| 摘要 |
PURPOSE:To prevent a main thyristor from damaging due to non-communication of a firing circuit drive signal by constructing to allow the firing signal of each firing circuit to become a firing circuit drive signal which operates other firing circuit. CONSTITUTION:When a transistor 4 of a drive circuit 3 turns ON and a transistor 16 of a firing circuit 10 turns ON by the light from a light emitting element 5, a current flows also to a light emitting element 40, which, in turn, emits a light. This light is fed through an optical fiber 43 to a photodetector 45, in which a current flows, and this current becomes the base current of a transistor 26 of a firing circuit 20, thereby causing the transistor 26 to turn ON. Thus, a firing signal is applied to a thyristor 2. Accordingly, any one of transmission lines of a firing circuit drive signals from the element 6, the optical fiber 9 and the element 25 of the drive circuit 3 is damaged, and even if the element 25 is not turned ON, the thyristor 2 can be fired. |
