JP2007115442A - Control circuit for fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide the control circuit for a fuel cell which detectes voltage of an individual cell and controlling the output of the fuel cell according to the detected voltage. <P>SOLUTION: The control circuit 21 for the fuel cell which controls the output of the fuel cell 20 in which a plurality of cells are connected in series and in a multistage, is equipped with: a detecting means 22 for detecting the maximum voltage V<SB>max</SB>and the minimum voltage V<SB>min</SB>from the voltages of the plurality of cells; a comparing means 23 for comparing the maximum voltage V<SB>max</SB>and the minimum voltage V<SB>min</SB>detected by the detecting means 22 with first reference voltage V<SB>ref1</SB>and a second reference voltage V<SB>ref2</SB>, respectively; and a control means for controlling the output of the fuel cell 20 according to the compared result with the comparing means 23. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fuel cell control circuit that controls the output of a fuel cell in which a plurality of battery cells are connected in multiple stages in series.

  Since fuel cells produce electricity by electrochemical reaction of hydrogen and oxygen, there is no emission of carbon dioxide and other harmful substances, and in recent years there has been increasing interest as a new energy that is environmentally friendly.

  A fuel cell is composed of a number of single cells connected in series (stacked) that are sandwiched by sandwiching the top and bottom of a MEA (Membrane Electrode Assembly) that combines an air electrode, an electrolyte, and a fuel electrode. Made. The separator of the cell is provided with a groove, and hydrogen gas, air (oxygen) and the like as fuel for generating electricity are injected from the groove. The theoretical electromotive force of the cell is about 1.23V, but the actual electromotive force is about 0.3V. Therefore, the fuel cell has a structure in which a large number of cells are stacked in series. Such a structure is generally called a “cell stack”.

  In the cell stack, the overall cell balance is important, but if this balance is lost and the fuel flow rate of some cells decreases, the battery performance deteriorates, such as a drop in the electromotive force between the electrodes or an increase in the resistance of the electrode reaction. It can happen or the life of the battery can be shortened. In addition, when a reverse voltage is accidentally applied to the fuel cell, a gas is generated between the electrolyte and the electrode, which may cause an increase in resistance of the electrode reaction or physical destruction such as peeling.

Japanese Patent Laid-Open No. 8-50902 (see Patent Document 1) discloses a fuel cell power generator that eliminates the influence of reverse voltage generated between each cell stack when a plurality of cell stacks are connected in parallel. ing. FIG. 1 quotes the block diagram of the fuel cell power generator disclosed in Patent Document 1. From FIG. 1, the fuel cell power generation device of Patent Document 1 is configured such that a diode is connected to both ends of a cell stack in a direction in which a generated current can flow, and such cell stacks are connected in parallel. Therefore, even when the power generation voltage of either of the two cell stacks becomes high, the exchange of reverse voltage between the two cell stacks is suppressed by the diodes at both ends of each cell stack, and the battery of Destruction can be avoided.
JP-A-8-50902

  However, although the invention described in Patent Document 1 can avoid the destruction of the battery due to the reverse voltage, the state of each cell in the cell stack is unknown and the abnormality of the cell cannot be detected. There is a problem.

  The present invention has been made in order to solve such a problem, the voltage of each cell is detected, whether the detected voltage is lower than a reference voltage serving as a lower limit for detecting a cell abnormality, Alternatively, an object of the present invention is to provide a fuel cell control circuit that controls the output of the fuel cell according to whether the reference voltage that is the upper limit for detecting an abnormality of the cell is exceeded.

  In order to achieve the above object, a fuel cell control circuit according to the present invention has the following characteristics.

  The fuel cell control circuit of the present invention is a fuel cell control circuit for controlling the output of a fuel cell in which a plurality of battery cells are connected in multiple stages in series, and a detecting means for detecting a minimum voltage from the voltages of the plurality of battery cells; Comparing means for comparing the minimum voltage detected by the detecting means with a reference voltage, and control means for controlling the output of the fuel cell when the minimum voltage is lower than the reference voltage by the comparing means. Features.

  Among the plurality of battery cells connected in multiple stages in this way, when the lowest voltage of the detected battery cell is lower than the reference voltage, the cell balance is broken, so the output of the fuel cell is controlled, The performance deterioration of the fuel cell can be prevented.

