STMicroelectronics has released the fourth generation of its STPower silicon carbide (SiC) MOSFET technology. ST claims the new MOSFETs will offer higher performance levels in terms of efficiency, power density, and robustness.
While suited to a range of high-voltage and high-power density industrial and e-mobility applications, the new generation MOSFETs specially target EV traction inverters, the essential element of an EV powertrain that converts DC power from the battery pack to three-phase AC to power the motor.
EV powertrain. Image used courtesy of Siemens
The new SiC MOSFETs will be available with 750-V and 1,200-V ratings to support both 400-V and 800-V battery bus voltages, the latter providing faster vehicle charge times and longer ranges. 750-V variants of the new MOSFETs have completed qualification, and the 1,200-V models are set to complete qualification in the first quarter of 2025. Commercial availability will follow soon after. In addition to EVs, the new MOSFETs can serve high-power industrial applications such as solar inverters, energy storage solutions, and data centers.
Improving EV Performance
Within an EV’s powertrain, the traction inverter converts DC power from the battery to three-phase AC to drive the EV’s electric motor. To do this, the traction inverter uses a bridge circuit constructed from discrete power MOSFETs or carefully sequenced power modules to generate the required AC motor drive waveforms. The performance of the inverter and its switching power components greatly impact the overall performance of the EV.
EV powertrain block diagram. Image used courtesy of STMicroelectronics
ST’s new Gen 4 SiC MOSFETs feature a lower on-resistance (RDS(on)) than prior generation devices; when the switches are on, they generate fewer I2R losses. This translates to more efficient power conversion and a lighter, more compact solution because of fewer thermal management concerns—all critical factors to an EV’s range, charge times, and cost.
Considering a figure of merit (FOM) of die size x RDS(on), ST claims that its Gen 4 SiC MOSFETs require 12% to 15% less silicon area to achieve a similar on-resistance to a Gen 3 device, saving space and reducing per-unit costs. Along with a lower RDS(on), higher switching speeds and increased robustness also contribute to a smaller, lighter, and less expensive EV drivetrain.
ST’s SiC Technology Roadmap
ST plans to continue delivering new SiC solutions through 2027 and beyond. To do this, the company has invested in a vertically integrated silicon carbide supply chain from substrate manufacturing to final device assembly and packaging. For the coming fifth generation of its SiC technology, ST is exploring new planar structures to improve power densities and lower on-resistances.
Silicon carbide wafer. Image used courtesy of STMicroelectronics
According to the company, ST has supplied more than five million STPower SiC devices globally for EV applications, including for traction inverters, onboard chargers (OBC), DC-DC converters, and charging stations.
