Patent ID: 7830120

Claim:
A battery protection circuit for protecting a plurality of batteries connected in series by controlling: (1) a discharging current flowing from the batteries through a load detachably attached between a positive terminal and a negative terminal, or (2) a charging current flowing to the batteries from a charger detachably attached between the positive terminal and the negative terminal, the battery protection circuit comprising: a controller for monitoring the batteries and outputting control signals based on predetermined conditions associated with the batteries; a first N-channel MOSFET and a second N-channel MOSFET coupled in a common-drain configuration in a low-side path, wherein at least one of the first and second N-channel MOSFETs turns off in response to the control signal received from the controller when at least one of the predetermined conditions is detected; and a gate protection circuit for preventing gate-to-source voltages of the first and second N-channel MOSFETs from exceeding a predetermined voltage level; wherein the gate protection circuit comprises: a small-signal FET having a drain coupled to a gate of the second N-channel MOSFET and a source coupled to the negative terminal, wherein the small-signal FET turns on and clamps the gate-to-source voltage of the second N-channel MOSFET when the gate-to-source voltage of the second N-channel MOSFET increases to a predetermined gate-to-source voltage level during a period when the second N-channel MOSFET is off and the charger is attached.