JP2006014542A - Power supply circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power supply circuit for acquiring a high output voltage from a power generation element if it is required, and efficiently storing power. <P>SOLUTION: The power supply circuit comprises n (n is an integer of 2 or more) power generation elements 1, 2; a power generation unit for outputting a unit output voltage Vu; switches 3, 4 for switching the connection method of the power generation elements to a series connection or a parallel connection; a control unit 8 for controlling the changeover of the connection method by the switches; and a voltage boosting circuit 11 for boosting the unit output voltage Vu and charging a capacitor 12. When the power generation elements 1, 2 are connected in series, the voltage boosting circuit 11 is activated by supplying the unit output voltage Vu as a power supply voltage through a diode 14. After the voltage boosting circuit 11 is activated, the voltage boosting circuit 11 is driven by its boosted voltage. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a power supply circuit that charges a power storage element such as a battery or a capacitor, and more particularly to a power supply circuit that charges the power storage element using generated power generated from a power generation element such as a solar battery.

  In recent years, power generation elements that generate electrical energy by receiving external energy such as light, such as solar power generation using solar cells, thermoelectric generation using thermoelectric elements, and power generation using pressure using piezoelectric elements, have been used. The power supply device and its application products have been put into practical use.

  However, since the power generation voltage of a general power generation element 1 cell is as low as 0.5 V or less, an electric device (electronic device) such as a digital camera is operated with the power generation voltage as it is, or a nickel cadmium battery, a nickel metal hydride battery, and a lithium battery. A secondary battery (storage battery) such as can not be charged. For this reason, it is common practice to increase the voltage by serializing power generation elements.

  FIG. 12 is a conventional example of a power supply circuit using serialization of solar cells. The power supply circuit in FIG. 12 includes a solar battery module composed of solar cells 101, 102 and 103 connected in series, a capacitor 104 charged with an output voltage from the solar cells connected in series, and a capacitor 104 The booster circuit 105 boosts the output voltage of the capacitor 104 and the capacitor 106 charged with the boosted voltage output from the booster circuit 105.

  In the power supply circuit configured as described above, assuming that the generated voltage per solar cell is 0.5 V, the total generated voltage of the solar cells 101, 102, and 103 connected in series is 1.5 V. It becomes. The booster circuit 105 operates using the 1.5V voltage as a power supply voltage, and the capacitor 106 is charged with a voltage obtained by boosting 1.5V (for example, 5V).

  However, when solar cells are serialized as shown in FIG. 12, an electrical problem occurs. When some 10% of the solar cells are shaded, the same effect as when some 10% of the entire solar cell module is shaded is produced, and the output is greatly reduced. For example, if 10% of one solar cell 102 is covered with shadow among the solar cells 101, 102, and 103, 10% of the entire solar cell module composed of the solar cells 101, 102, and 103 is obtained. It has the same effect as being covered by a shadow. This problem becomes more prominent as the number of solar cells connected in series increases. Thus, solar cells connected in series are vulnerable to shadows. In order to avoid this phenomenon, a bypass diode must be inserted in parallel with the solar cell.

  As a means for solving the problem of serialization as described above, a method of connecting all the solar cells in parallel can be considered. In this case, the generated power is approximately equal to the total value of the power generation amount of each solar battery cell, which can solve the problem of “weak to shadows” in series connection, but the output voltage is as low as about 0.5V. The voltage is too low to be used as a power source for electrical equipment or a secondary electron charging source. In addition, since a known booster circuit such as the booster circuit 105 requires a power supply voltage of 0.7 V or more to start operation, the booster circuit can be operated with the output voltage of a solar cell module in which solar cells are connected in parallel. Cannot be boosted.

  As a technique for solving such a problem caused by not using serial connection, a power supply circuit shown in FIG. 13 has been proposed (see, for example, Patent Document 1 below). The power supply circuit shown in FIG. 13 includes a solar cell module composed of solar cells 101, 102 and 103 connected in series, a capacitor 104 charged with an output voltage from the solar cells connected in series, and a series The solar cell 107 that is not connected and whose output voltage is about 0.5 V, the capacitor 108 that is charged by the solar cell 107, and the output voltage of the capacitor 108 while using the output voltage of the capacitor 104 as its own power supply voltage. A booster circuit 105 that boosts the voltage and a capacitor 106 that is charged with the boosted voltage output from the booster circuit 105 are configured.

  When light is applied to the solar cells 107 that are not connected in series that are to be boosted, the solar cells 101 that are connected in series, or the like, an electromotive force is generated respectively. The output voltage per one of these solar cells is a little over 0.5V. Since the booster circuit 105 uses the output voltage from the solar cells 101, 102 and 103 connected in series as the power supply voltage, it can be started up and boosted.

JP 2003-204072 A

  As described above, the method of connecting solar cells in series can obtain a relatively large output voltage, drive the booster circuit with the output voltage, or use it as a power source for electric equipment or a charge source for secondary electrons. However, there is a demerit that it is difficult to increase the efficiency of power storage because the influence of the shadow is large and the output is greatly reduced by the shadow.

  On the other hand, the method of connecting solar cells in parallel has the advantage that it is less affected by shadows than in series connection and enables highly efficient power storage, but the output voltage is as low as about 0.5 V. There are demerits that the voltage is too low to be used as a power source for equipment or a charge source for secondary electrons, and that the booster circuit cannot be activated or operated.

  Further, in the power supply circuit shown in FIG. 13, since the output voltage from the solar battery cell 107 is as low as about 0.5 V, it cannot be used as a power source for electric equipment or a charge source for secondary electrons without a booster circuit. . In order to increase the voltage by providing a booster circuit as shown in FIG. 13, solar cells 101, 102, and 103 that are separately connected in series for the power supply voltage are required, resulting in an increase in cost.

  Since the solar cells 101, 102, and 103 need only cover the power consumption of the booster circuit 105, small elements of about 1 to 3.3 square centimeters can be used. If the type and size of the solar cell are changed, the cost may be increased, and when such a small element is used for the solar cells 101, 102, and 103, the solar cells 101, 102, and 103 are merely formed with a small shadow. There is a problem that most of the voltage is covered with a shadow, which causes the booster circuit 105 to stop.

  In view of the above points, an object of the present invention is to provide a power supply circuit that can obtain a high output voltage from a power generating element as required and can store electricity with high efficiency.

  In order to achieve the above object, a power supply circuit according to the present invention is composed of n (n is an integer of 2 or more) power generation elements, and includes a power generation unit that outputs a unit output voltage and a method for connecting at least two power generation elements. It is characterized by comprising switching means capable of switching between serial connection and parallel connection, and control means for controlling switching of the connection method by the switching means.

  As a result, for example, the power generation element is connected in series only when the power generation voltage of the power generation element is low and the required output voltage cannot be supplied to the load side in parallel connection, and when the power generation voltage of the power generation element becomes high, it is switched to parallel connection. It is possible to use an optimal power generation element according to the conditions.

