Horology: time measuring systems or devices – Power supply details – Electrical
Reexamination Certificate
1998-10-06
2001-01-09
Miska, Vit (Department: 2859)
Horology: time measuring systems or devices
Power supply details
Electrical
C368S205000
Reexamination Certificate
active
06172943
ABSTRACT:
BACKGROUD OF THE INVENTION
1. Field of the Invention
The present invention relates to an electronic clock having an electric power generating element, and particularly to an electronic clock which can be driven even when the electromotive force of the electric power generating element is small. More particularly, the present invention relates to an electric clock in which an improvement of an electronic clock to reduce a current consumption of the peripheral circuit of the electric power generating element is performed.
2. Description of the Related Art
Up to now, it has been known that an electric power generating element consisting of a thermoelectric element or a solar battery has been employed as an electric power generating element of an electronic clock.
FIG. 2
shows a block diagram of a conventional electronic clock having an electric power generating element. This is an example in which the thermoelectric element is employed as the electric power generating element. A charging circuit
204
charges by an electromotive force (voltage) obtained by a thermoelectric element
201
. An electronic clock movement
202
is made up of an oscillating circuit
202
a,
a dividing circuit
202
b
and time display means
202
c
at the least as structural elements and driven by the voltage charged in the charging circuit
204
. A step-up circuit
203
inputs the voltage output by the charging circuit
204
and outputs a voltage stepped up by a clock oscillated by the oscillating circuit
202
a
to a circuit such as the time display means
202
c,
which requires a higher drive voltage than that required by the oscillating circuit or the dividing circuit.
The above-described conventional electronic clock having the electric power generating element requires, as the electromotive force of the electric power generating element, a voltage sufficient for making the circuits of the electronic clock acting as loads operative. This necessary voltage is normally about 0.6 to 1 V. Also, in order to maintain the operation of the electronic clock even when the electronic clock is located in an environment where the electric power generating element cannot generate an electric power, the electromotive force of the electric power generating element is charged in the charging circuit.
However, since the above-described conventional electronic clock having the electric power generating element requires about 0.6 to 1 V or more as the electromotive force of the electric power generating element, a large number of electric power generating elements must be connected in series in order to obtain the electromotive force. This leads to an increase in its area and volume, resulting in a problem when the large number of electric power generating elements are mounted on a small-sized electronic device (for example, an electronic clock).
Also, the clock could not be driven until an output voltage of the charging circuit such as a capacitor or a secondary battery is charged up to a voltage at which the clock can be driven. The electric power generating element converts an external energy such as a light or heat into an electric energy. However, if little difference in luminance, temperature or the like is obtained, it takes time to charge the charging circuit. For that reason, when the charging circuit is allowed to be charged from a state where there is no capacitance (voltage) in the charging circuit, it takes a long time until the clock starts to operate (hereinafter called as “oscillation start time”).
SUMMARY OF THE INVENTION
In order to solve the above problems, an electronic clock according to a first aspect of the present invention is designed to include a low-voltage oscillating circuit which can oscillate even when an electromotive force developed by an electric power generating element is of a low voltage, a step-up circuit which inputs an output signal of the low-voltage oscillating circuit for stepping up the output signal, and a charging circuit for charging a stepped-up voltage, in which the electronic clock is driven by the voltage charged in the charging circuit.
Also, in an electronic clock according to a second aspect of the present invention, a voltage detecting circuit detects the electromotive force (voltage) charged in the charging circuit, and when the voltage detecting circuit detects a voltage equal to or higher than a voltage at which an oscillating circuit within an electronic clock movement oscillates, the drive of the low-voltage oscillating circuit stops, to thereby reduce the current consumption of the low-voltage oscillating circuit. Simultaneously, a selecting circuit changes over from an input clock of the step-up circuit to a clock of signal generating means (for example, the oscillating circuit, a dividing circuit or the like) within the electronic clock movement (in particular, a clock IC) so that the electromotive force (voltage) developed by the electric power generating element is stepped up and charged in the charging circuit.
REFERENCES:
patent: 5705770 (1998-01-01), Ogasawara et al.
patent: 5740132 (1998-04-01), Ohshima et al.
patent: 5889734 (1999-09-01), Sato
Adams & Wilks
Miska Vit
Seiko Instruments Inc.
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