Abstract: An alternating-current and direct-current conversion apparatus includes a first converter unit, a switching unit electrically connected with the first converter unit, and a second converter unit electrically connected with the switching unit. The switching unit is connected between the first converter unit and the second converter unit and is operated to convert a direct-current power into an alternating-current power or to convert an alternating-current power into a direct-current power so that the direct-current power of the direct-current source is converted into an alternating-current power which can be used by the alternating-current source, and the alternating-current power of the mains power supply is converted into a direct-current power which can be used by the direct-current source.