External power supply and system connection detection unit applied thereto

A system connection detection unit applied to an external power supply, electrically connected to a power supply unit of the external power supply for detecting the connecting status between the external power supply and a system, the external power supply separably connected with a positive input terminal and a negative input terminal of the system respectively through a positive output terminal and a negative output terminal for providing electrical power to the system, the power supply unit electrically connected to the positive output terminal and the negative output terminal, the system connection detection unit having a system detection terminal which is used to connect with a system connection terminal of the system when the positive output terminal and the negative output terminal respectively connecting to the positive input terminal and the negative input terminal of the system, wherein the system connection terminal is electrically connected to one of the positive input terminal and the negative input terminal through at least one first resistive element;

• wherein the system connection detection unit detects the voltage of the system detection terminal and generates a connection status signal accordingly, and the connection status signal generated by the system connection detection unit switches the operation of the external power supply from a deep sleeping mode to a normal operation mode when the positive output terminal and the negative output terminal are respectively connecting to the positive input terminal and the negative input terminal of the system.