Power supply apparatus with fuel cell and method of controlling the same

• US 7,883,808 B2
• Filed: 02/21/2006
• Issued: 02/08/2011
• Est. Priority Date: 09/30/2005
• Status: Expired due to Fees

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Kikuchi, Mutsumi, Norimatsu, Yasuaki, Kanouda, Akihiko
• Primary Examiner(s): Yuan; Dah-Wei D
• Assistant Examiner(s): SCULLY, STEVEN M
• Application Number:
  US11/357,029
• Publication Number:
  US 20070077468A1
• Time in Patent Office: 1,813 Days
• Field of Search: 429 12- 46
• US Class Current: 429/432
• CPC Class Codes: H01M 16/006 of fuel cells with rechargeable batteries
• CPC Class Codes: H01M 8/04007 related to heat exchange
• CPC Class Codes: H01M 8/04291 Arrangements for managing water in solid electrolyte fuel cell systems H01M8/04119 takes precedence
• CPC Class Codes: H01M 8/04365 of other components of a fuel cell or fuel cell stacks
• CPC Class Codes: H01M 8/04559 of fuel cell stacks
• CPC Class Codes: H01M 8/04567 of auxiliary devices, e.g. batteries, capacitors
• CPC Class Codes: H01M 8/04597 of auxiliary devices, e.g. batteries, capacitors
• CPC Class Codes: H01M 8/04619 of fuel cell stacks
• CPC Class Codes: H01M 8/04626 of auxiliary devices, e.g. batteries, capacitors
• CPC Class Codes: H01M 8/0488 of fuel cell stacks
• CPC Class Codes: H01M 8/04888 of auxiliary devices, e.g. batteries, capacitors
• CPC Class Codes: H01M 8/0494 of fuel cell stacks
• CPC Class Codes: H01M 8/04947 of auxiliary devices, e.g. batteries, capacitors
• CPC Class Codes: H01M 8/1011 Direct alcohol fuel cells [DAFC], e.g. direct methanol fuel cells [DMFC]
• CPC Class Codes: H02J 2300/30 The power source being a fuel cell
• 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: Y02E 60/10 Energy storage using batteries
• CPC Class Codes: Y02E 60/50 Fuel cells

Abstract

A power supply apparatus has a fuel cell unit as a source of input power. A control device limits the output of the fuel cell unit within an operating range of up to a maximum power point, even if a load power is not lower than the maximum power of said fuel cell unit. In addition to the fuel cell, a charge storing device is provided at the output side of the power supply apparatus. The charge storing device is capable of making up a shortage of power of the fuel cell.

Claims

1. A power supply apparatus comprising:

a fuel cell unit;

a circuit section that performs DC/DC conversion of an output from the fuel cell unit and provides an output to a power supply output terminal;

a power charge storing device which is provided between the circuit section and the power supply output terminal so as to charge the output of the circuit section and supply charged power to a load so as to make up for a power shortage of the fuel cell unit and when a requested load power from a load is greater than a fuel cell maximum power of the fuel cell unit; and

a control device for the circuit section that performs PWM (Pulse Width Modulation) control;

wherein the control device comprises a PWM logic circuit that controls a pulse width modulation switching operation of the circuit section so that stable output power of the circuit section is obtained, a duty limit circuit that limits a duty cycle for the PWM control in proportion to an input voltage of the circuit section, the duty limit circuit enabling stopping of the PWM switching operation of the circuit section by controlling the PWM logic circuit when the input voltage of the circuit section becomes not greater than a predetermined voltage, a fuel cell voltage limiting terminal that is connected between the fuel cell and the circuit section so as to provide the input voltage of the circuit section to the duty limit circuit, a power charge storing device voltage receiving terminal that receives a divided voltage between dividing resistances connected in parallel to the power charge storing device and that provides an output resulting from comparing the divided voltage with a predetermined reference voltage, an output voltage receiving terminal that is connected to an output side of the circuit section so as to provide the output of the circuit section to the PWM logic circuit, and a control terminal that is connected to the circuit section so as to control the circuit section;

wherein the control device controls an amount of power supply so that an operating input voltage range for the power supply apparatus is not lower than a maximum power voltage of the fuel cell unit and controls a maximum duty cycle for the PWM control so that as a difference between a fuel cell unit output voltage and the predetermined voltage becomes larger, the maximum duty cycle for the PWM control increases;

wherein the output voltage receiving terminal also provides a constant current to the fuel cell voltage limiting terminal via a constant current circuit; and

wherein the predetermined voltage which is used as a reference voltage for stopping of the PWM logic circuit is set by adding a margin voltage generated by flowing the constant current through a resistor disposed between the fuel cell unit and the fuel cell voltage limiting terminal to the maximum power voltage of the fuel cell unit.

2. The power supply apparatus according to claim 1,

wherein the resistor for making the margin voltage is constituted by a NTC (Negative Temperature Coefficient) thermistor through which the constant current from the constant current circuit flows;

and

wherein the predetermined voltage increases as the temperature of the fuel cell unit increases.

3. The power supply apparatus according to claim 1,

wherein the duty limit circuit limits the duty cycle for the PWM control in proportion to a difference voltage between an output voltage and the input voltage of the circuit section.