PURPOSE: To cut off a large DC current without generating a power loss with a small-size and a simple structure.
CONSTITUTION: A breaker 31 is connected in parallel to a charge limiting diode 1 in which impurity concentration in the thin part near a PN bonding surface is increased stepwise. The positive electrode of a DC power source 32 is connected to the cathode 1K of the charge limiting diode 1, the negative electrode to the positive electrode input terminal of a load 33, and the negative electrode of the DC power source 32 is connected to the negative electrode input terminal of the load. At the moment the breaker 31 is opened, the current flows into the depletion layer on the bonding surface of the charge limiting diode 1, and current zero point is generated in the breaker 31, so that in cut-off is conducted. Then, the charge current of the charge limiting diode 1 is rapidly reduced, and the cut-off is completed.