Series-connected rechargeable cells, series-connected rechargeable cell device, voltage-balance correcting circuit for series-connected cells

• US 8,692,515 B2
• Filed: 06/21/2007
• Issued: 04/08/2014
• Est. Priority Date: 06/22/2006
• Status: Active Grant

• Current Assignee: FDK Corporation (Fujitsu Limited)
• Original Assignee: FDK Corporation (Fujitsu Limited)
• Inventors: Nakao, Fumiaki, Katsube, Yasuyuki
• Primary Examiner(s): Dunn, Drew A
• Assistant Examiner(s): GRANT, ROBERT J
• Application Number:
  US12/305,518
• Publication Number:
  US 20090278496A1
• Time in Patent Office: 2,483 Days
• Field of Search: 320157-159, 320162-164, 324425-434
• US Class Current: 320/116
• CPC Class Codes: H02J 7/0016 using shunting, discharge or bypass circuits
• CPC Class Codes: H02J 7/0018 using separate charge circuits
• CPC Class Codes: Y02T 10/70 Energy storage systems for electromobility, e.g. batteries

Abstract

[Object] There is provided series-connected rechargeable cells in which a large number of cells are series-connected and that makes it possible to improve performance on operations such as assembly or exchange and to perform speedy and smooth voltage-balance correcting for all cells.

[Means for Solution] Series-connected rechargeable cells includes: a large number of rechargeable cells that are series-connected, and that are divided into a plurality of series-connected cell groups placed continuously in order of connecting; and a voltage-balance correcting circuit that balances the voltages of the cells, and that is provided with an inter-cell voltage-balance correcting circuit that performs voltage-balance correcting between adjacent cells in each of the cell groups and an inter-group voltage-balance correcting circuit that performs balance correcting of series-connection voltages of the cell groups by AC-coupling formed with a transformer coil and a switching circuit.

Claims

1. A series-connected rechargeable cell device, comprising:

a plurality of rechargeable cells that are series-connected, and that are divided into a plurality of series-connected cell groups placed continuously in order of connecting; and

a voltage-balance correcting circuit that balances the voltages of the cells, and that is provided with;

an inter-cell voltage-balance correcting circuit that performs voltage-balance correcting between adjacent cells in each of the cell groups and confined within the cell group, wherein one end of an inductor is connected between a common point between the two cells to be balanced, and the other end of the inductor is connected between two switching circuits, and

an inter-group voltage-balance correcting circuit that performs balance correcting of series-connection voltages of the cell groups by AC-coupling formed with a transformer coil and a switching circuit,

the inter-group voltage-balance correcting circuit including;

a plurality of transformer coils each having ends respectively connected to series-connection ends of each of the series-connected cell groups, that are magnetically coupled at the transformation ratio of 1;

1, and

a plurality of switching circuits, disposed between the transformer coils and the cell groups, respectively, that apply a current to each of the transformer coils simultaneously by being turned ON/OFF in phase in accordance with a periodic pulse signal.

2. The series-connected rechargeable cell device according to claim 1, characterized in that

the inter-cell voltage-balance correcting circuit performs voltage-balance correcting between a first cell and a second cell that are adjacent, by charging and discharging by an inductor current between the cells.

3. The series-connected rechargeable cell device according to claim 2, characterized in that the inter-cell voltage-balance correcting circuit is configured using an inductor that is connected alternately to the first cell and the second cell and that performs charge and discharge by the inductor current.

4. The series-connected rechargeable cell device according to claim 2, characterized in that the inter-cell voltage-balance correcting circuit is configured using

a first inductor that discharges itself through a charge path of the second cell when the first inductor is charged by the inductor current from the first cell,

a second inductor that discharges itself through a charge path of the first cell when the second inductor is charged by the inductor current from the second cell, and

a switching circuit that switches charge and discharge of the first and second inductors.

5. The series-connected rechargeable cell device according to claim 2, characterized in that

a plurality of the inductors that the inter-cell voltage-balance correcting circuit is composed of are disposed in the cell groups, and

the inductors are magnetically coupled with each other.

6. A series-connected rechargeable cell device comprising:

a plurality of rechargeable cells that are series-connected, and that are divided into a plurality of series-connected cell groups placed continuously in order of connecting; and

a voltage-balance correcting circuit that balances the voltages of the cells, and that is provided with;

an inter-cell voltage-balance correcting circuit that performs voltage-balance correcting between adjacent cells in each of the cell groups and confined within the cell group, wherein one end of an inductor is connected between a common point between the two cells to be balanced, and the other end of the inductor is connected between two switching circuits, and

an inter-group voltage-balance correcting circuit that performs balance correcting of series-connection voltages of the cell groups by AC-coupling formed with a transformer coil and a switching circuit,

the inter-group voltage-balance correcting circuit including;

a primary coil that connects to an end of all series-connected cell groups;

a primary coil-side switching circuit that is series-connected to the primary coil;

a plurality of secondary coils that respectively connect to an end of each of the series-connected cell groups and that are magnetically coupled to each other with the transformation ratio between each other being 1;

1; and

a plurality of secondary coil-side circuits, disposed between the secondary coils and the cell groups, respectively, that apply a current to each of the secondary coils simultaneously in accordance with a periodic pulse signal.

