Battery pack and charging method for the same

• US 20090295334A1
• Filed: 05/18/2009
• Published: 12/03/2009
• Est. Priority Date: 06/03/2008
• Status: Active Grant

• Current Assignee: Samsung SDI Company Limited
• Original Assignee: Samsung SDI Company Limited
• Inventors: Segawa, Susumu, Sim, Sesub, Yang, Jongwoon
• Granted Patent: US 8,217,628 B2
• Time in Patent Office: Days
• US Class Current: 320/134
• CPC Class Codes: H02J 7/0031 using battery or load disconnect circuits H02J9/002 takes precedence
• CPC Class Codes: H02J 7/0071 with a programmable schedule
• CPC Class Codes: H02J 7/00711 with introduction of pulses during the charging process
• CPC Class Codes: H02J 7/00714 in response to battery charging or discharging current
• CPC Class Codes: H02J 7/007182 in response to battery voltage
• CPC Class Codes: H02J 7/007194 of the battery
• CPC Class Codes: H02M 1/00 Details of apparatus for conversion
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

A battery pack includes a battery including a positive electrode and a negative electrode, a switching module including a charge switching device and a discharge switching device, the charge switching device and discharge switching device being electrically connected to a high current path of the battery, a battery management unit (BMU) electrically connected to the switching module, the BMU being configured to adjust a limit value for a charging current supplied by the charge switching device and to set a magnitude of the charging current supplied by the charge switching device to be equal to or less than the adjusted.

Claims

1. A battery pack, comprising:

a battery including a positive electrode and a negative electrode;

a switching module including a charge switching device and a discharge switching device, the charge switching device and discharge switching device being electrically connected to a high current path of the battery; and

a battery management unit (BMU) electrically connected to the switching module, the BMU being configured to adjust a limit value for a charging current supplied by the charge switching device and to set a magnitude of the charging current supplied by the charge switching device to be equal to or less than the adjusted limit value.

2. The battery pack as claimed in claim 1, wherein the BMU is configured to automatically adjust and set the limit value of the charging current according to a temperature change of the battery.

3. The battery pack as claimed in claim 2, wherein the BMU is configured to adjust and set the limit value of the charging current, such that a charge ratio of the battery is about 100% at a room temperature and is below 100% at a temperature other then room temperature, room temperature being about 18°

C. to about 30°

C.

4. The battery pack as claimed in claim 1, further comprising:

a temperature sensor electrically connected to the BMU and to the high current path of the battery; and

a voltage smoothing circuit electrically connected to the charge switching device, the BMU, and the high current path of the battery,

wherein the BMU is configured to apply a pulse-width modulation (PWM) signal to the voltage smoothing circuit and to regulate the charging current of the charge switching device by varying a duty ratio of the PWM signal according to a temperature measured by the temperature sensor.

5. The battery pack as claimed in claim 4, wherein the temperature sensor is a thermistor, and the BMU is configured to detect temperature of the battery by detecting a resistance changing rate of the thermistor.

6. The battery pack as claimed in claim 4, wherein the voltage smoothing circuit is configured to convert the PWM signal to a direct current (DC), and the BMU is configured to regulate the DC by regulating the duty ratio of the PWM signal.

7. The battery pack as claimed in claim 6, wherein the charge switching device includes a field-effect transistor (FET) having a source, a drain, and a gate, the source and drain being electrically connected to the high current path of the battery, the gate being electrically connected to the BMU, and the gate and source being configured to receive a DC voltage output from the voltage smoothing circuit.

8. The battery pack as claimed in claim 7, wherein the voltage smoothing circuit includes a resistor electrically connected to the gate of the FET and to the BMU, and a capacitor electrically connected to the gate and to the source of the FET, the source being between the gate and the capacitor.

9. The battery pack as claimed in claim 8, wherein the voltage smoothing circuit further includes a buffer resistor electrically connected in parallel to the capacitor.

10. The battery pack as claimed in claim 1, further comprising a current detection device, the BMU unit being electrically connected to the current detection device to calculate a current flowing in the high current path of the battery.

