JPWO2011074680A1 - Power extraction circuit and power supply system - Google Patents

Abstract

Without performing the maximum power point tracking control, the power that can be extracted from the DC power supply is increased, and the power that can be supplied to the load is increased. When both the first switch and the second switch are turned on, the capacitor and the DC power supply are connected in series, and the electromotive force when viewed as the entire power supply system is increased. As a result, the current passing through the inductor increases, and the power that can be extracted from the DC power supply increases. When both the first switch and the second switch are turned off, the magnetic energy stored in the inductor is transferred to the capacitor, and as a result, the voltage across the capacitor increases. As a result, the power supplied to the load increases.

Description

  The present invention relates to a power extraction circuit that forcibly extracts power from a power source such as a solar cell or a thermoelectric element and supplies the power to a load, and a power supply system including the power extraction circuit.

  In recent years, development of power supply systems using solar cells has been actively conducted. Regarding solar cells, output characteristics vary depending on the amount of solar radiation and temperature. That is, as shown in FIG. 1, there is a VI curve according to the irradiance to the solar cell and the module temperature, and the maximum power point Pmax (V × I in the VI curve) for each VI curve. = P is the maximum). Based on such characteristics, many techniques relating to Maximum Power Point Tracking (MPPT) have been proposed in order to efficiently extract electric power from solar cells.

  For example, Patent Document 1 discloses a solar power generation system that converts the output of a solar cell into AC power using an inverter. The operating voltage corresponding to the maximum power point corresponding to the amount of solar radiation and temperature is stored in the database, the varying amount of solar radiation and temperature are sequentially measured, and the operating voltage corresponding to the measured amount of solar radiation and temperature is stored from the database. This is a control method that selects and sets the operating voltage (optimum value) for the inverter. Further, Patent Document 2 discloses a technology that achieves both the followability and stability of the maximum power point follow-up control by changing the conduction ratio of the switching elements constituting the DC / DC converter connected to the photovoltaic power generator. It is disclosed.

JP 2000-181555 A JP 2003-216255 A

All of these technologies are intended to supply power close to the maximum power point to a load connected to the solar cell as a direct current power source in consideration of the internal impedance. This maximum power point Pmax is the power supplied to the load when R = r, where E is the electromotive force of the DC power supply, r is its internal resistance, and R is the resistance of the load connected to this DC power supply. Pmax = E ² / 4r (FIG. 2). In other words, the maximum power point tracking control is a technique for supplying power close to Pmax = E ² / 4r to the load. Here, what can be a direct current power source is not limited to one using solar power generation, one using wind power generation, one using temperature difference power generation (power supply constituted by thermoelectric elements such as Seebeck elements), etc. Exists. For each power generation method, a technology related to maximum power point tracking control has been proposed, and power close to the maximum power point at that time is supplied to the load in correspondence with conditions such as wind speed, air temperature, and water temperature that change every moment. I have to.

  Many techniques relating to the maximum power point tracking control have been proposed and put into practical use. However, the conventional maximum power point tracking control requires a mechanism for specifying the maximum power point that varies depending on the environment and load. Further, the specified maximum power point, such as a mechanism for setting the operating voltage of the inverter shown in Patent Document 1, a mechanism for changing the conduction ratio of the switching elements constituting the DC / DC converter shown in Patent Document 2, and the like. A feedback mechanism or the like for following the movement was necessary. In addition, the current output power itself must be monitored. Due to these factors, there is a problem that a system including a circuit and software for maximum power point tracking control becomes complicated.

  The present invention has been made to solve such problems, and its purpose is to increase the power that can be extracted from the DC power supply by a simple circuit and system as compared with the conventional maximum power point tracking control. And providing a power extraction circuit capable of improving power generation efficiency and a power supply system including the power extraction circuit.

(Configuration of power extraction circuit and power supply system)
The present invention solves the above problems by a power extraction circuit and a power supply system described below. FIG. 3 shows an outline of the power extraction circuit 10 and the power supply system 1 of the present invention. The power extraction circuit 10 forcibly extracts power from a DC power source 2 such as a solar cell or Seebeck element and supplies the power to the load 3. It comprises an inductor 11, diodes 12 and 13, a capacitor 14, and switches 15 and 16. The power supply system 1 includes a DC power source 2 connected to an input terminal of the power extraction circuit 10, a power extraction circuit 10, and a load 3 connected to an output terminal of the power extraction circuit 10.

