| 摘要 |
PURPOSE:To prevent the destruction of a transistor for amplifying an electric power by providing a photocoupler for detecting an abnormal voltage between a collector and an emitter of a transistor for amplifying the electric power and interrupting a base electric current by the signal to obtain the AND of the signal and the pulse signal of a pulse oscillator. CONSTITUTION:The voltage between a collector and an emitter is increased, a photocoupler 6 is turned on by the voltage and an abnormal voltage is detected. The AND of the signal to detect the abnormal voltage and the pulse signal from a pulse oscillator 1 is generated by a logic circuit 7. When a transistor 2 for amplifying the electric power from the logic circuit 7 is on and the photocoupler 6 detects the abnormal voltage, a switch 8 is operated. Thus, the base electric current supplied to the transistor for amplifying the electric power is interrupted, the transistor 2 for amplifying the electric power is turned off and destruction is prevented at the time of the abnormality.
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