JP2006203983A - Charger - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To shorten the time required for charging an electric double-layer capacitor in a charger for charging the electric double-layer capacitor by a charging power supply. <P>SOLUTION: This charger includes (a) a chopper type step-down circuit 50 having a function for converting the power supplied from a solar battery to the capacitor, so that a voltage lower than a voltage generated by the solar battery 12 may be applied to the electric double-layer capacitor 14 (hereinafter referred to as a capacitor) as the charging power supply, on the other hand, a current larger than a current generated by the solar battery may be supplied to the capacitor; (b) and control circuits 60-66 which control the step-down circuit 50 so that the voltage generated by the solar battery may not be lowered to below a lower limit value, by charging the capacitor with the solar battery based on a relation between a response voltage corresponding to a voltage generated by the solar battery and the reference voltage. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a charging device that is used by being connected to the charging power source and the electric double layer capacitor in order to charge the electric double layer capacitor with the charging power source, and more particularly, to the electric double layer by the charging power source. The present invention relates to a technique for shortening the time required for charging a capacitor.

  Secondary batteries and electric double layer capacitors (hereinafter simply referred to as “capacitors”) are used to store electrical energy. Secondary batteries use chemical reactions of chemical substances to convert electrical energy into chemical energy and store it. For this reason, in the use of secondary batteries, it is required to consider the problems related to the limit on the number of repetitions of charging and discharging, the health damage due to the toxicity of chemical substances, the pollution of the global environment due to the disposal of consumables.

  On the other hand, the capacitor stores electric energy as it is, that is, without performing energy conversion. For this reason, this capacitor has no depleting elements, can be repeatedly charged and discharged indefinitely, its product life is theoretically permanent, and even if discarded, it contaminates the global environment. No worries.

  Therefore, in recent years, attention has been focused on a technology for storing electric energy in a capacitor, in which the use of resources and the provision of products that are friendly to humans and the global environment have been screamed.

A charging device is used to charge the capacitor with a charging power source. As the power source for charging, it is possible to use a solar cell, a hand-driven generator, a wind power generator, or the like. Solar cells are DC generators, and hand-driven generators and wind generators are usually AC generators. A conventional example in which a capacitor is charged by a solar cell is described in Patent Document 1.
Japanese Patent No. 3401486

  It is desirable to charge the capacitor in as short a time as possible. However, when charging a capacitor in a discharged state with a charging power source such as a solar cell, a hand-driven generator, a wind power generator, etc., the voltage and power of the charging power source are conventionally reduced. Because of this, it took a long time to charge the capacitor.

  In view of such circumstances, the present invention provides a charging power source in a charging device that is used connected to the charging power source and the electric double layer capacitor in order to charge the electric double layer capacitor with the charging power source. It is an object to shorten the time required for charging the electric double layer capacitor by the above.

  The following aspects are obtained by the present invention. Each aspect is divided into sections, each section is given a number, and is described in a form that cites other section numbers as necessary. This is to facilitate understanding of some of the technical features that the present invention can employ and combinations thereof, and the technical features that can be employed by the present invention and combinations thereof are limited to the following embodiments. Should not be interpreted. That is, it should be construed that it is not impeded to appropriately extract and employ the technical features described in the present specification as technical features of the present invention although they are not described in the following embodiments.

  Further, describing each section in the form of quoting the numbers of the other sections does not necessarily prevent the technical features described in each section from being separated from the technical features described in the other sections. It should not be construed as meaning, but it should be construed that the technical features described in each section can be appropriately made independent depending on the nature.

(1) A charging device that is used by being connected to the charging power source and the electric double layer capacitor to charge the electric double layer capacitor with the charging power source,
A voltage lower than the power generation voltage of the charging power source is applied to the electric double layer capacitor, while a current larger than the power generation current of the charging power source is supplied to the electric double layer capacitor. A chopper type step-down converter having a function of converting electric power supplied to the electric double layer capacitor;
Control that controls the step-down converter based on a relationship between a response voltage that is responsive to the generated voltage and a reference voltage so that the generated voltage does not fall below a lower limit value due to charging of the electric double layer capacitor by the charging power source. A charging device including a circuit.

