JP2008125211A - Charging system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an improved technique which equally charges a plurality of electric double-layer capacitors connected in series with one another. <P>SOLUTION: A charging system (10) includes a solar cell (12), an accumulator(14) where a plurality of capacitor units (32) having at least one electric double-layer capacitor each are connected in series, a plurality of bypass circuits (34) which are connected to every capacitor unit to perform bypass operation selectively, a switching regulator (38) which is connected to the solar cell and the accumulator, and a charge controller (80) which controls each switch (40). The charge controller executes usual charge control before substantial full charge of a plurality of capacitor units. After substantial full charge, it executes limited charge control so that the power generated by a solar cell decreases more than in usual charge control. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a technique for charging an electric double layer capacitor, and more particularly to an improvement in a technique for charging a plurality of electric double layer capacitors connected in series with each other equally.

  It has already been done to use electric double layer capacitors to store electrical energy. An electric double layer capacitor (hereinafter simply referred to as “capacitor”) used to store electric energy generally has a low withstand voltage, that is, an upper limit value of the voltage of electric energy that can be stored in the capacitor.

  Therefore, in order to store electric energy using a capacitor, it has already been performed to use a plurality of capacitors connected in series with each other.

  However, when charging a plurality of capacitors connected in series with each other using a common power source (for example, a power generation device or a commercial power source), the capacitance, leakage current, and equivalent parallel resistance of each capacitor. Since the value and the like vary between the capacitors, the terminal voltage also varies between the capacitors during the charging process.

  Therefore, when charging a plurality of capacitors connected in series with each other, if no measures are taken, an excessive voltage may be applied to one of the capacitors, which may cause deterioration of the capacitor characteristics. In addition, it may not be possible to fully use the storage capacity of all capacitors.

  Therefore, when charging a plurality of capacitors connected in series with each other, in order to charge all the capacitors effectively (that is, fully utilizing the withstand voltage), charge the capacitors equally. Is essential.

  In order to explain the above-described situation more specifically, it is assumed that two capacitors having capacitances C1 and C2 are connected in series and charged.

  In this case, when the capacitors are charged from a state where their voltage is 0 [V], the capacitor property (so-called capacitor property), that is, the charge Q (= CV) between the two capacitors is generated. Because of the nature of matching each other, the voltages V1 and V2 of these two capacitors are

V1 / V2 = C2 / C1

It is expressed by the following formula.

  When it is necessary to store electric energy using a plurality of capacitors connected in series with each other, the capacitances are matched to each other so that the charging voltages are matched between the capacitors. A plurality of capacitors are used.

  However, for the convenience of manufacturing, it is difficult to avoid that the capacitance varies among a plurality of capacitors. Therefore, even if the same amount of charge is supplied to the capacitors during the charging process, a voltage difference is generated between the capacitors. It is hard to avoid.

  In view of this, several techniques have already been proposed for charging capacitors so that a voltage difference does not occur between a plurality of capacitors despite variations in capacitance.

  For example, in Patent Document 1, a series circuit of a transformer and a switch is arranged for each stage of a plurality of stages of capacitors connected in series. When a certain capacitor reaches a specified voltage, a switch corresponding to the capacitor is arranged. A technique is disclosed in which the capacitor and the transformer are made conductive with each other turned on.

  Therefore, according to this technique, when a certain capacitor reaches a fully charged state, an excess current that should have flowed into the capacitor is bypassed by the effect of the transformer corresponding to the capacitor, It is transferred to another circuit part. This prevents the charging voltage of the fully charged capacitor from exceeding a specified voltage.

  Further, in Patent Document 2, a series circuit of a resistor and a switch is arranged for each stage of a plurality of stages of capacitors connected in series, and when a certain capacitor reaches a specified voltage, the capacitor corresponds to the capacitor. A technique is disclosed in which a switch is turned on to cause the capacitor and resistor to conduct with each other.

  Therefore, according to this technique, when a capacitor reaches a fully charged state, the effect of the resistor corresponding to the capacitor allows the surplus current that should have flowed into the capacitor to be bypassed. In the resistor, it is converted into heat and consumed. This prevents the voltage of the fully charged capacitor from exceeding the specified voltage.

  In Patent Document 3, for each stage of a plurality of stages of capacitors connected in series with each other, a parallel monitor is arranged in parallel with each stage capacitor, and the charge voltage of the corresponding capacitor is monitored in the parallel monitor. In addition, a technique for bypassing the corresponding capacitor when the charging voltage exceeds a specified voltage is disclosed.

  Therefore, according to this technique, when a certain capacitor reaches a full charge state, the effect of the parallel monitor corresponding to the capacitor allows the surplus current that should have flowed into the capacitor to be bypassed. In the parallel monitor, it is converted into heat and consumed. This prevents the voltage of the fully charged capacitor from exceeding the specified voltage.

  In this technology, when the charging voltage of the capacitors exceeds a specified voltage, the charging devices connected in common to the capacitors are controlled so that the charging current supplied to the capacitors is reduced.

  Therefore, according to this technique, when the charging voltage of a capacitor exceeds a specified voltage, the charging current supplied to the capacitor from the charging device is limited, and thereby the amount of heat generated in the parallel monitor to consume surplus current. Decrease.

  As an example of the power source for charging the capacitor described above, there is a power generation device. As an example of the power generation device, there is a power generation element that generates electric energy using natural energy. And a solar cell exists as an example of this power generation element.

  Generally, a solar cell has a characteristic that generated power changes so as to have a maximum point with respect to a generated voltage and a generated current. Therefore, when using a solar cell, when the power generation voltage or power generation current of the solar cell changes, the generated power, that is, the output of the solar cell changes accordingly.

  Therefore, in order to charge the capacitor at high speed with the solar cell, it is necessary to control the power generation state of the solar cell so that the generated power of the solar cell is maximized.

  Patent Document 4 discloses an example of a charging device that is used by being connected to the solar cell and the capacitor. This conventional example includes a switching converter having a switch, a coil, and a diode, a current detection circuit that detects a power generation current of the solar battery, a voltage detection circuit that detects a power generation voltage of the solar battery, the switching converter and the current detection. A controller is connected to the circuit and the voltage detection circuit.

In this conventional example, the controller sets the duty ratio of the switch so that the generated power of the solar cell is maximized based on the generated current detected by the current detecting circuit and the generated voltage detected by the voltage detecting circuit. Determine the optimal value. This controller controls the on / off state of the switch so that the optimum value of the determined duty ratio is realized.
JP 7-322515 A Japanese Utility Model Publication No. 5-23527 JP-A-10-174283 JP 2002-199614 A

  The present inventor has studied a technique for charging a plurality of electric double layer capacitors connected in series with each other equally by using solar cells.

  As a result, when the inventors charge a plurality of capacitors connected in series with each other using a solar cell, at least one or all of the plurality of capacitors reach a substantially fully charged state. I noticed the fact that switching the capacitor charging mode with solar cells before and after is effective to achieve both the effect of shortening the capacitor charging time and the effect of suppressing the overcharging of the capacitor. .

  Specifically, the inventor performs normal charge control before substantial full charge, while after the substantial full charge, the reduced power is supplied to the capacitor side than during normal charge control. It has been found that the fact that the limited charging control that enables this is effective is effective in achieving both the effect of shortening the charging time of the capacitor and the effect of suppressing the overcharging of the capacitor.

  Furthermore, the inventor has realized that it is possible theoretically and practically to execute the normal charge control and the limited charge control using a circuit common to them, and further, It has also been realized that the adoption of circuits facilitates system design, resulting in simplified structure and reduced costs.

  Based on the knowledge described above, the present invention has been made with an object of improving a technique for uniformly charging a plurality of electric double layer capacitors connected in series with each other.

  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 solar cell in which the generated power changes so as to have a maximum point with respect to the generated voltage and generated current;
A power storage device in which a plurality of capacitor units each having at least one electric double layer capacitor are connected in series;
A plurality of bypass circuits connected to all or a part of the plurality of capacitor units for each capacitor unit, wherein each bypass circuit has a voltage of the corresponding capacitor unit exceeding a specified voltage, Performing bypass operation to bypass each capacitor unit,
A step-down switching regulator connected to the solar cell and the power storage device, having at least a switch, and supplying electric power corresponding to the duty ratio of the switch from the solar cell to the power storage device in a step-down manner things and,
A charge control device that determines the duty ratio, controls the switch so that the determined duty ratio is realized, and thereby controls charging of the power storage device by the solar cell, and
The charge control device is
Before all or some of the plurality of capacitor units reach a substantially fully charged state, normal charge control is performed, while all or some of the plurality of capacitor units are substantially fully charged. In the normal charging control, the operating point of the solar cell is substantially set to the maximum output operating point at which the generated power is substantially maximized. While the value for matching is adopted as the value of the duty ratio, during the limited charging control, the solar cell operating point is set to have the generated power less than the generated power corresponding to the maximum output operating point. A charging system that employs a value for substantially matching a limited output operating point realized in a battery as the value of the duty ratio.

  In this charging system, the mode for charging a plurality of capacitor units is switched between normal charging control and limited charging control.

  Specifically, normal charge control is performed before all or some of the plurality of capacitor units are substantially fully charged, while all or some of the plurality of capacitor units are substantially fully charged. Later, limited charge control is performed.

  Further, in this charging system, during the limited charging control, the generated power less than the generated power corresponding to the maximum output operating point is generated in the solar cell, that is, the solar power is reduced to the generated power corresponding to the maximum output operating point. The power generated by the battery is limited.

  Therefore, according to this charging system, it is possible to reduce the burden on the bypass circuit (for example, the amount of generated heat) during the limited charging control and to reduce the performance (for example, the capacity) required for the bypass circuit.

  Therefore, according to this charging system, it is easy to achieve both the effect of shortening the charging time of the capacitor unit and the effect of suppressing overcharging of the capacitor unit.

  Further, in this charging system, normal charge control and limited charge control, that is, different from each other with respect to the purpose to be achieved, are common to each other in that the duty ratio of the switch is controlled in order to achieve each purpose. The type of control is performed by the same charge controller.

  Therefore, according to this charging system, the design and structure of the charging system can be simplified and the cost can be reduced as compared with the case where normal charging control and limited charging control are realized by using different charging control devices. It becomes easy.

  In this charging system, during normal charging control, the charging control device is, for example, a physical quantity that is at least one of output power, output voltage, and output current of the solar battery (ie, a physical quantity that reflects the operating state of the solar battery). And the duty ratio is determined based on information including at least one of the physical quantity that is at least one of the charging power, the charging voltage, and the charging current of the power storage device (that is, the physical quantity that reflects the operating state of the power storage device) It is possible to operate in such a manner.

  As will be described in detail later in the section of [Embodiment of the Invention], in general, when a solar cell is used as a power generation device, reducing the output current of the solar cell necessarily reduces the output power of the solar cell. It will not be. On the other hand, a proportional relationship is not necessarily established between the duty ratio of the switch and the output current of the solar cell.

  However, the present inventor, when changing the output current of the solar cell within a region smaller than the output current corresponding to the maximum output operating point, the output voltage of the solar cell hardly changes. I noticed that there is a generally proportional relationship with the output power. This knowledge is neither disclosed nor suggested in Patent Document 3.

  Furthermore, the present inventor has also noticed that a generally proportional relationship is established between the duty ratio and the output current of the solar cell when the magnitude of the duty ratio of the switch is within a specific range. . This knowledge is neither described nor suggested in Patent Document 3.

  Furthermore, the present inventor concluded that, when these findings are combined, a generally proportional relationship is established between the duty ratio of the switch and the output power of the solar cell. This knowledge is neither described nor suggested in Patent Document 3.

  Furthermore, the present inventor does not directly select the power of the power storage device as a direct control target in order to limit the power transferred from the solar cell to the power storage device, but directly uses the power of the power generation device called the solar cell. I devised to choose the right control object. As will be described in detail later, when the power of a solar cell is selected as a direct control target, the solar cell itself can easily reduce the burden on the power storage device by converting surplus power into heat and dissipating heat. It is. This knowledge is neither described nor suggested in Patent Document 3.

  Based on such knowledge, the charging system according to this section controls the output power of the solar cell by directly controlling the duty ratio of the switch (without interposing other physical quantities) during the limited charging control. Control is performed so as to decrease during normal charging control.

  Therefore, it should be determined that this charging system is significantly distinguished from the technique described in Patent Document 3.

(2) During the normal charge control, the charge control device determines the duty ratio value as a variable value based on a physical quantity reflecting an operating state of the solar cell or the power storage device, while the limited charge is performed. The charging system according to item (1), wherein a fixed value set in advance without depending on the physical quantity is adopted as the value of the duty ratio during the control.

  In this charging system, a fixed value set in advance is adopted as the value of the duty ratio without depending on the physical quantity reflecting the operating state of the solar cell or the power storage device during the limited charging control. Therefore, according to this charging system, the duty ratio employed during the limited charging control can be determined more easily than the case where the duty ratio is determined as a variable value based on the physical quantity.

(3) The charge control device
Duty for performing duty ratio control on the switch by repeating a single switching cycle in which an ON period in which the switch is ON and an OFF period in which the switch is OFF are alternately repeated once each A ratio control unit;
A duty ratio determining unit that determines the duty ratio so that the ON time in each switching cycle of the switch is shorter during the limited charge control than during the normal charge control (1) or (2) The charging system according to item.

  In this charging system, the duty ratio is determined so that the ON time in each switching cycle of the switch is shorter during the limited charging control than during the normal charging control.

  Therefore, according to this charging system, the output current of the solar cell is reduced during the limited charging control, and the output power is also reduced. As a result, a burden (for example, heat generation amount) imposed on each bypass circuit in order to prevent the voltage of each capacitor unit from exceeding a specified voltage is reduced.

