Patent ID: 8643337
Filing Date: 2014-02-04
Classification: H02J

Abstract:
1. 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 during a connecting first state the control circuit activates the first enable signal and de-activates the second enable signal; wherein during an isolating second state the control circuit activates the second enable signal and de-activates the first enable signal; wherein the control circuit further comprises: a direction control input that indicates a direction of intended current flow in the channel of the power transistor; wherein when the direction control input indicates a forward direction, the control circuit activates the connecting first state when the compare output is in a true state, and activates the isolating second state when the compare output is in a false state; wherein when the direction control input indicates a reverse direction, the control circuit activates the connecting first state when the compare output is in the false state, whereby the isolating second state is activated for the forward direction and 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.