In the past, the majority of applications such as uninterruptible power supplies (UPS), photovoltaic (PV) inverters, and motor drive have utilized IGBTs for the power devices due to the combination of highvoltage ratings exceeding 1 kV and high current capability. Usable switching frequency of IGBTs has typically been limited to 20–30 kHz, due to the high turnoff losses caused by the long turnoff current tail. Design comparisons have shown that SiC MOSFET designs can operate at considerably higher switching frequency and achieve the same or better efficiency. Although the device cost of the SiC MOSFETs are higher than the equivalent IGBTs, the significant savings in transformer, capacitor, and enclosure size results in a lower system cost.
The availability of Silicon MOSFETs with voltage ratings up to 900 V and low RDS(on) below 150 mΩ is improving. Beyond 900 V, low RDS(on) MOSFETs are not available. Although Si-MOSFET designs can be realized at considerably higher switching frequency than IGBTs, the cost of high-current and high-voltage Si MOSFETs is considerably higher than IGBTs.