  In general, when an electric double layer capacitor in a discharged state (hereinafter simply referred to as “capacitor”) is to be charged by a charging power source, the voltage of the capacitor is 0 at the start of charging, so the voltage of the charging power source Therefore, the electric power generated by the charging power source is also zero. However, if the charging power source continues to be conducted to the capacitor in the discharged state, the current continues to be supplied from the charging power source to the capacitor, and eventually the charging of the capacitor by the charging power source is completed. However, it takes a long time to charge the capacitor if the current generated by the charging power source is simply supplied to the capacitor.

  On the other hand, when a current larger than the generated current of the charging power supply is supplied to the capacitor in the discharge state of the capacitor, the charging time of the capacitor is shortened compared to the case where the generated current of the charging power supply is supplied to the capacitor as it is. In order to supply a current larger than the generated current of the charging power source to the capacitor, that is, to increase the current, a step-down converter may be provided between the charging power source and the capacitor.

  However, in order to increase the current, it is necessary to secure the generated power of the charging power source. For this purpose, the step-down converter described above is a chopper type, and the inflow current flowing from the charging power source to the step-down converter may be reduced by chopping the switching element of the step-down converter.

  Based on the knowledge described above, in the charging device according to this section, a chopper type step-down converter is provided between the charging power source and the capacitor, and this step-down converter causes a current larger than the generated current of the charging power source to be charged to the capacitor. To be supplied. Therefore, according to this charging device, the charging time required for charging the capacitor (the time required for shifting the capacitor from the discharged state to the fully charged state) is greater than when the generated current of the charging power source is supplied to the capacitor as it is. ) Is shortened.

  Furthermore, in this charging apparatus, the chopper type step-down converter is controlled by the control circuit so that the power generation voltage of the charging power supply does not fall below the lower limit value due to charging of the capacitor by the charging power supply. That is, the control circuit has a function of preventing a decrease in generated voltage.

  Therefore, according to this charging apparatus, compared with the case where the control circuit does not have the above-described power generation voltage drop prevention function, the power generation voltage of the charging power supply is kept high. Therefore, according to this charging device, even when the voltage of the capacitor is close to 0, a state in which the generated power of the charging power source is converted and supplied to the capacitor is ensured. Charging becomes possible.

  In addition, the “charging power source” in this section refers to a power source that generates power using natural energy, such as a solar cell or a wind power generator, a manual power generator that generates power by human power, an automobile, etc. It is also possible to provide a generator that generates power using the kinetic energy of a vehicle including a bicycle.

  In addition, the “response voltage” in this section is generally defined to mean the divided voltage of the charging power supply, but does not exclude the possibility of being defined to mean the full voltage.

(2) The control circuit controls the step-down converter so that an inflow current flowing from the charging power source into the step-down converter decreases when the response voltage is made lower than the reference voltage. The charging device described.

  In this charging device, when the response voltage is going to be lower than the reference voltage, the step-down converter is controlled so that the inflow current flowing from the charging power source into the step-down converter is reduced. Therefore, according to this charging device, the response voltage is suppressed from lowering than the reference voltage, and as a result, the power generation voltage of the charging power supply is lowered below the lower limit value due to charging of the electric double layer capacitor by the charging power supply. Is suppressed.

(3) The charging device according to (2), wherein the control circuit controls the step-down converter so that the inflow current increases when the response voltage is higher than the reference voltage.

  Generally, the high capacity of a charging power supply to charge a capacitor tends to depend on the voltage level of the charging power supply. Therefore, in order to optimize the charging capacity of the capacitor, the voltage of the charging power supply It is desirable to maintain a certain value or range.

  Based on this knowledge, in the charging device according to this section, when the response voltage is going to be lower than the reference voltage, the inflow current flowing from the charging power source to the step-down converter is reduced, while the response voltage is higher than the reference voltage. When trying to do so, the step-down converter is controlled so that the inflow current increases. If the inflow current decreases, as described above, the tendency of the power and voltage of the charging power supply to decrease is suppressed. Conversely, if the inflow current increases, the power and voltage of the charging power supply tend to increase. Is suppressed.

  Therefore, according to this charging apparatus, the voltage of the charging power source is maintained at a height corresponding to the reference voltage while the capacitor is charged by the charging power source.

