Power supply unit and sensor unit

Abstract

The present invention provides a power supply device and a sensor device that can suppress the voltage drop of the power supply capacitor. [Solution] The power supply device is characterized by comprising: a solar cell; a power capacitor charged by the solar cell; a rectifier element provided between the solar cell and the power capacitor to rectify the flow of current from the solar cell to the power capacitor; a changeover switch that switches between a first state in which the power stored in the power capacitor can be supplied to a load and a second state in which the supply of power to the load is stopped; a voltage detection circuit that causes the changeover switch to switch to the first state when the voltage of the power capacitor exceeds a first threshold, and causes the changeover switch to switch to the second state when the voltage of the power capacitor falls below a second threshold lower than the first threshold after exceeding the first threshold; and a backup circuit that suppresses the voltage drop of the power capacitor.

Description

Technical Field

[0001] Aspects of the present invention generally relate to a power supply device and a sensor device.

Background Art

[0002] There has been a consideration of using, in a toilet space, a sensor device including a power supply device using a solar cell as a power source and a sensor circuit operating based on the power supplied from the power supply device. The sensor device is used, for example, in a remote control device for toilet flushing. For example, a user's hand (hand waving operation) is detected non-contact by the sensor device, and in response to the detection of the user's hand, a toilet flushing signal is transmitted from the remote control device to a control device having a toilet flushing function.

[0003] Thus, by enabling non-contact operation, the hygiene of the remote control device can be improved. Also, by using a solar cell as a power source, it is possible to eliminate the need for securing power from a commercial power supply (electrical work), improve the workability, and also eliminate the need for battery replacement, etc., thereby improving the maintainability.

[0004] The power supply device charges a power supply capacitor that becomes a circuit power source by a solar cell, energizes a load when the voltage of the power supply capacitor is charged to a predetermined voltage, terminates the load energization when the power supply capacitor is discharged by the load energization, and repeats this. Thus, by driving the load intermittently, the power consumption can be reduced. Thereby, even when the illumination in the toilet space is dim and the output of the solar cell is small, the load can be appropriately driven.

[0005] However, in a toilet space, the illumination may be turned off when not in use. Particularly, in a toilet space inside a building without windows, when the illumination is turned off, it becomes completely dark, and the output of the solar cell approaches zero. If the completely dark state continues, the voltage of the power supply capacitor gradually decreases due to the leakage current of the circuit or the like, and eventually becomes zero.

[0006] In this state, even if a toilet user arrives, the load cannot be driven until the lights are turned on, the solar panels begin outputting power, and the voltage of the power capacitor reaches a voltage sufficient to supply power to the load. For example, if the power supply is applied to a remote control device for flushing a toilet, the toilet cannot be flushed until the lights are turned on and the voltage of the power capacitor reaches a voltage sufficient to supply power to the load. Therefore, for example, the toilet cannot be flushed at the timing intended by the user, which may cause discomfort to the user.

[0007] Therefore, in power supply devices using solar cells and sensor devices using them, it is desirable to suppress the voltage drop of the power capacitor even when the environment becomes such that sufficient power cannot be supplied from the solar cells due to the turning off of lights, and to minimize the time required to charge the power capacitor when power supply from the solar cells is resumed. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 9-101754 [Patent Document 2] Patent No. 6544247 [Overview of the Initiative] [Problems that the invention aims to solve]

[0009] This invention was made based on the recognition of the above problems, and aims to provide a power supply device and a sensor device that can suppress the voltage drop of the power supply capacitor. [Means for solving the problem]

[0010] The first invention is a power supply device characterized by comprising: a solar cell; a power capacitor charged by the solar cell; a rectifier element provided between the solar cell and the power capacitor for rectifying the flow of current from the solar cell toward the power capacitor; a changeover switch for switching between a first state in which the power stored in the power capacitor can be supplied to a load and a second state in which the supply of power to the load is stopped; a voltage detection circuit for detecting the voltage of the power capacitor, causing the changeover switch to switch to the first state when the voltage of the power capacitor becomes equal to or greater than a first threshold, and causing the changeover switch to switch to the second state when the voltage of the power capacitor falls to or less than a second threshold lower than the first threshold after becoming equal to or greater than the first threshold; and a backup circuit for suppressing the voltage drop of the power capacitor.

[0011] This power supply unit allows the backup circuit to suppress the voltage drop of the power capacitor when the solar panel output is low and sufficient power cannot be supplied from the solar panel. As a result, when the solar panel output increases and charging of the power capacitor by the solar panel begins, the time it takes for the voltage of the power capacitor to exceed the first threshold can be shortened. This shortens the time it takes for power to be supplied to the load after the solar panel output changes from a low to a high state, making it possible to operate the load sooner.

[0012] The second invention is a power supply device characterized in that, in the first invention, the backup circuit has a backup capacitor with a larger capacitance than the power supply capacitor, the backup capacitor is charged by the solar cell via a resistive element and a first diode, and is connected to the power supply capacitor via a second diode, thereby suppressing a voltage drop in the power supply capacitor.

[0013] This power supply unit allows for the appropriate suppression of voltage drops in the power supply capacitor through the backup capacitor. Furthermore, by charging the backup capacitor via a resistive element, charging of the power supply capacitor based on the output of the solar cell can be prioritized over charging the backup capacitor. This prevents the delay in power supply to the load that would otherwise be caused by charging the backup capacitor.

[0014] The third invention is a power supply device characterized in that, in the first invention, the backup circuit has a primary battery connected to the power supply capacitor via a diode, and the magnitude of the voltage obtained by subtracting the forward voltage of the diode from the voltage of the primary battery is lower than the first threshold.

[0015] This power supply unit allows for the appropriate suppression of voltage drop across the power capacitor using the primary battery. Furthermore, by setting the magnitude of the voltage obtained by subtracting the forward voltage of the diode from the primary battery voltage to be lower than the first threshold, it is possible to suppress the consumption of primary battery power by driving the load. This allows for the appropriate use of primary battery power to suppress voltage drop across the power capacitor when the environment becomes low-light and the output of the solar cell decreases. Therefore, the primary battery consumption only needs to be calculated for the backup time (the time for suppressing voltage drop across the power capacitor), making it easy to estimate the primary battery life (calculate the required battery capacity).

