JP2017192180A - Autonomous terminal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an autonomous terminal that includes a power generation unit and uses both a secondary battery and a capacitor for power storage and that ensures long term reliability by extended power supply life.SOLUTION: The autonomous terminal comprises: a power generation unit including a power generation element that generates power by a power generation factor according to an external environment; a secondary battery that is charged by being supplied with the power supplied by the power generation unit: a power storage capacitor that is charged by being supplied with the power supplied by the power generation unit and that has an upper limit voltage higher than a nominal voltage of the secondary battery; a load that operates by being supplied with the power; and a switch circuit provided between the secondary batter and the power storage capacitor, and the load. When a terminal voltage of the storage capacitor is higher than a terminal voltage of the secondary battery, the switch circuit enters a switched state in which a terminal voltage of the power storage capacitor is supplied to the load. When the terminal voltage of the power storage capacitor becomes equal to or higher than a lower limit voltage of the power storage capacitor, the switch circuit enters a switched state in which the terminal voltage of the secondary battery is supplied to the load.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a self-supporting terminal suitable for use in a wireless sensor terminal or the like attached to an external environment such as a bridge over a long period of time.

  For example, in a wireless sensor terminal or the like that is attached to an external environment such as a bridge, once it is attached to the use environment, it is necessary to make it as maintenance-free as possible and to make human work as unnecessary as possible. Therefore, it is not practical to use a primary battery that requires frequent battery replacement as a power source.

  Therefore, this type of wireless sensor terminal or the like is provided with a power generation unit that generates power using a power generation factor corresponding to the external environment, such as solar energy, vibration energy, temperature energy, wind energy, and the like. Electric power is used as a power source. However, since these environmental energies are not always obtained, a configuration of a self-supporting power source that employs a configuration in which the generated power is stored and the stored power is used in a period when the generated energy cannot be obtained. It is often said.

  In this case, the storage element includes a secondary battery and a capacitor. However, the secondary battery and the capacitor have advantages and disadvantages, and various problems arise when either one is used alone. Therefore, conventionally, a secondary battery and a capacitor are used in combination.

  For example, in Patent Document 1 (Japanese Patent Application Laid-Open No. 11-346404), power is supplied from a capacitor to a large current load such as when a vehicle starts, and switching to power supply from a battery is performed after a predetermined time has elapsed since the start. An electric vehicle power supply device has been proposed.

  Further, Patent Document 2 (2007-282347) discloses that “a battery output at the time of fluctuation in power consumption of a load based on a power supply assist from an electric double layer capacitor in which a main battery and an electric double layer capacitor are connected in parallel. "Power supply system that can suppress voltage fluctuation" is described.

  Further, Patent Document 3 (Japanese Patent Laid-Open No. 2015-156765) states that “an electric vehicle capable of improving performance at low temperatures by securing a battery output using a capacitor used in combination with a battery. Is described.

Japanese Patent Laid-Open No. 11-346404 JP 2007-282347 A JP 2015-156765 A

  By the way, it is desirable that the wireless sensor terminal can be operated in a maintenance-free manner for a long period of time such as 10 years in the external environment such as a bridge described above. Therefore, in this type of wireless sensor terminal, it is desired to extend the life of the power source including the power generation unit and the power storage unit so that the replacement is unnecessary for a long period of time as described above.

  However, in the case of a secondary battery that is one of the elements constituting the power storage unit, the number of times of charging and discharging is as small as about 1000 in the case of a lithium ion battery, for example. As described above, the power generation unit using energy harvesting energy cannot always generate power, and the number of charge / discharge cycles of the storage element increases. Therefore, in the case where the power storage unit is configured by only the secondary battery, the life of the power source is shortened by repeated charging and discharging.

  On the other hand, the electric double layer capacitor, the lithium ion capacitor, and the like have a charge / discharge count of 100,000 times or more, which contributes to a long life. However, when the power storage unit is configured with the capacitor alone, the capacitor has a problem that the capacitance per unit volume is larger than that of the secondary battery in order to supplement the power generation shortage of the power generation unit. For example, the capacitance per unit volume of a lithium ion capacitor is 1/50 that of a lithium ion battery.

  Thus, even in this type of wireless sensor terminal, it is conceivable that long-term reliability of the power supply can be ensured by using a secondary battery and a capacitor in combination in the power storage unit of the power supply circuit.

  However, as described above, the conventional technique of using the secondary battery and the capacitor together switches the both according to the load, suppresses the fluctuation of the battery output voltage by the capacitor, or secures the output of the battery. Therefore, it is a technique for controlling the output voltage when a battery and a capacitor are used in combination, and it has not been proposed to ensure long-term reliability by extending the life of the power source described above.

  In view of the above points, the present invention is a self-supporting terminal that is equipped with a power generation unit and that can ensure long-term reliability by extending the life of a power supply in a self-supporting terminal that uses a secondary battery and a capacitor together for power storage. The purpose is to provide a terminal.

