Thermistors may be small, but their role in electronic circuits, especially power supply boards, is massive. Among them, NTC (Negative Temperature Coefficient) thermistors are frequently used as inrush current limiters. This post walks you through how NTC thermistors work, why they’re wired in series with hotlines, and how to test or diagnose them.     What Is an NTC Thermistor? An NTC thermistor is a temperature-sensitive resistor that decreases its resistance as temperature increases. When cold, it provides high resistance; as it heats up (due to current flow), its resistance drops, allowing higher current to flow safely into the circuit. This makes it perfect for power-up scenarios where large capacitors or switching components could otherwise cause a surge. Why Is It Wired in Series on the Hot Line? The primary role of an NTC thermistor in a power circuit is inrush current suppression. It is always installed in series with the AC input "hotline." On s...

An NTC (Negative Temperature Coefficient) thermistor is an essential component used in the power supply section of electronic devices. It is commonly connected in series with the AC input line and is responsible for suppressing inrush current at the moment of power-up.     Structure and Principle of NTC Thermistor An NTC thermistor consists of a semiconductor ceramic element whose resistance decreases as the temperature rises. At room temperature, it maintains high resistance, limiting the inrush current when power is first applied. As the device warms up, the resistance rapidly drops, allowing stable current flow with minimal power loss. Main Functions of NTC Thermistor Suppressing inrush current: protects bridge diodes and capacitors from surge damage Gradual startup of power supply: ensures smooth charging of electrolytic capacitors Thermal protection: can act as a safety element if placed near heating elements     ...