EE Times’ second annual Advanced Automotive Tech Forum (formerly Roadmap to Next Gen EV & AV) examined the fast-changing landscape in the automotive market for electric vehicles (EVs) and autonomous driving technology. The EV (Electric Vehicle) panel discussion, comprised of keynote speakers in the powertrain and charging stations tracks, discussed wide ranging topics from wide-bandgap (WBG) semiconductors, including silicon carbide (SiC) and gallium nitride (GaN), to renewable energy used in the manufacture of SiC wafers.
Maurizio Di Paolo Emilio, editor-in-chief of AspenCore’s Power Electronics News, and moderator of the panel, conducted a roundtable discussion on key trends in the EV industry. A portion of the discussion centered on WBG semiconductors and their growing adoption in EVs and other e-mobility applications, thanks to their higher efficiency and weight and size savings.
This dove-tailed into several key trends including the move to 800-volt (V) systems from the current 400-V standard, higher power DC charging stations at 350 kilowatts (kW) and higher, wireless battery management systems, and the future of wireless charging. The cost of SiC wafer manufacturing and the need for additional capacity also was on the agenda.
Panelists also examined several roadblocks to widespread adoption of EVs including the cost of vehicles, range anxiety, and the need for faster charging, along with technology challenges. An overriding theme among the panelists, despite the challenges they still face in the EV market, is their enthusiasm for their work in creating a more sustainable and greener world and developing technologies that contribute to energy savings.
The panel was comprised of five industry experts. Panelists, who participated in the EV charging track include Igor Spinella, CEO and CTO of Eggtronic, who addressed EV wireless charging technologies and the potential for dynamic charging, and Gopal Mitra, industrial segment leader of ABB Power Conversion, and Daan Nap, global business development at ABB E-Mobility, who both discussed EV charging solutions and power and charging infrastructure challenges.
Panelists, who contributed to the powertrain for EVs track, include Ryan Manack, director of Automotive Systems, for Texas Instruments’ Systems Engineering Marketing, who highlighted advances in GaN and advanced battery management systems, and John Palmour, CTO and co-founder, Wolfspeed, who provided insight into the adoption of SiC for drive train inverters in batteries for EVs.
Here are the highlights from the panel discussion.
Enabling technologies
TI’s Ryan Manack kicked off the roundtable with a discussion on some of the key obstacles that need to be addressed to drive widespread adoption of EVs. Two of those challenges are vehicle cost and range anxiety.
Manack said new innovations can help overcome some of the barriers to widespread adoption, including WBG technology such as GaN, which can help extend the driving range thanks to its higher efficiency operation, and advanced battery management systems. There are also trends like the use of lithium iron phosphate (LFP) to reduce costs versus nickel manganese cobalt and other chemistries and new wireless BMS “that’s a game changer for cost, manufacturability, and serviceability, he said.
Governments around the world are motivated to reduce CO2 emission and OEMs are committed to developing and delivering these zero-emission vehicles, Manack said. “There is a lot of work to be done but it’s hard to imagine a more exciting place to be spending time right now than automotive electronics.”
Similarly, Wolfspeed’s CTO Palmour discussed the benefits of using SiC in powertrain inverters. The higher efficiency has “real value to the automotive OEMs,” but he stressed that it is not a component-to-component comparison with silicon IGBTs. There has to be a system-level analysis “but the bottom line is using SiC makes the vehicle cheaper because it can save on battery costs and/or extend the range.”
Palmour said SiC is gaining very rapid traction – no pun intended – in the inverters for electric vehicles at 400-V busses along with a big push for an 800-V bus “where SiC shines even more versus the silicon IGBTs,” which allows for fast charging.
Even though SiC manufacturing is more energy-intensive than silicon, that extra energy is returned in about a 13-to-1 ratio for an 800-V bus over the lifecycle of a vehicle, he said.
The payback is even higher for an electric bus or long-haul truck. It’s about a 32-to-1 payback on the energy and that represents very significant savings to the owner in terms of energy usage across the lifetime, Palmour added.
So how will the 800-V system trend affect the choice of power devices? There is no doubt that moving from 400 V to 800 V is a trend and it is all about improving performance and charge times, said Manack. “There are many device options in the market today – silicon, IGBT, SiC, and GaN. All four of these are going to continue to coexist within the automobile and within the charging station as well. Each brings unique characteristics to the design.”
TI’s strategy is to integrate the driver within the GaN device, which reduces the switching inductance and enables up to 150 V per nanosecond of switching and TI’s devices can run up to 2.2 MHz, Manack said. “Being able to switch faster enables smaller magnetics in a DC-to-DC converter in an onboard charger (OBC), and shrinking the size of the magnetics by up to 60% is huge. We’re talking about weight reduction in the vehicle. Having that opportunity to number one shrink the size of the magnetics and number two to operate more efficiently, these are advantages that WBG semiconductors like GaN bring to the table.”
WBG semiconductors offer the ability to push extremely high-switching-frequency power conversion with very high efficiency, said Manack. DC-to-DC is a very important space for GaN with its size and weight savings from the magnetics, high efficiency, and simpler thermal management, even for onboard charging in select applications, he added.
