Among the USB ports, the two most commonly used specifications on the market are USB2.0 and USB3.0. In addition to the difference in data transmission rate, the current output is different. The current output of USB2.0 is 5V500MA, and the current output of USB3 The current output of .0 is 5V900MA.
USB 3.0 Port is divided into Standard Downstream Port (SDP) and Charging Downstream Port (CDP), SDP current limit is 900mA, CDP current limit is 1.5A, BC1.2 protocol supports CDP, generally SDP, CDP in BC1.2 protocol It is necessary to communicate between the charging device and the notebook, and switch between SDP and CDP modes through a specific chip on the notebook. This chip always works when the USB charging function is turned on, so the notebook will also consume power when it is turned off, and it consumes about 15% of the power in one night. Therefore, if this function is enabled on a model that supports the usb charge function, the battery will still be consumed in the power-off state without any external USB device.
Note:
To protect the battery life of the device being charged, the usb charge function switches between different modes to control the charging current.