JP2006210240A - Fuel cell protection circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell protection circuit capable of stabilizing power supply to a load by reducing the load of fuel battery power generating cells and heightening response to a sudden change of the load, capable of maintaining power generation facility of the fuel cell of an early stage by preventing power generation at a deterioration mode of the fuel cell. <P>SOLUTION: For evading damage of the fuel battery power generating cell caused by transient over voltage due to lowering of an output of the fuel cell caused by inability of the output of the fuel cell to follow a sudden change of the load like a pulse load, the load on the fuel battery power generating cells is reduced by increasing an output capacity of the fuel cell. Further, for preventing the deterioration mode of the fuel cell, a function for preventing rush-current output from the fuel cell and a means for preventing an inverse current flowing from an external circuit or electric double layer capacitor to the fuel cell are provided. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a circuit for a fuel cell, and more particularly to a protection circuit for a fuel cell as a power source for a small portable device.

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.
Recently, fuel cells have attracted attention as small energy sources with high energy density. In this fuel cell, two types of electrodes are sandwiched between electrolytes. Electricity is generated by oxidizing a fuel such as hydrogen or methanol at the fuel electrode and reducing oxygen in the atmosphere at the oxygen electrode. Among fuel cells, a polymer electrolyte fuel cell is expected to be applied as a power source for portable devices because it can generate power near room temperature and has a high output density and can be miniaturized.
However, it is known that fuel cells have low load responsiveness compared to primary batteries and secondary batteries. This is one of the reasons for the low response of fuel gas diffusion.
Conventionally, there has been known a fuel cell power generator in which a fuel cell and a capacitor are connected in parallel, and when the output of the fuel cell decreases due to a delay in the response of the fuel cell due to a sudden increase in load current, the discharge current from the capacitor compensates for the insufficient current (For example, refer to Patent Document 1).
JP-A-6-275296 (page 10, FIG. 5)

  According to the conventional method, the compensation of the current with respect to the load response using the capacitor is controlled by collation with the voltage-current characteristic data of the fuel cell prepared in advance. However, in this method, the control method is complicated, and the discharge of insufficient current from the capacitor by collation with the voltage-current characteristic data causes a delay in the control, etc. However, it is impossible to follow the load demand, the fuel cell output is lowered, and the damage of the fuel cell power generation cell due to the transient overvoltage cannot be avoided.

  In addition, when a sudden drop in the fuel cell voltage occurs due to a stop in the output of the fuel cell or a trouble in the fuel cell, no measures are taken to avoid damage to the fuel cell due to the backflow of current from the capacitor. . This is because when a capacitor with a large capacity and low equivalent series resistance such as an electric double layer capacitor is used to cope with a sudden load fluctuation such as a pulse load, a large current flows into the fuel cell, resulting in fatal damage. There is a risk of giving.

  Furthermore, no measures are taken for overloading the fuel cell due to rush current that occurs when charging a capacitor having a large capacity and a low equivalent series resistance.

  Fuel cell overload and reverse current flow cause fuel cell inversion, resulting in fuel cell output due to performance degradation due to elution and aggregation of catalyst metals such as electrolyte membranes and conductive materials in fuel cell power generation cells. , Leading to a reduction in life and shortening the lifespan, which must be avoided.

  In the conventional method, not only fuel supply control but also air supply control is performed, and a configuration necessary for downsizing such as mounting in a small portable device has not been considered.

  The power source of a small portable device is limited in size, and is particularly required to be small and lightweight. Therefore, the present invention does not use auxiliary equipment that requires volume, increases the output capacity of the fuel cell, reduces the load on the fuel cell power generation cell, and at the same time stabilizes the power supply to the load such as a pulse response, Provided is a fuel cell protection circuit capable of preventing power generation in a deterioration mode of a fuel cell and a backflow of current to the fuel cell and maintaining the initial power generation capability of the fuel cell.

