The third generation of power semiconductor devices, such as GaN HEMTs, have been increasingly used in the design of power converters, due to their advantages of low loss, high efficiency, fast switching speed and high operating frequency. However, high dv/dt and di/dt slew rates of GaN devices will generate more electromagnetic interference (EMI) noise in power converters, and GaN devices themselves are more sensitive to EMI noise due to the lower threshold voltage, which leads to more instability and fault factors. In this paper, conducted EMI is analyzed for GaN HEMT-based LLC resonant converter, and the effect of high-frequency transformer is also investigated, which provides the common mode (CM) EMI propagation path. Then, CM EMI equivalent circuit model of LLC resonant converter is proposed to predict the conducted CM EMI noise. Finally, experiments are carried out to verify the effectiveness of the conducted CM EMI modeling method of GaN-based LLC resonant converter.

LLC resonant converters have been widely used in industry because of its soft switching characteristics in the full load range. However, due to the increasing switching frequency with the help of wideband-gap devices, electromagnetic interference (EMI) of LLC resonant converters has become a key problem in such systems. High dv/dt or di/dt of wideband-gap (WBG) semiconductor switches produce a large number of high-frequency harmonic components, thus common-mode (CM) and differential-mode (DM) noise signals are generated in LLC resonant converters. In order to investigate EMI issues, an improved CM and DM models are established respectively to represent the high-frequency behavior, and the equivalent circuit parameters of CM and DM impedances are extracted according to the experimental results. The calculated CM and DM impedances are in good agreement with the measured ones from the vector network analyzer (VNA), which verifies the effectiveness of the proposed high-frequency CM and DM models.

The performance of silicon carbide (SiC) metal oxide semiconductor field effect transistor (MOSFET) is better than silicon devices in terms of switching speed, switching loss and temperature tolerance. Due to the higher di/dt and dv/dt during the switching process and the combined effect of various parasitic parameters, serious bridge-leg crosstalk will be generated in the SiC MOSFET bridge circuit. This paper firstly analyzes the mechanism of crosstalk, and based on the parameters extracted from the device data sheet and experiments, the maximum values of the bridge-leg crosstalk voltage under different operation conditions are calculated. Secondly, a passive Miller clamp circuit on crosstalk suppression in SiC MOSFET bridge-leg configuration is proposed in this paper. When the crosstalk occurs, the proposed driver circuit shunt the Miller current to the ground, and the gate-source parasitic capacitance of SiC MOSFET is bypassed. The advantages of the proposed crosstalk suppression circuit are that the switching speed is not sacrificed, the circuit topology is relatively simple, and it is easy to be integrated into the driver circuit of SiC MOSFETs. Finally, experimental results prove the effectiveness of the proposed crosstalk suppression circuit.