WO2015037350A1

WO2015037350A1 - Sensor

Info

Publication number: WO2015037350A1
Application number: PCT/JP2014/069821
Authority: WO
Inventors: 恭孝前川
Original assignee: 株式会社村田製作所
Priority date: 2013-09-10
Filing date: 2014-07-28
Publication date: 2015-03-19

Abstract

An energy conversion element gathers energy from the surrounding environment, generates electrical energy, and outputs same as an electrical signal. An amplifier operates on power supplied by an electricity-storage device. The electrical signal outputted by the energy conversion element is inputted to the electricity-storage device and the amplifier via a current pathway. This results in a sensor in which, even if the state of charge of an electricity-storage device drops, said electricity-storage device does not need to be replaced.

Description

Sensor

The present invention relates to a sensor provided with a power storage device.

In order to operate various sensors such as an optical sensor, an operational amplifier (op amp) for amplifying an output signal from the sensor is necessary. Therefore, an operational amplifier power supply must be prepared. When a commercial power source is used as the power source, it is necessary to provide wiring for the commercial power source. In the case of using a power storage device as a power source, the power storage device must be periodically replaced according to the degree of consumption of the power storage device. There is a need for a sensor that does not require periodic replacement of a power storage device.

Patent Document 1 discloses a lighting system that is independent from commercial power and does not require maintenance. FIG. 9 shows a block diagram of this illumination system. The lighting system includes a power supply unit 110 and a lighting unit 120. The power supply unit 110 includes a solar cell module 111, a secondary battery 112, a backflow prevention diode 113, and a sunshine discrimination switch circuit 114. The illumination unit 120 includes a light emitting diode 121 and a lighting control circuit 122.

The solar cell module 111 has a function as a power generation element and a function of a sunshine discrimination sensor. The sunshine discrimination switch circuit 114 is turned on / off depending on whether or not there is an output from the solar cell module 111. During the day, the secondary battery 112 is charged with the electric power generated by the solar cell module 111. At night, the power stored in the secondary battery 112 is supplied to the lighting unit 120. The light-emitting diode 121 blinks by the lighting control circuit 122 controlling the blinking period, the duty ratio, the peak current value, and the like.

JP-A-7-219467

In the lighting system shown in FIG. 9, since the secondary battery 112 is charged by sunlight energy during the day, periodic battery replacement is unnecessary. However, since the output power of the solar cell module 111 is supplied to the secondary battery during the daytime, it is difficult to use the solar cell module 111 as an optical sensor.

An object of the present invention is to provide a sensor that does not require replacement of a power storage device even when the state of charge of the power storage device decreases.

According to one aspect of the invention,
An energy conversion element that harvests energy from the surrounding environment to generate electrical energy and outputs it as an electrical signal;
A power storage device;
An amplifier that operates by receiving power from the power storage device;
A sensor having a current path for inputting an electric signal output from the energy conversion element to the power storage device and the amplifier is provided.

When the electric signal output from the energy conversion element is input to the power storage device, the power storage device is charged. For this reason, the battery replacement resulting from the reduced state of charge of the power storage device is unnecessary. In addition, when the electrical signal output from the energy conversion element is input to the amplifier, the amplifier outputs an electrical signal corresponding to the surrounding environmental energy. Thereby, the output of the amplifier can be used as the sensor output.

The power output terminal for taking out power from the power storage device may be further included. As a result, the sensor can be used as a power source for an external device.

The current path includes a switching element that switches between a first connection state in which an electrical signal output from the energy conversion element is input to the power storage device and a second connection state input to the amplifier. It is good also as a structure. When the switching element is in the first connection state, the power storage device is charged, so that a decrease in the state of charge can be compensated.

The power storage device may further include a power storage monitoring circuit that detects a charge state of the power storage device and switches a connection state of the switching element based on the charge state of the power storage device. An excessive decrease in the state of charge of the power storage device can be prevented.

