JP2018038224A - Charging circuit using solar cell as power source and design panel having the same - Google Patents

Abstract

When charging a secondary battery using a solar cell as a power source, charging with low illuminance is made possible. When a DC-DC converter 3 charges a secondary battery 4 with electric power from a dye-sensitized solar cell (DSC) 2 capable of generating power at low illuminance, the DC-DC converter 3 is placed before the DC-DC converter 3. The switch element 51 (Q3) is provided, and the ON / OFF control circuit 72 completely disconnects the converter 3. A storage element 6 (C1) is provided between the solar cell 2 and the switch element 51 (Q3). When the storage element 6 (C1) is charged and the charging voltage increases, the voltage monitoring circuit 71 is turned on / off. The switch element 51 (Q3) is turned on by the OFF control circuit 72. Therefore, it is possible to easily raise the output voltage of the solar cell 2 at low illuminance by disconnecting the load (DC-DC converter 3), and the electric power until the output voltage rises after being disconnected is accumulated in the storage element 6 and used. Even in a low light environment, solar energy can be captured more efficiently. [Selection] Figure 2

Description

  The present invention relates to a circuit for charging a secondary battery or an electric double layer capacitor as a power storage device using a solar battery as a power source, and a self-illuminated design panel using the circuit.

  2. Description of the Related Art A secondary battery charging circuit using a solar battery as a power source is provided with a DC-DC converter so that it can be charged with a stable voltage by stepping up or down. The DC-DC converter operates by itself using the output power of the solar cell as a power source. Specifically, it operates when a voltage of a predetermined value or higher is applied to the enable terminal EN of the converter IC. Therefore, when a DC-DC converter is connected to a solar cell, particularly a dye-sensitized solar cell that can generate power under low illuminance, the load caused by the DC-DC converter is too great, and the output voltage of the solar cell does not rise. Therefore, there is a problem that power cannot be extracted effectively.

  Therefore, the present applicant has previously proposed Patent Document 1. FIG. 9 is a block diagram of the charging circuit 11 according to Patent Document 1. In FIG. This charging circuit 11 uses a dye-sensitized solar cell (DSC) 2 suitable for indoor use and capable of generating power even at low illuminance as a power source, and a DC-DC converter 3 uses two output powers as a solar cell. The secondary battery 4 is charged.

  Here, FIG. 10 shows the output characteristics of the solar cell. In the case of a load line a having a somewhat large load, the solar battery generates electric power with high efficiency if the illuminance is high (voltage Va, current Ia), but in the case of low illuminance, the voltage decreases to Vb and can be taken out. The power (Ib * Vb) is also reduced. However, even with the low illuminance, in the case of the load line b with a small load, the power is (Ib * Vb ′), and the power generation efficiency is improved.

  Therefore, the charging circuit 11 is provided with an MPPT (Maximum Power Point Tracking) control circuit 12 that changes the load according to the intensity of the illumination light in order to operate the solar cell 2 at the maximum power point. As shown in FIG. 10, even if the output power is different, the voltage at the maximum power point of the solar cell is substantially constant. Therefore, when the MPPT control circuit 12 has strong illumination light, a large load current (Ia) is obtained. When the illumination light is weak, the solar cell 2 can be operated at the maximum power point by reducing the load current (Ib).

  Then, the operation of the MPPT control circuit 12 is started once the output voltage of the solar cell 2 is sufficiently high, for example, at a voltage corresponding to the maximum power point of the light amount A, as shown in FIG. This is performed with a predetermined hysteresis that stops the operation at the voltage of the minimum load. For example, if the illuminance of sunlight during midsummer day is 1 Sun, the light amount A corresponds to 0.5 Sun and the light amount B corresponds to 0.05 Sun.

  Therefore, once the MPPT control by the control circuit 12 is activated, the secondary battery 4 can continue to be charged even if the intensity of the illumination light changes to some extent (even if it decreases to 1/10 in the above example). . However, when the solar battery 2 is connected to the secondary battery 4 (the DC-DC converter 3 is operated), the DC-DC converter 3 starts with a setting with a large load as described above, so that the illumination light is If it is weak, a large load current flows suddenly, the output voltage of the solar cell 2 decreases, and as a result, the DC-DC converter 3 does not start up (locks out), and the MPPT control of the control circuit 12 does not work. . Thereafter, when strong illumination light is applied, the DC-DC converter 3 starts to operate and the MPPT control of the control circuit 12 starts to function, but there is a problem that charging cannot be performed during that time.

  Therefore, in the charging circuit 11 of Patent Document 1, when the illuminance is less than a predetermined threshold value and there is no output from the DC-DC converter 3, a trigger is provided to reset the DC-DC converter 3 at predetermined time intervals. A reset circuit 13 is provided. The reset operation is performed when the enable terminal EN of the DC-DC converter 3 is reset (Lo input). By doing so, the oscillation of the DC-DC converter 3 is completely stopped, the input current from the solar battery 2 is only 0.3 mA, and the DC-DC converter 3 and the secondary battery 4 that are loads are When disconnected from the solar cell 2, the output terminal of the solar cell 2 becomes an open end, and the terminal voltage is restored. FIG. 12 shows such a change in load.

JP, 2006-57762, A

  In Patent Document 1, light energy can be acquired even when the amount of light is in the range of MPPT control indicated by reference symbol W1, specifically, for example, in the range of 0.05 to 0.5 Sun, when startup is unstable.