[0016] The fourth invention is a power supply device characterized in that, in the second invention, the backup circuit further comprises a charging capacitor connected in parallel with the solar cell and a switching element connected in parallel with the resistive element, wherein the charging capacitor is charged by the solar cell, the switching element has an on state and an off state, and the backup circuit charges the backup capacitor with the charge accumulated in the charging capacitor by setting the switching element to the off state when the changeover switch switches to the second state and setting the switching element to the on state when the changeover switch switches to the first state.

[0017] This power supply unit utilizes the fact that the higher the output of the solar cell, the higher the frequency of intermittent drive to the load (the frequency of switching between the first and second states). This allows for appropriate charge control, where the amount of charge to the backup capacitor increases as the output of the solar cell increases, without the need to add circuits to determine the power generation status of the solar cell.

[0018] The fifth invention is a power supply device characterized in that, in the first invention, the backup circuit comprises a backup capacitor having a larger capacitance than the power supply capacitor and a charging capacitor connected in parallel with the solar cell, the charging capacitor is charged by the solar cell, the backup capacitor is connected to the charging capacitor via a switching element and a first diode and is charged by the charge stored in the charging capacitor, and is also connected to the power supply capacitor via a second diode to suppress a voltage drop in the power supply capacitor, the switching element has an on state and an off state, and the backup circuit charges the backup capacitor by the charge stored in the charging capacitor by setting the switching element to the off state when the changeover switch switches to the second state and setting the switching element to the on state when the changeover switch switches to the first state.

[0019] According to this power supply device, the backup capacitor can appropriately suppress the voltage drop of the power supply capacitor, and by utilizing the operation that the higher the output of the solar cell, the higher the frequency of the intermittent drive to the load (the frequency of switching between the first state and the second state), without adding a circuit for determining the power generation state of the solar cell, etc., it is possible to perform appropriate charging control such that the higher the output of the solar cell, the greater the amount of charge to the backup capacitor.

[0020] A sixth invention is a sensor device comprising a power supply device according to any one of the first to fifth inventions, and a sensor circuit connected to the power supply device as the load, which performs a predetermined detection operation by receiving power supply from the power supply device and outputs a detection signal according to the detection result of the detection operation.

[0021] According to this sensor device, when the output of the solar cell is small and sufficient power supply cannot be obtained from the solar cell, the backup circuit can suppress the voltage drop of the power supply capacitor. Thereby, when the output of the solar cell increases and charging of the power supply capacitor by the solar cell is started, the time until the voltage of the power supply capacitor becomes equal to or higher than the first threshold value can be shortened. After the output of the solar cell changes from a small state to a large state, the time until power is supplied to the sensor circuit can be shortened, and the sensor circuit can be operated earlier.

Effect of the Invention

[0022] According to an aspect of the present invention, it is possible to provide a power supply device and a sensor device that can suppress a voltage drop of a power supply capacitor.

Brief Description of the Drawings

[0023] [Figure 1] It is a block diagram schematically showing a remote control device according to an embodiment. [Figure 2] It is a graph schematically showing an example of the operation of the power supply device. [Figure 3]It is a graph schematically showing an example of the operation of a power supply device. [Figure 4] It is a block diagram schematically showing a modification example of a power supply device. [Figure 5] It is a graph schematically showing an example of the operation of a modified power supply device. [Figure 6] It is a block diagram schematically showing a modification example of a power supply device. [Figure 7] It is a graph schematically showing an example of the operation of a modified power supply device. [Figure 8] It is a block diagram schematically showing a modification example of a power supply device. [Figure 9] It is a block diagram schematically showing a modification example of a power supply device.

Embodiments for Carrying Out the Invention

[0024] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In each drawing, the same components are denoted by the same reference numerals, and detailed descriptions thereof are omitted as appropriate. FIG. 1 is a block diagram schematically showing a remote control device according to an embodiment. As shown in FIG. 1, the remote control device 2 includes a sensor device 4, a radio transmitter 5, and switching elements 6 and 7.

[0025] The remote control device 2 is installed and used in a toilet space. The toilet space is, for example, a public toilet space (toilet room) provided in a public facility such as a commercial facility or an office. The remote control device 2, for example, non - contact detects the user's hand (hand - waving operation) and transmits a toilet cleaning signal to a control device having a toilet cleaning function in response to the detection of the user's hand. The remote control device 2 is, for example, a remote control device for toilet cleaning. The control device is, for example, a control device that performs opening and closing control of a solenoid valve that switches the supply of cleaning water to the toilet and the stop of the supply of cleaning water. The toilet is, for example, a flush toilet (western - style sitting toilet). In this case, the remote control device 2 is installed and used together with the toilet in a toilet booth (private room) provided in the toilet space.

[0026] The sensor device 4 comprises a power supply unit 10 and a human body sensor 12 (sensor circuit). The power supply unit 10 supplies power to the human body sensor 12. The human body sensor 12 is connected to the power supply unit 10 as a load and, by receiving power from the power supply unit 10, performs a predetermined detection operation and outputs a detection signal according to the detection result of the detection operation. The human body sensor 12 has a pair of power terminals. The human body sensor 12 performs the detection operation by receiving DC power from the power supply unit 10 via the pair of power terminals.

[0027] The human body sensor 12 performs a non-contact detection operation to detect the user's hand, for example, by receiving power from the power supply unit 10. The human body sensor 12 is, for example, an active type photoelectric sensor. The human body sensor 12 performs, for example, infrared irradiation and infrared reception. The human body sensor 12 detects the user's hand non-contact when the irradiated infrared light is reflected by the user's hand and the magnitude of the received infrared light exceeds a threshold.

[0028] The radio transmitter 5 has a pair of power terminals. The switching elements 6 and 7 have a pair of main terminals and a control terminal. The switching elements 6 and 7 also have an ON state in which current flows between the pair of main terminals and an OFF state in which the flow of current between the pair of main terminals is interrupted. The switching elements 6 and 7 are semiconductor switching elements such as FETs. Note that the OFF state is not limited to a state in which no current flows at all between the pair of main terminals, but may also be a state in which a weak current flows between the pair of main terminals that does not affect the operation of the remote control device 2. In other words, the OFF state is a state in which the magnitude of the current flowing between the pair of main terminals is smaller than that of the ON state.

[0029] The control terminal of the switching element 6 is connected to the human body sensor 12. One main terminal of the switching element 6 is connected to the control terminal of the switching element 7. The other main terminal of the switching element 6 is electrically connected to the common potential (ground potential) portion of the power supply unit 10. One main terminal of the switching element 7 is connected to the output terminal of the power supply unit 10. The other main terminal of the switching element 7 is connected to one power supply terminal of the radio transmitter 5. The other power supply terminal of the radio transmitter 5 is electrically connected to the common potential portion of the power supply unit 10.

