JP5633383B2 - Power generation device, secondary battery and electronic device - Google Patents

Description

  The present invention relates to a power generation device, a secondary battery, and an electronic device.

When piezoelectric materials such as lead zirconate titanate (PZT), quartz (SiO ₂ ), and zinc oxide (ZnO) are deformed by external force, electric polarization is induced inside the material, and positive and negative charges appear on the surface. . Such a phenomenon is called a piezoelectric effect. A power generation method has been proposed in which the cantilever is vibrated by repeatedly applying a load to the piezoelectric material by utilizing such properties of the piezoelectric material, and electric charges generated on the surface of the piezoelectric material are extracted as current.

  For example, an alternating current is generated by vibrating a metal cantilever provided with a weight at the tip and attached with a thin plate of piezoelectric material, and taking out positive and negative charges alternately generated in the piezoelectric material due to the vibration. A technique has been proposed in which this alternating current is rectified by a diode, stored in a capacitor, and extracted as electric power (Patent Document 1). In addition, a technique has been proposed in which a direct current can be obtained without causing a voltage loss in a diode by closing a contact only while a positive charge is generated in a piezoelectric element (patent) Reference 2). If these technologies are used, the power generation device can be reduced in size. For this reason, applications such as incorporation in small electronic components instead of batteries are expected.

JP-A-7-107752 JP 2005-31269 A

  However, the proposed conventional power generator has a problem that the voltage obtained is limited to the voltage generated by the electric polarization of the piezoelectric material. For this reason, in most cases, a separate booster circuit is required, and there is a problem that it is difficult to sufficiently reduce the size of the power generation device. In addition, normal power is required to drive the booster circuit, but once the vibration stops, the power for driving the booster circuit is interrupted, which makes it difficult to restart. In addition, when a battery for restarting is separately provided, there is a problem that the power generation device is enlarged and the life of the power generation device is reduced due to the life of the battery.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms or application examples.

  [Application Example 1] A power generation device according to this application example includes a piezoelectric unit including a piezoelectric material that generates electric charges by repeatedly deforming by switching a deformation direction according to an external force, and the piezoelectric unit can be deformed in a deformable state. A support for supporting the piezoelectric portion, a pair of electrodes used for taking out the electric charge generated by deformation of the piezoelectric portion as a current, a first switch connected to one side of the pair of electrodes, and the first switch An inductor that is connected to the pair of electrodes and forms a resonance circuit with a capacitance component of the piezoelectric portion, and the first switch is short-circuited when the deformation direction of the piezoelectric portion is switched, A first that opens the first switch when a time corresponding to a half period of a resonance period has elapsed and when a voltage lower than a lower limit voltage that can control the first switch is supplied. A switch rectifier, a bridge rectifier that rectifies the alternating current output from the pair of electrodes into a pulsating current and converts it into a first direct current voltage, and converts the alternating current output from the pair of electrodes into a pulsating current A voltage doubler rectifier that rectifies and converts to a second DC voltage higher than a voltage between the pair of electrodes, a power storage unit that stores a pulsating current supplied from the bridge rectifier or the voltage doubler rectifier, and A second switch that selects either the bridge rectifier or the voltage doubler rectifier, and the voltage doubler rectifier using the second switch when the first DC voltage is lower than the lower limit voltage A second switch control device, wherein the first switch control device and the second switch control device are driven using either the first DC voltage or the second DC voltage. To do.

According to this, positive and negative charges are generated in the piezoelectric portion by the piezoelectric effect by repeatedly deforming the piezoelectric portion by switching the deformation direction according to the external force. In addition, the amount of charge generated increases as the amount of deformation of the piezoelectric portion increases. And when the magnitude | size of deformation | transformation becomes the maximum (namely, when a deformation | transformation direction switches), a 1st switch is short-circuited and a piezoelectric part is connected to an inductor. Since the piezoelectric part can be regarded as a capacitor in terms of an electric circuit, a resonance circuit is formed by being connected to an inductor.
Then, the electric charge generated in the piezoelectric part flows into the inductor. Since the piezoelectric portion and the inductor constitute a resonance circuit, the current flowing into the inductor overshoots and flows into the piezoelectric portion from the terminal on the opposite side. During this period (that is, the period until the electric charge flowing out from one electrode of the piezoelectric part flows again into the piezoelectric material from the opposite electrode through the inductor), the resonance of the resonance circuit formed by the piezoelectric part and the inductor Half the cycle. Therefore, the piezoelectric part and the inductor are connected by short-circuiting the first switch at the timing when the deformation direction of the piezoelectric part is switched, and then the piezoelectric part and the inductor are connected at the timing when half the resonance period has elapsed. If the first switch is used for opening, the arrangement of positive and negative charges generated in the piezoelectric portion before connecting the inductor can be reversed.

From this state, when the piezoelectric portion is deformed in the opposite direction, charges generated by the piezoelectric effect are accumulated in addition to the charges accumulated in the reverse direction. As a result, it is possible to accumulate charges generated by repeatedly deforming the piezoelectric portion in the piezoelectric portion. Further, since the voltage between the terminals is increased by the amount of charge accumulated in the piezoelectric portion, a voltage higher than the voltage generated by the electric polarization of the piezoelectric material can be generated without preparing a booster circuit separately. As a result, a small and efficient power generator can be obtained.
Here, in order to perform the above-described power generation operation, it is necessary to actively control the first switch that connects / opens the piezoelectric portion and the inductor.
That is, once the voltage applied to the first switch control device falls below the lower limit voltage, the first switch cannot be actively controlled, and the above-described power generation operation cannot be performed.

  In this case, the second switch is switched using the second switch control device, and the device for converting to a DC voltage is switched to the voltage doubler rectifier. Therefore, a voltage close to twice the voltage at the piezoelectric unit is applied to the first switch control device, so that a higher voltage can be stored in the power storage unit compared to the bridge rectification unit. Thereby, even if the voltage given to a 1st switch control apparatus falls below a minimum voltage, electric power generation operation can be continued.

