Animated lighting in vehicle designs
01 November 2021
Melexis MeLiBu animated lighting applications
Solid state lighting has proven to be of enormous benefit to the automotive industry, enabling substantial operational improvements over previously used incandescent bulbs. These improvements can be seen right across reducing the power consumed by vehicle lighting systems, expanding the prospective functionality that may be supported & achieving far greater reliability levels.
This article was originally featured in the November 2021 issue of EPDT magazine [read the digital issue]. And sign up to receive your own copy each month.
Here, Michael Bender, Product Line Manager for Embedded Lighting at microelectronics engineering company, Melexis explores the scope for high-speed animated lighting in vehicle designs – and the technology needed to enable it…
Though at first, solid state lighting implementations tended to mainly focus on higher end car models, uptake has become more widespread in recent years – with even economy models reaping the rewards. A study conducted by analysts at market intelligence provider, TrendForce concludes that this technology is now employed in over 53% of new passenger cars, and 85% of new electric vehicles (EVs). It projects that these figures will have reached 60% and 90% respectively by the end of 2021.
The breadth of applications being addressed via solid state illumination is likewise increasing, with LED-based lighting solutions being pivotal from both a safety and comfort perspective. Such technology can also prove to be an important differentiator for manufacturers – allowing them to enhance the internal or external aesthetics of their vehicles, helping make them more visually appealing to potential buyers.
The ability to go beyond static lighting and implement more complex dynamic arrangements is something that many leading vehicle brands are now looking to explore. Multi-colour ambient illumination is already becoming popular. This enables vehicle occupants to alter the lighting hue and intensity within the cabin, so that it can be aligned with their own personal preferences. This may be easily adjusted as their mood changes. Now, however, there are opportunities to take things even further, with more sophisticated animated lighting being incorporated into the latest car models.
Melexis MeLiBu animated lighting interior applications
Emergence of animated lighting
Examples of the various different ways in which animated lighting technology can add a higher degree of vibrancy to vehicle designs are shown in Figure 1. Among the wealth of possibilities are animated turn indicators, daytime running lights, logo badges and steering wheels. All of these will make vehicles featuring them stand out – and manufacturers appreciate that this will give them a clear competitive advantage, through which they can look to grow market share. As well as allowing upgrading of the aesthetic dimension, animated lighting is certain to have a vital role to play when it comes to the wellbeing of road users. By placing greater visual emphasis on any safety-critical situation occurring, it will mean that the driver can be alerted quicker, so that evasive measures are taken and the risk of injury averted.
Installation of animated lighting technology
Access to exciting new lighting effects, such as the ones described herein, will of course result in system complexity levels being raised. This will, in turn, place strain onto the supporting in-vehicle networking infrastructure. The legacy controller area network (CAN) and local interconnect network (LIN) communication protocols on which many cars still rely are unfortunately not likely to be up to the job. In simple terms, the LED implementations required for animated lighting functions will be on too great a scale for CAN and LIN to cope. There will be so many different LEDs involved, and they will be changing colour at such a rapid pace, on too frequent a basis, for these protocols to control them efficiently. These protocols would only be able to deal with animated content rendered on relatively small LED matrices, moving at a relatively slow speed – and that will not be enough to gain the interest of the customer base. Consequently, an alternative approach must be found.
The CAN Flexible Datarate (CAN-FD) protocol offers superior performance parameters to conventional CAN. It is capable of delivering sufficient bandwidth to support animated lighting. However, because of its architecture and related requirements, it is just too expensive to justify. That poses a problem for vehicle manufacturers, as they do not want to have to restrict animated lighting to just luxury models. Ideally, they want it to be possible to deploy this innovation across the whole product portfolio. Also, it should be noted that even CAN-FD would have problems when it comes to handling the number of drivers necessary for larger scale LED matrices.
With opportunities to make serious revenues in this emerging market, the number of companies producing RGB-LED matrices for automotive usage is growing dramatically. This presents yet another challenge for car manufacturers though, with the prospect of system integration of different matrices becoming more difficult – especially when the respective colour sensitivities need to be adjusted.
Melexis MeLiBu overview
There are other key aspects that need to be considered. For instance, making certain that there is adequate flexibility in the car architecture for this lighting technology to be utilised without the inconvenience of having to reprogram the body control module (BCM). Then there is the need to ensure that the lighting system has the resilience necessary to deal with the uncompromising application environments that automobiles represent – with regard to electromagnetic interference (EMI) and electrostatic discharge (ESD) strikes. On top of all this, there will be space constraints to consider. As the average modern vehicle is packed with electronic hardware, there is now very little room for accommodating further additions - especially if they will call for more wire harnessing (which increases vehicle weight, impacting on fuel economy figures).
In order to address the difficulties that vehicle manufacturers face when looking to incorporate animated lighting into the upcoming models, Melexis has developed its own dedicated protocol specifically for this purpose. Melexis Light Bus (or MeLiBu) is an automotive-grade connectivity platform for high-speed communication which satisfies the need for streamlined cost-effective deployments with minimal components involved. The result is a robust solution that can deal with the intricate LED matrices needed for animated lighting, but only has a low bill-of-materials (BoM) associated with it.
Based on the existing 2Mbit/s CAN-FD PHY and utilising UART communication with self-synchronisation, MeLiBu is supported on the company’s current MLX81116 and MLX81117 LED driver ICs, as well as its MLX81130 OLED driver IC. This license-free protocol enables real-time updating of thousands of RGB-LEDs within the full car, so that animated content can be rendered without any latency issues being experienced. Although MeLiBu is enabling sophisticated functionality to be actioned within the vehicle, it only requires standard wire harnessing, thanks to its differential bus architecture. The high bus thresholds (CAN-FD-PHY) gives the system a very high robustness against EMC disturbances to secure that the light output stays stable under any circumstances. The CAN-FD PHY supports advanced safety applications, in accordance with the ISO26262 functional safety standard.
Animated lighting could be a way for vehicle manufacturers adopting it to set themselves apart from their rivals, but there are serious engineering obstacles that must be overcome first. In particular, ensuring there is enough networking bandwidth to control the countless LEDs involved. What is thus mandated is high-speed automotive bus protocol that will make it simpler for vehicle manufacturers to embrace the many functional possibilities that can be derived from use of animated lighting. This protocol has to be highly scalable and inherently flexible, so that LED matrices of different sizes and produced by different vendors can all be accommodated. Further, it must avoid the need to make any significant changes to the BCM or add to the wire harnessing. Through MeLiBu, Melexis has introduced a streamlined solution that is viable from both a technical and a commercial standpoint. It combines the performance required with a low BoM. Vehicles from prominent automobile companies that will feature MeLiBu are already on the road.
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