(4) The switching regulator further includes a coil connected in series between the switch and the power storage device,
The on-time during the limited charge control is set such that the current flowing through the coil increases from zero and decreases to zero at each switching cycle of the switch. The charging system described.

  According to this charging system, the total current flowing through the coil during each switching cycle is only focused on the current switching cycle, regardless of the magnitude of the current flowing through the coil during the previous switching cycle. It can be calculated with.

  Therefore, according to this charging system, the sum of the currents flowing in the coils during each switching cycle is determined only by the operating conditions of the switching regulator during that switching cycle, and as a result, during each switching cycle. The ease of managing the total sum of currents flowing through the coils and the management accuracy are improved.

(5) Each of the plurality of bypass circuits outputs a bypass operation signal indicating whether or not each bypass circuit is performing a bypass operation,
The charging control device receives a plurality of bypass operation signals output from the plurality of bypass circuits, respectively, and the received bypass operation signals indicate that none of the plurality of bypass circuits is in a bypass operation. If the normal charging control is selected, the limited charging control is performed when the received bypass operation signal indicates that at least one of the plurality of bypass circuits is performing the bypass operation. The charging system according to any one of (1) to (4), including a selection unit to be selected.

  In this charging system, the charging mode to be realized by the charging control device is switched between normal charging control and limited charging control in accordance with a bypass operation signal indicating whether or not each bypass circuit is performing a bypass operation.

  The bypass operation signal is substantially in the sense that it is sufficient to discretely represent two states, a state indicating that the corresponding bypass circuit is in the bypass operation and a state indicating that the bypass circuit is not in the bypass operation. It can be handled as a binary signal.

  Therefore, according to this charging system, there is a possibility that signal processing for switching the charging mode may be easier than switching the charging mode based on the multilevel signal.

(6) The charge control device
A continuous time measuring unit that measures a time during which at least one bypass circuit in the bypass operation among the plurality of bypass circuits continuously performs the bypass operation as a continuous time; and
The charging system according to any one of (1) to (5), further including: a first determining unit that determines the duty ratio so that the generated power of the solar cell decreases as the measured continuous time increases.

  In this charging system, when at least one capacitor unit is bypassed by at least one bypass circuit, the at least one capacitor unit needs to perform a bypass operation, that is, from the solar cell. The degree to which the power supplied to the device is excessive (that is, the degree to which the capacitor unit is overcharged) is monitored as the length of time (continuous time) during which at least one bypass circuit continuously performs the bypass operation. The longer the continuous time, the higher the amount of power generated by the solar cell is excessive.

  Therefore, according to this charging system, it is possible to indicate whether or not the generated power of the solar cell is excessive at each moment, but at each moment, the type of signal that the generated power of the solar cell is excessive and cannot be expressed to some extent. Even if only the bypass operation signal (for example, the bypass operation signal) is used, it is possible to monitor the degree of excessive power generated by the solar cell by monitoring the temporal transition (history) of such a signal.

  Furthermore, in this charging system, the duty ratio is determined so that the power generated by the solar cell decreases as the time during which at least one bypass circuit continuously performs the bypass operation is longer.

  Therefore, according to this charging system, the generated power of the solar cell is reduced as the generated power of the solar cell is excessive and higher.

(7) The continuous time measuring unit is continuous when at least one bypass circuit that is performing a bypass operation among the plurality of bypass circuits focuses on each bypass circuit and views it individually. The charging system according to (6), wherein a time for performing the bypass operation is measured as the continuous time.

  According to this charging system, the measured value of the continuous time reflects the degree to which the generated power of the solar cell is excessive individually for each bypass circuit.

(8) The continuous time measuring unit continuously performs a bypass operation when a plurality of bypass circuits that are performing a bypass operation among the plurality of bypass circuits are viewed comprehensively without distinguishing each other from each other. The charging system according to item (6), in which the time for performing is measured as the continuous time.

  According to this charging system, the measured value of the continuous time comprehensively reflects the degree to which the generated power of the solar cell is excessive for the entire bypass circuit.

(9) The charge control device
A number measuring unit for measuring the number of bypass circuits among the plurality of bypass circuits,
The charging system according to any one of (1) to (8), further including a second determination unit that determines the duty ratio so that the generated power of the solar cell decreases as the measured number increases.

  In this charging system, when at least one capacitor unit is bypassed by at least one bypass circuit, the at least one capacitor unit needs to perform a bypass operation, that is, from the solar cell. The degree to which the power supplied to the device is excessive is monitored as the magnitude of the number of bypass circuits that are performing the bypass operation. The larger the number, the higher the amount of power generated by the solar cell is excessive.

  Therefore, according to this charging system, it is possible to indicate whether or not the generated power of the solar cell is excessive at each moment, but at each moment, the type of signal that the generated power of the solar cell is excessive and cannot be expressed to some extent. Even if only the bypass operation signal (for example, the bypass operation signal) is used, it is possible to monitor the degree of excessive power generated by the solar cell by comprehensively monitoring such kind of signals for a plurality of bypass circuits. It becomes.

  Furthermore, in this charging system, the duty ratio is determined so that the power generated by the solar cell decreases as the number of bypass circuits that are performing the bypass operation increases.

  Therefore, according to this charging system, the generated power of the solar cell is reduced as the generated power of the solar cell is excessive and higher.

(10) Of the generated power corresponding to the maximum point, the solar cell is converted into heat in the solar cell by the amount of power that is not output to the power storage device, and the heat from the surface of the solar cell to the atmosphere The charging system according to any one of items (1) to (9), wherein the power generation device is of a type discharged to

  In this charging system, of the generated power corresponding to the maximum point of the solar cell (maximum possible generated power), the power that is not actually output to the power storage device is converted into heat in the solar cell. Is done. Thus, the heat generated in the solar cell is radiated from the surface of the solar cell to the atmosphere.

  Therefore, in this charging system, at least a part of the power consumed in the bypass circuit in the past (for example, the power consumed after being converted into heat) is consumed as heat in the solar cell. It will be.

  By the way, in general, it is easy to ensure a large surface area (heat dissipating area) of the solar cell as compared with the bypass circuit. Therefore, even if at least a part of the power consumed in the bypass circuit in the prior art is consumed in the solar cell, the temperature increase amount of the solar cell does not increase so much.

(11) In the solar cell, a change in the generated voltage with respect to a decrease in the generated current from a generated current corresponding to the maximum point is that the generated current increases from a generated current corresponding to the maximum point. A power generation device of a type having a characteristic smaller than a change in the generated voltage with respect to
The charging system according to any one of (1) to (10), wherein the charge control device reduces the duty ratio during the limited charge control and during the normal charge control.

  In this charging system, the duty ratio is reduced during the limited charging control and during the normal charging control. When the duty ratio is decreased, the switch is more likely to be throttled than during normal charging control, so that the generated current of the solar cell is reduced from the generated current corresponding to the maximum output operating point (near the maximum point).

  Further, in this charging system, when the generated current of the solar cell decreases from the generated current corresponding to the maximum output operating point, the generated voltage of the solar cell changes with a gentler slope than when it increases.

  Therefore, according to this charging system, it is possible to reduce the generated power of the solar cell while restricting the change in the generated voltage of the solar cell during the limited charging control. As a result, it is possible to predict the generated power of the solar cell during the limited charge control while neglecting or ignoring the change in the generated voltage of the solar cell.

  Specifically, according to this charging system, as will be described in detail later, during the limited charging control, a linearity is generated between the generated power Iss of the solar battery and the switch duty ratio τ (switch ON time Ton). The relationship will be established. Therefore, it is possible to predict the generated power Iss of the solar cell directly from the switch duty ratio τ (switch ON time Ton).

  Therefore, according to this charging system, it is possible to manage the generated power of the solar cell during the limited charge control in direct relation to the magnitude of the duty ratio of the switch, that is, the length of the on-time of the switch. .

(12) a power storage device in which a plurality of capacitor units each having at least one electric double layer capacitor are connected in series;
A plurality of bypass circuits connected to all or a part of the plurality of capacitor units for each capacitor unit, wherein each bypass circuit has a voltage of the corresponding capacitor unit exceeding a specified voltage, Performing bypass operation to bypass each capacitor unit,
A switch connected to the power storage device for controlling power supplied from an external device to the power storage device via the switch;
A charge control device that controls the switch, thereby controlling charging of the power storage device by the external device, and
Each of the plurality of bypass circuits outputs a bypass operation signal indicating whether or not each bypass circuit is performing a bypass operation,
The charge control device includes:
When a plurality of bypass operation signals respectively output from the plurality of bypass circuits are received, and the received bypass operation signals indicate that none of the plurality of bypass circuits is in a bypass operation, normal charging is performed. A selection unit that selects limited charge control when the received bypass operation signal indicates that at least one of the plurality of bypass circuits is performing a bypass operation,
And a control unit that controls the switch so that an on-time in which the switch is in an on state is shorter when the limited charge control is selected than when the normal charge control is selected.

  In this charging system, the mode for charging a plurality of capacitor units is switched between normal charging control and limited charging control.

  Specifically, when the plurality of bypass operation signals indicate that none of the plurality of bypass circuits is performing the bypass operation, that is, before the substantial full charge of the plurality of capacitor units, the normal charge control is performed. Is executed.

  On the other hand, when the plurality of bypass operation signals indicate that at least one of the plurality of bypass circuits is performing the bypass operation, that is, after the plurality of capacitor units are substantially fully charged, the limited charging is performed. Control is executed.

  Further, in this charging system, the on-time of the switch is reduced during the limited charging control and during the normal charging control, thereby reducing the power of the external device. Therefore, according to this charging system, it is possible to reduce the load on the bypass circuit during the limited charging control and to reduce the performance required for the bypass circuit.

  Therefore, according to this charging system, it is easy to achieve both the effect of shortening the charging time of the capacitor unit and the effect of suppressing overcharging of the capacitor unit.

  Further, in this charging system, normal charge control and limited charge control, that is, different from each other with respect to the purpose to be achieved, are common to each other in that the duty ratio of the switch is controlled in order to achieve each purpose. The type of control is performed by the same charge controller.

  Therefore, according to this charging system, the design and structure of the charging system can be simplified and the cost can be reduced as compared with the case where normal charging control and limited charging control are realized by using different charging control devices. It becomes easy.

  An example of the “external device” in this charging system is a solar cell, but instead of this, for example, a wind power generator or a commercial power source can be used.

(13) Further, a coil connected in series between the switch and the power storage device is included,
The controller repeats a single switching cycle in which an on period in which the switch is in an on state and an off period in an off state are alternately repeated once each, thereby performing the normal charging control and the Alternatively perform limited charge control,
The on-time during the limited charge control is set such that the current flowing through the coil increases from zero and decreases to zero in each switching cycle of the switch. The charging system described.

  According to this charging system, in accordance with the same principle as that of the charging system according to the item (4), the ease of managing the total sum of currents flowing through the coils during each switching cycle and the management accuracy are improved.

(14) The control unit
A continuous time measuring unit that measures a time during which at least one bypass circuit in the bypass operation among the plurality of bypass circuits continuously performs the bypass operation as a continuous time; and
The charging system according to (12) or (13), further including an on-time determining unit that determines the length of the on-time of the switch so that the measured continuous time becomes shorter.

  According to this charging system, according to the same principle as the charging system according to the above (6), it is possible to indicate whether or not the power of the external device is excessive at each moment. Even if only a kind of signal that is excessive in power and cannot be expressed to some extent (for example, the bypass operation signal) is used, the power of the external device is monitored to some extent by monitoring the temporal transition of such a signal. It becomes possible.

(15) The charge control device may change the value of the duty ratio during the limited charge control to a variable value according to the value of the duty ratio actually employed during one or more normal charge controls preceding it. The charging system according to item (1) to be determined.

  According to this charging system, for each limited charging control, the value of the duty ratio during the limited charging control is the normal charging control state that precedes it, and the operating state of the charging system (daily illuminance of the solar cell, It is easy to make an appropriate decision so as to follow changes in what reflects the power generation state of the solar cell reflecting the deterioration over time and the like and the power storage state of the power storage device.

  In this charging system, the value of the duty ratio during the limited charge control is set to, for example, the value of the duty ratio actually employed during one normal charge control preceding it, or a plurality of values preceding the current limited charge control. A combined value (for example, an average value) of a plurality of duty ratios and a fixed coefficient (for example, a value within a range of about 0.1 to about 0.3) that are actually adopted during each normal charging control. It can be determined using the product.

(16) A charging device for storing electric energy from a solar cell in a plurality of stages of electric double layer capacitors connected in series via a switching regulator, wherein the voltage of the plurality of stages of electric double layer capacitors is stored. In order to equalize each other, including a bypass circuit that performs a bypass operation of bypassing the electric double layer capacitor when detecting that the voltage of the electric double layer capacitor of each stage has reached a specified voltage,
A charging apparatus comprising: an on-time control unit configured to control an on-time of the switch to a specified value when a voltage of at least one electric double layer capacitor exceeds the specified voltage.

  As will be described in detail later in the section of [Embodiment of the Invention], in general, when a solar cell is used as a power generation device, reducing the output current of the solar cell necessarily reduces the output power of the solar cell. It will not be. On the other hand, a proportional relationship is not necessarily established between the on-time of the switch and the output current of the solar cell.

  However, the present inventor, when changing the output current of the solar cell within a region smaller than the output current corresponding to the maximum output operating point, the output voltage of the solar cell hardly changes. I noticed that there is a generally proportional relationship with the output power.

  Furthermore, the present inventor has also noticed that a generally proportional relationship is established between the on-time and the output current of the solar cell when the length of the on-time of the switch is within a specific range. .

  Furthermore, the present inventor concluded that, when these findings are combined, a generally proportional relationship is established between the on-time of the switch and the output power of the solar cell.

