U.S. patent application number 10/334722 was filed with the patent office on 2003-07-24 for power switching unit of a portable telephone capable of monitoring and controlling a battery supply voltage thereof.
This patent application is currently assigned to Fujitsu Limited. Invention is credited to Aota, Masahiro, Nagatani, Hiroyuki, Satoh, Kazuhiro.
Application Number | 20030139156 10/334722 |
Document ID | / |
Family ID | 29424643 |
Filed Date | 2003-07-24 |
United States Patent
Application |
20030139156 |
Kind Code |
A1 |
Satoh, Kazuhiro ; et
al. |
July 24, 2003 |
Power switching unit of a portable telephone capable of monitoring
and controlling a battery supply voltage thereof
Abstract
A power switching unit of a portable telephone which stores data
such as telephone numbers and operates with a battery. The unit
includes a battery for supplying power to a radio unit and a
control unit which contains a data storage function and controls
operation of the radio unit, a first voltage monitor for monitoring
a supply voltage of the battery to output a first voltage drop
signal when the supply voltage falls below a first predetermined
value, and a communication disconnection device for stopping power
supply to the radio unit upon reception of the first voltage drop
signal. The power switching unit further includes a voltage
adjustment device for adjusting voltage supplied to the control
unit from the battery to a predetermined operating voltage of the
control unit for supplying it to the control unit.
Inventors: |
Satoh, Kazuhiro;
(Kawasaki-shi, JP) ; Nagatani, Hiroyuki;
(Kawasaki-shi, JP) ; Aota, Masahiro; (Sendai-shi,
JP) |
Correspondence
Address: |
ARMSTRONG,WESTERMAN & HATTORI, LLP
1725 K STREET, NW
SUITE 1000
WASHINGTON
DC
20006
US
|
Assignee: |
Fujitsu Limited
Kawasaki
JP
|
Family ID: |
29424643 |
Appl. No.: |
10/334722 |
Filed: |
January 2, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10334722 |
Jan 2, 2003 |
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08962619 |
Nov 3, 1997 |
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08962619 |
Nov 3, 1997 |
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08520731 |
Aug 29, 1995 |
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08520731 |
Aug 29, 1995 |
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08025331 |
Feb 24, 1993 |
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Current U.S.
Class: |
455/127.1 |
Current CPC
Class: |
Y02D 30/70 20200801;
H04W 52/0277 20130101; Y02D 70/00 20180101 |
Class at
Publication: |
455/127 |
International
Class: |
H04B 001/04; H01Q
011/12 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 27, 1992 |
JP |
04-041677 |
Mar 9, 1992 |
JP |
04-050179 |
Claims
What is claimed is:
1. A power switching unit of a portable telephone comprising a
radio unit and a control unit which contains a data storage
function and controls operation of the radio unit, said power
switching unit comprising: a battery for supplying power to the
control unit and the radio unit; first voltage monitor means for
monitoring a supply voltage of said battery to output a first
voltage drop signal when said supply voltage falls below a first
predetermined value; and communication disconnection means for
stopping power supply to said radio unit upon reception of said
first voltage drop signal.
2. The power switching unit of the portable telephone as claimed in
claim 1 further including a display, wherein said control unit
causes said display to display a communication disable message when
said first voltage drop signal is received.
3. The power switching unit of the portable telephone as claimed in
claim 1 further including: second voltage monitor means for
monitoring the supply voltage of said battery to output a second
voltage drop signal when said supply voltage falls below a second
predetermined value lower than said first predetermined value;
control disconnection instruction means for outputting a control
disconnection signal upon reception of said second voltage drop
signal; and control disconnection means for stopping power supply
to said control unit upon reception of said control disconnection
signal.
4. The power switching unit of the portable telephone as claimed in
claim 1 further including voltage adjustment means for adjusting
voltage supplied to the control unit from said battery to a
predetermined operating voltage of said control unit for supplying
it to said control unit.
5. The power switching unit of the portable telephone as claimed in
claim 3 further including a display, wherein said control
disconnection instruction means is adapted to output said control
disconnection signal in a predetermined time after reception of
said second voltage drop signal and said control unit causes said
display to display a prompting message for said predetermined time
for requesting the user to charge said battery.
6. The power switching unit of the portable telephone as claimed in
claim 4 further including: third voltage monitor means for
monitoring voltage supplied to said voltage adjustment means to
output a power shutoff signal when said voltage falls below a lower
limit of input voltage at which said voltage adjustment means can
work; and power shutoff means for stopping power supply to said
control unit and said radio unit upon reception of said power
shutoff signal.
