Horology: time measuring systems or devices – Chronological – With supplemental power source
Patent
1995-12-05
1999-03-30
Miska, Vit W.
Horology: time measuring systems or devices
Chronological
With supplemental power source
368 66, 368157, 368204, 368205, 320 1, G04C 2300, G04D 100, H02J 700
Patent
active
058897348
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to an electronic timepiece which has a power supply whose output voltage is not constant and varies within a certain voltage range, e.g., a power supply consisting of combination of a solar cell and an electric double layer capacitor, and uses a stepping motor as a driving source.
BACKGROUND ART
Conventionally, electronic timepieces are commercially available in which a solar cell is arranged on the dial plate of the timepiece in place of a battery, and the solar cell is combined with an electric double layer capacitor to constitute a power supply, thereby avoiding troublesome battery exchange. However, the output voltage of this power supply using a solar cell varies depending on solar rays or illumination light. More specifically, this power supply is charged upon reception of an optical energy and increases the output voltage. However, when the timepiece load is driven without receiving the optical energy for a long time, e.g., during nighttime, the power is consumed, and the voltage gradually decreases. In the electronic timepiece using this power supply, when the electric double layer capacitor is charged to 2.6 V, and the timepiece load is continuously driven from this state without being charged midway, the output voltage gradually decreases, as shown in FIG. 1.
In a conventional electronic timepiece of this type, the minimum voltage allowing to drive hands as a timepiece load, i.e., the minimum driving voltage is 1.3 V. For this reason, the driving time is t.sub.1, as indicated by V.sub.D in FIG. 1. However, the electric circuit of the electronic timepiece can operate at a lower voltage of about 0.8 V. Therefore, when a large hand driving pulse necessary for driving the hands is independently prepared, the minimum driving voltage can be decreased up to 1.05 V. As a result, the driving time can be increased to t.sub.2, as is apparent from FIG. 1. This means that the electronic timepiece does not stop for a long time even when it is left in an uncharged state, and the charge during the discharge prolongs the driving time, resulting in an increase in product value of electronic timepieces.
From such a viewpoint, an electronic timepiece having a circuit arrangement as shown in FIG. 2 can be considered by applying a pulse width change driving technique disclosed in Japanese Examined Patent Publication No. 61-15386 to an electronic timepiece using a power supply formed of a combination of a solar cell and an electric double layer capacitor.
Referring to FIG. 2, reference numeral 40 denotes a power supply means constituted by a solar cell 1 serving as a power generation means, and an electric double layer capacitor 2 serving as an accumulation means, which serves as a power supply for an electronic timepiece. Reference numeral 4 denotes a quartz oscillation circuit; 5, a time counting circuit; 107, a pulse preparation circuit; and 108, a pulse selection circuit. The pulse preparation circuit 107 and the pulse selection circuit 108 constitute a driving pulse preparation means 109. Reference numeral 11 denotes a driver circuit; 12, a rotation detection circuit; and 13, a stepping motor. The solar cell 1 is arranged on the dial plate of the timepiece to convert an external optical energy into an electric energy. The electric double layer capacitor 2 accumulates the electric energy generated in the solar cell 1 and supplies the power to a timepiece circuit 100 including the quartz oscillation circuit 4, the time counting circuit 5, the pulse preparation circuit 107, the pulse selection circuit 108, the driver circuit 11, and the rotation detection circuit 12. The quartz oscillation circuit 4 outputs a 32,768-Hz signal on the basis of a vibration of the quartz oscillator. The time counting circuit 5 frequency-divides the 32,768-Hz signal output from the quartz oscillation circuit 4 and outputs a signal necessary for preparing a driving pulse or a signal at a one-second period which is a timing for rotating the stepping motor 13 to the pulse preparation circuit
REFERENCES:
patent: 4634953 (1987-01-01), Shoji et al.
patent: 4702613 (1987-10-01), Ohtawa
patent: 4730287 (1988-03-01), Yoshino et al.
patent: 4760564 (1988-07-01), Odagiri
patent: 4785435 (1988-11-01), Inoue et al.
Citizen Watch Co. Ltd.
Miska Vit W.
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