(4) The charging device according to (3), further including a charge blocking circuit that blocks charging of the electric double layer capacitor by the charging power supply when the charging voltage exceeds an upper limit value thereof.

  In the charging device according to the item (3), when the response voltage is going to be higher than the reference voltage, the step-down converter is controlled so that the inflow current increases. If the inflow current increases, the tendency of the power and voltage of the charging power supply to increase is suppressed, and the power supplied to the capacitor from the charging power supply increases, and as a result, the tendency to increase the charging voltage of the capacitor increases. . On the other hand, in a capacitor, it is necessary that its charging voltage does not exceed its upper limit (for example, withstand voltage).

  Based on such knowledge, in the charging device according to this section, when the charging voltage of the capacitor exceeds the upper limit value thereof, charging of the electric double layer capacitor by the charging power source is prevented.

(5) The step-down converter is provided on an inductor that forms an LC filter in cooperation with the electric double layer capacitor, a flywheel diode, and a line through which the generated current is supplied to the electric double layer capacitor. The charging device according to any one of (2) to (4), which is a non-insulated step-down switching regulator including a switching element.

(6) The charging device according to (5), wherein the control circuit controls a duty ratio of the switching element based on a voltage difference that is a difference between the response voltage and the reference voltage.

  The “control circuit” in this section can be implemented, for example, in such a manner that the duty ratio is changed stepwise according to the voltage difference, or in a manner in which it is continuously changed. According to the latter aspect, it is easy to finely control the charging voltage.

(7) The control circuit has a duty ratio of the switching element according to the shortage amount so that a conduction time in which the switching element is turned on is reduced according to the shortage amount of the response voltage with respect to the reference voltage. (5) or the charging device according to (6).

  In this charging apparatus, the conduction time during which the switching element is turned on is reduced according to the insufficient amount of the response voltage with respect to the reference voltage. On the other hand, as the conduction time of the switching element is shorter, the inflow current flowing from the charging power source into the capacitor is reduced, and as a result, the voltage drop of the charging power source is suppressed. Therefore, according to this charging device, the generated voltage is prevented from lowering from its lower limit value by controlling the conduction time of the switching element.

(8) The control circuit includes:
A signal output unit for detecting the voltage difference and outputting a signal reflecting the detected voltage difference;
An on / off control unit that performs on / off control of the switching element, and the on / off control unit controls a duty ratio of the switching element based on a signal output from the signal output unit (6) or (7) The charging device described in 1.

(9) The charging device according to any one of (5) to (8), further including a switching circuit that continuously switches the switching element to an off state when the charging voltage exceeds an upper limit value thereof. .

  In this charging apparatus, when the charging voltage of the capacitor exceeds the upper limit value thereof, the switching element is continuously switched off. After the switching, the capacitor is electrically disconnected from the charging power source, thereby preventing additional charging of the capacitor by the charging power source. Therefore, according to this charging apparatus, it is suppressed that the charging voltage of a capacitor tries to exceed the upper limit value.

  Hereinafter, one of more specific embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows an electrical circuit diagram of a charging device according to an embodiment of the present invention. The charging device 10 is connected to the solar cell 12 and the electric double layer capacitor 14 in order to charge an electric double layer capacitor (hereinafter simply referred to as “capacitor”) 14 by a solar cell 12 as a power source for charging. used. The solar cell 12 is a physical cell that converts light energy into electrical energy. The solar cell 12 converts light energy into DC power.

  The charging device 10 is connected to the positive side and the negative side of the solar cell 12 at its positive input terminal 20 and negative input terminal 22, respectively. The charging device 10 is further connected to the plus side and the minus side of the capacitor 14 at its plus output terminal 30 and minus output terminal 32, respectively.

  As shown in FIG. 1, the charging apparatus 10 is connected to each other by a positive line 40 that connects the positive input terminal 20 and the positive output terminal 30 to each other, while the negative input terminal 22 and the negative output terminal 32 are connected to each other. They are connected to each other by a negative line 42 to be connected. In the middle of the plus side line 40, a diode 44 for biasing it in the forward direction is connected. The minus side line 42 is grounded.

