Toyota launched in Japan a program to test silicon carbide power semiconductors in hybrid vehicles.

Using a Camry hybrid prototype and a fuel cell bus, Toyota Motor Corporation said the tests will evaluate the performance of silicon carbide (SiC) power semiconductors, which it believes could lead to significant efficiency improvements in hybrids and other vehicles with electric powertrains.

Power semiconductors are found in power control units (PCUs), which are used to control motor drive power in hybrids and other vehicles with electric powertrains. PCUs play a crucial role in the use of electricity, managing and supplying battery power to the motors during operation and recharging the battery using energy recovered during deceleration.

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Toyota stated as it stands, power semiconductors account for approximately 20 percent of a vehicle’s total electrical losses, meaning that raising the efficiency of the power semiconductors is a promising way to increase powertrain efficiency.

By comparison with existing silicon power semiconductors, Toyota explained the newly developed silicon carbide (SiC) power semiconductors create less resistance when electricity flows through them.

The technologies behind these SiC power semiconductors were developed in Japan jointly by Toyota, Denso Corporation, and Toyota Central R&D Labs., Inc.


In the Camry hybrid prototype, Toyota said it is installing SiC power semiconductors (transistors and diodes) in the PCU’s internal voltage step-up converter and the inverter that controls the motor. Data gathered is said to include PCU voltage and current as well as driving speeds, driving patterns, and conditions such as outside temperature. By comparing this information with data from silicon semiconductors currently in use, Toyota’s engineers believe they will be able to assess the improvement to efficiency achieved by the new SiC power semiconductors.

Road testing of the Camry prototype will begin (primarily in Toyota City) in early February 2015, and will last for about one year.

Similarly, on January 9, 2015, Toyota stated it began collecting operating data from a fuel cell bus currently in regular commercial operation in Toyota City. The bus features SiC diodes in the fuel cell voltage step-up converter, which is used to control the voltage of electricity from the fuel cell stack.

Data from testing will be reflected in development, with Toyota having the goal of putting the new SiC power semiconductors into practical use as soon as possible.