| 摘要 |
PROBLEM TO BE SOLVED: To provide a highly reliable protection circuit, where the protective action is not canceled unless it is performed by normal cancel operation, once it enters protective operation. SOLUTION: This protective circuit is of such constitution, that it is equipped with a current application loop being made between a PTC element 1, whose temperature goes up by with the heat generation accompanying the excessive current at abnormal phenomena and whose resistance value increases significantly and a power supply source, and another current application loop which is made between an NTC element 2 thermally coupled with the PTC element 1 and the power supply source, and the PTC element 1 exhibits protective function at abnormal phenomena, and the NTC element 2 is heated by the heat generated in the PTC element 1 so as to reduce the element resistance value and increase the current flowing to the NTC element, whereby the protective function of the PTC element 1 is not canceled, simply because apparently an excessive current has vanished by supplying the PTC element 1 with a large quantity of heat from the NTC element 2.
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