POWER SUPPLY DEVICE AND METHOD OF CONTROLLING THE SAME

• US 20110175452A1
• Filed: 01/13/2011
• Published: 07/21/2011
• Est. Priority Date: 01/21/2010
• Status: Active Grant

• Current Assignee: NEC Corporation
• Original Assignee: NEC Corporation
• Inventors: Hoshino, Tomonori
• Granted Patent: US 9,054,556 B2
• Time in Patent Office: Days
• US Class Current: 307/66
• CPC Class Codes: H02J 7/34 Parallel operation in networks using both storage and other dc sources, e.g. providing buffering H02J7/14 takes precedence
• CPC Class Codes: H02J 9/005 using a power saving mode for copiers G03G15/5004
• CPC Class Codes: Y02B 70/30 Systems integrating technologies related to power network operation and communication or information technologies for improving the carbon footprint of the management of residential or tertiary loads, i.e. smart grids as climate change mitigation technology in the buildings sector, including also the last stages of power distribution and the control, monitoring or operating management systems at local level
• CPC Class Codes: Y04S 20/20 End-user application control systems

Abstract

A power supply device includes a power conversion circuit, a secondary battery, a table, and a control circuit. The power conversion circuit converts alternating-current or direct-current power into direct-current power to supply power to a load. The secondary battery is connected between the power conversion circuit and the load and charged with power from the power conversion circuit so that power is supplied to the load when the charging power is discharged. On the table, power conversion efficiency of the power conversion circuit associated with output power and charging efficiency of the secondary battery associated with charging power are recorded. The control circuit looks up the table to calculate power loss, which is based on the power conversion efficiency of the power conversion circuit associated with the output power in the case where power is supplied from the power conversion circuit to the load, and power loss, which is based on the charging efficiency of the secondary battery associated with the charging power in the case where power is output from the power conversion circuit so that the power conversion efficiency is at the highest level and the secondary battery is charged with extra power that is left after power is supplied to the load, makes a determination, on the basis of both the calculated power losses, as to whether the supply of power from the secondary battery to the load leads to a smaller power loss, makes a determination, when the supply of power from the secondary battery to the load leads to a smaller power loss, as to whether there is a remaining capacity in the secondary battery, and performs a control process, when there is no remaining capacity in the secondary battery, so that power is supplied from the power conversion circuit to the load and the secondary battery is charged for a predetermined period of time.

Claims

1. A power supply device comprising:

a power conversion circuit that converts alternating-current or direct-current power into direct-current power to supply power to a load;

a secondary battery that is connected between the power conversion circuit and the load and charged with power from the power conversion circuit so that power is supplied to the load when the charging power is discharged;

a table on which power conversion efficiency of the power conversion circuit associated with output power and charging efficiency of the secondary battery associated with charging power are recorded; and

a control circuit that looks up the table to calculate power loss, which is based on the power conversion efficiency of the power conversion circuit associated with the output power in the case where power is supplied from the power conversion circuit to the load, and power loss, which is based on the charging efficiency of the secondary battery associated with the charging power in the case where power is output from the power conversion circuit so that the power conversion efficiency is at the highest level and the secondary battery is charged with extra power that is left after power is supplied to the load, makes a determination, on the basis of both the calculated power losses, as to whether the supply of power from the secondary battery to the load leads to a smaller power loss, makes a determination, when the supply of power from the secondary battery to the load leads to a smaller power loss, as to whether there is a remaining capacity in the secondary battery, and performs a control process, when there is no remaining capacity in the secondary battery, so that power is supplied from the power conversion circuit to the load and the secondary battery is charged for a predetermined period of time.

2. The power supply device according to claim 1, wherein

the control circuit performs a control process in a way that stops the power conversion circuit after the secondary battery is charged to supply power from the secondary battery to the load and in a way that activates the power conversion circuit when the remaining capacity of the secondary battery becomes less than or equal to a predetermined value to supply power to the load and charge the secondary battery.

