Patent ID: 7767353

Claim:
A fuel cell system, comprising: a fuel cell; a fuel cell DC/DC converter that steps up an output voltage of the fuel cell to a voltage of a first predetermined value to output; an electric storage device; an electric storage device DC/DC converter that converts an output voltage of the electric storage device; and a charge circuit that charges the electric storage device, and wherein a step-up ratio of the fuel cell DC/DC converter has an upper limit, wherein an output terminal of the fuel cell DC/DC converter, an output terminal of the electric storage device DC/DC converter, and an input terminal of the charge circuit are connected together, wherein the charge circuit is turned on and off according to a voltage at a connecting point of the output terminal of the fuel cell DC/DC converter, the output terminal of the electric storage device DC/DC converter, and the input terminal of the charge circuit, and wherein when the step-up ratio reaches the upper limit, the voltage at the connecting point drops to a second predetermined value lower than the first predetermined value.