Introduction to PTC Thermistor

Thermistors can be divided into positive temperature coefficient thermistors (PTCR) and negative temperature coefficient thermistors (NTCR) according to their resistance-temperature characteristics. PTC is the abbreviation of Positive Temperature Coefficient, which means positive temperature coefficient. NTC is the abbreviation of Negative Temperature Coefficient, which means negative temperature coefficient. Among them, the positive temperature coefficient thermistor (PTCR) includes: mutation type (step type) PTC thermistor and slow-change type (linear) PTC thermistor. The mutation type (step type) PTC thermistor is subdivided into two categories. One type is ceramic PTC thermistor (CPTC), which is mixed with semiconducting elements in BaTiO3, V2O5, and BN. The PTC effect can be found. At present, the BaTiO3 series PTC thermistor is widely used; the second type is the organic polymer PTC thermistor (PPTC), in which carbon black is mixed into polyethylene polymer material to form the PTC effect. What is introduced here is the BaTiO3 series PTC thermistor, which is a typical direct heating step-type positive temperature coefficient thermistor. When the temperature increases above the Curie temperature, its resistance value increases stepwise, which can reach 4 to 10 orders of magnitude. The temperature change can be obtained by the current flowing through the thermistor, or by the external input of heat energy or the superposition of the two.

Application and advantages of PTC thermistor:

1. As a ceramic PTC element for heating, it has the characteristics of automatic constant temperature, which can save a set of temperature control circuit;

2. As a ceramic PTC component for switch, it has overcurrent and overheat protection functions to avoid damage to electrical equipment, simple and reliable structure;

3. As a ceramic PTC element for temperature protection, it has a large resistance temperature coefficient near the temperature control point. A simple comparator circuit can be configured to achieve more accurate temperature control;

4. Wide adjustment range of switch temperature: -40℃～320℃;

5. High temperature coefficient of resistance: up to 40%/℃;

6. Large resistance value range: 0.1Ω～20kΩ

7. Large working voltage range: 3V～1000V