The potential of Silicon carbide (SiC) for automotive applications

June 14, 2017 // By Aly Mashaly, Rohm Semiconductor
Limited resources, the discussion about CO2 and protection of the environment are predominant themes in the public discussion today. Meanwhile, it is common sense that the efficient handling of energy is one of the most urgent challenges for the future.

From the building technology to the transport of passengers and freight, we are facing substantial upheavals in all areas of the daily life. A brand-new topic is electromobility. Automotive manufacturers, industrial companies and research institutes work hand in hand to implement entirelly electrically driven vehicles and the necessary infrastructure. The prospects for electric vehicles have improved significantly in the recent past. New drive concepts have been researched and tested by various companies during the last few years. The first models of hybrid and electric vehicles are now available on the market. New components such as power electronics systems are integrated into the car which have not existed in conventional diesel / gasoline vehicles.

Examples include systems such as:

  • Drive inverters to drive the drive motor (up to 300 kW)
  • Battery chargers (onboard chargers) from 3,6 kW to 22 kW
  • Inductive charge (wireless charging) from 3,6 kW to 22 kW
  • DC/ DC converter up to 5 kW
  • Inverter for auxiliary units such as air conditioning, steering support, water pumps, etc.

 


Fig. 1: Power electronics plays a decisive role for electromobility

For the abovementioned systems, power electronics plays a decisive role in ensuring the functionality of hybrid respectively electric vehicles.

SiC- efficient semiconductor material

The requirements of the automotive OEMs placed on power electronics systems are a great challenge for the developers of such systems. In particular, space requirements, weight and efficiency play a significant role. In addition, the entire system costs and the effort in the product design phase are to be kept low while at the same time, product quality and operational safety have to be guaranteed as well.

The efficiency of conventional power electronics is based on silicon semiconductor technologies and generally varies between 85% and 95%. This means that during each power conversion about 10% of the electrical energy gets lost as heat. Generally, it can be said that the efficiency of power electronics is mainly limited by the performance characteristics of power semiconductors. Due to its physical properties, the semiconductor material SiC has great potential to meet the requirements of these market trends.

Compared to silicon semiconductor devices, the electrical field strength of SiC is nearly ten times higher (2.8MV/cm vs. 0.3MV/cm). The higher electric field strength of this very hard SiC substrate makes it possible to apply a thinner layer structure, the so-called epitaxial layers, to the SiC substrate. This corresponds to one tenth of the layer thickness of Si epitaxial layers. The doping concentration of SiC can reach two orders of magnitude higher than that of their Si counterparts for the same blocking voltage. Thus, the surface resistance (RonA) of the component is reduced which results in a considerable reduction in pass-through losses.

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