By: Sofiane Serbouh, Technical Marketing – Vehicle Electrification Segment, Fairchild Semiconductor
Health and environmental concerns around air pollution and Global Climate Change have pushed governments for decades to legislate the reduction of polluting emissions, particularly in the automotive industry. Many improvements have been achieved thanks to the introduction of cleaner fuel, catalytic converters, particle filters and more efficient engines. However, all these improvements have been offset by the growing number of cars sold every year and governments need to apply more stringent restrictions with cost penalties to vehicle manufacturers for not meeting the targeted reduction of polluting emissions such as CO2. Figure 1 shows how the CO2 emissions of passenger cars worldwide have been continuously dropping as well as the ever decreasing target emission goals of several major governments.A way for vehicle manufacturers to reduce CO2 emissions from the Internal Combustion Engine (ICE) and meet their targets is to electrify cars, similar to what has been done with electric trains. Hybrid Electric Vehicles (HEVs) combine an ICE with a 50kW to 100kW electric motor that can boost or take over completely for the ICE whenever possible, enabling a 20 to 40% CO2 reduction. Electric Vehicles (EVs) fully rely on a 200kW or more electric motor and do not emit any pollution since they operates without ICEs.
Due to the high power required to operate an HEV or EV’s electric motor, the need to limit the current to a reasonable level, the necessity of keeping the wiring relatively light and the requirement to comply with high voltage safety standards, EVs and HEVs need a bulky, high voltage battery and a complete redesign of the vehicle’s electric architecture. The additional cost for such a system ranges from $4,000 to $10,000 depending on the level of electrification. Unfortunately, this often makes HEVs and EVs too expensive for most people and makes it questionable if such vehicles can spread widely enough in the market to mitigate the emissions from millions of other vehicles on the road.
To reduce costs, vehicle manufacturers are looking at reducing the weight and size of their high voltage systems, resulting in intense investments in research and development to come out with battery systems that are smaller, more efficient and can last longer. Significant research has gone into developing semiconductor materials that dissipate less power, which operate at higher temperature and that generate less noise; with package solutions that are smaller and introduce less parasitic noise, that better dissipate the heat generated during operation and that can withstand higher temperatures. With smaller batteries, smaller and lighter cooling systems, and smaller noise filtering systems, the additional cost for EVs and HEVs should eventually drop and allow a wider spread of EVs and HEVs in the market.
As an alternative to the present cost limitation of EVs and HEVs, European vehicle manufacturers are working on mild hybrid vehicles relying on a 48V board net. The battery voltage has been selected just below the high voltage safety threshold so that it does not require stringent and costly precautions to protect against high voltage safety hazards while still offering sufficient power to operate a 10kW to 20kW Belt Starter Generator electric motor. This approach can reduce CO2 emissions by 20 to 30%, by offering basic functions such as start/stop and passive coasting. In addition, a 48 V board net overcomes the power limitation of the 12V battery and permits to auxiliary devices such as water pumps and turbochargers to be operated electrically for a better engine management. For the same performance, engines can be reduced in size and consequently consume less fuel yielding lower CO2 emissions. Finally, the 48V board net also offers enough power to operate independently the A/C compressor and other types of pumps that are otherwise driven with a belt by the engine in a conventional vehicle and that will continue to operate when the engine stops for fuel saving purposes (e.g. coasting, start/stop).
The additional cost for such a 48V board net is around $2,500, which offers a better ratio between CO2 and fuel savings and the higher cost of HEVs or EVs. It is also no more expensive than the diesel engines that are widely accepted in the mass market, thus increasing the likelihood of widespread adoption in the market. However, such a vehicle still comes with an additional cost, which still remains a barrier that needs to be removed.
The challenges to further reducing the cost of 48V systems are similar to EVs and HEVs : the need to continuously develop smaller, lighter and more efficient systems, which can be achieved only if supported by the entire automotive supply chain including the semiconductor industry.
Fully committed to supporting CO2 reduction, Fairchild Semiconductor is continuously working with vehicle manufacturers and system suppliers to develop and make available state-of-the-art technologies to the automotive industry. With its Shielded Gate MOSFETs, Field Stop Trench IGBTs and SuperFETs – all covering a large range of medium voltage classes from 30V to 100V and high voltage classes from 600V to 900V – Fairchild has dramatically increased the performance of silicon. Improvements are such that the package containing the silicon dies has become the limiting factor and in this area again, Fairchild has responded by developing advanced package solutions such as power modules, H-PSOF (TOLL) and PQFN5x6 which, in a smaller footprint, permits higher currents with lower electrical parasitic losses. With a large portfolio of components with higher power density, Fairchild enables system designers to create scalable solutions, reduce the number of components in parallel in their system, simplify their board design, facilitate the assembly and fitting of power semiconductors in areas not possible before and eventually reduce the size and weight of their systems while achieving the highest reliability.
Naturally, such solutions need to fully meet the automotive requirements in terms of manufacturability, quality and reliability under stringent operating conditions, which explains why, among many possible solutions, only few can be successful in the market.
The electrification of vehicles is growing very fast and, in a very competitive environment, the time-to-market and the need to limit development expenses have always been very critical. The automotive industry is traditionally very conservative and very cautious to adopt anything new and unproven, and it is a real challenge for semiconductor companies to support it with new products. Because of the fast growing market, the traditional trial and error approach is no longer acceptable and semiconductor companies must improve their modeling capabilities. With its unique physical scalable models  in combination with package cross coupled models [ 3] Fairchild gives the designers the possibility to easily predict the silicon performance in a package and optimize it to their exact needs despite the complexity of the process and underlying physics.
Last but not least, even in the automotive industry, the supply chain including semiconductor companies strives to be more environment-friendly by better managing natural resources, reducing waste and by proactively using environment-friendly materials in the assembly process. This is how, for example, power modules are developed using green materials in full compliance with the RoHS requirements, with no lead at all in the die-attach solder, while still meeting automotive requirements for long reliability under stringent operating conditions under the hood.
To summarize, cars have continuously been reducing their CO2 emissions but it has been offset by the continuously growing number of cars on the road. Governments have defined stringent CO2 reduction targets that can be achieved by electrifying cars. Solutions exist with EV and HEVs which have driven significant innovation, but due to the high cost of these systems, their wide spread adoption remains questionable. As an alternative, the 48V board net system offers a far a better ratio between fuel and CO2 reduction and cost. In a fast growing market, Fairchild has brought to the automotive industry state-of-the art silicon with advanced package solutions and unique modeling capabilities enabling vehicle manufacturers and system suppliers to optimize their systems to their specific need, reduce size and weight, save fuel and eventually reduce CO2 emissions.
 International Council on Clean Transportation, Global Comparison of Passenger Car and Light- commercial Vehicle Fuel Economy/GHG Emissions Standards (February 2014)
 J. Victory, D. Son, T. Neyer, K. Lee, E. Zhou, J. Wang, and M. Baghaie Yazdi, “A physically based scalable SPICE model for high-voltage super-junction MOSFETs”, PCIM Europe 2014. Power Electronics, Intelligent Motion, Power Quality and Energy Management, p. 956-63, 2014
 Dynamic Electric-Thermal Reduced Order Modeling of Power Electronics by ICEPAK-Simplorer Integration, Neumaier, K., et al., ACUM 2014, Nürnberg, 5/6 June