The transition from fossil fuels to electric vehicles (EVs) is accelerating, driven by ambitious targets like the EU’s 2035 zero-emission milestone. For EVs to appeal to consumers, they must offer sufficient range, quick charging, and affordability. A key technology enabling this transition is silicon carbide (SiC) semiconductors, particularly MOSFETs, which provide significant performance gains in power electronics.
The Advantages of SiC MOSFETs
SiC MOSFETs outperform traditional silicon devices at higher voltages by delivering higher efficiency, faster switching, and better performance with less heat dissipation. This technology allows for more compact modules without compromising efficiency or peak power in traction inverters and on-board chargers (OBC), resulting in lighter vehicles with more usable space.
- Left: M1 Technology (Planar square cell)
- Center: M2 Technology (Planar elongated hex cell with thin wafer technology)
- Right: M3S Technology (Planar stripe cell, thin wafer technology with significant unit cell reduction)
Enhanced Performance in EV Applications
SiC MOSFETs are increasingly replacing Si MOSFETs, diodes, and IGBTs in critical EV applications. While IGBT technology is cost-efficient for low- to mid-range EVs, SiC offers higher switching frequencies, improving efficiency through reduced conduction and switching losses and increasing power and current density.
Using onsemi’s EliteSiC MOSFETs, designers can create 22 kW OBC power stages for battery voltages up to 800 V and HV-LV DC-DC converters that step down high voltage from a 400 V or 800 V battery to a 12 V low voltage power net. To maximize SiC MOSFET gains, other system components, such as gate drivers, should be optimized for this technology.
Traction Inverters and Market Growth
Traction inverters, which convert DC power to AC power for EV motors, are another critical application where SiC devices are replacing traditional silicon IGBTs. According to IDTechEx, SiC MOSFETs will dominate the EV inverter market by 2035. These inverters require HV components rated from 600 V to 1200 V and operate at current levels up to 200 A peaks per phase, with power levels from 50 kW to 250 kW or more.
IDTechEx forecasts that the global market for power electronics in EVs will reach $36 billion by 2035, with a compound annual growth rate (CAGR) of 17% from 2025 to 2035.
The Role of Gate Drivers
High-performance power systems with SiC MOSFETs need isolated gate drivers with high source and sink peak current capability for optimal efficiency. Gate drivers manage the switching speed of power transistors like SiC MOSFETs, delivering the precise gate voltage (VGS) and current required for rapid switching. This is crucial for minimizing switching and conduction losses.
Dedicated gate drivers provide the necessary voltage and drive current to the MOSFET’s gate, integrating the required isolation barrier between low and high voltage sides. This improves reliability, circuit robustness, and safe operation with features like galvanic isolation, independent under-voltage lockout, and protection against various fault conditions.
Isolated Gate Driver with Integrated Negative Bias Control
onsemi's NCV51752 is a single-channel gate driver designed to drive SiC MOSFETs, ensuring fast and reliable switching. With a short propagation delay of 36 ns and high dV/dt immunity of 200 V/ns, the NCV51752 enhances SiC-based system performance. Its integrated negative bias control and high-isolation voltage further improve reliability and safety.
SiC MOSFETs are fast-switching devices that can create high slew rates, leading to parasitic turn-on due to Miller capacitance. The NCV51752 mitigates this issue by swinging VGS below 0V during turn-off, preventing spurious turn-on and saving overall system costs by eliminating the need for an external negative bias rail.
SiC and high-performance gate drivers are revolutionizing EV power systems by providing higher efficiency, faster switching, and better performance. As the EV market continues to grow, these technologies will play a crucial role in meeting consumer expectations and regulatory targets, driving the future of sustainable transportation.
Additional Resources
Enhancing Performance, Efficiency and Safety with SiC Isolated Gate Drivers
System Solution GuideOn Board Charger (OBC)
