Assessing next-generation discretes
by Dr. Thomas Barbieri, Wolfspeed, A Cree Company, Power Systems Design, Nov 05 2015
Focus:
Despite improvements in the performance and quality of SiC Schottky diodes over several generations of their development, some designers still have concerns about the dV/dt ruggedness of these diodes. In this article, the author asserts that an industry-standard test method is needed to assess dV/dt ruggedness, presents test circuits developed for this purpose, and gives test results for newer 600-V and 1200-V SiC Schottkys from Wolfspeed. After reviewing the history of SiC Schottkys with respect to dV/dt ruggedness, and explaining the impact of this spec on power converter switching losses, the article describes the design and construction of a high-speed, high voltage pulse generator (pulser). One version of this pulser uses bipolar junction transistors (BJTs) designed for avalanche operation for testing the 600-V Schottkys, while the other uses BJTs and SiC MOSFETs for testing the 1200-V Schottkys. The Wolfspeed devices are found to achieve reverse (turn-off) dV/dt values that are (at least) six times faster than the typically reported values.
What you’ll learn:
- How to test the dV/dt ruggedness of SiC Schottky diodes
- How to understand the level of dV/dt performance available from latest-generation SiC Schottkys
- How to understand the impact of dV/dt capability of SiC Schottkys on a power converter’s switching losses
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