Feature Rich LED Driver ICs: Enable High Power Automotive LED Headlamps

October 22, 2014 // By Jeff Gruetter, Linear Technology
The market size for high brightness (HB) LEDs is expected to reach $20.2 billion by 2015 (source: Strategies Unlimited). One of the key application areas driving this growth is the LEDs used in automobile designs. Applications range from headlights, daytime running lights and brake lights; to instrument cluster display backlighting, as well as all kinds of in-cabin vanity lighting.

This impressive growth rate is driven by not only by LED's high reliability, reduced power consumption and more compact form factors, but also by enabling innovative designs such as steerable headlights and antiglare dimming. Furthermore, in an automotive environment, all of these improvements must be optimized while also withstanding the rigors of the relatively caustic automotive electrical and physical environment. It goes without saying that these solutions must offer very low profile, compact footprints while simultaneously enhancing overall cost effectiveness.

Although LEDs have been used in daytime running lights, brake lights, turn signals and interior lighting for several years; it’s relatively recent that a handful of headlamp specific applications have emerged such as the Audi A8 and R8 and Lexus’s LS600h. However, in the past year, several automotive manufacturers have introduced LED headlamps in their most popular models. In 2014, Toyota offered LED headlamps in their bestselling car, the Toyota Corolla as seen in Figure 1. Additionally, several other models of Toyotas, Hondas, Nissans, Porsches and Audis offer LED headlamps in most of their upcoming models. Most estimate that the current LED headlamp market will surpass $3B in 2014.

Figure 1. 2014 Toyota Corolla LED Headlamp

One of the biggest challenges for automotive lighting systems designers is how to optimize all the benefits of the latest generation of HB LEDs. HB LEDs generally require an accurate and efficient DC current source and a means for dimming. The LED driver IC must be designed to address these requirements under a wide variety of conditions. As a result, power conversion solutions must be highly efficient, robust in features and reliability while being very compact and cost effective. Arguably, one of the most demanding applications for driving HB LEDs is found in automotive headlamp applications as they are subjected to the rigors of the automotive electrical environment, must deliver high power (typically between 50W to 75W) and must fit into thermally and space

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