  The fuel cell control circuit of the present invention is a fuel cell control circuit for controlling the output of a fuel cell in which a plurality of battery cells are connected in multiple stages in series. The detecting means detects the highest voltage from the voltages of the plurality of battery cells. And comparison means for comparing the highest voltage detected by the detection means with a reference voltage, and control means for controlling the output of the fuel cell when the highest voltage exceeds the reference voltage by the comparison means. It is characterized by that.

  Among the plurality of battery cells connected in multiple stages in this way, when the detected maximum voltage of the battery cell exceeds the reference voltage, the cell balance is broken, so the output of the fuel cell is controlled, The shortening of the life of the fuel cell can be prevented.

  The fuel cell control circuit of the present invention is a fuel cell control circuit for controlling the output of a fuel cell in which a plurality of battery cells are connected in series in a plurality of stages, wherein each connection point of the plurality of battery cells is set at a predetermined interval T. Switching means for switching the switching means, delay means for delaying a signal indicating the voltage at the connection point switched by the switching means by a time T, and a reference for generating a reference voltage for each connection point corresponding to the switching of the switching means. A voltage generating means, a comparing means for comparing the voltage at the connection point switched by the switching means with a reference voltage generated by the reference voltage generating means, and controlling the output of the fuel cell according to the output of the comparing means And a control means.

  As described above, by detecting the voltage of each cell and comparing the voltage with the reference voltage by one comparison means, it is possible to detect a cell abnormality in real time. In addition, since it is not necessary to measure the voltages of all the cells, the configuration can be simplified.

  The fuel cell control circuit of the present invention is a fuel cell control circuit for controlling the output of a fuel cell in which a plurality of battery cells are connected in series in a plurality of stages, wherein each connection point of the plurality of battery cells is set at a predetermined interval T. Switching means for switching at the same time, delay means for delaying a signal indicating the voltage at the connection point switched by the switching means by time T, voltage at the connection point switched by the switching means and voltage delayed by the delay means Differential means for outputting a difference from the voltage of the signal indicating the difference, comparison means for comparing the output of the difference means with a reference voltage, and control means for controlling the output of the fuel cell in accordance with the output of the comparison means; It is characterized by having.

  As described above, by detecting the voltage of each cell and comparing the voltage and the reference voltage sequentially, it is possible to detect the abnormality of the cell in real time. In addition to not having to measure the voltages of all cells, there is no need to provide a means for generating a reference voltage corresponding to the switching of the switching means, and if a constant voltage source is used as the reference voltage, Since it is good, the configuration can be further simplified.

  Furthermore, in the fuel cell control circuit of the present invention, the control means controls the output of the fuel cell from the output time of the comparison means, controls the output of the fuel cell after a certain time from the output time of the comparison means, or The output of the fuel cell is controlled so as to gradually decrease the output from the output point of the comparison means.

  Thus, the control operation can be selected according to the load of the output stage of the fuel cell. Further, when the output is controlled after a certain time from the output time of the comparison means, or when the output of the fuel cell is controlled so as to gradually decrease the output from the output time of the comparison means, stable control can be performed.

  According to the fuel cell control circuit of the present invention, the voltage of each cell of the fuel cell is detected, and the detected voltage falls below the reference voltage that is the lower limit for detecting the cell abnormality or the cell abnormality is detected. The output of the fuel cell can be controlled according to whether the reference voltage that is the upper limit for detection is exceeded.

  The form of the Example of this invention is demonstrated with reference to drawings.

〔Constitution〕
FIG. 2 is a diagram showing an example of a basic configuration of a fuel cell system having a control circuit according to the present invention. The fuel cell system of FIG. 2 includes a fuel cell 20 made by connecting a plurality of battery cells in series, a control circuit 21, a control output control switch 26, and a power storage device 27, and its output is connected to a load 25. ing. The control circuit 21 is a means for controlling the output of the fuel cell 20 in accordance with the voltages of a plurality of battery cells, and includes a detection means 22, a comparison means 23, and a control means 24.

Detecting means 22 is a means for detecting the maximum voltage _{V max} and the minimum voltage _{V min} from the voltage of the plurality of battery cells of the fuel cell 20, the cell voltage measuring unit 221, a memory 222, the maximum voltage detecting unit 223 and the minimum voltage It has a detection means 224. Each cell voltage measuring means 221 measures the voltage of each cell of the fuel cell 20. The memory 222 stores the cell voltage measured by each cell voltage measuring means 221. The maximum voltage detecting means 223 detects the maximum voltage V _max from the cell voltage stored in the memory 222. The lowest voltage detection unit 224 detects the lowest voltage V _min from the cell voltage stored in the memory 222. The highest voltage V _max detected by the highest voltage detection means and the lowest voltage V _min detected by the lowest voltage detection means are supplied to the comparison means 23.

