Power supply device, boost circuit control device, and boost circuit output evaluation device

Abstract

To increase the output power.SOLUTION: A power source device 1 includes a power generation element 2, a booster circuit 3 that receives input power Pin and outputs output power Pout that is obtained by boosting input voltage Vin to output voltage Vout higher than the input voltage Vin, and a controller 5 that outputs a control signal φ to the booster circuit 3. The booster circuit 3 includes a first capacitor part 31a and a second capacitor part 31b. The controller 5 includes a first control signal φ1 including a charging operation to the first capacitor part 31a and a charging operation to the second capacitor part 31b that is performed after a first charging operation, and a second control signal φ2 including a charging operation to a first synthesis capacitor part 31s formed by the first capacitor part 31a and the second capacitor part 31b. The controller 5 outputs one of the first control signal φ1 and the second control signal φ2 to the booster circuit 3 in accordance with the state of the input power Pin.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a power supply device, a control device for a boost circuit, and an output evaluation device for a boost circuit. [Background technology]

[0002] Technologies that utilize previously unused environmental energy such as vibration and heat are attracting attention. Such technologies are called energy harvesting. Energy harvesting is attracting attention as a power supply technology to be applied to sensors for the so-called IoT (Internet of Things). For example, sensors that use energy harvesting technology are powered by energy recovered from vibration and heat present in the environment in which the device is installed. Patent documents 1 to 3 are known as technologies related to energy harvesting. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2011-172377 A [Patent Document 2] Patent No. 534052 [Patent Document 3] Patent No. 588008 Summary of the Invention [Problem to be solved by the invention]

[0004] For example, one of the devices that supports energy harvesting technology is a thermoelectric generator that converts thermal energy into electricity. The power output by the thermoelectric generator using heat from the surrounding environment is very weak. The power output by the thermoelectric generator is smaller than the power required by the load device such as a sensor or a communication IC. Therefore, a device is needed that converts the power output by the thermoelectric generator into the power required by the load device. An example of a power conversion device is a charge pump circuit. A charge pump circuit repeatedly accumulates the input power in a capacitor to increase the voltage. In the field of energy harvesting technology, it is desirable to further increase the power output from the charge pump circuit.

[0005] An object of the present invention is to provide a power supply device capable of increasing output power, a control device for a boost circuit, and an output evaluation device for a boost circuit. [Means for solving the problem]

[0006] One aspect of the present invention is a power supply device that supplies power based on a required voltage required by a load device. The power supply device includes a power generation unit that receives external energy and generates power, a boost unit that receives the power generated by the power generation unit as input power and outputs output power by boosting the input voltage of the input power to an output voltage higher than the input voltage, and a control unit that outputs a first control signal or a second control signal to the boost unit. The boost unit has a plurality of capacitance units including a first capacitance unit and a second capacitance unit. The control unit has a first control signal that converts the input power to output power, including a first charging operation to the first capacitance unit and a charging operation to the second capacitance unit executed after the first charging operation, and a second control signal that converts the input power to output power, including a charging operation to a composite capacitance unit formed by the first capacitance unit and the second capacitance unit. The control unit outputs either the first control signal or the second control signal to the boost unit depending on a state of the input power.

[0007] The output characteristics of the boost unit are affected by the input power input from the power generation unit. The power supply device switches the mode of boost operation in the boost unit depending on the state of the input power. As a result, the boost unit can have a circuit configuration according to the input power, thereby increasing the output power.

[0008] In one embodiment, in an operation of converting input power into output power, the product of the number of charging operations and the size of the capacitance section in each charging operation may be constant between the operation based on the first control signal and the operation based on the second control signal. With this configuration, it is possible to reliably improve the output power.

[0009] The power supply device of one embodiment may further include an output evaluation unit that acquires operation status data indicating an operation status of the boost unit and acquires operation evaluation data that evaluates the operation status of the boost unit in the state indicated by the operation status data. The control unit may output either a first control signal or a second control signal to the boost unit according to the operation evaluation data. With this configuration, it is possible to evaluate the output power. Therefore, while switching the circuit configuration of the boost unit, it is possible to acquire operation evaluation data and evaluate the output characteristics of the boost unit using the acquired operation evaluation data. Therefore, it is possible to determine the circuit configuration of the boost unit that can maximize the output power.

[0010] The boost unit of the power supply device of one embodiment may further include a drive signal generating unit that generates a drive signal that controls a charging operation to the first capacitance unit, a charging operation to the second capacitance unit, and a charging operation to the composite capacitance unit. The drive signal may include a charging operation component that executes a charging operation to the first capacitance unit, a charging operation to the second capacitance unit, and a charging operation to the composite capacitance unit. The output evaluation unit may include a drive signal acquiring unit that acquires the drive signal as the operation state data, and a counting unit that counts the number of charging operation components per unit time included in the drive signal that is the operation state data, and acquires the number of charging operation components as operation evaluation data. With this configuration, the operation evaluation data can be obtained.

[0011] The output evaluation unit of the power supply device of one embodiment may include a measured load generating unit that generates a measured load current for the boost unit, a voltage comparing unit that obtains an output voltage when the measured load current is received as operation state data and compares the output voltage with a required voltage, and a determining unit that obtains a measured load current at which the output voltage is lower than the required voltage as operation evaluation data. With this configuration, the operation evaluation data can also be obtained.

[0012] The power supply device according to one embodiment may further include an input evaluation unit that acquires an input voltage corresponding to a state of the input power. The control unit may output one of a first control signal and a second control signal to the boost unit according to the input voltage. With this configuration, it is possible to output one of the first control signal and the second control signal to the boost unit directly from the input voltage without requiring a repetitive operation.

[0013] Another aspect of the present invention is a control device for a boost circuit that receives power as input power from a power generation unit that receives external energy and generates power, outputs output power by boosting the input voltage of the input power to an output voltage higher than the input voltage, and has a plurality of capacitance units including a first capacitance unit and a second capacitance unit. The control device for the boost circuit includes a control unit that outputs a first control signal or a second control signal to the boost circuit, and an output evaluation unit that acquires operation state data indicating an operation state of the boost circuit and obtains operation evaluation data for evaluating the operation state of the boost circuit in the state indicated by the operation state data. The control unit has a first control signal that converts the input power into output power, including a first charging operation to the first capacitance unit and a charging operation to the second capacitance unit executed after the first charging operation, and a second control signal that converts the input power into output power, including a charging operation to a composite capacitance unit formed by the first capacitance unit and the second capacitance unit. The control unit outputs either the first control signal or the second control signal to the boost circuit depending on the state of the input power.

[0014] According to this control device for a boost circuit, the output power of the boost circuit can be increased.

[0015] Yet another embodiment of the present invention is a control device for a boost circuit that receives electric power as input power from a power generation unit that receives external energy and generates electric power, outputs output power by boosting an input voltage of the input power to an output voltage higher than the input voltage, and has a plurality of capacitive units including a first capacitive unit and a second capacitive unit. The control device for the boost circuit includes a control unit that outputs a first control signal or a second control signal to the boost circuit, and an input evaluation unit that obtains an input voltage according to a state of the input power. The control unit outputs either the first control signal or the second control signal to the boost circuit according to the input voltage.

[0016] This boost circuit control device also makes it possible to increase the output power of the boost circuit.

[0017] Yet another aspect of the present invention is an output evaluation device for a boost circuit that evaluates the output of a boost circuit that outputs an output power obtained by boosting an input voltage of an input power to an output voltage higher than the input voltage. The output evaluation device for a boost circuit includes a drive signal acquisition unit that acquires from the boost circuit a drive signal including a charging operation component that causes a plurality of capacitance units in the boost circuit to perform a charging operation, and a counting unit that counts the number of charging operation components per unit time included in the drive signal and acquires the number of charging operation components as operation evaluation data for evaluating the output of the boost circuit.

[0018] According to this boost circuit output evaluation device, the suitability of the boost circuit for the input power can be evaluated.

[0019] Yet another aspect of the present invention is an output evaluation device for a boost circuit that evaluates the output of a boost circuit that outputs output power obtained by boosting an input voltage of an input power to an output voltage higher than the input voltage. The output evaluation device for a boost circuit includes a measurement load generating unit that generates a measurement load current for the boost circuit, a voltage comparing unit that obtains an output voltage when the measurement load current is received and compares the output voltage with a required voltage required by a load device that receives the output voltage, and a determining unit that obtains a measurement load current at which the output voltage is lower than the required voltage as operation evaluation data for evaluating the output of the boost circuit.

