covered the LED; interconnect of the Chip on Board LED device within a luminaire utilizing a TE Connectivity (TE) scalable or Zhaga compliant socket; and the various device-level interconnects commonly used in lighting applications.  Today, I would like to discuss additional product aspects for consideration in regards to control, circuit protection and power aspects of SSL luminaires.

Control capabilities are increasingly more prevalent within the macro trends of energy efficient and intelligent buildings.  Lighting is a key focus of energy efficiency efforts within a building in that they consume roughly 30 percent of the building’s power consumption. There are significant gains that can be realized by controlling light levels. Adding intelligence to lighting is a key element to a comprehensive building plan to conserve energy.

Traditionally, the most practical and cost effective lighting control is the common wall switch. Its fault is that incorporates a human element and we all know how variable this element can be. To remove the human from the control equation, building intelligence needed to evolve to a sense, communicate and control environment via available technology. A simple implementation such as installing an occupancy sensor that senses movement in the room and directly controls a light fixture can offer immediate energy savings. Tie this sensor into a network of other occupancy sensors as well as daylight and ambient light sensors, and suddenly the building is “intelligently” able to react to its occupants and environment.

This effect of increasing levels of control required within building lighting systems ripples through to new requirements for components used within the systems.  For example, TE’s well established RT series relays have been on the market for years but needed to be further refined to meet the increasing demands of switching the more energy efficient fluorescent and SSL fixtures coming to market.  The high input current spikes characteristic of today’s drivers drove a radically new switching technology that was incorporated into TE’s RTX relay and new contact structure built into the RT1 Inrush Power relay.

The electronification of lighting and related controls also increased susceptibility to potentially damaging surges caused by ‘dirty power’ and / or lightning. While traditional incandescent lamps were relatively immune to this, SSL luminaires require some level of circuit protection to protect the end product from power fluctuations and surges.  A fuse offers some level of protection. However, fuses are typically “once & done” devices that render the fixture inoperable after an event. A better solution is a self-resetting device such as TE’s 2Pro AC device. The 2Pro AC device offers designers an integrated, self-resetting device that protects sensitive downstream electronics against damage from overcurrent and overvoltage events. By combining a PPTC (polymeric positive temperature coefficient) device and a thermally enhanced MOV (metal-oxide varistor) into one package, a more robust and more easily integrated level of protection can be included into lighting control products.

Another less often discussed topic within controls is conducted emissions and susceptibility. With the increasing use of microprocessors throughout lighting control systems, electrically noisy power systems can wreak havoc on a control network. Increasing use of power line (data/broadband) communication within a building can further fuel a noisy power environment for building controls. Conversely, particularly noisy control devices such as drivers and power supplies that run at higher frequencies and harmonics can often induce noise into the building power system and affect other electronic devices. The latter is especially weighty in hospital and other medical environments where such noise could have catastrophic results given the right conditions. Conducted emission filters such as TE’s FB & VB series are increasingly used in these applications to both protect devices from incoming conducted RFI and likewise limit any outgoing emissions on the power lines.

There’s no doubt the lighting environment is changing. This is visually evident throughout the world. In a less obvious manner, the environment is changing fixture and system designs and is spawning a host of new supporting products. The end result must be to ensure that the consumer gets the best, most controllable light possible that meets the adage, “The best light is the one you don’t notice”.

I’ve covered a few new topics above that are changing the face of lighting and lighting controls. I’m interested in hearing about other challenges and issues you’re seeing. If you have a minute, send me a note with your thoughts and comments. Please send me an email at

Categories Blog

Extending Dim Range with Phase-Cut Dimmers

Users quickly notice shimmer and flicker in LED lighting. The strobing effect that is generated by misfiring phase-cut dimmers is unacceptable to end-users and dimmable bulbs that don’t work with a majority of local dimmers will not be successful.

Dimming range – the minimum (and maximum) output light that can be delivered by the lamp when connected to a dimmer – is also an important characteristic for LED light bulbs. At the bottom end of the dimming range an LED bulb will have either turned off, or reached minimum light output. Dimming range is usually expressed as a ratio of maximum to minimum light output. Driver manufacturers tend to look at the output current ratio as an approximation of dimming range.

The typical dimming range requirement for leading-edge TRIAC dimmers is a 10:1 current step; for trailing edge dimmers the figure is above 5:1. To understand what controls dimming range and why the accepted performance for leading-edge and trailing-edge dimmers is different, it is necessary to understand how minimum output current is achieved in a phase-cut dimmer.


