U.S. patent number 3,894,389 [Application Number 05/425,899] was granted by the patent office on 1975-07-15 for electronic watch.
This patent grant is currently assigned to Kabushiki Kaisha Suwa Seikosha. Invention is credited to Teiji Miura, Hiroshi Takeshita.
United States Patent |
3,894,389 |
Miura , et al. |
July 15, 1975 |
Electronic watch
Abstract
A digital display for an electronic timepiece admitting of
reduced power consumption by providing improved circuitry for
driving same. The circuitry applies drive signals to each digit
representative of a unit of time in a sequential manner so as to
light each unit sequentially. The duty cycle is selected to render
all of the display digits visible to the human eye
simultaneously.
Inventors: |
Miura; Teiji (Suwa,
JA), Takeshita; Hiroshi (Suwa, JA) |
Assignee: |
Kabushiki Kaisha Suwa Seikosha
(Tokyo, JA)
|
Family
ID: |
14949259 |
Appl.
No.: |
05/425,899 |
Filed: |
December 18, 1973 |
Foreign Application Priority Data
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|
|
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Dec 18, 1972 [JA] |
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47-127003 |
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Current U.S.
Class: |
368/224; 368/239;
377/112; 968/955; 345/51 |
Current CPC
Class: |
G04G
9/082 (20130101) |
Current International
Class: |
G04G
9/00 (20060101); G04G 9/08 (20060101); G04b
019/30 (); H05b 039/09 () |
Field of
Search: |
;58/5R ;235/92EA
;340/324,336 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Jackmon; Edith Simmons
Attorney, Agent or Firm: Blum, Moscovitz, Friedman &
Kaplan
Claims
What is claimed is:
1. In an electronic timepiece having oscillator means for producing
high frequency timekeeping signals; multi-state divider circuit
means for producing a low frequency timing signals from said high
frequency timekeeping signal, and digital display means for the
digital display of time in response to said timing signals, said
digital display means including at least two digits of time each
digit of time being defined by a plurality of segments, the
selective energization of certain segments effecting the display of
numerals from 0 to 9, the improvement which comprises timing
control circuit means operatively coupled to each of said segments
of said digital display means to sequentially and repetitively
energize each segment of each digit of time, said timing circuit
control means being coupled to said divider means for receiving an
intermediate frequency cycle control signal therefrom whereby each
segment of each digit is actuated during a separate slot of each
cycle of said timing control circuit means.
2. An electronic timepiece as recited in claim 1, wherein said
digital display means includes digits for the display of at least
hours and minutes, said timing control circuit means additionally
sequentially actuating the hours digits as a unit and the minutes
digits as a unit.
3. An electronic timepiece as recited in claim 1, wherein said
timing circuit control means sequentially energizes each of the
digits of time.
4. An electronic timepiece as recited in claim 3, wherein the duty
cycle for the sequential energization of each of the segments and
digits of the digital display means is such as to render said
digits simultaneously visible to the human eye.
5. An electronic timepiece as recited in claim 1, wherein the duty
cycle of the timing control circuit means for the sequential
driving of all of said segments is such as to render same
simultaneously visible to the human eye.
Description
BACKGROUND OF THE INVENTION
In general, this invention is directed to small-sized electronic
timepieces such as wrist watches, and in particular to circuitry
for driving a digital display in a small-sized electronic timepiece
in a manner which produces minimal power consumption.
In small-sized electronic timepieces of the prior art, each of the
digital display elements representing units of time such as hours,
minutes and seconds are driven simultaneously to thereby render
same viewable to the human eye. Because of the excessive amount of
power required to light such digital displays, it has been
necessary to limit the length of time that the digital display
elements could remain lit. If the amount of time is not
considerably limited, the increased power consumption caused by
lighting the digital display elements will have a marked effect of
the life of the battery used in the electronic timepiece, it being
recognized that the capacity of such batteries is seriously limited
in small sized electronic timepieces by obvious space limitations.
Thus, it is necessary to provide a digital display which is easily
viewable yet provides minimum power consumption.
SUMMARY OF THE INVENTION
Generally speaking, in accordance with the invention, an electronic
timepiece circuit is provided for driving a digital display in a
manner which reduces the power consumption thereof. The electronic
timekeeping circuit includes a high frequency signal generating
oscillator, a multi-digit digital display, each digit adapted to
display a particular unit of time, and logic circuitry for
receiving the high frequency time standard signal from the
oscillator and providing same to drive circuits which are adapted
to energize the display elements. Within the logic circuit is a
timing control circuit which causes the drive signals supplied by
the drive circuits to the display elements to be applied to each
digit sequentially, the duty cycle being selected so as to render
the display elements simultaneously visible to a viewer.