[0030] The human body sensor 12 performs detection operations in response to power supplied from the power supply unit 10. When it does not detect a user's hand, it turns off the switching element 6, and when it detects a user's hand, it turns on the switching element 6. This detection signal is output to the control terminal of the switching element 6.

[0031] When the switching element 6 switches from the off state to the on state in response to the detection of the user's hand, it switches the switching element 7 from the off state to the on state. As a result, power is supplied from the power supply unit 10 to the radio transmitter 5 in response to the detection of the user's hand by the human body sensor 12.

[0032] The radio transmitter 5 starts operating in response to power supply from the power supply unit 10 and transmits a toilet flushing signal wirelessly to the control unit. As a result, when the human body sensor 12 detects the user's hand, the toilet flushing signal is transmitted to the control unit and the toilet is flushed.

[0033] The configuration of the remote control device 2 is not limited to the above. The configuration of the remote control device 2 may be any configuration that can appropriately transmit a toilet flushing signal to the control device in response to the detection of the user's hand by the human body sensor 12. The toilet flushing signal transmitted from the remote control device 2 to the external control device is not limited to a radio wave signal, but may also be a radio signal (infrared signal) for infrared communication, for example. The toilet flushing signal transmitted from the remote control device 2 to the external control device may also be a wired signal, for example. In this case, for example, the detection signal from the human body sensor 12 may be transmitted to the external control device as a toilet flushing signal. In this case, for example, the sensor device 4 may be used as the remote control device 2.

[0034] The power supply unit 10 includes a solar cell 20, a power capacitor 22, a rectifier element 24, a changeover switch 26, a voltage detection circuit 28, and a backup circuit 30.

[0035] The solar cell 20 has a positive electrode and a negative electrode. The solar cell 20 receives light and, using the photovoltaic effect, converts the light energy into electrical energy (power), thereby generating a DC power between the positive and negative electrodes whose magnitude corresponds to the intensity of the received light. As a result, the power supply device 10 uses the solar cell 20 as a power source. The common potential of the power supply device 10 is, for example, the potential of the negative electrode of the solar cell 20.

[0036] The power capacitor 22 has a pair of electrodes. One electrode of the power capacitor 22 is connected to the positive electrode of the solar cell 20. The other electrode of the power capacitor 22 is connected to the negative electrode of the solar cell 20. As a result, the power capacitor 22 is charged by the solar cell 20.

[0037] The rectifier element 24 is placed between the solar cell 20 and the power capacitor 22. More specifically, the rectifier element 24 is placed between the positive electrode of the solar cell 20 and one electrode of the power capacitor 22. The rectifier element 24 rectifies the flow of current from the solar cell 20 toward the power capacitor 22. In other words, the rectifier element 24 suppresses the current flowing from the power capacitor 22 toward the solar cell 20. The rectifier element 24 is, for example, a diode.

[0038] The changeover switch 26 switches between a first state in which the power stored in the power capacitor 22 can be supplied to the load, which is the human body sensor 12, and a second state in which the supply of power to the human body sensor 12 is stopped.

[0039] The changeover switch 26, like the switching elements 6 and 7, is a semiconductor switching element such as an FET. The changeover switch 26 has a pair of main terminals and control terminals, and has an on state and an off state. One main terminal of the changeover switch 26 is connected to one electrode of the power supply capacitor 22. The other main terminal of the changeover switch 26 is connected to one power supply terminal of the human body sensor 12. The other power supply terminal of the human body sensor 12 is electrically connected to the common potential portion of the power supply unit 10 (the negative electrode of the solar cell 20).

[0040] In this example, by turning the changeover switch 26 to the ON state, a first state is achieved in which the power stored in the power capacitor 22 can be supplied to the human body sensor 12, and by turning the changeover switch 26 to the OFF state, a second state is achieved in which the supply of power to the human body sensor 12 is stopped.

[0041] In this way, the power supply unit 10 uses the power stored in the power capacitor 22 as the power supply for the human body sensor 12. In other words, the human body sensor 12 receives power from the power supply unit 10 and performs detection operations in response to the changeover switch 26 switching to the first state.

[0042] In this example, one main terminal of the switching element 7 is connected to one electrode of the power capacitor 22. As a result, the power supply unit 10 also uses the power stored in the power capacitor 22 as the power source for the radio transmitter 5. The radio transmitter 5 operates when the changeover switch 26 switches to the first state, the human body sensor 12 is activated, and the human body sensor 12 detects the user's hand and receives power from the power supply unit 10.

[0043] The configuration for switching between the first and second states is not limited to the above, and any configuration that allows for appropriate switching between the first and second states by switching the changeover switch 26 between the on and off states is acceptable.

[0044] The voltage detection circuit 28 detects the voltage of the power supply capacitor 22. The voltage detection circuit 28 is connected to a pair of electrodes of the power supply capacitor 22, thereby detecting the voltage between the pair of electrodes of the power supply capacitor 22. When the voltage of the power supply capacitor 22 exceeds a first threshold, the voltage detection circuit 28 causes the changeover switch 26 to switch to the first state. After the voltage of the power supply capacitor 22 exceeds the first threshold, when it drops to or below a second threshold (which is lower than the first threshold), the changeover switch 26 causes the changeover switch 26 to switch to the second state.

[0045] The voltage detection circuit 28 is connected, for example, to the control terminal of the changeover switch 26. The voltage detection circuit 28 causes the changeover switch 26 to switch to the first state by switching it from the off state to the on state when, for example, the voltage of the power supply capacitor 22 becomes above a first threshold. Then, the voltage detection circuit 28 causes the changeover switch 26 to switch to the second state by switching it from the on state to the off state when, for example, the voltage of the power supply capacitor 22 has become above the first threshold and then fallen to below a second threshold which is lower than the first threshold. A reset IC is used in the voltage detection circuit 28, for example.

[0046] The backup circuit 30 suppresses a voltage drop across the power supply capacitor 22. The backup circuit 30 prevents the voltage of the power supply capacitor 22 from falling below a predetermined voltage below a second threshold. In other words, the backup circuit 30 delays the discharge of the power supply capacitor 22 when its voltage drops to a predetermined voltage. For example, the backup circuit 30 slows the discharge rate of the power supply capacitor 22 in the range below the predetermined voltage compared to the discharge rate of the power supply capacitor 22 in the range above the predetermined voltage.

