| 摘要 |
PURPOSE:To simplify the overvoltage and overcurrent detectors by insulating with one photocoupler and producing a signal when any of overvoltage and overcurrent detecting means operates. CONSTITUTION:An overvoltage detector formed of a transistor 62, zener diode 63 for detecting the overvoltage when the voltage detected by a voltage detector of a DC power source formed by a converter is larger than the reference voltage detects the overcurrent when the DC current supplied to a semiconductor switching element is larger than the reference current value. Further, an over current detector formed of a current detecting resistor 66 and a variable resistor 78 is provided to detect by insulating the detection signal detected when any of the detection signals of the detectors is detected via a photocoupler 77. In this manner, any of the overvoltage and overcurrent detection signals which is produced by the logic OR of the analog signals is insulated via a photocoupler and signal can be transmitted. Accordingly, the circuit arrangement can be simplified. |