  As shown in FIG. 3, the power extraction circuit 10 includes a positive input terminal connected to the positive electrode of the DC power supply 2 and a negative input terminal connected to the negative electrode. The power extraction circuit 10 includes a first path composed of an inductor 11, a first diode 12, and a first switch 15 connected between the positive electrode and the negative electrode of the DC power supply 2, and the positive electrode and the negative electrode of the same DC power supply 2. A second path including the inductor 11, the second switch 16, and the second diode 13 connected to each other is included. This inductor 11 is connected to the positive electrode of the DC power source 2. The anode of the first diode 12 is connected to the inductor 11, the cathode is connected to the first switch 15, and the first switch 15 controls conduction between the cathode and the negative electrode of the DC power supply 2. On the other hand, the second switch 16 is connected to the inductor 11, the anode of the second diode 13 is connected to the second switch 16, the cathode is connected to the negative electrode of the DC power supply 2, and the second switch 16 is connected to the anode And the conduction of the inductor 11 is controlled. A capacitor 14 is connected between the cathode of the first diode 12 and the anode of the second diode 13. Output terminals are provided at both ends of the capacitor 14, and the load 3 is connected in parallel with the capacitor 14.

(Operation of power extraction circuit)
3, the electromotive force of the DC power source 2 is assumed to be V _1. First, when both the switches 15 and 16 are in an OFF state (this state is referred to as a state I), assuming that the forward voltage drops of the diodes 12 and 13 are V _F1 and V _F2 , they are connected in parallel with the load 3. The voltage V ₂ between the terminals of the capacitor 14 is a value obtained by subtracting the forward voltage drop V _F1 + V _F2 of the diodes 12 and 13 from the electromotive force V ₁ , and is expressed by Equation 1.
V ₂ = V ₁ − (V _F1 + V _F2 ) (1)

Next, when both the switches 15 and 16 are turned ON (this state is referred to as state II), the capacitor 14 and the DC power source 2 of the electromotive force V1 are connected in series, and the electromotive force when the power supply system 1 is viewed as a whole. Becomes higher than V1. As a result, as compared with the state I, the internal impedance of the DC power supply 2 and the current passing through the inductor 11 increase. Here, when the current passing through the inductor 11 is I and the inductance of the inductor 11 is L, the magnetic energy U shown in the following formula (2) is stored in the inductor 11.
U ⁼ LI 2/2 ··· formula (2)
That is, when the current flowing through the inductor 11 increases, the stored magnetic energy U increases in proportion to the square of the current.

  Assuming that the magnetic energy increased from state I to state II is dU, this dU does not instantaneously become zero even when both the switches 15 and 16 are turned OFF, and resists the decrease in the current flowing through the inductor 11. Try to keep the current flowing. As a result, a current larger than the current flowing in the inductor 11 in the state I where both the switches 15 and 16 are initially OFF flows in the inductor 11. Then, the finally increased magnetic energy dU is transferred to the capacitor 14, and as a result, the terminal voltage of the capacitor 14 becomes higher than that in the state I.

  Further, since the voltage between the terminals of the capacitor 14 becomes higher than that in the state I, when both the switches 15 and 16 are turned on next time, the DC power source is in the state II where both the switches 15 and 16 were previously turned on. A current larger than the internal impedance of 2 and the current flowing through the inductor 11 flows through the internal impedance of the DC power source 2 and the inductor 11. Thus, by repeating ON / OFF control of the switches 15 and 16 at the same time, the voltage between the terminals of the capacitor 14, that is, the voltage between the terminals of the load increases, and more power can be taken out from the DC power supply 2. It becomes like this.

  The amount of increase in the voltage between the terminals of the capacitor 14 due to repeated switching described above varies depending on the load, switching frequency and switching time, inductance L, and the like. When the energy supply to the capacitor 14 and the energy release by the load are balanced, the terminal voltage of the capacitor 14 (terminal voltage of the load 3) becomes constant. The current flowing through the load 3 increases due to the increase in the voltage between the terminals due to the repetition of the switching, and the power consumed by the load increases. Since the law of energy conservation is established here, the power is supplied from the DC power source 2.

