From the occurrence of the short circuit event to achieving a safe state of the system, several processes are experienced as explained below:
- The current reaches the SCP threshold. The time usually depends on the type of short circuit event, the inductance on the current path, the margin of the SCP threshold, and so forth.
- The current sensor reports SCP signal. The time usually depends on the response time of current sensor, which is critical and is elaborated on in this document.
- The SCP signal is transmitted to the gate driver. This time mainly depends on the components in the SCP signal path, which is closely related to the customer high-level architecture design.
- VGS starts to decrease. The time of this part mainly depends on the typical propagation delay of the gate driver.
- The system enters to a safe state. The time mainly depends on the shutdown feature of the gate driver, the turn-off resistance, SiC MOSFET characteristic parameters, inductance in the main circuit, and so on.
The total system SCP response time is defined as the sum of the above response time, which is the final requirement from SiC MOSFET. The comparison among different designs mainly lie in the selection of current sensors, and other parts remain the same.