JP4969018B2 - Power supply - Google Patents

Description

  The present invention relates to a power supply device.

  Currently, in portable electronic / electrical devices such as personal computers, secondary batteries such as lithium ion batteries and nickel metal hydride batteries are used as power supply devices. However, the secondary battery can supply power to the personal computer only for a maximum of about 4 hours. Recently, a fuel cell that can supply power to a personal computer continuously for 20 to 40 hours has attracted attention.

A typical method of a fuel cell using methanol as a fuel is a circulation type. FIG. 9 is a block diagram showing a configuration of a conventional circulating fuel cell. In FIG. 9, 111 is a return pump, 112 is a dilution tank, 113 is a methanol pump, 114 is a methanol tank, 116 is a fuel cell, 117 is a fuel cell controller, and 901 is a gas-liquid separator. The fuel cell 116 includes a stack 122, a fuel pump 123, and an air pump 124.
The methanol tank 114 stores several percent to 100% of methanol (CH ₃ OH).

  The methanol pump 113 sends methanol from the methanol tank 114 to the dilution tank 112 based on a command from the fuel cell control unit 117. The dilution tank 112 dilutes several percent to 100% methanol to 5% wt methanol. The fuel pump 123 sends methanol diluted from the dilution tank 112 to the stack 122 based on a command from the fuel cell control unit 117. The air pump 124 sends air into the stack 122 based on a command from the fuel cell control unit 117.

In the stack 122, methanol is supplied to the fuel electrode (−) and air is supplied to the air electrode (+). In the fuel electrode (-), methanol reacts with water to form carbon dioxide, hydrogen ions, and electrons in a region called a three-phase interface where the reactants methanol and water, the catalyst (electrode surface), and the electrolyte come into contact with each other. (CH ₃ OH + H ₂ O → CO ₂ + 6H ⁺ + 6e ⁻ ). Hydrogen ions pass through the polymer membrane, and electrons pass through the external load and arrive at the air electrode (+). At the air electrode (+), oxygen in the air encounters hydrogen ions at the three-phase interface, takes electrons from the catalyst (electrode surface) and reacts to become water (3 / 2O ₂ + 6H ⁺ + 6e ⁻ → 3H ₂ O ).

  The stack 122 discharges used 3 to 5% wt methanol, carbon dioxide, and water from the fuel electrode (−) side. The stack 122 discharges water and air from the air electrode (+) side. The gas-liquid separator 901 separates and discharges carbon dioxide from methanol, carbon dioxide, and water discharged from the stack 122. The return pump 111 sends the methanol and water remaining after separation into the dilution tank 112. Methanol and water are reused in the dilution tank 112 to make diluted methanol.

  Patent Document 1 (Japanese Patent Laid-Open No. 2000-173636) discloses a conventional fuel cell device that supplies power from a secondary battery when an external load suddenly changes. FIG. 10 is a block diagram showing the configuration of the fuel cell device of Patent Document 1. In FIG. The fuel cell main body 1001 uses hydrogen as a fuel gas. When a sudden load fluctuation occurs and the output voltage of the fuel cell main body 1001 temporarily decreases to a predetermined voltage V3 or less, the output from the sensor unit 1009 is output to the charging control unit 1006 as a circuit switching control unit. Stop at 1007. Further, when the output voltage decreases and becomes equal to or lower than a predetermined voltage V4, the output to the auxiliary device 1002 is stopped by the circuit switching control unit 1007 by the signal from the sensor unit 1009, and simultaneously, the output to the auxiliary device 1002 is stopped. The output power is switched to the output power from the secondary battery 1005. The fuel cell device of Patent Document 1 performs control so that stable external load output can be performed based on the output voltage of the fuel cell main body 1001.

  Patent Document 2 (Japanese Patent No. 2775890) discloses a control device for a conventional fuel cell power generation system that maintains a storage battery 1206 at a target charge amount (for example, 80% to 90%). FIG. 11 is a block diagram showing the configuration of the control device of the fuel cell power generation system of Patent Document 2. The discharge electricity quantity calculator 1115 takes the output of the storage battery current detector 1111 and calculates the discharge electricity quantity of the storage battery 1106. The controller 1116 determines the power generation amount of the fuel cell so as to replenish the storage battery 1106 with the amount of electricity corresponding to the amount of discharged electricity every predetermined cycle, and controls the auxiliary machine controller 1110 and the DC-DC converter 1104 to control them. Is output. The control device of the fuel cell power generation system of Patent Document 2 can stably supply power to the load based on the amount of electricity discharged from the storage battery 1106 to keep the storage battery 1106 at the target charge amount.

  Patent Document 3 (Japanese Patent Laid-Open No. 2000-12059) discloses a conventional fuel cell system and fuel cell control method that operates at an operating point with the highest energy conversion efficiency. FIG. 12 is a block diagram showing the configuration of the fuel cell system of Patent Document 3. As shown in FIG. The reformer 1228 generates hydrogen-rich gas (reformed gas) containing hydrogen from methanol and water charged as the fuel 1224 by a steam reforming reaction of methanol. The fuel cell 1236 generates electric power using this hydrogen rich gas as a fuel gas. The control unit 1220 calculates the point with the highest energy conversion efficiency in the fuel cell 1236 based on the gas flow rate, and operates the fuel cell 1236 at this point.

JP 2000-173636 A Japanese Patent No. 2775890 JP 2000-12059 A

  In the conventional circulating fuel cell, since it is difficult to separate only carbon dioxide from the spent fuel, there is a problem that a considerable amount of methanol is exhausted together with carbon dioxide. For this reason, 10% of the supplied amount of methanol was not effective electric power, and the fuel utilization rate was poor (details will be described later).

  In the fuel cell, the amount of fuel supplied to the fuel cell is increased or decreased, so that a certain delay occurs until the electric power output from the fuel cell increases or decreases. For example, in the fuel cell device described in Patent Document 1, it is necessary for the fuel cell to immediately change the supply power in accordance with the load fluctuation. In the fuel cell device described in Patent Document 1, it has been necessary to continue to supply fuel that exceeds the required amount to the fuel cell so that it can immediately respond to a sudden increase in load. This deteriorated the fuel utilization rate of the fuel cell. In a fuel cell using methanol as a fuel, there is a problem that a large amount of methanol is discharged.

In the control device of the fuel cell power generation system of Patent Document 2, since the power generation amount of the fuel cell is changed in a short cycle, the control is difficult and the mechanism of the fuel cell is complicated.
Since the fuel cell system and the fuel cell control method of Patent Document 3 have a reformer, there is a problem that the apparatus becomes expensive and large. In Patent Document 3, the fuel cell 1236 is operated at a point where the energy conversion efficiency (= power generation efficiency × gas utilization rate) is the best. Since it is necessary to supply fuel sufficiently, when the fuel cell system and the fuel cell control method of Patent Document 3 are applied to a non-circulating DMFC (direct methanol fuel cell), methanol that is not used from the fuel cell Will be discharged in large quantities. Therefore, the method for purifying the discharged methanol has become a problem.

  A non-circulating fuel cell is a type of fuel cell that discharges spent fuel without circulating the fuel. In the fuel cell, methanol supplied from the inlet of the fuel cell is gradually consumed and discharged from the outlet. However, there is a problem in that the output voltage of the fuel cell suddenly drops if the methanol to be supplied is insufficient with respect to the output current. In order to enable the fuel cell to stably output power and to cope with sudden changes in load, a considerable amount of methanol that was not used in the conventional non-circulation fuel cell is discharged from the fuel cell. It had been. However, since methanol is toxic, it cannot be discharged as it is. Since the fuel is discharged without being used to some extent, the non-circulating fuel cell was considered not suitable as a fuel cell using toxic methanol as fuel.

