A typical silicon power semiconductor versus Toyota’s new silicon carbide (SiC) version
Toyota has announced a new silicon carbide (SiC) power semiconductor for use in its automotive power control units (PCU). Developed in collaboration with Denso, the material – currently used to make carbon ceramic brake discs – is touted to increase the fuel efficiency of its hybrid vehicles such as the Prius by up to 10% on the Japanese JC08 test cycle.
While PCUs play an important role in all vehicles with electrified powertrains – sending electricity from the battery to the motor to power the car, as well as the other way round during regenerative braking – they account for approximately 25% of the total power loss in hybrids, about 20% of which comes from the silicon semiconductors currently used in them. Increasing the efficiency of these components, specifically by reducing the resistance encountered by the current passing through them, therefore seems like the logical next step.
A current production power control unit (PCU) versus an expected future PCU with SiC semiconductors
The SiC semiconductors not only deliver the aforementioned gains in fuel efficiency, but also allow Toyota to design PCUs that are up to 80% smaller than current units. With a low power loss enabling efficient current flow even at higher frequencies, the coil and capacitor – which together make up about 40% of the PCU’s size – can be made smaller. The size reduction is particularly beneficial at a time where tightening fuel efficiency and emissions regulations are forcing cars to become more aerodynamic.
Research on the technology has been done since the 1980s by Toyota Central R&D Labs (Toyota CRDL) and Denso, with Toyota itself joining in 2007 to develop the SiC semiconductors for practical use. The technology will be on display until May 23 at the Pacifico Yokohama convention centre in Japan.