Patent ID: 7683574

Claim:
A battery charger having a constant current mode and a constant voltage mode, the battery charger comprising: a pair of input terminals adapted to be coupled to a source of DC voltage; a pair of output terminals adapted to be coupled to a battery cell; a charging circuit coupled between said input terminals and said output terminals, said charging circuit comprising: a converter comprising a voltage regulator for controlling the DC voltage applied to said input terminals, said regulator initially configured to provide a charging voltage in a constant current mode of operation relatively higher than said charging voltage in said constant voltage mode; a switching device coupled between said input terminals and said output terminals, said switching device for selectively connecting and disconnecting said pair of output terminals from said charging circuit, said voltage comparator coupled to said regulator; a voltage comparator for comparing the battery open circuit voltage with a reference voltage; a microprocessor operatively coupled to said pair of output terminals for monitoring the open circuit voltage of said battery cell under charge and selectively providing a signal representative of the battery cell open circuit voltage to said voltage comparator forming a first feedback loop, said open circuit voltage representative signal also used to control said regulator in order to reduce said battery charging voltage during a constant voltage charging mode forming a secondary feedback loop when said open circuit voltage reaches a predetermined value less than said charging voltage in said constant current mode.