  Application Example 2 In the power generation device according to the application example described above, the power storage unit is connected in series between the anode pair side and the cathode pair side of the bridge rectification unit, and the first power storage element and the second power storage element The second switch is provided between the first power storage element and the second power storage element and between one side of the pair of electrodes, and the second switch control device includes: When the bridge rectifier is selected, the second switch is opened, and when the voltage doubler rectifier is selected, the second switch is short-circuited.

  According to the application example described above, the bridge rectification unit can be switched to the voltage doubler rectification unit simply by closing the second switch. Therefore, it is possible to provide a power generation device that can suppress an increase in the number of parts, have high power generation efficiency, and can self-recover. In addition, when the voltage equal to or higher than the lower limit voltage is maintained, it is possible to operate as the bridge rectification unit by opening the second switch, so that it is possible to generate power without reducing the power generation efficiency.

  Application Example 3 In the power generation device according to the application example described above, the power storage unit includes a power storage element connected between an anode pair side and a cathode pair side of a bridge rectification unit, and the second switch Provided between the anode pair side of the bridge rectification unit and one of the pair of electrodes, the second switch control device opens the second switch when selecting the bridge rectification unit; When the voltage doubler rectifier is selected, the second switch is short-circuited, and the capacitance component is used as a capacitor when driving the voltage doubler rectifier.

  According to the application example described above, the bridge rectification unit can be switched to the voltage doubler rectification unit simply by closing the second switch, so that an increase in the number of components is suppressed and high power generation efficiency is provided, and self-recovery is possible. It is possible to provide a simple power generator. In addition, when the voltage equal to or higher than the lower limit voltage is maintained, the bridge rectification unit is formed by opening the second switch, so that power generation can be performed without reducing the power generation efficiency. Furthermore, when operated as a voltage doubler rectifier, half-wave voltage doubler rectification is performed using the capacitive component of the piezoelectric part, so that the storage elements are not connected in series (storage elements of the same capacity are connected in series) In such a case, the effective capacity is halved).

  Application Example 4 In the power generation apparatus according to the application example described above, the first switch is a normally-off switch that is in an open state when no driving voltage is applied, and the second switch has a driving voltage of When not applied, it is a normally-on switch that takes a short-circuit state.

  According to the application example described above, when the output voltage of the power generator is lower than the lower limit voltage, the bridge rectifier is switched to the voltage doubler rectifier. In addition, since the inductor connected in parallel with the piezoelectric portion is cut, voltage doubler rectification is quickly performed when the piezoelectric portion is repeatedly deformed. Therefore, it is possible to provide a power generator that can self-recover in a short time and has high power generation efficiency.

  Application Example 5 A secondary battery according to this application example includes the power generation device described above.

  According to this, even when the secondary battery is once discharged and the first switch cannot be controlled, voltage doubler rectification is performed when the piezoelectric portion is repeatedly deformed. Then, after obtaining a voltage equal to or higher than the lower limit voltage, promptly shifting to a rectification state with high power generation efficiency, to provide a secondary battery that has higher power generation efficiency than normal bridge rectification and that can be self-recovered. It becomes possible.

  Application Example 6 An electronic apparatus according to this application example includes the secondary battery described above.

  According to this, since the power generation efficiency is higher than that of normal bridge rectification and the self-recoverable secondary battery is provided, it is possible to provide an electronic device that can operate without battery replacement.

(A) is the schematic diagram which showed the structure of the electric power generating apparatus, (b) is the circuit diagram of an electric power generating apparatus. (A)-(d) is the graph which showed operation | movement of the electric power generating apparatus in the steady state. (A) is a circuit diagram which shows the electric current path when the switch with which a bridge rectification part is equipped is short-circuited, (b) is the equivalent circuit schematic which extracted the part regarding the path | route through which an electric current flows. (A) is a circuit diagram of a power generator, and (b) is a circuit diagram showing a current path when a switch provided in a bridge rectifier is short-circuited. The circuit diagram which extracted the component which is functioning effectively when 1st switch SW1 is open | released and 2nd switch SW2 is short-circuited. The circuit diagram for explaining the modification 1. The circuit diagram for explaining the modification 2. FIG. 9 is a circuit diagram for explaining a third modification. The circuit diagram for explaining the modification 4. 6 is a flowchart for determining whether to take an operation in a steady state or an operation to obtain a starting voltage. The circuit diagram of a secondary battery. Schematic which shows schematic structure of the pedometer (trademark) as an electronic device.

(Embodiment: power generation device having a first configuration)
Hereinafter, embodiments embodying the present invention will be described with reference to the drawings.
Fig.1 (a) is the schematic diagram which showed the structure of the electric power generating apparatus of this embodiment. The mechanical structure of the power generation unit 125 provided in the power generation apparatus 100 shown in the present embodiment is a cantilever structure in which a beam 104 having a weight 106 at the distal end is fixed to the support end 102 at the proximal end side. Yes. Further, a piezoelectric portion 108 made of a piezoelectric material such as lead zirconate titanate (PZT) is fixedly supported on the surface of the beam 104 as a support, and a metal thin film or the like is formed on both surfaces of the piezoelectric portion 108. A first electrode 109a and a second electrode 109b are provided as a pair of electrodes using the conductor. In the example shown in FIG. 1, the piezoelectric portion 108 is provided on the upper surface side of the beam 104. However, the piezoelectric portion 108 may be provided on the lower surface side of the beam 104, or the upper surface side and the lower surface side of the beam 104. Both of them may be provided with the piezoelectric portion 108. Note that “upper” refers to the direction in which the first electrode 109a is viewed from the piezoelectric portion 108 (the positive direction of u in the figure), and “lower” refers to the direction opposite to “upper”.

