When run continuously at temperatures above 80°C, the LED can fail in less than 10,000 hours. At temperatures near 80°C, the light output falls off rapidly in the first 10,000 hours. But, thereafter, the LED continues to generate a reduced light output for long. At more moderate temperature levels, the LED produces a relatively consistent light output over its entire lifetime.
Although LEDs have evolved to become very efficient sources of light, every LED system design is a tradeoff between light output, efficacy and heat-sink design. It may be necessary to drive a power LED at a reduced power level to meet temperature and heat-sink design requirements. Furthermore, packaging requirements of the lighting fixture might limit the ability to provide good heat-sinking.
 [stextbox id=”info”]The most common method for dimming in large installations is analogue 0-10v DC control. it can be incorporated into the design using an analogue-to-digital converter (ADC) channel.[/stextbox]
Power LEDs with power levels exceeding 3W have become widely available. However, it is still easier to meet thermal design requirements using multiple smaller LEDs in the 1-2W power range. Furthermore, greater efficacy can be obtained when the LED is driven at a lower current. LED system designs will continue to become more practical as the efficacy of the LED is increased.
