Automotive LEDs Deliver Greater Design Flexibility for Safety, Style and Efficiency
LED lighting has been making major inroads into the automotive market for two key reasons: safety concerns and energy consumption. Aesthetics also have played a major role, driven by consumer demand and growing requirements for vehicle differentiation in a very competitive sector. In fact, one of the most popular trucks in the U.S., the Ford F-150 for model year 2015 will be the first pickup with a complete forward lighting solution from OSRAM Opto Semiconductors, giving the vehicle a brand-new appearance. This lighting system includes dipped-beam and high-beam headlights, turn indicators, parking lights and control module. While meeting all durability requirements, it also consumes less energy than conventional lighting technologies.
There are a variety of new applications driving LED demand, including enhanced night vision, head-up displays, daytime running lamps (DRLs), and advanced forward lighting systems (AFS). With continued improvements in LED technology, automotive suppliers are finding that they can deliver greater visibility to meet safety concerns and higher efficiency to lower energy consumption in many lighting systems throughout the vehicle. Other benefits of LEDs include longer life, high vibration resistance, smaller packaging and greater design flexibility for different shapes and sizes.
The global automotive lighting market, comprised of halogen, xenon/HID and LED technologies, is forecast to reach $33.22 billion by 2020*, according to a report from MarketsAndMarkets. The report cites three major reasons for the growth: mounting concerns for road safety, new lighting legislation and higher efficiency of automotive LED technology. There is also increasing consumer demand for new advanced technologies including AFS and DRLs.
Innovative applications for LEDs in automotive
Today LED lighting can be found throughout the exterior and interior of vehicles. In exterior applications, LEDs are used in headlamps, DRLs, rear-combo lamps, turn signals and stop lamps, while interior applications range from head-up displays to varying indicator lamps. As LED technology continues to improve, so do new opportunities for LED adoption, particularly in headlight and DRL applications. A European Union (EU) regulation that calls for all vehicles to have DRLs is expected to significantly drive the adoption of LEDs. Daytime running lights were adopted to improve visibility during the day and to eliminate the use of more power-hungry low beams. LED DRLs are said to require about 90 percent less power than using low beams. Here in the U.S., while not a legal requirement, car makers continue to add DRLs due to design and styling factors. In addition to safety regulations, another reason for LED adoption is energy efficiency thanks to stricter carbon emissions regulations by the EU.
One innovative LED that addresses both issues – safety and efficiency – also simplifies the implementation of advanced forward lighting systems. The OSRAM OSTAR Headlamp Pro adapts the illumination direction to the direction of the curves in the road when driving. The configuration for forward lighting is a bit different than other applications, so that is where devices like the multi-chip OSRAM OSTAR Headlamp Pro come into play. The five chips in the multi-chip LED can be individually controlled, which means they can be switched on and off according to driving conditions and position of other road users. A distinct bright-dark contrast of 1:65 between illuminated and non-illuminated chips is required so the light beam on the road is optimally transmitted, which means the concealed chips must be genuinely dark and must not be illuminated by their adjacent chips. An integrated shutter is included to enable a clearly defined light beam from the headlight.
Fig. 1: The multi-chip OSRAM OSTAR Headlamp Pro is designed specifically for advanced forward lighting systems.(Source: OSRAM Opto Semiconductor)
A staple of elegance in luxury cars
Styling is also important for car buyers. The look of the vehicle’s exterior and interior is a large part of the attraction by consumers, particularly for buyers who are not on a budget. LEDs are being used in passenger cars today and can be found in most luxury vehicles.
“If the look of the vehicle drives the consumer to the showroom, the interior is what really seals the deal,” said Mike Godwin, director of visible LED products in North America for OSRAM Opto Semiconductors. “I don’t think you can find one luxury brand without an LED, whether it is for DRLs, tail lights or some type of high-beam/low-beam combination of LED lights.”
Godwin noted that the adoption of LED technology in vehicles generally varies by geographic market. For example, the DRL regulation in the EU is tied to efficiency and carbon dioxide emissions, resulting in the adoption of LEDs because they are more efficient than the incumbent halogen technology.
