U.S. patent application number 10/508629 was filed with the patent office on 2005-08-11 for electronic device and power supply control method.
Invention is credited to Masui, Ichiro, Ogawa, Katsunori, Sakai, Kenichi.
Application Number | 20050174710 10/508629 |
Document ID | / |
Family ID | 28035532 |
Filed Date | 2005-08-11 |
United States Patent
Application |
20050174710 |
Kind Code |
A1 |
Masui, Ichiro ; et
al. |
August 11, 2005 |
Electronic device and power supply control method
Abstract
The present invention relates to an electronic apparatus and a
power supply controlling method with which input power source is
switched efficiently in accordance with a load of a device. A power
controller 50, upon detecting a USB connection, monitors power
consumption of a CPU 44 based on the operation status of the CPU
44, and controls a switch 42 in accordance with a current supplied
from a USB cable 2. When the current is less than or equal to 500
mA, the switch 42 is switched to a terminal a. Before
configuration, when the current is less than or equal to 100 mA,
the switch 42 is switched to the terminal a, and then a regulator
43 is controlled so that the current will not exceed 100 mA. In USB
suspend, the switch 42 is switched to a terminal b, and a regulator
53 stops output to a backup battery 54. The present invention can
be applied to a digital still camera supporting USB.
Inventors: |
Masui, Ichiro; (Chiba,
JP) ; Ogawa, Katsunori; (Kanagawa, JP) ;
Sakai, Kenichi; (Tokyo, JP) |
Correspondence
Address: |
William S Frommer
Frommer Lawrence & Haug
745 Fifth Avenue
New York
NY
10151
US
|
Family ID: |
28035532 |
Appl. No.: |
10/508629 |
Filed: |
September 16, 2004 |
PCT Filed: |
January 24, 2003 |
PCT NO: |
PCT/JP03/00645 |
Current U.S.
Class: |
361/92 |
Current CPC
Class: |
G06F 1/28 20130101; G06F
1/266 20130101; G06F 1/3203 20130101 |
Class at
Publication: |
361/092 |
International
Class: |
H02H 003/24 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 20, 2002 |
JP |
P2002-077730 |
Claims
1. An electronic apparatus that can be connected to another
electronic apparatus via a cable, the electronic apparatus
comprising: first switching means for switching between first
electric power of the electronic apparatus and second electric
power supplied from the another electronic apparatus via the cable,
and supplying either the first electric power or the second
electric power to a first power supply line; second switching means
for switching from the first electric power to the second electric
power and supplying the second electric power to a second power
supply line when the second electric power is supplied from the
another electronic apparatus; determining means for determining
whether the second electric power supplied from the another
electronic apparatus is less than or equal to a predetermined
threshold value; and controlling means for controlling the first
switching means based on a result of determination by the
determining means.
2. An electronic apparatus according to claim 1, further comprising
detecting means for detecting a connection with the another
electronic apparatus; wherein the determining means determines
whether the second electric power is less than or equal to the
predetermined threshold value when the detecting means has detected
a connection with the another electronic apparatus, and wherein the
controlling means controls switching of the first switching means
so that the second electric power will be supplied to the first
power supply line when the determining means has determined that
the second electric power is less than or equal to the
predetermined threshold value.
3. An electronic apparatus according to claim 1, further comprising
setting processing means for executing processing for setting that
is needed for connection with the another electronic apparatus,
wherein the determining means determines whether the second
electric power is less than or equal to the predetermined threshold
value when the setting processing means is finished, and wherein
the controlling means controls switching of the first switching
means so that the second electric power will be supplied to the
first power supply line when the determining means has determined
that the second electric power is less than or equal to the
threshold value.
4. An electronic apparatus according to claim 1, further comprising
charging means for charging a backup battery when the second
electric power is being supplied from the another electronic
apparatus via the cable.
