JP2010186338A - Charging/discharging device and integrated circuit element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To efficiently charge a pre-charge capacitor regardless of light quantity to be input to a solar battery. <P>SOLUTION: A charging/discharging device 1000 is configured to charge a pre-charge capacitor 50 with a power generated by a solar battery 10 having the maximum output point where the product of a generated voltage and output currents is made maximum, and to discharge the charged power, and provided with: a first switch element 30 for switching a measurement period in which the open-circuit voltage of the solar battery is measured and an electricity accumulation period in which the generated power is accumulated in the pre-charge capacitor; and a charge block 200 for controlling the discharging of the pre-charge capacitor so that the charged voltage of the pre-charge capacitor is turned to be the voltage of the maximum output point. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a charge / discharge device that charges a power storage unit with generated power generated by a power generation element and discharges the charged power, and an integrated circuit element.

Various power supply circuits have been developed that store the generated power generated by power generation elements such as solar cells and use the stored power.
For example, Patent Document 1 discloses a solar battery rechargeable lighting device in which a capacitor and a secondary battery are connected in series to charge generated power to a storage battery and discharge the charged power. This technology uses the rapid charge / discharge characteristics of a capacitor to make it possible to use a high voltage and a wide range of voltage. Further, Patent Document 1 discloses a method of charging a capacitor or a secondary battery with a solar battery.

In the ubiquitous society, there is a need for a smaller power source that can store electricity quickly and supply power with a desired output specification even in a weak energy environment such as low illuminance with a small solar panel.

JP-A-11-232914

By the way, since the solar cell has an equivalent internal resistance, a voltage current that can obtain the maximum output power when the power is extracted at a current value that is about 0.7 times the open circuit voltage. It has characteristics.
However, although the technique disclosed in Patent Document 1 can be used in an environment where a large amount of solar panel is used to store energy as abundant energy for a long time, consideration is given to effective charging even in weak solar energy. Not.
That is, when the light intensity is large to some extent, the open circuit voltage of the solar cell maintains a predetermined value. However, in the case of faint light, the open circuit voltage has light quantity (energy) dependence and the voltage at the maximum output power point is not fixed. There are no problems.

  The present invention has been made to solve the above-described problems, and provides a charge / discharge device and an integrated circuit element that can efficiently charge the power storage unit regardless of the energy input to the power generation element. Objective.

In order to achieve the above-mentioned object, the present invention provides the power storage unit (precharge capacitor 50) with the power generated by the power generation element (solar cell 10) having the maximum output point at which the product of the generated voltage and the output current is maximum. A charge / discharge device (1000) for charging and discharging the charged charging power, wherein the switch switches between a measurement period for measuring an open circuit voltage of the power generation element and a power storage period for storing the generated power in the power storage unit An element (first switch element 30), and a discharge control means (charge block 200) for controlling discharge of the power storage unit so that a charge voltage of the power storage unit becomes a voltage at the maximum output point. And In addition, the character code in a parenthesis is an illustration.

A power generation element (for example, a solar cell) having an internal resistance in series has a maximum output power point at a voltage about 0.7 times the open circuit voltage (usually about 3 V). In order to charge the power storage unit at the maximum output power point, a switching element that switches between a measurement period in which the open-circuit voltage is measured with no load on the solar cell and a charging period in which the generated power is charged to the precharge capacitor that is the power storage unit. Provided. Further, even if the number of cell stages of the solar battery is undecided or the light is weak and the open circuit voltage is uncertain, the MPP voltage can be easily determined by measuring the open circuit voltage of the power generating element.
Further, by periodically switching between the measurement period and the charging period, the MPP voltage can be determined even when the light is weak and the open circuit voltage is low. That is, various energy sources ranging from weak power to high power can be charged to the power storage unit by MPP control.

  According to the present invention, it is possible to efficiently charge the power storage unit with the generated power generated by the power generation element.

It is a block diagram of the charging / discharging apparatus which is 1st Embodiment of this invention, Comprising: It is the figure which showed the relationship between a boot block and a charge block especially. It is a block diagram of the charging / discharging apparatus which is 1st Embodiment of this invention, Comprising: It is the figure which showed the relationship between a charge block and a work block especially. It is an equivalent circuit diagram of a solar cell. It is a block diagram at the time of start-up which charges a precharge capacitor. It is a block diagram at the time of charge up to the main capacitor. It is a figure which shows the IV characteristic of a solar cell, the time characteristic of a precharge capacitor voltage, and the time characteristic of a main capacitor voltage. It is a block diagram at the time of a work (at the time of discharge).

(First embodiment)
The charging / discharging device of 1st Embodiment of this invention is demonstrated using FIG.1 and FIG.2.
The charging / discharging device 1000 includes three functional blocks: a boot block 100, a charge block 200 that functions as a discharge control unit, and a work block 300. FIG. 1 shows the relationship between the boot block 100 and the charge block 200. FIG. 2 shows the relationship between the charge block 200 and the work block 300. The boot block 100, the charge block 200, and the work block 300 constitute an integrated circuit element. This integrated circuit element can use an SOI (Silicon On Insulate) substrate, a sapphire substrate (SOS: Silicon on Sapphire substrate) or the like when the charging circuit has a high voltage. In the figure, a broken line arrow indicates a control signal, and a solid line arrow indicates a flow of power.

