Power supply capacity is one of the most important parameters of the charging cable, the main function of the charging cable is to charge, but now different places do not publicize the power supply capacity of the charging cable in the same way. Some places claim the maximum current, some claim the maximum power.

Then what kind of relationship exists between power and current?

Here we will look at it together.

1. Maximum voltage
①USB-A to USB-C charging cable The vast majority of USB-A to USB-C cable does not support the PD protocol, only supports the QC protocol and the private protocol, because the maximum voltage of these protocols is 20V, the maximum voltage of the USB-A to USB-C cable can be defaulted to 20V, Xiaomi cell phone standard charging cable supports the PD protocol, but it only supports the PD3.0 protocol. Although the standard charging cable of Xiaomi phone supports PD protocol, it only supports PD3.0 protocol (voltage ≤ 20V), so the maximum voltage of the charging cable is still 20V.
To summarize, the maximum voltage of USB-A to USB-C charging cable is 20V by default.

② USB-C to USB-C charging cable The dual-head USB-C charging cable supports the PD protocol by default, and the PD protocol has PD 3.0 (maximum voltage 20V), PD 3.1 (maximum voltage 48V) and other versions of the maximum voltage supported by the maximum voltage, depending on whether it supports the PD 3.1 fast-charging protocol to make a judgment.
The maximum voltage of USB-C to USB-C charging cables (USB-C to USB-C charging cables that come standard with cell phones and tablet PCs, and USB-C to USB-C charging cables that come standard with the vast majority of laptop power adapters) that only support the PD 3.0 protocol and don’t support the PD 3.1 protocol is 20V, and if there is no special labeling on the charging cable page that says If there is no special label on the charging cable’s page stating that it “supports PD 3.1 protocol” and “maximum charging power of 240W”, then this charging cable generally only supports a maximum of 20V.
The maximum voltage of USB-C to USB-C charging that supports PD 3.1 protocol is 48V, and it is generally indicated with words like “supports PD 3.1 fast charging” and “maximum charging power 240W” etc. The charging specification of 240W cable is 48V 5A, and the charging specification of 140W cable is 28V 5A. The charging specification of the 140W cable is 28V 5A.