The comparison unit 23 is a unit that compares the maximum voltage V _max detected by the detection unit 22 with the first reference voltage V _ref1 and the minimum voltage V _min with the second reference voltage V _ref2 . The first reference voltage V _ref1 is a reference voltage for detecting an abnormality when the voltage of a single cell rises, and the second reference voltage V _ref2 is a voltage of a single cell. When the voltage drops, the voltage becomes a reference for detecting the abnormality. These comparison results are supplied to the control means 24.

The control means 24 is means for controlling the output of the fuel cell according to the comparison result in the comparison means 23, and the maximum voltage V _max exceeds the first reference voltage V _ref1 or the minimum voltage V _min is the second voltage V _min . The control signal is transmitted to the output control switch 26 when it falls below the reference voltage V _ref2 .

  The output control switch 26 is a switch for controlling the output of the fuel cell 20 and operates to control the power supply from the fuel cell 20 to the load 25 in accordance with a control signal from the control means 24.

The power storage device 27 is provided in parallel before the load 25 in order to cope with the peak current of the load 27. For example, it may be a secondary battery or a high capacity capacitor.
[Operation]
[Normal operation]
The normal operation when power is supplied from the fuel cell 20 to the load 25 will be described. In this operation, the output control switch 26 operates so that electric power is supplied to the load 25. The electric power of the fuel cell 20 is supplied to the load 25 via the output control switch 26 and further charges the power storage device 27.
[Operation at the time of abnormality (part 1)]
A case will be described in which the voltage of one cell of the fuel cell 20 decreases and the cell balance of the entire fuel cell 20 is lost.

Each cell voltage measuring means 221 of the detecting means 22 measures the voltage of each cell of the fuel cell 20, and those voltages are stored in the memory 222. The voltage of the stored cell memory 222, the maximum voltage detecting means 223 is the maximum voltage _{V max,} the minimum voltage detecting means 224 detects the minimum voltage _{V min.} The detected maximum voltage V _max and minimum voltage V _min are compared with the first and second reference voltages V _ref1 and V _ref2 by the comparison means 23, respectively. In a state where the voltage of one cell of the fuel cell 20 is lowered and the cell balance of the entire fuel cell 20 is lost, the minimum voltage V _min is lower than the second reference voltage V _ref2 in the comparison unit 23. As a result, the control unit 24 transmits a control signal for cutting off or reducing the output of the fuel cell 20 to the output control switch 26. The output control switch 26 operates to cut off or reduce the power supply from the fuel cell 20 to the load 25 when the comparison result is output from the comparison means 23 (that is, when the minimum voltage _Vmin is detected). .
[Operation at the time of abnormality (2)]
The case where the voltage of one cell of the fuel cell 20 rises and the cell balance of the entire fuel cell 20 is lost will be described.

Each cell voltage measuring means 221 of the detecting means 22 measures the voltage of each cell of the fuel cell 20, and those voltages are stored in the memory 222. The voltage of the stored cell memory 222, the maximum voltage detecting means 223 is the maximum voltage _{V max,} the minimum voltage detecting means 224 detects the minimum voltage _{V min.} The detected maximum voltage V _max and minimum voltage V _min are compared with the first and second reference voltages V _ref1 and V _ref2 by the comparison means 23, respectively. When the voltage of one cell of the fuel cell 20 rises and the cell balance of the entire fuel cell 20 is lost, the maximum voltage V _max exceeds the first reference voltage V _ref1 in the comparison unit 23. As a result, the control unit 24 transmits a control signal for cutting off or reducing the output of the fuel cell 20 to the output control switch 26. Output control switch 26, when the comparison result from the comparing means 23 is output (i.e., the maximum voltage V _max is the time it was detected) operates to cut off or reduce the power supply from the fuel cell 20 to the load 25 . [Return from abnormal condition]
The operation of restarting the power supply that has been cut off due to the abnormal state of the cell will be described.

The detection means 22 measures the voltage of each cell and detects the maximum voltage V _max and the minimum voltage V _min as described above, and the detected maximum voltage V _max and minimum voltage V _min are detected by the comparison means 23. The first and second reference voltages V _ref1 and V _ref2 are respectively compared. When the comparison means 23 confirms that the maximum voltage V _max and the minimum voltage V _min are within the range of the first reference voltage V _ref1 to the second reference voltage V _ref2 , the control means 24 performs output control. A control signal is transmitted to the switch 26 so that the power supply to the load 25 is resumed. The output control switch 26 operates according to a signal from the control means 24 so as to release the interruption of the output or gradually increase the lowered output amount.

