| 摘要 |
PURPOSE:To prevent a danger such as over heating and firing by an abnormal vibrating current by providing a circuit for detecting the abnormal vibrating current accompanying the contact failure of a load wiring system carried to a switching noise filter circuit, and outputting a control signal. CONSTITUTION:A contact failure detecting circuit 21 detects the presence of an abnormal vibrating current component caused by a contact failure contained in a high frequency current of several MHz carried to the capacitor Cs1 and resistance element Rs of a switching noise filter circuit 11 discriminatingly from the case having only a switching noise, and outputs a detection signal. A timer circuit 17 outputs a control signal to a start circuit 19 when the detection signal is present for a determined time, and stops also an oscillating circuit 20. According to this constitution, the contact failure of a load wiring system 14 is detected with less additional part by utilizing the switching noise filter circuit 11, and the heating, fuming and firing accompanying the contact failure can be avoided by stopping inverter output. |
