The rising consumer demand, increasing environmental awareness, and expanding range of available options are driving the adoption of electric vehicles (EVs). A recent study by Goldman Sachs reveals that by 2023, EV sales will account for 10% of global vehicle sales, projected to grow to 30% by 2030, and potentially reach 50% by 2035. However, "range anxiety," or the fear that an EV's battery will not last long enough on a single charge, remains a significant barrier to widespread adoption. Extending vehicle range without significantly increasing costs is crucial.
This article explores how using Silicon Carbide (SiC) Metal-Oxide-Semiconductor Field-Effect Transistors (MOSFETs) in the main drive inverter can increase EV range by up to 5%. Additionally, it discusses why some Original Equipment Manufacturers (OEMs) are hesitant to transition from Silicon-based Insulated Gate Bipolar Transistors (IGBTs) to SiC devices and the efforts by onsemi to alleviate these concerns and boost confidence in this mature wide-bandgap semiconductor technology.
1.Trends in Main Drive Inverter Design
The main drive inverter in EVs converts DC battery voltage into AC voltage, meeting the electric traction motor's requirements to drive the vehicle. Current design trends in main drive inverters include:
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Increased Power: Higher inverter power output leads to faster acceleration and quicker response for drivers.
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Maximized Efficiency: Reducing the inverter's power consumption to increase the power available for driving the vehicle.
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Higher Voltage: The industry is moving towards 800V systems from the traditional 400V to reduce current, cable thickness, and weight. Thus, main drive inverters must handle higher voltages and use appropriate components.
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Reduced Weight and Size: SiC offers higher power density (kW/kg) than silicon IGBTs, which helps reduce system size (kW/L), decrease inverter weight, and lessen the motor load. This weight reduction extends vehicle range with the same battery and reduces the drivetrain size, increasing passenger and cargo space.
2.Advantages of SiC over Silicon
Silicon Carbide offers several material advantages over silicon, making it a superior choice for main drive inverter design. SiC has a higher physical hardness (9.5 on the Mohs scale compared to silicon's 6.5), better thermal conductivity (4.9 W/cm.K versus silicon's 1.15 W/cm.K), and a higher breakdown voltage (2500 kV/cm compared to silicon's 300 kV/cm). These properties allow SiC to operate reliably at higher temperatures and voltages, making it ideal for the increasing voltage architectures (800V) in EVs. Moreover, SiC's wider bandgap results in lower losses and faster switching speeds.
3.Addressing OEM Concerns About SiC
Despite its advantages, some automotive OEMs are reluctant to abandon traditional silicon-based devices like IGBTs for main drive inverters. Concerns include:
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Perceived Immaturity of SiC Technology
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Implementation Challenges
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Lack of Suitable Packaging for Main Drive Applications
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Supply Chain Concerns
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Higher Costs Compared to IGBTs
The following sections will address these concerns and explain why OEMs should confidently adopt SiC in EV main drive inverters.
4.Demonstrating Efficiency Gains with SiC
Boosting OEM confidence starts with demonstrating the clear performance benefits of using SiC in main drive inverter designs. Simulation results with onsemi's NVXR17S90M2SPB (1.7 mΩ Rdson) and NVXR22S90M2SPB (2.2 mΩ Rdson) EliteSiC Power 900V modules showed:
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At 10kHz switching frequency, 450V DC bus voltage, and 550Arms power transfer, SiC modules had a junction temperature (Tvj) of 111°C, compared to IGBT's 142°C—a 21% reduction.
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NVXR17S90M2SPB reduced average switching losses by 34.5%, and NVXR22S90M2SPB by 16.3% compared to IGBTs.
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Overall, full main drive inverter designs with NVXR17S90M2SPB showed over 40% lower power losses and 25% lower with NVXR22S90M2SPB, leading to an overall EV efficiency increase of 5%.
These improvements can extend an EV's range by 5%, such as extending a 500 km range EV to 525 km with onsemi's EliteSiC power modules. Moreover, the cost of using SiC in such inverters would be 5% lower than silicon IGBTs.
5.Enhanced Power Transmission
For OEMs considering transitioning from IGBTs, onsemi offers similarly sized SiC modules that simplify integration without manufacturing process changes. SiC modules also deliver higher power at the same junction temperature; for example, NVXR17S90M2SPB provides 760Arms compared to IGBT's 590Arms—a 29% power increase. Advanced interconnect technology in press-mold packages improves SiC module power density and reduces parasitic inductance, essential for high-speed switching efficiency. Higher switching frequencies also reduce the size and weight of passive components, and varied operating temperatures (up to 200°C) lower OEM cooling requirements, potentially allowing smaller pumps for thermal management.
6.Broad Adoption of SiC in EV Architecture
As EV battery voltages rise, reducing current while maintaining the same power output becomes feasible. System-wide, this means thinner cables throughout the vehicle. Transitioning to SiC is increasingly sensible as SiC devices generate less heat, achieve higher power density, and impact broader EV architecture beyond the main drive inverter.
7.Alleviating OEM Concerns About SiC Supply
onsemi has heavily invested in a fully integrated and mature SiC supply chain and ecosystem, including wafer epitaxy and 150mm manufacturing (with plans to move to 200mm), covering discrete products, integrated circuits, modules, and reference designs. With over a decade of development, Onsemi's expertise helps automotive OEMs address all concerns about adopting SiC.