Further, the charging / discharging device 1000 charges the power storage unit (precharge capacitor) 50 with the power generation energy of the solar cell (solar cell) 10 in which the boot block 100 is a power generation element, and the charge block 200 boosts the charging voltage. The main capacitor (main power storage unit) 400 connected to the outside is charged, and the work block 300 boosts the charged voltage to external load via the work capacitor (output power storage unit) 150 and the regulator 160 (FIG. 2). It is configured to supply DC power to Z0. At this time, the boot block 100 measures the open circuit voltage Voc of the solar cell 10 (FIG. 6A), and discharge power discharged from the precharge capacitor 50 to the main capacitor 400 according to the open circuit voltage Voc of the solar cell 10. It is set near the maximum output power point.

FIG. 3 shows an equivalent circuit of the solar cell 10 that is a power generation element. The solar cell 10 is expressed by a parallel circuit of a low current source _Iph , a diode D and a resistor R _sh and a series circuit of the resistor R _s, and a voltage V is generated when the current I flows.
In the solar cell 10, the current value of the low current source IPh increases / decreases depending on the amount of light (incident energy), the open circuit voltage Voc becomes the forward voltage of the diode D, and when there is a sufficient amount of light, the ON voltage of the diode D is a predetermined open circuit. The voltage is Voc. However, when the solar cell 10 has a very small amount of light, the obtained current value decreases, and the open circuit voltage Voc also depends on the amount of light. Further, the solar cell 10 has a maximum output power point (MPP) corresponding to a current voltage value determined by a series resistance and a parallel resistance represented by an equivalent circuit.

In FIG. 1, a boot block 100 includes a sample hold period generator 40 that periodically samples and holds the generated voltage of the solar cell 10 that is a power generation element, and a voltage monitor that monitors the hold voltage sampled and held by the sample hold period generator 40. 60, an MPP voltage generator 65 that multiplies the monitor voltage by a predetermined value of 1 or less to generate MPP voltage data, a boot capacitor 20 to which the generated power of the solar cell 10 is supplied via the first switch element 30, Drive for driving the second switch element 35 with the signal level of the pre-charge capacitor 50 and the sample and hold period generator 40 to which the generated power of the solar cell 10 is supplied via the second switch element (other switch element) 35 A level shifter 45 for level shifting to a level, a reference voltage generator 80, a determiner 70, It comprises a shutdown circuit 90 and the like. With these configurations, the boot block 100 periodically switches between a measurement period in which the first switch element 30 measures the open circuit voltage of the solar cell 10 and a charging period in which the generated power is charged in the precharge capacitor 50. It has become.

The charge block 200 includes a charge pump 130 that is a booster that boosts the voltage of the main capacitor 400, a comparator 110 that compares the charge voltage of the precharge capacitor 50 and the voltage of the MPP voltage generator 65, and a reference voltage Vref. A comparator 114 that compares the voltage of the main capacitor 400, a determiner 72 that determines whether the charge pump 130 needs to be driven using the comparison result of the comparator 114 and the comparison result of the comparator 110, and a determiner 72 The clock generator 120 that generates the clock signal of the charge pump 130 using the determination result of the above, and the second switch element 35 and the main capacitor 400 are directly connected without passing through the precharge capacitor 50 and the charge pump 130. The final stage switching element 38, the reference voltage and the voltage of the main capacitor 400 Comparing, and a comparator 112 which controls the final stage switch element 38. Here, when an electric double layer capacitor is used for the main capacitor 400, the charge pump 130 is used to boost the voltage to around 2.5 V of the maximum applied voltage even when the power generation voltage of the solar cell 10 is low with a small amount of light. Can do.

In FIG. 2, a work block (output unit) 300 includes a charge pump 135 that boosts the voltage of the main capacitor 400, a work capacitor (output power storage unit) 150 that is charged with the boosted voltage of the charge pump 135, and a work capacitor 150. A regulator 160 that adjusts the voltage to the external load Z0 with low dropout (LDO), a clock generator (other clock generator) 125 that drives the charge pump 135, a boost voltage of the charge pump 135, and a reference voltage (load) Voltage), a shutdown circuit 95 that compares the boosted voltage of the charge pump 135 with a reference voltage to instruct shutdown, a comparison result of the comparator 116, and an output of the shutdown circuit 95. Determination to determine whether the charge pump 135 needs to be driven And a 74.

(Description of operation)
In the block diagrams shown in FIGS. 1 and 2, the operation will be described separately for each of the following operation patterns.
(1) The operation of the start-up circuit as a preparation stage for voltage conditioning as a ubiquitous power supply.
(2) MPP (Maximum Power Point) control operation for charging sunlight with high efficiency, and charging the voltage to the main capacitor (main power storage unit) 400 in a form close to a constant value according to the input voltage. Operation for.
(3) An operation related to a method capable of adjusting the output voltage and performing high-efficiency discharge using the main capacitor 400 and the work capacitor 150 in combination.
(4) Operation related to shutdown.

