Device and method for charging and controlling the charge of a battery

1. An apparatus for charging and for charge monitoring of a rechargeable battery, comprising:

a charging circuit which includes the rechargeable battery and a charging device for charging the rechargeable battery, and a measurement device, wherein the measurement device includes a device for determining the rechargeable-battery current and the state of charge of the rechargeable battery; and

a control device which compares a value that is proportional to the rechargeable-battery current with a set value, and controls the charging device by adjusting the rechargeable-battery current until a difference between the value that is proportional to the rechargeable-battery current and the set value disappears,

wherein the control device contains a regulator unit and a control signal converter connected to it,

wherein the control signal converter contains a digital-to-analog converter, and

wherein the digital-to-analog converter provides an analog control signal to control the charging device.

2. The apparatus as claimed in claim 1 , wherein the rechargeable battery is based on lithium.

3. The apparatus as claimed in claim 1 , wherein the measurement device contains a measured-value detection device and a downstream signal converter.

4. The apparatus as claimed in claim 3 , wherein the signal converter contains a means for conversion of a voltage drop to a digital signal.

5. The apparatus as claimed in claim 4 , wherein the means for conversion of the voltage drop to a digital signal contains a voltage/frequency converter or a sigma-delta converter.

6. The apparatus as claimed in claim 3 , wherein the device for determining the rechargeable-battery current contains an evaluation device whose input side is connected to the signal converter.

7. The apparatus as claimed in claim 6 , wherein the evaluation device contains:

an accumulating counter, having a value that corresponds to the state of charge of the rechargeable battery, and

an instantaneous current counter, having a value that is proportional to the instantaneous value of the rechargeable-battery current.

8. The apparatus as claimed in claim 1 , in which the state of charge of the rechargeable battery is determined by means of the accumulating counter and a timebase.

9. The apparatus as claimed in claim 1 , wherein the value of the instantaneous current counter and a reference value are applied to the input side of a comparator for the control device.

10. The apparatus as claimed in claim 1 , wherein the charging device contains a transistor.

11. The apparatus as claimed in claim 10 , in which the transistor is connected as an external component to an integrated circuit arrangement.

12. The apparatus as claimed in claim 1 , wherein the charging device contains a resistor for setting a bias voltage.

13. The apparatus as claimed in claim 12 , in which the resistor is connected as an external component to an integrated circuit arrangement.

14. The apparatus as claimed in claim 1 , wherein the apparatus is in the form of an integrated circuit arrangement.

15. The apparatus as claimed in claim 1 , wherein the measurement device contains an external component for measured-value detection.

16. The apparatus as claimed in claim 1 , wherein the measurement device detects the magnitude and direction of the rechargeable-battery current.

17. A method for charging and for charge monitoring of a rechargeable battery, comprising the steps of:

detecting a measurement signal for the rechargeable-battery current;

producing a digital measurement signal from the measurement signal;

processing the digital measurement signal in order to form a first current value for determining the state of charge of the rechargeable battery;

processing the digital measurement signal in order to form a second current value;

comparing the second current value with a reference value, and determining a difference result;

producing a control manipulated variable from the difference result by a regulator;

converting the control manipulated variable into an analog control signal by a control signal converter comprising a digital-to-analog converter;

controlling a charging device for the rechargeable battery with the aid of the analog control signal; and

adjusting the rechargeable-battery current until the difference result between the second current value and the reference value disappears.

18. The method as claimed in claim 17 , wherein the digital measurement signal is produced as an upward-counting signal or as a downward-counting signal.

19. The method as claimed in claim 17 , wherein the digital measurement signal is added periodically recurrently using an instantaneous current counter and a timebase to form a value, in that this value is stored at the end of a period, and in that the value is then reset.

20. The method as claimed in claim 19 , wherein the digital measurement signal is added continuously using an accumulating current counter and a timebase to form a current value which corresponds to the state of charge of the rechargeable battery.

21. The method as claimed in claim 20 , wherein an instantaneous current and an accumulated current are derived from the gain of a signal converter, the time duration of the timebase and the value of a measurement resistor.

22. An apparatus for charging and for charge monitoring of a rechargeable battery, comprising:

a charging circuit which includes a rechargeable battery and a charging device for charging the rechargeable battery, and a measurement device, wherein the measurement device includes a device for determining the rechargeable-battery current and the state of charge of the rechargeable battery; and

a control device which compares a value that is proportional to the rechargeable-battery current with a set value, and controls the charging device by adjusting the rechargeable-battery current until a difference between the value that is proportional to the rechargeable-battery current and the set value disappears,

wherein the charging device contains a transistor,

wherein the charging device contains a resistor for setting a bias voltage, and

wherein the resistor is connected between a control terminal of the transistor and a first terminal of the transistor,

the first terminal of the transistor is connected to a charging source, and

the control device provides a control signal which is applied to the control terminal of the transistor.