  Here, as shown in FIG. 4, the switches 15 and 16 may be constituted by semiconductor switches (for example, MOSFETs). Since the switches 15 and 16 can be switched at high speed, the inductance L and the capacitance C of the capacitor 14 can be reduced, and the power extraction circuit 10 can be downsized. Further, as shown in FIG. 5, the time for which the switches 15 and 16 are turned on may be controlled by the control device 20 so that the voltage between the terminals of the capacitor 14 is maximized. The control device 20 is configured by a semiconductor circuit.

  According to the present invention, it is possible to increase the power that can be extracted from the DC power source without performing the conventional maximum power point tracking control, and to improve the power generation efficiency. Further, in the power extraction circuit and power supply system of the present invention, the measurement mechanism, current and voltage of environmental conditions (sunshine amount, wind speed, temperature, water temperature, etc.) required for performing the conventional maximum power point tracking control. Measurement mechanism, maximum power point specifying mechanism, feedback mechanism for following the maximum power point (for example, a mechanism for setting an operating voltage of an inverter shown in Patent Document 1, a DC / DC converter shown in Patent Document 2) No mechanism or the like for changing the conduction ratio of the switching element is required, and the circuit and system can be simplified.

  The power extraction circuit of the present invention is applicable not only to solar cells but also to DC power supplies in general. In addition, the power supply system of the present invention efficiently supplies power generated by solar power generation, wind power generation, temperature difference power generation, and the like to a load without being limited by the maximum power point.

FIG. 1 is a diagram showing a VI curve according to the irradiance to the solar cell and the module temperature, and respective maximum power points. FIG. 2 is a diagram showing the maximum power point in the VI curve. FIG. 3 is a circuit diagram showing a power extraction circuit and a power supply system. FIG. 4 is a circuit diagram when a MOSFET is used as a switch of the power extraction circuit. FIG. 5 is a circuit diagram when the switch of the power extraction circuit is controlled by the control device. FIG. 6 is a circuit diagram when measuring input power and output power in the power extraction system. FIG. 7 shows an apparatus for measuring the maximum power point. FIG. 8 is a diagram comparing the maximum power point when not passing through the power extraction circuit and the power extracted by the power extraction circuit. FIG. 9 is a diagram showing the relationship between the duty ratio and the power (P _O ).

[1. Confirmation of efficiency improvement by power extraction circuit]
The inventors confirmed the operation of the power supply system of the present invention and the effect of the power extraction circuit using the apparatus shown in FIG. As the DC power source 2, a solar cell was used. This solar cell generates electricity by illuminating a “portable solar cell panel (model number 738 SM1000-12V-FP)” manufactured by Akizuki Dentsu Co., Ltd. with 12 electric bulbs (AC100V, 40W) from a certain distance. The rated voltage when the output of the solar cell panel is released is 12 V, and the maximum current when short-circuited is 1000 mA. Light bulbs were arranged so as to face the surface of the solar cell panel in parallel (4 × 3 rows), and the whole surface was adjusted so that the light bulbs were illuminated almost uniformly. In this experiment, a motor was connected as the load 3. When the electric power supplied to the motor increases, the rotational speed of the motor increases, and it can be confirmed that more electric power is extracted from the solar cell.

(Experimental example 1)
As described with reference to FIG. 3, first, the switches 15 and 16 are turned off (state I). In this experimental example, the inductance of the inductor 11 is 10 mH, and the capacitance of the capacitor 14 is 2200 μF. Here, the power consumption of the control device 20 that controls the switching of the switches 15 and 16 is supplied from the solar cell. That is, the power supply source of the power supply system shown in FIG. 6 is only the solar battery as the DC power supply 2, and no other power is supplied from the outside. In this state, the voltage between the terminals of the solar cell is measured by the voltmeter 31, and the current flowing through the inductor 11 is measured by the ammeter 32. The voltage measured by the voltmeter 31 at this time is defined as the input voltage V _O , and the current measured by the ammeter 32 is defined as the input current I _O. On the other hand, the voltage across the load 3 (the voltage across the capacitor 14) is measured by the voltmeter 33, and the current flowing through the load 3 is measured by the ammeter 34. At this time, a voltage measured by the voltmeter 33 is an output voltage V _L , and a current measured by the ammeter 34 is an output current I _{L. V} O in this _state, I _{O, V L,} and the value of _{I L} shown in Table 1 (switching stop state). Further, the values of input power P _O = V _O × I _O and output power P _L = V _L × I _L at this time are also shown.

