Impact of radiation in LED automotive lighting design

Guoliang XIE¹, Ying LEI¹, Ling DAI ¹, Stephane Albin² , Christine Roucoules²,

^1, Valeo Lighting Systems China Technical Center

41 Chuangye road, WEDZ, 430056 Wuhan, China

^2, VLS 34 rue saint Andre Bobigny 93102 France

Email: guoliang.xie@valeo.com, ying.lei@valeo.com, ling.dai@valeo.com, stephane.albine@valeo.com, christine.roucoules@valeo.com,

Abstract

LED lighting function has become a main stream for premium and compact vehicle since first full LED headlamp was introduced in the worldwide market in 2008. LED Headlamp is in constant evolution to achieve performance and original light shape through the creation of new optical elements or combination of multiple elements. To maintain LED performance and product reliability, heat management of LED and design of the cooling system through simulation has been the main challenge during design.  However with increasing need of optical performance or application of new technology such as laser diode, the contribution of LED optical emission to the heat dissipated is becoming a need for material choice.

In this paper, the impact of the radiative emission of LED on the material choice of lighting system is investigated through simulation. The paper will present first an overview of the LED optical emission contribution, and the different radiative models used in simulation to predict material limit. Different LED sources are used in this study from a range of 1W to 5W.  The impact of those sources on different materials in a confined environment representative of a headlamp is evaluated. Comparison between discrete ordinate, grey model and ray tracing model on the material temperature for different optical emissions is done.  The study shows the ray tracing model has a most significant effect on the material temperature depending on the aspect of the material and proximity of the source.  An application of this correct radiation model with conduction and convective thermal simulation shows the benefit for accurate material choice on LED new optical system. The use of appropriate radiation model in the development of new Valeo LED lighting system enables to insure a more robust design to met customer quality.

Keyword: Radiation, Simulation, Ray tracing, Automotive lighting, LED