JPS61211715A - Small electronic equipment with solar battery - Google Patents

Abstract

PURPOSE:To enable to execute normal operation at once by providing a resistance component between a solar battery and a capacitor, controlling to make resistance value large at the time of starting charging to the capacitor and stabilizing output voltage at a connecting point of the solar battery and resistance component to voltage for driving electronic circuit. CONSTITUTION:A charging circuit in which charging current flows from a solar battery 1 to a capacitor 2 is formed, and a reverse current preventing diode 3 that prevents loss current is provided. An N type MOS transistor 4 is used as a load, and the resistance value is variably controlled according to output of an operational amplifier 5 applied to the gate, and constitutes a quick starting circuit 6 that quick starts an electronic circuit 11 at the time of starting charging. Output voltage VIN from the connecting point of the solar battery 1 and N type MOS transistor 4 is applied to minus input terminal of an operational amplifier 9 that constitutes a voltage regulator circuit 8 through a P type MOS transistor 10 of insulating gate depression type. The voltage regulator circuit 8 stabilizes driving voltage supplied to the electronic circuit 11.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a small electronic device with a solar cell that uses a solar cell as a power source.

[Prior art and its problems]

Conventionally, when solar cells are used in small electronic devices, a capacitor is connected in parallel to the solar cells.1. The electromotive force from the solar cell charges the capacitor, and the voltage across the capacitor drives the electronic circuit. For example, if we consider an on-board electronic calculator (calculator) as a small electronic device with a solar battery, since calculators are generally used in bright places, the capacitor can be constantly charged by light. , the capacitor capacity may be small. On the other hand, in the case of an electronic wristwatch, a capacitor with a large capacity must be used because it must be driven even when there is no light, such as at night. However, when the capacitor capacity is increased, there is a problem in that once the capacitor is completely discharged, it takes time to recharge, making it impossible to perform a timekeeping operation immediately.

[Purpose of the invention]

This invention was made against the background of the above-mentioned circumstances, and its purpose is to provide a solar cell that can immediately perform normal operation of an electronic circuit when charging a capacitor starts, and that also has a simplified circuit configuration. Our goal is to provide small electronic devices with attached devices.

[Key points of the invention]

In order to achieve the above-mentioned object, the present invention provides a small electronic device with a solar cell equipped with a capacitor that is charged with the output voltage of the solar cell, in which a resistance component is provided between the solar cell and the capacitor, and a resistance component is provided between the solar cell and the capacitor. a control circuit that controls the resistance value of the resistance component to increase at the start of charging, and a power supply stabilization circuit that stabilizes the output voltage at the connection point between the thick battery and the resistance component to a voltage for driving the electronic circuit; The main point is that a reference voltage generation circuit is provided which is shared by these control circuits and power supply stabilization circuits.

[Configuration of Example]

Hereinafter, the present invention will be specifically described based on an embodiment shown in the drawings. FIG. 1 is a block circuit diagram of a power supply section in which the present invention is applied to an electronic timepiece. 1 in the figure is, for example, a solar cell with a maximum electromotive force of -3.5V, and a large-capacity five-capacitor 2 is connected in parallel to this thick @m pond 1, and a charging current flows from the solar cell 1 to the capacitor 2. A charging circuit is formed. This charging circuit is provided with a backflow prevention diode 3 that prevents loss current from flowing from the capacitor 2 to the solar cell 1 when the potential of the solar cell 1 is lower than that of the capacitor 2. Also, there is N between the solar cell 1 and the capacitor 2.
type MOS) transistor 4 is provided, and this N type MO'S
) The drain side of the transistor 4 is connected to the capacitor 2, and the source side is connected to the battery 1. This N-type MOS) transistor 4 is used as a load, and has six ports so that its resistance value can be variably controlled in accordance with the output of the operational amplifier 5 applied to its gate. Thus, the N-type MOS transistor 4 and the operational amplifier 5 constitute a quick start circuit 6 that quickly starts the electronic circuit 11 to start charging. The output voltage VIN from the connection point between the solar cell 1 and the N-type MOS transistor 4 is applied to the negative input terminal of the operational amplifier 5 as a voltage to be compared, and the reference voltage generation circuit 7 supplies the reference voltage to the positive input terminal of the operational amplifier 5. A voltage vr6 is applied, and as a result of comparing both voltages, a signal -Out is output and applied to the gate of the N-type MOS transistor 4.

In addition to inputting the reference voltage vro to the quick start circuit 6, the reference voltage generation circuit 7 also inputs the reference voltage vro to the positive input terminal of the operational amplifier 9 constituting the voltage regulator circuit 8. The output voltage from the connection point between the solar cell 1 and the N-type MOS transistor 4 is applied to the negative input terminal via the insulated gate depression type P-type MOS transistor 10, and is output from the operational amplifier 9. A binary level signal is applied to the gate of the P-type MOS transistor 10. Therefore, the voltage regulator circuit 8 stabilizes the driving voltage supplied to the electronic circuit (load) 11, and this electronic circuit 11 constitutes a clock circuit, and performs a timekeeping operation according to the driving voltage from the voltage regulator circuit 8. Execute.