3. The power supply device according to claim 1, wherein

the control circuit performs a control process in a way that stops an operation of the power conversion circuit when it is determined that there is a remaining capacity in the secondary battery to supply power to the load only from the secondary battery.

4. The power supply device according to claim 1, wherein

the control circuit sets, before a determination is made as to whether there is a remaining capacity in the secondary battery, a threshold value by which whether there is a remaining capacity in the secondary battery is determined according to a degradation characteristic of the secondary battery.

5. The power supply device according to claim 1, wherein

the control circuit stops the power conversion circuit when power is not being supplied from an alternating-current or direct-current line to the power conversion circuit to supply power from the secondary battery to the load.

6. The power supply device according to claim 1, wherein:

the secondary battery includes various secondary batteries that are different in the charging efficiency;

the table includes a power conversion efficiency table where the power conversion efficiency of the power conversion circuit associated with the output power is recorded and a charging efficiency table where the charging efficiency of the secondary battery associated with the charging power is recorded;

the secondary battery and the charging efficiency table are provided as a battery in a way that makes it possible to separate the secondary battery and the charging efficiency table from the power supply device; and

the control circuit reads the charging efficiency out from the charging efficiency table of the battery in accordance with the type of the secondary battery.

7. A method of controlling a power supply device including a power conversion circuit that converts alternating-current or direct-current power into direct-current power to supply power to a load and a secondary battery that is connected between the power conversion circuit and the load and charged with power from the power conversion circuit so that power is supplied to the load when the charging power is discharged, the method comprising:

looking up a table, on which power conversion efficiency of the power conversion circuit associated with output power and charging efficiency of the secondary battery associated with charging power are recorded, to calculate power loss, which is based on the power conversion efficiency of the power conversion circuit associated with the output power in the case where power is supplied from the power conversion circuit to the load, and power loss, which is based on the charging efficiency of the secondary battery associated with the charging power in the case where power is output from the power conversion circuit so that the power conversion efficiency is at the highest level and the secondary battery is charged with extra power that is left after power is supplied to the load;

making a determination, on the basis of both the calculated power losses, as to whether the supply of power from the secondary battery to the load leads to a smaller power loss;

making a determination, when the supply of power from the secondary battery to the load leads to a smaller power loss, as to whether there is a remaining capacity in the secondary battery; and

performing a control process, when there is no remaining capacity in the secondary battery, so that power is supplied from the power conversion circuit to the load and the secondary battery is charged for a predetermined period of time.

8. The method according to claim 7, further comprising:

performing a control process in a way that stops the power conversion circuit after the secondary battery is charged to supply power from the secondary battery to the load and in a way that activates the power conversion circuit when the remaining capacity of the secondary battery becomes less than or equal to a predetermined value to supply power to the load and charge the secondary battery.

9. The method according to claim 7, further comprising:

performing a control process in a way that stops an operation of the power conversion circuit when it is determined that there is a remaining capacity in the secondary battery to supply power to the load only from the secondary battery.

10. The method according to claim 7, further comprising:

setting, before a determination is made as to whether there is a remaining capacity in the secondary battery, a threshold value by which whether there is a remaining capacity in the secondary battery is determined according to a degradation characteristic of the secondary battery.

11. The method according to claim 7, further comprising:

stopping the power conversion circuit when power is not being supplied from an alternating-current or direct-current line to the power conversion circuit to supply power from the secondary battery to the load.

12. The method according to claim 7, wherein:

the secondary battery includes various secondary batteries that are different in the charging efficiency;

the table includes a power conversion efficiency table where the power conversion efficiency of the power conversion circuit associated with the output power is recorded and a charging efficiency table where the charging efficiency of the secondary battery associated with the charging power is recorded; and

the secondary battery and the charging efficiency table are provided as a battery in a way that makes it possible to separate the secondary battery and the charging efficiency table from the power supply device, the method further comprising;

reading the charging efficiency out from the charging efficiency table of the battery in accordance with the type of the secondary battery.