JP2007043888A - Electronic equipment, battery pack used in same, and load apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide electronic equipment capable of supplying electric power from a fuel cell to a load apparatus having a large variation in load. <P>SOLUTION: In the electronic equipment, a bidirectional voltage converter 103 is connected between a fuel cell 101 and a secondary battery 102. Further, if a plurality of voltage converters 211, 212, 221, 222 of the load apparatus 200 are provided, when each output voltage is closer to an output voltage of the secondary battery 102 than an output voltage of the fuel cell 101, they are classified into a first voltage-converter group 201, while being closer to the output voltage of the fuel cell 101 than the output voltage of the secondary battery 102, they are sorted out as a second voltage-converter group 202. Then, the secondary battery 102 is connected in parallel with the first voltage-converter group 201 and the fuel cell 101 is connected in parallel with the second voltage-converter group 202. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electronic device provided with a fuel cell, a battery pack and a load device used in the electronic device, and more particularly to a circuit configuration of a suitable power supply unit.

  Conventionally, electronic devices such as notebook computers and mobile phones have a plurality of voltage converters. A plurality of voltage converters are provided by a voltage converter that steps down the voltage of the secondary battery or a voltage converter that steps up the voltage of the secondary battery. It has a power supply to output. As an input power source for the plurality of voltage converters, a method of connecting to a secondary battery is common.

  FIG. 10 is a block diagram of a conventional electronic device such as a commercially available notebook computer. The battery pack 400 does not include a fuel cell and includes only the secondary battery 102, and both terminals 106 and 108 of the secondary battery 102 are connected to both terminals 306 and 308 of the load device 300. In the load device 300, all the input power of the four voltage converters 311 to 314 is supplied from the secondary battery 102, and the voltage converters 311 to 314 output the converted voltages V1 to V4 to the functional circuit 303.

  In recent years, fuel cells that can supply power continuously for a long time have attracted attention as power sources for electronic devices such as notebook computers and mobile phones. These electronic devices generally have a heavy load fluctuation, but the generated power of the fuel cell cannot be changed suddenly. Therefore, while charging the secondary battery with the generated power of the fuel cell, A so-called hybrid fuel cell system for supplying electric power from various types has been proposed in various forms. Among them, for example, Patent Document 1 discloses a method for improving energy utilization efficiency using a portable terminal having a fuel cell, a plurality of secondary batteries, and a plurality of functional circuits.

  On the other hand, in order to charge the power generated by the fuel cell to the secondary battery, a voltage converter (DC / DC converter) that converts the voltage of the fuel cell into the voltage of the secondary battery is required. In this case as well, a plurality of voltage converters are required. As the input power source, a method of connecting to a secondary battery is generally used, and a method of controlling the output voltage of the fuel cell to a constant value has been proposed (for example, see Patent Document 2).

  FIG. 11 is a diagram showing current-voltage characteristics with respect to the amount of fuel supplied by a fuel cell in which six cells are connected in series. In FIG. 11, the vertical axis represents the output voltage (V) of a DMFC (Direct Methanol Fuel Cell), and the horizontal axis represents the output current (A) of the DMFC. C11, C12, and C13 indicate current-voltage characteristic curves when the total fuel supply amount is 0.6 cc / min, 1.2 cc / min, and 1.8 cc / min, respectively.

  FIG. 11 shows that the higher the fuel supply amount, the higher the output current can be obtained. Moreover, as shown to C11-C13, it turns out that output voltage is reducing as output current increases.

  Further, when the output voltage of the fuel cell is controlled to be constant, the output current (A) increases as the amount of fuel (methanol) supplied increases. In the example shown in FIG. 11, when the output voltage of the fuel cell is controlled to be constant at 2.4 V, the current (A) increases to I1, I2, and I3 when the total fuel supply amount is C11, C12, and C13, respectively. To do. Therefore, the generated power of the fuel cell can be controlled by controlling the total amount of fuel supplied. Thus, in order to control the generated power of the fuel cell with the fuel supply amount, a method of controlling the output voltage of the fuel cell to be constant is desirable.

  FIG. 12 is a block diagram of a conventional electronic device using a battery pack including a fuel cell. The load device 300 shown in FIG. 12 is configured in the same manner as in FIG. 10, and the battery pack 500 includes a fuel cell 101, a voltage converter 103, and a secondary battery 102.

In the load device 300, there is a voltage converter group 301 including four voltage converters 311 to 314 of 12V, 10V, 1.5V, and 1.25V, and the 12V and 10V voltage converters 311 and 312 are boosting circuits, The 1.5V and 1.25V voltage converters 313 and 314 are step-down circuits, and the power consumption of these four voltage converters 311 to 314 is all supplied from the secondary battery 102 as in FIG. It is.
JP 2004-208344 A US Pat. No. 6,590,370

  However, in the conventional hybrid fuel cell system, it is difficult to supply power from the fuel cell to a functional circuit with a heavy load fluctuation. This is because the output power of the fuel cell does not change abruptly even if the flow rate of the supplied fuel is changed, so that the current value of the load device corresponds to a sudden change in the power consumption due to the output current characteristics of the fuel cell. Because it is unsuitable.

  In the conventional electronic device shown in FIG. 12, for example, when the output voltage of the fuel cell 101 is 2.4V and the output voltage of the secondary battery 102 is 6 to 8.4V, the voltages are 1.5V and 1.25V. The power of the converters 313 and 314 is steadily boosted by the voltage converter 103 to charge the secondary battery 102 with the voltage from the fuel cell 101 and then stepped down to 1.5V and 1.25V from there. After boosting the output voltage of the fuel cell 101, the output voltage is further lowered. Therefore, power loss occurs and is inefficient.

  Further, when the output voltage of the fuel cell 101 is 10V and the output voltage of the secondary battery 102 is 6 to 8.4V, the power of the 12V and 10V voltage converters 311 and 312 is constantly the voltage from the fuel cell 101. Is stepped down by the voltage converter 103 and charged to the secondary battery 102 and then boosted to 12V and 10V. After the output voltage of the fuel cell 101 is stepped down, it is further boosted and used. Therefore, power loss occurs and is inefficient.

