Digital Camera Patent Abstract
A digital camera includes an interface via which the digital signals
of a photographed image are transferred to an external data processing
device, an internal power supply for the digital camera, and a power
supply circuit that receives power from the data processing device.
Connecting the data processing device to an interface of the camera
via an interface in order to transfer image data from the camera
to the device causes a control interface circuit to detect a connection
detection signal which is turned on when the camera is connected
to the device. Then, the power of an output of a DC/DC converter
of the camera is switched from the internal battery to the power
supply circuit of the device. The camera is started and put in a
communication wait state. In response to a control signal from the
device, the camera starts operation to transfer an image. Digital Camera Patent Claims
What is claimed is:
1. A digital camera for photographing a subject to output image
signals representing the subject, comprising: an interface connectable
to an external data processing device, the interface transferring
the image signals to the data processing device; an internal power
supply for supplying a first power to components of said digital
camera; an external power receiving circuit for receiving a second
power from the data processing camera; a first switching circuit
for selectively switching between said internal power supply and
said external power receiving circuit to supply the first or the
second power to the components of said digital camera; a connection
detection circuit for detecting that the data processing device
has been connected to said interface; and a control circuit for
controlling said first switching circuit in response to said connection
detection circuit, wherein said control circuit controls said first
switching circuit in such a way that, when said connection detection
circuit does not detect that said interface is connected to the
data processing device, the first power is supplied to the components
of said digital camera, and when said connection detection circuit
detects that said interface is connected to the data processing
device, said internal power supply is disconnected and the second
power is supplied to the components of said digital camera, and
wherein said internal power supply comprises a secondary battery,
and said digital camera, further comprises an adapter connector
for connecting a charging adapter to charge said secondary battery
by a commercial power supply, a charging circuit for charging said
secondary battery, and a second switching circuit for charging said
secondary battery selectively through said charging circuit or through
the charging adapter via said adapter connector, the charging adapter
connected to the secondary battery without passing through the charging
circuit.
2. The digital camera is accordance with claim 1, wherein, when
said connection detection circuit detects that the data processing
device is connected to said digital camera, said control circuit
transfers the image signals to the data processing device in response
to an instruction from the data processing device.
3. The digital camera in accordance with claim 1, wherein, when
said connection detection circuit detects that said digital camera
is connected to the data processing device and data is not being
transferred to the data processing device, said control circuit
turns off the second power to the components of said digital camera
and allows the secondary battery to be charged through said charging
circuit.
4. The digital camera in accordance with claim 1, wherein, when
said connection detection circuit detects that said digital camera
is connected to the data processing device, said control circuit
allows said first switching circuit to supply the second power to
the components of said digital camera while said secondary battery
is charged through said charging circuit.
Digital Camera Patent Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a digital camera and particularly
to the control of power supply of a digital camera connected to
a data processing device such as a personal computer.
2. Description of the Background Art
When displaying or browsing an image photographed by a digital
camera, data representative of the photographed image is usually
transferred for editing to a data processing device such as a personal
computer. An image photographed by a digital camera is transferred
to a personal computer, for example, in the following ways: (1)
multiple frames are once stored in the image memory of the camera
and then, via a cable or a memory card, transferred to an external
personal computer, or (2) image data captured by a digital camera
is transferred directly to a personal computer, almost at the same
time the image is photographed, via a high-speed digital interface
between the digital camera and the personal computer. An example
of the latter is disclosed in Japanese Patent Laid-Open Publication
Nos. 121147/1995 and 163209/1997.
Japanese Patent Laid-Open Publication No. 121147/1995 discloses
an integrated structure of a video camera and a personal computer,
in which digital signals generated in the camera are directly transferred
to the personal computer. When transferring digital signals from
the camera to the personal computer at a higher transmission rate,
this method uses a connector structure that does not include a cable
and the like as a transmission line but connects, directly in a
short distance, the camera to the personal computer to reduce a
waveform distortion that might have been caused by the resistance
and/or the parasitic capacitance of the transmission line, and to
reduce a high-frequency noise radiation during high-speed data transfer.
The integrated structure of the camera and the personal computer
eliminates an image memory from being installed in a camera, resulting
in a reduced cost. However, because the camera is powered by the
battery of the personal computer, extending the available time as
a whole of the camera and personal computer requires proper power
management when both are used as portable equipment.
