The magic of NTC thermistor in mobile phone chargers: say no to surge current

What should I do if my mobile phone runs out of power? Of course, you can charge your mobile phone by plugging it into a 220V socket. Mobile phone chargers can not only charge mobile phones, but also other electrical appliances, as long as the charging port of other appliances is consistent with the charging port of the mobile phone charger.

Do you know what else is in a mobile phone charger besides the necessary rectifier circuit? A mobile phone charger contains thermistors, electrolytic capacitors, filter circuits, transformers, buffer circuits, ICs, etc. It can be said that it is small but has all the necessary components.

After the mobile phone charger is connected to the power supply, the 220V AC power is output to the mobile phone circuit after full-bridge rectification. However, the equivalent resistance of the capacitor is very small at the moment of power on, and the current in the circuit is too large, which is prone to surge current. The generation of surge current has a great impact on electronic equipment. At the least, it will cause the performance of electronic equipment to decline and the service life to be shortened. At the worst, 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 power-on and reduce the harm 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, and its resistance decreases as the temperature increases. When the circuit is not working, the resistance of NTC thermistor is very high at room temperature. At the moment the switch is turned on, the capacitor charges and generates a large current, but due to the presence of NTC thermistor, the excessive current is limited, effectively suppressing the surge current. After the circuit has been running for a period of time, the temperature rises, and the resistance of NTC thermistor drops to a very small value as the temperature rises. At this time, the power consumed by NTC thermistor can be ignored and will not affect the normal working current.

NTC thermistors can effectively suppress the inrush current when the power is turned on. Therefore, using NTC thermistors in the power supply circuit is a simple and effective measure to suppress the inrush current when the power is turned on and protect the electronic equipment from damage.

Zhixu Electronic Thermistor

In order to effectively suppress the surge current when the circuit is turned on, it is necessary to ensure that the NTC thermistor used in the power circuit is of high quality. Using inferior or poor quality NTC thermistors will not only fail to suppress the surge current, but will more easily cause damage to electronic equipment, which is not worth the loss. Therefore, you must be cautious when choosing a thermistor and choose a thermistor with a good reputation and excellent quality.