(1) Operation of Start-up Circuit as Ubiquitous Power Supply The ubiquitous power supply is only supplied with unstable energy sources such as sunlight that is unevenly distributed around it. Therefore, in order to control charging / discharging using only the power from the energy source, it is necessary to prepare for various startups from unstable input energy.

FIG. 4 is a block diagram at start-up when the input energy source is sunlight. The operation will be described with reference to the block diagram of FIG.
The output energy from the solar cell 10 is stored up to a predetermined voltage in the boot capacitor 20 and the precharge capacitor 50 and needs to be discharged. The purpose of the boot capacitor 20 is to generate a reference voltage to be referenced in the circuits of the charge block 200 and the work block 300.

In addition, the precharge capacitor 50 (which will be described in detail later) plays a role of a charge reservoir for charging with high efficiency when the main capacitor (main power storage unit) 400 is charged up.
The boot capacitor 20 is charged from the solar cell 10 via the first switch element 30 and the diode D2. The first switch element 30 is attached to alternately perform the open-circuit voltage measurement of the solar cell 10 for storing electricity in an optimum state (MPP: Maximum Power Point) and the charging to the boot capacitor 20 side. . That is, the first switch element 30 is switched to the voltage monitor 60 side (a side) to measure the open circuit voltage of the solar cell 10, and the charging period to switch to the boot capacitor 20 side (b side) and charge. Is switched. Note that the duty ratio (ratio of the power supply time to the MPP sampling side with respect to the power supply time to the boot side) may be a small value of several percent or less.

Further, according to the charging voltage to the boot capacitor 20, the reference voltage generator 80 generates a reference voltage using a band gap circuit or the like. For example, the reference voltage generator 80 generates a constant voltage of 1.3V. The generated voltage is sent to various places that require a reference voltage, and the reference voltage is used as various control voltages in this circuit.

On the other hand, charging from the solar cell 10 to the precharge capacitor 50 is performed via the second switch element 35. In order to control so that the precharge capacitor 50 does not start to be charged until the boot capacitor 20 reaches the reference voltage (firstly, the boot capacitor 20 is charged enough to stabilize the start-up operation). The level shifter 45 detects that the band gap voltage does not change with time, and when the change disappears (reaches the band gap voltage), the second switch element 35 is turned on to start charging the boot capacitor 20. That is, the second switch element 35 is turned on after a while in a state where the boot capacitor 20 is charged to a predetermined voltage value.

The sample and hold period generator 40 incorporates an RC oscillation circuit, a ring oscillator, and the like, and controls the switching timing of the first switch element 30. Thereby, the switching between the measurement period and the charging period by the first switch element 30 is periodically performed, and it is possible to cope with the fluctuation of the open-circuit voltage that sequentially varies due to the fluctuation of the light amount, and the measured open-circuit voltage is used. Thus, the MPP voltage is set appropriately.
The first switch element 30 is indispensable for a high-efficiency ubiquitous power supply. For example, unless switching is performed by the first switch element 30, power supply is always required for MPP control. It is consumed without being stored.

The first switch element 30 and the second switch element 35 control the input voltage from the solar cell 10. Generally, when the control is performed by a MOS switch or the like, a voltage larger than the voltage value is used. Switch (gate) control is required. Therefore, the level shifter 45 generates a voltage higher than the output voltage of the sample and hold period generator 40, and drives the MOS switch.
The power generated by the solar cell 10 is supplied to the sample-and-hold period generator 40, the level shifter 45, or various gates associated therewith via the diode D1.

As described above, the circuits necessary for establishing the ubiquitous power supply are for the boot capacitor 20, the reference voltage generator 80, and the optimal solar control (matching control between the conversion element and the charging circuit for harvesting the ambient energy). The first switch element 30, the sample hold period generator 40 for controlling the first switch element 30, and the level shifter 45 are basic components. In addition, the second switch element 35 is added to precharge the boot capacitor after it is sufficiently charged. In the circuit of FIG. 4, the solar cell 10 is provided with a reverse current prevention diode D1 and an overvoltage protection diode Dz in the subsequent stage, and a sample hold period generator 40, a level shifter 45, The power is supplied to the power supply terminal Vdd of the first switch element 30 and the second switch element 35. The comparator 110 is fed from the precharge capacitor 50 to the power supply terminal Vdd.

(2) Operation at the time of charging MPP control and main capacitor Next, description of the operation of MPP control for storing solar energy with high efficiency and charging the main capacitor 400 at a substantially constant voltage according to the input voltage. The operation for this will be described.
FIG. 5 is a block diagram at the time of charge-up. The voltage monitor 60 monitors the open circuit voltage Voc of the solar cell 10 via the first switch element 30, and the MPP voltage generator 65 divides the open circuit voltage Voc to generate the MPP voltage. The MPP voltage is normally set to a voltage equivalent to 0.7 to 0.78 times the open circuit voltage Voc of the solar cell 10, for example, 0.76 times the open circuit voltage using resistance voltage division or diode on-resistance. Is set. The comparator 110 is a hysteresis comparator, and compares the MPP voltage with the charge voltage (precharge voltage) charged in the precharge capacitor 50. That is, the comparator 110 turns on the hysteresis comparator output when the precharge voltage slightly exceeds the MPP voltage, and turns off the hysteresis comparator output when it falls slightly below. The output of the comparator 110 becomes an assert signal of the charge pump 130 via the determiner 72 which is an AND gate.

