Automotive supplier Denso Corp. (Kariya, Japan) has developed its first-ever inverter with silicon carbide (SiC) semiconductors. This inverter, which is incorporated in the eAxle, an electric driving module developed by BluE Nexus Corporation, will be used in the new RZ, Lexus’ first battery electric vehicle (BEV) model that has been released recently.
A driving test carried out with a BEV with SiC inverters showed the efficiency gain that can be expected in practice: In the test, the power loss was reduced by more than half compared to a vehicle with inverters using conventional silicon technology. This efficiency gain is directly reflected in a correspondingly increased range of the vehicle.
Denso’s inverter is equipped with SiC power semiconductors with the company’s proprietary trench-type metal-oxide-semiconductor (MOS) structure which improve the output per chip due to reducing the power loss caused by heat generated. Through this unique structure, the transistors achieved high voltage and low on-resistance operation – however, Denso did not specify these data in detail.
The inverter was built using SiC epitaxial wafers developed by Denso in collaboration with Toyota Central R&D Labs. This development incorporated the results of work commissioned by Japan’s national R&D agency New Energy and Industrial Technology Development Organization (NEDO). As a result of these R&D activities, the Denso semiconductor experts were able to halve the number of crystal defects that prevent the device from operating normally due to the disorder of the atomic arrangement of the crystal. By reducing crystal defects, the quality of SiC power semiconductor devices used in vehicles and their stable production were ensured.
Denso baptised its SiC technology “REVOSIC”. The company said it plans to use it to comprehensively develop technologies for products ranging from wafers to semiconductor devices and modules such as power cards. Power transistors using this technology have been used already in Toyota’s Mirai, a hydrogen fuel-cell vehicle which entered the market in December, 2020.