Method and apparatus for charging rechargeable batteries

• US 20010048288A1
• Filed: 07/11/2001
• Published: 12/06/2001
• Est. Priority Date: 01/11/1999
• Status: Active Grant

• Current Assignee: Qisda Corporation
• Original Assignee: Siemens AG
• Inventors: Hebding, Uwe, Koch, Georg
• Granted Patent: US 6,489,750 B2
• Time in Patent Office: Days
• US Class Current: 320/139
• CPC Class Codes: H02J 7/00 Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries

Abstract

A method and apparatus for charging a rechargeable battery with a current from a controllable current source. In order to adjust the rated current of the controllable current source, at least one operating parameter of the rechargeable battery, such as the rechargeable battery voltage which is produced as a consequence of a charging process, is detected. A pulsed control signal with a duty ratio which corresponds to the desired rated current is produced as a function of the operating parameter. The duty ratio of the pulsed control signal is evaluated, and the rated current of the current source is adjusted as a function of the duty ratio of the pulsed control signal.

Claims

1. A method for charging a rechargeable battery, which comprises:

charging a rechargeable battery with an unpulsed rated current supplied from a variable current source;

detecting at least one operating parameter of the rechargeable battery;

providing a pulsed control signal having a specific duty ratio and producing the duty ratio as a function of the operating parameter; and

adjusting the unpulsed rated current supplied from the current source as a function of the duty ratio of the pulsed control signal.

2. The method according to

claim 1

, which comprises:

detecting a rechargeable battery voltage that is produced as a consequence of charging the rechargeable battery; and

using the rechargeable battery voltage as the operating parameter.

3. The method according to

claim 2

, which comprises:

increasing the duty ratio of the pulsed control signal if the detected rechargeable battery voltage of the rechargeable battery is less than a desired charging voltage; and

reducing the duty ratio if the detected rechargeable battery voltage of the rechargeable battery is greater than the desired charging voltage.

4. The method according to

claim 2

, which comprises digitally averaging the rechargeable battery voltage before evaluating the rechargeable battery voltage.

5. The method according to

claim 1

, which comprises digitally averaging the detected operating parameter of the rechargeable battery before evaluating the detected operating parameter.

6. The method according to

claim 1

, which comprises adjusting the duty ratio of the pulsed control signal as a function of a current characteristic that is specific to the current source.

7. The method according to

claim 6

, which comprises:

before starting the step of charging the rechargeable battery, measuring the input impedance of the current source to determine a type of the current source; and

basing the charging on a current characteristic that corresponds to the determined type of the current source.

8. The method according to

claim 1

, which comprises adjusting the duty ratio of the pulsed control signal as a function of a type of rechargeable battery.

9. The method according to

claim 1

, which comprises:

detecting a temperature of the rechargeable battery; and

using the detected temperature as the operating parameter.

10. The method according to

claim 1

, which comprises performing the step of determining the operating parameter of the rechargeable battery at regular intervals.

11. The method according to

claim 1

, which comprises increasing the unpulsed rated current of the current source as the duty ratio of the pulsed control signal increases.

12. The method according to

claim 11

, which comprises defining the duty ratio as a ratio between a pulse duration and a pause duration of the pulsed control signal.

13. The method according to

claim 11

, which comprises:

varying the duty ratio of the pulsed control signal by;

increasing the duty ratio of the pulsed control signal if the detected rechargeable battery voltage of the rechargeable battery is less than a desired charging voltage, and

reducing the duty ratio if the detected rechargeable battery voltage of the rechargeable battery is greater than the desired charging voltage.

14. The method according to

claim 13

, which comprises:

obtaining a difference between the detected rechargeable battery voltage and the desired charging voltage; and

performing the step of varying the duty ratio by changing the duty ratio in coarser steps as the difference increases.