  However, the present applicant is currently able to perform charging even in the extremely low illuminance range that cannot be charged in Patent Document 1 indicated by the reference symbol W2, specifically, for example, in the range of less than 0.05 Sun. I came up with the idea.

  An object of the present invention is to effectively capture light energy even in an extremely low illuminance light amount in a charging circuit that charges a secondary battery or an electric double layer capacitor with the output power from a solar cell as a power source. It is providing the charging circuit which can be performed, and a design panel provided with the same.

  The charging circuit according to the present invention is interposed between a DC-DC converter that converts the output power of the solar battery into a charging voltage and a charging current that are predetermined for the secondary battery, and is provided in front of the DC-DC converter, A storage element charged with the output power of the solar cell, a switch element interposed between the storage element and the DC-DC converter, and a charge voltage of the storage element are monitored, and the charge voltage is a predetermined voltage. Then, a control circuit for operating the DC-DC converter by turning on the switch element and supplying charging power of the power storage element to the DC-DC converter is included.

  According to the above configuration, when charging the secondary battery by using the solar battery as a power source, the DC-DC converter converts the output power of the solar battery into a charging voltage and a charging current predetermined for the secondary battery. Since the DC-DC converter operates by itself using the output power of the solar cell as a power source, the DC-DC converter is used for a solar cell, particularly a dye-sensitized solar cell capable of generating power under low illuminance. When the converter is connected, the load caused by the converter is too large, and the solar cell may not rise in output voltage, and may be in a shutdown state and cannot effectively extract power.

  Therefore, a switch element is provided in the previous stage of the DC-DC converter so that the DC-DC converter can be completely separated from the solar cell. On the other hand, a power storage element is provided between the solar cell and the switch element, and the power storage element is first charged with the output power of the solar cell. A solar cell, particularly a dye-sensitized solar cell, is a current source element, and continuously generates a generation current corresponding to the amount of light at that time, and the charging voltage of the storage element becomes the open-circuit voltage of the dye-sensitized solar cell. When it reaches, charging is terminated. The power storage element is a capacitive element such as a capacitor, and the charging is completed earlier as the amount of light increases. Therefore, a control circuit for monitoring the charging voltage and turning on / off the switch element according to the monitoring result is provided.

  The control circuit turns off the switch element until the charging voltage reaches a predetermined voltage, shuts off the input to the DC-DC converter, and turns on when the charging voltage reaches a predetermined voltage to charge the power storage element. Power is supplied to the DC-DC converter to operate the DC-DC converter. The predetermined voltage is close to the open-circuit voltage of the solar cell and is an input voltage range that is efficient for the DC-DC converter, and is equal to or lower than the rated voltage of the power storage element including a capacitor.

  Therefore, the DC-DC converter is disconnected at the time of low illuminance, and the storage element composed of a capacitor having a DC resistance value of almost infinite is connected, so that the load on the solar cell becomes light to the limit, The electric current (charge) of the solar cell is accumulated in the electric storage element. When the charging voltage of the storage element rises to a predetermined voltage, the control circuit turns on the switch element and operates the DC-DC converter with the raised voltage. Since the storage element is a device suitable for instantaneously supplying a large current, even if the startup input current of the DC-DC converter is large, the DC-DC converter can be started up without any problem.

  On the other hand, when the discharge of the storage element progresses with the operation of the DC-DC converter and the charging voltage decreases to the predetermined voltage, the control circuit turns off the switch element and stops the power supply to the DC-DC converter. Then, the operation is stopped and charging of the power storage element is started again.

  As a result, light energy of a light amount in a range less than the predetermined voltage (a light amount range W2 that cannot be charged in the related art shown in FIG. 11) is taken in and stored in the storage element, so that it could not be used for power generation until now. For example, it is possible to take in solar energy more efficiently by utilizing light of extremely low illuminance such as light of a room light. In particular, when a solar cell is installed indoors, solar energy can be acquired more efficiently, which is preferable.

  Further, the charging circuit of the present invention is a charging circuit for charging an electric double layer capacitor with the output power using a solar cell as a power source. The charging power of the solar cell is set to a charging current equal to or lower than a rated voltage of the electric double layer capacitor. Charge injection means for converting and injecting, a storage element interposed in front of the charge injection means and charged by output power of the solar cell, and a switch interposed between the storage element and the charge injection means The charge voltage of the power storage element is monitored, and when the charge voltage reaches a predetermined voltage, the switch element is turned on to supply the charge power of the power storage element to the charge injection means, And a control circuit for operating the injection means, wherein the charge injection means injects charges with a large current that is less than or equal to the rated voltage and is possible from a charge amount of the storage element. To.

  According to said structure, when using an electrical double layer capacitor as an electrical storage apparatus, solar energy can be taken in more efficiently. The electric charge injection means for injecting electric charge into the electric double layer capacitor is only required to protect the electric double layer capacitor at the maximum voltage, and can be an overvoltage protection circuit or the like. However, it is desirable to transfer the electric charge accumulated in the electric storage element to the electric double layer capacitor as soon as possible and to return to the light energy accumulation mode again. On the other hand, even if the power storage device is a secondary battery or an electric double layer capacitor, when the voltage is low, a large current flows at the time of charging. Therefore, as the charge injection means, only the large current flows. Therefore, a DC-DC converter is most suitable.

