JPS5922460B2 - solar battery charging device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a solar cell charging device that allows a battery charged by a solar cell to be charged in an optimal state at all times.

Since solar cells can supply almost unlimited energy in the presence of light, they are widely used in artificial satellites, unmanned lighthouses, and small electronic devices.

Especially in the case of small electronic devices such as electronic watches,
As rechargeable batteries, there are products that use general nickel-cadmium batteries, silver oxide batteries, or mercury batteries under certain charging conditions, but all of them are miniaturized batteries. Therefore, the lifespan of the rechargeable battery tends to be shorter than that of a large rechargeable battery.Also, due to the operation of the electronic watch, the rechargeable battery is charged and discharged at the same time, which is a so-called floating state. Depending on the carrying conditions, there are factors that accelerate the deterioration of the rechargeable battery, such as an increase in the amount of light irradiated to the solar battery, resulting in overcharging, and the lifespan of the rechargeable battery is currently limited. , it is said to last about 5 to 6 years at most.
Furthermore, in order to reduce the above-mentioned factors, the optimal number of solar cells connected in series has already been set at the design stage, but during charging, all solar cells are irradiated with external light, and each solar cell is Since the battery is charged by the sum of the photovoltaic voltage of the battery, when the charging battery is sufficiently charged, that is, when sufficient voltage is secured to normally operate the load circuit such as a clock circuit, the solar If the battery is exposed to strong light for a long time, the number of solar cells set above can no longer cover the battery, and the rechargeable battery becomes extremely overcharged.As a result, the rechargeable battery swells due to the generation of gas, making it impossible to use it. Sometimes it becomes impossible. In addition, in order to prevent this, it is recommended to reduce the number of solar cells connected or increase the current limiting resistor connected to the charging circuit, that is, the charging current limiting resistor. When batteries are used in These disadvantages include the difficulty of maintaining the voltage necessary for the normal operation of load circuits such as the above for a long period of time.

An object of the present invention is to force a heavy load using the battery as a power source to discharge the battery for a predetermined time by an output signal of a voltage detection circuit that detects the voltage of the battery when a battery charged by a solar battery is in an overcharged state. Another object of the present invention is to provide a solar battery charging device that has a charging battery protection function that allows the battery to recover from an overcharged state in a short period of time.

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a plan view showing a solar powered wristwatch according to an embodiment of the present invention, in which 1 is a wristwatch case, and 2 to 4 are push buttons provided on the wristwatch case 1, each of which is a push button for selecting a correction digit. 2. Display switching function between hour and minute time display and month/day calendar display, push button 3 as a correction function when the correction digit is selected by push button 2, and push button 4 for illumination. It's summery. Reference numeral 5 denotes a windshield glass attached to the wristwatch case 1. The inner surface of the windshield glass 5 has a colored portion 5a, which separates the display portion.

Reference numeral 6 denotes a liquid crystal cell disposed under the windshield 5, which has a colored portion 61 applied to the surface of the liquid crystal cell 6 and is divided into a time display portion 6a and a light valve portion 6b.

In the figure, the time display section 6a shows 12:35, and the light valve section 6a shows 12:35.
b shows the state in which the light valve is open. Reference numeral 6c indicates a pair of transparent electrodes for the light valve formed on the upper and lower glass substrates of the light valve section 6b, and 7a indicates a hole in the reflection plate 7 disposed below the liquid crystal cell 6, so that the light valve of the light valve section 6b When open, the solar cell 8g placed under the reflecting plate 7 is configured to be irradiated with light through the hole 7a, and when the light valve of the light valve section 6b is closed, the solar cell 8g placed under the reflecting plate 7 is irradiated with sunlight. The light that should be irradiated onto the battery cell 8g is blocked by the light valve section 6b.

8a to 8f are solar cells arranged planarly offset from the liquid crystal cell 6, and are electrically connected in series with the solar cell 8g.

Reference numeral 9 denotes a partition plate in which through holes 9a are formed corresponding to the positions where the liquid crystal cell 6 and the solar cells 8a to 8f are arranged.

FIG. 2 is a cross-sectional view showing the movement of the solar powered wristwatch shown in FIG. A solar cell circuit board 11 on which cells 8a to 8f are mounted is mounted. 11a is a position regulating pin implanted in the solar cell circuit board 11;
Connection springs b and 11c are fixed to the lower surface of the solar cell circuit board 11, and are connected to a wiring pattern (not shown) formed on the watch circuit board 12.

