Application of NTC Thermistor in Mobile Phone Charger

Do you know what else is in the mobile phone charger besides the necessary rectification circuit? There are thermistors, electrolytic capacitors, filter circuits, transformers, buffer circuits, ICs, etc. in the mobile phone charger.

After the mobile phone charger is powered on, the 220V AC (Chinese household voltage) is rectified by the full bridge and then output to the mobile phone circuit. However, the equivalent resistance of the capacitor at the moment of power-on is very small, and the current in the circuit is too large, which is prone to surge current. The generation of inrush current has a great impact on electronic equipment, which may lead to a decrease in the performance of electronic equipment and shorten the use time, and even more, the electronic equipment is prone to failure and damage.

In order to suppress the surge current generated in the electronic circuit at the moment of starting up and reduce the damage of the surge current to the electronic equipment, an NTC thermistor is usually connected in series in the power circuit.

NTC thermistor is a negative temperature coefficient thermistor whose resistance value decreases with the increase of temperature. When the circuit is not working, the resistance value of the NTC thermistor is very high at room temperature. At the moment when the switch is started, the capacitor charging generates a large current, but due to the existence of the NTC thermistor, the excessive current is limited and the inrush current is effectively suppressed. When the circuit runs for a period of time, the temperature rises, and the resistance value of the NTC thermistor drops to a small value as the temperature rises. At this time, the power consumed by the NTC thermistor can be ignored, and it will not affect the normal operating current of the circuit.

The NTC thermistor can effectively suppress the inrush current when starting up. Therefore, the use of NTC thermistors in the power circuit is a simple and effective measure to suppress the startup surge current and ensure that electronic equipment is not damaged.

In order to effectively suppress the inrush current when the circuit is powered on, it is necessary to ensure that the NTC thermistor used in the power circuit is of high quality. JYH HSU(JEC) Electronics Ltd (or Dongguan Zhixu Electronic Co., Ltd.) is an electronic components manufacturer whose factories are  ISO 9000 and ISO 14000 certified. Visit JEC website: www.jeccapacitor.com