7. The power switching unit of the portable telephone as claimed in
claim 4 further including fourth voltage monitor means for
monitoring output voltage from said voltage adjustment means to
output a reset signal when said output voltage falls below a third
predetermined value, wherein said control unit is adapted to be
reset upon reception of said reset signal.
8. The power switching unit of the portable telephone as claimed in
claim 7 wherein said first predetermined value is a lower limit of
voltage at which said radio unit can work and said third
predetermined value is a lower limit of voltage at which said
control unit can work, said third predetermined value being less
than said first predetermined value.
9. A power switching unit of a portable telephone comprising a
radio unit and a control unit which contains a data storage
function and controls operation of the radio unit, said power
switching unit comprising: a first battery for supplying power to
the control unit; a second battery normally for supplying power to
the radio unit; first voltage monitor means for always monitoring a
supply voltage of said first battery to output a first voltage drop
signal when said supply voltage of said first battery falls below a
first predetermined value; power supply instruction means for
outputting a power supply instruction signal upon reception of said
first voltage drop signal; power supply means for supplying power
to said control unit from said second battery upon reception of
said power supply instruction signal; second voltage monitor means
for always monitoring a supply voltage of said second battery to
output a second voltage drop signal when said supply voltage of
said second battery falls below a second predetermined value; power
disconnection instruction means for outputting a power
disconnection signal upon reception of said second voltage drop
signal; and power disconnection means for stopping power supply to
said radio unit from said second battery upon reception of said
power disconnection signal.
Description
BACKGROUND OF THE INVENTION
[0001] (1) Field of the Invention
[0002] This invention relates to a power switching unit of a
portable telephone operated with a battery and more particularly to
a power switching unit of a portable telephone having a storage
function of data such as telephone numbers.
[0003] (2) Description of the Related Art
[0004] Recently, as the demand for mobile communication has
increased, high functions and high performance as well as a simple
radiotelephone function are required for a portable telephone.
[0005] One of the high functions is a storage function which
enables the portable telephone to store data such as telephone
numbers and names for reading out the data. This function is called
"electronic pocket notebook function" in this specification.
[0006] With such a portable telephone, if the output voltage of an
internal battery falls below the threshold voltage required for a
radio unit to operate at the minimum, power supply from the battery
is shut off to stop all functions of the portable telephone in
order to prevent the radio unit from operating abnormally.
[0007] In such a portable telephone, the electronic pocket notebook
function section consumes much less power than the communication
function section. If the battery output voltage drops and operation
of the communication function becomes impossible, often the
electronic pocket notebook function can be used. Formerly, however,
when the battery output voltage dropped, power supply was stopped
not only to the communication function section, but also to the
electronic pocket notebook function section. Thus, the electronic
pocket notebook function as well as the communication function
became unavailable.
SUMMARY OF THE INVENTION
[0008] Accordingly, it is an object of the invention to provide a
power switching unit of a portable telephone having a data storage
function such as an electronic pocket notebook function that can be
used even if a supply voltage from a battery drops.
[0009] To the end, according to a first embodiment of the
invention, there is provided a power switching unit of a portable
telephone comprising a radio unit and a control unit which contains
a data storage function and controls operation of the radio unit,
the power switching unit comprising:
[0010] a battery for supplying power to the control unit and the
radio unit;
[0011] first voltage monitor means for monitoring a supply voltage
of the battery to output a first voltage drop signal when the
supply voltage falls below a first predetermined value; and
[0012] communication disconnection means for stopping power supply
to the radio unit upon reception of the first voltage drop
signal.
[0013] The power switching unit of the portable telephone further
includes voltage adjustment means for adjusting the voltage
supplied to the control unit from said battery to a predetermined
operating voltage of the control unit for supplying it to the
control unit.
[0014] According to a second embodiment of the invention, there is
provided a power switching unit of a portable telephone comprising
a radio unit and a control unit which contains a data storage
function and controls operation of the radio unit, the power
switching unit comprising:
[0015] a first battery for supplying power to the control unit;
[0016] a second battery normally for supplying power to the radio
unit;
[0017] first voltage monitor means for always monitoring a supply
voltage of the first battery to output a first voltage drop signal
when the supply voltage of the first battery falls below a first
predetermined value;
[0018] power supply instruction means for outputting a power supply
instruction signal upon reception of the first voltage drop
signal;
[0019] power supply means for supplying power to the control unit
from the second battery upon reception of the power supply
instruction signal;
[0020] second voltage monitor means for always monitoring a supply
voltage of the second battery to output a second voltage drop
signal when the supply voltage of the second battery falls below a
second predetermined value;
[0021] power disconnection instruction means for outputting a power
disconnection signal upon reception of the second voltage drop
signal; and
[0022] power disconnection means for stopping power supply to the
radio unit from the second battery upon reception of the power
disconnection signal.