[0047] The backup circuit 30 includes, for example, a first diode 31, a second diode 32, a resistor 33, and a backup capacitor 34.

[0048] The capacitance of the backup capacitor 34 is greater than that of the power supply capacitor 22. For example, the capacitance of the backup capacitor 34 is 100 times or more than that of the power supply capacitor 22. Thus, the backup circuit 30 has, for example, a backup capacitor 34 with a larger capacitance than the power supply capacitor 22.

[0049] One end of the resistive element 33 is connected between the solar cell 20 and the rectifier element 24. More specifically, one end of the resistive element 33 is connected between the positive electrode of the solar cell 20 and the anode of the rectifier element 24. The other end of the resistive element 33 is connected to the anode of the first diode 31. The cathode of the first diode 31 is connected to one electrode of the backup capacitor 34. The other electrode of the backup capacitor 34 is connected to the negative electrode of the solar cell 20.

[0050] Furthermore, one electrode of the backup capacitor 34 is connected to the anode of the second diode 32. In other words, the anode of the second diode 32 is connected between the cathode of the first diode 31 and one electrode of the backup capacitor 34. The cathode of the second diode 32 is connected between the rectifier element 24 and the power supply capacitor 22. More specifically, the cathode of the second diode 32 is connected between the cathode of the rectifier element 24 and one electrode of the power supply capacitor 22.

[0051] As a result, the backup capacitor 34 is charged by the solar cell 20 via the resistor 33 and the first diode 31, and connected to the power supply capacitor 22 via the second diode 32, thereby suppressing the voltage drop of the power supply capacitor 22. Note that the connection order of the first diode 31 and the resistor 33 may be reversed. For example, the anode of the first diode 31 may be connected between the solar cell 20 and the rectifier element 24, the cathode of the first diode 31 may be connected to one end of the resistor 33, and the other end of the resistor 33 may be connected to one electrode of the backup capacitor 34.

[0052] Figures 2 and 3 are graphs that schematically represent an example of the operation of the power supply unit. Figure 2 schematically illustrates an example of the operation of the power supply unit 10 when the backup capacitor 34 is not charged. Figure 3 schematically illustrates an example of the operation of the power supply unit 10 when the backup capacitor 34 is charged.

[0053] In toilet spaces, the lights may be turned off when not in use. In particular, in toilet spaces located inside buildings and without windows, when the lights are turned off, it becomes completely dark, and the output of the solar panel 20 approaches zero. If the darkness continues, the voltage of the power capacitor 22 will gradually decrease due to leakage current in the circuit, etc., and will eventually become zero.

[0054] The power capacitor 22 is charged by the solar cell 20 when the lights in the toilet space are turned on and the output of the solar cell 20 increases. When the power capacitor 22 is charged by the solar cell 20 and the voltage V1 of the power capacitor 22 becomes equal to or greater than the first threshold VTH, the voltage detection circuit 28 causes the changeover switch 26 to switch to the first state. As a result, the power stored in the power capacitor 22 is supplied to the human body sensor 12, and the human body sensor 12 performs detection.

[0055] At this time, the human body sensor 12 detects the user's hand and switches the switching element 6 to the ON state, thereby supplying the power stored in the power capacitor 22 to the radio wave transmitter 5. In this way, the power supply unit 10 supplies power to the sensor circuit (human body sensor 12) and also supplies power to another device (radio wave transmitter 5) connected to the sensor device 4 when the voltage V1 of the power capacitor 22 becomes equal to or greater than the first threshold VTH. In other words, the power capacitor 22 supplies the stored power to the sensor circuit and also supplies the stored power to another load when the voltage V1 of the power capacitor 22 becomes equal to or greater than the first threshold VTH.

[0056] When the human body sensor 12 performs a detection operation, the power consumption by the human body sensor 12 causes the voltage V1 of the power supply capacitor 22 to drop. When the voltage V1 of the power supply capacitor 22 drops to a second threshold VTL which is lower than the first threshold VTH, the voltage detection circuit 28 causes the changeover switch 26 to switch to the second state. As a result, the power supply to the human body sensor 12 is stopped, and the human body sensor 12 stops its detection operation.

[0057] When the power supply to the human body sensor 12 is stopped, the voltage V1 of the power capacitor 22 rises again due to charging from the solar cell 20. The power supply unit 10 then repeats this process. In this way, the power supply unit 10 intermittently drives the human body sensor 12, which is the load. This reduces the power consumption of the power supply unit 10 and the human body sensor 12. As a result, the human body sensor 12 can be driven appropriately even when, for example, the lighting in the toilet space is dim and the output of the solar cell 20 is low. In addition, the frequency of intermittent driving can be appropriately set by appropriately setting the first threshold VTH and the second threshold VTL, for example. This improves the responsiveness to operations such as hand gestures even when the human body sensor 12 is driven intermittently.

[0058] As shown in Figures 2 and 3, when the lights in the toilet space are turned on and the output of the solar cell 20 increases, the backup capacitor 34 is also charged by the solar cell 20. At this time, since there is a resistive element 33 between the solar cell 20 and the backup capacitor 34, the output of the solar cell 20 prioritizes charging the power capacitor 22 over the backup capacitor 34. This reduces the inconvenience of the intermittent drive of the load being slowed down due to the charging of the backup capacitor 34.

[0059] As shown in Figure 2, when the output of the solar cell 20 is substantially zero, if the voltage V2 of the backup capacitor 34 is substantially zero, then the voltage V1 of the power capacitor 22 is also substantially zero. In this case, when the output of the solar cell 20 increases, charging of the power capacitor 22 begins from a state where the voltage V1 of the power capacitor 22 is substantially zero, so it takes time for the voltage V1 of the power capacitor 22 to reach the first threshold VTH.

[0060] In contrast, as shown in Figure 3, when the output of the solar cell 20 is virtually zero and there is still voltage remaining in the backup capacitor 34, the magnitude of the voltage V1 of the power capacitor 22 is the voltage V2 of the backup capacitor 34 minus the forward voltage VF2 of the second diode 32.

[0061] In this way, the power supply unit 10 can suppress the voltage drop of the power supply capacitor 22 by the backup circuit 30. The backup circuit 30 has a backup capacitor 34 with a larger capacitance than the power supply capacitor 22. This makes it possible to speed up the charging rate of the power supply capacitor 22 by the solar cell 20, while suppressing the voltage drop of the power supply capacitor 22 by the backup capacitor 34.

