Distribution
Delivering the brighter
tomorrow today! W
According to Felix Corbett attention to detail in the selection of support components is the key to realising solid-state lighting’s full potential
hile that headline deserves a quivering voice-over from a 1950s science fiction film,
LED lighting is indeed today’s big thing, and deservedly so. High Brightness LED manufacturers have successfully increased the luminous flux from successive generations of devices to levels now sufficient to allow a wide range of applications and markets to benefit from the many practical advantages of solid-state lighting.
The high efficiency of today’s power LEDs, in terms of lumens per Watt, is a major attraction, particularly for home owners and businesses looking to control their carbon emissions as well as spiralling utility bills. There are, however, many further exciting aspects to this lighting revolution; advantages such as smaller dimensions, lower operating voltages, longer lifetimes, opportunities for processor-controlled lighting effects, and surface-mount package technology of power LEDs promise to change the way lamps and lighting are designed and used. For the technology to deliver its full potential, however, producers of supporting components such as interconnects, passives, power supplies and thermal management products must follow the example set by LED and control IC manufacturers; in typical semiconductor marketing style, they have been diligent in preparing complete, turnkey solutions for their customers.
Powering the lights
Lighting design using Power LEDs is fundamentally different to building conventional incandescent lamps. An LED light comprises multiple individual emitters connected in series, and a suitable ballast or controller must maintain a constant current to achieve the desired level of illumination. This has implications regarding the capacitive and resistive components used in conjunction with the semiconductor devices managing the current and voltage supplied to the LED string. Whereas components for
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conventional ballasts are typically chosen on price, solid-state technology requires higher-quality components to withstand high thermal loads and support the significantly longer operating lifetimes. Some designers are specifying higher-performing capacitors featured for demanding applications such as laptop computers to ensure the thermal stability and reliability required in the solid-state lighting application space. Temperature-related effects also compromise the performance of conventional resistors when controlling LED driving current, demanding careful consideration of the temperature coefficient (TCR) when selecting suitable components. In applications requiring an off- board power supply, customers need access to a box-level solution. These are often deployed at the installation stage; hence low volumes of units capable of satisfying individual power demands are required. Power supply vendors and distributors offer constant-current or constant-voltage AC/DC modules, at voltage and power levels suitable for LED-lighting applications, to provide “plug-and-play” power solutions for their customers including lighting designers and installer communities.
Managing the heat
Heatsinking to maintain lifetime performance and reliability is another key aspect of any solid-state lighting solution. In some cases, this can be achieved by providing vents in the enclosure and attaching heatsinks directly to power semiconductor components such as the voltage converter/regulator ICs. Pre-formed copper or aluminium heat sinks are available off-the-shelf for most power
packages, and tend to be heavily finned to maximise heat dissipation while occupying a small total volume. Alternatively, ceramic heat sinks can be formed in almost any shape and give almost as good heat conduction as copper.
Even more effective heat removal can be achieved using new types of heatsinks such as Aavid Thermalloy HiContact Cold Plates. These feature built-in liquid-filled pipes to conduct the heat away from the device to the environment more efficiently than a solid material. This form of quasi- passive cooling enables more effective cooling for a given mass, making a smaller heat sink more effective. Heatsinking in a solid-state lamp must often be applied directly to the LED emitters to prevent excessive die temperature, which otherwise leads to reduced light output and shortens the LED’s lifetime. When designing retrofittable replacement units for industry-standard form factors such as MR16 bulbs, designers can choose from a variety of off-the-shelf heatsinks that are compatible with the desired overall shape and dimensions of the bulb. As far as more innovative lighting designs are concerned, a custom solution is more often required. A good technical distributor can help designers and installers realise unique solutions meeting the exact mechanical dimensions and thermal performance required for a given application. Careful consideration of thermal management early in the design can bring dividends in the long term, by giving designers more freedom and
flexibility to select the best performing LEDs, optimise the number of individual LEDs used, and determine the most suitable drive current, while at the same time avoiding excessive operating temperatures that can impair performance and reliability in the field.
Installation challenges When it comes to fitting solid-state lighting solutions in the field, installers need access to a variety of suitable interconnection solutions. Ease of assembly, robustness, and solutions for connecting large numbers of PCBs or standalone modules are extremely important to enable applications such as architectural lighting, signage, emergency lighting and mood lighting to derive the maximum benefit from the versatility and efficiency of power- LED technology. Interconnect solutions conceived for the LED era are entering the market, including specific module-to-module, board-to-board, wire-to-board and wire- to-wire interconnects in current and voltage ratings for LED applications. This helps installers achieve quick space-efficient assembly and installation, as well as high reliability. Among these, miniature wiring systems optimised for rapid assembly in confined spaces such as inside cabinets or appliances can be procured in custom lengths and as kits of components or as complete cable/connector assemblies ready to install in the field. Clearly, although power LED technology has proved its credentials, there is still some way to go as far as system-level components are concerned. Installer communities, in particular, need a greater choice of products and services matching special requirements of solid-state lighting applications. Here is an opportunity for component OEMs and their technical channel partners to build an even stronger case for solid-state lighting.
Avnet Abacus |
www.avnet-abacus.com Felix Corbett is Marketing Director Northern Europe, Avnet Abacus
Components in Electronics
www.cieonline.co.uk
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