First, the description will be made ignoring other inputs of the determination unit 72 connected to the outputs of the comparators 115 and 116. As an operation in this case, since the charge pump 130 is turned on near the MPP voltage, the solar cell 10 is always connected in a state where the maximum power can be supplied. On the other hand, the charge pump 130 is in a low impedance state because the main capacitor 400 is not sufficiently charged when the MPP voltage is exceeded and the first switch element 30 is turned on.
For this reason, the main capacitor 400 is charged by a rapid current flow from the precharge capacitor 50. As a result, the precharge capacitor 50 is discharged and a voltage drop occurs. Therefore, when the voltage value of the precharge capacitor 50 decreases by about 5% to 10% from the MPP voltage, the charge pump 130 is stopped and the first switch element 30 is turned off. Thereafter, the precharge capacitor 50 is charged again and the same is repeated, and the main capacitor 400 is charged and the voltage is increased.

In the above description, the comparator 110 compares the hysteresis between the MPP voltage and a voltage value that is about 5% to 10% lower than the MPP voltage (hysteresis voltage ΔV (FIG. 6B)). However, the MPP voltage may be compared with a voltage value that is higher than the MPP voltage by a predetermined voltage, or may be compared between a voltage that is higher than the MPP voltage by a predetermined voltage and a voltage that is lower than the predetermined voltage. May be. That is, the voltage of the precharge capacitor 50 may be controlled near the MPP voltage.

FIG. 6A illustrates the IV characteristics (current-voltage characteristics) of the solar cell 10. FIG. 6B shows a temporal change in charging / discharging in the precharge capacitor, and FIG. 6C shows a temporal change in charging in the main capacitor.
In FIG. 6A, the horizontal axis indicates the current I, and the vertical axis indicates the voltage V. When the solar cell 10 is irradiated with predetermined sunlight and light energy is input, the open voltage Voc is generated when the current I = 0, and the short-circuit current when the voltage V = 0. Isc flows. Note that the value of the short-circuit current Isc increases or decreases according to the amount of light.
When the current is gradually increased from I = 0, the solar cell 10 tends to gradually decrease from the open circuit voltage Voc due to internal resistance. The point where the product of the voltage V and the current I is maximum is MPP (Maximum Power Point), and the voltage at this point is the MPP voltage.
Comparator 110 (FIGS. 1 and 4) sets the hysteresis width to ΔV and controls so that the voltage of precharge capacitor 50 falls between MPP voltage and (MPP voltage−ΔV).
That is, as shown in FIG. 6B, when the voltage of the precharge capacitor 50 is smaller than the MPP voltage, the charge pump 130 is stopped and the generated power of the solar cell 10 flows, so the voltage of the precharge capacitor 50 Increases linearly, and the voltage of the precharge capacitor 50 becomes larger than the MPP voltage, the charge pump 130 is driven, and the voltage of the precharge capacitor 50 decreases.

At this time, as shown in FIG. 6 (c), the voltage of the main capacitor 400 is raised at the time of driving the pump 130 by a predetermined voltage [Delta] V _N, with a change in time, increase of the voltage are repeated until the rated voltage V _R To rise.

Next, the AND gate of the determiner 72 will be described.
When a voltage higher than the maximum applied voltage is applied together with the MPP control by the comparator 110, there is a risk that the main capacitor 400 is destroyed.
Further, in order to effectively use a small amount of power, the main capacitor 400 capable of obtaining a stable voltage supplies the power supply voltage to the charge pump 130, the clock generator 120, and the like. The main capacitor 400 is shown in FIG. Since the voltage is gradually increased from a low voltage, the operation of the charge pump 130 and the like becomes unstable. In order to avoid this, it is necessary to set a voltage at which the charge pump 130 is started, and to control the charge pump 130 when the set voltage is exceeded.

For this reason, the charging / discharging device 1000 is provided with a determination unit 72 and stops charging at the maximum applied voltage (for example, usually 2.5 V for an electric double layer capacitor) together with MPP control using the comparator 110 which is a hysteresis comparator. The operation and the control for starting the charge pump 130 are executed simultaneously.
That is, the determination result of the comparator 110 when the voltage of the precharge capacitor 50 falls below the MPP voltage, the determination result of the comparator 115 when the voltage of the main capacitor 400 reaches the maximum applied voltage, When the voltage does not reach a voltage sufficient to drive the charge pump 130, the output of the comparator 116 is ANDed so that the charge-up can be stopped and the charge can be stopped. The on / off state of the pump 130 is determined. The comparator 116 and the voltage divider 65a constitute a shutdown circuit 90.

