| 摘要 |
PURPOSE:To shorten the turn-off time of an SCR and to reduce the gate-cathode current to suppress the heating of the SCR by applying the reverse bias of a high level and then the reverse bias of a low level when the gate turn-off (GTO) SCR is turned off. CONSTITUTION:Rectifying diodes 12 and 13 are connected to a power supply 20 via a pulse transformer 11, and the DC voltage is applied to a capacitor 18 from the supply 20. The capacitor 18 and a transistor TR16 are connected in series between the gate and the cathode of a GTOSCR19. At the same time, an insulated element 14 for signal transmission is connected to the gate of the TR16 via a monostable circuit 15 to supply the drive signal. Furthermore a Zener diode 17 is connected in parallel to the circuit 15. Then the reverse bias of a high level is applied when the SCR19 is turned off, and the TR16 is actuated at a fixed level of voltage after a prescribed period of time. Then the voltage of a low level is applied to the gate of the SCR19. Thus the turn-off time of the SCR is shorten and therefore the gate-cathode current is reduced. |
