Fast switching 1200 V 50 A silicon carbide BJT´s in boost converters

Silicon carbide (SiC) bipolar junction transistors (BJT´s) are normally-off fast switching devices with very low collector-emitter voltages (V_CE), combining the best of properties from unipolar and bipolar technology. They switch fast with turn-offs from semi saturated state without current tails and have the same time extremely low saturated UCE values. SiC BJT´s free from bipolar degradation were fabricated and packaged in TO-247 packages. The BJT´s fabricated were characterized both statically and dynamically in a setup similar to a switching application, as well as tested for stability. A SPICE model was developed and simulations of the switching transitions were done and compared to measurements. The good properties of SiC BJT´s make a large impact on system design. Higher efficiencies can be achieved at higher switching frequencies, which reduce size of inductances and heat sinks, as has been shown by simulations.