Fact or Fiction LEDs don稚 produce heat
An often-quoted advantage of LEDs is that they don稚 produce heat, and are cool to the touch. Fact or fiction?
In one sense this is true: LEDs are cool to the touch because they generally don't produce heat in the form of infrared (IR) radiation (unless of course they are IR LEDs).
IR radiation heats the enclosures and surroundings of incandescent bulbs and other sources, making them hot to the touch. The absence of IR radiation allows LED fixtures to be positioned in locations where heating from conventional sources would cause a particular problem e.g. illuminating food or textiles.
However, crucially, heat is produced within the LED device itself, due to the inefficiency of the semiconductor processes that generate light. The wall-plug efficiency (optical power out divided by electrical power in) of LED packages is typically in the region of 5-40%, meaning that somewhere between 60 and 95% of the input power is lost as heat.
The energy consumed by a 100-watt GLS incandescent bulb produces around 12% heat, 83% IR and only 5% visible light. In contrast, a typical LED might produce15% visible light and 85% heat.
Especially with high-power LEDs, it is essential to remove this heat through efficient thermal management. Without good heat sinking, the internal (junction) temperature of the LED rises, and this causes the LED characteristics to change.
