Powertrain Technologies for EV – Panel


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To maximize the driving range per charge for a given battery capacity, the entire power conversion chain must achieve the maximum efficiency possible. In a panel discussion at the Roadmap to Next-Gen EV & AV virtual conference, three industry experts examined the powertrain challenges confronting EV manufacturers, OEMs and Tier 1 suppliers. Joining EE Times for the discussion were Mike Kultgen, general manager for battery management systems at Analog Devices; Joseph Notaro, vice president for worldwide automotive strategy and business development at ON Semiconductor; and Mike Doogue, senior vice president for technology and products at Allegro MicroSystems. Here are some highlights from their conversation.
Power Technologies
EE Times: The EV revolution is accelerating the drive toward a more sustainable future. EV battery and propulsion systems are the keys to improved performance in the vehicles’ design. The relevant design parameters are the power level, conversion efficiency, operating temperature in the vehicle powertrain system, thermal energy dissipation capacity, and system package. What’s your take on the progress and challenges in these areas?
Mike Doogue: The market is quickly transitioning over from internal-combustion–engine powertrains to electrified powertrains. So, obviously, in power systems, measuring current is a very important thing to do.  Allegro’s current sensors help our customers improve efficiency, improve range, and improve the performance of the car.
We use a magnetic principle to measure current, so we actually measure the magnetic field created by a current-carrying conductor. As such, we actually don’t need to make electrical connection to that conductor, so we can sense current levels ranging from small to very large currents on a conductor that’s sitting at ground potential or at 800 volts. When you’re sensing with galvanic isolation, the IC itself really doesn’t know the difference in terms of the voltage on the node that you’re sensing, because you’re not making electrical connection with a semiconductor device to that node. It gives our devices a lot of flexibility, and not only in terms of the operating voltage; we can measure down to 1 amp all the way up to more than 4,000 amps with rather good accuracy. We can offer solutions with lower ohmic heating losses relative to shunt and amplifier-based solutions, particularly solutions that require opto-isolators. We have the isolation built into our ICs, and they are being used to help improve performance, [in designs] from inverters to chargers, DC/DCs, and battery management systems.
Mike Kultgen: There are really three categories of interest. There’s the powertrain, where the battery is a major component of that system. There’s autonomous driving or ADAS, where you really need high-efficiency, low-noise, and compact power supplies. And then, of course, there’s the in-cabin experience; whether that’s audio or head-up displays, noise cancellation is a requirement. The in-cabin experience is really transforming with electric vehicles. Focusing on the powertrain side of things, my business is primarily in the battery area, and what we try to do is safely maximize the energy throughput of the battery pack, because that really translates into what the customer experience is, which is longer driving range, faster charging, even lower cost, if you can get more mileage out of fewer batteries.
So, there are a lot of interesting problems to be solved in battery space. It’s mostly cell measurement, [for example,] trying to extract 4 volts of cell voltage on top of 800 volts of common mode and get a resolution of 1 millivolt. There could be hundreds of volts of transients;  it’s a very difficult, very nasty environment inside the battery. There are other powertrain applications: the inverter, the on-board charger. We provide the things that go around the switch, and as that business transitions to silicon carbide, specialized gate drivers are going to be needed; isolated power is always going to be needed. For the in-cabin experience, the processing power keeps going up, and the requirements on powering those devices keep going up. And again, [ensuring] low noise and high efficiency — all these things and a good power supply as well — is where we’d like to play.
Joseph Notaro: We’re focusing on ADAS/autonomous driving, and EVs. In ADAS/autonomous driving, I think the problem statement is how we generate data, manipulate the data, move the data, while in EVs it’s really, how do we manage energy? So, energy is really driven by power. And that’s really what the focus is. Because today, it’s exciting to be in automotive, especially in EVs. The challenges are really in the technology. How do we get better materials and better batteries? How do we really manage the energy better, and bring down costs, but also address the challenges for the consumer, which are charging and range anxiety? The second aspect is the infrastructure.
