The use of silicon carbide (SiC) devices within automotive powertrains has long been investigated, and recent developments indicate that it is gradually becoming a realistic solution.
SiC is a semiconductor material and differs from silicon, which is widely used today; they are different materials and have different physical parameters, but the general advantages are that SiC is well suited to high voltage applications up to 1200V. SiC also has higher thermal conductivity, which means it can operate at higher temperatures—up to 200 degrees Celsius. Energy efficiency is also significantly higher compared to traditional silicon.
All things considered, and from a less technical standpoint, this means that SiC semiconductors are ideal for applications such as on-board chargers and inverters used within plug-in hybrid (PHEV) and fully electric vehicles (EVs). Automakers that make use of rapid charging solutions, such as Tesla, for example, already use SiC within their vehicle architectures today. It is a technology that has been adopted by the automotive industry, having already found use within other high power applications, such as the military and renewable energy spaces.
To ensure that EVs can operate over long distances and charge within a reasonable timeframe, it is paramount that the vehicle’s power electronics are capable of handling high temperatures. In some respects, these devices essentially dictate the functionality of a battery electric vehicle, and energy efficiency is absolutely vital. SiC semiconductors benefit from more than 95% energy efficiency, meaning that only 5% of energy is lost as heat during instances of power conversion—such as recharging the vehicle at a high power rapid-charger.
“For fast chargers, there is definite value for SiC,” advised Kunal Goray, Team Leader Power Electronics Design at AVL SFR during a recent Automotive World webinar. “For regular chargers, there is less of a benefit.”
In April 2019, the University of Arkansas received a US$1.5m grant from the US Department of Energy, targeted at aiding the development of next-generation power modules. More specifically, the five-year award will see researchers develop SiC-based power modules designed for PHEVs and EVs.
In Japan, the University of Tokyo has been working with Mitsubishi Electric Corporation to enhance the reliability of SiC semiconductor devices. Earlier in 2017, Mitsubishi Electric revealed a new ultra-compact SiC inverter designed for hybrid vehicles, with mass commercialisation targeted for around 2021. Toyota has been working with Tier 1 supplier Denso to a similar end for years, and since as far back as 2014 has been developing SiC-based power control units for hybrid electric vehicles. In 2015, the automaker trialled a prototype Camry hybrid that had been equipped with SiC power semiconductors. At the time it had found that standard power semiconductors accounted for around 20% of a vehicle’s total electrical energy losses.
SiC is another discrete element of an electrified vehicle that, while diminutive, can have a significant benefit to its overall efficiency. Advances in SiC semiconductors are expected to continue as the technology is proven out further, and automakers will hope it solves part of the puzzle in meeting consumer requirements for range and recharging performance.