5. An electronic apparatus according to claim 4, further comprising
detecting means for detecting a suspend status of the electronic
apparatus connected to the another electronic apparatus via the
cable, wherein when the detecting means has detected the suspend
status, the charging means stops charging of the backup battery,
and wherein the controlling means controls switching of the first
switching means so that the first electric power will be supplied
to the first power supply line.
6. An electronic apparatus according to claim 1, wherein the cable
is a USB cable or an IEEE 1394 cable.
7. A power supply controlling method for an electronic apparatus
that is connected to another electronic apparatus via a cable, the
power supply controlling method comprising: a first switching step
of switching between first electric power of the electronic
apparatus and second electric power supplied from the another
electronic apparatus via the cable, and supplying either the first
electric power or the second electric power to a first power supply
line; a second switching step of switching from the first electric
power to the second electric power and supplying the second
electric power to a second power supply line when the second
electric power is supplied from the another electronic apparatus; a
determining step of determining whether the second electric power
supplied from the another electronic apparatus is less than or
equal to a predetermined threshold value; and a controlling step of
controlling processing in the first switching step based on a
result of determination by processing in the determining step.
Description
TECHNICAL FIELD
[0001] The present invention relates to electronic apparatuses and
power supply controlling methods. Particularly, the present
invention relates to an electronic apparatus and a power supply
controlling method with which input power source is switched in
accordance with a load of a device when a portable electronic
device such as a digital still camera is connected to another
electronic device via an external interface.
BACKGROUND ART
[0002] Recently, battery-operated portable electronic devices
having USB (Universal Serial Bus) interfaces, such as digital still
cameras, are becoming common. Such devices can be connected to
other electronic devices via USB cables.
[0003] Such a portable electronic device is capable of operating by
electric power supplied from another electronic device via a USB
cable, without using a battery.
[0004] According to the USB standard, a current up to 500 mA can be
supplied. However, when a portable electronic device is connected
to another electronic device via a USB cable, if the power source
is simply switched to electric power supplied from the USB cable,
operation is not allowed when a current exceeding 500 mA is
needed.
[0005] Furthermore, in a portable electronic device, when a backup
battery (e.g., a secondary battery or a capacitor) is charged
during USB suspend, a consumption current supplied from the USB bus
becomes greater than or equal to 500 .mu.A, so that the USB
standard is not satisfied.
[0006] That is, when the current exceeds the value defined by the
USB standard, error could occur in signal processing or the
like.
DISCLOSURE OF INVENTION
[0007] The present invention has been made in view of the situation
described above, and it aims at switching input power source
efficiently in accordance with a load of a device.
[0008] A power supply controlling apparatus according to the
present invention comprises first switching means for switching
between first electric power of an electronic apparatus and second
electric power supplied from another electronic apparatus via a
cable, and supplying either the first electric power or the second
electric power to a first power supply line; second switching means
for switching from the first electric power to the second electric
power and supplying the second electric power to a second power
supply line when the second electric power is supplied from the
another electronic apparatus; determining means for determining
whether the second electric power supplied from the another
electronic apparatus is less than or equal to a predetermined
threshold value; and controlling means for controlling the first
switching means based on a result of determination by the
determining means.
[0009] The power supply controlling apparatus may be such that
detecting means for detecting a connection with the another
electronic apparatus is further provided, the determining means
determines whether the second electric power is less than or equal
to the predetermined threshold value when the detecting means has
detected a connection with the another electronic apparatus, and
that the controlling means controls switching of the first
switching means so that the second electric power will be supplied
to the first power supply line when the determining means has
determined that the second electric power is less than or equal to
the predetermined threshold value.
[0010] The power supply controlling apparatus may also be such that
setting processing means for executing processing for setting that
is needed for connection with the another electronic apparatus is
further provided, the determining means determines whether the
second electric power is less than or equal to the predetermined
threshold value when the setting processing means is finished, and
that the controlling means controls switching of the first
switching means so that the second electric power will be supplied
to the first power supply line when the determining means has
determined that the second electric power is less than or equal to
the threshold value.
