Patent ID: 8760121

Claim:
A charging apparatus for supplying a charging current to a secondary battery, comprising: a back flow prevention unit through which the charging current is supplied to the secondary battery; a constant current source; a detector, the detector including a reference current means for providing a reference current branch and a judgment current means for providing at least two judgment current branches, the reference current means and the judgment current means being connected between an input terminal of the back flow prevention unit and the constant current source, wherein the detector selects one of the judgment current branches in response to a select signal determined depending on a chargeable voltage of the secondary battery to generate a selected judgment voltage with the aid of the selected judgment branch and the reference current branch, and wherein the detector additionally compares a comparison voltage that is based on a voltage at an output terminal of the back flow prevention unit with the selected judgment voltage to detect a fully charged state of the secondary battery; and an interrupter for interrupting supply of the charging current to the back flow prevention unit when the detector detects that the secondary battery is in a fully charged state.