In order to solve the above problems, the invention of claim 1
A power generation unit including a power generation element that generates power by a power generation factor according to an external environment;
A secondary battery that is charged by receiving power from the power generation unit;
Charged by receiving power supply from the power generation unit, a capacitor for storage having an upper limit voltage higher than the nominal voltage of the secondary battery,
A load that operates with power supply, and
A switch circuit provided between the secondary battery and the storage capacitor and the load;
With
When the terminal voltage of the storage capacitor is higher than the terminal voltage of the secondary battery, the switch circuit is in a switching state in which the terminal voltage of the storage capacitor is supplied to the load, and the terminal of the storage capacitor When the voltage becomes equal to or lower than the lower limit voltage of the storage capacitor, a self-supporting terminal is provided in which the terminal voltage of the secondary battery is switched to be supplied to the load.

  In the self-supporting terminal according to the first aspect of the present invention, the upper limit voltage of the capacitor is higher than the nominal voltage of the secondary battery. For this reason, when the capacitor is charged by the power generation unit, it is possible to charge up to the upper limit voltage, and if charging is performed by the power generation unit, the terminal voltage of the capacitor is higher than the nominal voltage of the secondary battery. Become.

  When the terminal voltage of the storage capacitor is higher than the terminal voltage of the secondary battery, the switch circuit switches to a switching state in which the terminal voltage of the storage capacitor is supplied to the load. For this reason, in the state where the power storage capacitor is charged by the power generation unit, the terminal voltage of the power storage capacitor is always supplied as the power supply voltage to the load.

  Even if the external environment fluctuates and power generation at the power generation unit becomes impossible, the terminal voltage of the storage capacitor is discharged due to power consumption at the load in a normal state where the state is short. Thus, before the voltage of the secondary battery becomes lower than that of the secondary battery, charging of the storage capacitor is resumed by the power generation voltage of the power generation unit. For this reason, in the normal state, the storage capacitor is charged by the power generation voltage of the power generation unit and is repeatedly discharged by the load, but the terminal voltage of the storage capacitor is higher than the terminal voltage of the secondary battery. Maintained.

  On the other hand, when the power generation unit has become unable to generate power for a relatively long period due to changes in the external environment, the terminal voltage of the storage capacitor is lower than the lower limit voltage and is higher than the terminal voltage of the secondary battery. Lower. Then, the switch circuit enters a switching state in which the terminal voltage of the secondary battery is supplied to the load as the power supply voltage. During the switching state in which the terminal voltage of the secondary battery is supplied to the load as the power supply voltage, the power storage capacitor is not discharged, and only the power generation unit is charged.

  Thereafter, when the terminal voltage of the storage capacitor becomes higher than the terminal voltage of the secondary battery by charging, the switch circuit returns to the switching state in which the terminal voltage of the storage capacitor is supplied to the load again. Thereafter, the above-described operation is repeated.

  As described above, according to the first aspect of the present invention, for example, when the power generation unit uses solar energy as an external environmental factor, the storage capacitor is usually charged in the daytime and at night at the nighttime. The battery is discharged by the load, the terminal voltage of the storage capacitor is maintained higher than the terminal voltage of the secondary battery, and the terminal voltage of the storage capacitor is supplied to the load as the power supply voltage. And, in an exceptional weather fluctuation, for example, when it is raining for 10 days, the terminal voltage of the storage capacitor becomes lower than the lower limit voltage, and the terminal voltage of the secondary battery is supplied to the load as the power supply voltage. It becomes an aspect.

  Therefore, the storage capacitor is repeatedly charged and discharged frequently, but the secondary battery is discharged and charged by using its terminal voltage as a power supply voltage only in exceptional cases. Less. As described above, since the allowable number of times of charging / discharging of the storage capacitor is larger than that of the secondary battery, even if charging / discharging is repeated frequently, the influence on extending the life is small. And although the allowable number of times of charging / discharging of the secondary battery is small, in the invention of claim 1, the number of times of charging / discharging of the secondary battery can be very small, which contributes to a long life.

  According to the invention of claim 1, since not only the storage capacitor but also the secondary battery is used in combination, the size of the storage capacitor is smaller than that of the storage capacitor used alone. That's it.

The invention of claim 2 is a self-supporting terminal of the invention of claim 1,
When the terminal voltage of the storage capacitor is higher than the terminal voltage of the secondary battery, the switch circuit is in a switching state in which the terminal voltage of the storage capacitor is supplied to the load. When the terminal voltage of the storage capacitor is less than or equal to the lower limit voltage of the storage capacitor and less than or equal to the terminal voltage of the secondary battery, a switching state in which the terminal voltage of the secondary battery is supplied to the load; And
The switch circuit includes a first diode provided between the secondary battery and the load, and a second diode provided between the storage capacitor and the load. To do.

  In the second aspect of the present invention, the switch circuit includes a first diode provided between the secondary battery and the load, and a second diode provided between the storage capacitor and the load. That is, the anode of the first diode is connected to the output terminal of the secondary battery, and the anode of the second diode is connected to the output terminal of the storage capacitor. The cathode of the first diode and the cathode of the second diode are connected in common, and the common connection point is connected to the load.

  Therefore, when the terminal voltage of the storage capacitor is higher than the terminal voltage of the secondary battery, the second diode is turned on, and the voltage at the common connection point with the first diode is higher than the terminal voltage of the secondary battery. Therefore, the first diode is turned off.