  Furthermore, the present inventor does not directly select the power of the power storage device as a direct control target in order to limit the power transferred from the solar cell to the power storage device, but directly uses the power of the power generation device called the solar cell. I devised to choose the right control object. As will be described in detail later, when the power of a solar cell is selected as a direct control target, the solar cell itself can easily reduce the burden on the power storage device by converting surplus power into heat and dissipating heat. It is.

  Based on such knowledge, in the charging device according to this item, when the voltage of at least one stage of the electric double layer capacitor exceeds the specified voltage, the on-time of the switch is controlled to the specified value, thereby the output of the solar cell. The power is reduced as compared with the case where the voltage of the electric double layer capacitor of at least one stage does not exceed the specified voltage.

(17) The on-time control unit includes:
Time measuring means for measuring the length of time that the voltage of the electric double layer capacitor at each stage continuously exceeds the specified voltage;
The charging device according to item (16), further including specified value changing means for changing the specified value in accordance with the measured length of time.

  In this charging device, at least one stage of the electric double layer capacitor requires a bypass operation, that is, the power supplied from the solar cell to the at least one stage of the electric double layer capacitor is excessive (that is, at least 1). The electric double layer capacitor of the stage is to some extent overcharged), and is monitored as the length of time (continuous time) that the voltage of the electric double layer capacitor of each stage continuously exceeds the specified voltage. The longer the continuous time, the higher the amount of power generated by the solar cell is excessive.

  Further, in this charging device, the specified value is changed according to the length of time that the voltage of the electric double layer capacitor at each stage continuously exceeds the specified voltage. Therefore, according to this charging device, at least one stage of the electric double layer capacitor can be adapted to the specified value to some extent by overcharging.

  This charging apparatus is implemented in such a manner that the specified value changing means changes the specified value so that the specified value is decreased as the measured time length increases, for example.

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

  FIG. 1 conceptually shows a charging system 10 according to the first embodiment of the present invention in a system diagram.

  The charging system 10 includes a solar battery 12, a power storage device 14 that stores electrical energy generated by the solar battery 12, and a charging device 16 that is connected to the solar battery 12 and the power storage device 14 for use. It is configured to include. The charging device 16 is used to charge the power storage device 14 with the solar battery 12.

  The solar battery 12 constitutes an example of a power generation device and constitutes an example of an external device for the charging device 16. The electrical energy generated by the solar cell 12 and accumulated in the power storage device 14 is consumed by a load (not shown) such as an electric device such as a lighting fixture or a motor.

  As shown in FIG. 1, the charging device 16 has a positive electrode line 20 and a negative electrode line 22. The positive electrode line 20 has external terminals 24 and 26 at both ends, and the negative electrode line 22 has external terminals 28 and 30 at both ends.

  The charging device 16 is electrically connected to the positive terminal and the negative terminal of the solar cell 12 at the external terminal 24 of the positive line 20 and the external terminal 28 of the negative line 22, respectively. Furthermore, the charging device 16 is electrically connected to the positive terminal and the negative terminal of the power storage device 14 at the external terminal 26 of the positive line 20 and the external terminal 30 of the negative line 22, respectively.

  In FIG. 1, the generated voltage (that is, output voltage) of the solar battery 12 is represented by “Vs”, and the generated current (that is, output current) is represented by “Is”, while the charging voltage of the power storage device 14 is represented by “Vc”, The charging current is indicated by “Ic”.

  The solar cell 12 converts solar energy into electric energy. This solar cell 12 has a characteristic that the generated power (that is, output power) Ps changes according to the illuminance of sunlight. The solar cell 12 also has a characteristic that the generated power Ps has a maximum point with respect to the generated voltage Vs and the generated current Is, as shown in the graph of FIG.

  Therefore, when this solar cell 12 is used, when the generated voltage Vs or the generated current Is of the solar cell 12 changes, the generated power Ps of the solar cell 12, that is, the output energy changes accordingly. That is, in the solar cell 12, its operating point moves along the graph shown in FIG. 2 as the generated voltage Vs or the generated current Is changes.

  FIG. 2 is a graph showing characteristics in which the generated voltage Vs and the generated current Is change under the condition that the illuminance of sunlight (= daily illuminance) is constant. In FIG. 2, the intersection A between the graph and the straight line L1 indicates that the resistance value of the load when the charging device 16 is considered to be a load for the solar battery 12 (a resistor having a resistance value (= Vs / Is)). In order to be optimal, the product of the generated current Is and the generated voltage Vs, that is, the generated power Ps is a maximum value.

  That is, the intersection A between the graph representing the characteristics of the solar cell 12 and the straight line L1 indicates the maximum output operating point at which the output power Ps of the solar cell 12 is the maximum among the plurality of operating points that the solar cell 12 can take. -ing

  Further, in FIG. 2, the intersection B between the graph and the straight line L2 is that the generated power Ps of the solar cell 12 is not the maximum value because the resistance value of the charging device 16 as a load for the solar cell 12 is larger than the optimum value. Is shown.

  That is, the intersection B between the graph representing the characteristics of the solar cell 12 and the straight line L2 indicates that the output current Is of the solar cell 12 corresponds to the maximum output operating point A among a plurality of operating points that the solar cell 12 can take. The output current (hereinafter referred to as “maximum output output current”) indicates a limited output operating point limited to a value smaller than Is0. The significance of the limited output operating point B will be described in detail later.

  Further, as shown in FIG. 2, the solar cell 12 has a sensitivity (that is, a gradient) of the generated voltage Vs with respect to a decrease in the generated current Is from the maximum output output current Is0, and the generated current Is has the maximum output output current Is0. It has a characteristic that is lower than the sensitivity of the generated voltage Vs to increase.

  In the solar cell 12, the decrease in the generated current Is from the maximum output output current Is0 and the increase in power generation current Is are common to each other in that the generated power Ps is decreased.

  However, even if the generated current Is decreases from the maximum output output current Is0, the generated voltage Vs changes only slowly or is kept almost constant, whereas the generated current Is exceeds the maximum output output current Is0. When it increases, the generated voltage Vs suddenly decreases.

  In the present embodiment, the limited output operating point B is selected as an operating point that is reached when the generated current Is decreases from the maximum output output current Is0. The significance of such selection will be described in detail later.

  The power storage device 14 stores the electric energy generated by the solar cell 12. In order to increase the energy that can be stored in the power storage device 14, as shown in FIG. 1, a plurality (three in the present embodiment) of capacitor units 32-1 and 32-2 connected in series with each other. , 32-3.

  Each of the capacitor units 32-1, 32-2, and 32-3 is configured to include at least one electric double layer capacitor (hereinafter simply referred to as “capacitor”). Each capacitor is characterized in that the voltage varies greatly depending on its charge state, that is, the amount of charge accumulated in the capacitor. This feature is unique to the capacitor and does not exist in other types of power storage elements.

  Each capacitor unit 32-1, 32-2, 32-3 includes, for example, a plurality of capacitors connected in parallel to each other when it is necessary to further increase the energy that can be stored. It is possible to configure. However, all the capacitor units 32-1, 32-2, and 32-3 are configured to have the same withstand voltage.

  As shown in FIG. 1, the power storage device 14 further includes a plurality of bypass circuits 34-1, 34-2, and 34-3 respectively corresponding to the plurality of capacitor units 32-1, 32-2, and 32-3. It has. The configurations of these bypass circuits 34-1, 34-2, 34-3 will be described in detail later.

  As shown in FIG. 1, in this power storage device 14, capacitor units 32-1, 32-2, and 32-3 and bypass circuits 34-1, 34-2, and 34-3 correspond to each other. Three power storage units 36-1, 36-2, and 36-3 are configured.

  As shown in FIG. 1, the charging device 16 includes a step-down switching regulator 38.

  The switching regulator 38 includes a chopper type switch (for example, a semiconductor switch) 40, a coil (inductor) 42, and a diode (flyhole diode) 44. The switch 40 and the coil 42 are connected in series with each other in the positive electrode line 20 in that order. The diode 44 is connected to an intermediate line 46 extending from a portion of the positive electrode line 20 between the switch 40 and the coil 42 and reaching the negative electrode line 22.

  The switching regulator 38 applies a voltage lower than the power generation voltage Vs of the solar cell 12 to the power storage device 14, while supplying a current larger than the power generation current Is of the solar cell 12 to the power storage device 14. Has a function of converting power supplied to the power storage device 14.

  As is well known, the switching regulator 38 is a method of smoothing a square wave (intermittent waveform) generated by turning on and off the switch 40. This method is employed when the output voltage, that is, the charging voltage Vc of the power storage device 14 is lower than the input voltage, that is, the power generation voltage Vs of the solar battery 12.

  In the switching regulator 38, the electrical energy of the solar cell 12 is stored as magnetic energy in the coil 42 via the switch 40 during a period in which the switch 40 is in an on (conducting) state. Thereafter, when the switch 40 is switched to an off (cut-off) state, the magnetic energy stored in the coil 42 is converted into electric energy by the closed circuit including the coil 42, the power storage device 14, and the diode 44 and supplied to the power storage device 14. Is done.

  By repeatedly turning on and off the switch 40, the electric energy of the solar cell 12 is supplied to the power storage device 14, whereby the power storage device 14 is charged by the solar cell 12.

  At this time, the charging voltage Vc of the power storage device 14 is based on the duty ratio of the switch 40, that is, the value obtained by dividing the on-time Ton when the switch 40 is on by the sum of the on-time Ton and the off-time Toff. The generated voltage Vs of the solar cell 12 has a reduced height. 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 power storage device 14 in return.

  That is, the switching regulator 38 performs voltage / current conversion (power conversion) between the solar cell 12 and the power storage device 14, and specifically stores power between the solar cell 12 and the power storage device 14. The high voltage and small current electricity in the solar cell 12 is converted into the low voltage and large current electricity in the power storage device 14 under the condition that the electricity is stored. Thereby, the charging efficiency of the power storage device 14 by the solar battery 12 is improved.

  As shown in FIG. 1, the charging device 16 further includes a capacitor 48 on the upstream side of the switching regulator 38. The capacitor 48 is connected in parallel to the solar cell 12 in a state of being connected to the positive electrode line 20 and the negative electrode line 22.

  The capacitor 48 allows the electric energy to be discharged from the solar cell 12 in the OFF state of the switch 40 and temporarily stores the discharged electric energy. On the other hand, the capacitor 48 sends the electrical energy stored in the capacitor 48 to the power storage device 14 via the switch 40 when the switch 40 is in the ON state.

  As a result, according to the capacitor 48, the ripple voltage (variation of the output voltage Vs of the solar cell 12) resulting from the switching operation of the switch 40 is suppressed, and consequently, the variation of the output power Ps of the solar cell 12 is suppressed. .

  In short, the capacitor 48 has a function of stabilizing the power generation voltage Vs of the solar cell 12 regardless of the on / off operation of the switch 40. In order to perform this function, it is necessary that the voltage of the capacitor 48 does not change sensitively during the switching period of the switch 40 (for example, 10 μs).

  Therefore, the capacitor 48 has a smaller capacitance than the power storage device 14. The capacitance of the capacitor 48 is set according to the length of the switching cycle of the switch 40 (for example, 10 μs), the amount of current flowing out from the solar cell 12 through the switch 40 in the ON state of the switch 40, and the like.

  Here, with reference to FIG. 1, the three bypass circuits 34-1, 34-2, and 34-3 will be described in more detail. However, since these bypass circuits 34-1, 34-2, 34-3 have a common configuration, only one bypass circuit 34-1 will be described as a representative.

  The bypass circuit 34-1 is connected in parallel to the corresponding capacitor unit 32-1. The bypass circuit 34-1 includes a bypass resistor (resistor having a fixed resistance value) 50-1 as a current bypass element and a transistor 52-1 as a switching element, which are connected in series to each other. It is provided in a state of being connected in parallel to the corresponding capacitor unit 32-1.

  When the transistor 52-1 is turned off, no current flows from the solar cell 12 into the bypass resistor 50-1, whereas when the transistor 52-1 is turned on, the current flows from the solar cell 12. Flows into the bypass resistor 50-1. When the current flows into the bypass resistor 50-1, the bypass current is converted into heat and consumed in the bypass resistor 50-1.

  That is, when the transistor 52-1 is turned on, at least a part of the current that should have flowed from the solar cell 12 into the corresponding capacitor unit 32-1 is caused by the bypass resistor 50-1. The capacitor unit 32-1 can be bypassed. This prevents the terminal voltage of the capacitor unit 32-1 from exceeding a specified voltage.

  Therefore, the resistance value of the bypass resistor 50-1 is set so that the terminal voltage of the capacitor unit 32-1 does not become higher than the specified voltage, that is, the current flowing into the transistor 52-1 flows into the capacitor unit 32-1. It is set in advance so as to be larger than the charging current.

  In addition, in place of the bypass resistor 50-1, the above-described current bypass element replaces the surplus current with another circuit (for example, other capacitor units 32-2 and 32-3 that have not reached the full charge state). A transfer element (for example, a transformer) for transferring can be used. The transistor 52-1 can be configured as a semiconductor switch such as a bipolar transistor or FET.

  As shown in FIG. 1, in the bypass circuit 34-1, a driver 54-1 is connected to the transistor 52-1, and the driver 54-1 switches the transistor 52-1 between an on state and an off state. . That is, the driver 54-1 has a function of driving the transistor 52-1.

  The driver 54-1 is also connected to the positive side and the negative side of the corresponding capacitor unit 32-1, and has a function of monitoring the terminal voltage (individual charging voltage) of the capacitor unit 32-1. Yes. In this driver 54-1, the terminal voltage of the corresponding capacitor unit 32-1 is equal to the specified voltage (the specified voltage of the terminal voltage of the capacitor unit 32-1 (also referred to as “withstand voltage”, for example, 2 [V]). The transistor 52-1 is driven so that the transistor 52-1 is turned on when the value exceeds (or a value lower than that).