The present invention has been made in view of such problems, and an object thereof is to provide a power supply apparatus that is cleanly discharged.
An object of this invention is to provide the power supply device with the excellent fuel utilization rate.
It is an object of the present invention to provide a power supply device that can supply stable power against load power fluctuations without violently changing the power generation of the fuel cell.
An object of this invention is to provide the power supply device of simple structure.

In order to solve the above problems, the present invention has the following configuration. The invention according to claim 1 is a fuel cell using methanol as a fuel, a secondary cell that supplies power to a load, and a fuel cell controller that controls the amount of fuel and / or reaction air supplied to the fuel cell. A power converter that converts power output from the fuel cell into a predetermined voltage or current and supplies power to a load and / or the secondary battery; and a secondary battery that detects a remaining capacity of the secondary battery A remaining capacity detector, and the fuel cell control unit has at least three power generation modes to be switched based on at least the remaining capacity of the secondary battery, and each unit time has a different value in each power generation mode. A constant amount of fuel is supplied to the fuel cell, and the at least three power generation modes include a first power generation mode for supplying a fuel amount of a first value to the fuel cell and a value greater than the first value. There a second generator mode for supplying the amount to the fuel cell of the fuel in the second value, the greater than the first value, and the amount of fuel the fuel of the second value smaller than the third value A third power generation mode for supplying to the battery , wherein the fuel cell control unit, when the remaining capacity of the secondary battery decreases to the first remaining capacity in the third power generation mode, When switching to the second power generation mode and the remaining capacity of the secondary battery increases in the third power generation mode to become a second remaining capacity larger than the first remaining capacity, the first power generation Switching to the mode, and in the second power generation mode, when the remaining capacity of the secondary battery is increased to a third remaining capacity that is larger than the first remaining capacity and smaller than the second remaining capacity, Switching to the third power generation mode, the first power generation Switching the over-de, the reduced residual capacity of the secondary battery, when it becomes the first and greater than the remaining capacity of the second remaining capacity is smaller than the fourth remaining capacity of the third generation mode This is a power supply device.

In the present invention, the minimum value and the maximum amount of fuel per unit time supplied to the fuel cell.
In addition to the large value, one or more standard values are set. For example, the load is the same as the power consumption at the standard
In the meantime, the secondary battery is hardly charged or discharged. fuel
The state where the amount of fuel supplied to the battery is set constant can be continued for a long time. As a result, further combustion
A power supply device with a high fuel utilization rate of the battery can be realized.
When the amount of fuel per unit time supplied to the fuel cell is switched, the fuel utilization rate deteriorates transiently. By providing hysteresis in the condition for switching the amount of fuel supplied to the fuel cell, the amount of fuel supplied to the fuel cell is prevented from being frequently switched. As a result, a power supply device with a higher fuel utilization rate of the fuel cell can be realized.
The present invention has an effect that a power supply device that supplies appropriate power according to the remaining capacity of the secondary battery can be realized by a simple control method. When the amount of fuel per unit time supplied to the fuel cell is switched, the fuel utilization rate deteriorates transiently. For example, by setting the number of power generation modes to 2 to 3, the number of times of switching the amount of fuel per unit time supplied to the fuel cell can be minimized. As a result, it is possible to realize a power supply apparatus that has a higher fuel utilization rate of the fuel cell and a clean discharge.

  Conventionally, there has been no idea of driving a fuel cell under conditions such that the amount of methanol contained in the fuel cell discharge is almost eliminated. For example, in the fuel cell system and the fuel cell control method disclosed in Patent Document 3, the fuel cell is operated at an operating point with the highest energy conversion efficiency under the condition of supplying a sufficient amount of fuel to the fuel cell. Therefore, the operating conditions of the fuel cell described in Patent Document 3 are completely different from the operating conditions of the fuel cell of the present invention.

The invention according to claim 2 is characterized in that the secondary battery remaining capacity detector detects the remaining capacity of the secondary battery based on the voltage of the secondary battery. It is a power supply device.
As a method of detecting the remaining capacity of the secondary battery, there is a method of detecting a current of the secondary battery and calculating a time integral value thereof. However, this method has a problem that errors gradually accumulate. For example, when a lithium battery is used as the secondary battery, the remaining capacity can be accurately detected without causing error accumulation by detecting the voltage of the secondary battery. If the secondary battery is close to full charge, the power supplied to the fuel cell is set to be less than the total power supplied to the load. The secondary battery gradually discharges. This prevents the secondary battery from being overcharged. If the secondary battery is close to a fully discharged state, the power supplied from the fuel cell is set to be larger than the total power supplied to the load. The secondary battery is gradually charged. This prevents the secondary battery from being overdischarged.

The invention according to claim 3 is the power supply device according to claim 1, wherein the fuel cell is a balance type that balances the fuel and the output power of the fuel cell.
The present invention has the effect of realizing a small and inexpensive power supply device that does not require a separator. The present invention has an effect that it is possible to realize a power supply device having a high fuel utilization rate of a fuel cell as compared with a conventional non-circulating fuel cell or a conventional circulating fuel cell.

According to a fourth aspect of the present invention, the first value, the second value, and the third value for the amount of fuel are a minimum value, a maximum value, and an intermediate value, respectively, and the third remaining capacity and In a state where the fourth remaining capacity is the same and the amount of fuel supplied to the fuel cell is an intermediate value, if the remaining capacity of the secondary battery reaches the second remaining capacity , The amount of fuel supplied to the fuel cell is switched to the minimum value, and when the amount of fuel supplied to the fuel cell is the minimum value, the remaining capacity of the secondary battery decreases to reach the fourth remaining capacity . If so, the amount of fuel supplied to the fuel cell is switched to an intermediate value, and in a state where the amount of fuel supplied to the fuel cell is an intermediate value, the remaining capacity of the secondary battery decreases and the first Once it reached the remaining capacity of the fuel supplied to the fuel cell Switching to the maximum value, in the state amount is the maximum value of the fuel supplied to the fuel cell, if the remaining capacity of the secondary battery reaches the third remaining capacity increases, the fuel cell Switch the amount of fuel supplied to an intermediate value,
The power supply device according to claim 3.

  In the present invention, hysteresis is provided in the switching condition of the amount of fuel supplied to the fuel cell, and a standard value (intermediate value) of 1 other than the minimum and maximum values as the amount of fuel per unit time supplied to the fuel cell. Is provided. This standard value is a value commensurate with the average supply power of the load, and therefore the drive time at the standard value is long. As a result, a power supply device with a higher fuel utilization rate of the fuel cell can be realized.

According to a fifth aspect of the present invention, the first value, the second value, and the third value for the amount of fuel are a minimum value, a maximum value, and an intermediate value, respectively, and the fuel supplied to the fuel cell When the remaining capacity of the secondary battery reaches the second remaining capacity in a state where the amount of fuel is at an intermediate value, the amount of fuel supplied to the fuel cell is switched to the minimum value and supplied to the fuel cell. In the state where the amount of fuel to be reduced is the minimum value, if the remaining capacity of the secondary battery decreases and reaches the fourth remaining capacity , the amount of fuel supplied to the fuel cell is switched to an intermediate value, In a state where the amount of fuel supplied to the fuel cell is an intermediate value, if the remaining capacity of the secondary battery decreases and reaches the first remaining capacity , the amount of fuel supplied to the fuel cell is Switch to the maximum value and the amount of fuel supplied to the fuel cell In the state which is larger value, if the remaining capacity of the secondary battery reaches the third remaining capacity increases, it switches the quantity of fuel supplied to the fuel cell to an intermediate value, characterized in that It is a power supply device of Claim 3.