In addition, as other embodiments, these connection springs 11b and 11c
Conductive rubber can also be used instead. Reference numeral 9 denotes a partition plate that allows only the solar cells 8a to 8f and the liquid crystal cell 6 to be seen from the display surface side, as described above, and is fixed to the upper surface of the substrate 10.

13a and 13b are conductive rubber in which conductive parts and insulating parts are alternately laminated, and each lead electrode (not shown) of the liquid crystal cell 6
The structure is such that the liquid crystal cell 6 is electrically connected to a wiring pattern (not shown) on the watch circuit board 12, and the liquid crystal cell 6 is elastically pressed and held against the board 10 side.

Reference numeral 14 denotes an acrylic light guide plate disposed only under the time display section 6a, which is used to uniformly illuminate the time display section 6a with light from the lamp 34, and is disposed below the light valve section 6b. Not yet.

The reflecting plate 7 is disposed below the light guide plate 14, and has a hole 7a extending to the lower part of the light valve part 6b and forming a parting frame of the solar cell 8g. 15 is an IC chip disposed on the watch circuit board 12, 16 is a battery, and 17 is a metal plate, which serves as a reinforcing board for the watch circuit board 12 and a spring portion 17a that presses and holds the side surface of the battery 16.
is formed.

18 is a board made of plastic material, and a battery 1 is placed in the center.
6, and serves as a positioning member for other timepiece parts (not shown) and as a cover member on the back side of the movement.

Reference numeral 19 denotes a tube embedded in the substrate 18, which is connected to the metal plate 1.
7. It is provided for laminating the substrate 10, the parting plate 9, etc., and is held and fixed by screws 20.

FIG. 3 is a cross-sectional view showing the vicinity of the light valve part 6b of the liquid crystal cell 6 in more detail, where 6d is the first polarizing plate, 6e is the upper glass substrate, and 6c is formed on the surface of the upper glass substrate 6d and subjected to alignment treatment. 6f is a lower glass substrate, 6C2 is a transparent electrode formed on the surface of the lower glass substrate 6f and subjected to alignment treatment, 6g is a second polarizing plate, 6h is an upper and lower glass substrate 6d,
The periphery of the glass substrate 6f is joined by a sealing member 61, and a twisted nematic liquid crystal having an electric field effect is filled in the gap between the two glass substrates 6d and 6f.

Further, below the light valve section 6b of the liquid crystal cell 6, a reflecting plate 7 having a hole section 7a is arranged. Note that the light guide plate 14 indicated by a dotted line in the figure is disposed only below the time display section 6a, and does not need to be disposed below the light valve section 6b. Further, under the reflecting plate 7 corresponding to the hole 7a, a solar cell 2 ==
::↑Replacement weight: Shun - The mounting structure for mounting can be achieved by soldering the wiring patterns 12a, 12b formed on the watch circuit board 12 and the electrodes of the solar cell 8g, or as in this example. The wiring patterns 12a, 12 are coated with a conductive paint made of a mixed solution of carbon and vinyl acetate ethylene or a mixed solution of carbon and urethane solution with an epoxy adhesive added.
8g of solar cells are placed on the conductive paint in a non-dry state before the conductive paint solidifies, and then the conductive paint is solidified and fixed by air drying or heat drying.

In particular, a mixed solution of carbon and vinyl acetate ethylene, or a mixed solution of carbon and urethane solution with epoxy adhesive has a considerable adhesion strength by itself, and also has high elasticity and conductivity after solidification, so it can be easily damaged by impact, etc. A shock-resistant mounting structure suitable for electrically and mechanically connecting and fixing 8 g of brittle solar cells that are easily broken is provided. In addition, the mounting structure of solar cells using this conductive paint is as follows:
It is also applied to the mounting structure of the solar cell circuit board 11 mounted on the solar cell circuit board 11 (although not shown). Here, if the amount of incident light on the light valve part 6b is called LOl and the amount of irradiation light transmitted through the light valve part 6b and incident on the surface of the solar cell 8g is called L1, then the transmittance ε of the light valve part L6b is ε=-1×10
For example, when the polarization axes of the first polarizing plate 6d and the second polarizing plate 6g are arranged to be orthogonal to each other, as shown in FIG. The transmittance ε is the liquid crystal applied voltage V applied between the transparent electrodes 6c, 6c2.
It can be seen that the transmittance ε significantly changes depending on the value of , and the light valve section 6b can be sufficiently operated as a light valve by controlling the voltage V applied to the liquid crystal.