[0023] If the voltage supplied from the battery drops, power supply
to the radio unit is shut off, but power supply to the control unit
having the data storage function is continued, so that the user can
use only the data storage function such as the electronic pocket
notebook function.
[0024] The above and other objects, features, and advantages of the
present invention will become apparent from the following
description when taken in conjunction with the accompanying
drawings which illustrate preferred embodiments of the present
invention by way of example.
BRIEF DESCRIPTION OF THE DRAWINGS
[0025] In the drawings:
[0026] FIG. 1 is an external view of a portable telephone according
to the invention;
[0027] FIG. 2 is a circuit diagram showing the configuration of a
power switching unit of a portable telephone according to a first
embodiment of the invention;
[0028] FIG. 3 is a graph showing the time characteristic of battery
voltage;
[0029] FIG. 4 is a block diagram showing the internal configuration
of a control unit;
[0030] FIG. 5 is a flowchart showing a switching control sequence
by a control unit according to a first embodiment of the
invention;
[0031] FIG. 6 is a block diagram showing the configuration of a
power switching unit of a portable telephone according to a second
embodiment of the invention;
[0032] FIG. 7 is a flowchart showing a power switching control
sequence by a control unit according to the second embodiment of
the invention;
[0033] FIG. 8 is a block diagram showing the configuration of a
power switching unit of a portable telephone according to a third
embodiment of the invention;
[0034] FIG. 9 is a flowchart showing a power switching control
sequence by a control unit according to the third embodiment of the
invention;
[0035] FIG. 10 is a block diagram showing the configuration of a
power switching unit of a portable telephone according to a fourth
embodiment of the invention; and
[0036] FIG. 11 is a flowchart showing a power switching control
sequence by a control unit according to the fourth embodiment of
the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0037] Referring now to the accompanying drawings, there are shown
embodiments of the invention.
[0038] FIG. 1 is an external view of a portable telephone according
to the invention. A loudspeaker 11, a display section 12, an open
cover 13, and a microphone 17 are provided on the top of the
portable telephone 10. The display section 12 displays telephone
numbers and names previously stored as a telephone number list and
also displays information such as an alarm. Push buttons 14 are
located on the inside of the open cover 13. With the open cover 13
opened, the portable telephone 10 can be used as a telephone for a
calling through an antenna 15, but with the open cover 13 unopened,
the portable telephone 10 can be used as a telephone when a calling
is received. The push buttons 14 can also be used to store and
update a telephone number list and to instruct the list to be
displayed.
[0039] On the other hand, a battery housing section 16 is provided
at the bottom of the portable telephone 10. This battery housing
section 16 can be removed together with a battery to enable the
user to charge the battery without taking it out from the battery
housing section 16.
[0040] FIG. 2 is a circuit diagram showing the configuration of a
power switching unit of a portable telephone according to a first
embodiment of the invention. The embodiment uses a battery 80 as a
power source. A nickel-cadmium battery of a relatively large
charging capacity is used for the battery 80. From the battery 80,
power is supplied through a control disconnection circuit 20 to a
control unit 60 and through a communication disconnection circuit
30 to a radio unit 70. The output voltage value of the battery 80
(5V) is always monitored by voltage monitor circuits 40 and 50.
[0041] The voltage monitor circuit 40 consists mainly of resistors
R1 and R2, a voltage stabilizer 41, and an operational amplifier
42. The resistors R1 and R2 multiply the output voltage value of
the battery 80 by R2/(R1+R2). (Assume that R1 and R2 represent the
resistance values of the resistors R1 and R2.) The voltage
stabilizer 41 uses the supply voltage (5V) finally sent to the
control unit 60 and the radio unit 70 to generate a constant
reference voltage.
[0042] The operational amplifier 42 outputs a voltage Vx to the
control unit 60 in response to the difference between the reduced
battery voltage and the reference voltage. The voltage Vx is set
high when the output voltage of the battery 80 is equal to or
greater than the lower limit of voltage Va, at which the control
unit 60 can operate; otherwise, the voltage Vx is set low.