The voltage dividers 65a and 65b are provided for setting the start-up voltage of the main capacitor 400 and the maximum applied voltage of the main capacitor 400, and can be easily set by dividing the reference voltage by the voltage dividing ratio of the resistor. is there. When the reference voltage is low, the monitor voltage of the main capacitor 400 may be divided and compared. As for the clock generator 120 for operating the charge pump 130, similarly to the charge pump 130, MPP control, maximum applied voltage control, and start-up voltage control are performed.

Further, when the charge pump 130 cannot be activated sufficiently, that is, when the main capacitor 400 is not sufficiently charged, a path for charging at a low voltage without charging up is provided from the precharge capacitor 50. The battery can be charged from a low voltage state.
The last-stage switch element 38 and the comparator 112 are provided for this purpose, and compare the voltage of the main capacitor 400 with a reference voltage (adjusted to a voltage value at which the charge pump 130 can be started). When the operation of the charge pump 130 becomes possible, the final stage switch element 38 is turned off, and charging is performed through the route of the charge pump 130. If the final-stage switch element 38 is not provided and the solar cell 10 is in a short circuit state, the solar cell 10 gradually charges up the main capacitor 400 at a low voltage. However, in this state, the charge pump 130 is not in operation, so boost charge cannot be performed.

Next, a method for setting the charge voltage magnification of the charge pump 130 will be described. The generated voltage of the solar cell 10 is about 3V in a single-stage solar cell element, and an electric double layer capacitor having a maximum applied voltage of about 2.5V is used for the main capacitor 400 after the voltage drop of the diode D1 (FIG. 4). Although it is appropriate, since the power generation voltage is reduced in minute sunlight, in order to store the main capacitor 400 at a predetermined voltage, the charge-up magnification must be changed. In addition, since the generated voltage is variable depending on the number of stages of the solar cells 10 (for example, about 2V to several tens of volts), it is appropriate to make the charge-up magnification variable.

Therefore, the comparator 118 compares the voltage value of the solar cell 10 with a desired voltage value charged in the main capacitor 400, and switches the charge magnification in the charge pump 130 according to the magnitude of the voltage value. The charge pump 130 is provided with a switch element and a capacitor corresponding to the charge magnification. The switching magnification can be easily switched by setting the resistance voltage of the reference voltage using the voltage divider 65c when setting a desired charge voltage.

Further, there arises a problem that an accurate reference voltage cannot be obtained when the voltage of the boot capacitor 20 is lower than the voltage of the main capacitor 400. For this reason, when the main capacitor 400 is connected to the boot capacitor 20 via the diode D4 (FIG. 5) and the voltage of the boot capacitor 20 decreases, the main capacitor 400 can be charged.

(3) Operation related to a method capable of adjusting the output voltage and performing high-efficiency discharge using the main capacitor 400 and the work capacitor 150 (FIG. 7) in combination (discharge operation)
FIG. 7 is a block diagram at the time of work (discharge). The work block 300 is configured such that the charge stored in the main capacitor 400 is stored in the work capacitor 150 along two paths.
One path is boosted to a voltage corresponding to the output voltage by the charge pump 135 and charged to the work capacitor 150, and the other path is connected to the work capacitor 150 from the main capacitor 400 via the diode D5 for preventing backflow. 150 is a route charged to 150. The path through the diode D5 is a path that is charged at a low voltage until the work capacitor 150 is sufficiently charged (until the voltage at which the charge pump 135 can operate), and the other is that the charge pump 135 can operate. This is a path in which the work capacitor 150 is charged up (down) and charged to the work capacitor 150.

The charge pump 135 is asserted when the voltage of the work capacitor 150 reaches the operating voltage of the charge pump 135, and is deasserted when the voltage of the work capacitor 150 reaches near the voltage of the device (external load) that the user wants to use.
The two comparators 116 and 117 are composed of hysteresis comparators, which compare the reference voltage with the divided voltage obtained by dividing the voltage of the work capacitor 150 by the voltage divider 65d and the voltage divider 65e, respectively. And take the output result. As a result, if the voltage of the work capacitor 150 is higher than the starting voltage of the charge pump 130 and lower than the output voltage of the external load, the clock generator 125 and the charge pump 130 are asserted, and the work capacitor 150 receives the work from the main capacitor 400 via the charge pump 130. The capacitor 150 is charged.

The charge pump 135 temporarily stops when the work capacitor 150 reaches a prescribed maximum voltage (use voltage of the load). However, the voltage is lowered by the amount of power consumed by the external load, and the charge pump 135 starts again. As a result, the work capacitor 150 reciprocates between the hysteresis voltages of the comparator 116 including the hysteresis comparator, and a desired output voltage is supplied from the work capacitor 150.

Further, in order to obtain a stable output, a regulator 160 such as a low dropout power supply (LDO) is connected to the subsequent stage of the work capacitor 150 to give a desired voltage to the external load Z0.
Here, the comparator (hysteresis comparator) 117 that determines the start-up voltage of the charge pump 130 becomes a noise when the storage capacity fluctuates at a low voltage, so that a peak voltage such as noise prevention or jitter is generated. A hysteresis comparator is used to prevent this from happening (it is possible without hysteresis).