  When the terminal voltage of the storage capacitor is lower than the lower limit voltage and lower than the terminal voltage of the secondary battery, the voltage at the common connection point between the first diode and the second diode is changed to the secondary battery. The terminal voltage is lower. Then, the first diode is turned on, and the voltage at the common connection point becomes the terminal voltage of the secondary battery, which is higher than the terminal voltage of the storage capacitor, so that the second diode is turned off.

  As described above, in the invention of claim 2, the first diode and the second diode of the switch circuit are turned on or off independently depending on the terminal voltage of the secondary battery and the terminal voltage of the storage capacitor. Turn off. That is, according to the second aspect of the present invention, a control circuit for switching the switch circuit is unnecessary, and power consumption in the control circuit can be omitted. The configuration of the self-supporting terminal can be simplified.

  According to the present invention, in a self-supporting terminal that includes a power generation unit and uses a secondary battery and a capacitor together for power storage, a self-supporting terminal that can ensure long-term reliability by extending the life of a power supply is provided. be able to.

It is a figure which shows the circuit structural example of the self-supporting power supply circuit as a principal part of embodiment of the self-supporting terminal by this invention. It is a figure for demonstrating the outline | summary of the wireless sensor terminal which is embodiment of the self-supporting terminal by this invention. It is a block diagram for demonstrating the structural example of the electronic circuit of the wireless sensor terminal which is embodiment of the self-supporting terminal by this invention. It is a figure used for description of the component of the self-supporting power supply circuit of the example of FIG. It is a figure used for operation | movement description of the self-supporting power circuit of the example of FIG. It is a figure which shows the other example of a circuit structure of the self-supporting power supply circuit as a principal part of embodiment of the self-supporting terminal by this invention.

  Hereinafter, an embodiment in which a self-supporting terminal according to the present invention is applied to a wireless sensor terminal will be described with reference to the drawings. In the wireless sensor terminal of this embodiment, a solar cell module is used for the power generation unit.

  FIG. 2 is a diagram for explaining a configuration example of the wireless sensor terminal 100 of this embodiment. In the wireless sensor terminal 100 of this embodiment, a solar cell module is used for the power generation unit. The wireless sensor terminal 100 of this embodiment is configured by providing each electronic circuit component constituting the wireless sensor terminal 100 in a package 101 having a rectangular parallelepiped shape that is substantially flat in appearance. FIG. 2B is a diagram illustrating the wireless sensor terminal 100 when the package 101 is viewed from a direction orthogonal to a surface on the side of taking in external light, as will be described later. 2A is a cross-sectional view taken along the line AA in FIG. 2B and is a diagram for describing a configuration example in the package 101. FIG.

  The package 101 is a highly durable material capable of maintaining the performance of the internal circuit even when exposed to a harsh external environment such as salt damage, high temperature and high humidity. In this embodiment, the package 101 is a non-metallic material, Compared to the above, it is made of a ceramic material that has toughness, is lightweight, and has electrical insulation. As shown in FIG. 2A, the package 101 includes a box-shaped package body 102 having an opening at the top and a recess 104 surrounded by a wall 102W, and a lid 103.

  In this embodiment, the package main body 102 is configured by stacking LTCC (Low Temperature Co-fired Ceramics) substrates. The lid 103 is made of a translucent ceramic material. The lid 103 is bonded to the package main body 102 at the end surface of the wall 102W via a bonding member 105 made of low-melting glass, whereby the package 101 is sealed in a highly airtight manner. It is structured.

  In this embodiment, the package main body 102 includes a signal processing circuit for detecting external environmental factors using a power supply system including a self-supporting power source and a plurality of sensors such as a vibration sensor and a temperature sensor, and wirelessly transmitting the detection output. An electronic circuit comprising the system is accommodated. Main components of this electronic circuit are accommodated in the recess 104 of the package body 102. However, the antenna for wireless communication is provided embedded in the wall 102W of the package body 102. The antenna to be embedded is formed of a conductor filled in vias penetrating at least one layer of the ceramic layer, formed in a pattern shape between the ceramic layers, or formed by a combination of vias and patterns.

[Electronic circuit configuration example]
FIG. 3 is a block diagram showing a configuration example of an electronic circuit of the wireless sensor terminal 100 of this embodiment. As shown in FIG. 3, the wireless sensor terminal 100 of this embodiment includes a self-supporting power supply circuit 200 and a load circuit 210, and the voltage from the self-supporting power supply circuit 200 is supplied to the load circuit 210 as a power supply voltage. The load circuit 210 is an example of a load that performs a predetermined operation using the voltage from the self-supporting power supply circuit 200.

  As will be described in detail later, the self-supporting power circuit 200 includes a solar cell module 201 that constitutes a power generation unit, a secondary battery 202 and a storage capacitor 203 that constitute a power storage unit.

  In the load circuit 210, a plurality of sensors such as a vibration sensor 212, a trigger sensor 213, and a temperature sensor 214 are connected to a processing control circuit 211 for controlling the entire wireless sensor terminal 100, and communication control is performed. A circuit 215 is connected. An antenna 216 is connected to the communication control circuit 215.

