| 摘要 |
PURPOSE:To surely interrupt the load, by operating the switching transistor with the increase or decrease of the current of the detection transistor which detects the transistor amplifying circuit deviates a given operation range, if the detection transistor is defective. CONSTITUTION:When the output DC current level of the output terminal T4 is shifted outside the desired range due to abnormal operation of the OCL power amplifying circuit 1, the switching transistor Q5 or Q6 is conductive with the detection transistor Q3 or reference transistor Q4 consisting of IC2, TrQ7 of the drive circuit 4 is driven via the OR circuit 3, exciting circuit flows to the relay 5, SW is operated to interrupt the circuit and the burning out of the speaker SP can be prevented. If the detection TrQ3 having possibility of damage due to power input surge is faulty, the current increases or decreases with the open wire or short circuit due to failure, switching transistor Q6 or Q5 is conductive, the relay 5 is operated through driving TrQ7, and the load SP is compulsively interrupted from the output of the circuit 1. |