The power supply voltage to the charge pump 135, the determination unit (AND gate) 74, the clock generator 125, the regulator 160, and the comparators (hysteresis comparators) 116 and 117 is supplied from the work capacitor 150 having the highest voltage (desired) May be supplied from the main capacitor 400 when the output voltage is lower than the charging voltage of the main capacitor 400).
By adopting the configuration as described above, when the current flowing through the external load Z0 is large, the charge pump 135 always operates and power is supplied from the main capacitor 400, and when the current flowing through the external load Z0 is small. Since the voltage of the work capacitor 150 continues to stay within the hysteresis voltage of the comparator (hysteresis comparator) 116, power is supplied only from the work capacitor 150 to the external load Z0, and no power is supplied from the charge pump 135.

Therefore, even when power such as charging is consumed to some extent when consuming a large amount of power, the power consumed by the external load Z0 is small when the external load Z0 is on standby, so that no power is consumed by the discharge circuit such as the charge pump 135. In general, the standby time is long. Conventionally, even if the power consumption is weak, voltage regulation is always performed by the regulator 160 from the capacitor (consuming power) to supply power. In this method, no power is consumed in standby for a long time, power can be supplied only from the work capacitor 150, and power is consumed by the charge pump 135 only at high power, so the total power consumption is significantly reduced. There is an effect that can be done.

(4) Operation related to shutdown (1) Start-up operation and (2) Charge-up operation, when the input voltage from the solar cell 10 falls below a certain value (creates a reference voltage by dividing the reference voltage), Shut down. The shutdown is an off operation such as attaching an NMOS switch to the input of each active element, asserting the gate of the NMOS transistor, and dropping the input to the ground level. The shutdown is performed for each active element (charge pump 130, clock generator 125, comparator 110, etc.).

(3) Regarding the discharge operation, when the voltage of the work capacitor 150 is smaller than the voltage for starting the charge pump 135 by comparing the voltage of the work capacitor 150 with a reference voltage, various active elements (charge The pump 135, the clock generator 125, the comparator 114, and the regulator 160) are shut down. At this time, even if the voltage of the main capacitor 400 is lowered, a desired output voltage is not generated. Therefore, the shutdown is performed when the voltage of one or both of the work capacitor 150 and the main capacitor 400 is a predetermined value or less.
By performing these shutdown operations, the charging / discharging device 1000 can individually manage the shutdown in the charge block 200 and the work block 300, and effective charging / discharging as a ubiquitous power source is performed, resulting in wasteful power consumption. Low power consumption operation is possible.

For example, when the solar cell 10 is used, charging cannot be performed when it becomes dark, so the charge block 200 is shut down, but discharging is possible. When not in use or in standby operation, charging for discharging is performed. The pump 135 does not move at all, and energy management such that only charging by the charge pump 130 is performed becomes possible.

As described above, according to this embodiment,
1. The boot block 100 is a first switch that periodically switches between a measurement period in which the solar cell 10 is unloaded and the open circuit voltage Voc is measured, and a charging period in which the generated power is charged in the precharge capacitor 50 that is a power storage unit. An element 30 was provided. Further, the charge block 200 stores power from the precharge capacitor 50 to the main capacitor 400 as a main power storage unit via a charge pump 130 as a booster. Further, the MPP voltage obtained by multiplying the measured open circuit voltage Voc by a predetermined value (for example, 0.76) and the voltage of the precharge capacitor 50 are subjected to hysteresis comparison, and the clock for driving the charge pump 130 is turned on.・ Off is controlled. Thereby, even when the incident light of the solar cell 10 is weak and the open-circuit voltage Voc is unstable, the precharge capacitor near the MPP voltage at which the supply power (supply power) of the solar cell 10 becomes maximum. 50 is charged.

In other words, by power-conditioning various energy sources ranging from weak power to high power (MPP control), it is possible to quickly charge the main power storage unit such as an electric double layer capacitor with high storage efficiency. Is possible.
Further, even if the number of cell stages of the solar battery 10 is undecided and the open circuit voltage is uncertain, the MPP voltage can be easily determined by measuring the open circuit voltage Voc of the solar battery 10.

The charging / discharging method disclosed in Patent Document 1 can be used as a power source for lighting that is used at a certain wide voltage value, but is connected to a device that requires a stable power source voltage such as a communication device or a precision machine. I couldn't. Moreover, in the charge / discharge system disclosed in Patent Document 1, the secondary battery or the capacitor can be charged and discharged, but the power obtained from the solar battery (power generation element) cannot be charged / discharged with high efficiency. There has been a problem that the voltage cannot be flexibly adjusted to a desired voltage.
The charge / discharge device 1000 of the present embodiment solves these problems, is small in size, can absorb environmental energy efficiently, has excellent rapid charge / discharge characteristics, and is highly efficient in charge / discharge conversion. Satisfied that it is possible and that independent power control is possible.