  The driver 54-1 uses, for example, a commercially available voltage comparator IC whose output changes from “0” to “1” when the input (terminal voltage of the capacitor unit 32-1) is to be higher than a specified voltage. It is possible to configure.

  As shown in FIG. 1, the bypass circuit 34-1 further includes a photodiode 56-1 at a position where power is supplied when the transistor 52-1 is turned on. The photodiode 56-1 is an electric element that emits light when energized.

  In the present embodiment, the photodiode 56-1 is connected in parallel to the bypass resistor 50-1, and when the transistor 52-1 is turned on, the bypass resistor 50-1 and the photodiode 56-1 are turned on. A current flows in together. Therefore, the light emission of the photodiode 56-1 indicates that the bypass resistor 50-1 is performing a bypass operation that bypasses the corresponding capacitor unit 32-1.

  As shown in FIG. 1, the charging device 16 further includes an output current detection circuit 60 that detects the output current Is of the solar cell 12.

  The output current detection circuit 60 is provided to convert the output current Is of the solar battery 12 into a voltage, amplify it, and output it to the charge control circuit 80 described later.

  Specifically, the output current detection circuit 60 is connected to a connection point of the negative electrode line 22 with the negative terminal of the solar cell 12 in order to detect the amount of current output from the solar cell 12, that is, the amount of the output current Is. A current detection resistor 62 connected to the portion between the points is provided. The current detection resistor 62 has a function of converting a current flowing through the solar cell 12 into a voltage.

  In addition, in this embodiment, the current detection resistor 62 is disposed on the side closer to the solar cell 12 than the capacitor 48 in the circuit of the charging device 16 in the present embodiment. That is, the current detection resistor 62 is arranged in a closed circuit of the solar cell 12 and the capacitor 48.

  As a result, according to the current detection resistor 62, the output current Is of the solar cell 12 is directly detected, and is a current that flows through the switch 40 and is a ripple current caused by the switching operation of the switch 40. What contains a lot of is not directly detected.

  The output current detection circuit 60 further includes an amplifier (DC amplifier) 64 that amplifies the voltage of the current detection resistor 62 at a constant magnification. The amplifier 64 outputs an analog signal representing the output current Is of the solar cell 12. The amplifier 64 is configured as a DC linear amplifier, for example.

  As shown in FIG. 1, the charging device 16 further includes an output voltage detection circuit 70 that detects the output voltage Vs of the solar cell 12. The output voltage detection circuit 70 is connected to the positive electrode line 20 that is equipotential with the output voltage Vs of the solar cell 12. In the present embodiment, the output voltage detection circuit 70 is configured as a simple conducting wire, but necessary changes can be made.

  As shown in FIG. 1, the charging device 16 further includes a charging control circuit 80. The charging control circuit 80 controls the charging of the power storage device 14 by the solar battery 12 by performing duty ratio control on the switch 40.

  Specifically, the charge control circuit 80 performs normal charging before any one of the three capacitor units 32-1, 32-2, and 32-3 reaches a substantially fully charged state. While the control is executed, the limit charge control is executed after any one of the plurality of capacitor units 32-1, 32-2, and 32-3 reaches a substantially full charge state.

  More specifically, the charging control circuit 80 is for making the operating point of the solar cell 12 substantially coincide with the maximum output operating point A at which the generated power Ps is substantially maximized in the normal charging control. The value is adopted as the value of the duty ratio τ of the switch 40.

  On the other hand, in the limited charging control, the charging control circuit 80 uses a limited output operation in which the generated current Is1 is less than the generated current Is0 corresponding to the maximum output operating point A. A value for substantially matching the point B is adopted as the value of the duty ratio τ of the switch 40.

  In the present embodiment, the limited output operating point B is set such that the corresponding generated current Is1 has a magnitude greater than zero. Therefore, according to this embodiment, when the terminal voltage is about to exceed the specified voltage for only some of the plurality of capacitor units 32-1, 32-2, and 32-3, the terminal voltage is set to the specified voltage. As for another capacitor unit 32 (capacitor unit that has not reached a fully charged state) 32 that is not going to exceed, charging by the solar cell 12 is continued.

  As a result, according to the present embodiment, it is possible to fully utilize the storage capacity of all the capacitor units 32-1, 32-2, and 32-3 while preventing characteristic deterioration due to overcharging.

  The charge control circuit 80 determines the value of the duty ratio τ as a variable value based on the generated power Ps (= Is × Vs) as a physical quantity reflecting the operating state of the solar cell 12 during normal charge control. During the limited charge control, a fixed value set in advance so as not to depend on any physical quantity is adopted as the value of the duty ratio τ (that is, the limited duty ratio τc).

  In the present embodiment, the charging control circuit 80 detects the output current Is and the output voltage Vs of the solar battery 12 at substantially the same timing during normal charging control, and outputs them as the product of these two detection values. The power Ps is calculated.

  Further, the charge control circuit 80 causes the switch 40 to switch to the switch 40 by repeating one switching cycle in which the ON period in which the switch 40 is in the ON state and the OFF period in which the switch 40 is in the OFF state are alternately repeated once. On the other hand, duty ratio control is executed. Further, the charge control circuit 80 determines the duty ratio τ so that the on-time Ton in each switching cycle is shorter in the limited charge control than in the normal charge control.

  The charge control circuit 80 itself generates an on / off pulse to be supplied to the switch 40 in order to cause the switch 40 to perform a switching operation in order to perform duty ratio control on the switch 40 to the switch 40. It is possible to configure so as to output the output.

  Alternatively, the charging control circuit 80 can be configured to connect a PWM circuit to the switch 40 and output the length of the on-time Ton of the switch 40 to the PWM circuit.

  In order to realize the function described above, the charging control circuit 80 is connected to the output current detection circuit 60 at the output terminal of the amplifier 64 as shown in FIG. The charge control circuit 80 is further connected to the output voltage detection circuit 70.

  As shown in FIG. 1, the charging device 16 further includes the same number of phototransistors 82-1, 82-2, 82-3 as the number of photodiodes 56-1, 56-2, 56-3. Of the photodiodes 56-1, 56-2, and 56-3 and the phototransistors 82-1, 82-2, and 82-3, those corresponding to each other, three sets of photocouplers 84-1, 84-2, 84-3 is configured. Each set of photocouplers 84-1, 84-2, 84-3 is provided for each capacitor unit 32-1, 32-2, 32-3.

  Corresponding to the phototransistors 82-1, 82-2, and 82-3, the charging control circuit 80 has the same number of detection terminals 86-1, 86 as the number of the phototransistors 82-1, 82-2, 82-3. -2, 86-3. The charge control circuit 80 has the same number of detection terminals 86-1, 86-2, 86-3 (three detection terminals 86-1, 86-2, 86-3 in this embodiment). The transistors are electrically connected to the phototransistors 82-1, 82-2, and 82-3, respectively.

  As a result, the charging control circuit 80 causes the bypass circuit 34-1 to pass through the corresponding photocouplers 84-1, 84-2, 84-3 for each of the capacitor units 32-1, 32-2, and 32-3. , 34-2 and 34-3 are optically connected.

  In the present embodiment, the phototransistor 82-optically coupled to the photodiode 56-1 corresponding to the most upstream of the three capacitor units 32-1, 32-2, and 32-3. 1 output signal is denoted as “PT1”, and the output signal of the phototransistor 82-2 optically coupled to the photodiode 56-2 corresponding to the second capacitor unit 32-2 is denoted as “PT2”. The output signal of the phototransistor 82-3 optically coupled to the photodiode 56-3 corresponding to the capacitor unit 32-3 located on the most downstream side is denoted as “PT3”.

  Any of the output signals PT1, PT2, PT3 is an analog signal. However, in the charge control circuit 80, as will be described in detail later, corresponding photodiodes 56-1, 56-2, 56-3 are used for signal processing. Is treated as a binary signal indicating whether or not the terminal voltage of the corresponding capacitor unit 32-1, 32-2 or 32-3 exceeds a specified voltage.

  Thus, in this embodiment, since the charge control circuit 80 monitors the operation of each bypass circuit 34-1, 34-2, 34-3 individually, the charge control circuit 80 and each bypass circuit 34-1. , 34-2 and 34-3 are optically connected instead of electrically. As a result, the current flowing through each bypass circuit 34-1, 34-2, 34-3 is prevented from leaking to the charge control circuit 80 unplanned.

  In addition, in this embodiment, in the present embodiment, each bypass circuit 34-1, 34-2, 34-3 is in charge control circuit 80, and each bypass circuit 34-1, 34-2, 34-3 is in bypass operation. (That is, whether or not the terminal voltages of the corresponding capacitor units 32-1, 32-2, and 32-3 exceed the specified voltage) are wirelessly coupled in a state where information can be transmitted. .

  In order to realize the wireless coupling, photocouplers 84-1, 84-2, 84-3 that optically couple the bypass circuits 34-1, 34-2, 34-3 to the charging control circuit 80 are used. . For example, each of the photocouplers 84-1, 84-2, and 84-3 replaces each bypass circuit 34-1, 34-2, and 34-3 with a transformer that is magnetically coupled to the charge control circuit 80, The bypass circuits 34-1, 34-2, and 34-3 can be replaced with capacitors that are electrostatically coupled to the charge control circuit 80.

  As conceptually shown in the block diagram of FIG. 3, the charging control circuit 80 is configured mainly with a computer 90. The computer 90 is configured by connecting a CPU 92, a ROM 94, and a RAM 96 to each other via a bus 98.

  The charge control circuit 80 further includes an I / O interface 100 (for example, an AD converter or a DA converter can be incorporated). Through the I / O interface 100, the computer 90 is electrically connected to the switch 40, the output current detection circuit 60, the output voltage detection circuit 70, and the three phototransistors 82-1, 82-2, and 82-3. Has been.

  By the way, in this embodiment, natural energy called sunlight is used as an energy source of the power storage device 14. Unlike artificial energy, natural energy tends to fluctuate over time. Therefore, the power generation energy of the solar cell 12 is also likely to change with time, and eventually the charging energy of the power storage device 14 is also likely to change with time.

  On the other hand, the generated current of the solar cell 12 is bypassed to the capacitor units 32-1, 32-2, and 32-3 in the fully charged state, and the bypass current is bypassed by the bypass resistors 50-1, 50-2, and 50−. 3 is always accompanied by heat generation of the bypass resistors 50-1, 50-2, 50-3.

  By the way, when charging the power storage device 14 with the solar battery 12, assuming that there is no electrical loss in the charge control circuit 80, all of the generated energy of the solar battery 12 is transferred to the power storage device 14 side. Should be.

  For example, when a current is sequentially passed through each of the bypass resistors 50 of the n (n> 1) stage capacitor units 32 that sequentially reach the specified voltage, a maximum of (n−1) bypass resistors 50, that is, , Current may flow through the bypass resistors 50 corresponding to the (n-1) stage capacitor units 32, respectively. This is because the charging device 16 is normally designed so that charging is stopped when the voltages of the capacitor units 32 of all stages reach the specified voltage.

  Therefore, electrical energy corresponding to (n−1) / n times the output energy of the solar cell 12 at the maximum may be converted into heat by the (n−1) bypass resistors 50. For example, when the capacitor unit 32 is connected in five stages in series (n = 5) and the series capacitor unit 32 is charged by the solar battery 12 whose output is 100 [W],

  Ps × (n−1) / n

= 100 [W] x (5-1) / 5

= 80 [W]

There is a possibility that the electrical energy of will be changed to heat.

  In addition, in order to allow the surplus current of the solar cell 12 to be bypassed by the bypass resistors 50-1, 50-2, 50-3, the capacitor units 32-1, 32-2, 32-3 with the maximum power. It is necessary to design the system so that the current bypass can be performed in an appropriate amount even during the charging period.

  Therefore, it is possible to allow a large current to flow through the bypass circuits 34-1, 34-2, and 34-3 that are required in the same number as the capacitor units 32-1, 32-2, and 32-3. It is necessary to design.

  As a result, in order for the surplus current of the solar cell 12 to be bypassed by the bypass resistors 50-1, 50-2, 50-3, a large number of circuit components that can withstand a large current are used in the charging system 10. In addition, the amount of heat generated by these circuit components increases.

  On the other hand, in the case of charging using a natural energy source such as sunlight, a charging control function for charging by using natural energy as efficiently as possible is usually incorporated in the charging device 16.

  Therefore, when charging using a natural energy source, the charging current of the power storage device 14 tends to increase. However, if priority is given to the increase in the charging current, the bypass circuits 34-1 and 34- 2, 34-3 tends to be excessive, and the amount of heat generated by the bypass circuits 34-1, 34-2, 34-3 also tends to be excessive.

  Therefore, in the present embodiment, the charge control circuit 80 controls the duty ratio τ of the switch 40 to thereby control the charging of the power storage device 14 by the solar battery 12, so that a plurality of stages connected in series are connected. When none of the capacitor units 32-1, 32-2, and 32-3 reaches the specified voltage, the duty ratio τ of the switch 40 is explored so that the output power Ps of the solar cell 12 is maximized. On the other hand, when any one of the plurality of capacitor units 32-1, 32-2, and 32-3 reaches a specified voltage, limited charge control is performed.

  In the limited charge control, the same charge control circuit 80 directly reduces the duty ratio τ of the switch 40 (without mediating another physical quantity), thereby establishing a current path between the solar cell 12 and the power storage device 14. The aperture, thereby limiting the power generation energy of the solar cell 12 itself.

  As a result, the currents flowing through the plurality of bypass circuits 34-1, 34-2 and 34-3 that are required in the same number as the series stages of the capacitor units 32-1, 32-2 and 32-3 are reduced. The total amount of heat generated in the entire bypass circuits 34-1, 34-2, 34-3 is reduced.

  Here, the operation of the charge control circuit 80 will be conceptually described with respect to the limited charge control.

