New Silicon Carbide Semi-Conductors Could Boost the Efficiency of Toyota’s Hybrids By Up to Ten Percent

Posted by John Dolan | Posted in Automotive, Community, Driving, Hybrids, News | Posted on 20-05-2014


In the spirit of one of Toyota’s vital principles, Kaizen (Continuous Improvement) the company has developed a new semiconductor it says can boost fuel efficiency in hybrid cars such as the Prius by up to 10 percent.

The world’s largest manufacturer of gasoline-electric cars with it’s relentless efficiency improvements aims to extend its lead in hybrid technology.  This particular advancement, which was developed with Toyota’s in-house technology partner Denso, is focused on the semiconductors that manage the flow of electricity through the power control unit (PCU) that integrates a hybrid’s battery, motor and generator.  The new semiconductors utilize only a tenth of the energy that today’s chips gobble up and enable the PCU to be 80 percent smaller, according to Toyota’s press release.

The technology has the potential to deliver a ten percent increase in fuel efficiency because less energy is lost when the battery powers the car’s electric motor or when regenerative braking recharges the battery.  Better internal combustion engines (ICEs), traction batteries and aerodynamics are a key part of Toyota’s plans for future hybrids, including the next generation Prius.  But the company has targeted the performance of these power-hungry PCU chips that also sap energy.

Although Toyota still has a commanding sales lead in the hybrid segment, especially with the pioneering segment-leading Prius, competition had gotten keener and the world’s largest producer has been ramping up research on ways to squeeze out better mpg.  “We are aiming for great improvement in fuel economy and miniaturization, says Kimimori Hamada, the project manager of Toyota’s electronics development division.

Toyota opened a vast semiconductor development center at its Hirose plant in Toyota City last year to expand this new technology.  That facility already makes semiconductors for Toyota’s existing hybrid systems.  Toyota has historically developed hybrid technology and components in-house, starting with the development of the first-generation Prius which began in 1993 and the car company holds over two  thousand of patents on hybrid systems and components.

Toyota’s new approach with semiconductors is to use silicon carbide (SiC), instead of simply silicon, to make the semiconductor wafers.  Silicon carbide wafers have a few distinct advantages.  Just as an internal combustion engine experiences ineffiency due to heat loss, whenever energy (in this case current) passes through the PCU semiconductor, power is lost as heat.  In fact, Toyota says, semiconductors account for about 20 percent of all power loss in hybrid systems.

toyotadeveloSilicon carbide semiconductors experience only a tenth of the energy loss of the silicon-based chips in use today.  Also, Toyota engineers say that silicon carbide semiconductors can switch on and off at much higher frequencies.  That makes them more efficient and obviates the need for space-clogging coils and capacitors that are used in PCUs to temporarily store power.  Capacitors and coils take up about 40 percent of the space in a typical PCU.  Because fewer of these components are needed with silicon carbide semiconductors, the overall size and weight of the PCU can be made 80 percent smaller.  The new PCU is about the size of a shoe box.  The new silicon carbide semiconductors will be applicable to hybrid, all-electric or fuel cell power trains and can be mated to lithium ion or nickel-metal hydride batteries according to Toyota’s press release.

Toyota’s next generation Prius is already expected to see a 10 percent improvement in efficiency compared to the current model, with a touted fuel economy just above 55 mpg.  The new semiconductors have not been confirmed for the next Prius, though Toyota does say it intends to “boost development activities” so that it can implement the technology sooner, not later.  Each Prius generation has come with a 10 percent improvement in fuel efficiency over the outgoing model and the next Prius will surely benefit from this.  Add the fact that Toyota is also developing new, highly efficient gasoline engines that achieve an amazing thermal efficiency and fuel efficiency improvements of at least 10 percent and you can count on the the next Prius being the most efficient hybrid so far.

  Sources: Toyota Pressroom, Toyota GB, Automotive News,, greencarreport


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