Charging device

A charging device configured to charge a secondary battery with power supply from outside via a charge adapter configured to be attachably and detachably connected to the charging device, comprising:

• a switching device configured to receive the power supply from outside via the charge adapter, the switching device being configured to be turned on and off on the basis of a switching signal to supply a charge current to the secondary battery;
• a shunt resistor connected between the switching device and a positive electrode of the secondary battery, the shunt resistor being configured to detect a current flowing through the secondary battery;
• and
• a charge controller configured to receive input of voltages at two ends of the shunt resistor in synchronization with turning on of the switching device, the charge controller being configured to set an on-time during which the switching device is turned on based on the inputted voltages at the two ends of the shunt resistor to control the charge current of the secondary battery, wherein
• a resistance value of the shunt resistor is set equal to or above a value obtained by dividing a least resolution of an A/D conversion voltage when the charge controller converts an inputted analog voltage into a digital voltage by a minimum detectable value of the charge current of the secondary battery.