  For example, it usually enjoys the benefits of “highly efficient power storage possible” due to parallel connection as parallel connection, and benefits from series connection as a series connection only when a relatively large unit output voltage is required (to obtain a relatively high output voltage) Etc.), and the like can be used.

  Further, for example, a boosting unit that boosts the unit output voltage and outputs the boosted voltage to the first power storage unit may be provided, and the power supply voltage of the boosting unit may be supplied from the first power storage unit.

  Thereby, even if the magnitude | size of the electric power generation voltage by an electric power generation element is small, an arbitrarily big voltage (voltage larger than the magnitude | size of an electric power generation voltage) can be obtained. In addition, since the boosting means is driven using the output voltage of the first power storage means charged with the boosted voltage as the power supply voltage, it is not necessary to separately prepare a power source for driving the boosting means, and the unit output voltage Even when the voltage is so low that the booster cannot be driven, the booster can be operated.

  In addition, for example, when the power supply voltage supplied to the booster is smaller than the minimum operating voltage of the booster and the booster is not operating, the connection method is in series connection, The unit output voltage may be temporarily supplied to the first power storage means.

  This eliminates the need for a power supply for starting up the boosting means. In addition, at the time of starting up the boosting means, the unit output voltage in which the connection method is connected in series is temporarily supplied to the first power storage means, and the first power storage means is temporarily charged by the unit output voltage. Therefore, more reliable activation of the boosting means is realized. When the connection method is a series connection, the unit output voltage is larger than that of the parallel connection. Therefore, when the boosting unit is started, the connection method is a series connection. This is because the output voltage of the voltage rises and the boosting means is easily activated.

  Also, for example, when the power supply voltage supplied to the control means is smaller than the minimum operating voltage of the control means and the control means is not operating, the connection method may be connected in series. Good.

  Thereby, when the control means is not operating, such as when the power supply circuit is activated, the power generating elements are connected in series. The magnitude of the individual power generation voltages of the power generation elements is often small, and when the power generation elements are connected in parallel at the time of startup or the like, the output voltage of the first power storage means charged by the unit output voltage is supplied to the boosting means or the like. Even if it is supplied as a voltage, the boosting means or the like may not be activated. However, according to the above configuration, since the power generating elements are connected in series when the power supply circuit is started, a unit output voltage larger than that in the parallel connection can be obtained. Therefore, it is possible to reliably start up the boosting means and the control means by supplying the unit output voltage as a power supply voltage to the boosting means and the control means.

  For example, when the magnitude of the output voltage of the first power storage unit is equal to or greater than a predetermined threshold, the connection method may be parallel connected by the control unit.

  When the boosting means is not operating, the boosting means cannot be driven with the boosted voltage (the output voltage of the first power storage means charged only by the boosted voltage). Thus, for example, when the boosting means is started, it is conceivable that the connection method capable of supplying a relatively high voltage supplies the series output unit output voltage as a power supply voltage to the boosting means to start the boosting means. However, from the viewpoint of realizing highly efficient power storage, the connection method is preferably parallel connection.

  Therefore, the magnitude of the output voltage of the first power storage means is, for example, the minimum operating voltage of the boosting means (the magnitude of the power supply voltage necessary for performing the boosting operation in which the boosting means boosts the unit output voltage and outputs the boosted voltage) After the boosting means is activated, the connection method is set to parallel connection. Thereby, the merit by having the said connection method being parallel connection can be enjoyed, and highly efficient electrical storage is attained.

  In addition, when adopting a configuration in which the unit output voltage is temporarily supplied to the first power storage means while the connection method is connected in series when the boosting means is started up, the first power storage means charged by the unit output voltage If the magnitude of the output voltage exceeds the magnitude of the absolute maximum rated voltage with respect to the power supply voltage terminal of the boosting means, the boosting means is damaged or deteriorated. Therefore, for example, when the output voltage of the first power storage means reaches the absolute maximum rated voltage, the connection method is switched from series connection to parallel connection. Thereby, further increase in the output voltage of the first power storage means is suppressed, and overvoltage protection of the boosting means is achieved.

  In addition, for example, when the unit output voltage when the connection method is a series connection exceeds a predetermined threshold value, the connection method is switched from the series connection to the parallel connection by the control means. Also good.

  By making the connection method in series, a relatively large unit output voltage can be obtained, and the utility value is high, such as starting up the boosting means and the control means with the unit output voltage. However, after the start-up or the like is completed, it is desirable to switch the connection method to parallel connection from the viewpoint of realizing highly efficient power storage.

  Therefore, for example, when the connection method is a series connection, the unit output voltage magnitude is the minimum operating voltage of the boosting unit or the minimum operating voltage of the control unit (the power supply voltage necessary for the control unit to operate normally). When the value becomes equal to or greater than the lower limit of the size, the connection method is switched from serial connection to parallel connection by the control means. As a result, highly efficient power storage is realized while ensuring the start-up of the boosting means and the control means.

  Further, when the boosting means and the control means are activated, when the configuration in which the unit output voltage is temporarily supplied as the power supply voltage of the boosting means while adopting the connection method in series connection, the magnitude of the unit output voltage is small. Exceeding the magnitude of the absolute maximum rated voltage with respect to the power supply voltage terminal of the boosting means or the like causes damage or deterioration of the boosting means or the like. Therefore, for example, when the magnitude of the unit output voltage reaches the magnitude of the absolute maximum rated voltage, the connection method is switched from serial connection to parallel connection. As a result, the unit output voltage decreases, and overvoltage protection of the boosting means and the like is achieved.

  Further, for example, the switching means switches a connection method of m (m <n) power generation elements among the n power generation elements, and excludes the m power generation elements (n− The m power generating elements may be connected in parallel to the m power generating elements.

  If the connection method can be switched for all of the n power generating elements, the number of switch means for switching is inevitably increased, leading to an increase in power loss in the switch means. However, if configured as described above, the power loss can be reduced, and the size and cost of the power supply circuit can be reduced due to the reduction of the switch means.

  The power supply circuit according to the present invention includes n (n is an integer of 2 or more) power generation elements, and switching means capable of switching a connection method of at least two power generation elements to either serial connection or parallel connection. A control means for controlling switching of the connection method by the switching means; and a boosting means for boosting the power generation voltages output from the n power generating elements, respectively, and outputting the boosted voltages to the first power storage means. It is characterized by comprising.

  As a result, even if the power generation voltages of the individual power generation elements are different, if the battery or the like is stored with the boosted voltage output by the boosting means, all of the generated power is fully utilized. .

  Further, for example, a second power storage unit having a capacity larger than that of the first power storage unit is connected to the output side of the boosting unit in parallel with the first power storage unit via the switch unit, and the first power storage unit is charged when charged. When the magnitude of the voltage charged in one power storage means is smaller than a predetermined threshold value, the switch means may be shut off to prohibit charging to the second power storage means.

