| 摘要 |
PURPOSE:To early prevent the damage of a transistor by turning OFF the transistor before becoming the current and voltage that a hot spot occurs in the transistor. CONSTITUTION:A reactor 15 and a diode 16 are inserted between a DC power source having a rectifier 2 and a capacitor 3 and a transistor bridge 4, and the rate of change of the defective current of the transistor in the bridge 4 is limited. The fact that the voltage at both terminals of transistors 41, 44 exceeds 1/2 of the DC side voltage of the bridge 4 is detected by photocouplers 20, 21. The detected voltage is inputted to an AND circuit 24. The output of the AND circuit 24 is inputted to a defect detector 28, the malfunction of other transistor and the output of an overcurrent detector 14 are detected by the detector 28, and a transistor drive signal is turned OFF by a logic circuit 11. |