Figure 1. The effect of TRIAC dimming angle on LED driver output current

Trailing-edge dimmers use internal logic circuitry to control the dimming angle which requires power. This power is delivered to the driver when the TRIAC is turned-off (not delivering power to the lamp). To ensure this happens, trailing-edge dimmers tend to have higher dimming angle than equivalent leading-edge types.

Typically this was not a problem with incandescent bulbs because their light output changes exponentially with power at low brightness levels (the bulb gives very little light output at low conduction angles) which means low brightness occurs significantly above the limit the power storage requirement imposes.


Figure 2. Maximum and minimum dimming angles for highline dimmers (Source: Power Integrations) – The range of maximum and minimum dimming angles makes wide dimming range challenging

Controlling factors for dimming range
The red trace in figure one shows an LED driver output current that is directly proportional to the conduction angle. The LED load takes a high load current even at relatively low conduction angles, but does not reduce current sufficiently by the time the minimum conduction range for TRIAC dimmer is reached. The high load current delivered using this approach means that TRIACs will see high holding currents, reducing the likelihood of shimmer or flicker.

The designer can elect to increase the dimming-slope of the LED driver to arrive at a lower output current at a higher dimming angle (blue trace in figure 1). This allows the bulb to dim to a lower brightness but risks causing shimmering and/or flickering as the load current drops. In a practical design this means that a significant amount of extra power must be drawn by a bleed circuit to keep the TRIAC from misfiring (this region is shown in red area in figure 1). This reduces driver efficiency making the need for heat sinking or potting materials more likely in the final design.

An alternative approach is to employ an adaptive bleeder circuit such as shown in the driver in figure 3. The bleeder circuit draws more current in deep dimming to compensate for the reduced output current but preventing excess heating at full brightness


Figure 3. Dimmable bulb driver with smart (lossless) bleeder function. The driver also shuts off at very low output current (deep dimming) to reduce the risk of TRIAC dimmer misfiring and causing shimmer (

Dimming range, like so many of the design considerations for a TRIAC dimmable LED driver, cannot be considered in isolation. A design requirement that pushes for excellent dimmer compatibility and extended dimming range will (with presently available driver circuitry) lead to increased solution cost.

Categories LED

Innovative AC LED: Ready for Prime Time

There has been a lot of exciting talk about AC LEDs. The ability to bypass costly AC to DC LED drivers, reduce systems size and cost, all while still providing leading edge light quality is an attractive proposition for luminaire manufacturers, lighting designers and specifiers. In the past, however, there have been necessary sacrifices in order to reap these benefits. But, recent advances have made this technology a winning proposition. By using AC to directly drive the LED light source, the system will greatly simplify the application programs, making the system reach 90 percent efficiency. Let’s explore this.

The Technology
As you may know, in conventional LED lights a driver is required to provide a regulated constant voltage or current to the LED light engine. However, the converter circuit not only increases costs but also shortens the lifespan of the LED lights. In the report, Solid-State Lighting Product Quality Initiative, by the DOE and Next Generation Lighting Industry Alliance, drivers are responsible for a 52 percent failure rate of the luminaires tested.

However, AC LEDs can be connected directly to 120V or 230V line voltage and do not require a driver. The sinusoidal waveform circuit means that at each particular time half the LEDs are off while the other half is on, emitting light. This stage is reversed and repeated continually, producing a constant stream of light.[1]

With AC, power is transmitted and used much more efficiently. Basically, by putting LEDs directly on the end without having to include complex electronics to convert AC back into DC, the power is distributed efficiently and delivered more effectively without intervening electronics.

Eliminating the Driver
A LED driver is a power module to generate the voltage or current to driver LED module from AC mains. However, an AC LED doesn’t need to have LED driver. Let me explain. By eliminating the LED driver and operating the light source from direct mains voltages (120VAC/60Hz in the US and 240VAC/50Hz in the Eurozone) the system is more reliable, it offers greater design flexibility and the failure rate is lessened.

The thermal management requirements are slightly reduced as drivers are not efficient and generate excess system heat as a result.  An additional benefit of the removal of the external driver is space saving and weight.  A typical 20-watt LED driver takes up nine cubic inches of space and often requires an enclosure or junction box of some kind for agency approvals.