Note that the light valve operation of the light valve section 6b does not necessarily require that the polarization axes of the polarizing plates 6C1 and 6C2 be orthogonal to each other as in this embodiment.
Polarizing plate 6C1 is used to tilt the polarization axes of 1 and 6C2, or to reverse the direction of the liquid crystal applied voltage V and the light valve operation.
It is also possible to set the polarization axes of and 6C2 to be parallel to each other. At this time, if the polarization axis taken by the time display part 6a of the liquid crystal cell 6 and the polarization axis taken by the light valve part 6b are different, the polarizing plates 6C1 and 6C2 are used for the time display part 6a and the light valve part 6b, respectively.
It is preferable to provide a separate body corresponding to the above. Furthermore, as shown in FIG. 5, the solar cell 8g has the characteristic that the photovoltaic current D increases extremely with an increase in the irradiation light amount L1 of the solar cell 8g. The amount of irradiation light incident on the solar cell 8g can be adjusted by appropriately changing the voltage V applied to the liquid crystal according to the amount of charge of the battery 16 being charged, that is, the battery voltage, and accordingly changing the transmittance ε of the light valve portion 6b. It is understood that L1 was regulated and controlled so that the battery 16 could always be charged in an optimal state. That is, when the battery voltage of the solar cells 8a to 8g is higher than a certain first set voltage value, an operating point N is set at which the voltage V applied to the liquid crystal of the light valve part 6b is set to V=1, and the light is turned off. The light valve is closed in a direction that reduces the transmittance ε of the valve part 6b, and when the voltage of the battery 16 falls below a certain first set voltage value, the liquid crystal applied voltage is immediately set to 0.
The operating point N. , and the transmittance ε of the light valve portion 6b is
The light valve is opened in a direction that increases the transmittance ε, and the amount of irradiated light L1 is automatically controlled by increasing or decreasing the transmittance ε, so that the battery 16 is always charged in an optimal state, and furthermore, the voltage is lower than the first set voltage. When the battery voltage drops below the second set voltage, the time display section 6a displays the time.
It is configured such that an instruction to irradiate light to the solar cells 8a to 8g, which also serves as a battery life warning display function, is given as a blinking display state with a second period, that is, a display modulation state. The specific circuit configuration of this solar battery wristwatch will be explained below. FIG. 6 is a circuit diagram of a solar battery wristwatch showing an embodiment of the present invention, in which 21 is a crystal resonator, 23 is an oscillation circuit that outputs an oscillation frequency signal of 32768 Hz by the connection configuration of the crystal resonator 22, and 23 is a 15-bit oscillation circuit. It consists of a frequency divider with a 64Hz signal PO from the middle stage and a 1H signal from the rear stage.
A frequency dividing circuit that outputs the signal P1 of z, 24 indicates seconds, minutes, hours,
25 is a decoder; 26 is a drive circuit for driving the time display section 6a of the liquid crystal cell 6; The drive circuit 26 keeps the time display section 6a in a constant display state as shown in the figure, and when the signal A takes zero, the drive circuit 26 uses the output of the NAND gate 27 to display the time display section 6a for 1 second while displaying the time. It is configured to take on a periodic blinking display state.

28 is a signal P.

And the signal P2 with a period of 1 minute from the counter 24 is input, and the pulse width of the waveform is 1/64 seconds and the period is 1 as shown in FIG.
29 is a signal P.
and a waveform shaping circuit which inputs a signal P1 with a period of 5 seconds from the counter 24 and outputs a signal φ2 with a waveform pulse width of 1/64 seconds and a period of 5 seconds as shown in FIG. 8; the oscillation circuit 22
, the frequency dividing circuit 23, the counter 24, and the waveform shaping circuits 28 and 29 constitute a sampling signal generating means. 30 is a time adjustment control circuit which receives as input the opening/closing signals of the switch 2a interlocking with the push button 2 and the switch 3a interlocking with the push button 3; 4a is a switch interlocking with the push button 4; 31 is the opening/closing signal of the switch 4a; 0R gate inputs signal B, which will be described later; 32 is a resistor connected between the output terminal of 0R gate 31 and the base of lamp driving transistor 33; 34 is a resistor for illuminating time display section 6a of liquid crystal cell 6; Lamp, 8 is solar cell 8a~
8g connected in series, battery 1 is connected through 35 reverse current prevention diodes and 36 current limiting resistors.
6 is connected and configured to charge the battery.