[0020] This boost circuit output evaluation device can also be used to evaluate the suitability of a boost circuit for an input power. Effect of the Invention

[0021] According to the power supply device, the control device for a boost circuit, and the output evaluation device for a boost circuit of the present invention, it is possible to increase the output power. [Brief description of the drawings]

[0022] [Figure 1] FIG. 1 is a functional block diagram showing the configuration of a power supply device according to a first embodiment. [Diagram 2] Fig. 2(a) is a diagram illustrating a first connection configuration of the capacitive section, and Fig. 2(b) is a diagram illustrating a second connection configuration of the capacitive section. [Diagram 3] FIG. 3 is a flowchart showing the operation of the power supply device. [Figure 4] FIG. 4 is a functional block diagram showing the configuration of a power supply device according to the second embodiment. [Diagram 5] FIG. 5 is a diagram illustrating an example of a circuit configuration of an output power monitor device. [Figure 6] FIG. 6 is a diagram for explaining a process for obtaining the maximum load current in the output power monitor device. [Figure 7] FIG. 7 is a functional block diagram showing the configuration of a power supply device according to the third embodiment. [Figure 8] FIG. 8 is a diagram illustrating a circuit configuration of a power supply device according to the embodiment. [Figure 9] Fig. 9(a) is a diagram showing an example of a connection configuration, and Fig. 9(b) is a diagram showing an equivalent circuit of Fig. 9(a). [Figure 10] Fig. 10(a) is a diagram showing another example of a connection configuration, and Fig. 10(b) is a diagram showing an equivalent circuit of Fig. 10(a). [Figure 11]Fig. 11(a) is a contour diagram showing the relationship between the number of steps and unit capacitance when the open circuit voltage is 0.5 V in Study Example 1. Fig. 11(b) is a contour diagram showing the relationship between the number of steps and unit capacitance when the open circuit voltage is 0.7 V in Study Example 1. [Figure 12] Fig. 12(a) is a contour diagram showing the relationship between the number of steps and unit capacitance when the open circuit voltage is 1.0 V in Study Example 1. Fig. 12(b) is a contour diagram showing the relationship between the number of steps and unit capacitance when the open circuit voltage is 1.5 V in Study Example 1. [Figure 13] FIG. 13 is a graph showing the relationship between the open-circuit voltage and the number of stages, and the relationship between the open-circuit voltage and the unit capacity in Study Example 2. [Figure 14] FIG. 14 is a graph comparing the output characteristics of a boost circuit that controls the circuit configuration in Study Example 3 and a power supply device of a comparative example in which the configuration of the boost circuit is unchanged. [Figure 15] FIG. 15 is a diagram for explaining a computer that constitutes the output power monitor device and the controller. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] Hereinafter, examples of a power supply device, a control device for a boost circuit, and an output evaluation device for a boost circuit will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same elements are given the same reference numerals. In the description of the drawings, duplicated descriptions will be omitted.

[0024] As shown in FIG. 1, the power supply device 1 generates power by using external energy. The power supply device 1 supplies power to a load device 200. For example, assume that the power supply device 1 generates power by using thermal energy, and the load device 200 is a communication device. With this configuration, the power supply device 1 and the load device 200 function as a fire alarm. When the temperature of the power supply device 1 rises due to a fire, the power supply device 1 starts generating power. When the power output from the power supply device 1 reaches an amount sufficient for the operation of the communication device, which is the load device 200, the communication device outputs a signal indicating that a fire has occurred to the outside. In other words, the fire alarm constituted by the power supply device 1 and the load device 200 can notify the occurrence of a fire without receiving power from an outside source. In addition, the fire alarm does not need to have its own battery.

[0025] Note that the explanation of the power supply device 1 and the load device 200 constituting a fire alarm is merely an example. The external energy used by the power supply device 1 is not limited to thermal energy. The external energy used by the power supply device 1 may be mechanical energy such as vibration. Furthermore, the load device 200 is not limited to a communication device. The load device 200 may be a measuring device that measures the state of the surrounding environment.

[0026] The power supply device 1 has a power generating element 2 (power generating section), a boost circuit 3 (boosting section), an output power monitor device 4 (output evaluation section), and a controller 5 (control section). A load device 200 is not included in the components of the power supply device 1. The output power monitor device 4 and the controller 5 constitute a control device 6 of the boost circuit 3. In addition, the output power monitor device 4 is an output evaluation device for the boost circuit 3.

[0027] The power generating element 2 receives external energy and converts the external energy into electrical energy. The power generating element 2 may be any of various elements capable of receiving external energy and generating electrical energy.

[0028] Examples of power generating elements for DC voltage include solar cells that utilize solar energy and thermoelectric conversion elements that utilize bias in electric charge due to temperature difference, while examples of power generating elements for AC voltage include piezoelectric elements that utilize disturbance in dipole moment due to vibration, vibration elements that utilize electromagnetic induction voltage, pyroelectric elements that utilize the pyroelectric effect, RF elements that generate power by receiving radio waves, etc. If the power generating element 2 outputs an AC voltage, a device (converter) that converts the AC voltage into a DC voltage may be provided between the power generating element 2 and the boost circuit 3.

[0029] In particular, thermoelectric conversion elements are expected to have a wider range of applications in the future, since they use thermal energy, which is the most common form of energy. Materials used in thermoelectric conversion elements include inorganic semiconductors and organic conductive polymers. Elements using carbon nanotubes (CNTs) are flexible and lightweight. Furthermore, elements using carbon nanotubes (CNTs) are thin-film elements. Therefore, by adopting an element using carbon nanotubes (CNTs) as the power generation element 2, it is possible to realize a structure that can increase the temperature difference more than other materials in the same environment. As a result, the environments in which the power generation element 2 can be installed are greatly expanded. Therefore, the range of applications can be expanded.

[0030] As the carbon nanotube (CNT), a single-walled carbon nanotube (single-walled CNT) and a multi-walled carbon nanotube (multi-walled CNT) can be used. As the carbon nanotube (CNT), it is preferable to use a single-walled CNT. As the CNT, a single-walled CNT or a multi-walled CNT may be used alone. The CNTs may be used in a mixture. When used in a mixture, the content ratio of the single-walled CNT is preferably 50 mass% or more. Furthermore, the content ratio of the single-walled CNT is more preferably 70 mass% or more. Furthermore, the content ratio of the single-walled CNT is preferably 90 mass% or more. The average diameter of the single-walled CNT is 0.7 nm or more and 15 nm or less. The single-walled CNT preferably has a ratio of the G band peak intensity to the D band peak intensity in the Raman spectrum (G / D ratio) of 1 to 20. The single-walled CNT preferably has an average length of 100 μm or more of the fibrous carbon nanostructure during synthesis. The BET specific surface area of ​​the single-walled CNT is 600 m 2 / g or more. The BET specific surface area is preferably 800 m 2 / g or more. The BET specific surface area is preferably 2500 m 2 / g or less. The BET specific surface area is preferably 1200 m 2 It is more preferable that the molecular weight is not more than 1 / g.

[0031] For example, the super growth method (see International Publication No. 2006 / 011655) may be used to manufacture single-walled CNTs. The super growth method dramatically improves the catalytic activity of the catalyst layer. For example, a raw material compound and a carrier gas are supplied onto a substrate having a catalyst layer for manufacturing carbon nanotubes on its surface. That is, when synthesizing CNTs by chemical vapor deposition (CVD), a small amount of oxidizing agent (catalyst activation material) is made to exist in the system. According to this method, the formation of the catalyst layer on the substrate surface is performed by a wet process, so that it can be manufactured efficiently. In the following, carbon nanotubes obtained by the super growth method may be referred to as "SGCNTs". SGCNTs (Super Growth Carbon nanotubes) have a higher purity than other CNTs. Furthermore, SGCNTs have a high power generation capacity (Seebeck coefficient) due to the high doping effect. Therefore, SGCNTs are highly suitable as thermoelectric conversion elements. SGCNTs are characterized by low cost and high material purity. Furthermore, SGCNTs have the characteristic of being easy to dope.

[0032] The boost circuit 3 receives the power generated by the power generating element 2 as input power Pin. The boost circuit 3 boosts the input voltage Vin of the input power Pin to an output voltage Vout higher than the input voltage Vin. The boost circuit 3 then outputs an output power Pout based on the output voltage Vout.

[0033] The boost circuit 3 is a so-called charge pump. The boost circuit 3 has a first capacitance section 31a, a second capacitance section 31b, a third capacitance section 31c, and a fourth capacitance section 31d. The first capacitance section 31a, the second capacitance section 31b, the third capacitance section 31c, and the fourth capacitance section 31d can be switched in connection configuration by a switch circuit 32. For example, when the boost circuit 3 has the first capacitance section 31a, the second capacitance section 31b, the third capacitance section 31c, and the fourth capacitance section 31d, the boost circuit 3 can have a first connection configuration shown in FIG. 2(a) and a second connection configuration shown in FIG. 2(b). The first connection configuration and the second connection configuration can be mutually switched by the operation of the switch circuit 32. The switch circuit 32 switches the connection configuration according to a control signal φ output by the controller 5.