[0062] As shown in Figure 3, in the power supply unit 10, when the output of the solar cell 20 increases, charging of the power supply capacitor 22 begins when the voltage V1 of the power supply capacitor 22 is in the state of V2-VF2. In this example, the predetermined voltage is V2-VF2. The backup circuit 30 prevents the voltage of the power supply capacitor 22 from dropping below V2-VF2.

[0063] This makes it possible to shorten the time it takes for the voltage V1 of the power supply capacitor 22 to reach the first threshold VTH, compared to the case where charging of the power supply capacitor 22 starts from a state where the voltage V1 of the power supply capacitor 22 is virtually zero.

[0064] Thus, in the power supply unit 10, when the output of the solar cell 20 is low due to the lighting in the toilet area being turned off, and sufficient power cannot be supplied from the solar cell 20, the backup circuit 30 can suppress the voltage drop of the power capacitor 22. As a result, when the output of the solar cell 20 increases and charging of the power capacitor 22 by the solar cell 20 begins, the time until the voltage of the power capacitor 22 reaches or exceeds the first threshold VTH can be shortened. This shortens the time from when the output of the solar cell 20 changes from a low state to a high state until power is supplied to the load, making it possible to operate the load earlier.

[0065] Furthermore, in the power supply unit 10, the backup capacitor 34 can appropriately suppress the voltage drop of the power supply capacitor 22. Also, by charging the backup capacitor 34 via the resistor element 33, charging of the power supply capacitor 22 based on the output of the solar cell 20 can be given priority over charging of the backup capacitor 34. This prevents the time it takes for power to be supplied to the load from being extended due to charging of the backup capacitor 34.

[0066] The voltage V2 of the backup capacitor 34 charges and eventually reaches the same level as the voltage V1 of the power supply capacitor 22. However, due to the voltage drop (forward voltage VF2) at the second diode 32, the backup capacitor 34 is never used to drive the load. The backup capacitor 34 only performs the role of suppressing the discharge of the power supply capacitor 22. The backup capacitor 34 is not unintentionally consumed by the load and does not experience a voltage drop.

[0067] For example, the time between a user entering the toilet and flushing the toilet bowl can be as short as 30 seconds for urination. Also, if the previous user forgot to flush, the user will want to flush the toilet bowl immediately upon entering. Therefore, it is desirable to be able to flush the toilet bowl as quickly as possible.

[0068] Even if the output of the solar cell 20 is small, the charging time can be short if the capacity of the power capacitor 22 is small. However, if an active photoelectric sensor is used for the human body sensor 12, for example, infrared light is irradiated towards the human body, which requires a large current instantaneously, and the capacity of the power capacitor 22 must be large enough to supply that current.

[0069] Furthermore, when transmitting a toilet flushing signal via radio waves or infrared rays, the power capacitor 22 requires a predetermined capacity to supply the transmission energy. For example, in the remote control device 2, the capacity of the power capacitor 22 must be determined considering not only the power consumption of the human body sensor 12 but also the power consumption of the radio wave transmitter 5. The human body sensor 12 is driven when the power capacitor 22 is charged to the first threshold VTH (the voltage of the power capacitor 22 drops slightly), and even when the radio wave transmitter 5 transmits radio waves, the remaining voltage of the power capacitor 22 must be above the operating voltage for radio wave transmission. The capacity of the power capacitor 22 and the voltage of the voltage detection circuit 28 are determined accordingly. In this way, when it is necessary to secure the minimum capacity and charging voltage of the power capacitor 22 according to the human body sensor 12 (sensor circuit) and the radio wave transmitter 5 (another load), the charge that needs to be stored in the power capacitor 22 increases, and the charging time of the power capacitor 22 also increases accordingly.

[0070] Based on these requirements, for example, if the operating voltage of the device is 3V and the required capacitance of the power capacitor 22 is 100μF, and the output of the solar cell 20 is 10μA, it will take approximately 30 seconds to charge from 0V to 3V. If the illumination in the toilet is low, it will take even longer. This may be unacceptable as a waiting time before the toilet bowl can be flushed.

[0071] In contrast, the power supply device 10 according to this embodiment suppresses the voltage drop of the power supply capacitor 22 by the backup circuit 30, thereby shortening the time until power is supplied to the load. Therefore, for example, compared to a configuration without the backup circuit 30, the time until toilet flushing can be performed can be shortened. For example, it is possible to prevent the toilet from being flushed at the timing intended by the user, which could cause discomfort to the user.

[0072] Figure 4 is a block diagram schematically representing a modified power supply unit. As shown in Figure 4, the power supply unit 10a has a backup circuit 30a which includes a diode 40 and a primary battery 42. Components that are substantially the same in function and configuration as those in the above embodiment are denoted by the same reference numerals, and detailed explanations are omitted.

[0073] The cathode of diode 40 is connected between the rectifier element 24 and the power supply capacitor 22. More specifically, the cathode of diode 40 is connected between the cathode of the rectifier element 24 and one electrode of the power supply capacitor 22. The anode of diode 40 is connected to the positive electrode of the primary battery 42. The negative electrode of the primary battery 42 is connected to the negative electrode of the solar cell 20.

[0074] Thus, the backup circuit 30a has a primary battery 42 connected to the power supply capacitor 22 via a diode 40. As a result, in the backup circuit 30a, the primary battery 42 is connected to the power supply capacitor 22 via the diode 40, thereby suppressing the voltage drop of the power supply capacitor 22.

[0075] Figure 5 is a graph that schematically represents an example of the operation of a modified power supply unit. As shown in Figure 5, the magnitude of the voltage obtained by subtracting the forward voltage VFa of the diode 40 from the voltage VB of the primary battery 42 is lower than the first threshold VTH. The magnitude of the voltage obtained by subtracting the forward voltage VFa of the diode 40 from the voltage VB of the primary battery 42 is, for example, lower than the second threshold VTL.

[0076] As a result, in the backup circuit 30a, when the output of the solar cell 20 is substantially zero, the magnitude of the voltage V1 across the power capacitor 22 can be set to the magnitude of the voltage obtained by subtracting the forward voltage VFa of the diode 40 from the voltage VB of the primary battery 42. In this example, the predetermined voltage is VB-VFa. The backup circuit 30a suppresses the voltage of the power capacitor 22 from falling below VB-VFa.