  When the charging control circuit 80 takes out the maximum energy from the solar battery 12, if there is no transmission loss of the charging control circuit 80, the maximum energy flows to the capacitor (that is, the power storage device 14). The electrical energy extracted from the solar cell 12, that is, the generated power Ps, is

Ps = Vs × Is

It is expressed by the following formula. In contrast, the energy flowing into the capacitor, that is, the charging power Pc is

Pc = Vc × Ic

It is expressed by the following formula. Since the electric power Pc is determined by the output state of the solar cell 12 and the voltage Vc of the capacitor is determined by the charging progress state, the capacitor current Ic is determined by the output state of the solar cell 12 and the charged state of the capacitor.

  Since the current flowing through each bypass resistor 50-1, 50-2, 50-3, that is, the bypass current must be larger than the current Ic of each capacitor unit 32-1, 32-2, 32-3, each bypass resistor The capacitors 50-1, 50-2, 50-3 and the transistors 52-1, 52-2, 52-3 have a bypass current larger than the current Ic of each capacitor unit 32-1, 32-2, 32-3. Must be able to withstand.

  On the other hand, if the output current of the solar cell 12 (current flowing from the solar cell 12 via the switch 40 to the power storage device 14) can be limited to a small value, the bypass current can also be limited to a small value.

  All the voltages of the three capacitor units 32-1, 32-2, and 32-3 are defined voltages (the upper limit value of the terminal voltage of each of the capacitor units 32-1, 32-2, and 32-3 is 2 [V]. If the specified voltage is lower than 2 [V], for example, the normal charging control is executed. As a result, the maximum energy is taken in from the solar cell 12 by the operation of the charge control circuit 80 and supplied to the capacitor units 32-1, 32-2, and 32-3. At this time, no current flows through any of the bypass resistors 50-1, 50-2, 50-3.

  Now, if charging proceeds and, for example, only the terminal voltage of the second capacitor unit 32-2 reaches a specified voltage (for example, 2 [V]), the corresponding driver 54-2 shifts to the bypass operation state. To do. As a result, the driver 54-2 turns on the transistor 52-2 corresponding to the driver 54-2, and as a result, a current flows through the corresponding bypass resistor 50-2 and the photodiode 56-2.

  The photodiode 56-2 emits light when a current flows through it, and the emitted light is received by the phototransistor 82-2 corresponding to the photodiode 56-2. As a result, the phototransistor 82-2 is turned on, and the output signal PT2 thereof is input to the charge control circuit 80 as an active signal (for example, an on signal). When the charge control circuit 80 receives the active output signal PT2, the charge control circuit 80 sets the duty ratio τ of the switch 40 to a preset specified value (limit duty ratio τc).

  As a result, the limited charge control is started, whereby the energy output from the solar cell 12 through the switch 40 is reduced, and both the electric energy flowing to the power storage device 14 and the bypass current are reduced.

  Assuming that the terminal voltage of the third capacitor unit 32-3 has also reached the specified voltage in a state where the terminal voltage of the second capacitor unit 32-2 has reached the specified voltage, the second capacitor unit 32-2 has In addition to the corresponding driver 54-2 shifting to the bypass operation state, the driver 54-3 corresponding to the third capacitor unit 32-3 also shifts to the bypass operation state.

  As a result, the transistor 52-3 corresponding to the third capacitor unit 32-3 is also turned on, and a current flows through the corresponding bypass resistor 50-3 and the photodiode 56-3. As a result, the corresponding phototransistor 82-3 is also turned on. The output signal PT3 is input to the charge control circuit 80 as an active signal.

  However, since the active output signal PT2 has already been input to the charging control circuit 80 at this time, the charging control circuit 80 continues the limited charging control already started with the same duty ratio τc.

  As is clear from the above description, in this embodiment, when at least one of the three capacitor units 32-1, 32-2, and 32-3 reaches the specified voltage, the charge control circuit 80 The limited charge control is executed using a duty ratio τc smaller than the duty ratio τ during the charge control.

  In FIG. 4, the switching operation of the switch 40 and the temporal transition of the current flowing through the coil 42 are schematically represented using a graph.

  In the normal charge control, the charge control circuit 80 outputs a switch control signal for turning on / off the switch 40 as shown by a solid line graph in FIG. On the other hand, in the limited charge control, the charge control circuit 80 outputs a switch control signal for turning on / off the switch 40 as indicated by a broken line graph in FIG.

  In the normal charging control, the current flowing through the coil 42, that is, the current flowing through the power storage device 14 changes with time as shown by the solid line graph in FIG. On the other hand, in the limited charge control, the current flowing through the coil 42 changes with time as shown by the broken line graph in FIG. Change from transition.

  In addition, the two types of current waveforms shown in FIG. 4B are waveforms when the voltage of the solar cell 12 does not change within the switching period of the switch 40 because of the capacitor 48.

  In addition, in each graph of FIG. 4B, in each switching cycle of the switch 40, the current supplied from the switch 40 to the coil 42 during the ON period of the switch 40 is indicated by a dashed line rising to the right. On the other hand, the current supplied from the flywheel diode 44 to the coil 42 during the OFF period of the switch 40 is indicated by a dashed line with a lower right.

  In the current waveform shown by the broken line graph in FIG. 4B, when the current of the coil 42 increases, the current flows from the switch 40 to the coil 42, whereas when the current of the coil 42 decreases, the fly Current flows from the wheel diode 44 to the coil 42.

  The charging system 10 is generally designed so that the current of the coil 42 does not become zero as shown in the solid line graph of FIG. 4B in the normal charging control, but when the limited charging control is executed, As shown by the broken line graph in FIG. 4B, the period is designed such that the current of the coil 42 is zero.

  Specifically, during the limited charging control, the length of the on-time Ton and the value of the duty ratio τc employed during the limited charging control are set so that there is a period in which the current of the coil 42 is zero. It is set in advance. This will be described in detail later.

  Here, the operation of the charging control circuit 80 will be described with reference to FIG.

  As described above, FIG. 2 is a characteristic diagram showing the relationship between the output voltage Vs of the solar cell 12 and the output current Is. During normal charging control, the switch 40 is controlled so that the solar cell 12 operates in the vicinity of the maximum output operating point A. On the other hand, during the limited charge control, the switch 40 is controlled so that the solar cell 12 operates at the limited output operation point B.

  Specifically, the charging control circuit 80 normally controls the switch 40 so that the solar cell 12 outputs the maximum power. On the other hand, any of the bypass circuits 34-1, 34-2, 34-3 shifts to the bypass operation state, and a bypass current flows to any of the bypass resistors 50-1, 50-2, 50-3. In the charging control circuit 80, the switch 40 is controlled so that the solar cell 12 operates at the limited output operating point B, that is, the operating point where the output of the solar cell 12 decreases from the maximum output operating point A. Thereby, the output power Ps of the solar cell 12, that is, the transfer power to the power storage device 14 side is reduced.

  As shown in FIG. 2, in the solar cell 12, when its output current Is increases from the maximum output operating point A, the output voltage Is suddenly changes, whereas the output current Is increases from the maximum output operating point A. Even if it decreases, the output voltage Vs changes only slowly.

  In general, when the voltage V is applied to the coil 42 having the inductance L, the current i flowing through the coil 42 is expressed as “t” as follows:

  i = V × t ÷ L

It is expressed by the following formula. At the end of the ON period of the switch 40, the peak value of the current flowing in the coil 42 (hereinafter referred to as “peak current”) ip is

  ip = (Vs−Vc) × Ton ÷ L

It is expressed by the following formula. When the switch 40 is turned off from this state, the current id of the coil 42 decreases. The current id flowing through the coil 42 is obtained when the time t has elapsed since the end of the OFF period of the switch 40.

  id = (Vs−Vc) × Ton ÷ L−Vc × t ÷ L

It is expressed by the following formula. The first half of this equation represents the current flowing through the coil 42 at the end of the OFF period of the switch 40, that is, the peak current ip, and the second half represents the amount of decrease from the peak current ip.

  Since the circuit of the charging device 16 includes the flywheel diode 44, no current flows in the reverse direction. Therefore, according to the above equation, when the current id of the coil 42 decreases, the current id may become zero, but the current id does not become negative.

  In the present embodiment, the on time Ton of the switch 40 is decreased during the limited charge control. Meanwhile, the output voltage Vs of the solar cell 12 and the charging voltage Vc of the power storage device 14 are substantially constant, and therefore the voltage (= Vs−Vc) of the coil 42 is also substantially constant.

  Therefore, the peak current ip of the coil 42 decreases proportionally as the on-time Ton of the switch 40 decreases, as is apparent from the above equation. Therefore, depending on the set value of the ON time Ton, a state occurs in which the current id of the coil 42 becomes zero during the OFF period of the switch 40.

  Because of such characteristics, when the duty ratio τ decreases from the optimum value (value corresponding to the maximum output operating point A), as shown by the broken line graph in FIG. After the end, the current of the coil 42 becomes zero until the start of the next ON period. That is, in this embodiment, the current flowing through the coil 42 increases from zero and decreases to zero at each switching cycle.

  Therefore, the sum total of the currents flowing through the coil 42 during one switching cycle can be calculated only by paying attention to the current switching cycle, regardless of the current flowing through the coil 42 in the previous switching cycle. Become.

  Therefore, according to the present embodiment, the sum of the currents flowing through the coil 42 during each switching cycle is determined only by the operating conditions of the switch 40, the coil 42, and the flywheel diode 44 during that switching cycle. As a result, the manageability and prediction accuracy of the sum total of the currents flowing through the coil 42 during each switching cycle are improved.

  Here, the relationship that is established between the output power Ps of the solar cell 12 that passes through the switch 40 and the ON time Ton of the switch 40 will be described in detail.

  For convenience of explanation, the current (average value) flowing through the switch 40 is represented by “Iss”, and is the power (average value) passing through the switch 40 (that is, passing through the coil 42), that is, the output power Ps of the solar cell 12. What passes through the switch 40 is represented by “Pss”.

  Further, the inductance of the coil 42 is represented by “L”, the switching period of the switch 40 is represented by “T”, and the peak value of the current of the switch 40 (that is, the current flowing through the switch 40 and the coil 42 at the end of the ON period of the switch 40). ) Is represented by “ip”.

  Regarding these physical quantities, the relationship represented by the following equation is established.

  ip = (Vs−Vc) × Ton ÷ L

Iss = 1/2 × ip × Ton ÷ T
= 1/2 × (Vs−Vc) × Ton ÷ L × Ton ÷ T

Pss = Vs × Iss
= 1/2 * Vs * (Vs-Vc) * Ton / L * Ton / T

  Here, the switching period T corresponds to the reciprocal of the switching frequency of the switching regulator 38. For example, 100 [μsec] (= 10 kHz), 10 [μsec] (= 100 kHz), and the like are conceivable.

  In addition, the above formula describing the power Pss is theoretically established when the voltage Vs of the solar cell 12 and the voltage Vc of the power storage device 14 do not change during the on-time Ton. .

  In this regard, as described above with reference to FIG. 2, the voltage Vs of the solar cell 12 is kept substantially constant during the limited charge control. Further, the voltage Vc of the power storage device 14 does not substantially change during the on-time Ton regardless of whether the normal charge control or the limited charge control is being performed.

  Therefore, it can be said that the above equation describing the power Pss approximates an actual electrical phenomenon in the charging system 10 with high accuracy at a practical level.

  Since the voltage Vc of the power storage device 14 is a voltage when the power storage device 14 starts discharging, it is also a voltage when the power storage device 14 is nearly fully charged. Further, during the limited charge control, the voltage Vs of the solar cell 12 has a small temporal change as described above. Further, neither the inductance L nor the switching period T changes with time.

  Accordingly, in the above formula describing the power Pss, all of “Vs”, “Vs”, “L” and “T” can be regarded as being substantially constant. Therefore, it can be seen that a linear relationship is established between the power Pss and the ON time Ton of the switch 40.

  As a result, it can be seen that the power Pss can be accurately controlled only by the on time Ton of the switch 40. That is, by using the above formula, the required on-time Ton of the switch 40 can be obtained by calculation as long as the output power of the solar cell 12, that is, the input power to the power storage device 14, is determined in advance. is there.

  In the present embodiment, by using the value of the on-time Ton calculated as described above, the value of the duty ratio τ employed for the limited charge control is set in advance as a fixed value (for example, τc in FIG. 5). Has been.

  Here, the calculation of the on-time Ton and the duty ratio τc employed for the limited charge control will be described more specifically.

  For convenience of explanation, the solar cell 12 is a solar cell having a maximum output of 100 [W], an output voltage (corresponding to the point A in FIG. 2) when the maximum power is output is 16 [V], and a power storage device. 14 is assumed to have a 5-stage series capacitor (that is, a 5-stage series capacitor unit 32) each having a rated voltage of 2 [V].

  In this case, when the output power of the solar cell 12 is limited to 25 [W], which is 1/4 times the maximum output, the output voltage is about 20 [V] (corresponding to the point B in FIG. 2), and the output current is It becomes about 1.25 [A].

  When power of 25 [W] flows into the capacitor in the five stages of series, the maximum amount of heat generated in the bypass resistor 50 at that time is 25 [W] × (5-1) / 5 from the above formula. = 20 [W].

  When a bypass current flows through these bypass resistors 50, the total voltage of the series capacitors is approximately 10 [V]. Therefore, by substituting Vs = 20 [V], Vc = 10 [V], L = circuit design value, and T = circuit design value into the above equation, the on-time Ton is obtained by calculation. If the value (sec) of the obtained on-time Ton is converted, the duty ratio τc during the limited charge control is acquired.

  By the way, the solar cell 12 generates electric energy according to the illuminance of sunlight. In the above numerical example, only 25 [W] is extracted from the 100 [W] electric energy generated in the solar cell 12 having the maximum output of 100 [W] to the series capacitor side. As a result, 75 [W] of electrical energy disappears as heat in the solar cell 12.

