What is a Resettable Chip Fuse?

A resettable chip fuse, also known as a PTC (Positieve temperatuurcoëfficiënt) resettable fuse, is a type of surface mount device (SMD) that protects electronic circuits from overcurrent and overheating. It acts like a traditional fuse but can automatically reset itself after a fault is cleared. When a fault like an overcurrent or short circuit occurs, the fuse’s resistance increases, limiting the current flow. Once the fault is removed and the fuse cools down, its resistance returns to normal, allowing current to flow again.

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SMD Fuse Resettable 1812 16V 2A Surface Mount Chip for Com-Communications Overcurrent Protection

The resettable chip fuse (PPTC) is an overcurrent protection element based on the positive temperature coefficient characteristics of a polymer. It has an automatic reset function and is widely used in circuit protection of electronic equipment. The following are its core points:

1. Structure and working principle
‌Material composition‌
It is composed of a specially treated polymer resin (such as PE polymer) and conductive particles (carbon black or metal particles). Under normal conditions, the conductive particles form a low-resistance path (0.1-several ohms)‌.
‌Protection Mechanism‌
When overcurrent occurs, the thermal effect of the current causes the resin to melt and expand, the conductive network breaks, and the resistance suddenly increases to a high resistance state (up to the megohm level), limiting the current to the microampere level‌.
After the fault is resolved, the conductive particles cool and shrink, reconnect, and return to a low resistance state, without the need for manual replacement‌.
PTC Behavior:
Resettable fuses utilize a Polymeric Positive Temperature Coefficient (PPTC) material. This material exhibits a significant increase in resistance as temperature rises.

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Overcurrent Protection Surface Mount PPTC Resettable Fuse 6V 30V 33V 60V SMD

Overcurrent Protection:
When a current exceeds the fuse’s rated value flows, the PPTC material heats up, causing its resistance to increase. This increase in resistance reduces the current flow, preventing damage to the circuit.

Automatische reset:
Once the fault is removed and the fuse cools down, the resistance decreases, allowing normal current flow to resume.

Key Features and Benefits:
Self-Resetting:
The ability to automatically reset after a fault event makes it a reusable alternative to traditional fuses.

Overcurrent Protection:
Protects circuits from damage caused by excessive current, short circuits, or overheating.

Space-Saving:
SMD packaging allows for integration into compact electronic devices.
Wide Range of Applications:
Found in various devices, including computers, mobiele telefoons, medische apparatuur, and automotive electronics.

Voorbeeld:
Imagine a situation where a USB port on a laptop is accidentally short-circuited. A resettable fuse on the USB power line would detect the overcurrent and increase its resistance, limiting the current and preventing damage to the laptop’s power supply and other components. Once the short is removed, the fuse would reset, and the USB port would be ready to use again.