One of the most important things when
planning with LEDs.
The temperature has a great influence on light output of a LED. Why? The colder the environment, the more efficient the LED works. Cold locations are more ideal.
That is why LEDs can be used in outdoor lighting or as a light source for cooling rooms.
High temperatures, however, have a negative effect on the light output. The service life may be shortened. Serious manufacturers specify an ambient temperature for their LEDs at which the luminous flux and service life of their LED lights and modules can be achieved.
Unlike incandescent or halogen lamps emitted the light from an LED is not warm, but as with other lamps also diodes only set a part of the energy into light - heat is generated inside of the semiconductor. This heat has to be dissipated so the LEDs can work more efficiently and achieve a long service life. This is especially important for LEDs that operate with high operating current.
LEDs do not fail. Their light intensity decreases over time. The service life (L) of a LED must be defined for each application. The end of service life is reached when the LED is only 70 percent (L70) or 50 percent (L50) emits the light flux was measured at the beginning. The end of service life is reached when the LED ony emits 70 percent (L70) or 50 percent (L50) of the luminous flux that was measured at the beginning. The service life of a LED depends on the ambient and operation temperature. The graphic shows: if the LED is operated at a higher temperature (Tc1) or with poor thermal management, its service life is shortened.
Different types of "cooling" (heat
For heat dissipation provides the so-called thermal management. The heat is dissipated through board and lamp housing (= passive cooling). A large-scale, fixed connection between the circuit board and housing aids in heat dissipation. In some lighting models bigger fin surface, thereby reducing the temperature at different building types and air or water cooling (= active cooling) are used. The optimal cooling, however, provides for high performance LEDs currently passive 2-phase hybrid cooling. This form of cooling transmits the heat through evaporation and condensation of a working medium in a vacuum. Thus, the heat dissipation compared to copper and aluminum heat sinks is increased by 100 times. As a result, lights can be operated at higher ambient temperatures and with considerably longer.