Additional Advantages

  • AC driven without converter or driver
  • Simplified circuit design
  • No conversion loss
  • Reduced costs
  • No lifespan reduction by secondary components
  • Dimming available
  • No power supply to clog thermal path

With the introduction of LED modules with a driver IC integrated for current control that is designed to be used in any 24V system and AC LED modules that allow LEDs to be driven from direct 120V AC without using any capacitors, coils or resistors, manufacturers don’t have to give up anything but cost and complexity.

Thermal Management
When designing with a direct AC input LED light source the design does not need to accommodate the driver but still must properly manage the thermal requirements and optical outputs. In many cases the existing luminaire will have adequate exposed surface area to the ambient to afford a much smaller heatsink or allow for the elimination of one altogether.  As a rule of thumb, four exposed square inches of surface area to ambient per watt is all a system needs to keep the operating temperature in the safe and optimal range.  This allows for lower profile fixtures such as wall sconces, four and six inch down lights, track light heads and pendant mount luminaires.

In a research paper, “Issues of Thermal Testing of AC LEDs,” the authors provide an excellent description of thermal management with AC LEDs. According to the paper, in the case of AC driven LEDs the sinusoidal AC mains voltage results in a periodic waveform of the actual heating power, after an initial transitional period while heating up the LED junctions. Once the shapes of the waveforms of the heating power and the junction temperature do not change any more we can say that the AC LED is in a stationary state. As our systems are nearly linear in the thermal domain the thermally stationary situation can be treated similarly.[2]

Dimming Challenges
An important element of AC LEDs is the dimming feature, which is compatible with phase-cut dimmers. A good dimming system should only lower the light output without sacrificing the color accuracy, unless that is the manufacturer’s desired result. A dimming rate of two percent is ideal, however it is not easily achieved, resulting in the CCT going from 4000K to 2000K. A more realistic dimming rate is five to 10 percent. However, while dimming performance varies significantly across many types of commercially available LED sources, less-than-ideal behavior shows up most frequently when integral LED replacement lamps are installed on circuits controlled by phase-cut dimmers.

It’s important to remember that dimming problems are not caused by any shortcomings of SSL technology. Rather, they’re due to the fact that almost all of the existing dimmers in this country were designed for traditional lighting fixtures. Nearly the entire installed base of traditional line-voltage (phase-cut) dimming controls was designed for incandescent light sources. There can be compatibility issues between these controls and an LED light source’s driver. That said, well-designed SSL products will work with existing dimming control systems without adding unwanted flickering.  Additionally, there are also many dimmers designed for specifically for LED products and are currently on the market.

Light Flickering
One of the main drawbacks of the AC LED is light flicker. Because it is directly driven by AC line voltage, which oscillates at 60Hz (or 50Hz), the AC LED produces light flicker at twice the frequency of the AC line frequency (e.g., 120Hz in North America). According to past research, even the perception of light flicker is undesirable in lighting applications.

Studies have linked flicker to health problems. So, even though flicker at these frequencies may not be visible to the naked eye, there is evidence that the human brain can detect light flicker frequencies as high as 200Hz. Potential problems include headaches, eye strain, impaired visual performance or, in extreme cases, epileptic seizure.

The ENERGY STAR requirement for lamps, due to go into effect Sept. 30, 2014, specifies that the highest percent flicker and highest flicker index be reported, but does not specify a maximum allowable limit for either.[3]

In a lighting system, a good solution should reduce light flicker without sacrificing power factor and power efficiency. But what is a good solution to this problem? One is to add components that will shorten the “off” time. Another is engineering a circuit board that uses a separate AC power and control signal. Unfortunately, it’s difficult to define the “safe” amount of flicker to the overall population because it’s perceived as a matter of human recognition.

Ready for Prime Time
There is no longer the need to sacrifice power factor, luminous efficiency, or light quality to gain the benefits of using AC LED lighting technology. These lights are a compelling platform for retrofit lamps, architectural and landscape lighting and other general lighting applications. This technology offers tremendous benefits over more traditional DC LED lights.

Categories Lighting

Let There Be (LED) Light

As purveyors of nascent yet demonstrably helpful technology, those of us that sell LED lighting solutions have a responsibility to act as an ambassador to the field. LED technology, technology about which we obviously care strongly, is clearly making inroads with the public, but it has yet to reach true universal adoption. The reasons for this are many in number and can be debated elsewhere, but the fact is that there is a lot of misinformation about LED among the public, a fact that’s harmful to the industry.