[0011] The power supply controlling apparatus may further comprise
charging means for charging a backup battery when the second
electric power is being supplied from the another electronic
apparatus via the cable.
[0012] The power supply controlling apparatus may be such that
detecting means for detecting a suspend status of the electronic
connected to the another electronic apparatus via the cable is
further provided, and that when the detecting means has detected
the suspend status, the charging means stops charging of the backup
battery, and the controlling means controls switching of the first
switching means so that the first electric power will be supplied
to the first power supply line.
[0013] The cable may be a USB cable or an IEEE 1394 cable.
[0014] A power supply controlling method according to the present
invention comprises a first switching step of switching between
first electric power of an electronic apparatus and second electric
power supplied from another electronic apparatus via a cable, and
supplying either the first electric power or the second electric
power to a first power supply line; a second switching step of
switching from the first electric power to the second electric
power and supplying the second electric power to a second power
supply line when the second electric power is supplied from the
another electronic apparatus; a determining step of determining
whether the second electric power supplied from the another
electronic apparatus is less than or equal to a predetermined
threshold value; and a controlling step of controlling processing
in the first switching step based on a result of determination by
processing in the determining step.
[0015] In the electronic apparatus or the power supply controlling
method according to the present invention, switching between first
electric power of an electronic apparatus and second electric power
supplied from another electronic apparatus via a cable is executed
and either the first electric power or the second electric power is
supplied to a first power supply line. When the second electric
power is supplied from the another electronic apparatus, switching
from the first electric power to the second electric power takes
place and the second electric power is supplied to a second power
supply line. It is determined whether the second electric power
supplied from the another electronic apparatus is less than or
equal to a predetermined threshold value, and electric power
supplied to the first power supply line is switched based on a
result of the determination.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 is a diagram showing an example connection between a
personal computer and a digital still camera according to the
present invention.
[0017] FIG. 2 is a diagram showing example internal configurations
of the personal computer and the digital still camera.
[0018] FIG. 3 is a flowchart for explaining a power supply
process.
[0019] FIG. 4 is a flowchart for further explaining a power supply
process before USB configuration, i.e., step S2 in FIG. 3.
[0020] FIG. 5 is a flowchart for further explaining a power supply
process in an established USB connection, i.e., step S4 in FIG.
3.
BEST MODE FOR CARRYING OUT THE INVENTION
[0021] Now, an embodiment of the present invention will be
described with reference to the drawings.
[0022] FIG. 1 is a diagram showing an example connection between a
personal computer and a digital still camera according to the
present invention. Referring to the figure, a USB port 11 of a
personal computer 1 is connected to one end of a USB cable 2, and
the other end of the USB cable 2 is connected to a USB port 21 of a
digital still camera 3. Thus, the personal computer 1 and the
digital still camera 3 are USB-connected to each other.
[0023] The personal computer 1 is either connected to a power
source that is not shown and operates by a power supply voltage
thereof, or operates by electric power of a battery that is not
shown. Furthermore, the personal computer 1 supplies electric power
to the digital still camera 3 through the USB cable 2.
[0024] The digital still camera 3 operates by electric power of a
battery 41 (FIG. 2), and also operates by electric power that is
supplied from the personal computer 1 through the USB cable 2.
[0025] FIG. 2 is a diagram showing example internal configurations
of the personal computer 1 and the digital still camera 3. Note
that the figure only shows components relating to power supply.
[0026] The personal computer 1 includes a power supply controller
31, a USB host controller 32, and the USB port 11. Although not
shown, the personal computer 1 also includes a central processing
unit (CPU) for executing various processing, a read only memory
(RAM) for storing programs for executing various processing, a
random access memory (RAM) for storing data needed for executing
various processing, input devices such as a keyboard and a mouse, a
display implemented by a cathode-ray tube (CRT) display or a liquid
crystal display (LCD), a speaker, a hard disk drive, and so
forth.
