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Gallium nitride (GaN) semiconductors, while still at an early stage in automotive applications, are moving rapidly into higher voltages, as recently seen at APEC 2023.
“Gallium nitride technology is gaining traction in the automotive industry given its high-power density and efficiency,” said Gianfranco DiMarco, a marketing manager at STMicroelectronics (ST). “Suitable for both low- and high-voltage applications, it’s applicable to various automotive systems. GaN has the potential to greatly improve overall efficiency and ST expects it to have a significant impact on the automotive industry.”
IDTechEx agrees. In a recent report on power electronics for EVs, researchers Luke Gear and James Edmondson predicted: “The demand for EV power electronics will increase dramatically in the next 10 years, primarily driven by rapid growth in the battery electric vehicle (BEV) car market where IDTechEx predicts a 15% CAGR globally over the next decade.” The report asserts that drive-cycle efficiency must come to the forefront of powertrain design as the time has come for high-voltage wide-bandgap (WBG) power electronics.
GaN has been around a while, but for automotive apps, it’s just beginning to gain ground. Why has it taken so long to get here?
Stephen Oliver, a marketing exec at Navitas Semiconductor, said that Navitas will be in production with GaN for automotive in 2025, and has been in production since 2018 with several other products.
“Automotive takes more confidence, more quality, more proof,” he added. “Meanwhile, we are continuing to innovate with our GaN power IC design, including more features and functions to make the chip itself rock solid and to improve the reliability of the system.”
GaN challenges in automotive
IDTechEx’s Gear reports that, “A barrier for wider GaN adoption in EVs is the material’s production quality, which depends on the epitaxial substrate: GaN, silicon carbide (SiC) or silicon (Si). A primary source of material degradation is mismatches between the epitaxial growth and the substrate, so the ideal case is homoepitaxy, or bulk GaN (GaN-on-GaN), as there is always some level of mismatch between different materials.”
He cites an example of GaN use in high-voltage EV inverters. Gear said it requires either improving mismatches between GaN-on-Si during production or achieving low-cost production of bulk GaN. The GaN-on-Si usage will initially grow for EV applications because it’s much lower in terms of cost, and the EV industry is extremely cost sensitive.
While Navitas has been working on GaN for several years, the company is firm in its belief that proving the technology, especially for the automotive space, is paramount. In an EV with power steering or brakes, should something fail to work, that’s extremely serious. It’s all about proof points and qualification, credibility, reliability and meeting specs.
ST representatives said that, while they are optimistic about the longer term, GaN still faces challenges to broad EV adoption, including cost, standardization, supply chain and the newness of the technology. ST also identified integration issues and reliability related to thermal management and voltage spikes.
“To overcome these challenges, manufacturers are working to improve processes, develop innovative packaging techniques, establish industry standards, and create more resilient supply chains,” DiMarco said.
Overall, there are several benefits that design engineers are increasingly aware of, but the challenges are also significant in creating efficient and reliable EV systems. What’s interesting are the misconceptions that exist regarding GaN.
Misconceptions about GaN
With any new technology, there’s often a lot that isn’t grasped, or is partly grasped. IDTechEx’s Gear, for example, said, “A misconception is that SiC is the only WBG material suitable for high-voltage or power applications. GaN as a material has much greater theoretical potential, yet it’s often just considered for telecommunications or optoelectronics. GaN achieves double the thermal conductivity of silicon and is superior to SiC in almost every other metric, from electron mobility and efficiency to breakdown voltage and efficiency, which is very important for EVs.”
Navitas’ Oliver weighed in on GaN misconceptions, saying, “Some people think that all GaN is the same. It isn’t. Some in the industry are doing a discrete and still think it’s difficult technology. They might have experienced problems with prototyping and delays based on quality and reliability, for instance. We come in and say that nightmare is over—just drop this little baby in because it’s a power IC rated at 2,000-V ESD protection, which you can’t get with a discrete device.”
GaN automotive applications
Silicon isn’t obsolete, and GaN and SiC aren’t the only power players of the future.
Application specifications will continue to dictate the semiconductor material used. Silicon’s price point and reliability will continue to be relevant for devices rated from 15 V to 650 V. GaN, however, is the only viable WBG alternative to silicon in low-power apps and more devices will be introduced that bring efficiency improvements.
Onboard chargers (OBCs) and DC-DC converters operate at much lower power, between 1-22 kW compared with approximately 300 kW for an inverter. Although they don’t directly contribute to the vehicle’s traction when it’s in motion, WBG solutions like GaN are beneficial for increasing overall power density and efficiency with faster charging of the battery.
Next, vehicle-to-everything (V2x) has the potential to bring EV power to other loads at homes, clinics and other vehicles. Navitas’ EV Design Center platform includes a 6.6 kW ‘3-in-1’ design featuring consolidated bi-directional OBC and DC-DC functions for up to 17% energy savings and a 1.6× increase in power density over competing solutions.
“That’s a big trend in the industry to go to this bi-directional OBC, which will also go from 400 V back to AC for your home,” Oliver said. “The three-in-one covers charge, discharge and down-convert, as you still need 12 V for your radio or your windshield wipers.”
It’s much easier and a lower risk to apply GaN to OBCs and converters as a first market entry point to start building automotive experience and establish trust with the technology, according to Gear.
That’s the consistent message from companies active in WBC technology, especially for EVs. While it may be early in the product rollout phase, it isn’t early for planning, gearing up and entering the space. If you intend to be relevant in GaN, better start before it’s too late.
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