Patent ID: 7372236

Claim:
A charger that charges a secondary cell through a converter for constantly controlling input electric power from a cell having relatively large output impedance when electric power is supplied, such as a fuel cell or a solar cell as an input source, comprising: a current control circuit having the secondary cell provided at an output thereof, that is connected to the secondary cell, and supplies a charging current flowing into the secondary cell as a current value which is obtained from a control amount necessary for keeping an output voltage of the converter at a dropping voltage to be set, wherein, when charging to the secondary cell is started, the current control circuit performs constant current charging in which the charging current flowing into the secondary cell is used as a current value determined according to an input electric power value, and at an end period of the charging when the voltage of the secondary cell reaches approximately an output voltage, the current control circuit stops performing constant control of the input electric power and detects a rise in an input voltage, thereby stopping the charging.