Rohm Debuts 650 V IGBTs for EVs and Industrial Inverters

Rohm has developed a 4th-generation family of 650 V IGBTs for automotive electric compressors and high-voltage heaters, as well as inverters for industrial equipment. The devices achieve a collector-emitter saturation voltage of 1.55 V, which the company calls class-leading among automotive-grade 650 V products. It withstands short circuits for 7 µs and complies with the AEC-Q101 automotive reliability standard.

The RGAxxTS65HR and RGAxxTS65EHR series and IGBT wafer. Image used courtesy of Rohm

Working the Loss-Tolerance Trade-Off

Conduction loss and short-circuit ruggedness pull in opposite directions in IGBT design. Lowering VCE(sat) generally means raising channel density and thinning the drift region, which concentrates more current in the die during a fault and shortens the time the device can survive before thermal destruction.

That survival window is critical because the inverter and heater circuits require sufficient short-circuit tolerance to withstand the time it takes protection circuitry to detect an overcurrent and interrupt it, typically several microseconds. Rohm stated it redesigned the device structure, including the fabrication process and the edge termination, to loosen that trade-off.

The devices are built on the company's field-stop trench architecture, which pairs a trench-gate cell for high channel density with a field-stop layer that halts the electric field near the collector, permitting a thinner drift region and lower losses without giving up blocking capability. The 4th-generation parts increase current density while reducing both conduction and switching losses, yet still ensure a short-circuit withstand time of 7 µs at a junction temperature of 25°C. For comparison, the company's industrial field-stop trench IGBTs in the RGT series carry a 5-µs rating.

The company's 3rd-generation industrial 650V IGBTs, launched in 2018, reached a slightly lower VCE(sat) of 1.5 V, but those parts weren’t automotive-qualified. The new generation is distinct in that it combines conduction loss with AEC-Q101 qualification and longer withstand time in a single device.

650V Silicon in the EV Era

SiC MOSFETs continue to displace silicon in EV traction inverters, where 800-V architectures and drive-cycle efficiency gains justify their premium.

Auxiliary systems, however, present a different calculation, with electric air-conditioning compressors typically operating at single-digit kW and PTC and coolant heaters at roughly 5-10 kW at modest switching frequencies. EVs lack engine waste heat, so cabin and battery heating draw directly on the pack, and the switches driving them must be cheap, efficient, and robust.

At these power levels, the absolute energy savings a SiC device would provide are small, so cost per amp becomes a major deciding factor. Discrete SiC MOSFETs have historically sold at roughly three times the price of comparable silicon IGBTs, with the substrate the largest cost contributor, according to analysis from PGC Consultancy.

The IGBT wafer. Image used courtesy of Rohm

Rohm positioned the technologies as complementary: SiC for high-power traction, IGBTs for lower-power auxiliary systems, plus industrial motors and compressors, where the company expects demand to keep expanding. Auxiliary electrification is also broadening the addressable market as electric compressors and higher-power heaters become standard equipment across EV platforms, meaning unit volumes for 650 V-class switches continue to climb.

Lineup, Packages, and Availability

The launch lineup comprises 12 discrete products in the through-hole TO-247N package, forming the RGAxxTS65HR and RGAxxTS65EHR series, plus 10 bare wafer products in the SG83xxWN series for module manufacturers. The TO-247N parts can be purchased through online distributors including DigiKey and Farnell.

A further 12 products in the four-lead TO-247-4L package, the RGAxxTR65HR and RGAxxTR65EHR series, are in development. The fourth lead provides a Kelvin-emitter connection that separates the gate return path from the load current, reducing switching losses at higher frequencies.

Rohm also plans compact surface-mount devices in the TO-263L package and top-side-cooled packages, extending the family toward higher-density board designs.