[0077] Therefore, in the power supply unit 10a, as in the above embodiment, the voltage drop of the power supply capacitor 22 can be suppressed by the backup circuit 30a. In the power supply unit 10a, when the output of the solar cell 20 increases, charging of the power supply capacitor 22 begins when the magnitude of the voltage V1 of the power supply capacitor 22 is VB-VFa. As a result, as in the above embodiment, the time it takes for the voltage V1 of the power supply capacitor 22 to reach the first threshold VTH can be shortened compared to the case where charging of the power supply capacitor 22 begins when the voltage V1 of the power supply capacitor 22 is substantially zero.

[0078] Thus, in the power supply unit 10a, the primary battery 42 can appropriately suppress the voltage drop of the power capacitor 22. Furthermore, by setting the magnitude of the voltage obtained by subtracting the forward voltage of the diode 40 from the voltage of the primary battery 42 to be lower than the first threshold VTH, it is possible to suppress the consumption of power from the primary battery 42 in driving the load. As a result, when the environment becomes low light and the output of the solar cell 20 decreases, the power from the primary battery 42 can be appropriately used to suppress the voltage drop of the power capacitor 22. Therefore, the consumption of the primary battery 42 only needs to be calculated by calculating the backup time (the time for suppressing the voltage drop of the power capacitor 22), making it easy to estimate the lifespan of the primary battery 42 (calculation of the required battery capacity).

[0079] The power supply unit 10a has, for example, a battery holder (not shown) that detachably supports the primary battery 42. This makes the primary battery 42 replaceable in the power supply unit 10a. Furthermore, by making the primary battery 42 detachable in this way, it is possible to, for example, not install the primary battery 42 when the lighting in the toilet space is bright and sufficient power can be obtained from the solar cell 20, and to install the primary battery 42 only when the lighting in the toilet space is dim and sufficient power cannot be obtained from the solar cell 20. The backup circuit 30a may have, for example, a battery support section that detachably supports the primary battery 42, and may be configured so that the primary battery 42 can be installed only when necessary.

[0080] Figure 6 is a block diagram schematically representing a modified power supply unit. As shown in Figure 6, the backup circuit 30b of the power supply unit 10b further includes a charging capacitor 35 and a switching element 36, in addition to the configuration of the backup circuit 30 shown in Figure 1.

[0081] The charging capacitor 35 is connected in parallel with the solar cell 20. As a result, the charging capacitor 35 is charged by the solar cell 20. The capacitance of the charging capacitor 35 is smaller than that of the backup capacitor 34. The capacitance of the charging capacitor 35 is, for example, smaller than that of the power supply capacitor 22. For example, the capacitance of the charging capacitor 35 is 0.1 times or less the capacitance of the power supply capacitor 22.

[0082] The switching element 36 is connected in parallel with the resistive element 33. The switching element 36 is a semiconductor switching element, such as an FET, similar to the changeover switch 26. The switching element 36 has a pair of main terminals and control terminals, and has an on state and an off state.

[0083] The backup circuit 30b charges the backup capacitor 34 with the charge stored in the charging capacitor 35 by turning off the switching element 36 when the changeover switch 26 switches to the second state and turning on the switching element 36 when the changeover switch 26 switches to the first state.

[0084] The control terminals of the switching element 36 are connected, for example, to the control terminals of the changeover switch 26. In other words, the control terminals of the switching element 36 are connected to the voltage detection circuit 28. As a result, the switching element 36 switches between an on state and an off state in response to the on state and off state of the changeover switch 26. In this example, when the changeover switch 26 is turned on, the switching element 36 turns on, and when the changeover switch 26 is turned off, the switching element 36 turns off.

[0085] Figure 7 is a graph that schematically represents an example of the operation of a modified power supply unit. As shown in Figure 7, in the backup circuit 30b as well, when the lights in the toilet space are turned on and the output of the solar cell 20 increases, the power capacitor 22 is charged by the solar cell 20, and the backup capacitor 34 is charged by the solar cell 20 through the charging current via the resistor element 33.

[0086] Furthermore, in the backup circuit 30b, when the output of the solar cell 20 increases, the charging capacitor 35 is also charged by the solar cell 20. At this time, the capacity of the charging capacitor 35 is smaller than the capacity of the power supply capacitor 22 and the backup capacitor 34, so the charging of the charging capacitor 35 is completed faster than the charging of the power supply capacitor 22 and the backup capacitor 34.

[0087] When the voltage V1 of the power supply capacitor 22 exceeds the first threshold VTH, the voltage detection circuit 28 causes the changeover switch 26 to switch to the first state, and the power stored in the power supply capacitor 22 is supplied to the human body sensor 12, and the switching element 36 is turned on.

[0088] When the switching element 36 is turned on, the terminals of the resistor 33 become conductive due to the switching element 36, and the charge stored in the charging capacitor 35 is transferred to the backup capacitor 34. The switching element 36 switches in response to the switching of the changeover switch 26, and each time the switching element 36 is switched to the on state, the charge stored in the charging capacitor 35 is supplied to the backup capacitor 34. As a result, the backup circuit 30b can charge the backup capacitor 34 faster compared to the case where the backup capacitor 34 is charged only through the resistor 33.

[0089] In the method of limiting the charge amount of the backup capacitor 34 using a resistor element 33, if the resistance value of the resistor element 33 is small, the backup capacitor 34 will charge faster, but the current supplied to the power capacitor 22 will decrease, which may slow down the frequency of intermittent drive of the load. Conversely, if the resistance value of the resistor element 33 is large, the backup capacitor 34 will not charge very well. It would be good to change the resistance value of the resistor element 33 according to the power generation state of the solar cell 20 (lower the resistance value when power generation is high), but this would require a circuit to determine the power generation state of the solar cell 20, and the power consumption of the circuit that determines this would increase.

[0090] The backup circuit 30b utilizes the fact that the frequency of intermittent drive to the load increases as the output of the solar cell 20 increases. This enables appropriate charge control, where the amount of charge to the backup capacitor 34 increases as the output of the solar cell 20 increases, without the need to add a circuit to determine the power generation status of the solar cell 20.

[0091] For example, it is conceivable to omit the charging capacitor 35 and provide only the switching element 36. However, in this case, since the on-time of the switching element 36 is the same as the load energization time, the on-time may be too short to charge the backup capacitor 34 from the solar cell 20, potentially preventing charging from progressing.

[0092] Therefore, a charging capacitor 35 is provided. This allows the output of the solar cell 20 to be temporarily stored in the charging capacitor 35, and then the charge to be transferred from the charging capacitor 35 to the backup capacitor 34. As a result, even if the on-time of the switching element 36 is short, the backup capacitor 34 can be charged.

