Self-resetting PTC fuse (also called resettable fuse or polyfuse) from the manufacturer Bourns
It is made of a polymeric material with a positive temperature coefficient (PTC). This means that its resistance increases sharply when it gets too hot due to excessive current.
🛠️ How it works in practice
Normal operation:
– At normal current consumption (up to approx. xx A), the fuse has low resistance and allows current to flow freely through the circuit.
Overcurrent / short circuit:
– When the current exceeds (trip current), the PTC material starts to heat up.
– When it gets hot enough, the resistance increases sharply (from a fraction of an ohm to several ohms).
– This dramatically reduces the current and "protects" the rest of the circuit from damage.
Automatic reset:
– When the fault/overload is removed and the component cools down, the resistance drops back to a low value and the fuse returns to normal condition without needing to be replaced.