JP2004199895A - Output control device of fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an output control device of a fuel cell for effectively and stably using a fuel cell as a power supply. <P>SOLUTION: The device converts an input current from the fuel cell 10 into a voltage by a resistor R2 via a transistor Tr to detect the current, compares the detected current from the fuel cell 10 with a reference voltage Vref1 set to a value of 2×IavexR2 corresponding to twice the value of an average value Iave of a target current from the fuel cell 10 by an operational amplifier OP1, and controls the average value of the output current from the fuel cell 10 at the desired value by controlling ON/OFF of the transistor Tr, based on the output from the amplifier OP1. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a fuel cell output control device that controls and outputs an input from a fuel cell, and more particularly to a fuel cell output control device suitable for application to a charging circuit such as a lithium battery using a fuel cell.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, as a device using a fuel cell, there is a device employed in an electric vehicle as disclosed in Patent Document 1, or a device employed in a power generation system as disclosed in Patent Document 2.
[0003]
By the way, recently, an attempt to use a fuel cell as a power source of a small portable device such as a mobile phone has been proposed.
[0004]
In this case, the stability cannot be ensured if the output of the fuel cell is directly used as the power supply. Therefore, a secondary battery such as a lithium battery is charged using the output of the fuel cell, and the power is supplied from the output of the secondary battery. A configuration for taking out is considered.
[0005]
[Patent Document 1]
JP-A-6-225406 [Patent Document 2]
JP-A-8-213032 [Problems to be Solved by the Invention]
However, when the fuel cell is used as a power source for a small portable device such as a mobile phone, a secondary battery such as a lithium battery charged by the fuel cell is required to be downsized, and its capacity is limited.
[0006]
Further, in general, a fuel cell has a limitation in its power supply capability, and when power exceeding this limit is taken out, power supply is stopped.
[0007]
Therefore, when a secondary battery with a limited capacity is charged with the output of a fuel cell and used as a power source for a small portable device, the output current from the fuel cell is limited so that power supply to the fuel cell does not stop. There is a need.
[0008]
Accordingly, it is an object of the present invention to provide a fuel cell output control device in which a fuel cell can be used effectively and stably as a power source.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, an invention according to claim 1 is an output control device for a fuel cell that controls and outputs an input from a fuel cell, wherein an input current detection circuit that detects an input current from the fuel cell; An input current control circuit that controls an average value of the input current from the fuel cell by limiting a peak value of the input current from the fuel cell based on the input current of the fuel cell detected by the input current detection circuit. It is characterized by doing.
[0010]
According to a second aspect of the present invention, in the first aspect of the invention, the input current control circuit sets the peak value of the input current of the fuel cell detected by the input current detection circuit to a value approximately twice a target average value. By controlling the average value of the input current from the fuel cell to the target average value.
[0011]
The invention of claim 3 is the invention of claim 2, further comprising a switching element for switching the output of the fuel cell, and a switching control circuit for controlling the switching element, wherein the input current detection circuit comprises: An input current from the fuel cell is detected based on an output of the switching element.
[0012]
The invention according to claim 4 is the invention according to claim 3, further comprising an inductor for inputting an output of the fuel cell, wherein the switching control circuit controls the switching element based on a current flowing through the inductor. It is characterized by.
[0013]
According to a fifth aspect of the present invention, in the third aspect of the present invention, the input current detection circuit is connected in parallel with the switching element, and a current mirror circuit that flows a current 1 / N of the current flowing through the switching element. And detecting an input current from the fuel cell based on a current flowing through the current mirror circuit.
[0014]
According to a sixth aspect of the present invention, in the fuel cell output control device for controlling and outputting the input from the fuel cell, at least an inductor for inputting the output of the fuel cell and a switching element for switching the output of the inductor are provided. A converter having an input current detection circuit for detecting an input current from the fuel cell based on a current flowing through the switching element of the converter, and a current value detected by the input current detection circuit and a preset target current value. And a control circuit that controls the switching of the switching element based on the output of the comparison circuit to control the average value of the input current from the fuel cell in accordance with the target current value. It is characterized by doing.
[0015]
According to a seventh aspect of the present invention, in the sixth aspect, a charging current for charging the secondary battery is output based on the output of the converter.
[0016]
According to an eighth aspect of the present invention, in the invention of the sixth aspect, the target current value is set so as to correspond to approximately twice a target average value of the input current.
[0017]
According to a ninth aspect of the present invention, in the sixth aspect of the present invention, the converter comprises a self-excited up-converter that self-excitably controls switching of the switching element based on a current flowing through the inductor. .