A control circuit 37 is supplied with power from the battery 16 and receives signals φ from the waveform shaping circuits 28 and 29.
1 and φ2 as inputs, and outputs signals A and B according to the battery voltage E of the battery 16.

38 is a drive circuit that drives the light valve section 6b by the signal B. When the signal B is SO'' (:1), the light valve section 6b opens the light valve, and when the signal B is SO'', the light valve section 6b opens the light valve. The light valve is driven in the direction of closing.

FIG. 7 is a circuit diagram showing in detail the configuration of the control circuit 37 in FIG. 6, where 39 is a switching circuit that switches and outputs either signal φ1 or φ2 according to the output signal of an AND gate 40, which will be described later; is an AND gate which inputs the signals λ and B and obtains a signal for operating the switching circuit 39;
41 and 42 are 0R gates;
2 is connected to receive the output of the switching circuit 39, the other input of the 0R gate 41 is supplied with the signal B, and the other input of the 0R gate 42 is supplied with the signal B. A is supplied. 43 is a voltage detection circuit, which receives the output of the 0R gate 41 as an input.
Channel MOS transistor 43a (hereinafter simply PMOS)
Tr), an adjustment resistor 43b connected to the drain side of the PMOSTr 43a, and an inverter 43c.
A second set voltage value of 35 volts is set, and a voltage detection operation on the low voltage range side of the battery 16 is performed using the sampling signal that is the output of the 0R gate 41.

44 is a voltage detection circuit, which includes a PMOSTr44a inputting the output of the 0R gate 42, an adjustment resistor 44b connected to the drain side of the PMOSTr44a, and an inverter 4.
4c, and in the case of this embodiment, an adjustment resistor 44b
The first set voltage value is set to 1.8 volts, and 0
The sampling signal that is the output of the R gate 42 causes the battery 16 to
Detection of voltage on the high voltage range side, that is, detection operation to determine whether or not an overcharge state is performed.

45 is a hold circuit that stores the output contents of the voltage detection circuit 43 using the sampling signal of the 0R gate 41, and generates an A-bi signal when the voltage of the battery 16 falls below 1.35 volts. Output A.

Furthermore, 46 is composed of a D-type flip-flop, and 0
The voltage detection circuit 4 uses the sampling signal of the R gate 42.
This is a hold circuit that stores the output contents of 4, and the battery 16 is
．． In an overcharged state where the voltage is 8 volts or more, B = 'signal B
Output.

47 is the signal A which is the output of the hold circuits 45 and 46;
This is an AND gate provided to prevent B from becoming A=B='pi at the same time, and if A=B=ゞ1'' when the battery is installed, the AND gate 47 activates the hold circuits 45 and 46. The connection is configured to perform a reset operation.

Next, the operation will be explained based on the above configuration.

First, when the solar cell section 8 is not irradiated with sufficient light and the battery 16 is in an undercharged state with a voltage value of 1.35 volts or less, the sampling signal φ2 of the 0R gate 41 causes
When the PMOSTr 43a of the voltage detection circuit 43 is turned on, the channel resistance and the adjustment resistor 43b perform a voltage division operation on the battery voltage.