[0043] The voltage monitor circuit 50 consists mainly of resistors
R3 and R4, a voltage stabilizer 51, and an operational amplifier
52. The resistors R3 and R4 multiply the output voltage value of
the battery 80 by R4/(R3+R4). (Assume that R3 and R4 represent the
resistance values of the resistors R3 and R4.) Like the voltage
stabilizer 41, the voltage stabilizer 51 uses the supply voltage
(5V) finally sent to the control unit 60 and the radio unit 70 to
generate a constant reference voltage.
[0044] The operational amplifier 52 outputs a voltage Vy to the
control unit 60 and the communication disconnection circuit 30 in
response to the difference between the reduced battery voltage and
the reference voltage. The voltage Vy is set high when the output
voltage of the battery 80 is equal to or greater than the lower
limit of voltage Vb, at which the radio unit 70 can operate;
otherwise, the voltage Vx is set low.
[0045] FIG. 3 is a graph showing the time characteristic of voltage
of the battery 80 when the portable telephone 10 operates. As seen
in the figure, the output voltage of the battery 80 reaches the
lower limit of voltage Vb, at which the radio unit 70 can operate
at time t1; then at time t2, the output voltage reaches the lower
limit of voltage Va, at which the control unit 60 can operate. That
is, when the output voltage of the battery 80 drops, first the
voltage Vy goes low; then the voltage Vx goes low.
[0046] Returning to FIG. 2, at the communication disconnection
circuit 30, the output voltage Vy of the voltage monitor circuit 50
is input via a resistor R5 to the base of a transistor T1. When the
output voltage of the battery 80 is sufficient and the voltage Vy
is high, the transistor T1 operates, thereby operating another
transistor T2 for supplying power from the battery 80 to the radio
unit 70.
[0047] On the other hand, if the output voltage of the battery 80
drops and the voltage Vy goes low, the transistor T1 does not
operate, thus the transistor T2 does not operate either. Therefore,
power supply from the battery 80 to the radio unit 70 is
stopped.
[0048] The control unit 60 has the electronic pocket notebook (or
system pocket notebook) function which stores data such as
telephone numbers and names and other various pieces of information
such as calendars for display on the display section 12. The
control unit 60 also controls power switching operation, message
display, etc. Further, it may also be provided with a function of
causing the radio unit to perform call originating operation based
on a read-out telephone number.
[0049] FIG. 4 shows the internal configuration of the control unit
60. The control unit 60 consists of components such as a CPU 61
which performs electronic pocket notebook function processing and
power switching control, a ROM 62 which stores electronic pocket
notebook function processing and power switching control programs,
a RAM 63 which stores various data pieces such as telephone
numbers, and an input/output interface 64 to which the operational
amplifier 42 of the voltage monitor circuit 40, the operational
amplifier 52 of the voltage monitor circuit 50, the control
disconnection circuit 20, the push buttons 14, the display section
12, and others are connected.
[0050] Returning to FIG. 2, first, when the output voltage Vy from
the voltage monitor circuit 50 goes low, the communication
disconnection circuit 30 stops power supply to the radio unit 70,
thus the control unit 60 causes the display section 12 to display a
communication disable message. Next, when the output voltage Vx
from the voltage monitor circuit 40 goes low, the control unit 60
causes the display section 12 to display a prompting message for
requesting the user to charge the battery 80, then outputs a
control disconnection instruction signal to the control
disconnection circuit 20 in the predetermined time after display of
the prompting message is started.
[0051] The control disconnection circuit 20 has the same
configuration as the communication disconnection circuit 30; when
the control disconnection instruction signal is input, the control
disconnection circuit 20 becomes out of continuity, stopping power
supply to the control unit 60. The control disconnection control
signal is indicated when the output voltage from the control unit
60 goes low. Normally, high voltage is input to the control
disconnection circuit 20 from the control unit 60. Therefore, the
control disconnection circuit 20 is normally in a continuity state
for supplying power to the control unit 60; when the control
disconnection instruction signal which is low is input, the control
disconnection circuit 20 becomes out of continuity, stopping power
supply to the control unit 60.
[0052] FIG. 5 is a flowchart showing a switching control sequence
by the control unit 60 according to the first embodiment of the
invention.
[0053] At step S1, the voltage Vy is checked to see if the output
voltage value of the battery 80 falls below Vb. If so, then the
control sequence proceeds to step 32 otherwise, step S1 is
repeated.
[0054] At step S2, the display section 12 is made to display a
communication disable message.
[0055] At step S3, the voltage Vx is checked to see if the output
voltage value of the battery 80 falls below Va. If so, then the
control sequence proceeds to step S4; otherwise, step S3 is
repeated.