  The beam 104 is fixed to the support end 102 at the base end side, and a weight 106 is provided at the tip end side. Therefore, when vibration or the like is applied, the beam 104 is shown by a white arrow in the figure. The tip of oscillates greatly. As a result, the piezoelectric portion 108 attached to the surface of the beam 104 is repeatedly deformed by an external force, and a compressive force and a tensile force act alternately. Then, the piezoelectric portion 108 generates positive and negative charges due to the piezoelectric effect, and the charges appear on the first electrode 109a and the second electrode 109b and are taken out as current.

FIG.1 (b) is a circuit diagram of the electric power generating apparatus in this embodiment. The piezoelectric unit 108 can be electrically expressed as a current source I0 and a capacitor C0 that stores electric charge. An inductor L is connected in parallel to the piezoelectric portion 108 to form an electrical resonance circuit together with the capacitive component C0 of the piezoelectric portion 108. A first switch SW1 for short-circuiting / opening the resonance circuit is connected in series to the inductor L. The short circuit / opening of the first switch SW1 and the short circuit / opening of the second switch SW2 are controlled by the switch control device 110 as the first switch control device and the second switch control device. In addition, the first electrode 109a and the second electrode 109b provided in the piezoelectric unit 108 are connected to a bridge rectification unit 120 including four diodes D1 to D4. More specifically, the power storage elements Ca and Cb connected in series are configured such that the cathode pair in which the cathodes of the diodes D1 and D3 constituting the bridge rectifying unit 120 are electrically coupled and the anode of the diodes D2 and D4 are electrically connected. Between the positively coupled anode pair.
Here, Schottky barrier diodes having lower forward voltage drop than the junction type diodes are used for the diodes D1 to D4. The forward voltage drop of the junction type diode is about 0.6V, but the forward voltage drop of the Schottky barrier diode is about 0.3V. Therefore, when full-wave rectification or voltage doubler rectification is performed, a voltage drop at the diodes D1 to D4 can be suppressed.
The diodes D1 to D4 function as the bridge rectification unit 120 when the second switch SW2 is opened. And it functions as the direct current converter 140 which changes an alternating current into a direct current voltage with electrical storage element Ca and Cb.
In addition, the diodes D1 to D4 function as the voltage doubler rectifier 120a when the second switch SW2 is short-circuited. Then, it functions as a voltage doubler DC device 140a including power storage elements Ca and Cb.
Positive and negative charges generated by the piezoelectric unit 108 are taken out by the first electrode 109a and the second electrode 109b and become an alternating current. And this alternating current is converted into a pulsating current by the bridge rectification part 120 and the voltage doubler rectification part 120a provided with the diodes D1-D4. This pulsating current is stored in the storage elements Ca and Cb.

(Operation in steady state)
2A to 2D are graphs showing the operation of the power generator in a steady state. Here, the steady state indicates a case where a voltage that can control the operation of the first switch SW1 and the second switch SW2 is supplied to the switch control device 110.
FIG. 2A shows the movement of the displacement position of the tip of the beam 104. The vertical axis represents displacement u, and the horizontal axis represents time t. The unit of displacement is an arbitrary unit. As shown in FIG. 2A, it is shown that the displacement U of the tip of the beam 104 changes with the vibration of the beam 104. A positive displacement U represents a state in which the beam 104 is warped upward (a state in which the upper surface side of the beam 104 is concave), and a negative displacement (−U) represents a state in which the beam 104 is warped downward. (A state where the lower surface side of the beam 104 is concave). FIG. 2B shows the state of current generated by the piezoelectric unit 108 as a result of the deformation of the beam 104 and the electromotive force generated inside the piezoelectric unit 108 as a result. In FIG. 2B, the state in which charges are generated in the piezoelectric portion 108 is expressed as the amount of charges generated per unit time (that is, current Ip). Here, the current Ipzt flowing through the piezoelectric portion 108 is taken as the vertical axis. Further, the electromotive force generated in the piezoelectric part 108 is represented by the potential difference Vpzt generated between the first electrode 109a and the second electrode 109b as the vertical axis. When the steady state operation is performed, the second switch SW2 is opened.

  As shown in FIGS. 2A and 2B, while the displacement of the beam 104 is increasing, the piezoelectric portion 108 generates a current in the positive direction. (That is, the current Ip takes a positive value). Along with this, the potential difference Vp between the first electrode 109a and the second electrode 109b increases in the positive direction. If the positive potential difference Vp is larger than the sum of the voltage VC1 between the storage elements Ca and Cb and twice the forward voltage drop Vf of the diode constituting the bridge rectifying unit 120, that is, VC1 + 2Vf, The electric charges generated thereafter can be taken out as a direct current and stored in the electric storage elements Ca and Cb. Further, while the displacement of the beam 104 is decreasing, the piezoelectric portion 108 generates a negative current (that is, the current Ip takes a negative value). Accordingly, the potential difference Vp between the first electrode 109a and the second electrode 109b increases in the negative direction. If the potential difference Vp in the negative direction is larger than the sum of VC1 and 2Vf of the bridge rectifying unit 120, the generated charge can be taken out as a direct current and stored in the storage elements Ca and Cb. This is a general power generation method. Here, a method of performing more efficient power generation by controlling the first switch SW1 will be described.