When the display elements are formed from segmented digital display
elements, the timing control circuit is further adapted to provide
sequential energization of the segments as well, the duty cycle
combining with the after-image effect of the display elements to
render the display elements simultaneously viewable by the
viewer.
Accordingly, it is an object of this invention to provide an
improved small-sized electronic timepiece including a digital
display wherein power consumption is minimized.
It is a further object of the instant invention to provide an
improved small-sized electronic timepiece wherein hours, minutes
and seconds are not displayed simultaneously yet appear to be when
viewed.
It is a further object of the instant invention to provide an
improved small-sized electronic timepiece wherein voltage drops
caused by the internal resistance of the digital display are
eliminated.
It is still a further object of this invention to provide an
improved electronic timepiece including a digital display wherein
battery life is extended by the sequential energization of the
digital display elements.
Still other objects and advantages of the invention will in part be
obvious and will in part be apparent from the specification.
The invention accordingly comprises the features of construction,
combination of elements, and arrangement of parts which will be
exemplified in the construction hereinafter set forth, and the
scope of the invention will be indicated in the claims.
BRIEF DESCRIPTION OF THE DRAWINGS
For a fuller understanding of the invention, reference is had to
the following description taken in connection with the accompanying
drawings, in which:
FIG. 1 is a circuit diagram of an electronic timepiece including a
digital display for providing minimal power consumption and
constructed in accordance with the instant invention;
FIG. 2 is a wave diagram of signals applied to the display circuit
depicted in FIG. 1;
FIG. 3 is a circuit diagram of an electronic timepiece including a
digital display constructed in accordance with still another
embodiment of the instant invention;
FIG. 4 is a wave diagram of the pulses applied to the digital
display depicted in FIG. 3; and
FIG. 5 is a wave diagram of the signals of still another
embodiment, the signals being applied to the digital display in
accordance with the instant invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to FIG. 1, an electronic time-keeping circuit in
accordance with the invention is provided, including a
high-frequency signal generator A, the output of which is applied
to logic circuit B, the output of which is, in turn, applied to
drive circuits C. Said drive circuits are coupled to a digital
display D. The high-frequency signal produced by the oscillator of
signal generator A is provided to a divider circuit 10 formed from
a chain of multi-stage dividers which produce a lower frequency
signal; for example, a one-second signal for application to
counter/decoder circuit 12, and an intermediate frequency signal
for application to timing control circuit 11.
Timing control circuit 11 consists of a digital matrix which
produces, from the signal applied thereto, eight sequential pulse
signals to more particularly shown in FIG. 2, six of which are
applied to the output of timing control circuit 11, which output is
applied to drive circuit 13 and counter/decoder circuit 12.
Counter/decoder circuit 12 includes a further divider chain, which
produces time-keeping signals representative of each digit of time
on a continuous basis from the signal received from divider circuit
10. Display D includes an hour, minute and seconds display having
six digits, each of the digits formed of seven segments. The
segmented display, generally known as a seven-bar display, is
depicted, by way of example, in FIG. 3 of U.S. Pat. No. 3,756,011,
which issued on Sept. 4, 1973. The display elements defining each
segment of each digit are preferably formed of gallium arsenide
phosphide light-emitting diodes in the timepiece in accordance with
the invention. In order to minimize power consumption, each of the
six digits of time is sequentially energized for the duration of
the associated pulse from timing control circuit 11 as shown in
FIG. 2. The duty cycle for the output of timing control circuit 11
is chosen so that one viewing the display would not notice the
flickering thereof due to retinal retention. A preferable pulse
width is of the order of 1/256th of a second. Thus, instead of
simultaneously energizing all of the digits, the digits are
sequentially displayed at such speeds that it appears that all are
lighted simultaneously. Such a display sequence utilizes one-half
or less of the power that a digital display utilizes when all of
the digits are lit at the same time. The embodiment of FIG. 1 may
take two forms. In a first embodiment, like segments on each of the
six digits would be connected to a common drive circuit 14, which
in turn could be connected to respective decoders or to a common
decoder connected to respective counter circuits, the selection of
the counter circuit coupled through drive circuit 14 to the digital
display being controlled by the pulses from timing control circuit
11 in coordination with the actuation of the digits through drive
circuit 13. This embodiment would save substantial circuit
elements, requiring only a single drive circuit 14, or if desired,
a single decoder for converting the BCD output of the respective
counters into a seven signal output suitable for driving the seven
bar display. In such an embodiment, a logic circuit incorporated in
counter/decoder 12 would perform the selective connection of either
the counters or decoders, if more than one decoder is provided.