  Furthermore, in the charging circuit of the present invention, the changeover switch in which the solar cell is connected to a common contact and the storage element is connected to one individual contact, the other individual contact of the changeover switch, and the DC-DC converter Alternatively, the bypass line connecting the charge injection means and the illuminance are monitored, and if the illuminance is higher than a predetermined threshold, the changeover switch is connected to the other individual contact so that the illuminance is lower than the threshold. And an illuminance sensor for connecting the changeover switch to one individual contact.

  According to the above configuration, by providing the power storage element in front of the DC-DC converter or the charge injection means, it is possible to generate power with low illuminance as described above. However, the DC-DC converter can be used only through the power storage element. The output power of the solar cell cannot be taken. Therefore, at high illuminance, switching (cycle) of the switch element is frequent, but the output power of the solar cell cannot be transferred to the DC-DC converter while the switch element is OFF. Further, when the illuminance is high, a continuous operation state is established, and the loss of the charge / discharge switching time by the switch element cannot be ignored.

  Therefore, when a high illuminance detection function by an illuminance sensor is provided, for example, when high illuminance of 10,000 lux or more is detected, the illuminance sensor switches a changeover switch provided between the solar cell and the storage element, and passes through a bypass line. Thus, the output power of the solar cell is directly applied to the DC-DC converter or the charge injection means. Thereby, the loss of taking in solar energy can be eliminated.

  Furthermore, in the charging circuit of the present invention, the power storage element is an electric double layer capacitor.

  According to said structure, although a capacitor | condenser is common as said electrical storage element, when the cycle of charging / discharging is short, it will become more efficient if it uses an electric double layer capacitor with a large capacity | capacitance.

  In the charging circuit of the present invention, the solar cell is a dye-sensitized solar cell.

  According to the above configuration, when the solar cell is a dye-sensitized solar cell (DSC), the power generation efficiency at low illuminance is higher than that of a general silicon solar cell, so that power generation at low illuminance is possible. At low illuminance, the generated power is small and the load by the DC-DC converter or the charge injection means is too large to effectively extract the power.

  Therefore, the charging circuit of the present invention is suitable for a dye-sensitized solar cell (DSC).

  Furthermore, in the charging circuit of the present invention, the solar cell is characterized in that a design based on a difference in the thickness of the dye and / or the power generation layer is formed on the light receiving surface thereof.

  According to said structure, the design can be formed in a light-receiving surface using the difference in a pigment | dye by making the said solar cell into a dye-sensitized solar cell (DSC). In the dye-sensitized solar cell (DSC), the design can be formed also by the difference in the thickness (number of layers) of the power generation layer (typically titanium dioxide).

  In addition, the design panel of the present invention includes a solar cell panel portion made of the solar cell, a self-illuminated design panel portion having a light emitting element matched to a desired design inside, and the design panel portion and the solar cell panel portion. And the lighting circuit for lighting the light emitting element, the secondary battery or the electric double layer capacitor for energizing the lighting circuit, and the charging circuit. And a supporting member.

  According to said structure, in the design panel used as a collar etc. which a support member supports from below in the state where the design panel part stood substantially perpendicularly, a panel part of a solar cell is provided in the back of the design panel part, A self-illuminated design panel in which the light-emitting elements in the design panel unit are lit by the electric power generated thereby.

  Therefore, when making a design panel such as a bag into a self-illuminating type, by first using a solar cell, energy saving and further maintenance such as battery replacement can be eliminated. Next, as described above, the solar cell is a dye-sensitized solar cell (DSC) that can generate power even at low illuminance, so that the time during which the design panel is lit can be extended even when the solar cell is used. . As a result, a design panel that is provided indoors and operates with a low illuminance room light can be realized.

  Furthermore, in the design panel of the present invention, the solar cell panel unit and the substrate of the design panel unit that are integrated on the front and back sides are translucent, and the emitted light in the back direction of the design panel unit is the light emitted from the design panel unit. Regenerative power generation is performed using a dye-sensitized solar cell.

  According to the above configuration, taking advantage of the feature of a dye-sensitized solar cell (DSC) that power generation is possible on both the front and back sides, in general, in addition to the dye-sensitized solar cell (DSC) having translucency, the front and back are integrated. The substrate of the design panel portion to be formed is also formed to be translucent.

  As a result, the light emitted from the design panel part, which has not been used so far, can be regenerated by a dye-sensitized solar cell (DSC) that can generate power even at low illuminance. Efficiency can be further improved.

  As described above, the charging circuit of the present invention uses a solar cell as a power source, and in the charging circuit that charges a secondary battery or an electric double layer capacitor with its output power, a switching element in front of a DC-DC converter or charge injection means The DC-DC converter or the charge injection means can be completely separated from the solar cell, and an electric storage element is provided between the solar cell and the switch element. With the output power of the solar cell, First, the storage element is charged, and when the charging voltage becomes high, the control circuit turns on the switch element.

  Therefore, the output voltage of the solar cell at low illuminance can be easily raised by disconnecting the load, and the electric power until the output voltage rises after being disconnected is also stored and used in the storage element, so it is more efficient. Solar energy can be taken in.

