JP2015102628A - Design panel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form an optional and definite design on a design panel which can perform self-illumination (inner illumination) independently (without power feeding from outside) by using a solar battery.SOLUTION: A design panel does not serve as a solar battery, a design panel part 111 and a solar battery panel part 121 are produced individually, and they are overlapped so that they serve as a front surface and rear surface respectively and are integrated, without simple connection. Then, the overlapped object is disposed on a window side for example, the solar battery panel part 121 is on the window side, and the design panel part 111 is on an inside of room side, the design panel part is used as a shield representing commendation, or medal. Therefore, the design panel part 111 can have an optional and definite design, and the solar battery panel part 121 is used as it is, and it is also possible to change (exchange) only the design panel part 111. In addition, various states of use modes according to request from a designer and an advertiser are achieved, and it is used for novel application.

Description

  The present invention relates to a design panel, and more particularly to a self-illuminating (inner illumination) type panel.

  Such a self-illuminated (inner-illumination) design panel has been conventionally used in advertising billboards and the like. For example, Patent Document 1 shows a technique for suppressing luminance unevenness with a large design panel such as the advertising billboard. Patent Document 2 shows an example of a small emergency guide lamp provided on a wall surface.

  On the other hand, in a solar cell panel, in the case of a dye-sensitized solar cell (DSC) having a good power generation capability even at low illuminance, there are a plurality of dyes that are adsorbed on the porous oxide semiconductor and emit electrons when exposed to light. Patent Document 3 proposes a solar cell panel that can be used in various types, and that has been given design properties by utilizing its properties.

JP 2009-104197 A JP 2007-199518 A JP 2002-75472 A

  Patent Document 3 displays characters, symbols, figures, and pictures by forming a porous oxide semiconductor layer with different adsorbed dyes in a region divided by glass frit. And since it is a solar cell, a unique self-illumination (internal illumination) design panel can be realized by storing the generated power and using it as a power source for internal lighting. However, there are restrictions on the color depending on the usable dye, and it is necessary to classify the porous oxide semiconductor with the glass frit for each color. It is difficult to do. Moreover, once created, the design cannot be changed. For example, there is no problem as long as the same display is made throughout the year as in the case of the emergency guide light, but in order to change the design according to the season, the solar cell (design panel) must be replaced.

  An object of the present invention is to provide a design panel capable of forming a free and fine design in a design panel that can be self-illuminated (internally illuminated) by using a solar cell panel (without power supply from the outside). Is to provide.

  The design panel of the present invention is a self-illuminated design panel using solar cells, and has a design panel portion and a solar cell panel portion, and these are individually manufactured. The design panel portion and the solar cell panel portion Are overlapped so as to be front and back to each other, or are formed in a rectangular shape and connected on one side, and are arranged back-to-back with each other in a U-shape or facing each other in a U-shape. And

  According to the above configuration, in a design panel that can be self-illuminated (internally illuminated) by using a solar cell (without power supply from the outside), the design panel does not double as a conventional solar cell. The design panel portion and the solar cell panel portion are individually manufactured. And the configuration of the present invention is not a configuration in which a solar cell panel is simply connected to a design panel, for example, as seen at a bus stop or the like. use.

  Specifically, they are overlapped so as to be the front and back surfaces of each other, for example, arranged at the window, with the panel surface of the solar cell panel portion facing the window side and the panel surface of the design panel portion facing the indoor side. Alternatively, it is formed in a rectangular shape and connected on one side so that it can be freely opened and closed, widely opened in a letter (V) shape, and the design panel part and the solar cell panel part are back-to-back, that is, a mountain shape placed on a desk It arrange | positions like a calendar | calender, or it opens small mutually in the shape of (V) mutually, and the said design panel part and solar cell panel part face, ie, arrange | position like a folding screen.

  Therefore, an arbitrarily fine design can be given to the design panel part, and the solar cell panel part can be used as it is, and only the design panel part can be changed (replaced). In addition, it can be used in various modes according to the demands of designers and advertisers, and can be developed for new applications. The design panel portion is not limited to a configuration having internal illumination, and may be a panel capable of self-emission, such as an EL element, and may be a self-illuminating panel.

  In the design panel of the present invention, the solar cell panel section is composed of a dye-sensitized solar cell, and a design based on a difference in the dye is formed on the light receiving surface.

  According to said structure, by making the said solar cell panel part into a dye-sensitized solar cell (DSC), it becomes possible to generate electric power with low illuminance and for indoor use such as the above-mentioned Yamagata calendar and folding screen. It is advantageous. In addition, the dye-sensitized solar cell (DSC) has more restrictions (becomes simpler) than the design panel, but it is possible to form a design due to the difference in the dye on the light receiving surface, so that the design panel section In addition, for example, the design can be formed on both the front and back surfaces in the case of the above-described lamination, and on the two surfaces in the case of a mountain-shaped calendar and folding screen.

  Furthermore, in the design panel of the present invention, the design panel part and the solar cell panel part are arranged so as to be on the front and back surfaces, and the design panel part is decorated with a design from the front side. A panel, a diffuser plate for diffusing the illumination light, a light guide plate for propagating the illumination light, and a reflection plate are laminated, and a light emitting element is provided at an edge of the light guide plate. Features.

  According to said structure, since the design panel part is comprised with an edge light type internal illumination type panel, the thickness reduction of this design panel is attained.

  Further, in the design panel of the present invention, the light guide plate is such that the illumination light incident from the light emitting element repeats reflection in the thickness direction and propagates in the surface direction, and print dots are locally formed. Illumination light formed and taken out by the dot portion is irradiated from the back side of the decorative panel.

  According to said structure, a decoration panel can be locally illuminated with the illumination light of edge light, and it becomes possible to make the design of the said decoration panel stand out effectively.

  Furthermore, in the design panel of the present invention, the decorative panel has the design formed by halftone printing a desired plurality of colors, the light-emitting element has a light source of a plurality of colors, and a print color and a light source The design selectively emits light in combination with a color.

  According to the above configuration, by combining the color printing of the decorative panel and the color light emission of the light source, only the design of the color that matches the color of the light source is emitted or by using a white light source, It is possible to make the design emit light.

  Moreover, in the design panel of this invention, the said design panel part and solar cell panel part integrated by the front and back are used in the state stood substantially perpendicular | vertical, and support them in the said standing state on the lower part side. A lighting circuit for lighting the light emitting element, a secondary battery for energizing the lighting circuit, and a charging circuit for charging the secondary battery with electric power generated by the solar battery panel unit Is provided on the lower side of the design panel portion and the solar cell panel portion or in the support member.

  According to said structure, it becomes possible to use the said design panel as an award of recognition, recognition, recognition. And in such a kite, when illuminating a decoration panel locally as mentioned above, it becomes possible, for example, to make only a specific mark and a crown part shine.

  Furthermore, the design panel of the present invention includes a charging circuit that charges a secondary battery that uses a solar battery as a power source and energizes the light-emitting element with the output power, and the charging circuit uses the output power of the solar battery as the power supply. A DC-DC converter that converts and supplies a secondary battery with a predetermined charging voltage and charging current, and monitors the output voltage of the solar battery, and the DC-DC converter is in a period during which the output voltage is less than a predetermined threshold voltage. And a first converter control circuit for operating the DC-DC converter when the voltage becomes equal to or higher than the threshold voltage.

