Patent ID: 7719252

Claim:
A power supply comprising: a fuel cell; a DC-DC converter that adjusts a voltage outputted from the fuel cell, and then outputs the voltage to a load device connected thereto in parallel; a signal generator for generating a PWM signal that controls the DC-DC converter and outputting the PWM signal to the DC-DC converter; a rechargeable battery connected to the load device in parallel; and a voltmeter for measuring a voltage outputted from the DC-DC converter, wherein the signal generator calculates a duty ratio of the PWM signal on the basis of a target fuel cell voltage indicating a target value of the voltage outputted from the fuel cell and a measured value of the voltage measured by the voltmeter, the DC-DC converter is a boost type DC-DC converter; and the signal generator calculates the duty ratio of the PWM signal by performing a computation expressed by Equation (1) using the target fuel cell voltage and the voltage measured by the voltmeter, D [%]=(1− Vt/V out)×100 (1): where D is the duty ratio, Vt is the target fuel cell voltage, and Vout is the voltage measured by the voltmeter.