  The vibration sensor 212 is for detecting the vibration of the place where the wireless sensor terminal 100 is attached as a detection target attribute. In this example, the vibration sensor 212 is configured as a MEMS sensor. The trigger sensor 213 is for detecting a sudden event such as an impact applied to the wireless sensor terminal 100 as a detection target attribute, and is also configured as a MEMS sensor in this example. The temperature sensor 214 is for detecting the temperature in the recess 104 of the package body 102 of the wireless sensor terminal 100 as a detection target attribute, and this is also configured as a MEMS sensor in this example.

  In this example, the processing control circuit 211 is configured by, for example, an MPU (Micro Processor Unit). The processing control circuit 211 has a time management function, and takes in vibration information and temperature information detected by the vibration sensor 212 and the temperature sensor 214 at a predetermined timing. Then, the processing control circuit 211 generates transmission information from the captured vibration information and temperature information, and wirelessly transmits the transmission information to the outside through the communication control circuit 215. In this example, the wireless transmission signal generation circuit includes a processing control circuit 211 and a communication control circuit 215.

  In this embodiment, transmission information generation and wireless transmission based on the vibration sensor 212 and the temperature sensor 214 are intermittently executed based on time management in the processing control circuit 211. Further, the processing control circuit 211 monitors the detection output of the trigger sensor 213, and when a sudden event is detected, the processing control circuit 211 generates transmission information based on the detection output of the trigger sensor 213 at the time of detection, and performs communication control. Wireless transmission to the outside through the circuit 215.

  The communication control circuit 215 converts the transmission information from the processing control circuit 211 into a signal of a predetermined modulation method, and generates a wireless transmission signal that is wirelessly transmitted through the antenna 216. In this example, the radio transmission signal has a carrier frequency (carrier frequency) of, for example, 920 MHz. In this embodiment, the communication control circuit 215 has not only a transmission function but also a reception function, and the processing control circuit 211 processes a signal received from the outside through the communication control circuit 215. And a function of a control processing circuit for performing predetermined control based on a processing result in the wireless reception signal processing circuit.

[Example of arrangement of electronic circuit components in package 101]
In this example, as shown in FIG. 2A, the inner surface on the concave portion 104 side of the wall portion 102W of the package body 102 is on the concave portion 104 side from the bottom surface of the concave portion 104 to a predetermined height h1. It is configured to overhang. The height h1 is lower than the height h0 corresponding to the depth of the recess 104, that is, the distance from the bottom surface of the recess 104 to the end surface of the wall 102W of the package body 102 (h1 <h0). .

  As a result, the recess 104 of the package body 102 is provided with a stepped portion 106 having a stepped shape as shown in FIGS. 2A and 2B, and the recess 104 has a cross-sectional area surrounded by the stepped portion 106. Has a small concave portion 104a and a large concave portion 104b having a large cross-sectional area surrounded by the wall portion 102W other than the step portion 106.

  In this example, the solar cell module 201 is disposed on the step portion 106 so as to close and seal the small recess 104a. The secondary battery 202, the storage capacitor 203, the processing control circuit 211, and the like are disposed on the bottom surface in the small recess 104a.

  In this embodiment, the package body 102 is configured by stacking LTCC substrates. And while providing a conductor pattern between the several LTCC board | substrates laminated | stacked and providing the via | veer with which each of the several LTCC board | substrate was filled with the conductor, electrical connection between each electronic circuit component is performed. I am doing so.

  Further, the wall portion 102W made of the LTCC substrate is filled with a conductor for electrical connection between the components of the self-supporting power supply circuit 200 disposed in the small recess 104a and the solar cell module 201. Are provided, and electrical connection with the terminals of the solar cell module 201 is made at the end face of the stepped portion 106.

  As shown in FIG. 2, the antenna 216 is arranged in the package 101 so as to be embedded in the wall 102 </ b> W of the package main body 102. In this embodiment, the antenna 216 is composed of two rod-shaped conductors 216a and 216b, and is configured to be omnidirectional.

  The solar cell module 201 of this embodiment has a rectangular flat plate shape, and the rectangular shape portion is similar to the concave portion 104, and its peripheral portion collides with the end face portion of the stepped portion 106. In such a state, it is housed in the large recess 104b and joined by, for example, an adhesive. Therefore, the solar cell module 201 fits comfortably in the large recess 104b of the package body 102. For this reason, when viewed from the direction orthogonal to the lid 103, the solar cell module 202 is disposed at the wall portion of the package body 102 in which the two rod-shaped conductors 216 a and 216 b constituting the antenna 216 are embedded. It will not overlap with 102W. In other words, the antenna 216 is in a state where it can transmit and receive radio waves without being disturbed by the solar cell module 202 at all.

  In this case, the small recess 104a is filled with a predetermined filler 109, for example, a resin so that at least the electronic circuit component does not touch the air layer. By filling the filling material 109, the electronic circuit components disposed in the small recess 104a do not touch the air layer, so that the electronic circuit components in the small recess 104a are not rusted or corroded by moisture or moisture. And can have long-term airtightness.