  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. A first converter control circuit for controlling the operation of the DC-DC converter is provided, and the first converter control circuit is provided for the DC-DC converter that starts operation when the output voltage of the solar cell rises. Monitors the output voltage of the solar cell, and during the period when the output voltage is less than a predetermined threshold voltage (basically the maximum voltage of the solar cell) (which can drive the load (secondary battery)) The DC converter is stopped and the operation is started when the threshold voltage is exceeded.

  Therefore, when the secondary battery is connected to the solar battery where the DC-DC converter starts operation, the output power of the solar battery rises to a level sufficient for driving the load (secondary battery). By repeatedly connecting the load before the output power rises and further lowering the output voltage of the secondary battery, it is possible to prevent such a problem that the start-up becomes impossible. Thereby, even when sunlight is weak, a DC-DC converter can be started reliably and charge of a secondary battery can be started. In addition, if sunlight remains weak even after charging is started, the output voltage of the secondary battery is lowered when the DC-DC converter is operating, and the DC-DC converter stops and cannot be charged. In this case, intermittent charging is performed, but the charging opportunity can be increased as compared with a case where charging cannot be performed at all. It is particularly suitable when the solar cell panel is a dye-sensitized solar cell (DSC) that can be used at low illuminance.

  Further, the design panel of the present invention includes a charging circuit that charges a secondary battery that uses a solar cell as a power source and energizes the light emitting element with the output power, and the charging circuit uses the output power of the solar cell as the power. A DC-DC converter that converts the secondary battery into a predetermined charging voltage and charging current, and an output voltage of the solar battery is monitored, and the DC-DC converter is operated so that the output voltage is constant. Thus, the second converter control circuit for performing MPPT control for operating the solar cell at the maximum power point, and detecting the rise of the output voltage due to the start of the solar cell, over the predetermined time from the rise timing, And a third converter control circuit for setting the MPPT control by the second converter control circuit to a minimum load state.

  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. When a second converter control circuit that performs MPPT control on the DC-DC converter is provided, the DC-DC converter starts operating when the output voltage of the solar cell rises, and the second converter control circuit performs MPPT control. The MPPT control operates under a relatively large load, and when the load is connected to the solar cell via the DC-DC converter, the output voltage of the rising solar cell rapidly decreases, As a result, the DC-DC converter is locked out (cannot start up).

  Therefore, a third converter control circuit is provided to detect the rise of the output voltage due to the start-up of the solar cell, and the MPPT control by the second converter control circuit is performed in a minimum load state over a predetermined time from the rise timing. Let me. Specifically, even if the illuminance of sunlight is different, the voltage at the point where the solar cell is the maximum power point is substantially equal, and a difference in output power is generated between the output currents. The DC converter is operated to have a minimum output (charge) current.

  Therefore, even if the charging circuit starts operating with weak sunlight, the DC-DC converter can be started up normally (the operation is started) without being locked out. It is particularly suitable when the solar cell panel is a dye-sensitized solar cell (DSC) that can be used at low illuminance.

  As described above, the design panel according to the present invention is a design panel that can be self-illuminated (internally lit) using a solar cell independently (without power supply from the outside). The design panel part and the solar cell panel part are produced separately, for example, stacked on the front and back so that they are placed on the windows, or formed into a rectangular shape and connected on one side to open and close It can be freely opened and arranged like a mountain-shaped calendar, or it can be opened small and arranged like a folding screen.

  Therefore, an arbitrarily fine design can be given to the design panel part, and the solar cell panel part can be used as it is, and only the design panel part can be changed (replaced). In addition, it can be used in various ways according to the demands of designers and advertisers, and can be developed for new applications.

It is a perspective view of the design panel which concerns on one Embodiment of this invention. It is a figure of the panel block in the said design panel. It is a figure of one Embodiment of the said panel block. It is a front view of the light guide plate of one Embodiment used as a light guide plate of the said panel block. It is a front view of the light-guide plate of other embodiment used as a light-guide plate of the said panel block. It is a perspective view of the design panel which concerns on the other form of implementation of this invention. It is a perspective view of the design panel which concerns on the other form of implementation of this invention. It is a block diagram which shows the electric constitution of the charging circuit which concerns on one Embodiment of this invention. It is a graph which shows the output characteristic of a solar cell. It is a block diagram which shows typically only the structure of the charge stop at the low illumination intensity in the said charging circuit. It is a figure for demonstrating the function of the said charge stop. It is a graph which shows the output characteristic of a solar cell. It is a wave form diagram for demonstrating operation | movement of the monostable multivibrator circuit in the said charging circuit. It is a block diagram which shows typically only the structure which performs MPPT control in the said charging circuit, and its lockout prevention control. It is a figure for demonstrating the said MPPT control and a lockout prevention control function. It is a block diagram which shows typically only the structure which performs the prohibition control by the overcharge protection function in the said charging circuit, and its battery absence (no load) detection. 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 wave form diagram for demonstrating the battery discharge control function in the charging circuit shown in FIG. It is a block diagram which shows typically the structure relevant to the battery discharge control function in the charging circuit shown in FIG.

(Embodiment 1)
FIG. 1 is a perspective view of a design panel 101 according to an embodiment of the present invention. 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. As a power source for the internal illumination to be lit, a solar cell panel is provided on the back side, and a charging circuit and a secondary battery described later are provided in the lower part.

  2A and 2B are views of the panel block 102, where FIG. 2A is a front view and FIG. 2B 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 a charging circuit 108 is disposed on the other side. A battery box is disposed below the circuits 107 and 108. 109 is provided. In the battery box 109, for example, two AAA secondary batteries are accommodated in series.

  For example, the height H3 of the circuits 107 and 108 is 25 mm, and the height H4 including the battery box 109 is 45 mm. On the outer side of the charging circuit 108, a switch 110 for switching whether or not to use the internal illumination of the design panel 101, and a light emitting diode D31 indicating a charging state and a light emitting diode D32 indicating a full charge, as will be described later. Is provided. In the example shown in FIGS. 1 and 2, the circuits 107 and 108 and the battery box 109 are mounted with the panel block 102 extended, but may be housed in the support member 103.

  FIG. 3 is a view of one embodiment of the panel block 102, (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. 3B, in order to facilitate understanding of the laminated structure of the panel block 102 as described above, the thickness is emphasized (drawn thicker) than in FIGS.

  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.

  FIG. 4 is a front view of a light guide plate 114 a according to an embodiment used as the light guide plate 114. The light guide plate 114a is configured such that, for example, an 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. The illumination light incident from the LED board 106 is repeatedly reflected in the thickness direction of the light guide plate 114a and propagates in the surface direction, and is taken out in the thickness direction only at the uneven portion 117, that is, only the design portion 104. Then, the reflection plate 115 restricts the take-out direction only to the front surface side and irradiates from the back side of the decorative panel 112.

