Electronic device, and system for DC voltage conversion

• US 20080179955A1
• Filed: 11/20/2007
• Published: 07/31/2008
• Est. Priority Date: 01/30/2007
• Status: Active Grant

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Yokota, Koichi, Nakashima, Yoshiyasu, Kazama, Satoshi
• Granted Patent: US 7,816,812 B2
• Time in Patent Office: Days
• US Class Current: 307/48
• CPC Class Codes: B60L 58/30 for monitoring or controlling fuel cells
• CPC Class Codes: H02J 1/10 Parallel operation of dc sources
• 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: Y02T 90/40 Application of hydrogen technology to transportation, e.g. using fuel cells

Abstract

An electronic device includes: a first input terminal to which a first DC supply voltage of a fuel cell system having a controllable supply voltage is provided; a second input terminal to which a second DC supply voltage of a rechargeable secondary battery is provided; a DC voltage conversion circuit which receives the first and second DC supply voltages from the first and second input terminals, and supplies a current of a desired voltage to a load; a charging circuit which receives the first DC supply voltage from the first input terminal, and supplies a DC supply voltage for charging to the second input terminal; and a control circuit which determines a desired value of the first DC supply voltage in accordance with a value of the second DC supply voltage of the secondary battery, and provides the determined desired value to the fuel cell system.

Claims

1. An electronic device comprising:

a first input terminal to which a first DC supply voltage of a fuel cell system having a controllable supply voltage is provided;

a second input terminal to which a second DC supply voltage of a rechargeable secondary battery is provided;

a DC voltage conversion circuit receiving the first and second DC supply voltages from said first and second input terminals, and supplying a current of a desired voltage to a load;

a charging circuit receiving the first DC supply voltage from said first input terminal, and supplying a DC supply voltage for charging to said second input terminal; and

a control circuit determining a desired value of the first DC supply voltage in accordance with a value of the second DC supply voltage of said secondary battery, and providing the determined desired value to said fuel cell system.

2. The electronic device according to claim 1, wherein said control circuit determines the desired value of the first DC supply voltage to be a sum of the value of the second DC supply voltage of said secondary battery and a predetermined value.

3. The electronic device according to claim 1, further comprising a load state determination unit determining a state of the load,

wherein said control circuit determines the desired value of the first DC supply voltage in accordance with the value of the second DC supply voltage of said secondary battery and the state of the load determined by said load state determination unit.

4. The electronic device according to claim 1, further comprising a load state determination unit determining a state of the load,

wherein said control circuit looks up a table and determines a predetermined value corresponding to the state of the load in the table based on the state of the load determined by said load state determination unit, and determines the desired value of the first DC supply voltage to be a sum of the value of the second DC supply voltage of said secondary battery and a predetermined value.

5. The electronic device according to claim 4, wherein the state of the load is a CPU occupancy.

6. The electronic device according to claim 4, wherein the state of the load is a load power in said electronic device.

7. The electronic device according to claim 1, wherein when said secondary battery is not full and can be charged by the first DC supply voltage of said fuel cell system, said control circuit determines the desired value of the first DC supply voltage to be a value higher than a voltage required for charging said secondary battery.

8. The electronic device according to claim 1, wherein when said secondary battery is not full and can be charged by the first DC supply voltage of said fuel cell system, said control circuit determines the desired value of the first DC supply voltage to be a value not less than a maximum DC supply voltage of said secondary battery.

9. The electronic device according to claim 1, wherein said control circuit allows said charging circuit to start charging said secondary battery when a remaining power of said secondary battery is lower than a predetermined percentage of full remaining power of said secondary battery.

10. The electronic device according to claim 1, wherein a communication between said fuel cell system and said control circuit is performed through said first input terminal in a superimposed manner.

11. The electronic device according to claim 1, wherein a communication between said fuel cell system and said control circuit is performed by wireless communication.

12. A DC voltage conversion system comprising:

a first input terminal to which a first DC supply voltage of a fuel cell system having a controllable supply voltage is provided;

a second input terminal to which a second DC supply voltage of a rechargeable secondary battery is provided;

a DC voltage conversion circuit receiving the first and second DC supply voltages from said first and second input terminals, and supplies a current of a desired voltage to a load;

a charging circuit receiving the first DC supply voltage from said first input terminal, and supplies a DC supply voltage for charging to said second input terminal; and

a control circuit determining a desired value of the first DC supply voltage in accordance with a value of the second DC supply voltage of said secondary battery, and provides the determined desired value to said fuel cell system.

13. A program for an electronic device stored on a computer-readable storage medium, the electronic device comprising:

a DC voltage conversion circuit receiving a first DC supply voltage from a fuel cell system and a second DC supply voltage from a rechargeable secondary battery and supplies a current at a desired voltage to a load, a charging circuit, and a control circuit, said program being operable to effect;

determining a desired value of the first DC supply voltage in accordance with a value of the second DC supply voltage of the secondary battery,

providing the determined desired value to the fuel cell system, and causing the fuel cell system to supply the first DC supply voltage at the determined desired value, and

causing the charging circuit to receive the first DC supply voltage at the determined desired value and supply a DC supply voltage for charging to the secondary battery.

14. The program for an electronic device stored on a computer-readable storage medium according to claim 13, wherein the step of determining a desired value of the first DC supply voltage comprises determining the desired value of the first DC supply voltage to be a value higher than a voltage required for charging the secondary battery when the secondary battery is not full and can be charged by the first DC supply voltage of the fuel cell system.

15. The program for an electronic device stored on a computer-readable storage medium according to claim 13, wherein the step of determining a desired value of the first DC supply voltage comprises determining the desired value of the first DC supply voltage to be a value not less than a maximum DC supply voltage of the secondary battery when the secondary battery is not full and can be charged by the first DC supply voltage of the fuel cell system.

16. The program for an electronic device stored on a computer-readable storage medium according to claim 13, wherein the step of causing the charging circuit to receive the first DC supply voltage comprises allowing the charging circuit to start charging the secondary battery when a remaining power of the secondary battery is lower than a predetermined percentage of full remaining power of the secondary battery.