Electricity: electrical systems and devices – Safety and protection of systems and devices – With specific voltage responsive fault sensor
Reexamination Certificate
1999-01-22
2001-12-04
Leja, Ronald W. (Department: 2836)
Electricity: electrical systems and devices
Safety and protection of systems and devices
With specific voltage responsive fault sensor
C307S087000, C307S130000
Reexamination Certificate
active
06327127
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a variety of electronic instruments, such as electronic watches, portable communication instruments, or electric home appliances, and particularly to preventing an erroneous operation from occurring when the voltage of a power source circuit of a low power consumption instrument has been lowered.
Hitherto, in electronic watches, portable communication instruments, and other various electronic instruments, as signals come to be digitally processed, a frequency-dividing circuit, a central processing unit (CPU), a flip-flop circuit, or the like has been used.
FIG. 9
is a block diagram of a conventional electronic instrument. In
FIG. 9
, a power source circuit
901
is made up of a thermoelectric conversion element
902
as an electric power generating means, and a rectifying circuit
903
for preventing countercurrent. Electric power generated by the thermoelectric conversion element
902
is stored in a storage means
904
through the rectifying circuit
903
. A load circuit
905
made up of a MOS transistor, a bipolar transistor, and the like operates using the generated electric power or stored electric power as a power source. For example, in the case where the electronic instrument is a clock system of an electric watch, this load circuit is made up of an oscillating circuit, a frequency-dividing circuit for frequency dividing an output signal of the oscillating circuit, a time display means for displaying a time on the basis of an output signal of the frequency-dividing circuit, and the like.
In such a conventional electronic instrument, for the purpose of making the electronic instrument miniaturized and lightweight, the power source circuit
901
is also required to be made miniaturized and lightweight, and with this, there is a tendency that the power supply capability of the power source circuit
901
is decreased. On the other hand, by virtue of need of prolonging the operation time of the electronic instrument, the storage means
904
is forced to have its capacity made large. These are noticeable especially in a portable electronic instrument such as an electronic watch or a portable telephone.
In such a case, when the storage means
904
is charged, from a non-charged state, with electric power supplied from the power source circuit
901
, the power source voltage to the load circuit
905
is not quickly raised, but a long time is required until the power source voltage is increased up to a voltage at which the load circuit
905
operates normally. Thus, a period of time when the power source voltage remains in the vicinity of an operation start voltage at which the operation of the load circuit
905
becomes unstable, becomes long. Accordingly, there have been problems in that not only does the start of operation of the load circuit
905
become delayed, but also the load circuit
905
can perform an erroneous operation.
In order to prevent this erroneous operation, there is generally used a method in which a power on clear circuit is used, which detects the quick increase of voltage at the start of power supply and outputs a clear signal, and with the start of power supply, the clear signal is supplied to a frequency-dividing circuit, a CPU, and the like to reset them into a predetermined initial state, and then, a normal operation is started.
However, even if the power on clear circuit is used, the power source voltage is not quickly raised because of the foregoing reason, so that a sufficient clear signal can not be generated and it has been difficult to solve the erroneous operation of the load circuit
905
.
Besides, in the case where the load circuit is a clock system, a MOS transistor having large driving capability is used in the load circuit to the power source in order to drive a stepping motor. Thus, when the power source voltage of the load circuit enters into a voltage range where the operation of the circuit is unstable, a large current flows by a through current. In this case, the electric power supplied from the power source circuit
901
is consumed by the above through current, so that there is a case where the storage means
904
can not be charged. When the through current flows once, the power source voltage does not become larger than a voltage at which the through current of the stepping motor driving MOS transistor balances with the power supply capability of the power source circuit
901
. Thus, there has been a problem in that if the balancing voltage is less than an operation voltage of the load circuit
905
, the load circuit
905
does not start a normal operation for a long time.
Besides, some load circuits
905
have such a mechanism that when a power source voltage is low, more current flowns. In this case, when the power source circuit
901
starts to supply electric power, the voltage of the storage means
904
is gradually increased, so that more current flowns when the voltage is low. Thus, there has been a problem in that voltage drop occurs and the voltage is not increased.
Further, even in an electronic instrument which does not include an electric power generating means and a large capacity storage means as described above, in such a case that a relatively large smoothing capacitor is used to stabilize the power source voltage, quick rising of the power can not be obtained. Thus, there has been a problem that a sufficient clear signal can not be obtained by the foregoing power on clear circuit, so that an erroneous operation occurs.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an electronic instrument which can prevent an erroneous operation immediately after feeding even in the case where a power source voltage is not quickly raised. Another object of the present invention is to prevent such a case that in an electronic instrument including electric power generating means and storage means, a large current flows through a load circuit at a halfway power source voltage so that the power source voltage can not be increased.
An electronic instrument of the present invention includes an electronic instrument main body circuit, a control circuit capable of operating at a threshold voltage lower than that of the electronic instrument main body circuit, and a power source circuit for feeding the electronic instrument main body circuit and the control circuit, and is characterized in that the control circuit outputs a control signal to stop the operation of the electronic instrument main body circuit until the feeding voltage from the power source circuit to the electronic instrument main body circuit becomes a minimum operation voltage at which electronic instrument main body circuit normally operates. When the power source circuit start to feed, the control circuit having the low threshold voltage first starts to operate with the increase of the power source voltage, and outputs the control signal to stop the operation of the electronic instrument main body circuit. When the power source voltage is further increased and becomes the voltage at which the electronic instrument main body circuit can normally operate, the control circuit operates the electronic instrument main body circuit through the control signal. By this, an erroneous operation of the electronic instrument is prevented.
The power source circuit may be made up of electric power generating means for generating electric power and storage means for storing the electric power generated in the electric power generating means. It is preferable to use a thermoelectric conversion element as the electric power generating means in view of miniaturization.
Moreover, when a boosting circuit for boosting the output voltage of the thermoelectric conversion element to charge the storage means is provided, the performance of the whole charging system is improved.
In the case where the electronic instrument main body circuit includes an electric element having high driving capability to the power source, the electric element is maintained in an off state by the control signal until the fe
Utsunomiya Fumiyasu
Yoshida Yoshifumi
Adams & Wilks
Leja Ronald W.
Seiko Instruments Inc.
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