Charge balancing systems and methods

• US 6,841,971 B1
• Filed: 05/24/2003
• Issued: 01/11/2005
• Est. Priority Date: 05/29/2002
• Status: Active Grant

• Current Assignee: Alpha Technologies Services, Inc. (EnerSys)
• Original Assignee: Alpha Technologies Incorporated (EnerSys)
• Inventors: Jennings, Seth W., Spée, René, Le, Thanh
• Primary Examiner(s): Tso, Edward H.
• Application Number:
  US10/444,208
• Time in Patent Office: 598 Days
• Field of Search: 320/116, 320/119, 320/120, 320/127, 320/137
• US Class Current: 320/119
• CPC Class Codes: H01M 10/44 Methods for charging or discharging circuits for charging H02J7/00
• CPC Class Codes: H02J 7/0016 using shunting, discharge or bypass circuits
• CPC Class Codes: Y02E 60/10 Energy storage using batteries
• CPC Class Codes: Y02T 10/70 Energy storage systems for electromobility, e.g. batteries

Abstract

A system for equalizing the voltages across first and second batteries coupled in series at a common terminal comprising a capacitive storage element, first and second inductive storage elements, first and second switch circuits, and a control unit. The capacitive storage element is coupled to first and second nodes. The first inductive storage element is coupled between the first node and the first battery. The second inductive storage element is coupled between the second node and the second battery. The first switch circuit is coupled between the first node and the common terminal. The second switch circuit is coupled between the second node and the common terminal. The control circuit operates the first and second switch circuits to control current flow to the first and second batteries.

Claims

1. A system for equalizing the voltages across first and second main storage elements coupled in series at a common terminal, the system comprising:

a capacitive storage element coupled to first and second nodes;

a first inductive storage element coupled between the first node and the first main storage element;

a second inductive storage element coupled between the second node and the second main storage element;

a first switch circuit coupled between the first node and the common terminal;

a second switch circuit coupled between the second node and the common terminal; and

a control circuit for operating the first and second switch circuits to control current flow to the first and second main storage elements.

2. A system as recited in claim 1, in which the first and second switch circuits each comprise a switch element and a diode connected in anti-parallel with the switch element.

3. A system as recited in claim 1, in which the control circuit generates first and second control signals for operating the first and second switch circuits, where the second control signal is the inverse of the first signal.

4. A system as recited in claim 1, in which the first and second control signals have a duty cycle of approximately fifty-percent.

5. A system as recited in claim 1, in which the control circuit operates the first and second switch circuits such that the first switch circuit allows current flow when the second switch circuit prevents current flow and the second switch circuit allows current flow when the first switch circuit prevents current flow.

6. A system as recited in claim 1 in which the control circuit operates the first and second switch circuits such that at least one of the first and second switch circuits is open at all times.

7. A system as recited in claim 1, in which the control circuit operates the first and second switches such that current flowing into any of the first and second main storage elements is substantially continuous.

8. A system as recited in claim 1, in which the control circuit comprises:

a clock circuit for generating a clock signal; and

an isolation circuit for isolating the clock circuit from switch circuits.

9. A system as recited in claim 3, in which the first and second control signals are generated based on predetermined system parameters.

10. A system as recited in claim 3, in which the first and second control signals are generated based on a clock pulse.

11. A system as recited in claim 9, in which the first and second control signals are further generated based on a clock pulse.

12. A system as recited in claim 9, in which the first and second control signals are generated based on a comparison of the predetermined system parameters with a reference.

13. A system for equalizing the voltages across a plurality of main storage elements coupled in series at at least one common terminal, the system comprising:

a capacitive storage element associated with each pair of adjacent main storage elements coupled at one of the common terminals, where each capacitive storage element is coupled to first and second nodes;

first and second inductive storage elements associated with each capacitive storage element, where

the first inductive storage elements are coupled between the first nodes and a first main storage element of each pair of adjacent main storage elements, and

the second inductive storage elements are coupled between the second nodes and a second main storage element of each pair of adjacent main storage elements;

first and second switch circuits associated with each capacitive storage element, where

the first switch circuits are coupled between the first nodes and the common terminal associated with each pair of adjacent main storage elements, and

the second switch circuits are coupled between the second nodes and the common terminal associated with each pair of adjacent main storage elements; and

a control circuit for operating the first and second switch circuits to control current flow to the main storage elements.

