| 摘要 |
PROBLEM TO BE SOLVED: To block a reverse current from ground to the common grounding terminal of an apparatus or equipment and to prevent the failure of or damage to the apparatus or equipment caused by the reverse current. SOLUTION: A voltage detecting part 10 detects a forward voltage generated between a common grounding terminal and a grounding. When the detected voltage satisfies a voltage set by an operating voltage setting part 20 and exceeds an internal reference voltage, a control voltage is given from a control voltage generating part 30 to the Gate G of an SCR 4a in a switching part 40 to turn on the SCR 4a. This makes a current flow from the common grounding terminal to the grounding to protect an apparatus. If a current caused by a thunderbolt, etc., flows on the ground and a reverse voltage is applied between the common grounding terminal and the grounding, the control voltage is not applied to the Gate G of the SCR 4a and by making use of the phenomenon that a reverse voltage is applied between the anode A and cathode K, the SCR 4a is turned off to isolate the common grounding terminal and the grounding for the prevention of the phenomenon of the reverse current. |
