A detachable adapter is provided for being detachably connected to a data bus of a receptacle of a portable device to form a portable system. The adapter includes a conversion circuit and can inform the portable device that whether a power source is available and inform the portable device of connection status of the adapter through the data bus. The portable device can be connected to the power source through one of the receptacles of the adapter so that the portable device is powered or charged, and the portable device can be connected to at least one client device through the other receptacle of the adapter simultaneously.