A fuse is a safety device in an electrical circuit that blows when the intensity of the current exceeds a certain limit. In other words, a fuse is an instrument used to protect circuit components from overloads or short circuits.

Generally, a fuse is a disposable electronic accessory because after the fuse’s wire blows, it cannot conduct electricity or protect the circuit, and cannot be used in the circuit again. While some fuses are reusable, it is not by blowing the fuse to protect the circuit, it is by adjusting the size of the resistance to stop the flow of current and thus play a protective effect on the circuit.

According to whether the fuse can be reused or not, we can categorize the fuses as follows:

Disposable fuses:
This type of fuse is single-use because the internal filament melts once it is used. Therefore, when an electrical overload occurs, the fuse must be replaced.

Self-Resetting Fuse:
This is a type of fuse that can be used multiple times. When the current is too strong, the fuse heats up and increases its resistance, thus stopping the flow of current. Then, as the current intensity decreases, the fuse cools and returns to its initial low resistance state.
A self-resetting fuse consists of a specially treated polymer resin with conductive particles (Carbon Black) distributed inside.
Under normal operation, the polymer resin binds the conductive particles on the outside of the crystal structure, forming a chain-like conductive path. At this time, the self-recovery fuse is in a low-resistance state (8a), and the current flowing through the self-recovery fuse generates very little thermal energy and does not change the crystal structure.
When a short circuit or overload occurs in the line, the heat generated by the high current flowing through the self-recovery fuse will melt the polymer resin, the volume increases rapidly, forming a high-resistance state (b), the operating current will drop rapidly, thus limiting and protecting the circuit.
When the fault is removed, the self-recovery fuse will be cooled and crystallized again, thus shrinking in size, the conductive particles will form the conductive path again, and the self-recovery fuse will return to the low-resistance state, thus completing the protection of the circuit without the need for manual operation.

Intelligent Fuses:
This type of fuse is a hybrid of the first two types of fuses. It is a type of fuse that allows the reuse of fuses

How to choose:

Whether to choose a conventional fuse or a PTC self-resetting fuse depends on the specific product circuit, and each has its own advantages.
For example, many computers, peripherals, and portable devices (e.g., smartphones, tablets, etc.) are designed to require the use of a PTC because they can reset themselves. If a conventional fuse is used, it must be replaced every time there is an overcurrent, which is unacceptable to the user.
In other cases, it is preferable to use conventional fuses, which are capable of completely shutting off the current in the event of a fault. This may be preferable where safety is a priority or to avoid damage to downstream circuit equipment. The use of fuses is also very useful for troubleshooting and can help the designer and user of the equipment to find the source of an overcurrent fault.