A: A resettable fuse, also known as a PTC (Positive Temperature Coefficient) fuse or a polymeric positive temperature coefficient (PPTC) device, is an electronic component that protects circuits from overcurrent conditions. Unlike traditional fuses that require replacement once they blow (open) due to excessive current, resettable fuses are designed to “trip” or increase their resistance when exposed to an overcurrent situation, limiting the current flow and protecting the circuit.

The key characteristic of a resettable fuse is its positive temperature coefficient behavior. This means that as the current passing through the fuse increases beyond a certain threshold, the device’s temperature rises, causing its resistance to increase rapidly. This higher resistance reduces the current flow through the circuit, protecting sensitive components or preventing potential hazards like overheating, short circuits, or damaging current surges.

Once the overcurrent condition is removed and the device cools down, the resettable fuse returns to its low-resistance state, effectively “resetting” itself. This self-resetting feature eliminates manual replacement, making resettable fuses a cost-effective and convenient solution for protecting electronic circuits from transient overcurrent events.

Resettable fuses find applications in various electronic devices and systems, such as power supplies, battery charging circuits, USB ports, automotive electronics, and more, where protection against overcurrent conditions is essential to ensure safe and reliable operation.