It is a block diagram which shows the electric constitution of the charging circuit which concerns on one Embodiment of this invention. It is an electric circuit diagram which shows the specific structure of the said charging circuit. It is a wave form diagram for demonstrating operation | movement of the said charging circuit. It is a block diagram which shows the electric constitution of the charging circuit which concerns on other embodiment of this invention. It is a perspective view which shows one form of the design panel using the said charging circuit. It is a figure of the panel block of the said design panel. It is a figure of the panel block of the said design panel. It is a front view of the light-guide plate in the said design panel. It is a block diagram which shows the electric constitution of the charging circuit of a prior art. It is a graph which shows the output characteristic of a solar cell. It is a figure for demonstrating MPPT control. It is a graph which shows the change of the output characteristic of the solar cell by the charging circuit of FIG. It is a graph for demonstrating operation | movement of an electrical storage element.

(Embodiment 1)
FIG. 1 is a block diagram showing an electrical configuration of a charging circuit 1 according to an embodiment of the present invention. This charging circuit 1 uses a solar battery 2 as a power source, and a DC-DC converter 3 converts the output power into a charging voltage and a charging current that are predetermined for a secondary battery 4 that is a power storage device, and the secondary battery 4 The battery 4 is charged. In the present embodiment, the solar cell 2 is a dye-sensitized solar cell (DSC) that can generate power at low illuminance and can be used indoors, and the secondary battery 4 is a nickel-hydrogen battery. The secondary battery 4 is assumed to connect two AAA sizes in series. Therefore, the rated voltage is 1.2V × 2 = 2.4V.

  It should be noted that in the charging circuit 1, first, the switch element 51 is provided in the front stage of the DC-DC converter 3 so that the DC-DC converter 3 can be completely separated from the solar cell 2. This is because the DC-DC converter 3 operates by itself using the output power of the solar cell 2 as a power source, so that the solar cell 2, particularly the dye-sensitized solar cell capable of generating power under low illuminance. Remarkably in the case of (DSC), if the DC-DC converter 3 is connected, the load caused by the DC-DC converter 3 is too large, and the output voltage of the solar cell 2 does not rise, and the shutdown state cannot be taken out effectively. Because there is.

  Also, it should be noted that a storage element 6 is provided between the solar cell 2 and the switch element 51, and this storage element 6 is first charged by the output power of the solar cell 2. In addition, a control circuit 7 is provided in relation to the power storage element 6 and the switch element 51. The control circuit 7 monitors the charging voltage of the storage element 6 and turns on / off the switch element 51 according to the monitoring result. Specifically, the control circuit 7 includes a voltage monitoring circuit 71 that monitors the charging voltage, and an ON / OFF control circuit 72 that controls ON / OFF of the switch element 51 in response to the monitoring result. The ON / OFF control circuit 72 turns off the switch element 51 and stops the DC-DC converter 3 until the charging voltage monitored by the voltage monitoring circuit 71 becomes a predetermined voltage, and then becomes the predetermined voltage. The power is turned on, and the charging power of the storage element 6 is supplied to the DC-DC converter 3 to operate the DC-DC converter 3. The predetermined voltage is close to the open-circuit voltage of the solar cell 2 and is an input voltage range that is efficient for the DC-DC converter 3 and is equal to or lower than the rated voltage of the power storage element 6 including a capacitor.

  By comprising in this way, the load of the solar cell 2 becomes light by the DC-DC converter 3 being first separated at the time of low illumination. On the other hand, a storage element 6 is connected to the solar cell 2, and a capacitor (including an electric double layer capacitor: EDLC) having a DC resistance value close to infinity is used as the storage element 6. The resistance becomes infinite, and in FIG. 10, the load line becomes substantially horizontal c and intersects with the open circuit voltage Voc. On the other hand, as shown in FIG. 13, the charging voltage of the storage element 6 is charged with a current having an IV characteristic of the solar cell 2 and finally reaches the open voltage Voc of the solar cell 2.

  As a result, the output voltage of the solar cell 2, and hence the charging voltage of the storage element 6, is likely to rise, a certain amount of charge can be accumulated, and when it rises to a predetermined voltage, the ON / OFF control circuit 72 turns on the switch element 51. Thus, the DC-DC converter 3 can be reliably operated with the rising voltage. When the charging voltage of the storage element 6, that is, the input voltage of the DC-DC converter 3 is lowered to a voltage with low efficiency of the DC-DC converter 3, the ON / OFF control circuit 72 turns off the switching element 51 and again The power storage element 6 is charged. The ON / OFF control circuit 72 repeats such an operation.

  The power in the range below the predetermined voltage (the power in the range W2 that cannot be charged in FIG. 11) is accumulated in the power storage element 6, and thus has not been used for power generation, Solar energy can be taken in more efficiently by utilizing such extremely low illuminance light. In the case where the solar cell 2 is installed indoors, particularly at a window where the illuminance changes remarkably, solar energy can be acquired more efficiently, which is preferable.

  FIG. 2 is an electric circuit diagram showing a specific configuration of the charging circuit 1 configured as described above. The DC-DC converter 3 includes a circuit module, and includes a converter IC31, resistors R19, R21, and R22, capacitors C6 and C7, and an inductor L1. The high-side input voltage in from the switch element 51 via the high-side line 32 is input to the power supply input terminal VIN of the converter IC31 via the resistor R19 and pulls up the enable terminal EN. The high-side input voltage in is supplied to the terminal L of the converter IC 31 via the inductor L1. Further, a capacitor C6 is provided between the inductor L1 and the GND line 33. Between the lines 32 and 33, a capacitor C7 for removing noise due to resonance described later is provided.