FIG. 2C is a graph showing the timing at which the first switch SW1 is short-circuited (ON), and is ON only for the time indicated as “ON”. FIG. 2D shows a voltage waveform obtained when the first switch SW1 is short-circuited (ON) at the timing shown in FIG. The vertical axis represents the potential difference Vgen generated between the first electrode 109a and the second electrode 109b as the generated voltage.
The first switch SW1 is short-circuited (ON) at the timing shown in FIG. 2C (timing at which the displacement of the piezoelectric portion 108 takes the maximum or minimum). Then, as shown in FIG. 2 (d), a phenomenon occurs in which the voltage waveform between the first electrode 109a and the second electrode 109b sandwiching the piezoelectric portion 108 is shifted at the moment when the first switch SW1 is short-circuited. To do. For example, in the period B indicated as “B” in FIG. 2D, the voltage indicated by the thick broken line such that the potential difference Vp indicated by the thin broken line corresponding to the electromotive force of the piezoelectric portion 108 is shifted in the negative direction. A waveform appears between the first electrode 109a and the second electrode 109b sandwiching the piezoelectric portion 108.
Further, in the period C indicated as “C” in FIG. 2D, a thick broken voltage waveform appears in which the potential difference Vp corresponding to the electromotive force of the piezoelectric portion 108 is shifted in the positive direction. Similarly, in the subsequent period D, period E, period F, and the like, a thick broken voltage waveform appears in which the potential difference Vp corresponding to the electromotive force of the piezoelectric portion 108 is shifted in the positive direction or the negative direction.
This is obtained by utilizing a resonance phenomenon in a resonance circuit including the inductor L and the capacitance component C0 of the piezoelectric portion 108. When the first switch SW1 is short-circuited (ON) at the timing when the displacement of the piezoelectric portion 108 is minimized (when the displacement is −u in FIG. 2A), the current flowing through the inductor L resists the inductance of the inductor L. And gradually begin to flow. When the voltage across the capacitive component C0 becomes 0, the current flowing through the inductor L becomes maximum. Subsequently, current continues to flow due to the inductance of the inductor L, and the current becomes 0 in a state where the voltage across the capacitance component C0 is inverted. Here, the first switch SW1 is opened (OFF).

  Thereafter, the piezoelectric portion 108 bends in the opposite direction. That is, the current Ip takes a positive value and charges the capacitive component C0 in the positive direction. In the above-described operation, the electric charge stored in the capacitance component C0 is held in an inverted state, so that a new positive electric charge is added to a value that can be generated by the piezoelectric unit 108 in a general operation. Take a big value.

  Then, by performing the same operation when the displacement of the piezoelectric portion 108 reaches a maximum (when the displacement becomes u in FIG. 2A), this time, the absolute value can be generated by a general operation. A larger negative potential difference Vg. That is, the piezoelectric switch 108 is short-circuited at a timing at which the displacement of the piezoelectric portion 108 takes the maximum or minimum, and the first switch SW1 is short-circuited for a half period of the resonance cycle of the resonance circuit constituted by the capacitive component C0 and the inductor L. Therefore, it becomes possible to take out electric power more efficiently.

  In this case, unless the electric charge flows out from the piezoelectric part 108, the electric charge in the piezoelectric part 108 increases every time the piezoelectric part 108 is deformed. Therefore, the voltage between the first electrode 109a and the second electrode 109b sandwiching the piezoelectric portion 108 is increased.

  Here, in the portion exceeding the sum of VC1 and 2Vf (the portion shown by hatching in FIG. 2D), the electric charge generated in the piezoelectric portion 108 is stored in the storage elements Ca and Cb. Therefore, electric charges flow out from the piezoelectric unit 108 to the power storage elements Ca and Cb, and the voltage between the first electrode 109a and the second electrode 109b sandwiching the piezoelectric unit 108 is the sum of the voltages between the terminals of the power storage elements Ca, Cb and 2Vf. Is clipped at a voltage (VC1 + 2Vf). As a result, the voltage waveform between the first electrode 109a and the second electrode 109b is a waveform indicated by a thick solid line in FIG.

  The case where the first switch SW1 shown in FIG. 2B is kept open, and the case where the first switch SW1 is short-circuited at the timing when the deformation direction of the beam 104 is switched as shown in FIG. As is clear from the comparison, in the power generation apparatus 100 of the present embodiment, it is possible to efficiently store charges in the power storage elements Ca and Cb by short-circuiting / opening the first switch SW1 at an appropriate timing. .

  In addition, electric charges are stored in the storage elements Ca and Cb, and both ends of the storage elements Ca and Cb (the cathode pair side where both cathodes of the diodes D1 and D3 are connected to one end and the anode pair side where both anodes of the diodes D2 and D4 are connected to each other) As the voltage at the other end increases, the voltage waveform shift amount increases accordingly. For example, the period B in FIG. 2D (state in which no charge is stored in the power storage elements Ca and Cb) and the period H in FIG. 2D (state in which charge is stored in the power storage elements Ca and Cb) ), The shift amount of the voltage waveform is larger in the period H. Similarly, when the period C and the period I in FIG. 2D are compared, the shift amount of the voltage waveform is larger in the period I in which the charges stored in the power storage elements Ca and Cb are increasing. . As a result, in the power generation apparatus 100 of the present embodiment, by deforming the piezoelectric portion 108, a voltage greater than the potential difference Vp generated between the first electrode 109a and the second electrode 109b is stored in the power storage elements Ca and Cb. It becomes possible. As a result, it is not necessary to provide a special booster circuit, and a small and highly efficient power generator can be obtained. Hereinafter, this rectification operation is referred to as a boost rectification operation.

(Operation when no starting voltage is applied)
Returning to FIG.
As a result of the step-up rectifying operation described above, when a voltage capable of operating the switch control device 110 is supplied as an initial state, the electric power applied from the piezoelectric unit 108 can be extracted with higher efficiency than the conventional technique. If the operating voltage (for example, 3.3 V) is not applied to the switch control device 110 at the time, the first switch SW1 cannot be short-circuited / opened, and the boost rectification operation cannot be performed. Therefore, it is necessary to temporarily store power for starting up the switch control device 110. For example, when considering application to a wristwatch, the piezoelectric unit 108 cannot generate power when the wristwatch is removed from the arm. Therefore, when the energy stored in the storage elements Ca and Cb is used up, it is difficult to restart the switch control device 110, and the power generation device 100 cannot start the boost rectification operation. For this reason, it is necessary to temporarily accumulate the power necessary for restarting the power generation apparatus 100.