Next, the switches 15 and 16 were repeatedly turned ON / OFF by the control device 20. The switching frequency was 20 kHz. Thereby, _VL rises through the state II mentioned above. V _L is _V O in a stable _state, I O, _{V L,} and the value of _{I L} shown in Table 1 (switching state). Also shows the values of _{P O} and _{P L} at this time. From comparison in Table 1, whereas _{P O} is 2.58W in a switching stop state, since _{P O} in the switching state is 4.66W, has increased the power itself is taken out from the solar cell 80% . Further, in the comparison of the power supplied to the load, whereas _{P L} is 2.04W in a switching stop state, since _{P L} in the switching state is 3.21W, the power supplied to the load is increased by 57% ing. That is, while the power taken out from the solar cell in the switching stopped state is 2.58 W, the power supplied to the load in the switching state is 3.21 W, and the power that can be supplied to the load in the switching stopped state is 124% can be supplied to the load. That is, the power extraction circuit 10 forcibly extracts power from the solar cell and supplies it to the load.

(Experimental example 2)
Next, the same experiment as in Experimental Example 1 was performed by replacing the capacitor 14 with a capacitor having a capacity of 12200 μF. The results are shown in Table 2.

From the comparison in Table 2, while _{P O} is 2.60W in a switching stop state, since _{P O} in the switching state is 4.56W, the power itself is taken out from the solar cell is increased to 75% . Further, in the comparison of the power supplied to the load, whereas _{P L} is 2.04W in a switching stop state, since _{P L} in the switching state is 3.22W, the power supplied to the load is increased 58% ing. That is, the power extracted from the solar cell in the switching stop state is 2.60 W, whereas the power supplied to the load in the switching state is 3.22 W, and the power that can be supplied to the load in the switching stop state is 124% can be supplied to the load. That is, the power extraction circuit 10 forcibly extracts power from the solar cell and supplies it to the load. From the results shown in Tables 1 and 2, changing the capacitance of the capacitor 14 did not significantly affect the results.

(Experimental example 3)
Next, an experiment similar to Experimental Example 1 was performed by bringing the positions of the 12 light bulbs closer to the surface of the solar cell panel. The switching frequency when the switches 15 and 16 were repeatedly turned on / off was 20 kHz. Table 3 (switching state) shows the values of V _O , I _O , V _L , I _L , P _O and P _{L when} V _L is stable. As shown in Table 3, P _O is increased by closer bulbs in solar cell panel surface, it has been an increase in the P _L accordingly. In addition, when the experiment shown in Table 1 and Table 2 was conducted, it confirmed with the thermometer that the surface temperature of a solar cell panel rose in a switching state.

(Experimental example 4)
Next, V _O , I _O , V _L , I _L , P _O when air is blown to the surface of the solar cell panel from the state of Experimental Example 3 (the state where the light bulb is close to the solar cell panel) and cooled. and Table 4 (switching state) the value of _{P L.} Compared to the results in Table 3, P _O is increased by cooling the solar panel surface, it has been an increase in the P _L accordingly.

[2. Comparison with maximum power point]
(Experimental example 5)
The maximum power point of the solar cell used as the DC power source 2 in the above experiment was measured using the apparatus shown in FIG. An electronic load device “PLZ164WA” manufactured by Kikusui Electronics Co., Ltd. was used as the load 3, and this was set to a constant current mode. In this state, the point where the electric power supplied from the solar cell is maximized was specified. That is, the power Pmax when the value obtained by multiplying the voltage V _O measured by the voltmeter 35 shown in FIG. 7 and the current I _O measured by the ammeter 36 becomes the maximum is specified. As a _result, I O = _0.336A, power when the V O = 14.56V becomes 4.89W next maximum.

(Experimental example 6)
Next, an experiment similar to Experimental Example 1 was performed using an electronic load device as a load. The same solar cell 2 as in Experimental Example 1 was used, and the electronic load device set to the conditions (current value, voltage value) when the maximum power Pmax was obtained in Experimental Example 5 was used as the load 3. As a result, Table 5 (switching state) shows values of V _O , I _O , V _L , I _L , P _O, and P _L when the power extraction circuit is in the switching state.

