Intelligent contact charging devices and methods

1. A contact charging device comprising:

a communication circuit configured to:

detect a power adapter that is coupled with the contact charging device; and

perform a negotiation process with the power adapter, the negotiation process determining an input voltage provided to the contact charging device by the power adapter;

a power converter circuit configured to supply, from the input voltage, charging power for charging a battery of an electronic device; and

a control circuit configured to determine a charging current limit and a charging voltage of the power converter circuit for charging the battery, the determining the charging current limit and the charging voltage including:

setting the charging current limit of the power converter circuit to an initial charging current limit and setting the charging voltage to an initial charging voltage;

determining whether the power converter circuit is operating in a current limit mode or a voltage limit mode; and

iteratively modifying the charging current limit of the power converter circuit until the power converter circuit dithers between the current limit mode and the voltage limit mode.

2. The contact charging device of claim 1 , wherein the power converter circuit is a direct-current-to-direct-current (DC-DC) step down converter.

3. The contact charging device of claim 1 , wherein determining whether the power converter circuit is operating in a current limit mode or a voltage limit mode includes at least one of:

determining an output current of the power converter circuit and comparing the output current to the charging current limit; and

determining an output voltage of the power converter circuit and comparing the output voltage to the charging voltage.

4. The contact charging device of claim 3 , further comprising an analog-to-digital converter configured to determine the output current of the power converter circuit based on the output voltage of the power converter circuit and a value of an output sense resistor.

5. The contact charging device of claim 1 , wherein iteratively modifying the charging current limit of the power converter circuit until the power converter circuit dithers between the current limit mode and the voltage limit mode includes:

while the power converter circuit is operating in the current limit mode, iteratively increasing the charging current limit until the power converter circuit changes from operating in the current limit mode to operating in the voltage limit mode; and

while the power converter circuit is operating in the voltage limit mode, iteratively decreasing the charging current limit until the power converter circuit changes from operating in the voltage limit mode to operating in the current limit mode.

6. The contact charging device of claim 5 , wherein iteratively increasing the charging current limit includes iteratively increasing the charging current limit until the charging current limit equals an upper charging current limit.

7. The contact charging device of claim 6 , wherein the control circuit is configured to limit an amount of time the contact charging device operates at the upper charging current limit.

8. The contact charging device of claim 1 , wherein iteratively modifying the charging current limit of the power converter circuit includes waiting a period of time between each modification of the charging current limit of the power converter circuit.

9. A method for charging a battery of an electronic device, the method comprising:

detecting, by a contact charging device, a power adapter that is coupled with the contact charging device;

performing, by the contact charging device, a negotiation process with the power adapter, the negotiation process determining an input voltage provided to the contact charging device by the power adapter;

supplying, by a power converter circuit of the contact charging device from the input voltage, charging power for charging the battery of the electronic device; and

determining, by the contact charging device, a charging current limit and a charging voltage of the power converter circuit for charging the battery, the determining the charging current limit and the charging voltage including:

setting the charging current limit of the power converter circuit to an initial charging current limit and setting the charging voltage to an initial charging voltage;

determining whether the power converter circuit is operating in a current limit mode or a voltage limit mode; and

iteratively modifying the charging current limit of the power converter circuit until the power converter circuit dithers between the current limit mode and the voltage limit mode.

10. The method of claim 9 , wherein determining whether the power converter circuit is operating in a current limit mode or a voltage limit mode includes at least one of:

determining an output current of the power converter circuit and comparing the output current to the charging current limit; and

determining an output voltage of the power converter circuit and comparing the output voltage to the charging voltage.

11. The method of claim 9 , wherein iteratively modifying the charging current limit of the power converter circuit until the power converter circuit dithers between the current limit mode and the voltage limit mode includes:

while the power converter circuit is operating in the current limit mode, iteratively increasing the charging current limit until the power converter circuit changes from operating in the current limit mode to operating in the voltage limit mode; and

while the power converter circuit is operating in the voltage limit mode, iteratively decreasing the charging current limit until the power converter circuit changes from operating in the voltage limit mode to operating in the current limit mode.

12. The method of claim 11 , wherein iteratively increasing the charging current limit includes iteratively increasing the charging current limit until the charging current limit equals an upper charging current limit.

13. The method of claim 12 , further comprising limiting an amount of time the contact charging device operates at the upper charging current limit.

14. The method of claim 13 , further comprising, after the amount of time the contact charging device operates at the upper charging current limit has passed:

resetting the charging current limit of the power converter circuit to the initial charging current limit; and

resetting the charging voltage to the initial charging voltage.

15. The method of claim 9 , wherein iteratively modifying the charging current limit of the power converter circuit includes waiting a period of time between each modification of the charging current limit of the power converter circuit.

16. A contact charging device comprising:

a two-port interface configured to be operatively coupled to a surface contact connector on an electronic device;

a power converter circuit configured to supply, from an input voltage received from a cable attached to a charger, charging power for charging a battery in the electronic device via a bypass charger in the electronic device; and

a control circuit configured to determine a charging current limit and a charging voltage of the power converter circuit for charging the battery, to prevent the bypass charger from remaining in a regulation mode during the charging of the battery in the electronic device, the control circuit implementing a number of states of finite state machine, the states including:

a first current limit state that includes setting the charging current limit of the power converter circuit to an initial charging current limit and setting the charging voltage to an initial charging voltage;

a second current limit state that includes incrementing the charging current limit in response to the contact charging device operating in a current limit mode;

a third current limit state that includes operating the contact charging device at an upper current limit of the contact charging device; and

a voltage limit state that includes decrementing the charging current limit in response to the contact charging device operating in a voltage limit mode.

17. The contact charging device of claim 16 , wherein the contact charging device is configured to transition from the first current limit state to the second current limit state in response to the contact charging device operating in the current limit mode.

18. The contact charging device of claim 16 , wherein the contact charging device, when operating in the second current limit state, is configured to periodically increment the charging current limit in response to the contact charging device continuing to operate in current limit mode.

19. The contact charging device of claim 18 , wherein the contact charging device is configured to transition from the second current limit state to the third current limit state in response to the contact charging device operating in the current limit mode and the charging current limit being equal to the upper current limit of the contact charging device.

20. The contact charging device of claim 16 , wherein the contact charging device is configured to transition from the second current limit state to the voltage limit state in response to the contact charging device operating in the voltage limit mode.