  The plus side line 40 is connected to one end of the electrolytic capacitor 46 between the diode 44 and the plus output terminal 30. The other end of the electrolytic capacitor 46 is grounded. The electrolytic capacitor 46 is provided in order to prevent the charging voltage Vs of the solar cell 12 from fluctuating when the capacitor 14 is charged by the solar cell 12.

  The charging device 10 includes a step-down inverter 50 across the plus side line 40 and the minus side line 42. The step-down inverter 50 is configured as a non-insulated step-down switching regulator.

  Specifically, the step-down inverter 50 includes a chopper type switching circuit 52 and an inductor 54 connected in series with each other in the middle of the plus side line 40 as shown in FIG. The inductor 54 is connected to the capacitor 14 to form an LC filter. The step-down inverter 50 further includes a flywheel diode (hereinafter simply referred to as “diode”) connected between a portion between the switching circuit 52 and the inductor 54 in the plus side line 40 and the minus side line 42. .) 56.

  The step-down inverter 50 is configured so that a voltage lower than the power generation voltage Vs of the solar cell 12 is applied to the capacitor 14 while a current larger than the power generation current Is of the solar cell 12 is supplied to the capacitor 14. 14 has a function of converting power supplied to the power supply 14.

  As is well known, the step-down inverter 50 is a method of smoothing a square wave (intermittent waveform) generated by turning on and off the switching circuit 52 using the above-described LC filter. This method is employed when the output voltage, that is, the charging voltage Vc of the capacitor 14 is lower than the input voltage, that is, the generated voltage Vs of the solar battery 12.

  In the step-down inverter 50, the electrical energy of the solar cell 12 is accumulated in the inductor 54 through the switching circuit 52 during the period in which the switching circuit 52 is in the on (conducting) state. Thereafter, when the switching circuit 52 is switched to an off (cut-off) state, the electrical energy stored in the inductor 54 is supplied to the capacitor 14 by a closed circuit including the inductor 54, the capacitor 14, and the diode 56. By repeating ON / OFF of the switching circuit 52, the electric energy of the solar cell 12 is supplied to the capacitor 14, and thereby the capacitor 14 is charged by the solar cell 12.

At this time, the charging voltage Vc of the capacitor 14, the duty ratio of the switching circuit 52, i.e., the conduction time _{T ON} of the switching circuit 52 is turned on, divided by the sum of its conduction time _{T ON} and the non-conduction time _{T OFF} The generated voltage Vs of the solar cell 12 has a reduced height based on the obtained value. If the voltage obtained by stepping down the generated voltage Vs becomes the charging voltage Vc, the current obtained by increasing the generated current Is of the solar battery 12 becomes the charging current Ic of the capacitor 14 in return.

Further, in the step-down inverter 50, the inflow current flowing from the solar cell 12 in the step-down inverter 50, the product of the power generation voltage Vs from the charging voltage Vc a value and flowing time by subtracting t (= integrated value of the conduction time T _ON) Determined based on As the inflow current increases, more electric power is supplied from the solar cell 12 to the capacitor 14, which causes the power generation voltage Vs to decrease.

  As shown in FIG. 1, the switching circuit 52 is connected to the PWM circuit 60. The PWM circuit 60 is designed to perform pulse width modulation (PWM), which is an example of duty ratio control of the switching circuit 52, on the switching circuit 52.

  This PWM circuit 60 is connected to a triangular wave generation circuit 62. The triangular wave generating circuit 62 generates a triangular wave at a constant frequency (for example, 1 [kHz]) as shown by a graph in FIG. If a threshold value Vth is applied to the generated triangular wave, a pulse wave whose duration, that is, the pulse width is modulated according to the threshold value Vth is generated. When this pulse wave is supplied to the switching circuit 52, the switching circuit 52 is turned on / off at a duty ratio corresponding to the modulated pulse width.

  As shown in FIG. 1, the PWM circuit 60 is further connected to a comparison circuit 64. The comparison circuit 64 is provided for inputting the threshold value Vth to the PWM circuit 60.

  The first input terminal (−) and the second input terminal (+) of the comparison circuit 64 are connected to the plus side line 40 and the reference voltage generation circuit 66, respectively. A divided voltage Vsd (which will be described in detail later) of the generated voltage Vs is applied as a continuous value to the first input terminal (−). The comparison circuit 64 has a threshold value Vth that changes continuously according to the difference between the divided voltage Vsd and the reference voltage Vref, more specifically, according to the voltage difference ΔV of the divided voltage Vsd with respect to the reference voltage Vref. Is output as a threshold signal.