  In order to achieve the above object, the present invention is directed to a fuel cell in order to avoid damage to the fuel cell power generation cell due to generation of a transient overvoltage because the fuel cell output does not follow the load request and the fuel cell output decreases. Increase the output capacity and reduce the load on the fuel cell.

  A fuel cell protection circuit connected to a fuel cell that supplies power to an external circuit, which increases the output capacity of the fuel cell and reduces the load on the fuel cell, and an electric double layer capacitor in series A discharge circuit connected to prevent the backflow of current from the electric double layer capacitor to the fuel cell power generation cell; and a rush current preventing means connected in parallel to the electric double layer capacitor and the discharge circuit.

  It consists of a fuel cell power generation cell that can extract power from the fuel by a chemical reaction, and a fuel cell protection circuit that reduces the load on the fuel cell power generation cell and stabilizes the power supply to the load. In the fuel cell to be supplied, the fuel cell protection circuit has an electric double layer capacitor in order to increase the output capacity of the fuel cell and reduce the load on the fuel cell. The equivalent series resistance (ESR) value of the electric double layer capacitor is not more than the maximum value of the internal resistance value of the fuel cell power generation cell. As the capacity of the electric double layer capacitor, an appropriate capacity is selected by measuring the transient response of the fuel cell power generation cell. In particular, it is desirable to select an electric double layer capacitor having an ESR value lower than the equivalent internal resistance value of the fuel cell in order to stably supply power as a power source against a sudden load fluctuation such as a pulse load. .

  In addition, the fuel cell protection circuit has a rush current prevention means, a rush current prevention circuit for preventing a rush current output from the fuel cell power generation cell, and an external circuit or an electric double layer capacitor to the fuel cell power generation cell. A reverse current prevention means for preventing a reverse current, and prevents power generation in the deterioration mode of the fuel cell. The fuel cell protection circuit further includes a switch for switching the fuel cell output, a bypass circuit for bypassing the rush current prevention means, and a discharge circuit for the electric double layer capacitor to avoid damage to the fuel cell.

  The discharge circuit is composed of at least a comparator, a resistor, and a switch. The electric circuit based on the voltage of the fuel cell power generation cell is used so that the voltage of the electric double layer capacitor does not exceed the voltage of the fuel cell power generation cell. Controls the discharge amount of the double layer capacitor.

  The rush current prevention means includes at least a current limiting element and a bypass circuit for the output current from the fuel cell power generation cell, and controls the fuel cell output current based on a voltage drop of the current limiting element.

  The fuel cell protection circuit has a rush current prevention circuit composed of a resistor, a semiconductor switch element, or both a resistor and a semiconductor switch element in order to prevent a rush current output from the fuel cell power generation cell. ing.

  The resistance value of the resistor of the rush current prevention circuit, the on-resistance value of the semiconductor switch element having the rush current prevention means, and the combined resistance value of the rush current prevention means including the resistor and the semiconductor switch element are surely rushed. Set a resistance that can prevent current. That is, the resistance value of the rush current prevention means is obtained by dividing the open circuit voltage value of the fuel cell power generation cell by the maximum current value at which the fuel cell power generation cell is 0 V, and the open circuit voltage of the fuel cell power generation cell. When the load is applied to the power generation cell at the maximum slew rate in the electronic load device, it is set between the value divided by the current value at which no undershoot of the voltage of the fuel cell power generation cell occurs. When a semiconductor switching element having rush current preventing means is used, the resistance value of the rush current preventing means is the maximum resistance value obtained from the semiconductor switching element and the open circuit voltage value of the fuel cell is 0 V for the fuel cell power generation cell. It is set between the values divided by the maximum current value.

The bypass circuit is configured by a bypass transistor in order to avoid the voltage drop of the fuel cell output by the rush current prevention circuit when power is supplied from the fuel cell to the external load. When charging of the electric double layer capacitor is completed, the fuel cell output bypasses the rush current prevention circuit when power is supplied from the fuel cell to the external circuit.
Furthermore, the bypass circuit has a function of controlling the charging current of the electric double layer capacitor by controlling the bias voltage to the bypass transistor. Further, since the voltage across the bypass circuit is detected, it has not only a bypass function but also a current detection function. When the detection voltage of the bypass circuit becomes higher than the set value, the current can be limited by reducing the gate voltage of the bypass element and increasing the resistance.