GaN is about looking at areas where the high switching frequency is valued and the 150 V per nanosecond switching performance is leveraged to achieve the ultimate in power density in these applications, said Manack. “Anything we can do to reduce the weight and reduce the cost of the vehicle is going to increase the range and make it more attractive to consumers.”
Manack also noted there’s no reason why a traditional bridge couldn’t be used at 400 V where two 400-V power supplies are stacked on top of one another. “We see that certainly as a trend and that really delivers redundancy within the systems.”
From a battery management system (BMS) standpoint, the wireless trend is starting to heat up with automobile manufacturers, said Manack. At the higher voltages, there are “a lot of cells that are stacked in series and each of these cells has to be monitored and if you are talking about LFP that has to be monitored very accurately.”
In a traditional wired BMS a cell monitor is monitoring 12 or 16 cells, then the next cell monitor is measuring the next 12 to 16 and these are daisy chained through wires, which has a couple of challenges including latency and potentially manual assembly, which adds cost and time, he explained.
With a wireless BMS, the wires are eliminated and there is an RF link between each of the cell monitors directly to the battery management unit, so latency is reduced and there is direct communication to the VMU [vehicle management unit] and manufacturability becomes a lot simpler, said Manack.
Roadblocks to wireless charging
One of the biggest roadblocks to the adoption of EVs, besides the range anxiety, is the lack of charging stations, along with the speed of charging the battery. One possible answer is wireless charging. A growing number of companies are looking to offer wireless charging, which offers a range of benefits, including the elimination of cables, convenience, and potentially the elimination of charging times, according to Eggtronic’s CEO & CTO Spinella.
Panelists don’t believe wireless charging will become mainstream any time soon for EVs due to several factors including efficiency, cost, infrastructure, and standardization. Also, higher power electronics brings its own set of challenges, said Mitra.
There are several reasons to choose a wireless technology, but nobody is adopting wireless charging in EVs because of these challenges, said Spinella. He discussed the differences and limitations of both static and dynamic wireless charging and how to overcome these challenges. Also, a discussion on standardization is always needed when talking about wireless charging, he added.
Static wireless charging is the most probable in the short term and can take off pretty quickly, said Spinella. In contrast, dynamic wireless charging is more complicated but developing the infrastructure for it should be worked on, but it is for the longer term, he added.
At lower wattages wireless charging for phones and consumer devices are mainstream but for higher power there is a significant challenge on how to transfer this power wirelessly without much losses, said Mitra.
“But that being said there have been test tracks in place for both dynamic and static charging. There has been progress in this area and maybe in five to six years it could be the way we charge our vehicles but for right now and in the foreseeable future cable-based charging is going to be the way to go,” he added.
Future of DC charging stations
One of the biggest challenges to the adoption of EVs is the availability of chargers for all the different uses cases, said ABB Power Conversion’s Mitra. A tertiary challenge is the power electronic topology to support those use cases, he added.
ABB E-Mobility’s Nap addressed the trend for higher power charging at 350 kW, primarily for heavier vehicles like trucks and busses, and up to 1 megawatt (MW) for long-haul trucking and even higher for electric ferries and electric aviation. Today, there are very limited passenger EVs capable of charging at 350 kW today, but Nap said it will happen as automotive OEMs move to 800-V systems.
High-power charging is going to get more common and as you need more power the challenge is the current, said Mitra. “To keep the current manageable, you have to go to higher voltages – a 800-V battery – and there are some companies even looking at 1500 V, so the upper limit is going to keep getting pushed.”
In addition, with the higher power topologies, there are a number of considerations for efficiency because with high currents and high voltages there could be a significant focus on energy losses and adjusting the topologies to minimize that, he said. “Even a one percent savings is a notable savings at that amount of power. We are going to see more high-powered chargers out there with a varying number of topologies, especially some with common DC buses being connected to different energy sources, even green energy sources, too, connected to the same grid.”
“This is really an exciting time where electric vehicles are coming, the charging is there, and it fits into a broader ecosystem with renewable energy and local energy storage and generation, so if we discuss this in 10 or 15 years from now the world will look significantly different,” said Nap.
Will electrification be better with a greener electrical grid? The adoption of green energy has been driven by environmental considerations for the most part and there are many sources of green energy – mainly solar, wind, and hydro – that are currently contributing to the energy market, said Mitra.
He also noted that digital management with green energy will be essential. The biggest challenge is recognizing that each of these energy sources has their own generation profile.
“Wind doesn’t blow 24 hours a day and neither does the sun shine for 24 hours a day and matching this generation profile to the grid demand profile is always a challenge,” said Mitra.
To do that on a regional level or on a city level, power producers and energy distributors leverage digital power management tools, he added. “As we see this energy transformation from fossil fuel to green energy, there is going to be a shift in the way we manage green energy and in the way we consume it.”
The panel discussion was summed up nicely by Manack who said: “The world is changing fast and it’s really amazing just how quickly things have shifted, seeing the number of electric vehicles on the road and the number of solar panels and windmills. Even looking back a decade, it’s like an order of magnitude shift in just a short time. We’re continuing to work hard to solve these key problems in the industry on efficiency, on cost, and on speed. We’re all going to be critical to make electrification continue to proliferate and to make the world cleaner and greener, so it makes it an exciting journey to be on.”
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