A power storage monitoring circuit for detecting a state of charge of the power storage device;
A charge state output terminal for outputting an electrical signal corresponding to the charge state detected by the power storage monitoring circuit;
It is good also as a structure which further has a state switching terminal into which the switching signal for switching the connection state of the said switching element is input.
The external control device can determine the state of charge of the power storage device and charge the power storage device. Further, if necessary, the sensor output can be obtained from the amplifier by switching the switching element to the second connection state.

The energy conversion element may be configured to convert light energy into electrical energy. As a result, an optical sensor that does not require periodic replacement based on consumption of the power storage device is realized.

FIG. 1 is a block diagram of a sensor according to the first embodiment. FIG. 2A is a graph showing an example of the current-voltage characteristics of the energy conversion element used in the sensor according to Example 1, and FIG. 2B is a graph showing an example of the relationship between the illuminance of the energy conversion element and the amount of power generation. It is. FIG. 3 is a graph showing an example of the relationship between the illuminance of the energy conversion element used in the sensor according to Example 1 and the open circuit voltage. FIG. 4 is a graph illustrating an example of a time change of various signals of the sensor according to the first embodiment. FIG. 5 is a block diagram of a sensor according to the second embodiment. FIG. 6 is a block diagram of a sensor according to the third embodiment. FIG. 7 is a graph illustrating an example of temporal changes of various signals of the sensor according to the third embodiment. FIG. 8 is a block diagram of a sensor according to the fourth embodiment. FIG. 9 is a block diagram of a conventional lighting system.

[Example 1]
FIG. 1 shows a block diagram of a sensor 10 according to the first embodiment. The energy conversion element 11 harvests energy from the surrounding environment to generate electric energy, and outputs the electric energy as an electric signal. As the energy conversion element 11, for example, a solar cell, an optical sensor, a vibration sensor, or the like can be used. When solar cells and light sensors are used, light energy is harvested from the surrounding environment. When a vibration sensor is used, vibration energy is harvested from the surrounding environment.

The electrical signal output from the energy conversion element 11 is input to the power storage device 15 and the amplifier 16 via the current path 12. For example, a capacitor, a secondary battery, or the like is used for the power storage device 15. As the amplifier 16, for example, a non-inverting amplifier circuit using an operational amplifier (op amp) is used. The input impedance of the amplifier 16 is almost infinite, and the output impedance is almost zero.

The current path 12 includes a switching element 13 and a charging step-up / down circuit 14. The switching element 13 switches between a first connection state in which the electrical signal output from the energy conversion element 11 is input to the power storage device 15 and a second connection state input to the amplifier 16. When the switching element 13 is in the first connection state, the step-up / step-down circuit 14 steps up or down the voltage of the electronic signal output from the energy conversion element 11 to match the rated charging voltage of the power storage device 15. When the voltage of the electric signal output from the energy conversion element 11 is within the range of the rated charging voltage of the power storage device 15, the step-up / down circuit 14 may be omitted. When the switching element 13 is in the first connection state, the power storage device 15 is charged by the electrical signal from the energy conversion element 11. The operation in which the power storage device 15 is charged is referred to as “charging mode”.

The power output from the power storage device 15 is supplied as power to the amplifier 16 via the step-up / step-down circuit 17. The step-up / step-down circuit 17 steps up or down the output voltage of the power storage device 15 to match the rated power supply voltage of the amplifier 16. The amplifier 16 operates by receiving power supply from the power storage device 15 and outputs a voltage signal depending on the electric signal output from the energy conversion element 11 from the sensor output terminal 20. This operation is referred to as “sensor mode”.

The power storage monitoring circuit 18 monitors the state of charge (SOC) of the power storage device 15 and switches the switching element 13 based on the state of charge of the power storage device 15. When a capacitor is used for the power storage device 15, the stored electric energy is proportional to the square of the output voltage. For this reason, monitoring the state of charge of the power storage device 15 is equivalent to monitoring the output voltage.