[0093] Furthermore, the amount of charge applied to the backup capacitor 34 per load energization cycle can be set by the capacitance value of the charging capacitor 35. Therefore, the ratio in which the output of the solar cell 20 is distributed between load energization and charging of the backup capacitor 34 can be easily set by the capacitance of the charging capacitor 35.

[0094] Figure 8 is a block diagram schematically representing a modified power supply unit. As shown in Figure 8, in the power supply unit 10c, the resistor element 33 is omitted in the backup circuit 30c compared to the configuration of the backup circuit 30b shown in Figure 6.

[0095] In the backup circuit 30c, the backup capacitor 34 is connected to the charging capacitor 35 via the switching element 36 and the first diode 31, and is charged by the charge stored in the charging capacitor 35. It is also connected to the power supply capacitor 22 via the second diode 32, thereby suppressing the voltage drop of the power supply capacitor 22.

[0096] The backup circuit 30c charges the backup capacitor 34 with the charge stored in the charging capacitor 35 by turning off the switching element 36 when the changeover switch 26 switches to the second state and turning on the switching element 36 when the changeover switch 26 switches to the first state.

[0097] In the backup circuit 30c, when the lights are turned on and the intermittent operation of the load (human body sensor 12) begins, the switching element 36 is switched between on and off in sync with this, and charging from the charging capacitor 35 to the backup capacitor 34 is repeated. As a result, the backup circuit 30c can charge the backup capacitor 34 according to the brightness of the toilet space (the output level of the solar cell 20).

[0098] In the backup circuit 30c, the backup capacitor 34 can appropriately suppress the voltage drop of the power supply capacitor 22. Furthermore, by utilizing the fact that the intermittent drive frequency to the load (the switching frequency between the first and second states) increases as the output of the solar cell 20 increases, appropriate charge control becomes possible, where the amount of charge to the backup capacitor 34 increases as the output of the solar cell 20 increases, without the need to add a circuit to determine the power generation status of the solar cell 20.

[0099] Furthermore, if the resistor element 33 is not present, the backup capacitor 34 will not be charged at illumination levels insufficient to operate the human body sensor 12. For example, if the lighting is turned off and there is not enough light to operate the human body sensor 12, but it is not completely dark, having the resistor element 33 in parallel with the switching element 36 allows even a small current to compensate for leakage current in the circuit.

[0100] Furthermore, the resistor element 33 alone cannot charge the backup capacitor 34 in accordance with the brightness. As a result, the charging of the backup capacitor 34 becomes slow. Also, the switching element 36 alone cannot charge the backup capacitor 34 in low light conditions. If the resistor element 33 and the switching element 36 are connected in parallel, the roles can be divided according to the brightness: the switching element 36 charges the backup capacitor 34 in bright environments, and the resistor element 33 charges the backup capacitor 34 in dark environments. Therefore, it is preferable to provide both the resistor element 33 and the switching element 36, as shown in the configuration of the backup circuit 30b in Figure 6.

[0101] Figure 9 is a block diagram schematically representing a modified power supply unit. As shown in Figure 9, the power supply unit 10d has a backup circuit 30d that, in addition to the configuration of the backup circuit 30b shown in Figure 6, further includes a diode 40 and a primary battery 42. Thus, a backup capacitor 34 and a primary battery 42 may be used in combination as a backup means to suppress the voltage drop of the power supply capacitor 22.

[0102] The backup capacitor 34 of the power supply capacitor 22 is backed up by the excess power of the solar cell 20, which charges the backup capacitor 34. However, depending on the lighting environment of the toilet space, there may not even be enough power to charge the backup capacitor 34. In such cases, the primary battery 42 becomes useful in toilet spaces with poor lighting conditions (such as toilet spaces where the lights are off for long periods of time).

[0103] As in the backup circuit 30d, both a backup capacitor 34 and a primary battery 42 (battery support) are provided, allowing them to be used interchangeably depending on the lighting environment of the toilet space. This increases the versatility of the power supply unit 10d, for example.

[0104] The above embodiments show examples in which the sensor device 4 is applied to the remote control device 2 for flushing the toilet. The sensor device 4 is not limited to the remote control device 2 for flushing the toilet, but may be applied to other devices used in the toilet space. For example, the sensor device 4 may be used in an automatic faucet (hand basin) that detects the user's hand using a human body sensor 12 and automatically dispenses water. In this case, the sensor device 4 outputs a detection signal representing the detection result of the user's hand to a control device that controls the water dispensing.

[0105] Furthermore, in each of the above embodiments, a human body sensor 12 that detects the user's hand non-contact is shown as an example of a sensor circuit that performs a detection operation. The sensor circuit is not limited to the human body sensor 12 that detects the user's hand, but can be any sensor circuit that receives power from a power supply device, performs a predetermined detection operation, and outputs a detection signal according to the detection result of the detection operation.

[0106] The sensor circuit could be, for example, a proximity detection sensor that detects the approach of a user. In this case, the sensor circuit outputs a detection signal to, for example, the control device of a heated toilet seat that heats the toilet seat, so that the toilet seat can be heated (instantaneous heating) in response to the detection of a user's approach. Examples of proximity detection sensors include infrared sensors and radio wave sensors.

[0107] The sensor circuit could be, for example, an entry detection sensor that detects when a user enters a private room (toilet booth). In this case, the sensor circuit could output a detection signal to the control device of a display device that shows occupancy information (information indicating whether the private room is occupied or not), thereby enabling the display of occupancy information in response to the detection of a user entering the private room. Alternatively, the sensor circuit could output a detection signal to the control device of an audio device that outputs music, thereby enabling the output of music in response to the detection of a user entering the private room. Examples of entry detection sensors include infrared sensors and radio wave sensors.

[0108] The sensor circuit could be, for example, an open / close detection sensor that detects the opening and closing of a private room door. In this case, the sensor circuit outputs a detection signal to, for example, the control device of the toilet seat device that opens and closes the toilet lid, so that the toilet lid can be opened in response to the detection that the door has opened. Examples of open / close detection sensors include infrared sensors and radio wave sensors.

[0109] In each of the embodiments described above, the load of the power supply is shown as a sensor circuit. However, the load of the power supply is not limited to a sensor circuit and may be any load.

