JP2537600B2 - Solar cell clock - Google Patents

Description

The present invention relates to a power supply method for a solar cell timepiece.

[Conventional technology]

Conventional electronic timepieces have a limited battery life depending on the current consumption of the system and the capacity of the built-in battery, and efforts are being made to reduce the current consumption of the system and to increase the capacity of the battery to be installed in order to extend the service life. Are doing Further, there are a solar cell timepiece using a solar cell as a power source of the system, a solar cell timepiece combining a solar cell and a secondary battery, and a solar cell timepiece combining a solar cell and a capacitor. Further, as shown in FIG. 3, there is a solar cell timepiece having a constant voltage circuit for controlling the output voltage of the solar cell and a circuit for preventing charging from the solar cell to the chemical cell, using the solar cell and the chemical cell as system power sources. .

[Problems to be solved by the invention]

However, in the conventional technology as described above, the current consumption of the system is almost determined by the IC used, and the current consumption of the IC cannot be dramatically reduced.
Moreover, the capacity of the current is determined by the size, and the size that can be built into the watch is limited, so it is difficult to increase the capacity. Therefore, at present, it can be said that the life of an electronic timepiece incorporating a primary battery is almost saturated. On the other hand, there is an electronic timepiece that uses a solar cell as a power source in an electronic timepiece designed to have a semi-permanent life regardless of the battery life. However, in such a solar cell clock, if the power source is only the solar cell, the clock must be placed in a bright place where the solar cell can generate a certain level of illuminance, that is, enough power to operate the system. Does not work. In other words, there is a problem that the clock stops at night and the clock must be set every morning. Also, in order to solve the problems of such solar cell clocks, there is also a solar cell and capacitor clock that has a capacitor and is charged in a bright place and operates in a dark place where the solar cell does not generate electric power due to its electric charge. is there. However, in such a solar cell and capacitor watch, the capacity of the capacitor that can store electric charge is extremely small compared to the primary battery, and with the current technology, even when the capacitor is fully charged, it only takes a few days in the dark. Only the clock can be operated. Therefore, the current solar cell timepiece has a problem that the timepiece is stopped when it is considered to be used, and the time must be adjusted each time. This problem is serious not only for general users but also for watch retailers. The reason for this is that when they were received, they were put out of the box and left in the dark for many days, so the clocks stopped and I had to adjust the time each time. Depending on the brightness of the display, there is a problem that the clock is stopped during the display. Furthermore, in the winter when people wear long-sleeved clothing, wristwatches are often hidden in the sleeves, and in that case, there is a problem that the wristwatch may stop when wearing it. There is.

Further, since the current capacitor has a small capacity, there is a problem that a function requiring a large current such as an alarm or a lamp cannot be realized. Furthermore, when a solar cell and a secondary battery are combined, the secondary battery charges and discharges, thereby making the secondary battery overcharge prevention circuit and the overdischarge prevention circuit excellent, so that the circuit load is excessive. Since a discharge prevention circuit is required, the circuit load becomes very large, and in consideration of element destruction, there is a risk of explosion due to overcharge of the secondary battery,
Moreover, the cost will increase.

Furthermore, in the conventional solar cell timepiece in which the solar cell having the system configuration as shown in FIG. 3 is used as the first power source in parallel with the chemical cell, the actual situation when the chemical cell 18 becomes the system power source due to the charging prevention circuit Voltage (voltage applied to the power supply terminal of the watch IC15) goes down. For example, assuming that the current consumption of the system is 1 μA, the voltage of the anti-charge diode 32 and the anti-charge resistor 31 causes a voltage drop of about 0.3 V (to prevent charging from the solar cell 00 to the chemical cell 16). Requires a charging prevention resistor 31 and a charging prevention diode 32 that have such strength. Then, for example, when the lower limit of the operating voltage of the timepiece IC 15 is 2.6V, the timepiece can normally be used until the chemical battery 18 reaches 2.6V.
In the case of the system shown in the figure, the watch can be used only until the chemical battery 18 reaches 2.9 V by adding 0.3 V of voltage down, and the life of the watch is increased due to the solar cell added to extend the life of the watch. It has a big problem of making it short.

The present invention solves such a problem, and an object thereof is to provide a solar cell timepiece which has a long life, is efficient, operates normally in a dark place, is safe, and can withstand a heavy load and is inexpensive. is there.