[0027] The power supply controller 31, based on a power supply
voltage supplied from a power source that is not shown, exercises
control to supply electric power to the components of the personal
computer 1, and exercises control to supply electric power to the
USB host controller 32, the USB port 11, and the digital still
camera 3 connected via the USB cable 2.
[0028] The USB host controller 32 exercises connection control
(configuration) for the digital still camera 3 connected via the
USB port 11 and the USB cable 2 so that electric power will be
supplied from the power supply controller 31 to the digital still
camera 3.
[0029] The digital still camera 3 includes a USB port 21, a battery
41, switches 42 and 45, regulators 43, 46, 47, and 53, a CPU 44, a
USB clock 48, a USB device controller 49, a power controller 50, a
real-time clock (RTC) 51, an interrupt controller (INTC: Interrupt
Clock) 52, and a backup battery 54. Although not shown, the digital
still camera 3 also includes a camera signal processor that
executes predetermined processing on captured images of objects,
and an LCD that displays captured images.
[0030] A terminal a of the switch 42 receives electric power
through the USB cable 2, and a terminal b thereof receives electric
power from the battery 41. The switch 42, under the control of the
power controller 50, is switched to the terminal a when electric
power from the USB cable 2 is to be supplied to a power supply line
1, and is switched to the terminal b when electric power from the
battery 41 is to be supplied to the power supply line 1.
[0031] A terminal a of the switch 45 receives electric power from
the USB cable 2, and a terminal b thereof receives electric power
from the battery 41. The switch 45, upon detecting a USB connection
(i.e., when a current is detected due to connection with the USB
cable 2), is forcibly switched to the terminal a so that electric
power from the USB cable 2 will be supplied to a power supply line
2. On the other hand, when a USB connection is not detected, the
switch 45 is switched to a terminal B so that electric power from
the battery 41 will be supplied to the power supply line 2.
[0032] The regulator 43, under the control of the power controller
50, converts the power supply voltage supplied via the switch 42
from the USB cable 2 or the battery 41 into a voltage of a constant
level needed by the CPU 44, and supplies the voltage to the CPU 44
through one or more output lines (three lines in this example).
Thus, the CPU 44 is allowed to operate by the electric power
supplied from the regulator 43.
[0033] The regulator 46 converts the power supply voltage supplied
via the switch 45 from the USB cable 2 or the battery 41 into a
voltage of a constant level needed by the power controller 50, the
real-time clock 51, and the interrupt controller 52, and supplies
the voltage to each of these components. Thus, the power controller
50, the real-time clock 51, and the interrupt controller 52 are
allowed to operate by the electric power supplied from the
regulator 46. The regulator 46 also supplies the voltage of the
constant level obtained by the conversion to the regulator 47 and
the regulator 53.
[0034] The regulator 47, under the control of the power controller
50, converts the voltage supplied from the regulator 46 into a
voltage of a constant level needed by the USB device controller 49,
and supplies the voltage to the USB device controller 49 and to the
USB clock 48. Thus, the USB clock 48 and the USB device controller
49 are allowed to operate by the electric power supplied from the
regulator 47.
[0035] The regulator 53, under the control of the power controller
50, converts the voltage supplied from the regulator 46 into a
voltage of a constant level needed by the backup battery 54, and
supplies the voltage to the backup battery 54.
[0036] The USB device controller 49 operates by a voltage supplied
from the regulator 47, and exercises connection control
(configuration) on the personal computer 1 connected via the USB
port 21 and the USB cable 2. Configuration refers to, for example,
loading configuration data that defines setting information (logic
functions or wire connections) for USB connection.
