JP2012050248A - Power control circuit and communication apparatus having the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power control circuit capable of charging efficiently and to provide a communication apparatus comprising the power control circuit.SOLUTION: A power control circuit 3 includes a small-capacity capacitor 31, a large-capacity capacitor 32, a coil 35, and switches A, B. A connection state of the switches A, B can be switched ON and OFF according to a potential of an input node. When the switch A is ON, electric power input into the power control circuit 3 is stored in the small-capacity capacitor 31 and the large-capacity capacitor 32. When the switch A is switched from ON to OFF, a current flows into a closed loop composed of the coil 35, the large-capacity capacitor 32 and a diode 34 from a ground line GL by an electromotive force generated at the coil 35, and the electric power is stored in the large-capacity capacitor 32. Thus, the charging efficiency of the large-capacity capacitor 32 is improved to complete charging into the large-capacity capacitor 32 in a short time.

Description

  The present invention relates to a power control circuit that stores generated power and outputs the stored power to a subsequent circuit, and a communication device that performs wireless communication using power supplied from the power control circuit.

  In recent years, various environmental energy existing around us has been utilized. For example, in addition to solar power generation devices that generate power by receiving sunlight, vibration power generation devices that generate power using vibrations of people, cars, electrical appliances, and the like have been developed.

  Patent Document 1 below discloses a power control device that charges generated power and supplies power to a load circuit. This power control device is connected to an input / output node, connected to the input / output node via an initial power storage device that stores current input to the input / output node, a variable conductance element having a variable conductance, and a variable conductance element. A backup power storage device that stores current input to the input / output node is provided. The backup power storage device is configured to store a larger amount of power than the initial power storage device.

JP 2006-158043 A

  According to the power control device, it is possible to realize a fast rise of the load circuit and a long driving time, and it is possible to suppress a rapid fluctuation in the voltage supplied to the load circuit. However, there is a problem that it takes a long time to complete the charging of the backup power storage device.

  This invention is made | formed in view of such a point, and it aims at providing a communication apparatus provided with the power control circuit which can charge efficiently, and this power control circuit.

  A first aspect of the present invention relates to a power control circuit. The power control circuit according to this aspect includes a first capacitor connected between the input node and the ground line, a second capacitor connected between the input node and the ground line, and having a larger capacity than the first capacitor. A first switch connected in series between the second capacitor and the input node, a second switch provided between the input node and the output node, and connecting or disconnecting the input node and the output node; And a current exciter for causing a current to flow from the ground line to the second capacitor when the first switch is switched from the closed state to the opened state.

  A 2nd aspect of this invention is related with a communication apparatus. A communication device according to this aspect includes the power control circuit according to the first aspect, a power generation apparatus that supplies power to an input node, and a wireless apparatus that receives information from the output node and transmits information.

ADVANTAGE OF THE INVENTION According to this invention, the power control circuit which can be charged efficiently, and a communication apparatus provided with this power control circuit can be provided.

  The effects and significance of the present invention will become more apparent from the following description of embodiments. However, the following embodiment is merely an example for carrying out the present invention, and the present invention is not limited by the following embodiment.

It is a figure which shows the structure of the wireless sensor which concerns on embodiment. It is a figure explaining the ON / OFF characteristic of the switch which concerns on embodiment. It is a figure explaining operation | movement of the power control circuit which concerns on embodiment. It is a figure explaining operation | movement of the power control circuit which concerns on embodiment. It is a figure explaining operation | movement of the power control circuit which concerns on embodiment. It is a figure which shows the structure of the comparative example of the wireless sensor which concerns on embodiment, and the figure which shows the result of having performed simulation about the voltage stored in a large capacity capacitor.

  In the present embodiment, the present invention is applied to a wireless sensor as a communication device that performs wireless communication using generated electric power. The wireless sensor according to the present embodiment is a small device that is mounted on, for example, an indoor wall and transmits various information wirelessly. In order to achieve maintenance-free operation that eliminates the need for equipment wiring work and battery replacement, the wireless sensor of the present embodiment includes a power generation device that generates power using light such as indoor lighting, and the power generated by the power generation device. To perform various detections and wireless transmission.

