Circuits and methods for battery charging

1. A circuit for charging a battery pack, said circuit comprising:

a transformer operable for receiving an input power and for providing a charging power according to a driving signal to charge said battery pack; and

a charger controller coupled to said transformer and operable for monitoring a status of said battery pack, for selecting a charging mode from a plurality of charging modes according to said status, for generating said driving signal according to said charging mode to adjust said charging power, wherein said charger controller further executes a state machine that stores data indicating a plurality of predetermined battery statuses that cause saturation of said transformer, and that selects a protection mode in which said charging power is restricted if said status of said battery pack matches to one of said predetermined battery statuses.

2. The circuit as claimed in claim 1 , wherein said predetermined battery statuses comprise a sudden removal of said battery pack.

3. The circuit as claimed in claim 1 , wherein said predetermined battery statuses comprise an abnormal condition selected from a group consisting of an over-temperature condition and an over-current condition.

4. The circuit as claimed in claim 1 , wherein said transformer provides galvanic isolation between input circuitry and output circuitry of said circuit, wherein said input circuitry shares a first ground potential with said input power, and said output circuitry shares a second ground potential with said charging power, and wherein said charger controller is integrated on an integrated circuit chip in said output circuitry.

5. The circuit as claimed in claim 4 , wherein said charger controller further comprises:

a pulse width modulator operable for generating a pulse signal as said driving signal, wherein said pulse signal is transferred from said output circuitry to a switch in said input circuitry to control said charging power.

6. The circuit as claimed in claim 1 , wherein said circuit further comprises:

a switch coupled between said transformer and said battery pack, wherein said charger controller generates a switch control signal to turn off said switch in said protection mode.

7. A method for charging a battery pack, said method comprising:

receiving an input power;

providing a charging power to charge said battery pack;

monitoring a status of said battery pack;

selecting a charging mode from a plurality of charging modes according to said status to adjust said charging power;

accessing data indicating a plurality of predetermined battery statuses that cause saturation of a transformer coupled to said battery pack; and

selecting a protection mode in which said charging power is restricted if said status of said battery pack matches one of said predetermined battery statuses.

8. The method as claimed in claim 7 , wherein said predetermined battery statuses comprise a sudden removal of said battery pack.

9. The method as claimed in claim 7 , wherein said predetermined battery statuses comprise an abnormal condition selected from a group consisting of an over-temperature condition and an over-current condition.

10. The method as claimed in claim 7 , wherein input circuitry that is coupled to said transformer shares a first ground potential with said input power, and output circuitry that is coupled to said input circuitry shares a second ground potential with said charging power, and wherein said method further comprises:

generating a pulse signal according to said charging mode by said output circuitry; and

transferring said pulse signal from said output circuitry to a switch in said input circuitry to adjust said charging power.

11. The method as claimed in claim 7 , further comprising:

generating a switch control signal to turn off a switch coupled between said transformer and said battery pack in said protection mode.

12. A system for controlling a power converter that provides charging power to a battery pack, said system comprising:

a charger controller comprising a state machine operable for monitoring a status of said battery pack and for selecting a selected operation mode from a plurality of operation modes, wherein said operation modes comprise a plurality of charging modes and a protection mode; and

a pulse width modulator coupled to said charger controller and operable for providing a pulse signal to said power converter according to said selected operation mode to control said charging power,

wherein said state machine further stores data indicating a plurality of predetermined statuses that cause saturation of said power converter, and selects said protection mode to restrict said charging power if said status of said battery pack matches one of said predetermined battery statuses.

13. The system as claimed in claim 12 , wherein said charger controller is integrated on an integrated circuit chip.

14. The system as claimed in claim 12 , further comprising:

a protection circuit coupled to said pulse width modulator, and operable for generating an alert signal if said status of said battery pack indicates said battery pack is in an abnormal condition, wherein said pulse width modulator controls said pulse signal in response to said alert signal to switch said charger controller to said protection mode.

15. The system as claimed in claim 14 , wherein said predetermined battery statuses comprise a sudden removal of said battery pack.

16. The system as claimed in claim 14 , wherein said predetermined battery statuses comprise an abnormal condition selected from a group consisting of an over-temperature condition and an over-current condition.

17. The system as claimed in claim 12 , wherein said power converter provides galvanic isolation between input circuitry and output circuitry, wherein said input circuitry shares a first ground potential with input power, and said output circuitry shares a second ground potential with said charging power, and wherein said charger controller is in said output circuitry and said pulse signal is transferred from said output circuitry to said input circuitry to adjust said charging power.