Si, SiC, and GaN for Power Devices, Part Four: FTEX GaN-Powered e-Vehicle Powertrains and Controls

The fourth and final part of our series contrasting power devices of silicon, silicon carbide, and gallium nitride.

Which semiconductor is the power powerhouse? In this four-part series, we have taken an in-depth look at the differences between silicon (Si), silicon carbide (SiC), and gallium nitride (GaN) to understand which is best for power devices and why.

In part one, we reviewed electron energy and semiconductors.

In part two, we looked at legacy silicon devices like the IGBT and the power MOSFET.

In part three, we examined GaN cascode FETs and GaN Enhancement High Mobility Electron Transistors (E-HMETs).

In this fourth and final part, we chat with Alexandre Cosneau, the Chief Technology Officer (CTO) at FTEX, a powertrain solutions company. This Canadian startup employs GaN devices in its light e-vehicle power train and controls solutions.

Figure 32. Alexandre Cosneau, CTO at FTEX in Montreal, Quebec, Canada. (Image courtesy of FTEX.)

Alexandre Cosneau is an FTEX co-founder, and a trailblazer in high-frequency and high-power converters as well as controllers for electric motors. Cosneau is finding ways of optimizing power conversions, from battery design to motor efficiency, which are paramount to FTEX technology and solutions. In his role as CTO, he oversees the technology development team. Alexandre holds two MSc degrees in Electrical & Electronics Engineering.

Alexandre Cosneau: I earned my undergraduate degree in Electrical Engineering and then completed an MSc in High-Frequency Telecommunications. My second MSc degree is in Power Electronics. I was introduced to GaN devices by Professor João P. Trovão. High-Frequency Telecommunications and Power Electronics was “the perfect mix” to tackle GaN solutions.

We discovered that datasheets tend to be overstated and optimistic. Application assistance from GaN manufactures was lacking. When the design began “little to few” companies could really assist with driver design. Driver design is critical to garnering all of the capabilites promised by GaN. We made many iterations and simulations.

It depends on the application. In telecommunications GaNs are switched at GHz frequencies, but the power levels are very low. In automotive and high-power industries, the switching frequencies range from 20 kHz to 250 kHz (for the state of the art). At FTEX we have the technology and know how to push the boundaries from 250 kHz to 1 MHz. In high-power converter applications, there is a big demand to operate at higher frequencies as the size of the transformer magnetics, capacitors and inductors are reduced.

To control a motor efficiently, you want to reach the “perfect waveform”. GaN switches must open and close quickly and sharply to get the best waveform possible. In the case of inverters, the goal is a perfect sinusoidal waveform.

We designed the first production printed circuit board with attention to Design for Manufacturing (DFM). The development from prototype moved quickly to a salable product in about 6 months.

No, we went directly to GaN. We received some excellent application assistance from GaN Systems, Inc. We developed a clean inverter waveform to drive a motor. The motor has less heat loss and runs more efficiently.

Battery development is a slow process. Further, the more energy you condense in a smaller area, the more dangerous the battery becomes. In contrast, on a system level changes can be made more rapidly—even several times per year.

Figure 33. FTEX GaNRunner motor controllers. (Image courtesy of FTEX.)

We are a team of 14 at this time. Eight are engineers—six Electrical Engineers, one Mechanical Engineer, and one Industrial Designer. The focus of FTEX is the power train from the battery to the motor of light electrical vehicles.

On a typical thermal engine, the peak efficiency occurs between 2000-30000 RPM where the gearbox provides the full speed range of the vehicle, while keeping it in a decent efficiency state. However, for electric motors, a gearbox is a major point of failure due to high-torque-at-start form of electric motors. In a standard electric powertrain, a gearbox is then not an option, and therefore, the industry standard is to use software based enhancement (in detriment of the efficiency) to cover the full speed range of the vehicle. Now, at FTEX we took the direction toward a solid-state gearbox system by adding a highly efficient and power dense DC to DC power converter. We call it the “Dynamic Drive”. FTEX has developed this solid-state gearbox. Its use increases the range of the vehicle and improves the efficiency throughout the speed range.

Electric Vehicle manufacturers (OEMs) are struggling to design electric powertrains as it is a complex system made up of very different elements by nature, which must converge together at some point to cover a very wide range of operating conditions. (In essence, a battery is a slow electro-chemical system, while a motor is a very complex synchronous machine reacting on instantaneous electro-magnetic effects).

Due to many constraints such as weight, size, operating conditions, safety, and cost, just to name a few, the sizing is a matter of pros and cons that must be balanced to meet the market demands, which naturally impacts the efficiency and thus the range of the vehicle.

FTEX provides the Dynamic Drive solution to increase the system efficiency without compromising the selection of the motor and the battery. We act as a buffer if you will, so that the OEM has a much wider selection of components at their disposal and are free to make less compromises, thus increasing even more the range of the vehicle.

We plan to announce our Dynamic Drive. This ecosystem senses the environment and adapts to optimize the system. It adapts to the user—a slow, steady driver as opposed to a “racy” driver. The “environment” includes the driver characteristics, the battery condition, and the motor parameters. The Dynamic Drive will provide the best system performance and range on the vehicle. Of course, the “racy driver” will not enjoy as much range as the slow, steady driver, but on the same vehicle will have both options. The system will adapt if one day the “racy” decides to drive for a long distance. FTEX technology is highly scalable from very low power (like e-motor cycles) to very high power (like automotive or trucks).

The Dynamic Drive is designed to adapt to aging batteries and the motor characteristics (which tend to be very stable) over the life span of the vehicle (typically 5 years for the battery pack).

The point to be made here is that battery aging is one of the major problems that the Dynamic Drive answers, by adapting the whole vehicle powertrain to a new characteristic (here the aging of the battery) in order for the vehicle to still be functional for a couple more years as we adapt the power requirements on the fly. This answers a big environmental issue that is coming. The high-density batteries are getting used very rapidly without caution, and thus creating harmful waste when we could still use them for a couple of more years.

Certifications are mandatory. Some of our products operate on more than 48 VDC. Our products are DFM ready. Certification is very important for design and manufacturing. ISO is a must to prove that we answer to high standards. But certification is required to meet safety and regulatory standards, like CE (Europe), FCC (America), CCC (China), and CSA (Canada).

Figure 34. FETX Dynamic Drive (Image courtesy of FTEX.)

Review and Conclusions

FTEX started their product designs using GaN technology. GaN datasheets tend to be biased toward the optomistic and manufacturers may not be able to offer insight to GaN driver design. This is not unusual when implementing a newer technology. FTEX has received excellent support and collaboration with GaN Systems. On July 21, 2021 GaN Systems announced a partnership with FTEX to deliver the next-generation GaN-powered motor drives for personal electric vehicles (EVs) including e-scooters, e-bikes, and e-mopeds.

This concludes our four-part series contrasting Si, SiC, and GaN for power devices. Here’s a list of the previous entries:

Part One: Electron Energy and the Semiconductors

Part Two: IGBTs, Si MOSFETs, Super-Junction Si MOSFETs and SiC MOSFETs

Part Three: GaN Cascode FETs and E-HMETs