Typically, automotive LED lights are not high-power LEDs. They generally use 0.5 watt white LEDs that can be used as “signature” lights, creating a line of light along the shape of the vehicle. One example is OSRAM’s Advanced Power TOPLED LEDs. These devices use a larger chip for more light output and deliver better thermal performance.
Also delivering better thermal performance is the Super 0.5 watt PLCC-4 surface-mount LED from Avago Technologies that can be used in a number of exterior automotive lighting applications including DRL, rear-combination lights, number-plate lights and turn signals. Offering higher-flux output, the PLCC-4 devices are available in cool white or warm white. These devices can be driven at higher current due to their package design and can dissipate heat more efficiently compared to the Power PLCC-4 SMT LEDs. In signaling applications, Avago also offers the standard PLCC-4 package with additional heat sinking so it can be driven at higher current along with high brightness and a wide-viewing angle. Examples include the PLCC-4 Mono Color series, PLCC-4 with lens Mono Color Series, Super 0.5 watt power PLCC-4, and Envisium power PLCC-4 surface-mount LEDs.
The efficiency and unique capabilities of the LEDs are also fueling innovation and new applications in vehicles. One example is adaptive driving beam (ADB), which allows for partial headlight dimming when there is oncoming traffic to reduce glare while still providing driver visibility. This function is primarily found on luxury models, including Mercedes and Audi in the EU, but not in the U.S., due to government regulations.
The digital nature of LEDs is driving adoption as well, lending it to new applications and making the vehicle more efficient. “Digital control means energy savings. Vehicle architectures are being designed to take energy efficiency into account, where you can take advantage of the LEDs by dimming or shutting them down when they are not needed. It helps vehicle designers manage their power budgets when they have to look at those constraints,” Godwin added.
As an example, OSRAM’s converted yellow (ceramic conversion) technology called Oslon Signal delivers a typical brightness of 100 lumens at an operating current of 350 mA thanks to OSRAM’s UX:3 chip technology in combination with a highly efficient, thermally stable ceramic converter on the blue chip that does a better job of heat dissipation. The LEDs can be used in turn signals, as well as traffic lights and warning lights.
More color options
Not to ignore interior applications, colors are playing a bigger role in the interior of the vehicle and LED improvements are paving the way. For example, OSRAM’s RGB MultiLED series delivers a very broad blue color range with a wavelength of up to 447 nm (nanometers) and high brightness. At 370 mcd (millicandela) the blue is much brighter than in other multi-chip LEDs on the market. And even deep saturated blue tones can now be produced thanks to the use of three LED chips in red, green and blue (RGB). Other features include an integrated ESD protection diode and improved corrosion resistance.
The three independently controlled LED chips in the MultiLED are available in different brightness groups thanks to binning. The MultiLEDs deliver high-luminous intensity. For example, in the upper blue wavelength range, up to 560 mcds is achieved at an operating current of 20 mA. In addition, it’s housed in a standard SMT package measuring
3.3 x 3.0 x 1.8 mm
Another interior lighting example comes from Avago Technologies. The company offers a series of PLCC-packaged (PLCC-2/4) devices for interior applications. These include the Super 0.5 watt Power PLCC-4 series of LEDs in a small 3.2 x 2.8 x 1.9 mm form factor, delivering high-intensity brightness with optimum flux. For interior backlighting, some choices include the PLCC-2 (flat top) and PLCC-4 (flat top, 30° lens, 50° lens), long-life white PLCC-4 surface-mount and mini PLCC-2 SMT LEDs (blue, green, white). With 30° and 50° lens versions, these products can be used for center high-mounted stop lights (CHMSLs), displays and traffic lights. The external reflector makes them easy to implement with light pipes or light guides for larger area backlighting.
As LED technology continues to improve in areas of efficiency, thermal management, packaging and phosphor technologies, they will continue to enable reliable, highly efficient products for the automotive environment, while driving innovative and creative lighting vehicle applications.