ROHM’s Hybrid IGBTs Target Performance by Adding a SiC Schottky Barrier Diode
Combining traditional silicon IGBT technology with silicon carbide Schottky barrier diodes, ROHM is hoping to create a new hybrid class of power solutions.
As power solutions continue to evolve, new electronic topologies emerge. Silicon carbide Schottky barrier diode (SiC-SBD) devices claim to offer superior performance to Si fast recovery Diodes (Si-FRD).
This week, ROHM announced a ‘hybrid’ IGBT device that integrates a SiC-SBD within its IGBT products, thereby attempting to create a family of devices with a performance boost over existing options.
The ‘hybrid’ IGBT and SiC-SDB from ROHM, the RGWxx65C series. Image used courtesy of ROHM
Today, this article will look at the new devices being offered in this hybrid series and examine how adding a SiC-SBD to an IGBT could improve its performance in high-voltage, high-power applications.
Three New Hybrid IGBTs
With this release, ROHM brings out three new components: the RGW60TS65CHR, the RGW80TS65CHR, and the RGW00TS65CHR, which are part of this hybrid class of IGBTs. All three members are rated at 650 Vces, with an Ic rating from 30 A to 50 A, and are available in a TO-247N package.
The new device family is said to provide 67% lower loss when compared to conventional IGBTs (with 24% lower loss than super junction MOSFETs).
The loss comparisons between three power classes. Image used courtesy of ROHM
All three include a SiC-SBD, which provides is the "hybrid" element to this release. The SBD potentially has favorable operating characteristics when designed for applications in the 400 V to 3.3 kV range.
Operating voltage ranges of FRDs, PNDs & SBDs. Image used courtesy of ROHM
Each variant is AEC-Q101 qualified, lead-free, and ROHS compliant. They are slated to enter mass production in December 2021.
After learning about this new family, it raises some questions: why is ROHM integrating SiC-SBD into its power products, and how does a SiC-SBD compare to a Si-based fast recovery diode?
Head-to-Head IGBT Datasheets: SiC-SBD vs FRD
Digging into the datasheets for two ROHM IGBT products, this article will compare the performance parameters of a built-in fast recovery diode (FRD) vs. a SiC-SBD. ROHM’s RGW60TS65DHR is an IGBT with an internal FRD.
The RGW60TS65CHR, on the other hand, is one of ROHM’s three new SiC-SBD hybrid IGBTs. The basic operating parameters for each device are identical, 650 V (Vces) with 30 A (Ic).
The basic parameters of the IGBT itself are nearly identical between the two models, excepting the worse collector cut-off current (Ices) for the IGBT and SiC-SBD.
Across the board, the SiC-SBD provides faster switching parameters with higher potential power efficiency over the FRD. For example, the forward voltage (max) of the SiC-SBD is rated to be 0.35 V less than the FRD.
The SBD contributes to superior power conversion. Image used courtesy of ROHM
Additionally, the reverse recovery time is decreased by ~60% (from 87 ns to 34 ns).
Faster recovery times contribute to lower losses. Image used courtesy of ROHM
The performance benefits of SiC-SBD over FRD also include lower component noise, along with characteristics that are independent of temperature.
Despite all this, ROHM’s FRD technology isn’t going to be phased out but instead will become an alternative technology to the newer hybrid IGBTs.
A Focus on Effective Power Solutions
With this release, ROHM has indicated that it is committed to providing a host of technologies for SiC, silicon, and other driver-based applications.
This commitment aligns, conveniently, with an industry trend in power electronics to create ever more efficient designs, which in turn aims to push forward the electrification of our society.
However, as any engineer learns early in their career, there are no easy trade-offs in systems engineering. It is not as simple to replace existing fossil fuel-based energy systems with electronic power systems without innovation, significantly improving the latter option. Despite that, this new series of hybrid IGBTs could be one small building block towards that goal.