JP2005094893A - Method and apparatus for charge judging electric double layer capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily and accurately judge reaching to full charge, etc. at predetermined charging for charging an electric double layer capacitor. <P>SOLUTION: A method for charge judging the electric double layer capacitor includes a step of monitoring the charging voltage of the electric double layer capacitor (12) to switch from a constant current charging to a constant voltage charging, a step of detecting the abrupt change of the charging current flowing to the electric double layer capacitor in the case of the constant voltage charging, and a step of judging by this change that the electric double layer capacitor arrives at the predetermined charging. An apparatus for charge judging the electric double layer capacitor includes a charging means (charging circuit 4) for constant current charging the electric double layer capacitor at the initial charging, and switching from the constant current charging to the constant voltage charging in response to the charging voltage of the electric double layer capacitor, and a judging means (voltage comparator 50) for detecting the abrupt charge of the charging current flowing to the electric double layer capacitor to judge that the electric double layer capacitor reaches the predetermined charged state by this change. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

The present invention relates to charging of an electric double layer capacitor including a single or a plurality of electric double layer capacitors, and in particular, an electric double layer capacitor that determines whether a predetermined charge such as a full charge of the electric double layer capacitor has reached a predetermined charge by changing a current. The present invention relates to a charging determination method and apparatus therefor.

  The electric double layer capacitor is small and has a large capacity, but has a low withstand voltage. Therefore, an electric double layer capacitor device is serialized to form an electric double layer capacitor device, thereby increasing the withstand voltage. This is a high breakdown voltage as an electric double layer capacitor device, and does not increase the breakdown voltage of each electric double layer capacitor in series. Therefore, it is necessary to control the charging voltage of each electric double layer capacitor constituting the electric double layer capacitor device so as not to exceed the withstand voltage and to monitor the charging state.

The following patent documents exist in the prior art regarding such an electric double layer capacitor device.
Utility Model Registration No. 2575358 Patent Document 1 discloses an electric double layer capacitor device in which a plurality of electric double layer capacitors are connected in series. The electric double layer capacitor device is connected in parallel to each electric double layer capacitor. A transistor is connected as a current control means, the charging voltage of the electric double layer capacitor is compared with the reference voltage, and the current flowing through the transistor is controlled according to the difference voltage, thereby balancing the charging voltage of each electric double layer capacitor. It is the structure to make.

  By the way, in such an electric double layer capacitor device, when the electric double layer capacitor is charged with a constant current, when the charging voltage rises to the vicinity of the rated voltage of the electric double layer capacitor, the voltage rise becomes slow, and the charging voltage is reduced. It takes considerable time to reach the rated voltage. This is because a charging current flows through the electric double layer capacitor, but the voltage rise becomes dull in the charged state immediately before the rated voltage is reached, and the charging efficiency is lowered. In this case, since the electric energy stored in the electric double layer capacitor is proportional to the square of the voltage applied to the electric double layer capacitor, the higher the charging voltage, the larger the stored electric energy. Therefore, in order to use an electric double layer capacitor as a power source, it is desirable to charge the electric double layer capacitor to a value closer to the rated voltage. In this case, it is necessary to monitor the charging status with the voltage between terminals. It becomes. When the charging voltage becomes close to the rated voltage, the increase value becomes dull, and if the voltage change is measured to determine whether to reach a predetermined charge such as full charge, the measurement accuracy of the voltmeter is increased. Countermeasures are necessary. For this reason, it is desired to easily and accurately monitor the charging voltage such as full charge of the electric double layer capacitor. Such a problem is neither disclosed nor suggested in the above patent document, and means for solving it is not disclosed.

  In view of this, an object of the present invention is to easily and accurately determine whether or not an electric double layer capacitor has been charged, such as full charge.

In detail, when the charging voltage of the electric double layer capacitor changes in the vicinity of the rated voltage, paying attention to the fact that the change in the charging current is larger than the charging voltage, the predetermined charging such as full charging is performed. This makes it possible to detect and determine the arrival at the position easily and with high accuracy.

  To achieve the above object, the electric double layer capacitor charging determination method of the present invention monitors the charging voltage of the electric double layer capacitor (12, 121 to 12N) and switches from constant current charging to constant voltage charging. In the case of constant voltage charging, a rapid change in the charging current flowing through the electric double layer capacitor is detected, and it is determined that the electric double layer capacitor has reached a predetermined charge due to this change.