7. A series-connected rechargeable cell device, comprising:

a plurality of rechargeable cells that are series-connected;

a voltage-balance correcting circuit in which;

a semiconductor switching device includes a MOS-FET and is configured to balance the voltage between the cells, the MOS-FET being turned on or off by a control signal having a first level for turning on and a second level for turning off; and

a level conversion circuit configured to convert the second level of the control signal to a third level to control the MOS-FET to be in an intermediate state between an ON state and an OFF state, the MOS-FET acting as a resister in the intermediate state to allow current to flow therethrough, wherein

the level conversion circuit is configured not to operate in a normal condition, but to operate in an overcharge condition to convert the second level of the control signal to the third level to cause the MOS-FET to be a bypass circuit so that a charging current flows through the MOS-FET to bypasses the researchable cells.

8. The series-connected rechargeable cell device according to claim 7, wherein the voltage-balance correcting circuit has a configuration in which

both ends of two switching devices that are series-connected and are alternately turned ON are connected in parallel to both ends of two rechargeable cells that are adjacent in order in the series-connection, and

in which an inductor bridges a middle connecting point of the two rechargeable cells and a middle connecting point of the two switching devices and is connected therebetween.

9. The series-connected rechargeable cell device according to claim 7, wherein

the level conversion circuit comprises a diode, a resistor, and a bias voltage source.

10. A voltage-balance correcting circuit for series-connected cells, comprising:

a plurality of rechargeable cells that are series-connected;

a plurality of transformer coils that are wound around a same magnetic core having the same number of turns and that have the transformation ratio of 1;

1;

switches that are turned ON/OFF in conjunction with each other and through which the rechargeable cells are connected to the transformer coils on a one-to-one basis so that the voltage of each of the cells is balanced; and

a commutation circuit that during a period when the switches change from ON to OFF, a self-induced current generated in the coil that is supplied with a primary current from the rechargeable cell discharges through a path for charging the cell other than the cell that is not connected to the coil,

the commutation circuit including a first discharge circuit and a second discharge circuit that are connected between a first transformer coil and a second transformer coil,

the first discharge circuit being configured in such a manner that a self-induced current that is generated when the first transformer coil is supplied with the primary current charges the rechargeable cell that corresponds to the second transformer coil through a backflow-preventing diode, and

the second discharge circuit being configured in such a manner that a self-induced current that is generated when the second transformer coil is supplied with the primary current charges the rechargeable cell that corresponds to the first transformer coil through a backflow-preventing diode.

11. The voltage-balance correcting circuit for series-connected cells according to claim 10, wherein the first discharge circuit and the second discharge circuit are disposed between the transformer coils that are connected through the switches respectively to two adjacent series-connected rechargeable cells.

12. The voltage-balance correcting circuit for series-connected cells according to claim 10, wherein

the commutation circuit is disposed for each pair of two sets of the transformer coil and the rechargeable cell, and

either one of the first discharge circuit and the second discharge circuit is disposed for a set of a transformer coil and a rechargeable cell that are not mated.

13. The voltage-balance correcting circuit for series-connected cells according to claim 12, wherein the rechargeable cell that is not mated has a larger charge and discharge capacity than another cell.

14. The voltage-balance correcting circuit for series-connected cells according to claim 10, wherein a magnetic core around which the transformer coil is wound is provided with a magnetic route gap.

15. The voltage-balance correcting circuit for series-connected cells according to claim 10, wherein the transformer coil is formed by a flat loop body in which a flat cable belt is used and that is formed by bending the flat cable belt, the flat cable belt being formed by lining in parallel coated wires the number of which is the number of the coils.

16. The voltage-balance correcting circuit for series-connected cells according to claim 10, wherein the transformer coil is formed by wiring a conductor pattern with a through hole, the conductor pattern being formed on a front surface and a back surface of a printed wiring board.

17. The voltage-balance correcting circuit for series-connected cells according to claim 10, wherein at least one of a first discharge loop and a second discharge loop is disposed in which a self-induced current is released while charging a plurality of the series-connected cells connected to others, the self-induced current being generated in either one of the transformer coil that is provided on a high-level end of series-connected rechargeable cells and the transformer coil that is provided on a low-level end.

18. The voltage-balance correcting circuit for series-connected cells according to claim 10, wherein the backflow-preventing diode is configured using a rectifier diode.