  On the other hand, FIG. 5 is a front view of a light guide plate 114 b of another embodiment used as the light guide plate 114. The light guide plate 114b is configured by forming dots 118 on the entire surface of a transparent resin plate 116 having a thickness of 3 mm, for example. The dots 118 are formed by screen printing or the like. Further, the dots 118 are formed so that the LED substrate 106 side (lower side), which is a light source, is rough and the opposite side (upper side) is dense, and compensates for a decrease in the amount of light due to a distance difference. Are configured to shine substantially uniformly. The illumination light incident from the LED substrate 106 is repeatedly reflected in the thickness direction of the light guide plate 114b and propagates in the surface direction, is taken out in the thickness direction by the dots 118, and is taken out by the reflecting plate 115. The direction is limited to the front side only, and irradiation is performed from the back side of the decorative panel 112. As the light guide plate 114b, an acrylic plate that emits light only by entering light from an edge is used even when the dot 118 is not formed on the surface when the light propagating in the surface direction is taken out in the thickness direction. May be.

  By comprising in this way, the decoration panel 112 can be illuminated locally or entirely with the illumination light of edge light, and the design part 104 of the said decoration panel 112 can be made to stand out effectively. it can.

  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 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. Therefore, a simple design (characters, figures, designs, etc.) due to the difference of the pigment can be formed on the light receiving surface on the solar cell panel 121.

  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. When the switch 110 is turned on, the solar cell panel unit 121 generates power while the illuminance level is high, the secondary battery is charged by the charging circuit 108, and when the illuminance level is low, the LED control circuit 107 is activated. As described above, the LED of the LED substrate 106 is turned on by the power of the secondary battery, and the design portion 104 of the decorative panel 112 is made to stand out.

  Therefore, the design panel 101 of the present embodiment is a design panel that can be self-illuminated (internally illuminated) using a solar cell (without power supply from the outside), and the design panel also serves as a solar cell. The design panel unit 111 and the solar cell panel unit 121 are individually manufactured, and the design panel unit is not a configuration in which the solar cell panel is simply connected to the design panel, for example, as seen at a bus stop or the like. 111 and the solar cell panel part 121 are connected and used as a single unit, so that the design panel part 111 can be given an arbitrary fine design, and the design panel part 111 is left as it is. It is also possible to change (exchange) only. In addition, it can be used in various ways according to the demands of designers and advertisers, and can be developed for new applications. Furthermore, the design panel 101 according to the present embodiment does not require special maintenance, and is maintenance-free and can be charged with sunlight and illuminated using the charging power.

  In the above-described embodiment, the design panel unit 111 is an edge light (internal illumination) type design panel using the LED substrate 106, but a self-luminous design panel using an organic or inorganic EL element or the like. It may be.

(Embodiment 2)
6 and 7 are perspective views of design panels 201 and 301 according to another embodiment of the present invention. These design panels 201 and 301 are similar to the above-described design panel 101, and corresponding portions are denoted by the same reference numerals and description thereof is omitted. While the above-described design panel 101 has the design panel portion 111 and the solar cell panel portion 121 laminated back to back, these design panels 201 and 301 have the design panel portion 111 and the solar cell panel portion 121. Are formed in a rectangular shape, connected on one side, and back-to-back with each other in a U-shape (FIG. 6) or opposite each other in a U-shape (FIG. 7).

  That is, the design panel unit 111 and the solar cell panel unit 121 are connected on one side so that they can be opened and closed. The design panel 201 shown in FIG. 6 is obtained, for example, an arrangement like a mountain calendar placed on a desk. On the other hand, the structure opened in the shape of mutual (V) at a small angle θ2 is the design panel 301 of FIG. Even if it comprises in this way, the design panel part 111 can give an arbitrary fine design arbitrarily, and the solar cell panel part 121 is left as it is, and the usage which changes (exchanges) only the design panel part 111 Is also possible. In addition, it can be used in various ways according to the demands of designers and advertisers, and can be developed for new applications.

  Furthermore, since the solar cell panel unit 121 is made of a dye-sensitized solar cell (DSC), the dye-sensitized solar cell (DSC) has more restrictions (becomes simpler) than the design panel unit 111, Since it is possible to form a design based on the difference in the pigment on the light receiving surface, the design can be formed on both surfaces together with the design panel unit 111. In particular, a dye-sensitized solar cell (DSC) is suitable for indoor use with low illuminance, and in the case of an arrangement such as the mountain-shaped calendar or folding screen, the design on two sides can be easily visually recognized. is there.

  In the design panels 201 and 301, the LED control circuit 107, the charging circuit 108, and the battery pack 109 are one of the design panel unit 111 and the solar cell panel unit 121 (the solar cell panel unit 121 in the examples of FIGS. 6 and 7). ).

(Embodiment 3)
Next, the charging circuit 1 which is a specific example suitable as the charging circuit 108 will be described below. FIG. 8 is a block diagram showing an electrical configuration of charging circuit 1 according to the embodiment of the present invention. The charging circuit 1 uses the solar battery 8 as a power source and charges the secondary battery 9 with the output power. The solar cell 8 is a dye-sensitized solar cell (DSC) that includes the solar cell panel unit 121 and can generate power with low illuminance and can be used indoors as described above. As the secondary battery 9, two single AAA secondary batteries housed in the battery box 109 can be used, and a nickel metal hydride battery can be used. Therefore, the rated voltage is 1.2V × 2 = 2.4V.

  The charging circuit 1 generally includes a DC-DC converter 2 that converts the output power of the solar battery 8 into a predetermined charging voltage and charging current that are given to the secondary battery 9, and the DC-DC converter 2. And control circuits 3 to 7.

  The DC-DC converter 2 includes a converter IC 21, an input voltage limiting circuit 22, a constant voltage circuit 23, diodes D21 to D23, resistors R20 to R29, smoothing capacitors C21 and C22, capacitors C23 to C29, and an inductor. L21. The output voltage of the solar cell 8 is output between the high-side power supply line K1 and the common GND line K2. The power supply line K1 is provided with a backflow prevention diode D21 and an input resistor R23, and an input voltage limiting circuit 22 and a smoothing capacitor C21 are connected between the power line K1 and the GND line K2 downstream of the diode D21. On the downstream side of the input resistor R23, there is provided a capacitor C24 for removing noise due to resonance described later. The input voltage limiting circuit 22 includes a series circuit of a Zener diode D24 and a diode D25. Thus, the output voltage of the solar cell 8 is input to the power supply input terminal IN of the converter IC 21 with the maximum voltage limited to 5.5 V even for lightning.

  Using the input voltage, converter IC21 performs a step-up / step-down operation using inductor L21 and capacitors C24 and C26 externally connected to terminal L from between input resistor R23 and diode D21, and drives a large capacity load. A voltage of 3.3 to 2.6 V is output from the output terminal OUT, and a charging voltage of approximately 3.0 V is output from the noise removing capacitor C26 to the power supply line K3 via the diode D22 and the resistor R26. To do. A secondary battery 9 is connected between the power supply line K3 and the common GND line K2.