Furthermore, since this divided voltage is set in advance by the adjustment resistor 43b so that it is below the threshold voltage of the inverter 43c,
As a result, the output signal A of the hold circuit 45 is stored and held as A-B. Therefore, this signal A outputs the 1 second signal P1 to the NAND gate 27, and this signal P1
The driver 26 modulates the time display section 6a to display a low voltage warning of the battery 16 by flashing at a one-second cycle, and irradiates the solar cell section 8 with light to alert the user that the battery 16 is undercharged. Appropriate instructions can be given to charge the battery. Note that when the signal A is low, the sampling signal is not supplied to the voltage detection circuit 44 and the hold circuit 46 on the high voltage range side by the 0R gate 42, and the output signal B is in a stopped state. ″
O''. Moreover, at this time, AND gate 4
Since the output of 0 is SO'', the switching circuit 39 outputs the signal φ
2 is output, and this signal φ2 is further input to the voltage detection circuit 43 via the 0R gate 41 inputted as B-゜0''.
The holding circuit 45 is periodically sampled at a rate of once per minute to avoid unnecessary energy consumption of the battery 16. From this state, the battery 16 changes from 1.35 volts to 1 volts by irradiating the solar cell section 8 with light.
．． When it is charged to within the voltage value range of 8 volts, the signal A, which has been holding 2 volts, is changed to 2 o'' and its signal by causing the voltage detection circuit 43 and the hold circuit 45 to perform sampling operation by the signal φ2. A is inverted. Therefore, the blinking display of the time display section 6a is stopped and the normal display state is established, and the signal φ2 output from the switching circuit 39
is the 0R gate 42 and B where A=ゞO'' is input.
Both voltage detection circuits 43 and 44 and both hold circuits 45 and 46
At the same time, the sampling operation is performed.
In this state, the signal φ2 is always used to electrically monitor whether the voltage of the battery 16 reaches a low voltage range or a high voltage range. For example, when the voltage of the battery 16 falls below 1.35 volts, signal A becomes Therefore, the above-mentioned time display section 6a blinks, and the solar cell section 8 is irradiated with light for a long period of time, or even for a short period of time when it is irradiated with strong light and the battery 16 becomes over 1.8 volts. When the battery is in the charging state, first, the voltage detection circuit 44 and the hold circuit 46 perform sampling operations based on the signal φ2, so that an output that changes the signal B to B-B is obtained. At this time, the signal A is naturally in the state of A=0'', so the AND
The output of the gate 40 becomes 2, and the switching circuit 39 outputs a signal φ1. As mentioned above, this signal φ1 has a very short period of 5 seconds compared to the signal φ2 which has a period of 1 minute.
From now on, when the voltage of the battery 16 is 1.8 volts or more, the voltage detection circuit 44 and the hold circuit 46 perform a sampling operation in which the voltage detection time is accelerated by the signal φ1. On the other hand, the battery 16 is equivalently placed in a heavy load state and the discharge amount of the battery 16 is increased to return to the normal voltage value range of 1.35 volts to 1.8 volts. Note that at this time, in this embodiment, the 0R gate 41
Although the configuration is such that the sampling operation of the voltage detection circuit 43 and the hold circuit 45 is stopped by the signal B that is inputted rapidly, for example, in order to place the battery 16 in a more equivalent heavy load state, 0R is applied. It may be configured such that the gate 41 is removed and the signal φ1 is directly supplied to the voltage detection circuit 43 and the hold circuit 45 to perform the sampling operation. Furthermore, in the case of this embodiment, when the battery 16 is in an overcharged state, the lamp 34, which is heavily loaded, is forcibly turned on by the signal B for a period of [cycle of signal (φ1)] x [number of sampling]. The battery 16 is discharged early and the normal voltage range (1.
35 volts to 1.8 volts). In addition, as another embodiment of the lamp 34, for example, in the case of an alarm clock equipped with a piezoelectric or electromagnetic buzzer, the buzzer sound and tone when the normal alarm time coincides are controlled by the signal B mentioned above. It is also possible to create a heavy load state by forcing the buzzer to sound.
It is an effective means to forcibly bring the battery 16 into a heavy load state when it is in an overcharged state. Note that the term "heavy load" here refers to an electrical component with a lower resistance than a clock circuit, which would discharge the battery 16 in a short period of time if it was constantly connected to the battery 16. It may be a coil or a simple resistance element. Furthermore, in this embodiment, the battery 1
6 eliminates the cause of overcharging. For example, it is necessary to avoid situations where solar-powered watches are displayed for long periods of time in illuminated show windows at watch shops, etc., or where they are left in environments where they are exposed to strong direct sunlight. However, conventionally, the user has not been able to determine whether the battery 16 is being charged properly or is overcharged and take appropriate measures, so the battery 16 may be overcharged. It was not possible to avoid this from being in a charging state. Therefore, in this embodiment, in consideration of these, when the battery 16 becomes overcharged exceeding 1.8 volts, the voltage detection circuit 44 and the hold circuit 46 are operated by the relatively short cycle signal φ2. to output signal B as a signal. Further, a drive circuit 38 receiving this signal B supplies a liquid crystal applied voltage V to close the light valve of the light valve portion 6b located above the solar cell 8g. As a result, the amount of irradiated light L1 incident on the solar cell 8g is almost O due to the decrease in the transmittance ε of the light valve portion 6b, so that no light is irradiated. Note that when the solar cell 8g is not irradiated with light, it functions as a diode connected in the opposite direction to the polarity of the photovoltaic voltage generated from the other solar cells 8a to 8f. The charging function operation for the battery 16 can be automatically stopped. Therefore, even if the solar cell watch is exposed to light, the battery 16 will not be overcharged any further, and even if the battery 16 is under heavy load due to forced lighting of the lamp 34, etc. In order to discharge the battery 16 to quickly restore it to the normal voltage range, the battery 16
The battery will not be left in an overcharged state for a long period of time. Furthermore, when the voltage of the battery 16 drops from this state and recovers to the voltage range from 1.35 volts to 1.8 volts, the voltage detection circuit 44 and the hold circuit 46 again perform the sampling operation of the signal φ1 so that the signal B becomes =SO'' is output, and under the control of this signal B, the drive circuit 38 opens the light valve of the light valve section 6b, and the voltage V applied to the liquid crystal becomes V=o, which is a non-applied state, and the lamp 34 is turned off and switched on. 39 is switched to output the signal φ2, and from now on, this signal φ2
The voltage detection circuits 43, 44 and the hold circuit 45,
46 performs a sampling operation with a one-minute period with little energy loss and constantly monitors the voltage of the battery 16. As described above, the solar battery charging device for a solar battery watch, etc. according to the present invention automatically discharges into a heavy load such as a lamp, so even if the solar battery is irradiated with strong light, the battery is not set. The voltage will not be maintained for a long period of time, and the battery can recover from an overcharged state in a short period of time, and this recovery may cause the battery to swell due to gas generation or become unusable due to the acceleration of gas generation. disappears.