Here, in the state where the second switch SW2 is opened, that is, in the step-up rectifying operation state, a voltage obtained by full-wave rectifying the voltage generated by the piezoelectric unit 108 by the bridge rectifying unit 120 is applied to the switch control device 110. . For example, it is assumed that the inductor L is electrically disconnected using a normally-off switch for the first switch SW1, and full-wave rectification is performed by the bridge rectification unit 120. The piezoelectric unit 108 generates a voltage of approximately 2.0 V, depending on the amplitude of the piezoelectric unit 108. This voltage is referred to as VC.
When rectification is performed using the bridge rectification unit 120, when the forward voltage drop Vf is 0.3 V assuming that a Schottky barrier diode is used, the voltage after rectification becomes a value represented by the following equation. When the bridge rectification unit 120 is used, a voltage twice as large as Vf is lost because it passes through the diode twice.
VC-2 * Vf = 2V-0.3V * 2 = 1.4V.
Since this voltage does not reach the voltage for starting the switch control device 110, the step-up rectification operation cannot be started.

Therefore, the second switch SW2 is short-circuited to operate as the voltage doubler rectifier 120a. As a method for short-circuiting the second switch SW2 in a state where the voltage is lowered, it is also preferable to use a normally-on switch as the second switch SW2. In this case, the diodes D1 to D4 and the storage elements Ca and Cb function as the voltage doubler DC device 140a. 3A is a circuit diagram when the second switch SW2 included in the bridge rectification unit 120 is short-circuited and a circuit diagram showing a current path, and FIG. 3B is an equivalent diagram in which a portion related to a path through which a current flows is extracted. It is a circuit diagram. FIG. 1 (b) and FIG. 3 (a) basically have common components. With respect to this common configuration, when the second switch SW2 is opened, the DC converter 140 operates. When the second switch SW2 is short-circuited, it operates as the voltage doubler DC device 140a. Therefore, it is possible to provide the power generation apparatus 100 that can suppress the increase in the number of parts, have high power generation efficiency, and can self-recover.
Hereinafter, according to FIG. 3A, a current flow when the second switch SW2 is operated as the voltage doubler DC device 140a by short-circuiting will be described.
First, when the first electrode 109a is positive and the second electrode 109b is negative, current flows along a solid arrow. First, after leaving the first electrode 109a, it passes through the diode D1 and leaves the storage element Ca (here, the storage element Ca is charged). Then, it passes through the short-circuited second switch SW2 and flows to the second electrode 109b.
Next, when the first electrode 109a is negative and the second electrode 109b is positive, the current flows along the dashed arrow. First, after exiting the second electrode 109b, the second switch SW2 that has been short-circuited is exited, and the electrical storage element Cb is exited (the electrical storage element Cb is charged here). Then, it passes through the diode D2 and flows to the first electrode 109a.
Then, as shown in FIG. 3B, this circuit, in which a portion related to the path through which the current flows is extracted, is a typical voltage doubler rectifier circuit between the first electrode 109a and the second electrode 109b sandwiching the piezoelectric part 108. It is possible to supply a voltage that is approximately twice the voltage of VC.
In this step, the storage element Ca and the storage element Cb are charged so that the potential difference between the terminal A and the terminal B becomes large. Therefore, the potential difference between the terminal A and the terminal B is represented by the following formula.
(VC-Vf) + (VC-Vf) = 3.4V.
Since such a voltage is applied to the switch control device 110, the switch control device 110 becomes operable. In this case, the second switch SW2 may be quickly opened and the charging operation by the first switch SW1 may be started. However, after the charge is stored in the storage elements Ca and Cb with some allowance, the first switch SW1 is controlled. Then, the boost rectification operation may be started.

(Power generation device having the second configuration)
Hereinafter, the electric power generating apparatus provided with the 2nd structure is demonstrated based on drawing. In the description of the power generation device having the second configuration, the same reference numerals are given to the same configurations as those of the power generation device having the first configuration, and description thereof is omitted.
FIG. 4A is a circuit diagram for explaining the present embodiment, and FIG. 4B is a circuit diagram showing a current path when the second switch SW2 included in the bridge rectifier 120 is short-circuited. The main difference in the circuit diagram between the power generation device 101 shown in FIG. 4A and the power generation device 100 shown in FIG. 3 is that the power storage device C is replaced with the power storage device Ca and the power storage device Cb connected in series. It is used, and the second switch SW2 opens and shorts the diode D4.
The storage element C is provided between a cathode pair in which the cathodes of the diodes D1 and D3 constituting the bridge rectifying unit 120 are electrically coupled, and an anode pair in which the anodes of the diodes D2 and D4 are electrically coupled. ing.
Here, the positive and negative charges generated by the piezoelectric portion 108 are taken out by the first electrode 109a and the second electrode 109b and become an alternating current. And this alternating current is converted into a pulsating current by the bridge rectification part 120 and the voltage doubler rectification part 120a provided with the diodes D1-D4. This pulsating current is stored in the storage element C and converted into a DC voltage.
The operation in the case where the switch control device 110 operates in a stable state and the voltage that can control the operation of the first switch SW1 and the second switch SW2 is supplied to the switch control device 110 is the same as the step-up rectification operation described above. In addition, the diodes D1 to D4 operate as the bridge rectification unit 120, and the diodes D1 to D4 and the storage element C operate as the direct current converter 140, and thus the description thereof is omitted.