  In the present invention, two intermediate threshold values are provided in addition to the minimum threshold value and the maximum threshold value of the remaining capacity of the secondary battery as a condition for switching the amount of fuel supplied to the fuel cell. This reduces the frequency of switching the amount of fuel supplied to the fuel cell. As a result, a power supply device with a higher fuel utilization rate of the fuel cell can be realized.

According to a sixth aspect of the present invention, when increasing the power output from the fuel cell, after increasing the amount of fuel, the power supplied to the power converter is increased and the power output from the fuel cell is decreased. 2. The power supply device according to claim 1, wherein when the operation is performed, the amount of fuel is decreased after the power supplied to the power converter is decreased. 3.
If the amount of methanol to be supplied is insufficient with respect to the output current, there is a problem that the output voltage of the fuel cell rapidly decreases. According to the present invention, it is possible to prevent the output voltage of the fuel cell from rapidly decreasing when the amount of fuel supplied to the fuel cell is switched. A fuel cell that stably supplies power can be realized.

According to a seventh aspect of the present invention, in the first power generation mode in which the amount of fuel supplied to the fuel cell is a minimum value, the power output by the fuel cell is the same as the self-power consumption of the power supply device. The power supply device according to claim 1.
For example, when the load is in the power save mode or the standby mode, and the power consumption is very low, the power supply device of the present invention will eventually provide the first power generation with the minimum amount of fuel supplied to the fuel cell. Enter mode. At this time, the power output from the fuel cell is substantially the same as the self-power consumption of the power supply device. The fuel cell has almost no methanol discharged from the fuel cell and maintains a very high fuel utilization rate. Since the secondary battery hardly charges or discharges, this state can be continued stably for a long time.

The invention according to claim 8 is characterized in that when the power supply device is activated, the fuel cell control unit initially sets the first power generation mode in which the amount of fuel supplied to the fuel cell is a minimum value. The power supply device according to claim 1.

It takes a while (for example, about 15 minutes) until the fuel cell can supply power to the load after startup (until the fuel cell reaches a predetermined temperature). During that time, almost no power can be supplied to the load. In the meantime, the fuel cell discharge contains a lot of methanol that was not consumed. In the present invention, the fuel cell is initially set to the first power generation mode in which the amount of fuel supplied to the fuel cell is the minimum value until the fuel cell can operate in earnest after startup. Minimize the absolute amount of methanol discharged. Thereby, the quantity of methanol which a purification | cleaning part processes at the time of starting can be minimized. The present invention can realize a power supply device that is cleanly discharged.

According to the present invention, there is an advantageous effect that it is possible to realize a power supply device that can supply necessary power to the main body device without frequently changing the output power of the fuel cell.
According to the present invention, since the fuel cell discharges only a very small amount of methanol, an advantageous effect that a power supply device with a clean discharge can be realized by providing a purification unit having a simple configuration.
According to the present invention, an advantageous effect that a power supply device having an excellent fuel utilization rate can be realized.
According to the present invention, since the output power of the fuel cell is determined based on the remaining capacity of the secondary battery, an advantageous effect that a power supply device having a simple configuration can be realized.
According to the present invention, it is possible to obtain an advantageous effect that the fuel cell can discharge only a small amount of methanol and realize a small and inexpensive power supply device.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments that specifically show the best mode for carrying out the present invention will be described below with reference to the drawings.
Embodiment 1

The power supply device according to the first embodiment will be described with reference to FIGS.
First, the configuration of the power supply device according to the first embodiment will be described. FIG. 1 is a block diagram showing a configuration of a power supply apparatus according to Embodiment 1 of the present invention. In FIG. 1, 101 is a power supply device, and 102 is a main device. The power supply device 101 includes a return pump 111, a dilution tank 112, a methanol pump 113, a methanol tank 114, a purification unit 115, a fuel cell 116, a fuel cell control unit 117, and a fuel cell output current detector that detects an output current of the fuel cell 116. 118, a DC-DC converter 119, a secondary battery 120, and a secondary battery output voltage detector 121 that detects an output voltage of the secondary battery 120. The fuel cell 116 includes a stack 122, a fuel pump 123, and an air pump 124. The main device 102 has a load 131.

The fuel cell 116 is a balance type fuel cell (a non-circulation type fuel cell that balances the amount of fuel used and the amount of electric power to be output) using methanol as a raw material. The secondary battery 120 is a lithium ion secondary battery. The capacity of the secondary battery 120 is 16 Wh. The methanol tank 114 stores several percent to 100% of methanol (CH ₃ OH). The main device 102 is a personal computer.

  The electric power output from the fuel cell 116 is controlled by the DC-DC converter 119 so as to become a target current. If the power output from the fuel cell 116 (DC-DC converter 119) remains even if power is supplied to the main body device 102, the power supply device 101 supplies the power output from the fuel cell 116 to the main body device 102. The secondary battery 120 is charged with electric power. When the power supplied to the main body device 102 is not enough for the power output from the fuel cell, the secondary battery 120 discharges the insufficient power. The power supply apparatus 101 supplies the main body apparatus 102 with power that is a combination of the power output from the fuel cell 116 and the power discharged from the secondary battery 120.

  The fuel cell control unit 117 has three power generation modes, and supplies a certain amount of fuel per unit time, which is a different value in each power generation mode, to the fuel cell 116. The fuel cell control unit 117 obtains the remaining capacity of the secondary battery 120 from the output voltage of the secondary battery 120 detected by the secondary battery output voltage detector 121. The fuel cell control unit 117 selects a power generation mode based on the remaining capacity of the secondary battery 120 (controls the output power of the fuel cell 116) (details will be described later). The fuel cell control unit 117 instructs the value of the input target current to the DC-DC converter 119 according to the selected power generation mode. As will be described later, when a certain amount of fuel is supplied to the fuel cell, the relationship between the output voltage and the output current is represented by a certain function on the graph. The DC-DC converter 119 controls the output current so that the output current of the fuel cell 116 (the input current of the DC-DC converter 119) detected by the fuel cell output current detector 118 matches the input target current as much as possible. . That is, the fuel cell 116 outputs predetermined output power (= output current of the fuel cell 116 × output voltage corresponding to the output current), and the DC-DC converter 119 converts the output power of the fuel cell 116, The load 131 and / or the secondary battery 120 are supplied.

  Specifically, the fuel cell control unit 117 uses the return pump 111, the methanol pump 113, the fuel pump 123, and the air pump 124 to adjust the amount of fuel and air supplied to the fuel cell 116. The methanol pump 113 sends methanol from the methanol tank 114 to the dilution tank 112 based on a command from the fuel cell control unit 117. The dilution tank 112 dilutes several percent to 100% methanol to 6% wt methanol. The fuel pump 123 sends methanol diluted from the dilution tank 112 to the stack 122 based on a command from the fuel cell control unit 117. The air pump 124 sends air into the stack 122 based on a command from the fuel cell control unit 117.