[0056] At step S4, the display section 12 is made to display a
prompting message for requesting the user to charge the battery
80.
[0057] At step S5, in the predetermined time after the output
voltage value of the battery 80 falls below Va, a control
disconnection instruction signal is output to the control
disconnection circuit 20 for stopping power supply to the control
unit 60.
[0058] The embodiment is designed to stop power supply only to the
radio unit 70 if the output voltage value of the battery 80 falls
below the lower limit of voltage Vb, at which the radio unit 70 can
operate, thus the control unit 60 which consumes low power can be
operated. Even if the battery output voltage drops and the portable
telephone 60 cannot be used for communication as a telephone, the
electronic pocket notebook function can be continued.
[0059] The embodiment is also designed to stop power supply to the
control unit 60 as well as to the radio unit 70 if the output
voltage value of the battery 80 falls below the lower limit of
voltage Va, at which the control unit 60 can operate, thus the
control unit 60 can be prevented from malfunctioning, etc.
[0060] Next, a second embodiment of the invention is described.
[0061] FIG. 6 is a block diagram showing the configuration of a
power switching unit of a portable telephone according to the
second embodiment of the invention. Like the power switching unit
according to the first embodiment, the power switching unit
according to the second embodiment is contained in the portable
telephone 10 shown in FIG. 1. The second embodiment uses power
sources of a control battery 110 for supplying power only to a
control unit 150 and a communication battery 120 for supplying
power normally to a radio unit 160. A nickel-cadmium battery of a
relatively large charging capacity is used for the communication
battery 120 and a small-sized lithium battery is used for the
control battery 110.
[0062] Power from the control battery 110 is supplied to the
control unit 150 through a diode D1. On the other hand, power from
the communication battery 120 is supplied via a power disconnection
circuit 170 to the radio unit 160. The output voltage value (5V) of
each of the batteries 110 and 120 is always monitored by a voltage
monitor circuit 130.
[0063] The voltage monitor circuit 130 contains two circuit parts
similar to the voltage monitor circuits 40 and 50 used with the
first embodiment (FIG. 2) for monitoring output voltages of the
batteries 110 and 120. When the output voltage value of the control
battery 110 falls below a first predetermined value, the voltage
monitor circuit 130 outputs a control voltage drop signal to the
control unit 150. The first predetermined value is set based on the
lower limit of voltage at which the control unit 150 can be
operated accurately. When the output voltage value of the
communication battery 120 falls below a second predetermined value,
the voltage monitor circuit 130 outputs a communication voltage
drop signal to the control unit 150. The second predetermined value
is set based on the lower limit of voltage at which the radio unit
160 can be operated accurately.
[0064] A power supply circuit 140 and the diode D1 are located
between the control and communication batteries 110 and 120. The
power supply circuit 140 is a switch circuit made of a transistor
T3; when receiving a power supply instruction signal from the
control unit 150, the power supply circuit 140 supplies power from
the communication battery 120 to the control unit 150. In this
case, the diode D1 prevents current from flowing from the
communication battery 120 to the control battery 110.
[0065] A power disconnection circuit 170 is a switch circuit made
of a transistor like the power supply circuit 140 or mechanical
switch means such as a relay. When receiving a power disconnection
instruction signal from the control unit 150, the power
disconnection circuit 170 stops power supply to the radio unit
160.
[0066] The configuration of the control unit 150 is similar to that
of the control unit 60 used with the first embodiment (FIG. 2).
When the output voltage value of the control battery 110 drops and
a control voltage drop signal is received from the voltage monitor
circuit 130, the control unit 150 outputs a power supply
instruction signal to the power supply circuit 140. Then, power is
supplied from the communication battery 120 to the control unit 150
for continuing, the operation of the control unit 150. At the time,
the control unit 150 causes a display section 12 to display a
prompting message for requesting the user to exchange the control
battery 110 for a new one.
[0067] When the output voltage value of the communication battery
120 drops and a communication voltage drop signal is received from
the voltage monitor circuit 130, the control unit 150 sends a power
disconnection instruction signal to the power disconnection circuit
170. Then, the power disconnection circuit 170 stops power supply
from the communication battery 120 to the radio unit 160. At the
time, the control unit 150 causes the display section 12 to display
a communication disable message
[0068] FIG. 7 is a flowchart showing a switching control sequence
by the control unit 150 according to the second embodiment of the
invention.