(Operation when no starting voltage is applied)
Even in this case, when there is no operating voltage (for example, 3.3 V) in the switch control device 110 at the time of activation, the first switch SW1 cannot be short-circuited / opened, and the boost rectification operation cannot be performed. Therefore, even in this case, it is necessary to perform voltage doubler rectification in order to temporarily store power for starting the switch control device 110. Even in this case, the problem can be solved by opening the first switch SW1, short-circuiting the second switch SW2, and diverting the diodes D1 to D4 to the voltage doubler rectifier 120a. This can be dealt with, for example, by using a normally-off switch for the first switch SW1 and a normally-on switch for the second switch SW2. In this case, the diodes D1 to D4 and the storage element C function as the voltage doubler DC device 140a. The capacity of the piezoelectric unit 108 also functions as the voltage doubler DC device 140a. 4A is a circuit diagram when the second switch SW2 is short-circuited, FIG. 4B is a circuit diagram showing a current path when the voltage doubler DC converter 140a is operated, and FIG. It is the equivalent circuit diagram which extracted the part regarding the path | route which flows. FIG. 4A and FIG. 4B basically have common components. In other words, in a state where the second switch SW2 is short-circuited, the diodes D1 to D4, the storage element C, and the capacitor C0 operate as the voltage doubler DC converter 140a. Therefore, it is possible to provide a power generation device that can suppress an increase in the number of parts, have high power generation efficiency, and can self-recover.

Next, the operation for accumulating the starting voltage will be described with reference to FIG. Note that the description of writing the piezoelectric part 108 as the current source I0 and the capacitor C0 that stores electric charge is not a very general method for drawing the voltage doubler rectifier circuit, so the piezoelectric part 108 stores electric charge as the voltage source V0. The description is continued by switching to an equivalent circuit in which the capacitor C0 is connected in series.
When the first electrode 109a side outputs a negative voltage and the second electrode 109b side outputs a positive voltage, a current flows along a dashed arrow.
The current supplied from the voltage source V0 passes through the second electrode 109b, passes through the diode D2 and the first electrode 109a, charges the capacitor C0, and returns to the voltage source V0.
When the first electrode 109a side outputs a positive voltage and the second electrode 109b side outputs a negative voltage, a current flows along a solid arrow.
In this case, in addition to the voltage from the voltage source V0, the voltage of the capacitor C0 is also added to function as one voltage source. The voltage of the capacitor C0 is obtained by subtracting the voltage drop of the diode D2 from the voltage VC of the piezoelectric unit 108.
First, it passes through the capacitor C0, passes through the first electrode 109a, passes through the diode D1, and charges the storage element C. Then, the voltage returns to the voltage source V0 through the second electrode 109b. Here, since the voltage drop Vf of the diode D1 is received when the storage element C is charged, the voltage between the terminals of the storage element C takes the following value.
(VC-Vf) + (VC-Vf) = (2-0.3) + (2-0.3) = 3.4V.
FIG. 5 is a circuit diagram in which components functioning effectively when the first switch SW1 is opened and the second switch SW2 is short-circuited are extracted. This circuit is a typical voltage doubler rectifier circuit, and it is shown that a voltage approximately twice as high as VC, which is the voltage between the first electrode 109a and the second electrode 109b across the piezoelectric part 108, is supplied.

(Operation sequence)
Hereinafter, an operation sequence of the above-described power generation apparatus will be described. FIG. 10 is a flowchart for determining whether to take an operation in a steady state or an operation to obtain a starting voltage.
First, in step S1, it is determined whether or not the boost rectification operation is possible. Specifically, it is determined whether or not a voltage equal to or higher than the minimum starting voltage of the switch control device 110 is output.
If a voltage lower than the minimum starting voltage is output (step S1: N), the process proceeds to step S5.
In step S5, the boost rectification operation status is set to NG (no boost rectification operation possible).
Next, as step S6, voltage doubler rectification is executed.
Next, in step S4, it is determined whether the boost rectification operation is possible.
If a voltage equal to or higher than the minimum starting voltage is output (step S4: Y), the process returns to step S2.
If a voltage lower than the minimum starting voltage is output (step S4: N), the process returns to step S5.
When a voltage lower than the minimum starting voltage is output at START, the sequence described above is taken.
When a voltage equal to or higher than the minimum starting voltage is output at START, the sequence described below is taken.
In step S1, when a voltage equal to or higher than the minimum starting voltage is output (step S1: Y), the process proceeds to step S2.
In step S2, the step-up rectification operation status is OK (step-up rectification operation is possible).
Next, as step S3, a boost rectification operation is performed.
Next, in step S4, it is determined whether the boost rectification operation is possible.
If a voltage equal to or higher than the minimum starting voltage is output (step S4: Y), the process returns to step S2.
If a voltage lower than the minimum starting voltage is output (step S4: N), the process returns to step S5.
In this case, the operation sequence operates with an infinite loop. In this state, the operation cannot be stopped. Therefore, when a Break signal is received after waiting for a Break signal from the outside in Step S4 (Step S4: With Break signal), it is also preferable to have a function of stopping power generation. For example, when power generation is semipermanently, the Break signal input process can be omitted.
Note that by changing the boost rectification operation status, it is possible to perform control such as waiting for start-up until the status becomes OK, for example, for a load (not shown) connected to the power generation devices 100 and 101.
The above power generation circuit has the following effects.

  As shown in FIG. 2, by using the resonance phenomenon in the resonance circuit including the inductor L and the capacitance component C0 of the piezoelectric unit 108, the voltage that can be generated by the piezoelectric unit 108 alone as described above is larger. A voltage can be obtained. Therefore, since electric power can be taken out more efficiently from the piezoelectric portion 108, a small and efficient power generation device can be obtained.

