New Power Module Integrates SiC MOSFETs and IGBTs to Cut EV Costs
Silicon carbide (SiC) continues to carve out a place for itself in power electronics after decades of dominance by silicon. SiC-based power switches are becoming the gold standard in the three-phase EV traction inverters due to their ability to handle higher voltages with better thermal conductivity and faster switching speeds. Such features lead to better power efficiency and a reduction in system cooling requirements. Faster switching speeds drive up power density by enabling the use of smaller magnetics and passives.
However, these power-handling advantages come at a cost. SiC power MOSFETs can cost up to 3X more than the IGBTs currently used throughout the EV. The price difference is driven by the complexity of the manufacturing process and the unyielding properties of the underlying material.
SiC is significantly harder and more brittle than silicon, which makes it more costly to process and polish the chips without damaging them. This could cut into the cost savings achievable at the system level with SiC power devices.
The “Fusion” Power Module
Infineon Technologies is trying to bring together the best of both technologies with what it calls the first “fusion” power module—the HybridPack Drive G2 Fusion. It puts SiC MOSFETs and silicon IGBTs in a single package.
The new plug-and-play module is all about striking a balance between the power efficiency of SiC and the cost efficiency of silicon, said Andreas Wiethege, product marketing manager of high-voltage power modules at Infineon (for more details, check out the video above). He discussed the innovations behind the automotive-grade power module with Electronic Design senior editor James Morra, and how the module could fit into the EV’s future.
By replacing only part of the power electronics under the hood, Infineon said the “fusion” module can reduce the SiC content in the EV. This reduces the overall BOM cost of the system without sacrificing the most significant gains in power density, said Wiethege. The fusion module contains a pair of IGBTs plus a single SiC MOSFET, and it supports up to 220 kW in the 750-V class.
According to Infineon, traction inverters based on it come close to the same efficiency at the system level as all-SiC power designs, with SiC using 30% of the area while silicon occupies 70%.
The Si-and-SiC power module expands the company’s family of HybridPack Drive power modules, and as a result, it can be integrated rapidly into traction inverters without requiring any complex adjustments or configurations. Infineon said this enables easy re-design from full-IGBT or full-SiC systems to what it calls “fusion” or “hybrid” inverters that put both power switching technologies in one device, optimizing performance based on load currents.
Hitting power levels as high as 300 kW, a traction inverter is a core building block of the EV, converting the DC supply from the high-voltage battery into the three-phase AC driving the electric motor. But it’s also one of the primary culprits of power loss—and, hence, heat—in the EV. The traction inverter operates most of the time at under 30% of its full load, while handling higher currents under heavy loads—for instance, during acceleration.
Under smaller loads, the fusion inverter uses SiC MOSFETs to run more efficiently due to their faster switching speeds and reduced on-resistance (RDS(on)), which results in minimal power losses during conduction. As the current entering the load comes closer to its peak, the IGBTs bear the brunt of it.
Despite the higher switching losses that can occur at these heavy loads, IGBTs can handle high currents very efficiently. They also have the upper hand on SiC MOSFETs in preventing short circuits or other transients that can damage a power supply.
Hybrid Inverter: A Stepping-Stone to All-SiC MOSFETs?
The hybrid inverter has the potential to be a valuable tool in the toolbox for power engineers. But it is probably more of a stopgap as the costs of manufacturing SiC power MOSFETs come down. By squeezing more power out of the battery and increasing charging rates, the SiC MOSFET is integral to the future of the EV, and many companies are taking steps to boost production.
In 2024, Infineon launched the world’s largest 200-mm chip fab for SiC power devices, marking a major step in scaling the output of these high-voltage components.
While SiC MOSFETs tend to have faster switching speeds than silicon, the IGBTs in the Fusion module also have very fast turn-on times, giving you the ability to use a single gate driver or dual gate drivers. Infineon said it can add another dimension to the power module by packaging the SiC MOSFETs and IGBTs with its gate -river ICs and high-precision current sensors to enable more accurate and efficient motor control.
The power module operates over a wide temperature range of −40 to 175°C, and the packaging improves thermal conductivity. That enables more efficient cooling of the EV’s power electronics, which usually run hot.