Japanese Patent Laid-Open Publication No. 163209/1997 discloses
a digital camera system that controls the photographing operation
of the digital camera in response to control signals from a data
processing device connected to the digital camera. To transfer digital
data from the camera to a personal computer at a high speed, this
system uses, for example, a general-purpose parallel-port PCMCIA
standard interface intended for personal computers, and an in-camera
power-on control command sent from the personal computer via the
interface in response to an instruction from the operator in order
to take a picture. This system keeps camera powered on only when
the camera operator issues an instruction, and keeps the same powered
off in other cases, to minimize power consumption.
Both of the prior-art technologies described above implement the
digital camera function on such a way that a digital camera unit
(imaging function) and a data processing device such as a personal
computer, connected to the camera unit, work together. The digital
camera unit and the personal computer when working together increase
operability and reduce power consumption.
However, in the prior art, the photographing part and the personal
computer must be interconnected to configure a digital camera as
a whole in order to implement the digital camera function. Therefore,
when taking a picture, both the digital camera and the personal
computer are required. Because photographing and recording cannot
be executed by a camera only, the system in the prior art is extremely
inconvenient as a portable system.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a digital camera
that overcomes the aforementioned drawbacks encountered in the prior
art and that reduces the consumption of a power supply within the
digital camera.
It is another object of the present invention to provide a digital
camera that does not necessarily require a special AC charging-adapter
or a special charging unit.
In accordance with the present invention a digital camera for photographing
a subject to output image signals representing the subject comprises
an interface connectable to an external data processing device,
and transferring the image signals to the data processing device;
an internal power supply supplying first power to components of
the digital camera; an external power receiving circuit receiving
second power from the data processing device; a first switching
circuit selectively switching between the internal power supply
and the external power receiving circuit to supply the first or
second power to the components of the digital camera; a connection
detection circuit detecting that the data processing device has
been connected to the interface; and a control circuit controlling
the first switching circuit in response to the connection detection
circuit, wherein the control circuit controls the first switching
circuit in such a way that, when the connection detection circuit
does not detect that the interface is connected to the data processing
device, the first power is supplied to the components of the digital
camera and, when the connection detection circuit detects that the
interface is connected to the data processing device, the internal
power supply is disconnected and the second power is supplied to
the components of the digital camera.
Specifically, the digital camera in accordance with the present
invention operates as follows. For example, when the digital camera
is connected to an external data processing device, such as a personal
computer, to transfer a photographed digital image to the data processing
device, the connection detection circuit determines when the digital
camera is connected to the data processing device. Then, the power
is supplied from the data processing device to the components of
the digital camera to start feeding the components of the digital
camera, and to activate the communication with the data processing
device. After this, image data may be transferred from the digital
camera under the control of the data processing device. Then, the
power fed from the internal power supply within the digital camera
is turned off so that the internal power supply will not be used,
thus minimizing the consumption of the battery.
When the digital camera is connected to the data processing device
without transferring image data, the power fed to the components
of the digital camera is turned off under the control of the data
processing device. In this case, the digital camera will enter the
standby state and allow the charging circuit to receive power from
the data processing device to charge the secondary battery of the
digital camera.
In addition, even when the digital camera is connected to the data
processing device to transfer image data, connecting the internal
power supply to the charging circuit under the control of the data
processing device allows power to be supplied from the data processing
device not only to feed the components of the camera but also to
charge the second battery of the internal power supply, thereby
increasing efficiency more.
Thus, the digital camera in accordance with the present invention,
which is adapted to be detachable from a data processing device
such as a personal computer when a picture is taken, has the camera
function not only for photographing but also for processing signals
and storing image data, and is suitable to carry. In addition, when
image data is transferred, the digital camera receives power supplied
from the data processing device to be turned on the consumption
of the power supply within the digital camera being minimized.
The present invention provides a digital camera capable of transferring
digital image data, which is photographed by the digital camera,
to an external data processing device at a high speed, wherein the
digital camera is convenient for carrying, thus minimizing the consumption
of the battery in the camera. Also, with the digital camera connected
to the external data processing device, the secondary battery in
the digital camera may be efficiently charged while the camera is
idle, for example, image data is not being transferred.
