A Charge-Based Analytical Model for Accurate Switching Transient Description of Half-Bridge GaN HEMTs

Gallium nitride high electron mobility transistors (GaN HEMTs) empower designs with higher efficiency and higher power density, but it can also suffer from severe electrical stress and undergoing complex transient waveforms if without careful design. Therefore, it is critical to accurately evaluate its switching transient performance, which however is hard to estimate and describe generally in conditions with wide operating range as a result of multivariable and nonlinear characteristics. Conventional switching transient analytical model based on C-V curve data from the datasheet brings barrier and face challenges for accurate description of switching transient, especially in conditions with wide ranges. Fundamentally, charge balance holds physically and can be utilized to directly describe charging/discharging process, which has the capability to represent the entire dynamic characteristic of system. In combination with Qg-Vgs, this paper proposes an accurate switching transient analysis model characterized entirely in the form of charge, taking all critical parasitic parameters and nonlinear effect into consideration. Through the dynamic Qgd test, it is found that the Cgd in the actual opening is different from the Cgd in the static test of C-V. At the same time, the gate charge curve Qg-Vgs in the datasheet is the result of the device under the switching dynamic test, which can be used for the switching process analysis. The comparison results show that the model can accurately evaluate the switching performance of GaN HEMTs compared with traditional models.