11. The battery pack as claimed in claim 10, wherein the current detection device includes a sense resistor, the BMU being electrically connected to the sense resistor to receive reference voltages of both ends of the sense resistor to detect the current flowing in the high current path of the battery.

12. The battery pack as claimed in claim 1, wherein the BMU includes:

an analog front end electrically connected to the battery and to the switching module via a voltage smoothing circuit, the analog front end being configured to detect voltage in an open circuit voltage of the battery and to turn on/off the charge switching device and discharge switching device in the switching module; and

a microprocessor unit electrically connected to the analog front end, the microprocessor unit being configured to control a current of the charge switching device in the switching module.

13. The battery pack as claimed in claim 12, wherein the analog front end includes:

a voltage detector electrically connected to the battery, the voltage detector being configured to detect the voltage in the open circuit of the battery and determine the battery state based on the detected voltage, the battery state being one of an over-discharge mode, a full discharge mode, a full charge mode, and an overcharge; and

a power drive circuit, the power drive circuit being configured to turn on/off the charge switching device and the discharge switching device.

14. The battery pack as claimed in claim 13, wherein the power drive circuit is configured to amplify a PWM signal generated in the microprocessor unit and to supply the amplified power to the switching device.

15. The battery pack as claimed in claim 13, wherein the analog front end is an application specific integrated circuit (ASIC).

16. The battery pack as claimed in claim 1, wherein a maximum rated power of the charge switching device is set according to a charging voltage of the charger, an open circuit voltage of the battery, and a limit value of a charging current, the maximum rated power being about 80% to about 120% of a calculated power, the calculated power being a product of the charging current in the high current of the battery and a voltage difference between the open circuit voltage and the charging voltage.

17. The battery pack as claimed in claim 1, wherein the BMU is configured to be pre-charged according to a charging capacity of the battery after maintaining the initial current of the charge switching device low for a predetermined time period during the initial charging operation of the battery, the battery management unit pre-charges the battery by increasing the charging current according to a charging capacity of the battery after a lapse of a predetermined time period.

18. The battery pack as claimed in claim 1, wherein the charge switching device and discharge switching device include respective charge FET and discharge FET electrically connected to the high current path of the battery, and a parasitic diode electrically connected in parallel to the respective charging FET, the parasitic diode being connected in a reverse direction with respect to a charge current.

19. A charging method for a battery pack having a battery with positive and negative electrodes, the method comprising:

electrically connecting a battery management unit (BMU) to a switching module, the switching module including a charge switching device and a discharge switching device, the charge switching device and discharge switching device being electrically connected to a high current path of the battery;

setting a limit value for a charging current supplied by the charge switching device to the battery with respect to temperature of the battery via the BMU; and

automatically regulating a magnitude of a charging current supplied by the charge switching device to the battery, such that the magnitude of the charging current is equal to or less than the adjusted limit value set by the BMU.

20. A charging method for a battery pack, comprising:

detecting temperature and current of a battery;

comparing the detected current to a value set using a limit value for the charging current for the detected temperature, limit values varying with temperature; and

regulating a charging current of the battery, such that the charging current of the battery does not exceed the limit value of the charging current.

21. The charging method as claimed in claim 20, wherein regulating the charging current of the battery includes:

determining whether the detected current of the battery is above a hysteresis region, the hysteresis having positive and negative deviations with respect to current values for a given temperature; and

reducing the charging current below the hysteresis region when the detected current of the battery is above the hysteresis region for the detected temperature.

22. The charging method as claimed in claim 20, wherein regulating charging current of the battery includes:

determining, after calculating a consumption power consumed by the charge switching device, whether the consumption power of the charge switching device exceeds a limit power setting value; and

reducing the charging current below a specific threshold value when the consumption power of the charge switching device exceeds the limit power setting value.

23. The charging method as claimed in claim 22, wherein the consumption power of the charge switching device is set according to a charging voltage of the charger, an open circuit voltage of the battery, and the limit value of the charging current, and is obtained by multiplying the charging current by a difference between the charging voltage and the open circuit voltage.