Experimental evaluation of medium-voltage cascode gallium nitride (GaN) devices for bidirectional DC-DC converters

Wide bandgap (WBG) semiconductors, such as silicon carbide (SiC) and gallium nitride (GaN), exhibit superior physical properties and demonstrate great potential for replacing conventional silicon (Si) semiconductors with WBG technology, pushing the boundaries of power devices to handle higher blocking voltages, switching frequencies, output power levels, and operating temperatures. However, tradeoffs in switching performance and converter efficiency when substituting GaN devices for Si and SiC counterparts are not well-defined, especially in a cascode configuration. Additional research with further detailed investigation and analysis is necessitated for medium-voltage GaN devices in power converter applications. Therefore, the aim of this research is to experimentally investigate the impact of emerging 650/900 V cascode GaN devices on bidirectional dc-dc converters that are suitable for energy storage and distributed renewable energy systems. Dynamic characteristics of Si, SiC, and cascode GaN power devices are examined through the double-pulse test (DPT) circuit at different gate resistance values, device currents, and DC bus voltages. Furthermore, the switching behavior and energy loss as well as the rate of voltage and current changes over the time are studied and analyzed at various operating conditions. A 500 W experimental converter prototype is implemented to validate the benefits of cascode GaN devices on the converter operation and performance. Comprehensive analysis of the power losses and efficiency improvements for Si-based, SiC-based, and GaN-based converters are performed and evaluated as the switching frequency, working temperature, and output power level are in-creased. The experimental results reveal significant improvements in switching performance and energy efficiency from the emerging cascode GaN devices in the bidirectional converters.