As described above, the fuel cell control circuit according to the present embodiment detects the voltage of each cell, and detects whether the detected voltage is lower than the reference voltage that is the lower limit for detecting the cell abnormality or detects the cell abnormality. Therefore, it is possible to control the output of the fuel cell depending on whether the reference voltage that is the upper limit to do so is exceeded.
[Modification]
In this embodiment, the detection means 22 detects both the maximum voltage and the minimum voltage of a plurality of cells of the fuel cell. However, either the maximum voltage or the minimum voltage is detected depending on the purpose of detection and control or the convenience of the circuit configuration. It may be configured to detect only one. Even in such a case, the operation of the fuel cell system is the same as that described above.

  In this embodiment, the output control of the fuel cell 20 is performed by the operation of the output control switch 26, but the amount of fuel (for example, alcohol) injected into the fuel cell is controlled. Also good. In that case, the control means 24 transmits a control signal to a means (not shown) for controlling fuel injection.

In this embodiment, the output control switch 26 outputs the output of the fuel cell 20 at the time when the comparison result is supplied from the comparison means 23 to the control means 24 (that is, when the highest voltage and / or the lowest voltage is detected). the was operated to interrupt or reduce, compared to operate after a predetermined time T _o from a supply point results, or comparison may be controlled so as to gradually reduce its output operates from a supply time point t _d results . FIG. 3 shows the output of the fuel cell shut off by such control. In FIG. 3, the output when the output control switch 26 is controlled to operate from the output time t _d of the comparison means 23 by the signal from the control means 24 is (1), and the output time t of the comparison means 23 is output when controlled to operate after a predetermined time T _o from _d is (2), or the output when it is controlled to gradually decrease the output operates from the output time t _d of the comparison means 23 Is represented by (3).

〔Constitution〕
FIG. 4 is a diagram showing a partial configuration of a fuel cell control circuit according to another embodiment of the present invention. In FIG. 4, the fuel cell control circuit of the present invention comprises a switching means 41, a delay means 42, a reference voltage generating means 43, a comparing means 44, and a control means 45. The switching means 41 is means for switching the connection points of the plurality of battery cells of the fuel cell 40 with a predetermined interval T. The delay means 42 is a means for delaying the signal indicating the voltage at the connection point switched by the switching means 41 by time T. The reference voltage generating means 43 is a means for generating a reference voltage for each connection point in accordance with the switching of the switching means 41, and adds the initial voltage _Vz and the voltage of the signal indicating the voltage delayed by the delay means 42. To generate a reference voltage. The initial voltage V _z is a reference voltage for detecting an abnormality when the voltage of a single cell drops. The comparison means 44 is shown in the form of an operational amplifier in FIG. 4 and is a means for comparing the voltage at the connection point switched by the switching means 41 with the reference voltage generated by the reference voltage generation means 43. The control means 45 is means for controlling the output of the fuel cell 40 in accordance with the output of the comparison means 44, and the output is supplied to the output control switch of the fuel cell system.

For example, the reference voltage generating means 43 is constituted by an analog circuit as shown in FIG. In FIG. 5, the reference voltage generating means 43 is configured by combining two circuits of operational amplifiers. The first-stage circuit is an adder circuit that adds the initial voltage V _z determined by the Zener diode and the input voltage from the delay means 42. The second-stage circuit is an inverting circuit for further inverting and returning the output of the first-stage adder circuit with respect to the input. The output of this inverting circuit becomes the reference voltage input to the comparison means 44 in FIG.

In FIG. 4, the number of battery cells constituting the fuel cell 40 is four. At that time, voltages at both ends of each cell are represented as V ₁ , V ₂ , V ₃ , V ₄ , respectively. It is assumed that terminals coming from connection points between cells are represented as J ₁ , J ₂ , J ₃ , and J ₄ .
[Operation]
[Normal operation]
First, the switching means 41, it switched to the point A is connected to the terminal J _1. Thus, the voltage at terminal J ₁ to be supplied to the inverting input terminal of the delay means 42 and comparing means 44, the voltage V ₁ of the first cell. The reference voltage generating means 43 has an initial voltage V _z at this time, and the initial voltage V _z is supplied to the non-inversion side input terminal of the comparison means 44 as a reference voltage. The comparison means 44 outputs a difference X ₁ (= V _z −V ₁ ) between the voltage V ₁ of the first cell and the reference voltage V _z . A cell abnormality is detected by determining whether the difference is positive or negative. Since the initial voltage V _z is a reference voltage for detecting an abnormality when the voltage of a single cell is lowered, when the voltage V ₁ of the first cell is lower than this, the first cell V _z Can be determined to be abnormal. If the voltage V ₁ of the first cell does not fall below the initial voltage V _z , the switching means 41 switches so that the point A is connected to the terminal J ₂ after a certain time T.