[0034] The first connection configuration shown in FIG. 2(a) is a configuration in which the first capacitance section 31a, the second capacitance section 31b, the third capacitance section 31c, and the fourth capacitance section 31d are connected in series. First, the input voltage Vin is charged to the first capacitance section 31a. Next, the first boost voltage obtained by adding the input voltage Vin and the voltage charged to the first capacitance section 31a is charged to the second capacitance section 31b. Next, the second boost voltage obtained by adding the input voltage Vin and the first boost voltage is charged to the third capacitance section 31c. Each time such a charging operation is repeated, the voltage increases. Then, the number of charging operations performed in the boost operation while the boost circuit 3 boosts the input voltage Vin to the output voltage Vout is represented as the "number of stages". In other words, the "number of stages" in the first connection configuration is the number of capacitance sections used in the boost operation while the boost circuit 3 boosts the input voltage Vin to the output voltage Vout. That is, in the first connection configuration, the charging operation to the first capacitance section 31a, the charging operation to the second capacitance section 31b, the charging operation to the third capacitance section 31c, and the charging operation to the fourth capacitance section 31d are performed in this order. Therefore, the number of stages N of the first connection configuration is 4.

[0035] In the second connection configuration, the first combined capacitance section 31s and the second combined capacitance section 31k are connected in series. The first combined capacitance section 31s is a parallel connection of the first capacitance section 31a and the second capacitance section 31b. The second combined capacitance section 31k is a parallel connection of the third capacitance section 31c and the fourth capacitance section 31d. In the second connection configuration, the first combined capacitance section 31s is first charged with the input voltage Vin. Next, the second combined capacitance section 31k is charged with a first boost voltage obtained by adding the input voltage Vin and the voltage applied to the first combined capacitance section 31s. That is, in the second connection configuration, the number of charging operations performed in the boost operation while boosting the input voltage Vin to the output voltage Vout is two. In other words, in the second connection configuration, the first combined capacitance section 31s and the second combined capacitance section 31k are used while boosting the input voltage Vin to the output voltage Vout. In other words, the number of capacitive sections is substantially 2. Therefore, the number of stages N of the second connection configuration is 2.

[0036] As described above, the number of capacitance sections constituting the "number of stages" does not necessarily mean the number of the first capacitance section 31a, the second capacitance section 31b, the third capacitance section 31c, and the fourth capacitance section 31d in the boost circuit 3. Depending on the connection configuration, one capacitance section may constitute one stage, or multiple (e.g., two) capacitance sections may constitute one stage.

[0037] Here, the capacitances of the first capacitance section 31a, the second capacitance section 31b, the third capacitance section 31c, and the fourth capacitance section 31d are the same. The above-mentioned "number of stages" is denoted as N. Furthermore, the capacitance per stage is denoted as "C". Then, the product of the number of stages N and the unit capacitance C is preserved between the first connection configuration and the second connection configuration. In other words, even if the connection configuration of the multiple capacitance sections is switched in the boost circuit 3, the product of the number of stages N and the unit capacitance C is constant. For example, in the first connection configuration, it is assumed that there are four stages (N=4), and the unit capacitance C, which is the capacitance per stage, is 1 (C=1). In this case, the product is 4. And, in the second connection configuration, it is assumed that there are two stages (N=2), and the unit capacitance C, which is the capacitance per stage, is 2 (C=2). When the first capacitance section 31a having a capacitance of 1 and the second capacitance section 31b having a capacitance of 1 are connected in parallel, the capacitance of the first combined capacitance section 31s is 2. Therefore, the product is also 4 in the second connection configuration.

[0038] The areas of the rectangles showing the first capacitance section 31a, the second capacitance section 31b, the third capacitance section 31c, and the fourth capacitance section 31d shown in Fig. 2(a) and Fig. 2(b) can also be considered to correspond to the capacitance of each capacitance section. The capacitance correlates with the area on the circuit. Then, the areas of the rectangles showing the first capacitance section 31a, the second capacitance section 31b, the third capacitance section 31c, and the fourth capacitance section 31d can also be considered to correspond to the area of ​​the capacitance section shown on the circuit board. The area of ​​the capacitance section on the circuit board does not change whether the connection configuration shown in Fig. 2(a) or the connection configuration shown in Fig. 2(b) is used. In other words, even if the circuit configuration is changed to correspond to the input power Pin, the area of ​​the capacitance section on the circuit board does not change.

[0039] The boost circuit 3 employs a configuration that switches the connection configuration of a plurality of capacitance sections, and the product of the number of stages N and the unit capacitance C is constant in any connection configuration. The inventors have come to the conclusion that such a configuration makes it possible to suppress a decrease in the output power Pout of the boost circuit 3.

[0040] Note that the constant product of the number of stages N and the unit capacitance C is not limited to being strictly equal in value. In other words, the product of the number of stages N and the unit capacitance C includes a range that can be considered constant. This range may be determined based on a range in which the effect of suppressing the decrease in the output power Pout of the boost circuit 3 can be obtained. In addition, it may be determined based on the variation in the capacitance of each of the first capacitance section 31a, the second capacitance section 31b, the third capacitance section 31c, and the fourth capacitance section 31d.

[0041] The charging operations of the first capacitance section 31a, the second capacitance section 31b, the third capacitance section 31c, and the fourth capacitance section 31d are controlled by a drive signal θ. The boost circuit 3 has a drive signal generating section 33 that generates the drive signal θ. When the drive signal θ is output, the boost circuit 3 provides the load device 200 with an output power Pout. When the drive signal θ is stopped, the boost circuit 3 does not provide the load device 200 with an output power Pout. The drive signal θ is a clock signal including a drive pulse (charging operation component) that is output with a predetermined period. The drive signal generating section 33 determines whether or not to output the drive signal θ based on the output voltage Vout. When the output voltage Vout is lower than the required voltage Vd required by the load device 200, the drive signal generating section 33 outputs the drive signal θ including the drive pulse. When the output voltage Vout is higher than the required voltage Vd required by the load device 200, the drive signal generating section 33 does not output the drive signal θ including the drive pulse.

[0042] The output power monitor device 4 obtains operation evaluation data based on the operation state data. The operation state data indicates the operation state of the boost circuit 3. In this embodiment, the operation state data is the drive signal θ. The operation evaluation data evaluates the operation state of the boost circuit 3 in the state indicated by the operation state data. In this embodiment, the operation evaluation data is the number of drive pulses EP per unit time. When the operation of the boost circuit 3 is good, the output power per drive pulse is large. Therefore, the number of drive pulses EP for satisfying the required power Pd is small. Conversely, when the operation of the boost circuit 3 is not good, the output power per drive pulse is small. Therefore, the number of drive pulses EP for satisfying the required power Pd is large. As a result, based on the number of drive pulses EP, it is possible to know whether the operation state of the boost circuit 3 is good or not. Therefore, the number of drive pulses EP per unit time can be used to evaluate the operation state of the boost circuit 3.

[0043] The output power monitor device 4 may be configured as a physical electric circuit. Also, the output power monitor device 4 may be a computer, and each of the above-mentioned operations may be realized by executing a program. In this case, the output power monitor device 4 has a drive signal acquisition unit 41a and a drive pulse counter 41b as functional components. The drive signal acquisition unit 41a receives a drive signal θ from the drive signal generation unit 33 of the boost circuit 3. The drive signal acquisition unit 41a outputs the drive signal θ to the drive pulse counter 41b. The drive pulse counter 41b counts the number of drive pulses EP per unit time in the drive signal θ. The drive pulse counter 41b outputs the drive pulse number EP to the controller 5.

[0044] The controller 5 outputs a control signal φ for the switch circuit 32. The output operation performed by the controller 5 includes two operations. The first operation is a search operation. In the search operation, the controller 5 searches for a circuit configuration of the boost circuit 3 that provides a good operating state. Specifically, the controller 5 searches for a connection configuration of the first capacitance section 31a, the second capacitance section 31b, the third capacitance section 31c, and the fourth capacitance section 31d that provides a maximum output power Pout. In other words, the controller 5 searches for the number of stages N and the unit capacitance C per stage that provide a maximum output power Pout. The second operation is a steady operation. In the steady operation, the controller 5 outputs a control signal φs to the boost circuit 3 that provides the number of stages N and the unit capacitance C per stage that provide a good operating state obtained by the search operation. For example, the controller 5 performs a search operation at the beginning of a predetermined period. Then, the controller 5 performs the steady operation for the remaining period of the predetermined period. Then, the controller 5 repeats the search operation and the steady operation.

[0045] The controller 5 may be configured as a physical electric circuit. The controller 5 may also be a computer, and each of the above-mentioned operations may be realized by executing a program. In this case, the controller 5 has, as functional components, an operation evaluation data acquisition unit 51, a determination unit 52, a counter 53, a control signal output unit 54, and a storage unit 55.

