SYSTEM AND METHOD FOR COMPENSATING FOR IMPEDANCE LOSS ASSOCIATED WITH AN EXTERNAL CHARGING UNIT

• US 20110260678A1
• Filed: 04/23/2010
• Published: 10/27/2011
• Est. Priority Date: 04/23/2010
• Status: Active Grant

• Current Assignee: Psion Inc (Zebra Technologies Corporation)
• Original Assignee: Psion Teklogix (Motorola Solutions, Inc.)
• Inventors: FORSYTHE, Lawrence
• Granted Patent: US 8,508,183 B2
• Time in Patent Office: Days
• US Class Current: 320/107
• CPC Class Codes: H02J 7/00036 Charger exchanging data with battery
• CPC Class Codes: H02J 7/00041 in response to measured battery parameters, e.g. voltage, current or temperature profile
• CPC Class Codes: H02J 7/00047 with provisions for charging different types of batteries
• CPC Class Codes: H02J 7/0071 with a programmable schedule

Abstract

There is disclosed a charging unit for charging a rechargeable battery on an external mobile device, the charging unit configured to be electrically coupled to the mobile device for electrical communication thereof, the charging unit comprising: a charging circuit comprising a charger, the charger configured to: operate in a first mode to provide a constant pre-defined charge current to the external battery based on an output voltage of the charger; operate in a second mode to provide a constant pre-defined charge voltage to the external battery; switch from the first mode to the second mode when the output voltage of the charger reaches a predefined threshold voltage; and an offset compensator configured for applying an offset voltage to the charger to maintain the charger in the first mode to compensate for impedance loss between the charger and the external battery thereby allowing the external battery voltage to reach the threshold voltage.

Claims

1. A charging unit for charging a rechargeable battery on an external mobile device, the charging unit configured to be electrically coupled to the mobile device for electrical communication thereof, the charging unit comprising:

a charging circuit comprising a charger, the charger configured to;

operate in a first mode to provide a constant pre-defined charge current to the external battery based on an output voltage of the charger;

operate in a second mode to provide a constant pre-defined charge voltage to the external battery;

switch from the first mode to the second mode when the output voltage of the charger reaches a predefined threshold voltage; and

an offset compensator configured for applying an offset voltage to the charger to maintain the charger in the first mode to compensate for impedance loss between the charger and the external battery thereby allowing the external battery voltage to reach the threshold voltage.

2. The charging unit of claim 1, wherein the charging circuit further comprises:

a charging processor configured for;

receiving pre-defined battery parameters associated with the rechargeable battery from the mobile device;

determining an occurrence of a current decrease for the battery being prior to a measured battery voltage being at least at the pre-defined threshold voltage based on the pre-defined battery parameters; and

providing a trigger to the offset compensator in response to the occurrence;

wherein the offset compensator is configured for applying the offset voltage in response to the trigger to adjust the output voltage of the charger such as to maintain the charger in the first mode.

3. The charging unit of claim 1, wherein the offset compensator is configured to apply the offset voltage to the charger to increase the pre-defined threshold voltage to compensate for the impedance loss.

4. The charging unit of claim 2, wherein the offset voltage is related to a difference between the measured battery voltage and the pre-defined threshold voltage.

5. The charging unit of claim 2, wherein the offset compensator is configured to continually apply the offset voltage to maintain the charger in the first mode until the measured battery voltage provided by the battery parameters is at least at the pre-defined threshold voltage.

6. The charging unit of claim 2, wherein the charging processor is configured to poll a power processor of the mobile device across a digital communication path for receiving battery parameters in response to the polling.

7. The charging unit of claim 1 further comprising an electrical power source for providing an electrical power charge to the charging circuit for propagation to the rechargeable battery.

8. The charging unit of claim 7 further comprising a connector configured for electrically coupling the charging circuit and the electrical power source to electrical contacts of the rechargeable battery.

9. The charging unit of claim 2 wherein the offset voltage is a difference value between the measured battery voltage and the output voltage of the charger.

10. The charging unit of claim 3 wherein the offset voltage is further related to an output charge current of the charging circuit.

11. A method for charging an external battery on a mobile device by a charging unit, the charging unit configured to be electrically coupled to the mobile device for electrical communication thereof, the method comprising:

operating in a first mode to provide a constant pre-defined charge current to the external battery based on an output voltage of the charger;

operating in a second mode to provide a constant pre-defined charge voltage to the external battery;

switching from the first mode to the second mode when the output voltage of the charger reaches a predefined threshold voltage; and

applying an offset voltage to the charger to maintain the charger in the first mode to compensate for impedance loss between the charger and the external battery thereby allowing the external battery voltage to reach the threshold voltage.

12. The method of claim 11 further comprising:

receiving pre-defined battery parameters associated with the rechargeable battery from the mobile device;

determining an occurrence of a current decrease for the battery being prior to a measured battery voltage being at least at the pre-defined threshold voltage based on the pre-defined battery parameters; and

providing a trigger in response to the occurrence;

applying the offset voltage in response to the trigger to adjust the output voltage of the charger such as to maintain the charger in the first mode.

13. The method of claim 11 further comprising applying the offset voltage to the charger to increase the pre-defined threshold voltage to compensate for the impedance loss.

14. The method of claim 12, wherein the offset voltage is related to a difference between the measured battery voltage and the pre-defined threshold voltage.

15. The method of claim 12, further comprising continually applying the offset voltage to maintain the charger in the first mode until the measured battery voltage provided by the battery parameters is at least at the pre-defined threshold voltage.

16. The method of claim 12, further comprising polling a power processor of the mobile device across a digital communication path for receiving battery parameters in response to the polling.

17. The method of claim 12 wherein the offset voltage is a difference value between the measured battery voltage and the output voltage of the charger.

18. The method of claim 15 wherein the offset voltage is further related to an output charge current of the charging circuit.