| 摘要 |
PURPOSE:To prevent commutation failure in a chopper thyristor by giving the discharge or charge action of a capacitor to a turn-off pulse generating circuit at the minimum width pulse and preparing the next generation of turn-off pulses. CONSTITUTION:When clock pulses 200c are inputted at t3 time, modulation signals 500 are supplied and the thyristor chopper is at ON while the discharge of the capacitor 40b is started. When the Q' output of a J-KFF 52 reaches L, output 600 is made L by means of a minimum width pulse generating circuit 58, thus obstructing the inversion of the FF 52. The FF 52 is not inverted even when matching signals 110 reaches L at t4 time. Consequencly, the output 600 of the circuit 58 is held at L only for T2 time, and the discharge time of the capacitor 40b is held. Accordingly, the capacitor 40b can be discharged completely in a one-shot multivibrator 40, the reverse bias time does not shorten when turning the chopper thyristor off, and the turn-off failure of the chopper thyristor is prevented. |
