Cell voltage detecting system and drive voltage maintaining method

• US 8,274,292 B2
• Filed: 01/22/2010
• Issued: 09/25/2012
• Est. Priority Date: 01/23/2009
• Status: Expired due to Fees

• Current Assignee: Honda Motor Co., Ltd. (Honda Motor Company)
• Original Assignee: Honda Motor Co., Ltd. (Honda Motor Company)
• Inventors: Minoda, Yuji, Ariyoshi, Toshiaki
• Primary Examiner(s): Dunn, Drew A
• Assistant Examiner(s): PELTON, NATHANIEL R
• Application Number:
  US12/692,167
• Publication Number:
  US 20100188093A1
• Time in Patent Office: 977 Days
• Field of Search: 324/427
• US Class Current: 324/427
• CPC Class Codes: G01R 31/3835 involving only voltage measurements
• CPC Class Codes: G01R 31/396 Acquisition or processing of data for testing or for monitoring individual cells or groups of cells within a battery
• CPC Class Codes: H01M 8/04552 of the individual fuel cell
• CPC Class Codes: H01M 8/04559 of fuel cell stacks
• CPC Class Codes: Y02E 60/50 Fuel cells

Abstract

In a cell voltage detecting system detecting cell voltages of a fuel cell connected in series, a voltage detector detects cell voltages. An auxiliary power supply generates a voltage equal to or greater than a minimum voltage for driving the voltage detector at positive and negative terminals thereof. First and second diodes are connected to a positive drive terminal of the voltage detector to supply the power to the drive terminal of the voltage detector from a high voltage side between the fuel cell or the auxiliary power supply. A negative terminal of the fuel cell, the negative drive terminal, and the negative terminal of the auxiliary power supply are connected to have a same potential. A method of maintaining a drive voltage for the voltage detector is also disclosed in which the drive voltage for the voltage detector is supplied from the high voltage side.

Claims

1. A cell voltage detecting system that detects voltages of cells in a fuel cell connected in series, comprising:

a voltage detector that detects voltages of the cells and includes positive and negative drive terminals and comprises a multiplexer for selecting a positive terminal of one of the cells in the fuel cell to detect a potential of the selected positive terminal and applying the detected potential to a differential amplifier, wherein the differential amplifier calculates a voltage differential between the voltage potential of the selected positive terminal of the cell and a reference potential and multiplies the difference by a predetermined value;

an auxiliary power supply that generates a voltage equal to or greater than a minimum voltage necessary for driving the voltage detector between positive and negative terminals thereof, wherein the auxiliary power supply comprises a DC-DC converter;

a first diode connected to a positive terminal of the fuel cell and the positive drive terminal in such a direction as to allow a current to flow therethrough from the positive terminal of the fuel cell to the positive drive terminal; and

a second diode connected to the positive terminal of the auxiliary power supply and the positive drive terminal in such a direction as to allow a current to flow therethrough from the positive terminal of the auxiliary power supply to the positive drive supply terminal,

wherein the cells are divided into a plurality of blocks as the cells are connected in series, each block including a negative terminal;

wherein a negative terminal of a last cell in series of the fuel cell, the negative drive terminal of the voltage detector, the negative terminal of the auxiliary power supply, a negative drive terminal of the multiplexer and the reference potential of the differential amplifier are connected to have a same potential;

wherein the DC-DC converter comprises a plurality of isolated DC-DC converting devices that belong to respective blocks, each of the isolated DC-DC converting devices including primary and secondary sides isolated, including the negative terminal of the DC-DC converter on the secondary side, and generating the voltage between the positive and negative terminals on the secondary side;

wherein the voltage detector comprises a plurality of voltage detecting devices that belong to respective blocks, each detecting voltages of the cells in the block and including the positive and negative drive terminals, and

wherein the negative terminal on the secondary side of the isolated DC-DC converting device, and the negative drive terminal of the voltage detecting device in the block are equalized to a potential of the negative terminal of the block, and the primary side in each block is connected to the auxiliary power supply.

2. The cell voltage detecting system as claimed in claim 1, wherein the auxiliary power supply further comprises an external power supply for generating an output voltage, and wherein the output voltage of the auxiliary power supply is smaller than an output voltage of the external power supply.