  As described above, the electronic circuit component is arranged in the small recess 104a, the inside of the small recess 104a is filled with the filler 109, and the small recess 104a is sealed by the solar cell module 202. When the lid 103 is sealed and bonded to the main body 102, the recess 104 is sealed, and the package 101 has airtightness. Note that a USB (Universal Serial Bus) terminal 209 constituting an external charging terminal, which will be described later, is provided on the side portion of the package 101 of this embodiment so as to be exposed to the outside, and a self-supporting power supply circuit in the small recess 104a. It is connected to a part of the circuits 200.

  In this case, as described above, the lid 103 needs to transmit the incident light to the solar cell module 202 in the recess 104, and therefore, in this embodiment, the lid 103 is made of a translucent ceramic (alumina). .

  In this embodiment, the lid 103 is sealed and joined to the package main body 102 by heating only the joint of the peripheral edge of the lid 103 with the end surface of the wall 102W of the package main body 102 by the laser LZ. Like that. In this embodiment, a low melting point material, in this example, a low melting point glass is used as the bonding member 105 provided between the end surface of the wall 102W of the package body 102 and the lid 103.

  Furthermore, in this embodiment, the heat radiation via 110 for radiating the heat generated by the laser LZ fills the wall portion 102W of the package body 102 with a conductor in the via that penetrates at least one layer of the LTCC substrate. Embedded and provided. As shown in FIG. 2B, a plurality of the heat radiating vias 110 are provided in the wall portion 102W of the package main body 102 at a predetermined interval.

  As shown in FIG. 2B, the wireless sensor terminal 100 according to this embodiment is arranged on the bottom side of the package main body 102 in a direction perpendicular to the wall 102W rather than the wall 102W of the package main body 102. A flange 102F is formed so as to protrude. And the through-hole 102Fa, 102Fb, 102Fc, 102Fd for attachment is formed in this collar part 102F, Through this through-hole 102Fa, 102Fb, 102Fc, 102Fd and the through-hole pierced by the attachment object part, for example, A bolt made of ceramic is allowed to pass through and can be fixed with a nut made of ceramic.

  When the through hole cannot be drilled in the attachment target portion, the bottom surface side of the package 101 is bonded to an object to be detected by the vibration sensor 212, for example, a bridge, a tunnel accessory, or a road accessory with an adhesive. However, since the area of the bonding portion and the bonding portion with the object to which the wireless sensor terminal 100 is to be attached is increased by the amount of the flange portion 102F, it can be more firmly attached and fixed to the object. I have to.

[Example of configuration of self-supporting power supply circuit]
FIG. 1 is a circuit diagram showing a configuration example of a self-supporting power supply circuit 200 of the wireless sensor terminal 100 of this embodiment. In this embodiment, the solar cell module 201 has a rectangular shape in which one or a plurality of flat-plate solar cells are arranged in a planar shape. The solar cell module 201 of this example outputs a generated voltage of 2.42 volts to 15 volts, for example.

  Moreover, the secondary battery 202 is comprised with the lithium ion battery 202B in this example. As shown in FIG. 4B, the lithium ion battery 202B in this example has a nominal voltage (rated voltage) of 4.1 volts, and the allowable number of charge / discharge cycles is about 1000 times. Here, the nominal voltage means a voltage value determined as a standard between terminals obtained when the secondary battery 202 is used in a normal state. When the secondary battery 202 is in a fully charged state, a terminal voltage higher than the nominal voltage is obtained. However, when discharging progresses or when a large current is supplied to the load, the terminal voltage is lower than the nominal voltage. Become.

  The storage capacitor 203 in this example is configured to have an upper limit voltage (charge upper limit voltage) higher than the nominal voltage of the secondary battery 202. In this example, a lithium ion capacitor is used as the storage capacitor 203. However, as shown in FIG. 4A, one lithium ion capacitor has an upper limit voltage (rated voltage) of 3.8 volts and a lower limit voltage. The number of charging / discharging allowed is 2.2 volts and about 100,000 times. Therefore, the storage capacitor 203 is configured by connecting two lithium ion capacitors 2031 and 2032 in series. As a result, the storage capacitor 203 has an upper limit voltage of 7.6 volts, which is higher than the nominal voltage (4.1 volts) of the secondary battery 202, and a lower limit voltage of 4.4 volts.

  Here, the upper limit voltage of the capacitor is a voltage when charging is stopped (fully charged), and the lower limit voltage is a value of a voltage that must be charged by stopping discharging of the capacitor.

  The generated voltage from the solar cell module 201 is supplied to the DC / DC converter 204 and the DC / DC converter 205. The DC / DC converter 204 constitutes a charging circuit for the secondary battery 202 and has an overcharge preventing function. In this example, the DC / DC converter 204 generates an output voltage of 4.4 volts from the generated voltage from the solar cell module 201. The DC / DC converter 205 constitutes a charging circuit for the storage capacitor 203 and has an overcharge prevention function. In this example, the DC / DC converter 205 generates an output voltage of 7.9 volts from the generated voltage from the solar cell module 201.

  The output voltage of the DC / DC converter 204 is supplied to the secondary battery 202 through the diode D3. Since the forward voltage drop of the diode D3 is 0.3 volts, the voltage value at the input terminal of the secondary battery 202 is 4.1 volts, which is the same as the nominal voltage of the lithium ion battery 202B of the secondary battery 202. Thus, overcharging of the secondary battery 202 is prevented.