[0037] The power controller 50 operates by a voltage supplied from
the regulator 46. Upon detecting a USB connection, the power
controller 50 monitors power consumption of the CPU 44 based on the
operation status of the CPU 44 (e.g., ON/OFF of 3V circuitry,
ON/OFF of 5V circuitry, and ON/OFF of the power of the LCD). The
power controller 50 exercises control so that the switch 42 will be
switched to the terminal a when the current supplied from the USB
cable 2 is less than or equal to 500 mA and so that the switch 42
will be switched to the terminal b when the current supplied from
the USB cable 2 is greater than 500 mA.
[0038] Before configuration, the power controller 50 monitors power
consumption based on the operation status of the CPU 44. The power
controller 50 exercises control so that the switch 42 will be
switched to the terminal a when the current supplied from the USB
cable 2 is less than or equal to 100 mA and controls the regulator
43 so that the current supplied from the USB cable 2 will not
exceed 100 mA when the switch 42 is switched. Under this situation,
the USB device controller 49 executes configuration.
[0039] More specifically, before USB configuration, when the
current supplied from the USB cable 2 exceeds 100 mA, the switch 42
is kept switched to the terminal b even if a current is being
supplied from the USB cable 2.
[0040] During USB suspend, the power controller 50 exercises
control so that the switch 42 will be switched to the terminal b
and so that the regulator 53 will stop output to the backup battery
54.
[0041] The power controller 50 controls the respective operations
of the CPU 44, the regulator 47, the USB clock 48, and other
parts.
[0042] The backup battery 54 is implemented by a device that is
included in the digital still camera 3 and that allows charging and
discharging, such as a secondary battery or a capacitor, the device
allowing execution of basic functions of the digital still camera 3
(e.g., internal clock and memory) when the digital still camera 3
is detached from a power source such as the battery 41. The backup
battery 54 is charged by a voltage that is supplied from the
regulator 53.
[0043] Next, a power supply process that is executed by the digital
still camera 3 will be described with reference to a flowchart
shown in FIG. 3.
[0044] In step S1, the power controller 50 determines (detects)
whether a USB connection with the personal computer 1 via the USB
port 21 and the USB cable 2 is established, and waits until a USB
connection is established.
[0045] When it is determined in step S1 that a USB connection is
established, the process proceeds to step S2, in which a power
supply process before USB configuration is executed.
[0046] Now, the power supply process before USB configuration will
be described in detail with reference to a flowchart shown in FIG.
4.
[0047] In step S11, the power controller 50 monitors power
consumption based on the operation status of the CPU 44, and
determines whether the current supplied from the USB cable 2 is
less than or equal to 100 mA. If it is determined that the current
supplied from the USB cable 2 exceeds 100 mA, the process proceeds
to step S14.
[0048] In step S14, the power controller 50 exercises control so
that the switch 42 will be kept switched to the terminal b. Then,
the process returns to step S11, and the process described above is
repeated. That is, when the current supplied from the USB cable 2
exceeds 100 mA, electric power from the battery 41 is supplied to
the power supply line 1.
[0049] If it is determined in step S11 that the current supplied
from the USB cable 2 is less than or equal to 100 mA, the process
proceeds to step S12, in which the power controller 50 exercises
control so that the switch 42 will be switched to the terminal a.
Thus, electric power from the USB cable 2 is supplied to the power
supply line 1.
[0050] In step S13, the power controller 50 controls the regulator
43 so that the current from the USB cable 2 will not exceed 100 mA
when the switch 42 is switched. The USB device controller 49
executes configuration with the personal computer 1 connected via
the USB cable 2. The process then returns to step S3 shown in FIG.
3.
[0051] In step S3, the USB device controller 49 determines whether
configuration is completed. If it is determined that configuration
is not completed, the process returns to step S2, and the
processing described above is repeated.
[0052] If it is determined in step S3 that configuration is
completed, the process proceeds to step S4, in which a power supply
process in an established USB connection is executed.
[0053] Now, the power supply process in an established USB
connection will be described with reference to a flowchart shown in
FIG. 5.