[0069] At step S11, input of a control voltage drop signal from the
voltage monitor circuit 130 is checked to see if the output voltage
value of the control battery 110 drops. If the battery voltage
drops, the control sequence proceeds to step S12; otherwise, the
control sequence jumps to step S14.
[0070] At step S12, a power supply instruction signal is sent to
the power supply circuit 140 for supplying power from the
communication battery 120 to the control unit 150.
[0071] At step S13, the display section 12 is made to display a
prompting message for requesting the user to exchange the control
battery 110 for a new one.
[0072] At step S14, input of a communication voltage drop signal
from the voltage monitor circuit 130 is checked to see if the
output voltage value of the communication battery 120 drop. If the
battery voltage drops, the control sequence proceeds to step S15;
otherwise, the control sequence is returned to step S11.
[0073] At step S15, a power disconnection instruction signal is
sent to the power disconnection circuit 170 for stopping power
supply to the radio unit 160.
[0074] At step S16, the display section 12 is made to display a
communication disable message.
[0075] The second embodiment is designed to supply power from the
communication battery 120 to the control unit 150 if the output
voltage value of the control battery 110 drops, thus the control
unit 150 can always be operated.
[0076] The second embodiment is also designed to stop power supply
from the communication battery 120 to the radio unit 160 if the
output voltage value of the communication battery 120 drops, thus
abnormal operation of the radio unit 160 caused by the voltage drop
can be prevented.
[0077] Next, a third embodiment of the invention is described.
[0078] FIG. 8 is a block diagram showing the configuration of a
power switching unit of a portable telephone according to the third
embodiment of the invention. Like the power switching unit
according to the first embodiment, the power switching unit
according to the third embodiment is contained in the portable
telephone 10 shown in FIG. 1. The third embodiment uses a battery
200 as a power source.
[0079] Power from the battery 200 is supplied to a radio unit 204
via a switching circuit 201, a switching circuit 202, and a voltage
transformation circuit 203 in order, and is also supplied to a
control unit 206 via the switching circuit 201 and a voltage
transformation circuit 205 in order. The switching circuit 201 is
made of mechanical switch means such as a relay; when receiving a
power disconnection signal from a voltage monitor circuit 207
described below, the switching circuit 201 is opened. The switching
circuit 202 consists of a transistor circuit; when receiving a
communication shutoff signal from the control unit 206, the
switching circuit 202 becomes out of continuity. The voltage
transformation circuit 203 steps down normal supply voltage 6V
received from the battery 200 to normal operating voltage of the
radio unit 220, 5V. When the supply voltage from the battery 200
exceeds 5V, the voltage transformation circuit 205 steps it down to
5V when the supply voltage falls below 5V, automatically the
circuit 205 steps it up to 5V so as to always supply normal
operating voltage of the control unit 240, 5V, to the control unit
240. The minimum input voltage from the battery 200 that can be
stepped up to 5V by the voltage transformation circuit 205 is
1V.
[0080] A voltage monitor circuit 208 consists of two operational
amplifiers 208a and 208b, each of which serves as a comparator. The
operational amplifier 208a monitors output voltage of the battery
200 to the radio unit 204 at the output stage of the switching
circuit 201; when the output voltage of the battery 200 falls below
5V, the operational amplifier 208a outputs a low voltage detection
signal to the control unit 206. The voltage 5V corresponds to the
input voltage of the voltage transformation circuit 203 required to
provide the lower limit voltage (about 4.2V) at which the radio
unit 204 can operate. The operational amplifier 208b monitors
supply voltage to the control unit 206 at the output stage of the
voltage transformation circuit 205; when the supply voltage falls
below the lower limit voltage 4.2V at which the control unit 206
can operate, the operational amplifier 208b outputs a reset signal
to the control unit 206.
[0081] When receiving the low voltage detection signal, the control
unit 206 sends a communication shutoff signal to the switching
circuit 202 to place the switching circuit 202 out of continuity
for shutting off power supply to the radio unit 204. When receiving
the reset signal, the control unit 206 is reset for preventing the
internal CPU from being upset.
[0082] The voltage monitor circuit 207, which consists of an
operational amplifier as a comparator, monitors input voltage of
the voltage transformation circuit 205 at the output stage of the
switching circuit 201; when the input voltage falls below 1V, the
voltage monitor circuit 207 outputs a power shutoff signal to the
switching circuit 201. The voltage 1V is the Lower limit of input
voltage from which the voltage transformation circuit 205 can
generate output voltage 5V.
