JP2012033500A - Fuel cell system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small fuel cell system capable of taking a configuration with simple structure, preventing power generation in an overload state of a fuel cell, preventing deterioration of the fuel cell system, and obtaining stable output from the fuel cell, in the fuel cell system using the fuel cell as a power supply.SOLUTION: An overload state of all single cells 1a, 1b, and 1c constituting a fuel cell is detected. If the overload state is detected, fuel cell output is controlled so that the fuel cell output is cut off or the cell in the overload state is returned to a normal power generation state.

Description

  The present invention relates to a fuel cell system, and in particular, has been devised so as to be useful as a power source of a small electronic device such as a portable device by preventing deterioration of a fuel cell single cell due to inversion or overload.

  In recent years, power consumption of mobile devices typified by mobile phones has been steadily increasing as the functionality of the devices has increased, and improving the capacity of the power source has become a major issue. Under such circumstances, fuel cells are attracting attention as small energy power sources with high energy density.

  In a fuel cell, two types of electrodes are sandwiched between electrolytes, and electricity is generated by oxidizing a fuel such as hydrogen or methanol at a fuel electrode and reducing oxygen in the atmosphere at an oxygen electrode. Among the fuel cells, the polymer electrolyte fuel cell (PEFC) is capable of generating power near room temperature and has high output density and can be miniaturized, so it is expected to be applied as a power source for portable devices. Has been.

  When a fuel cell is used as a power source, the practical operating voltage of a single cell of the fuel cell is around 0.5V. Therefore, in order to obtain a voltage necessary for a practical load, the required number of single cells are connected in series to obtain a predetermined high output voltage.

  Thus, by connecting the single cells of the fuel cell in series, a high voltage / high output fuel cell can be obtained. However, when a plurality of single cells are connected in series, the output of each single cell is Due to the variation, there arises a problem that the power generation performance of the fuel cell as an assembly of the single cells deteriorates. This is because a single cell with low power generation performance becomes a resistance component and reduces the output of the fuel cell. For this reason, in order to suppress the variation in the output of each single cell, a device has been proposed such as controlling the fuel supply method using auxiliary devices or the like (see, for example, Patent Document 1).

Japanese Patent Laid-Open No. 06-103998 (page 3, FIG. 1)

  Fuel cells have lower load responsiveness than primary batteries, secondary batteries, etc., and cause a voltage drop due to various overvoltages (activation overvoltage, resistance overvoltage, diffusion overvoltage) as the load current increases. Furthermore, even if the load current value is constant, the output voltage from the fuel cell has a larger voltage fluctuation range than the primary battery or the secondary battery. In particular, in the power generation region where the influence of the voltage drop of the fuel cell voltage due to the diffusion overvoltage becomes significant, the ratio of the voltage drop to the increase in load current is large.

  Application of a load in an overload state of a fuel cell having such characteristics is not preferable because it causes deterioration such as inversion of the fuel cell.

  Incidentally, the conventional fuel supply control alone cannot cope with the sudden increase in load when the fuel cell is powered or when power is supplied to an external load. In such a state, if a single cell with low power generation performance is forced to operate in an overload state, and the fuel cell continues to generate power in the presence of a single cell operating in an overload state, an overload state The single cell that is operated in the above-described manner causes performance deterioration due to deterioration of the electrolyte membrane, elution and aggregation of the catalyst metal, and the like. As a result, the output of the fuel cell system using the fuel cell including the single cell is lowered.

  Furthermore, as a fuel cell system for a small electronic device such as a portable device, the fuel supply system as described above is not suitable because the device for supplying the fuel becomes large. In particular, power supplies for small portable devices are required to be light and compact with limited dimensions. Therefore, power generation in an overloaded state of the fuel cell can be prevented without using a large volume of auxiliary equipment. It is essential that the fuel cell system prevent deterioration and obtain a stable output from the fuel cell.

  In view of the above prior art, the present invention effectively prevents the inversion / overload operation of each unit cell connected in series and constitutes the fuel cell, and also realizes the function recovery of each unit cell. The purpose is to provide.

The first aspect of the present invention for achieving the above object is as follows:
A fuel cell comprising at least two unit cells connected in series;
When the inversion / overload state is detected continuously for a predetermined time or more by the abnormality detection means for detecting power generation in the inversion / overload state of each single cell, the inversion / And protective means for cutting off the output of the fuel cell based on an overload state signal.

  According to this aspect, since the output of the fuel cell is cut off when the polarity detection / overload of the single cell is detected by the abnormality detection means, the deterioration of the single cell that is in the polarity / overload state is prevented in advance. Can be prevented. Furthermore, according to the present embodiment, since the output is shut off after a predetermined time after the inversion / overload state is detected, the influence of the chattering phenomenon is removed and the inversion / overload is accurately performed. While detecting the state, it is possible to reliably perform the output shut-off operation only when necessary.

  In particular, fuel cells have lower load responsiveness than primary batteries and secondary batteries, and at the same time, as the load current increases, voltage drops due to various overvoltages (activation overvoltage, resistance overvoltage, diffusion overvoltage) occur. Even if the load current value is constant, the output voltage from the fuel cell has a characteristic that the fluctuation range is wider than that of the primary battery or the secondary battery. Therefore, it is important from the viewpoint of effectively using the output of the fuel cell to ensure its stable operation by interposing a delay element in consideration of the load response of the fuel cell in the protection means. is there.

The second aspect of the present invention is:
A fuel cell comprising at least two unit cells connected in series;
When the inversion / overload state is detected continuously for a predetermined time or more by the abnormality detection means for detecting power generation in the inversion / overload state of each single cell, the inversion / Protection means for sending overload status signals;
And a current limiting means for starting operation upon receiving the reversal / overload state signal and controlling the output current of the fuel cell to gradually decrease.

  According to this aspect, since the output current of the fuel cell can be limited at the time when the inversion / overload of the single cell is detected by the abnormality detection means, the single cell in the inversion / overload state can be limited. Deterioration can be prevented in advance. At the same time, the current supply can be continued, although limited. Furthermore, according to this aspect, since the current limit is performed after a predetermined time after the inversion / overload state is detected, the influence of the chattering phenomenon is removed and the inversion / overload state is accurately performed. The current limiting operation can be surely performed only when necessary while detecting the above.

The third aspect of the present invention is:
A fuel cell comprising at least two unit cells connected in series;
When the polarity / overload state is detected by the abnormality detection means for detecting the power generation in the polarity / overload state of each single cell, the fuel cell is controlled based on the polarity / overload state signal representing this state. Protection means to shut off the output;
Output recovery means is provided for starting operation upon receiving the reversal / overload state signal and recovering the output of the fuel cell.

  According to this aspect, the output recovery of the fuel cell can be performed while the output of the fuel cell is cut off as in the first aspect.

