Charging system and charging method of universal serial bus

A charging method for a universal serial bus (USB), a charging system of the USB comprising a primary power source, a power source controller, a first switch, a second switch, a third switch, a fourth switch, a first port, and a second port, the power source controller comprising an auxiliary power source, a load detection circuit, a first auxiliary power terminal coupled to the auxiliary power source, and a second auxiliary power terminal coupled to the auxiliary power source, the first auxiliary power terminal being used for providing a first detection current, the second auxiliary power terminal being used for providing a second detection current, the power source controller being coupled to the primary power source, a first terminal of the first switch being coupled to the primary power source, a control terminal of the first switch being coupled to the power source controller, a first terminal of the second switch being coupled to the primary power source, a control terminal of the second switch being coupled to the power source controller, a first terminal of the third switch being coupled to the first auxiliary power terminal, a control terminal of the third switch being coupled to the power source controller, a first terminal of the fourth switch being coupled to the second auxiliary power terminal, a control terminal of the fourth switch being coupled to the power source controller, the first port being coupled to a second terminal of the first switch and a second terminal of the third switch, the second port being coupled to a second terminal of the second switch and a second terminal of the fourth switch, and the method comprising:

• the power source controller turning off the first switch and the second switch and turning on the third switch and the fourth switch, the auxiliary power source providing the first detection current to the first port and the second detection current to the second port;
• when the load detection circuit detects that the first detection current is less than a threshold value, the power source controller determining that the first port is disconnected, or a first wire connected the first port is floating, and the power source controller maintaining the first switch to be off and the third switch to be on;
• when the load detection circuit detects that the first detection current is greater than the threshold value, the load detection circuit determining that the first wire connected to the first port is coupled to a first device;
• when the load detection circuit determines that the first wire is coupled to the first device, the power source controller setting the primary power source with a first power capability option, turning off the third switch and turning on the first switch to enable the primary power source to provide a first output power to a first device through the first switch, the first output power being corresponding to the first power capability option;
• the power source controller communicating a power profile with the first device and selecting a power capability option from the power profile to determine a first output power level;
• and
• the power source controller controlling the primary power source to provide the first output power to the first device;
• wherein the power profile comprises the first power capability option and a plurality of other power capability options.