Patent ID: 7833670

Claim:
A fuel cell system comprising: a fuel cell comprising a cathode and an anode; an oxidant-containing gas supply path along which an oxidant-containing gas is supplied to said cathode; a reformer producing a hydrogen-containing gas from a raw fuel and supplying said hydrogen-containing gas to said anode; a power converter comprising an output terminal connected to an external load, and comprising a function of converting an output of said fuel cell to power according to an application as well as a constant-current operating function; a first switch connected in series to said power converter; a short-circuit resistor; a second switch connected in series to said short-circuit resistor; and a current-value control section configured to control a current value output from said fuel cell, wherein a pair of said power converter and said first switch is connected between said cathode and said anode, a pair of said short-circuit resistor and said second switch is also connected between said cathode and anode, when stopping electricity production by said fuel cell, said current-value control section outputs a current command value to said power converter as well as keeps said first switch on and said second switch off to cause said output of said fuel cell to be consumed in said external load through said power converter during a time period after stopping the supply of said oxidant-containing gas to said cathode while maintaining the supply of said hydrogen-containing gas from said reformer to said anode until an output voltage of said fuel cell is reduced to a constant threshold value, and switches said first switch to the off state and said second switch to the on state when said output voltage of said fuel cell falls below said threshold value, and thereafter stops the supply of said hydrogen-containing gas to said anode so as to control the current value output from said fuel cell when said output voltage of said fuel cell is reduced to approximately zero, and the current value control section includes a first voltage detector outputting a first signal when an input voltage from said power converter falls below an operable lower limit voltage value of said power converter which corresponds to said constant threshold value, and a second voltage detector detecting said output voltage of said fuel cell and outputting the result of detection as a second signal.