  Specifically, the comparison circuit 64 sets the threshold value Vth so as to decrease as the divided voltage Vsd approaches the reference voltage Vref from a level lower than the reference voltage Vref, while the divided voltage Vsd is decreased to the reference voltage Vref. It is set to increase as it approaches the reference voltage Vref from a higher level.

  In FIG. 2A, the threshold value Vth set by the comparison circuit 64 is represented by a graph taking two typical cases as an example in relation to the triangular wave generated by the triangular wave generation circuit 62. ing. The comparison circuit 64 operates so that the voltage of the first input terminal (−) and the voltage of the second input terminal (+) are close to each other because the DC gain of the operational amplifier 96 is maximum.

  When the MOSFET 80 is turned on at the initial stage of charging the capacitor 14, a large current flows from the solar cell 12 to the capacitor 14 because the voltage difference between the generated voltage Vs of the solar cell 12 and the charging voltage Vc of the capacitor 14 is large. For this reason, the power generation voltage Vs greatly decreases only when the MOSFET 80 is turned on for a short time. As a result, in a state where the threshold value Vth is at the level of the threshold value VB (see FIG. 2C), the voltage at the first input terminal (−) and the voltage at the second input terminal (+) of the operational amplifier 96 Are equal to each other.

  On the other hand, when the MOSFET 80 is turned on in the latter stage of charging of the capacitor 14, only a small current flows from the solar cell 12 to the capacitor 14 because the voltage difference between the generated voltage Vs of the solar cell 12 and the charging voltage Vc of the capacitor 14 is small. Therefore, even if the MOSFET 80 is turned on for a long time, the amount of decrease in the generated voltage Vs can be reduced. As a result, in a state where the threshold value Vth is at the level of the threshold value VA (see FIG. 2B), the voltage at the first input terminal (−) and the voltage at the second input terminal (+) of the operational amplifier 96 Are equal to each other.

  Therefore, according to this comparison circuit 64, since the power generation voltage Vs of the solar cell 12 is kept constant, the value of the current flowing from the solar cell 12 to the capacitor 14 as shown in FIGS. 2 (d) and 2 (e). And the length of the ON time of the MOSFET 80 is proportional to the charging power of the capacitor 14. Further, in this comparison circuit 64, since the integrating capacitor is attached to the operational amplifier 96, the ripple generated by the switching operation of the step-down inverter 50 is sufficiently absorbed, whereby the comparison circuit 64 has a stable threshold value. A voltage Vth is generated.

When the threshold value Vth output from the comparison circuit 64 to the PWM circuit 60 is the threshold value VA, the conduction time T _ON is longer than the non-conduction time T _{OFF as} shown in the graph of FIG. A pulse wave is generated, and the switching circuit 52 is turned on / off according to the pulse wave. On the other hand, when the threshold value Vth output from the comparison circuit 64 to the PWM circuit 60 is the threshold value VB, the conduction time _TON is the non-conduction time as shown in the graph of FIG. A pulse wave shorter than T _OFF is generated, and the switching circuit 52 is turned on / off according to this pulse wave.

  When the threshold value Vth output from the comparison circuit 64 to the PWM circuit 60 indicates the highest level, the switching circuit 52 is continuously turned on, and continuous power supply from the solar cell 12 to the capacitor 14 is possible. It becomes.

  When the capacitor 14 is close to the discharging state, the charging voltage Vc of the capacitor 14 is close to 0, so that the voltage difference from the power generation voltage Vs of the solar cell 12 is large. Nevertheless, if the conduction time for allowing the solar cell 12 to conduct to the capacitor 14 is lengthened, a large amount of electric power flows from the solar cell 12 to the capacitor 14, and as a result, the power generation voltage Vs of the solar cell 12 tends to decrease.

On the other hand, in the step-down inverter 50, as the conduction time T _ON of the switching circuit 52 is short, it limits the amount of current flowing out of the solar cell 12 to the capacitor 14, as a result, the generated voltage Vs of the solar cell 12 is less likely to decrease Become.