[0046] Here, a computer constituting the output power monitor device 4 and the controller 5 will be described. FIG. 15 shows a hardware configuration of the computer 300. As shown in FIG. 15, the computer 300 physically includes a central processing unit (CPU) 301, which is an arithmetic device, a random access memory (RAM) 302, which is a recording medium, a read only memory (ROM) 303, a communication module 304, and an input / output module 306. The computer 300 may include devices other than these components as necessary. These components are electrically connected to each other. The computer 300 may include a display, a keyboard, a mouse, a touch panel display, etc., as the input / output module 306. The computer 300 may include a data recording device such as a hard disk drive and a semiconductor memory, etc., as the input / output module 306. The computer 300 may also be configured by a plurality of computers.

[0047] The functional components of the output power monitor device 4 and the controller 5 shown in FIG. 1 are realized by the following operations. First, the computer 300 loads a program onto hardware such as the CPU 301 and the RAM 302. Next, the computer 300 operates the communication module 304 and the input / output module 306 under the control of the CPU 301. Furthermore, the computer 300 reads and writes data from and to the RAM 302. The CPU 301 of the computer 300 executes a computer program in which the control process of the boost circuit is described, thereby causing the computer 300 to function as the functional components of FIG. 1. Then, the process related to the control of the boost circuit is sequentially executed. All of the various data required for the execution of the computer program and the various data generated by the execution of the computer program are stored in the built-in memory such as the ROM 303 and the RAM 302, or in a storage medium such as a hard disk drive.

[0048] First, the function of each component during the search operation will be described. During the search operation, the controller 5 repeats a signal output operation for outputting a control signal φ to the boost circuit 3 and a pulse number acquisition operation for acquiring a drive pulse number EP obtained by a circuit configuration based on the control signal φ. Then, the control signal φs with the circuit configuration that results in the highest output power Pout is determined. The repetition of the signal output operation and the pulse number acquisition operation is controlled by a counter variable k.

[0049] The operation evaluation data acquiring section 51 receives the number of drive pulses EP from the output power monitor device 4. The operation evaluation data acquiring section 51 outputs the number of drive pulses EP to the determining section 52.

[0050] The determination unit 52 compares whether the drive pulse number EP(k) obtained by the kth signal output operation and pulse number acquisition operation is greater than the drive pulse number EP(k-1) obtained by the k-1th signal output operation and pulse number acquisition operation. When the drive pulse number EP(k) is greater than the drive pulse number EP(k-1), the determination unit 52 determines the control signal φ from which the drive pulse number EP was obtained as the control signal φs to be used for steady operation. When the drive pulse number EP(k) is less than the drive pulse number EP(k-1), the determination unit 52 adds 1 to the counter variable k.

[0051] The storage unit 55 stores in advance combinations of the number of stages N and unit capacity C. This combination can be specified by a counter variable k. The storage unit 55 specifies a combination of a predetermined number of stages N and unit capacity C from a plurality of combinations based on the counter variable k. Information on the combination of the number of stages N and unit capacity C is output to the control signal output unit 54.

[0052] The control signal output unit 54 generates a control signal φ based on information on the combination of the number of stages N and the unit capacitance C. Then, the control signal output unit 54 outputs the control signal φ to the boost circuit 3. The control signal φ includes a plurality of ON / OFF signals provided to each of the multiple switches included in the switch circuit 32. The control signal output unit 54 determines which switches to turn ON and which switches to turn OFF based on the information on the combination of the number of stages N and the unit capacitance C.

[0053] The storage unit 55 may store ON / OFF information of the switches that realize a combination of a predetermined number of stages N and unit capacitance C. In this case, the controller 5 outputs the control signal φ directly from the storage unit 55 without going through the control signal output unit 54.

[0054] Next, the function of each component during steady operation will be described. During steady operation, the control signal φs determined during the search operation is output. During steady operation, the controller 5 outputs information on the combination of the selected number of stages N and unit capacitance C stored in the storage unit 55 to the control signal output unit 54. The control signal output unit 54 generates and outputs a control signal φs based on the information on the combination of the selected number of stages N and unit capacitance C.

[0055] FIG. 3 is a flowchart showing an example of a search operation performed by the controller 5.

[0056] The controller 5 sets the counter variable k to an initial value (1) (step S01). Next, the controller 5 outputs a control signal φ to the boost circuit 3 (step S02). Specifically, the controller 5 reads combination information from the storage unit 55 based on the counter variable k. Then, the controller 5 inputs the combination information to the control signal output unit 54. The control signal output unit 54 generates and outputs a signal that determines whether the switch circuit 32 is turned on or off based on the combination information.

[0057] Next, the controller 5 obtains operation evaluation data (step S03). The operation evaluation data is essentially the maximum value of the output current Iout. In the processing of the first embodiment, the operation evaluation data is the number of drive pulses EP per unit time contained in the drive signal θ. The controller 5 obtains the operation evaluation data from the output power monitor device 4. The controller 5 associates the obtained operation evaluation data with the counter variable k (step S04). Next, the controller 5 compares the operation evaluation data (step S05). The controller 5 reads out the operation evaluation data from the memory unit 55 to the determination unit 52. The read out operation evaluation data is the value obtained in the previous loop.

[0058] In this description, the number of drive pulses EP is selected as the operation evaluation data. When generating an output power Pout that satisfies the required power Pd, if the output power Pout corresponding to one drive pulse is large, the number of drive pulses required to generate the output power Pout that satisfies the required power Pd may be small. In this case, it can be said that the configuration of the boost circuit 3 corresponds to the input power Pin. When the output power Pout corresponding to one drive pulse is small, many drive pulses are required to generate the output power Pout that satisfies the required power Pd. In this case, it cannot be said that the configuration of the boost circuit 3 corresponds to the input power Pin. In the search operation, the input power Pin that the circuit configuration corresponds to in the initial state is the minimum setting value. And, each time the loop is repeated, the input power Pin that the circuit configuration corresponds to becomes larger.

[0059] In many cases, the input power Pin is between the minimum and maximum set values. In this case, the circuit configuration in the initial state does not correspond to the input power Pin. Then, each time the loop is repeated, the circuit configuration approaches the input power Pin. That is, since the output power Pout corresponding to one drive pulse becomes larger, the number of drive pulses required to generate the output power Pout that satisfies the required power Pd gradually decreases. Therefore, if the comparison result shows that the performance evaluation data obtained in the current loop is smaller than the performance evaluation data obtained in the previous loop, it can be said that the circuit configuration is approaching the optimal circuit configuration. Therefore, since the circuit configuration has not yet reached a state suitable for the input power Pin, the circuit configuration is changed and the number of drive pulses EP is obtained again. The change in the circuit configuration is expressed by counting up the counter variable k (step S05).

[0060] Then, when the input power Pin corresponding to the circuit configuration becomes larger than the input voltage Vin actually received, the output power Pout corresponding to one drive pulse decreases. That is, the number of drive pulses required to generate the output power Pout that satisfies the required power Pd changes from a decrease to an increase. Therefore, it can be seen that the circuit configuration set in the operation immediately before the operation in which the number of drive pulses changes from a decrease to an increase is most suitable for the input power Pin actually received. That is, if the comparison result shows that the operation evaluation data obtained in the current loop is greater than the operation evaluation data obtained in the previous loop, the process proceeds to step S06. Then, the controller 5 stores in the memory unit 55 the combination of the number of stages and capacitance indicated by the counter variable (k-1) as the optimal configuration at that time.

[0061] The output characteristics of the boost circuit 3 are affected by the input power Pin input from the power generating element 2. The power supply device 1 acquires a drive signal θ as operation state data reflecting the state of the input power Pin. Then, the number of drive pulses is obtained from the drive signal θ as operation evaluation data. The number of drive pulses is used to determine whether the configuration of the boost circuit 3 is appropriate for the input power Pin. This makes it possible to switch the mode of boost operation in the boost circuit 3. As a result, the boost circuit 3 can be configured in accordance with the input power Pin, thereby increasing the output power Pout.

[0062] <Second embodiment> A power supply device 1A of the second embodiment shown in Fig. 4 will be described. In the power supply device 1 of the first embodiment, the operating state data is the drive signal θ, and the operating evaluation data is the number of drive pulses. In the power supply device 1A of the second embodiment, the operating state data is the output voltage Vout when a measured load current Itest is applied, and the operating evaluation data is the maximum value of the measured load current Itest.

[0063] The power supply device 1A includes a power generating element 2, a boost circuit 3, an output power monitor device 4A, and a controller 5A. The configurations of the power generating element 2 and the boost circuit 3 are similar to those of the first embodiment, and therefore detailed description thereof will be omitted.

