This quick post is about Power NTC Thermistors & Inrush Current Limiting!
At the time of powering on an electronic device such as a switch-mode power supply, the device is charged with an instantaneous abnormal current with a high peak.
It is called an inrush current, and without protection, it may destroy a sensitive semiconductor device or have a harmful effect on the service life of a smoothing capacitor.
Power NTC thermistors are used as inrush current limiters (ICLs) to protect circuits of electrical and electronic devices against inrush currents easily and effectively.
Basically, NTC thermistor is a temperature-dependent non-linear resistor that employs special semiconductor ceramics with a negative temperature coefficient (NTC).
An NTC thermistor has a high resistance at room temperature, and when it is energized, it generates heat by itself and the resistance falls as the temperature rises.
With this property, it can be used as a current protection device to limit inrush currents.
In a nutshell, Power NTC Thermistors are made of a metal-oxide ceramic material in the form of ceramic discs that help provide protection against damaging inrush currents upon equipment startup and/or switching on.
As such, Power NTC Thermistors are commonly referred to as Inrush Current Limiters (ICLs) and help reduce downstream component damage.
NTC Thermistor General Information - Technical Overview (TDK) PDF ⇲
How to select NTC thermistors for inrush current limiting?
In practice, there are 3 major criteria for selecting the best NTC thermistor inrush current limiter, surge suppressor for an application:
- Rated resistance (R25)
- Maximum permissible continuous current under rated operating conditions (Imax, DC or RMS values for AC)
- Maximum capacitance CT to be switched
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