Toyota developing chips to boost hybrid efficiency up to 10%

Toyota says new silicon carbide semiconductors enable the automaker to build much smaller and more efficient power control units in its hybrid vehicles.

Photo credit: HANS GREIMEL
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TOKYO -- Toyota Motor Corp., aiming to extend its lead in hybrid technology, 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 biggest maker of gasoline-electric cars said it has already achieved a 5 percent improvement in fuel efficiency in test vehicles and aims to commercialize the technology around 2020.

The advancement comes in the semiconductors that manage the flow of electricity through the power control unit that integrates a hybrid vehicle’s battery, motor and generator.

The new semiconductors eat up only a tenth of the energy of today’s chips and enable the PCU to be 80 percent smaller, Toyota engineers said today at a briefing.

The technology has the potential to deliver 10 percent better fuel efficiency because less energy is lost when the battery powers the car’s electric motor or when the regenerative brakes recharge the battery.

“One of the keys to improving fuel efficiency is improving power semiconductor efficiency,” said Kimimori Hamada, project general manager of Toyota’s electronics development division.

With rival automakers stealing share in the hybrid segment that Toyota pioneered with the Prius, the world’s biggest automaker is ramping up research on ways to eke out better mpg.

Better engines, batteries and aerodynamics are part of Toyota’s formula for future-generation hybrids, including the next Prius. But the automaker also aims to squeeze better performance from the power-hungry PCU chips that sap energy.

“We are aiming for great improvement in fuel economy and miniaturization,” he said. “This is a very challenging target.”

Toyota opened a sprawling semiconductor development building at its Hirose plant in Toyota City in December to spearhead the new technology. That plant already makes semiconductors for use in Toyota’s existing hybrid systems. Toyota has historically developed them in-house, starting with the first-generation Prius that debuted in 1997.

Toyota’s new approach is using silicon carbide, instead of simply silicon, to make the semiconductor wafers, Hamada said.

Silicon carbide wafers have a couple of advantages.

Every time a current passes through PCU semiconductors, power is lost as heat. In fact, Toyota says, semiconductors account for about 20 percent of all power loss in hybrid systems.

But silicon carbide semiconductors experience only a tenth of the energy loss of the silicon-based chips used today.

Also, silicon carbide semiconductors can switch on and off at much higher frequencies. That makes them more efficient and alleviates the need for space-hogging coils and capacitors that are used in PCUs to temporarily store power.

Capacitors and coils take up to 40 percent of the space in a typical PCU. Because fewer such components are needed, the overall size of the PCU can be made 80 percent smaller.

At today’s briefing, Toyota displayed a bulky PCU used in its current hybrid lineup next to its new shoebox-sized one.

Toyota aims to commercialize silicon carbide semiconductors around 2020, Hamada said. But cost remains the biggest obstacle.

Currently, silicon carbide semiconductors cost “an order of magnitude” more than silicon semiconductors. And because silicon carbide is one of the world’s hardest materials, it is difficult and costly to process into wafers, Hamada said.

“There are still enormous technical barriers,” he said, adding he would be satisfied with achieving only 70 percent of his energy efficiency and miniaturization goals by 2020.

The silicon carbide semiconductors will be applicable to hybrid or all-electric drivetrains and can be mated to lithium ion or nickel-metal hydride batteries, Toyota said.

Toyota is developing the new semiconductor technology in-house with assistance from Toyota Central R&D Labs Inc. and Denso Corp., the Toyota Group’s biggest parts supplier.

You can reach Hans Greimel at hgreimel@crain.com. -- Follow Hans on Twitter


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