Conceptual Development of Automotive Forward Lighting System Using White Light Emitting Diodes 2009-01-0593

This paper focuses on redesigning the headlamp subsystem functional architecture. The design involves meeting three major functional requirements: Achieving the lumen requirements according to Economic Commission for Europe (ECE) 324 regulations, Meeting the illumination pattern, and Maintaining the Light Emitting Diode’s (LED) junction temperature at 90°C. White LEDs are considered in the design to satisfy the functional requirements due to their high lumen efficacy, compact size, and long life. These benefits, when compared to existing headlight systems benchmarked, present enough potential to warrant further conceptual virtual prototyping. The prototyping focused on solutions that allowed control of sizing and numbering of LEDs, illumination pattern limits, and temperature to achieve the multiple functions a dynamic headlight system. A primary challenge in this design is to maintain the LED’s junction temperature within a recommended operational range. A conceptual design is presented with metal foam meta-material which act as both a heat exchanger to maintain the LED’s junction temperature and a structural member. The metal foam design also exploits the environmental conditions of the vehicle operation to meet the desired functionality. An analytical thermal model is used to predict the LED’s junction temperature, thus allowing for optimization of the metal foam constituent properties. A finite element model is developed to view the thermal affects of an LED on adjacent LEDs. The results of the finite element model are used in conjunction with an optical analysis to determining any LED arrangement pattern restrictions and limitations. The number of LEDs required is derived from the lumen requirements set by ECE directive while including lumen deficiencies. Finally, the results of the individual model are integrated to meet the functional requirements of the headlamp subsystem.