The operating principle of self recovering fuse PPTC in USB protection

　　Self healing fuse (PPTC) is a very important electronic component widely used in the protection of USB interfaces. It has the characteristics of automatic protection and automatic recovery. When the current exceeds the set value, the circuit will be immediately cut off, and when the current returns to the normal range, the path will be automatically restored. This self-healing fuse plays a crucial role in USB protection.

　　PPTC is a special type of polymer thermistor with a structure similar to a thin wire. When current passes through, the conductive material inside the filament heats up, causing the polymer to expand and block the current path. This blocking effect can effectively cut off the circuit and prevent safety accidents such as fires and short circuits caused by current overload.

　　When current overload or short circuit occurs, PPTC will immediately sense the abnormal situation and automatically cut off the circuit. This is because the material of PPTC has a negative temperature coefficient, which means that as the temperature increases, its resistance will rapidly increase. Once the current exceeds the range that PPTC can withstand, causing an increase in temperature, the resistance of PPTC will rapidly rise, reaching an impedance value that disconnects the circuit and locks the current path.

　　After PPTC cuts off the circuit, the current stops flowing, thus avoiding damage to other electronic components and equipment. At the same time, PPTC itself also has certain protection capabilities, which can prevent excessive heat caused by overload or short circuit duration, thereby reducing the risk of fire.

　　When the abnormal situation is resolved, i.e. the current returns to the normal range, PPTC will automatically restore the circuit. This is because the material of PPTC has a memory effect, and once the temperature drops within the normal range, the polymer will return to its original state and be re energized. During the process of restoring the circuit, PPTC will generate a certain self heating effect, which accelerates the recovery speed of the polymer and enables the circuit to resume normal operation as soon as possible.

　　The automatic protection and recovery features of PPTC make it an ideal protective component for USB interfaces. This self-healing fuse can quickly cut off the circuit, effectively preventing damage to equipment caused by abnormal situations such as overcurrent, overload, and short circuit. After the abnormality is resolved, it can automatically restore the circuit without manual intervention. At the same time, PPTC also has the characteristics of durability and high reliability, which can work stably for a long time.

　　PPTC is widely used in key positions such as power lines and data lines in USB interfaces. It can protect various aspects such as USB interfaces, host devices, and external devices, ensuring that they are not affected by abnormal current during use and enhancing the safety and stability of the entire system.

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