  When the magnitude of the voltage charged in the first power storage means is smaller than, for example, the magnitude of the minimum operating voltage of the boosting means, charging to the large capacity second power storage means is prohibited, and only to the first power storage means having a small capacity. Charging is performed. Therefore, if the output voltage of the first power storage means is supplied as the power supply voltage of the boosting means, the boosting means is activated in a short time and the entire power supply circuit is activated even if the generated power of the power generating element is small.

  As described above, according to the power supply circuit of the present invention, a high output voltage can be obtained from the power generation element as necessary, and highly efficient power storage is possible.

<< First Embodiment >>
Hereinafter, a first embodiment in which the present invention is applied to a power supply circuit will be described with reference to the drawings. FIG. 1 is a circuit configuration diagram of a power supply circuit according to the first embodiment.

  The power supply circuit in FIG. 1 is schematically composed of power generating elements 1 and 2, switches 3 and 4, diodes 5 and 6, a capacitor 7 as a power storage element (power storage means), a control unit 8, and a power source 9.

(Fig. 1: Explanation of configuration)
First, the configuration of the power supply circuit in FIG. 1 will be described. The high voltage side of the power generation element 1 is connected to the anode of the diode 5, and the low voltage side is commonly connected to one end of the switch 3 and one end of the switch 4. The high voltage side of the power generation element 2 is commonly connected to the anode of the diode 6 and the other end of the switch 4, and the low voltage side is commonly connected to the other end of the switch 3 and the cathode (low voltage side) of the capacitor 7. The cathode of the diode 5 and the cathode of the diode 6 are both connected to the anode (high voltage side) of the capacitor 7, and a load 10 is connected between both poles (both ends) of the capacitor 7. The control unit 8 gives each of the switches 3 and 4 a control signal for turning on / off each switch independently. The power supply 9 supplies a power supply voltage Vcc1 to the control unit 8 with reference to the ground.

  The power generation elements 1 and 2 are power generation elements that generate external energy by receiving external energy such as light. Specifically, solar cells that receive light to generate electrical energy, thermoelectric elements that generate electrical energy by the thermoelectric effect, piezoelectric elements that generate electrical energy by the piezoelectric effect (elements that generate voltage when strain is generated), etc. It may be configured by unit cells, or may be a module in which a plurality of unit cells are connected in series or a module in which a plurality of unit cells are connected in parallel. In the following description, the power generation elements 1 and 2 will be described more specifically on the assumption that they are made of solar cells.

  The power generating elements 1 and 2 are each a solar cell unit cell having an output voltage of about 0.5 V, a solar cell module in which a plurality of unit cells are connected in parallel, or a solar cell module in which a plurality of unit cells are connected in series. As the solar cell, those that are generally widely used, such as those using single crystal silicon, polycrystalline silicon, amorphous silicon, and compound semiconductors, can be used. Although the power supply circuit of the present embodiment includes two power generation elements, it may be three or more, or a power supply circuit may be configured by combining different types of power generation elements or power generation elements having different characteristics. I do not care.

  The switches 3 and 4 are, for example, a switch for manually switching on / off, various relay switches, a bipolar transistor, and the like. The switches 3 and 4 are connected to or cut off (open) between both ends of the switch in response to a control signal from the control unit 8. is there. The switches 3 and 4 function as switching means that can switch the connection method of the two power generating elements 1 and 2 to either serial connection or parallel connection as will be described later. In the power supply circuit of this embodiment, Corresponding to the number of power generation elements (power generation elements 1 and 2) being two, the number of switches is set to a minimum of two. However, three or more switches may be provided according to the switching control method of the control unit 8, and when the number of power generating elements is three or more, the number of switches may be increased accordingly. Good.

  The diodes 5 and 6 are, for example, rectifying silicon diodes or Schottky barrier diodes having a low forward voltage, and when the anode voltage of the capacitor 7 is higher than the high voltage side voltages of the storage means 1 and 2, respectively. , Functions as a backflow prevention means for preventing current from flowing back. For simplification of explanation, the following explanation will be made ignoring the voltage drop at the diodes 5 and 6.

  The capacitor 7 is, for example, an electrolytic capacitor or an electric double layer capacitor, and various types of batteries may be adopted. Further, the capacitor 7 may be configured by combining capacitors of different types and characteristics.

(Fig. 1: Explanation of operation)
Next, the operation of the power supply circuit configured as described above will be described. The power supply circuit of FIG. 1 can operate in two modes: a serial mode in which the connection method of the power generation elements 1 and 2 is connected in series, and a parallel mode in which the connection method of the power generation elements 1 and 2 is connected in parallel. Thus, the mode is selected by the control unit 8 controlling the on / off of the switches 3 and 4.

  When operating in the serial mode, the switches 3 and 4 are turned off (cut off) and turned on (conducted), respectively. A sum of voltages generated by the power generation elements 1 and 2 is applied to both ends of the capacitor 7, and the capacitor 7 is charged. On the other hand, when operating in the parallel mode, the switches 3 and 4 are turned on (conductive) and turned off (shut off), respectively. The voltage generated by each of the power generation elements 1 and 2 is applied to both ends of the capacitor 7 as it is, and the capacitor 7 is charged.

  When the voltage across the capacitor 7 is defined as the unit output voltage Vu, the two power generation elements 1 and 2 constitute a power generation unit that outputs the unit output voltage Vu according to the selected mode.

  When the power generation elements 1 and 2 output a voltage of 3V per one, when a voltage of 6V should be supplied to the load 10, the series mode may be selected, and the state of the load 10 changes and the load 10 is supplied. When the power voltage becomes 3V, the parallel mode may be selected.

  Further, the power generation voltage (output voltage) of the power generation elements 1 and 2 generally varies greatly depending on the amount of energy (solar energy in the case of a solar cell) serving as a power generation source. Therefore, when the voltage to be supplied to the load 10 is always required to be 2 V or more, when the generated voltage per generator element is less than 2 V, the series mode is selected to maintain the voltage to the load 10 at 2 V or more. It is also possible to select the parallel mode when the generated voltage per unit becomes 2V or more. In this case, a voltage detection unit (not shown) that detects the voltage across the load 10 and supplies the detection result to the control unit 8 may be provided, and the control unit 8 may select a mode according to the result.

  As described above, by changing the connection method of the power generation elements fixed in series connection (see FIG. 12) or parallel connection in the conventional example, it becomes possible to use the most suitable power generation element according to the use situation.

  For example, when the power generating elements 1 and 2 are formed of solar cells, a relatively large output voltage can be obtained by selecting the series mode, and the booster circuit is driven by the output voltage, or the power supply of the electric device Although there is a merit that it can be used as a charge source for secondary electrons, there is a demerit that high-efficiency power storage is difficult because the influence of the shadow is large and the output is greatly reduced by the shadow.

  On the other hand, if the parallel mode is selected, there is a merit that the influence of the shadow is less than that of the serial connection and high-efficiency power storage is possible. However, the output voltage is about 0.5 V (in the case of a solar cell unit cell). Therefore, there is a demerit that the voltage is too low to be used as a power source for electric equipment or a secondary electron charging source, and the booster circuit cannot be operated.