15. The method according to

claim 1

, which comprises:

detecting a rechargeable battery voltage that is produced as a consequence of charging the rechargeable battery;

using the rechargeable battery voltage as the operating parameter;

varying the duty ratio of the pulsed control signal by;

increasing the duty ratio of the pulsed control signal if the detected rechargeable battery voltage of the rechargeable battery is less than a desired charging voltage, and

reducing the duty ratio if the detected rechargeable battery voltage of the rechargeable battery is greater than the desired charging voltage;

obtaining a difference between the detected rechargeable battery voltage and the desired charging voltage; and

performing the step of varying the duty ratio by changing the duty ratio in coarser steps as the difference increases.

16. The method according to

claim 1

, which comprises upon initiating the charging, setting the duty ratio of the pulsed control signal to a minimum value.

17. The method according to

claim 1

, which comprises uniquely associating each duty ratio value of the pulsed control signal with a specific value of the rated current supplied by the current source.

31. The apparatus according to

claim 15

, wherein said control device includes a microcontroller.

18. The method according to

claim 18

, which comprises adjusting the duty ratio of the pulsed control signal as a function of the detected operating parameter such that the rated current supplied by the current source is varied in accordance with a square law.

19. An apparatus for charging a rechargeable battery, comprising:

a variable current source for providing an unpulsed rated current for recharging a rechargeable battery;

a detection device for detecting at least one operating parameter of the rechargeable battery;

a control device for producing a pulsed control signal having a specific duty ratio formed as a function of the detected at least one operating parameter of the rechargeable battery; and

a current source control device for detecting the duty ratio of the pulsed control signal from said control device and for producing an adjustment signal for said variable current source such that the unpulsed rated current supplied by said current source is adjusted as a function of the duty ratio of the pulsed control signal.

20. The apparatus according to

claim 19

, wherein:

a rechargeable battery voltage of the rechargeable battery is produced as a consequence of recharging the rechargeable battery;

said detection device is constructed to detect the rechargeable battery voltage;

said rechargeable battery voltage is one of the at least one operating parameter of the rechargeable battery.

21. The apparatus according to

claim 20

, comprising an analog/digital converter that is connected between said detection device and said control device.

22. The apparatus according to

claim 19

, comprising an analog/digital converter that is connected between said detection device and said control device.

23. The apparatus according to

claim 19

, wherein:

said variable current source has a specific current characteristic; and

said control device is designed to adjust the duty ratio of the pulsed control signal to match the current characteristic that is specific to said variable current source.

24. The apparatus according to

claim 23

, wherein:

said current source has an input impedance and a type;

said control device includes a current characteristic memory for storing current characteristics for various current source types;

said control device is designed to measure said input impedance of said current source before charging the rechargeable battery; and

said control device is designed to deduce said type of said current source as a function of the measured input impedance so that one of the current characteristics that corresponds to

said deduced type of said current source can be used as a basis for subsequently charging the rechargeable battery.

25. The apparatus according to

claim 24

, comprising:

a control line supplying the pulsed control signal from said control device to said current source control device;

said control device being constructed to measure the input impedance of said current source using said control line.

26. The apparatus according to

claim 19

, wherein:

said detection device includes a temperature detection device for detecting a temperature of the rechargeable battery as one of the at least one operating parameter; and

said control device is constructed to adjust the duty ratio of the pulsed control signal by taking account of the detected temperature of the rechargeable battery.

27. The apparatus according to

claim 19

, wherein:

said rechargeable battery has a type;

said detection device includes a rechargeable battery type identification means for identifying the type of said rechargeable battery; and

said control device is constructed to adjust the duty ratio of the pulsed control signal by taking account of the identified type of the rechargeable battery.

28. The apparatus according to

claim 19

, wherein the pulsed control signal has a plurality of duty ratio values and each one of the plurality of the duty ratios has a uniquely associated corresponding value of the rated current of said current source.

29. The apparatus according to

claim 19

, in combination with an appliance that is operated with the rechargeable battery, wherein said control device is constructed in the appliance.

30. The combination according to

claim 29

, wherein the appliance is a mobile telephone.