2. The charge pump 130 is composed of a plurality of stages of capacitors, so that the boosting magnification can be varied. The boosting magnification is determined by the comparator 118 (FIG. 5) comparing the voltage of the solar cell 10 with the divided voltage obtained by dividing the reference voltage by resistance. Thereby, it is possible to adjust the voltage to be output from the stored energy source only by performing simple setting such as changing the resistance voltage dividing ratio.

3. The charge / discharge device 1000 can be reduced in size by integrating the boot block 100, the charge block 200, and the work block 300 into one chip. Further, by making the boosting ratio of the charge pump 130 variable and making the number of boosting stages of the work block 300 variable, the degree of freedom is increased, and it is not necessary to individually select elements for input and output.

4). The work block 300 is configured such that the clock is on / off controlled so that the output voltage of the charge pump 135, that is, the voltage of the work capacitor 150 falls within a predetermined hysteresis range. For this reason, when large power is consumed, the charge pump 135 is driven to receive power from the main capacitor 400, and when low power is consumed, the charge pump 135 is turned off and the work capacitor 150 is turned off. It can only be discharged.

This makes it possible to eliminate power consumption by the power conditioner such as the charge pump 135 and the clock generator 125 when the connected device consumes a long time with a small amount of power as in the sleep mode. High-efficiency discharge can be performed in accordance with each state at the time of high power and low power from the end.

5). The boot block 100 shuts down the sample and hold period generator 40, the level shifter 45, the determiners 70 and 72, the comparator 110, the clock generator 120, and the charge pump 130 if the voltage of the solar cell 10 is not a predetermined value or more. If the output voltage of the charge pump 135, that is, the voltage of the work capacitor 150 is not equal to or higher than a predetermined value, the work block 300 shuts down the clock generator 125 and the charge pump 135 via the determination unit 74, and The regulator 160 is configured to shut down.
That is, power conditioning such as wake-up and shutdown can be performed by natural energy alone such as sunlight, so there is no need to prepare an external power source.
In addition, since the regulator 160 is also shut down, there is no extra power consumption after the output voltage value falls below.
Further, since the reference voltage generator 80 and the switch elements 30 and 35 are charged until they sufficiently function and wake up to start charging, the occurrence of malfunctions is reduced.

6). When power is stored in the main capacitor 400, which is the main power storage unit, in particular, when an electric double layer capacitor is used, a voltage limit that is limited within the maximum applied voltage is required. The main capacitor 400 can be charged with a desired boosting magnification by adjusting the piezoelectric resistor.

7). When the value of the input power is small, the power is supplied from the main capacitor 400, so that the power storage circuit operates and can store power even when there is little power around.
Further, when the value of the input power becomes smaller and the value of the input power becomes smaller than the power consumed by the charge pump 130 or the like, the charge pump 130 or the like is shut down.

(Modification)
In the first embodiment, a system for charging and discharging energy obtained from a solar cell has been described. However, a thermoelectric conversion element other than a solar cell, a vibration system (piezo, seismo, electret, etc.), a rectenna for receiving wireless power, and the like are used. It can also be used for all energy harvesting inputs.
Moreover, it is possible to use a secondary battery such as a capacitor, an electric double layer capacitor, a Li ion capacitor, a Li ion battery, a nickel metal hydride battery, a nickel cadmium battery, a lead storage battery, a solid battery, or a film battery as the main power storage unit. . The boot capacitor, precharge capacitor, and work capacitor can use the capacitor system and the secondary battery system that can be charged / discharged quickly for the purpose of detecting a voltage drop.
As the regulator system, the charge pump system using a plurality of switches and capacitors is shown in the first embodiment, but a switching regulator system may be used.
The voltage divider divides voltage by a resistor, and this resistor can be simulated by a switched capacitor method using a switch and a capacitor.
The output stage regulator 160 is exemplified by an LDO power supply, but a general regulator system such as a normal series regulator or a DC / DC converter may be used.
It is also effective to increase or decrease the mobile power by changing the clock frequency generated by the clock generators 120 and 125 that drive the charge pumps 130 and 135.
The boot capacitor 20 is connected in parallel with a third switch element (another switch element) that operates in synchronization with the first switch element 30, and a diode is attached to one end of the boot capacitor 20. The switch element can be turned on after a certain period of time when the precharge capacitor 50 is charged and the boot capacitor 20 is charged to a predetermined voltage value.

