초록 ▼

A power supply system includes a fuel cell and a battery connected in parallel. A DC-DC converter is connected to the battery. A maximum output ratio of the fuel cell and the battery is set to be in a range where the output of the fuel cell is within 65 to 80% of the total output. Accordingly, elect

A power supply system includes a fuel cell and a battery connected in parallel. A DC-DC converter is connected to the battery. A maximum output ratio of the fuel cell and the battery is set to be in a range where the output of the fuel cell is within 65 to 80% of the total output. Accordingly, electric power loss owing to conversion performed by the DC-DC converter is reduced to achieve a high energy efficiency.

대표청구항 ▼

1. A direct current power supply system for a vehicle, comprising:a pair of terminals that provide an electric power; a fuel cell connected to the terminals; a DC/DC converter connected to the terminals; an electric power storage unit that is connected to the terminals via the DC-DC converter in par

1. A direct current power supply system for a vehicle, comprising:a pair of terminals that provide an electric power; a fuel cell connected to the terminals; a DC/DC converter connected to the terminals; an electric power storage unit that is connected to the terminals via the DC-DC converter in parallel with the fuel cell, the electric power storage unit being able to be charged and discharged, wherein a maximum output power of the fuel cell is greater than a maximum output power of the electric power storage unit; and a control unit adapted to set a lower limit of an output ratio of said fuel cell to said electric power storage unit, set an upper limit of the output ratio of said fuel cell to said electric power storage unit, and set an actual output ratio based upon said lower limit, said upper limit and an energy efficiency of the vehicle. 2. A direct current power supply system according to claim 1, further comprising fuel-cell accessories that operate to drive the fuel cell, wherein at least a part of the fuel-cell accessories is directly connected to the electric power storage unit such that the at least a part of the fuel-cell accessories can be driven by the electric power storage unit serving as a power supply.3. A direct current power supply system according to claim 1, further comprising a controller that controls an output voltage of the DC/DC converter to be substantially equal to an output voltage of the fuel cell.4. A direct current power supply system according to claim 1, further comprising a controller that controls an output voltage of the DC/DC converter to a predetermined voltage at which the electric power storage unit is allowed to be charged by one of the fuel cell and the terminals.5. A direct current power supply system according to claim 1, wherein the electric power storage unit comprises a secondary battery.6. The direct current power supply system of claim 1, wherein said control unit is adapted to set the lower and upper limits of the output ratio of said fuel cell to said electric power storage unit based on vehicle driving conditions.7. A vehicle comprising:a motor serving as a driving power source, a drive circuit that drives the motor by electric power, a direct current power supply unit that supplies the electric power to the drive circuit, wherein the direct current power supply unit comprises: a pair of terminals that provide an electric power; a fuel cell connected to the terminals; a DC/DC converter connected to the terminals; and an electric power storage unit that is connected to the terminals via the DC-DC converter in parallel with the fuel cell, the electric power storage unit being able to be charged and discharged, wherein a maximum output power of the fuel cell is greater than a maximum output power of the electric power storage unit; and a control unit adapted to set a lower limit of an output ratio of said fuel cell to said electric power storage unit, set an upper limit of the output ratio of said fuel cell to said electric power storage unit, and set an actual output ratio based upon said lower limit, said upper limit and an energy efficiency of the vehicle. 8. A vehicle according to claim 7, further comprising vehicle accessories that operate to drive the vehicle, wherein at least a part of the vehicle accessories is directly connected to the electric power storage unit such that the at least one of the vehicle accessories can be driven by the electric power storage unit serving as a power supply.9. A vehicle according to claim 7, further comprising fuel-cell accessories that operate to drive the fuel cell, wherein at least a part of the fuel-cell accessories is directly connected to the electric power storage unit such that the at least a part of the fuel-cell accessories can be driven by the electric power storage unit serving as a power supply.10. A vehicle according to claim 7, further comprising a controller that controls an output voltage of the DC/DC converter to be substantially equal to an output voltage of the fuel cell.11. A vehicle according to claim 7, further comprising a controller that controls an output voltage of the DC/DC converter to a predetermined voltage at which the electric power storage unit is allowed to be charged by one of the fuel cell and the terminals.12. A vehicle according to claim 7, wherein the electric power storage unit comprises a secondary battery.13. The vehicle of claim 7, wherein said control unit is adapted to set the lower and upper limits of the output ratio of said fuel cell to said electric power storage unit based on vehicle driving conditions.14. A method for supplying a direct current from a fuel cell and an electric power storage unit that can be charged and discharged to output terminals, which are connected in parallel with the output terminals, wherein a maximum output power of the fuel cell is greater than a maximum output power of the electric power storage unit, the method comprising:(a) operating the fuel cell to generate a predetermined voltage; (b) converting a voltage generated by the electric power accumulating unit by using the DC-DC converter to a voltage equal to the predetermined voltage generated by the fuel cell and applying the converted voltage to the terminals; and setting an output ratio of said fuel cell to said electric power storage unit by setting a lower limit of the output ratio, setting an upper limit of the output ratio, and setting the output ratio based upon said lower limit, said upper limit and an energy efficiency of the vehicle. 15. The method of claim 14, wherein the lower and upper limits of the output ratio of said fuel cell to said electric power storage unit are set based on vehicle driving conditions.16. A direct current power supply system for a vehicle, comprising:a pair of terminals that provide an electric power; a fuel cell connected to the terminals; a DC/DC converter connected to the terminals; an electric power storage unit that is connected to the terminals via the DC-DC converter in parallel with the fuel cell, the electric power storage unit being able to be charged and discharged, wherein a maximum output power of the fuel cell is greater than a maximum output power of the electric power storage unit; and control means for setting a lower limit of an output ratio of said fuel cell to said electric power storage unit based on vehicle driving conditions, setting an upper limit of the output ratio of said fuel cell to said electric power storage unit based on vehicle driving conditions, and setting an actual output ratio based upon said lower limit, said upper limit and an energy efficiency of the vehicle. 17. The direct current power supply system of claim 16, wherein said control means sets the lower and upper limits of the output ratio of said fuel cell to said electric power storage unit based on vehicle driving conditions.