[0064] The output power monitor device 4A provides a load current for measurement. When the measured load current Itest is small, the output power Pout of the boost circuit 3 can maintain the required voltage Vd. When the measured load current Itest is large, the output power Pout of the boost circuit 3 cannot maintain the required voltage Vd. According to the measured load current Itest that can maintain the required voltage Vd, the operating state of the output power Pout of the boost circuit 3 can be evaluated. For example, when the measured load current Itest that can maintain the required voltage Vd is large, the output power Pout of the boost circuit 3 can be said to be large. When the measured load current Itest that can maintain the required voltage Vd is small, the output power Pout of the boost circuit 3 can be said to be small. Therefore, as described above, the power supply device 1A uses the output voltage Vout when the measured load current Itest is provided as operating state data, and uses the maximum value of the measured load current as operating evaluation data.

[0065] The power supply device 1A will be described with reference to Figs. 4 and 5. The output power monitor device 4A has a measurement load generator 42a, a voltage comparator 42b, and a maximum load current judger 42c. The measurement load generator 42a provides a measurement load current Itest to the boost circuit 3. The measurement load generator 42a may be configured to generate a plurality of measurement load currents Itest. For example, the measurement load generator 42a may include a plurality of load resistors, the connection configurations of which may be mutually switched. The measurement load generator 42a is connected to the output of the boost circuit 3.

[0066] The voltage comparison unit 42b compares the reference voltage Vref and the output voltage Vout. The voltage comparison unit 42b is a so-called comparator. The inverting input of the voltage comparison unit 42b is connected to the output of the boost circuit 3 via a resistor R1. That is, the inverting input of the voltage comparison unit 42b receives the output voltage Vout. The non-inverting input of the voltage comparison unit 42b receives the reference voltage Vref via a resistor R2. The reference voltage Vref may be, for example, the required voltage Vd of the load device 200. When the output voltage Vout is greater than the reference voltage Vref, the voltage comparison unit 42b outputs "0". When the output voltage Vout is lower than the reference voltage Vref, the voltage comparison unit 42b outputs "1". The output Vdet of the voltage comparison unit 42b is output to the maximum load current determination unit 42c.

[0067] The maximum load current determination unit 42c determines whether the measured load current Itest output by the measured load generating unit 42a is a maximum value. FIG. 6 is a diagram for explaining the operation of determining whether the measured load current Itest is a maximum value. The horizontal axis is the measured load current Itest. The vertical axis is the output Vdet of the voltage comparing unit 42b. When the measured load current Itest is small, the output voltage Vout is higher than the reference voltage Vref, so the output Vdet of the voltage comparing unit 42b is "0". When the output Vdet of the voltage comparing unit 42b is "0", the maximum load current determination unit 42c outputs a control signal to the measured load generating unit 42a to increase the measured load current Itest. The output Vdet of the voltage comparing unit 42b being "0" means that the target voltage (reference voltage Vref) is being output. When the measured load current Itest is increased stepwise, a state occurs in which the output voltage Vout becomes lower than the reference voltage Vref. When the output voltage Vout becomes lower than the reference voltage Vref, the voltage comparator 42b outputs "1" as the output Vdet. In the example of Fig. 6, the maximum load current determination unit 42c outputs the largest measured load current Itest among several measured load currents Itest at which the output Vdet of the voltage comparator 42b becomes "0" as the maximum value of the measured load current Itest to the controller 5A. In the following description, the maximum value of the measured load current Itest is also referred to as the maximum load current Itest, max.

[0068] The controller 5A uses the maximum value of the measured load current Itest to determine the circuit configuration of the boost circuit 3 set by the controller 5A. That is, the controller 5A of the second embodiment is common to the controller 5 of the first embodiment in that it repeats an operation of controlling the circuit configuration of the boost circuit 3 and an operation of acquiring and determining the operation evaluation data obtained by the circuit configuration. Therefore, the controller 5A has an operation evaluation data acquisition unit 51, a judgment unit 52A, a counter 53, a control signal output unit 54, and a storage unit 55 as components. Among them, the configurations and operations of the operation evaluation data acquisition unit 51, the counter 53, the control signal output unit 54, and the storage unit 55 are generally common to the controller 5 of the first embodiment. In the power supply device 1A of the second embodiment, the operation state data and the operation evaluation data are different from those of the first embodiment. Therefore, the operation of the judgment unit 52A of the second embodiment is different from the operation of the judgment unit 52 of the first embodiment.

[0069] The judgment unit 52A compares whether the maximum load current Itest,max(k) obtained by the k-th signal output operation and maximum load current acquisition operation is greater than the maximum load current Itest,max(k-1) obtained by the k-1-th signal output operation and maximum load current acquisition operation. When the maximum load current Itest,max(k) is smaller than the maximum load current Itest,max(k-1), the judgment unit 52A determines the control signal φ(k) that obtained the maximum load current Itest,max(k-1) as the control signal φs to be used for steady operation.

[0070] The operation of the power supply device 1A will now be described. In the second embodiment, the repetition of the signal output operation and the operation of obtaining the maximum load currents Itest, max in the search operation further includes a repetitive operation of obtaining the maximum load currents Itest, max.

[0071] The controller 5A sets the counter variable k to an initial value (1). Next, the controller 5A outputs a control signal φ to the boost circuit 3. Next, the controller 5A obtains performance evaluation data from the output power monitoring device 4A. The output power monitoring device 4A repeats an operation of outputting the measured load current Itest and an operation of comparing the output voltage Vout with the reference voltage Vref. Then, the measured load current Itest when the output voltage Vout falls below the reference voltage Vref is determined to be a maximum value (performance evaluation data, maximum load current Itest, max).

[0072] Next, the controller 5A evaluates the operation of the boost circuit 3 based on the maximum load current Itest,max. As described in the first embodiment, the controller 5A starts a search operation from a circuit configuration corresponding to a case where the input power Pin is small. Then, the configuration of the boost circuit 3 gradually approaches a configuration that is optimal for the input power Pin. That is, the output power Pout increases. As a result, the maximum load current Itest,max also gradually increases. Then, when the input power Pin corresponding to the circuit configuration becomes larger than the input power Pin actually received, the output power Pout decreases. Therefore, the controller 5A compares the k-th maximum load current Itest,max(k) with the k-1-th maximum load current Itest,max(k-1), and when the maximum load current Itest,max(k) is smaller than the maximum load current Itest,max(k-1), the controller 5A determines the control signal φ(k) from which the maximum load current Itest,max(k) is obtained as the control signal φs to be used for steady operation. Then, the controller 5A stores the combination of the number of stages N and the unit capacity C indicated by the counter variable (k-1) in the storage unit 55 as the optimal configuration at that time. On the other hand, if the maximum load current Itest,max(k) is greater than the maximum load current Itest,max(k-1), the circuit configuration suitable for the input power Pin has not been achieved. Therefore, after changing the circuit configuration, the maximum load current Itest,max is obtained again.

[0073] The power supply device 1A of the second embodiment can also determine the configuration of the boost circuit 3 according to the state of the input power Pin. Therefore, even if the open circuit voltage Voc of the power generating element 2 fluctuates, a sufficient output power Pout can be output.

[0074] <Third embodiment> A power supply device 1B of a third embodiment shown in Fig. 7 will be described. The configuration of the boost circuit 3 is essentially determined by the state of the input power Pin. Therefore, in order to determine the configuration of the boost circuit 3, the boost circuit 3 may be controlled based on the input voltage Vin input to the boost circuit 3. The power supply device 1B of the third embodiment controls the boost circuit 3 based on the input voltage Vin.

[0075] The power supply device 1B includes a power generating element 2, a boost circuit 3, a controller 5B, and an input voltage monitor device 7 (input evaluation unit). The power supply device 1B may also include an auxiliary power supply 8, if necessary. The configurations of the power generating element 2 and the boost circuit 3 are similar to those of the first embodiment, and therefore detailed description thereof will be omitted.

[0076] The input voltage monitoring device 7 obtains the input voltage Vin. That is, the input voltage monitoring device 7 obtains the open circuit voltage Voc of the power generating element 2. The input voltage monitoring device 7 is connected to the output of the power generating element 2. The input voltage monitoring device 7 may be, for example, a voltmeter. The input voltage monitoring device 7 outputs the input voltage Vin to the controller 5B.

[0077] The controller 5B outputs a control signal φ based on the input voltage Vin. According to a second study example described later, for the input voltage Vin (open voltage Voc), there exists a step number N that maximizes the output power Pout. Similarly, for the input voltage Vin (open voltage Voc), there exists a unit capacity C that maximizes the output power Pout. In other words, once the input voltage Vin is determined, the step number N and the unit capacity C are determined. In other words, unlike the power supply device 1B of the first embodiment, the power supply device 1B of the third embodiment does not need to search for a combination of the step number N and the unit capacity C that maximizes the output power Pout by repeating the output of the control signal φ and the acquisition of the operating state evaluation data that is output due to the control signal φ.

