Usb power supply

A universal serial bus (USB) power supply including:

• a first unit, and
• a second unit releasably connectable with said first unit,
• wherein said first unit is releasably connectable to a direct current (DC) power source for receiving a DC power there-from, said first unit including a first USB connection part electrically connectable with said DC power source,
• wherein said second unit includes a second USB connection part releasably connectable with said first USB connection part to establish electrical connection and data communication there-between and a connector electrically connected with said second USB connection part,
• wherein said power supply is operable in a detached mode in which said first unit is out of connection with said second unit and in an attached mode in which said first unit is releasably connected with said second unit, and
• wherein, when in said attached mode, said power supply is adapted to automatically change the voltage of a DC power output from said connector.