  As described above, in the case of the conventional hybrid type fuel cell system, since the power to the load device 300 is supplied from the secondary battery 102, the power supply voltage of the functional circuit 303 is lower than the output voltage of the fuel cell 101. For example, even when the functional circuit 303 is a CPU circuit or the like, the input of the voltage converter that supplies power to the functional circuit 303 needs to be supplied from the secondary battery 102. As a result, after boosting the output voltage of the fuel cell 101 to the output voltage of the secondary battery 102, the output voltage of the secondary battery 102 is lowered to the power supply voltage of the functional circuit 303 lower than the output voltage of the fuel cell 101. On the contrary, after the output voltage of the fuel cell 101 is stepped down to the output voltage of the secondary battery 102, the output voltage of the secondary battery 102 is higher than the output voltage of the fuel cell 101. Since the power supply voltage is boosted, power conversion loss occurs due to energy use efficiency, which is an undesirable situation.

  An object of the present invention is to provide an electronic device that can supply electric power from a fuel cell to a load device with severe load fluctuations.

  An electronic apparatus according to the present invention includes a power supply unit and a load device, and the power supply unit is connected between a fuel cell, a secondary battery, and the fuel cell and the secondary battery, and the fuel cell. And a bidirectional voltage converter that bidirectionally converts the output voltage of the secondary battery and the output voltage of the secondary battery, and the load device is connected in parallel to the fuel cell.

  In this electronic device, the voltage output from the fuel cell is adjusted to be constant by the bidirectional voltage converter. At this time, since the bidirectional voltage converter is used, when the consumption current of the load device connected to the fuel cell increases rapidly and is consumed more than the generated power of the fuel cell, Even when the fuel cell generated power does not increase abruptly when the fuel flow rate increases, etc., and is smaller than the power consumption of the load device, that is, even when the fuel cell generated power is smaller than the power consumed by the load device, both The counter voltage converter supplies power from the secondary battery to the output side of the fuel cell, and the voltage across the fuel cell is kept constant. Therefore, since power is stably supplied to the load device, power can be supplied from the fuel cell even when the load device has a large load fluctuation with time.

  The load device includes a first voltage converter that outputs a voltage closer to the output voltage of the secondary battery than an output voltage of the fuel cell, and a voltage closer to the output voltage of the fuel cell than the output voltage of the secondary battery. A second voltage converter that outputs, and a functional circuit that is supplied with electric power from the first and second voltage converters and that executes the function of the load device, the first voltage converter including the secondary battery Preferably, the second voltage converter is connected in parallel to the fuel cell.

  In this case, a first voltage converter that outputs a voltage closer to the output voltage of the secondary battery than the output voltage of the fuel cell is connected in parallel to the secondary battery, and is closer to the output voltage of the fuel cell than the output voltage of the secondary battery. Since the second voltage converter that outputs a voltage is connected in parallel to the fuel cell, the step-up ratio or step-down ratio of the first and second voltage converters can be as close to 1 as possible. Therefore, the voltage is boosted in the power supply unit and then stepped down by the first and second voltage converters to use power, or the voltage is stepped down in the power supply unit and then boosted by the first and second voltage converters to use power. Therefore, it is possible to provide an electronic device that reduces power loss in the first and second voltage converters and improves energy use efficiency. Moreover, the continuous use time of an electronic device can also be extended compared with the past.

  The power supply unit includes a battery pack that can be attached to and detached from the load device, and the load device includes a switch that short-circuits or opens an input of the first voltage converter and an input of the second voltage converter. Further, it is preferable that the switch is opened only when the battery pack is attached to the load device, and is short-circuited otherwise.

  In this case, when a battery pack including a fuel cell connected in parallel to the second voltage converter is not mounted, the input of the first voltage converter and the input of the second voltage converter are short-circuited. The first and second voltage converters can be regarded as one voltage converter group like a conventional electronic device, and instead of a battery pack including a fuel cell connected in parallel to the second voltage converter, a conventional fuel cell Even when the battery pack is replaced with a conventional battery pack including a fuel cell, the load device can be used with compatibility maintained.

  The first voltage converter includes a plurality of first voltage converters that output a voltage closer to an output voltage of the secondary battery than an output voltage of the fuel cell, and the second voltage converter includes the secondary battery. A plurality of second voltage converters that output a voltage closer to the output voltage of the fuel cell than the output voltage of the fuel cell, wherein the plurality of first voltage converters are connected in parallel to the secondary battery, The two voltage converters are preferably connected in parallel to the fuel cell.

  In this case, after boosting in the power supply unit by classifying the plurality of voltage converters into the first and second voltage converter groups so that the step-up ratio or step-down ratio of the voltage converters included in each group is as close to 1 as possible. It is possible to avoid using the power by stepping down the first and second voltage converter groups, or using the power by stepping up the voltage in the first and second voltage converter groups after stepping down in the power supply unit. The power loss in a large number of voltage converters can be reduced, and the energy utilization efficiency can be further improved.

  When the generated current of the fuel cell is smaller than the consumption current of the load device, the bidirectional voltage converter supplies a shortage of the consumption current of the load device from the secondary battery to the load device, When the generated current is larger than the consumption current of the load device, it is preferable to supply a surplus of the generated current of the fuel cell to the secondary battery.

  In this case, when the generated current of the fuel cell is smaller than the consumption current of the load device, the shortage of the consumption current of the load device is supplied from the secondary battery to the load device, so the voltage across the fuel cell is kept constant, When it is possible to supply power to the load device and when the generated current of the fuel cell is larger than the consumed current of the load device, the surplus of the generated current of the fuel cell is supplied to the secondary battery. Electric power can be stored in the secondary battery, and the electric power of the fuel cell can be used effectively.

  The output voltage of the fuel cell is lower than the output voltage of the secondary battery, and the bidirectional voltage converter includes a boost type bidirectional voltage converter that boosts the output voltage of the fuel cell to the output voltage of the secondary battery. Preferably, the power supply unit further includes a control circuit that detects the output voltage of the fuel cell and controls the boost type bidirectional voltage converter so that the output voltage of the fuel cell becomes constant.

  In this case, since the boost type bidirectional voltage converter is controlled so that the output voltage of the fuel cell is detected and the output voltage of the fuel cell becomes constant, the output voltage of the fuel cell is lower than the output voltage of the secondary battery. In this case, it is possible to supply power to the load device while keeping the voltage at both ends of the fuel cell constant, and it is possible to store surplus power of the fuel cell in the secondary battery, and to effectively use the power of the fuel cell. be able to.

  When the voltage on the fuel cell side is V1, the voltage on the secondary battery side is V2, and the duty ratio of the PWM signal is Dt, the boost type bidirectional voltage converter has V2 / V1 = 1 / (1-Dt It is preferable that the control circuit controls the duty ratio Dt of the PWM signal so that the output voltage of the fuel cell becomes constant.

