Protective circuit for a secondary battery pack and method of operating the same

• US 20060077603A1
• Filed: 09/02/2005
• Published: 04/13/2006
• Est. Priority Date: 09/07/2004
• Status: Active Grant

• Current Assignee: Samsung SDI Company Limited
• Original Assignee: Samsung SDI Company Limited
• Inventors: Kim, Jong Sam
• Granted Patent: US 7,583,060 B2
• Time in Patent Office: Days
• US Class Current: 361/90
• CPC Class Codes: H02H 7/18 for batteries; for accumulators
• CPC Class Codes: H02J 7/0019 using switched or multiplexed charge circuits
• CPC Class Codes: H02J 7/00302 Overcharge protection
• CPC Class Codes: H02J 7/00306 Overdischarge protection
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

A protective circuit for a secondary battery pack advantageously having a simple circuit configuration while maintaining the safety of banks in the circuit. Each protective circuit has banks adapted to be charged or to discharge voltage, each bank being coupled to a controller that senses the charging or discharging voltage of the bank and outputs a predetermined value if overcharging or over-discharging is sensed. A level shifter is adapted to shift the voltage output from the controller to an adjusted voltage approximately equal to the voltage output from one of the other controllers. A switching means controls the stopping of charging or discharging of the banks.

Claims

1. A protective circuit for a secondary battery pack comprising:

a plurality of banks adapted to be charged or to discharge voltage;

a plurality of controllers, each one of the plurality of controllers being adapted to sense a charging or discharging voltage of a respective one of the plurality of banks and output a predetermined voltage if overcharging or over-discharging is sensed;

at least one level shifter adapted to shift a voltage output from one of the plurality of controllers to create an adjusted voltage output approximately equal to an output voltage from one of another of the plurality of controllers; and

a switching means adapted to stop the charging or discharging of the plurality of banks.

2. The protective circuit for a secondary battery pack as claimed in claim 1, wherein each of the plurality of banks is comprised of a plurality of chargeable or dischargeable cells coupled in series and in parallel.

3. The protective circuit for a secondary battery pack as claimed in claim 1, wherein the number of the plurality of banks and the number of the plurality of controllers is each n and the number of the at least one level shifter is n-1.

4. The protective circuit for a secondary battery pack as claimed in claim 1, wherein the switching means comprises:

a first switch adapted to be toggled on/off in response to the output voltage from one or more of the plurality of controllers or from the adjusted voltage from the at least one level shifter, and

a second switch coupled with a large-current line for charging or discharging each of the plurality of banks and adapted to be toggled on/off in response to the first switch.

5. The protective circuit for a secondary battery pack as claimed in claim 4, wherein the first switch has an input end coupled to an OR gate adapted to receive the adjusted voltage output from the at least one level shifter or the voltage output from at least one of the plurality of controllers and when the OR gate receives the adjusted voltage output from the at least one level shifter or the voltage output from at least one of the plurality of controllers, the OR gate outputs a voltage to the first switch and the first switch is toggled on.

6. The protective circuit for a secondary battery pack as claimed in claim 1, wherein the at least one level shifter comprises:

a light-emitting diode adapted to emit a predetermined wavelength of light based on the voltage output from one of the plurality of controllers;

a photo transistor adapted to be turned on by the light from the light-emitting diode; and

a load resistor coupled to an emitter of the photo transistor.

7. A protective circuit for a secondary battery pack comprising:

a first bank adapted to be charged or to discharge voltage and having a plurality of cells coupled in series and in parallel;

a second bank adapted to be charged or discharge voltage and coupled in series to the first bank and having a plurality of cells coupled in series and in parallel;

a first controller adapted to sense the charging or discharging voltage of the first bank and output a voltage output from the first controller if overcharging or over-discharging is sensed;

a second controller adapted to sense the charging or discharging voltage of the second bank and output a voltage output from the second controller if overcharging or over-discharging is sensed;

a level shifter adapted to shift the voltage output of the second controller to approximately the same voltage output of the first controller to create an adjusted voltage output;

a first switch adapted to be toggled on/off in response to the voltage output from the first controller or from the adjusted voltage output from the level shifter; and

a second switch coupled with a large-current line for charging or discharging each of the first bank and the second bank, and adapted to be toggled on/off to stop the charging or discharging of the first bank and the second bank in response to whether the first switch is toggled on/off.

