A highly efficient non-isolated DC-DC buck-boost converter with a cascode GaN-FET and SiC-Schottky diode

Growing demand for more efficient power converters, corresponding with increased renewable energy generation, is necessitating high performance semiconductor power devices. Though most power devices are currently made from silicon (Si), these devices are approaching their theoretical performance limits as they suffer from high conduction and switching losses under harsh operating conditions. Wide bandgap (WBG) semiconductors such as silicon carbide (SiC) and gallium nitride (GaN) contain superior materials allowing power devices to operate efficiently at higher blocking voltages, switching frequencies, and junction temperatures. The objective of this research is to design a highly efficient non-isolated dc-dc buck-boost converter with a hybrid Cascode GaN-FET/SiC-Schottky diode power device for residential PV applications. The performance and efficiency of the converter with this combination of power devices is compared against a common Si-MOSFET/Si-diode. The switching behavior of each device is evaluated, as well as energy loss when the switch current is increased. Total power loss and efficiency are assessed at varying switching frequencies, output power levels, and load currents. The hybrid Cascode GaN-FET/SiC-Schottky diode improves the switching performance, reduces power loss, and increases the efficiency of the buck-boost converter.