Automotive headlamps demand buck-boost LED drivers

May 29, 2013 // By Jeff Gruetter, Linear Technology
LED penetration in vehicles is increasing, but in the headlamp domain, conventional lighting techniques so far defend their dominance. High-brightness LEDs can be deployed in this application field - as long as certain design constraints are taken into account.

Background

The very definition of an automobile is in more flux today than ever before. For the last century, it has been dominated by internal combustion drive trains, mainly gasoline powered with a smattering of diesel drive trains. However, we now have automotive drive trains ranging from purely electric (EV) to high efficiency internal combustion, to a myriad of combinations (commonly referred to as hybrids). All of these designs share a common goal of increasing fuel efficiency while simultaneously reducing carbon emissions. New power train designs include direct fuel injection, turbo charging, engine stop/start systems, regenerative braking, higher ethanol content fuels and cleaner diesel combustion. As more hybrids are developed, they are becoming much more dependent on cleaner electric power sources. Despite this level of progress, one aspect of their designs has remained relatively constant, and that is the need to provide forward illumination for driving at night and in less than perfect weather conditions. Furthermore, the means to generate the required light illumination has also evolved from Halogen lamps to High Intensity Discharge (HID) Lamps to most recently high brightness (HB) LED based designs, fueling yet another avenue for HB LED growth.

The market size for high brightness (HB) LEDs is expected to reach $12 billion this year 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 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. However, in order to maintain this impressive growth rate, LEDs must not only offer enhanced reliability, reduced power consumption and more compact form factors, but 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

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