[Means for solving problems]

A solar cell timepiece of the present invention includes a chemical battery as a first power source, and a switch means for switching series-parallel connection of a plurality of capacitors, and lowering the voltage of the chemical battery by switching connection between the capacitors and the chemical cells. A solar cell as a second power source, a voltage control unit that controls the output voltage of the solar cell, and a clock circuit that uses the output voltage of the step-down circuit as a power source. It is characterized in that it is connected in parallel to at least one of the capacitors constituting the circuit.

[Action]

According to the above configuration of the present invention, when there is a certain amount of illuminance, energy is always supplied to the step-down power supply terminal from the solar cell that is the second power supply, and the step-down power supply system circuit is the second
It operates by the energy from the power source (solar cell), the energy supply from the step-down capacitor is no longer necessary, and at the same time, the step-down capacitor itself is always supplied with energy from the second power source (solar cell), so the chemical cell step down The current consumed to charge the capacitor for use is reduced, the consumption of the battery is reduced, and the life is extended.

Further, since the solar cell is applied as the power source to the step-down voltage, the number of stages of the solar cell can be reduced as compared with the case where the solar cell is applied to the power source voltage.

Further, the chemical cell and the solar cell are not directly connected, but when they are connected in parallel, they are connected via a capacitor, so the voltage control circuit should fail and the solar cell may have a large output voltage. Even so, the impact of charging a chemical battery is very small. Therefore, an efficient and safe solar cell clock can be realized.

〔Example〕

Hereinafter, the solar cell timepiece of the invention will be described in detail based on examples. FIG. 2 is an example of the system configuration of the solar cell of the present invention. The step-down circuit 14 of this embodiment is a 1/2 step-down circuit. Step-down circuit 14 consists of two step-down capacitors 12,1
3 and several MOS switching transistors. The step-down capacitors 12 and 13 may be provided in the central circuit of the timepiece IC 15 or may be provided as external elements. To explain the operation of the solar cell timepiece of the invention, first, the normal operation of the step-down circuit 14 and the step-down power supply terminal Vss123 of the step-down circuit are performed.
4 and 5 show the operation when power is externally applied to the
This will be described with reference to FIG. 6 and FIG. Here, the battery voltage is 3.0V. FIG. 4 is a diagram showing the operation of the circuit of the step-down circuit 14, which takes the states a and b depending on the clock input.
The potential difference across the step-down capacitor 13 at this time is shown in FIG.
Shown in 63. When the love circuit 14 is in the state of b, the step-down capacitors 12, 13 of 22 are charged by the chemical battery 18. Assuming that the capacities of the two step-down capacitors 12 and 13 are equal to one, the two step-down capacitors 12 and 13 each have 1.5V (battery voltage 1/2). At this time, the voltage across the step-down capacitor 13 changes as in the state of b in 63 of FIG. Next, the step-down circuit takes the state of a. Then, the two step-down capacitors are disconnected from the chemical battery 18, receive no power supply from anywhere, and serve as the power supply for the circuit between V _DD 25 and V _SS 123, so that they are discharged as shown at 63a. Next, the step-down circuit again takes the state of b, the capacitors 12 and 13 are charged, and the voltage is 1.5V which is 1/2 of the battery voltage. In this way, power is normally supplied to the step-down power supply system circuit 40. Next, a case where a voltage is applied to the step-down power supply terminal (V _SS 123) from the second power supply 50 as in the present invention will be described with reference to FIGS. 5 and 6. Now the second
It is assumed that the voltage of the power supply 50 is 1/2 of the battery voltage, that is, 15V. Then, the step-down capacitor 12 receives the power supply of 1.5V from the second power supply 50 in both the state of a and the state of b, and always keeps the voltage of 1.5V. On the other hand, the step-down capacitor 13 is also supplied with power of 1.5 V in the state of a, but is not supplied with power from the second power source in the state of b. However, since the discharge is not performed due to the power supply from the second power source in the state of a which discharges in the normal operation, the charge received from the chemical battery 18 in the state of b is only the loss at the time of circuit switching. , Almost constant 1.
Keep 5V voltage. Therefore, the chemical battery 18 is hardly consumed. Further, even if the voltage of the second power source 50 is half or less of the potential of the chemical battery 18, if it is a voltage equal to or higher than the final discharge voltage of the step-down capacitors 12 and 13 in the state of normal operation a. Since the voltage after discharge of the step-down capacitors 12 and 13 does not decrease further, the amount of charge from the chemical battery 18 in the state of b can be small, and therefore the consumption of the chemical battery can be reduced, which is effective. The solar cell timepiece of the invention utilizes such behavior of the capacitor, uses a solar cell as the second power supply, and uses a solar cell as the second power supply. However, the output voltage of the solar cell 00 changes depending on the illuminance, and when it exceeds half the voltage of the chemical cell 18, the chemical cell 18 is charged through the step-down capacitors 12 and 13. However, since this charging is via a capacitor, it can be almost ignored except when the capacitance of the capacitor is very large and there is almost no resistance in the circuit. However, in the present invention, to ensure higher safety. Voltage control circuit to control the output voltage of solar cell 00
01 was set up. In the system shown in FIG. 2, the voltage control circuit 01 is composed of a Zener diode 20 and a resistor 21. When the voltage across the Zener diode 20 becomes high, the Zener diode 20 becomes a heavy load and carries an electric current.
The output voltage of the solar cell 20 is controlled by measuring the pressure of 21 minutes.
In the solar cell system shown in Fig. 1, the voltage control circuit 01
Is composed of only 10 resistors. Resistor 10 is a watch IC 15 VDD2
The voltage control effect is achieved by setting Vss123 as the voltage divided by the output voltage of the solar cell 00 by setting the resistance value between 5 and Vss123 to the same order of magnitude, and absorbing the fluctuation of the output voltage.

