Horology: time measuring systems or devices – Power supply details – Electrical
Reexamination Certificate
2002-03-18
2003-10-21
Martin, David (Department: 2841)
Horology: time measuring systems or devices
Power supply details
Electrical
C368S203000, C368S205000
Reexamination Certificate
active
06636459
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an electronic timepiece (clock and watch) incorporating an electric power generator for generating electric energy by utilizing externally available energy, and storage means for storing the electric energy generated by the electric power generator, and capable of performing a time-keeping operation by use of the electric energy generated or the electric energy stored, and a method of controlling the same.
BACKGROUND TECHNOLOGY
There have lately become commercially available and been put to practical applications various types of electronic timepieces incorporating an electric power generator for converting external energy such as optical energy, mechanical energy and so forth into electric energy, and capable of driving timing means by utilizing the electric energy.
Among the electronic timepieces incorporating such an electric power generator, there are included a solar cell electronic timepiece using a solar cell for the electric power generator, a mechanical power generation type electronic timepiece for utilizing electric energy converted from mechanical energy generated by rotation of a rotary weight, a temperature difference electric power generation timepiece for generating electric power by utilizing difference in temperature between the opposite ends of a plurality of thermocouples connected in series and so forth.
The electronic timepieces incorporating any of these electric power generators have storage means as well which is incorporated therein for storing electric energy generated by an electric power generator thereof by use of the external energy when die external energy is available so as to enable the electronic timepieces to be driven continuously and stably all the time even after the external energy is gone.
Such electronic timepieces as described above come to stop performing a time-keeping operation without supply of the external energy and upon completing discharge of the electric energy stored in the storage means. However, at least after the restart of the supply of the external energy, these electronic timepieces resume the time-keeping operation.
Among the electronic timepieces incorporating various types of electric power generators as described above, a solar cell timepiece is disclosed in, for example, JP, H4-50550, B.
A power supply system of such a conventional electronic timepiece is described hereinafter with reference to
FIGS. 6 and 7
.
FIG. 6
is a circuit diagram showing the configuration of the conventional electronic timepiece, and
FIG. 7
is a circuit diagram showing the circuit configuration of a common transmission gate.
With the electronic timepiece shown in
FIG. 6
, electric power generator
1
is connected with storage means
3
and timing means
2
via charge/discharge control means
4
.
The electric power generator
1
, which is a solar cell, a diode
43
, and the timing means
2
form a closed circuit. The timing means
2
is comprised of a timing block
5
for executing a time display operation by use of electric energy, and a capacitor
23
having a capacitance on the order of 10 &mgr;F, which are connected with each other in parallel.
Further, the electric power generator
1
, a diode
44
, second switching means
42
, and the storage means
3
form another closed circuit The second switching means
42
is for use in charging the storage means
3
, but description thereof is omitted herein.
A transmission gate
60
, which is first switch means
41
, interconnects the negative terminal of the capacitor
23
and that of the storage means
3
such that the capacitor
23
and the storage means
3
are connected in parallel.
In order to enable the timing means
2
to restart its operation by connecting the electric power generator
1
with only the timing means
2
when power generation by the electric power generator
1
is restarted after complete discharge of electric energy from the storage means
3
, the transmission gate
60
is made up to be controlled so as to be in the OFF condition at the time of reactivation.
Similarly, the second switching means
42
is also made up to be controlled so as to be In the OFF condition at the time of the reactivation of the timing means
2
.
That is, the operation of the timing means
2
remains suspended when the electric power generator
1
is not generating power while the storage means
3
has been discharged substantially to its fully depleted state, however, upon the restart of power generation by the electric power generator
1
, electric energy generated is delivered only to the timing means
2
.
However, as shown in
FIG. 7
, the transmission gate
60
normally has a configuration of two transistors connected in parallel, that is, the configuration wherein the source terminal (S) and the drain terminal (D) of a transistor
61
, and those of a transistor
62
have connections in common, respectively. In this case, for both the transistors
61
,
62
, a MOS field effect transistor (hereinafter referred to as “MOSFET”) is used.
Further, in a normal configuration, a P-channel MOSFET is used for the transistor
61
and an N-channel MOSFET is used for the transistor
62
.
Because controlling of on/off of the transistor
61
as well as the transistor
62
requires an inverting signal respectively, there is a need for providing an internal inverter
63
.
The internal inverter
63
, and the transistors
61
,
62
come into operation by a switching control signal S
4
outputted from the timing block
5
inside the timing means
2
. The switching control signal S
4
is a signal which will be at the level of a potential of the negative terminal VSS
1
of the timing means
2
when a voltage between the terminals of the capacitor
23
is at a predetermined value or higher, and will be at the ground potential level when the voltage is lower than the predetermined value.
For turning off the transmission gate
60
, it is necessary to render a potential of the gate terminal of the transistor
62
identical to that of the source terminal thereof, and further, to render a potential of the gate terminal of the transistor
61
identical to the ground potential by the agency of the internal inverter
63
. However, even if such control as described can be effected, the transistors
61
,
62
have a PN junction formed therein respectively, and particularly, in the transistor
62
, there is formed a diode wherein current flows in the direction of the arrow Q from the source terminal (S) to the drain terminal (D).
Accordingly, the transistor
62
has a circuit configuration wherein even if the transistor
62
is in the off condition, its circuit is not completely cut off so that electric energy stored in the storage means
3
is dischargeable towards the timing means
2
all the time.
Thereupon, an oscillation circuit, and other control circuits within the timing block
5
of the timing means
2
are not completely turned off, and wasteful leakage current continues to flow for many hours, thereby resulting in progress in the discharge from the storage means
3
.
As a result, there have arisen problems in that, once the electronic timepiece described in the foregoing is kept out of use for many hours, even if power generation is rested, time ranging from several tens of minutes to several hours from the restart of power generation is required for recharging up to a level enabling the tiring means
2
to continue its operation, and if power generation by the electric power generator
1
comes to a stop during a period of the recharging, the timing means
2
stops its operation immediately,
In other words, even if power generation is restarted by the electric power generator
1
, electric energy generated by the electric power generator
1
is used simply for charging the storage means
3
during a period of recharging the storage means
3
to replenish a portion of the electric energy stored in the storage means
3
over-discharged due to leakage current as described above, thereby preventing the electric energy generated to be directly utilized as energy
Citizen Watch Co. Ltd.
Lindinger Michael L.
Martin David
LandOfFree
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