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Application Principle and Application Scope of NTC Thermistors and PTC Thermistors

Application Principle and Application Scope of NTC Thermistors and PTC Thermistors

This article introduces the application principle and application scope of NTC thermistor and PTC thermistor in detail.


PTC thermistor application principle: connect the overcurrent protection and overvoltage protection PTC thermistor in series in the power circuit. When the circuit is in a normal state, the current flowing through the PTC is less than the rated current, the PTC is in the normal state, and the resistance is small. Will not affect the normal operation of the protected circuit such as electronic equipment. When the circuit current greatly exceeds the rated current, the PTC suddenly heats up, and the resistance value suddenly increases to a high resistance state, thereby limiting or blocking the current and protecting the circuit from damage. After the current returns to normal, the PTC automatically returns to a low resistance state, and the circuit resumes normal operation. Similarly, when the external voltage fluctuates, the varistor plays an over-voltage protection function, so that the increase in the current flowing through the PTC thermistor can also make the PTC suddenly heat up, and the resistance value suddenly increases to a high resistance state, thereby limiting or blocking the current and protecting the voltage. The sensitive resistor and the following circuit are not damaged. In the traditional fuse circuit, it cannot recover by itself after it is blown, while the PTC thermistor can restore its protection function after the fault is removed, such as one of the functions of PTC thermistors in motors.


Application range: mainly used in current, overload, short circuit protection of smart meters, transformers, motors, switching power supplies, chargers, adapters, instruments, control panels, household appliances, air conditioners, microwave ovens, etc.


Application principle of NTC thermistor: In order to avoid the surge current generated in the electronic circuit at the moment of power-on, a power NTC thermistor is connected in series in the power supply circuit, which can effectively suppress the surge current during power-on, and complete the wave After the inrush current suppression effect, due to the continuous effect of its current, the resistance of the power thermistor will drop to a very small extent, and the power it consumes can be ignored and will not affect the normal operating current, so using a power NTC thermistor in the power circuit is the simplest and most effective measure to suppress the startup surge current to protect electronic equipment from damage.

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