So, our mission is to create energy-efficient semiconductors that help to make the world greener, safer, inclusive, and connected. This is based on two pillars. One is technology. We want to give the best solution to our partners to create energy-efficient systems. The other is manufacturing —  being able not only to make the parts, but make them in high volumes required by this emerging market, and make them reliably with high quality and low cost. [To achieve] greater efficiency, you want to maximize the energy from the tank, [and thus] the charging to the wheels, so you spend more time driving and less time charging. That’s really our mission and what we are focusing on.
Battery Management Systems
EE Times: When building a large battery pack, both battery monitoring and battery balancing are required to maintain high battery capacity for the lifetime of the battery pack. How can battery management system solutions address this, and what is the current state of the art?
Kultgen: The goal of any battery management system is to safely get the most energy and power into and out of the battery pack, because that maximum throughput is what affects the vehicle. Safety is paramount. So, before you talk about anything, you consider safety; it affects the electronics design, battery cell design, mechanical design, software, temperature control systems — everything in the pack. The heart of every battery management system is the measuring and balancing of every single cell in the stack. That could be hundreds of cells or thousands of cells, some of them being in parallel, and the state of the art is measuring every single cell voltage, current, and temperature in the pack with up to 800 volts of common-mode voltage, and hundreds of volts and noise, and doing those measurements over a moderate temperature range up to 85°C, even 125°C. So, measurement accuracy is key.
EE Times: While there is an increasing need to find eco-friendly systems that can revolutionize the way we move, there is also a need to ensure that the new green technologies are as efficient and effective as possible in terms of price and performance. The addition of higher-voltage batteries to meet the increased power requirements has, in turn, increased the complexity of power delivery architectures and posed new demands in terms of size and efficiency. There are many electrification choices, but most manufacturers are opting for a 48-volt mild-hybrid system rather than a full-hybrid powertrain. Where does 48-volt technology plug in to the future of mobility? And what do you think of the trend to move to higher voltages (i.e., 800 volts) for fully electric vehicles? How will this affect the choice of power devices?
Doogue: There are various architectures being adopted in different places; mild-hybrid cars are real. Certainly, various industry experts predict a strong ramp in the number of mild-hybrid cars, which rely heavily on a 48-volt battery; we see that happening with our customers. So, we do believe that this portion of the EV revolution is real and that 48-volt battery power, mild hybrids will drive some volume in the marketplace in the years to come. At the same time, 800-volt technologies are accelerating more quickly as well. And sometimes I like to remind myself that a lot of those technologies already exist, and that electrified buses and other vehicles are already using 800-volt batteries. And we’ve started to see, whether it’s Porsche or other Tier 1 manufacturers, [companies] adopting 800-volt technologies.
Notaro: The 48-volt system definitely is a system that is compatible with vehicle ICs, so today you could upgrade a vehicle and really bring down the CO2 emissions at relatively low cost. The 48-volt [segment] is a reality; there are many cars on the market. In 2025, one-quarter of all new vehicles will be electrified; from 2030 on, [at least] one-half will be electrified, and that’s a combination, really, of 48 volts and 400 to 800 volts. So, there’s definitely a market that’s growing and has great advantages. On the other side, when we look at plug-in EVs, that’s where you start seeing the value of going to higher voltages, because in the end you have to deal with physics — you cannot change that. When we think of electrifying [powertrains] now for the high volts of plug-in electrification, along with that comes an infrastructure. Even with mild hybrids, 48-volt, you’ll need an infrastructure that is standalone.