  Specifically, the holes and electrons excited in the solar cell 12 by the solar energy are recombined in the solar cell 12 before being extracted to the outside, and are converted into heat, and disappear as electrical energy. It turns into thermal energy.

  Thermal energy generated in the solar cell 12 is radiated from the surface of the solar cell 12 to the atmosphere. Therefore, in the present embodiment, the amount of heat generated by the solar cell 12 increases as the amount of heat generated by the bypass resistors 50-1, 50-2, and 50-3 in the power storage device 14 decreases.

  However, since the surface area (heat radiation area) of the solar cell 12 is easy to ensure a larger area than the surface areas of the bypass resistors 50-1, 50-2, 50-3, the bypass resistor 50-1. , 50-2, 50-3, even if the heat generated by the solar cell 12 is partially replaced, the temperature rise of the solar cell 12 does not increase so much.

  In addition, as is apparent from the above description, in this embodiment, the power generation device for charging the power storage device 14 sets the duty ratio τ of the switch 40 in the direction in which the output current of the solar cell 12 decreases. Even if it is changed, it is configured as a solar cell 12 in which the fluctuation of the output voltage of the solar cell 12 is small (for example, the same applies to a commercial power supply). It is.

  On the other hand, if the power generation device for charging the power storage device 14 changes the duty ratio τ of the switch 40 and the output voltage of the power generation device fluctuates greatly, the switch 40 can be switched even if the duty ratio τ is decreased. It is presumed that it is difficult to effectively apply the limited charge control in which the bypass current is reduced by reducing the duty ratio τ because the amount of electric energy passing therethrough is small.

  Next, changes in the voltages of the capacitor units 32-1, 32-2, and 32-3 will be described.

  In order that the voltage of each capacitor unit 32-1, 32-2, and 32-3 does not become a value that is higher than the specified voltage, the corresponding bypass current flowing through the transistors 52-1, 52-2, and 52-3 is In general, the charging system 10 is designed to be larger than the charging current to the capacitor units 32-1, 32-2, and 32-3.

  Therefore, when the current bypass to each of the transistors 52-1, 52-2, 52-3 is started, the surplus current bypasses each capacitor unit 32-1, 32-2, 32-3. There is a possibility that the voltage rises of 32-1, 32-2, and 32-3 are suppressed.

  When current bypass to each transistor 52-1, 52-2, 52-3 is started, the charge of each capacitor unit 32-1, 32-2, 32-3 is further transferred to each transistor 52-1, 52-. 2, 52-3 may cause the capacitor units 32-1, 32-2, and 32-3 to discharge.

  Therefore, when current bypass to each of the transistors 52-1, 52-2, and 52-3 is started, the voltage of each of the capacitor units 32-1, 32-2, and 32-3 is eventually lower than the specified voltage.

  Theoretically, when each capacitor unit 32-1, 32-2, 32-3 begins to discharge, its voltage should immediately fall below the specified voltage. However, in reality, the voltage detection by the drivers 54-1, 54-2, 54-3 is usually designed to have hysteresis in order to stabilize the circuit operation. Therefore, after a while from the start of discharge, the corresponding transistors 52-1, 52-2, 52-3 are turned off.

  If charging progresses, for example, if the terminal voltage of the second capacitor unit 32-2 exceeds the specified voltage, the control shifts to limited charging control, and as a result, the charging current flowing into the entire power storage device 14 decreases. .

  When the charging current of the second capacitor unit 32-2 is lower than the discharging current, the voltage of the capacitor unit 32-2 starts to decrease, and the corresponding transistor 52-2 is turned off. When the transistor 52-2 is turned off, the charge control circuit 80 returns to normal charge control, that is, normal control for maximizing the output power of the solar cell 12.

  Then, the charging current becomes larger than the discharging current for the second capacitor unit 32-2, and as a result, the voltage of the capacitor unit 32-2 rises, and eventually the voltage of the capacitor unit 32-2 becomes the specified voltage. To try to exceed.

  As described above, the charging of the second capacitor unit 32-2 proceeds while repeating the ON / OFF operation of the corresponding transistor 52-2. During the limited charge control, the first and third capacitor units 32-1 and 32-3 may be discharged. In the first and third capacitor units 32-1 and 32-3, the ON / OFF operation of the corresponding transistors 52-1 and 52-3 may be repeated at a timing different from that of the second capacitor unit 32-2. There is.

  Therefore, in this embodiment, the normal charging control and the limited charging control are alternately repeated, and all the capacitor units 32-1, 32-2, and 32-3 have their terminal voltages equal to the specified voltage. In this way, the batteries are charged equally.

  As shown in FIG. 3, the charge control circuit 80 starts with a charge control program and a maximum output duty ratio determination routine in the ROM 94 in order to selectively execute the normal charge control and the limited charge control. Various programs are stored.

  FIG. 5 conceptually shows the charging control program in a flowchart, while FIG. 6 conceptually shows a maximum output duty ratio determination routine in the flowchart.

  In the present embodiment, the duty ratio control is repeatedly executed at the duty ratio control cycle Ts regardless of whether the charge control is normal charge control or limited charge control. In each duty ratio control, the switching operation of the switch 40 (an operation in which ON and OFF are repeated once) is repeatedly executed in the switching period T.

  In one example, the duty ratio control cycle Ts is 0.1 [s] and the switching cycle T is 100 [μs]. In this example, 1,000 switching operations (switching cycles) are performed in one duty ratio control cycle. The duty ratio τ of the switch 40 is kept constant during a plurality of switching cycles belonging to the same duty ratio control cycle.

  Therefore, the charge control program shown in FIG. 5 is repeatedly started and executed at the duty ratio control cycle Ts. At the time of each execution, first, in step S100, three output signals PT1, PT2, PT3 are inputted from the three phototransistors 82-1, 82-2, 82-3. The output signal PT1 takes a logical value “1” when the phototransistor 82-1 is on, and takes a logical value “0” when the phototransistor 82-1 is off. The other output signals PT2 and PT3 have the same logical value.

  Next, in step S200, it is determined whether the sum of the logical values of the three output signals PT1, PT2, PT3 is “0”. In this determination, it is determined whether any of the transistors 52-1, 52-2, and 52-3 is off because none of the bypass circuits 34-1, 34-2, and 34-3 is in the bypass operation. To be done.

  This time, assuming that the sum of logical values is “0”, the determination in step S200 is YES, and the charge control program proceeds to step S1000. On the other hand, this time, assuming that the sum of the logical values is not “0”, the determination in step S200 is NO, and the charge control program proceeds to step S300.

  That is, when any of the bypass circuits 34-1 34-2, and 34-3 is performing a bypass operation and the sum of logical values is not “0”, the charge control program is not executed in step S1000. Instead, the process proceeds to step S300.

  In step S1000, the maximum output duty ratio (the optimum value of the duty ratio τ), which is the duty ratio τ for enabling the maximum energy (maximum output power) to be taken in from the solar cell 12, is determined as the current duty ratio τ. Is done. The determined current duty ratio τ is temporarily stored in the RAM 96.

  The details of step S1000 are conceptually shown in the flowchart of FIG. 6 as the maximum output duty ratio determination routine, which will be described later.

  Thereafter, in step S400 of FIG. 5, the current duty ratio τ is read from the RAM 96, and the read current duty ratio τ is output to the switch 40.

  Thus, since the determination in step S200 is YES this time, normal charging control is performed by executing steps S1000 and S400. This completes one execution of the charging control program.

  On the other hand, when the determination in step S200 is NO, in step S300, as shown in FIG. 2, the limit duty ratio τc (fixed value) that is the duty ratio employed during the limit charge control is the ROM 94. Read from. The read limit duty ratio τc is temporarily stored in the RAM 96 as the current duty ratio τ.

  The limit duty ratio τc is set in advance so as to have a value smaller than the lower limit value of the changeable range of the optimum value (variable value) of the duty ratio τ employed during normal charge control. Therefore, the on time Ton of the switch 40 during the limited charge control is shorter than the on time Ton of the switch 40 during the normal charge control.

  Thereafter, step S400 is executed in the same manner as in the case where the determination in step S200 is YES.

  Thus, since the determination in step S200 is NO this time, limited charge control is performed by executing steps S300 and S400. This completes one execution of the charging control program.

  Here, the maximum output duty ratio determination routine shown in FIG. 6 will be schematically described.

  When the execution of the maximum output duty ratio determination routine is started, the duty ratio τ is discretely changed by the current change amount Δτ in each duty ratio control cycle. The direction in which the duty ratio τ is changed, that is, the sign of the current change amount Δτ is substantially equal to the next output power Ps according to the response of the output power Ps to the previous change in the duty ratio τ in the previous duty ratio control cycle. To be maximized.

  Specifically, in each duty ratio control cycle, the output power Ps detected in the previous duty ratio control cycle (the output power Ps not affected by the previous change amount Δτ, which is referred to as “previous power Ps0”). )) And the output power Ps detected before the duty ratio τ is changed in the current duty ratio control cycle (the output power Ps affected by the previous change Δτ, which is referred to as “current power Ps”). Are compared with each other.

  Assuming that the current power Ps is greater than the previous power Ps0, changing the duty ratio τ in the same direction as the previous time leads to the maximization of the output power Ps, and the sign of the change amount Δτ is maintained.

  On the other hand, assuming that the current power Ps is smaller than the previous power Ps0, changing the duty ratio τ in the opposite direction leads to maximization of the output power Ps, and the sign of the change amount Δτ is inverted. .

  The maximum output duty ratio determination routine has been schematically described above, but will be specifically described below with reference to FIG.

  When this maximum output duty ratio determination routine is executed, first, in step S1100, the current value of the output current Is of the solar cell 12 is input from the output current detection circuit 60, and further, the solar cell 12 is output from the output voltage detection circuit 70. The current value of the output voltage Vs is input.

  Next, in step S1200, the current value of the output power Ps of the solar cell 12 is calculated as the current power Ps as the product of the current value of the input output current Is and the current value of the output voltage Vs.

  Subsequently, in step S1300, it is determined whether or not the calculated current power Ps is greater than the previous power Ps0 that is the previous value of the output power Ps of the solar cell 12.

  The previous power Ps0 is acquired by the previous execution of the maximum output duty ratio determination routine and stored in the RAM 96. If the stored previous power Ps0 does not exist, it is assumed that the previous power Ps0 is “0”, and this step S1300 is executed.

  Assuming that the current power Ps is not greater than the previous power Ps0, the determination in step S1300 is NO, and in step S1400, the current value of the change amount Δτ of the duty ratio τ is equal to the previous value of the change amount Δτ. Is determined so that the sign is inverted. The absolute value of the change amount Δτ is set in advance so as to have a value corresponding to 1% of the standard value of the duty ratio τ during normal charge control, for example.

  Thereafter, in step S1500, the determined current change amount Δτ is added to the previous value of the duty ratio τ, thereby calculating the current value of the duty ratio τ. Since the sign of the current change amount Δτ is obtained by inverting the sign of the previous change amount Δτ, this time, the duty ratio τ is calculated to change in the opposite direction.

  Therefore, after that, when step S400 of FIG. 5 is executed and the current value of the duty ratio τ is output to the switch 40, the switch 40 changes the charging current of the power storage device 14 in the opposite direction to the previous time. To be operated. As a result, the output power Ps of the solar battery 12 is changed in the direction opposite to the direction in which the output power Ps has changed in the previous duty ratio control cycle.

  After execution of step S1500 in FIG. 6, in step S1600, the previous power Ps0 is updated to be equal to the current power Ps in preparation for the next execution of the maximum output duty ratio determination routine. Thus, one execution of the maximum output duty ratio determination routine is completed, and then the computer 90 proceeds to S400 in FIG.

  On the other hand, assuming that the current power Ps is greater than the previous power Ps0, the determination in step S1300 in FIG. 6 is YES, and the maximum output duty ratio determination routine skips step S1400 and proceeds to step S1500. As a result, the current value of the change amount Δτ of the duty ratio τ is the same as the previous value of the change amount Δτ in absolute value and sign.

  In step S1500, the current change amount Δτ is added to the previous value of the duty ratio τ to calculate the current value of the duty ratio τ. Since the sign of the current change amount Δτ matches the sign of the previous change amount Δτ, this time, the duty ratio τ is calculated to change in the same direction as the previous time.

  Therefore, when step S400 in FIG. 5 is subsequently executed and the current value of the duty ratio τ is output to the switch 40, the switch 40 causes the charging current of the power storage device 14 to change in the same direction as the previous time. As a result, the output power Ps of the solar cell 12 is changed in the same direction as the direction in which the output power Ps has changed in the previous duty ratio control cycle.

  After execution of step S1500 in FIG. 6, through execution of step S1600, one execution of this maximum output duty ratio determination routine is completed, and then the computer 90 proceeds to S400 in FIG.

  In FIG. 7, an example of the operation of the charging device 16 is represented by a graph.

  In FIG. 7A, the charging device 16 is in a state where none of the bypass circuits 34-1, 34-2, 34-3 performs the bypass operation, and therefore, at least one bypass circuit 34-1, 34- 2, 34-3 shifts to a state where the bypass operation is not performed, and further, any bypass circuit 34-1, 34-2, 34-3 shifts to a state where the bypass operation is not performed. Is represented by a graph.

  On the other hand, in FIG. 7B, the charging device 16 performs normal charging control in a state where none of the bypass circuits 34-1, 34-2, 34-3 performs the bypass operation, while at least one The state in which the limited charge control is performed in a state in which the bypass circuits 34-1, 34-2, and 34-3 are performing the bypass operation is represented by a graph.

  In limited charge control, a smaller duty ratio τ is employed than in normal charge control. When the charging device 16 returns from the control charge control to the normal charge control, the duty ratio τ increases discretely by the change amount Δτ from the limit duty ratio τc every time the duty ratio control cycle Ts elapses.

