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Principles and Applications of PPTC Thermistors

January 08, 2024

PPTC is the abbreviation of Positive Temperature Coefficient, and its Chinese name is positive temperature coefficient resistor. It is a special type of resistor with a positive temperature coefficient characteristic, also known as a reset fuse or thermistor.


Principles and Applications of PPTC Thermistors
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PPTC resistors have a low resistance value at normal operating temperature, but under overcurrent or overtemperature conditions, their resistance value will increase rapidly, limiting the flow of current. This characteristic allows PPTC resistors to play the role of overload protection in circuits. When the current or temperature returns to normal, the PPTC resistor will automatically return to a lower resistance state. This self-restoring feature allows it to be used multiple times.

 

Thermistors are composed of complex polymer materials. Among them, common polymer compositions include:

 

1. Polypropylene

2. Polyethylene

3. Polystyrene

4. Polyethylene terephthalate (PET)

5. Polycarbonate (PC)

 

These polymer materials usually have good insulation properties, heat resistance and mechanical strength, and can work stably under various environmental conditions. By controlling the formula and structure of these polymer materials, the characteristics of the PPTC thermistor can be adjusted so that it has a suitable temperature-resistance characteristic curve, thereby realizing the overload protection function.

 

Polymer PPTC thermistors are widely used in consumer electronics products, mainly in the following aspects:

1. Charging equipment: In the charging cables or chargers of consumer electronics such as smartphones, tablets, and laptops, polymer PPTC thermistors are often used as overload protection components to avoid damage to the equipment due to excessive charging current. cause damage.

 

2. Battery protection: In battery packs for consumer electronics products, polymer PPTC thermistors can be used to provide overcharge and over-discharge protection to prevent batteries from being damaged or causing safety issues due to abnormal conditions.

3. USB devices: In devices such as USB flash drives and mobile hard disks, polymer PPTC thermistors are also often used to provide overload and short-circuit protection to ensure the security of the device and data.

4. Electronic accessories: In various accessories and peripheral equipment of consumer electronics such as headphones, power banks, and digital cameras, polymer PPTC thermistors are also used to provide overload protection.

 

Polymer PPTC thermistors play an important protective role in consumer electronics products, ensuring the safety of equipment and users, while improving product reliability and stability.


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