  If the electric double layer capacitor is charged by switching to constant voltage charging after constant current charging, the advantages of both constant current charging and constant voltage charging can be utilized. That is, when the charging voltage is low, rapid charging can be performed with a constant current, and when the charging voltage increases, the charging current decreases. Therefore, switching to constant voltage charging is performed, and a current necessary for charging is supplied. Such charging is suitable for an electric double layer capacitor. Therefore, in the present invention, constant current charging is performed at the beginning of charging, the charging voltage is monitored and switched to constant voltage charging, and a predetermined charging voltage is realized. In such charging, in constant voltage charging, when the electric double layer capacitor reaches a predetermined voltage, the charging current rapidly decreases. As the charging voltage increases, the change in the charging current becomes conspicuous. By detecting this change in the charging current, it is possible to easily reach the predetermined charging such as full charging and to determine with high accuracy. Even when the change in current is converted into voltage and taken out, the charging current shows an extremely decreasing tendency, so a high-precision voltmeter is not necessary, and the determination of reaching a predetermined charge such as full charge can be made with high accuracy. Is possible.

  In order to achieve the above object, the electric double layer capacitor charging determination apparatus of the present invention performs constant current charging at the initial stage of charging of the electric double layer capacitor, and determines from the constant current charging according to the charging voltage of the electric double layer capacitor. Charging means (charging circuit 4) for switching to voltage charging and a rapid change in the charging current flowing through the electric double layer capacitor during the constant voltage charging are detected, and the electric double layer capacitor reaches a predetermined charge due to this change. It is the structure provided with the determination means (voltage comparator 50) which determines with having carried out.

  According to such a configuration, the charging state of the electric double layer capacitor can be grasped as a sudden change in the charging current, and arrival at a predetermined charging such as full charging can be determined with high accuracy and ease.

  In order to achieve the above object, a resistor 14 may be connected in series with the electric double layer capacitor, and a rapid decrease value of the charging current may be detected by a voltage drop due to the charging current flowing through the resistor.

With such a configuration, it is possible to take out the sudden decrease value of the charging current in the predetermined charging such as full charging of the electric double layer capacitor by converting it into a voltage with a resistor, and by measuring the voltage, the full charging etc. Can be determined with high accuracy and easily.

  As described above, according to the present invention, the following effects can be obtained.

  (1) After switching from constant current charging to constant voltage charging, it is possible to easily and accurately know the charging status such as full charge by capturing the sudden change in charging current of the electric double layer capacitor during constant voltage charging. The conventional high-accuracy voltmeter or the like is not necessary, and the control accuracy of the charging circuit can be increased by using the determination result, for example.

  (2) The detection accuracy and determination accuracy of predetermined charge such as full charge can be improved, and the charging efficiency of the electric double layer capacitor can be improved.

(3) If charging current is converted into voltage by a resistor and taken out, a sudden change in charging current can be taken out as a voltage drop, and it is possible to easily and accurately determine the arrival of a predetermined charge such as full charge. it can.

  A first embodiment of the present invention will be described with reference to FIG. FIG. 1 shows a method for determining the charge of an electric double layer capacitor together with the electric double layer capacitor device according to the first embodiment of the present invention.

In the electric double layer capacitor device 2, the charging circuit 4 can perform constant current charging or constant voltage charging by, for example, rectifying the AC input of the commercial AC power supply 6 to generate a constant DC voltage or a constant current. . An electric double layer capacitor 12 is connected between the output terminals 8 and 10 of the charging circuit 4 via a resistor 14. The resistor 14 constitutes current detection means for detecting the charging current ic flowing through the electric double layer capacitor 12. In this case, if the voltage between the terminals of the electric double layer capacitor 12 is V ₁ [V], the voltage between the terminals generated in the resistor 14 is V _2, and the resistance value of the resistor 14 is R, the voltage V ₂ is
V ₂ = ic × R [V] (1)
It is.

In such a configuration, the capacitance C of the electric double layer capacitor 12 is 600 [F], its rated voltage V _T is 2.5 [V], the resistance value R of the resistor 14 is 0.1 [Ω], and charging is performed. When the charging current ic of the electric double layer capacitor 12 from the circuit 4 is charged with a constant current, for example, 1 [A], the charging time t is
t = V _T × C / ic = 2.5 × 600/1 = 1500 [sec]
= 25 [minutes] (2)
It becomes.

  Incidentally, the charging circuit 4 is configured as shown in FIG. 2, for example. FIG. 2 shows a specific circuit configuration example of the charging circuit 4.

