A PTC thermistor is a positive temperature coefficient thermistor whose resistance increases as the temperature increases. This kind of resistor is usually made of barium titanate. Through different production processes and different applications, a special shape element needs to be made. We often use its three characteristics of resistance-temperature, voltage-current and current-time, The different characteristics are rooted in that different packaging should be adapted to different occasions.

1. Overvoltage, overcurrent, overload and other protection

PTC overvoltage, overcurrent, overload and other protections are very widely used. In the direct series circuit of PTC, the circuit is short-circuited or caused by other reasons, the PTC thermistor can suppress the current from being too large, and even prevent the components or circuits required for current protection. It is mainly used for overcurrent and thermal protection of power transformers, various chargers, and various instruments and meters. This is the most widely used function of PTC thermistors. We also see more, especially in power equipment. .

The PTC thermistor is connected in series in the circuit as an overcurrent protection element, that is, a protection transformer. When the circuit causes an excessive current due to a short circuit of a component or load for various reasons, the PTC thermistor will play a role at this time, which will inhibit the circuit from generating excessive current. It is important to note that factors such as rated zero-power resistance, operating temperature range, and component packaging should also be considered when choosing the maximum reactive current and operating voltage. Generally, it is appropriate to choose about 1.5 times the maximum working current when the circuit is working normally.

2. Start-up assistance for motors, motors, compressors, etc.

The motor must overcome its own inertia when starting. For example, single-phase starting requires a large torque when starting. When the rotation is normal, the required torque is not very large. At this time, the auxiliary circuit can be added to the motor, which can be understood as an auxiliary source, which is equivalent to the electric vehicle needing more power for climbing. Connect the PTC thermistor in series to form a auxiliary circuit.

For example, for a refrigerator compressor, the resistance thermal resistance value becomes larger during startup, the startup winding of the compressor motor is energized, and the main winding of the compressor runs at the same time. When the resistance becomes very large, the start winding is equivalent to disconnection and the compressor can operate normally.

The role of PTC thermistors is not only used in switching power supplies, but also in many aspects.

3. Degaussing applications such as color TV sets and picture tubes

The role of the PTC thermistor is to eliminate the influence of stray magnetic fields such as chromatic aberration and geomagnetism on the color picture. The automatic degaussing circuit of ordinary color TV is generally composed of two parts: degaussing coil and degaussing resistance. The PTC demagnetizing element works with its current-time characteristics.

After the degaussing circuit is connected in series, since the initial resistance of the PTC element is small, the initial current passing through the degaussing coil is large, so that the coil generates a strong alternating magnetic field. Due to the self-heating of the PTC demagnetization element, the resistance will increase, and the current in the circuit will gradually decay, so that the alternating magnetic field in the coil will also weaken, so as to achieve the purpose of demagnetization. This series of products are used in the degaussing circuit of color TV, color TV monitor and other crt.

In addition to the above three functions, PTC thermistor also has many functions such as temperature detection and control, motor overheat protection, constant temperature maintenance of electric soldering iron, filament preheating delay start, LED constant current compensation and so on.