Driving Greater Performance and Safety from Advanced Automotive Lighting
June 27, 2017
|By: Yin Wu
Automotive Business Manager, Maxim Integrated
According to Car and Driver, automotive lighting "is at its most transformational stage since the U.S. government deregulated rectangular and round sealed-beam units in the mid-'80s." The publication notes that the NHTSA and IIHS will begin considering headlamp performance in their overall new car ratings by 2019.
The emergence of LED lighting technology has paved the way for more beautiful headlamp designs, not to mention brighter, smarter, and more energy-efficient lights. LED matrix headlights (which currently aren't approved for cars in the U.S., although automakers are pushing for approval) open up even more options with their ability to actively shade and illuminate sections of the road. Matrix lighting, when backed by smarter software and sensitive infrared cameras, can also illuminate pedestrians while blacking out their faces, or brighten speed-limit signs without overwhelming the scene with bright light, according to Car and Driver. As lighting technologies have grown more sophisticated, headlamps have become important parts of automotive safety and advanced driver assistance systems (ADAS).
Designing automotive LED lighting comes with challenges that, if not addressed, can severely impact performance. For example, in high-brightness (HB) LEDs, inherently high switching frequency can result in electromagnetic interference (EMI) that degrades or inhibits circuit performance. In matrix lighting, LED drivers and controllers are challenged when switching LEDs at high speeds, which can cause overshoots and undershoots in current. Also, matrix lighting applications have a lot of LED lights in a densely concentrated area, making EMI particularly tough to eliminate. Car makers end up spending a lot of time, money, and effort lowering EMI via experimentation with different layouts and filtering methods. Left unchecked, EMI can hamper performance of the lighting as well as other automotive sub-systems, such as the radio or anything with a high-speed link. Ironically, though, some techniques for minimizing EMI—the levels of which are required to meet automotive regulatory specifications—can actually induce flickering.
Maxim's newest automotive-grade controller—the MAX20078 synchronous buck, high-brightness LED controller—addresses these design challenges, driving higher performance for automotive lighting systems.
Simplified Design, Better Lighting Performance
The MAX20078 is the market's only LED controller that delivers both fast response time and low EMI for exterior LED lighting and improved safety applications. The controller is ideal for matrix lighting designs, enabling designers to achieve high performance and fast time to market while easing the design process. Switching LEDs at fast speeds is difficult yet essential for high performance of advanced lighting applications. Many parts aren’t able to handle such switching speeds, but this is an area where the MAX20078 excels. The driver also:
- Removes the trade-off between low EMI and fast LED switching speeds, with one-clock-cycle response time and nearly fixed frequency for easier prediction and reduction of EMI
- Shorts/opens LEDs while maintaining current regulation, which is ideal for matrix lighting applications
- Eliminates the need for compensation components
- Offers wide dimming ratio
- Features integrated fault protection and monitoring circuitry
With these capabilities, resulting designs can deliver brighter, more constant lighting with better efficiency and directional control. Hysteretic bucks are another option to deliver this performance level, but they come with variable frequency that makes designs more complex. With hysteretic parts, the more you switch the LEDs in and out, the more the frequency will fluctuate, causing EMI challenges that will add to the bill of materials (BOM) cost. Using the MAX20078 simplifies designs because it eliminates the need for compensation components, integrated fault protections, and monitoring circuitry.
Maxim's newest automotive controller offers an ideal option for a variety of applications such as front and rear lighting, high beams, low beams, daytime running lamps, heads-up display, and turn signals. A MAX20078 evaluation kit is available. With automotive lighting playing such an integral role in the safety of drivers, passengers, and pedestrians, continued advancements in LED lighting technology is welcome news.