PTC has been widely used in the electronics industry in various fields, and that is what is PTC ? How it is the work of the?

PTC is a ceramic semiconductor fever, when the outside temperature lower, PTC then reduce the value of resistance, but the heat will increase accordingly.

The working principle of PTC

PTC thermistor (positive temperature coefficient of thermal resistance) is a semiconductor with temperature sensitivity of the resistance, once over a certain temperature (Curie temperature), its resistance with increasing temperature is almost a step - The increase. PTC thermistor body temperature changes can flow from the current PTC thermistor to obtain, can also be imported from outside heat or that the superposition of the two to obtain. Ceramic materials are usually used for high-quality insulation resistance, And ceramic PTC thermistor is BaTiO3-based, the other doped polycrystalline ceramics manufacturer, has a low resistance and semi-guided characteristics. Purpose of doping through a chemical material as a higher price Crystal lattice yuan to achieve: in the lattice of barium titanate-ion or part of the higher price was replaced by the Ion, which has generated a certain number of free electronic conductivity.

The PTC thermistor effect, which is resistance step increase because of the organization is composed of many small-ceramic components, in the grain interface, the so-called grain boundaries (boundary) formed on the potential Barrier and impede cross-border electronic access to the adjacent area to, and have a high resistance. This in effect was offset by lower temperatures: the grain boundaries on the high dielectric constant and spontaneous polarization in the cold when hampered Barrier and the formation of the free flow of electronic. And this effect at a high temperature, dielectric constant and polarization drastically reduced, leading to resistance barrier and significantly higher, showing a strong PTC effect.

PTC thermistor is to develop early and variety, more mature development of sensitive components. PTC thermistor from the semiconductor ceramic materials, the use of the principle of resistance is caused temperature changes. If the electron and hole concentrations were n, p, migration rates were μ n, μ p, while the conductivity of semiconductors: σ = q (n μ n + p μ p) because n, p, μ n, μ p are dependent on the function of temperature T , The conductivity is a function of temperature, it can be measured conductivity and the level of projected temperature, and can make resistance - temperature characteristic curves. This is the semiconductor thermistor works.

Thermistor including positive temperature coefficient (PTC) and negative temperature coefficient (NTC) thermistor, and the critical temperature thermistor (CTR). Their resistance - temperature characteristics as shown in Figure 1. PTC thermistor is the main characteristics: ① high sensitivity, temperature coefficient of resistance than the metal 10 to 100 times more than can detect temperature changes in the 10-6 ℃; ② wide temperature range, at room temperature devices apply to -- 55 ℃ ~ 315 ℃, the temperature is higher than high-temperature devices to 315 ℃ (currently a maximum reach 2000 ℃), low-temperature devices to -273 ℃ ~ 55 ℃; ③ small size, other thermometer to measure the gap can not be measured, and body cavity The body temperature of the blood vessels; ④ easy to use, resistance values can be 0.1 ~ 100 k Ω between arbitrary choice; ⑤ easily processed into complex shapes, can be mass-produced; ⑥ good stability, Guozainengli strong.

PTC thermistor

PTC (Positive Temperature Coeff1Cient) refers to a sharp increase in temperature resistance, with positive temperature coefficient of thermal resistance phenomenon or materials can be used for specialized constant temperature sensor. The material is BaTiO3 or SrTiO3 or PbTiO3 as the main components of Sinter, which trace the incorporation Nb, Ta, Bi, Sb, Y, La oxides, such as price control for atomic而使half lead, and often this The BaTiO3, such as semiconductor materials referred to as semi-guided (CARICOM) porcelain, while also adding increasing its temperature coefficient of resistance is the Mn, Fe, Cu, Cr oxides and the role of other additives, forming a general ceramic technology, High-temperature sintering而使titanate platinum, and other semi-solid solution and its derivative, and thus gained is of PTC thermistor materials. Its temperature coefficient and the Curie temperature components and sintering conditions (in particular, the cooling temperature) and the different changes.

PTC thermistor in 1950, appeared, followed in 1954 with a barium titanate as the main material of the PTC thermistor. PTC thermistor can be used in industrial temperature measurement and control, also used in automotive parts of a certain temperature detection and regulation, but also for the large number of civilian equipment, such as instant Kai Shuiqi control the temperature, the temperature of air conditioners and cold storage, use Gas for heating their own analysis and wind speed and other aspects. Below briefed on the case heater, motors, transformers, high-power transistors and other electrical heating and overheating protection of the application.

PTC thermistor except for the heating elements, while a "switch", both sensitive components, heaters and switching three functions, known as "thermal switch", as shown in Figure 2 and 3 . After the current components caused by temperature rises, the temperature rise of fever, when more than Curie temperature, the resistance increases, thereby limiting the current increase, so the current decline led to lower the temperature components, resistance and to reduce the value of the current circuit Increase, component temperature increases, the cycle, with the temperature in a specific range of functions, also play a role switch. The use made of this resistance-temperature heat source, as the heating elements of a heater, electric irons, bake wardrobe, air conditioning, electrical appliances may also play a role in the protection of overheating.