Patent ID: 7629775

Claim:
A battery connection detection circuit for detecting whether a secondary battery is operable and whether the secondary battery is reliably connected to a charging device, comprising: a current supplying circuit configured to supply a current to the secondary battery; a constant voltage circuit configured to control the current from the current supplying circuit so that a voltage on a connection terminal T1 for connecting the secondary battery is constant; a constant current circuit configured to control the current from the current supplying circuit so that the current supplied to the secondary battery is constant; and a determination circuit configured to concurrently determine operation states of both the constant voltage circuit and the constant current circuit, said determination circuit determining whether the secondary battery is operable and whether the secondary battery is reliably connected to the charging device according to the operation states of the constant voltage circuit and the constant current circuit, wherein when it is determined that the current flowing through the secondary battery is higher than a predetermined value from the operation state of the constant current circuit, the determination circuit determines that the secondary battery is operable and the secondary battery is reliably connected to the connection terminal T1.