The fourth aspect of the present invention is:
A fuel cell comprising at least two unit cells connected in series;
Protection means for sending a polarity / overload state signal indicating the state when the polarity / overload state is detected by an abnormality detection means for detecting power generation in the polarity / overload state of each single cell; ,
A current limiting means for starting operation upon receiving the reversal / overload state signal and controlling the output current of the fuel cell to gradually decrease;
Output recovery means is provided for starting operation upon receiving the reversal / overload state signal and recovering the output of the fuel cell.

  According to this aspect, it is possible to perform the fuel cell output recovery measure while performing the same current limitation as in the second aspect.

According to a fifth aspect of the present invention,
In the third or fourth aspect,
The inversion / overload state signal is formed on condition that the inversion / overload state is continuously detected for a predetermined time or more by the abnormality detecting means.

  According to this aspect, after the inversion / overload state is detected, the output is interrupted or the current is limited in the third or fourth aspect after a predetermined time. It is possible to accurately perform necessary operations such as shutting off the output or limiting the current only when necessary, while removing and accurately detecting the inversion and overload conditions.

The sixth aspect of the present invention is:
In any one of the third to fifth aspects,
The output recovery means is characterized in that a recovery measure is performed only for a single cell in which a polarization / overload state is detected.

  According to this aspect, the recovery measures for each single cell are performed. As a result, the treatment work required for the recovery measure is minimal.

The seventh aspect of the present invention is
In any one of the third to fifth aspects,
The output recovery means performs a recovery measure for all the single cells constituting the fuel cell including the single cells in which the inversion / overload state is detected.

  According to this aspect, an integral recovery measure is performed for the entire fuel cell. As a result, the state of each single cell can be made uniform, and the output of the single cell in which no reversal or overload is detected is improved.

The eighth aspect of the present invention is
In any one of the third to seventh aspects,
The protection means has a switch means for short-circuiting both ends of each single cell, and when a dipole / overload state is detected, both ends of the single cell in this state are short-circuited by the switch means. It is characterized by having constituted so.

  According to this aspect, the single cell in which the inversion / overload is detected is bypassed by the switch means, and the inversion / overload state can be recovered while supplying the current to the remaining cells connected in series. it can.

The ninth aspect of the present invention provides
In any one of the third to eighth aspects,
The output recovery means removes water generated near the electrode of the single cell.

  One of the root causes of inversion and overload is considered to be insufficient fuel and oxygen supply to the load. The generated water in the vicinity of the electrode not only inhibits the supply of oxygen, but the produced water may back-diffuse the electrolyte membrane and inhibit the fuel supply of the fuel electrode. Thereby, oxygen and fuel are deficient relative to the load. Therefore, the function of the single cell in the inversion / overload state can be recovered by removing the water on the electrode.

  According to this aspect, water generated in the vicinity of the electrode can be removed, so that the function of the single cell in the inversion / overload state can be recovered.

The tenth aspect of the present invention provides
In any one of the first to ninth aspects,
The protection means determines that the state is inversion or overload when the voltage at both ends of each single cell is equal to or lower than a predetermined value.

  Inversion means that the output voltage of a single cell constituting the fuel cell is inverted. That is, a state in which a negative voltage is detected from the positive electrode when the negative electrode is used as a reference. In addition, overload refers to a state in which power generation is performed in a region where the rate of decrease in the fuel cell output voltage increases as the fuel cell output current increases in the output characteristics of the fuel cell. Specifically, it refers to a power generation region in which the voltage of a single fuel cell is 65% or less of the operation voltage of the single cell.

  In this aspect, it is possible to detect an abnormality in the generated voltage by detecting the voltage at both ends of each single cell.

The eleventh aspect of the present invention is
In any one of the first to ninth aspects,
The protection means is characterized in that when the temperature of the electrode of each single cell is equal to or higher than a predetermined value, it is determined that the state is inversion or overload.

  In a fuel cell system in which the temperature of a single cell or fuel is not adjusted, the fuel cell is not heated or cooled, and therefore, a relative relationship is established between the heat generated by power generation and the output of the fuel cell. Therefore, it is not necessary to perform fuel flow, fuel humidification or heating, cell heating, etc., and is particularly a passive type fuel cell system that can grasp the output of the fuel cell by detecting the heat generation of the fuel cell. Although effective, it is possible to detect an abnormality in the generated voltage by detecting the temperature of the single cell.

The twelfth aspect of the present invention provides
In any one of the first to eleventh aspects,
The protection means further includes a counting means for counting the number of times each single cell is in a reversal / overload state, and when the reversal / overload of the same single cell is continuously detected a specified number of times or more. The output of the fuel cell is cut off.

  According to this aspect, by managing the number of times of continuous detection of the inversion / overload state, the operation efficiency as the fuel cell system is maintained as high as possible, and at the same time, the inversion / overload state is detected. By shutting off the output of the fuel cell, it is possible to appropriately protect the single cell that is in a reversal / overload state.

The thirteenth aspect of the present invention provides
In the second or fourth,
The current limiting means controls the output current to gradually decrease from the maximum output current of the fuel cell.

  According to this aspect, it is possible to perform a reasonable current limit and to obtain the maximum output current of the fuel cell at the time of recovery.

The fourteenth aspect of the present invention provides
In the thirteenth,
The current limiting means performs control so that the output current gradually decreases from the maximum output current of the fuel cell, and the return of the fuel cell to a normal state that is not a reversal / overload state is detected during the control. In this case, the output current value is fixed to the output current value at the time of return, while the same control is repeated so as to further reduce the output current when receiving the reversal / overload signal again. It is characterized by being.

  According to this aspect, it is possible to realize a reasonable current limit that prevents the deterioration of the single cell in which the inversion / overload state is detected, while maintaining the function as the fuel cell system to the maximum extent.

The fifteenth aspect of the present invention provides
In the second, fourth, thirteenth or fourteenth,
Further, the apparatus includes a current detection unit that detects an output current supplied to the external load, and is configured to reset the operation of the current limiting unit when the output current detected by the current detection unit becomes zero. And

  According to this aspect, since it is detected that there is no need to limit the current when the output current becomes zero and the operation of the current limiting unit is reset, the current supply to the next external load can be smoothly performed. Can do.

  According to the present invention, it is possible to generate power in a fuel cell inversion or overload due to a sudden increase in load when power is supplied to an external load, supply of electric power to an external load, or a shortage of fuel. Because it can prevent the fuel cell system operating efficiency as high as possible, it can prevent power generation in the degradation mode of the fuel cell and maintain the initial power generation capacity of the single fuel cell. As a result, it is possible to extend the life of the fuel cell system without deteriorating the operation efficiency.

  Further, when an appropriate recovery measure is combined, or when an output cut-off or current limit operation is performed in consideration of the number of consecutive occurrences of inversion / overload conditions, the overall operation efficiency can be further improved.

