The commitment to reduce greenhouse gases has been almost universal, yet the European Union (EU) has been more ambitious than others in setting their goals – promising to make an 80% reduction in their emission levels by 2050. As automobiles currently account for a significant proportion of these emissions, the stretching goal will not be achieved without a significant reduction in emissions from vehicles. Although not quite as ambitious, the American Corporate Average Fuel Economy (CAFE) standards are also challenging to the automotive industry. The result of these commitments and standards is that every automotive manufacturer will be under pressure to reduce fuel consumption significantly.
The key to this is likely to be electric vehicles (EVs) and Hybrid Electric Vehicles (HEVs) although adoption rates will have to increase to achieve the commitments. Currently adoption is relatively low with countries such as the US, Germany, China, France, Japan and the UK reporting adoption levels below 1.5%. Norway and the Netherlands currently lead the way at 20% and 10% respectively, but even this level will not be sufficient to achieve the goals. In fact, Bloomsberg New Energy Finance estimates that a global figure of 35% will be required by, equating to around 41 million vehicles being shipped. This significant increase will need an equally significant change in the way consumers view EV/HEV technology.
One significant barrier to adoption is ‘range anxiety’ – the concern about how far an EV can go on a single charge, and what will happen if the battery is depleted without a charging station available. The long time taken to charge is a significant convenience issue, extending journey times and, to cap it all, the less convenient EVs are currently more expensive than current internal combustion vehicles – mostly due to expensive energy storage and conversion.
Increasing the efficiency of EVs is key to addressing the convenience and cost issues. If stored energy could be used more effectively, then range would increase and the battery and inverter could be made smaller, reducing the size and weight and further increasing range. While conventional technologies are close to the limit of what can be achieved, new wide bandgap technologies including gallium nitride (GaN) and silicon carbide (SiC) are showing huge potential. With higher breakdown voltages than comparable silicon devices, wide bandgap devices have lower losses and are able to switch faster, allowing for the development of more efficient power conversion solutions.
Managing heat in densely packed modern vehicles can be a space-consuming and costly exercise. The greater efficiency of wide bandgap devices reduces the need for thermal management, such as heatsinking and fans, thereby reducing cost and space requirements.
GaN technology that is suitable for automotive applications is now available – one example is GaN Systems’ GS6650x series of GaN-based devices with 650V breakdown. In addition to the wide bandgap benefits, proprietary Island Technology allows current to be drawn vertically from the device. This innovative approach saves weight and space by removing the need for bus bars as well as reducing inductance, allowing for faster switching and further reducing operating losses. GaN Systems’ small GANPX™ packaging provides reduced inductance and lower thermal resistance, delivering further performance improvements.
Other GaN devices are available such as Panasonic’s X-GaN™ power transistor range that has a breakdown voltage in excess of 600V. This makes them suitable for automotive applications, as does their small form factor and ability to function with very few external components.
As their name suggests, GeneSiC uses SiC technology in their GA100SIC IGBT products. Due to the use of SiC-based Schottky rectifiers in place of silicon-based freewheeling diodes these advanced IGBTs have dramatically improved switching losses – important in modern high frequency power conversion.
Clearly, these devices that are available now show how designers will be able to take automotive power designs to the next level of efficiency, beyond what is currently possible with silicon. The more efficient designs that they will enable will be smaller, lighter and lower cost, resulting in better range, lower purchase costs and lower operating costs – all of which will significantly contribute to accelerated adoption of EVs.
While the significant benefits of wide bandgap technology and devices will be enjoyed by designers and consumers, perhaps their greatest impact will ultimately be on the environment, allowing governments to achieve their challenging greenhouse reduction goals.