Fuse element with rare short judgment function

摘要

PROBLEM TO BE SOLVED: To supply a interlayer short circuit decision device, protecting an electric wire from the overcurrent of rare shorting. SOLUTION: A fuse element with interlayer short circuit decision function F is provided with a current sensor 2, IC7 and a microcomputer 8. When a detection current L flows in a load 5 via an FET 4, a potential difference is generated in both ends of the current sensor 2. When the potential difference is inputted, IC7 compares the potential difference with a prescribed voltage threshold. The microcomputer 8 compares the characteristic value of detection current L with a reference value, based on the comparison result of IC7. Namely, the microcomputer 8 conducts decision as to interlayer short circuit, based on at least one of four characteristic value: the abnormal current value while a current value related to an input detection signal exceed a prescribed current threshold, the time when the abnormal current value exceeding the prescribed threshold flows, the on-duty ratio, or the number of times passing which exceeds the prescribed current threshold. At the time of interlayer short circuit, the FET 4 is turned off.