  The converter IC 21 supplies control power from the external power output terminal Vaux, which is its own power supply, to the power supply line K4 via the diode D23 and the resistor R27. A smoothing capacitor C22, a noise removing capacitor C28 and a constant voltage circuit 23 are connected between the power supply line K4 and the GND line K2. The constant voltage circuit 23 includes voltage dividing resistors R28 and R29 and a shunt regulator D26. Thus, the control power supplied to the other control circuits 3 to 7 is stabilized at 3.9V.

  Furthermore, a resistor R20 and a capacitor C29 are connected in series between the power supply line K3 and the GND line K2, and the power supply line K5 is drawn from the connection point between them. Therefore, the voltage of the secondary battery 9 is stabilized and output between the power supply line K5 and the GND line K2, and this power supply voltage is output from the external power supply output terminal of the converter IC 21 at low illumination or at night. Since the output voltage from Vaux becomes unstable, it is used as a power source for the comparators 32, 43, 72 and the operational amplifier 53 described later (in FIG. 1, the power sources for the comparators 43, 72 are omitted). The comparators 32 and 72 are sealed in one package, and the comparator 43 and the operational amplifier 53 are sealed in one package. Since the current consumption of these circuits is about 15 μA in total, the secondary battery 9 The impact on the discharge is small.

  The control circuit 3 performs an overcharge protection operation on the DC-DC converter 2, and includes a reference voltage circuit 31, a comparator 32, resistors R301, R302, R31 to R37, capacitors C31, C32, and a switch. Elements Q31 to Q33, a transistor Q34, and light emitting diodes D31 and D32 are provided. The reference voltage circuit 31 includes resistors R38 to R40 connected in series between the lines K4 and K2, and a shunt regulator D33. The shunt regulator D33 controls the voltage at the connection point between the resistors R38 and R39 according to the voltage at the connection point between the resistors R39 and R40. Thus, the reference voltage circuit 31 is supplied from the control power supply of 3.9V. A reference voltage of 1.65 V is created and applied to the non-inverting input terminal of the comparator 32 via the input resistor R31.

  The comparator 32 is supplied with power from the power supply line K5 and is a voltage obtained by dividing and smoothing the charging voltage output between the lines K5 and K2 input to the inverting input terminal by the resistors R301 and R302 and the capacitor C31. And the 1.65V reference voltage, and when the charging (divided) voltage becomes equal to or higher than the reference voltage, an overcharge protection operation for stopping the DC-DC converter 2 is performed. The overcharge protection operation is performed by setting the output terminal of the comparator 32 connected to the power supply line K4 by the pull-up resistor R32 to a low level (short circuit to the GND line K2). The output terminal of the comparator 32 is set to high level (open). A feedback resistor R33 is provided between the output terminal and the non-inverting input terminal of the comparator 32, and the comparator 32 includes a Schmitt trigger circuit having hysteresis.

  The output of the comparator 32 is given to the gate of the switch element Q31. The drain of this switch element is connected to the power supply line K4 via the resistor R34, and is connected to the base of the transistor Q34, and the source is the GND. Connected to line K2. The collector of the transistor Q34 is connected to a connection point between the resistor R35 and the capacitor C32 connected in series between the lines K4 and K2, and is also connected to the enable terminal EN of the converter IC21. The emitter of the transistor Q34 is connected to the GND line K2.

  Accordingly, when the charging voltage is low and the comparator 32 outputs a high level, the switch element Q31 is turned on, the base voltage of the transistor Q34 is lowered, the transistor Q34 is turned off, and the enable terminal EN of the converter IC21 is turned on. Becomes high level, and the converter IC 21 operates. On the other hand, when the charging voltage increases to an overcharge level (over 3.0 V), the comparator 32 outputs a low level, the switch element Q31 is turned OFF, and the base voltage of the transistor Q34 is changed by the resistor R34. Pulled up, the transistor Q34 is turned on, the enable terminal EN of the converter IC21 becomes low level, the converter IC21 stops operating, and the overload is performed by disconnecting the load (power supply line K3 to the secondary battery 9). A protection operation is performed.

  Further, the control circuit 3 is provided with two light emitting diodes D31 and D32 as display elements for displaying the state of charge. The light emitting diode D31 indicating charging is connected between the output terminal OUT of the converter IC21 and the line K2 by a series circuit of the light emitting diode D31, the current limiting resistor R36, and the switch element Q32. On the other hand, the light-emitting diode D32 indicating full charge stops the converter IC 21 when full charge occurs. Therefore, a current limiting resistor R37, between the power supply line K3, that is, the positive electrode of the secondary battery 9 and the GND line K2, The light emitting diode D32 and the switch element Q33 are connected by a series circuit.

  The output of the comparator 32 is given to the gate of the switch element Q31. Therefore, when the charging voltage is low and the comparator 32 outputs a high level, the switch element Q32 is turned on and the light emitting diode D31 is lit. On the other hand, the gate of switch element Q33 is connected to the drain of switch element Q32. Therefore, the switch element Q33 performs an inverting operation with the switch element Q32. When the switch 32 is fully charged and the comparator 32 outputs a low level, the switch element Q33 is turned on and the light emitting diode D32 is lit.

  In addition to the basic charging circuit configured as described above, in the charging circuit 1 of the present embodiment, first, a control circuit 4 is added. The control circuit 4 functions as a stop circuit for the DC-DC converter 2 at low illuminance. The control circuit 4 includes voltage dividing circuits 41 and 42, a comparator 43, an output switch element Q41, a pull-up resistor R41, and a feedback resistor R42.

  The voltage dividing circuit 41 is configured by voltage dividing resistors R43 and R44 connected in series between the lines K1 and K2. The voltage dividing circuit 41 divides the output voltage of the solar cell 8 by a predetermined voltage dividing ratio. Give to the inverting input terminal. Similarly, the voltage dividing circuit 42 is configured by voltage dividing resistors R45 and R46 connected in series between the lines K5 and K2, and the internal drive voltage of the 3.9V DC-DC converter is determined in advance. The voltage is divided by the voltage dividing ratio and supplied to the non-inverting input terminal of the comparator 43. The output terminal of the comparator 43 is connected to the power supply line K4 by a pull-up resistor R41, and is connected to a non-inverting input terminal via a feedback resistor R42. Thus, the comparator 43 is positively fed back to form a Schmitt trigger circuit and has hysteresis.

  The output of the comparator 43 is given to the gate of the output switch element Q41, the source of the output switch element Q41 is connected to the GND line K2, and the drain is connected to the low voltage of the converter IC21 via the resistor R22 in the DC-DC converter 2. The voltage is applied to the voltage lock terminal LVLO. The low voltage lock terminal LVLO is connected to the power supply line K1 through a pull-up resistor R21. The converter IC 21 operates when the input voltage of the low voltage lock terminal LVLO is 250 mV or higher, stops when the input voltage is lower, and disconnects the load (secondary battery 9).

  Therefore, the comparator 43 outputs a low level when the divided voltage of the output voltage of the solar cell 8 from the voltage dividing circuit 41 is equal to or higher than the divided voltage of the internal drive voltage from the voltage dividing circuit 42, and the output switch element. Q41 is turned OFF, the low voltage lock terminal LVLO of the converter IC21 is pulled up, and the converter IC21 operates. On the other hand, when the divided voltage of the output voltage of the solar cell 8 from the voltage dividing circuit 41 is less than the divided voltage of the internal drive voltage from the voltage dividing circuit 42, the comparator 43 outputs a high level, The output switch element Q41 is turned ON, the low voltage lock terminal LVLO of the converter IC 21 becomes low level, and the converter IC 21 stops.