In addition, with power supplied from the external data processing
device, the digital camera may be used not only in the image data
transfer mode but also in the photographing mode under the control
of the external data processing device.
BRIEF DESCRIPTION OF THE DRAWINGS
The objects and features of the present invention will become more
apparent from consideration of the following detailed description
taken in conjunction with the accompanying drawing in which: the
sole FIGURE is a functional block diagram showing a preferred embodiment
of a digital camera according to the present invention that is connected
to, and powered from, an external personal computer, and, for example,
can transfer image data to the latter.
DESCRIPTION OF THE PREFERRED EMBODIMENT
With reference to the accompanying drawing, a preferred embodiment
of a digital camera according to the present invention will be described
in detail. Basically, this embodiment comprises a digital camera
100 and a personal computer 200 that is adapted to receive image
data from the digital camera 100. The digital camera 100 and the
personal computer 200 are detachably interconnected via a camera
interface 150 and a personal computer interface 250. Both interfaces
150 and 250 include a connector, not shown in the FIGURE. In this
embodiment, the digital camera unit 100 is interconnected directly
to the personal computer 200 via this connector. Instead of directly
connecting the digital camera to the personal computer, they may
be connected with a cable, and the like. In the description below,
a signal is represented by the reference numeral of a line on which
the signal is sent.
The camera interface 150 comprises a data interface (I/F) 113,
a control signal interface circuit (CONT) 114, and a power supply
circuit 115. The personal computer interface 250 comprises a data
interface 213, a control signal interface 214, and a power supply
circuit 215.
The digital camera 100 has a photographing lens 101 thereon. The
lens 101 is an optical system that forms an optical image which
is conveyed by the incident light from a subject not shown in the
FIGURE, on a photosensitive array, not shown, an imaging device
102 such as a charged coupled device (CCD). The CCD imaging device
102 is a photoelectric transducer that transduces, one pixel at
a time, an optical image formed on the photosensitive array to an
electrical signal 171 having a corresponding analog amplitude, and
outputs the signal from the output line 171. The output line 171
is connected to an analog-to-digital (A/D) converter 103. In response
to an image signal transferred in the form of output electrical
signal 171 from the CCD imaging device 102, the analog-to-digital
converter 103 converts the signal to a corresponding digital signal
for convenience in the subsequent signal processing. An output digital
signal 173 output from the analog-to-digital converter 103 is sent
to a digital signal processor (DSP) 104.
The digital signal processor 104 has a digital-signal-processing
function, by which in response to the image signal data 173 that
has been converted to digital signals by the analog-to-digital converter
103, the digital signal processor 104 compresses and transfers image
data under the control of a central processing unit (CPU) 106 that
will be described later. Generally, the digital image signal 173
obtained from the imaging device 102 is a large quantity of data.
Therefore, to save a memory area for storage and to increase the
transmission speed, the digital signal processor 104 compresses
the data to eliminate the redundancy of the image signals. In this
embodiment, the still image data is compressed with the JPEG (Joint
Photographic Experts Group) standard. An output 305 from the digital
signal processor 104, which is data to be transferred externally,
is transferred to the personal computer 200 via the camera interface
150. The digital signal processor 104 has an output 175 connected
to a memory 105.
The memory 105, with a storage capacity of several frames of image
data, is a temporary storage unit implemented by a semiconductor
or a rewritable disk. The digital signal processor 104 stores digitally
converted image data 175 to this memory, or reads out the data from
the memory under the control of the central processing unit 106.
The central processing unit 106 plays the role of a system control
unit built in the digital camera 100. In response to a control signal
304 from an operation unit 107 that will be described later, or
to a control signal 302 from the external personal computer 200,
the central processing unit 106 sets the photographing mode of the
digital camera 100, and controls the transfer of image data, and
the display of a photographed image and the operation mode of the
digital camera 100 on a monitor display unit 120 that will be described
later. The central processing unit 106 also outputs a switch control
signal 301 to control the switching of the power to be supplied
to the components of the digital camera 100.
