5R1NTC 5W
NTC resistor
NTC ( Negative Temperature Coefficient)
Many power-supply manufacturers use a negative temperature coefficient (NTC) resistor in series with the line. An NTC resistor offers tens of ohms of resistance when cool, dropping to less than one ohm as its temperature increases.
If the power supply is cool when turned on, the NTC provides good inrush-current limiting. Its effect on efficiency is reduced as the power supply warms up. However, this approach is not effective over large temperature extremes.
A power supply used outdoors in the northern winter may never warm up enough for the NTC's resistance to drop. Conversely, a supply in the hot summer sun will be very warm even with the power off, so that the warm NTC resistor will fail to provide adequate inrush-current protection on startup.
An NTC resistor can also be problematic when a user turns the system off and then immediately switches it back on. The capacitor voltage may drop, but the NTC resistor will not cool quickly enough to provide inrush-current protection.
