**1. Introduction**

Compared with the counterpart of silicon devices, SiC power semiconductor devices can operate at a higher frequency because the switching time of Si-IGBT (silicon based insulated gate bipolar transistor) ranges from 50 ns to 200 ns while it decreases to 10–20 ns for SiC devices [1–4]. Combined with the parasitic parameters of SiC devices and/or modules, the higher switching frequency and higher allowable negative gate-source voltage as well as the lower threshold voltage for SiC devices can also raise some issues, such as voltage overshoot [5], power loss [6], EMI (electromagnetic interference) emission [7–10], shoot-through or cross-talk fault [11–16], and switching oscillation [17–22]. These problems have brought grea<sup>t</sup> challenges for adopting SiC devices and/or modules into the mainstream power conversion application with high frequency.

The switching transient issues for a half-bridge power module has been investigated by many researchers. For example, reference [23] analyzed the switching resonance phenomenon that occurred during the process of fully turn-on and turn-off. Reference [24] investigated the influence of parasitic element of a discrete SiC MOSFET device on the switching performance, especially on drain-source voltage (*vDS*) characteristics at turn-on transient. Reference [25,26] investigated the effects of increasing load current/output power on Miller plateau voltage and turn-off transient. It is concluded that the output power has grea<sup>t</sup> influence on the characteristics of drain current (*iDS*), drain-source voltage (*vDS*), and gate-source voltage (*vgs*) at turn-off transients.

For the *vgs* characteristics at switching transient, reference [27] investigated the negative gate-source voltage (*vgs*) spike issue of the upper-side switch and viewed this negative voltage spike as a crosstalk issue. The peers only studied the interaction between the upper-side and lower-side switches, and they put efforts in designing gate driver circuits to alleviate the negative *vgs* spike issues [28,29]. However, the influence of output power on the *vgs* characteristics at turn-on transients, and the difference between the *vgs* characteristics for the upper-side and lower-side switches is not fully studied.

In order to study the influences of output power on the turn-on *vgs* characteristics for high-power high-frequency application, a 1200V/200A full-SiC high-power module and an inductive load double-pulse test rig were fabricated in this work. The amplitudes of *vgs* spike and oscillation under different output power conditions were investigated. By building up two different equivalent RLC circuit models of the gate loop path for the upper-side and lower-side, the characteristics of the *vgs* spike at turn-on transient were compared between upper-side and lower-side; the mechanisms behind these different characteristics were also analyzed with the model.

The paper is organized as follows. Section 2 introduces the experiment setup which includes the developed high-frequency full-SiC power module and a clamped inductive load double pulse test rig. Typical turn-on switching process for a SiC power module is also discussed in this section. Section 3 shows the experimental results of the turn-on *vgs* characteristics under different output power conditions for both upper-side and lower-side switches. Furthermore, in Section 4, equivalent RLC circuit models of the gate loop path is established for the upper-side and lower-side to analyze the negative *vgs* spike and oscillation issues in different output power cases. The simulation results are compared to the experimental results. Finally, Section 5 concludes the article.