[0054] In step S21, the power controller 50 monitors power
consumption based on the operation status of the CPU 44, and
determines whether the current supplied from the USB cable 2 is
less than or equal to 500 mA. If it is determined that the current
supplied from the USB cable 2 is less than or equal to 500 mA, the
process proceeds to step S22.
[0055] In step S22, the power controller 50 exercises control so
that the switch 42 will be switched to the terminal a. Thus,
electric power from the USB cable 2 is supplied to the power supply
line 1.
[0056] If it is determined in step S21 that the current supplied
from the USB cable 2 exceeds 500 mA, the process proceeds to step
S23, in which the power controller 50 exercises control so that the
switch 42 will be switched to the terminal b. Thus, electric power
from the battery 41 is supplied to the power supply line 1.
[0057] Upon completion of processing in step S22 or step S23, the
process returns to step S5 shown in FIG. 3.
[0058] In step S5, the power controller 50 determines whether the
USB connection is disconnected. If it is determined that the USB
connection is disconnected, the process returns to step S1, and the
subsequent processing described above is repeated.
[0059] If it is determined in step S5 that the USB connection is
not disconnected, i.e., when it is determined that the USB
connection is maintained, the process proceeds to step S6.
[0060] In step S6, the power controller 50 determines whether USB
suspend has been entered. If it is determined that USB suspend has
not been entered, the process returns to step S4, and the
subsequent processing described above is repeated.
[0061] If it is determined in step S6 that USB suspend has been
entered, the process proceeds to step S7, in which the power
controller 50 exercises control so that the switch 42 will be
switched to the terminal b and so that the regulator 53 will stop
output to the backup battery 54. Thus, electric power from the
battery 41 is supplied to the power supply line 1, and the charging
of the backup battery 54 is stopped. Accordingly, the current
supplied from the USB bus is maintained to be less than or equal to
500 .mu.A.
[0062] In step SB, the power controller 50 determines whether the
device has returned from USB suspend. If it is determined that the
device has not returned from USB suspend, the process returns to
step S7, and the processing described above is repeated.
[0063] If it is determined in step S8 that the device has returned
from USB suspend, the process returns to step S4, and the
subsequent processing described above is repeated. That is, the
power supply process in an established USB connection, described
with reference to FIG. 5, is executed again.
[0064] As described above, the power controller 50 of the digital
still camera 3 switches input power source in accordance with a
load of the device, so that electric power from the USB bus is used
efficiently and the load of the battery 41 is reduced.
[0065] During USB suspend, charging of the backup battery 54 is
stopped, so that wasteful power consumption is minimized.
[0066] Furthermore, in an established USB connection, the blocks
that are at least needed for the operation of the device (the power
controller 50, the real-time clock 51, the interrupt controller 52,
etc.) are allowed to operate by electric power supplied from the
USB bus. This reduces the load of the battery 41 in an established
USB connection.
[0067] The description has been made hereinabove in the context of
an example where the personal computer 1 and the digital still
camera 3 are USB-connected with each other. However, the present
invention can be applied widely to information processing
apparatuses that are capable of supplying electric power to
electronic devices supporting USB and that include the USB host
controller 32, as well as the personal computer 1. Also, the
present invention can be applied widely to portable electronic
devices supporting USB, such as camcorders and personal digital
assistants (PDAs), as well as the digital still camera 3.
[0068] Furthermore, according to the present invention, although
input power source is efficiently switched in an established USB
connection, without limitation to USB, for example, when a
connection with an IEEE 1394 (Institute of Electrical and
Electronic Engineers) bus is established, it is possible to switch
input power source efficiently in accordance with the standard. In
that case, input power source is switched according to whether the
current supplied through the IEEE 1394 bus exceeds 1.5 A.
Industrial Applicability
[0069] According to the present invention, input power source is
switched efficiently according to a load of a device.
[0070] Furthermore, according to the present invention, when an
electronic device is connected to another electronic device via an
external interface, input power source is switched efficiently
according to a load of the device. This reduces the load of a
battery.
* * * * *