  On the other hand, when the capacitor 14 is close to a fully charged state, the charging voltage Vc of the capacitor 14 is close to the upper limit value thereof, so that the voltage difference from the generated voltage Vs of the solar cell 12 is small. Therefore, even if the conduction time for conducting the solar cell 12 to the capacitor 14 is lengthened, a large amount of current does not flow from the solar cell 12 to the capacitor 14, and as a result, the power generation voltage Vs of the solar cell 12 does not decrease. It will end.

Therefore, the step-down inverter 50, in the low voltage period of the charging voltage Vc of the capacitor 14 (the first half of the charging period) are operated so that conduction time T _ON of the switching circuit 52 becomes shorter. As a result, the current flowing from the solar cell 12 into the step-down inverter 50 is reduced, and the power generation voltage Vs of the solar cell 12 can be maintained at a constant voltage.

In contrast, down inverter 50, in the high voltage period of the charging voltage Vc of the capacitor 14 (the latter half of the charging period) are operated so that conduction time T _ON of the switching circuit 52 becomes longer. As a result, the capacitor 14 is efficiently charged by the solar battery 12.

  As is clear from the above description, in this embodiment, the voltage difference is detected as the relationship between the divided voltage Vsd and the reference voltage Vref, and the result is reflected in the duty ratio of the switching circuit 52. As a result, while the divided voltage Vsd is held at the reference voltage Vref, a low voltage high current is supplied to the capacitor 14 when the capacitor 14 is close to a discharging state, and a high voltage small current is supplied to the capacitor 14 when the capacitor 14 is close to a fully charged state. .

  Thus, in the present embodiment, by monitoring the magnitude relationship between the divided voltage Vsd and the reference voltage Vref, the voltage applied from the step-down inverter 50 to the capacitor 14 gradually increases as the charging voltage Vc of the capacitor 14 increases. On the other hand, the applied voltage and the supply current are adaptively controlled so that the current supplied from the step-down inverter 50 to the capacitor 14 gradually decreases.

  As a result, according to the present embodiment, even when the capacitor 14 in a discharged state starts to be charged by the solar cell 12, the capacitor 14 is made efficient by the solar cell 12 by securing the generated power of the solar cell 12. It becomes possible to charge well.

  As shown in FIG. 1, the charging device 10 further includes an overcharge prevention circuit 70. The overcharge prevention circuit 70 electrically cuts off the solar cell 12 from the capacitor 14 by continuously turning off the switching circuit 52 when the charging voltage Vc of the capacitor 14 exceeds the upper limit value thereof. To be operated.

  FIG. 3A conceptually shows a graph of an example of temporal transition indicated by the power generation voltage Vs of the solar battery 12 when the charging device 10 is used. In this example, the holding voltage at which the generated voltage Vs is held is set to 12.0 [V]. FIG. 3B conceptually shows a graph of an example of temporal transition indicated by the charging voltage Vc of the capacitor 14 when the charging device 10 is used. In this example, the upper limit value of the charging voltage Vc is set to 12.5 [V].

  FIG. 4 is an electric circuit diagram showing an example of a more specific configuration of the charging device 10. In this example, the capacitor 14 is configured by connecting two series circuits of five individual capacitors in parallel to each other. Since the withstand voltage of each individual capacitor is 2.5 [V], the withstand voltage of the entire capacitor 14 is 12.5 [V].

  As shown in FIG. 4, the switching circuit 52 is configured mainly with a MOSFET 80. The PWM circuit 60 includes a transistor 82 and a comparator 84.

  The collector of the transistor 82 is connected to the gate electrode of the MOSFET 80, and the emitter is grounded. The base of the transistor 82 is connected to the output terminal of the comparator 84.

  The comparator 84 has a first input terminal (−) and a second input terminal (+). The first input terminal is connected to an output terminal of an operational amplifier 96 described later, while the second input terminal is connected to the triangular wave generation circuit 62.

  The comparator 84 is at a low level when the voltage at the first input terminal (reflecting the threshold value Vth) is higher than the voltage at the second input terminal (reflecting a triangular wave), and is at a high level otherwise. Is output.

