Application of a Normally OFF Silicon Carbide Power JFET in a Photovoltaic Inverter

Conventional wisdom that the SiC JFET is only a normally on device has recently been superseded by the first practical normally off SiC JFET. This new true enhancement mode, three-terminal, pure-SiC design provides designers with a normally off solution that retains all the benefits of the normally on SiC JFET. With only a simple change in series gate impedance, the EM SiC JFET can be used with common IC drivers and is a drop-in replacement for current silicon power devices in most applications. The device characteristics for the normally off SiC JFET are superior to MOSFETs and IGBTs and offer the possibility of efficiency improvements from reduced conduction and switching losses. The work presented in this paper demonstrates the drop-in replacement of 4 IGBTs with 4 normally off SiC JFET in a commercially available solar inverter based on a full-bridge topology. While demonstration as a drop-in replacement device was the main goal, system efficiency for operation with each device was observed and compared and an immediate improvement observed for the SiC JFET.