Battery charger for a handheld computing device and an external battery

• US 8,063,606 B2
• Filed: 05/11/2007
• Issued: 11/22/2011
• Est. Priority Date: 05/11/2007
• Status: Active Grant

• Current Assignee: Malikie Innovations Limited (Key Patent Innovations Limited)
• Original Assignee: Blackberry Limited
• Inventors: Veselic, Dusan
• Primary Examiner(s): Tso; Edward
• Assistant Examiner(s): TORRES RUIZ, JOHALI ALEJANDRA
• Application Number:
  US11/747,388
• Publication Number:
  US 20080278119A1
• Time in Patent Office: 1,656 Days
• Field of Search: 320/119
• US Class Current: 320/119
• CPC Class Codes: H02J 7/0013 acting upon several batteries simultaneously or sequentially H02J7/1423 takes precedence
• CPC Class Codes: H02J 7/00714 in response to battery charging or discharging current
• CPC Class Codes: H02J 7/04 Regulation of charging current or voltage

Abstract

A battery charger includes a power source for supplying a primary charge current to a first battery, and a charge manager for charging a second battery. The charge manager is coupled to the power source and is configured to charge the second battery with a secondary charge current in accordance with a continuous comparison between a predefined maximum current limit and a total current drawn from the power source.

Claims

1. A battery charger comprising:

a power source for supplying a primary charge current to a first battery; and

a charge manager for charging a second battery, the charge manager being coupled to the power source and being configured to charge the second battery with a secondary charge current in accordance with a continuous comparison between a predefined maximum current limit and a total current drawn from the power source;

wherein the charge manager includes a controlled current/voltage source for supplying the secondary charge current, and a charge manager controller coupled to the controlled source, the charge manager controller being configured to control a magnitude of the secondary charge current by outputting to a control input of the controlled source an analog difference signal proportional to a difference between a magnitude of the maximum current limit and the total drawn current.

2. The battery charger according to claim 1, wherein the charge manager controller comprises a voltage reference, a current monitor coupled to the power source, and a differential amplifier coupled to the voltage reference and the current monitor, the voltage reference being proportional to the maximum current limit, the current monitor being configured to output an analog voltage proportional to the total drawn current, the differential amplifier being configured to output the analog difference signal, the analog difference signal being proportional to a difference between the voltage reference and the analog voltage.

3. The battery charger according to claim 2, wherein the voltage reference is configured to limit the primary charge current to less than a maximum current limit of the power source.

4. The battery charger according to claim 1, wherein the charge manager and the power supply are disposed within a common charger housing, the charger housing comprising comprises a first indicator for indicating a charge state of the first battery, and a second indicator for indicating a charge state of the second battery.

5. The battery charger according to claim 4, wherein the first battery is disposed within a handheld computing device, the charger housing is configured to capture the second battery externally thereto, and further comprises a battery interface for electrically interfacing with the second battery, and a charger output for supplying the primary charge current to the handheld computing device.

6. The battery charger according to claim 1, wherein the charge manager is configured such that, while the handheld computing device charges the first battery with a continuously decreasing portion of the primary charge current, the controlled source charges the second battery with a continuously increasing portion of the secondary charge current, the total of the decreasing portion and the increasing portion being substantially equal to the maximum current limit.

7. The battery charger according to claim 6, wherein the charge manager is configured to charge the second battery with a second major constant portion of the secondary charge current, after a current drawn by the second battery during the continuously increasing charging step exceeds a maximum current threshold, the second major constant portion being substantially equal to the maximum current threshold.

8. The battery charger according to claim 6, wherein the charge manager is configured to charge the second battery with a minor constant portion of the secondary charge current prior to the continuously increasing charging step, while the handheld computing device charges the first battery with a first major constant portion of the primary charge current, the total of the first major portion and the minor portion being substantially equal to the maximum current limit.

9. The battery charger according to claim 7, wherein the charge manager is configured to charge the second battery with a minor constant portion of the secondary charge current prior to the continuously increasing charging step, while the handheld computing device charges the first battery with a first major constant portion of the primary charge current, the total of the first major portion and the minor portion being substantially equal to the maximum current limit.

10. A method of simultaneously charging batteries from a power source, the method comprising supplying a primary charge current from the power source to a first of the batteries, while charging a second of the batteries with a secondary charge current from the power source in accordance with a continuous comparison between a predefined maximum current limit and a total current drawn from the power source;

wherein the second battery charging includes controlling a magnitude of the secondary charge current by outputting to a control input of a controlled current/voltage source an analog difference signal proportional to a difference between a magnitude of the maximum current limit and the total drawn current.

11. The method according to claim 10, wherein the analog difference signal is determined in accordance with a difference between a voltage reference and an analog voltage signal, the voltage reference being proportional to the maximum current limit, the analog voltage signal being proportional to the total drawn current.

12. The method according to claim 11, wherein the voltage reference limits the primary charge current to less than a maximum current limit of the power source.

13. The method according to claim 10, wherein the first battery is disposed within a handheld computing device, and the second battery charging step comprises charging the second battery with a continuously increasing portion of the secondary charge current while the handheld computing device charges the first battery with a continuously decreasing portion of the primary charge current, the total of the decreasing portion and the increasing portion being substantially equal to the maximum current limit.

14. The method according to claim 13, wherein the second battery charging further comprises charging the second battery with a minor constant portion of the secondary charge current prior to the continuously increasing charging step, while the handheld computing device charges the first battery with a first major constant portion of the primary charge current, the total of the first major portion and the minor portion being substantially equal to the maximum current limit.

15. The method according to claim 13, wherein the second battery charging further comprises charging the second battery with a second major constant portion of the secondary charge current, after a current drawn by the second battery during the continuously increasing charging step exceeds a maximum current threshold, the second major constant portion being substantially equal to the maximum current threshold.

16. The method according to claim 15, wherein the second battery charging further comprises charging the second battery with a minor constant portion of the secondary charge current prior to the continuously increasing charging step, while the handheld computing device charges the first battery with a first major constant portion of the primary charge current, the total of the first major portion and the minor portion being substantially equal to the maximum current limit.