Design and Experimental Verification of a High-Voltage Series-Stacked GaN eHEMT Module for Electric Vehicle Applications

A gallium nitride (GaN) power switching module with extended rated voltage is proposed for electric vehicle power conditioning system. Limited breakdown voltage of GaN high-electron-mobility transistors (HEMTs) hinders their usage in high-voltage applications. The presented GaN module is composed of two series-stacked enhancement-mode HEMTs for the purpose of duplicating the breakdown voltage. An integrated series-switch driver (SSD) is used to drive the stacked eHEMTs. The SSD provides adequate gate charge for both HEMTs in the module, and guarantees balanced voltage sharing between the devices during the switching transitions and steady state. The operation principle of the module is described thoroughly, and an analytical model has been derived considering parasitic inductances. Simulation analysis is carried out to study the performance of the SSD in various conditions. Also, the effect of variation in the SSD parameters on the gate-source voltage oscillation is investigated. Finally, an experimental setup of a bidirectional boost converter with two 1.3-kV GaN eHEMT modules is developed and tested under various scenarios. Moreover, a loss comparison between the proposed 1.3-kV GaN module and a 1.2-kV SiC MOSFET is carried out. The simulation and experimental results show that the developed GaN eHEMT module has satisfying dynamic and static performance with less than 10% voltage mismatch during the steady-state period for all scenarios. Also, the GaN module proved to have 35%-55% lower power loss (for different switching frequencies) compared to the SiC MOSFET counterpart.