1 is a block diagram of a fuel cell power supply system according to a first embodiment of the present invention. It is a block diagram of the fuel cell power supply system which concerns on the 2nd Embodiment of this invention. It is a block diagram of the fuel cell power supply system which concerns on the 3rd Embodiment of this invention. FIG. 4 is a circuit diagram illustrating a detailed example of a boost control circuit in FIG. 3. It is a block diagram of the abnormality detection part which concerns on the 4th Embodiment of this invention. It is a block diagram of the fuel cell power supply system which concerns on the 5th Embodiment of this invention. It is a block diagram of the fuel cell power supply system which concerns on the 6th Embodiment of this invention. FIG. 8 is a circuit diagram showing a detailed example of the boost control circuit of FIG. 7. It is a block diagram of the abnormality detection part which concerns on the 7th Embodiment of this invention. It is a block diagram of the abnormality detection part which concerns on the 8th Embodiment of this invention. It is a flowchart for demonstrating the operation | movement of FIG. It is a block diagram of the abnormality detection part which concerns on the 4th Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  In general, when a polymer electrolyte fuel cell (PEFC) is used as a fuel cell, hydrogen is in a state of liquid hydrogen, hydrogen gas, or hydrogen atom, a high-pressure cylinder, a hydrogen storage alloy, a carbon nanotube, fullerene, etc. It is stored by at least one means of the group consisting of carbon materials. On the other hand, it is also possible to extract hydrogen by chemical changes such as reforming and hydrolysis of hydrogen-containing chemical substances such as alcohol, inorganic chemical hydride, and organic chemical hydride.

  On the other hand, when using a direct fuel cell such as a direct methanol fuel cell (DMFC), methanol is used as the fuel. Moreover, it is also possible to use alcohols, such as dimethyl ether (DME), 2-propanol, and ethanol, as a fuel instead of methanol. Furthermore, an aqueous solution of a metal hydride complex compound such as sodium borohydride can be used as a fuel for a direct fuel cell.

  The present invention can be applied to any type of fuel cell.

<First Embodiment>
In this embodiment, the operation of the single cell constituting the fuel cell is prevented from being operated in the inversion state. When the inversion state is detected, the output of the fuel cell is cut off.

  As shown in FIG. 1, the fuel cell system includes a PEFC fuel cell 1 that can extract electric power from fuel by a chemical reaction as a power source, and a boost control circuit 2 that boosts the output of the fuel cell 1 as a boost control circuit. 2 battery lithium ion secondary battery 3 (hereinafter abbreviated as LIB3) having a capacity of 400 mAh as a storage element, Schottky diode 4 for preventing reverse current flow of LIB3, and single fuel cell 1 The protection circuit 5 prevents the operation in a pole / overload state, and power is supplied to the external load 6.

  The fuel cell 1 is configured by connecting three unit cells 1a, 1b, and 1c of a fuel cell in series. The open circuit voltage of the fuel cell 1 was 2.93V. The output voltage value of the boost control circuit 2 was set to 8.5V. A DC electronic load device was connected to the external load 6.

  The protection circuit 5 switches the output of the fuel cell 1 with three comparators 7a, 7b, 7c, a three-input AND gate logic circuit 8 for comparing the voltages at both ends of each single cell 1a, 1b, 1c. An N-ch MOSFET 9 and a drive circuit 10 having a delay operation function for driving the N-ch MOSFET 9 are provided.

  Here, since the protection circuit 5 in the present embodiment detects power generation particularly in the inversion state, the inverting input terminals of the comparators 7a, 7b, 7c are connected to the fuel of the single cells 1a, 1b, 1c. The electrodes are directly connected, and the non-inverting input terminals are connected to the oxygen electrodes of the respective single cells 1a, 1b, 1c. The outputs of the comparators 7a, 7b, and 7c are supplied to an n-input AND gate logic circuit 8.

  The delay operation reflects the result when holding the value for 5 seconds when the polarity / overload status signal indicating the polarity / overload status is generated (actually the status signal status changes). . By interposing such a delay operation, the influence of the chattering phenomenon can be removed and the inversion / overload state can be accurately detected.

  In addition, the electronic elements used in the boost control circuit 2 and the protection circuit 5 are supplied with electric power from the LIB 3 that is a storage element. As the storage element, at least one of a group consisting of a secondary battery, a capacitor, a capacitor, and the like can be arbitrarily selected. Secondary batteries include lithium ion secondary battery, lithium polymer secondary battery, metallic lithium secondary battery, nickel metal hydride secondary battery, nickel cadmium secondary battery, nickel iron secondary battery, nickel zinc secondary battery, silver zinc oxide At least one of the group consisting of a secondary battery, a zinc halogen secondary battery, a lead storage battery, a redox flow battery, a sodium sulfur battery, and the like can be arbitrarily selected.

  In the fuel cell system according to this embodiment having the above-described configuration, when all the single cells 1a, 1b, and 1c of the fuel cell 1 perform normal power generation, the outputs of the comparators 7a, 7b, and 7c are H level. Output. Since the H level outputs of the comparators 7a, 7b, and 7c are input to the 3-input AND gate logic circuit 8, the output of the 3-input AND gate logic circuit 8 is at the H level. As a result, the drive circuit 10 turns on the N-ch MOSFET 9 and inputs the output of the fuel cell 1 to the boost control circuit 2. Thus, power can be supplied to the external load 6 via the boost control circuit 2.

  On the other hand, when at least one of the single cells 1a, 1b, 1c of the fuel cell 1 is in a reversed state, a negative voltage is output from the single cells 1a, 1b, 1c of the fuel cell 1, and the single cells 1a, 1b, One of the outputs of the comparators 7a, 7b and 7c connected to the cell in the inverted state in 1c becomes L level. As a result, all signal levels input to the 3-input AND gate logic circuit 8 are not at the H level, and the output of the 3-input AND gate logic circuit 8 is at the L level. When the output level of the 3-input AND gate logic circuit 8 continues for 5 seconds or more, the drive circuit 10 turns off the N-ch MOSFET 9. Thereby, the output of the fuel cell 1 is shut off. Thus, power generation in the inversion state is prevented. After the output of the fuel cell 1 is cut off, necessary electric power is supplied to the external load 6 via the LIB 3 that is a power storage element.

  In addition, the fuel cell 1 has a low load responsiveness compared to a primary battery or a secondary battery, and at the same time causes a voltage drop due to various overvoltages with an increase in load current, and even if the load current value is constant, The output voltage from the fuel cell has a characteristic that the fluctuation range is wider than that of the primary battery or the secondary battery. Therefore, the drive circuit 10 which is a delay element considering the load responsiveness of the fuel cell 1 is interposed in the protection circuit 5 to ensure its stable operation, so that the output of the fuel cell 1 can be used effectively. It is important from the viewpoint of doing.

<Second Embodiment>
In this embodiment, the operation of the single cell constituting the fuel cell is particularly prevented from being operated in an overload state, and the output of the fuel cell is cut off when an overload state is detected. That is, the first embodiment shown in FIG. 1 has the same configuration except that the input structure to the inverting input terminals of the comparators 7a, 7b, and 7c is different. Therefore, the same parts as those in FIG.