  Then, by the configuration of the Schmitt trigger circuit, the comparator 43 operates the converter IC 21 at a level where the output voltage of the solar cell 8 becomes 5V, for example, and stops the converter IC 21 at a level where it becomes 3.5V. In this way, the operation of the converter IC 21 can be stabilized against illuminance fluctuation at low illuminance.

  Here, FIG. 9 shows the output characteristics of the solar cell. As shown in FIG. 9, when the illumination light is strong, the solar cell can input a large current Ia at the voltage Va to the DC-DC converter. However, when the illumination light is weak, the current Ib is small at the voltage Vb. Only power can be input.

  On the other hand, the output power Po is determined by the product of the charging current Ib and the charging voltage Vb. If the input power from the solar cell is Pi and the conversion efficiency of the DC-DC converter is η, the DC-DC converter functions normally when Pi ≧ Po / η is input to the DC-DC converter. In the case of Pi <Po / η, the DC-DC converter does not function and charging is not performed. Therefore, in the case of FIG. 9, the DC-DC converter functions normally and can be charged when Pi = Va · Ia, but stops and is not charged when Pi = Vb · Ib. That is, there is a problem that the DC-DC converter cannot be charged unless a certain amount of sunlight is obtained.

  Therefore, in the present embodiment, the control circuit 4 is provided, and the solar battery 8 is used as a power source, and the DC-DC converter 2 is charged in advance so that the secondary battery 9 outputs the output power Pi of the solar battery 8. When charging the secondary battery 9 by converting it into a voltage and a charging current, the control circuit 4 provides the control circuit 4 with respect to the DC-DC converter 2 that starts operation when the output voltage of the solar battery 8 rises. The output voltage of the solar cell 8 is monitored, and the output voltage is determined in advance (the load (secondary battery 9) can be driven) below a threshold voltage (basically, the maximum voltage of the solar cell≈Po / η). Stops the DC-DC converter, and starts the operation when the voltage exceeds the threshold voltage.

  Therefore, when the secondary battery 9 is connected to the solar battery 8 where the DC-DC converter 2 starts to operate, the output power Pi of the solar battery 9 rises to a level sufficient for driving the load (secondary battery 9). Therefore, it is possible to prevent a problem that the start-up failure occurs by repeatedly connecting the load before the output power of the solar cell 8 rises and further lowering the output voltage of the solar cell 8. Thereby, even when illumination light is weak, a DC-DC converter can be started reliably and a secondary battery can be charged. In addition, since the comparator 43 includes a Schmitt trigger circuit that is positively fed back, the operation of the comparator 43 can be provided with hysteresis, and the start-up operation can be performed more stably. In the charging circuit 1, only a configuration for stopping charging at such a low illuminance is schematically shown in FIG. 10.

  FIG. 11 is a diagram for explaining a function of the control circuit 4 as a stop circuit of the DC-DC converter 2. (A) shows the output voltage of the solar cell 9, and (b) shows the output of the DC-DC converter 2. FIG. 11 shows a case where the state of weak illumination light continues even after charging is started. When the DC-DC converter 2 is operating, the output voltage of the solar cell 9 is rapidly lowered, and the DC -The DC converter 2 is stopped and cannot be charged and restarted. In this way, the control circuit 4 stops the DC-DC converter 2 to perform intermittent charging. However, the charging opportunity can be increased as compared with the case where the charging cannot be performed at all due to the inability to start. When the illumination light becomes stronger, the control circuit 4 shifts the DC-DC converter 2 to continuous charging.

  Further, in the charging circuit 1 of the present embodiment, the output voltage of the solar cell 8 is monitored and the DC-DC converter 2 is operated so that the output voltage becomes constant, whereby the solar cell 8 is maximized. A control circuit 5 that performs MPPT control to operate at a power point is provided. In relation to the control circuit 5, a rise of the output voltage due to the activation of the DC-DC converter 2 is detected, and predetermined from the rise timing. A control circuit 6 is provided for setting the MPPT control by the control circuit 5 to a minimum load state for a predetermined time. The control circuit 5 includes a voltage dividing circuit 51, a reference voltage circuit 52, an operational amplifier 53, resistors R51 to R53, and a capacitor C51.

  The voltage dividing circuit 51 is configured by voltage dividing resistors R54 and R55 connected in series between the lines K1 and K2. The voltage dividing circuit 51 divides the output voltage of the solar cell 8 by a predetermined voltage dividing ratio and inputs the input resistor R51. To the inverting input terminal of the operational amplifier 53. The reference voltage circuit 52 includes resistors R56 to R58 connected in series between the lines K4 and K2 and a shunt regulator D51, similarly to the reference voltage circuit 31 described above. The shunt regulator D51 controls the voltage at the connection point between the resistors R56 and R57 according to the voltage at the connection point between the resistors R57 and R58. Thus, the reference voltage circuit 52 is supplied from the control power supply of 3.9V. A reference voltage of 2.0 V is created and applied to the non-inverting input terminal of the operational amplifier 53 via the input resistor R51.

  The operational amplifier 53 is supplied with power from the power supply line K5, and the output thereof is output between the resistors R24 and R25 connected in series between the lines K3 and K2 in the DC-DC converter 2 via the output resistor R53. Given to connection points. The connection point is connected to the feedback terminal FB of the converter IC 21. The converter IC 21 controls the voltage of the output terminal OUT so that the input voltage to the feedback terminal FB becomes 500 mV. A capacitor C25 for stabilizing the voltage at the connection point is provided in parallel with the resistor R24. The output of the operational amplifier 53 is negatively fed back from the output resistor R53 via a feedback capacitor C51 and a feedback resistor R52.

  Here, FIG. 12 shows the output characteristics of the solar cell. The MPPT control is generally control for operating a solar cell at a maximum power point, and changes a load in accordance with the intensity of illumination light. And even if the output power is different, the voltage that becomes the maximum power point is substantially constant, so that a large amount of load current flows when the illumination light is strong, and a load current when the illumination light is weak. By reducing the size, the solar cell can be operated at the maximum power point. Specifically, the operational amplifier 53 compares the divided voltage of the output voltage of the solar cell 8 from the voltage dividing circuit 51 with the divided voltage of the internal power supply voltage from the reference voltage circuit 52 so that they are equal. Then, the voltage of the feedback terminal FB of the converter IC21 is changed.

  However, once the MPPT control is activated, charging of the secondary battery 9 can be continued even if the intensity of illumination light changes, but the solar battery 8 is connected to the secondary battery 9 (the DC-DC converter 2 is operated). When the illumination light is weak, the DC-DC converter 2 starts with a high power setting, so that a large load current flows suddenly and the output voltage of the solar cell 2 decreases, resulting in a DC -The DC converter 2 does not rise (locks out), and the MPPT control of the control circuit 5 does not work. Thereafter, when strong illumination light strikes, the DC-DC converter 2 starts to operate and the MPPT of the control circuit 5 starts to function, but there is a problem that charging cannot be performed during that time.