  In the power supply circuit in FIG. 1, it is possible to select a series mode and a parallel mode according to the use situation in consideration of the merits and demerits of such series connection and parallel connection. For example, you can usually select the parallel mode and enjoy the benefits of “highly efficient storage”, select the series mode only when a relatively large unit output voltage is required, and “boost circuit can be driven” etc. It is effective to use such benefits.

(FIG. 2; modification of FIG. 1)
Further, the power supply circuit in FIG. 1 may be modified as shown in FIG. 2 differs from FIG. 1 in that the switches 3 and 4 in FIG. 1 are an N-channel (N-type semiconductor) MOS transistor (insulated gate field effect transistor) 3a and a P-channel (P-type semiconductor) MOS, respectively. This is a point replaced with the transistor 4a, and is the same in other points. Therefore, the description of the operation and connection relation of the points that are the same is omitted.

  That is, the low voltage side of the power generation element 1 is commonly connected to the drain of the MOS transistor 3a and the drain of the MOS transistor 4a, and the high voltage side of the power generation element 2 is commonly connected to the source of the MOS transistor 4a and the anode of the diode 6, The low voltage side of the power generation element 2 is commonly connected to the source of the MOS transistor 3 a and the cathode of the capacitor 7. The control unit 8 supplies control signals to the gates of the MOS transistors 3a and 4a.

  If MOS transistors are used as the switches 3 and 4 in this way, a base current required for a bipolar transistor is unnecessary, and an on-resistance can be easily reduced, so that an efficient power supply circuit can be configured. In addition, since the MOS transistors 3a and 4a and the control unit 8 can be manufactured in the same process, and all of them can be housed in one chip, compared with the case where a mechanical switch or the like is used. Thus, it is possible to achieve a significant reduction in size and cost. Moreover, since there is no mechanical wear, a long life can be expected.

<< Second Embodiment >>
Next, a second embodiment in which the present invention is applied to a power supply circuit will be described with reference to the drawings. FIG. 3 is a circuit configuration diagram of the power supply circuit according to the second embodiment. In FIG. 3, the same parts as those in FIG. 1 are denoted by the same reference numerals, and the operation and connection relationship thereof are the same as those in FIG.

  In the power supply circuit of FIG. 3, both ends of the capacitor 7 are connected to the booster circuit 11, and the booster circuit boosts the unit output voltage Vu (for example, 1V) to an arbitrary boosted voltage (for example, 5V), It outputs to the capacitor | condenser 12 as an electrical storage element (electric storage means). The step-up circuit 11 may be a step-up chopper type regulator using a coil or a charge pump system using a capacitor. Since the circuit configuration and operation principle of the booster circuit 11 are well-known techniques, description thereof is omitted. The power supply 13 supplies the power supply voltage Vcc2 to the booster circuit 11.

  The capacitor 12 is, for example, an electrolytic capacitor or an electric double layer capacitor, and various types of batteries may be adopted. Further, the capacitor 12 may be configured by combining capacitors of different types and characteristics.

  For example, as the power generation elements 1 and 2, a solar cell unit cell in which each power generation voltage varies in the range of 0.2 to 0.5V depending on the amount of light is used, and the booster circuit 11 boosts the unit output voltage Vu to 5V. Consider the case. When the control unit 8 selects the serial mode, the unit output voltage Vu becomes 0.4 to 1V, and the booster circuit 11 boosts the unit output voltage Vu with the booster as a boost target, and charges the capacitor 12 with the boost voltage 5V. To do. As a result, the output voltage Vo of the capacitor 12 (this voltage Vo is equal to the output voltage of the power supply circuit) becomes equal to the boosted voltage of 5V. Similarly, when the control unit 8 selects the parallel mode, the unit output voltage Vu is 0.2 to 0.5 V, and the booster circuit 11 boosts this unit output voltage as a boost target, and at the boost voltage 5 V The capacitor 12 is charged. As a result, the output voltage Vo of the capacitor 12 becomes equal to the boosted voltage of 5V.

  According to the power supply circuit in the present embodiment, it is possible to store an arbitrarily high voltage (a voltage higher than the generated voltage) in the capacitor 12 even if the generated voltage by the power generating elements 1 and 2 is low. As the connection method of the power generating elements 1 and 2, it is possible to select either the parallel connection or the series connection which is convenient.

<< Third Embodiment >>
Next, a third embodiment in which the present invention is applied to a power supply circuit will be described with reference to the drawings. FIG. 4 is a circuit configuration diagram of the power supply circuit according to the third embodiment. 4, the same parts as those in FIG. 3 are denoted by the same reference numerals, and the operation and connection relation thereof are the same as those in FIG. 3, and thus detailed description thereof will be omitted.

  In the power supply circuit in FIG. 4, the boosted voltage of the booster circuit 11 (equal to the output voltage Vo of the capacitor 12) is supplied as the power supply voltage of the control unit 8 and the booster circuit 11. Therefore, the power supply 9 and the power supply 13 (see FIG. 3) are not necessary. Further, since the unit output voltage Vu is not directly supplied to the booster circuit 11 or the like as a power supply voltage, even if the generated voltage by the power generating elements 1 and 2 is so low that the control unit 8 and the booster circuit 11 cannot be driven, the control is performed. The unit 8 and the booster circuit 11 can operate.

  In addition, a diode 14 having an anode and a cathode connected to the anode of the capacitor 7 and the anode of the capacitor 12 is provided. That is, the power supply voltage supplied to the booster circuit 11 is lower than the minimum operating voltage of the booster circuit 11 (the lower limit of the power supply voltage necessary for the booster circuit 11 to boost the input voltage). In such a case, the unit output voltage Vu is temporarily supplied to the capacitor 12 via the diode 14 and used as the power supply voltage of the control unit 8 and the booster circuit 11. Thereby, it is not necessary to separately prepare a power source for starting up the booster circuit 11.

  Further, as shown in FIG. 5, the power supply voltage supplied to the control unit 8 (that is, the output voltage Vo of the capacitor 12) is the minimum operating voltage of the control unit 8 (operation necessary for the control unit 8 to operate normally). When the control unit 8 is not operating (not operating normally), the switch 3 is turned off, the switch 4 is turned on, and the power generating elements 1 and 2 are connected in series. Has been.

  In order to realize this, a switch that turns off when the control signal is low level may be used as the switch 3, and a switch that turns on when the control signal is low level may be used as the switch 4. This is because when the control unit 8 is not operating, the control signals supplied to the switches 3 and 4 are both at a low level. Further, when a MOS transistor is employed as the switch 4, a depletion type MOS transistor in which the drain and the source are conducted even when there is no potential between the gate and the source because the drain and the source are conducted when the gate voltage is at a low level. Should be adopted.

  The individual power generation voltages of the power generation element 1 and the like are often low, and when the power generation elements 1 and 2 are connected in parallel at the time of startup or the like, the unit output voltage Vu is supplied via the diode 14 as the power supply voltage of the booster circuit 11 In many cases, however, the booster circuit 11 cannot be started. For example, when the power generation voltage of the power generation elements 1 and 2 is 0.5V, the booster circuit 11 having the minimum operating voltage of 0.7V cannot be activated.

