Charging the same mobile phone, the efficiency is determined by the internal resistance of the data line (including the contact resistance of the USB connector at both ends), the output voltage of the charging head, and the maximum output power.

The output of the charging head passes through the charging line, and the voltage reaching the power management component of the mobile phone is reduced due to the presence of the internal resistance of the charging line. The charging current multiplied by the internal resistance of the data line is the voltage drop of the data line.

At the same time, the power management chip will set a minimum acceptable voltage, such as 4.7v, below this value will not accept charging.

The same charging head uses different charging lines to charge the same mobile phone, and the charging head dynamically adjusts the output current to ensure that the voltage reaching the mobile phone can meet the requirements.

From: Denise Wang