Patent ID: 8518589

Claim:
An apparatus to control an open circuit voltage (OCV) of a fuel cell stack having an anode side and a cathode side, the apparatus comprising: a first valve installed at an outlet of the anode side, to control the flow of anode off-gas to an inlet of the cathode side, to control the flow of anode off-gas to an inlet of a burner to heat the stack, and to adjust the internal pressure in the anode side; a second valve installed between an outlet of the first valve and the inlet of the cathode side; and a control unit configured to control the first valve, so as to: mix the anode off-gas with air that is supplied to the cathode side while increasing the internal pressure in the anode side by partially closing the first valve to restrict the anode off-gas discharged from the anode side, during a start-up mode or a shut-down mode, while the stack is in an OCV state, and cut off the supply of the anode off-gas to the cathode, during a normal operating mode.