  As shown in (Operation in Steady State), unless the electric charge flows out from the piezoelectric part 108, the electric charge in the piezoelectric part 108 increases every time the piezoelectric part 108 is deformed. For this reason, the voltage between the terminals of the piezoelectric portion 108 increases. For this reason, the voltage between the terminals of the piezoelectric unit 108 can be sequentially increased without considering the loss or the like when the charge flows through the inductor L or the first switch SW1. Therefore, it is possible to generate power by naturally boosting the voltage necessary for driving the electric load without providing a special booster circuit.

  Once the lower limit voltage required for the step-up rectification operation falls below, the first switch SW1 cannot be actively controlled and the above-described power generation operation cannot be performed. In this case, the switch control device An operation of switching 110 from the bridge rectifier 120 to the voltage doubler rectifier 120a is performed. Therefore, a voltage close to twice the voltage at the piezoelectric unit 108 is applied to the switch control device 110. When the switch control device 110 reaches a voltage capable of step-up rectification operation by performing voltage doubler rectification, the switch control device 110 is switched to the bridge rectification unit 120 side, and the switch control device 110 is operated by the rectification mechanism described above. Thus, it is possible to provide a power generator capable of self-return and having high power generation efficiency.

  Since the bridge rectification unit 120 can be switched to the voltage doubler rectification unit 120a simply by closing the second switch SW2, a power generation device having high power generation efficiency while suppressing an increase in the number of parts and capable of self-recovery is provided. It becomes possible. In addition, when the voltage equal to or higher than the lower limit voltage is maintained, the bridge rectification unit 120 is obtained simply by opening the second switch SW2, so that power generation can be performed without reducing the power generation efficiency.

  By using a Schottky barrier diode having a lower forward voltage drop than the junction diode as the diodes D1 to D4, a higher voltage can be supplied. The forward voltage drop of the junction type diode is about 0.6V, but the forward voltage drop of the Schottky barrier diode is about 0.3V. Therefore, when full-wave rectification is performed, a voltage drop at the diode can be suppressed.

  As a capacitor for voltage doubler rectification, one capacitor can be omitted by performing half-wave voltage doubler rectification using a capacitor C0 equivalently provided in the piezoelectric unit 108. In addition, since one capacitor C is used instead of the power storage elements Ca and Cb connected in series, the effective capacity is doubled, so that a more stable DC current can be output.

  When a normally-off switch is used as the first switch SW1 and a normally-on switch is used as the second switch SW2, the bridge rectifier 120 is a diode when the voltage from both ends of the power storage elements Ca and Cb is interrupted. Since it operates as the voltage doubler rectification unit 120a by D1 and D2, it is possible to provide a power generation device capable of self-recovery and having high power generation efficiency.

(Secondary battery)
Hereinafter, an example in which a secondary battery is formed will be described. FIG. 11 is a circuit diagram of the secondary battery. The secondary battery 200 includes a power generation device 101 and a voltage stabilization circuit 130. Since the power generation device 101 has been described above, repeated description is avoided.
The voltage stabilization circuit 130 receives power from the power generation apparatus 101 and supplies power to a load (not shown). Here, although the example using the power generation device 101 has been described, the power generation device 100 may be used.

The secondary battery 200 described above has the following effects.
Even if the voltage between the terminals of the storage element C falls below the lower limit voltage described above, voltage rectification is performed as described above once vibration is applied. When the voltage reaches the lower limit voltage or higher, the voltage is switched to the boost rectification operation, and the voltage stabilization circuit 130 receives the voltage adjustment and can efficiently provide a stabilized voltage to a load (not shown). Become.

(Electronics)
Hereinafter, examples of electronic devices will be described. FIG. 12 is a schematic diagram showing a schematic structure of a pedometer (registered trademark) as an electronic device. The pedometer (registered trademark) 1 includes a reset button 10, a display unit 11, and a secondary battery 200. When the pedometer (registered trademark) 1 is stationary for a long period of time, the voltage between the terminals of the storage element C (see FIG. 11) provided in the secondary battery 200 is in a state below the lower limit voltage described above. .
Here, when vibration is applied to the pedometer (registered trademark) 1 once, the secondary battery 200 performs voltage doubler rectification as described above, and immediately accumulates a voltage equal to or higher than the lower limit voltage. Then, the step-up rectification operation is performed, and the pedometer (registered trademark) 1 operates.
In this example, the pedometer (registered trademark) 1 is taken as an example of the electronic device, but this is not limited to the pedometer (registered trademark). For example, a wristwatch, a wearable device, or mechanical vibration is used. It is also possible to apply to electronic devices that operate in response to this. In particular, the step-up rectifying operation is a highly efficient rectifying method, and thus can be suitably used for an electronic device that consumes a large amount of power and is compatible with a purpose of operating wirelessly.

The electronic device described above has the following effects.
Since the secondary battery 200 performs step-up rectification operation with high power generation efficiency, the secondary battery 200 can efficiently provide power even with a small vibration. Therefore, for example, as a function of the pedometer (registered trademark) 1, a calculation function that requires power, such as calorie calculation, can be added.

  Note that the present invention is not limited to the above-described embodiment, and various modifications and improvements can be added to the above-described embodiment. A modification is shown below. In the description of the modification, the same components as those in the above-described embodiment are denoted by the same reference numerals, and the description thereof is omitted.

[Modification 1]
Description will be made with reference to FIG. 3 and FIG. FIG. 6 is a circuit diagram for explaining the first modification.
When the voltage doubler rectifier 120a operates, the diode D3 and the diode D4 do not contribute to rectification. A Schottky barrier diode has a feature that a forward voltage drop is lower than that of a junction diode, but has a disadvantage that a reverse leakage current is large. In this case, by using at least one of the diode D3 and the diode D4 as a junction diode, it is possible to quickly reach a voltage at which the switch control device 110 can operate by suppressing leakage. FIG. 6 shows a circuit diagram in the case where both the diode D3 and the diode D4 are replaced with junction diodes.

