A new overcurrent detection method of “monitoring gate voltage while periodically repeating discharging and charging of constant gate charge (MGDC)” is proposed, which enables overcurrent detection while IGBTs are ON by measuring gate-to-emitter voltage (VGE). In MGDC, while the IGBTs are ON, constant gate charge is periodically discharged and charged, and when VGE dropped by each discharge is less than the reference voltage, it is detected as the overcurrent. In a single-pulse test of an inductive load at 300 V for an IGBT with a pulse rating of 150 A, a current-source 6-bit digital gate driver IC was used to perform MGDC with 1.3-us cycle, and MGDC successfully detected an overcurrent of 250 A with a relative energy increase of only 0.8 %.