The converter IC 31 performs a step-up / step-down operation on the input voltage to the power input terminal VIN using the inductor L1 and the capacitors C6 and C7, and the voltage out from the output terminal Vout for driving a large capacity load to the high side line 34. The voltage out is applied as a charging voltage to the secondary battery 4 from the noise removing capacitor C2 via the diode D1 and the current limiting resistor R18. The output voltage out from the output terminal Vout to the high-side line 34 is 0.3V, which is the drop of the diode D1, and the current limiting resistor R18 so that the charging voltage of the secondary battery 4 is 3.0V or less. Including the voltage drop V _R18 of 3.3 V + V _R18 . The voltage drop V _R18 at a current limiting resistor R18, the charging voltage of the secondary battery 4 output current of the minimum (2.0 V) at the DC-DC converter 3 is maximum, the current value at that time, DC -It is set so as to be within the specifications of the DC converter 3.

  The output voltage out is also input to the feedback terminal FB via the voltage dividing resistors R21 and R22, and the converter IC31 outputs a constant voltage. This feedback may be the MPPT (Maximum Power Point Tracking) method. In that case, load control optimum for the current-voltage characteristics of the dye-sensitized solar cell (DSC) can be performed, and light energy can be effectively acquired even under low illuminance such as indoor light.

  On the other hand, in this embodiment, two solar cells 2 are the dye-sensitized solar cells (DSCs) connected in series, and the maximum value of the output voltage V1 is 6V. The voltage V1 output from the solar cell 2 between the high-side line 73 and the GND line 33 is limited by the Zener diode Z1 so as to be the rated voltage of the storage element (capacitor) C1, and the storage element 6 is Charge. The capacitor C1 is generally used as the power storage element 6 as shown in FIG. 2. However, when the charge / discharge cycle is short, it is more efficient to use an electric double layer capacitor having a large capacity.

  The ON / OFF control circuit 72 includes switch elements Q1, Q2, and Q4, resistors R1 to R7 and R17, and a capacitor C5. The voltage V1 output from the solar cell 2 to the high-side line 73 is DC-DC as the input voltage in (voltage V4) from the high-side line 32 via the switch element Q3 made of FET as the switch element 51. It is given to the converter 3. Voltage dividing resistors R4 and R5 are connected between the high side line 73 and the GND line 33, and the charging voltage V1 of the capacitor C1 is divided by the voltage dividing resistors R4 and R5 to output a voltage V2. The This voltage V2 is applied to the gate of the FET Q2, the source of the FET Q2 is connected to the GND line 33, and the drain is connected to the high side line 73, that is, the source of the FET Q3 via the resistors R7 and R6.

  Therefore, electric charges are accumulated in the capacitor C1, and the charging voltage V1 of the secondary battery C1 rises as shown in FIG. 3A. Accordingly, as shown in FIG. 3B, the gate voltage of the FET Q2 is increased. When V2 rises and becomes equal to or higher than the ON voltage Vth, the FET Q2 is turned on. As a result, the drain voltage V3 of the FET Q2 changes as shown in FIG. 3C, and the gate voltage of the FET Q3 is divided by the resistors R6 and R7 from the voltage V1 pulled up by the resistor R6. FETQ3 is turned on. As the FET Q3 is turned on, the voltage V4 (in) of the high-side line 32 decreases as the secondary battery C1 is discharged, as shown in FIG. 3 (d). When the FET Q2 is turned on, current is drawn from the high-side line 73 through the resistors R1 and R2, thereby reducing the gate voltage of the FET Q1, the FET Q1 is turned on, and the base of the FET Q2 is connected through the resistor R3. Positive feedback that stabilizes the voltage V2 is performed, and chattering is prevented.

  When the FET Q3 as the switch element 51 is turned on, the voltage V4 (in) is applied to the enable terminal EN of the converter IC31, and the converter IC31 operates, and as shown in FIG. 3E, the stabilized voltage V5 ( out) is output.

  The voltage monitoring circuit 71 includes a shunt regulator IC1, a comparator IC2, a diode D2, capacitors C3 and C4, and resistors R8 to R16. First, the voltage V5 (out) of the high side line 34 is taken in through the diode D2 and the resistor R10, smoothed by the capacitor C3, and used as the power supply voltage V6 of the voltage monitoring circuit 71. The voltage V6 is supplied to the power supply input terminal of the comparator IC2, and is divided by the resistors R13, R11, R12, and is connected in parallel with these resistors R11, R12 with reference to the voltage between the resistors R11, R12. It is stabilized by the shunt regulator IC1.

  The voltage controlled by the shunt regulator IC1 is applied from the resistor R14 to the capacitor C4 and stabilized, and is input to the non-inverting input terminal of the comparator IC2 as the voltage V8. An input voltage in (voltage V4) to the DC-DC converter 3 is divided by resistors R8 and R9 and input to the inverting input terminal of the comparator IC2. The output of the comparator IC2 is positively fed back by the resistor R15, and the output terminal is pulled up to the power supply voltage V6 by the resistor R16.

  The output of the comparator IC2 is sent to the ON / OFF control circuit 72 and given from the differentiation capacitor C5 to the discharge resistor R17, and the voltage V10 at the connection point between the capacitor C5 and the resistor R17 is given to the gate of the FET Q4. It is done. The FET Q4 is provided for grounding the gate voltage V2 of the FET Q2 to the GND line 33.