[0110] The embodiment may include the following configurations. (Composition 1) Solar cells and The power capacitor charged by the aforementioned solar cell, A rectifier element is provided between the solar cell and the power capacitor, which rectifies the flow of current in the direction from the solar cell to the power capacitor, A changeover switch that switches between a first state in which the power stored in the power capacitor can be supplied to the load, and a second state in which the supply of power to the load is stopped. A voltage detection circuit that detects the voltage of the power supply capacitor, causes the changeover switch to switch to the first state when the voltage of the power supply capacitor becomes equal to or greater than a first threshold, and causes the changeover switch to switch to the second state when the voltage of the power supply capacitor, after becoming equal to or greater than the first threshold, falls to or below a second threshold lower than the first threshold, A backup circuit to suppress the voltage drop of the aforementioned power supply capacitor, A power supply device characterized by having the following features.

[0111] (Configuration 2) The backup circuit has a backup capacitor with a larger capacitance than the power supply capacitor. The power supply device according to configuration 1, characterized in that the backup capacitor is charged by the solar cell via a resistive element and a first diode, and connected to the power supply capacitor via a second diode, thereby suppressing a voltage drop in the power supply capacitor.

[0112] (Composition 3) The backup circuit has a primary battery connected to the power capacitor via a diode. The power supply device according to configuration 1 or 2, characterized in that the magnitude of the voltage obtained by subtracting the forward voltage of the diode from the voltage of the primary battery is lower than the first threshold.

[0113] (Composition 4) The backup circuit further comprises a charging capacitor connected in parallel with the solar cell and a switching element connected in parallel with the resistive element. The charging capacitor is charged by the solar cell, The switching element has an ON state and an OFF state. The power supply device according to configuration 2, characterized in that the backup circuit charges the backup capacitor with the charge stored in the charging capacitor by setting the switching element to the off state when the changeover switch switches to the second state, and setting the switching element to the on state when the changeover switch switches to the first state.

[0114] (Composition 5) The backup circuit includes a backup capacitor with a larger capacitance than the power supply capacitor, and a charging capacitor connected in parallel with the solar cell. The charging capacitor is charged by the solar cell, The backup capacitor is connected to the charging capacitor via a switching element and a first diode, and is charged by the charge stored in the charging capacitor. It is also connected to the power supply capacitor via a second diode, thereby suppressing the voltage drop of the power supply capacitor. The switching element has an ON state and an OFF state. The power supply device according to configuration 1, characterized in that the backup circuit charges the backup capacitor with the charge stored in the charging capacitor by setting the switching element to the off state when the changeover switch switches to the second state, and setting the switching element to the on state when the changeover switch switches to the first state.

[0115] (Composition 6) A power supply unit as described in one of configurations 1 to 5, A sensor circuit connected to the power supply as the load, which receives power from the power supply to perform a predetermined detection operation and outputs a detection signal corresponding to the detection result of the detection operation, A sensor device characterized by having the following features.

[0116] Embodiments of the present invention have been described above. However, the present invention is not limited to these descriptions. Modifications made by those skilled in the art to the above-described embodiments are also included within the scope of the present invention, as long as they retain the features of the present invention. For example, the shape, dimensions, materials, and arrangement of each element of the power generation module and remote control device are not limited to those exemplified and can be modified as appropriate. Furthermore, the elements of each of the above-described embodiments can be combined to the extent technically feasible, and combinations thereof are also included within the scope of the present invention, as long as they retain the features of the present invention. [Explanation of Symbols]

[0117] 2…Remote control device, 4…Sensor device, 5…Radio wave transmitter, 6, 7…Switching elements, 10, 10a~10d…Power supply device, 12…Human body sensor, 20…Solar cell, 22…Power supply capacitor, 24…Rectifier element, 26…Changeover switch, 28…Voltage detection circuit, 30, 30a~30d…Backup circuit, 31…First diode, 32…Second diode, 33…Resistor element, 34…Backup capacitor, 35…Charging capacitor, 36…Switching element, 40…Diode, 42…Primary battery

Claims

1. Solar cells and The power capacitor charged by the aforementioned solar cell, A rectifier element is provided between the solar cell and the power capacitor, which rectifies the flow of current in the direction from the solar cell to the power capacitor, A changeover switch that switches between a first state in which the power stored in the power capacitor can be supplied to the load, and a second state in which the supply of power to the load is stopped. A voltage detection circuit that detects the voltage of the power supply capacitor, causes the changeover switch to switch to the first state when the voltage of the power supply capacitor becomes equal to or greater than a first threshold, and causes the changeover switch to switch to the second state when the voltage of the power supply capacitor, after becoming equal to or greater than the first threshold, falls to or below a second threshold lower than the first threshold, A backup circuit to suppress the voltage drop of the aforementioned power supply capacitor, A power supply device characterized by having the following features.

2. The backup circuit has a backup capacitor with a larger capacitance than the power supply capacitor. The power supply device according to claim 1, characterized in that the backup capacitor is charged by the solar cell via a resistive element and a first diode, and connected to the power supply capacitor via a second diode, thereby suppressing a voltage drop in the power supply capacitor.

3. The backup circuit has a primary battery connected to the power capacitor via a diode. The power supply device according to claim 1, characterized in that the magnitude of the voltage obtained by subtracting the forward voltage of the diode from the voltage of the primary battery is lower than the first threshold.

4. The backup circuit further comprises a charging capacitor connected in parallel with the solar cell and a switching element connected in parallel with the resistive element. The charging capacitor is charged by the solar cell, The switching element has an ON state and an OFF state. The power supply device according to claim 2, characterized in that the backup circuit charges the backup capacitor with the charge stored in the charging capacitor by setting the switching element to the off state when the changeover switch switches to the second state, and setting the switching element to the on state when the changeover switch switches to the first state.

5. The backup circuit includes a backup capacitor with a larger capacitance than the power supply capacitor, and a charging capacitor connected in parallel with the solar cell. The charging capacitor is charged by the solar cell, The backup capacitor is connected to the charging capacitor via a switching element and a first diode, and is charged by the charge stored in the charging capacitor. It is also connected to the power supply capacitor via a second diode, thereby suppressing the voltage drop of the power supply capacitor. The switching element has an ON state and an OFF state. The power supply device according to claim 1, characterized in that the backup circuit charges the backup capacitor with the charge stored in the charging capacitor by setting the switching element to the off state when the changeover switch switches to the second state, and setting the switching element to the on state when the changeover switch switches to the first state.

6. A power supply device according to any one of claims 1 to 5, A sensor circuit connected to the power supply as the load, which receives power from the power supply to perform a predetermined detection operation and outputs a detection signal corresponding to the detection result of the detection operation, A sensor device characterized by having the following features.

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