  In this case, since the duty ratio of the PWM signal is controlled so that the output voltage of the fuel cell is constant, the duty ratio of the PWM signal is changed when the output voltage of the fuel cell is lower than the output voltage of the secondary battery. Using a simple control method, the electric power can be supplied to the load device while keeping the voltage at both ends of the fuel cell constant, and the surplus power of the fuel cell can be stored in the secondary battery. The battery power can be used effectively.

  The output voltage of the fuel cell is higher than the output voltage of the secondary battery, and the bidirectional voltage converter includes a step-down bidirectional voltage converter that steps down the output voltage of the fuel cell to the output voltage of the secondary battery. The power supply unit may further include a control circuit that detects the output voltage of the fuel cell and controls the step-down bidirectional voltage converter so that the output voltage of the fuel cell becomes constant. .

  In this case, since the step-down bidirectional voltage converter is controlled so that the output voltage of the fuel cell is detected and the output voltage of the fuel cell becomes constant, the output voltage of the fuel cell is higher than the output voltage of the secondary battery. In this case, it is possible to supply power to the load device while keeping the voltage at both ends of the fuel cell constant, and it is possible to store surplus power of the fuel cell in the secondary battery, and to effectively use the power of the fuel cell. be able to.

  The step-down bi-directional voltage converter has V2 / V1 = (1-Dt) where V1 is the voltage on the fuel cell side, V2 is the voltage on the secondary battery side, and Dt is the duty ratio of the PWM signal. Preferably, the control circuit includes a synchronous rectification type bidirectional DC / DC voltage converter that satisfies the relationship, and the control circuit controls the duty ratio Dt of the PWM signal so that the output voltage of the fuel cell becomes constant.

  In this case, since the duty ratio of the PWM signal is controlled so that the output voltage of the fuel cell becomes constant, the duty ratio of the PWM signal changes when the output voltage of the fuel cell is higher than the output voltage of the secondary battery. Using a simple control method, the electric power can be supplied to the load device while keeping the voltage at both ends of the fuel cell constant, and the surplus power of the fuel cell can be stored in the secondary battery. The battery power can be used effectively.

  The fuel cell preferably includes a methanol direct fuel cell. In this case, since the fuel cell can be downsized and the power supply unit can be downsized, the electronic device can be downsized.

  The secondary battery preferably includes a Li ion battery. In this case, since the secondary battery can be downsized and the power supply unit can be downsized, the electronic device can be downsized.

  The battery pack according to the present invention is connected between a fuel cell, a secondary battery, and the fuel cell and the secondary battery, and outputs an output voltage of the fuel cell and an output voltage of the secondary battery. And a bidirectional voltage converter for bidirectional conversion.

  When this battery pack is attached to the load device, the voltage output from the fuel cell is adjusted to be constant by the bidirectional voltage converter. At this time, since the bidirectional voltage converter is used, even when the generated power of the fuel cell is smaller than the power consumed by the load device, the bidirectional voltage converter supplies power from the secondary battery to the output side of the fuel cell. The voltage across the fuel cell is kept constant. Therefore, since power is stably supplied to the load device, power can be supplied from the fuel cell even when the load device has a large load fluctuation with time.

  The load device according to the present invention is a load device using a battery pack including a fuel cell and a secondary battery, and outputs a voltage closer to the output voltage of the secondary battery than the output voltage of the fuel cell. Power is supplied from the first voltage converter, the second voltage converter that outputs a voltage closer to the output voltage of the fuel cell than the output voltage of the secondary battery, and the load A functional circuit for performing the function of the device; a first terminal for supplying power from the secondary battery to the first voltage converter; and for supplying power from the fuel cell to the second voltage converter. Second terminal.

  When a battery pack including a fuel cell and a secondary battery is attached to the load device, power is supplied from the secondary battery to the first voltage converter using the first terminal, and the first voltage converter serves as the fuel cell. A voltage closer to the output voltage of the secondary battery than the output voltage of the secondary battery is output, power is supplied from the fuel cell to the second voltage converter using the second terminal, and the second voltage converter outputs the output voltage of the secondary battery. Since the voltage closer to the output voltage of the fuel cell is output, the step-up ratio or step-down ratio of the first and second voltage converters can be as close to 1 as possible. Therefore, it is possible to avoid using the power by stepping down after boosting, or by using the power by boosting after stepping down, reducing the power loss in the voltage converter and improving the energy utilization efficiency. An electronic device can be provided.

  According to the present invention, the voltage output from the fuel cell is adjusted to a constant voltage by the bidirectional voltage converter. At this time, since the bidirectional voltage converter is used, even when the generated power of the fuel cell is smaller than the power consumed by the load device, the bidirectional voltage converter keeps the voltage at both ends of the fuel cell constant. Electric power can be supplied from the secondary battery to the output side of the fuel cell. Therefore, since power is stably supplied to the load device, power can be supplied from the fuel cell even when the load change of the load device is large in time, and power is supplied from the fuel cell to the load device with severe load fluctuation. can do.

  Embodiments according to the present invention will be described below with reference to the drawings.

(First embodiment)
First, an electronic apparatus according to the first embodiment of the present invention will be described. FIG. 1 is a block diagram of an electronic device according to the first embodiment of the present invention.

  1 includes a battery pack 100 and a load device 600. The battery pack 100 includes a fuel cell 101, a secondary battery 102, a bidirectional voltage converter 103, a control circuit 104, and a rectifying element. 110. The fuel cell 101 is obtained by connecting six active DMFCs (Direct Methanol Fuel Cells) in series, and the secondary battery 102 is obtained by connecting two Li ion batteries in series.

  The fuel cell and the secondary battery are not particularly limited to the above example, and a passive DMFC, a DDFC (Direct DME Fuel Cell), an RMFC (Reformed Methanol Fuel Cell), or the like may be used as the fuel cell. As an alternative, a nickel-hydrogen storage battery or the like may be used, and the number of batteries connected in series can be variously changed.

  The rectifying element 110 is connected between the fuel cell 101 and the bidirectional voltage converter 103, and prevents the current from flowing into the fuel cell 101 when the voltage generated by the fuel cell 101 is lower than the target voltage. Further, a switch may be provided in place of the rectifying element 110 and this switch may be opened when a current is supplied from the secondary battery 102 to the load device 600.

