Analytical Loss Model of High Voltage GaN HEMT in Cascode Configuration

This paper presents an accurate analytical model to calculate the power loss of a high voltage Gallium Nitride high electron mobility transistor (GaN HEMT) in cascode configuration. The proposed model considers the package and PCB parasitic inductances, the nonlinearity of the junction capacitors, and the transconductance of the cascode GaN transistor. The switching process is illustrated in detail, including the interaction of the low voltage Si MOSFET and the high voltage GaN HEMT in cascode configuration. The switching loss is obtained by solving the equivalent circuits during the switching transition. The analytical results show that the turn-on loss dominates in hard-switching conditions while the turn-off loss is negligible, due to the intrinsic current source driving mechanism. The accuracy of the proposed model is validated by numerous experimental results. The results of both the analytical model and experiments suggest that soft-switching is critical for high voltage GaN in high-frequency high-efficiency applications.