[0018]
According to a tenth aspect of the present invention, in the invention of the sixth aspect, the input current detection circuit is connected in parallel with the switching element, and a current mirror circuit that flows a current that is 1 / N of the current flowing through the switching element. And detecting an input current from the fuel cell based on a current flowing through the current mirror circuit.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of a fuel cell output control device according to the present invention will be described in detail with reference to the accompanying drawings.
[0020]
FIG. 1 is a block diagram showing the overall configuration of a secondary battery charging device configured by applying the fuel cell output control device according to the present invention.
[0021]
This charging device controls the output of the fuel cell 10 by a charging control device 20 to charge a secondary battery 30 such as a lithium battery, and is used as a power source for a small portable device such as a mobile phone.
[0022]
FIG. 2 is a circuit diagram showing a detailed configuration of the charging control device 20 shown in FIG.
[0023]
The circuit shown in FIG. 2 receives the output Vin of the fuel cell 10 shown in FIG. 1 from the input terminals T11 and T12, and outputs the output Vout for charging the secondary battery 30 from the output terminals T21 and T22. is there.
[0024]
The circuit shown in FIG. 2 includes a coil (inductor) L1 connected to the input terminal T11, a capacitor C1 connected between the connection line between the input terminal T11 and the coil L1 and the ground, and a coil C1 connected between the coil L1 and the output terminal T21. , A capacitor C2 connected between the connection line between the diode D2 and the output terminal T21 and the ground, a transistor Tr (switching element) having a collector connected to a connection line between the coil L1 and the diode D2, a coil A coil (auxiliary winding) L2 connected in reverse phase to L1, a resistor R1 and a diode D1 connected between the coil L2 and the base of the transistor Tr, a resistor R2 connected between the emitter of the transistor Tr and ground, and a transistor The negative input is connected to the connection line between the emitter of Tr and the resistor R2, and the positive input is the reference voltage. The operational amplifier OP1 connected to ref1, the resistor R3 and the diode D3 connected between the output of the operational amplifier OP1 and the base of the transistor Tr, the negative input is connected to the output terminal T21 via the resistor R4, and the positive input is the reference voltage. It comprises an operational amplifier OP2 connected to Vref2, and a diode D4 connected between the output of the operational amplifier OP2 and the base of the transistor Tr.
[0025]
Here, the operation of the circuit shown in FIG. 2 is as follows.
[0026]
1) When the voltage generated in the coil L is zero and the transistor Tr is off, the output of the operational amplifier OP1 is at a high level.
[0027]
2) When the output of the operational amplifier OP1 is at a high level, the base of the transistor Tr becomes a high level due to the presence of the resistor R3, the transistor Tr turns on, a current flows through the transistor Tr, and the voltage input to the negative input of the operational amplifier OP1. Gradually increases.
[0028]
3) At this time, a voltage corresponding to the current flowing through the coil L1 is generated in the auxiliary winding L2, and this voltage biases the base of the transistor Tr to a higher level due to the presence of the resistor R1.
[0029]
4) When a current flows through the transistor Tr and the voltage input to the negative input of the operational amplifier OP1 becomes the same potential as the reference voltage Vref1 due to the presence of the resistor R2, the output of the operational amplifier OP1 becomes low level. As a result, the diode D3 , The base of the transistor Tr becomes low level, and the transistor Tr is turned off.
[0030]
5) When the transistor Tr is turned off, the voltage generated in the auxiliary winding L2 is inverted, and the base of the transistor Tr is kept at a low level by the diode D1.
[0031]
6) When the energy stored in the coil L1 gradually decreases, the current flowing through the coil L1 becomes zero, and when the voltage generated in the coil L1 and the voltage generated in the auxiliary coil become zero, the state returns to the above state 1).
[0032]
7) The state of 1) is repeated from the state of 1), the collector voltage of the transistor Tr is smoothed by the diode D2 and the capacitor C2, and the input voltage Vin applied to the input terminals T11 and T12 is applied to the output terminals T21 and T22. An up-converted output voltage Vout is generated.
[0033]
That is, in the circuit of FIG. 2, the circuit including the coil L1, the auxiliary coil L2, the diode D1, the resistor R1, the transistor Tr, the resistor R2, the operational amplifier OP1, the diode D3, the resistor R3, the diode D2, and the capacitor C2 is a self-excited type. A converter is configured such that when the potential input to the negative input of the operational amplifier OP1 becomes the same potential as the reference voltage Vref1, the output of the operational amplifier OP1 becomes low level and the transistor Tr is turned off. The peak value of the current flowing through the coil L1 is limited by the voltage of the reference voltage Vref1.
[0034]
Here, the resistor R2 forms a current detection circuit that generates a voltage corresponding to the current flowing through the coil L1 via the transistor Tr. The circuit including the operational amplifier OP1, the diode D1, and the resistor R1 is a coil L1 A current limiting circuit for limiting the peak value of the current flowing through the circuit in accordance with the reference voltage Vref1.