When the point A is connected to terminal J _2, the voltage at the terminal J ₂ is supplied to the inverting input terminal of the delay means 42 and comparing means 44, the voltage V ₁ of the first cell voltage of a second cell is the sum _V 1 + _{V 2} and V _2. On the other hand, the delay means 42 delays the signal indicated by the input voltage by the time T, and therefore outputs the voltage V ₁ of the first cell input previously. The reference voltage generating means 43 generates a reference voltage by adding the initial voltage V _z and the output V ₁ of the delay means 42. That is, the reference voltage supplied to the non-inverting input terminal of the comparator means 44 is the sum V _z + V ₁ of the voltage V ₁ of the initial voltage V _z and the first cell. The comparison means 44 outputs the difference X ₂ (= (V _z + V ₁ ) − (V ₁ + V ₂ ) = V _z −V ₂ ) between the voltage V ₁ + V _{2 at} the terminal J ₂ and the reference voltage V _z + V _1. To do. Therefore, when the voltage V ₂ of the second cell does not fall below the initial voltage V _z , the switching means 41 switches so that the point A is connected to the terminal J ₃ after a certain time T.

Hereinafter, A point similar processing is performed also when connected to the terminal J ₃ and J _4, the voltage of each cell is detected and compared. When the voltage is detected and compared for all four cells, the process returns to the beginning and again detects and compares the voltage of the first cell. Of course, the same applies to the case where the number of cells is four or more or less.

  FIG. 6 shows transitions over the switching time of the switching means 41 for the reference voltage generated by the reference voltage generating means 43 in FIG. 4, the voltage at the point A, and the output voltage of the comparing means 44.

Switching means 41 is connected at time t = _{t 0} the point A to the terminal _{J 1,} then after the time T has elapsed, switched to connect the point A to the terminal _{J 2.} Assuming that the delay time associated with this switching is α, the point A is connected to J ₁ from time t ₀ to t ₀ + T−α. As described above, the reference voltage at that time is the initial voltage V _z . There, the voltage at point a is the voltage _{V 1} of the first cell, the output of the comparison means 44 are these differences _{X 1} = V _z -V 1. Further, after time T has elapsed, that is, at time t = t ₀ + 2T, the switching means 41 switches so as to connect the point A to the terminal J ₃ . Similarly, from time t ₀ + T to t ₀ + T−α, the point A is connected to J ₂ , and the reference voltage at that time is the sum of the initial voltage V _z and the voltage V ₁ of the first cell. V _z + V ₁ , and the voltage at point A is the sum V ₁ + V ₂ of the voltage V ₁ of the _first cell and the voltage V ₂ of the second cell, and the output of the comparison means 44 is the difference between these it is X ₁ = V _z -V _2. Hereinafter, the same applies to the case where the point A by switching means 41 is connected to the terminal J ₃ and J _4.
[Operation at the time of abnormality]
In the fuel cell control circuit of FIG. 4, a case is considered where the voltage of the i-th cell of the fuel cell 40 decreases and the cell balance of the entire fuel cell 40 is lost. _Assuming that the voltage of the i-th cell whose voltage has _dropped is V _low , the output of the comparison unit 44 at this time is X _i = V _z −V _low . Since the initial voltage V _z is a reference voltage for detecting an abnormality when the voltage of a single cell decreases, the cell voltage V _low is lower than the initial voltage V _z , that is, X _i is If positive (X _i > 0), the cell is abnormal. When it is detected that the cell is abnormal, the control means transmits a control signal to the output control switch so as to cut off or reduce the output of the fuel cell. In response to the control signal, the output control switch operates to cut off or reduce the output of the fuel cell 40 when it is detected that the cell is abnormal.

  As described above, the fuel cell control circuit according to the present embodiment detects the voltage of each cell, and controls so as to cut off or reduce the output of the fuel cell when the detected voltage becomes a predetermined voltage or less. Can do.