In the stack 122, methanol is supplied to the fuel electrode (−) and air is supplied to the air electrode (+). At the fuel electrode (−), methanol reacts with water to become carbon dioxide, hydrogen ions, and electrons (CH ₃ OH + H ₂ O → CO ₂ + 6H ⁺ + 6e ⁻ ). Hydrogen ions pass through the polymer membrane, and electrons pass through the external load and arrive at the air electrode (+). At the air electrode (+), hydrogen ions and oxygen in the air meet and take electrons from the electrode surface and react to become water (3 / 2O ₂ + 6H ⁺ + 6e ⁻ → 3H ₂ O).

  The stack 122 discharges 0.5% wt methanol, carbon dioxide, and water that are consumed from the fuel electrode (−) side and further reduced in concentration. The purification unit 115 purifies the discharged methanol by changing it to carbon dioxide and water using a catalyst. The stack 122 discharges water and air from the air electrode (+) side. The return pump 111 sends water discharged from the air electrode (+) side to the dilution tank 112. The water discharged from the air electrode (+) side is reused as a solvent for diluting methanol in the dilution tank 112.

  FIG. 2 shows the output current-output voltage characteristic, output current-output power characteristic, and output current-methanol discharge rate characteristic of the fuel cell 116 depending on the amount of fuel in the balanced fuel cell of the power supply device according to Embodiment 1 of the present invention. FIG. In FIG. 2, the horizontal axis represents output current (A), and the vertical axis represents output voltage (V) and output power (W). 201, 202, and 203 indicate output current-output voltage characteristics when the amounts of fuel are 0.1 cc / min, 0.2 cc / min, and 0.3 cc / min, respectively. Reference numerals 204, 205, and 206 indicate output current-output power characteristics when the amounts of fuel are 0.1 cc / min, 0.2 cc / min, and 0.3 cc / min, respectively. Reference numeral 207 denotes a methanol discharge rate discharged by the fuel cell 116 when the amount of fuel is 0.3 cc / min. The output current-output voltage characteristics and output current-output power characteristics of the fuel cell 116 vary depending on the amount of fuel supplied to the fuel cell 116. If the amount of fuel is determined to be a certain value, the output current-output voltage characteristic and the output current-output power characteristic with the amount of fuel are uniquely determined.

The power supply apparatus 101 according to the first embodiment performs constant current control on the output of the fuel cell 116. A case where the amount of fuel is 0.3 cc / min will be described. In the output current-output power characteristic 206, when the output current is 0 to A ₃ (A), the power increases as the output current increases. When the output current is A ₃ (A), the power becomes the maximum value. When the output current exceeds A ₃ (A), the power decreases rapidly as the output current increases.
Also in the output current-output voltage characteristic 203, when the output current is 0 to A ₃ (A), the voltage decreases slightly as the output current increases, but a stable voltage is maintained. When the output current exceeds A ₃ (A), the decrease rate of the output voltage increases as the output current increases.

At the methanol discharge rate 207, as the output current of the fuel cell 116 increases from 0 to A ₃ (A), the amount of methanol discharged (the amount of methanol remaining in the discharge of the fuel cell 116) decreases. When the output current becomes A ₃ (A), the amount of methanol to be discharged becomes very small. Thereafter, as the output current further increases, the amount of methanol discharged decreases slightly.
That is, when the output current is in the range of 0 to A ₃ (A), the fuel cell 116 discharges the remaining methanol without using up the supplied methanol. When the output current is equal to or greater than A ₃ (A), the fuel cell 116 almost uses up the supplied methanol and discharges only a trace amount of methanol. When the output current is larger than A ₃ (A) by a predetermined amount or more, the output voltage of the fuel cell 116 suddenly drops. The same applies when the amount of fuel is 0.2 cc / min or 0.1 cc / min.

The balanced fuel cell according to Embodiment 1 of the present invention supplies a fixed amount of fuel per unit time to the fuel cell 116 in each power generation mode, and the current value from the current value at which the output power is maximized by the amount of the fuel. Power is generated within a range up to a value greater by a predetermined amount. The range is determined according to the amount of fuel.
The fuel cell control unit 117 of the power supply apparatus 101 according to the first embodiment is based on an output current-output voltage characteristic and an output current-output power characteristic diagram (for example, FIG. 2) using the amount of fuel as a parameter. The amount of fuel and the corresponding target output current value (from the current value at which power is maximized by the amount of fuel to the current value that is a predetermined amount greater than the current value (current value before the output voltage suddenly drops)) (Values within the range) are stored in association with each other. The fuel cell controller 117 instructs the target output current value corresponding to the amount of fuel to the DC-DC converter 119. For example, when methanol is supplied to the stack 122 at an amount of fuel of 0.1 cc / min, the fuel cell control unit 117 determines that the output current value of the fuel cell 116 is A _{1 to} A ₁ + α (α is a positive number) based on the above characteristic diagram. The DC-DC converter 119 is instructed to have a value within the range.

  FIG. 3 is a diagram showing the fuel utilization rates of the conventional circulating fuel cell and the balanced fuel cell according to Embodiment 1 of the present invention. In FIG. 3, the amount of electric power when the supplied amount of methanol is converted to electric power without loss is represented as 100%, and the amount of active electric power and the amount of electric power lost are represented. A significant difference between the conventional circulating fuel cell and the balanced fuel cell according to Embodiment 1 of the present invention is loss due to evaporation during separation. Since the circulation fuel cell of the conventional example has difficulty in separating and discharging only carbon dioxide, methanol is also discharged when discharging carbon dioxide. Therefore, in the conventional circulating fuel cell, 28% of the supplied methanol was lost due to evaporation during separation. Thus, since it is not allowed to exhaust a large amount of toxic methanol into the air as it is, a measure for purifying the large amount of methanol (to change it into carbon dioxide and water) was necessary.

On the other hand, as described with reference to FIG. 2, the balanced fuel cell according to Embodiment 1 of the present invention generates power within a range from the current value at which power is maximized to a value that is a predetermined amount greater than the current value. For this reason, the supplied methanol is almost used up and only a trace amount of methanol is discharged. Therefore, the balanced fuel cell according to Embodiment 1 of the present invention discharges only 2% of the supplied methanol. The discharged trace amount of methanol can be easily purified by the purification unit 115.
As a result, the effective power amount of the conventional circulating fuel cell is 7.6% (the loss power amount is 92.4%), whereas the effective power amount of the balanced fuel cell according to the first embodiment of the present invention is 15. 9% (power loss is 84.1%). The balanced fuel cell according to Embodiment 1 of the present invention can supply more than twice the conventional power with the same fuel.

  As can be seen from the output current-output voltage characteristics of FIG. 2, the output voltage drops abruptly when the output current increases even slightly within the range of the output current. For this reason, it is not preferable that the output power of the fuel cell 116 fluctuate rapidly because the output voltage may drop rapidly. In the present embodiment, since the secondary battery 120 responds to a sudden change in the power supplied to the load, the fuel cell 116 may continue to supply a constant power in one power generation mode. In the first embodiment, the output current substantially coincides with the target output current value (a value within a range from the current value at which the power is maximum with the amount of fuel to a current value that is larger by a predetermined amount than the current value). It is sufficiently possible to maintain

Next, a method for controlling the power supply device according to the first embodiment will be described. The control method of the power supply device according to the first embodiment of the present invention is a control method in which the fuel cell 116 can maintain as constant output power as possible.
The operation modes of main device 102 according to the first embodiment of the present invention are roughly classified into four operation modes classified based on the approximate value of average power consumption. The four operation modes of the main unit 102 (personal computer) will be described using Table 1 below.