  However, in the present embodiment, when the power supply voltage supplied to the control unit 8 is smaller than the minimum operation voltage of the control unit 8 and the control unit 8 is not operating, the connection method of the power generating elements 1 and 2 is a series connection. Therefore, a unit output voltage Vu larger than that in the parallel connection can be obtained at the time of startup or the like, and the booster circuit 11 and the control unit 8 can be started more reliably. For example, when the power generation voltage of the power generation elements 1 and 2 is 0.5 V, the unit output voltage Vu = 1.0 V is supplied as the power supply voltage to the booster circuit 11 having the minimum operating voltage of 0.7 V via the diode 14. Thus, the booster circuit 11 can be started (however, the voltage drop in the diode 14 is ignored).

  Further, when the power supply voltage of the control unit 8 is equal to or higher than the minimum operating voltage of the control unit 8, the control unit 8 can perform an operation of controlling the switches 3 and 4, and therefore the control The unit 8 switches the connection method of the power generation element 1 and the power generation element 2 as necessary.

  Instead of providing the diode 14, a power source (not shown) such as a battery is connected in parallel with the capacitor 12, and the output voltage Vo of the capacitor 12 is supplied to the control unit 8 and the booster circuit 11 when the control unit 8 and the booster circuit 11 are started. Alternatively, a method of holding the voltage at the minimum operating voltage or higher may be employed.

(Figure 6: Connection switching operation)
Next, switching control of the connection method of the power generating elements 1 and 2 by the control unit 8 will be described in more detail with reference to FIG. In FIG. 6, a curve L1 represents a voltage waveform of the unit output voltage Vu, and a curve L2 represents a voltage waveform of the output voltage Vo of the capacitor 12. In the following description, the minimum operating voltages of the control unit 8 and the booster circuit 11 are both 0.7 V, and the voltage drop in the diode 14 is ignored for the sake of simplicity of description.

  At timing t0, both the unit output voltage Vu and the output voltage Vo are 0V, and neither the control unit 8 nor the booster circuit 11 is operating. At timing t1, light is applied to each of the power generation elements 1 and 2 formed of solar cells, and the respective power generation voltages rise from 0 V. At timing t2, the unit output voltage Vu is the lowest operation of the control unit 8 and the booster circuit 11. Assume that the voltage reaches 0.7V.

  During the period from timing t0 to immediately before timing t2, the unit output voltage Vu is less than 0.7V, so the control unit 8 is not operating, and the connecting method of the power generating elements 1 and 2 is serial as shown in FIG. In addition to being connected, the unit output voltage Vu and the output voltage Vo match (because the voltage drop at the diode 14 is ignored).

  When the output voltage Vo reaches 0.7 V at timing t2, the booster circuit 11 starts to start the boosting operation, and thus the output voltage Vo starts to rise. When the output voltage Vo reaches the threshold voltage Vth1 (Vth1> 0.7V) at the timing t3, the control unit 8 switches the connection method of the power generating elements 1 and 2 from the conventional serial connection to the parallel connection. As a result, the unit output voltage Vu decreases (for example, decreases from 0.8 V to half of 0.4 V). After timing t3, the output voltage Vo is stabilized (for example, 5 V) with the voltage set by the booster circuit 11. Further, when the amount of power generated by the generated voltages 1 and 2 decreases so that the output voltage Vo cannot be stabilized, the output voltage Vo also decreases, and when the output voltage Vo falls below the threshold voltage Vth1 at timing t4. The connecting method of the power generating elements 1 and 2 is switched from the parallel connection to the series connection by the control unit 8.

  In order to realize the operation of FIG. 6, a voltage detection unit (not shown) that detects the voltage value of the output voltage Vo and gives the detection result to the control unit 8 may be provided.

  As described in the background art, when the power generating elements 1 and 2 are fixed in parallel connection, there is a merit that high-efficiency power storage is possible, but the unit output voltage Vu is reduced (for example, 0.5 V). Therefore, there is a demerit that the booster circuit 11 cannot be started with the voltage. On the other hand, when the power generating elements 1 and 2 are fixed in series, the unit output voltage Vu becomes high (for example, about 1 V), so that there is a merit that the booster circuit 11 can be started with the voltage, but the high efficiency of power storage There is a demerit that it is difficult.

  However, in the power supply circuit according to the present embodiment, the booster circuit 11 operates during the period from the timing t0 to t2 when starting, that is, the power supply voltage supplied to the booster circuit 11 is lower than the lowest operating voltage of the booster circuit 11. During this period, the connection methods of the power generating elements 1 and 2 are connected in series, and the unit output voltage Vu is temporarily supplied as the power supply voltages of the control unit 8 and the booster circuit 11 via the diode 14. The Since the unit output voltage Vu by the series connection is higher than that by the parallel connection, the booster circuit 11 can be started more reliably. In other words, it can be said that the power supply circuit according to the present embodiment does not have the disadvantage of the parallel connection that the unit output voltage is low and the booster circuit cannot be activated (in other words, enjoys the advantage of the series connection). ).

  When the output voltage Vo reaches a voltage sufficient to operate the control unit 8 and the booster circuit 11 (after timing t3 in FIG. 6), in other words, the boosted voltage of the booster circuit 11 is a predetermined threshold voltage. When Vth1 or higher, the connecting method of the power generating elements 1 and 2 is parallel connection. Thereby, the merit that the electric power generation elements 1 and 2 are parallel connection can be enjoyed. Once in this parallel connection state, even if most of the power generating elements 1 and 2 are covered with shadows and the power generation voltages of the power generating elements 1 and 2 are low (for example, 0.2 V), the booster circuit 11 The operation can be continued. That is, highly efficient power storage (power storage in the capacitor 12) is always possible regardless of the amount of light.

  Further, if this threshold voltage Vth1 is the same as the minimum operating voltage (0.7V) of the booster circuit 11, the merits of the power generating elements 1 and 2 being connected in parallel can be enjoyed to the maximum, resulting in higher efficiency. Power storage is realized.

  Furthermore, from the viewpoint of overvoltage protection for the control unit 8 and the booster circuit 11, the threshold voltage Vth1 may be set to be equal to or lower than the absolute maximum rated voltage of the power supply voltage of each of the control unit 8 and the booster circuit 11. When the connecting method of the power generating elements 1 and 2 is a serial connection, the unit output voltage Vu becomes a relatively high voltage, and when the voltage exceeds the absolute maximum rated voltage of each of the control unit 8 and the booster circuit 11, the control unit 8 Or the booster circuit 11 is damaged or deteriorated. However, if the threshold voltage Vth1 is set to be equal to or lower than the absolute maximum rated voltage of the power supply voltage of the control unit 8 and the booster circuit 11, the unit output voltage Vu in the case where the connection method of the power generating elements 1 and 2 is connected in series. However, since the series connection is switched to the parallel connection before the absolute maximum rated voltage is exceeded, overvoltage protection of the control unit 8 and the booster circuit 11 is achieved.