As proponents of LED, that’s why we have an obligation to provide the kind of products and insight into the technology to ensure that we’re presenting it in its best light, making obvious its advantages not just because it personally benefits us, but also because it’s a technology that is objectively both cost- and energy-saving.

As the owner of an LED Source franchise, my job is to demonstrate the many advantages of LED to businesses interested in retrofitting their existing lighting, correcting falsehoods about it along the way. This misinformation has lead to a few common questions I get from clients, questions I’m more than happy to answer but that often have unspoken assumptions built-in.

When will LED pay off for me?
This question, in its many forms, is the most common one I receive and for good reason: businesses most often approach me for the advertised financial benefits of switching to LED lighting. The question behind this question, I feel, is that most people believe that LED lighting will take a long time to pay off. This could not be further from the truth; most clients, I’ve found, notice that their solutions pay for themselves in as little as two years, with energy bill savings apparent soon after the installation.

How expensive are LED solutions?
Like the previous question, this one touches on the finances involved in LED lighting use. Because LED is still considered state-of-the-art, it is often thought that the technology is expensive right out of the gate. Beyond the fact that LED prices have dropped precipitously since the technology first started to hit the shelves, grants and rebates are made available on a state-to-state basis that can help offset the cost of LED technologies. With bulbs as cheap as $20 that save $10 a year over their incandescent counterparts and last for years, combined with incentives from the government and utility companies, this myth is pretty easily put to bed.

Since LED technology is so new, all providers are the same, right?
This question is predicated on the belief that new technology is not easily mass-produced by less credible sources. This, as we well know, is false. Cheap wholesale LED lighting from overseas is more prone to failure, lacks the substantial warranty provided by respected LED providers and simply doesn’t compare to technology provided by authoritative industry leaders. The old chestnut about getting what you pay for definitely holds true in this case.

As ambassadors to the industry, disabusing would-be LED users of myths and fallacies pertaining to the technology does more than sell them a product. By getting rid of those notions in individuals, the facts that foster our passion for the technology spread, helping both the industry and those who would most benefit from LED lighting. That’s good for business, and it’s good for the world at large.

Categories Blog

Great Achievements Inspire Greater Expectations

Not since the Chicago World’s Fair in 1893 when President Grover Cleveland pushed a button to light 100,000 incandescent lamps to create the “City of Light” has the lighting industry experienced the global attention that it has today.  We have recently witnessed a Nobel Peace prize in Physics for LED lighting in recognition that LED lamps hold great promise for increasing the quality of life for over 1.5 billion people around the world who lack access to electricity grids.  In addition, the United Nations has declared 2015 to be the International Year of Light to raise awareness of how light and optical technologies promote sustainable development and provide solutions to worldwide challenges in energy, education, agriculture, communications and health.  These are momentous occasions, and they occur at a time when consumer awareness of LEDs has never been higher.  However, as LEDs continue to become more mainstream and our industry garners more attention and recognition, this is leading to even higher expectations from us and the future of the lighting.

Though light bulbs and switches have historically represented the way most people think about lighting – a basic, mechanical tool that we use for illumination – the UN realized that lighting has become so much more. Driven by solid state lighting technology, lighting is on the cusp of playing an entirely new role in our lives.  Though our industry’s relentless pursuit of energy efficiency has been quite successful, sustainability has become commoditized, and we’re already starting to feel the reality of diminishing returns. The rise of tunable color technology is an example of the added value we’re already seeing from SSL, but it is only a matter of time before it becomes a commodity as well.

The light quality and price of LED lamps have reached a point where these products have become a real alternative for consumers, who have never been more educated about the lighting choices available to them. As we continue to introduce a broader portfolio of LED products and innovative technology to the consumer market, adoption of these products will accelerate much faster as we approach the tipping point to SSL, creating exciting growth opportunities for LEDs in the consumer and commercial markets.

Above all, one thing is clear: the future of lighting is a bright one and we are certainly heading in the right direction. As we look ahead to 2015, we should not only be proud of our ability to adapt within our industry, we should ensure we’re thinking bigger than tunable light and energy efficiency. Light is getting smarter, and we need to start envisioning the opportunities that smarter lighting can offer as we mold it into our world and our lives. Today’s SSL innovations are already changing the way we work, shop, eat and live – tomorrow’s challenge will be to push the boundaries of our industry’s imagination in a way that is worthy of the UN’s global celebration of light and light-based technologies.