During the period when the switching element 13 is in the first connection state, the state of charge of the power storage device 15 rises. When the state of charge becomes equal to or greater than the upper limit threshold, the storage monitoring circuit 18 switches the switching element 13 from the first connection state to the second connection state. As a result, the electrical signal output from the energy conversion element 11 is input to the amplifier 16. During the period in which the switching element 13 is in the second connection state, power is supplied from the power storage device 15 to the amplifier 16, so that the charge state is lowered. When the state of charge becomes equal to or lower than the lower limit threshold, the storage monitoring circuit 18 switches the switching element 13 from the second connection state to the first connection state. Thereby, charge of the electrical storage apparatus 15 is started and a charge state rises.

FIG. 2A shows an example of the current-voltage characteristics of the energy conversion element 11, and FIG. 2B shows an example of the relationship between the illuminance of the energy conversion element 11 and the amount of power generation. The horizontal axis of FIG. 2A represents the voltage in the unit “V”, and the vertical axis represents the current density in the unit “μA / cm ² ”. The horizontal axis of FIG. 2B represents the illuminance in the unit “lx”, and the vertical axis represents the power generation amount in the unit “μW / cm ² ”. The current-voltage characteristics shown in FIG. 2A are measured under conditions where the illuminance is 200 lux. The power generation amount shown in FIG. 2B represents the maximum power that can be extracted from the energy conversion element 11. It can be seen that when the illuminance of the surrounding environment is 200 lux, a power generation amount of about 7 μW / cm ² can be obtained.

FIG. 3 shows the relationship between the illuminance of the energy conversion element 11 and the open circuit voltage. The horizontal axis represents illuminance in the unit “lx”, and the vertical axis represents the open circuit voltage in the unit “mV”. It can be seen that the open circuit voltage increases as the illuminance increases. For this reason, the energy conversion element 11 can be utilized as an illuminance detection element. In FIG. 3, the open circuit voltage when the illuminance is 200 lux is about 460 mV. This open circuit voltage corresponds to the voltage when the current density is 0 in FIG. 2A.

FIG. 4 shows an example of a time change of various signals of the sensor according to the first embodiment. The upper graph in FIG. 4 represents the time change of the input from the environment, for example, the illuminance, the second graph represents the time change in the state of charge of the power storage device, and the third graph represents the switching element 13. The connection state is shown, and the lowermost graph shows the time change of the output of the amplifier 16.

At time t0, the switching element 13 is set to the first connection state CS1. When the switching element 13 is in the first connection state CS1, the power storage device 15 is charged by the output power from the energy conversion element 11, so that the state of charge of the power storage device 15 increases with time. At time t1, the state of charge reaches the upper limit threshold SOCU. When the power storage monitoring circuit 18 (FIG. 1) detects that the charging state has reached the upper limit threshold value SOCU, the switching element 13 is switched from the first connection state CS1 to the second connection state CS2.

When the switching element 13 is in the second connection state CS2, the electrical signal output from the energy conversion element 11 is input to the amplifier 16 (FIG. 1). As a result, a voltage signal corresponding to the illuminance of the surrounding environment is output from the amplifier 16. Since electric power is supplied from the power storage device 15 to the amplifier 16, the state of charge of the power storage device 15 decreases with the passage of time.

At time t2, the state of charge of the power storage device 15 decreases to the lower limit threshold SOCL. When the power storage monitoring circuit 18 detects that the state of charge has decreased to the lower limit threshold SOCL, the switching element 13 is switched from the second connection state CS2 to the first connection state CS1.

The charging of the power storage device 15 is resumed, and the state of charge rises with time. At time t3, the state of charge reaches the upper limit threshold SOCU. The power storage monitoring circuit 18 switches the switching element 13 from the first connection state to the second connection state. As a result, a voltage signal corresponding to the illuminance of the surrounding environment is output from the amplifier 16.

In the first embodiment, the energy conversion element 11 acts as a power generation element during the period from time t0 to t1, and from time t2 to t3, the period from time t1 to t2, and the period after time t3, energy conversion. The element 11 functions as an illuminance detection element. For this reason, the sensor 10 (FIG. 1) can detect illuminance in the period from time t1 to t2 and in the period after time t3.

