Bench Talk

As High Intensity Discharge (HID, xenon) and LED technologies are the only truly modern vehicle light sources, unless you own a luxury vehicle chances are you (like me) are missing out actually being able to see well into the night. The difference between what these two technologies and 50-year-old quartz-halogen bulbs deliver is like night and day. Fortunately, thanks to the dramatic advances and reduced cost of high-brightness LEDs, high-performance forward lighting is now about to be available to the rest of us.

HID lighting has never broadly made its way down to the mid and lower levels of vehicle manufacturer’s product lines for several reasons. They are expensive to manufacture, produce less light output with age, and some use radioactive substances as well as mercury (a heavy metal), which present disposal problems. When they first appeared (and even today) drivers complained loudly about glare. HID lights are still offered but are about to succumb to the siren song of high-brightness LEDs.  

Until recently, high cost, available brightness, and other factors kept LEDs from service as forward lighting sources. However, huge advances in LEDs, power management, and other LED-related factors and a consistent reduction in cost are allowing the auto industry to focus on them as a wholesale replacement for all other forward-lighting types.

As usual, the first car with LED headlights was a luxury car, the 2007 Lexus LS 600 sedan, which used them only for the low-beam, followed by the Audi R8 that uses LEDs for high- and low-beams. Also as usual, U.S. regulators were slow to approve the use of LED forward lighting. That problem solved, the path in the U.S. was wide open for what LEDs can do, not just in terms of affordability, brightness, and efficiency but the ability to more effectively solve the problem of glare.

For example, Mercedes-Benz and BMW combine them with adaptive high-beam functionality and other features – and 2013 Audi R8 set a new standard by incorporating digitally-controlled adaptive high-beams in a matrix array of 25 LEDs, the first car to split the beam so that it would present both a highly visible path for the driver but a less-intense beam for oncoming vehicles. (Could Texas Instruments’ TPS92661-Q1, the LED matrix manager for automotive headlight systems be involved?)

Figure 1: TI's TPS92661-Q1 device is a compact, highly-integrated solution for shunt FET dimming for large arrays of high-brightness LEDs in applications such as automotive headlights.

So, thanks to the aforementioned advances, LEDs will appear in 2017 models of lower-priced vehicles, rendering all other types of history…for now. That’s because laser diodes demonstrated in Europe have even greater potential than LEDs. Laser headlights can be up to 1000 times brighter than LEDs while consuming half the power, are about 100 times smaller than LEDs (which allows hundreds of them to be used to create the headlight even while reducing its size), are less deep (requiring less rearward space), and provide better illumination in fog as their light is less diffused, which actually reduces glare. Maybe laser diodes will be in the newer luxury cars while the rest of us have LEDs. But LEDs have made a huge leap in technology after decades of regular old headlights, and that’s just fine with me.