| 摘要 |
PURPOSE:To protect a switching element surely at short-circuit and also to decrease a residual voltage at operation by providing a photocoupler thyristor resetting the operation of a detecting circuit section and also triggering a triac. CONSTITUTION:Since photocoupler thyrisors 8, 9 are driven immediately when a prescribed overcurrent flows, the operation of a sensor circuit 11 is reset and also the triac 5 is triggered, then a short-circuit current flows to the triac 5 and does not flow to a thyristor 10 of the switching element for output switching so as to protect the thyristor 10. Although a short-circuit current flowing to the triac 5 is limited by a current limit resistor R3, because the surge current rating of the triac 5 is larger than that of the thyristors 8, 9, the resistance value of the resistor R3 is decreased. Thus, the residual voltage produced by the resistor R3 at normal operation is decreased. |