FIG. 2 shows in detail the block circuit diagram of FIG. MO consisting of a combination of an N-type MOS) transistor and a P-type MQS transistor
It has a circuit configuration using 8IO, and has a normal configuration with a load MO8. Here, among each MO8) Langisthu-1 to 7-4 constituting the reference voltage generation circuit 7, the MOS
) Reference voltage Vr6f is output from the connection point where the drains of Ranjistaf-2 and 7-4 are commonly connected, and each MO
8) Among the transistors 5-1 to 5-7, a voltage ``0'' is applied to the gate of the MOS transistor 5-3, and to the sources of the MOS transistors 5-5 to 5-7. On the other hand, the reference voltage ■r from the base M voltage generation circuit 6
6f is applied to the gate of the MC)S) transistor 9-3 among the MO8) transistors 9-1 to 9-7 constituting the operational amplifier 9 of the voltage regulator circuit 8.

[Operation of the embodiment]

Figures 3 (a) and (b) are diagrams for explaining the operating principle.
3rd m (a) is when charging starts to capacitor 2,
FIG. 3(b) corresponds to a fully charged state.

Now, when the solar cell 1 is not irradiated with light, the discharge of the capacitor 2 progresses, and when the solar cell 1 is irradiated with light while the capacitor 2 is completely discharged, the electromotive force from the solar cell 1 ■B8 occurs. Here, at the start of charging the capacitor 202, the potential difference between both ends of the capacitor 2 is VDD-v.

is small, so the potential difference of v − ■ 〉V r θ
The potential difference is f DD N-VDD. Here, vref and vI,
Since A is actually a negative voltage, the potential is ■.

ef<■IN, but VDD (if there is a potential difference of 4, then Vr e f' DD > vI N
' DD becomes. As a result, the operational amplifier 5 configuring the quick start circuit 6 outputs V +IR=V
A predetermined voltage is applied to the gate of the N-type MO transistor 4 connected in series to the capacitor 2 so that the resistance and current of the N-type MO transistor 4 are controlled so that the voltage becomes r. In this case, the ON resistance of the N-type MO8) transistor 4 increases and the flowing current decreases, so the potential difference between the source of the N-type M08 transistor 4 and VDD becomes large, and the voltage at the source of the N-type MO8) transistor 4 increases. The electronic circuit 11 is supplied via the voltage regulator 8, so
The electronic circuit 11 can be operated immediately after charging starts (see FIG. 3(a)).

As a result, the capacitor 2 is completely charged and the potential difference vDD-Vo between both ends of the capacitor 2 becomes large.
When the potential difference of vr8f-VDD becomes less than the potential difference of VIN'DD, the N-type M'O8) transistor 4 becomes completely turned on according to the output of the operational amplifier 5, and the circuit configuration as shown in FIG. 3(b) is established. Therefore, the voltage drop caused by the N-type MO transistor 4 is eliminated.

Even at the start of charging when the solar cell 1 is irradiated with light while the capacitor 2 is completely discharged,
Since a predetermined voltage can be supplied to the electronic circuit 11, normal operation of the electronic circuit 11 can be ensured at the start of charging. Further, the reference voltage V from the single reference voltage generation circuit 7
Since the configuration is such that the tights r θ f are supplied to the start circuit 6 and the voltage regulator 8, respectively, that is, the reference voltage generating circuit 7
Since the configuration is such that the circuit configuration is shared, the circuit configuration can be simplified.

It should be noted that the present invention is not limited to the above-mentioned embodiments, and may be modified and applied without departing from the scope of the present invention.

〔Effect of the invention〕

As explained in detail above, the present invention provides a small electronic device with a solar cell equipped with a capacitor that is charged with the output voltage of the solar cell, in which a resistance component is provided between the solar cell and the capacitor, and this resistance component is A control circuit that controls this resistance value to increase when charging starts to the capacitor, and a 11! A power supply stabilization circuit is provided to stabilize the output voltage at the connection point between the battery and the resistance component to a voltage for driving the electronic circuit, and the output of a single reference voltage generation circuit is supplied to these control circuits and the power supply stabilization circuit. Since the reference voltage generating circuit is shared, the electronic circuit can immediately operate normally when the capacitor starts charging, and the circuit configuration can be simplified.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention; FIG. 1 is a block circuit diagram, FIG. 2 is a detailed circuit configuration diagram, and FIG. 3'(a), (
b) is a diagram showing the operating principle. 1...Solar cell, 2...Capacitor,
4...N-type MO8) transistor, 5...
- Operational amplifier, 8...Voltage regulator circuit, 11...Electronic circuit. Patent applicant Casio Computer Co., Ltd. 1, 'i, ;, ', ::', ';, L sword Figure 1

Claims (1)

[Claims] A solar cell, a capacitor charged with the output voltage of the solar cell, a resistance component provided between the solar cell and the capacitor, a reference voltage generation circuit, and an output voltage of the reference voltage generation circuit and the capacitor. a control circuit that variably controls the resistance value of the resistance component by comparing the output with the output; and an output voltage at the connection point between the solar cell and the resistance component based on the output of the reference voltage generation circuit as a voltage for driving an electronic circuit. A small electronic device with a solar battery equipped with a power supply stabilization circuit that stabilizes the power supply.