  Hereinafter, the wireless sensor according to the present embodiment will be described with reference to the drawings.

  FIG. 1 is a diagram illustrating a configuration of the wireless sensor 1. A wireless sensor 1 according to the present embodiment includes a power generation device 2, a power control circuit 3, and a wireless device 4. The ground line GL of the circuit of the wireless sensor 1 is grounded. The node in the upper left part of the circuit of the wireless sensor 1 is hereinafter referred to as “input node”, and the node in the upper right part of the circuit of the wireless sensor 1 is hereinafter referred to as “output node”.

  The power generation device 2 is a solar power generation device that receives sunlight to generate power. The current input from the power generation device 2 to the input node is a direct current. The power generation device 2 supplies power to the power control circuit 3 through the input node.

  The power control circuit 3 stores the power generated by the power generation device 2 via the input node and supplies power to the wireless device 4 via the output node. The power control circuit 3 includes a small capacitor 31, a large capacitor 32, diodes 33 and 34, a coil 35, and switches A and B.

  The small capacitor 31 has a capacity of about 100 μF, and is connected between the potential line VL and the ground line GL. The large-capacitance capacitor 32 has a capacity of about 0.1 to 10 F, one terminal is connected to the ground line GL, and the other terminal is connected to the coil 35. The small-capacitance capacitor 31 and the large-capacity capacitor 32 are configured so that the capacity of the small-capacitance capacitor 31 is several steps smaller than the capacity of the large-capacitance capacitor 32.

The diodes 33 and 34 are connected in series between the potential line VL and the ground line GL so that the anode side faces the ground line GL. The coil 35 has one terminal connected to the large-capacitance capacitor 32 and the other terminal connected to the terminal A2 of the switch A. The line between the diodes 33 and 34 and the line between the coil 35 and the switch A are short-circuited.

  The switch A has terminals A 1 and A 2, the terminal A 1 is connected to the potential line VL, and the terminal A 2 is connected to the coil 35. The switch A is an analog switch (so-called hysteresis switch) that switches the connection state to ON / OFF according to the potential of the input node. The switch B has terminals B1 and B2, and is connected in series to the input node and the output node. The switch B is an analog switch (so-called hysteresis switch) that switches the connection state to ON / OFF according to the potential of the input node.

  The threshold values of the potentials of the input nodes at which the switch A and the switch B are switched ON / OFF are different from each other. The characteristics of the switch A and the switch B will be described later with reference to FIG.

  The wireless device 4 includes a sensor unit and a wireless communication unit, detects predetermined items (for example, temperature, humidity, light amount, presence / absence of vibration, etc.) by the sensor unit, and wirelessly communicates a detection signal from the wireless communication unit. This is a device that transmits to outside. The wireless device 4 is driven by using power supplied from the power control circuit 3 via the output node.

  FIG. 2 is a diagram for explaining the ON / OFF characteristics of the switches A and B. FIG. FIG. 4A shows the ON / OFF characteristic of the switch A, and FIG. 4B shows the ON / OFF characteristic of the switch B.

  Referring to FIG. 5A, when switch A is OFF, if the potential of the input node becomes larger than threshold value Va1, switch A is turned ON and terminal A1 and terminal A2 are connected. Further, when the potential of the input node becomes smaller than the threshold value Va0 when the switch A is ON, the switch A is turned OFF and the terminal A1 and the terminal A2 are disconnected.

  Referring to FIG. 4B, when the switch B is OFF and the potential of the input node becomes larger than the threshold value Vb1, the switch B is turned ON and the terminal B1 and the terminal B2 are connected. Further, when the potential of the input node becomes smaller than the threshold value Vb0 when the switch B is ON, the switch B is turned OFF and the terminal B1 and the terminal B2 are disconnected.