  The load device 600 includes a functional circuit such as a CPU circuit that has severe load fluctuations, a voltage converter that supplies power to the functional circuit, and the like. As the load device 600 (electronic device), a mobile device is used, for example, a notebook personal computer, a mobile phone, or the like.

  First, the case where the output voltage of the fuel cell 101 is set lower than the output voltage of the secondary battery 102 will be described. In the present embodiment, a boost type bidirectional voltage converter described below is used as the bidirectional voltage converter 103, and the control circuit 104 is configured to increase the output voltage of the fuel cell 101 to 2.4V. The duty ratio of the PWM signal applied to the bidirectional voltage converter 103 is adjusted. Further, the output voltages of the fuel cell and the secondary battery are not particularly limited to the above examples, and various changes are possible, and the same applies to other embodiments.

  FIG. 2 is a circuit diagram showing a configuration of a boost type bidirectional voltage converter used as bidirectional voltage converter 103 shown in FIG. A boost type bidirectional voltage converter 103 shown in FIG. 2 includes a coil 11, switching elements 12 and 13, an inverter 14, and capacitors 15 and 16.

  The capacitor 15 is connected between the output terminal on the fuel cell 101 side and a common ground terminal on the fuel cell 101 side and the secondary battery 102 side, and the capacitor 16 is connected to the output terminal on the secondary battery 102 side and the fuel cell 101. And a common ground terminal on the secondary battery 102 side. One end of the coil 11 is connected to the output terminal on the fuel cell 101 side, and the other end is connected to one end of the switching elements 12 and 13. The other end of the switching element 12 is connected to a common ground terminal on the fuel cell 101 side and the secondary battery 102 side, and the other end of the switching element 13 is connected to an output terminal on the secondary battery 102 side.

  The control terminal of the switching element 12 receives a PWM signal from the control circuit 104, and the switching element 12 is turned on when a high level signal is input and turned off when a low level signal is input. The inverter 14 inverts the PWM signal from the control circuit 104 and outputs the inverted signal to the control terminal of the switching element 13. The switching element 13 is turned on when a high level signal is input, and a low level signal is input. Turn off. For example, FETs can be used as the switching elements 12 and 13.

  A synchronous rectification type bidirectional DC / DC converter is constituted by the above elements, and the bidirectional voltage converter 103 functions as a step-up type bidirectional voltage converter, and the output voltage 2 of the fuel cell 101 is as follows. .4V is boosted to an output voltage 6-8.4V of the secondary battery 102.

  FIG. 3 is a waveform diagram for explaining the duty ratio of the PWM signal output from the control circuit 104 shown in FIG. The control circuit 104 outputs the PWM signal shown in FIG. 3 to the bidirectional voltage converter 103, and is given a duty ratio Dt expressed by the following equation (1) from the high period Ton and one period T of the PWM signal.

Dt = Ton / T (1)
The control circuit 104 outputs a PWM signal at a high level during the period Ton, short-circuits the switching element 12 and simultaneously opens the switching element 13. Further, the control circuit 104 outputs a PWM signal at a low level during the period of Toff, opens the switching element 12 and simultaneously shorts the switching element 13. Thus, when the switching elements 12 and 13 are operated, the voltage V1 (left side) of the fuel cell 101, the output voltage V2 (right side) of the secondary battery 102, and the duty ratio Dt of the PWM signal are as follows: The relationship of Formula (2) is materialized.

V2 / V1 = 1 / (1-Dt) (2)
The control circuit 104 detects the voltage V1 of the fuel cell 101, calculates the difference between the detected voltage and the target 2.4V, and uses the equation (2) to calculate the duty of the PWM signal so that the difference becomes zero. The ratio Dt is calculated, and the PWM signal having the calculated duty ratio Dt is output to the bidirectional voltage converter 103.

  Thus, in this embodiment, the fuel cell 101 is measured by measuring the voltage V1 of the fuel cell 101, calculating an error from the target 2.4V, and determining the duty ratio so that the error becomes zero. The voltage V1 of 101 can be controlled to a constant value of 2.4V.

  Next, a current supply state to the load device 600 will be described. FIG. 4 is a diagram for explaining the current-voltage characteristics with respect to the amount of fuel supplied from the fuel cell 101 in which six cells are connected in series, and the current supply status to the load device 600. In the upper part of FIG. 4, the vertical axis represents the output voltage (V) of the fuel cell 101, and the horizontal axis represents the output current (A) of the fuel cell 101. C11, C12, and C13 indicate current-voltage characteristic curves when the total fuel supply amount is 0.8 cc / min, 1.6 cc / min, and 3.2 cc / min, respectively.

  The power generation current of the fuel cell 101 is small when the voltage is constant, such as when the generated power at the start-up of the fuel cell 101 is small, or when the current consumption of the load device 600 increases abruptly. When the current is smaller than the consumption current of the load device 600, for example, when the generated current shown in FIG. 4 is I1, the generated current of the fuel cell 101 is supplied from the secondary battery 102 to the load device 600. The shortage is supplied from the secondary battery 102 to the load device 600.

  On the other hand, when the power generation of the fuel cell 101 is stable, the generated current of the fuel cell 101 becomes sufficiently large when the voltage is constant, and the generated current of the fuel cell 101 is larger than the consumption current of the load device 600, for example, as shown in FIG. When the generated current is I3, the generated current of the fuel cell 101 is supplied to the load device 600, and the surplus is supplied to the secondary battery 102, and the secondary battery 102 is charged.

  That is, the output voltage of the fuel cell 101 is constant regardless of the magnitude relationship among the generated current Io of the fuel cell 101, the consumption current Ic of the load device 600, and the current Is to the secondary battery 102. Equation (3) is established.

Io = Ic + Is (3)
However, the current Is to the secondary battery 102 means that a current flows from the secondary battery 102 to the load device 600 when minus.

  As described above, in the present embodiment, a current flows from the fuel cell 101 side (V1 side) to the bidirectional voltage converter 103 and a current is supplied from the bidirectional voltage converter 103 to the fuel cell 101 side (V1 side). In either case, the voltage V1 of the fuel cell 101 can be controlled to be constant by the boost type bidirectional voltage converter 103 having the circuit configuration shown in FIG. As a result, since the power is stably supplied to the load device 600, even when the load fluctuation of the load apparatus 600 is large in time, it is possible to supply power from the fuel cell 101, and the load having a heavy load fluctuation from the fuel cell 101. The device 600 can be powered.

