Short-circuits in power semiconductor devices are categorized into three types [9, 10]. In case of a short-circuit type 1 (SCT 1), the short circuit is already present in the system and a MOSFET actively switches on in this short circuit. On the contrary, a short-circuit type 2 (SCT 2) occurs while the MOSFET is already switched on. In case of a short-circuit type 3 (SCT 3), the short circuit happens while the body diode of the MOSFET is in the freewheeling state.

Figure 1-1, Figure 1-2, Figure 1-3 shows the current path of three types of short circuit scenarios. The current path indicates where the current sensor is placed to detect the short circuit fault. By comparing three types of short circuits, placing the current sensor on HV BUS- was found to be the best position, as this can cover all three different cases.

Figure 1-1 Short Circuit Scenario 1

Figure 1-2 Short Circuit Scenario 2

Figure 1-3 Short Circuit Scenario 3

Several methods for short-circuit detection are described in the literature. One possibility is to measure the drain source voltage of the MOSFETs to determine over currents [11]. Another possibility is to measure the short-circuit current directly with various sensors to detect faults [12, 13]. Monitoring the dc-link voltage to detect faults in sufficient time is another option [14].

This document focuses on the SCT 1 for comparing and analyzing state of the art short-circuit protection methods for SiC MOSFETs. First, the principle of the short-circuit detection for SiC MOSFET are analyzed. Second, three protection methods are described and verified with measurements in detail. Finally, the performance of all three methods is compared based on important parameters.