  The output voltage of the DC / DC converter 205 is supplied to the storage capacitor 203 through the diode D4. Since the forward voltage drop of the diode D4 is 0.3 volts, the voltage value at the input terminal of the storage capacitor 203 is 7.6 volts, and the two lithium ion capacitors 2031 constituting the storage capacitor 203 are used. And 2032 are equivalent to the upper limit voltage of the series circuit, and overcharging of the storage capacitor 203 is prevented.

  The terminal voltage of the secondary battery 202 and the terminal voltage of the storage capacitor 203 are supplied to the DC / DC converter 207 through the switch circuit 206. In this embodiment, the switch circuit 206 includes two diodes D1 and D2, and the terminal voltage of the secondary battery 202 is supplied to the DC / DC converter 207 through the diode D1. The terminal voltage is supplied to the DC / DC converter 207 through the diode D2. That is, the output terminal of the secondary battery 202 is connected to the anode of the diode D1, and the output terminal of the storage capacitor 203 is connected to the anode of the diode D2. The cathodes of the diode D1 and the diode D2 are connected to each other, and the connection point Po is connected to the input terminal of the DC / DC converter 207.

  As will be described later, one of the diode D1 and the diode D2 constituting the switch circuit 206 is turned on according to the value of the terminal voltage of the secondary battery 202 and the value of the terminal voltage of the storage capacitor 203 ( Conduction) and the other is off (non-conduction state). That is, the switch circuit 206 is not switched by the control signal, but is automatically switched according to the value of the terminal voltage of the secondary battery 202 and the value of the terminal voltage of the storage capacitor 203.

  Based on the voltage from the switch circuit 206, the DC / DC converter 207 generates a power supply voltage VDD of 2.5 volts in this example for the load circuit 210. Then, the DC / DC converter 207 supplies the generated power supply voltage VDD to each part of the load circuit 210.

  In this embodiment, in order to charge the secondary battery 202 in an emergency evacuation manner when the charging by the solar cell module 201 cannot be performed for a long period of time, the USB constituting the external charging terminal exposed to the outside A terminal 209 is provided, and the USB terminal 209 is connected to the secondary battery charging circuit 208. In this case, when a USB connector plug is connected to the USB terminal 209, a voltage of 5 volts is input through the USB cable. The secondary battery charging circuit 208 generates a constant voltage (constant current) of 4.1 volts from an input voltage of 5 volts and supplies the secondary battery 202 with the constant voltage.

[Operation of Stand-alone Power Supply Circuit 200]
Since the self-supporting power supply circuit 200 is configured as described above, when the solar battery module 201 generates power and the secondary battery 202 and the storage capacitor 203 are sufficiently charged, Since the upper limit voltage is selected to be higher than the nominal voltage of the secondary battery 202, the terminal voltage of the storage capacitor 203 is higher than the nominal voltage of the secondary battery 202. Then, the diode D2 of the switch circuit 206 is turned on (conductive state), and the potential at the common connection point Po between the cathodes of the diode D1 and the diode D2 becomes higher than the terminal voltage of the secondary battery 202. For this reason, the diode D1 is turned off (non-conducting state), and the secondary battery 202 is maintained in that state after being fully charged.

  Therefore, at this time, the terminal voltage of the storage capacitor 203 is supplied to the DC / DC converter 207 through the diode D2, and the DC / DC converter 207 generates the power supply voltage VDD from the terminal voltage of the storage capacitor 203, Supply to the load circuit 210.

  And during the normal state where solar energy is repeatedly obtained at relatively short intervals, the storage capacitor 203 is charged by the generated voltage of the solar cell module 201 before the terminal voltage drops below the lower limit voltage. As a result, the terminal voltage of the storage capacitor 203 is maintained at the lower limit voltage or higher.

  That is, FIG. 5 is a diagram for explaining the change in the solar energy and the corresponding change in the terminal voltage of the storage capacitor 203, the curve 301 shows the change in the solar energy, and the broken line 302 is The change of the terminal voltage of the capacitor 203 for electrical storage is shown.

  As shown in FIG. 5, during the period in which the solar energy indicated by the curve 301 is obtained, the storage capacitor 203 is charged by the power generation voltage of the solar cell module 201 and the terminal voltage of the storage capacitor 203 indicated by the broken line 302. Maintains the upper limit voltage, for example. When the solar energy disappears at night, the terminal voltage of the storage capacitor 203 indicated by the broken line 302 gradually decreases due to discharge due to power consumption in the load circuit 210. 5, the storage capacitor 203 is charged by the solar energy obtained next before the lower limit voltage indicated by the alternate long and short dash line in FIG. 5, and the terminal voltage of the storage capacitor 203 indicated by the broken line 302 is maintained above the lower limit voltage. To do.

  However, for example, when there is an exceptional weather fluctuation such as rainy weather for 10 consecutive days or an infrastructure installation environment fluctuation where, for example, construction does not receive sunlight, the terminal voltage of the storage capacitor 203 indicated by the broken line 302 is as shown in FIG. As shown in FIG. 4, the voltage drops below the lower limit voltage. When the terminal voltage of the storage capacitor 203 becomes lower than the terminal voltage of the secondary battery 202, the potential at the connection point Po in FIG. 1 also becomes lower than the terminal voltage of the secondary battery 202, so that the diode D1 is turned on ( Conductive state). Since the diode D1 is turned on, the potential at the connection point Po becomes higher than the terminal voltage of the storage capacitor 203 at that time, so that the diode D2 is turned off (non-conducting state).

