Working principle of polymer PTC thermistor

时间:2019-06-27 丨 预览:122 人次

The polymer PTC thermistor is a conductive polymer material with positive temperature coefficient. The most obvious difference between it and the fuse is that the former can be used repeatedly. Both products can provide over-current maintenance effect, but the same polymer PTC thermistor can provide this kind of maintenance many times, and the fuse must be replaced with another one after supplying over-current maintenance.


Polymer PTC thermistors can be used in computers and their external equipment, battery packs, industrial control equipment, mobile phones, transformers, long-distance communication and network equipment, automobiles and other electronic products, and have the effect of over-current or over-temperature maintenance.


The primary difference between a polymer PTC thermistor and a bimetallic circuit breaker is that the former has not been cleaned up at the end of the incident and has never been reset due to a shutdown condition, but the bimetallic circuit breaker can reset itself when the incident still exists. This may cause electromagnetic waves and sparks during reset. At the same time, switching on the circuit from scratch when the circuit is in a fault condition may damage the device, and therefore is not safe. Polymer PTC thermistors can always maintain high resistance until the fault is removed. The difference between the polymer PTC thermistor and the ceramic PTC thermistor lies in the initial resistance of the device, the action time and the size of the scale. Compared with the ceramic PTC thermistor, the polymer PTC thermistor with the same holding current has a smaller scale and lower resistance, and has a faster response.


The polymer PTC thermistor is made of polymer material filled with carbon black particles. This material has a certain ability to conduct electricity, so it can pass additional current. If the current through the thermistor is too high, its heating power is greater than the heat dissipation power, at this time the temperature of the thermistor will continue to rise, and at the same time the polymer matrix in the thermistor begins to expand, which causes the carbon black particles to separate And cause the resistance to rise, and then very effectively reduce the current in the circuit. At this time, there is still a small current flowing through the circuit. This current keeps the thermistor to meet the temperature and then sticks to the high resistance condition. After the fault is cleared, the polymer PTC thermistor will quickly cool down and return to its original low resistance condition, so that it can work from scratch like a new thermistor.