  The comparison circuit 64 includes an operational amplifier 96 and a capacitor 98 in order to perform subtraction and integration. The output terminal of the operational amplifier 96 is connected to the first input terminal of the comparator 84. The operational amplifier 96 has a first input terminal (−) and a second input terminal (+).

  The first input terminal (−) of the operational amplifier 96 is not applied with the power generation voltage Vs of the solar cell 12 as it is, but the total voltage of the solar cell 12 is divided by the voltage dividing resistors 100, 102, and 104. The aforementioned partial voltage Vsd is applied. On the other hand, the second input terminal (+) of the operational amplifier 96 is connected to the reference voltage generation circuit 66, and a reference voltage Vref which is a fixed value is applied.

  The divided voltage Vsd is divided by a variable resistor so that it becomes equal to the reference voltage Vref which is a fixed value when the total voltage of the solar cell 12 is equal to the above-mentioned holding voltage of 12.0 [V]. It is set by the resistor 102. That is, in the present embodiment, this divided voltage Vsd is an example of the “response voltage” in the item (1).

  The comparison circuit 64 outputs an output analog signal by subtracting a signal obtained by integrating the input analog signal representing the response voltage with respect to time from the input analog signal representing the reference voltage Vref. The output analog signal is a continuous value.

As shown in FIG. 4, the overcharge prevention circuit 70 includes voltage dividing resistors 110, 112, and 114 for taking out a divided voltage Vcd obtained by dividing the total voltage of the capacitor 14. The overcharge prevention circuit 70 further includes a first input terminal (−) to which the voltage Vcd is applied and a second input terminal (+) to which the reference voltage V ₀ is applied from the reference voltage generation circuit 66. And a comparator 120 having the same.

The output terminal of the comparator 120 is connected to the base of the transistor 82. When the divided voltage Vcd exceeds the reference voltage V ₀ , the comparator 120 outputs a signal for turning off the transistor 82 and turning off the MOSFET 80 to the base of the transistor 82. Correspondingly voltage Vcd, when the total voltage of the capacitor 14 is equal to that of the withstand voltage, to be equal to the reference voltage V ₀ is a fixed value, is set by the voltage dividing resistors 112 a variable resistor .

The comparator 120 outputs a high level signal when the voltage at the first input terminal (reflecting the divided voltage Vcd) is higher than the voltage at the second input terminal (reflecting the reference voltage V ₀ ), while If not, a low level signal is output.

  That is, in the present embodiment, by feeding back the difference between the divided voltage Vsd of the solar battery 12 and the reference voltage Vref, at least proportional control is executed with respect to the duty ratio of the step-down inverter 50, thereby The generated power of the solar battery 12 is converted with characteristics suitable for shortening the charging time of the capacitor 14 while keeping Vsd from deviating from the reference voltage Vref.

  As is apparent from the above description, in the present embodiment, the step-down inverter 50 constitutes an example of the “chopper type step-down converter” in the above item (1), and includes a PWM circuit 60, a triangular wave generation circuit 62, and a comparison circuit 64. The reference voltage generating circuit 66 and the reference voltage generating circuit 66 constitute an example of the “control circuit” in the same term, the above-mentioned item (2) and the above-mentioned item (3).

  Further, in the present embodiment, the overcharge prevention circuit 70 constitutes an example of the “charge blocking circuit” in the above section (4), and the step-down inverter 50 is an example of the “step-down switching regulator” in the above section (5). The switching circuit 52 constitutes an example of the “switching element” in the same term, and the PWM circuit 60, the triangular wave generation circuit 62, the comparison circuit 64, and the reference voltage generation circuit 66 cooperate with each other in the term (6). It constitutes an example of a “control circuit”.

  Furthermore, in the present embodiment, the comparison circuit 64 and the reference voltage generation circuit 66 cooperate with each other to form an example of the “signal output unit” in section (7), and the PWM circuit 60 and the triangular wave generation circuit 62 are In cooperation with each other, an example of the “on / off control unit” in the same section is configured, and the overcharge prevention circuit 70 configures an example of the “switching circuit” in the section (8).

  In addition, in the present embodiment, the solar battery 12 is used as a charging power source, but other types of generators can be used. For example, it is possible to use a hand-driven generator or a wind generator.