  Therefore, the control circuit 6 is provided. The control circuit 6 is composed of a monostable multivibrator circuit. Specifically, the control circuit 6 includes transistors Q61 and Q62, a switch element Q63, capacitors C61 and C62, resistors R61 to R66, and diodes D61 and D62.

  The capacitor C61 detects the activation of the DC-DC converter 2 as a pulse from the voltage of the output terminal OUT. The output of the capacitor C61 is given to the base of the transistor Q61 via the diode D61. Between the connection point between the capacitor C61 and the diode D61 and the GND line K2, a negative pulse is prevented from being applied to the transistor Q61 when the output voltage of the DC-DC converter 2 at the point A becomes 0V. A resistor R61 for differential (= pulse) output of the discharge diode D62 and the capacitor C61 is provided. The base of the transistor Q61 is connected to the GND line K2 through the resistor R62, and is connected to the gate of the switch element Q63 through the resistor R63. The emitter of the transistor Q61 is connected to the GND line K2, and the collector is connected to the power supply line K4 via the resistor R64, and is connected to one end of the capacitor C62 for time limit operation. The other end of the capacitor C62 is connected to the power supply line K4 via the resistor R65 and is also connected to the base of the transistor Q62. The emitter of the transistor Q62 is connected to the GND line K2, and the collector is connected to the power supply line K4 via the resistor R66 and also to the gate of the switch element Q63. The drain of the switch element Q63 is connected to the connection point between the resistors R54 and R55 in the control circuit 5, that is, the inverting input terminal of the operational amplifier 53 via the input resistor R51, and the source is connected to the GND line K2.

  FIG. 13 is a waveform diagram for explaining the operation of the control circuit 6 functioning as the monostable multivibrator circuit. In the stable state, as shown in FIG. 13 (d), the base of the transistor Q62 is pulled up by the resistor R65, the transistor Q62 is turned on, and its collector voltage is low as shown in FIG. 13 (e). At the level, the switch element Q63 is OFF.

  Therefore, the divided voltage of the output voltage of the solar cell 8 is applied to the voltage dividing point B in the voltage dividing circuit 51 in the control circuit 5, that is, to the inverting input terminal of the operational amplifier 53. As a result, the operational amplifier 53 outputs a voltage corresponding to the difference between the divided voltage of the output voltage of the solar cell 8 and the divided voltage of the reference voltage to the feedback terminal FB of the converter IC 21, and the DC-DC converter 2. The load state (output current) is controlled in a relatively large state. During this time, when the transistor Q62 is turned on, a charging current flows through the path of the resistor R62-capacitor C62-transistor Q62, and the capacitor C62 is charged to 3.9 V that is the voltage of the power supply line K4.

  Then, when the output voltage of the solar cell 8 rises and, as shown in FIG. 13A, the DC-DC converter 2 starts to operate and the output voltage at point A rises, it is shown in FIG. 13B. Thus, the start pulse is output from the capacitor C61. When this starting pulse exceeds the ON voltage of the transistor Q61 of 0.6V, the transistor Q61 is turned ON, and the collector voltage is reduced to approximately 0V as shown in FIG. As a result, as shown in FIG. 13D, the base voltage of the transistor Q62 is -3.9-0.6 = -3 by adding the charging voltage of the capacitor C62 that has been charged up to that time as a reverse voltage. After dropping to 3V, the voltage rises as the capacitor C62 is discharged. The time constant of the rise is set to τ = C62 * R65, for example, 90 msec, and becomes the time limit of this monostable multivibrator circuit.

  During the time limit in which the base voltage of the transistor Q62 is lower than 0.6V, the transistor Q62 is turned off, and its collector voltage becomes high level as shown in FIG. Element Q63 is turned on. Therefore, the voltage at the voltage dividing point B in the voltage dividing circuit 51 in the control circuit 5, that is, the voltage at the inverting input terminal of the operational amplifier 53 is reduced to approximately 0V. As a result, the operational amplifier 53 outputs a high level, the input voltage to the feedback terminal FB of the converter IC 21 increases, and the converter IC 21 operates in the minimum load state.

  When the time limit elapses, the base voltage of the transistor Q62 reaches 0.6V, the transistor Q62 is turned on, the switch element Q63 is turned off, and charging of the capacitor C62 is started. In this way, the control circuit 6 can realize the monostable multivibrator as described above. In the charging circuit 1, only a configuration for performing such MPPT control and lockout prevention control is schematically shown in FIG.

  FIG. 15 is a diagram for explaining the MPPT control of the DC-DC converter 2 by the control circuits 5 and 6 and its lockout prevention control function. (A) shows the output voltage of the solar cell 9, (b) shows the output of the DC-DC converter 2, and (c) shows the operation of the monostable multivibrator. Note that the drain potential of the switch element Q63, which is the output of the monostable multivibrator, is opposite to (c).

  Therefore, when the control circuit 5 that performs MPPT control of the DC-DC converter 2 is provided, the control circuit 6 is provided to detect the rise of the output voltage due to the activation of the DC-DC converter 2 and is predetermined from the rise timing. Over time, the MPPT control by the control circuit 5 is set to a minimum load state (in this embodiment, the DC-DC converter 2 is operated so as to have a minimum output (charge) current, so that weak illumination light is used. Even when the charging circuit 1 starts operating, the DC-DC converter 2 can be normally started up (operation is started) without being locked out.

  In the charging circuit 1 according to the present embodiment, after the control circuit 4 starts the operation of the DC-DC converter 2, the MPPT to the DC-DC converter 2 by the control circuit 5 is controlled by the control circuit 6 when the illuminance is low. Since the control is in the minimum load state, the DC-DC converter 2 and the MPPT control can be started up more reliably at low illuminance.

  Furthermore, in the charging circuit 1 of the present embodiment, a control circuit 7 that performs battery-free (no load) detection is provided in association with the control circuit 3 that performs an overcharge protection operation. The control circuit 7 includes a reference voltage circuit 71, a comparator 72, a resistor R71, voltage dividing resistors R75 and R76, a diode D71, and a switch element Q71. The reference voltage circuit 71 includes resistors R72 to R74 connected in series between the lines K5 and K2, and a shunt regulator D72. The shunt regulator D72 controls the voltage at the connection point between the resistors R72 and R73 in accordance with the voltage at the connection point between the resistors R73 and R74, and thus the reference voltage circuit 71 is supplied from the control power supply of 3.9V. A reference voltage of 1.65 V is created and applied to the inverting input terminal of the comparator 72. The output voltage of the DC-DC converter 2, that is, the charging voltage of the secondary battery 9 is applied to the non-inverting input terminal of the comparator 72 by being divided by the voltage dividing resistors R 75 and R 76. The output terminal of the comparator 72 is connected to the power supply line K4 via the pull-up resistor R71, and is connected to the gate of the switch element Q71. The drain of the switch element Q71 is connected to the base of the transistor Q34 in the control circuit 3, and is connected to the drain of the switch element Q32 and the gate of the switch element Q33 via the diode D71. The source of the switch element Q71 is connected to the GND line K4.