  When the number of fuel cells used as a power source is small and it is difficult to secure a power source for electronic elements inside the fuel cell protection circuit, a boost converter is mounted in the fuel cell protection circuit, and the fuel cell protection circuit The power supply for the internal electronic elements is obtained from the boost converter.

  The switch for switching the output of the fuel cell is set so that the switch is turned on when the fuel cell is close to the open circuit voltage, and conduction is obtained. For example, when the switch for switching the fuel cell output detects a voltage of 80% or more of the open circuit voltage of the fuel cell, the fuel cell output is input into the fuel cell protection circuit. Furthermore, the switch for switching the fuel cell output gives a hysteresis to the switch operation with respect to the voltage detection of the fuel cell output voltage. That is, the switch is turned on when a voltage of 80% or more of the open circuit voltage of the fuel cell is detected, and the switch is turned off when a fuel cell output voltage is detected at a certain set value, for example, the voltage value at the maximum output point obtained from the fuel cell. The fuel cell output is shut off.

  When a polymer electrolyte fuel cell (PEFC) is used as a fuel cell to be used as a power source, hydrogen is in a state of either liquid hydrogen, hydrogen gas, or hydrogen atom, a high-pressure cylinder, a hydrogen storage alloy, a carbon nanotube, Stored by at least one means of the group consisting of carbon materials such as fullerenes. Alternatively, hydrogen can be taken out by modifying a chemical substance containing hydrogen such as alcohol, inorganic chemical hydride, or organic chemical hydride.

  When a direct fuel type fuel cell represented by a direct methanol type fuel cell (DMFC) is used, methanol is used as a 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.

According to the present invention, it is possible to cope with a sudden load fluctuation such as when an external circuit is started or during a pulse load, and at the same time reducing the load on the fuel cell power generation cell when the load fluctuation occurs. It becomes possible to stabilize the power supply.
Further, according to the present invention, since a rectifying element having a voltage drop characteristic such as a diode is not used by the discharge circuit, it is possible not only to increase the power supply efficiency but also to prevent the backflow of current to the fuel cell.

  Furthermore, according to the present invention, it is possible to prevent the rush current from the fuel cell and to prevent the power generation in the deterioration mode, and the initial power generation capability of the single fuel cell is maintained. Long service life is possible.

Embodiments of the present invention will be described below with reference to the drawings.
Three fuel cell power generation cells were connected in series and used as a power source. In addition to this embodiment, a power source such as a primary battery or a secondary battery such as a solar battery or a thermoelectric element can be used as a power source.

Example 1 of a fuel cell according to the present invention will be described below with reference to FIG.
The fuel cell includes a PEFC fuel cell 1 that uses hydrogen as a power source that can extract electric power from the fuel by a chemical reaction, and a fuel that reduces the load on the fuel cell 1 and at the same time stabilizes the power supply to the load. The battery protection circuit 2 is configured to supply power to the external circuit 3. The fuel cell protection circuit 2 prevents the electric double layer capacitor 4, the switch 5 for switching the fuel cell output, the rush current prevention circuit 6, and the current that flows backward from the electric double layer capacitor 4 or the external circuit 3 to the fuel cell 1. For this purpose. Further, the switch 5 is provided with a power generation prevention function in a deterioration mode that operates based on the fuel cell voltage. When supplying the output of the fuel cell 1 to the external circuit 3, the circuit is configured by using the current detection amplifier 8, the comparator 9, and the voltage reference 10 so that the output of the fuel cell 1 can bypass the rush current prevention resistor. did.