The first operation mode is a mode in which a USB (Universal Serial Bus) device (for example, a hard disk drive connected by USB), a PC card, or the like is connected to a personal computer and the connected devices are driven. The first operation mode is a short time because it is only the time during which the connected device is actually driven. Since a large amount of power is required to drive the device, the average power consumption in the first operation mode is 20 W.
The second operation mode is a mode in which a personal computer is playing back a moving image. The average power consumption in the second operation mode is 14W.
The third operation mode is a mode in which application software is executed on the personal computer (for example, a key input operation of a word processor is performed). Normally, this operation mode is the most frequently used mode for a long time. The average power consumption in the third operation mode is 10W.
The fourth operation mode is a mode in which the personal computer is in a standby state or a hibernation state. The fourth operation mode is a mode that is used next to the third operation mode and is frequently used for a long time. The average power consumption in the fourth operation mode is 0.5 W.
Note that the average power consumption required to start the main unit is 14 W.

The fuel cell 116 according to Embodiment 1 of the present invention has three power generation modes in which the power generation amount is a maximum value (17 W power generation mode), an intermediate value (13 W power generation mode), and a minimum value (3 W power generation mode). The DC-DC converter 119 outputs 17 W, 13 W, and 3 W in each power generation mode. The three power generation modes of the fuel cell 116 will be described using Table 2 below.
Table 2 shows the charge / discharge power of the secondary battery 120 when the operation mode of the main device 102 and the power generation mode of the fuel cell 116 are combined. The power (self-consumption power) for operating the fuel cell 116 is 3 W in any power generation mode. In Table 2, the total power consumption is a value obtained by adding the average power consumption (Table 1) of the main unit 102 and the self-power consumption (3 W) of the fuel cell 116. In Table 2, charge / discharge power of the secondary battery 120 = average power consumption of the main body device 102 (Table 1) + self power consumption of the fuel cell 116 (3 W) −generated power of the fuel cell 116 (a positive value is Discharge, negative value is charged).

When the main device 102 is in the third operation mode with the highest frequency (during key input operation), the generated power of the fuel cell 116 in which the secondary battery 120 is neither discharged nor charged is 13 W. As a result, the intermediate value of the power generation amount is set to 13W. When the main device 102 is in the fourth most frequently operating mode (standby, hibernation), the power generated by the fuel cell 116 in which the secondary battery 120 is neither discharged nor charged is 3.5 W. The minimum power generation amount is 3W.
When the main unit 102 is in the third operation mode and the power generation amount of the fuel cell 116 is an intermediate value (13 W power generation mode), the secondary battery 120 hardly charges or discharges. The fuel cell 116 can continue the 13 W power generation mode for a long time. Similarly, when the main body device 102 is in the fourth operation mode and the power generation amount of the fuel cell 116 is the minimum value (3 W power generation mode), the power output from the fuel cell 116 is the self-power consumption of the power supply device 101. Is substantially the same. The secondary battery 120 discharges 0.5 W, but the fuel cell 116 can continue the 3 W power generation mode for over 10 hours.

  When the fuel cell 116 is in the 17 W power generation mode and the main body device 102 is in the first operation mode, the secondary battery 120 is in a 6 W (= 20 + 3-17) discharge state. If main device 102 is in the second operation mode, secondary battery 120 is in a state of neither discharging nor charging (0 = 14 + 3-17). When main device 102 is in the third operation mode, secondary battery 120 is in a 4 W (= | 10 + 3-17 |) charge state. When the main device 102 is in the fourth operation mode, the secondary battery 120 is in a charged state of 13.5 W (= | 0.5 + 3-17 |).

  When the fuel cell 116 is in the 13W power generation mode, if the main device 102 is in the first operation mode, the secondary battery 120 is in a 10 W (= 20 + 3-13) discharge state. When main device 102 is in the second operation mode, secondary battery 120 is in a 4 W (= 14 + 3-13) discharge state. If main device 102 is in the third operation mode, secondary battery 120 is in a state of neither discharging nor charging (0 = 10 + 3-13). When the main device 102 is in the fourth operation mode, the secondary battery 120 is in a charged state of 9.5 W (= | 0.5 + 3-13 |).

  When the fuel cell 116 is in the 3W power generation mode, if the main device 102 is in the first operation mode, the secondary battery 120 is in a 20 W (= 20 + 3-3) discharge state. When main device 102 is in the second operation mode, secondary battery 120 is in a 14 W (= 14 + 3-3) discharge state. When main device 102 is in the third operation mode, secondary battery 120 is in a 10 W (= 10 + 3-3) discharge state. When main device 102 is in the fourth operation mode, secondary battery 120 is in a 0.5 W (= 0.5 + 3-3) discharge state.

As described above, the fuel cell control unit 117 obtains the remaining capacity of the secondary battery 120 from the output voltage of the secondary battery 120. The fuel cell control unit 117 determines the power generation mode of the fuel cell 116 based on the remaining capacity of the secondary battery 120.
FIG. 4 is a diagram showing discharge characteristics (remaining capacity-voltage characteristics) of a general secondary battery (for example, a lithium battery). In FIG. 4, the horizontal axis represents the remaining capacity (%), and the vertical axis represents the output voltage (V). As shown in FIG. 4, if the output voltage of the secondary battery 120 is detected, the remaining capacity of the secondary battery 120 can be known. In order to prevent the secondary battery 120 from being overcharged or overdischarged, and for example, until the fuel cell 116 can supply power when the fuel cell 116 is activated, the secondary battery 120 alone supplies power to the load. In order to always have as much power as possible, the power supply device 101 according to the first embodiment of the present invention controls the remaining capacity of the secondary battery 120 to be in the range of 35% to 95%.

A method for determining the power generation mode of the fuel cell of the power supply device according to the first embodiment will be described.
FIG. 5 is a flowchart showing transition of the power generation mode of the fuel cell of the power supply device according to Embodiment 1 of the present invention. In FIG. 5, when the main apparatus 102 is turned on, the fuel cell control unit 117 sets the fuel cell 116 to the 3W power generation mode in step 501. In step 502, the fuel cell control unit 117 determines whether or not the fuel cell 116 has reached a predetermined temperature. Until the fuel cell 116 reaches a predetermined temperature, the fuel cell control unit 117 maintains the 3W power generation mode. The fuel cell 116 can stably generate power when the temperature reaches 40 ° C. to 60 ° C. In other words, the fuel cell 116 cannot perform sufficient power generation until the temperature of the stack 122 rises to 40 ° C. to 60 ° C. (normally, it takes about 15 minutes to reach this temperature after the power is turned on). . Even if the fuel cell control unit 117 is set to the 17 W power generation mode, for example, and supplies a large amount of methanol to the fuel cell 116 by the time the fuel cell 116 reaches a predetermined temperature, the fuel cell 116 cannot process and a large amount of methanol is consumed. Will be discharged. Therefore, in order to prevent this from occurring, the fuel cell control unit 117 maintains the 3W power generation mode until the fuel cell 116 reaches a predetermined temperature. In the first embodiment, the predetermined temperature is 40 ° C.

  When the fuel cell 116 reaches a predetermined temperature, the process proceeds to step 503. In step 503, the fuel cell control unit 117 determines whether or not the remaining capacity SOC of the secondary battery 120 is smaller than 95%. If the remaining capacity SOC of the secondary battery 120 is smaller than 95%, the process proceeds to step 504. In step 504, the fuel cell control unit 117 determines whether or not the remaining capacity SOC of the secondary battery 120 is greater than 35%. If the remaining capacity SOC of the secondary battery 120 is greater than 35%, the process proceeds to step 505. In step 505, the fuel cell control unit 117 sets the fuel cell 116 to the 13W power generation mode. Returning to step 503, the processing is repeated.