  Here, the switches A and B are configured so that the thresholds Va1, Va0, Vb1, and Vb0 satisfy at least the relationships of Va0 <Va1, Vb0 <Vb1, Vb0 <Va0, and Vb1 <Va1. Further, in the present embodiment, the switches A and B are configured to satisfy the relationship Va0 <Vb1, but the switches A and B may be configured to satisfy the relationship Vb1 <Va0.

  3 and 4 are diagrams illustrating the operation of the power control circuit 3 when power generation is performed by the power generation device 2. The potential at the input node is hereinafter referred to as “node potential”. The states of the wireless sensor 1 after the start of power generation are shown on the left side of FIGS. 3 (a), 3 (b), 3 (c), 4 (a), 4 (b), and FIGS. 3 (a), 3 (b). , (C), and the right side of FIGS. 4 (a) and 4 (b), the node potential in each state is shown.

FIG. 3A is a diagram illustrating a state in which power generation is performed by the power generation device 2 from a state in which power is not stored in the small-capacitance capacitor 31 and the large-capacitance capacitor 32. When power generation is performed by the power generation device 2, current flows from the input node to the small-capacitance capacitor 31, and electric power is stored in the small-capacitance capacitor 31. As a result, the node potential rises. At this time, due to the action of the diode 33, no current flows through the large-capacitance capacitor 32, and no electricity is stored. Thus, when the node potential reaches Vb1, the switch B is turned on as shown in FIG. Thereby, electric power is supplied to the wireless device 4 and the wireless device 4 is driven.

  When power generation is further performed by the power generation device 2 from the state of FIG. 3B and the node potential reaches Va1, the switch A is turned on as shown in FIG. As a result, current flows through the switch A to the coil 35. As a result, electric power is stored in the large-capacity capacitor 32. Thereafter, when the node potential becomes lower than Va0, the switch A is turned OFF as shown in FIG. As a result, power storage in the small-capacitance capacitor 31 proceeds and the node potential rises.

  In FIG. 4A, when the switch A is turned off, the current flowing in the coil 35 is interrupted, and an electromotive force is generated in the coil 35. As a result, as shown by the broken line in FIG. 4A, a current flows from the ground through the ground line GL to a closed loop including the large-capacitance capacitor 32, the coil 35, and the diode 34, and electric power is stored in the large-capacity capacitor 32. .

  From the state of FIG. 4A, when the power generation device 2 further generates power and the node potential reaches Va1 again, the switch A is turned ON again as shown in FIG. 4B. As a result, current flows through the switch A to the coil 35, and electric power is stored in the large-capacitance capacitor 32.

  After that, when the node potential becomes lower than Va0 again, the switch A is turned off as in the case of FIG. At this time, electromotive force is generated again in the coil 35, and power is stored in the large-capacitance capacitor 32.

  As described above, when the power generation device 2 continues to generate power, the state of the power control circuit 3 alternately becomes the state shown in FIGS. 4 (a) and 4 (b). As a result, electric power is gradually stored in the large-capacity capacitor 32.

  FIG. 5 is a diagram for explaining the operation of the power control circuit 3 when power generation is not performed after the power generation apparatus 2 generates power. Here, it is assumed that the potential of the small capacitor 31 is larger than the potential of the large capacitor 32 and the potential of the large capacitor 32 is larger than Vb0.

  For example, when power generation by the power generation device 2 is not performed in the state of FIG. 4B, the power stored in the small-capacitance capacitor 31 is supplied to the wireless device 4 and the large-capacity capacitor 32. Thereafter, when the discharge of the small capacitor 31 proceeds and the node potential falls below Va0, the switch A is turned OFF as shown in FIG. As a result, the power supply from the small capacitor 31 to the large capacitor 32 is cut off, and the power from the small capacitor 31 is supplied only to the wireless device 4 as shown by the broken line arrow in FIG.

