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.