[0035]
In the circuit shown in FIG. 2, the circuit including the resistor R4, the operational amplifier OP2, and the diode D4 forcibly lowers the base of the transistor Tr when the voltage Vout generated at the output terminals T21 and T22 exceeds the reference voltage Vref2. Level, the transistor Tr is turned off, and a control circuit for maintaining the voltage output from the output terminals T21 and T22 at a constant voltage is configured.
[0036]
FIG. 3 is a waveform chart for explaining the operation of the circuit shown in FIG.
[0037]
In FIG. 3, a waveform W indicates a waveform of a current flowing through the coil L1 in the circuit shown in FIG.
[0038]
By the way, in the circuit shown in FIG. 2, by repeating the states 1) to 6), the transistor Tr is turned on and off, and the triangular wave current as shown by the waveform W in FIG. Flows.
[0039]
In the circuit shown in FIG. 2, the current flowing through the coil L1 is converted into a voltage by the resistor R2 and detected, and the peak value Ipeak of the current is limited according to the set voltage of the reference voltage Vref1.
[0040]
Assuming that the value of the desired average current of the fuel cell 10 shown in FIG. 1 to be controlled is Iave, the reference voltage Vref1 is twice the value of this IavexR2, that is, 2 × IavexR2 in the circuit shown in FIG. , The input current from the fuel cell 10 can be limited to a desired average value Iave.
[0041]
That is, in the circuit shown in FIG. 2, the peak value Ipeak of the output current of the fuel cell 10 to be controlled is changed to the average value Iave of the output current required for the fuel cell 10 to operate stably without stopping. By limiting the value to approximately twice the value of the above, stable operation of the fuel cell 10 is guaranteed.
[0042]
Further, in the circuit shown in FIG. 2, the current flowing through the coil L1 is detected only when the transistor Tr is on and not detected when the transistor Tr is off. The required loss can be reduced.
[0043]
FIG. 4 is a circuit diagram showing another detailed configuration of charge control device 20 shown in FIG.
[0044]
The circuit shown in FIG. 4 differs from the circuit shown in FIG. 2 only in that a field effect transistor (FET) is used as a switching element and that a current flowing through the coil L1 is detected by using a current mirror circuit. The other points are basically the same as the circuit shown in FIG. 2 including the operation principle.
[0045]
That is, in the circuit shown in FIG. 4, the FET Q1 is connected to the connection line between the coil L1 and the diode D2, the FET Q2 whose gate is commonly connected in parallel to the FET Q1, and the current detection is connected to the drain of the FET Q2. Is connected. Further, a capacitor C3 is connected between the diode D1 and the gates of the FETs Q1 and Q2. Other configurations are the same as those of the circuit shown in FIG. In FIG. 4, for simplification of description, circuit portions common to FIG. 2 are denoted by the same reference numerals as those used in FIG.
[0046]
In the circuit shown in FIG. 4, the loss required for detecting the current flowing through the coil L1 is reduced by forming a current mirror circuit with the FET Q1 and the FET Q2.
[0047]
That is, in the circuit shown in FIG. 4, the size (current amount) of the FET Q2 constituting the current mirror circuit is set to 1 / N of the size of the FET Q1.
[0048]
For example, assuming that the resistance value of the resistor R2 is R and the current flowing through the transistor Tr is I in the circuit of FIG. 2, the loss generated in the resistor R2 for detecting the current flowing through the coil L1 is I ＾ 2 × R. .
[0049]
On the other hand, in the circuit shown in FIG. 4, the current I ′ flowing through the FET Q2 is 1 / N of the current flowing through the FET Q1. Here, assuming that the resistance value of R2 is N × R in order to make the voltage level generated in R2 the same, the loss generated in the resistor R2 in the circuit shown in FIG. 4 is I ＾ 2 × R / N, The loss caused by the resistor R2 can be reduced to 1 / N.
[0050]
In the circuit shown in FIG. 2 as well, a current mirror circuit similar to the circuit in FIG. 4 can be formed by using a bipolar transistor. With this structure, the loss caused by the resistor R2 is greatly reduced. be able to.
[0051]
FIG. 5 is a circuit diagram showing still another detailed configuration of charge control device 20 shown in FIG.
[0052]
In the circuit shown in FIG. 5, the configuration using the auxiliary winding L2 electromagnetically coupled to the coil L1 of the circuit shown in FIG. 4 is eliminated, and the ON / OFF of the FET Q1 is controlled by the output of the control circuit CO. It is what was constituted. In FIG. 5, for simplification of the description, circuit portions common to FIG. 4 are denoted by the same reference numerals as those used in FIG.