Categories Lighting

What About “Smarter” LED Lighting?

The typical image of “Smart” lighting is an LED Lamp or Luminaire connected wirelessly and controlled via a mobile device to turn on and off, set dimming level and in some cases, change the color. If we look at the recent announcements from Light+Building in Germany last month, the discussion on Smart Lighting tends to be dominated by the choice of wireless interface: ZigBee Lightlink, Wi-Fi, Bluetooth or some proprietary network approach and the merits or limitations of having to install a bridge to connect your home network. For a comparison of different networking approaches, Insteon has published a white paper.

Traditionally the world of controls and light sources has been separated.  Simple residential dimmer switches, occupancy or vacancy sensors were wired to control the delivery of AC power to the load.  Smart lighting has now merged controls into the light source.  With the addition of ambient light, proximity, and passive-IR sensors, these smart lighting solutions can become even smarter.  For example integrating a photo sensor inside a lamp with some intelligence allows occupancy detection and ambient light monitoring so that when you walk into your house or open a closet the light will immediately turn on if insufficient ambient light is not available.  Smart LED light bulbs that have this function are already on the market from companies such as Ohyama Lighting. Beyond motion based control, perhaps a more useful autonomous smart light is one that has vacancy control.  This may require the integration of Passive IR sensors, but once a light is turned on, if a room becomes un-occupied, it will automatically turn off after an appropriate delay. For a parent with teenagers, this could be a real energy saver.

By integrating ambient light and/or Passive IR sensors, self-directed smart lighting solutions offer an additional path to smarter lighting systems especially in residential spaces where controls are less commonly found.  In commercial applications, more sophisticated variations of these control concepts are being mandated.  In January 2014, California revised their Title 24 Building codes and added in a newer series of light control requirements.  In new and remodeled buildings, corridors, stairwells and even library stacks must incorporate ‘bi-level’ occupancy control when the space is un-occupied to ensure a minimal level of light for safety while still capturing energy savings.

Combining sensors with wireless control within an LED light source/luminaire offers a path to improving local lighting control based on the lighting application environment and enables “smarter” LED lighting compared to the alternative of the classical lighting controls framework.  Hubbell Lighting’s Kim Light Group recently introduced an interesting take on smart lighting with a new family of outdoor in-grade architectural LED spot lights controlled by Bluetooth Low Energy (BLE).  Currently, when reviewing the choices of smart lighting networking options, BLE does not necessarily jump to the forefront.  In this case, it presents an interesting use case as the main purpose of making the fixture wireless was not day-to-day operation, but more system configuration and provisioning used to aim the light and set the dimming level after installation to appropriately light the scene.  Moreover since this is an outdoor application, BLE is readily available with most smartphones, has good range and can be paired to the light for configuration but does not need to be connected to a network for ongoing operation.  Once programmed, the light stores the desired light output level and position state but it can be reprogrammed if needs change.

The same approach could be used for configuring new lights and luminaries to set, for example, the appropriate dimming level for a bi-level motion sensor in an office corridor or the amount of time to keep on a bedroom light equipped with a vacancy sensor. As the industry transitions from simple LED bulb replacements to “smarter” LED Lighting solutions, we can expect to see continued innovation in both autonomous lighting controls that can provide light when you need it without reaching for a switch and still deliver minimal energy usage.

Categories Bulb

Reliability and Lifetime Matter Most for Bulbs – Part 2

The short answer is yes. MTBF is an expression of the likelihood of failure during the product’s lifetime. Put simply, the longer the MTBF is, the less likely it is that the device will fail during its lifetime. For example, the brakes in your car have a relatively short lifetime, perhaps three years with average use, but you want them to be very reliable during that time. End-of life is defined as failure – but what is ‘failure’ anyway?

There are lots of phrases that describe this – perhaps the best one for lighting applications is also one of the simplest: “if the product can no longer perform the application for which it is intended then it has failed”. The phrase ‘no longer fit-for-purpose’ should be relatively easy to define for an LED bulb – if you no longer get enough light out of it, then that is a failure. Moreover, when the light flickers and hiccups for a long time during start-up that could also be considered a failure. However, the typical specification for an LED bulb runs to perhaps  20 or more line items (a lot more if it is a smart bulb), but an aging bulb that fails to meet many of them would not fit the average user’s definition of failure as described above.