  Therefore, by the operation of the converter IC31 shown in FIG. 3E, the voltage V8 at the non-inverting input terminal of the comparator IC2 is stabilized at a constant voltage as shown in FIG. The voltage V7 decreases as the capacitor C1 is discharged. When voltage V7 becomes lower than voltage V8, the output of converter IC31 changes from low level to high level. As a result, the output V9 of the comparator IC2 shown in FIG. 3 (g) rises to the power supply voltage V6, is differentiated by the capacitor C5, and the voltage V10 shown in FIG. 3 (h) is given to the gate of the FET Q4, and the FET Q4 is turned on. To do. As a result, the FET Q2 and hence the FET Q3 are turned OFF, and the DC-DC converter 3 is turned OFF as shown in FIG. Thus, the DC-DC converter 3 is driven intermittently so as to be driven only during the period T2 and to rest during the periods T1 and T3.

As described above, according to the charging circuit 1 of FIG. 2, the DC-DC converter 3 can be disconnected when the illuminance is low, and the output voltage V1 of the solar cell 2 can be reliably raised. In addition, the output voltage V1 is less than a predetermined voltage, and power that has not been used for power generation so far, as indicated by the reference symbol range W2 in FIG. Such a charging circuit 1 can be suitably implemented by using it as a power source for a guide light, a foot illuminating device, or a LAN module at the time of a power failure used indoors, as a power source thereof. .
(Embodiment 2)
FIG. 4 is a block diagram showing an electrical configuration of a charging circuit 1a according to another embodiment of the present invention. The charging circuit 1a is similar to the above-described charging circuit 1, and corresponding portions are denoted by the same reference numerals and description thereof is omitted. First, in this charging circuit 1a, an electric double layer capacitor (EDLC) 4a is used as a power storage device. As a result, deterioration of the power storage device is suppressed and maintenance-free is achieved. However, since the electric double layer capacitor (EDLC) 4a is simply discharged along the discharge curve of the capacitor, the constant voltage circuit 10 is interposed between the electric double layer capacitor (EDLC) 4a and the load.

  In the charging circuit 1a, the electric double layer capacitor (EDLC) 4a is used as the power storage device, so that the output power from the solar cell 2 is equal to or higher than the terminal voltage of the electric double layer capacitor (EDLC) 4a. Charging can be performed by using the injection means. Therefore, the charge injection means can be realized only by a charge pump circuit or an overvoltage protection circuit that performs maximum voltage protection. However, it is desirable to transfer the electric charge accumulated in the electric storage element 6 to the electric double layer capacitor (EDLC) 4a as soon as possible and to return to the light energy accumulation mode again. On the other hand, even if the power storage device is the secondary battery 4 or the electric double layer capacitor (EDLC) 4a, a large current flows during charging when the voltage is low. Therefore, the charge injection means requires an element capable of flowing a large current, and in this embodiment, the DC-DC converter 3a is used. However, a simple configuration can be used for the DC-DC converter 3a as compared with the DC-DC converter 3 corresponding to the load line a in FIG.

  Furthermore, in this charging circuit 1a, a changeover switch 52 and a bypass line 8 for bypassing the storage element 6 are provided, and an illuminance sensor 9 for changing over the changeover switch 52 is provided in association therewith. The changeover switch 52 is provided between the solar cell 2 and the storage element 6, the solar cell 2 is connected to the common contact, the storage element 6 is connected to one individual contact, and the other individual contact is connected to the bypass line 8. Connected. The bypass line 8 can bypass the power storage element 6 and directly connect the solar cell 2 and the DC-DC converter 3a.

  This is because power storage with low illuminance is possible by providing the power storage element 6 in front of the DC-DC converters 3, 3 a, but the DC-DC converters 3, 3 a can be Although the output power cannot be captured and the switch element 51 is frequently switched (cycle) at high illuminance, the output power of the solar cell 2 is changed to DC− while the switch element 51 is OFF. This is because it cannot be transferred to the DC converters 3 and 3a. In particular, when the illuminance is high, the switch element 51 is in a continuous operation state, and the loss of charge / discharge switching time cannot be ignored.

Therefore, the illuminance sensor 9 monitors the illuminance, and if the illuminance is high illuminance equal to or higher than a predetermined threshold value, the changeover switch 52 is connected to the other individual contact, that is, the bypass line 8, and the illuminance sensor 9 has low illuminance less than the threshold value. If there is, the changeover switch 52 is connected to one individual contact, that is, the power storage element 6. For example, when high illuminance is detected by the high illuminance sensor 9 such as 10,000 lux or more, the illuminance sensor 9 bypasses the storage element 6 and directly outputs the output power of the solar cell 2 from DC-DC. Since it is given to the converters 3 and 3a, it is possible to eliminate the loss of taking in solar energy.
(Embodiment 3)
FIG. 5 is a perspective view showing one form of the design panel 101 using the charging circuit 1 or 1a configured as described above. The design panel 101 is configured such that a panel block 102 which is a self-illuminated design panel using solar cells is supported by a support member 103 so as to stand substantially vertically. For example, the design panel 101 can be placed on a desk, a window, or the like, and used as an award, award, award for award, or the like. In this design panel 101, the design panel 101 can shine only a specific mark or crown design portion 104 or the entire surface, as described later. The panel portion 121 (FIG. 7) of the solar cell 2 is provided on the back side as a power source for the internal illumination (LED substrate 106 (FIG. 6)) that shines. The lower support member 103 accommodates the above-described charging circuit 1, 1 a and the secondary battery 4 or electric double layer capacitor (EDLC) 4 a, the LED substrate 106, its control circuit 107 (FIG. 6), and the like. .

