One of the main properties affecting the LED lifetime is the junction temperature. Without any feedback on the LED junction temperature or environmental temperature the feed current levels has to be rated with large margin to ensure safe operation area. However depending on the environment the led current and therefore the light level could be significantly higher if there would be a temperature feedback. A led module with thermoelectric cooler and an electric junction temperature measurement was developed. The module includes four LEDs, their electronic controller and a Peltier cooler. The test setup includes a heat sink and a cooling fan. This setup gives possibilities to create higher light levels with safe temperatures in variable environments or even high temperature environments. The direct feedback on the junction temperature can be utilized as temperature monitor or temperature limiter. When the temperature reaches the allowed limit, the cooler can be utilized for keeping the temperature at safe levels for ensuring desired LED lifetime. The temperature measurement is based on measuring the LED forward voltage during short 200 us constant low current pulses fed to the LED every 20 ms. The junction temperature is a function of the measurement current level and the junction temperature. The measurement is used for controlling the cooler and limiting the temperature rise at the LED junction.
|Title of host publication||Book of Abstracts|
|Subtitle of host publication||ICT/ECT 2012, The 31st International & 10th European Conference on Thermoelectrics, July 9th-12th, 2012, Aalborg, Denmark|
|Publication status||Published - 2012|
|MoE publication type||Not Eligible|
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