Since the electric power necessary for the sensor 10 to operate in the sensor mode is stored in the power storage device 15, the sensor 10 according to the first embodiment does not need to be supplied with electric power from a commercial power source. Furthermore, since the power storage device 15 is charged by the electric power generated by the energy conversion element 11, periodic replacement based on a decrease in the charged state of the power storage device 15 is also unnecessary. Since the energy conversion element 11 serves as both a power generation element and an illuminance detection element, it is possible to reduce the size and cost as compared with a case where the power generation element and the illuminance detection element are prepared separately. is there.

[Example 2]
FIG. 5 is a block diagram of the sensor 10 according to the second embodiment. Hereinafter, differences from the first embodiment will be described, and description of the same configuration will be omitted.

The sensor 10 according to the second embodiment has a power output terminal 21. The power output terminal 21 is connected to the power storage device 15. Power can be taken from the power storage device 15 to an external device via the power output terminal 21.

The sensor 10 according to the second embodiment can be used as a power source for external devices in addition to the function as a sensor.

[Example 3]
FIG. 6 is a block diagram of the sensor 10 according to the third embodiment. Hereinafter, differences from the first embodiment will be described, and description of the same configuration will be omitted.

The sensor 10 according to the third embodiment includes a charging state output terminal 22 and a state switching terminal 23. The power storage monitoring circuit 18 monitors the charge state of the power storage device 15 and outputs the charge state monitoring result to the charge state output terminal 22.

The charge state monitoring result output from the charge state output terminal 22 is input to the external control device 30. The control device 30 inputs a state switching signal to the state switching terminal 23 based on the charge state monitoring result. The connection state of the switching element 13 is switched by the state switching signal input to the state switching terminal 23.

In Example 1, the sensor mode and the charging mode of the sensor 10 are autonomously switched based on the charging state of the power storage device 15. In the third embodiment, the sensor mode and the charging mode can be switched from the external control device 30.

FIG. 7 shows an example of a time change of various signals of the sensor according to the third embodiment. The first to fourth graphs in FIG. 7 represent the same signal time change as the first to fourth graphs in FIG. 4, respectively. At time t0, the switching element 13 is set to the first connection state CS1. Control device 30 (FIG. 6) periodically determines whether or not the state of charge of power storage device 15 is equal to or greater than intermediate threshold value SOCM at determination times t11, t21, t31,.

When the state of charge of the power storage device 15 is equal to or greater than the intermediate threshold value SOCM, the control device 30 sends a state switching signal for switching from the first connection state to the second connection state to the switching element 13. In the example illustrated in FIG. 7, the state switching in which the control device 30 switches the switching element 13 from the first connection state to the second connection state at the determination times t11, t21, t31, t41, t51, t71, and t91. Send a signal. As a result, the switching element 13 enters the second connection state, and the operation of the sensor 10 is switched to the sensor mode. Thereby, the state of charge of power storage device 15 is lowered.

At the time when a certain time has elapsed from the time when the state switching signal is sent to the switching element 13 (hereinafter referred to as “sensor mode end time”; in FIG. 7, times t12, t22, t32, t42, t52, t72, and t92). The control device 30 sends to the switching element 13 a state switching signal for switching from the second connection state to the first connection state. Thereby, charging of the power storage device 15 is resumed. The state of charge at the next determination time is determined according to the state of charge at the sensor mode end time and the amount of power generated by the energy conversion element 11.

For example, during the period from the sensor mode end time t12 to the determination time t21, since the amount of power generated by the energy conversion element 11 is large, the state of charge at the next determination time t21 has recovered to the intermediate threshold SOCM or more. The state of charge at the sensor mode end time t22 is equal to or greater than the intermediate threshold value SOCM. For this reason, even if the amount of power generation in the period from the sensor mode end time t22 to the next determination time t31 is not large, the state of charge at the next determination time t31 becomes equal to or greater than the intermediate threshold value SOCM.