The operation unit 107 allows an operator to manually enter operation
mode data, such as a photographing instruction to the digital camera
100 or a photographed-image display mode. The instruction signal
304 is sent form the operation unit 107 to the central processing
unit 106. The display unit 120 is adapted to receive a signal 177,
such as a photograph image monitor signal or a mode signal of the
digital camera 100, from the digital signal processor 104, and display
the signals visually.
The digital camera 100 has a DC/DC converter 109. This converter
is a power supply circuit that produces a voltage, required for
the components of the digital camera 100, from the power supplied
either from the power supply circuit 115 or from an internal power
supply 112 that will be described later. The converter 109 then
distributes the produced voltage to the components of the camera
as indicated symbolically by a line 179. The DC/DC converter 109
contains, among its functions, a switch circuit 110 as shown in
the FIGURE. In response to the control signal 301 from the central
processing unit 106, this switch circuit selects one of two powers:
the power from the internal power supply 112 and the power from
the power supply circuit 115. The switch circuit 110 is a bi-state
selection circuit that alternatively connects one of its two input
terminals 181 and 183, to its output terminal 179. As shown in the
FIGURE, one input terminal 181 is connected to the internal power
supply 112, and the other input terminal 183 to the power supply
circuit 115. When the digital camera 100 is used alone, the switch
circuit 110 is connected to the internal power supply as opposite
to the connection shown in the FIGURE. In response to the switch
control signal 301 from the personal computer 200, the switch circuit
110 switches the power to the power supply circuit 215 of the personal
computer 200. The internal power supply 112 includes a battery in
the digital camera 100. In this embodiment, a re-chargeable secondary
battery is used as the internal power supply 112.
The data interface 113 of the camera interface 150 is an interface
circuit for an image data. The data interface 113 is adapted to
transform data processed by the digital signal processor 104, or
the image data 305 stored in the memory 105, to a transmission format
when transferring those data to the personal computer 200 at high
speed. The control signal interface circuit 114 is adapted to transfer
control signals between the digital camera 100 and the personal
computer 200. The control signal interface circuit 114 contains
a connection detection circuit, not shown, that determines when
the digital camera 100 is connected to the personal computer 200.
The power supply circuit 115 is an interface circuit that receives
power 313 from the power supply circuit 215 of the personal computer
200.
In this embodiment, the data interface 113, the control signal
interface circuit 114, and the power supply circuit 115 are integrated
in the form of a card interface structure that functions as the
camera interface 150. The card interface structure has the above-mentioned
connector, by which the digital camera 100 is connected to the personal
computer 200. These circuits 113, 114 and 115 may be provided separately
or connected via cables. The present invention is not limited to
a specific type of connection structure.
The power supply circuit 115 has two outputs: one 183 is connected
to the DC/DC converter 109 and the other 117 to a charging circuit
140. The charging circuit 140 receives power from the power supply
circuit 115 and supplies the received power to the internal secondary
battery 112 for charging. The charging circuit 140 has an output
185 connected to the internal power supply, that is, the secondary
battery 112, via a switch 141.
The switch 141 is a bi-state selection circuit that, in response
to a switching signal 306 from the central processing unit 106,
connects selectively one of two input terminals, 185 and 187, to
an output terminal 142. As shown in the FIGURE, one input terminal
185 is connected to the output of the charging circuit 140, the
other input terminal 187 is connected to an AC adapter terminal
160 and, in addition, the output terminal 142 is connected to the
internal power supply 112. The switch 141 operates as follows in
response to the control signal 306 from the central processing unit
106. That is, when the digital camera 100 uses the power supplied
from the commercial power, the switch 141 connects the output terminal
142 to the other input terminal 187; when the digital camera 100
is connected to the personal computer 200, the switch 141 connects
the output terminal 142 to the input terminal 185 to connect to
the power supply circuit 215 of the personal computer 200, and the
internal power supply 112 is charged with the charging circuit 140.
For connection to the commercial power supply, the digital camera
100 in this embodiment has the AC adapter terminal 160 for external
charging. Connecting an AC adapter, not shown, to the digital camera
100 through the AC adapter terminal 160 changes mechanically the
setting of the switch 141. That is, the power supply to the internal
power supply 112 is switched from the charging circuit 140 to the
AC adapter terminal 160.