Furthermore, the fuel cell control circuit according to the present embodiment measures the voltage of each cell at regular intervals, whereas the fuel cell control circuit according to the first embodiment measures the voltage of all the cells of the fuel cell. However, it is possible to detect an abnormality in the voltage of each individual cell in real time. Therefore, an abnormal cell can be easily identified. Furthermore, since it is not necessary to measure the voltages of all the cells, the configuration is simplified compared to the first embodiment.
[Modification]
In this embodiment, the initial voltage V _z of the reference voltage generating means 43 in FIG. 4 is a reference voltage for detecting an abnormality when the voltage of a single cell is lowered. When the voltage of the cell rises, it may be a reference voltage for detecting the abnormality. In this case, the comparison means 44 is set to detect a cell abnormality when the output X _i is negative (X _i <0). Therefore, when the detected voltage becomes equal to or higher than a predetermined voltage, it is possible to control the output of the fuel cell to be cut off or reduced.

〔Constitution〕
FIG. 7 is a diagram showing a partial configuration of a control circuit according to still another embodiment of the present invention. In FIG. 7, the control circuit of the present invention includes a switching means 71, a delay means 72, a difference means 73, a comparison means 74, and a control means 75. As in the second embodiment, the switching unit 71 is a unit that switches each connection point of the plurality of battery cells of the fuel cell 70 with a predetermined interval T, and the delay unit 72 is a connection point that is switched by the switching unit 71. This is a means for delaying a signal indicating the voltage of time by time T. The difference means 73 is shown in FIG. 7 in the form of an operational amplifier, and is a means for outputting the difference between the voltage at the connection point switched by the switching means 71 and the signal voltage indicating the voltage delayed by the delay means. The comparison means 74 is shown in FIG. 7 in the form of an operational amplifier, and is a means for comparing the output of the difference means 73 with the reference voltage _Vref . The reference voltage V _ref is a voltage that serves as a reference for detecting an abnormality when the voltage of a single cell drops. The control means 75 is means for controlling the output of the fuel cell 70 in accordance with the output of the comparison means 74, and the output is supplied to the output control switch of the fuel cell system.

In FIG. 7, the number of battery cells constituting the fuel cell 70 is four. At that time, the voltages at both ends of each cell are represented as V ₁ , V ₂ , V ₃ , V ₄ . It is assumed that terminals coming from connection points between cells are represented as J ₁ , J ₂ , J ₃ , and J ₄ .
[Operation]
[Normal operation]
First, the switching means 71, it switched to the point A is connected to the terminal J _1. Thus, the voltage at terminal J ₁ to be supplied to the non-inverting input terminal of the delay unit 72 and the differential unit 73 is the voltage V ₁ of the first cell. At this time, 0 V is output from the delay means 72, and this is supplied to the inverting side input terminal of the difference means 73. The difference means 73 outputs the voltage V ₁ of the first cell of the fuel cell 70 because the voltage supplied to the inverting input terminal is 0V. The comparison means 74 compares the voltage V ₁ with the reference voltage V _ref , and the output is the difference X ₁ (= V _ref −V ₁ ) between the voltage V ₁ of the first cell and the reference voltage V _ref. . A cell abnormality is detected by determining whether the difference is positive or negative. Since the reference voltage V _ref is a reference voltage for detecting an abnormality when the voltage of a single cell drops, the reference voltage V _ref is the first cell when the voltage V ₁ of the first cell is lower than this. Can be determined to be abnormal. If the voltage V ₁ of the first cell is not less than the reference voltage V _ref, switching means 71 is switched to the point A is connected to the terminal J ₂ after a predetermined time T.

When the point A is connected to terminal J _2, the non-inverting side voltage terminal J ₂ supplied to the input terminal of the delay unit 72 and the differential unit 73 includes a voltage V ₁ of the first cell of the second cell is the sum _V 1 + _{V 2} between the voltage _{V 2.} On the other hand, the delay means 72 delays the signal indicated by the input voltage by the time T, and therefore outputs the voltage V ₁ of the first cell input previously. The difference means 73 is supplied with this voltage V ₁ at its inverting side input terminal, and outputs the voltage V ₂ (= (V ₁ + V ₂ ) −V ₁ ) of the second cell of the fuel cell 70. The comparison means 74 compares the voltage V ₂ of the second cell with the reference voltage V _ref, and the output is the difference X ₂ (= V _ref −) between the voltage V ₂ of the second cell and the reference voltage V _ref. V ₂ ). Therefore, when the voltage V ₂ of the second cell is not less than the reference voltage V _ref, switching means 71 is switched to the point A is connected to the terminal J ₃ after a predetermined time T.

