Paul Ward, Opto Product Manager at Farnell element 14 uncovers some inspiring LED ideas that are emerging, keeping lighting dynamic and exciting
High-performance LEDs for lighting applications are exciting a broad range of audiences, including engineers, designers, architects and end users, as well as governments facing the challenges of managing growing energy demands, diminishing resources and ambitious carbon-reduction pledges.
According to the recently published ‘Lighting the Way: Perspectives on the Global Lighting Market’ report by McKinsey & Company, global revenues from LED lighting markets are expected to reach EUR 65 billion by 2020 and will represent around 60 percent of the total lighting market.
Architectural lighting has been the major early adopter of LED technology; LED’s currently have around 39 percent market share, rising to more than 85 percent by 2020 according to the McKinsey report, which cites the technological edge in colour control as a key reason for the sector’s enthusiasm.
Indeed, the families of LEDs offered by today’s leading manufacturers typically provide a choice of several types of white such as cool white, warm white and neutral white. These can be used effectively to create various types of moods in locations such as hotel lobbies, offices or living rooms.
Another trend is very small footprint high output LEDs that can be used in multiple arrays in light panels for ceilings and light strips; this configuration is especially useful for retail applications. The technology sees the LEDs closely grouped and a diffuser used to ensure a uniform look without spotting.
The versatile controllability of LEDs opens many new design avenues, not least through the ability to mix red, green and blue light from individual emitters to produce almost any colour within the visible spectrum.
By placing individual red, green and blue LEDs close together, controlling the current supplied to each colour permits mixing to achieve a variety of static or dynamically changing effects. These can be used in applications such as interior mood lighting, novelty illuminations, emergency lighting, electronic posters or large video walls.
The short response times of LEDs enable designers to display fast-changing effects or moving images.Three-colour devices containing individual red, green and blue LED chips in a single package help to simplify design and assembly.
Optomising the opto colour mix
Better colour mixing is also achieved, since the light sources can be spaced more closely than the industry-accepted minimum spacing of 5mm for effective colour mixing. More recently, RGBW LEDs have arrived on the market featuring an additional high-brightness white chip for extra flexibility and more dramatic effects.
High-brightness RGB and RGBW LEDs for lighting applications make use of today’s most thermally efficient package technologies to maintain long-term reliability, as well as lenses displaying high thermal stability that effectively prevent degradation of optical performance.
In fact, the success of LEDs, generally, in lighting applications, has been dependent upon advances in packaging that have allowed high continuous driving current and effective heat removal to prevent thermal damage to the LED chip.
Controlling the LED junction temperature holds the key to maintaining consistent lighting characteristics over time, and ensuring each lighting fixture will achieve its intended lifetime.
The packages used by high-performance device families utilise high thermal conductivity materials such as ceramics, aluminium and copper, to provide the mounting for the LED die and create an efficient thermal connection to the motherboard.
Typically, the chip carrier substrate has an efficient thermal connection to an exposed pad on the back of the package, which is soldered onto a corresponding large copper pad on the motherboard acting as a heatsink. Individual white high-brightness LEDs packaged in this way are able to sustain continuous forward current up to around 2000mA.
High-performance plastics such as polyphthalamide are being chosen both for the package housing and the reflector. This class of materials can operate under high-temperature and high-UV conditions for long periods while maintaining surface reflectivity, delivering performance that contrasts with that of inferior plastics that display surface yellowing or browning after exposure to high temperatures leading to a noticeable reduction in light output and quality after a relatively short time.
Presenting an alternative to the multi-chip LED for colour-mixing applications, Farnell is one of the first distributors to offer colour-tunable Organic Light Emitting Diodes (OLEDs), through its distribution agreement with Verbatim. OLEDs utilise the phenomenon of organic electroluminescence, and have been widely used to create ultra-thin displays and flat-panel TV screens.
New materials and production technologies now allow colour-tunable OLEDs for lighting applications. Verbatim’s Velve framed OLEDs enable designers to create extremely thin and lightweight lighting designs by enabling white or RGB colour adjustment, high brightness, large panel sizes up to 150cm2, and constant-flux/constant-colour dimming.
High-brightness white, RGB and RGBW LEDs, and white and new colour-tunable OLED lighting, are currently available from several leading manufacturers; choice and performance are increasing quickly as electronic lighting technology in general is moving forward.
In addition, new optical materials and components, colour-mixing reference designs and supporting products such as interconnects, heatsinks and modules are evolving quickly.
Designers can keep up to date with the latest developments using web resources such as Farnell’s dedicated LED-lighting microsite.
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