Because of higher switching speed of silicon carbide MOSFET, the crosstalk in a phase-leg configuration will be more serious, which hinders the increase of switching frequency and lowers the reliability of the power electronic equipment. The displacement current of the gate-drain capacitor and the voltage drop on the common-source inductors can induce the crosstalk. In order to suppress the crosstalk, this paper proposes a novel gate driver, in which two additional capacitors are added to create the low turn-off gate impedance. With this proposed driver, the common-source parasitic inductor can be decoupled from the gate loop and the displacement current of the gate-drain capacitor can be bypassed. In addition, the operating principle and the parameters design are also analyzed. Finally, the crosstalk in the non-Kelvin package and the Kelvin package are tested by experiments, the validity of the analysis and the effectiveness for suppression the crosstalk are proved as well.

The conventional hysteresis current control (C-HCC) in VIENNA rectifier is one of the simplest and economic strategies. However, current harmonics content and switching number are high, and the coupling among the three-phase cannot be eliminated. The vector control based on SVPWM has a higher control accuracy. However, SVPWM needs a large amount of computation, and the implementation process is complicated. Therefore, it is significant to research a control strategy which can combine the simplicity and rapidity of C-HCC and good control performance of vector control. In this paper, a space vector switching pattern hysteresis control (SVSP-HC) strategy is proposed. It refers to the concept of voltage vector and does not require a carrier. Compared with other hysteresis-based methods, SVSP-HC can get a better current control performance with a similar or even lower equivalent switching frequency. Moreover, the switching numbers of three-phase bridge legs are basically balanced to each other. Finally, the effectiveness and advantages of SVSP-HC have been verified through simulation and experiments.

An optimal dual-phase-shift control strategy of an isolated buck-boost converter is proposed in this paper. The theoretical analysis of dual-phase-shift control strategy is complemented, and the three-dimensional graphs of the output current versus two control variables are given. The optimal operating point is determined by the peak current of a clamped inductor and is shown as control trajectories in the three-dimensional graphs. Moreover, with the optimal dual-phase-shift control strategy, low current value, soft-switching operation, wide input voltage range regulation, whole load range regulation, and high-efficiency performance can be achieved. Furthermore, parameter design method deriving from the minimum peak current of the clamped inductor is given. At the end of this paper, a 1000 W-output prototype is fabricated to verify the effectiveness of the proposed control strategy.

GaN devices are developed rapidly in recent years, which makes it possible to produce power electronic converters with higher efficiency and higher power density. However, with the circuit parasitic parameters, large di/dt and dv/dt caused by the GaN devices’ extremely fast switching can easily lead to voltage and current oscillations. This problem affects circuit stabilities and increases the difficulty of application with GaN devices. In this paper, oscillation problems will be explained by oscillator theory and an oscillation suppression method will be introduced. All the researches here are based on Cascode GaN devices. Considering all circuit parasitic parameters, negative conductance models of the GaN devices in the switching-on and switching-off process have been established according to oscillation mechanism analysis. And stability criteria of the GaN-based circuit have been derived which can well predict that whether the oscillations will happen and how will the oscillations last. Besides, the suppression method that placing a ferrite bead in power loop in series has been introduced based on the established model. Selection method is provided quantitively and suppression effect can be calculated. All the achievements of this research have been verified by simulations and experiments.

A control strategy with three control variables that containing switching frequency and two duty cycle ratios for isolated buck-boost (IBB) converter is proposed in this paper. The converter only operates in discontinuous current mode (DCM), and boundary current mode (BCM) in the whole voltage range and load range which can achieve excellent soft-switching performance, low energy circulation, and high efficiency. On the basis of operational principle and variables simplification, the optimal operating point that has minimum clamped inductor peak current value is obtained. Under variable frequency control strategy, the converter characteristics are analyzed, such as the direct energy transfer time ratio, peak current value of the clamped inductor and switching frequency. Moreover, the implementation of closed-loop variable frequency control strategy is given with three operational modes: variable frequency BCM mode, constant frequency BCM mode, and variable frequency DCM mode. A 380-V 1-kW output prototype is fabricated, and the experimental results indicate that high efficiency over overall load range has been achieved under variable-frequency control strategy due to the excellent soft-switching performance in the whole range. What’s more, smooth transition between three operational modes is achieved.

A SiC MOSFET is a suitable replacement for a Si MOSFET due to its lower on-state resistance, faster switching speed, and higher breakdown voltage. However, due to the parasitic parameters and the low damping in the circuit, the turn-on overcurrent and turn-off overvoltage of a SiC MOSFET become more severe as the switching speed increases. These effects limit higher frequency applications of SiC MOSFET. Based on the causes of overcurrent and overvoltage of SiC MOSFET, a novel gate driver with the variable driving voltage and variable gate resistance is proposed in this paper to suppress the overcurrent and overvoltage of SiC MOSFETs. The proposed gate driver can realize the variation in driving voltage and gate resistance during switching transitions. It not only suppresses the overcurrent and overvoltage of SiC MOSFETs, but also has little effect on switching loss. The working principle of the proposed gate driver is analyzed in this paper. Finally, experimental verification on a double-pulse test platform is performed to verify the effectiveness of the proposed gate driver.