By Emily Newton, a tech journalist and the Editor-in-Chief of Revolutionized.
Engineers continually look for feasible ways to improve electric vehicles (EVs) as they become more in-demand. One increasingly frequent approach is to use wide-bandgap semiconductors in their design. Here are some compelling examples of how these components improve EV performance.
1. Enabling Faster Charging Capabilities
It takes only a couple of minutes to fill a car’s fuel tank at the gas pump, but recharging EV batteries can take hours. However, ON Semiconductor is banking on semiconductor choices having drastic impacts on charging speed.
The company introduced a silicon carbide (SiC) charging module that reportedly brings a 100x reduction in conduction losses compared to silicon counterparts. That advantage, combined with faster switching speeds, could make significantly more efficient charging a reality.
Progress is also underway with gallium nitride (GaN) metal-oxide-semiconductor field-effect transistors (MOSFETs) and field-effect transistors (FETs). Engineers often choose them for today’s level 3 charging systems. They provide up to 20 range miles per minute, making them impressively quick.
Why Are GaN Semiconductors Well-Suited for Fast Charging? Ramanan Natarajan, marketing and applications manager of high-voltage power products at Texas Instruments, gave some insights into GaN’s appropriateness for fast charging. “GaN FETs are well-suited for the AC/DC on-board charger and the high-voltage to low-voltage [HV-to-LV] DC/DC converter in the electric vehicle,” he said. Integrated gate drivers allow a 60% reduction in size and have double the power density, with switching speeds up to 2.2 MHz.
Natarajan continued, “OEMs are demanding these powertrain systems to deliver more and more power to reduce EV charging times but without an increase in their size, as the passenger space in the car cannot be compromised. The key to achieving high power density is to maintain efficient operation at high switching frequencies. GaN FETs can switch at >100 V/ns, and they have zero reverse recovery. As a result, they have extremely low switching power losses.”
2. Paving the Way for Better Sustainability and Reliability People want high EV performance, but sustainability often plays a significant role in their buying decisions. There’s also a growing amount of choice when consumers shop for these cars. For example, a 2021 report found approximately 370 electric vehicles on the market worldwide in 2020, which was a 40% increase over 2019’s numbers. The increased availability pushes researchers to work toward improving cars of the future.
Achieving a Breakthrough in Semiconductor Design Researchers at the University of Bristol have made a world-first development with a method to quantify the electric field inside a semiconductor. Their ongoing work involves using GaN, among other non-silicon materials. They plan to use an optical device to directly measure the electric field inside the semiconductors. Previous efforts relied on simulations, which were difficult to trust.
Professor Martin Kuball, who’s involved in this project, said the increased precision from the new measurement capabilities would make it easier to determine when newer semiconductors might be prone to failure. In that case, engineers could spot issues earlier and work to combat them.
He explained, “Considering that these devices are operated at higher voltages, this also means electric fields in the devices are higher and this in turn means they can fail easier. The new technique we have developed enables us to quantify electric fields within the devices, allowing accurate calibration of the device simulations that, in turn, design the electronic devices so the electric fields do not exceed critical limits and fail.”
This approach should mean electronics in EVs and numerous other applications, ranging from planes to clean power stations, become more efficient. The reduced energy loss also minimizes society’s dependence on available resources, bringing more sustainability. That’s crucial, considering forecasts indicate an estimated 80% of electricity will go through power electronics devices by 2030.
3. Giving Electric Vehicles a Longer Range
Besides efforts to give the cars themselves longer ranges, various endeavors aim to make it progressively easier for a person to recharge when needed. For example, one company brings a modular EV charging station to a customer’s location. That approach gives the car 15 miles of range in only 15 minutes, making it great for someone short on time.
EV range and charging station availability are two significant factors that shape how happy vehicle owners are with their purchases, a 2021 study found. Stated and actual battery ranges accounted for about 20% of people’s overall satisfaction with their cars.
Having convenient places to plug the cars in was also a notable factor among people with premium and mass-market electric vehicles. Satisfaction over public charging station availability was 305 points higher among Tesla owners than those with other brands. It also doesn’t hurt that Tesla uses wide-bandgap semiconductors in its EV models.
In 2018, the company was the first to add SiC MOSFETs to an in-house inverter design. It did so with its Model 3. Now, due to the combination of that inverter and a permanent magnet motor, the cars achieve 97% efficiency, extending their range capabilities without raising battery capacity.
Most electric car owners or people thinking about buying them probably won’t care what kinds of semiconductors their vehicles have. However, the results they see while driving will matter. Being able to go on longer journeys before recharging will make a big difference in whether or not they buy these cars.
When considering how to enhance EV performance with a longer range, the initial instinct may be to explore tweaking the battery. However, a team at Germany’s Fraunhofer Institute for Reliability and Microintegration IZM is taking a similar approach to Tesla. It’s focusing on using wide-bandgap semiconductors in power inverters and determining how best to keep them cool. These drivetrain tweaks should combine to make a meaningful difference.
Eugen Erhardt, who’s working on the project, said, “We expect that by optimizing the drivetrain in this way, the range of electric cars will ultimately be extended by up to 6%.” An electric car braking, accelerating or moving at high speeds causes power losses due to the large amount of current flow traveling between the motor, inverter and battery. However, SiC semiconductors reduce that effect.
The team also used 3D printing to aid their efforts to keep the inverters from overheating. EV power inverters get cooled with water. A solid cooling element with fins rests in the water and helps handle the heat buildup in the transistors.
In this case, a 3D printer allowed making a cooling element with thinner walls than traditional counterparts offered. The transistors sit on metal plates only a few millimeters thick, which are supported by the cooling fin’s design. The transistors’ location close to the water helps with temperature control.
EVs are like most other technologies in that they improve through innovations and better methods. Wide-bandgap semiconductors are already proving crucial in enhancing EV performance. The advantages detailed here show much of what’s possible, and more perks will inevitably become apparent as people do further research in this area.
Continued progress will help consumers overcome the hesitations they may have about purchasing electric cars. As adoption rates rise, we can look forward to a greener future with less dependence on fossil fuels.
Emily Newton is a tech journalist and the Editor-in-Chief of Revolutionized.