Due to the increasing demand for battery electric vehicles (BEVs), high-voltage DC/DC converters and on-board chargers (OBCs) are gaining increased importance[1–4]. Lately, 800V BEVs are rapidly entering the market which allows for fast charging [5]. Silicon carbide (SiC) metal-oxide semiconductor field-effect transistors (MOSFETs) have several advantages over silicon (Si) insulated gate bipolar transistors (IGBTs). The most important advantages include higher thermal conductivity, faster switching speed, higher junction temperature and higher blocking voltage [6]. Therefore, utilization of SiC MOSFET in automotive systems is growing rapidly.

However, the use of SiC MOSFET poses new challenges. The differences between SiC MOSFET and IGBT in dealing with short-circuit scenarios are mainly reflected in the following two aspects. [7]

• Smaller chip size of SiC MOSFET compared to IGBT
  • The SiC MOSFET die has lower thermal dissipation capability. During short circuit conditions, the surge current generates a significant amount of joule heating and the die can be destroyed in a short period of time without enough capability to dissipate the heat.
• Difference in operating region during normal ON operation
  • IGBT typically works in the saturation region during the normal ON state. When a short circuit happens, the collector current I_C increases and goes through a sharp transition from the saturation region to the active region. The collector current gets self-limited and becomes independent of V_CE.
  • SiC MOSFET works in the linear region during normal ON operation and SiC MOSFET has a larger linear region. During a short circuit event, the transition from the linear region to saturation region happens significantly higher. The drain current keeps increasing along with the increasing V_DS. The device is destroyed before reaching the transition point.

These characteristics lead to the fact that SiC MOSFETs in HV DC/DC converters and OBCs need faster and reliable short-circuit protection measures to meet the high safety standards in automotive. The challenges particularly lie in the speed of detection and disconnection of the short-circuit event to prevent damage of the system [8]. The system short circuit protection (SCP) response time is defined to verify reliable short circuit protection.