Patent ID: 7999512

Claim:
A battery protection circuit comprising: a battery node for connecting to a terminal of a battery; a charger node for connecting to a terminal of a charger that charges the battery; a power transistor having a channel connected between the battery node and the charger node, and a gate that controls the channel, the gate connected to a first gate node; a comparator having inputs connected to the battery node and to the charger node, for generating a compare output from a voltage difference between the battery node and the charger node; a control circuit that receives the compare output from the comparator and generates a first enable signal and a second enable signal; a voltage booster, receiving a clock, for generating a boosted clock, the boosted clock having a higher high voltage than a high voltage of the clock; a first switch, receiving the boosted clock from the voltage booster, for applying the boosted clock to the first gate node in response to the first enable signal; a gate-coupling transistor having a channel connected between the charger node and the first gate node, and a gate that controls the channel, the gate connected to a second gate node; a second switch, receiving the boosted clock from the voltage booster, for applying the boosted clock to the second gate node in response to the second enable signal; and a grounding transistor that connects the second gate node to a ground when the second switch is not applying the boosted clock to the second gate node; wherein the control circuit further generates a third enable signal; wherein during a connecting first state the control circuit activates the first enable signal and de-activates the second enable signal and the third enable signal; wherein during an isolating second state the control circuit activates the second enable signal and de-activates the first enable signal and the third enable signal; wherein during an isolating third state the control circuit activates the third enable signal and de-activates the first enable signal and the second enable signal, whereby the power transistor is biased by the gate-coupling transistor to shut off and isolate the battery node from the charger node when the second enable signal is activated and the first enable signal is de-activated.