An E-mode GaN HEMTs based three-level bidirectional DC/DC converter used in Robert Bosch DC-grid system

Instead of using 1200V SiC MOSFETs for the >600V applications, this paper utilized 650V E-mode GaN HEMTs to build a three-level DC/DC converter. The DC-bus voltage is 800V, the output voltage of 380V and the power is 2.5kW with the bidirectional power-flow capability. Simulation and experimental results show that such design strategy is superior to a single 1200V SiC MOSFET based DC/DC converter in terms of the switching and conduction performance. On the other hand, in order to better understand the performance of GaN HEMTs, hard-switching technology is used to fully test the switching behaviors. Two GaN HEMTs are in parallel to enhance the power capability, which requires the special focus on the parasitic parameters. The effects of parasitics especially the stray inductance in the commutation loop and the gate-drive loop during switching transitions have been comprehensively analyzed and discussed in this paper.