Portable devices such as mobile phones and tablets can achieve faster charging speeds than before. To achieve fast charging times, the voltage on the charging device must be maintained at an appropriate level. If this is not the case, the charger may reduce the charge current to a lower (but still acceptable) level, ultimately extending the overall charging time. A drop in voltage on the charging cable can result in insufficient voltage.
For example, if you choose a charging cable like most low-quality cables, the internal impedance is 500 milliohms, then a 1V current charging will produce a voltage drop of 0.5V, which means that if you The charger is charged at 5V, and the charging voltage on the mobile phone is only 4.5V. Most smart phones will not even charge at this voltage, which explains many of the problems we have encountered in charging.
Moreover, with the large-scale application of smart devices, the charging current becomes higher and higher. Many devices like pads and tablets use 2A current to charge, so the quality of charging cables is now becoming more important.
Also take the above example to explain, in the 2A charging current, will produce a voltage drop of 1V, the device side charging voltage is only 4V. In addition to the potential for security issues, such a low voltage does not even charge the device for smart devices.
If the 5V converter is designed to provide a maximum output current of 2.1A, the expected voltage drop across the cable will be 0.6V. For a fixed converter voltage of 5.0V, the voltage at the end of the cable will drop to 4.4V. For USB devices, this voltage value is a lower voltage limit, and the cause of potential problems with high current loads is obvious. Using a heavier USB cable will help, while a long USB cable with a smaller gauge cable will cause the charging rate to be below the maximum. Some measures must be taken to further increase the charging current.
A common solution is to increase the no-load output set voltage, which is typically 5.0V, to 5.15V to 5.20V as much as possible (for USB 3.0, the maximum is 5.25V). This solution provides sufficient (though still the minimum) headroom at a maximum current of 2.1A. For higher load currents, this method will soon be difficult to support.