Overvoltage and Oscillation Suppression Circuit With Switching Losses Optimization and Clamping Energy Feedback for SiC MOSFET

Abstract

The snubber circuit is a cost-effective solution to reduce the severe turn-OFF overvoltage and oscillation caused by the fast switching characteristics of SiC MOSFET. However, the turn-ON switching losses will significantly increase as the snubber decouples the power loop parasitic inductance during the switching process. In this article, the effect of the power loop parasitic inductance on the switch performance of SiC MOSFETs and the quasizero voltage switching (QZVS) turn-ON condition are studied. On this basis, an SiC MOSFET overvoltage and oscillation suppression circuit (OVSC) with not only the switching losses optimization feature but also the clamping energy feedback characteristic is proposed. The overvoltage and oscillation can be effectively suppressed by clamping capacitors, and those capacitors do not participate in the switching process until the overvoltage occurs, which is of benefit to the switching losses reduction compared with the other normal snubber circuits. Besides, the turn-OFF overvoltage and oscillation energy stored in the clamping capacitors can be feedback to dc and load side through a passive branch composed of an energy feedback inductor and a diode. The experimental studies and comprehensive comparison studies are carried out to verify the validity of the proposed OVSC. The experimental results show that OVSC has excellent overvoltage and oscillation suppression performance and can significantly reduce the switching losses.

A novel inductively coupled RLC damping scheme for eliminating switching oscillations of SiC MOSFET

“…Therefore, the power capability of snubbers needs to be redundant to ensure a safety margin for reliable operation in practice. But high-power loss elements will introduce parasitic inductance L snb into the snubber loop, which considerably increases power losses and impairs the damping effect [16,17]. Herein, the sensitivity of RLC damping and RC snubber to L snb is analyzed.…”

“…Herein, the three reasonable assumptions are introduced. it is ignored for circuit simplification and only the output capacitor C oss is considered [13][14][15][16][17].…”

“…Since the high‐frequency impedance of C bus is much smaller than the value of its equivalent resistance R esr , C bus is treated as a short circuit [13–17].…”

“…In Figures 14a and 14b, after the addition of RLC damping, turn‐on losses E on are greatly reduced, but at the cost of slightly increasing the turn‐off losses E off , which is mainly caused by the higher overvoltage. However, the total switching losses E total are significantly reduced in Figure 14c, while for the state‐of‐the‐art RC snubber, E total remain unchanged [12–16].…”

Performance Improvement Strategies for Discrete Wide Bandgap Devices: A Systematic Review

“…RC snubber offers reduced cost and complexity compared with the active gate driver and slightly less energy losses compared with the gate resistance method. RC snubber is a widely adopted solution for oscillation attenuation (McMurray, 1972;Josifović et al, 2011;Josifovic et al, 2012;Salem and Wood, 2014;Vaculik, 2014;Joko et al, 2015;Liu et al, 2016a;Liu et al, 2016b;Torsaeter et al, 2016;Chen et al, 2021;Yang et al, 2021). Choosing optimum values of snubber for effective oscillation suppression is essential.…”