Patent ID: 7638981

Claim:
A charging device comprising: a power source to supply a charging current to a secondary battery; an operational amplifier to control the supply of the charging current by the power source; a power element to control the supply of the charging current to the secondary battery; a setting unit corresponding to an adjustable voltage source, the adjustable voltage source coupled to the power source and an inverting input terminal of the operational amplifier and coupled between the power source and the inverting input terminal; a resistor coupled in series with the adjustable voltage source and coupled between the adjustable voltage source and the inverting input terminal; wherein a main charging is performed on the secondary battery by supplying a normal current to the secondary battery as the charging current, and a trickle charging is performed on the secondary battery by supplying a weak current, set by the setting unit, to the secondary battery as the charging current when the main charging is not performed, wherein the power element is turned on during the performance of the main charging and the trickle charging and during transition from the main charging to the trickle charging, and wherein the adjustable voltage source is set so as to adjust an input offset voltage of the operational amplifier so as to set a value of the weak current; and a switch coupled to the operational amplifier and operable to be turned off during the duration of the performance of the trickle charging.