  The charging circuit 4 is provided with a rectifier circuit 16 for rectifying an AC input from the commercial AC power supply 6, and the rectifier circuit 16 is constituted by a full-wave rectifier circuit including a diode bridge of four diodes 18. . A smoothing capacitor 20 is connected to the output side of the rectifier circuit 16 to remove fluctuation components such as a ripple component of the rectified output. On the DC output side of the rectifier circuit 16, a primary coil 22 </ b> P of a transformer 22, a field effect transistor (FET) 24 and a current detection circuit 26 are connected as switching elements in parallel with the capacitor 20. The detection output of the current detection circuit 26 is applied to the control unit 28, and the control output of the control unit 28 is applied to the gate of the transistor 24. With this configuration, the chopper circuit 30 is configured, and a switching current flows through the primary coil 22P of the transformer 22 due to the oscillation of the transistor 24. Due to the switching current on the primary side, a switching voltage is induced on the secondary side of the transformer 22. The transistor 24 is configured to obtain a constant current output during constant current charging and a constant voltage output during constant voltage charging.

  A rectifier circuit 36 composed of diodes 32 and 34 is connected to the secondary coil 22S of the transformer 22. The switching voltage is rectified by the rectifier circuit 36, and the fluctuation component is removed by the choke coil 38 and the capacitor 40. The resistor 42 is a current detection resistor and is a means for converting the charging current ic into a voltage, and takes out a sudden change in the charging current ic as a voltage change. Further, the DC output voltage generated between both terminals of the capacitor 40 is applied to the above-described electric double layer capacitor 12 through the diode 44 and used for charging.

The inter-terminal voltage Vc of the electric double layer capacitor 12 is applied to the first voltage comparator 46 and compared with the reference voltage V _REF of the reference voltage source 48. The voltage comparator 46 generates an output corresponding to the voltage difference between the two.

  In addition, since the voltage Vs is generated between the terminals of the resistor 42 due to the charging current ic flowing in the electric double layer capacitor 12, the voltage Vs between the terminals is applied to the second voltage comparator 50. Assuming that the resistance value of the resistor 42 is R, the inter-terminal voltage Vs is given by the product of the charging current ic and the resistance value R from the relationship shown in the equation (1) as described above, and is proportional to the charging current ic. The terminal voltage Vs is applied to the voltage comparator 50. As a result, the voltage comparator 50 is a determination unit that determines that the electric double layer capacitor 12 has shifted to a predetermined voltage as an opportunity to switch from constant current charging to constant voltage charging, and reduces the decrease in the charging current ic. It is determined that the inter-terminal voltage Vs to be expressed has decreased to a predetermined voltage, and the determination result is output.

The outputs of the voltage comparators 46 and 50 serve as control inputs for the control unit 28. The output of the voltage comparators 46 and 50 changes the control output of the control unit 28, and the voltage applied to the gate of the transistor 24 is changed. Adjusted. As a result, the conduction period of the switching frequency of the transistor 24 is adjusted. As a result, the pulse width control is performed, and the output current applied to the electric double layer capacitor 12 to be charged is switched from the constant current output to the constant voltage output. . In this case, for example, if the transistor 24 is turned ON / OFF at 100 kHz, the ON period is controlled by the total feedback of the feedback of the secondary current and the feedback of the charging voltage, that is, a constant output current, that is, In this configuration, a charging current i _C can be obtained. In this embodiment, both voltage and current feedback are used, but either one may be used.

When the electric double layer capacitor 12 is charged by using the charging circuit 4 which is switched to constant current charging at the initial stage of charging and constant voltage charging after reaching a predetermined voltage, the electric double layer capacitor 12 is charged. The characteristics will be described with reference to FIG. 3. FIG. 3 shows transitions of the inter-terminal voltage V ₁ (= Vc) and the inter-terminal voltage V ₂ . The inter-terminal voltage V ₁ gradually increases with the passage of time, whereas the inter-terminal voltage V ₂ depends on the charging current ic and rapidly decreases when shifting to constant voltage charging. In this case, the inter-terminal voltage V ₁ rises linearly up to about 2.25 [V], and the voltage rise becomes slow at a voltage exceeding 2.25 [V]. On the other hand, when the charging rate CA reaches 92%, the charging circuit 4 as a constant voltage power supply switches from the constant current (CC) mode to the constant voltage (CV) mode. Instead, the charging current ic is greatly reduced. This is because the charging current ic of the electric double layer capacitor 12 is suppressed when the inter-terminal voltage V ₁ of the electric double layer capacitor 12 approaches the rated voltage V _T by charging.

Thus, when the electric double layer capacitor 12 approaches a predetermined charge such as full charge, the rate of change ΔV ₁ of the inter-terminal voltage V ₁ becomes small, and from this change to a predetermined charge such as full charge of the electric double layer capacitor 12. However, the rate of change Δic of the charging current ic is large, and by observing this rate of change Δic, it is easily and accurately determined that the electric double layer capacitor 12 has reached the predetermined charge. be able to. In this embodiment, by converting the change rate Δic of the charging current ic in voltage, the change rate [Delta] V ₂ of the terminal voltage V ₂ of the resistor 14 is observed, the fully charged such an electric double layer capacitor 12 to a predetermined charge The arrival of is detected and judged.