Hereinafter, A point similar processing is performed also when connected to the terminal J ₃ and J _4, the voltage of each cell is detected and compared. When the voltage is detected and compared for all four cells, the process returns to the beginning and again detects and compares the voltage of the first cell. Of course, the same applies to the case where the number of cells is four or more or less.

  FIG. 8 shows transitions over the switching time of the switching means 71 for the output voltage of the delay means 72 and the voltage at the point A, the output voltage of the difference means 73 and the output voltage of the comparison means input to the difference means 73 of FIG. .

The switching means 71 switches the point A to the terminal J ₁ at time t = t ₀ , and then switches to connect the point A to the terminal J ₂ after the time T has elapsed. Assuming that the delay time associated with this switching is α, the point A is connected to J ₁ from time t ₀ to t ₀ + T−α, and as described above, the output of the delay means 72 at that time is zero. Yes, the voltage at point A is the voltage V ₁ of the first cell, the output of the difference means 73 is the difference between them, that is, the voltage V ₁ of the first cell, and the output of the comparison means 74 is the reference voltage A difference X ₁ = V _ref −V ₁ between V _ref and the output of the difference means 73, that is, the voltage V ₁ of the first cell. Further, after the time T has elapsed, that is, at time t = t ₀ + 2T, the switching means 71 switches so as to connect the point A to the terminal J ₃ . Similarly, between time t ₀ + T and t ₀ + T−α, point A is connected to J ₂ , and the output of the delay means 72 at that time is the voltage V ₁ of the first cell, and point A Is a sum V ₁ + V ₂ of the voltage V ₁ of the _first cell and the voltage V ₂ of the second cell, and the output of the difference means 73 is the difference between them, that is, the voltage V of the second cell. ₂ and the output of the comparison means 74 is the difference X ₂ = V _ref −V ₂ between the reference voltage V _ref and the output of the difference means 73, that is, the voltage V ₂ of the second cell. Hereinafter, the same applies to the case where the point A is connected to the terminals J ₃ and J ₄ by the switching means 71. From FIG. 8, it can be seen that the difference means 73 outputs the voltage of each cell of the fuel cell, and the output is compared with the reference voltage.
[Operation at the time of abnormality]
In the fuel cell control circuit of FIG. 7, consider a case where the voltage of the i-th cell of the fuel cell 70 decreases and the cell balance of the entire fuel cell 70 is lost. _Assuming that the voltage of the i-th cell whose voltage has _dropped is V _low , the output of the difference means 73 is V _low . At this time, the comparing means 74 compares the output voltage V _low of the difference means 53 with the reference voltage V _ref, and the output is X _i = V _ref −V _ilow . Since the initial reference voltage V _ref is a reference voltage for detecting an abnormality when the voltage of a single cell drops, the _initial reference voltage V _ref is lower than the reference voltage V _ref , that is, X _i. Is positive (X _i > 0), the cell is abnormal. When it is detected that the cell is abnormal, the control means transmits a control signal to the output control switch so as to cut off or reduce the output of the fuel cell. In response to this control signal, the output control switch operates to cut off or reduce the output of the fuel cell 70 when it is detected that the cell is abnormal.

  As described above, the fuel cell control circuit according to the present embodiment can sequentially detect the cell voltages, and control so as to cut off or reduce the output of the fuel cell when the detected voltage becomes a predetermined voltage or less. it can.

Further, the fuel cell control circuit according to the present embodiment is switched as in Embodiment 2 in addition to the advantages that the fuel cell control circuit according to Embodiment 2 has over the fuel cell control circuit according to Embodiment 1. There is no need to provide a means for generating a reference voltage corresponding to the switching of the means, and a constant voltage source may be used as the reference voltage, so that it has the advantage of being simpler than any of the embodiments described above. .
[Modification]
In the present embodiment, the reference voltage V _ref of the comparison means 74 in FIG. 7 is a voltage that serves as a reference for detecting an abnormality when the voltage of a single cell drops. When the voltage rises, it may be a reference voltage for detecting the abnormality. In this case, the comparison means 74 is set to detect a cell abnormality when its output X _i is negative (X _i <0). Therefore, when the detected voltage becomes equal to or higher than a predetermined voltage, it is possible to control the output of the fuel cell to be cut off or reduced.

