As the LED generates heat, the thermal design characteristics of the lamp itself come into play. The total amount of heat produced is actually relatively small - remember that total power consumption is typically less than 10 Watts and most of this is converted to light. Put your hand in front of a halogen light when it is operating, then do the same with an LED to appreciate this fully.

The problem is that the heat at the Thermal Junction is intense in a very small area and this area is critical to the performance and longevity of the LED itself. Many LED suppliers quote a generic 50,000 hour lifespan for the product, but this is normally calculated on the basis of a Thermal Junction temperature of 25 degrees Centigrade. Achieving a TJ temperature as low as this in an application is rare - it is normally only possible under laboratory conditions. The higher the TJ temperature, the faster the LED performance deteriorates.

The design of a good quality LED lamp will incorporate two main thermal design aspects. The first is a mechanism to draw heat rapidly away from the TJ. The second is a mechanism to remove the waste heat from the lamp entirely, to avoid heat build up. Primary heat transfer is normally achieved by the use of conductive materials to mount the LED to the main base substrate. This ensures that heat passes rapidly to the main thermal management system - normally either a heat sink or a heat pipe, or a combination of the two.

An ideal heat sink will have a very large surface area, with all surfaces exposed to an air flow. Consider car engine cooling systems, where a radiator has a very high surface area generated by the fins which make up its structure. Air is passed through the structure, either by the speed of the vehicle, or by a fan system. The heat sink on an LED must achieve a similar effect.

Many low cost LED lamps use die-cast heat sinks, which are cheap to produce, but are not very effective. The surface area is normally small and the bulk of material permits heat build up. Now look closely at a product such as the LightPlanet V3 GU10 bulb, which uses a very fine fin system and is therefore much more effective.

A further enhancement is active cooling, such as heat pipe and loop heat pipe technologies. This cooling technique, originally perfected for cooling processors in laptop computers, employs water evapouration and condensation in a closed pipe to carry heat away from its source. This is particularly effective in lamps which require a lot of light from a small area - a high light concentration - in such cases, the heat pipe can be used to transport heat far enough from the source to allow it to be dispersed in a cooler area. Our track lights employ heat pipe cooling to allow them to be used for retail lighting 24 hours a day without overheating.