  In step 504, if the remaining capacity SOC of the secondary battery 120 is 35% or less, the process proceeds to step 506. In step 506, the fuel cell control unit 117 sets the fuel cell 116 to the 17 W power generation mode. In step 507, the fuel cell control unit 117 determines whether the remaining capacity SOC of the secondary battery 120 is 65% or more. Until the remaining capacity SOC of the secondary battery 120 reaches 65%, the process returns to step 506, and the fuel cell control unit 117 maintains the 17 W power generation mode. If the remaining capacity SOC of the secondary battery 120 is 65% or more in step 507, the process proceeds to step 505. In step 505, the fuel cell control unit 117 sets the fuel cell 116 to the 13W power generation mode. Returning to step 503, the processing is repeated.

  In step 503, if the remaining capacity SOC of the secondary battery 120 is 95% or more, the process proceeds to step 508. In step 508, the fuel cell control unit 117 sets the fuel cell 116 to the 3W power generation mode. In step 509, the fuel cell control unit 117 determines whether the remaining capacity SOC of the secondary battery 120 is 65% or more. Until the remaining capacity SOC of the secondary battery 120 reaches 65%, the process returns to step 508, and the fuel cell control unit 117 maintains the 3W power generation mode. If the remaining capacity SOC of the secondary battery 120 is 65% or less in step 507, the process proceeds to step 505. In step 505, the fuel cell control unit 117 sets the fuel cell 116 to the 13W power generation mode. Returning to step 503, the processing is repeated.

A method for controlling the power supply device according to the first embodiment will be described in detail with reference to FIG. In FIG. 6, the horizontal axis represents time, and the vertical axis represents the remaining capacity (%) 611 of the secondary battery 120 and the output power (W) 612 of the fuel cell 116. However, the time on the horizontal axis is shown reduced or enlarged for convenience.
In 601, the main device 102 is turned on, and the main device 102 starts to start. The fuel cell 116 starts power generation in the 3W power generation mode (step 501). Between 601 and 602, the secondary battery 120 supplies (discharges) most of the average power consumption (14 W) required for starting the main body device 102 and the self-power consumption (3 W) of the fuel cell 116. In step 602, the main apparatus 102 is completely activated, and the main apparatus 102 executes a key input operation of a word processor that is application software (third operation mode). Between 602 and 603, the secondary battery 120 supplies (discharges) most of the operating power (10 W) of the main body device 102 and the self-power consumption (3 W) of the fuel cell 116. Between 601 and 603, the remaining capacity of the secondary battery 120 decreases.

  At 603, the fuel cell 116 reaches a predetermined temperature (Yes at step 502). The fuel cell control unit 117 switches to the 17 W power generation mode based on the remaining capacity (35% or less) of the secondary battery 120 (step 506). When completely switched to the 17 W power generation mode, the secondary battery 120 is charged by 4 W (the remaining capacity of the secondary battery 120 increases). At 604, the fuel cell control unit 117 determines the remaining capacity (65%) of the secondary battery 120 and switches to the 13 W power generation mode (step 505). When fully switched to the 13W power generation mode, the secondary battery 120 is neither discharged nor charged (the remaining capacity of the secondary battery 120 is constant).

In 605, the main apparatus 102 enters a standby state or a dormant state (fourth operation mode). Between 605 and 606, the secondary battery 120 is charged by 9.5 W (the remaining capacity of the secondary battery 120 increases). In 606, the fuel cell control unit 117 determines the remaining capacity (95%) of the secondary battery 120 and switches to the 3W power generation mode (step 508). When the mode is completely switched to the 3W power generation mode, the secondary battery 120 is discharged by 0.5 W (the remaining capacity of the secondary battery 120 is slowly decreased).
In 607, the main apparatus 102 is in the middle of moving image reproduction (second operation mode). Between 607 and 608, the secondary battery 120 is discharged by 14 W (the remaining capacity of the secondary battery 120 is reduced). At 608, the fuel cell control unit 117 determines the remaining capacity (65%) of the secondary battery 120 and switches to the 13 W power generation mode (step 505). After 608, the secondary battery 120 discharges by 4 W (the remaining capacity of the secondary battery 120 decreases).

  When the power output from the fuel cell 116 is increased, the power supplied from the power converter 119 to the load 131 is increased after the amount of fuel is increased, and when the power output from the fuel cell 116 is decreased. After reducing the power supplied to converter 119, the amount of fuel is reduced. Accordingly, for example, the operating point of the fuel cell 116 in FIG. 2 exceeds the range α of the output current-output voltage characteristic 201 to the right, and the output voltage of the fuel cell 116 can be prevented from dropping sharply.

In Embodiment 1, by changing the output power of the fuel cell with hysteresis, the continuous drive time in one power generation mode (constant output power) is lengthened, and the number of times of switching the power generation mode is minimized. Thereby, it is possible to make the amount of methanol discharged fine.
In the first embodiment, it is possible to double the amount of active power output by the fuel cell relative to the methanol supplied to the fuel cell, as compared with the conventional circulating fuel cell.
<< Embodiment 2 >>

The power supply device according to the second embodiment will be described with reference to FIGS. 2, 7, and 8. The DC-DC converter 119 of the first embodiment controls the output power so that the output current of the fuel cell 116 matches the target current. The DC-DC converter 719 of the second embodiment controls the output power so that the output voltage of the fuel cell 116 becomes the target voltage.
First, the configuration of the power supply device according to the second embodiment will be described. FIG. 7 is a block diagram showing the configuration of the power supply device according to the second embodiment of the present invention. The power supply device 701 according to the second embodiment includes a fuel cell output voltage detector 718 and a DC-DC converter 719 instead of the fuel cell output current detector 118 and the DC-DC converter 119 according to the first embodiment. In other respects, the power supply device 701 of the second embodiment is the same as that of the first embodiment. In FIG. 7, the same reference numerals are given to the same blocks as those in the first embodiment.

In FIG. 7, reference numeral 701 denotes a power supply device, and reference numeral 102 denotes a main body device. The power supply device 701 includes a return pump 111, a dilution tank 112, a methanol pump 113, a methanol tank 114, a purification unit 115, a fuel cell 116, a fuel cell control unit 117, and a fuel cell output voltage detector that detects the output voltage of the fuel cell 116. 718, a DC-DC converter 719, a secondary battery 120, and a secondary battery output voltage detector 121 that detects the voltage of the secondary battery 120. The fuel cell 116 includes a stack 122, a fuel pump 123, and an air pump 124. The main device 102 has a load 131. Description of the same block is omitted.
The fuel cell 116 is a balanced fuel cell using methanol as a raw material. The secondary battery 120 is a lithium ion secondary battery. The methanol tank 114 stores several percent to 100% of methanol (CH ₃ OH). The main device 102 is a personal computer.