(Second embodiment)
Next, an electronic apparatus according to the second embodiment of the present invention will be described. FIG. 5 is a circuit diagram showing a configuration of a step-down bi-directional voltage converter used in the electronic device according to the second embodiment of the present invention. In the electronic device of the present embodiment, both the output voltage of the fuel cell is set higher than the output voltage of the secondary battery, and the output voltage of the fuel cell is 10 V using a step-down bidirectional voltage converter. The duty ratio of the PWM signal input to the counter voltage converter is adjusted. Therefore, the difference between the present embodiment and the first embodiment is that the step-up type bidirectional voltage converter 103 shown in FIG. 2 is changed to the step-down type bidirectional voltage converter 103a shown in FIG. Since the other points are the same as those of the electronic apparatus shown in FIG. 1, FIG. 1 is used as an overall configuration diagram, and new illustration and detailed description are omitted.

  A bidirectional voltage converter 103 a shown in FIG. 5 includes a coil 11, switching elements 12 and 13, an inverter 14, and capacitors 15 and 16.

  The capacitor 15 is connected between the output terminal on the fuel cell 101 side and a common ground terminal on the fuel cell 101 side and the secondary battery 102 side, and the capacitor 16 is connected to the output terminal on the secondary battery 102 side and the fuel cell 101. And a common ground terminal on the secondary battery 102 side. One end of the switching element 13 is connected to the output terminal on the fuel cell 101 side, and the other end is connected to one end of the coil 11 and one end of the switching element 12. The other end of the coil 11 is connected to an output terminal on the fuel cell 101 side, and the other end of the switching element 12 is connected to a common ground terminal on the fuel cell 101 side and the secondary battery 102 side.

  The control terminal of the switching element 12 receives a PWM signal from the control circuit 104, and the switching element 12 is turned on when a high level signal is input and turned off when a low level signal is input. The inverter 14 inverts the PWM signal from the control circuit 104 and outputs the inverted signal to the control terminal of the switching element 13. The switching element 13 is turned on when a high level signal is input, and a low level signal is input. Turn off. For example, FETs can be used as the switching elements 12 and 13.

  A synchronous rectification type bidirectional DC / DC converter is constituted by each of the above elements, and the bidirectional voltage converter 103a functions as a step-down bidirectional voltage converter. The output voltage of the fuel cell 101 is 10V as follows. Is stepped down to an output voltage of 6 to 8.4 V of the secondary battery 102.

  The control circuit 104 outputs a PWM signal (see FIG. 3) having a duty ratio Dt to the bidirectional voltage converter 103a, outputs the PWM signal at a high level during the period of Ton, and short-circuits the switching element 12 at the same time. Is released. Further, the control circuit 104 outputs a PWM signal at a low level during the period of Toff, opens the switching element 12 and simultaneously shorts the switching element 13. Thus, when the switching elements 12 and 13 are operated, the voltage V1 (left side) of the fuel cell 101, the output voltage V2 (right side) of the secondary battery 102, and the duty ratio Dt of the PWM signal are as follows: The relationship of Formula (4) is materialized.

V2 / V1 = (1-Dt) (4)
The control circuit 104 detects the voltage V1 of the fuel cell 101, calculates the difference between the detected voltage and the target 10V, and uses the equation (4) so that the difference becomes zero, the duty ratio Dt of the PWM signal And outputs a PWM signal with the calculated duty ratio Dt to the bidirectional voltage converter 103a.

  As described above, in this embodiment, the voltage V1 of the fuel cell 101 is measured, an error from the target 10V is calculated, and the duty ratio is determined so that the error becomes zero. The voltage V1 can be controlled to a constant value of 10V.

  Also in the present embodiment, as described with reference to FIG. 4, the output voltage of the fuel cell 101 includes the generated current Io of the fuel cell 101, the consumed current Ic of the load device 600, and the secondary battery 102. It is the same as in the first embodiment that, regardless of the magnitude relationship of the current Is, it is constant and the following formula (5) is established for each current.

Io = Ic + Is (5)
As described above, also in this embodiment, when current flows from the fuel cell 101 side (V1 side) to the bidirectional voltage converter 103a, and when current flows from the bidirectional voltage converter 103a to the fuel cell 101 side (V1 side). In either case, the voltage V1 of the fuel cell 101 can be controlled to be constant by the step-down bidirectional voltage converter 103a having the circuit configuration shown in FIG. As a result, since the power is stably supplied to the load device 600, even when the load fluctuation of the load apparatus 600 is large in time, it is possible to supply power from the fuel cell 101, and the load having a heavy load fluctuation from the fuel cell 101. The device 600 can be powered.

(Third embodiment)
Next, an electronic apparatus according to the third embodiment of the present invention will be described. FIG. 6 is a block diagram showing a configuration of an electronic device according to the third embodiment of the present invention.

  6 includes a battery pack 100 and a load device 200. The battery pack 100 includes a fuel cell 101, a secondary battery 102, a bidirectional voltage converter 103, a control circuit 104, and a rectifying element. 110, a positive terminal 106 of the secondary battery 102, a positive terminal 107 of the fuel cell 101, and a common ground terminal 108 for the secondary battery 102 and the fuel cell 101.

  Similar to the first embodiment, the bidirectional voltage converter 103 includes the step-up type bidirectional voltage converter 103 shown in FIG. 2, and the output voltage of the fuel cell 101 is set to 2.4 V and the output voltage of the secondary battery 102 is changed. Boost to 6-8.4V. The control circuit 104 measures the voltage V1 of the fuel cell 101, calculates an error from the target 2.4V, and determines the duty ratio of the PWM signal so that the error becomes zero. The voltage V1 is controlled to be constant at 2.4V.

  The load device 200 includes a first voltage converter group 201 and a second voltage converter group 202 in which a plurality of voltage converters are assigned according to the magnitude of the output voltage, and a functional circuit 203 that executes a target function of the load device 200. A positive terminal 206 of the first voltage converter group 201 connected to the positive terminal 106 of the secondary battery 102 and a positive terminal of the second voltage converter group 202 connected to the positive terminal 107 of the fuel cell 101. 207, a common ground terminal 208 of the first voltage converter group 201 and the second voltage converter group 202 connected to the common ground terminal 108 of the secondary battery 102 and the fuel cell 101, and a first A switch 204 that short-circuits or opens the + terminal 206 of the voltage converter group 201 and the + terminal 207 of the second voltage converter group 202 is provided. .

