William Heath, Commercial Director at OMC UK explores how Light Engines are enabling effective LED lighting design across the industry for a better user experience
It is probably fair to say that LED technology for room (area) lighting has had somewhat of a challenging introduction. One-off demonstrations of this 'new exciting' lighting concept - which promises almost indefinite life, massive power savings and corresponding cost benefits - have been available since at least 2005, yet the widespread implementation of solid state lighting is still some way off.
Why is this? One of the main reasons is that in order to reap the benefits of LED technology there are factors to consider which are not immediately apparent to anyone who isn't an LED expert.
The end result is that while you can now walk into a DIY store and buy LED lamps and luminaires, many of them are of a fairly crude design which are unlikely to live up to the technology's potential. Consumers are often disappointed by the amount of light they produce and the rate at which defects emerge - and consequently horrified at the high price paid for them.
On the face of it, it appears to be a relatively straightforward task to replace an incandescent, halogen or fluorescent lamp with LEDs. However, this is not the case. There are several issues to consider.
Firstly, there is no direct LED equivalent for standard wattage bulbs, and also the appearance of the light itself is different - traditional bulbs generally emit a yellow white, whereas white LEDs are often produced in a range of colours. Although LEDs when correctly-specified can come very close to matching the colours of filaments and tubes, a more blue white is often chosen as it tends to produce the most impressive efficiency figures.
This is fine in certain applications but far from ideal in others, leading users to complain that the light from LEDs is cold and unfamiliar.
“For LEDs to become the preferred lighting solution across the board, the technology has to become simpler to use and easier to understand and apply”
A second problem concerns the nature of the fittings themselves. Filament bulbs only emit light when the filament reaches a certain temperature; therefore the bulb shape was designed for this purpose.
With LEDs - as in all semiconductor products - heat is a killer, so although there have been some very clever reverse-engineering solutions which have seen LEDs and associated semiconductor drive circuitry crammed into small bulb fixtures, thermal management challenges have often resulted in poor life and disappointing brightness levels.
Driver circuitry has been another issue: in an attempt to cut costs, far too many driver circuits have used bulky, electrolytic capacitors which can dry out and fail in warm environments, or due to the afore-mentioned thermal management problems.
Lastly, the optical performance of LEDS will vary considerably depending on how they are mounted, the steady-state temperature they reach, and how they are combined with lens/diffusion optics.
For LEDs to become the preferred lighting solution across the board, the technology has to become simpler to use and easier to understand and apply. Industry specialists such as OMC have formulated Light Engine technology to help customers make the most of solid state technology without having to learn all about driving and managing LEDs.
The company's Spectralux Light Engines are arrays of highly efficient, tightly-binned LED die material bonded to an aluminium or copper substrate with a phosphor coating.
In these designs the total chip area has been increased substantially and distributed optimally across the substrate surface to reduce current density while achieving more light output for the same drive current; optimising heat-dissipation and vastly increasing life-expectancy.
Either pre-encapsulated or post-encapsulated semiconductors are used depending on the optical design requirements of the light engine.
Chip junction temperatures are kept low and statistical models suggest that exceptional life expectancies of 40 years - or more in some circumstances - may be expected.