[0078] The controller 5B has an input voltage acquisition unit 51B, a control signal output unit 54, a storage unit 55, and a drive control unit 56. In other words, the controller 5B does not need to include elements such as a determination unit 52 and a counter 53 for a search operation. The input voltage acquisition unit 51B receives an input voltage Vin from the input voltage monitor device 7. The input voltage acquisition unit 51B provides the received input voltage Vin to the control signal output unit 54. The control signal output unit 54 generates a control signal φ based on the input voltage Vin. The control signal output unit 54 reads out information on the corresponding number of stages N and unit capacity C from the storage unit 55 using the input voltage Vin.

[0079] The storage unit 55 stores information on the number of stages N and the unit capacitance C linked to the input voltage Vin in advance. For example, the information may be that when the input voltage Vin is 1 V±0.25 V, the number of stages N is 7 and the unit capacitance C is 50 pF. In other words, the input voltage Vin linked to the number of stages N and the unit capacitance C may include a predetermined width.

[0080] In order to obtain the input voltage Vin (open circuit voltage Voc), it is necessary to stop the operation of the boost circuit 3. Therefore, the controller 5B has a drive control unit 56. The drive control unit 56 outputs a stop signal for stopping the operation of the boost circuit 3. The stop signal is input to the drive signal generating unit 33 of the boost circuit 3. The drive signal generating unit 33 stops outputting the drive signal θ in response to the stop signal.

[0081] The controller 5B and the input voltage monitor device 7 operate by receiving a part of the output power Pout of the boost circuit 3. Stopping the operation of the boost circuit 3 means that power is not supplied to the controller 5B. However, the operation of obtaining the input voltage Vin by the input voltage monitor device 7 and the operation of outputting the control signal φ by the controller 5B can be performed in an extremely short time. For example, the controller 5B and the input voltage monitor device 7 operate by outputting the power charged to the fourth capacitance section 31d, and during that time, the control operation of the boost circuit 3 can be performed by stopping the charging operation to the first capacitance section 31a. In other words, the state in which the charging to the first capacitance section 31a is stopped may be regarded as the stop of the boost circuit 3.

[0082] To perform a more reliable control operation of the boost circuit 3, the power supply device 1B may have an auxiliary power supply 8. The auxiliary power supply 8 supplies power to the controller 5B and the input voltage monitoring device 7 while the operation of the boost circuit 3 is stopped. The auxiliary power supply 8 may be a battery that initially stores power, or may be a battery that is charged by the output power of the boost circuit 3.

[0083] The operation of the power supply device 1B will be described. First, the controller 5B stops the operation of the boost circuit 3. Next, the input voltage monitor device 7 obtains the input voltage Vin (open voltage Voc) and then outputs the input voltage Vin to the controller 5B. Next, the controller 5B reads out the number of stages N and the unit capacity C stored in the memory unit 55 using the input voltage Vin. Next, the controller 5B outputs a control signal φ that realizes the read number of stages N and unit capacity C to the boost circuit 3. Then, the controller 5B starts the operation of the boost circuit 3.

[0084] The power supply device 1B of the third embodiment can also determine the configuration of the boost circuit 3 according to the state of the input power Pin. Therefore, even if the open circuit voltage Voc of the power generating element 2 fluctuates, a sufficient output power Pout can be output.

[0085] The power supply device 1B of the third embodiment can determine the configuration of the boost circuit 3 according to the state of the input power Pin without requiring a search operation. Therefore, the configuration of the controller 5B can be simplified. Furthermore, since the number of processes for determining the configuration of the boost circuit 3 is reduced, the time required to determine the configuration of the boost circuit 3 can be shortened. As a result, even if the open circuit voltage Voc of the power generating element 2 fluctuates in a short period of time, the operation for determining the configuration of the boost circuit 3 and the operation for switching the configuration of the boost circuit 3 can be made to follow the fluctuation of the open circuit voltage Voc.

[0086] <Example> A specific example of the electrical circuit configuration of the power supply device 100 will be described below with reference to FIGS.

[0087] The power supply device 100 has an output terminal 101a and a ground terminal 101b. The output terminal 101a is connected to a load device 200. The output terminal 101a outputs an output voltage Vout to the load device 200. The ground terminal 101b receives a reference potential from a ground potential GND. The power supply device 100 has a power generating element 102, a boost circuit 103, an output power monitor device 104, and a controller 105.

[0088] The power generating element 102 has an input terminal 102a and an output terminal 102b. The input terminal 102a and the output terminal 102b are connected to the boost circuit 103. The power generating element 102 has a power generating body 121 and an output resistor 122. The output resistor 122 is connected to the boost circuit 103 via the output terminal 102b. The power generating element 102 converts external energy into electric energy. The power generating element 102 outputs an open voltage Voc. The power generating element 102 may be any of various elements capable of generating electric energy using external energy. One example of the power generating element 102 is a TEG (Thermoelectric power Generator). The power generating element 102 generates electric power by utilizing thermal energy. The open voltage Voc is a DC voltage.

[0089] The boost circuit 103 is connected to the power generating element 102. The boost circuit 103 receives an open circuit voltage Voc from the power generating element 102. The boost circuit 103 boosts the open circuit voltage Voc. The boosted open circuit voltage Voc is an output voltage Vout. The boost circuit 103 outputs the output voltage Vout to the load device 200. The boost circuit 103 includes a drive signal generating unit 131 that outputs a drive signal θ, a voltage adding circuit 132A, and a voltage adding circuit 132B.

[0090] The drive signal generating unit 131 is connected in parallel to the power generating element 102. The drive signal generating unit 131 outputs a drive signal θ to the voltage adding circuit 132A. The drive signal generating unit 131 also outputs a drive signal θ to the voltage adding circuit 132B. The voltage adding circuit 132A is connected to the power generating element 102 via the input terminal 103a. The voltage adding circuit 132B is connected in series to the voltage adding circuit 132A. The voltage adding circuit 132B is connected to the load device 200 via the output terminal 103b.

[0091] The voltage addition circuit 132A includes a capacitor 133A, a capacitor 134A, a diode 135A, a switch 136A, a switch 137A, and a switch 138A. One end of the capacitor 133A is connected to the drive signal generating unit 131. The other end of the capacitor 134A is connected to the cathode side of the diode 135A. A switch 137A is disposed between the other end of the capacitor 133A and one end of the capacitor 134A. A switch 136A is disposed between one end of the capacitor 133A and one end of the capacitor 134A. A switch 138A is disposed between the other end of the capacitor 133A and the other end of the capacitor 134A. In addition, the anode of the diode 135A is connected to the power generating element 102 via the input terminal 103a of the boost circuit 103.

[0092] By switching the switches 136A, 137A, and 138A, it is possible to switch the connection state of the capacitor 133A and the capacitor 134A. For example, when the switch 137A is in the ON state and the switches 136A and 138A are in the OFF state, the capacitor 133A and the capacitor 134A are connected in series with each other. When the switch 137A is in the OFF state and the switches 136A and 138A are in the ON state, the capacitor 133A and the capacitor 134A are connected in parallel with each other. That is, by switching the switches 136A, 137A, and 138A, it is possible to control the capacitance of the composite capacitor formed by the capacitor 133A and the capacitor 134A. It is also possible to use only the capacitor 134A for operation by turning the switch 136A on and turning the switches 137A and 138A off.

[0093] The voltage adder circuit 132B has a capacitor 133B, a capacitor 134B, a diode 135B, a switch 136B, a switch 137B, and a switch 138B. The connection configuration of the voltage adder circuit 132B is the same as that of the voltage adder circuit 132A. Therefore, a description of the connection configuration of the voltage adder circuit 132B will be omitted. A diode 140 is disposed between the voltage adder circuit 132B and the output terminal 103b. That is, the output terminal 103b is located on the cathode side of the diode 140.

[0094] A switch 139A is disposed between the cathode side of the diode 135A in the voltage adder circuit 132A and the anode of the diode 135B in the voltage adder circuit 132B. The switch 139A switches between a state in which the voltage adder circuit 132A is connected in series to the voltage adder circuit 132B and a state in which the voltage adder circuit 132A is connected in series to the anode of the diode 140.

[0095] Furthermore, the boost circuit 103 includes a switch 139B. The switch 139B is disposed on a line connecting the input terminal 103a and the anode of the diode 135B. The switch 139B connects the input terminal 103a to the anode of the diode 135B without passing through the voltage adder circuit 132A. The switch 139B switches between an ON state and an OFF state in response to a control signal φ5.

[0096] For example, switch 139A is turned OFF and switch 139B is turned ON. As a result, voltage adder circuit 132A and voltage adder circuit 132B are connected in parallel to input terminal 103a and output terminal 101a. On the other hand, when switch 139A is turned ON and switch 139B is turned OFF, voltage adder circuit 132A and voltage adder circuit 132B are connected in series to input terminal 103a and output terminal 101a.