  As shown in FIG. 2, the inverting input terminals of the comparators 7 a, 7 b, and 7 c are connected to GND through the reference voltage generator 23. In this embodiment, the reference voltage generator is used in order to prevent power generation at 0.3 V or less in consideration of the single cell voltage at which the fuel cell 1 starts to show a significant voltage drop due to the diffusion overvoltage, which is 0.3 V. The reference voltage of 23 was set to 0.3V. The voltage of the single cells 1b and 1c is superimposed on the non-inverting input terminal of the comparator 7a, and the generated voltage of the single cell 1c is superimposed on the non-inverting input terminal of the comparator 7b. The influence of the superimposed voltage is removed by configuring so that the detection can be performed under the same conditions by the processing.

  In such a fuel cell system, when all the single cells 1a, 1b, 1c of the fuel cell 1 are generating power with a voltage of 0.3V or higher, the outputs of the comparators 7a, 7b, 7c are at the H level. Since the H level outputs of the comparators 7a, 7b, and 7c are input to the 3-input AND gate logic circuit 8, the output of the 3-input AND gate logic circuit 8 is at the H level. As a result, the drive circuit 10 turns on the N-ch MOSFET 9 and inputs the output of the fuel cell 1 to the boost control circuit 2. Thus, power can be supplied to the external load 6 via the boost control circuit 2.

  On the other hand, when at least one of the single cells 1a, 1b, 1c of the fuel cell 1 becomes 0.3 V or less, the comparator 7a connected to the overloaded cell of the single cells 1a, 1b, 1c of the fuel cell 1 , 7b, 7c become L level. As a result, all signal levels input to the 3-input AND gate logic circuit 8 are not at the H level, and the output of the 3-input AND gate logic circuit 8 is at the L level. When the output level of the 3-input AND gate logic circuit 8 continues for 5 seconds or more, the drive circuit 10 turns off the N-ch MOSFET 9. Thereby, the output of the fuel cell 1 is shut off. Thus, power generation in an overload state is prevented.

<Third Embodiment>
In particular, the present embodiment prevents the single cell constituting the fuel cell from operating in a poled state, and is configured to limit the output current of the fuel cell when the poled state is detected. That is, while the first embodiment shown in FIG. 1 cuts off the output of the fuel cell 1 by detecting the inversion state, in this embodiment, the output current of the fuel cell 1 is limited under the same conditions. I made it. Accordingly, many components are the same as those of the first embodiment shown in FIG. Therefore, the same parts as those in FIG.

  As shown in FIG. 3, the protection circuit 12 includes three comparators 7a, 7b and 7c, a three-input AND gate logic circuit 8, and a drive circuit 10 having a delay operation function. That is, the output of the fuel cell 1 is not interrupted even when a pole reversal state is detected. A polarity state signal representing a polarity state that is an output of the protection circuit 12 is input to the control terminal 15 of the boost control circuit 11. The step-up control circuit 11 has a current limiting unit 30, and limits the output current via the current limiting unit 30 when a polarity change state signal is supplied to the control terminal 15.

  In this embodiment, as in the first embodiment, when all of the single cells 1a, 1b, 1c of the fuel cell 1 are generating normal power, the output of the protection circuit 12 becomes an H level output. .

  On the other hand, when at least one of the single cells 1a, 1b, and 1c of the fuel cell 1 is in a reversed state, the output of the three-input AND gate logic circuit 8 is at the L level. When the output level of the 3-input AND gate logic circuit 8 continues for 5 seconds or more, the output of the protection circuit 12 becomes L level and is supplied to the boost control circuit 11 as a polarity change state signal indicating a polarity change state. As a result, the boost control circuit 11 limits the output current supplied from the boost control circuit 11 to the external load 6 until an H level input is obtained. The shortage of the load current to the external load 6 caused by this current limitation is supplied via the LIB 3.

  FIG. 4 shows an example of a detailed configuration of the boost control circuit 11. In this example, a switching regulator system is used as the boosting means. As for the output of the fuel cell, energy is stored in the inductor 19 when the N-ch MOSFET 20 is on. When the N-ch MOSFET 20 is on, no current flows through the diode 21. When the N-ch MOSFET 20 is turned off, the energy stored in the inductor 19 is supplied to the smoothing capacitor 22 and the external load 6 via the diode 21.

  Here, the output voltage is determined by the PWM control circuit 23 based on the ratio of the ON state to the OFF state of the N-ch MOSFET 20. The PWM control circuit 23 controls the voltage drop of the output of the boost control circuit 11 by the voltage dividing resistor 24 and the reference voltage applied from the reference voltage generator 25 to coincide with each other. Therefore, the output voltage can be arbitrarily set by changing the resistance ratio of the voltage dividing resistor 24.

  An input from the control terminal 15, that is, a polarity change state signal is input to a controller 27 that controls an input current from the fuel cell 1.

  When the signal input to the control terminal 15 of the boost control circuit 11 is at the H level, the controller 27 keeps the MOSFET 28, which is a switch means provided on the input side of the boost control circuit 11, in the ON state, and the base of the NPN transistor 29. No bias is applied to the terminals. Therefore, all the outputs of the boost control circuit 11 are supplied to the external load 6 side via the N-ch MOSFET 28. Therefore, the N-ch MOSFET 28 is preferably a low on-resistance MOSFET. Since the output of the fuel cell 1 is input to the booster circuit without being restricted, the maximum output can be obtained when the fuel cell 1 performs normal power generation.

  On the other hand, when the signal input to the control terminal 15 of the boost control circuit 11 is at L level, that is, when a pole state signal is supplied, the boost control circuit 11 performs control so as to decrease the output current of the fuel cell 1. To do. That is, the controller 27 lowers the potential of the gate of the N-ch MOSFET 28 to the ground, so that the output current of the fuel cell 1 does not flow through the N-ch MOSFET 28.

  Next, the controller 25 applies a bias to the base terminal of the NPN transistor 29 so that a current at which the maximum output of the fuel cell 1 can be obtained flows to the boost control circuit 11. Thereafter, the controller 27 gradually decreases the bias of the base terminal of the NPN transistor 29 and decreases the output current of the fuel cell 1.

  In the middle of the process, when the overloaded cell in the fuel cell 1 returns to the normal output state and the signal input to the control terminal 15 becomes H level, the controller 27 is connected to the base terminal of the NPN transistor 29. Fix the bias to be applied.

  On the other hand, when an L level signal is supplied to the control terminal 15 with the bias applied to the base terminal of the NPN transistor 29 fixed, the controller 27 applies a bias to be applied until an H level is input to the control terminal 15. Further decrease.

  The state in which the output of the fuel cell 1 is input to the boost control circuit 11 via the NPN transistor 29 is maintained until the external load 6 is eliminated. As a result, it is possible to prevent the fuel cell single cell from operating in a reversed state.