  Therefore, when making a design panel such as a bag into a self-illuminating type, by first using a solar cell, energy saving and further maintenance such as battery replacement can be eliminated. Next, as described above, the solar cell is a dye-sensitized solar cell (DSC) that can generate power even at low illuminance, so that the time during which the design panel 101 is lit can be lengthened even if the solar cell is used. it can. As a result, a design panel that is provided indoors and operates with a low illuminance room light can be realized.

  6A and 6B are views of the panel block 102, where FIG. 6A is a front view and FIG. 6B is a side view. The panel block 102 is configured, for example, by attaching peripheral circuit components to the lower part of a thin panel 105 having a width W of 200 mm, a height H1 of 300 mm, and a thickness D of 15 mm. As a peripheral circuit component, an LED substrate 106 having a height H2, for example, 5 mm, is provided immediately below the thin panel 105 as an edge light for the internal illumination. Below the LED board 106, an LED control circuit 107 is disposed on one side, and the charging circuit 1 or 1a is disposed on the other side, below these circuits 107; 1, 1a. A battery box is provided. In the battery box, for example, the two AAA secondary batteries 4 are accommodated in series.

  For example, the height H3 of the circuit 107; 1, 1a is 25 mm, and the height H4 including the battery box is 45 mm. In the example shown in FIGS. 5 and 6, the circuit 107; 1, 1 a and the battery box are mounted with the panel block 102 extended, but may be housed in the support member 103.

  FIG. 7 is a view of one embodiment of the panel block 102, where (a) is a front view and (b) is a side view. The panel block 102 has a design panel unit 111 and a solar cell panel unit 121, and they are individually manufactured. The design panel unit 111 and the solar cell panel unit 121 are front and back surfaces of each other. It is composed by overlapping.

  And the design panel part 111 is an edge light (internal illumination) type design panel using the said LED board 106, and the diffuser panel which diffuses illumination light from the surface side with the decorative panel 112 to which the design was given. 113, a light guide plate 114 that propagates the illumination light, and a reflection plate 115 are laminated, and the LED substrate 106 is provided on an edge of the light guide plate 114. The design panel 101 can be thinned by using such an edge light type internally illuminated panel. In FIG. 7B, the thickness is emphasized (drawn thicker) than in FIGS. 5 and 6 in order to facilitate understanding of the laminated structure of the panel block 102 as described above.

  The decorative panel 112 is configured by halftone printing a desired design of a plurality of colors on the design portion 104, for example, on the back surface of a 2 mm transparent resin plate. The light diffusing plate 113 is made of, for example, a 1 mm milky white plate, and uniformly diffuses illumination light via the light guide plate 114 in the surface direction. The reflection plate 115 is made of, for example, a 1 mm resin plate, a metal thin plate, or the like whose mirror surface is processed on the light guide plate 114 side. However, the reflective plate 115 has no reflective film formed on the design portion 104.

  As described above, the design portion 104 of the decorative panel 112 is formed by halftone printing a design of a plurality of colors, and the LED as a light emitting element mounted on the LED substrate 106 is also a plurality of colors. An element may be used so that the design portion 104 selectively emits light by a combination of a printing color and a light source color of an LED. For example, when a red LED emits light, a red design portion emits light, when a green LED emits light, a green design portion emits light, and when a white LED emits light, all color design portions emit light. It is like this. With this configuration, the degree of attention to the design portion 104 can be dramatically increased.

  The solar cell panel portion 121 thus configured is laminated back to back on the design panel portion 111 described above, and a frame 131 having a U-shaped cross section at a right angle is fitted to at least three sides of the peripheral portion. By being integrated, the panel block 102 is completed. Therefore, it is possible to use the solar battery panel 121 as it is, with only the design panel 111 being changed (exchanged).

  FIG. 8 is a front view of the light guide plate 114. The light guide plate 114 is configured such that, for example, unevenness 117 is formed only in the design portion 104 on the surface of a transparent resin plate 116 having a thickness of 3 mm. The unevenness 117 is formed by laser processing or NC router processing, or is formed by screen printing or etching. Then, the illumination light incident from the LED substrate 106 is repeatedly reflected in the thickness direction of the light guide plate 114 and propagates in the surface direction, and is taken out in the thickness direction only by the uneven portion 117, that is, only the design portion 104. It is irradiated from the back side of the decorative panel 112.

  At this time, the unevenness 117 of the design portion 104 causes the light propagation direction to change from the surface direction to the thickness direction, and the light emitted forward illuminates the design portion 104 as it is, but the back is not originally used. The light emitted to the light passes through a portion of the reflection plate 115 where there is no reflection film, and enters the solar cell panel unit 121. The solar cell panel unit 121 is composed of a dye-sensitized solar cell (DSC) as described above, and titanium oxide particles (not shown) adsorbed with a dye or an electrolytic solution are adsorbed between a pair of substrates 122 and 123 on which electrodes are formed. Enclosed and configured. Here, the rear substrate 122 has translucency. By constituting in this way, in the solar cell panel unit 121 and the design panel unit 111 integrated on the front and back, the solar cell panel unit 121 regenerates the emitted light in the back direction of the design panel unit 111. Can do.