  The first voltage converter group 201 includes a voltage converter 211 and a voltage converter 212. The output voltage of the voltage converter 211 is 12V, and the output voltage of the voltage converter 212 is 10V. The second voltage converter group 202 includes a voltage converter 221 and a voltage converter 222. The output voltage of the voltage converter 221 is 1.5V, and the output voltage of the voltage converter 222 is 1.25V. The number of voltage converters included in the first and second voltage converter groups 201 and 202 is not particularly limited to the above example, and may be one or three or more. In this embodiment, one functional circuit is used. However, the present invention is not particularly limited to this example, and a plurality of functional circuits may be used. Instead of being supplied with a voltage, a different voltage may be supplied from one or more predetermined voltage converters.

  In the present embodiment, the output voltage of the fuel cell 101 is set to be lower than the output voltage of the secondary battery 102. As in the first embodiment, the bidirectional voltage converter 103 is a boost type shown in FIG. The bidirectional voltage converter 103 is used, and the control circuit 104 adjusts the duty ratio of the PWM signal applied to the step-up type bidirectional voltage converter 103 so that the output voltage of the fuel cell 101 is 2.4V.

  When the generated power is small, such as when the fuel cell 101 is activated, or when the second voltage converter group 202 is large, the generated power of the fuel cell 101 is insufficient with respect to the power consumed by the load device 200. The bidirectional voltage converter 103 supplies power from the secondary battery 102 to the fuel cell 101 side, and the voltage across the fuel cell 101 is kept constant at 2.4V. This voltage is applied to the second voltage converter group 202 and supplied with electric power.

  When the amount of fuel supplied to the fuel cell 101 is increased and the generated power increases, the power of the fuel cell 101 is supplied to the secondary battery 102 while the voltage at both ends of the fuel cell 101 is kept constant. That is, regardless of the magnitude relationship between the power generated by the fuel cell 101 and the power consumption of the second voltage converter group 202, the voltage across the fuel cell 101 is kept constant.

  As described above, in this embodiment, the 1.5 V and 1.25 V voltage converters 221 and 222 operate by receiving a voltage of 2.4 V from the fuel cell 101, and the 12 V and 10 V voltage converters 211 and 212 are operated. The battery operates by receiving a voltage of 6 to 8.4 V from the secondary battery 102.

  Therefore, in the present embodiment, the output voltage 2.4 V of the fuel cell 101 is boosted to the output voltage 6 to 8.4 V of the secondary battery 102 as compared with the conventional example of FIG. Inefficient voltage conversion of stepping down to 1.25 V and 1.5 V in the group 202 can be avoided, and power loss due to voltage conversion can be reduced.

  Also in the present embodiment, as described with reference to FIG. 4, the output voltage of the fuel cell 101 includes the generated current Io of the fuel cell 101, the consumed current Ic of the load device 200, and the current to the secondary battery 102. It is the same regardless of the magnitude relationship of Is, and the fact that the following formula (6) is satisfied is the same as in the first and second embodiments.

Io = Ic + Is (6)
Thus, there are a case where current flows from the fuel cell 101 side (V1 side) to the bidirectional voltage converter 103 and a case where current is supplied from the bidirectional voltage converter 103 to the fuel cell 101 side (V1 side). Even in this case, the voltage V1 of the fuel cell 101 can be controlled to be constant by the boost type bidirectional voltage converter 103 having the circuit configuration shown in FIG. As a result, since the power is stably supplied to the load device 200, even when the load fluctuation of the load apparatus 200 is large in time, it is possible to supply power from the fuel cell 101, and the load having a heavy load fluctuation from the fuel cell 101. Power can be supplied to the device 200.

(Fourth embodiment)
Next, an electronic apparatus according to a fourth embodiment of the present invention will be described. FIG. 7 is a block diagram showing a configuration of an electronic device according to the fourth embodiment of the present invention. In the present embodiment, the point that the step-down voltage converter is used, and among the plurality of voltage converters, the lower output voltage is the first voltage converter group, and the higher output voltage is the second voltage converter group. Since the configuration other than the point assigned to each of them is the same as that of the third embodiment, detailed description of the same parts is omitted.

  7 includes a battery pack 100 and a load device 200. The battery pack 100 includes a fuel cell 101, a secondary battery 102, a bidirectional voltage converter 103a, a control circuit 104, and a rectifying element. 110, a positive terminal 106 of the secondary battery 102, a positive terminal 107 of the fuel cell 101, and a common ground terminal 108 for the secondary battery 102 and the fuel cell 101.

  Similar to the second embodiment, the bidirectional voltage converter 103a is composed of the step-down bidirectional voltage converter 103a shown in FIG. 5, and the output voltage 10V of the fuel cell 101 is changed to the output voltage 6 of the secondary battery 102. Step down to ~ 8.4V. The control circuit 104 measures the voltage V1 of the fuel cell 101, calculates an error from the target 10V, and determines the duty ratio of the PWM signal so that the error becomes zero, whereby the voltage V1 of the fuel cell 101 is obtained. Is constantly controlled to 10V.

  The load device 200 includes a first voltage converter group 401 and a second voltage converter group 402 in which a plurality of voltage converters are assigned according to the magnitude of the output voltage, and a functional circuit 203 having a target function of the load device 200. The positive terminal 206 of the first voltage converter group 401 connected to the positive terminal 106 of the secondary battery 102 and the positive terminal 207 of the second voltage converter group 402 connected to the positive terminal 107 of the fuel cell 101. And a common ground terminal 208 of the first voltage converter group 401 and the second voltage converter group 402 connected to the common ground terminal 108 of the secondary battery 102 and the fuel cell 101, and a first voltage. A switch 204 that short-circuits or opens the + terminal 206 of the converter group 401 and the + terminal 207 of the second voltage converter group 402 is provided.

  The first voltage converter group 401 includes a voltage converter 411 and a voltage converter 412, the output voltage of the voltage converter 411 is 1.5V, and the output voltage of the voltage converter 412 is 1.25V. The second voltage converter group 402 includes a voltage converter 421 and a voltage converter 422. The output voltage of the voltage converter 421 is 12V, and the output voltage of the voltage converter 422 is 10V. The number of voltage converters included in the first and second voltage converter groups 401 and 402 is not particularly limited to the above example, and may be one or three or more. In this embodiment, one functional circuit is used. However, the present invention is not particularly limited to this example, and a plurality of functional circuits may be used. Instead of being supplied with a voltage, a different voltage may be supplied from one or more predetermined voltage converters.