  In any of the embodiments using the fuel cell control circuit of the present invention, the operational amplifier is used as the comparison means, and the analog output is output to the control means. However, the logic signal converted by the logic circuit is output to the control means. You may do it. Furthermore, the output of the comparison means may be subjected to a modulation process such as frequency modulation or amplitude modulation, or may be an analog output and its output adjusted at an appropriate ratio. Other components may also be configured by either analog circuits or digital circuits, and it is sufficiently conceivable to adopt configurations other than the examples given in this specification.

1 is a configuration diagram of a fuel cell power generator disclosed in Japanese Patent Application Laid-Open No. 8-50902. It is a figure which shows the basic structural example of the fuel cell system which has a control circuit of this invention. It is a figure which shows the fuel cell control operation | movement by the control circuit of this invention. It is a one part block diagram of the control circuit which concerns on another Example of this invention. FIG. 5 is a diagram illustrating a configuration example of the reference voltage generating unit of FIG. 4 by an analog circuit. FIG. 5 is a diagram illustrating voltages at various parts of the control circuit in FIG. 4. It is a one part block diagram of the control circuit which concerns on another Example of this invention. It is a figure which shows the voltage of each part of the control circuit of FIG.

Explanation of symbols

1, 1A, 1B Series stack 2 Fuel cell stack (cell stack)
3 Charging / Discharging Switch 4 Inverter 5 Transformer 6 Diode 10, 20, 40, 50 Fuel Cell 21 Control Circuit 22 Detection Unit 23, 44, 74 Comparison Unit 24, 45, 75 Control Unit 25 Load 26 Output Control Switch 27 Power Storage Device 221 Each cell voltage measuring means 222 Memory 223 Maximum voltage detecting means 224 Minimum voltage detecting means 41, 71 Switching means 42, 72 Delay means 43 Reference voltage generating means 73 Difference means A, J ₁ , J ₂ , J ₃ , J ₄ terminals
R resistor _{T o, t, t d,} t 0, α Time _{V max} maximum voltage _{V min} minimum voltage _{V ref, V ref1, V ref2} reference voltage V _z initial voltage _{V 1, V 2, V 3} , V 4, V _n-1 , V _n cell voltage X ₁ , X ₂ , X ₃ , X ₄ output of comparison means

Claims (5)

In a fuel cell control circuit for controlling the output of a fuel cell in which a plurality of battery cells are connected in multiple stages in series,
Detecting means for detecting a minimum voltage from the voltages of the plurality of battery cells;
A comparing means for comparing the lowest voltage detected by the detecting means with a reference voltage;
And a control means for controlling the output of the fuel cell when the comparison means causes the minimum voltage to fall below the reference voltage. In a fuel cell control circuit for controlling the output of a fuel cell in which a plurality of battery cells are connected in multiple stages in series,
Detecting means for detecting a maximum voltage from the voltages of the plurality of battery cells;
Comparison means for comparing the highest voltage detected by the detection means with a reference voltage;
And a control means for controlling the output of the fuel cell when the highest voltage exceeds the reference voltage in the comparison means. In a fuel cell control circuit for controlling the output of a fuel cell in which a plurality of battery cells are connected in series in multiple stages,
Switching means for switching each connection point of the plurality of battery cells at a predetermined interval T;
Delay means for delaying a signal indicating the voltage at the connection point switched by the switching means by a time T;
Reference voltage generating means for generating a reference voltage for each connection point corresponding to the switching of the switching means;
A comparing means for comparing the voltage at the connection point switched by the switching means with the reference voltage generated by the reference voltage generating means;
And a control means for controlling the output of the fuel cell in accordance with the output of the comparison means. In a fuel cell control circuit for controlling the output of a fuel cell in which a plurality of battery cells are connected in multiple stages in series,
Switching means for switching each connection point of the plurality of battery cells at a predetermined interval T;
Delay means for delaying a signal indicating the voltage at the connection point switched by the switching means by a time T;
Differential means for outputting the difference between the voltage at the connection point switched by the switching means and the voltage of the signal indicating the voltage delayed by the delay means;
Comparing means for comparing the output of the difference means and a reference voltage;
And a control means for controlling the output of the fuel cell in accordance with the output of the comparison means.   The control means controls the output of the fuel cell from the output time of the comparison means, controls the output of the fuel cell after a certain time from the output time of the comparison means, or gradually from the output time of the comparison means. The fuel cell control circuit according to any one of claims 1 to 4, wherein the output of the fuel cell is controlled so as to reduce its output.

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