Voltage balancer device for battery pack

Abstract

A voltage balancer device has a plurality of discharge paths. Each pair of the discharge paths correspond to each secondary battery unit. Each of a pair of the discharge paths has a resistance of a different value. Discharging the voltage of each secondary battery unit is at first performed through the discharge path of a smaller resistance value. The voltage balancer device switches the currently used discharge path to another discharge path having a large resistance value at the time the voltage of the secondary battery unit nearly equal a desired voltage.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

A preferred, non-limiting embodiment of the present invention will be described by way of example with reference to the accompanying drawings, in which:

FIG. 1 is a view showing an entire configuration of a voltage balancer device for a battery pack according to a first embodiment of the present invention;

FIG. 2 is a timing chart showing a discharging process of discharging a voltage of a secondary battery unit under the control of the voltage balancer device according to the first embodiment shown in FIG. 1;

FIGS. 3A and 3B are views showing a relationship between a discharge current and a voltage in different voltage adjustment accuracy performed by the voltage balancer device of the first embodiment shown in FIG. 1;

FIGS. 4A to 4D are views showing timing charts of the discharging processes under the control of the voltage balancer device of the first embodiment shown in FIG. 1;

FIGS. 5A to 5D are timing charts showing the discharging process of a voltage balancer device according to a second embodiment of the present invention;

FIG. 6 is a view showing an entire configuration of a voltage balancer device for a battery pack according to a third embodiment of the present invention;

FIG. 7 is a view showing a relationship between a discharge current and a voltage in voltage adjustment accuracy under the control of the voltage balancer device of the third embodiment;

FIG. 8 is a view showing an entire configuration of a voltage balancer device for a battery pack according to a fourth embodiment of the present invention;

FIGS. 9A to 9C are views showing timing charts of the discharging process of the voltage balancer device of the fourth embodiment shown in FIG. 8;

FIG. 10 is a view showing an entire configuration of a voltage balancer device for a battery pack according to a fifth embodiment of the present invention;

FIG. 11 is a view showing a relationship between a discharge current and a voltage in a voltage adjustment accuracy under the control of the voltage balancer device of the fifth embodiment; and

FIG. 12 is a view showing an entire configuration of a voltage balancer device for a battery pack according to a sixth embodiment of the present invention.

Claims

1. A voltage balancer device, for a battery pack composed of a plurality of secondary battery units connected in series, configured to discharge a voltage of the secondary battery unit to a desired voltage for voltage adjustment between the secondary battery units, comprising: a discharge path connected in parallel to and placed per secondary battery unit; andcontrol means configured to limit a current flowing through the discharge path so that an actual current flowing through the discharge path at the desired voltage becomes lower than a current at the desired voltage determined on a straight line between an origin regarding a voltage of both ends of the discharge path and a current flowing through the discharge path and an actual value of the current at a beginning of the discharging of the secondary battery unit.

2. The voltage balancer device according to claim 1, wherein the control means has variable resistance means capable of increasing a resistance value of the discharge path through which the discharge current flows according to decreasing of the voltage of each secondary battery unit.

3. The voltage balancer device according to claim 2, wherein each discharge path comprises a resistance and a switching element capable of switching an electrical on-off connection of the discharge path, and the variable resistance means selects the discharge path to be used for the discharging according to the state of the switching element under the control of the control means.

4. The voltage balancer device according to claim 1, wherein the discharge path comprises a switching element, and the control means comprises an operational amplifier, and one input terminal of the operational amplifier is connected to a connection node between the resistance and the switching element, and a voltage of more than 0V is applied to the other input terminal of the operational amplifier.

5. The voltage balancer device according to claim 4, further comprises switch means configured to switch the electrical connection between the output terminal of the operational amplifier and an activation control terminal of the switching element, and the control means controls the switching means in order to electrically connects the output terminal of the operational amplifier to the activation control terminal of the switching element in order to adjust the voltage of the secondary battery unit.