[0097] The boost circuit 103 shown in Fig. 8 includes two voltage adder circuits 132A and 132B. However, the boost circuit 103 may include three or more voltage adder circuits. That is, the boost circuit 103 may include a voltage adder circuit 132A, a voltage adder circuit 132B, and an additional voltage adder circuit connected in series to the voltage adder circuit 132B. For example, the voltage adder circuit 132A includes two capacitors and three switches. The number of capacitors and switches included in the voltage adder circuit 132A and the connection configuration thereof may be changed as appropriate.

[0098] In the example shown in FIG. 9(a), the controller 105 outputs a first control signal φ1, a second control signal φ2, and a control signal φ3 to the boost circuit 103. The first control signal φ1 turns off the switches 136A and 136B. The second control signal φ2 turns on the switches 137A and 137B. The control signal φ3 turns off the switches 138A and 138B. The controller 105 also outputs a control signal φ4 to the boost circuit 3 so as to connect the voltage adder circuit 132A in series with the voltage adder circuit 132B by switching the switch 139A. Furthermore, the controller 105 outputs a control signal φ5 to the switch 139B to turn off the switch 139B. At this time, the circuit shown in FIG. 9(a) is equivalent to the circuit shown in FIG. 9(b).

[0099] In the example shown in FIG. 10(a), the controller 105 outputs a first control signal φ1, a second control signal φ2, and a control signal φ3 to the boost circuit 103. The first control signal φ1 turns on the switches 136A and 136B. The second control signal φ2 turns off the switches 137A and 137B. The control signal φ3 turns on the switches 138A and 138B. The controller 105 also outputs a control signal φ4 to the boost circuit 103 so as to connect the voltage adder circuit 132A in series to the anode of the diode 140 by switching the switch 139A. Furthermore, the controller 105 outputs a control signal φ5 to the switch 139B to turn on the switch 139B. At this time, the circuit shown in FIG. 10(a) is equivalent to the circuit shown in FIG. 10(b).

[0100] <Study example 1> When the number of stages N and the unit capacitance C of the boost circuit 103 are variables, there is a correlation between these variables and the output power Pout. Specifically, when the product of the number of stages N and the unit capacitance C is preserved, the output power Pout can be maximized.

[0101] Figures 11(a), 11(b), 12(a) and 12(b) show the results of confirming this relationship by circuit simulation. In the contour diagrams shown in Figures 11(a), 11(b), 12(a) and 12(b), the vertical axis indicates unit capacitance C and the horizontal axis indicates the number of stages N. The shade of hatching corresponds to the magnitude of the output power Pout. Dark hatching indicates that the output power Pout is relatively large. Light hatching indicates that the output power Pout is relatively small. The relationship between each contour diagram and the open circuit voltage Voc is as follows: Figure 11(a): Open circuit voltage Voc=0.5V. Figure 11(b): Open circuit voltage Voc=0.7V. Figure 12(a): Open circuit voltage Voc=1.0V. Figure 12(b): Open circuit voltage Voc=1.5V.

[0102] It can be seen that in each contour diagram, there exists a combination of the number of stages N and the unit capacity C that maximizes the output power Pout. This maximum combination of the number of stages N and the unit capacity C is indicated by point M. The combination of the number of stages N and the unit capacity C that maximizes the output power Pout varies depending on the magnitude of the open circuit voltage Voc. When Fig. 11(a), Fig. 11(b), Fig. 12(a) and Fig. 12(b) are considered comprehensively, it is found that the combination of the number of stages N and the unit capacity C that maximizes the output power Pout exists on a certain curve Gp. This curve Gp is ​​a function represented by the product of the number of stages N and the unit capacity C. The curve Gp shows an inversely proportional relationship. For example, it can be said that the unit capacity C is proportional to the inverse of the number of stages N.

[0103] According to the results of study example 1, when there is a circuit in which the number of stages N and the unit capacitance C can be switched, it was found that the combination of the number of stages N and the unit capacitance C that maximizes the output power Pout is finite. As a result, it was found that it is possible to increase the output power Pout by preparing in advance combinations in which the product of the number of stages N and the unit capacitance C is a certain value, and selecting a combination of the number of stages N and the unit capacitance C from among them. According to the results of study example 1, it was found that the combination of the number of stages N and the unit capacitance C that maximizes the output power Pout is determined by the open circuit voltage Voc. As a result, the power supply device 1 can operate in the following two operating modes.

[0104] First, a method can be adopted in which a combination of the number of stages N and the unit capacity C that maximizes the output power Pout can be selected based on the open circuit voltage Voc. The power supply device 1B of the third embodiment adopts this method. Second, a method can be adopted in which the output power Pout is obtained for each combination of the number of stages N and the unit capacity C that has been prepared in advance, and the combination of the number of stages N and the unit capacity C that generates the maximum output power Pout can be selected. The power supply device 1 of the first embodiment and the power supply device 1A of the second embodiment adopt this method. This can be adopted because the combination of the number of stages N and the unit capacity C that maximizes the output power Pout is finite to the extent that the combination of the number of stages N and the unit capacity C that maximizes the output power Pout can be identified even by a brute force search.

[0105] In the first place, when the input resistance of the boost circuit 103 is equal to the output resistance of the power generating element 102, the output power Pout can be maximized. In other words, if the circuit configuration of the boost circuit 103 is controlled so that the input resistance of the boost circuit 103 is equal to the output resistance of the power generating element 102, the output power Pout can be maximized regardless of the open circuit voltage Voc. When the open circuit voltage Voc is high, the number of stages N that maximizes the output power Pout decreases. When the number of stages N decreases, the input resistance of the boost circuit 3 also decreases. The decrease in input resistance can be compensated for by increasing the electrostatic capacitance (unit capacitance C) per stage. Therefore, by selecting a circuit configuration that preserves the product of the number of stages N and the unit capacitance C, the decrease in the output power Pout can be suppressed.

[0106] <Study example 2> In study example 2, the relationship between the open circuit voltage Voc and the number of stages N at which the output power Pout is maximized was confirmed. Also, in study example 2, the relationship between the open circuit voltage Voc and the unit capacitance C at which the output power Pout is maximized was confirmed. The results of study example 2 are shown in FIG. 13. In FIG. 13, graph G13a shows the relationship between the open circuit voltage Voc and the number of stages N. Also, graph G13b shows the relationship between the open circuit voltage Voc and the unit capacitance C. The horizontal axis represents the open circuit voltage Voc. The first vertical axis represents the number of stages N. The second vertical axis represents the unit capacitance C.

[0107] With reference to graph G13a, it was found that the number of stages N at which the output power Pout is maximized decreases as the open circuit voltage Voc increases. The boost ratio of the boost circuit 103 is proportional to the number of stages N. When the open circuit voltage Voc is low, it is necessary to increase the boost ratio. Therefore, the number of stages N at which the output voltage Vout is maximized is large. When the open circuit voltage Voc is high, it is not necessary to increase the boost ratio. Therefore, the number of stages N at which the output power Pout is maximized is small. With reference to graph G13b, it was found that the unit capacitance C at which the output voltage Vout is maximized increases as the open circuit voltage Voc increases.

[0108] <Study example 3> In Study Example 3, the effect of the boost circuit 3 of the embodiment was confirmed by comparing it with a boost circuit of a comparative example. The boost circuit 3 of the embodiment has variable number of stages N and capacitance of the boost circuit 3 so that the output power Pout is maximized according to the open circuit voltage Voc. The boost circuit 3 of the comparative example has fixed number of stages N and capacitance of the boost circuit 3 regardless of the open circuit voltage Voc. The results of Study Example 3 are shown in FIG. 14. In FIG. 14, the horizontal axis represents the open circuit voltage Voc. The vertical axis represents the output power Pout. Graph G14a corresponds to the boost circuit 3 of the embodiment. Graph G14b corresponds to the boost circuit of the comparative example.

[0109] With reference to the graphs G14a and G14b, it was found that the output power Pout also increases with an increase in the open circuit voltage Voc. However, it was found that there is a difference in the rate of increase in the output power Pout with an increase in the open circuit voltage Voc. For example, when the open circuit voltage Voc increases from 1V to 2V, that is, when the open circuit voltage Voc is doubled, the output power Pout of the boost circuit of the comparative example increases from 100μW to 200μW. That is, the output power Pout of the boost circuit 3 of the comparative example is doubled. On the other hand, the boost circuit 3 of the embodiment increases from 120μW to 720μW. That is, the output power Pout is six times. According to the study example 3, it was found that the boost circuit 3 of the embodiment can obtain a larger output power Pout than the boost circuit of the comparative example. [Explanation of symbols]

[0110] 1, 1A, 1B, 100...power supply device, 2...power generation element (power generation section), 3, 103...booster circuit (booster section), 4...output power monitor device (output evaluation section), 5...controller (control section), 6...control device for boost circuit, 31a...first capacitance section, 31b...second capacitance section, 33, 131...drive signal generating section, 41a...drive signal acquiring section, 41b...drive pulse counting section, 42a...measured load generating section, 42b...voltage comparing section, 42c...maximum load current determining section, 52, 52A...determination section, 200...load device, φ1...first control signal, φ2...second control signal, θ...drive signal (operating state data), EP...number of drive pulses (operating evaluation data).