[0083] The control unit 206 and the voltage monitor circuit 207
have the same configurations as the control unit 60 and the voltage
monitor circuit 40 used with the first embodiment (FIG. 2)
respectively. The voltage monitor circuit 208 has the same
configuration as the voltage monitor circuit 130 used with the
second embodiment (FIG. 6).
[0084] FIG. 9 is a flowchart showing a switching control sequence
according to the third embodiment of the invention.
[0085] At step S21, the voltage monitor circuit 208 determines
whether or not the output voltage of the battery 200 to the radio
unit 204 is 5V or higher. If it is 5V or higher, step S21 is
repeated; if the voltage is lower than 5V, the voltage monitor
circuit 208 outputs a low voltage detection signal to the control
unit 206, and the control sequence proceeds to step S22.
[0086] At step S22, the control unit 206 sends a communication
shutoff signal to the switching circuit 202 to place the switching
circuit 202 out of continuity for shutting off power supply to the
radio unit 204. Then, the radio unit 204 does not work, but the
voltage transformation circuit 205 steps up voltage to enable the
control unit 206 to continue operation. Therefore, the electronic
pocket notebook function of the control unit 206 is effective;
various data pieces can be stored and displayed on a display
section 12 although the output voltage of the battery 200
drops.
[0087] At step S23, the voltage monitor circuit 208 determines
whether or not the voltage supplied to the control unit 206 is the
lower limit voltage 4.2 V or higher at which the control unit 206
can operate. If it is 4.2V or higher, the control sequence jumps to
step S25; if the voltage is Lower than 4.2V, the voltage monitor
circuit 208 outputs a reset signal to the control unit 206, and the
control sequence proceeds to step S24.
[0088] At step S24, when receiving the reset signal, the control
unit 206 is reset.
[0089] At step S25, the voltage monitor circuit 208 determines
whether or not the input voltage to the voltage transformation
circuit 205 is 1V or higher. If it is 1V or higher, the control
sequence returns to step S23; if the voltage is lower than 1V, the
voltage monitor circuit 208 outputs a power shutoff signal to the
switching circuit 201.
[0090] At step S26, when receiving the power shutoff signal, the
switching circuit 201 is opened to shut off power supply from the
battery 200 to the radio unit 204, the control unit 206, etc.
[0091] In the third embodiment shown in FIG. 8, the switching
circuit 202 and the voltage transformation circuit 203 may be
removed for direct connection of the switching circuit 201 to the
radio unit 204 (broken line arrow 209) wherein the control unit
206, upon reception of a low voltage detection signal from the
voltage monitor circuit 208, may control the radio unit (broken
line arrow 210) to save power of the radio unit 204 and stop the
communication function of the same.
[0092] Although it is possible that the voltage transformation
circuit 203 steps up voltage Like the voltage transformation
circuit 208, it is not preferable that the voltage transformation
circuit 203 for the radio unit 204 steps up voltage because output
of a voltage transformation circuit which steps up voltage
generally contains much noise.
[0093] In the third embodiment, the voltage transformation circuit
205 which can step up voltage is provided between the control unit
206 and the battery 200, thus even if the supply voltage drops and
the radio unit 204 becomes unavailable, the control unit 206 can be
worked until the supply voltage reaches the lower limit 1V at which
the voltage transformation circuit 205 can output stepped-up
voltage.
[0094] Next, a fourth embodiment of the invention is described.
[0095] FIG. 10 is a block diagram showing the configuration of a
power switching unit of a portable telephone according to the
fourth embodiment of the invention. The fourth embodiment is
characterized by the normal operating voltage of a control unit 306
which is 3V lower than that of a radio unit 204, 5V, but basically
the fourth embodiment has the same configuration as the third
embodiment. In the description to follow, the same parts as those
shown in FIG. 8 are designated by the same reference numerals in
FIG. 10, and will therefore not be discussed again.
[0096] The voltage transformation circuit 305 steps down input
voltage 6V from a battery 200 to 3V. Even if the input voltage
drops from 6V, the voltage transformation circuit 305 continues to
output 3V, but if the input voltage falls below 3.2V, the circuit
305 becomes unable to output 3V. Unlike the voltage transformation
circuit 205 used with the third embodiment, the voltage
transformation circuit 305 does not have the voltage step-up
function.
[0097] The voltage monitor circuit 308 monitors output voltage of
the battery 200 to the radio unit 204, and if the output voltage of
the battery 200 falls below 5V, it outputs a low voltage detection
signal to the control unit 306, as with the voltage monitor circuit
208 of the third embodiment. Also, the voltage monitor circuit 308
monitors voltage supplied to the control unit 306, and if the
voltage falls below the operating voltage of the control unit 306,
3V, it outputs a reset signal to the control unit 306.