  From the results shown in Table 5, when the power extraction circuit is switched, the power value that can be taken out is 5.45W. As shown in FIG. 8, 111.4% of the maximum power Pmax = 4.89 W when not passing through the power extraction circuit could be extracted from the solar cell. From FIG. 8, it can be understood that the power extraction circuit of the present invention has an unprecedented effect. In particular, in recent years, conventional maximum power point tracking, which is commonly used as a technology for optimizing power supply, is a technology that sets a line. In the present invention, there is no need for a mechanism for specifying the maximum power point that fluctuates depending on the environment, load, or the like, and no feedback mechanism or the like for following the specified maximum power point. The very simple circuit shown in FIG. 3 can increase the amount of power supplied to the load.

As shown in Table 5, the power _{P L} which can be supplied to the load became 4.79W. This is because the power consumed by the power extraction circuit is 5.45-4.79 = 0.66 W, although the value is lower than the maximum power Pmax = 4.89 W. By reducing the power consumed by the power extraction circuit, it is possible to supply a larger amount of power to the load itself. For example, since it is possible to reduce the power consumption of the control device 20 shown in FIG. 6, it is possible to supply a larger amount of power to the load.

[3. Experiments using other DC power supplies]
(Experimental example 7)
The present invention is not limited to a solar battery, but increases the power that can be extracted from a DC power source. The present inventors conducted an experiment using a power source constituted by a Seebeck element instead of a solar cell. The power source used is “Thermoelectric Modules for Power Generation” (model number TGM-287-1.0-1.5) from Kryotherm. For this power source, the maximum power point was measured by the method shown in Experimental Example 5 before connecting the power extraction circuit 10. At this time, the heat absorption side temperature was set to 80 ° C. and the heat release side temperature was set to 27.3 ° C. As a result, the power when I _O = 0.430 A and V _O = 1.66 V was 0.71 W, which was the maximum.

Next, the power source configured by the Seebeck element is used as the DC power source 2, and the electronic load device set to the conditions (current value, voltage value) when the maximum power Pmax is obtained is used as the load 3. An experiment similar to Experimental Example 1 was performed using the apparatus shown in FIG. 6 (a solar cell replaced with a Seebeck element). The capacitance of the capacitor 14 used here is 50F. The switching frequency was 20 kHz, the duty ratio of the switching pulse was increased from 40% to 50% in 1% increments, and the results of measuring V _O , I _O , and P _O for each duty ratio are shown in Table 6 and As shown in FIG.

When the measurement was started, the duty ratio was 40%. At this time, the heat absorption side temperature was 80.2 ° C., and the heat release side temperature was 26.2 ° C. Thereafter, the duty ratio was increased by 1%, and V _O , I _O , and P _O were measured. When the final temperature was 50%, the endothermic temperature was 80.1 ° C., and the endothermic temperature was 26.3 ° C. After the measurement, the power extraction circuit 10 was removed, and the maximum power point was measured again by the method shown in Experimental Example 5. As a _result, I O = _0.445A, power when the V O = 1.85V becomes 0.82W next maximum. The horizontal axis of FIG. 9 is a duty ratio and the vertical axis represents P _O. As shown in FIG. 9, _PO in the switching state exceeds both the maximum power point before the start of measurement and the maximum power point after the end of measurement regardless of the duty ratio.

  From the results shown in Table 6 and FIG. 9, it was possible to confirm a remarkable effect by operating the power extraction circuit. During operation of the power extraction circuit, the amount of heat absorbed by the Seebeck element increased, and it was confirmed that a large amount of power was forcibly extracted from the power source by the power extraction circuit. Application of the present invention makes it possible to extract a large amount of power even in an environment where the temperature difference is small.

  In addition, even a primary battery such as a dry battery can efficiently use energy by forcibly extracting power by a power extraction circuit when the voltage becomes low. In the case of a fuel cell, the consumption of oxygen is increased by using the power extraction circuit, but the output per unit volume is increased and the size can be reduced.