  This makes use of the feature of a dye-sensitized solar cell (DSC) that power can be generated on both sides, and in addition to the substrates 122 and 123 of a dye-sensitized solar cell (DSC) generally having translucency, Realized by forming the substrate of the design panel unit 111 to be integrated (in the case of the present embodiment, the light guide plate 114 and the reflection plate 115 are equivalent) to be transparent (the design portion 104 where the reflection film is not formed). In addition, light in the back direction that has not been used so far can be regenerated by a dye-sensitized solar cell (DSC) that can generate power even at low illuminance, and the power generation efficiency can be further improved.

  And the solar cell panel part 121 can form a design in a light-receiving surface using the difference in a pigment | dye by comprising a dye-sensitized solar cell (DSC). In the dye-sensitized solar cell (DSC), the design can be formed also by the difference in the thickness (number of layers) of the power generation layer (typically titanium dioxide). In this way, the design part 104 of the design panel part 111 and the design which is different in the front and back can also be displayed. Moreover, in the said Example, although the uneven | corrugated pattern was formed in the light-guide plate 114, the uneven | corrugated pattern was not formed in the light-guide plate 114, but the board which formed the unevenness | corrugation in a transparent plate separately as a mere transparent board is said decorative panel 112. It is good also as a structure arrange | positioned between the and the diffuser plate 113.

DESCRIPTION OF SYMBOLS 1, 1a Charging circuit 2 Solar cell 3, 3a DC-DC converter 31 Converter IC
4 Secondary battery 4a Electric double layer capacitor (EDLC)
DESCRIPTION OF SYMBOLS 51 Switch element 52 Changeover switch 6 Power storage element 7 Control circuit 71 Voltage monitoring circuit 72 ON / OFF control circuit 8 Bypass line 9 Illuminance sensor 10 Constant voltage circuit 101 Design panel 102 Panel block 103 Support member 104 Design part 106 LED board 107 Control circuit DESCRIPTION OF SYMBOLS 111 Design panel part 112 Decoration panel 113 Light diffuser plate 114 Light guide plate 115 Reflector plate 116 Resin board 117 Concavity and convexity 121 Solar cell panel part 122,123 Board | substrate 131 Frame C1-C7 Capacitor D1, D2 Diode IC2 Comparator L1 Inductor Q1-Q4 Switch element R1-R19, R21, R22 resistance

Claims (9)

In a charging circuit that uses a solar cell as a power source and charges a secondary battery with its output power,
A DC-DC converter that converts the output power of the solar battery into a predetermined charging voltage and charging current for the secondary battery,
A power storage element interposed in a front stage of the DC-DC converter and charged with output power of the solar cell;
A switch element interposed between the power storage element and the DC-DC converter;
The charging voltage of the storage element is monitored, and when the charging voltage reaches a predetermined voltage, the switch element is turned on to supply the charging power of the storage element to the DC-DC converter. And a control circuit for operating the converter. A charging circuit using a solar cell as a power source. The solar cell is connected to a common contact, the storage element is connected to one individual contact, a changeover switch,
A bypass line connecting the other individual contact of the changeover switch and the DC-DC converter;
The illuminance is monitored, and if the illuminance is higher than a predetermined threshold, the changeover switch is connected to the other individual contact, and if the illuminance is lower than the threshold, the changeover switch is connected to one individual contact. The charging circuit using the solar cell as a power source according to claim 1, further comprising an illuminance sensor. In a charging circuit for charging an electric double layer capacitor with the output power using a solar cell as a power source,
Charge injection means for converting and injecting the output power of the solar cell into a charging current equal to or lower than the rated voltage of the electric double layer capacitor;
A power storage element that is interposed in the front stage of the charge injection means and is charged with the output power of the solar cell,
A switch element interposed between the storage element and the charge injection means;
The charge voltage of the power storage element is monitored. When the charge voltage reaches a predetermined voltage, the switch element is turned on to supply the charge power of the power storage element to the charge injection means. A control circuit to be operated,
The charging circuit using a solar cell as a power source, wherein the charge injection means injects a charge with a large current possible from a charge amount of the storage element at a voltage lower than the rated voltage. The solar cell is connected to a common contact, the storage element is connected to one individual contact, a changeover switch,
A bypass line connecting the other individual contact of the changeover switch and the charge injection means;
The illuminance is monitored, and if the illuminance is higher than a predetermined threshold, the changeover switch is connected to the other individual contact, and if the illuminance is lower than the threshold, the changeover switch is connected to one individual contact. 4. A charging circuit using a solar cell as a power source according to claim 3, further comprising an illuminance sensor.   The charging circuit using a solar cell as a power source according to any one of claims 1 to 4, wherein the storage element is an electric double layer capacitor.   The said solar cell consists of a dye-sensitized solar cell, The charging circuit which used the solar cell of any one of Claims 1-5 as a power supply.   The charging circuit using a solar cell as a power source according to claim 6, wherein the solar cell has a light-receiving surface formed with a design based on a difference in thickness of the pigment and / or the power generation layer. A solar cell panel portion of the solar cell;
A self-illuminated design panel having inside a light emitting element adapted to the desired design;
The design panel unit and the solar cell panel unit are integrated on the front and back sides, and supported from below in a substantially vertical state, and a lighting circuit for lighting the light emitting element, the secondary battery for energizing the lighting circuit, or A design panel comprising: an electric double layer capacitor; and a support member that accommodates the charging circuit according to claim 6 or 7.   The solar cell panel unit and the substrate of the design panel unit that are integrated on the front and back sides have translucency, and the light emitted in the back direction in the design panel unit is regenerated by the dye-sensitized solar cell. The design panel according to claim 8.

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