This is important. If a bulb at the end of its life was required to deliver output that met the complete specification at the beginning of its life, electrolytic output capacitors would not be used to limit current ripple (for example). Replacing the aluminum electrolytic output capacitors with ceramics (which have an extremely long life) would insure that output capacitance stayed high, but the capacitance per unit volume and price of ceramics makes their use impracticable.


Replacing an aluminum Electrolytic capacitor with ceramics in a bulb would be challenging.


So the engineer has the challenge of deciding which parts of the specification the bulb needs to meet as it begins to age and which parts it does not.  For most applications, increasing output ripple will not be seen as a cause of failure by the user, so the engineer can accept the reduction in performance that comes with using components (such as electrolytic output capacitors) that are necessary for a practical design.

Yet electrolytic capacitors cannot be used everywhere in the circuit because they can cause the type of failure that users will not accept. The use of single stage LED drivers, PFC and constant current (CC) combined into a single switching stage, eliminates electrolytic bulk capacitors from the input stage. (A weakness of two stage converters, which have separate PFC s and CC driver stages, is that they need a bulk -capacitor which, as it ages, reduces capacitance and eventually results in a bulb that may be reluctant to start or may fail completely.)


2-stage converters use a bulk capacitor in a location, which will eventually cause a hard failure.


Single-stage converters have no lifetime-ending bulk capacitor but accept non-lifetime ending higher output current ripple.


Perhaps the best known trade-off in performance against time is in the drop off in light output (lumens) that is associated with the degradation of the phosphors in the LED. Figures like L-70 (a subject for another discussion) are used to describe how well the LEDs in an application perform above a minimum light output specification.

If a light dims over time, often  it isn’t a problem as the user will typically notice; however if a bulb in the set fails and a replacement is added (assuming you can still find one of the same model and type) then the light output may be noticeably different. Fortunately, the human eye is poor at detecting relative light intensity, so light output requirements (at end-of life) that are implicit in the L-70 figure exploit this fact. It is possible to design a lamp that increases the drive current to compensate for a reduction in lumens per watt from the LEDs. This is not a common design requirement due to the cost of the necessary detection circuitry. The rise of smart lighting (especially in Europe and North America) may lead to the introduction of this kind of feature in more lighting applications in the future.

It is clear that the parts of the specification that a customer can accept are dependent on how the human eye perceives light, so in order to determine what parts of a lamp’s operation are critical to maintain over-time, it is  useful to understand what the human eye can distinguish and tolerate– therefore the next topic we will look at is Macadam ellipsis, intensity perception and frequency/amplitude considerations for output ripple.

Categories Lamp

What Goes into the Design of LED Retrofit Lamps?

In a LED retrofit lamp, it is the light engine comprised of LEDs (discrete or chip on board) that emits the light that you see. The LEDs in the lamp operate at a temperature much higher than ambient, resulting in lower lumens, and this thermal efficiency factor lowers the lamp efficacy (lumens per Watt or LPW) below that of the intrinsic LEDs. Depending on the application, some LED lamps also have a form of secondary optics to shape the pattern of the light. Not all the light emitted by the LEDs makes its way out of the lamp. There is a light extraction efficiency associated with the whole optical system and this also lowers the efficacy of the lamp below that of the intrinsic LEDs. Finally, there is a driver efficiency factor (not all of the input power to the lamp ends up being delivered to the LEDs) which again reduces the lamp efficacy. It is the product of these three individual efficiencies which gives the overall factor to help the designer determine the final lamp efficacy.

Lamp designers from reputable manufacturers focus on lamp performance while accounting for each of the efficiencies mentioned above and also keeping in mind the need for the product to be affordable. Fly-by-night vendors often do not understand or care about these efficiencies.

In general, higher thermal efficiency is associated with a lower LED solder point temperature. This is possible with good thermal management by a suitable combination of proper materials for the heat sink, adequate surface area, proper choice of interface materials and good contact protocols. High optical efficiency, especially for omni-directional lamps, may need suitable lens design and proper choice of optical materials.

