Automotive LED Lighting - A Look to the Future

One of the key application areas driving significant growth in LEDs for illumination purposes is the backlighting of automotive displays. These TFT-LCD applications range from infotainment systems, gauge clusters and a wide array of instrument displays. Of course, backlighting these displays with LEDs creates some unique LED driver IC design challenges in order to optimize display readability across a myriad of lighting conditions. This requires LED drivers to offer very wide dimming ratios and high efficiency conversion while also withstanding the rigors of the relatively caustic automotive electrical and physical environment. LEDs are ten times more efficient at producing light than incandescent bulbs and almost twice as efficient as fluorescent lamps, including cold cathode fluorescent lamps (CCFL); thereby reducing the amount of electrical power required to deliver a given amount of light output (measured in lumens per watt). As LEDs are further developed, their efficacy, or ability to produce lumens of light output from an electrical power source, will only continue to rise. The extended operating lifetime of LEDs allows them to be permanently embedded into the end-application. This is especially important for the backlighting of automotive clusters, instrumentation and infotainment panels - which are often embedded into a vehicle's dashboard, since they will not require replacement during the working life of the car. Furthermore, LEDs also have the ability to dim and turn on/off much faster than the human eye can detect, enabling significant improvements in backlighting of LCD displays while simultaneously allowing dramatic contrast ratios and a higher resolution picture. Nevertheless, one of the biggest obstacles facing automotive lighting systems designers is how to optimize all of the features and benefits provided by this newest generation of LEDs. Since LEDs generally require an accurate and efficient current source and a means for dimming them, a LED driver IC must be designed to address these requirements under a wide variety of operating conditions. Further, their power supply solutions must be highly efficient, rugged and reliable while also being very compact and cost effective. Many emerging automotive designs use a single panel to backlight all of the display gauges for driver control. Often, the LED backlighting for the instrument panel is shared with the infotainment system, creating an easy to read all-in-one control panel. Similarly, many vehicles including cars, trains and airplanes also have LCD displays that entertain passengers in the rearward seat(s) with movies, video games and so forth. Historically, these displays have used CCFL backlighting; however, it is becoming more common to replace these relatively large bulb designs with very low-profile arrays of white LEDs to provide more precise and adjustable backlighting as well as an extended service life. In conclusion, the benefits of using LED lighting in an automotive environment has several positive implications. First, they never need to be replaced, since their solid state longetivity is in excess of 100K hours - equivalent to 11.5 service years, thereby surpassing the life of the vehicle. This allows automobile manufactures to permanently embed them into "in cabin" backlighting without requiring accessibility for replacement. Yes, the future is bright indeed for automotive LED lighting. www.linear.com