FUEL CELL SYSTEM AND BOOST CONVERTER FOR FUEL CELL

• US 20100291445A1
• Filed: 12/26/2008
• Published: 11/18/2010
• Est. Priority Date: 12/28/2007
• Status: Active Grant

• Current Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Original Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Inventors: Igarashi, Fusaki
• Granted Patent: US 8,673,514 B2
• Time in Patent Office: Days
• US Class Current: 429/428
• CPC Class Codes: B60L 1/003 to auxiliary motors, e.g. for pumps, compressors
• CPC Class Codes: B60L 2210/14 Boost converters
• CPC Class Codes: B60L 2240/12 Speed
• CPC Class Codes: B60L 50/51 characterised by AC-motors
• CPC Class Codes: B60L 58/40 for controlling a combination of batteries and fuel cells
• CPC Class Codes: H01M 8/04567 of auxiliary devices, e.g. batteries, capacitors
• CPC Class Codes: H01M 8/0491 of fuel cell stacks
• CPC Class Codes: H02M 3/158 including plural semiconductor devices as final control devices for a single load
• CPC Class Codes: Y02E 60/50 Fuel cells
• CPC Class Codes: Y02T 10/70 Energy storage systems for electromobility, e.g. batteries
• CPC Class Codes: Y02T 10/72 Electric energy management in electromobility
• CPC Class Codes: Y02T 90/40 Application of hydrogen technology to transportation, e.g. using fuel cells

Abstract

Provided is a fuel cell system including a fuel cell which is a DC power source and boosting unit which boosts the output voltage of the fuel cell for supply to a load. The boosting unit has: a main boosting unit which has a switch and a coil and boosts the output voltage of the fuel cell by a back electromotive force of the coil generated by a switching operation of the switch with respect to the coil; and a sub boosting unit having a snubber capacitor which adjusts a potential difference between the both electrodes of the switch by an accumulation amount and reduces the switching loss of the switch by adjusting the accumulation amount of the snubber capacitor upon a switching operation. The electricity of the snubber capacitor discharged when reducing the accumulation amount of the snubber capacitor is made to flow into processing unit other than the fuel cell by the sub boosting unit.

Claims

1. A fuel cell system comprising:

a fuel cell as a DC power source; and

a boost unit boosting an output voltage of said fuel cell,

said boost unit including;

a main boost unit having a switch and a coil, and boosting the output voltage of said fuel cell with counter electromotive force of said coil that is generated by said switch performing a switching operation with respect to said coil; and

an auxiliary boost unit having a snubber capacitor adjusting a potential difference between two poles of said switch with a quantity of accumulated electricity, and reducing a switching loss of said switch by adjusting the quantity of accumulated electricity of said snubber capacitor when performing the switching operation,

wherein said auxiliary boost unit conducts the electricity of said snubber capacitor, which is released when reducing the quantity of accumulated electricity of said snubber capacitor, to a processing unit other than said fuel cell to thereby process the electricity.

2. The fuel cell system according to claim 1, wherein said auxiliary boost unit regenerates the electricity released when reducing the quantity of accumulated electricity of said snubber capacitor into an electric path which connects said main boost unit as said processing unit to said fuel cell to thereby process the electricity, said fuel cell system further comprising a buffering unit which buffers a fluctuation in voltage of said electric path, which is caused by the regenerated electric power of said auxiliary boost unit.

3. The fuel cell system according to claim 1, wherein said auxiliary boost unit regenerates the electricity released when reducing the quantity of accumulated electricity of said snubber capacitor into an electric path which connects said main boost unit as said processing unit to said fuel cell to thereby process the electricity, said fuel cell system further comprising a constant voltage unit which, if the voltage of said electric path, which fluctuates due to the regenerated power of said auxiliary boost unit, exceeds a specified voltage, conducts the electricity of said electric path to the earth.

4. The fuel cell system according to claim 1, wherein said auxiliary boost unit regenerates the electricity released when reducing the quantity of accumulated electricity of said snubber capacitor into an electric path which connects said main boost unit as said processing unit to said fuel cell to thereby process the electricity, said fuel cell system further comprising a rectifying unit that prevents the regenerated power of said auxiliary boost unit from flowing to said fuel cell via said electric path.

5. The fuel cell system according to claim 1, further comprising a secondary battery as said processing unit,

wherein said auxiliary boost unit conducts the electricity released when reducing the quantity of accumulated electricity of said snubber capacitor to said secondary battery to thereby process the electricity.

6. The fuel cell system according to claim 1, wherein said main boost unit includes:

a first coil having one end connected to a cathode of said fuel cell;

a first switch having one end connected to the other end of said first coil and having the other end connected to an anode of said fuel cell;

a first diode connected, on the anode side, to the other end of said coil and connected, on the cathode side, to said load; and

a smoothing capacitor connecting the cathode side of said first diode to the other end of said first switch, and

said auxiliary boost unit includes;

a second diode connected, on the anode side, to an electric path branching off from said electric path connecting said first coil to said first switch;

said snubber capacitor connecting the cathode side of said second diode to the other end of said first switch;

a second coil having one end connected to an electric path branching off from said electric path connecting the cathode side of said second diode to said snubber capacitor;

a third diode connected, on the anode side, to the other end of said second coil; and

a second switch having one end connected to the cathode side of said third diode and having the other end connected to said processing unit.

7. A boost converter for a fuel cell, for boosting an output voltage of said fuel cell as a DC power source and thus supplying the output voltage to a load, comprising:

a main boost unit having a switch and a coil, and boosting the output voltage of said fuel cell with counter electromotive force of said coil that is generated by said switch performing a switching operation with respect to said coil; and

an auxiliary boost unit having a snubber capacitor adjusting a potential difference between two poles of said switch with a quantity of accumulated electricity, and reducing a switching loss of said switch by adjusting the quantity of accumulated electricity of said snubber capacitor when performing the switching operation,

wherein said auxiliary boost unit conducts the electricity of said snubber capacitor, which is released when reducing the quantity of accumulated electricity of said snubber capacitor, to a processing unit other than said fuel cell to thereby process the electricity.