  When a hand-driven generator or wind power generator is used as a charging power source, a voltage is generated in the generator in proportion to the number of revolutions of the generator. Therefore, this type of generator requires a large current / low voltage, that is, a high torque / low rotation speed in the discharging state of the capacitor 14, but as the full charge state is approached, a small current / high voltage, that is, a low speed. Torque and high rotation speed are required. Thus, when this type of generator is used, operating the generator so as to follow the transition of the charge / discharge state of the capacitor 14 stably charges the capacitor 14 with the generator. It is important to operate the generator as such.

  On the other hand, if the charging device 10 is used to charge the capacitor 14 with this type of generator, the charging device 10 automatically changes the current and voltage following the transition of the charging / discharging state of the capacitor 14. In order to perform the conversion, the electric power necessary to effectively charge the capacitor 14 is generated only by operating this type of generator at a constant torque and rotational speed. Therefore, according to the charging device 10, even when the capacitor 14 is charged by this type of generator, the capacitor 14 can be easily charged in a short time.

  Although one embodiment of the present invention has been described in detail with reference to the drawings, this is an exemplification and is based on the knowledge of those skilled in the art including the aspects described in the section of [Disclosure of the Invention]. The present invention can be implemented in other forms with various modifications and improvements.

1 is an electric circuit diagram showing a schematic configuration of a charging device 10 according to an embodiment of the present invention. 2 is a graph showing a temporal transition indicated by a power generation voltage Vs of a solar cell 12 and a temporal transition indicated by a charging voltage Vc of a capacitor 14 in one usage example of the charging device 10 shown in FIG. 1. 2 is a graph for explaining an operation principle of a PWM circuit 60 in FIG. 1. It is an electric circuit diagram which shows an example of the specific structure of the charging device 10 shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Charging device 12 Solar cell 14 Electric double layer capacitor 50 Step-down inverter 52 Switching circuit 54 Inductor 56 Flywheel diode 60 PWM circuit 62 Triangular wave generation circuit 64 Comparison circuit 66 Reference voltage generation circuit 70 Overcharge prevention circuit

Claims (9)

A charging device that is used by being connected to the charging power source and the electric double layer capacitor to charge the electric double layer capacitor with the charging power source,
A voltage lower than the power generation voltage of the charging power source is applied to the electric double layer capacitor, while a current larger than the power generation current of the charging power source is supplied to the electric double layer capacitor. A chopper type step-down converter having a function of converting electric power supplied to the electric double layer capacitor;
Control that controls the step-down converter based on a relationship between a response voltage that is responsive to the generated voltage and a reference voltage so that the generated voltage does not fall below a lower limit value due to charging of the electric double layer capacitor by the charging power source. A charging device including a circuit.   2. The charging device according to claim 1, wherein the control circuit controls the step-down converter so that an inflow current flowing from the charging power source into the step-down converter decreases when the response voltage becomes lower than the reference voltage. .   The charging device according to claim 2, wherein the control circuit controls the step-down converter so that the inflow current increases when the response voltage becomes higher than the reference voltage.   The charging device according to claim 3, further comprising a charge blocking circuit that blocks charging of the electric double layer capacitor by the charging power supply when the charging voltage exceeds an upper limit value thereof.   The step-down converter includes an inductor constituting an LC filter in cooperation with the electric double layer capacitor, a flywheel diode, a switching element provided on a line through which the generated current is supplied to the electric double layer capacitor, The charging device according to claim 2, wherein the charging device is a non-insulated step-down switching regulator.   The charging device according to claim 5, wherein the control circuit controls a duty ratio of the switching element based on a voltage difference that is a difference between the response voltage and the reference voltage.   The control circuit controls a duty ratio of the switching element according to the shortage amount so that a conduction time during which the switching element is turned on decreases according to the shortage amount of the response voltage with respect to the reference voltage. The charging device according to claim 5 or 6. The control circuit includes:
A signal output unit for detecting the voltage difference and outputting a signal reflecting the detected voltage difference;
The on-off control part which performs on-off control of the said switching element, The on-off control part controls the duty ratio of the said switching element based on the signal output from the said signal output part. Charging device.   The charging device according to claim 5, further comprising a switching circuit that continuously switches the switching element to an off state when the charging voltage exceeds an upper limit value thereof.

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