  Note that the protection circuit 12 in FIG. 3 may include a reference voltage generation circuit as in FIG. In this case, an overload condition is detected and current limiting is performed.

<Fourth embodiment>
This form is a case where the detection of the single cell of a dipole and an overload state is detected at each single cell temperature. That is, while the first to third embodiments shown in FIGS. 1 to 3 detect the power generation voltage of a single cell via the voltages across the single cells 1a, 1b, and 1c, The difference is that the detection is performed via the temperature of each single cell 1a, 1b, 1c. The other configuration is the same. Therefore, only portions different from those in FIGS. 1 to 3 are extracted and described, and descriptions of overlapping portions are omitted.

  As shown in FIG. 5, the temperature at which the fuel cell 1 is determined to be inversion / overloaded varies depending on the members and structure that constitute the fuel cell 1, but in the PEFC passive type non-humidified fuel cell 1, the cathode electrode When the vicinity exceeds 60 ° C., the membrane begins to dry, the internal resistance of the fuel cell 1 increases, and the output characteristics of the fuel cell 1 deteriorate. Even if the fuel cell 1 is outputting a constant current, if the temperature of each single cell 1a, 1b, 1c rises and the output characteristics deteriorate, the fuel cell 1 will be in a state equivalent to an overload.

  Therefore, the temperature for detecting the overload is detected as 45 to 110 ° C. while detecting the temperature in the vicinity of the electrodes of the single cells 1a, 1b and 1c of the fuel cell 1 by the temperature sensors 31a, 31b and 31c. It is desirable to set a value. For example, when the reference voltage of the reference voltage generator 23 sets the single cells 1a, 1b, 1c to a temperature higher than 45 to 110 ° C., the overload state is set. In this case, thermocouples or thermistors are suitable as the temperature sensors 31a to 31c.

  In this embodiment, the operations of the comparators 7a, 7b, 7c, etc. after at least one single cell 1a, 1b, 1c is overloaded are exactly the same as those in the first to third embodiments. is there.

  In this embodiment, the outputs of the temperature sensors 31a, 31b, and 31c are amplified by operational amplifiers 32a, 32b, and 32c and input to the comparators 7a, 7b, and 7c. However, it is not always necessary to form in this way, and the outputs of the temperature sensors 31a, 31b, 31c may be directly input to the comparators 7a, 7b, 7c.

  In the fuel cell system in which the temperature of the cell or the fuel is not controlled, the heating / cooling control of the fuel cell 1 is not performed, so that there is a correlation between the heat generation according to the power generation and the fuel cell output. For this reason, the output state and overload state of the fuel cell 1 can be detected by detecting the temperatures of the single cells 1a, 1b, and 1c. Therefore, there is no need to perform fuel flow, fuel humidification or heating, cell heating, etc., and a passive fuel cell system that can grasp the output of the fuel cell 1 by detecting the heat generation of the fuel cell. The fuel cell system according to this embodiment is particularly effective, but in any case, it is possible to detect an abnormality in the generated voltage by detecting the temperature of the single cells 1a, 1b, 1c, and an abnormal state is detected. In this case, the fuel cell 1 can be prevented from deteriorating in the same manner as in the first to third embodiments by shutting off the output and limiting the output current.

<Fifth embodiment>
In the present embodiment, the output of the single cell 1a, 1b, 1c is also actively recovered along with the interruption of the output accompanying the detection of the inversion / overload state. Therefore, the same parts as those in FIGS. 1 to 5 are denoted by the same reference numerals, and redundant description is omitted.

  As shown in FIG. 6, heaters 41a, 41b, and 41c are disposed on the anode chamber side of each single cell 1a, 1b, and 1c. Here, each heater 41a, 41b, 41c has a function of evaporating and removing excess water generated around the electrodes of each single cell 1a, 1b, 1c. This is mainly for the purpose of recovering the function of each single cell 1a, 1b, 1c by removing water that hinders gas diffusion on the catalyst layer and the gas diffusion layer. In this case, it is desirable to set the upper limit temperature of heating between 60 and 90 ° C.

  Each single cell 1a, 1b, 1c is provided with pressure sensors 42a, 42b, 42c, purge valves 43a, 43b, 43c, and safety valves 44a, 44b, 44c. The purge valves 43a to 43c are opened and closed by a signal from the output recovery control means 40. Furthermore, in this embodiment, the fuel supply to the fuel cell 1 is interrupted by a signal from the output recovery control means 40.

  The safety valves 44a to 44c for pressure reduction are adjusted so as to be opened when the anode chamber is at a pressure of 2.0 atmospheric pressure or higher than the atmospheric pressure by adjusting the spring pressure. Incidentally, it is preferably set between 1.0 and 3.0 atm. Here, it is also possible to use safety valves 44a to 44c using bimetal. In this case, the opening temperature is set to 80 to 100 ° C.

  The protection circuit 5 is basically the same as that shown in FIG. 1, but the polarity / overload state signal, which is the output signal of the AND gate logic circuit 8, is sent to the output recovery control means 40 together with the drive circuit 10. Is done.

  Here, the elements and devices related to the output recovery measure use the LIB 3 as a power source, similarly to the boost control circuit 2 and the protection circuit 5. On the other hand, the fuel cell 1 can also be used as a power source for the elements and devices related to these output recovery measures, the boost control circuit 2 and the protection circuit 5. Further, between the boost control circuit 2 and the external load 6 in the present embodiment, a current detection unit 45 that detects a load current supplied to the external load 6 and a charging unit 46 that charges the LIB 3 are provided.

  Thus, in this embodiment, when the current detection unit 45 detects that the load current to the external load 6 becomes zero, the charging unit 46 is operated to charge the LIB 3, and the LIB 3 is in a fully charged state. Is stopped when the charging means 46 detects it.

  It should be noted that there are no restrictions on providing the current detecting means 45 and the charging means 46 in the fuel cell system shown in FIGS. The fuel cell 1 according to the present embodiment has a dead end structure in which the anode chambers of the cells are separated from each other in addition to the series connection in the plane, for example, a fuel flow structure in which the cells are planarly connected and the anode chamber is separated, and the cells are planar. A fuel flow structure in which the anode chambers are connected and the anode chambers are connected in plane, and a PEFC and a DMFC having a common dead end or a structure stack structure in which the cells are connected in a plane may be used.

  In the present embodiment having the above configuration, when all the single cells 1a, 1b, and 1c of the fuel cell 1 perform normal power generation, the outputs of the comparators 7a, 7b, and 7c are H level outputs. Since the H level outputs of the comparators 7a, 7b, and 7c are input to the 3-input AND gate logic circuit 8, the output of the 3-input AND gate logic circuit 8 is at the H level. At this time, the drive circuit 10 turns on the N-ch MOSFET 9, the output of the fuel cell 1 is input to the boost control circuit 2, and power is supplied from the boost control circuit 2 to the external load 6.

