Resettable Fuse vs Regular Fuse
Resettable Fuse vs Regular Fuse
A polymer PTC “resettable fuse” increases resistance as it heats under excess current. A conventional fuse melts its element and stays open. They serve different protection goals; a PTC is not a drop-in substitute for a specified one-time fuse.
Which to choose
Use the protection component specified by the product design. A PTC can be useful for recoverable overload protection where its leakage and trip time are acceptable. A conventional fuse may be required to disconnect a circuit under a high-energy fault. A PTC can respond to a short circuit within its rated conditions, but it is not equivalent to a fuse that opens the circuit; the original claim that it “cannot protect against a hard short” was too absolute.
For a PTC, check normal current at the highest ambient temperature, trip behavior at the expected fault current, maximum circuit voltage/current and coordination with upstream protection. For a fuse, check the time-current curve and interrupt rating. Neither device automatically protects every semiconductor from damage before it operates.