6. The voltage balancer device according to claim 4, wherein the control means applies a voltage equal to an ordinary-using voltage of the battery pack to the other input terminal of the operational amplifier

7. The voltage balancer device according to claim 1, wherein each discharge path connects in parallel to corresponding secondary battery unit, and each discharge path comprises; a switching element configured to switch electrical connection/non-connection of each discharge path; anda constant current discharging means,wherein the control means activates the switching element in order to select the discharge path connecting the activated switching element for discharging.

8. A voltage balancer device, for a battery pack composed of a plurality of secondary battery units connected in series, configured to discharge to a desired voltage a voltage of each secondary battery unit or a voltage of a group composed of several secondary battery units in order to adjust the voltage of each secondary battery unit, comprising discharge paths, each discharge path being connected in parallel to and placed at each secondary battery unit, wherein each discharge path comprises a switching element capable of switching an electrical on-off connection of the discharge path.

9. A voltage balancer device, for a battery pack composed of a plurality of secondary battery units connected in series, configured to discharge to a desired voltage a voltage of each secondary battery unit or a voltage of a group composed of several secondary battery units in order to adjust the voltage of each secondary battery unit, comprising: a discharge path equipped with a switching element capable of switching an electrical on-off connection of the discharge path, and each discharge path being connected in parallel to and placed per secondary battery unit; andan operational amplifier whose output terminal being connected to an activation control terminal of the switching element,wherein one input terminal of the operational amplifier is connected to a connection node between the resistance and the switching element, and a voltage of more than 0V is applied to the other input terminal of the operational amplifier.

10. The voltage balancer device for a battery pack according to claim 8, wherein the discharge path further comprises a constant current discharge means connected to the switching element in series.

11. The voltage balancer device for a battery pack according to claim 8, wherein the discharge path further comprises a resistance connected to the switching element in series.

12. A voltage balancer device, for a battery pack composed of a plurality of secondary battery units connected in series, configured to discharge to a desired voltage a voltage of each secondary battery unit or a voltage of a group composed of some secondary battery units in order to adjust the voltage of each secondary battery unit, comprising: discharge paths, each discharge path being connected in parallel to and placed at the corresponding secondary battery unit; andcontrol means configured to limit an actual current flowing through the discharge path when the voltage of the corresponding secondary battery unit becomes equal to a desired voltage by changing a change rate of the current flowing through the discharge path corresponding to the change of the voltage of the secondary battery unit.

13. The voltage balancer device for a battery pack according to claim 12, wherein the control means comprises variable resistance means capable of increasing a resistance value according to decreasing the voltage of the secondary battery unit.

14. The voltage balancer device for a battery pack according to claim 13, wherein the discharge path is composed of a plurality of the discharge paths connected in parallel to the secondary battery units, each of the plural discharge paths has a resistance and a switching element capable of switching an electrical on-off connection of the discharge path, and the variable resistance means selects the discharge path to be used for discharging by controlling the switching element.

15. The voltage balancer device for a battery pack according to claim 12, wherein the discharge path is composed of a plurality of the discharge paths connected in parallel to the secondary battery units, each of the plural discharge paths has a constant current discharge means and a switching element capable of switching an electrical on-off connection of the discharge path, and the control means selects the discharge path to be used for discharging by activating the switching element.

16. The voltage balancer device for a battery pack according to claim 1, further comprising an average value detecting means configured to detect an average value of the voltage of each secondary battery unit, wherein the control means so controls that the secondary battery unit whose voltage is over than the average value is discharged through the discharge path corresponding to the secondary battery unit.

17. The voltage balancer device for a battery pack according to claim 8, further comprising an average value detecting means configured to detect an average value of the voltage of each secondary battery unit, wherein the control means so controls that the secondary battery unit whose voltage is over than the average value is discharged through the discharge path corresponding to the secondary battery unit.

18. The voltage balancer device for a battery pack according to claim 9, further comprising an average value detecting means configured to detect an average value of the voltage of each secondary battery unit, wherein the control means so controls that the secondary battery unit whose voltage is over than the average value is discharged through the discharge path corresponding to the secondary battery unit.

19. The voltage balancer device for a battery pack according to claim 12, further comprising an average value detecting means configured to detect an average value of the voltage of each secondary battery unit, wherein the control means so controls that the secondary battery unit whose voltage is over than the average value is discharged through the discharge path corresponding to the secondary battery unit.