  The switch 5 includes a switching Nch-FET 11 and an FET driver 12 that operates the Nch-FET 11, and the driver 12 can have a hysteresis in the switching operation with respect to voltage detection of the fuel cell output voltage. The rush current prevention circuit 6 includes a rush current prevention resistor 13, a bypass Nch-FET 14, and a driver 15 that operates the Nch-FET 14.

The fuel cell protection circuit 2 is further provided with a fuel cell output current value output terminal 16.
The fuel cell 1 was composed of three cells, ie, fuel cell power generation cells 1a, 1b, and 1c, and the open circuit voltage of the fuel cell 1 was 2.94V. As the electric double layer capacitor 4, “Supercapacitor EDL473Z3R6-1” manufactured by NEC TOKIN having a nominal capacitance of 0.047F and a maximum operating voltage of 3.6V was used. The power supply voltage of the electronic elements inside the fuel cell protection circuit 2 was all input from the fuel cell 1.

  FIG. 2 is a diagram showing the output characteristics of the fuel cell 1. The horizontal axis represents the output current of the fuel cell, the left vertical axis represents the voltage of the fuel cell 1, and the rhomboid plot represents the right vertical axis. The output was taken and plotted with a circle. The maximum output of the fuel cell 1 was 2.42 W, and the current value and voltage value at that time were 2.4 A and 1.01 V, respectively. The maximum current value that can be taken out from the fuel cell 1 is the current value when the fuel cell voltage in FIG. However, the measurement at the fuel cell voltage of 0 V may cause damage to the fuel cell 1 and is not measured, but the maximum current value is estimated to be 5.0A.

  The resistance value of the rush current prevention resistor 13 is 0.588Ω, which is obtained by dividing 2.94 V of the open circuit voltage of the fuel cell 1 by the maximum current value of 5.0 A that can be taken out of the fuel cell, and is an open circuit of the fuel cell 1. When a load of 2.94 V is applied to the fuel cell at a slew rate of 2 A / μsec, the voltage is set to a value between 30.0Ω divided by the current value at which the fuel cell voltage does not undershoot. This time, a 3.0Ω resistor was used as the rush current prevention resistor 13. The slew rate when applying the load was set so that the increase in load current per hour was maximized in the electronic load device.

  In the switch 5, the driver 12 operates to turn on the switch Nch-FET 11 when the output voltage of the fuel cell 1 is detected as 80% of the open circuit voltage, this time 2.4 V or more.

  Further, in the fuel cell output characteristics shown in FIG. 2, it can be seen that in the power generation region where the output current value is 4.3 A or more, the voltage drop due to the diffusion overvoltage is large, so that the fuel cell output is significantly reduced. When the output current value is 4.3 A, the voltage of the fuel cell 1 is 0.77 V. In order to prevent power generation in the deterioration mode, the driver 12 detects that the fuel cell output voltage has become 0.77 V or less. Then, Nch-FET11 was turned off and it adjusted so that a fuel cell output might be interrupted | blocked. Further, when the fuel cell output is cut off, a signal is transmitted to the driver 15 to reset the operation of the driver 15. When the driver 15 receives the signal from the driver 12, the Nch-FET 14 is turned off.

  The output of the current detection amplifier 8 is input to the inverting input terminal of the comparator 9. The voltage generated from the voltage reference 10 is input to the non-inverting input terminal of the comparator 9. The output of the comparator 9 outputs an H level when the current flowing through the rush current prevention resistor 13 decreases. This time, the output of the comparator 9 was adjusted to H level when the current flowing through the rush current prevention resistor 13 became 0.5 A or less.

  When an H level signal is input from the comparator 9, the driver 14 that operates the bypass Nch-FET 14 turns on the bypass Nch-FET 14 and the output of the fuel cell 1 bypasses the rush current prevention resistor 13.

A fuel cell system according to a second embodiment of the present invention will be described below with reference to FIG.
Using the fuel cell 1 and the fuel cell protection circuit 2 shown in the first embodiment, the output terminal of the fuel cell protection circuit 2 is connected to a step-up type DC-DC converter 17, and the output terminal of the DC-DC converter 17 is connected to an electronic load. Input to device 18.

