Infineon Brings Bidirectional Switching to Rugged SiC Power Designs
At power electronics trade shows, many companies are talking about bidirectional switching.
Many systems need controlled energy flow in both directions, from EV charging and solar-storage systems to rack-level HVDC power conversion, eFuses and pre-charge circuits. In a more conventional design, engineers achieve bidirectional blocking with two discrete MOSFETs in a back-to-back configuration. But this approach adds component count, board area, gate-drive coordination, parasitic effects, and EMI and thermal design complexity.
We recently discussed the developments around GaN bidirectional switches. In this article, we now look at Infineon Technologies’ latest “industry-first” silicon carbide (SiC) bidirectional switches (BDS) built on its 750 V CoolSiC G2 technology for high-density power conversion. The technology combines bidirectional blocking and conduction into a single compact device footprint by integrating two SiC MOSFET dies in a vertically integrated, common-drain configuration.
Infineon says the portfolio will span RDS(on) values from 14 mΩ to 66 mΩ and is aimed at applications where bidirectional power flow, ruggedness, and thermal performance must be addressed together. For power electronics engineers, the device should be evaluated as a new switching element that affects topology, gate drive, layout, EMI, protection, and cooling.
“BDS is moving from a niche concept to a viable replacement for discrete back-to-back switches in high-density, bidirectional systems. Infineon has set a benchmark in the market for bidirectional switch technology and is positioned as the only supplier offering BDS solutions in both CoolSiC and CoolGaN technologies,” says Zsolt Gyimesi, senior product marketing manager at Infineon Technologies, in an exclusive interview with Power Electronics News.
Ruggedness is central to SiC BDS
Infineon has emphasized the ruggedness of its 750-V CoolSiC BDS bidirectional switch because it targets power systems that face sustained electrical stress, fast load transients, voltage overshoot, thermal cycling, and fault events. These include AI power supplies, rack-level HVDC conversion, EV charging, solar storage systems, HVAC systems, industrial drives, and solid-state protection.
But in all this, efficiency remains important. A device that reduces conduction and switching losses must still survive the operating environment over the system’s expected lifetime. For EV charging operators, solar storage installers, and data center power designers, a field failure can result in maintenance costs, downtime, and service disruption.
“Reliability and ruggedness are paramount where devices face continuous stress over long operating periods. Engineers need components that can maintain performance around the clock under heavy loads, rapid transients and extreme thermal cycling,” Gyimesi notes.
The Infineon SiC BDS has an 840-V breakdown capability that provides additional margin for the system operating at bus voltages above 500 V. This is crucial in power architectures where line variation, switching transients, or energy stored in parasitic inductance can create voltage stress. In grid-connected and high-power systems, that voltage margin can become important as designers try to balance efficiency, compactness, and protection.
The 200 V/ns dv/dt rating is another important specification indicating that the Infineon SiC BDS is designed for fast-switching environments. High dv/dt capability can support higher-frequency operation and lower switching losses. But switching behavior still depends on the PCB layout, commutation-loop inductance, coupling capacitance, gate-loop design, and driver-source routing. The rating provides designers with the flexibility, but it does not eliminate the need for careful parasitic control.
Infineon highlights a 2 µs short-circuit withstand time and overload endurance with up to a 200 °C junction temperature for 100 hours. Short-circuit withstand time (SCWT) gives the protection circuit a limited window in which to detect and respond to a fault. The 200 °C overload capability provides designers with additional flexibility under abnormal or transient thermal stress.
“The device also has avalanche energy robustness (single-pulse rating of ~800 mJ). This means the device can absorb an inductive surge, such as when an AI server rack’s power draw suddenly drops, causing an overshoot, without failing,” Gyimesi adds.
Infineon specifies a typical threshold of 4.5V at 25°C and an ultra-low QGD/QGS ratio. The extended transient gate-bias tolerance of -11 V to +25 V also gives added margin against gate overshoot and switching-related stress. These parameters are important because unwanted turn-on, gate ringing, and transient gate stress can become major reliability risks.
“Engineers should treat these specifications as indicators of design margin under dynamic switching and fault conditions, not as reasons to relax system-level protection,” Gyimesi emphasizes.
The difference between SiC and GaN BDS
Infineon positions the CoolSiC and CoolGaN bidirectional switches as complementary platforms. Both address the same broad architectural need of replacing discrete back-to-back switching arrangements with a more integrated bidirectional switching function. But the two technologies are not interchangeable. The best choice depends on the converter’s voltage, frequency, thermal, and reliability requirements.
Infineon’s SiC BDS uses a dual-die structure with two SiC switches integrated in a common-drain configuration, as explained earlier. It’s CoolGaN BDS, by contrast, is monolithically integrated (Figure 2). The change comes from the underlying device technologies and leads to different engineering trade-offs. GaN’s monolithic structure supports a compact bidirectional switch with high-frequency performance, while SiC is more closely tied to voltage capability, current handling, ruggedness, and thermal performance in high-stress power systems.
For example, a 650 V class GaN BDS is suited for applications where very high frequency, compactness, and high integration are the primary design drivers. GaN is attractive in such use cases, where reducing passive size, increasing switching speed, and simplifying compact converter architectures are central goals. But the 750 V CoolSiC BDS is aimed at applications that require higher voltage and current capability, stronger thermal margin, sustained heavy-load operation, and fault robustness.
Top-side-cooled Q-DPAK
The packaging of Infineon SiC BDS is also a value proposition. Integrating two switches into one device concentrates heat. But Infineon’s 750-V CoolSiC BDS uses a top-side-cooled (TSC) Q-DPAK package to create a direct thermal path from the device to a heat spreader or heatsink. This is consequential in high-density power stages where the PCB cannot be treated as the primary heat removal path.
“The two chips inside the package are optimally positioned in the Q-DPAK package to make best use of the lead frame’s optimized side. In addition, the .XT soldering technology ensures superior thermal performance,” Gyimesi explains.
He continues, “When that is paired with a tight power loop and careful placement of nearby passive and gate-drive elements, integration can improve both thermal and electrical performance rather than forcing a compromise between them.”
For engineers, the TSC surface-mount package can also enable more compact power-stage layouts, better use of PCB area, and closer placement of gate-drive and passive components.
“The engineering point is that package integration should be evaluated as part of the complete thermal system: semiconductor, package, PCB, interface material, heatsink, and enclosure,” says Gyimesi.
Looking ahead
Infineon’s 750-V CoolSiC BDS shows how bidirectional switching is moving toward a more application-ready power-stage building block. The ruggedness specifications explain why Infineon is targeting demanding applications such as AI power supplies, EV charging, solar-storage systems, industrial power and solid-state protection.
The comparison with CoolGaN BDS explains that the choice is not SiC versus GaN. But which device best fits the converter’s voltage, frequency, thermal and reliability requirements? For engineers, the opportunity is in redesigning the power stage around bidirectional switching, SiC ruggedness, top-side cooling, and tighter electrical and thermal integration.
Cover image: Infineon Technologies
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