SERIES-CONNECTED RECHARGEABLE CELLS, SERIES-CONNECTED RECHARGEABLE CELL DEVICE, VOLTAGE-BALANCE CORRECTING CIRCUIT FOR SERIES-CONNECTED CELLS

• US 20090278496A1
• Filed: 06/21/2007
• Published: 11/12/2009
• 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
• Granted Patent: US 8,692,515 B2
• Time in Patent Office: Days
• US Class Current: 320/118
• 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. Series-connected rechargeable cells, comprising:

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.

2. Series-connected rechargeable cells 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. Series-connected rechargeable cells 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. Series-connected rechargeable cells 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. Series-connected rechargeable cells 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. Series-connected rechargeable cells according to claim 1, characterized in that

the inter-group voltage-balance correcting circuit is configured using a plurality of transformer coils that are magnetically coupled at the transformation ratio of 1:

1.

7. Series-connected rechargeable cells according to claim 1, characterized in that

the inter-group voltage-balance correcting circuit is configured using a transformer having

a primary coil that connects to an end of all series-connected cell groups through the switching circuit, and

secondary coils that respectively connect to an end of each of the series-connected cell groups through the switching circuit.

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

a plurality of rechargeable cells that are series-connected; and

a voltage-balance correcting circuit

in which a semiconductor switching device is used in order to balance the voltage between the cells, and

that the switching device is used to form a current by-pass circuit that is for protecting the rechargeable cells in overcharge condition.

9. A series-connected rechargeable cell device according to claim 8, characterized in that

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.

10. A series-connected rechargeable cell device according to claim 8, characterized in that

the current by-pass circuit is formed by causing the switching device that is not ON to act as a resistance element.

11. A series-connected rechargeable cell device according to claim 8, characterized in that

a MOS-FET is used as the switching device of the voltage-balance correcting circuit, and

a level conversion circuit is disposed, the level conversion circuit converting a OFF-setting level of a two-level control signal that controls ON/OFF of the MOS-FET, into a level at which the signal sets the FET at a predetermined resistivity.

12. 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.

13. A voltage-balance correcting circuit for series-connected cells according to claim 12, characterized in that

the commutation circuit consists of a first discharge circuit and a second discharge circuit that are connected between the two transformer coils,

the first discharge circuit is configured so that a self-induced current that is generated when one of the coils is supplied with the primary current charges the rechargeable cell that is on a side close to the other of the coils through a backflow-preventing diode, and

the second discharge circuit is configured so that a self-induced current that is generated when the other coils is supplied with the primary current charges the rechargeable cell that is on a side close to the one coil through a backflow-preventing diode.

14. A voltage-balance correcting circuit for series-connected cells according to claim 13, characterized in that

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.

15. A voltage-balance correcting circuit for series-connected cells according to claim 13, characterized in that

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.

16. A voltage-balance correcting circuit for series-connected cells according to claim 15, characterized in that

the rechargeable cell that is not mated has a larger charge and discharge capacity than another cell.

17. A voltage-balance correcting circuit for series-connected cells according to claim 12, characterized in that

a magnetic core around which the transformer coil is wound is provided with a magnetic route gap.

18. A voltage-balance correcting circuit for series-connected cells according to claim 12, characterized in that

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.

19. A voltage-balance correcting circuit for series-connected cells according to claim 12, characterized in that

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.

20. A voltage-balance correcting circuit for series-connected cells according to claim 12, characterized in that

at least either 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.

21. A voltage-balance correcting circuit for series-connected cells according to claim 12, characterized in that

the backflow-preventing diode is configured using a rectifier diode that is a non-linear element having two terminals.