Driver electronics is complicated. A high efficiency driver allows one to reduce the total input power to the lamp for a given lumen output from a specified light engine. This is because in a high efficiency driver fewer watts are lost in the driver circuitry with a larger fraction of the input power being delivered to the LEDs. Power dissipation in the driver results in heat so a higher efficiency driver helps lower the temperature of the driver components allowing the use of lower cost capacitors and inductors for example.

Various design attributes influence the driver efficiency. One of them is whether the driver is isolated or non-isolated. While the latter tends to have lower losses and higher efficiency, one has to be careful to ensure that electrical safety requirements are met to avoid any shock etc. Unlike fly-by-night vendors, reputable manufacturers of LED lamps pay proper attention to this. A non-isolated driver design generally calls for fewer components, allowing a smaller driver footprint, and so is preferred for smaller form factor lamps.

Dimming performance is directly related to the driver design. Dimming drivers, for example, incorporate a bleeder circuit with resistive and capacitive components that provides the latching and holding current and prevents the TRIAC from misfiring. Bleeders can be passive or active. An active bleeder, where the resistor is only on when needed, may be the preferred route when high driver efficiency is needed. This may happen when one has to design a higher wattage LEDr lamp while keeping the cost of the heat sink under control. In this case, driver component temperatures are very critical. A passive bleeder may suffice for low wattage LEDr lamps where the driver efficiency may not be that critical. Even the type of fuse that is used for the driver can influence the dimming performance and also affect the driver efficiency.

In summary, several complex technical variables influence the optical, thermal and driver efficiencies in a LED lamp. Reputable manufacturers differ from the crowd of lesser vendors in that the former pay attention to all of these efficiencies when they design lamps for the customer while keeping cost in mind.

Categories Lighting

UL Lighting Standards Update

UL Standards encompass UL’s extensive safety research, scientific expertise and uncompromising focus on quality. With over a century of experience and the development of more than 1,000 Standards, UL continues to break new ground in its mission to help create a safer, more sustainable world. The below standards update for the lighting industry was originally published in UL’s Lumen Insights Newsletter, Year-end edition.

UL 1598 – Luminaires (Tri-national standard)

  • Next revision cycle started, which will be a 2-year cycle. Call for Proposals due date was June 22, 2013. The UL proposals were prepared and sent on September 22, 2013 to CSA (the Publication Coordinator) for Technical Harmonization Committee review.

UL 1598C – Light-Emitting Diode (LED) Retrofit Luminaire Conversion Kits

  • Proposed 1st edition went out for ballot on March 15, 2013. The proposal achieved consensus and a STP meeting was held on July 17, 2013 to discuss the comments received. Responses have been posted and revisions were proposed in a recirculation Work Area in CSDS on November 8, 2013 with a due date of December 9, 2013.

UL 1993 – Self- ballasted Lamps and Lamp Adapters (Tri-national standard)

  • Next revision cycle started. Call for Proposals were due on September 22, 2013. The proposals are being prepared for Technical Harmonization Committee review.

UL 8750 – Light Emitting Diode (LED) Equipment For Use In Lighting Products

  • Proposal went out for ballot on September 21, 2012 and also discussed at November 2012 STP meeting. The proposal related to adding requirements for dimmable LED drivers for use with solid-state dimming controls electrically wired in series with the mains supply. The proposal went out for recirculation on May 31, 2013. The revisions were published on September 19, 2013.
  • Multiple proposals went out for preliminary review on October 24, 2012. These proposals were discussed at the November 2012 STP meeting. Some of the proposals were reworked and went out for ballot on June 7, 2013. The remaining topics will proceed separately.Error! Hyperlink reference not valid. Responses have been posted and revisions were proposed in a CSDS recirculation Work Area on October 11, 2013 with a due date of November 11, 2013.
  • Multiple proposals went out for preliminary review on October 14, 2013 with a due date of November 8, 2013. These proposals will also be discussed at the November 2013 STP meeting. Link to the summary of topics:
  • STP meeting is scheduled for November 19-20, 2013 at the Embassy Suites Hotel in Deerfield, IL.

UL 8752 / ULC-S8752 – Organic Light Emitting Diode (LED) Panels

  • Multiple proposals went out for preliminary review on May 28, 2013 and for ballot on July 12, 2013. The revisions were published on September 30, 2013. This is a joint UL/ULC Standard.

