LED Junction Temperature Measurement and its Applications to Automotive Lamp Design

There are more and more LEDs being used in an automobile to replace the incandescent lamps. All those applications require high brightness LED work at high ambient temperature. However, the luminous flux output of a LED is directly related to its junction temperature. Higher the LED junction temperature, lower the luminous output from the LED. In order to efficiently apply LED to an automotive application the temperature effects on luminous flux must be accounted for in any design of a LED assembly. A LED junction temperature measurement system is described in this paper to measure the differential junction temperature between a reference LED and the LED under test. And the results are used to improve the LED assembly design.