Novel Design of SiC MOSFET Active Drive Circuit Based on Improved Auxiliary Branch Method

Abstract

Excessive voltage and current spikes, oscillation, crosstalk and electromagnetic interference will be caused by the increase of switching frequency and switching speed in the application background of high-speed switching of SiC MOSFET. In order to solve these problems, SiC MOSFET active drive circuit is studied in this paper. Based on the dual-pulse test circuit platform with parasitic inductance, the SiC MOSFET voltage and current spike oscillation/crosstalk problems, transfer/output characteristics, turn-on/turn-off dynamic characteristics are simulated experiments, and the improved SiC MOSFET active drive circuit is innovatively designed. These simulation experiments show that the switching process of SiC MOSFET devices is accompanied by a higher rate of change of voltage and current. It is more prone to spikes and oscillations, and the influence of parasitic inductance in the circuit is not negligible. Meanwhile, the dynamic characteristics of SiC MOSFETs are compared and studied. On the basis of minimizing the sacrificing SiC MOSFET switching loss, a novel SiC MOSFET active drive circuit based on an improved auxiliary branch is proposed. Relying on the double-pulse test circuit platform, the design of the improved auxiliary branch and the calculation of related parameters have been completed, which have proved that the optimization effect of the oscillation and crosstalk of voltage and current spikes has reached 1/3. Compared with the traditional RCD absorption circuit and the typical active drive circuit, the SiC MOSFET active drive circuit based on the auxiliary branch designed in this paper can effectively suppress the voltage and current spikes and oscillation problems while reducing the complexity of the drive circuit. Meanwhile, on the basis of minimizing the sacrificial switching loss, the bridge crosstalk problem is effectively alleviated by adding a self-regulating mechanism. Finally, taking the improved synchronous Buck converter as an example, the improved design of the SiC MOSFET active drive circuit based on the auxiliary branch is verified for drive protection and anti-interference ability in actual application scenarios. Moreover, the conversion efficiency of the improved synchronous Buck converter is increased by 7.25%.