[Modification 2]
Description will be made with reference to FIG. 3 and FIG. FIG. 7 is a circuit diagram for explaining the second modification.
When the voltage doubler rectifier 120a operates, the diode D3 and the diode D4 do not contribute to rectification. That is, ideally, it is better not to perform voltage doubler rectification. Therefore, by using a normally-off MOS switch for at least one of the diode D3 and the diode D4, leakage can be suppressed and a voltage at which the switch control device 110 can operate quickly can be reached. It should be noted that once the switch control device 110 is operated, the full-wave rectification can be performed while suppressing the forward voltage loss by synchronously rectifying the MOS switch. FIG. 7 shows a circuit diagram when the diode D3 and the diode D4 are replaced with the switch SW3 and the switch SW4.

[Modification 3]
Description will be made with reference to FIG. 4 and FIG. FIG. 8 is a circuit diagram for explaining the third modification.
When operating with the voltage doubler rectifier 120a described above, the diode D3 and the diode D4 do not contribute to rectification (however, the diode D4 is in a state where the anode and the cathode are short-circuited, so there is no actual harm). A Schottky barrier diode has a feature that a forward voltage drop is lower than that of a junction diode, but has a disadvantage that a reverse leakage current is large. In this case, by setting the diode D3 as a junction diode, it is possible to quickly reach a voltage at which the switch control device 110 can operate by suppressing leakage. FIG. 8 shows a circuit diagram when the diode D3 is replaced with a junction diode.

[Modification 4]
Description will be made with reference to FIG. 4 and FIG. 9. FIG. 9 is a circuit diagram for explaining the fourth modification.
When the voltage doubler rectifier 120a operates, the diode D3 and the diode D4 do not contribute to rectification. (However, since the diode D4 is in a state where the anode and the cathode are short-circuited, there is no actual harm). That is, ideally, it is better not to perform voltage doubler rectification. Therefore, by using a normally-off MOS switch or the like instead of the diode D3, leakage can be suppressed and a voltage at which the switch control device 110 can operate quickly can be reached. It should be noted that once the switch control device 110 is operated, the full-wave rectification can be performed while suppressing the forward voltage loss by synchronously rectifying the MOS switch. FIG. 9 shows a circuit diagram when the diode D3 is replaced with the switch SW5.

  C ... electric storage element, Ca ... electric storage element, Cb ... electric storage element, D1 ... diode, D2 ... diode, D3 ... diode, D4 ... diode, L ... inductor, SW1 ... first switch, SW2 ... second switch, SW3 ... switch , SW4, switch, SW5, switch, 1 ... pedometer (registered trademark), 10 ... reset button, 11 ... display unit, 100 ... power generation device, 101 ... power generation device, 102 ... support end, 104 ... beam, 106 ... Weight: 108 ... piezoelectric part 109a ... first electrode 109b ... second electrode 110 ... switch control device 120 ... bridge rectification part 120a ... double voltage rectification part 125 ... power generation part 130 ... voltage stabilization circuit, 140 ... DC converter, 140a ... Double voltage DC converter, 200 ... Secondary battery.

Claims (6)

A piezoelectric part including a piezoelectric material that generates electric charges by repeatedly deforming by switching the deformation direction according to an external force;
A support that supports the piezoelectric part in a state where the piezoelectric part is deformable;
A pair of electrodes used for taking out the electric charge generated by the deformation of the piezoelectric part as a current;
A first switch connected to one side of the pair of electrodes;
An inductor that is connected to the pair of electrodes via the first switch and forms a resonance circuit with a capacitance component of the piezoelectric unit;
When the time corresponding to a half cycle of the resonance cycle of the resonance circuit has elapsed after the first switch is short-circuited when the deformation direction of the piezoelectric portion is switched, and a lower limit for controlling the first switch A first switch control device that opens the first switch when a voltage lower than the voltage is supplied;
A bridge rectifier that rectifies the alternating current output from the pair of electrodes into a pulsating current and converts it into a first direct current voltage;
A voltage doubler rectifier that rectifies the alternating current output from the pair of electrodes into a pulsating current and converts the current into a second direct current voltage higher than the voltage between the pair of electrodes;
A power storage unit that stores the pulsating current supplied from the bridge rectification unit or the voltage doubler rectification unit;
A second switch for selecting one of the bridge rectifier and the voltage doubler rectifier;
A second switch control device that selects the voltage doubler rectifier using the second switch when the first DC voltage is lower than the lower limit voltage;
The first switch control device and the second switch control device are driven using either the first DC voltage or the second DC voltage. The power generation device according to claim 1,
The power storage unit includes a first power storage element and a second power storage element connected in series between an anode pair side and a cathode pair side of the bridge rectification unit,
The second switch is provided between the first power storage element and the second power storage element and between one side of the pair of electrodes,
The second switch control device opens the second switch when selecting the bridge rectification unit, and shorts the second switch when selecting the voltage doubler rectification unit. The power generation device according to claim 1,
The power storage unit includes a power storage element connected between the anode pair side and the cathode pair side of the bridge rectification unit,
The second switch is provided between the anode pair side of the bridge rectification unit and one of the pair of electrodes,
The second switch control device opens the second switch when selecting the bridge rectification unit, and shorts the second switch when selecting the voltage doubler rectification unit, and converts the capacitance component to the voltage doubler. A power generation device that is used as a capacity when driving a rectifying unit.   The power generator according to any one of claims 1 to 3, wherein the first switch is a normally-off switch that takes an open state when no driving voltage is applied, and the second switch is A power generator that is a normally-on switch that takes a short-circuited state when a drive voltage is not applied.   A secondary battery comprising the power generator according to any one of claims 1 to 4.   An electronic apparatus comprising the secondary battery according to claim 5.

Images