  The reference voltage circuit 31 in the control circuit 3 creates the reference voltage of 2.0V at which the output voltage of the DC-DC converter 2, that is, the charging voltage of the secondary battery 9, becomes 3.0V. On the other hand, the reference voltage circuit 71 in the control circuit 7 creates the 3.42 V reference voltage to be compared with the output voltage of the DC-DC converter 2, that is, the charging voltage of the secondary battery 9. The comparator 72 outputs a low level when the charging voltage is lower than the reference voltage of the reference voltage circuit 71, and thereby the switch element Q71 is OFF. On the other hand, when the charging voltage becomes equal to or higher than the reference voltage of the reference voltage circuit 71, the comparator 72 determines that there is no load, that is, the secondary battery 9 is not connected, and outputs a high level. Overcharge protection operation by 3 is prohibited.

  Specifically, the switch element Q71 is turned OFF while the comparator 72 outputs a low level and the charging voltage is less than 3.42V. Therefore, the drain of the switch element Q71 is open, the switch element Q33 and the transistor Q34 operate as described above, and the overcharge protection operation is performed between 3.0 to 3.42 V, and the light emitting diodes D31 and D32 are also connected. Lights when charging and when fully charged.

  On the other hand, when the comparator 72 outputs a high level and the charging voltage becomes 3.42 V or more, the switch element Q71 is turned on. Therefore, the switch element Q34 remains OFF, the enable terminal EN of the converter IC21 becomes high level, invalidates the overcharge protection operation of the converter IC21, and turns off the switch element Q33 to turn on the light emitting diode D32. Is turned off, and the light emitting diode D31 is kept on.

  Thus, if the charging voltage is higher than the reference voltage of 3.42V, which is higher than the specified 3.0V, the control circuit 7 determines that the load (secondary battery 9) is not connected, and the control circuit 7 If the overcharge protection operation by 3 is invalidated and the overcharge protection operation is activated in such a case, the control circuit 3 performs the overcharge protection operation of the DC-DC converter 2 and stops the output or If it is made smaller, the charging voltage at the open end immediately decreases, the overcharge protection operation is canceled, the operation of the DC-DC converter 2 is started, and the overcharge protection operation is performed again. On the other hand, such a problem can be prevented.

  In addition, the control circuit 3 responds to the output of the comparator 32 and emits light when the charging voltage is less than the reference voltage of 3.0V to indicate that charging is in progress, and the charging voltage is 3.0V. In the no-load state, the two light emitting diodes D31 and D32 are alternately switched in response to the chattering in the above-described no-load state. In response to the output of the comparator 72 of the control circuit 7, a switching element Q32 is provided for fixing the display of the light emitting diodes D31 and D32 when the charging voltage is equal to or higher than the reference voltage of 3.42V. In this way, the user is not distrusted. In the charging circuit 1, only the configuration for performing such an overcharge protection function and prohibition control based on detection of no battery (no load) is schematically shown in FIG.

  Moreover, since the charging circuit 1 of the present embodiment can stabilize the operation of the DC-DC converter 2 at the time of low illuminance such as startup by providing the control circuits 4, 5, 6, as the solar cell 8, A silicon solar cell can also be used, but a dye-sensitized solar cell (DSC) advantageous for power generation at low illuminance can be preferably used, and is particularly suitable for indoor use at low illuminance.

(Embodiment 4)
FIG. 17 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. In the charging circuit 1a, first, the control circuit 3 is not provided with the light emitting diode D32 indicating full charge, that is, charging completion. This is to prevent power consumption from occurring after the converter IC 21 stops due to the full charge by causing the user to determine the completion of charging when the light emitting diode D31 indicating charging is turned off from the lighting state. It is a countermeasure. Therefore, in this charging circuit 1a, the current limiting resistor R37 and the switch element Q33 related to the light emitting diode D32 are not provided.

  Further, in the charging circuit 1a, a discharge control circuit 10 for the secondary battery 9 is provided. In the charging circuit 1 described above, the output voltage from the external power supply output terminal Vaux of the converter IC 21 becomes unstable at low illuminance, so that the overcharge is applied to the power supply line K5 where the voltage of the secondary battery 9 is stabilized and output. A comparator 32 for control and an operational amplifier 53 for MPPT control are connected. On the other hand, the charging circuit 1a is provided with power supply lines K6 and K7 that can be turned off when the output voltage of the converter IC 21 becomes 0 V at the time of the low illuminance, and supplies power to the power supply lines K6 and K7. The discharge control circuit 10 controls.

  The discharge control circuit 10 includes resistors R81 to R86, capacitors C81 and C82, a diode D81, and switch elements Q81 to Q83. The output voltage from the output terminal OUT of the converter IC 21 is divided by the voltage dividing resistors R81 and R82, stabilized by the capacitor C81, and applied to the gate of the switch element Q81. The source of switch element Q81 is connected to GND line K2, and the drain is connected to the gate of P-type switch element Q82 via resistor R84. A resistor R83 is provided between the gate and source of the switch element Q82, and the source is connected to the power supply line K3, and hence the positive electrode of the secondary battery 9.

  Therefore, when the electric charge is accumulated in the capacitor C81, that is, when the output voltage from the output terminal OUT becomes approximately 3V or more, the switch element Q81 is turned on, causing a potential difference between the gate and the source of the switch element Q82. The switch element Q82 is turned on. As a result, the voltage of the secondary battery 9 is output from the drain of the switch element Q82 to the power supply line K7, and the voltage of the secondary battery 9 is stabilized on the power supply line K6 by the resistor R86 and the capacitor C82. Is output.

  On the other hand, the capacitor C81 is connected to the power supply line K6 via a diode D81 and a resistor R85, and the connection point between the diode D81 and the resistor R85 can be grounded by a switch element Q83. The output of the comparator 32 is given to the gate of the switch element Q83. Therefore, during charging in which the charging voltage of the secondary battery 9 is low and the comparator 32 outputs a high level, the switch element Q83 is turned on to bypass the current from the resistor R85. On the other hand, when the comparator 32 is in a fully charged state that outputs a low level, the switch element Q83 is turned OFF, and the current from the resistor R85 is applied to the capacitor C81 via the diode D81. Thus, the ON state of the switch elements Q81 and Q82 is self-maintained by the current supplied from the switch element Q82 to the power supply line K6. When the charging voltage of the secondary battery 9 falls below the hysteresis level of the comparator 32 comprising the aforementioned Schmitt trigger circuit, the comparator 32 outputs a high level, charging is resumed, and the switch element Q83 is turned on, The self-holding state is canceled.

  Corresponding to such a discharge control circuit 10, the power supply line in the control circuit 3 that performs the overcharge protection operation is changed from K4 to K7, and the reference voltage of the reference voltage circuit 31 is also changed to the power supply. Supplied from line K6. In addition, the power source of the control circuit 7 that detects no battery (no load) is changed to the power source line K6, and the output voltage of the secondary battery 9 is obtained from the power source line K7. On the other hand, the detection of the power supply and charging voltage of the control circuit 4 that stops the DC-DC converter 2 is changed to the power supply line K4 from the external power supply output terminal Vaux of the converter IC21, and the operational amplifier 53 in the control circuit 5 that performs MPPT control. Is also changed to the power line K4.