1 ... Power supply system 2 ... DC power supply (solar cell, Seebeck element)
3 ... Load (motor, electronic load device)
DESCRIPTION OF SYMBOLS 10 ... Power extraction circuit 11 ... Inductor 12 ... Diode 13 ... Diode 14 ... Capacitor 15 ... Switch 16 ... Switch 20 ... Control device 31 ... Voltmeter 32 ... Ammeter 33 ... Voltmeter 34 ... Ammeter 35 ... Voltmeter 36 ... Current Total

Claims (6)

A first path composed of an inductor, a first diode, and a first switch connected between a positive electrode and a negative electrode of a DC power supply, and an inductor connected between the positive electrode and the negative electrode of the same DC power supply; And a second path comprising a second diode,
The inductor is connected to a positive electrode of the DC power supply;
The anode of the first diode is connected to the inductor, the cathode is connected to the first switch, and the first switch controls conduction between the cathode and the negative electrode of the DC power source,
The second switch is connected to the inductor, the anode of the second diode is connected to the second switch, the cathode is connected to the negative electrode of the DC power supply, and the second switch is connected to the anode and the anode. Which controls conduction between inductors,
A capacitor connected between the cathode of the first diode and the anode of the second diode;
By alternately repeating the control of making both the first switch and the second switch conductive and non-conductive, the current flowing through the inductor is increased, and the power that can be extracted from the DC power supply is increased. A power extraction circuit characterized by that. A first path composed of an inductor, a first diode, and a first switch connected between a positive electrode and a negative electrode of a DC power supply, and an inductor connected between the positive electrode and the negative electrode of the same DC power supply; And a second path comprising a second diode,
The inductor is connected to a positive electrode of the DC power supply;
The anode of the first diode is connected to the inductor, the cathode is connected to the first switch, and the first switch controls conduction between the cathode and the negative electrode of the DC power source,
The second switch is connected to the inductor, the anode of the second diode is connected to the second switch, the cathode is connected to the negative electrode of the DC power supply, and the second switch is connected to the anode and the anode. Which controls conduction between inductors,
A capacitor connected between the cathode of the first diode and the anode of the second diode;
A load connected to the capacitor in parallel by increasing the voltage across the capacitor by alternately repeating the control of making both the first switch and the second switch conductive and alternately non-conductive. A power extraction circuit characterized by increasing the power supplied to the battery. A first path composed of an inductor, a first diode, and a first switch connected between a positive electrode and a negative electrode of a DC power supply, and an inductor connected between the positive electrode and the negative electrode of the same DC power supply; And a second path comprising a second diode,
The inductor is connected to a positive electrode of the DC power supply;
The anode of the first diode is connected to the inductor, the cathode is connected to the first switch, and the first switch controls conduction between the cathode and the negative electrode of the DC power source,
The second switch is connected to the inductor, the anode of the second diode is connected to the second switch, the cathode is connected to the negative electrode of the DC power supply, and the second switch is connected to the anode and the anode. Which controls conduction between inductors,
A capacitor connected between the cathode of the first diode and the anode of the second diode;
By alternately repeating the control of making both the first switch and the second switch conductive and non-conductive, the current flowing through the inductor is increased, and the power that can be extracted from the DC power supply is increased. A power extraction circuit characterized by increasing the voltage between terminals of the capacitor, thereby increasing the power supplied to a load connected in parallel to the capacitor. A power supply system comprising a DC power supply, a power extraction circuit connected to the DC power supply, and a load connected to the power extraction circuit,
The power extraction circuit is connected between a first path consisting of an inductor, a first diode, and a first switch connected between a positive electrode and a negative electrode of the DC power supply, and a positive electrode and a negative electrode of the same DC power supply. A second path consisting of the inductor, the second switch, and the second diode,
The inductor is connected to a positive electrode of the DC power supply;
The anode of the first diode is connected to the inductor, the cathode is connected to the first switch, and the first switch controls conduction between the cathode and the negative electrode of the DC power source,
The second switch is connected to the inductor, the anode of the second diode is connected to the second switch, the cathode is connected to the negative electrode of the DC power supply, and the second switch is connected to the anode and the anode. Which controls conduction between inductors,
A capacitor connected between the cathode of the first diode and the anode of the second diode;
The load is connected in parallel to the capacitor;
By alternately repeating the control of making both the first switch and the second switch conductive and non-conductive, the current flowing through the inductor is increased, and the power that can be extracted from the DC power supply is increased. And the power supply system characterized by increasing the voltage between the terminals of the capacitor and thereby increasing the power supplied to the load. The power supply system according to claim 4,
The power supply system, wherein the DC power source is a solar battery. The power supply system according to claim 4,
The DC power supply is configured by a Seebeck element.

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