  Here, although not shown in the figure, the fuel cell protection circuit 2 shown in the first embodiment is provided with an external power supply input terminal so that the output of the DC-DC converter 17 can be inputted. The power source of the electronic elements used in the fuel cell protection circuit 2 is configured to be obtained from this external power input terminal. Thereby, for example, the gate application voltage of the FET 11 or FET 14 can be increased, the on-resistance of each FET can be reduced, and the power loss due to the resistance component in the fuel cell protection circuit 2 can be reduced.

  The DC-DC converter 17 is a switching regulator type booster circuit, and the output voltage value is fixed at 5V. The maximum power that can be extracted from the DC-DC converter 15 was a voltage value of 5.0 V and a current value of 0.636 A, and the output power at that time was 3.18 W.

  A third embodiment of the fuel cell system according to the present invention will be described below with reference to FIG.

  Using the fuel cell 1 shown in the first embodiment, the output end of the fuel cell 1 is connected to the input end of the DC-DC converter 17 without using the fuel cell protection circuit 2, and the output end of the DC-DC converter 17 is connected. Input to the electronic load device 18.

  As in the second embodiment, although not shown in the drawing, the fuel cell protection circuit 2 is provided with an external power input terminal so that the output of the DC-DC converter 17 can be input. The power source of the electronic elements used in the fuel cell protection circuit 2 was obtained from this external power input terminal. The maximum power that can be extracted from the DC-DC converter 17 was a voltage value of 5.0 V and a current value of 0.630 A, and the output power at that time was 3.15 W.

  Embodiment 4 of the fuel cell system according to the present invention will be described below with reference to FIG.

  In the configuration shown in the third embodiment, a PDC type mobile phone 19 is used instead of the electronic load device 18, and the output terminal of the DC-DC converter 17 is connected to the charging connector of the mobile phone 19. The lithium ion secondary battery attached to the cellular phone 19 was removed, and the cellular phone 19 was turned on. I checked the standby status and the camera shooting and data saving operations. However, when making and receiving calls and data communication, the power of the mobile phone is turned off when making calls and data, and the power is not turned off at the time of incoming calls, but the incoming call is impossible. It was possible. The standby time of the mobile phone 19 was 23 hours.

  Embodiment 5 of the fuel cell system according to the present invention will be described below with reference to FIG.

In the configuration shown in the fourth embodiment, the fuel cell protection circuit 2 shown in the first embodiment is inserted between the fuel cell 1 and the DC-DC converter 17 as shown in FIG. The output terminal was connected to the input terminal of the fuel cell protection circuit 2, and the output terminal of the fuel cell protection circuit 2 was connected to the input terminal of the DC-DC converter 17.
In the fourth embodiment, the outgoing and incoming calls, the telephone call, and the data communication of the mobile phone 19 whose operation could not be confirmed can be operated. When the same fuel as that shown in Example 4 was used, the standby time of the mobile phone 19 was 25 hours.

  A sixth embodiment of the fuel cell system according to the present invention will be described below with reference to FIG.

  In the configuration shown in the first embodiment, the configuration of the rush current prevention circuit 6 is changed as follows. In place of the rush current prevention resistor 13 in the first embodiment, the rush current prevention Nch-FET 20 is used. In the first embodiment, the bypass function including the amplifier 8, the comparator 9, and the voltage reference 10 is integrated in the rush current prevention Nch-FET 20 driver 21.

  When the switch 5 detects a voltage of 80% or more of the open circuit voltage of the fuel cell 1, the switch 5 turns on the FET 11 so that power can be input to the fuel cell protection circuit 2. Since the open circuit voltage of the fuel cell is applied to the inverting input terminal of the operational amplifier 22 and the voltage of the non-inverting input terminal is approximately 0 V, the output of the operational amplifier 22 is saturated. When this state is detected, the driver 21 gradually applies a bias to the gate terminal of the FET 20 to decrease the on-resistance value of the FET 20. The driver 21 was adjusted to raise the voltage applied to the gate terminal of the FET 20 to the input voltage of the driver 21 in 10 seconds.