  With this configuration, the DC-DC converter 2 stop function by the control circuit 4, the MPPT control function by the control circuit 5, and the lockout prevention control function by the control circuit 6, the external power output terminal of the converter IC 21 This is performed by supplying power from Vaux. Therefore, if the enable terminal EN terminal of the converter IC21 is at a high level, when the illuminance reaches a certain level (input voltage Vin> 0.5V from the solar cell 8), the voltage at the external power output terminal Vaux of the converter IC21 rises, Since each of the control circuits 4, 5, 6 that are fed is operated, when the DC-DC converter 2 outputs a specified high voltage, charging starts while those functions operate (overcharge detection). When the power supply voltage is not supplied to the control circuit 3, the transistor Q34 at the end of the control circuit 3 that performs the above operation is in an OFF state, so that the enable EN terminal maintains a high level state).

  However, as described above, the output voltage from the external power output terminal Vaux of the converter IC 21 to the power supply line K4 changes due to sunlight (0V at night) and becomes unstable at low illuminance. Therefore, in this embodiment, the overcharge detection function by the control circuit 3 and the no-load detection function by the control circuit 7 are operated by using the secondary battery 9 via the power supply lines K6 and K7 as a power source to stabilize the operation. ing. On the other hand, when the illuminance is low, such as at night, when the secondary battery 9 is not charged, only discharging is performed. Even if the current consumption is reduced as described above, the low illuminance is maintained for a long time. If the state continues, the accumulated value may not be ignored. Therefore, when the discharge control circuit 10 as described above is provided and the output voltage Vout of the output terminal OUT for driving the large-capacity load of the converter IC21 becomes 0V, the battery discharge control function operates and the power supply lines K6 and K7 are connected. By cutting off the power supply, undesired consumption of the secondary battery 9 is also prevented.

  When the converter IC 21 operates with high illuminance, power supply to the power supply lines K6 and K7 is resumed. When the converter IC 21 enters an overcharge (full charge) state, the converter IC 21 is stopped and the output voltage Vout is 0V ( However, the stop signal of the converter IC 21 is input from the comparator 32 to the control circuit 10 to keep the battery discharge control function stopped. Such an operation is shown in FIG. 18, (a) is the input voltage Vin from the solar cell 8, (b) is the output voltage Vout of the converter IC 21, and (c) is the overcharge (full charge) detection output, that is, the transistor Q34. (D) is a battery discharge control function, that is, a switch state of the switch element Q82. In the charging circuit 1a, a configuration related to such a battery discharge control function is schematically shown in FIG.

  When the night comes after the converter IC 21 stops charging due to overcharge (full charge), the power supply to the control circuits 3 and 7 continues, so the capacity of the secondary battery 9 decreases to some extent. However, when the overcharge release voltage slightly lower than the overcharge level is reached, the overvoltage detection is terminated, so that the self-holding is released, the power supply to these control circuits 3 and 7 is stopped, and 2 The secondary battery 9 is no longer discharged. The difference between the overcharge detection specified voltage and the overcharge release specified voltage is small, and therefore the consumption of the secondary battery 9 is slight.

1 Charging Circuit 2 DC-DC Converter 21 Converter IC
22 Input voltage limiting circuit 23 Constant voltage circuit 3 Control circuit 31 Reference voltage circuit 32 Comparator 4 Control circuit 43 Comparator 5 Control circuit 53 Comparator 6 Control circuit 7 Control circuit 72 Comparator 8 Solar cell 9 Secondary battery 10 Control circuit 101, 201, 301 Design Panel 102 Panel Block 103 Supporting Member 104 Design Part 105 Thin Panel 106 LED Board 107 LED Control Circuit 108 Charging Circuit 109 Battery Box 110 Switch 111 Design Panel 112 Decoration Panel 113 Light Diffusing Plate 114, 114a, 114b Light Guide Plate 115 Reflection Plate 116 Resin plate 117 Concavity and convexity 118 Dots 121 Solar cell panel portions 122 and 123 Substrate

Claims (8)

In a self-illuminated design panel using solar cells,
It has a design panel part and a solar cell panel part, and they are individually manufactured,
The design panel part and the solar cell panel part are overlapped with each other so as to be the front and back surfaces, or are formed in a rectangular shape and connected on one side, back to back in the shape of each other, or in the shape of each other. The design panel characterized by being arrange | positioned face-to-face.   The said solar cell panel part consists of a dye-sensitized solar cell, The design by the difference in a pigment | dye is formed in the light-receiving surface, The design panel of Claim 1 characterized by the above-mentioned. The design panel portion and the solar cell panel portion are arranged so as to be front and back,
The design panel section includes, from the surface side, a decorative panel on which a design is applied, a diffuser plate that diffuses illumination light, a light guide plate that propagates the illumination light, and a reflection plate, and a conductive plate. 3. The design panel according to claim 1, wherein a light emitting element is provided at an edge of the light plate.   In the light guide plate, the illumination light incident from the light emitting element is repeatedly reflected in the thickness direction and propagates in the surface direction, and printed dots are locally formed and taken out by the dot portions. The design panel according to claim 3, wherein the illumination light is irradiated from the back side of the decorative panel. The decorative panel has the design formed by halftone printing a desired plurality of colors,
The light emitting element has a light source of a plurality of colors,
The design panel according to claim 4, wherein the design selectively emits light by a combination of a printing color and a light source color. The design panel unit and the solar cell panel unit integrated on the front and back are used in a state of standing substantially vertically, and a lower side is provided with a support member for supporting them in the state of standing up,
A lighting circuit for lighting the light emitting element, a secondary battery for energizing the lighting circuit, and a charging circuit for charging the secondary battery with power generated by the solar cell panel unit include the design panel unit and the solar cell. The design panel according to claim 3, wherein the design panel is provided on a lower side of the battery panel portion or in the support member. A charging circuit for charging a secondary battery that uses a solar cell as a power source and energizes the light emitting element with its output power,
A DC-DC converter that converts the output power of the solar cell into a predetermined charging voltage and charging current for the secondary battery,
A first converter control that monitors the output voltage of the solar cell, stops the DC-DC converter during a period when the output voltage is less than a predetermined threshold voltage, and operates the DC-DC converter when the output voltage exceeds the threshold voltage. The design panel according to claim 1, further comprising a circuit. A charging circuit for charging a secondary battery that uses a solar cell as a power source and energizes the light emitting element with its output power,
A DC-DC converter that converts the output power of the solar cell into a predetermined charging voltage and charging current for the secondary battery,
A second converter control circuit that monitors the output voltage of the solar cell and performs MPPT control for operating the solar cell at a maximum power point by operating the DC-DC converter so that the output voltage is constant. When,
A third converter control circuit that detects a rise of the output voltage due to activation of the solar cell and sets the MPPT control by the second converter control circuit to a minimum load state for a predetermined time from the rise timing. The design panel according to any one of claims 1 to 7, wherein:

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