Claims

1. A power supply device that supplies power based on a voltage required by a load device, A power generation unit that receives external energy and generates electric power; a boosting unit that receives the power generated by the power generating unit as input power, and outputs output power by boosting an input voltage of the input power to an output voltage higher than the input voltage; an output evaluation unit that acquires operation status data indicating an operation status of the boost unit and obtains operation evaluation data for evaluating the operation status of the boost unit, which is the status indicated by the operation status data; a control unit that outputs a first control signal or a second control signal to the boost unit in response to the operation evaluation data; the boosting unit has a plurality of capacitance units including a first capacitance unit and a second capacitance unit, and a drive signal generating unit that generates a drive signal for controlling a charging operation to the first capacitance unit, a charging operation to the second capacitance unit, and a charging operation to a composite capacitance unit formed by the first capacitance unit and the second capacitance unit; the drive signal includes a charging operation component for executing a charging operation to the first capacitance unit, a charging operation to the second capacitance unit, and a charging operation to the combined capacitance unit; The output evaluation unit is a drive signal acquisition unit that acquires the drive signal as the operation state data; a counting unit that counts the number of the charging operation components per unit time included in the drive signal that is the operation state data, and acquires the number of the charging operation components as the operation evaluation data; The control unit is the first control signal instructing a first connection configuration for converting the input power to the output power by a charging operation to the first capacitance unit and a charging operation to the second capacitance unit executed after the charging operation to the first capacitance unit; a second control signal instructing a second connection configuration for converting the input power into the output power by a charging operation of the composite capacitance section formed by the first capacitance section and the second capacitance section, to the boost section.

2. A power supply device that supplies power based on a voltage required by a load device, A power generation unit that receives external energy and generates electric power; a boosting unit that receives the power generated by the power generating unit as input power, and outputs output power by boosting an input voltage of the input power to an output voltage higher than the input voltage; an output evaluation unit that acquires operation status data indicating an operation status of the boost unit and obtains operation evaluation data for evaluating the operation status of the boost unit, which is the status indicated by the operation status data; a control unit that outputs a first control signal or a second control signal to the boost unit in response to the operation evaluation data; the boosting unit has a plurality of capacitance units including a first capacitance unit and a second capacitance unit, The output evaluation unit is a measurement load generating unit that generates a measurement load current for the boosting unit; a voltage comparison unit that acquires the output voltage when the measured load current is received as the operating state data and compares the output voltage with a required voltage; a determination unit that acquires, as the operation evaluation data, the measured load current at which the output voltage becomes lower than the required voltage; The control unit is the first control signal instructing a first connection configuration for converting the input power to the output power by a charging operation to the first capacitance unit and a charging operation to the second capacitance unit executed after the charging operation to the first capacitance unit; a second control signal instructing a second connection configuration for converting the input power into the output power by a charging operation to a composite capacitance section formed by the first capacitance section and the second capacitance section, to the boost section.

3. 3. The power supply device according to claim 1, wherein in an operation of converting the input power into the output power, a product of the number of times the charging operation and the size of the capacitance section in each charging operation is constant between an operation based on the first control signal and an operation based on the second control signal.

4. A control device for a boost circuit, which receives power as input power from a power generation unit which receives external energy and generates power, and outputs output power by boosting an input voltage of the input power to an output voltage higher than the input voltage, and which has a plurality of capacitance units including a first capacitance unit and a second capacitance unit, and a drive signal generation unit which generates drive signals for controlling a charging operation to the first capacitance unit, a charging operation to the second capacitance unit, and a charging operation to a composite capacitance unit formed by the first capacitance unit and the second capacitance unit, an output evaluation unit that acquires operation status data indicating an operation status of the boost circuit and obtains operation evaluation data for evaluating the operation status of the boost circuit, which is the status indicated by the operation status data; a control unit that outputs a first control signal or a second control signal to the boost circuit in response to the operation evaluation data; the drive signal includes a charging operation component for executing a charging operation to the first capacitance unit, a charging operation to the second capacitance unit, and a charging operation to the combined capacitance unit; The output evaluation unit is a drive signal acquisition unit that acquires the drive signal as the operation state data; a counting unit that counts the number of the charging operation components per unit time included in the drive signal that is the operation state data, and acquires the number of the charging operation components as the operation evaluation data; The control unit is the first control signal instructing a first connection configuration for converting the input power to the output power by a charging operation to the first capacitance unit and a charging operation to the second capacitance unit executed after the charging operation to the first capacitance unit; a second control signal instructing a second connection configuration for converting the input power to the output power by a charging operation of the composite capacitance section formed by the first capacitance section and the second capacitance section, to the boost circuit;

5. 1. A control device for a boost circuit that receives external energy from a power generation unit that generates electric power as input power, and outputs output power by boosting an input voltage of the input power to an output voltage higher than the input voltage, and that has a plurality of capacitance units including a first capacitance unit and a second capacitance unit, an output evaluation unit that acquires operation status data indicating an operation status of the boost circuit and obtains operation evaluation data for evaluating the operation status of the boost circuit, which is the status indicated by the operation status data; a control unit that outputs a first control signal or a second control signal to the boost circuit in response to the operation evaluation data; The output evaluation unit is a measurement load generating unit for generating a measurement load current for the boost circuit; a voltage comparison unit that acquires the output voltage when the measured load current is received as the operating state data, and compares the output voltage with a required voltage required by a load device that receives the output voltage; a determination unit that acquires, as the operation evaluation data, the measured load current at which the output voltage becomes lower than the required voltage; The control unit is the first control signal instructing a first connection configuration for converting the input power to the output power by a charging operation to the first capacitance unit and a charging operation to the second capacitance unit executed after the charging operation to the first capacitance unit; a second control signal instructing a second connection configuration for converting the input power to the output power by a charging operation to a composite capacitance section formed by the first capacitance section and the second capacitance section, or a second control signal instructing a second connection configuration for converting the input power to the output power by a charging operation to a composite capacitance section formed by the first capacitance section and the second capacitance section, to the boost circuit.

6. An output evaluation device for a boost circuit, which receives power as input power from a power generation unit which receives external energy and generates power, outputs output power by boosting the input voltage of the input power to an output voltage higher than the input voltage, and has a plurality of capacitance units including a first capacitance unit and a second capacitance unit, and a drive signal generating unit which generates drive signals for controlling a charging operation to the first capacitance unit, a charging operation to the second capacitance unit, and a charging operation to a composite capacitance unit formed by the first capacitance unit and the second capacitance unit, by evaluating the output of the boost circuit, the control device, based on the operation evaluation data, a first control signal instructing a first connection configuration for converting the input power to the output power by a charging operation to the first capacitance unit and a charging operation to the second capacitance unit executed after the charging operation to the first capacitance unit; a second control signal instructing a second connection configuration for converting the input power into the output power by a charging operation to the composite capacitance section formed by the first capacitance section and the second capacitance section, a drive signal acquisition unit that acquires, from the boost circuit, a drive signal including a charging operation component that causes a charging operation to be performed on the plurality of capacitance units included in the boost circuit; a counting unit that counts the number of charging operation components per unit time contained in the drive signal and obtains the number of charging operation components as operation evaluation data for evaluating the output of the boost circuit.

7. An output evaluation device for a boost circuit, which receives power as input power from a power generation unit which receives external energy and generates power, outputs output power by boosting the input voltage of the input power to an output voltage higher than the input voltage, and has a plurality of capacitance units including a first capacitance unit and a second capacitance unit, and a drive signal generating unit which generates drive signals for controlling a charging operation to the first capacitance unit, a charging operation to the second capacitance unit, and a charging operation to a composite capacitance unit formed by the first capacitance unit and the second capacitance unit, by evaluating the output of the boost circuit, the control device, based on the operation evaluation data, a first control signal instructing a first connection configuration for converting the input power to the output power by a charging operation to the first capacitance unit and a charging operation to the second capacitance unit executed after the charging operation to the first capacitance unit; a second control signal instructing a second connection configuration for converting the input power into the output power by a charging operation to the composite capacitance section formed by the first capacitance section and the second capacitance section, a measurement load generating unit for generating a measurement load current for the boost circuit; a voltage comparison unit that acquires the output voltage when the measured load current is received, and compares the output voltage with a required voltage required by a load device that receives the output voltage; a determining unit that obtains the measured load current at which the output voltage becomes lower than the required voltage as operation evaluation data for evaluating the output of the boost circuit.

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