14. A system as recited in claim 13, in which the first and second switch circuits each comprise a switch element and a diode connected in anti-parallel with the switch element.

15. A system as recited in claim 13, in which the control circuit generates first and second control signals for operating the first and second switch circuits, respectively, where the second control signal is the inverse of the first signal.

16. A system as recited in claim 13, in which the first and second control signals have a duty cycle of approximately fifty-percent.

17. A system as recited in claim 13, in which the control circuit operates the first and second switch circuits such that the first switch circuits allow current flow when the second switch circuits prevent current flow and the second switch circuits allow current flow when the first switch circuits prevent current flow.

18. A system as recited in claim 13, in which the control circuit operates the first and second switch circuits such that at least one of the first and second switch circuits is open at all times.

19. A system as recited in claim 13 in which the control circuit operates the first and second switches such that current flowing into any of the first and second main storage elements is substantially continuous.

20. A system as recited in claim 13, in which the control circuit comprises:

a clock circuit for generating a clock signal; and

a plurality of isolation circuits for isolating the clock circuit from switch circuits.

21. A system as recited in claim 15, in which the first and second control signals are generated based on predetermined system parameters.

22. A system as recited in claim 15, in which the first and second control signals are generated based on a clock pulse.

23. A system as recited in claim 21, in which the first and second control signals are further generated based on a clock pulse.

24. A system as recited in claim 21, in which the first and second control signals are generated based on a comparison of the predetermined system parameters with a reference.

25. A method of equalizing the voltages across a plurality of main storage elements coupled in series comprising the steps of:

identifying at least one pair of adjacent main storage elements comprising first and second main storage elements connected at a common terminal;

providing a capacitive storage element for each pair of adjacent main storage elements;

coupling the capacitive storage element to first and second nodes;

providing first and second inductive storage elements for each capacitive storage element;

coupling the first inductive storage elements between the first nodes and the first main storage elements;

coupling the second inductive storage elements between the second nodes and the second main storage elements;

providing first and second switch circuits for each capacitive storage element;

coupling the first switch circuits between the first nodes and the common terminals;

coupling the second switch circuits between the second nodes and the common terminals; and

operating the first and second switch circuits to control current flow to the main storage elements.

26. A method as recited in claim 25, in which the step of operating the first and second switches comprises the steps of opening and closing the first and second switches such that current flowing into any of the first and second main storage elements is substantially continuous.

27. A method as recited in claim 25, further comprising the steps of:

forming a balancing module comprising one capacitive storage unit, one first inductive storage unit, second inductive storage unit, one first switch circuit, and one second switch circuit;

attaching one balancing module to each pair of adjacent main storage elements.

28. A system for charging a plurality of main storage elements coupled in series at at least one common terminal, the system comprising:

a charging system connected across the series connected main storage elements;

a capacitive storage element associated with each pair of adjacent main storage elements coupled at one of the common terminals, where each capacitive storage element is coupled to first and second nodes;

first and second inductive storage elements associated with each capacitive storage element, where

the first inductive storage elements are coupled between the first nodes and a first main storage element of each pair of adjacent main storage elements, and

the second inductive storage elements are coupled between the second nodes and a second main storage element of each pair of adjacent main storage elements;

first and second switch circuits associated with each capacitive storage element, where

the first switch circuits are coupled between the first nodes and the common terminal associated with each pair of adjacent main storage elements, and

the second switch circuits are coupled between the second nodes and the common terminal associated with each pair of adjacent main storage elements; and

a control circuit for operating the first and second switch circuits to control current flow to the main storage elements.