(Modification example of switching from series to parallel)
Further, when the condition that the output voltage Vo reaches the threshold voltage Vth1 (Vth1> 0.7V) is satisfied, the control unit 8 switches the connection method of the power generating elements 1 and 2 from the conventional series connection to the parallel connection. As described (see timing t3 in FIG. 6), instead of this, the unit output voltage Vu when the connecting method of the power generating elements 1 and 2 is in series connection reaches the threshold voltage Vth2 (Vth2> 0.7V). When the condition is satisfied, the control unit 8 may change the connection method of the power generating elements 1 and 2 from the conventional serial connection to the parallel connection (see timing t3 in FIG. 6).

  Even if it deforms in this way, as in the embodiment that does not deform, it is possible to enjoy the merit of the power generating elements 1 and 2 being connected in parallel while reliably starting up the booster circuit 11, and the threshold voltage Vth2 Is set to be equal to or lower than the absolute maximum rated voltage of the power supply voltage of each of the control unit 8 and the booster circuit 11, the overvoltage protection of the control unit 8 and the booster circuit 11 can be achieved.

  If the threshold voltage Vth2 is the same as the minimum operating voltage (0.7V) of the booster circuit 11 (provided that the voltage drop of the diode 14 is 0V), the power generating elements 1 and 2 are connected in parallel. The maximum merit of this can be enjoyed, and more efficient power storage is realized.

  In order to realize the operation of the modified example, a voltage detection unit (not shown) that detects the voltage value of the unit output voltage Vu and gives the detection result to the control unit 8 may be provided.

<< Fourth Embodiment >>
Next, a fourth embodiment in which the present invention is applied to a power supply circuit will be described with reference to the drawings. FIG. 7 is a circuit configuration diagram of the power supply circuit according to the fourth embodiment. In FIG. 7, the same parts as those in FIG. 4 are denoted by the same reference numerals, and the operation and connection relationship thereof are the same as those in FIG.

  Only the difference between the power supply circuit in FIG. 7 and the power supply circuit in FIG. 4 will be described. In the power supply circuit in FIG. 7, power generation elements 21 and 22 and diodes 23 and 24 are newly provided. The power generation elements 21 and 22 are the same as the power generation elements 1 and 2, and the diodes 23 and 24 are the same as the diodes 5 and 6.

  The high voltage side of the power generation element 21 and the high voltage side of the power generation element 22 are connected to the anode of the diode 23 and the anode of the diode 24, respectively. The low voltage side of the power generation element 21 and the low voltage side of the power generation element 22 are Are commonly connected to the cathodes. The cathodes of the diodes 23 and 24 are commonly connected to the anode of the capacitor 7.

  The power generating elements 1 and 2 can be switched between a serial connection and a parallel connection using the switches 3 and 4, but the power generating elements 21 and 22 are connected in parallel to the power generating elements 1 and 2, respectively. It is fixed to become.

  Consider the power loss of the power supply circuit configured as described above. For example, when MOS transistors are used as the switches 3 and 4, and the on-resistance between the drain and source of the MOS transistors is 1Ω (ohms) and the generated current per power generating element is 0.3A, 1Ω per switch. A power loss of × 0.3A × 0.3A = 0.09W occurs. Accordingly, a switch is provided for switching the connecting method of the power generating elements 1, 2, 21, and 22 between series connection and parallel connection (that is, between the low voltage side of the power generating element 2 and the cathode of the capacitor 7, the power generating element 21). Between the low voltage side of the power generation element 2 and the cathode of the capacitor 7, between the low voltage side of the power generation element 2 and the high voltage side of the power generation element 21, and between the low voltage side of the power generation element 21 and the high voltage side of the power generation element 22, respectively. If the switches are connected in parallel, a power loss of 0.09W × 3 = 0.27W for three switches will occur.

  On the other hand, the power supply circuit of FIG. 7 is configured to switch the connection method of two of the four power generation elements, so that the power loss in the switch can be suppressed to 0.09 W for one switch. As a result, a significant increase in efficiency can be achieved. In addition, since the number of switches can be reduced, the power circuit can be reduced in size and cost.

  In addition, what is necessary is just to determine suitably according to a use condition and a use how many connection methods of a power generation element can be switched using a switch. For example, the number of power generating elements that can be switched may be the minimum number (for example, two) that can ensure the minimum operating voltage of the booster circuit 11 when the unit output voltage Vu when connected in series is the minimum. The number may be larger than the number (for example, three). If the number of power generation elements that can be switched is larger than the minimum number, the power loss in the switch increases, but the unit output voltage Vu when connected in series becomes higher. The booster circuit 11 can be activated even if the power generation voltage of each power generation element is lower.

<< Fifth Embodiment >>
Next, a fifth embodiment in which the present invention is applied to a power supply circuit will be described with reference to the drawings. FIG. 8 is a circuit configuration diagram of the power supply circuit according to the fifth embodiment.

  In FIG. 7, the same components as those in FIG. 4 are denoted by the same reference numerals, and detailed description thereof is omitted. That is, the power generation elements 1 and 2, the switches 3 and 4, the control unit 8, and the capacitor 12 are the same as those in FIG. 4, and the control unit 8 controls the on / off of the switches 3 and 4 to generate power. The operation of switching the connection method of the elements 1 and 2 to serial connection or parallel connection is the same as that in FIG.

  The generated voltage output from the high voltage side of the power generating element 1 is supplied as a boost target to the booster circuit 31. The booster circuit 31 boosts the generated voltage and outputs the boosted voltage. The output of the booster circuit 31 is connected to the anode of the diode 33. The generated voltage output from the high voltage side of the power generating element 2 is supplied to the booster circuit 32 as a boost target, and the booster circuit 32 boosts the generated voltage and outputs the boosted voltage. The output of the booster circuit 32 is connected to the anode of the diode 34. The cathodes of the diode 33 and the diode 34 are commonly connected to the anode of the capacitor 12, and the cathode of the capacitor 12 is connected to the low voltage side of the power generation element 2 and the low voltage side of the power generation element 1 via the switch 3. ing. The anode of the capacitor 12 is connected to the power supply voltage terminals of the booster circuits 31 and 32 and the control unit 8, and the output voltage Vo of the capacitor 12 is supplied to the booster circuits 31 and 32 and the control unit 8, respectively. Is supplied as a power supply voltage.

  The booster circuits 31 and 32 are the same as the booster circuit 11 in FIG. 4, and the diodes 33 and 34 are the same as the diodes 5 and 6 in FIG.

  In the present embodiment, as described above, a booster circuit is provided for each power generating element. The booster circuit 31 outputs the boosted voltage with the generated voltage of the power generating element 1 as a boost target, and boosts the generated voltage of the power generating element 2. As a target, the booster circuit 32 outputs a boosted voltage, and each boosted voltage is given to the capacitor 12 via the diodes 33 and 34, and the capacitor 12 is charged. The power supply voltages of the booster circuits 31 and 32 and the control unit 8 are supplied from the output voltage Vo, but are supplied from the high-voltage side voltage of the power generating element 1 or an external power supply (not shown). It doesn't matter.