  Embodiment 7 of the fuel cell system according to the present invention will be described below with reference to FIG.

  In the configuration shown in Example 6, only one fuel cell power generation cell constituting the fuel cell 1 was used. The open circuit voltage of the fuel cell power generation cell 1a shown in FIG. 8 was 0.99V. Since the operable voltage of the electronic elements inside the fuel cell protection circuit 2 cannot be secured due to the voltage drop of the fuel cell power generation cell 1a due to the consumption current inside the fuel cell protection circuit 2, the charge pump type boost converter 23 is provided. As shown in FIG. 8, the fuel cell protection circuit 2 was mounted. The output voltage of the boost converter 23 is set to 3 V, and power is supplied to the power source of the electronic elements inside the fuel cell protection circuit 2.

An eighth embodiment of the fuel cell system according to the present invention will be described below with reference to FIG.
In the configuration shown in the first embodiment, the diode 7 and the switch 5 for preventing the backflow of the current of the fuel cell protection circuit 2 are omitted, and the discharge circuit 24 is used. The discharge circuit 24 has a function of preventing a backflow of current to the fuel cell, and is configured using a Pch-EFT 25, an Nch-FET 26, and a comparator 27.

  The voltage at the positive output terminal of the fuel cell output is input to the inverting input terminal of the comparator 27. The voltage of the positive terminal of the electric double layer capacitor 4 is input to the non-inverting input terminal of the comparator. The comparator 27 has a hysteresis. The hysteresis band was set to 50 mV.

  Normally, the output voltage of the fuel cell 1 is higher than the voltage of the electric double layer capacitor 4. At that time, the Pch-FET 26 is in the ON state and the Nch-FET 27 is in the OFF state, and charging / discharging of the electric double layer capacitor 4 is performed. Done normally.

  If the output voltage of the fuel cell 1 becomes lower than the voltage of the electric double layer capacitor 4 due to sudden load fluctuations in the external circuit 3 or excess or shortage of fuel supply to the fuel cell 1, Pch− The FET 26 is turned off and the Nch-FET 27 is turned on, so that the electrical path between the fuel cell 1 and the electric double layer capacitor 4 is cut off and the electric double layer capacitor 4 is discharged.

  Thereby, it is possible to prevent the backflow of the current from the external circuit side to the fuel cell 1 without using the diode for preventing the backflow of the current or the output switch of the fuel cell. In addition, it is possible to remove the resistance component between the electrical paths from the fuel cell 1 to the external circuit 3, and the power output from the fuel cell 1 can be used efficiently.

  In addition, this invention is not limited to the said embodiment, A change is possible in the implementation stage, unless it deviates from the summary. Further, the above embodiments include inventions at respective stages. Within the scope of the claims, a configuration by an appropriate combination of a plurality of disclosed configuration requirements can be extracted as an invention.

  The fuel cell of the present invention can improve the load responsiveness of the fuel cell and can stably operate electronic devices. Further, since the operation of the fuel cell in an overloaded state is prevented, the life of the fuel cell can be extended. Since it is possible to compensate for the shortcomings of the fuel cell with a simple configuration without using auxiliary equipment, it can be applied to a fuel cell as a power source for portable devices.

