| 摘要 |
PURPOSE:To effectively prevent the permanent damage of a GTO by bypassing an OFF pulse to another circuit when an anode current becomes abnormal during the energization of the OFF pulse. CONSTITUTION:The anode current of a GTO1 abnormally increases during the energization of OFF pulse of the GTO1, and when it exceeds the discriminated value of a current detector 4, the detector 4 outputs an OFF pulse inhibit signal. A gate control circuit 5 prohibits the energization of the OFF pulse by the OFF pulse inhibit signal. Simultaneously, when the OFF pulse inhibit signal is inputted to a thyristor 6, the thyristor 6 is fired, and the energy stored in the inductance of the OFF pulse passing route is bypassed through the thyristor 6 and circulated. Accordingly, when the detector 4 generates the OFF pulse inhibit signal, the current is immediately flowed to the GTO1 so that the OFF pulse becomes zero. |
