Mathematical analysis of GaN high electron mobility transistor false turn-on phenomenon

摘要

High-power density is required in power conversion systems used in various applications, especially in electric vehicles. Driving the power devices with high frequency is one of the successful solutions to downsize a circuit's magnetic components, and hence an overall high-power density of the circuit can be realised. Therefore, GaN high electron mobility transistor (HEMT) is widely used in many applications, owing to its high-speed switching characteristics, low power losses, and high heat and radiation resistances. However, the high-speed switching of GaN HEMT comes with a drawback. For instance, in a full-bridge inverter configuration, high-speed turn-on of one device may cause a false turn-on of the complementary device. If a power device has encountered a false turn-on, the GaN HEMT devices will suffer from overcurrent, excessive heat and is eventually destructed due to the short circuit. This phenomenon can be tackled by modifying the circuit conditions. In this Letter, the theoretical analysis of a three-phase full-bridge inverter is developed to figure out the behaviour of the GaN HEMT gate voltage, which is the key-factor parameter causing a false turn-on. On the basis of the proposed theoretical analysis, the circuit conditions which minimise the gate voltage spike are derived.