Patent ID: 7330097

Claim:
A direct current cutoff switch which is provided with a conductive fixed member and a movable member between which a dielectric member is inserted, said fixed member comprises a fixed contact which is formed in a prescribed position and is connected to a terminal in order to be connected to an external circuit, and said movable member comprises a movable contact which is formed on a position opposing the fixed contact, is connected to a terminal in order to be connected to the external circuit and is structured so as to push the movable contact against the fixed contact or open the contacts, for cutting off direct current which flows between the terminals connected to the external circuit by operating the movable contact so as to separate it from the fixed contact which the movable contact touches to open the contacts, comprising: a non-linear resistor which takes an arbitrary pillar shape, comprises an electrode on each of the top and bottom surfaces, and is parallel connected to a contact circuit composed of the fixed and movable contacts via these electrodes, said non-linear resistor has a resistance fluctuating area indicating the minimum resistance value while inter-contact voltage shifts from 0V to power voltage when the direct current is cut off by the opening of the movable contact, wherein said non-linear resistor is a positive temperature coefficient (PTC), and contact opening voltage at the time of the cutoff of the large direct current by the opening of the movable contact is in the range of 28V to 48V, wherein said PTC has a voltage/current characteristic that upper-limit voltage in a range where no thermal runaway occurs or a lower peak is 80V or more, and wherein said PTC has a voltage/current characteristic that the position of peak current against voltage in a range where no thermal runaway occurs is located in a range of 2V to 20V.