  According to the present embodiment, the limited charge control is performed during the execution of the current bypass operation for preventing the terminal voltages of the capacitor units 32-1, 32-2, and 32-3 from exceeding the specified voltage.

  As a result of execution of the limited charge control, the power transferred from the solar cell 12 to the power storage device 14 is reduced, so that circuits that bypass the capacitor units 32-1, 32-2, 32-3 (each bypass resistor) 50-1, 50-2, 50-3 and the maximum current flowing into each transistor 52-1, 52-2, 52-3) also decreases.

  Therefore, according to this embodiment, during the execution of the current bypass operation, the amount of heat generated by the circuit that bypasses each of the capacitor units 32-1, 32-2, and 32-3 is reduced.

  Furthermore, according to the present embodiment, during execution of the current bypass operation, the maximum current flowing into the circuit that bypasses each of the capacitor units 32-1, 32-2, and 32-3 is reduced, so that the capacitor unit 32-1 , 32-2 and 32-3, each of the plurality of circuits that need to be used can be configured using components having a small maximum rating.

  For example, when the output of the solar battery 12 is 100 [W] and the voltage of the power storage device 14 is 10 [V], a charging current of 10 [A] can flow through the power storage device 14. Therefore, it is necessary to allow a current of 10 [A] to flow in a circuit that bypasses the power storage device 14, and therefore, the circuit that bypasses the power storage device 14 can withstand the current of 10 [A]. It is necessary to configure using parts.

  On the other hand, according to the present embodiment, it is possible to limit, for example, the power transferred from the solar cell 12 to the power storage device 14 to 10 [W] during the limited charge control. If the transfer power is limited to 10 [W] and the current flowing through the power storage device 14 is limited to 1 [A], the circuit bypassing the power storage device 14 can withstand the current of 1 [A]. It is sufficient to configure using

  Therefore, according to the present embodiment, it becomes easy to improve the reliability and durability of a circuit that needs to be used for the charging device 16 in order to realize the current bypass operation, and further, the cost of the circuit can be reduced. It is also easy to reduce.

  As is apparent from the above description, in the present embodiment, the charge control circuit 80 constitutes an example of the “charge control device” in the item (1), and among the charge control circuit 80, step S400 in FIG. The part that executes step S3 constitutes an example of the “duty ratio control unit” in the section (3), and the part that executes steps S100 to S300 and S1000 in FIG. An example of the “duty ratio determining unit” is configured.

  Further, in the present embodiment, the output signals PT1, PT2 and PT3 each constitute an example of the “bypass operation signal” in the item (4).

  Furthermore, in the present embodiment, the charge control circuit 80 constitutes an example of the “charge control device” in the section (9), and the portion of the charge control circuit 80 that executes steps S100 and S200 in FIG. , Constituting an example of the “selection unit” in the same term, and a part of the charge control circuit 80 that executes steps S300, S400, and S1000 in FIG. 5 constitutes an example of the “control unit” in the same term, The output signals PT1, PT2, and PT3 each constitute an example of the “bypass operation signal” in the same section.

  In addition, in the present embodiment, the limited duty ratio τc during the limited charge control is determined as a fixed value regardless of the duty ratio τ (optimum value) employed during the normal charge control that precedes it. . On the other hand, the limit duty ratio τc during the limit charge control can be determined as a variable value according to the duty ratio τ (optimum value) adopted during the preceding one or more normal charge controls. It is.

  In the latter case, the limited duty ratio τc during the limited charge control is, for example, the duty ratio τ (optimum value) adopted during the preceding one normal charge control, or a plurality of times prior to the current limited charge control. A composite value (for example, an average value) of a plurality of duty ratios τ (optimum value) and a fixed coefficient (for example, a value within a range of about 0.1 to about 0.3) respectively employed during normal charge control. Can be determined using the product of

  Next, a second embodiment of the present invention will be described. However, this embodiment differs from the first embodiment only in terms of the elements that determine the limit duty ratio τc, and is common to other elements, so the same reference numerals or names are used for common elements. By quoting, the redundant description will be omitted, while different elements will be described in detail with reference to FIGS.

  In the first embodiment, the only candidate value for the limit duty ratio τc is preset as a fixed value, so that the limit duty ratio τc does not change during the same limit charge control.

  As described above, when a single candidate value is set as a fixed value for the limit duty ratio τc, it is ideal that the candidate value is still appropriate even if all operating environments and manufacturing variations of the charging system 10 are assumed. Is. However, it may be difficult to set such an ideal unique candidate value.

  On the other hand, in the present embodiment, a plurality of different candidate values for the limit duty ratio τc are preset as fixed values. Any one of these candidate values is selected according to a predetermined rule, and the selected candidate value is used as the final limit duty ratio τc.

  On the other hand, the time during which at least one bypass circuit in the bypass operation among the plurality of bypass circuits 34-1, 34-2, 34-3 continuously performs the bypass operation (that is, phototransistors 82-1, 82). Paying attention to the length of the continuous operation time of the bypass operation that is the time during which the output signal PT of the corresponding one of −2, 82-3 remains active), during the limited charge control, the output current Is of the solar cell 12 The larger the is, the longer the bypass operation continuous time is.

  Therefore, if the length of the bypass operation continuous time is monitored, it is determined whether or not the magnitude of the output current Is of the solar cell 12 is appropriate, that is, whether or not the magnitude of the limit duty ratio τc is appropriate. Is possible.

  Based on such knowledge, in the present embodiment, at least one bypass circuit that is performing the bypass operation among the plurality of bypass circuits 34-1, 34-2, and 34-3 continuously performs the bypass operation. The time (that is, the time during which the output signal PT of the corresponding one of the phototransistors 82-1, 82-2, 82-3 remains active) is measured as the bypass operation continuous time.

  Specifically, in the present embodiment, at least one bypass circuit that is performing a bypass operation among the plurality of bypass circuits 34-1, 34-2, and 34-3 is focused on each bypass circuit. When viewed individually, the time for continuously performing the bypass operation is measured as the bypass operation continuous time.

  Furthermore, in the present embodiment, any one of the plurality of candidate values is the final limit duty ratio τc so that the generated current of the solar cell 12 decreases as the measured bypass operation continuous time is longer. Selected as.

  Thus, in this embodiment, the limit duty ratio τc is changed so that the on-time Ton of the switch 40 becomes shorter as the bypass operation continuous time becomes longer.

  Therefore, according to the present embodiment, the size of the limit duty ratio τc and the length of the on-time Ton of the switch 40 are optimized through the length of the continuous operation time of the bypass operation. In spite of the execution, the terminal voltage of the same capacitor unit 32 continues to exceed the specified voltage, and as a result, the corresponding bypass circuit 34 is prevented from continuing to be in the bus operation.

  In this embodiment, in order to determine the limit duty ratio τc in this manner, as shown in FIG. 8, the ROM 94 of the computer 90 of the charge control circuit 80 stores (a) the charge control program in the first embodiment and Is a partially different charge control program, (b) a maximum output duty ratio determination routine in common with the maximum output duty ratio determination routine in the first embodiment, and (c) a limited duty ratio that does not exist in the first embodiment. A determination routine is stored in advance.

  Further, in the present embodiment, as shown in FIG. 8, the ROM 94 stores in advance two candidate values as the plurality of candidate values, that is, the first duty ratio τc0 and the second duty ratio τc1. Has been. Both of these two candidate values are stored in advance in the ROM 94 as fixed values.

  For example, the first duty ratio τc0 and the second duty ratio τc1 are set in advance to a value smaller than the lower limit value of the range in which the duty ratio τ can be obtained during normal charging control (a value that shortens the on-time Ton of the switch 40). Is set. Further, the first duty ratio τc0 is set in advance as a value larger than the second duty ratio τc1.

  FIG. 9 conceptually shows a flowchart of the charge control program in the present embodiment. Hereinafter, this charge control program will be described, but steps common to the charge control program in the first embodiment will be briefly described.

  The charge control program shown in FIG. 9 is activated and executed for each duty ratio control cycle Ts, similarly to the charge control program in the first embodiment.

  When each charge control program is executed, step S100 is first executed in the same manner as step S100 in the first embodiment, and then step S200 is executed in the same manner as step S200 in the first embodiment. The

  When the determination in step S200 is YES, in step S3000, the value of the counter TM1 indicating the length of time that the output signal PT1 of the phototransistor 82-1 has been active and the output of the phototransistor 82-2. Both the value of the counter TM2 indicating the length of time that the signal PT2 has been active and the value of the counter TM3 that indicates the length of time that the output signal PT3 of the phototransistor 82-3 has been active, It is initialized to “0”.

  In step S3000, the first duty ratio τc0 is further read from the ROM 94, and the read first duty ratio τc0 is stored in the RAM 96 as the limited duty ratio τc.

  Thus, in the present embodiment, the first duty ratio τc0 is used as the initial value of the limit duty ratio τc.

  Therefore, when the charging device 16 returns from the limited charge control state to the normal charge control state, the duty ratio τ is equal to the second duty ratio τc1, that is, the limited duty during the limited charge control, as shown in the graph of FIG. Rather than being changed discretely from the lower limit value of the ratio τc toward the optimum value, as shown in the graph of FIG. 12, from the first duty ratio τc0 that is the upper limit value of the limited duty ratio τc during the limited charge control. It will be changed discretely toward the optimum value.

  Therefore, according to the present embodiment, it is possible to shorten the time required until the duty ratio τ returns to the optimum value from the limit duty ratio τc.

  When the execution of step S3000 in FIG. 9 is completed, then step S1000 is executed in the same manner as step S1000 in the first embodiment.

  Subsequently, step S400 is executed in the same manner as step S400 in the first embodiment. This completes one execution of the charging control program.

  On the other hand, when the determination in step S200 is NO, in step S2000, by executing the limit duty ratio determination routine, the current limit duty ratio τc is changed to the first duty ratio as necessary. τc0 is changed to the second duty ratio τc1.

  In any case, thereafter, in step S300, the current limited duty ratio τc is stored in the RAM 96 as the current duty ratio τ. Subsequently, after execution of step S400, one execution of the limit duty ratio determination routine is completed.

  FIG. 10 conceptually shows the limit duty ratio determination routine in a flowchart.

  When this limiting duty ratio determination routine is executed, first, in step S2100, whether or not the logical value of the output signal PT1 is “1”, that is, the photodiode 82-1 is turned on (that is, the corresponding bypass circuit). It is determined whether or not 34-1 is in a bypass operation.

  This time, assuming that the logical value of the output signal PT1 is not “1” but “0”, the determination in step S2100 is NO, and in step S2150, the value of the counter TM1 is initialized to “0”. Is performed. Thereafter, the limited duty ratio determination routine proceeds to step S2200 described later.

  On the other hand, this time, assuming that the logical value of the output signal PT1 is “1”, the determination in step S2100 is YES, and in step S2110, the value of the counter TM1 is incremented by “1”.

  This limit duty ratio determination routine is executed for each duty ratio control period Ts in association with the execution of the charge control program. Therefore, the product of the value of the counter TM1 and the length of the duty ratio control period Ts is the bypass circuit 34. This corresponds to the length of the bypass operation continuous time for -1. This also applies to the other counters TM2 and TM3.

  Subsequently, in step S2120, it is determined whether or not the value of the counter TM1 is larger than the reference value TMa. This time, assuming that the value of the counter TM1 is not larger than the reference value TMa, the determination in step S2120 is NO, and thereafter, this limiting duty ratio determination routine skips step S2130 described later and proceeds to step S2200. . Therefore, at present, the limit duty ratio τc is maintained at the first duty ratio τc0.

  On the other hand, this time, assuming that the value of the counter TM1 is larger than the reference value TMa, the determination in step S2120 is YES, and in step S2130, the limiting duty ratio τc is the second duty ratio τc1, that is, the first duty. The duty ratio τ is set larger than the ratio τc0.

  As a result, this time, the limit duty ratio τc is decreased from the first duty ratio τc0 to the second duty ratio τc1, as shown in the graph of FIG. Therefore, this time, the output current Is of the solar cell 12 is reduced, and thereby the output power Ps of the solar cell 12 is also reduced.

  As a result, there is an increased possibility that the terminal voltage of the capacitor unit 32-1 corresponding to the current bypass circuit 34-1 will be lowered to a voltage lower than the specified voltage at an early stage. Thereafter, the limited duty ratio determination routine proceeds to step S2200.

  In this step S2200, as in step S2100, whether or not the logical value of the output signal PT2 is “1”, that is, the photodiode 82-2 is turned on (that is, the corresponding bypass circuit 34-2 is bypassed). Whether it is in operation) or not.

  This time, assuming that the logical value of the output signal PT2 is not “1” but “0”, the determination in step S2200 is NO, and in step S2250, the value of the counter TM2 is initialized to “0”. Is performed. Thereafter, the limited duty ratio determination routine proceeds to step S2300 described later.

  On the other hand, this time, assuming that the logical value of the output signal PT2 is “1”, the determination in step S2200 is YES, and in step S2210, the value of the counter TM2 is incremented by “1”. The product of the value of the counter TM2 and the length of the duty ratio control cycle Ts corresponds to the length of the bypass operation continuous time for the bypass circuit 34-2.

  Subsequently, in step S2220, it is determined whether or not the value of the counter TM2 is larger than the reference value TMa. If it is assumed that the value of the counter TM2 is not larger than the reference value TMa this time, the determination in step S2220 is NO, and then the limited duty ratio determination routine skips step S2230 described later and proceeds to step S2300. .

  On the other hand, this time, assuming that the value of the counter TM2 is larger than the reference value TMa, the determination in step S2220 is YES, and in step S2230, the limiting duty ratio τc is the second duty ratio τc1, that is, the first duty. The duty ratio is set larger than the ratio τc0.

