Modeling and Analysis of Bridge-Leg Crosstalk of GaN HEMT Considering Nonlinear Junction Capacitances

Gallium nitride high electron mobility transistor (GaN HEMT) has fast switching speed and low threshold voltage, which could result in a severe false triggering voltage pulse at the synchronous freewheeling transistor in bridge-leg circuit when the control transistor turns on. To suppress the crosstalk phenomenon, this article proposes an analytical model about the crosstalk voltage, with consideration of nonlinearities in capacitance-voltage (C-V) of GaN HEMT. By utilizing the equivalent circuit of control transistor and synchronous freewheeling transistor, the number of analytical model parameters to be extracted can be reduced significantly. Besides, the nonlinear characteristic of junction capacitances is taken into account in the model, and the accuracy is verified by the current-voltage (I-V) curve of capacitances. Based on the model, an exhaustive investigation into the impact of device and circuit parameters on the crosstalk phenomenon is conducted. Further, for the purpose of evaluating the oscillation of crosstalk voltage, the damping ratio and oscillation frequency are acquired. The proposed model can be applied to guiding GaN device selection and printed circuit board (PCB) circuit design. The effectiveness and superiority of the proposed model are verified with simulations and experiments on a double pulse test platform.