If the resistance value R of the resistor 14 for detecting the change in the charging current ic is set to a small value, for example, R = 0.1 [Ω], the electric double layer capacitor 12 is fully charged, etc. The transition can be detected and taken out with large change rates Δic and ΔV ₂ , and the voltage V ₂ between the terminals can be made smaller than the voltage V ₁ between the terminals, so that the power loss at the resistor 14 can be reduced.

  By the way, in the charging circuit 4 shown in FIG. 2, the output of the voltage comparator 50 is added to the presentation unit 52 which is a means for presenting arrival information representing the arrival of the electric double layer capacitor 12 to a predetermined charge, and the electric double layer capacitor 12 is presented to have reached a predetermined charge such as full charge. The presenting unit 52 can be composed of an LCD display, an LED indicator, or the like, and can visually display the arrival of a predetermined charge such as full charge. The presenting unit 52 may be configured with a buzzer or the like, and with such a configuration, auditory display is also possible. Further, the presenting unit 52 may be configured as a determination output unit, and the determination output may be used as control information for power supply control of an information device or the like, thereby configuring a charging completion notification unit.

  Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 4 shows an electric double layer capacitor device according to a second embodiment of the present invention.

A plurality of electric double layer capacitors 121, 122, 123... 12N having the same capacity are connected in series to the electric double layer capacitor device 54, and the series circuit of these electric double layer capacitors 121 to 12N is charged. A circuit 56 is connected. The charging circuit 56, for example, rectifies AC AC applied from the commercial AC power supply 6 to obtain a constant DC voltage V _DC , and the configuration is configured by the circuit shown in FIG.

  Each of the electric double layer capacitors 121 to 12N is individually connected with a balance circuit 81, 82, 83... 8N, and each of the balance circuits 81 to 8N balances the charging current ic so that each of the electric double layer capacitors 121 to 12N The charging voltage is made constant.

  With such a configuration, as already described with reference to FIG. 3, the rapid change of the charging current ic flowing in each of the electric double layer capacitors 121 to 12N is detected directly or indirectly by voltage conversion, thereby satisfying the above. Reaching a predetermined charge such as charging can be determined, and unnecessary charging can be prevented, and an efficient charging process can be realized.

  In the above embodiment, the configuration has been described in which the resistor 14 is installed as the current detection means, and a rapid current change is converted into a voltage and extracted. However, the current change is directly extracted using a detection circuit such as a transistor, and the electric double layer It may be determined whether the capacitor has reached a predetermined voltage, such as full charge.

As described above, the most preferable embodiment of the present invention has been described. However, the present invention is not limited to the above description, and is described in the claims or the best for carrying out the invention. It goes without saying that various modifications and changes can be made by those skilled in the art based on the gist of the invention disclosed in the embodiments, and such modifications and changes are included in the scope of the present invention.

According to the present invention, it is possible to easily and highly accurately detect and determine the arrival of a predetermined charge such as a full charge of the electric double layer capacitor, to equalize the charging voltage of the electric double layer capacitor, and to improve safety. This contributes to the provision of a high electric double layer capacitor device and is useful.

1 is a circuit diagram showing an electric double layer capacitor device according to a first embodiment of the present invention. It is a circuit diagram which shows an example of the charging circuit in an electrical double layer capacitor | condenser apparatus. It is a figure which shows the charge characteristic of an electrical double layer capacitor. It is a circuit diagram which shows the electric double layer capacitor | condenser apparatus which concerns on the 2nd Embodiment of this invention.

Explanation of symbols

2 Electric double layer capacitor device 4 Charging circuit (charging means)
12, 121, 122... 12N Electric double layer capacitor 14 Resistance 50 Voltage comparator (determination means)

Claims (3)

  The charging voltage of the electric double layer capacitor is monitored and switched from constant current charging to constant voltage charging, and a sudden change in the charging current flowing through the electric double layer capacitor in the case of the constant voltage charging is detected. A method for determining the charge of an electric double layer capacitor, comprising: determining that the electric double layer capacitor has reached a predetermined charge. Charging means for switching from constant current charging to constant voltage charging according to the charging voltage of the electric double layer capacitor, constant current charging at the beginning of charging of the electric double layer capacitor,
A determination unit that detects a sudden change in a charging current flowing through the electric double layer capacitor during the constant voltage charging, and determines that the electric double layer capacitor has reached a predetermined charge due to the change;
An electric double layer capacitor charge determination device comprising:   3. The electric double layer capacitor according to claim 2, wherein a resistance is connected in series to the electric double layer capacitor, and a sudden decrease value of the charging current is detected by a voltage drop due to the charging current flowing through the resistor. Charge determination device.

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