[0098] Like the control unit 206 of the third embodiment, when
receiving the low voltage detection signal, the control unit 306
sends a communication shutoff signal to a switching circuit 202 to
place the switching circuit 202 out of continuity for shutting off
power supply to the radio unit 204. When receiving the reset
signal, the control unit 306 is reset for preventing the internal
CPU from being upset.
[0099] A voltage monitor circuit 307 monitors input voltage of the
voltage transformation circuit 305; when the input voltage falls
below 3.2 V, the voltage monitor circuit 307 outputs a power
shutoff signal to a switching circuit 201. The voltage 3.2V is the
lower limit of input voltage from which the voltage transformation
circuit 305 can generate output voltage 3V as described above.
[0100] FIG. 11 is a flowchart showing a switching control sequence
according to the fourth embodiment of the invention.
[0101] At step S31, the voltage monitor circuit 308 determines
whether or not the output voltage of the battery 200 to the radio
unit 204 is 5V or higher. If it is 5V or higher, step S31 is
repeated; if the voltage is lower than 5V, the voltage monitor
circuit 308 outputs a low voltage detection signal to the control
unit 306, and the control sequence proceeds to step S32.
[0102] At step S32, the control unit 306 sends a communication
shutoff signal to the switching circuit 202 to place the switching
circuit 202 out of continuity for shutting off power supply to the
radio unit 204. Then, the radio unit 204 does not work, but power
is supplied to the control unit 306 which can then continue
operation. Therefore, the electronic pocket notebook function of
the control unit 306 is effective; various data pieces can be
stored and displayed on a display section 12 although the output
voltage of the battery 200 drops.
[0103] At step S33, the voltage monitor circuit 308 determines
whether or not the voltage supplied to the control unit 306 is the
operating voltage of the control unit 36, 3V, or higher. If it is
3V or higher, the control sequence jumps to step S35; if the
voltage is lower than 3V, the voltage monitor circuit 308 outputs a
reset signal to the control unit 306, and the control sequence
proceeds to step S34.
[0104] At step S34, when receiving the reset signal, the control
unit 306 is reset.
[0105] At step S35, the voltage monitor circuit 308 determines
whether or not the input voltage to the voltage transformation
circuit 305 is 3.2V or higher. If it is 3.2V or higher, the control
sequence returns to step S33; if the voltage is lower than 3.2V,
the voltage monitor circuit 308 outputs a power shutoff signal to
the switching circuit 201.
[0106] At step S36, when receiving the power shutoff signal, the
switching circuit 201 is opened to shut off power supply from the
battery 200 to the radio unit 204, the control unit 306, etc.
[0107] As in the fourth embodiment, even when the operating voltage
of the control unit 306 is lower than that of the radio unit 204,
if the voltage transformation circuit 305 which steps down voltage
is provided between the control unit 306 and the battery 200 to
cover the operating voltage of the control unit 306 and power
supply to the radio unit 204 is shut off in response to the output
voltage of the battery 200, the operation of the control unit 306
can be continued even when the supply voltage drops.
[0108] In the fourth embodiment shown in FIG. 10, as in the third
embodiment, the switching circuit 202 and the voltage
transformation circuit 203 may be removed for direct connection of
the switching circuit 201 to the radio unit 204 (broken line arrow
209) wherein the control unit 306, upon reception of a low voltage
detection signal from the voltage monitor circuit 308, may control
the radio unit (broken line arrow 210) to save power of the radio
unit 204 and stop the communication function of the same.
[0109] Instead of the voltage monitor circuits 207, 208, 307, and
308 used with the third and fourth embodiments, digital voltage
data into which analog data has been converted may be input to the
control unit 206 or 306 for judgment of the voltage value to switch
power supply.
[0110] Each of the first to fourth embodiments assumes that the
control unit contains the electronic pocket notebook function, but
the control unit may contain a simple data storage function of
storing and reading out data such as telephone numbers, in which
case it can be used for a redialing function which stores the
previously dialed telephone number and reads it out for
redialing.
[0111] The foregoing is considered as illustrative only of the
principles of the present invention. Further, since numerous
modifications and changes will readily occur to those skilled in
the art, it is not desired to limit the invention to the exact
construction and applications shown and described, and accordingly,
all suitable modifications and equivalents may be restored to,
falling within the scope of the invention in the appended claims
and their equivalents.
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