How do NTC thermistors limit surge currents?Infrared sensing module

　　Surge current is the peak current that occurs when the power supply is first applied to the load voltage, and is due to the resistance value in the filter capacitor of the power transformer or switching power supply (such as DC drive control or phase controlled SCR converter). If these peak currents are not limited, it may damage the power system or the windings of the DC motor.

　　There are several methods to limit surge current, one of which is to use NTC thermistor components, which change their resistance value based on temperature. Common thermistors have Negative temperature coefficient (NTC) and positive temperature coefficient (PTC).

　　At the beginning, NTC thermistors had high resistance values. When the power is turned on, they limit the surge current in terms of power consumption or heat. As the NTC thermistor heats up, its resistance drops to the point where most of the power supply voltage is applied to the load. In other words, the voltage drop of NTC thermistors will not affect normal circuit functionality. When the temperature increases, the positive temperature coefficient thermistor will increase its resistance value.

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