  The fuel cell control unit 117 has three power generation modes, and supplies a certain amount of fuel per unit time, which is a different value in each power generation mode, to the fuel cell 116. The fuel cell control unit 117 obtains the remaining capacity of the secondary battery 120 from the output voltage of the secondary battery 120 detected by the secondary battery output voltage detector 121. The fuel cell control unit 117 selects a power generation mode based on the remaining capacity of the secondary battery 120 (controls the output power of the fuel cell 116). The fuel cell control unit 117 instructs the value of the input target voltage to the DC-DC converter 719 according to the selected power generation mode. As described in the first embodiment, when a certain amount of fuel is supplied to the fuel cell, the relationship between the output voltage and the output current is represented by a certain function on the graph. The DC-DC converter 719 controls the output voltage of the fuel cell 116 detected by the fuel cell output voltage detector 718 (the input voltage of the DC-DC converter 719) so that it matches the input target voltage as much as possible. . That is, the fuel cell 116 outputs predetermined output power (= output voltage of the fuel cell 116 × output current corresponding to the output voltage), and the DC-DC converter 719 converts the output power of the fuel cell 116, The load 131 and / or the secondary battery 120 are supplied.

  If power output from the fuel cell remains even if power is supplied to the main device 102, the power supply device 701 supplies the power output from the fuel cell 116 to the main device 102 and charges the secondary battery 120 with the surplus power. To do. When the power supplied to the main body device 102 is not enough for the power output from the fuel cell, the secondary battery 120 discharges the insufficient power. The power supply device 701 supplies the main body device 102 with power that is a combination of the power output from the fuel cell 116 and the power discharged from the secondary battery 120. The control method of the fuel cell 116 has been described in detail in the first embodiment.

  FIG. 2 shows the output current-output voltage characteristic, output current-output power characteristic, and output current-methanol discharge rate characteristic of the fuel cell 116 depending on the amount of fuel of the balanced fuel cell of the power supply apparatus according to Embodiment 2 of the present invention. FIG. FIG. 2 has already been described. The output current-output voltage characteristics and output current-output power characteristics of the fuel cell 116 vary depending on the amount of fuel supplied to the fuel cell 116. If the amount of fuel is determined to be a certain value, the output current-output voltage characteristic and the output current-output power characteristic with the amount of fuel are uniquely determined.

In FIG. 2, the voltage at the point where the output power of the fuel cell 116 becomes maximum when the amount of fuel is 0.1 cc / min is V ₁ , and the current is A ₁ . When the amount of fuel is 0.2 cc / min, the voltage at the point where the output power of the fuel cell 116 becomes maximum is V ₂ and the current is A ₂ . When the amount of fuel is 0.3 cc / min, the voltage at which the output power of the fuel cell 116 becomes maximum is V ₃ and the current is A ₃ . The power supply apparatus 701 according to the second embodiment performs constant voltage control on the output of the fuel cell 116.

The balanced fuel cell according to Embodiment 2 of the present invention supplies a constant amount of fuel per unit time to the fuel cell 116 in each power generation mode, and the voltage value from the voltage value at which the output power is maximized by the amount of the fuel. Power is generated within a range up to a value lower by a predetermined amount. The range is determined according to the amount of fuel.
The fuel cell control unit 117 of the power supply apparatus 101 according to the second embodiment generates each power generation based on output current-output voltage characteristics and output voltage-output power characteristics diagrams (for example, FIGS. 2 and 8) using the amount of fuel as a parameter. A certain amount of fuel in the mode, and a corresponding target output voltage value (a value within a range from a voltage value at which power is maximum at the amount of fuel to a voltage value lower than the voltage value by a predetermined amount), It is stored in correspondence. The fuel cell control unit 117 instructs the target output voltage value corresponding to the amount of fuel to the DC-DC converter 719. For example, when methanol is supplied to the stack 122 at a fuel amount of 0.1 cc / min, the fuel cell control unit 117 determines that the output voltage value of the fuel cell 116 is V _{1 to} V ₁ -β (β is a positive number based on the above characteristic diagram. ) To the DC-DC converter 719 so that the value is within the range of In the first and second embodiments, the target operating point is substantially the same. For example, taking the case where the amount of fuel is 0.3 cc / min (output current-output voltage characteristic 203) as an example, the target current of constant current control in the first embodiment and the target of constant voltage control in the second embodiment are described. The point determined by the voltage is located on the output current-output voltage characteristic 203.

  In the first embodiment, the output of the fuel cell 116 is subjected to constant current control. However, the output current of the fuel cell 116 is equal to or greater than the current value at the point where the output power is maximum, and the current range in which the output voltage of the fuel cell is maintained above a certain value is narrow (the output is exceeded when the current exceeds a predetermined range). The voltage drops rapidly.) Therefore, the allowable range of current in constant current control is narrow (constant current control needs to be performed with high accuracy). In contrast, in the second embodiment, the output of the fuel cell 116 is controlled at a constant voltage. As shown in FIG. 2, in the region where the output voltage is lower than the point where the output power of the fuel cell 116 is maximum, the output voltage of the fuel cell 116 is equal to or lower than the voltage value at the point where the output power is maximum, and The voltage range in which the output voltage of the fuel cell is maintained above a certain level is relatively wide. The output voltage does not drop more sharply when the output voltage of the fuel cell 116 decreases from the target value by a certain rate or more than when the output current increases from the target value by a certain rate or more. Therefore, the constant voltage type balanced fuel cell of the second embodiment is easier to control than the constant current type balanced fuel cell of the first embodiment, and can supply stable power.

In order to compare with Embodiment 1 (constant current type), it demonstrated on the basis of the electric current using FIG. Since the fuel cell of the power supply device according to the second embodiment is a constant voltage type, the description will be made with reference to the voltage with reference to FIG.
FIG. 8 is a graph showing output voltage-output power characteristics according to the amount of fuel in the balanced fuel cell of the power supply apparatus according to Embodiment 2 of the present invention. FIG. 8 is a rewrite of FIG. 2 with the horizontal axis representing current, with the horizontal axis representing voltage. In FIG. 8, the horizontal axis represents the output voltage (V), and the vertical axis represents the output power (W). Reference numerals 801, 802, and 803 denote output voltage-output power characteristics when the amounts of fuel are 0.1 cc / min, 0.2 cc / min, and 0.3 cc / min, respectively. The slope of the output voltage-output power characteristic in the region where the voltage is lower than the point where the output power is maximum in FIG. 8 is the output current-output power characteristic in the region where the current is larger than the point where the output power is maximum in FIG. It is much gentler than the slope of. This indicates that the constant voltage control in the second embodiment is much easier than the constant current control in the first embodiment.
In the second embodiment, the DC-DC converter can supply more stable power than in the first embodiment by controlling the output power of the fuel cell so that the output voltage of the fuel cell becomes the target voltage. It is.
Here, the power supply device 701 of the second embodiment realizes a fuel utilization rate equivalent to that of the power supply device of the first embodiment (FIG. 3).

In Embodiments 1 and 2, a lithium ion secondary battery is used as the secondary battery, but other types of secondary batteries such as a lead storage battery, a nickel cadmium storage battery, and a nickel hydrogen storage battery may be used.
In the first and second embodiments, the main body apparatus 102 is a personal computer, but may be another apparatus that requires a power source.

  In FIG. 5, in the first and second embodiments, in either the 17W power generation mode or the 3W power generation mode, the mode is switched to the 13W power generation mode based on the intermediate threshold (residual capacity SOC is 65%) (step 507, 509). Instead of this, different intermediate threshold values may be set. For example, in step 507, the fuel cell control unit 117 determines whether or not the remaining capacity SOC of the secondary battery 120 is 75% or more. In step 509, the fuel cell control unit 117 determines that the remaining capacity SOC of the secondary battery 120 is 55%. It is determined whether or not: When switching from the 17W power generation mode to the 13W power generation mode from the first intermediate threshold (step 509) when switching from the 3W power generation mode to the 13W power generation mode (when the remaining capacity of the secondary battery decreases) The second intermediate threshold (step 507) when the remaining capacity increases (step 507) may be a large value or a small value.