When the state of charge at the sensor mode end time t52 is equal to or lower than the intermediate threshold value SOCM and the amount of power generation until the next determination time t61 is small, the state of charge at the determination time t61 does not recover to the intermediate threshold value SOCM. When the state of charge of power storage device 15 at the determination time is less than intermediate threshold value SOCM, control device 30 does not send a state switching signal to switching element 13. At the next determination time t71, when the charging state is recovered to the intermediate threshold value SOCM or more, the control device 30 sends a state switching signal to the switching element 13.

The intermediate threshold value SOCM in the charged state is set to a value with a sufficient margin as compared with the electric energy consumed from the determination time to the sensor mode end time. Therefore, the sensor 10 can operate in the sensor mode from the determination time to the sensor mode end time.

In FIG. 7, the state of charge is determined at a constant cycle. However, the state of charge may be determined in response to a request for illuminance measurement. In FIG. 7, the time from the determination time to the sensor mode end time is constant, but it is not always necessary to be constant. For example, when there is a sufficient margin in the state of charge, it is possible to lengthen the time from the determination time to the sensor mode end time.

In Example 1, the illuminance was measured autonomously, but in Example 3, the illuminance can be measured in response to a request from the outside.

[Example 4]
FIG. 8 is a block diagram of the sensor 10 according to the fourth embodiment. Hereinafter, differences from the second embodiment (FIG. 5) will be described, and description of the same configuration will be omitted.

In the sensor 10 according to the fourth embodiment, the switching element 13 inserted in the current path 12 (FIG. 5) of the second embodiment is omitted. The electrical signal output from the energy conversion element 11 is supplied to both the power storage device 15 and the amplifier 16 at the same time. For this reason, the sensor 10 according to the fourth embodiment can always measure the illuminance.

In Example 4, when the output signal from the energy conversion element 11 is input to the amplifier 16, the load impedance of the energy conversion element 11 does not become infinite. For this reason, a current is extracted from the energy conversion element 11. As shown in FIG. 2A, when a current is extracted from the energy conversion element 11, the voltage between its output terminals is lower than the open circuit voltage. In order to suppress a decrease in measurement accuracy of illuminance, it is preferable to use an energy conversion element 11 having a current-voltage characteristic with a small amount of voltage decrease when the current is increased from zero. Specifically, it is preferable to use an energy conversion element in which the shape of the graph showing the current-voltage characteristics (FIG. 2A) is close to a rectangle.

Although the present invention has been described with reference to the embodiments, the present invention is not limited thereto. It will be apparent to those skilled in the art that various modifications, improvements, combinations, and the like can be made.

DESCRIPTION OF SYMBOLS 10 Sensor 11 Energy conversion element 12 Current path 13 Switching element 14 Buck-boost circuit 15 Power storage device 16 Amplifier 17 Buck-boost circuit 18 Power storage monitoring circuit 20 Sensor output terminal 21 Power output terminal 22 Charge state output terminal 23 State switching terminal 30 Control device 110 Power supply unit 111 Solar cell module 112 Secondary battery 113 Backflow prevention diode 114 Sunlight discrimination switch circuit 120 Illumination unit 121 Light emitting diode 122 Lighting control circuit

Claims

An energy conversion element that harvests energy from the surrounding environment to generate electrical energy and outputs it as an electrical signal;
A power storage device;
An amplifier that operates by receiving power from the power storage device;
A sensor having a current path for inputting an electrical signal output from the energy conversion element to the power storage device and the amplifier.
The sensor according to claim 1, further comprising a power output terminal for taking out power from the power storage device.
The current path includes a switching element that switches between a first connection state in which an electrical signal output from the energy conversion element is input to the power storage device and a second connection state input to the amplifier. The sensor according to claim 1 or 2.
The sensor according to claim 3, further comprising a power storage monitoring circuit that detects a charge state of the power storage device and switches a connection state of the switching element based on the charge state of the power storage device.
A power storage monitoring circuit for detecting a state of charge of the power storage device;
A charge state output terminal for outputting an electrical signal corresponding to the charge state detected by the power storage monitoring circuit;
The sensor according to claim 3, further comprising a state switching terminal to which a switching signal for switching the connection state of the switching element is input.
The sensor according to any one of claims 1 to 5, wherein the energy conversion element converts light energy into electrical energy.