| 摘要 |
PURPOSE:To prevent a gate reverse bias voltage from being decreased by detecting a reverse recovery current of a snubber diode by a transformer and applying a voltage generated based on the output between the gate and cathode of an electrostatic induction thyristor. CONSTITUTION:When an SI thyristor 1 is turned off, a main current is commutated in a snubber circuit, a diode 6 is conducted and a voltage of a capacitor 8 is increased. Since a transformer 15 and a reactor 16 are provided, when a charging current of the capacitor 8 flows to the diode 6, a current flows to the secondary side of the transformer 15 in a path of transformer 15 reactor 16 transformer 15. A voltage EC generated across the reactor 16 is applied between the gate and cathode of the SI thyristor 1 via a diode 17 in a direction the same as the reverse bias voltage. Thus, the reverse bias is not decreased to the voltage EC or below. |