UL 8753 / ULC-S8753 – Standard for Field-Replaceable Light Emitting Diode (LED) Light Engines

  • The 1st edition of the joint UL/ULC Standard for Field-Replaceable Light Emitting Diode (LED) Light Engines, UL 8753 / ULC-S8753, was published on July 31, 2013. There is no current UL standards activity.

UL 8754 / ULC-S8754 – Holders, Bases, and Connectors for Solid-State (LED) Light Engines and Arrays

  • The 1st edition of the joint UL/ULC Standard for Holders, Bases, and Connectors for Solid-State (LED) Light Engines and Arrays, UL 8754 /ULC-S8754, was published on July 31, 2013. There is no current UL Standards activity.

UL 935, UL 1029, UL 542 – Ballasts (Tri-national Standard)

  • The draft of Part 1 of the proposed Standard, covering general construction and test requirements is being reviewed by the CANENA Harmonization Committee (THC34/SC34C) and being prepared for preliminary review.
  • The Part 2 documents which will include specific requirement for the various product types still need to be developed.

UL 935 (current UL Standard, 10th edition)

  • Proposal went out for preliminary review on May 29, 2013 related to the addition of requirements for ballasts intended to be dimmed using solid-state dimming controls electrically wired in series with the mains supply. Another proposal went out for preliminary review on July 26, 2013 related to revising the arcing test method in Section 30. These proposals went out for ballot on October 18, 2013 with a due date of December 2, 2013.

UL 153 – Portable Electric Luminaires

  • Proposal went out for preliminary review on October 4, 2013. The proposal was related to a revision for Paragraph 24.1, exception No. 3 and to add the definition of “LVLE” circuit. The proposal will be issued for ballot on November 15, 2013 with a due date of December 16, 2013.

UL 1786 – Direct Plug-In Nightlights (Bi-national Standard)

  • Next revision cycle started. Multiple proposals went out for preliminary review on October 17, 2013 with a due date of November 7, 2013. Link to the summary of topics:

UL 496 – Lampholders (Bi-national standard)

  • Multiple proposals went out for ballot on February 24, 2012 and recirculation on March 15, 2013. Link to the summary of topics: The proposals are being prepared for publication in the Standard. The revisions were published on November 25, 2013.

UL 1088 – Temporary Lighting Strings

  • Proposal went out for preliminary review on September 19, 2013. The proposal was to allow for the use of energy efficient light sources in temporary lighting strings. The proposal will be issued for ballot on November 1, 2013 with a due date of December 16, 2013.

UL 2108 – Low Voltage Lighting Systems

  • Multiple proposals went out for preliminary review on August 27, 2013. The proposals went out for ballot on October 4, 2013 with a due date of November 18, 2013. Link to the summary of topics:

UL 1573 – Stage and Studio Luminaires and Connector Strips

  • Proposal went out for preliminary review on September 13, 2013. The proposal went out for ballot on October 18, 2013 with a due date of November 18, 2013. The proposal was to add requirements of 2014 NFPA 70 Section 520.68 (A)(3) to UL 1573.

UL 1838 – Low Voltage Landscape Lighting Systems

  • Multiple proposals went out for preliminary review on September 20, 2013. Link to the summary of topics: The proposals will go out for ballot on November 8, 2013 with a due date of December 23, 2013.

UL 924 – Emergency Lighting and Power Equipment

  • Multiple proposals went out for preliminary review on April 24, 2013. The proposals went out for ballot on August 16, 2013 with a due date extended to October 30, 2013. Link to the summary of topics:
  • Proposal went out for preliminary review on September 11, 2013. The proposal went out for ballot on October 18, 2013 with a due date of November 18, 2013. The proposal is to delete SH3.2 (using photometric data to show conformance)

UL 676 – Underwater Luminaires and Submersible Junction Boxes

  • Proposal went out for ballot on July 12, 2013 and recirculation on September 30, 2013. The proposal was related to non-metallic and isolated, low voltage luminaires. The proposal is being prepared for publication.

UL 48 – Electric Signs

  • Proposal went out for preliminary review on December 24, 2012. The proposal was related to two topics: (1) Clarification of drain opening requirements and (2) Grounding and Bonding Marking. The next step is for the proposal to go out for ballot.

UL 48B – Changing Message Signs and Displays

  • UL is currently developing proposed 1st edition for UL48B.

UL 879 – Electric Sign Components

  • Call for Proposals went out on October 14, 2013 with new proposals due November 22, 2013.