  On the other hand, when at least one of the single cells 1a, 1b, and 1c of the fuel cell 1 is in a reversed state, a negative voltage is output from any of the single cells 1a, 1b, and 1c. Any one of the comparators 7a, 7b and 7c connected to 1c becomes L level. As a result, since the signal levels input to the 3-input AND gate logic circuit 8 are not all at the H level, the output is at the L level. When the output level of the 3-input AND gate logic circuit 8 continues for 5 seconds or more, the drive circuit 10 turns off the N-ch MOSFET 9 and maintains this state. As a result, the output of the fuel cell 1 can be cut off, so that it is possible to avoid power generation in the inversion state.

  When a polarity change state signal which is an L level signal from the three-input AND gate logic circuit 8 is received, the output recovery control means 40 operates simultaneously. When this output recovery control means 40 operates, the fuel supply is shut off, and the anode chamber is made a sealed space. Subsequently, the anode chamber is kept at 75 ° C. by the heaters 41a to 41c, and liquid water in the anode chamber is vaporized. When the internal pressure of the anode chamber exceeds 2.0 atmospheres, the safety valves 44a to 44c operate. As a result, gas is released at any time.

  When the pressure sensors 42a to 42c do not change the pressure for a predetermined time (in this embodiment, 10 minutes), the purge valves 43a to 43c are opened and closed within 2 seconds. Then, normal power generation is possible in all the single cells 1a, 1b, 1c by starting the fuel supply.

  Here, a timer is set for the operation of the heaters 41a to 41c, and the heaters 41a to 41c are set to be turned off when operated for 20 minutes.

  When the fuel supply is started, the protection circuit 5 turns on the N-ch MOSFET 9 to electrically connect the fuel cell 1 and the boost control circuit 2.

  In this embodiment, the recovery of the fuel cell 1 is performed by removing the generated water in the single cells 1a, 1b, and 1c by heating the heater, but this is not a limitation. Removing the water in the vicinity of the electrodes is useful as a recovery measure, but water can also be removed by using a blower to blow off water or a gas. In addition to the method of removing water, the following recovery means can be considered. 1) Forced circulation of the fuel in the anode chamber of each single cell 1a, 1b, 1c 2) Replacement of gas in the anode chamber of each single cell 1a, 1b, 1c 3) Humidification for wetting the electrolyte membrane And so on.

  In addition, the recovery measures are performed for only the single cells 1a, 1b, 1c in which the inversion / overload state is detected, and in the single cells 1a, 1b, in which the inversion / overload state is detected. The case where this is performed for all the single cells 1a, 1b, and 1c constituting the fuel cell 1 including 1c can be considered. Which one to select can be easily determined, for example, by determining an object to be controlled by the output recovery control means 40.

  However, when the recovery operation is performed on all the single cells 1a, 1b, 1c, there are the following merits. 1) It becomes possible to make the state of each single cell 1a, 1b, 1c uniform. 2) The output of the single cells 1a, 1b, 1c in which no inversion is detected is improved.

<Sixth Embodiment>
In this embodiment, in addition to the limitation of the output current accompanying the detection of the inversion / overload state, the individual cells 1a, 1b, 1c are also actively recovered. That is, this is a case where current limiting is performed instead of output current limiting associated with the detection of the inversion / overload state in the fifth embodiment shown in FIG. Therefore, the same parts as those in FIGS. 1 to 6 are denoted by the same reference numerals, and redundant description is omitted.

  As shown in FIG. 7, the fuel cell system shown in FIG. 3 is almost the same as the fuel cell system shown in FIG. However, in the present embodiment, the current control means 30 is reset when the current detection means 45 detects zero load current. This makes it possible to smoothly supply current to the next external load 6.

  FIG. 8 shows an example of a detailed configuration of the boost control circuit 51. The boost control circuit 51 has basically the same configuration as that of the boost control circuit 11 shown in FIG. 4, but has a function of resetting the current control means 30 described above, and includes an output side of the boost control circuit 51. The difference is that the current is controlled. That is, in this example, the NPN transistor 29 is disposed on the output side so that the NPN transistor 29 controls the output current of the boost control circuit 51. That is, the function itself of the controller 27 is the same, but the controller 27 in this example controls the output current via the NPN transistor 29 on the output side.

  Although there is no essential difference between limiting the current on the input side or the output side, in the boost control circuit 51, it is desirable to control the current on the output side where the voltage is higher. This is because easy and highly accurate control is possible. Therefore, it is desirable to control the current on the input side in the step-down control circuit.

  In this example, the reset signal from the current detection unit 45 is supplied to the controller 27 of the current control unit 30 via the terminal 53. Other operations are the same as those in FIG.

<Seventh embodiment>
In this embodiment, the protection circuit further includes a counter that counts the number of times each single cell is in a reversal / overload state, and the reversal / overload of the same single cell is continuously detected more than a specified number of times. In this case, the output of the fuel cell is cut off. Although this embodiment has output recovery means, it is not necessary to have this. Any combination can be used as long as the output is cut off when a polarity inversion / overload state is detected. The same parts as those in FIG. 1 to FIG.

  As shown in FIG. 9, the protection circuit 55 includes a counter 56 that branches and inputs the output signals of the comparators 7a, 7b, and 7c that are input to the 3-input AND gate logic circuit 8. The counter 56 counts the number of times that the single pole 1a, 1b, 1c has continuously caused the inversion / overload state, and when the count result exceeds a predetermined number (for example, 20 times), the counter 56 The output of the fuel cell 1 is cut off by turning off a certain N-ch MOSFET 9. At the same time, a light emitting diode (hereinafter referred to as LED) 57 is caused to emit light to display an error.

  On the other hand, in this embodiment, reference voltage generators 23a, 23b, and 23c are provided corresponding to the respective comparators 7a, 7b, and 7c, and a reference voltage (for example, 0.3 V) is applied to each inverting terminal. Yes. By providing the reference voltage generators 23a, 23b, and 23c individually as described above, the number increases, but more accurate reference voltages than those shown in FIG. 2 and the like can be supplied to the comparators 7a, 7b, and 7c. . The output recovery means 60 is an integrated part related to output recovery measures. For example, the output recovery control means 40, heaters 41a to 41c, pressure sensors 42a to 42c, purge valves 43a to 43c, and safety valves 44a to 44c in FIG. It is a concept that includes

  Also, when the three-input AND gate logic circuit 8 detects a reversal / overload state, the output of the fuel cell 1 is cut off separately by turning off the N-ch MOSFET 9 as the switch means.

  In this embodiment, by managing the number of times of continuous detection of the inversion / overload state, the operation efficiency of the fuel cell system is maintained as high as possible, and at the same time, the inversion / overload state is detected. By shutting off the output of the fuel cell, it is possible to appropriately protect the single cell that is in a reversal / overload state. Here, the output recovery means 60 implements a predetermined output recovery measure each time the three-input AND gate logic circuit 8 detects a polarization / overload state.