  Thereafter, when the discharge of the small capacitor 31 further progresses and the potential of the small capacitor 31 falls below the potential of the large capacitor 32, it is stored in the large capacitor 32 as shown by the broken line arrow in FIG. Electric power is supplied to the wireless device 4. As a result, the wireless device 4 is driven by the electric power stored in the large-capacitance capacitor 32.

  When the power stored in the large-capacitance capacitor 32 is consumed from the state of FIG. 5B and the node potential becomes smaller than Vb0, the switch B is turned off as shown in FIG. The electric power supplied to is cut off.

As described above, even when power generation by the power generation device 2 is not performed, the wireless device 4 is supplied with power stably and for a long time by the small capacitor 31 and the large capacitor 32 of the power control circuit 3. Will be.

  Next, the speed with which electric power is stored in a large-capacitance capacitor will be described while comparing the above-described embodiment and a comparative example (the above-mentioned Patent Document 1).

  FIG. 6A is a diagram illustrating a configuration of the wireless sensor 1 in the comparative example. In this comparative example, a power control circuit 5 is installed instead of the power control circuit 3 from the wireless sensor 1 shown in FIG.

  The power control circuit 5 includes a small capacitor 51 having the same capacity as the small capacitor 31, a large capacitor 52 having the same capacity as the large capacitor 32, a variable resistor 53, and a switch 54. Even when such a power control circuit 5 is used, power is supplied to the wireless device 4 stably and for a long time as in the above embodiment.

  Here, the present applicant performed a simulation on the voltage stored in the large-capacity capacitor 32 of the above embodiment and the voltage stored in the large-capacitance capacitor 52 of the comparative example shown in FIG. FIG. 6B shows the result of the simulation.

  As shown in FIG. 6B, it can be seen that the voltage is stored in the large-capacitance capacitor with the passage of time in both the embodiment and the comparative example. In the comparative example, the voltage of the large-capacitance capacitor 52 increases approximately in proportion to the passage of time. In contrast, in the above embodiment, it can be seen that the voltage increase of the large-capacitance capacitor 32 is steeper than in the comparative example. This is because, in the above-described embodiment, when the switch A is turned off, as described with reference to FIG. 4 (a), the large capacity capacitor 32 is charged. That is, it can be said that the embodiment can store power in the large-capacity capacitor 32 more quickly than the comparative example.

  As described above, according to the above-described embodiment, when power generation is performed, power is stored in the small-capacitance capacitor 31 and the node potential is quickly increased, so that the wireless device 4 can be started quickly. Further, the wireless device 4 can be driven for a long time by the electric power stored in the large-capacitance capacitor 32.

  Further, according to the above embodiment, when the switch B is turned on and power is supplied to the wireless device 4, the switch A is turned on and the large-capacitance capacitor 32 is turned on while the power supply is maintained. Electric power is stored. At this time, although the voltage supplied to the wireless device 4 gradually decreases, the switch A is turned off before the switch B is turned off, so that the voltage supplied to the wireless device 4 rises again. . Therefore, since a rapid change in voltage supplied to the wireless device 4 is prevented, the wireless device 4 can be driven stably.

  Further, according to the above embodiment, the switch A is turned ON, and the electric power generated by the power generation device 2 is directly stored in the large-capacitance capacitor 32. Further, even when the switch A is turned OFF, as shown in FIG. 3D, an electromotive force is generated in the coil 35, whereby electric power is stored in the large-capacitance capacitor 32. As a result, the charging efficiency of the large-capacity capacitor 32 is increased, and the charging of the large-capacity capacitor 32 can be completed in a short time.

  In the above embodiment, the threshold value Va1 shown in FIG. 2A is desirably set to a value slightly larger than the voltage value at which the power generation efficiency of the power generation device 2 is maximized. In this case, the switch A is turned on in the vicinity of the voltage value at which the power generation efficiency of the power generation device 2 is maximized, so that power can be efficiently stored in the large-capacitance capacitor 32.