The interface 250 of the personal computer 200 comprises the data
interface 213, the control signal interface circuit 214, and the
power supply circuit 215. The data interface 213, which functions
as an image data interface circuit of the personal computer 200,
receives image data 310 via the interface circuit 113 of the digital
camera 100 and transforms the received image data to the data signal
310 having a format suitable for processing by the personal computer
200. A control signal 311 controls the operation of the digital
camera 100. The control signal interface circuits 114 and 214 transfer
the control signal 311 between the digital camera 100 and the personal
computer 200. The control signal interface circuit 214 of the personal
computer 200 also generates a connection detection signal 312. This
signal 312 indicates that the digital camera 100 has been connected
to the personal computer 200, and is sent from the control signal
interface circuit 214 to the control signal interface circuit 114
of the digital camera 100. The power supply circuit 215 serves as
the external power supply of the digital camera 100, and is supplied
from the personal computer 200 to the digital camera 100. The power
supply output 313 is fed to the power supply circuit 115 of the
digital camera 100. In an application in which the camera interface
150 of the digital camera 100 has a card interface structure, the
interface 250 of the personal computer 200 also has accordingly
a card interface structure.
In operation, in the photographing mode with the digital camera
100 not connected to the personal computer 200, the central processing
unit 106 puts, by the control signal 301, the switch circuit 110
in the connection state opposite to that shown in the FIGURE. This
connection causes power to be supplied from the internal power supply
112 to the components of the digital camera 100. The optical image
of a subject, which has been formed through the lens 101 of the
digital camera 100, is transduced to the electrical signal 171 by
the CCD imaging device 102. This analog image signal 171 is then
converted to the digital image signal 173 by the analog-to-digital
converter 103. The digital signal processor 104 compresses the output
digital image signal 173 and stores the compressed coded data 175
in the memory 105. The digital signal processor 104 also performs
sub-sampling for the digital image signal 173 in order to monitor
the photographed image on the display panel or unit 120.
When the operator wants to transfer image data from the digital
camera 100 to the personal computer 200, he or she connects the
camera interface 150 to the personal computer interface 250. The
connection detection signal 312 is sent from the personal computer
200 via the control signal interface circuit 214 of the personal
computer interface 250. The connection signal detection circuit
in the control signal interface circuit 114 of the digital camera
100 detects the connection detection signal 312 and sends the detected
signal 302 to the central processing unit 106. In response to the
detected signal 302, the central processing unit 106 outputs the
power switch signal 301 to the DC/DC converter 109. In response,
the power switch circuit 110 switches from the power, which has
been supplied from the internal power supply 112, to the power which
is supplied from the power supply circuit 215 of the personal computer
200 via the power supply circuit 115 of the camera interface 150.
This allows the components of the digital camera 100 to be powered
by the power supply circuit 215 of the external data processing
device to bring the functional units of the digital camera 100 under
the control of the data processing device.
In this state, the digital camera 100 enters the communication
waiting state and waits for the personal computer 200 to send the
control signal 311. In response to the control signal 311 from the
personal computer 200, the central processing unit 106 of the digital
camera 100 outputs a transfer instruction signal 303 to the digital
signal processor 104 to ask it to transfer the image data 175 stored
in the image memory 105. The digital signal processor 104 receives
the image data 175 of a frame, which is specified by the transfer
instruction signal 303, from the memory 105 and outputs the image
data 305 to the data interface 113. The data interface 113 transforms
the image data 305 to a high-speed digital interface format and
transmits the transformed image in the form of the transmission
data 310. The data interface 213 of the personal computer 200 receives
the transmission data 310, performs required format conversion for
the received data, and the converted data is stored in a memory,
not shown, to allow the operator to edit the stored data on the
personal computer 200.
When the camera enters its so-called standby state in which the
digital camera 100 and the personal computer 200 are connected through
the camera interface 150 and the personal computer interface 250
but no image data is being transferred, the personal computer 200
sends the control signal 311 to the central processing unit 106
of the digital camera 100 to notify that the camera is now in the
standby state. Then, the central processing unit 106 outputs a control
signal 307 to the power supply circuit 115 to supply power from
the power supply circuit 115, not to the DC/DC converter 109, but
to the charging circuit 140. This causes the output 117 from the
power supply circuit 115 to be supplied to the charging circuit
140 only. The central processing unit 106 also sends the charging
instruction signal 306 to the switch 141 of the charging circuit
140. In response to this signal, the switch 141 connects the output
185 of the charging circuit 140 to the internal power supply 112
that is a secondary battery. In this way, this configuration allows
the internal power supply 112 to be charged by the personal computer
200.
