Using a PTC as a Fuse for Circuit Protection


#1

Fuses are commonly used for circuit protection because they’re cheap, readily available and easy to install - but once they blow they’re done. Why replace blown fuses when you can use a PTC, instead?

PTC

‘PTC’ is short for Positive Temperature Coefficient Thermistor, a device whose resistance to electrical current increases as it heats up, such as when it’s subjected to harmful surge currents in your circuit. This increase in resistance is very high, effectively blocking excessive current through the circuit until it cools back down and its resistance decreases again.

This ability to ‘reset’ allows a PTC thermistor to protect your circuit multiple times, unlike a one-and-done fuse. In devices like laptops, portable devices, and PC peripherals, PTCs are a great way to offer repeatable protection from unusual surge currents.

If you’re more concerned with ensuring that whatever has caused your fault condition is completely stopped however, such as with expensive industrial equipment or delicate calibration gear that cannot tolerate repeated shocks, then you should generally stick with fuses.


Reverse Current Protection in a System