The voltage-current characteristic, also known as the volt-ampere characteristic, refers to the relationship between the voltage at both ends of a pattern and its steady-state current in still air at room temperature. It can be seen from the figure that the curve is composed of two segments AB and BC: the resistance of the AB segment is basically unchanged, and the self-heating temperature of the component is not high. BC is near the switching temperature. Connect the PTC thermistor in series with the load, and select the resistance value and working status appropriately to protect the PTC components that generate heat. Under a certain voltage and standard environment, the measured stable temperature is called the PTC surface temperature (Ts). When in use, the PTC is in a very small temperature range centered on the surface temperature, and the power-environment reaches a dynamic balance to realize automatic temperature control. According to the needs of different applications, adjusting the process and formula can produce PTC components with different resistance ranges and different surface temperatures.