| 摘要 |
PURPOSE:To detect the ON/OFF state of a semiconductor stably without performing malfunction by detecting the ON/OFF state of the semiconductor depending upon presence or absence of a fluctuation in the voltage after presence of fluctuation of a DC voltage is detected. CONSTITUTION:A DC convertor 9 consisting of bridge formation of thyristors 13-18, converts alternately AC voltage Ea and DC voltage Ed and its DC output terminal is connected with a DC motor 20. On the other hand, a detecting circuit 10 connects resistors R1-R3 to the DC output terminal of the convertor 9 in series and detects the DC voltage Ed and gives a divided voltage Ed to a circuit for detecting voltage fluctuation 11 as a detecting signal of the voltage. This circuit 11 detects that the semiconductor is in the ON-state when there is a fluctuation in the voltage and till a tiny interval of time after the fluctuation disappears, and the semiconductor is in the OFF-state except the said period. |
