Battery protection method and circuit therefor
View Patent ↗In one embodiment, a circuit is formed to couple a battery to a charging voltage at least a portion of a time when the charging voltage is greater than zero volts and is less than a first voltage value. The circuit is also formed to decouple the battery from the charging voltage approximately when the charging voltage is greater than the first voltage and also approximately when the charging voltage is no greater than zero volts.
1. A method of forming a battery protection circuit comprising:
configuring a plurality of transistors of a first conductivity type to receive a charging voltage from a voltage source and responsively couple a battery to the charging voltage at least a portion of a first time when the charging voltage is greater than approximately zero volts and is less than a first voltage;
configuring the plurality of transistors to responsively decouple the battery from the charging voltage at least a portion of a second time when the charging voltage is less than approximately zero volts;
configuring the plurality of transistors to decouple the battery from the charging voltage at least a portion of a third time when the charging voltage is no less than the first voltage; and
coupling a first current carrying electrode of a first transistor of a second conductivity type to a control electrode of at least a first transistor of the plurality of transistors and to a second current carrying electrode of a second transistor of the plurality of transistors, coupling a control electrode of the first transistor of the second conductivity type to the control electrode of the second transistor of the plurality of transistors.
2. A method of forming a battery protection circuit comprising:
configuring a plurality of transistors of a first conductivity type to receive a charging voltage from a voltage source and responsively to the charging voltage couple a battery to the charging voltage at least a portion of a first time when the charging voltage is greater than approximately zero volts and is less than a first voltage;
configuring the plurality of transistors to decouple the battery from the charging voltage, responsively to the charging voltage, at least a portion of a second time when the charging voltage is less than approximately zero volts; and
configuring the plurality of transistors to decouple the battery from the charging voltage, responsively to the charging voltage, at least a portion of a third time when the charging voltage is no less than the first voltage.
3. The method of claim 2 wherein configuring the plurality of transistors of the first conductivity type to receive the charging voltage from the voltage source and couple the battery to the charging voltage includes configuring the plurality of transistors having a first current carrying electrode commonly coupled together, having a second current carrying electrode and having a control electrode, wherein the second current carrying electrode of a first transistor of the plurality of transistors is configured to receive a voltage from the battery and the second current carrying electrode of a second transistor of the plurality of transistors is configured to receive the charging voltage.
4. The method of claim 3 further including coupling the second current carrying electrode of a third transistor of the plurality of transistors to the control electrode of the first transistor of the plurality of transistors.
5. The method of claim 4 further including coupling the second current carrying electrode of the third transistor of the plurality of transistors to the control electrode of the second transistor of the plurality of transistors.
6. A battery protection method comprising:
providing a battery and a voltage source configured to provide a charging voltage;
coupling the battery to the charging voltage responsively to the charging voltage at least a portion of a first time when the charging voltage is greater than zero volts and is less than a first voltage;
decoupling the battery from the charging voltage responsively to the charging voltage at least a portion of a second time when the charging voltage is no greater than zero volts; and
decoupling the battery from the charging voltage responsively to the charging voltage at least a portion of a third time when the charging voltage is no less than the first voltage.
7. The method of claim 1 further including coupling commonly together a first current carrying electrode of a first transistor, a second transistor, and a third transistor, coupling a second current carrying electrode of the first transistor to receive the charging voltage, coupling a second current carrying electrode of the second transistor to receive a battery voltage from the battery, and enabling the first transistor and the second transistor for coupling the battery to the charging voltage.
8. The method of claim 7 wherein decoupling the battery from the charging voltage includes disabling the first transistor and the second transistor at least a portion of a fourth time when the charging voltage is no less than the first voltage.
9. The method of claim 7 wherein decoupling the battery from the charging voltage includes disabling the first transistor and the second transistor approximately when the charging voltage is less than zero.
10. The method of claim 7 wherein decoupling the battery from the charging voltage includes disabling the second transistor and the third transistor at least a portion of a fourth time when the charging voltage is greater than the first voltage and less than a second voltage that is greater than the first voltage.
11. The method of claim 7 wherein coupling the battery to the charging voltage includes disabling the third transistor.
12. The method of claim 7 wherein coupling the battery to the charging voltage responsively to the charging voltage at least a portion of the first time when the charging voltage is greater than zero volts and is less than the first voltage includes enabling a fourth transistor to couple a voltage to a control electrode of the first and second transistors and enable the first and second transistors.
13. A battery protection circuit comprising:
a plurality of transistors of a first conductivity type having a control electrode, having a first current carrying electrode commonly connected together, and having a second current carrying electrode wherein the second current carrying electrode of at least one transistor of the plurality of transistors is configured to receive a voltage from a battery and a second current carrying electrode of another transistor of the plurality of transistors is configured to receive a charging voltage for the battery, wherein the control electrode of a first transistor of the plurality of transistors is coupled to the second current carrying electrode of a second transistor of the plurality of transistors, and wherein the control electrode of a third transistor of the plurality of transistors is coupled to the control electrode of the first transistor and the control electrode of the second transistor of the plurality of transistors is coupled to receive a voltage that is limited to a second voltage value that is greater than a maximum voltage of the battery; and
a first transistor of a second conductivity type having a first current carrying electrode coupled to the control electrode of the third transistor of the plurality of transistors.
14. The battery protection circuit of claim 13 wherein the plurality of transistors of the first conductivity type are P-channel MOS transistors.
15. The battery protection circuit of claim 14 wherein the first transistor of the second conductivity type is an N-channel MOS transistor.
16. The battery protection circuit of claim 13 wherein a control electrode of the first transistor of the second conductivity type is coupled to the control electrode of the second transistor of the plurality of transistors.