8. The protective circuit for a secondary battery pack as claimed in claim 7, wherein the first bank and the second bank each have four cells coupled in series, wherein each of the four cells coupled in series is coupled in parallel to another cell not one of the four cells coupled in series.

9. The protective circuit for a secondary battery pack as claimed in claim 7, wherein a total charging or discharging voltage of the first bank and the second bank when the first bank and the second bank are coupled in series is approximately two times a charging or discharging voltage of the first bank.

10. The protective circuit for a secondary battery pack as claimed in claim 7, wherein a charging or discharging voltage of the second bank is added to a charging or discharging voltage of the first bank and a total charging or discharging voltage of the first bank and the second bank is output to the first controller.

11. The protective circuit for a secondary battery pack as claimed in claim 7, wherein the output voltage from the first controller is approximately two times the voltage output from the second controller.

12. The protective circuit for a secondary battery pack as claimed in claim 7, wherein the level shifter is a photo coupler.

13. The protective circuit for a secondary battery pack as claimed in claim 7, wherein the level shifter comprises:

a light-emitting diode adapted to emit a predetermined wavelength of light based on the voltage output from the second controller;

a photo transistor adapted to be turned on in response to the light emitted from the light-emitting diode; and

a load resistor coupled to an emitter portion of the photo transistor.

14. The protective circuit for a secondary battery pack as claimed in claim 13, wherein approximately the same voltage output from the first controller is applied to a collector portion of the photo transistor, approximately the same voltage output from the second controller is applied to a first end of the load resistor, and an output end of the level shifter is coupled to the emitter portion of the photo transistor and a second end of the load resistor, and the adjusted voltage output is output to the output end.

15. The protective circuit for a secondary battery pack as claimed in claim 7, wherein the first switch has an input end coupled to an OR gate adapted to receive an adjusted voltage output from the at least one level shifter or a voltage output from at least one of the plurality of controllers and when the OR gate receives an adjusted voltage output from the at least one level shifter or a voltage output from at least one of the plurality of controllers, the OR gate outputs a voltage to the first switch and the first switch is toggled on.

16. The protective circuit for a secondary battery pack as claimed in claim 7, wherein the first switch is a field effect transistor.

17. The protective circuit for a secondary battery pack as claimed in claim 7, wherein the second switch is a field effect transistor toggled on/off in response to the toggle state of the first switch.

18. The protective circuit for a secondary battery pack as claimed in claim 7, wherein the second switch comprises a fuse adapted to cut off in response to the toggle state of the first switch.

19. The protective circuit for a secondary battery pack as claimed in claim 7, wherein the second switch comprises a heating resistor operated by the first switch and a fuse cut off in response to the operation of the heating resistor.

20. A method of operating a protective circuit for a secondary battery pack, the method comprising:

in response to sensing overcharging or over-discharging from one of a plurality of banks, outputting a voltage at one of a plurality of controllers;

in response to at least one level shifter receiving a voltage output from one of the plurality of controllers, shifting at the at least one level shifter the voltage output from one of the plurality of controllers to create an adjusted voltage output, the adjusted voltage output being approximately equal to the voltage output from another one of the plurality of controllers; and

in response to the voltage output from one of the plurality of controllers or the adjusted voltage output from the at least one level shifter, a switching means controlling stopping the charging or discharging of a plurality of banks.

21. The method of operating a protective circuit for a secondary battery pack as claimed in claim 20, wherein the switching means to control stopping the charging or discharging of the plurality of banks comprises:

a first switch adapted to be toggled on/off in response to the voltage output from one or more of the plurality of controllers or from the adjusted voltage from the at least one level shifter; and

a second switch coupled with a large-current line for charging or discharging each of the plurality of banks and adapted to be toggled on/off in response to the first switch being toggled on/off.

22. The method of operating a protective circuit for a secondary battery pack as claimed in claim 20, wherein the voltage output from one of the plurality of controllers or the adjusted voltage from the at least one level shifter is received at an OR gate and the OR gate outputs a voltage to a first switch.