Reducing reverse conduction and switching losses in GaN HEMT-based high-speed permanent magnet brushless dc motor drive

The use of gallium nitride (GaN) high-electron mobility transistors (HEMTs) is a promising solution for a highly efficient motor drive design due to their high-switching speed and low on-state resistance. However, the higher reverse voltage drop of GaN HEMTs than that of the conventional silicon (Si) devices generates significant reverse conduction loss during the freewheeling period. This phenomenon can be exacerbated especially when regenerative braking or bipolar PWM is utilized since the reverse conduction period increases. It can also lead to a device failure when high freewheeling current flows through the reverse conduction channel. This paper suggests a critical design consideration of GaN HEMT-based high-speed permanent magnet brushless DC motor drive regarding the reverse conduction and switching losses minimization. A diode-free GaN-HEMT-based single-phase brushless DC motor has been designed to quantify the effect of reverse conduction loss on the overall motor drive efficiency. Three different solutions to reduce the reverse conduction loss are applied and compared in detail. The switching characteristics are also investigated to quantify the effect of the additional antiparallel diode in GaN HEMT-based motor drive.