Optoelectronics
Accelerating the migration of
Figure 1: ON Semiconductor’s NCV78763 reference design for LED front lighting
L
ED technology allows automotive engineers to incorporate superior functionality which HID lamps are not
able to deliver, such as the dimming or deactivating of certain LED strings (or individual LEDs) to permit changes in the light beam’s shape to better illuminate the road. It also presents them with a lighting solution that has much greater reliability than HID options can offer (20 times longer on average). The greater energy efficiency that LEDs can deliver in comparison to HIDs is another key advantage. It means that car manufacturers can make significant improvements to the vehicle’s fuel economy. In addition, it leads to better aesthetics - with lighting able to fit into form factors that have smaller dimensions, while still giving the same (or improved)
light output as a standard HID. This is proving to be a powerful reason for migration at the lower end of the market in particular. Greater compactness is also something that will help to counter the increasing space constraints within modern cars already discussed. Finally, it gives the impression that the car manufacturer is being innovative and this will be appreciated by potential car buyers. All of these attributes are becoming more attractive as the growing demand for LEDs is leading to larger economies of scale and lower unit costs. As demand increases, the price tag of LEDs keeps going down and further opportunities for its deployment in automotive applications open up.
LEDs in automotive front lighting The motivation for moving to LED
Figure 2: Compatibility of NCV78763 reference design LDM A with bulb based lighting systems - providing a plug-and-play migration scheme
30 September 2016 Components in Electronics
technology is universal, with car manufacturers across the globe all starting to implement it, but it is really in the Far East that it is exhibiting its greatest future potency. In developing economies, such as China, the introduction of solid state front lighting is taking place at a much faster pace. Here, it is a highly compelling way to show differentiation in a rapidly evolving and extremely competitive market. Automobile manufacturers are not just looking to implement solid state front lighting into their next generation models. They are also starting to ‘retrofit’ it into their existing models that are still leaving the production lines. A car model’s lifecycle is around five to seven years but after about three to four years of manufacturers shipping a particular model, they will need to give it a ‘facelift’. This allows them to revitalise market interest and boost sales. It is clear that revamping an older model through addition of solid state front lighting will give it a new lease of life. When looking to implement a front lighting system there are several key challenges that automotive engineers are going to face. Firstly, maximising power conversion efficiency needs to be accomplished at both device and system level (a figure of over 90 per cent is usually expected). Achieving operational flexibility is also critical to engineers both from a hardware and firmware perspective (as well those involved in the optics), as it is what will allow them to add greater differentiation into their lighting designs and make the vehicles that incorporate them stand out for the competition. Optimising resources is also important. Given their limited manpower, combined with time to market pressures, engineering teams do not like the idea of embarking on a completely new design for every vehicle model. They want to be able to follow a platform approach: the basic level design (that might be used in an economy model) can serve as a foundation, then additional LED strings and more complex functionality can be built on top of that to address the needs of higher end vehicles. By utilising the same hardware across the entire car manufacturer’s product portfolio, substantial cost savings can be realised and design cycles shortened. If engineers are to fully exploit the advantages of solid state lighting, then
they have to be able to mitigate the effect that electro-magnetic interference (EMI) will have on the lighting system’s performance. Engineering teams need to ensure that the benefits of solid state front lighting do not outweigh the costs involved. Also, each design project has a degree of risk associated with it. Failure to get it right first time can have serious consequences. If a design flaw is uncovered then there is the immediate cost of re-doing it that needs to be taken into account. If the design flaw is not caught until much later, the manufacturer will have to factor in the cost of a recall and the damage done to its brand as a consequence. It is clear that there is a need for a solid state lighting solution that can attend to the specific needs of automotive front lighting, so that existing bulb-based systems can be replaced. The high level functionality needed for luxury models could then be added onto the same core design that is used for the car manufacturer’s standard or mid-range vehicles. To do this, hardware involved needs to support the implementation of multiple configurations via firmware adjustments. ON Semiconductor is able to assist automotive engineers in upgrading front lighting systems to solid state technology thanks to its comprehensive NCV78763 bulb replacement reference design LDM A. This is highly suited to all forms of automobile LED front lighting, including day time running lights, position lights and turn indicators. It is backed up by a compact evaluation module, which gives engineers access to what is effectively a plug-and-play solution.
The automotive industry as a whole is now embracing solid state lighting, as the commercial and logistical appeal of using LEDs increase. Thanks to improved power efficiency, prolonged lifespan, lower space utilisation and greater operational flexibility their attractiveness is growing all the time. Through employing a highly versatile, user-friendly, low component count car bulb equivalent system replacement, such as the one described here, car manufacturers have a proven, risk-free route via which to migrate to front lighting based on solid state technology.
www.onsemi.com www.cieonline.co.uk
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