Short Protection Characteristic Research and Realization for Turn-off Circuit of IGCT Gate Unit

The cathode current commutation of IGCT relies on the energy stored in the turn-off capacitor stack to realize current transfer. Due to the loop parasitic resistance, the forward voltage of the turn-off circuit must higher than the reverse voltage generated by parasitic resistance during commutation. Therefore, the capacitance and voltage of the turn-off capacitor need to meet the turn-off demand at the maximum turn-off current, and meet the time constant of frequency charge and discharge at the same time. The turn-off capacitor stack is generally tens of mF. When the gate pole and cathode pole short together, the energy in the turn-off capacitor stack will discharge through the turn-off MOSFET stack, this process can cause failure of the turn-off MOSFET stack. This paper studies on the characteristics of the turn-off circuit, and compares the current characteristics of the MOSFET stack under regular turn-off and GK short, and proposes a short-circuit protection method to ensure that the gate unit can shutdown the turn-off circuit immediately when GK short and ensure the dynamic and static turn-off characteristics successfully.