  If the limiting duty ratio τc is the first duty ratio τc0 during the execution of step S2200, the limiting duty ratio τc is decreased from the first duty ratio τc0 to the second duty ratio τc1 by executing step S2230.

  In this case, the output current Is of the solar cell 12 is reduced, and thereby the output power Ps of the solar cell 12 is also reduced. Thereafter, the limited duty ratio determination routine proceeds to step S2300.

  On the other hand, when the limiting duty ratio τc is the second duty ratio τc1 when executing step S2200, the limiting duty ratio τc is maintained at the second duty ratio τc1 regardless of the execution of step S2230. . This is because in the present embodiment, the second duty ratio τc1 is set as the upper limit value of the limit duty ratio τc. Thereafter, the limited duty ratio determination routine proceeds to step S2300.

  In this step S2300, similarly to step S2100, whether or not the logical value of the output signal PT3 is “1”, that is, the photodiode 82-3 is turned on (that is, the corresponding bypass circuit 34-3 is bypassed). Whether it is in operation) or not.

  This time, assuming that the logical value of the output signal PT3 is not “1” but “0”, the determination in step S2300 is NO, and in step S2350, the value of the counter TM3 is initialized to “0”. Is performed. Thus, one execution of this limited duty ratio determination routine is completed.

  On the other hand, this time, assuming that the logical value of the output signal PT3 is “1”, the determination in step S2300 is YES, and in step S2310, the value of the counter TM3 is incremented by “1”. The product of the value of the counter TM3 and the length of the duty ratio control cycle Ts corresponds to the length of the bypass operation continuous time for the bypass circuit 34-3.

  Subsequently, in step S2320, it is determined whether or not the value of the counter TM3 is larger than the reference value TMa. If it is assumed that the value of the counter TM3 is not larger than the reference value TMa this time, the determination in step S2320 is NO, and thereafter, this limited duty ratio determination routine skips step S2330 described later. Thus, one execution of this limited duty ratio determination routine is completed.

  On the other hand, this time, assuming that the value of the counter TM3 is larger than the reference value TMa, the determination in step S2320 is YES, and in step S2330, the limiting duty ratio τc is the second duty ratio τc1, that is, the first duty. The duty ratio is set larger than the ratio τc0.

  If the limiting duty ratio τc is the first duty ratio τc0 during the execution of step S2300, the limiting duty ratio τc is decreased from the first duty ratio τc0 to the second duty ratio τc1 by executing step S2330.

  In this case, the output current Is of the solar cell 12 is reduced, and thereby the output power Ps of the solar cell 12 is also reduced. Thus, one execution of this limited duty ratio determination routine is completed.

  On the other hand, when the limiting duty ratio τc is the second duty ratio τc1 when executing step S2300, the limiting duty ratio τc is maintained at the second duty ratio τc1 regardless of the execution of step S2330. . Thus, one execution of this limited duty ratio determination routine is completed.

  As is apparent from the above description, in the present embodiment, the length of the bypass operation continuous time (that is, the time during which the output signal PT remains on) depends on the reference value TMa (or the upper limit value and the lower limit value). It may be a reference range having a defined width).

  Furthermore, in the present embodiment, when the length of the bypass operation continuous time exceeds the reference value TMa (or the upper limit value of the reference range), it is determined that the charging current Is of the solar cell 12 is too large, and the limited duty ratio τc is made smaller than the first duty ratio τc0 (standard value).

  On the other hand, when the length of the bypass operation continuous time does not exceed the reference value TMa (or the lower limit value of the reference range), it is assumed that the charging current Is of the solar cell 12 is appropriate, and the limiting duty ratio τc is It is made equal to 1 duty ratio τc0 (standard value).

  As is apparent from the above description, in this embodiment, a part of step S3000 in FIG. 9 and steps S2110, S2150, S2210, S2250, S2310, and S2350 in FIG. However, it constitutes an example of the “continuous time measuring unit” in each of the above items (5), (6) and (14).

  Further, in the present embodiment, in the charge control circuit 80, the portions that execute steps S2100, S2120, S2130, S2200, S2220, S2230, S2300, S2320, and S2330 in FIG. 10 are the items (5) and (6). Are configured as an example of the “first determination unit” and an example of the “on-time determination unit” in the above item (14).

  Next, a third embodiment of the present invention will be described. However, this embodiment differs from the second embodiment only in terms of the elements that determine the limited duty ratio τc, and is common to other elements, so the same reference numerals or names are used for common elements. By quoting, the redundant description will be omitted, while different elements will be described in detail with reference to FIG.

  In the second embodiment, the size of the limit duty ratio τc is decreased according to the length of the bypass operation continuous time. On the other hand, in the present embodiment, the size of the limit duty ratio τc is reduced according to the number of bypass circuits 34 that are performing the bypass operation.

  Specifically, in the present embodiment, by monitoring the on / off states of the output signals PT1, PT2, and PT3, the number of bypass circuits 34 that are performing the bypass operation is measured.

  Further, in the present embodiment, the relationship between the number of bypass circuits 34 that are performing the bypass operation and the limit duty ratio τc is preset. The set relationship is a relationship representing that the limiting duty ratio τc decreases according to the number of bypass circuits 34 that are performing the bypass operation. The set relationship is stored in the ROM 96 in the form of a table, a function expression or the like.

  Furthermore, in the present embodiment, the limit duty ratio τc corresponding to the measured number is determined according to the stored relationship.

  As a result, according to the present embodiment, as shown in the graph of FIG. 13, when the number of bypass circuits among the plurality of bypass circuits 34 during the limited charge control changes, the limited duty ratio τc accordingly. Changes.

  As described above, some of the embodiments of the present invention have been described in detail with reference to the drawings. However, these are exemplifications, and are 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 a system diagram conceptually showing a charging system 10 according to a first embodiment of the present invention. It is a graph showing the characteristic of the solar cell 12 in FIG. FIG. 2 is a block diagram conceptually showing the configuration of a charge control circuit 80 in FIG. 2 is a graph for explaining operations of a switch 40 and a coil 42 in FIG. 1. It is a flowchart which represents the charge control program in FIG. 3 notionally. 4 is a flowchart conceptually showing a maximum output duty ratio determination routine in FIG. 3. 2 is a time chart for explaining the operation of a charging control circuit 80 in FIG. 1. Fig. 7 is a block diagram conceptually showing a charge control circuit 80 in a charging system 10 according to a second embodiment of the present invention. It is a flowchart which represents the charge control program in FIG. 8 notionally. FIG. 9 is a flowchart conceptually showing a limiting duty ratio determination routine in FIG. 8. It is a time chart for demonstrating operation | movement of the comparative example for the charge control circuit 80 shown in FIG. It is a time chart for demonstrating operation | movement of the charge control circuit 80 shown in FIG. It is a time chart for demonstrating operation | movement of the charge control circuit 80 in the charging system 10 according to 3rd Embodiment of this invention.

Claims (17)

A solar cell in which the generated power changes so as to have a local maximum with respect to the generated voltage and generated current;
A power storage device in which a plurality of capacitor units each having at least one electric double layer capacitor are connected in series;
A plurality of bypass circuits connected to all or a part of the plurality of capacitor units for each capacitor unit, wherein each bypass circuit has a voltage of the corresponding capacitor unit exceeding a specified voltage, Performing bypass operation to bypass each capacitor unit,
A step-down switching regulator connected to the solar cell and the power storage device, having at least a switch, and supplying electric power corresponding to the duty ratio of the switch from the solar cell to the power storage device in a step-down manner things and,
A charge control device that determines the duty ratio, controls the switch so that the determined duty ratio is realized, and thereby controls charging of the power storage device by the solar cell, and
The charge control device is
Before all or some of the plurality of capacitor units reach a substantially fully charged state, normal charge control is performed, while all or some of the plurality of capacitor units are substantially fully charged. In the normal charging control, the operating point of the solar cell is substantially set to the maximum output operating point at which the generated power is substantially maximized. While the value for matching is adopted as the value of the duty ratio, during the limited charging control, the solar cell operating point is set to have the generated power less than the generated power corresponding to the maximum output operating point. A charging system that employs a value for substantially matching a limited output operating point realized in a battery as the value of the duty ratio.   The charge control device determines the value of the duty ratio as a variable value based on a physical quantity reflecting an operating state of the solar cell or the power storage device during the normal charge control, while during the limited charge control. The charging system according to claim 1, wherein a fixed value set in advance without depending on the physical quantity is adopted as the value of the duty ratio. The charge control device includes:
Duty for performing duty ratio control on the switch by repeating a single switching cycle in which an on period in which the switch is in an on state and an off period in which the switch is in an off state are alternately repeated once each. A ratio control unit;
The duty ratio determination part which determines the duty ratio so that the ON time in each switching cycle of the switch may become shorter during the limited charge control than during the normal charge control. Charging system. The switching regulator further includes a coil connected in series between the switch and the power storage device,
The on-time during the limited charge control is set so that the current flowing through the coil increases from zero and decreases to zero at each switching cycle of the switch. Charging system. Each of the plurality of bypass circuits outputs a bypass operation signal indicating whether or not each bypass circuit is performing a bypass operation,
The charging control device receives a plurality of bypass operation signals output from the plurality of bypass circuits, respectively, and the received bypass operation signals indicate that none of the plurality of bypass circuits is in a bypass operation. If the normal charging control is selected, the limited charging control is performed when the received bypass operation signal indicates that at least one of the plurality of bypass circuits is performing the bypass operation. The charging system according to any one of claims 1 to 4, further comprising a selection unit for selection. The charge control device includes:
A continuous time measuring unit that measures a time during which at least one bypass circuit in the bypass operation among the plurality of bypass circuits continuously performs the bypass operation as a continuous time; and
6. The charging system according to claim 1, further comprising: a first determination unit that determines the duty ratio so that the generated power of the solar cell decreases as the measured continuous time increases.   The continuous time measuring unit continuously performs a bypass operation when at least one of the plurality of bypass circuits performing a bypass operation focuses on each bypass circuit and views it individually. The charging system according to claim 6, wherein the time for performing the measurement is measured as the continuous time.   The continuous time measuring unit is a time for continuously performing a bypass operation when a plurality of bypass circuits out of the plurality of bypass circuits are comprehensively viewed without distinguishing each other from each other. The charging system according to claim 6, wherein is measured as the continuous time. The charge control device includes:
A number measuring unit for measuring the number of bypass circuits among the plurality of bypass circuits,
The charging system according to claim 1, further comprising: a second determination unit that determines the duty ratio so that the generated power of the solar cell decreases as the measured number increases.   In the solar cell, electric power that is not output to the power storage device among the generated electric power corresponding to the maximum point is converted into heat in the solar cell, and the heat is released into the atmosphere from the surface of the solar cell. The charging system according to any one of claims 1 to 9, wherein the charging system is a power generation device of a type. In the solar cell, the change in the generated voltage with respect to a decrease in the generated current from the generated current corresponding to the maximum point is caused by the change in the generated voltage from the generated current corresponding to the maximum point. It is a type of power generator having characteristics smaller than the change in voltage,
The charging system according to any one of claims 1 to 10, wherein the charge control device decreases the duty ratio during the limited charge control than during the normal charge control. A power storage device in which a plurality of capacitor units each having at least one electric double layer capacitor are connected in series;
A plurality of bypass circuits connected to all or a part of the plurality of capacitor units for each capacitor unit, wherein each bypass circuit has a voltage of the corresponding capacitor unit exceeding a specified voltage, Performing bypass operation to bypass each capacitor unit,
A switch connected to the power storage device for controlling power supplied from an external device to the power storage device via the switch;
A charge control device that controls the switch, thereby controlling charging of the power storage device by the external device, and
Each of the plurality of bypass circuits outputs a bypass operation signal indicating whether or not each bypass circuit is performing a bypass operation,
The charge control device includes:
When a plurality of bypass operation signals respectively output from the plurality of bypass circuits are received, and the received bypass operation signals indicate that none of the plurality of bypass circuits is in a bypass operation, normal charging is performed. A selection unit that selects limited charge control when the received bypass operation signal indicates that at least one of the plurality of bypass circuits is performing a bypass operation,
And a control unit that controls the switch so that an on-time in which the switch is in an on state is shorter when the limited charge control is selected than when the normal charge control is selected. Furthermore, between the switch and the power storage device, including a coil connected in series to them,
The controller repeats a single switching cycle in which an on period in which the switch is in an on state and an off period in an off state are alternately repeated once each, thereby performing the normal charging control and the Alternatively perform limited charge control,
The on-time during the limited charging control is set so that the current flowing through the coil increases from zero and decreases to zero at each switching cycle of the switch. Charging system. The controller is
A continuous time measuring unit that measures a time during which at least one bypass circuit in the bypass operation among the plurality of bypass circuits continuously performs the bypass operation as a continuous time; and
14. The charging system according to claim 12, further comprising: an on-time determination unit that determines a length of an on-time of the switch so that the measured continuous time is shorter.   The charge control device determines the value of the duty ratio during the limited charge control as a variable value according to the value of the duty ratio actually employed during one or a plurality of normal charge controls preceding the limit charge control. Item 2. The charging system according to Item 1. A charging device for storing electrical energy from a power source in a plurality of stages of electric double layer capacitors connected in series with each other via a switching regulator, and equalizing voltages of the plurality of stages of electric double layer capacitors Therefore, when it is detected that the voltage of the electric double layer capacitor at each stage has reached the specified voltage, including a bypass circuit that performs a bypass operation to bypass the electric double layer capacitor,
A charging apparatus comprising: an on-time control unit configured to control an on-time of the switch to a specified value when a voltage of at least one electric double layer capacitor exceeds the specified voltage. The on-time controller is
Time measuring means for measuring the length of time that the voltage of the electric double layer capacitor at each stage continuously exceeds the specified voltage;
The charging device according to claim 16, further comprising: a specified value changing unit that changes the specified value according to the measured length of time.

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