3. A method of maintaining a drive voltage for a cell voltage detector that detects voltages of cells in a fuel cell connected in series, using voltages of the fuel cell and an auxiliary power supply, wherein the auxiliary power supply comprises a DC-DC converter, wherein the voltage detector that detects voltages of the cells and includes positive and negative drive terminals, and wherein the voltage detector comprises a multiplexer for selecting a positive terminal of one of the cells in the fuel cell to detect a potential of the selected positive terminal and applying the detected potential to a differential amplifier, wherein the differential amplifier calculates a voltage differential between the voltage potential of the selected positive terminal of the cell and a reference potential and multiplies the difference by a predetermined value, the method comprising the steps of:

supplying the voltage of the fuel cell to the cell voltage detector when the voltage of the fuel cell is greater than the voltage of the auxiliary power supply;

supplying the voltage of the auxiliary power supply to the cell voltage detector when the voltage of the fuel cell is not greater than the voltage of the auxiliary power supply; and

determining the voltage of the auxiliary power supply to be equal to or greater than a minimum voltage necessary for driving the voltage detector between positive and negative terminals thereof,

wherein the DC-DC converter comprises a plurality of isolated DC-DC converting devices that belong to respective blocks, each of the isolated DC-DC converting devices including primary and secondary sides isolated, including the negative terminal of the DC-DC converter on the secondary side, and generating the voltage between the positive and negative terminals on the secondary side;

wherein the voltage detector comprises a plurality of voltage detecting devices that belong to respective blocks, each detecting voltages of the cells in the block and including the positive and negative drive terminals, and

wherein the negative terminal on the secondary side of the isolated DC-DC converting device, and the negative drive terminal of the voltage detecting device in the block are equalized to a potential of the negative terminal of the block, and the primary side in each block is connected to the auxiliary power supply, and

when an output voltage of the fuel cell is greater than the minimum voltage, supplying the voltage of the fuel cell to the voltage detector and when the voltage of the fuel cell is not greater than the minimum voltage, supplying the voltage of the auxiliary power supply to the voltage detector, comprising;

providing a first diode connected to a positive terminal of the fuel cell and a positive drive terminal of the voltage detector in such a direction as to allow a current to flow therethrough from the positive terminal of the fuel cell to the positive drive terminal of the voltage detector;

providing a second diode connected to the positive terminal of the auxiliary power supply and the positive drive terminal in such a direction so as to allow a current to flow therethrough from the positive terminal of the auxiliary power supply to the positive drive terminal; and

connecting a negative terminal of a last cell in series of the fuel cell, a negative drive terminal of the voltage detector, a negative terminal of the auxiliary power supply, a negative drive terminal of the multiplexer and the reference potential of the differential amplifier to each other to have a same potential.

4. The method as claimed in claim 3, further comprising the steps of:

(a) determining the voltage of the auxiliary power supply to be equal to or greater than a minimum voltage necessary for driving the voltage detector between positive and negative terminals thereof; and

(b) when an output voltage of the fuel cell is greater than the minimum voltage, supplying the voltage of the fuel cell to the voltage detector and when the voltage of the fuel cell is not greater than the minimum voltage, supplying the voltage of the auxiliary power supply to the voltage detector.

5. The method of maintaining a drive voltage as claimed in claim 4, wherein the step (b) comprising the steps of:

providing a first diode connected to a positive terminal of the fuel cell and a positive drive terminal of the voltage detector in such a direction as to allow a current to flow therethrough from the positive terminal of the fuel cell to the positive drive terminal of the voltage detector; and

a second diode connected to the positive terminal of the auxiliary power supply and the positive drive terminal in such a direction as to allow a current to flow therethrough from the positive terminal of the auxiliary power supply to the positive drive supply terminal; and

connecting a negative terminal of the fuel cell, a negative drive terminal of the voltage detector, and a negative terminal of the auxiliary power supply each other to have a same potential.

6. The method of maintaining a drive voltage as claimed in claim 4, wherein the auxiliary power supply comprises an external power supply for generating an output voltage and a DC-DC converter, the method further comprising the step of determining that the output voltage of the auxiliary power supply is smaller than an output voltage of the external power supply.