  In comparison with the power supply circuit of FIG. 4, consider the efficiency of the power supply circuit of FIG. 8 in parallel mode. In the following discussion, the power generation elements 1 and 2 are assumed to be solar cells (single cells) in which the respective power generation voltages vary from 0.2 to 0.5 V depending on the amount of light, and the booster circuits 31 and 32 and the booster circuit 11 ( FIG. 4) assumes that each boost target is boosted and a stabilized boosted voltage 5V is output.

  If the power generation element 1 receives a large amount of light and the power generation voltage of the power generation element 1 is 0.5 V, and the power generation element 2 receives a small amount of light and the power generation voltage of the power generation element 2 is 0.2 V, then the power generation element 4 is lower than the power generation voltage (0.5 V) of the power generation element 1, the power supply circuit of FIG. 4 cannot charge the capacitor 7 with the power generation voltage of the power generation element 2 in the parallel mode. That is, the power generated by the power generation element 2 is wasted. For this reason, only the power generation element 1 contributes to power storage in the capacitor 12.

  On the other hand, in the power supply circuit of FIG. 8, the booster circuit 31 boosts the power generation voltage (0.5 V) of the power generation element 1 to 5 V, charges the capacitor 12 with the boosted voltage, and the booster circuit 32 generates the power generation of the power generation element 2. The voltage (0.2V) is boosted to 5V, and the capacitor 12 is charged with the boosted voltage. That is, regardless of the difference between the power generation voltages of the power generation elements 1 and 2, all the power generation elements contribute to the power storage of the capacitor 12, so that highly efficient power storage using the generated power to the maximum is realized.

<< Sixth Embodiment >>
Next, a sixth embodiment in which the present invention is applied to a power supply circuit will be described with reference to the drawings. FIG. 9 is a circuit configuration diagram of the power supply circuit according to the sixth embodiment.

  9, the same parts as those in FIG. 8 are denoted by the same reference numerals, and detailed description thereof is omitted. That is, the power generating elements 1 and 2, the switches 3 and 4, the booster circuits 31 and 32, and the diodes 33 and 34 are the same as those in FIG. 8, and their connection relation is the same as that in FIG. Omitted.

  The cathodes of the diodes 33 and 34 are connected in common and connected to one end of the switch 43 and one end of the switch 44, respectively. The anode of the capacitor 41 is connected to the other end of the switch 43, and the cathode is commonly connected to the low voltage side of the power generation element 2 and the cathode of the capacitor 42. The anode of the capacitor 42 is connected to the other end of the switch 44. Further, the output voltage Vo1 of the capacitor 41 (the voltage of the anode of the capacitor 41 and the voltage charged in the capacitor 41) is supplied to the booster circuits 31 and 32 and the control unit 45 as the respective power supply voltages. . In addition, the cathode of the diode 46 is connected to the output side of the power generation element 1, and the anode of the diode 46 is connected to the anode of the capacitor 41. The power supply voltage is supplied from.

  The control unit 45 supplies a control signal for controlling on / off to not only the switches 3 and 4 but also each of the switches 43 and 44, and turns on / off each of the switches 3 and 4. Control to switch the connecting method of the power generating elements 1 and 2 to serial connection or parallel connection is the same as that of the control unit 8 in FIGS. 4 and 8. Further, the capacitance (capacitance) of the capacitor 41 <the capacitance (capacitance) of the capacitor 42 is established, the capacitance of the capacitor 41 is relatively small, and the capacitance of the capacitor 42 is relatively large.

  Further, the power supply voltage supplied to the control unit 45 is smaller than the minimum operation voltage of the control unit 45 (the lower limit of the operation voltage necessary for the control unit 45 to operate normally), and the control unit 45 is not operating ( Switch 43 is on and switch 44 is off.

  In order to realize this, a switch that turns on when the control signal is low level as the switch 43 and a switch that turns off when the control signal is low level may be used as the switch 44. This is because when the control unit 45 is not operating, the control signals supplied to the switches 43 and 44 are both at a low level. Further, when a MOS transistor is employed as the switch 43, a depletion type MOS transistor in which the drain and the source are conducted even when there is no potential between the gate and the source because the drain and the source are conducted when the gate voltage is at a low level. Should be adopted.

  The capacitors 41 and 42 are, for example, electrolytic capacitors, electric double layer capacitors, and various batteries may be adopted. The capacitors 41 and 42 may be configured by combining capacitors of different types and characteristics.

  The operation of the power supply circuit configured as described above will be described with reference to FIG. At timing t5, the output voltage Vo1 of the capacitor 41 and the output voltage Vo2 of the capacitor 42 (the voltage of the anode of the capacitor 42 and the voltage charged in the capacitor 42) are both 0 V, and the booster circuits 31, 32, and None of the control units 45 are operating. Therefore, the switch 43 is on and the switch 44 is off.

  At timing t6, light is irradiated to each of the power generation elements 1 and 2 formed of solar cells, and the respective power generation voltages rise from 0 V, the capacitor 12 is charged via the diode 46, and the power generation elements 1 and 2 The total generated voltage due to the series connection is supplied to the booster circuits 31 and 32 and the power supply voltage terminal of the control unit 45. When the total generated voltage reaches the minimum operating voltage, the booster circuits 31 and 32 and the control unit 45 are activated.

  Thereafter, the output voltage Vo1 is increased by the boosted voltage output from each of the booster circuits 31 and 32, and the output voltage Vo1 of the small-capacitance capacitor 41 is set to a predetermined threshold voltage Vth3 (threshold voltage Vth3 is the booster circuit) at timing t7. 31 and 32 and higher than the minimum operating voltage of the control unit 45), the control unit 45 turns off the switch 43 and turns on the switch 44. As a result, the power generated by the power generating elements 1 and 2 is charged into the large-capacitance capacitor 42 while the supply of the power supply is maintained for each of the booster circuits 31 and 32 and the control unit 45.

  The output voltage Vo1 drops due to power consumption by the booster circuit 31 and the like, and at the timing t8, the output voltage Vo1 becomes a predetermined threshold voltage Vth4 (the threshold voltage Vth4 is the lowest value of each of the booster circuits 31, 32 and the control unit 45). When the voltage reaches a value higher than the operating voltage, the control unit 45 turns on the switch 43 and turns off the switch 44 so that the small-capacitance capacitor 41 is charged again. When the output voltage Vo1 reaches the threshold voltage Vth3 at timing 9, the control unit 45 turns off the switch 43 and turns on the switch 44. Thereafter, the operations at timings t7 to t9 are repeated.