[0053]
The circuit shown in FIG. 5 employs a separately excited upconverter controlled by a control circuit CO instead of the self-excited upconverter shown in FIG.
[0054]
That is, in the configuration shown in FIG. 5, the output of the oscillator OS that oscillates a clock pulse of a predetermined frequency is input to the control circuit CO, and the outputs of the operational amplifiers OP1 and OP2 are input to the control circuit CO. The output controls on / off of the FET Q1.
[0055]
The circuit shown in FIG. 5 differs from the circuit shown in FIG. 4 only in that a self-excited upconverter or a separately-excited upconverter is employed.
[0056]
In the above-described embodiment, a case has been described in which the present invention is provided in a charging device for a secondary battery. However, it goes without saying that the present invention can be similarly applied to other configurations using a fuel cell.
[0057]
【The invention's effect】
As described above, according to the present invention, the input current from the fuel cell is detected by the input current detection circuit, and the current control circuit detects the input current from the fuel cell based on the input current of the fuel cell detected by the input current detection circuit. To provide an output control device for a fuel cell in which the average value of the input current from the fuel cell is controlled by limiting the peak value of the current, so that the fuel cell can be used effectively and stably as a power source. This has the effect that it can be performed.
[Brief description of the drawings]
FIG. 1 is a block diagram showing the overall configuration of a secondary battery charging device configured by applying a fuel cell output control device according to the present invention.
FIG. 2 is a circuit diagram showing a detailed configuration of a charge control device 20 shown in FIG.
FIG. 3 is a waveform chart for explaining the operation of the circuit shown in FIG. 2;
FIG. 4 is a circuit diagram showing another detailed configuration of the charge control device shown in FIG.
FIG. 5 is a circuit diagram showing still another detailed configuration of the charge control device shown in FIG.
[Explanation of symbols]
Reference Signs List 10 fuel cell 20 charge control device 30 secondary batteries T11, T12 input terminals T21, T22 output terminal L1 coil (inductor)
L2 coil (auxiliary winding)
C1, C2 Capacitors D1, D2, D3, D4 Diode Tr Transistor (switching element)
Q1, Q2 Field Effect Transistor (FET)
OS oscillator CO control circuit

Claims (10)

In a fuel cell output control device that controls and outputs an input from a fuel cell,
An input current detection circuit for detecting an input current from the fuel cell;
An input current control circuit that controls an average value of the input current from the fuel cell by limiting a peak value of the input current from the fuel cell based on the input current of the fuel cell detected by the input current detection circuit. An output control device for a fuel cell, comprising: The input current control circuit,
The average value of the input current from the fuel cell is controlled to the target average value by limiting the peak value of the input current of the fuel cell detected by the input current detection circuit to a value approximately twice the target average value. 2. The output control device for a fuel cell according to claim 1, wherein: A switching element for switching the output of the fuel cell;
A switching control circuit for controlling the switching element,
The input current detection circuit,
3. The output control device for a fuel cell according to claim 2, wherein an input current from the fuel cell is detected based on an output of the switching element. The fuel cell further includes an inductor for inputting an output of the fuel cell,
The switching control circuit,
4. The output control device for a fuel cell according to claim 3, wherein the switching element is controlled based on a current flowing through the inductor. The input current detection circuit,
A current mirror circuit connected in parallel to the switching element and flowing a current 1 / N of the current flowing through the switching element;
4. The fuel cell output control device according to claim 3, wherein an input current from the fuel cell is detected based on a current flowing through the current mirror circuit. In a fuel cell output control device that controls and outputs an input from a fuel cell,
A converter having at least an inductor for inputting the output of the fuel cell and a switching element for switching the output of the inductor,
An input current detection circuit that detects an input current from the fuel cell based on a current flowing through the switching element of the converter,
A comparison circuit that compares a current value detected by the input current detection circuit with a preset target current value;
A control circuit for controlling the average value of the input current from the fuel cell in accordance with the target current value by controlling switching of the switching element based on the output of the comparison circuit. Battery output control device. The fuel cell output control device according to claim 6, wherein a charging current for charging a secondary battery is output based on an output of the converter. The target current value is
7. The fuel cell output control device according to claim 6, wherein the output control device is set to correspond to approximately twice the target average value of the input current. The converter comprises:
7. The fuel cell output control device according to claim 6, further comprising a self-excited up-converter that self-excitably controls switching of the switching element based on a current flowing through the inductor. The input current detection circuit,
A current mirror circuit connected in parallel to the switching element and flowing a current 1 / N of the current flowing through the switching element;
7. The fuel cell output control device according to claim 6, wherein an input current from the fuel cell is detected based on a current flowing through the current mirror circuit.

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