In addition, since the battery is configured to automatically discharge to a heavy load when the battery voltage exceeds a set voltage, the danger of overcharging the battery is eliminated, and conversely, it is possible to increase the number of connected solar cells. It is also possible to set the current-limiting resistor value connected in series with the solar cell to a small value, and the battery can be quickly charged during normal or under-charged conditions, and the battery always maintains a stable voltage. Can be maintained for a long period of time. For example, by incorporating this solar cell charging device into an electronic watch or the like, stable time accuracy can be maintained for a long period of time. Also, during overcharging, the sampling signal input to the voltage detection circuit and the hold circuit is switched to a sampling signal with a short cycle, and the output signal of the hold circuit causes discharge to the heavy load at every sampling signal cycle (every predetermined period). Since a voltage detection operation is also performed at the same time, by setting the period of the sampling signal in a designed manner, over-discharge will not occur, and the battery can be discharged in a precise manner to compensate for over-charging.

[Brief explanation of the drawing]

Figure 1 is a plan view of the solar battery wristwatch of the present invention, Figure 2 is a sectional view showing the movement of the solar battery wristwatch of the invention, and Figure 3 is a cross section showing the area around the light valve shown in Figure 2 in detail. figure,
FIG. 4 is a characteristic diagram showing the transmittance with respect to the voltage applied to the liquid crystal applied to the light valve section, FIG. 5 is a characteristic diagram showing the photovoltaic current with respect to the amount of irradiation light of the solar battery cell, and FIG. A circuit diagram, FIG. 7 is a circuit diagram showing the control circuit shown in FIG. 6 in detail, and FIG. 8 is a circuit diagram showing the control circuit shown in FIG.
A waveform diagram showing φ2. 6...Liquid crystal cell, 6a...Time display section, 8...Solar cell section, 8a to 8g...
Solar cell, 16...Battery, 22...
・Oscillation circuit, 23... Frequency division circuit, 24...
...Counter, 27...NAND gate, 28
, 29... Waveform shaping circuit, 37... Control circuit, 39... Switching circuit, 26, 38...
...Drive circuit, 43, 44... Voltage detection circuit, 45, 46... Hold circuit, φ1 φ2, A, B... Signal.

Claims (1)

[Claims] 1. A plurality of solar cells connected in series, a battery charged by the plurality of solar cells, a heavy load using the battery as a power source, and a device for driving the heavy load. a heavy load drive circuit for detecting the voltage of the battery; a voltage detection circuit for periodically detecting the voltage of the battery through a sampling operation; and a sampling signal generating means for generating a plurality of sampling signals having different periods for causing the voltage detection circuit to perform a sampling operation. , comprising a hold circuit that stores the output content of the voltage detection circuit, and a switching circuit that selectively outputs one of the plurality of sampling signals to the voltage detection circuit according to the output signal of the hold circuit. , when the voltage detection circuit detects that the voltage of the battery is higher than the set voltage value, the switching circuit selectively outputs a sampling signal with a short cycle according to the output signal of the hold circuit, and A solar cell charging device characterized in that the heavy load is driven by the heavy load drive circuit every cycle of a sampling signal of a cycle. 2. A solar battery charging device characterized in that the heavy load recited in claim 1 is a lamp.