  As described above, a small-capacitance capacitor 41 (first power storage means) is connected to the output side of each of the booster circuits 31 and 32 via a switch 43, and a large-capacity capacitor via a switch 44 (switch means). A capacitor 42 (second power storage means) is connected in parallel with the capacitor 41, and when the capacitor 41 is charged, if the voltage charged in the capacitor 41 is lower than the threshold voltage Vth3 (period t6 to t7), the switch 44 is turned off to prohibit charging of the large-capacity capacitor 42 and only the small-capacitance capacitor 41 is charged. Since the capacitor 41 has a small capacity, even if the power generated by the power generating elements 1 and 2 is small, the output voltage Vo1 of the capacitor 41, that is, the power supply voltages of the booster circuits 31 and 32 and the control unit 45 are short. The operation of the entire power supply circuit can be started quickly.

  Further, the voltage output to the load (not shown) by the power supply circuit of FIG. 9 corresponds to the output voltage Vo2 of the capacitor 42. However, since the capacitor 42 has a large capacity, the generated power temporarily decreases. However, a stable voltage can be supplied to the load (not shown).

  If both the switches 43 and 44 are simultaneously turned on at the timing t7, the charge accumulated in the small-capacitance capacitor 41 flows out to the large-capacity capacitor 42 at a stretch, and the output voltage Vo1 of the capacitor 41 greatly decreases. In addition, the operation of the entire power supply circuit may be stopped. In order to avoid this, at timing t7, the switch 44 is turned on after the switch 43 is turned off.

  In order to realize the operation of the present embodiment, a voltage detection unit (not shown) that detects the voltage value of the output voltage Vo1 and gives the detection result to the control unit 8 may be provided. Moreover, this embodiment can be freely combined with the other embodiments described above. For example, when this embodiment is applied to the circuit configuration of FIG. 4, the circuit configuration is as shown in FIG.

  11, the same components as those in FIGS. 4 and 9 are denoted by the same reference numerals, and detailed description thereof is omitted. In FIG. 11, a terminal from which the boosted voltage of the booster circuit 11 is output is commonly connected to one end of the switch 43 and one end of the switch 44. The other end of the switch 43 is connected to the anode of the capacitor 41, and the other end of the switch 44 is connected to the anode of the capacitor 42. The cathodes of the capacitors 41 and 42 are connected in common and connected to the output terminal on the low voltage side of the booster circuit 11. That is, the boosted voltage output from the booster circuit 11 is supplied to the capacitor 41 via the switch 43 and also supplied to the capacitor 42 via the switch 44. Further, the output voltage Vo1 of the capacitor 41 is supplied as a power supply voltage to each of the booster circuit 11 and the control unit 45. When the output voltage Vo1 is lower than the unit output voltage Vu, the unit output voltage Vu is supplied via the diode 46. The capacitor 41 is charged. And the control part 45 controls on / off of the switches 43 and 44 according to the output voltage Vo1 similarly to what is shown in FIG.9 and FIG.10.

<< Other, deformation, etc. >>
Moreover, all the above-described embodiments may be combined with each other as long as no contradiction occurs. Further, although the case where the unit output voltage Vu is positive is illustrated, the circuit configuration may be modified to be negative. Moreover, although the case where the output voltages Vo, Vo1, and Vo2 are positive is illustrated, the circuit configuration may be modified so as to be negative.

  The present invention is suitable as a power supply circuit that efficiently charges an electric storage element represented by a battery or a capacitor. Further, the present invention is suitable for various electric devices (electronic devices) including a power supply circuit, such as a digital camera, a digital video camera, a mobile phone, a personal computer, and a solar power generation device.

1 is a circuit diagram of a power supply circuit according to a first embodiment of the present invention. It is a modification of the power supply circuit in FIG. It is a circuit diagram of the power supply circuit which concerns on 2nd Embodiment of this invention. It is a circuit diagram of the power supply circuit which concerns on 3rd Embodiment of this invention. It is a figure for demonstrating the state of the switch of FIG. It is a figure for demonstrating the state of the switch of FIG. It is a circuit diagram of the power supply circuit which concerns on 4th Embodiment of this invention. It is a circuit diagram of the power supply circuit which concerns on 5th Embodiment of this invention. It is a circuit diagram of the power supply circuit which concerns on 6th Embodiment of this invention. It is a figure for demonstrating the charge condition of the capacitor | condenser of FIG. It is a circuit diagram of the power supply circuit which combined 6th Embodiment and 3rd Embodiment. It is a circuit diagram of the conventional power supply circuit. It is a circuit diagram of the conventional power supply circuit.

Explanation of symbols

1, 2, 21, 22 Power generation element 3, 4 Switch (switching means)
3a, 4a MOS transistor 5, 6, 23, 24, 33, 34 Diode 7 Capacitor 8, 45 Control unit (control means)
9, 13 Power supply 10 Load 11, 31, 32 Booster circuit (boosting means)
14 Diode 12 Capacitor (first power storage means)
41 Capacitor (first power storage means)
42 Capacitor (second power storage means)
43 switch 44 switch (switch means)

Claims (10)

a power generation unit composed of n power generation elements (n is an integer of 2 or more) and outputting a unit output voltage;
Switching means capable of switching the connection method of at least two power generating elements to either serial connection or parallel connection;
A power supply circuit comprising control means for controlling switching of the connection method by the switching means. Boosting means for boosting the unit output voltage and outputting the boosted voltage to the first power storage means;
The power supply circuit according to claim 1, wherein the power supply voltage of the boosting means is supplied from the first power storage means. When the power supply voltage supplied to the booster is smaller than the minimum operating voltage of the booster and the booster is not operating, the connection method is connected in series and the unit output voltage The power supply circuit according to claim 2, wherein is temporarily supplied to the first power storage unit. 2. The connection method is a serial connection when the power supply voltage supplied to the control means is smaller than the minimum operating voltage of the control means and the control means is not operating. The power supply circuit according to claim 3. 4. The power supply circuit according to claim 2, wherein when the magnitude of the output voltage of the first power storage unit is equal to or greater than a predetermined threshold, the connection method is connected in parallel by the control unit. 5. . The connection method is switched from a serial connection to a parallel connection by the control means when the magnitude of the unit output voltage when the connection method is a serial connection becomes a predetermined threshold value or more. The power supply circuit according to claim 1. The switching means switches a connection method of m (m <n) power generation elements among the n power generation elements, and (n−m) number excluding the m power generation elements. 2. The power supply circuit according to claim 1, wherein each of the power generation elements is connected in parallel to each of the m power generation elements. n power generation elements (n is an integer of 2 or more);
Switching means capable of switching the connection method of at least two power generating elements to either serial connection or parallel connection;
Control means for controlling switching of the connection method by the switching means;
A power supply circuit comprising boosting means for boosting the power generation voltages output from the n power generation elements, respectively, and outputting the boosted voltages to the first power storage means. On the output side of the boosting means, a second power storage means having a larger capacity than the first power storage means is connected in parallel with the first power storage means via the switch means,
When charging the first power storage means, if the magnitude of the voltage charged in the first power storage means is smaller than a predetermined threshold, the switch means is shut off to prohibit charging to the second power storage means. The power supply circuit according to claim 2, 3, or 8.   An electric device comprising the power supply circuit according to any one of claims 1 to 9.

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