Electric power conversion systems – Current conversion – With means to introduce or eliminate frequency components
Reexamination Certificate
1999-12-03
2002-10-08
Vu, Bao Q. (Department: 2838)
Electric power conversion systems
Current conversion
With means to introduce or eliminate frequency components
C363S037000
Reexamination Certificate
active
06462967
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a power supply device suitable for reducing power consumption, a control method for the power supply device, a portable electronic device, a timepiece, and a control method for the timepiece.
2. Description of the Related Art
Small-sized electronic watches in the form of, e.g., wristwatches have been realized, each of the watches incorporating a power generator in addition to both a clocking circuit for counting time and a driving circuit for driving a motor coupled to a hand moving mechanism. Such devices operate with replaceable batteries. Those electronic watches have a function of charging electric power generated by power generators in capacitors, etc., and indicate the time of day with the power discharged from the capacitors when power is not generated.
Those electronic watches can therefore operate with stability for a long time without batteries. In consideration of the inconvenience of replacing batteries and a problem incidental to disposal of exhausted batteries, it is expected that power generators will be incorporated in more and more electronic watches in the future.
A power generator incorporated in a wristwatch, etc. comprises, for example, a solar cell for converting irradiated light to electrical energy, or a power generating system for capturing motion of the user's arm, etc. and converting kinetic energy to electrical energy. Such a power generator is very superior in utilizing energy present in environment of the user for conversion to electrical energy, but has problems that utilizable energy density is low and energy cannot be obtained in continuous fashion. Accordingly, power generation can not be continuously performed, and the electronic watch operates with the power accumulated in a capacitor while the power generation is suspended.
Because a power generator incorporated in a small-sized electronic watch has a small electromotive voltage, the voltage produced between terminals of a capacitor is not sufficient to operate a clocking circuit. For this reason, the voltage produced between the terminals of the capacitor is stepped up, and the stepped-up voltage is accumulated in second capacitor. Also, in order so that a stable source voltage is supplied regardless of fluctuations in the stepped-up voltage, the voltage across the second capacitor is stabilized using a constant-voltage circuit, and the stabilized voltage is supplied as a source voltage to the clocking circuit.
In the above electronic watch, to prolong a period of time during which the watch can be continuously used, total power consumption of the electronic watch must be reduced.
However, the constant-voltage circuit, itself, consumes power. It is therefore not preferable to operate the constant-voltage circuit at all times from the viewpoint of reducing power consumption. On the other hand, the constant-voltage circuit is essential to operate the clocking circuit in a stable way without malfunction.
OBJECTS OF THE INVENTION
Therefore, it is an object of the present invention to overcome the aforementioned problems.
The present invention has been made in view of the above situations in the art, and its object is to reduce power consumption by operating a constant-voltage circuit in a sampling (intermittent) manner.
Another object of the present invention is to control a constant-voltage circuit in accordance with fluctuations in an input voltage, thereby reducing power consumption and stabilizing a source voltage.
SUMMARY OF THE INVENTION
To solve the above problems, a power supply device according to the present invention is characterized in comprising a voltage stabilizer circuit or stabilizing means for producing an output voltage resulting from stabilizing an input voltage when supplied with power, a power supply or power supply means for supplying power to the voltage stabilizing circuit or means, a voltage fluctuation detector or detecting means for detecting a fluctuation in the input voltage or a condition in which a fluctuation in the input voltage is expected, and a controller or control means for controlling the power supply operation of the power supply means in accordance with a result detected by the voltage fluctuation detector or detecting means.
With the above features of the present invention, since the power supply operation of the power supply means can be controlled in accordance with fluctuations in the input voltage, the output voltage can be stabilized and power consumption can be reduced.
More concretely, the control means may control the power supply means so as to supply power to the voltage stabilizing means and stop the supply of power at a certain period when the input voltage is stable. When the voltage fluctuation detecting means detects a fluctuation in the input voltage or a condition in which the a fluctuation in the input voltage is expected, the control means may also cause the power supply means to set a ratio (defined as a time during which power is supplied to the voltage stabilizing means versus a time during which power is stopped) to a greater value than when the input voltage is stable. With the above features of the present invention, when the input voltage fluctuates, the time during which power is supplied can be prolonged so that the output voltage can be stabilized. On the other hand, when the input voltage is stable, the time during which the power supply is stopped can be prolonged so that the power consumption can be reduced.
Also, the control means may control the power supply means so as to intermittently supply power to the voltage stabilizing means when the input voltage is stable, and control the power supply means so as to supply power to the voltage stabilizing means at all times when the voltage fluctuation detecting means detects a fluctuation in the input voltage or a condition in which a fluctuation in the input voltage is expected. In this case, when the input voltage fluctuates, the voltage stabilizing means is operated at all times and therefore the output voltage can be further stabilized.
A portable electronic device according to the present invention is characterized in comprising the above power supply device, power generating means for generating power, and an electricity accumulator or accumulating means for accumulating the power from the power generating means and supplying an accumulated voltage, as the input voltage, to the power supply device. The voltage fluctuation detecting means is constituted as a charging detector or detecting means for detecting charging into the electricity accumulating means. In this case, fluctuations in the input voltage due to an internal resistance of the electricity accumulating means can be monitored by detecting charging into the electricity accumulating means.
In this connection, the charging detecting means may detect charging into the electricity accumulating means in accordance with a charging current flowing into the electricity accumulating means, or may detect charging into the electricity accumulating means in accordance with an electromotive voltage generated by the power generating means.
A portable electronic device according to the present invention is characterized in comprising the above power supply device, power generating means for generating power, first electricity accumulating means for accumulating the power from the power generating means, voltage transforming means for transforming a voltage of the first electricity accumulating means at a transformation amplification depending on the magnitude of the voltage of the first electricity accumulating means, and second electricity accumulating means for accumulating a voltage transformed by the voltage transforming means and supplying an accumulated voltage, as the input voltage, to the power supply device. The voltage fluctuation detecting means being constituted as an amplification change detector or detecting means for detecting a change of the transformation amplification in the voltage transforming means. In this cas
Fujisawa Teruhiko
Okeya Makoto
Laxton Gary L.
Seiko Epson Corporation
Vu Bao Q.
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