Electrical transmission or interconnection systems – Plural supply circuits or sources – Diverse or unlike electrical characteristics
Reexamination Certificate
1999-01-26
2001-11-20
Ballato, Josie (Department: 2836)
Electrical transmission or interconnection systems
Plural supply circuits or sources
Diverse or unlike electrical characteristics
C368S203000, C307S084000
Reexamination Certificate
active
06320280
ABSTRACT:
BACKGROUND OF THE INVENTION
1.Field of the Invention
The present invention relates to various kinds of electronic devices and appliances such as electronic wristwatches, portable communications devices, and domestic electrical appliances and, more particularly, to electronic devices fitted with power generators.
2. Description of the Prior Art
Heretofore, electronic devices fitted with power generators have been developed as electronic devices such as electronic wristwatches and the like. Various types are available as power generators. Especially, thermoelectric generators can be made compact and so they are being developed so as to be applied to various electronic devices and appliances.
An electronic wristwatch fitted with a thermoelectric generator is worn on an arm such that suction of heat by the thermoelectric generator is conducted from the arm. Heat is dissipated to the outside air. In this way, electric power is generated by making use of a temperature difference. Accordingly, when the electronic wristwatch is detached from the arm, no temperature difference is produced and so power generation may be stopped. If power generation is stopped for a long time, electric power stored in a storage device might be exhausted. Furthermore, when the outside air temperature and the body temperature on the arm become equal, power generation comes to a stop. In this case, there is the possibility that the electric power stored in the storage device is used up.
Since a thermoelectric generator produces only a small amount of electric power, if the storage device is exhausted, it is difficult to store a sufficient amount of electric power in the storage device is a short time after attaching the watch to an arm. For example, where a thermoelectric device has a temperature difference of about 2° C., the electric power that can be generated is about 13.3 &mgr;W, provided that the generated voltage is 0.4 V, the internal resistance is about 1500 &OHgr;, and the input impedance of a voltage step-up means for stepping up the generated voltage is 1500 &OHgr; and that the loss of the voltage step-up means is neglected. The electric power consumed by the electronic wristwatch is approximately 1 to 2 &mgr;W. Where a lithium-ion secondary battery having a diameter of 6 mm is used as a power storage device, energy of about 6.5 J can be stored. Accordingly, if the device is worn on an arm and should be fully charged, it takes a time of 135.8 hours even if consumption and loss in the load circuit are neglected.
Accordingly, if power generation of the thermoelectric generator is stopped for a long time as encountered when the electronic wristwatch is detached from the arm, the electric power storage device is exhausted. This brings the timepiece to a stop.
One proposed method for solving this problem is to reduce the frequency at which the second hand of a watch or clock is driven if the storage voltage drops, thus lowering the electric power consumed (see Patent Unexamined Publication No. 287080/1995). With this method, the electric power consumed can be decreased but cannot be reduced down to zero. Therefore, if power generation of the thermoelectric generator stops for a long time, there arises the problem that the storage device is exhausted.
If a thermoelectric generator is used in various electronic devices and appliances other than electronic wristwatches such as portable communications devices and domestic electric appliances, the same problem arises if no temperature difference occurs.
The present invention is intended to suppress decreases in the electric power stored in an electrical storage device of an electric device having a thermoelectric generator.
SUMMARY OF THE INVENTION
An electronic device fitted with power generators in accordance with the present invention is characterized by comprising: a thermoelectric generator; a solar generator; a switching means for delivering at least one of electric power generated by said thermoelectric generator and electric power generated by said solar generator; an electric energy storage means charged by output from said switching means; and an electronic device body circuit powered by said electric energy storage means. If there is a temperature difference, the thermoelectric generator generates electricity. The solar generator receives light such as sunlight and generates electricity. At least one of the electric power generated by the thermoelectric generator and the electric power generated by the solar generator is supplied to the storage means via the switching means, thus charging the storage means. The electronic device body circuit is powered by the storage means.
Accordingly, in regions where large temperature differences are obtained but the sunlight is weak and the hours of sunlight are short as in cold regions, the device can be chiefly charged by the thermoelectric generator. On the other hand, in areas where large temperature differences cannot be derived but the sunlight is strong and the hours of sunlight are long as in the vicinities of equatorial districts, the device can be mainly charged by the solar generator. Therefore, the drawbacks of the power generators can be compensated by using the thermoelectric generator and the solar generator in combination. The storage device can be charged without being affected greatly by regional environments. Decreases in the electric power stored in the storage means can be suppressed.
The voltage generated by the thermoelectric generator described above is relatively low and rises mildly. On the other hand, the voltage generated by the solar generator is relatively high and rises steeply. Therefore, it is desired to use the solar generator to power the voltage step-up means that steps up the voltage generated by the thermoelectric generator.
Since the voltage generated by the thermoelectric generator is comparatively low, if the voltage of the thermoelectric generator is insufficient to start the voltage step-up means, the solar cell generator is made of one stage of cell and used as a power supply for starting the voltage step-up means. After starting the voltage step-up means, the voltage generated by the thermoelectric generator is stepped up and used to power the voltage step-up means. In this way, the solar generator is used.
The aforementioned electric device body circuit can comprise an electronic timepiece circuit and a display means driven by the electronic timepiece circuit to provide a display of time.
The solar generator is disposed on the time display face of the display means. In normal use, the solar generator can be made to produce electricity and thus the device is charged.
The solar generator is disposed on the opposite side of the time display face of the display means so as to be capable of receiving light via a transparent rear cover. Hence, the appearance of the electronic device can be aesthetically improved.
REFERENCES:
patent: 4165477 (1979-08-01), Comte
patent: 4291266 (1981-09-01), Portmann
patent: 5705770 (1998-01-01), Ogasawara et al.
patent: 5901117 (1999-05-01), Delabre
Adams & Wilks
Ballato Josie
Rios Roberto
Seiko Instruments Inc.
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