Patent ID: 7502242

Claim:
A bidirectional insulated DC/AC inverter, comprising: a first power conversion unit, comprising a first AC input/output terminal and a first DC input/output terminal for receiving AC power from the first AC input/output terminal and outputting DC power to the first DC input/output terminal in a power conversion from AC to DC, and for receiving DC power from the first DC input/output terminal and outputting AC power to the first AC input/output terminal in a power conversion from DC to AC; a second power conversion unit, comprising a second AC input/output terminal and a second DC input/output terminal connected to the first DC input/output terminal of the first power conversion unit, for receiving AC power from the second AC input/output terminal and outputting DC power to the second DC input/output terminal in a power conversion from AC to DC, and for receiving DC power from the second DC input/output terminal and outputting AC power to the second AC input/output terminal in a power conversion from DC to AC; a third power conversion unit, comprising a third AC input/output terminal and a third DC input/output terminal connected to a battery, for receiving AC power from the third AC input/output terminal and outputting DC power to the third DC input/output terminal in a power conversion from AC to DC, and for receiving DC power from the third DC input/output terminal and outputting AC power to the third AC input/output terminal in a power conversion from DC to AC; a transformer connected to the second AC input/output terminal of the second power conversion unit and the third AC input/output terminal of the third power conversion unit; a control unit for controlling operations of each of the first through the third power conversion units; a plug for electrically connecting an external power source and the first AC input/output terminal of the first power conversion unit; an outlet, connected to the plug electrically and directly on a steady basis, for electrically connecting an external load and the first AC input/output terminal of the first power conversion unit; and a detection unit for detecting first voltage, which is a voltage of the first AC input/output terminal of the first power conversion unit, or second voltage, which is a voltage of the first DC input/output terminal of the first power conversion unit, wherein the control unit, based on voltage detected by the detection unit, is configured to determine whether or not AC power is input from the external power source to the first power conversion unit, and to inhibit at least a power conversion operation from DC to AC of the third power conversion unit when it is determined that AC power is input from the external power source to the first power conversion unit thereby preventing the AC power output from the third power conversion unit from being overlapped with the AC power input from the external power source without using a mechanical relay.