10 Solar cell (power generation element)
20 Boot capacitor 30 First switch element 35 Second switch element (other switch elements)
38 Last-stage switch element 40 Sample hold period generator 45 Level shifter 50 Precharge capacitor (power storage unit)
60 Voltage Monitor 65 MPP Voltage Generator 70, 72, 74 Determinator 80 Reference Voltage Generator 90, 95 Shutdown Circuit 100 Boot Block 110, 112, 114, 115, 116, 117, 118 Comparator
120 clock generator 125 clock generator (other clock generator)
130 Charge pump (booster)
135 Charge pump (other booster)
150 Work capacitor (output power storage unit)
160 Regulator 200 Charge block (discharge control means)
300 work block (output unit)
400 Main capacitor (main power storage unit)
1000 Charge / discharge device

Z0 External load Dz Zener diode D1, D2, D3, D4, D5, D6 Diode

Claims (19)

A charging / discharging device that charges a power storage unit with generated power generated by a power generation element having a maximum output point at which a product of generated voltage and output current is maximum, and discharges the charged charging power,
A switching element that switches between a measurement period for measuring an open-circuit voltage of the power generation element and a power storage period for storing the generated power in the power storage unit;
A charge / discharge device comprising: a discharge control unit configured to control discharge of the power storage unit such that a charging voltage of the power storage unit becomes a voltage at the maximum output point. 2. The charging device according to claim 1, wherein the power generation element has the maximum output point and the open circuit voltage depending on input energy, and the switch element periodically switches between the measurement period and the storage period. Discharge device. The discharge control means includes a charge pump that boosts a voltage of the power storage unit, and a clock generator that varies a clock frequency for driving the charge pump in accordance with the charge voltage. The charge / discharge device according to claim 2. The discharge control means includes a booster that boosts the voltage of the power storage unit using a clock signal, a hysteresis comparator that compares the charging voltage and the voltage at the maximum output point, and a comparison result of the hysteresis comparator, The charge / discharge device according to claim 1, further comprising: a clock generator that controls generation and stop of the clock signal. The charge / discharge device according to claim 3, further comprising a main power storage unit that charges a boosted voltage boosted by the charge pump. The main power storage unit is a single-stage electric double layer capacitor,
6. The charge / discharge according to claim 5, further comprising: another charge pump that boosts the voltage of the electric double layer capacitor to a load voltage; and an output power storage unit that charges an output voltage of the other charge pump. apparatus. A hysteresis comparator that compares the voltage of the output power storage unit with a desired reference voltage;
A clock generator for controlling the generation and stop of the clock signal of the other charge pump according to the comparison result of the hysteresis comparator;
When the power consumption is low, the clock signal is stopped, the output power is taken out only from the output power storage unit, and when the power consumption is high, the clock signal is generated and the output power is supplied from the other charge pump. The charge / discharge device according to claim 6. The charging / discharging device according to claim 7, wherein the desired reference voltage is variable by a variable resistor. The charge / discharge device according to claim 7 or 8, wherein a low dropout power source is inserted between the output storage unit and a load. 10. The charge / discharge device according to claim 9, wherein at least the charge pump, the other charge pump, the switch element, the hysteresis comparator, and the low dropout power source are formed on a sapphire substrate. . 11. The power generation element is any one of a solar cell, a Peltier semiconductor element, a piezoelectric element, a detection circuit connected to an antenna, Seismo, and an electrec. The charge / discharge device according to item 1. The power generating element is a solar cell in which the maximum output current value changes depending on the amount of incident light,
The main power storage unit is an electric double layer capacitor,
The charge pump is capable of changing the boost ratio,
12. The charging / discharging device according to claim 5, wherein the step-up ratio is determined based on a relationship between a withstand voltage of the electric double layer capacitor and an open circuit voltage of the solar cell. The charge pump shuts down when the power generation amount of the power generation element is small, or when the main power storage unit is fully charged,
The other charge pump is configured to shut down when the output power storage unit is fully charged, and to be shut down even when the voltage of one or both of the output power storage unit and the main power storage unit is equal to or lower than a predetermined value. The charge / discharge device according to any one of claims 5 to 12, wherein the charge / discharge device is provided. The main power storage unit and the output power storage unit include an electric double layer capacitor, a Li ion capacitor, a Li ion secondary battery, a nickel metal hydride battery, a nickel cadmium battery, a lead storage battery, a solid battery, a film battery, other capacitors, and a secondary The charging / discharging device according to any one of claims 6 to 13, wherein the charging / discharging device is constituted by a battery. The charging / discharging device according to any one of claims 1 to 14, further comprising a boot capacitor to which a voltage of the power generation element is applied and used as a power source for a reference voltage generator. The boot capacitor is connected in parallel with another switch element that operates in synchronization with the switch element, and a diode is attached to one end of the boot capacitor,
The charge / discharge device according to claim 15, wherein the other switch element conducts when storing electricity in the power storage unit. The charging / discharging device according to claim 16, wherein the other switch element is turned on after a while in a state where the boot capacitor is charged to a predetermined voltage value. The charge pump is connected in parallel with the final stage switch element,
The generated power generated by the solar cell can be stored in the main power storage unit and the output power storage unit via the final-stage switch element. The charging / discharging apparatus of any one of Claims. An integrated circuit element that charges the power storage unit with the generated power generated by the power generation element having the maximum output point where the product of the generated voltage and the output current is maximum, and discharges the charged charge power,
A switching element that switches between a measurement period for measuring an open-circuit voltage of the power generation element and a power storage period for storing the generated power in the power storage unit;
An integrated circuit element comprising: a discharge control unit configured to control discharge of the power storage unit so that a charging voltage of the power storage unit becomes a voltage at the maximum output point.

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