  In the present embodiment, the output voltage of the fuel cell 101 is set to be higher than the output voltage of the secondary battery 102. As in the second embodiment, the bidirectional voltage converter 103a is a step-down type shown in FIG. The bidirectional voltage converter 103a is used, and the control circuit 104 adjusts the duty ratio of the PWM signal applied to the step-down bidirectional voltage converter 103a so that the output voltage of the fuel cell 101 becomes 10V.

  When the generated power is small, such as when the fuel cell 101 is activated, or when the power consumption of the second voltage converter group 402 is large, the generated power of the fuel cell 101 is insufficient with respect to the power consumed by the load device 200. The bidirectional voltage converter 103a supplies power from the secondary battery 102 to the fuel cell 101, and the voltage across the fuel cell 101 is kept constant at 10V. This voltage is applied to the second voltage converter group 402 to supply power.

  When the generated power of the fuel cell 101 increases, the power of the fuel cell 101 is supplied to the secondary battery 102 while the voltage across the fuel cell 101 is kept constant. That is, regardless of the magnitude relationship between the generated power of the fuel cell 101 and the power consumption of the second voltage converter group 402, the voltage across the fuel cell 101 is kept constant, and these points are the first to third. This is the same as the embodiment.

  As described above, in this embodiment, the 12V and 10V voltage converters 421 and 422 operate by receiving a voltage of 10V from the fuel cell 101, and the 1.5V and 1.25V voltage converters 411 and 412 It operates by receiving a voltage of 6 to 8.4 V from the secondary battery 102.

  Therefore, in this embodiment, compared with the conventional example of FIG. 12, the step-down ratios of the 12V and 10V voltage converters 421 and 422 are close to 1, and the power loss is reduced. In particular, regarding the 12V voltage converter 421, the output voltage 10V of the fuel cell 101 is lowered to the output voltage 6 to 8.4V of the secondary battery 102, and the voltage is boosted to 12V by the 12V voltage converter. Voltage conversion can be avoided and power loss due to voltage conversion can be reduced.

  Also in the present embodiment, as described with reference to FIG. 4, the output voltage of the fuel cell 101 includes the generated current Io of the fuel cell 101, the consumed current Ic of the load device 200, and the current to the secondary battery 102. It is the same regardless of the magnitude relationship of Is, and the fact that the following formula (7) is satisfied is the same as in the first to third embodiments.

Io = Ic + Is (7)
Thus, there are a case where current flows from the fuel cell 101 side (V1 side) to the bidirectional voltage converter 103a and a case where current is supplied from the bidirectional voltage converter 103a to the fuel cell 101 side (V1 side). Even in this case, the voltage V1 of the fuel cell 101 can be controlled to be constant by the step-down bidirectional voltage converter 103a having the circuit configuration shown in FIG. As a result, since the power is stably supplied to the load device 200, even when the load fluctuation of the load apparatus 200 is large in time, it is possible to supply power from the fuel cell 101, and the load having a heavy load fluctuation from the fuel cell 101. Power can be supplied to the device 200.

(Fifth embodiment)
Next, an electronic apparatus according to a fifth embodiment of the invention will be described. FIG. 8 is a block diagram showing a configuration of an electronic device according to the fifth embodiment of the present invention. This embodiment is an electronic apparatus in which the conventional battery pack 400 shown in FIG. 10 is connected to the load device 200 shown in FIG. 6, and the load device 200 shown in FIG. 6 includes only two output terminals 106 and 108. It will be described below that the conventional battery pack 400 can be used.

  The load device 200 includes a switch 204 that short-circuits or opens the + terminal 206 of the first voltage converter group 201 and the + terminal 207 of the second voltage converter group 202. The switch 204 is normally configured to be short-circuited in order to short-circuit when the conventional battery pack 400 is attached. Therefore, when the battery pack 400 having only the two output terminals 106 and 108 of the secondary battery 102 is attached to the load device 200, the switch 204 is short-circuited, and the first voltage converter group 201 and the second Both of the voltage converter groups 202 are supplied with power from the secondary battery 102 and the functional circuit 203 operates.

  On the other hand, when the battery pack 100 having the three terminals 106 to 108 shown in FIG. 6 is attached to the load device 200, the switch 204 is mechanically connected to the battery pack 100 in order to operate the battery pack 100 and the load device 200. It is preferable to provide a mechanism for turning it off. In this case, when the battery pack 100 having the three terminals 106 to 108 is attached, the switch 204 is opened, and the battery pack 100 and the load device 200 can operate in the same manner as in the third embodiment. it can.

  For example, as the switch 204, a leaf switch or a mechanical switch that is turned on or off by mechanically bringing two connecting pieces into contact or non-contact is used, and a convex portion is provided on the battery pack 100. When attached to 200, this convex portion may press one of the connecting pieces of the switch 204 to open it.

  Further, a similar function may be realized based on an electrical signal. For example, a FET 204 that is turned on or off according to a control signal is used as the switch 204, and the battery pack 100 is mounted on the load device 200. In this case, a control signal for turning off the switch 204 may be output from the battery pack 100 to the switch 204.

(Sixth embodiment)
Next, an electronic apparatus according to a sixth embodiment of the present invention will be described. FIG. 9 is a block diagram showing a configuration of an electronic device according to the sixth embodiment of the present invention. The present embodiment is an electronic device in which a conventional battery pack 500 including the fuel cell 101 and the secondary battery 102 shown in FIG. 12 is connected to the load device 200 shown in FIG. 6, and the load device 200 shown in FIG. It will be described below that a conventional battery pack 500 having only two output terminals 106 and 108 can be used.

  When the battery pack 500 having only the two output terminals 106 and 108 of the secondary battery 102 is attached to the load device 200, the switch 204 is configured in the same manner as in the fifth embodiment and short-circuits. . Also in this case, as in the fifth embodiment, both the first voltage converter group 201 and the second voltage converter group 202 are supplied with power from the secondary battery 102, and the functional circuit 203 operates.

  The configurations related to the load device 200 and the battery pack 100 in the fifth and sixth embodiments can be similarly applied to the load device 200 and the battery pack 100 in the fourth embodiment. The effect of can be obtained.

  ADVANTAGE OF THE INVENTION According to this invention, in the electronic device using a fuel cell and a secondary battery, it becomes possible to supply the power of a functional circuit with severe load fluctuation from the fuel cell, and the voltage is stepped down after being boosted. In addition, it is possible to provide an electronic device with reduced power loss by realizing efficient voltage conversion by eliminating a useless voltage change that is boosted and used after stepping down the voltage. This is useful in an electronic device that requires a plurality of voltage output power sources.