It is the schematic which shows an example of a structure of the fuel cell concerning Example 1 of this invention. It is a graph which shows an example of the output characteristic of the fuel cell power generation cell concerning Example 1 of this invention. It is the schematic which shows an example of a structure of the fuel cell concerning Example 2 of this invention. It is the schematic which shows an example of a structure of the fuel cell concerning Example 3 of this invention. It is the schematic which shows an example of a structure of the fuel cell concerning Example 4 of this invention. It is the schematic which shows an example of a structure of the fuel cell concerning Example 5 of this invention. It is the schematic which shows an example of a structure of the fuel cell concerning Example 6 of this invention. It is the schematic which shows an example of a structure of the fuel cell concerning Example 7 of this invention. It is the schematic which shows an example of a structure of the fuel cell concerning Example 8 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel cell 1a, 1b, 1c Fuel cell power generation cell 2 Fuel cell protection circuit 3 External circuit 4 Electric double layer capacitor 5 Switch 6 Rush current prevention circuit 7 Schottky diode 8 Current detection amplifier 9 Comparator 10 Voltage reference 11 Nch-FET
12 FET driver 13 Rush current prevention resistor 14 Nch-FET
15 FET driver 16 Fuel cell output current value output terminal 17 DC-DC converter 18 Electronic load device 19 Mobile phone 20 Nch-FET
21 FET Driver 22 Operational Amplifier 23 Boost Converter 24 Discharge Circuit 25 Pch-FET
26 Nch-FET
27 Comparator 28 Resistor

Claims (10)

A fuel cell protection circuit connected to a fuel cell that supplies power to an external circuit,
An electric double layer capacitor that increases the output capacity of the fuel cell and reduces the load on the fuel cell;
A discharge circuit connected in series to the electric double layer capacitor to prevent a backflow of current from the electric double layer capacitor to the fuel cell power generation cell;
Rush current prevention means connected in series to the fuel cell and connected in parallel to the electric double layer capacitor and the discharge circuit;
A fuel cell protection circuit.   The discharge circuit is composed of at least a comparator, a resistor, and a switch, and is based on the voltage of the fuel cell power generation cell so that the voltage of the electric double layer capacitor does not exceed the voltage of the fuel cell power generation cell. The fuel cell protection circuit according to claim 1, wherein a discharge amount of the electric double layer capacitor is controlled.   3. The rush current prevention means includes at least a current limiting element and an output current bypass circuit from the fuel cell power generation cell, and controls the fuel cell output current based on a voltage drop of the current limiting element. The fuel cell protection circuit according to 1.   The current limiting element is a resistor, and a resistance value of the resistor is obtained by dividing an open circuit voltage value of the fuel cell power generation cell by a maximum current value at which the fuel cell power generation cell is 0 V, and the fuel The open circuit voltage of the battery power generation cell is set between a value obtained by dividing the open circuit voltage of the battery power generation cell by a current value at which an undershoot of the voltage of the fuel cell power generation cell does not occur when a step load is applied to the fuel cell power generation cell. The fuel cell protection circuit according to any one of 1 to 3.   5. The fuel cell protection circuit according to claim 1, further comprising a rush current prevention circuit including a semiconductor switch element, wherein the rush current prevention circuit includes a bypass circuit for an output current from the fuel cell power generation cell. The fuel cell protection circuit according to any one of the above.   The fuel cell protection circuit according to claim 1, wherein the current limiting element is a semiconductor switching element.   The rush current prevention circuit has means for changing an on-resistance value of the semiconductor switch element by controlling a gate applied voltage of the semiconductor switch element, and prevents the rush current from the fuel cell. The on-resistance value of the semiconductor switch element is between the maximum resistance value obtained from the semiconductor switch element and the value obtained by dividing the open circuit voltage value of the fuel cell by the maximum current value at which the fuel cell power generation cell becomes 0V. The fuel cell protection circuit according to claim 6, wherein   The semiconductor switch element has both a function of preventing a rush current from the fuel cell only by the semiconductor switch element and a function of a bypass circuit of an output current from the fuel cell power generation cell, The fuel cell protection circuit according to claim 7.   The bypass circuit includes a bypass transistor, and includes means for controlling a charging current to the electric double layer capacitor by changing a bias voltage to the bypass transistor. The fuel cell protection circuit according to claim 8. The fuel according to any one of claims 1 to 9, wherein an equivalent series resistance (ESR) value of the electric double layer capacitor is equal to or less than a maximum value of an internal resistance value of the fuel cell power generation cell. Battery protection circuit.

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