<Eighth Embodiment>
In this embodiment, the protection circuit further includes a counting unit that counts the number of times each single cell is in a polarization / overload state, and the polarity / overload of the same single cell is continuously detected more than a specified number of times. In this case, the output current of the fuel cell is limited. Although this embodiment has output recovery means, it is not necessary to have this. Any combination can be used as long as the current is limited when a polarization inversion / overload state is detected. The same parts as those in FIGS. 1 to 9 are denoted by the same reference numerals, and redundant description is omitted.

  As shown in FIG. 10, the protection circuit 55 includes a counter 56 that branches and inputs the output signals of the comparators 7a, 7b, and 7c that are input to the 3-input AND gate logic circuit 8. The counter 56 counts the number of times that the single pole 1a, 1b, 1c has continuously caused the inversion / overload state, and when the count result exceeds a predetermined number (for example, 20 times), the counter 56 The output of the fuel cell 1 is cut off by turning off a certain N-ch MOSFET 9. At the same time, a light emitting diode (hereinafter referred to as LED) 57 is caused to emit light to display an error.

  On the other hand, in this embodiment, reference voltage generators 23a, 23b, and 23c are provided corresponding to the respective comparators 7a, 7b, and 7c, and a reference voltage (for example, 0.3 V) is applied to each inverting terminal. Yes. By providing the reference voltage generators 23a, 23b, and 23c individually as described above, the number increases, but more accurate reference voltages than those shown in FIG. 2 and the like can be supplied to the comparators 7a, 7b, and 7c. .

  The output recovery means 60 is an integrated part related to output recovery measures. For example, the output recovery control means 40, heaters 41a to 41c, pressure sensors 42a to 42c, purge valves 43a to 43c, and safety valves 44a to 44c in FIG. It is a concept that includes

  In this embodiment, by managing the number of times of continuous detection of the inversion / overload state, the operation efficiency of the fuel cell system is maintained as high as possible, and at the same time, the inversion / overload state is detected. By shutting off the output of the fuel cell, it is possible to appropriately protect the single cell that is in a reversal / overload state.

  Here, the output recovery means 60 performs a predetermined output recovery measure each time the three-input AND gate logic circuit 8 generates a polarization / overload signal indicating a polarization / overload state. Similarly, current limiting is also performed by operating the current limiting means 30 according to the polarization / overload state signal.

  FIG. 11 is a flowchart showing an example of an operation flow of the fuel cell system according to the present embodiment.

  The fuel cell 1 is a PEFC having three single cells 1a, 1b, and 1c, and the cathode side is an open-air type. The fuel cell 1 has a fuel supply system (not shown), and pressure sensors 42a, 42b, 42c and purge valves 43a, 43b, 43c are provided on the anode chamber side of each single cell 1a, 1b, 1c. The purge valves 43a, 43b, 43c are opened when the internal pressure of the anode chamber becomes 1.5 atm or more by the pressure sensors 42a, 42b, 42c.

  As output recovery means, heaters 41a, 41b, and 41c were used and arranged in the anode chamber of each single cell. The power sources of the heaters 41a, 41b, and 41c are obtained from the output of the fuel cell 1. In the protection circuit 55, the abnormality detection means is configured to detect an overload state, and the reference voltage of the voltage reference is set to 0.3V.

  The counter 56 is configured to add a count when the abnormality detecting means continuously detects an overload state of the same single cell 1a, 1b, 1c. When the number of counts exceeds 20, a signal for turning off the switch 9 and a voltage are applied to the LED 57 to cause the LED 57 to emit light, and an error sign is obtained.

Here, the operation during operation of the fuel cell system will be described with reference to FIG.
1) The fuel cell system is activated to operate the external load 6 (step S1). If the error sign is lit in step S2, the process proceeds to step S10 and the operation is terminated.
2) If the error sign is not lit in step S2, fuel is supplied to the fuel cell 1 in step S3 and power generation is started.
3) In step S4, when the abnormality detecting means detects an overload state of the single cells 1a, 1b, 1c, the process proceeds to step S5, where it is the same single cell 1a, 1b, 1c as in the previous overload detection. Judge whether or not.
4) If it is the same single cell 1a, 1b, 1c, the process proceeds to step S6 and the addition is counted.
5) If the number of counts set in step S7 is equal to or greater than 20, here, the process proceeds to step S8. In step 8, the switch 9 is turned off and the LED 57 is lit to shut off the output of the fuel cell system.
6) Next, in step S9, the supply of fuel is stopped and power generation is terminated (step S10).
7) On the other hand, when the number of counts set in step S7 is equal to or less than 20, here, the process proceeds to step S12 to limit the output current of the fuel cell system.
8) Next, in step S13, the heaters 41a, 41b, 41c, which are recovery means, are driven to operate the timer. Here, the set time of the timer is 15 minutes.
9) After the output recovery means 60 operates for 15 minutes (step S14), the operation of the output recovery means 60 stops (step S15).
10) Next, in step S16, the restriction on the fuel cell output current is released, and the process returns to step S4.
11) If the overload detection is not the same single cell 1a, 1b, 1c as the previous overload detection in step S5, the process proceeds to step S11, the counter 56 is reset, and then the process proceeds to step S12. .
From step S12 to step S16, the processing as described above is performed.
12) If no overload is detected in step S4, the process proceeds to step S17. If the load does not stop here, the process returns to step S4 again.
13) When the load stops in step S17, the output recovery means 60 and the timer are operated (step S18). When the time set by the timer (here 15 minutes) has elapsed (step S19), the output recovery means 60 is turned on. Stop (step S20).
14) Thereafter, in step S9, the supply of fuel is stopped and the process ends (step S10).

  In the case of the seventh embodiment in which the output is cut off in the case of the polarity reversal / overload state, step S12 and step S16 are “cut off of the fuel cell output”.

<Ninth embodiment>
This embodiment has a switch means for short-circuiting both ends of each single cell together with the output recovery means, and when a reversal / overload state is detected, both ends of the single cell in this state are The switch means is configured to short-circuit. The same parts as those in FIGS. 1 to 10 are denoted by the same reference numerals, and redundant description is omitted.

  As shown in FIG. 12, in the fuel cell system according to this embodiment, in order to detect an overload state, each single cell 1a, 1b, 1c is associated with a comparator 7a, 7b, 7c, and each single cell 1a, 1b The non-inverting input terminal of each comparator 7a, 7b, 7c is connected to the positive electrode of 1c, and a voltage reference is connected between the negative electrode of each single cell 1a, 1b, 1c and the inverting input terminal of each comparator 7a, 7b, 7c. The reference voltage generators 23a, 23b and 23c for use are connected. The GND terminals of the comparators 7a, 7b, 7c and the reference voltage generators 23a, 23b, 23c are connected to the negative electrodes of the corresponding single cells 1a, 1b, 1c.