In this embodiment, the step-down circuit is a 1/2 step-down circuit, but it is 1/3.
It has a sufficient effect as a circuit for step-down.

〔The invention's effect〕

As described above, the solar cell timepiece of the present invention includes the chemical battery as the first power source and the step-down device for reducing the voltage of the chemical battery by switching the connection between the capacitor and the chemical battery including the switch means for switching the series and parallel of the plurality of capacitors. A solar cell as a second power source, a voltage control means for controlling the output voltage of the solar cell, and a clock circuit using the output voltage of the step-down circuit as a power source. The solar cell is a capacitor that constitutes the step-down circuit. Is connected in parallel to at least one of the above.

Therefore, since the capacitor in the step-down circuit is charged by the output voltage of the solar cell, the filling amount of the capacitor by the chemical cell can be reduced, and the service life of the chemical cell can be greatly extended.

On the other hand, when the amount of power generated by the solar cell drops, the capacitor in the voltage step-down circuit is charged by the chemical battery, so there is no need for a means to switch between the solar cell and the chemical cell as the power source for the clock circuit, while always supplying a stable voltage. It is possible.

Therefore, it is possible to obtain a solar cell timepiece having a simpler circuit configuration and capable of operating a timepiece circuit even in a dark place by using a chemical cell and a solar cell in combination.

Further, since the output of the solar cell is controlled by the voltage control means and applied to the capacitor, it is possible to prevent the danger that the chemical cell is charged even if the output of the solar cell increases. It is a thing.

[Brief description of drawings]

1 and 2 are system configuration diagrams of the solar cell timepiece of the invention, and FIG. 3 is a system configuration diagram of a conventional solar cell timepiece. FIGS. 4A and 4B are normal 1/2 step-down circuits. Operation diagram FIGS. 5 (a) and 5 (b) are operation diagrams of the 1/2 step-down circuit when the second power supply is applied to the step-down voltage terminal. FIG. 6 is a timing chart showing the state of the step-down capacitor of the 1/2 step-down circuit. Chart.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication H02J 7/35 H02J 7/35 K

Claims (1)

(57) [Claims] 1. A chemical battery as a first power source, and a step-down circuit including a switch means for switching series-parallel connection of a plurality of capacitors, and a step-down circuit for stepping down the voltage of the chemical cell by switching connection between the capacitor and the chemical cell. 2 a solar cell as a power source, a voltage control unit that controls the output voltage of the solar cell, and a clock circuit that uses the output voltage of the step-down circuit as a power source, and the solar cell constitutes the step-down circuit. A solar cell timepiece, which is connected in parallel to at least one of the capacitors.