  In the above embodiment, when the threshold difference (Va1-Va0) shown in FIG. 2A is set small, the switch A is frequently turned on / off while the power generation device 2 is generating power. Repeated OFF. As a result, the number of times power is stored in the large-capacitance capacitor 32 due to the electromotive force of the coil 35 increases. At this time, although energy is easily consumed by turning ON / OFF the switch A, it is possible to use a smaller coil 35 in order to promote power storage in the large-capacity capacitor 32 by electromotive force.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications other than those described above can be made to the embodiments of the present invention.

  For example, in the above-described embodiment, the power generation device 2 is a solar power generation device that outputs a direct current, but is not limited thereto, and may be a vibration power generation device that generates power by vibration. In this case, since the current output from the power generator 2 is an alternating current, a rectifier circuit is installed in the power generator 2. As a result, other circuits can be configured in the same manner as in the above embodiment, and thus the same effect as in the above embodiment can be obtained.

  Further, the power supply destination is not limited to the wireless device, and may be another device. Furthermore, the present invention can also be applied to devices other than wireless sensors.

  In addition, the embodiment of the present invention can be variously modified as appropriate within the scope of the technical idea shown in the claims.

3 ... Power control circuit 31 ... Small capacitor (first capacitor)
32 ... Large-capacitance capacitor (second capacitor)
33 ... Diode (second diode)
34 ... Diode (current excitation unit, first diode)
35 ... Coil (current excitation part)
A ... Switch (first switch)
B ... Switch (second switch)
Va0 ... threshold value Va1 ... threshold value Vb0 ... threshold value Vb1 ... threshold value

Claims (7)

A first capacitor connected between the input node and the ground line;
A second capacitor connected between the input node and the ground line and having a larger capacity than the first capacitor;
A first switch connected in series between the second capacitor and the input node;
A second switch that is provided between the input node and the output node and connects or disconnects the input node and the output node;
When the first switch is switched from a closed state to an open state, a current excitation unit that causes a current to flow from the ground line to the second capacitor;
A power control circuit comprising: The power control circuit according to claim 1,
The current excitation unit is
A coil connected in series between the second capacitor and the first switch;
A first diode having an anode connected to the ground line and a cathode connected between the coil and the first switch;
When the first switch is switched from the closed state to the opened state, an electromotive force generated in the coil causes a current from the ground line to enter a closed loop including the second capacitor, the coil, and the first diode. Flows in,
A power control circuit characterized by that. The power control circuit according to claim 2,
A second diode having an anode connected to the cathode of the first diode and a cathode connected to the input node;
A power control circuit characterized by that. The power control circuit according to any one of claims 1 to 3,
The first switch connects between the terminals of the first switch when the potential of the input node exceeds the threshold value Va1, and the terminal of the first switch when the potential of the input node falls below the threshold value Va0 (Va0 <Va1). Configured to be disconnected,
A power control circuit characterized by that. The power control circuit according to any one of claims 1 to 3,
The second switch connects the terminals of the second switch when the potential of the input node exceeds the threshold value Vb1, and the terminal of the second switch when the potential of the input node falls below the threshold value Vb0 (Vb0 <Vb1). Configured to be disconnected,
A power control circuit characterized by that. The power control circuit according to any one of claims 1 to 3,
The first switch connects between the terminals of the first switch when the potential of the input node exceeds the threshold value Va1, and the terminal of the first switch when the potential of the input node falls below the threshold value Va0 (Va0 <Va1). Configured to be disconnected,
The second switch connects the terminals of the second switch when the potential of the input node exceeds the threshold value Vb1, and the terminal of the second switch when the potential of the input node falls below the threshold value Vb0 (Vb0 <Vb1). Configured to be disconnected,
The thresholds Va0, Va1, Vb0, Vb1 satisfy the relationship of Vb0 <Va0, Vb1 <Va1.
A power control circuit characterized by that. A power control circuit according to any one of claims 1 to 6,
A power generator for supplying power to the input node;
A wireless device that receives power from the output node and transmits information;
Communication equipment characterized by this.

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