  When the outputs of the comparators 7a, 7b, and 7c are input to the 3-input AND gate logic circuit 8, when the generated voltages of the single cells 1a, 1b, and 1c are equal to or lower than the voltages set by the corresponding reference voltages, the polarity is reversed. • An overload status signal is sent. That is, as the outputs of the comparators 7a, 7b, 7c are inverted, the output of the 3-input AND gate logic circuit 8 is also inverted. As a result, an overload state is detected.

  On the other hand, each single cell 1a, 1b, 1c is connected to the cathode side of each single cell 1a, 1b, 1c and the drain terminal of each N channel EFT 66a, 66b, 66c by switching elements N-channel EFT 66a, 66b, 66c. Connected in parallel.

  Here, the N-channel EFTs 66a, 66b, 66c are always in the OFF state, but when a dipole / overload state is detected from a single cell 1a, 1b, 1c, the single cell 1a in the dipole / overload state, From the output terminals of the comparators 7a, 7b and 7c corresponding to 1b and 1c, drivers 67a, 67b for bypass N-channel EFTs 66a, 66b and 66c corresponding to the single cells 1a, 1b and 1c in the inverted / overloaded state A signal is supplied to 67c. When the drivers 67a, 67b, 67c receive the inversion / overload state signal, the bypass N-channel EFT is kept on for the time set by the operation timer of the output recovery means 60, and the output current of the fuel cell 1 is Bypass from the single cells 1a, 1b, 1c in the inversion / overload state.

  At the same time, when the polarity detection / overload state of the fuel cell 1 is detected by the abnormality detection means, the output recovery of the fuel cell 1 is performed based on the polarity / overload signal which is the output signal of the three-input AND gate logic circuit 8. Means 60 operates. The operation of the output recovery means 60 is controlled by a timer. When the time set by the timer elapses, the operation is stopped.

  In this manner, in this embodiment, the inversion / overload state is detected, the defective cell is bypassed, and the generated current of the fuel cell 1 is allowed to flow.

  In order to satisfactorily detect the inversion, the non-inverting input terminals of the respective comparators 7a, 7b and 7c are connected to the positive electrodes of the single cells 1a, 1b and 1c, and the inverting input terminals of the comparators are connected to the negative electrodes of the respective cells. And the GND terminal may be connected. As a result, it is possible to positively detect and use in the single cells 1a, 1b, 1c at any position in series connection.

  According to this aspect, the single cell in which the reversal / overload is detected is bypassed by the N-channel EFT 66a, 66b, 66c, and the reversal / overload state is provided while supplying the current to the remaining single cells connected in series. Recovery.

<Other embodiments>
As described above, through each embodiment, a plurality of types of abnormality detection circuits, a protection circuit, a current limiting unit, a boost control circuit, a storage unit, an output recovery unit, etc. are disclosed. Each element can be freely combined. Although not all combinations are disclosed, all derived combinations are included in the technical idea of the present invention.

  Furthermore, a charging element such as LIB3 is not essential. In the case of having this, there is a merit that electric power can be continuously supplied to the external load 6 when the fuel cell 1 is switched or overloaded, but it is not necessarily required to be integrated with the fuel cell system. Absent. In the same sense, the boost control circuit is not an essential component.

  Since the fuel cell system of the present invention prevents the fuel cell from operating in an overloaded state, it is possible to prevent corrosion of the fuel cell and deterioration of output characteristics. Prevention of power generation in the deterioration mode of the fuel cell and the initial power generation capability of the single fuel cell are maintained, and stable power supply is possible. Since a simple configuration is possible, it can be applied to miniaturization of a fuel cell system for portable devices.

DESCRIPTION OF SYMBOLS 1 Fuel cell 1a, 1b, 1c Single cell 2, 11 Boosting control circuit 3 Lithium ion secondary battery 5, 12, 55, 65 Protection circuit 6 External load 7a, 7b, 7c Comparator 8 3 input AND gate logic circuit 9 N- chMOSFET
DESCRIPTION OF SYMBOLS 10 Drive circuit 30 Current control means 31a, 31b, 31c Temperature sensor 41a, 41b, 41c Heater

Claims (11)

A fuel cell comprising at least two unit cells connected in series;
When the polarity / overload state is detected by the abnormality detection means for detecting the power generation in the polarity / overload state of each single cell, the fuel cell is controlled based on the polarity / overload state signal representing this state. Protection means to shut off the output;
Receiving an inversion signal and an overload state signal, and starting operation, and comprising an output recovery means for recovering the output of the fuel cell,
The protection means has a switch means for short-circuiting both ends of each single cell, and when a dipole / overload state is detected, both ends of the single cell in this state are short-circuited by the switch means. A fuel cell system configured to perform A fuel cell comprising at least two unit cells connected in series;
Protection means for sending a polarity / overload state signal indicating the state when the polarity / overload state is detected by an abnormality detection means for detecting power generation in the polarity / overload state of each single cell; ,
The operation is started in response to the reversal / overload state signal, and the current limiting means for controlling the output current of the fuel cell to gradually decrease, and the operation is started in response to the reversal / overload state signal, Output recovery means for recovering the output of the fuel cell,
The protection means has a switch means for short-circuiting both ends of each single cell, and when a dipole / overload state is detected, both ends of the single cell in this state are short-circuited by the switch means. A fuel cell system configured to perform In claim 1 or claim 2,
2. The fuel cell system according to claim 1, wherein the inversion / overload state signal is formed on condition that the inversion / overload state is continuously detected for a predetermined time or more by the abnormality detection means. In any one of Claims 1 to 3,
The fuel cell system according to claim 1, wherein the output recovery means performs a recovery measure only on the single cell in which the inversion / overload state is detected. In any one of Claims 1 to 3,
The fuel cell system characterized in that the output recovery means performs recovery measures for all the single cells constituting the fuel cell including the single cells in which the inversion / overload state is detected. In any one of Claims 1 to 5,
The fuel cell system, wherein the output recovery means removes water generated in the vicinity of the electrode of the single cell. In any one of Claim 1 thru | or 6,
The fuel cell system according to claim 1, wherein the protection means determines that the state is inversion / overload when the voltage across the single cell is equal to or lower than a predetermined value. In any one of Claim 1 thru | or 6,
The fuel cell system according to claim 1, wherein the protection means determines that the state is inversion or overload when the temperature of the electrode of each single cell is equal to or higher than a predetermined value. In any one of Claims 1 to 8,
The protection means further includes a counting means for counting the number of times each single cell is in a reversal / overload state, and when the reversal / overload of the same single cell is continuously detected a specified number of times or more. A fuel cell system for cutting off the output of the fuel cell. In claim 2,
The fuel cell system, wherein the current limiting means controls the output current to gradually decrease from the maximum output current of the fuel cell. In claim 10,
The current limiting means performs control so that the output current gradually decreases from the maximum output current of the fuel cell, and the return of the fuel cell to a normal state that is not a reversal / overload state is detected during the control. In this case, the output current value is fixed to the output current value at the time of return, while the same control is repeated so as to further reduce the output current when receiving the reversal / overload signal again. A fuel cell system comprising:

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