Lighting is the new chrome, turning vehicles into status symbols.

By Thomas Ulinski, Vice President of Product Marketing North America at Rutronik

Back in the day, any car considered a luxury vehicle had to have shining chrome. Today, lighting is the new chrome, turning vehicles into status symbols. LED technology has made this possible.

Unlike chrome, light can perform many different functions. Inside vehicles, depending on the brightness and color, it can influence the occupants’ emotions, making them feel at ease, comfortable, and less stressed, or cheered up and encouraged. Cognitive abilities can also be improved with light, preventing drivers from tiring as quickly and helping them to concentrate better.

An HMI system may also be useful for ensuring that the lighting color matches the driver’s physical and emotional condition.

Out of the comfort zone

While interior LED lighting was initially only used in luxury models, and purely as a comfort factor, it is now commonly used in mid-class vehicles. The main objective here is to establish LEDs as a functional feature for enhancing safety. Warnings when an object is too close, for example, are more readily noticed when shown in red light. Information on the status of the vehicle or incoming phone calls can also be elegantly communicated via LEDs to be quickly interpreted by the driver. Technical evolutions offer even more artistic and application opportunities. For example, LED strips can be integrated on flexible PCBs designed for challenging conditions along the edges of the roof and in the seating upholstery.

Dynamic light for limited space

For applications like the center console, a multi-channel driver such as the E521.38 from Elmos is recommended. The E521.38 is bus-controlled
and can drive four RGB- LEDs, even six when using multiplexing. Developed in accordance with ISO 26262 for ASIL-B applications, it can be used for functional safety systems. Its DFN18 package with wettable flanks helps make inspections easier. The differential digital interface makes it the leading choice for dynamic ambient lighting because, unlike other bus systems and large bus arrangements, it doesn’t cause lag effects resulting from insufficient data transfer rates. This means that consistent color displays and movements are guaranteed.

Adjustable light for every mood

For smaller LED modules, the E521.39 LIN-RGB/W driver is ideal. Controlled via LIN- bus, it is best for adjustable ambient lighting with hard or slow color transitions. The E521.39 has flash memory, which enables field firmware updates. It can withstand a supply voltage of up to 40V and has a low maximum idle current draw of 30μA. Thanks to a 12-bit ADC, it also offers high-resolution temperature measurement. The LED driver can use this to have the software compensate for aging and temperature effects.

The E521.38 multi-channel driver uses an integrated pulse width modulation (PWM) generator to generate a frequency of 1,000Hz with full 16-bit pulse width resolution. The E521.39 provides up to 700Hz with the same resolution. This puts them well above the requirements of the automotive OEMs, which specify 500Hz in their respective standards to ensure an absence of flickering in interior lighting. Elmos’ LED drivers are available from Rutronik, as are other ICs that can be used to create optical applications for HMIs, such as non-contact gesture control systems. Rutronik, as a  broadline distributor, can also supply all other electronic components needed for innovative ambient lighting.