Principles of LED technology
A light-emitting diode (LED) is a semiconductor component. LEDs are tiny electronic chips, about one millimetre in size, made from special semiconductor crystals. The chip emits light when electricity is passed through it. The LED chip is protected by a layer of plastic and rests on a thermally conductive element. Heat formation and reaction to changes in temperature Unlike light bulbs, light-emitting diodes don’t emit thermal radiation and give off hardly any heat in the form of IR light. However, as 50–80% of the energy produced by an LED takes the form of heat, and 20–50% the form of light, this heat has to be dissipated elsewhere, with active or passive cooling systems. Unlike HIT lamps, the working life and luminous efficacy of LED lighting do not decrease as temperatures go up. This means that effective thermal management is required in order to maintain the luminous efficacy and life expectancy of LED lights.
LEDs have an extremely long working life! While light bulbs fail after around 1,000 hours and HIT lamps after around 12,000 hours, high-performance LEDs have an average working life of 50,000 hours or more. This means that an LED lamp left on for 10 hours a day, 6 days a week, would last for around 16 years. This reduces the cost of swapping the lamps. LED lamps don’t suddenly stop working completely at the end of their lives. Instead, the intensity of the light decreases as time goes by. On average, LEDs still emit 70% of their original luminous power after 50,000 hours of use (L70 rating). One significant advantage of LEDs is that their luminous flux remains relatively constant over the course of their working lives, while the luminous flux of standard HIT lamps goes down to up to 60% of the original level after just a few months.
Swapping light sources
One point of note is that swapping LED light sources is more complicated than it is for conventional lights. LED modules are frequently built into the light in such a way that the entire light has to be changed at the end of the LED’s working life. The Zhaga standard defines mounting specifications that enable interchangeability of LED modules made by different manufacturers.
Luminous efficacy and luminous flux
LED technology is developing rapidly, which reflects its origins in the dynamic semiconductor industry. Luminous efficacy, measured in lumens per watt, has improved substantially in recent years and will continue to get better. The luminous efficacy of a warm-white LED has now reached around 115 lm/W, on a par with an HIT lamp. As a comparison, the luminous efficacy of a light bulb is 11–13 lm/W.
Colour rendering, light quality and energy consumption
In order to provide an alternative to traditional HIT lamps, LED lamps need to provide a colour rendering index (CRI) of 90, at a warm light colour of 3,000 kelvins, a luminous flux of around 4,000 lumens and a system output of < 40W. LED modules that meet these criteria have been on the market since 2013.
Quality features of LEDs
A strict selection process (binning) is required during production in order to achieve a consistent level of quality in terms of light colour and brightness. MAX FRANKE only works with selected, established LED manufacturers capable of supplying both the LED module and the ballast as a single system. This makes it possible to arrange system guarantees. Advantages of LED technology
Advantages of LED technology