Thermal management of LED system for automotive lighting

Guoliang XIE¹, Yezhi Sun²,

^1,2Valeo Lighting Systems China Technical Center

41 Chuangye road, WEDZ, 430056 Wuhan, China

Email: guoliang.xie@valeo.com, yezhi.sun@valeo.com

Abstract

In automotive lighting, LED technology is not only applied for signaling function, but also for lighting function thanks for the development of semiconductor technology. Especially nowadays, LED lamp becomes a main stream for high-end vehicle since first full LED headlamp was in the worldwide market in 2008. The main advantage for LED lamp includes CO₂ reduction, new styling concept, more compact product, security increase, long life time product etc. In contrast, the well known disadvantage is LED performance and LED life time strongly depends on the junction temperature of LED.

In order to predict the junction temperature and LED performance in different working conditions, a systematic thermal management was applied in lamp design. The thermal chain theoretical analysis, thermal resistance for LED heat dissipating system including LED, PCB, interface, and heat sink was studied firstly. Then CAD integrated CFD software numerical thermal simulation for LED subsystem was performed. It allows to quick evaluating the LED flux performance in stationary regarding the optical request for regulation. Furthermore, in order to take the real confinement of the lamp, and other heat source into account, a complete CFD numerical thermal simulation was done also. Finally, experimental temperature and flux measurement was performed in free air and in product to validate the simulation method. Both LED subsystem in free air and in headlamp have been correlated within 5 °C, the flux difference between simulation and measurement is also acceptable, which conclude the CFD thermal simulation is essential step in thermal management of LED system for automotive lighting.

Keyword: Thermal management, Thermal chain,  Automative lighting, LED, PCB