A second embodiment is depicted in FIG. 3 wherein like reference
numerals are applied to like elements. In this embodiment, each of
the segments of each of the digits are sequentially actuated. Thus,
not only are each of the digits sequentially actuated, but each of
the segments within each of the digits are sequentially actuated. A
low frequency output of divider 10, for example a 1-second signal,
is applied to counter/decoder 12' while intermediate frequency
outputs are applied to timing control circuit 11'. Said timing
control circuit generates seven kinds of segment codes,
corresponding to each segment of each digit, and six kinds of digit
codes, corresponding to each separate digit. Counter/decoder
circuit 12' produces timing signals representative of each digit of
time in a chain of counters. As discussed above in connection with
FIG. 1, these timekeeping signals can be applied to either a common
decoder or to separate decoders associated with each digit of time,
the output of the common decoder or separate decoders being applied
to a drive circuit 14'.
The output signals from timing control circuit 11' operate through
a logic circuit in counter/decoder circuit 12' so that each segment
of each digit is sequentially actuated. This effect is achieved by
assigning a time slot in the duty cycle to each segment of each
digit. The signal applied in each time slot can come from either a
common drive circuit 14' or decoder, in which case logic circuitry
in counter/decoder circuit 12' would selectively apply the output
of the respective counter circuits of the counter chain to the
common drive circuit 14', or through separate decoder and drive
circuits for each digit, in which case the output of the respective
drive circuit would be energized by the signals from timing control
11' through a suitable logic circuit.
Similarly, each of the digits would be separately energized by
signals applied from timing control circuit 11' through drive
circuit 13'.
It is noted that the segment code signals and the digit code
signals applied from divider 10 to timing control circuit 11' may
be of 2,048 Hz and 256 Hz respectively. The segment signals and
digit signals produced by timing control circuit 11' are shown in
FIGS. 4a and 4b respectively. Since there are seven segment
electrodes in each digit and six digits, there are 42 separate
elements that can be energized. If a duty cycle is selected to be
less than 1/42, each segment of the digit display can be
independently and sequentially lit. In this manner, only one
segment is energized at any instant, so that the energy required to
drive the display is 1/3 to 1/4 that consumed by a conventional
digital display wherein all of the digits are simultaneously
energized. Moreover, the frequency at which a display is energized
is greater than or equal to 32 Hz, the after-image effect of the
human eye eliminates the flicker in the display. In this manner,
low temperature operation with a continuous display can be achieved
in a satisfactory manner.
In a third embodiment of the arrangement in accordance with the
invention, advantage is taken of the fact that the viewer cannot
efficiently view the six digits of a time display simultaneously.
In the third embodiment, both hour digits, both minute digits and
both second digits are sequentially displayed in turn, two by two.
As more particularly shown in FIG. 5, the gate signals for driving
both hour digits is represented by waveform c, the gate signals for
driving both minute digits is represented by waveform d, and the
gate signals for driving both second digits are represented by
waveform e. If the delay time t is set at 1/16 second or more, a
distinct and readable time display is provided wherein the hours,
minutes and seconds are sequentially displayed. Further savings and
energy consumption can be achieved by combining the instant
embodiment with the embodiment of FIGS. 1 and 3 respectively.
Various embodiments of the invention in accordance with the
invention utilize the after-image effect of the human eye, as well
as the high light-producing efficiency in relation to current
characteristic of light emitting diodes to provide an electronic
timepiece having lower power consumption and an enhanced display.
The watch construction in accordance with the invention can be
simply constructed through the use of integrated circuitry
techniques.
It will thus be seen that the objects set forth above, among those
made apparent from the preceding description, are efficiently
attained and, since certain changes may be made in the above
construction, it is intended that all matter contained in the above
description or shown in the accompanying drawings shall be
interpreted as illustrative and not in a limiting sense.
It is also to be understood that the following claims are intended
to cover all of the generic and specific features of the invention
herein described, and all statements of the scope of the invention
which, as a matter of language, might be said to fall
therebetween.
* * * * *