  As a result, the terminal voltage of the secondary battery 202 is supplied to the DC / DC converter 207 instead of the terminal voltage of the storage capacitor 203, and the DC / DC converter 207 uses the terminal voltage of the secondary battery 202 to supply power. A voltage VDD is generated and supplied to the load circuit 210. At this time, the storage capacitor 203 is in a state where only charging is performed without discharging.

  Until the next solar energy is obtained, the state in which the power supply voltage VDD of the load circuit 210 is generated by the DC / DC converter 207 from the terminal voltage of the secondary battery 202 continues, during which the secondary battery 202 is The battery is discharged due to power consumption in the load circuit 210.

  When solar energy is obtained again, the storage capacitor 203 is charged and its terminal voltage rises. When the terminal voltage of the storage capacitor 203 becomes higher than the terminal voltage of the secondary battery 202, the terminal voltage of the storage capacitor 203 becomes higher than the potential at the connection point Po. ) And the diode D1 is turned off (non-conducting state).

  As a result, instead of the terminal voltage of the secondary battery 202, the terminal voltage of the storage capacitor 203 returns to the normal state where it is supplied to the DC / DC converter 207, and the DC / DC converter 207 The power supply voltage VDD is generated from the terminal voltage 203 and the state is returned to the load circuit 210. At this time, the secondary battery 202 is in a state where only charging is performed without discharging.

  As described above, in the self-supporting power supply circuit 200 of the wireless sensor terminal 100 of this embodiment, the storage capacitor 203 composed of the lithium ion capacitors 2031 and 2032 is charged by solar energy in a normal use state. And a state of discharging due to power consumption in the load circuit 210 are repeated. Since the allowable number of charging / discharging is as large as 100,000 or more, the lithium ion capacitor has little influence on the life even if the number of charging / discharging is large as in this embodiment.

  The secondary battery 202 is charged and discharged as a power storage element instead of the power storage capacitor 203 when the external environment deviates from the normal state. Therefore, the secondary battery 202 in this embodiment has a small number of charge / discharge cycles, and can be used for a long time even if the allowable number of charge / discharge cycles is small.

  In this embodiment, since the secondary battery 202 is used in addition to the storage capacitor 203, the lithium ion capacitor constituting the storage capacitor 203 is, for example, when rain continues for 10 days. Since the capacity may be lower than the lower limit voltage, a small one can be used.

  As described above, in this embodiment, the lithium ion capacitors 2031 and 2032 are used on a daily basis (day charge, night discharge), and the lithium ion battery 202B is used to cope with exceptional weather fluctuations and infrastructure installation environment fluctuations. Therefore, long-term reliability can be ensured.

  In addition, when exceptional weather fluctuations and infrastructure installation environment fluctuations last for a long time, the secondary battery 202 may be discharged to a voltage lower than the end voltage. In this embodiment, the USB terminal 209 is provided assuming such an emergency state. In such an emergency state, a voltage of 5 volts is supplied to the wireless sensor terminal 100 through the USB terminal 209. Then, the secondary battery charging circuit 208 charges the secondary battery 202 using the input voltage of 5 volts. As a result, the secondary battery 202 is charged and can generate the power supply voltage VDD of the load circuit 210. After that, if solar energy is obtained, the secondary battery 202 can be subsequently operated by the above-described operation.

[Other Embodiments]
In the above-described embodiment, the switch circuit 206 provided between the secondary battery 202 and the storage capacitor 203 and the DC / DC converter 207 includes the diode D1 and the diode D2, and includes, for example, an MPU. The switching control circuit is unnecessary.

  However, as shown in FIG. 6, a switching control circuit 220 may be provided to control the switching of the switch circuit 206. The other components in FIG. 6 are the same as the self-supporting power supply circuit 200 in FIG.

  In the example of FIG. 6, the terminal voltage of the storage capacitor 203 is supplied to the switching control circuit 220. When the terminal voltage of the storage capacitor 203 is higher than the lower limit voltage, the switching control circuit 220 selects the terminal voltage of the storage capacitor 203 and supplies the switch circuit 26 to the DC / DC converter 207. Switch. When the terminal voltage of the storage capacitor 203 becomes equal to or lower than the lower limit voltage, the switching control circuit 220 selects the switch circuit 26 to select the terminal voltage of the secondary battery 202, and sends it to the DC / DC converter 207. Switch to the supply state.

  In the case of the example of FIG. 6, the switching control circuit 220 is supplied with the power supply voltage VDD from the DC / DC converter 207 as the power supply voltage. In FIG. 6, the switching control circuit 220 is shown as a component of the self-supporting power supply circuit 200. However, the switching control circuit 220 may be a component of the load circuit 210, and the processing control circuit 211 may have the function of the switching control circuit 220. It can also be.