In the above embodiment, the power supply device has three power generation modes. However, the present invention is not limited to this, and the power supply device may have n (n is a positive integer of 2 or more) power generation modes.
In the first embodiment, the power supply device uses a value equal to or higher than the output current value of the fuel cell in a state where the output power is substantially maximum as the target current. Instead, the target current value may be a value smaller than the output current value of the fuel cell in a state where the output power is substantially maximum as long as the methanol discharged from the fuel cell does not increase so much. In the second embodiment, the power supply apparatus uses a value equal to or lower than the output voltage value of the fuel cell in a state where the output power is substantially maximum as the target voltage. Alternatively, the target current value may be larger than the output voltage value of the fuel cell in a state where the output power is substantially maximum as long as the methanol discharged from the fuel cell does not increase so much. However, the configurations of the first and second embodiments are preferable.
By applying the present invention, a power supply device having a separator can be realized, or a power supply device having a configuration without using a separator can be realized.

  The power supply apparatus of the present invention is useful as a power supply apparatus for various devices such as a personal computer.

The block diagram which shows the structure of the power supply device of Embodiment 1 of this invention. The figure which shows the output current-output voltage characteristic, the output current-output power characteristic, and the output current-methanol discharge rate characteristic with the quantity of the fuel of the balance type fuel cell of Embodiment 1 and 2 of this invention. The figure which shows the fuel utilization of the circulation type fuel cell of a prior art example, and the balance type fuel cell of Embodiment 1 of this invention. Diagram showing discharge characteristics of a typical secondary battery The flowchart which shows the transition of the electric power generation mode of the fuel cell of the power supply device of Embodiment 1 of this invention. The figure which shows an example of the change of the remaining capacity of the secondary battery of the power supply device of Embodiment 1 of this invention, and the electric power generation mode of a fuel cell. The block diagram which shows the structure of the power supply device of Embodiment 2 of this invention. The figure which shows the output voltage-output electric power characteristic with the quantity of the fuel of the balance type fuel cell of the power supply device of Embodiment 2 of this invention. Block diagram showing the configuration of a conventional circulating fuel cell Block diagram showing the configuration of the fuel cell device of Patent Document 1 The block diagram which shows the structure of the fuel cell power generation system control apparatus of patent document 2 Block diagram showing the configuration of the fuel cell system of Patent Document 3

Explanation of symbols

DESCRIPTION OF SYMBOLS 101,701 Power supply device 102 Main body apparatus 111 Return pump 112 Dilution tank 113 Methanol pump 114 Methanol tank 115 Purifying part 116 Fuel cell 117 Fuel cell control part 118 Fuel cell output current detector 119, 719 DC-DC converter 120 Secondary battery 121 Secondary battery output voltage detector 122 Stack 123 Fuel pump 124 Air pump 131 Load 718 Fuel cell output voltage detector

Claims (8)

A fuel cell fueled with methanol;
A secondary battery for supplying power to the load;
A fuel cell controller that controls the amount of fuel and / or reaction air supplied to the fuel cell;
A power converter that converts power output from the fuel cell into a predetermined voltage or current and supplies power to a load and / or the secondary battery;
A secondary battery remaining capacity detector for detecting the remaining capacity of the secondary battery;
Have
The fuel cell control unit has at least three power generation modes to be switched based on at least the remaining capacity of the secondary battery, and supplies a constant amount of fuel per unit time, which is a different value in each power generation mode, to the fuel cell. Supply
The at least three power generation modes include a first power generation mode that supplies a fuel amount of a first value to the fuel cell, and a fuel amount of a second value that is greater than the first value to the fuel cell. A second power generation mode for supplying , and a third power generation mode for supplying a fuel of a third value larger than the first value and smaller than the second value to the fuel cell ,
The fuel cell controller, when the remaining capacity of the secondary battery in the third generation mode becomes the first remaining capacity decreases, switched to the second power mode,
When the remaining capacity of the secondary battery increases in the third power generation mode to become a second remaining capacity larger than the first remaining capacity, the mode is switched to the first power generation mode,
In the second power generation mode, when the remaining capacity of the secondary battery increases to a third remaining capacity that is larger than the first remaining capacity and smaller than the second remaining capacity, Switch to power generation mode,
In the first power generation mode, when the remaining capacity of the secondary battery decreases to a fourth remaining capacity that is larger than the first remaining capacity and smaller than the second remaining capacity, power apparatus according to claim Rukoto switched to generator mode.   2. The power supply device according to claim 1, wherein the secondary battery remaining capacity detector detects a remaining capacity of the secondary battery based on a voltage of the secondary battery.   The power supply apparatus according to claim 1, wherein the fuel cell is a balance type that balances fuel and output power of the fuel cell. The first value, the second value, and the third value for the amount of fuel are a minimum value, a maximum value, and an intermediate value, respectively.
The third remaining capacity and the fourth remaining capacity are the same;
In a state where the amount of fuel supplied to the fuel cell is an intermediate value, if the remaining capacity of the secondary battery reaches the second remaining capacity , the amount of fuel supplied to the fuel cell is minimized. switching,
In a state where the amount of fuel supplied to the fuel cell is the minimum value, if the remaining capacity of the secondary battery decreases and reaches the fourth remaining capacity , the amount of fuel supplied to the fuel cell is reduced. Switch to an intermediate value,
In a state where the amount of fuel supplied to the fuel cell is an intermediate value, if the remaining capacity of the secondary battery decreases and reaches the first remaining capacity , the amount of fuel supplied to the fuel cell is Switch to the maximum value,
In a state where the amount of fuel supplied to the fuel cell is the maximum value, if the remaining capacity of the secondary battery increases to reach the third remaining capacity , the amount of fuel supplied to the fuel cell is Switch to intermediate value,
The power supply device according to claim 1. The first value, the second value, and the third value for the amount of fuel are a minimum value, a maximum value, and an intermediate value, respectively.
In a state where the amount of fuel supplied to the fuel cell is an intermediate value, if the remaining capacity of the secondary battery reaches the second remaining capacity , the amount of fuel supplied to the fuel cell is minimized. switching,
In a state where the amount of fuel supplied to the fuel cell is the minimum value, if the remaining capacity of the secondary battery decreases and reaches the fourth remaining capacity , the amount of fuel supplied to the fuel cell is reduced. Switch to an intermediate value,
In a state where the amount of fuel supplied to the fuel cell is an intermediate value, if the remaining capacity of the secondary battery decreases and reaches the first remaining capacity , the amount of fuel supplied to the fuel cell is Switch to the maximum value,
In a state where the amount of fuel supplied to the fuel cell is the maximum value, if the remaining capacity of the secondary battery increases to reach the third remaining capacity , the amount of fuel supplied to the fuel cell is Switch to intermediate value,
The power supply device according to claim 1.   When increasing the power output from the fuel cell, after increasing the amount of fuel, increase the power supplied to the power converter, and when decreasing the power output from the fuel cell, supply the power converter. The power supply apparatus according to claim 1, wherein the amount of fuel is reduced after the power is reduced. The power output from the fuel cell in the first power generation mode in which the amount of fuel supplied to the fuel cell is a minimum value is the same as the self-power consumption of the power supply device. The power supply described. 2. The power supply according to claim 1, wherein when the power supply device is activated, the fuel cell control unit initially sets the first power generation mode in which an amount of fuel supplied to the fuel cell is a minimum value. apparatus.

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