Patent ID: 8089251

Claim:
A battery charging control circuit, comprising: a trickle charging unit configured for charging a rechargeable battery with a first current in a trickle mode; a constant-current charging unit configured for charging a rechargeable battery with a second current greater than the first current in a constant-current mode, comprising: a current detection circuit configured for detecting current of the battery, and providing a detection voltage proportional to the current; and a detection switch is turned on or off under the control of the detection voltage, wherein, the detection switch is a low voltage activated switch comprising a control terminal, a first path terminal, and a second path terminal, the first path terminal of the detection switch is connected to an input port of the current detection circuit, the second path terminal of the detection switch is grounded, and the control terminal of the detection switch is connected to an output of the current detection circuit; a branch switch connected between the constant-current charging unit and an anode of the rechargeable battery, configured for enabling or disabling the constant-current charging unit, wherein the branch switch comprises a first switch and a first resistor, a control terminal of the first switch is connected to the control unit, a first path terminal of the first switch is connected to the control terminal of the detection switch, a second path terminal of the first switch is connected to the anode of the rechargeable battery; the first resistor is connected between the control terminal and the first path terminal of the first switch; a detection unit configured for detecting states of the rechargeable battery and outputting detection signals when detecting a predetermined state of the rechargeable battery, wherein, the detection switch and the current detection circuit are connected in parallel between the power source and the branch switch, the detection switch is turned on or off according to the detection voltage of the current detection circuit; and a control unit connected with the constant-current charging unit and the branch switch, configured for controlling the branch switch to turn off to disable the constant-current charging unit in response to the detection signal from the detection unit, wherein, if the branch switch is turned off, the constant-current charging unit is disabled and the trickle charging unit starts charging the rechargeable battery.