[Other variations]
In the above example, the storage capacitor 204 is composed of two lithium ion capacitors, but may be composed of one capacitor or three capacitors as long as the upper limit voltage condition is satisfied. You may comprise with the above capacitor. Further, the storage capacitor 204 is not limited to one using a lithium ion capacitor, and may be composed of other capacitors or an electric double layer capacitor.

  Needless to say, the secondary battery 203 is not limited to a lithium ion battery.

  Further, the power generation unit is not limited to one using a solar cell module as a power generation element. For example, it is possible to use power generation using vibrational energy whose external environmental factor is vibration at a place where a bridge is mounted, etc., and to use power generation energy based on external environmental factors such as temperature difference power generation, wind power generation, and geothermal power generation. You may make it perform the generated electric power. Also, instead of using these power generation energies alone, for example, combining solar cell modules and vibration power generation elements, by generating power using multiple types of power generation energy, it is possible to have a period when power generation opportunities cannot be obtained as much as possible. The power generation unit may be configured to be eliminated.

  In the above example, the USB terminal as the external charging terminal is provided in order to enable emergency evacuation charging. However, such an external charging terminal may be omitted. In that case, the package 101 of the wireless sensor terminal 100 can have a completely sealed structure.

  Moreover, although the above-mentioned embodiment is a case where a self-supporting terminal is a wireless sensor terminal, it cannot be overemphasized that the self-supporting terminal of this invention is not restricted to the above wireless sensor terminals. That is, the self-supporting terminal of the present invention can be applied to any terminal as long as the terminal includes a load that operates with a power supply voltage generated by a self-supporting power supply circuit.

DESCRIPTION OF SYMBOLS 100 ... Wireless sensor terminal, 101 ... Package, 200 ... Independent power supply circuit, 201 ... Solar cell module, 202 ... Secondary battery, 203 ... Capacitor for electrical storage, 204, 205 ... DC / DC converter, 206 ... Switch circuit, 210 ... Load circuit, 220 ... Switching control circuit, D1, D2, D3, D4 ... Diode

Claims (12)

A power generation unit including a power generation element that generates power by a power generation factor according to an external environment;
A secondary battery that is charged by receiving power from the power generation unit;
Charged by receiving power supply from the power generation unit, a capacitor for storage having an upper limit voltage higher than the nominal voltage of the secondary battery,
A load that operates with power supply, and
A switch circuit provided between the secondary battery and the storage capacitor and the load;
With
When the terminal voltage of the storage capacitor is higher than the terminal voltage of the secondary battery, the switch circuit is in a switching state in which the terminal voltage of the storage capacitor is supplied to the load, and the terminal of the storage capacitor The self-supporting terminal, wherein when the voltage becomes equal to or lower than the lower limit voltage of the storage capacitor, the terminal voltage of the secondary battery is switched to be supplied to the load. When the terminal voltage of the storage capacitor is higher than the terminal voltage of the secondary battery, the switch circuit is in a switching state in which the terminal voltage of the storage capacitor is supplied to the load. When the terminal voltage of the storage capacitor is less than or equal to the lower limit voltage of the storage capacitor and less than or equal to the terminal voltage of the secondary battery, a switching state in which the terminal voltage of the secondary battery is supplied to the load; And
The switch circuit includes a first diode provided between the secondary battery and the load, and a second diode provided between the storage capacitor and the load. The self-supporting terminal according to claim 1. The self-supporting terminal according to claim 1, wherein the storage capacitor includes a plurality of capacitors connected in series. A first DC / DC converter is provided between the power generation unit and the secondary battery to generate a voltage capable of charging the secondary battery from the output voltage of the power generation unit to a charge upper limit voltage. With
A second DC / DC converter is provided between the power generation unit and the storage capacitor to generate a voltage capable of charging the storage capacitor from the output voltage of the power generation unit to the upper limit voltage. The self-supporting terminal according to any one of claims 1 to 3, wherein the self-supporting terminal is provided. Between the load and the connection point of the first switch circuit and the second switch circuit, the voltage for the load is obtained from the voltage obtained through the first switch circuit or the second switch circuit. The DC / DC converter which produces | generates a power supply voltage is provided. The self-supporting terminal in any one of Claims 1-4 characterized by the above-mentioned. A third diode is connected between the first DC / DC converter and the secondary battery, and a second diode is connected between the second DC / DC converter and the capacitor. The self-supporting terminal according to claim 4, wherein four diodes are connected. The self-supporting terminal according to any one of claims 1 to 6, further comprising a charging circuit that charges the secondary battery through an external terminal. The self-supporting terminal according to claim 1, further comprising a control circuit that monitors a terminal voltage of the storage capacitor and controls the switching of the switch circuit. The self-supporting terminal according to any one of claims 1 to 8, wherein the secondary battery is a lithium ion battery. The self-supporting terminal according to any one of claims 1 to 9, wherein the storage capacitor is configured by connecting a plurality of lithium ion capacitors. The self-supporting terminal according to any one of claims 1 to 10, wherein the power generation element is a solar battery cell. 12. The load according to claim 1, wherein the load includes a sensor that detects a change in an environmental factor, and a communication circuit that wirelessly transmits the sensor output detected by the sensor to the outside. Free-standing terminal.

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