It is a block diagram of the electronic device by the 1st Embodiment of this invention. It is a circuit diagram which shows the structure of the step-up type bidirectional voltage converter used as the bidirectional voltage converter shown in FIG. It is a wave form diagram for demonstrating the duty ratio of the PWM signal output from the control circuit shown in FIG. It is a figure for demonstrating the current-voltage characteristic with respect to the supply amount of the fuel of the fuel cell which connected 6 cells in series, and the supply condition of the electric current to a load apparatus. It is a circuit diagram which shows the structure of the step-down type bidirectional voltage converter used for the electronic device by the 2nd Embodiment of this invention. It is a block diagram which shows the structure of the electronic device by the 3rd Embodiment of this invention. It is a block diagram which shows the structure of the electronic device by the 4th Embodiment of this invention. It is a block diagram which shows the structure of the electronic device by the 5th Embodiment of this invention. It is a block diagram which shows the structure of the electronic device by the 6th Embodiment of this invention. It is a block diagram of electronic devices, such as the conventional commercial notebook computer. It is a figure which shows the current-voltage characteristic with respect to the supply amount of the fuel of the fuel cell which connected 6 cells in series. It is a block diagram of the electronic device using the battery pack provided with the conventional fuel cell.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Coil 12, 13 Switching element 14 Inverter 15, 16 Capacitor 100 Battery pack 101 Fuel cell 102 Secondary battery 103 Bidirectional voltage converter 104 Control circuit 106 + terminal of secondary battery 107 + terminal of fuel cell 108 Ground terminal 110 Rectification Element 200, 600 Load device 201 First voltage converter group 202 Second voltage converter group 203 Functional circuit 204 Switch 206 + terminal of first voltage converter group 207 + terminal of second voltage converter group 208 Ground terminal 211, 212, 221, 222 Voltage converter

Claims (13)

A power supply unit and a load device;
The power supply unit is
A fuel cell;
A secondary battery,
A bi-directional voltage converter connected between the fuel cell and the secondary battery and bi-directionally converting the output voltage of the fuel cell and the output voltage of the secondary battery;
The load device is connected in parallel to the fuel cell. The load device is:
A first voltage converter that outputs a voltage closer to the output voltage of the secondary battery than the output voltage of the fuel cell;
A second voltage converter that outputs a voltage closer to the output voltage of the fuel cell than the output voltage of the secondary battery;
A function circuit that is supplied with power from the first and second voltage converters and that executes the function of the load device;
The first voltage converter is connected in parallel to the secondary battery,
The electronic device according to claim 1, wherein the second voltage converter is connected in parallel to the fuel cell. The power supply unit includes a battery pack that is detachable from the load device,
The load device further includes a switch for short-circuiting or opening the input of the first voltage converter and the input of the second voltage converter,
3. The electronic apparatus according to claim 2, wherein the switch is opened only when the battery pack is attached to the load device, and is short-circuited otherwise. The first voltage converter includes a plurality of first voltage converters that output a voltage closer to the output voltage of the secondary battery than the output voltage of the fuel cell;
The second voltage converter includes a plurality of second voltage converters that output a voltage closer to the output voltage of the fuel cell than the output voltage of the secondary battery,
The plurality of first voltage converters are connected in parallel to the secondary battery,
The electronic device according to claim 2, wherein the plurality of second voltage converters are connected in parallel to the fuel cell.   When the generated current of the fuel cell is smaller than the consumption current of the load device, the bidirectional voltage converter supplies a shortage of the consumption current of the load device from the secondary battery to the load device, 5. The electronic device according to claim 1, wherein when the generated current is larger than the consumption current of the load device, an excess of the generated current of the fuel cell is supplied to the secondary battery. The output voltage of the fuel cell is lower than the output voltage of the secondary battery,
The bidirectional voltage converter includes a boost type bidirectional voltage converter that boosts the output voltage of the fuel cell to the output voltage of the secondary battery,
The power supply unit further includes a control circuit that detects the output voltage of the fuel cell and controls the boost type bidirectional voltage converter so that the output voltage of the fuel cell becomes constant. The electronic device in any one of 1-5. When the voltage on the fuel cell side is V1, the voltage on the secondary battery side is V2, and the duty ratio of the PWM signal is Dt, the boost type bidirectional voltage converter has V2 / V1 = 1 / (1-Dt A synchronous rectification type bidirectional DC / DC voltage converter satisfying the relationship of
The electronic device according to claim 6, wherein the control circuit controls a duty ratio Dt of the PWM signal so that an output voltage of the fuel cell becomes constant. The output voltage of the fuel cell is higher than the output voltage of the secondary battery,
The bidirectional voltage converter includes a step-down bidirectional voltage converter that steps down the output voltage of the fuel cell to the output voltage of the secondary battery,
The power supply unit further includes a control circuit that detects the output voltage of the fuel cell and controls the step-down bidirectional voltage converter so that the output voltage of the fuel cell becomes constant. The electronic device in any one of 1-5. The step-down bi-directional voltage converter has V2 / V1 = (1-Dt) where V1 is the voltage on the fuel cell side, V2 is the voltage on the secondary battery side, and Dt is the duty ratio of the PWM signal. Including a synchronous rectification type bidirectional DC / DC voltage converter satisfying the relationship,
9. The electronic apparatus according to claim 8, wherein the control circuit controls a duty ratio Dt of the PWM signal so that an output voltage of the fuel cell becomes constant.   The electronic device according to claim 1, wherein the fuel cell includes a methanol direct fuel cell.   The electronic device according to claim 1, wherein the secondary battery includes a Li ion battery. A fuel cell;
A secondary battery,
A battery pack comprising: a bidirectional voltage converter connected between the fuel cell and the secondary battery, and bidirectionally converting the output voltage of the fuel cell and the output voltage of the secondary battery. . A load device using a battery pack including a fuel cell and a secondary battery,
A first voltage converter that outputs a voltage closer to the output voltage of the secondary battery than the output voltage of the fuel cell;
A second voltage converter that outputs a voltage closer to the output voltage of the fuel cell than the output voltage of the secondary battery;
A functional circuit which is supplied with electric power from the first and second voltage converters and executes the function of the load device;
A first terminal for supplying power from the secondary battery to the first voltage converter;
And a second terminal for supplying electric power from the fuel cell to the second voltage converter.

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