Figure 2: Cross-platform solutions (Source: Allegro MicroSystems)

Figure 3: fast-charge driving increased battery voltages. (Source: ON Semiconductor)

Pandemic’s impact
EE Times: In terms of manufacturing, what are the current issues, if any, arising from the Covid-19 pandemic? What has been the impact on the e-mobility market? I think that this situation might provide good traction, a good boost, for a greener future by pushing that market even more decisively toward electric vehicles.
Kultgen: What we’re facing right now is an unprecedented demand for electric vehicles at a time when the semiconductor supply chain is experiencing capacity shortages in every step of manufacturing. So, on the demand side, in some regions, EV sales were up 300% year over year, at a time when you know the automotive market is just trying to return to normal. Some of this is [a result of] government-related stimulus packages that have favored EVs, particularly in Europe (and maybe Shanghai, China, is another example). I think the COVID lockdown gave us an awareness of air quality. The new work-from-home, play-from-home scenario has changed people’s buying habits and has changed people’s priorities. It has changed the definition of what you use your car for. But it has also created this demand for semiconductors and electronics outside of the car world which has impacted the car world. On the supply side, we’re looking at shortages of wafers, lead frames, assembly capacity, semiconductor-processing equipment, and test equipment.
Doogue: I saw in our industry — or let’s say in the automotive industry — that in the early days of the pandemic many businesses were unaware of how it was all going to end, so conserving cash was the key maneuver most companies were making. What we saw as a result was a clear statement about what were the most important R&D programs within certain companies. They were cutting back where they could to save money, but certain programs were untouchable; those were the most important programs to define the future. And what we saw throughout the pandemic was probably an acceleration of focus on EV platforms from an engineering and development perspective. I think that [observation is] backed up by various car companies’ talking about their commitment to be 100% electric, whether [by] 2030 or 2035. It was really an interesting phenomenon of the pandemic in that I believe it probably did work to accelerate the EV revolution and accelerate R&D spending in what many believe is the future of the industry.
Notaro: These are stressful times. The EV market is really driven by power, and managing energy is really predominant in the car. So now, not only automotive but industrial, cloud [infrastructure] — all these applications are going to need large amounts of power. The supply of power devices is going to be very constrained in the next five years. And we look at silicon carbide even more, because then you look to the substrate, so we’re focusing a lot on the manufacturing side. But the power requirements in the market are going to just skyrocket, and it’s going to create jobs [but also increase the demands] on the supply chain.
Infrastructure Concerns
EE Times: Infrastructure is the next challenge we will have to face. Let’s just think about the electric grid and the need for more charging stations and smart grids for managing our electric vehicles. Can the use of solar energy and other clean energy sources be increased so as to ensure that EVs have zero emissions?
Kultgen: Electric vehicles are only as green as the energy source that charges them, so we have to be conscious of that. Then there’s the manufacturing of the vehicle: if it has a large carbon footprint, what good have we really done when it comes to the environmental impact? So, we tend to look at the whole ecosystem, particularly in the battery space. How are batteries produced, and how can they be maximized in their use to minimize the carbon footprint? You see the European Union already imposing standards, such as a digital passport for the battery to make sure that its overall footprint is low. We look at the entire ecosystem and where we can play to help solve this problem. Obviously, when it comes to the grid, that secondary storage is going to help level the grid. Our battery management systems can be taken out of the car and directly applied to energy storage on the grid. We all play in the cell-manufacturing space to get the highest-capacity cells created using the least amount of energy.
Doogue: One of our mission statements within Allegro is to move technology in the world toward a safer, a more sustainable future. So, we are very proud and happy when we [someone] like my neighbor, who has solar panels on his roof and a charging box on the wall in his garage and his Tesla parked inside. I think we all know that there will need to be significant investment in infrastructure. I know that it will be costly, but I also believe in innovation, and I believe innovation can make the situation more manageable. People talk about the [specter] of everyone coming home from work and plugging in their EVs at the same time, creating peak loads on the grid. But that is a very solvable problem. With some innovation and scheduling and additional technology, perhaps controlled over the internet, we can make the stress on the grid lower.
Notaro: Infrastructure is probably the biggest challenge today; [as evidenced by the different initiatives and investments that have emerged to address it]. You’ll need the EV to be fully charged every time, but the point is that you can get the first 50% to 80% charge, and then engine recuperation is fantastic on these cars. I have a plug-in hybrid, and I’ve been amazed at how far I could drive, even with an empty battery, just due to recuperation. So, it’s just a mindset difference. But governments are going to have to step up, because the infrastructure and the companies generating [it are] are highly regulated. So that’s one of the challenges to come.
And then you’re going to have alternative technology. Fuel cells for commercial vehicles, for example, are going to be a good solution. I always trust that engineers will find the right solution to any problem.

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