Improving automotive lighting designs with high-performance LED drivers

The market size for high brightness (HB) LEDs is expected to reach $12 billion in 2012 and grow to $20.2 billion by 2015 with a 30.6% CAGR ramp (source: Strategies Unlimited). One of the key application areas driving this significant growth in LEDs is their use in automobile designs. Applications range from headlights, daytime running lights, brake lights and turn signals, to instrument cluster display backlighting, as well as all kinds of in-cabin vanity lighting.

Almost all new model cars offer LED daytime running lights (DRLs) due to customer demands for stylistic preferences and safety benefits. Honda’s 2013 Accord uses LED DRLs in most models and offers LED headlights in both their touring and hybrid models (see Figure 1). In order to maintain this impressive growth rate, LEDs must not only offer enhanced reliability, reduced power consumption and more compact form factors, they must also enable 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, headlamp specific applications are relatively new. Currently, only a handful of production vehicles are offered with LED headlamps, including the Honda Accord, Audi A8 and R8, Lexus’s LS600h and RX450h, the Toyota Prius, Cadillac’s Escalade and Porsche's Cayenne. Some industry estimates indicate that the current LED headlamp market is approximately $1B for 2012 and is expected to surpass $2B by 2014 and continue to grow exponentially.

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 require an accurate and efficient DC current source with a means for dimming and must offer a variety of protection features. Additionally, these LED driver ICs must be designed to address these requirements under a wide variety of conditions.

As a result, power solutions must be highly efficient, robust in features and reliability while being very compact and cost effective. Arguably, the most demanding applications for driving HB LEDs  are found in automotive forward lighting applications, in both DRLs and headlamps as they are subjected to the rigors of the automotive electrical environment, must deliver high power, typically between 15W to 75W, and must fit into very space constrained enclosures, all while maintaining an attractive cost structure.