When an AC adapter is connected to the AC adapter terminal 160,
the switch 141 is switched to the side of the AC adapter terminal
160 to allow the internal power supply 112 to be charged by the
commercial power supply via the AC adapter.
Although the connection detection signal 312 is sent from the personal
computer 200 to the digital camera 100 in this embodiment, the connection
to the personal computer 200 need not always be detected by means
of the connection detection signal 312 from the personal computer
200. For example, the system may be adapted to sense the voltage
of the power supply circuit 215 from the personal computer 200 higher
than a specific threshold to determine when the digital camera 100
is connected to the personal computer 200. Also, the present invention
is not limited to the method described above. For example, the detection
of the grounding of the personal computer 200 with respect of the
internal power supply 112 or the detection of a mechanical connection
may be available to determine when the digital camera 100 is connected
to the personal computer 200.
In the embodiment described above, image data stored in the memory
105 is sent to the personal computer 200. Another operation mode
is also possible in which image data produced by the CCD imaging
device 102 is read out from the CCD imaging device 102 for direct
transfer to the personal computer 200. In such an operation mode,
the switch circuit 110 is also set to the side of the power supply
circuit 115 as long as the personal computer 200 is connected, and
it is possible to supply power from the power supply circuit 215
of the personal computer 200 to the components of the digital camera
100.
As described above, when it is detected that the digital camera
100 is connected to the personal computer 200 that is an external
unit, the internal power supply 112, such as a battery contained
in the digital camera 100, is not used but the power to the components
of the digital camera 100 is switched to the power supply circuit
215 of the personal computer 200 for transfer of data between the
digital camera 100 and the personal computer 200. This configuration
reduces the consumption of the battery 112 of the digital camera
100.
In addition, when the digital camera 100 is connected to the personal
computer 200 but is not used for photographing or data transfer,
the power to the components of the digital camera 100 is turned
off to put the camera in its standby state. In this state, the power
supply of the personal computer 200 is used to charge the secondary
battery 112 of the digital camera 100. This method makes it possible
to efficiently charge the battery 112 in a period of time during
which the digital camera 100 is not used.
As described above, the digital camera in this embodiment charges
the internal secondary battery 112 with the external power supply
when the digital camera 100 is not used. When data is being transferred,
the components of the digital camera 100 receive power from the
external device 200 with the internal secondary battery 112 disconnected
(opened) by the switch circuit 110 of the DC/DC converter 109. Therefore,
the digital camera 100 may also be configured such that the central
processing unit 106 issues the control signal 307 to keep on supplying
power from the power supply circuit 115 to the DC/DC converter 109
over the line 183 and, at the same time, connects the charging circuit
140 to the secondary battery 112 via the switch 141 to charge the
charging circuit 140 while supplying power to the components of
the digital camera 100. In this case, in response to the control
signal 311 from the personal computer 200, the central processing
unit 106 sends the charging instruction control signal 306 to the
switch 141 to supply power from the charging circuit 140 to the
internal power supply 112. This configuration makes it possible
to efficiently charge the internal secondary battery 112 while the
digital camera 100 remains connected to the external data processing
device.
As described above, when the digital camera according to the present
invention is connected to an external data processing device, such
as a personal computer, for high-speed data transfer to allow the
user to produce the device with image data which is produced by
the digital camera, and to edit the image data, the digital camera
detects that it is connected to the external data processing device
and waits for a signal from the external data processing device.
In response to a control signal from the external data processing
device, the digital camera switches the digital camera component
power from the internal power supply of the digital camera to the
power supply of the external data processing device and starts operation
of the digital camera to transfer image data. This configuration
reduces the consumption of the internal battery of the digital camera.
In addition, when the digital camera is not transferring image
data, the power supplied to the components of the camera is stopped
and, instead, the power from the external data processing device
is supplied to the charging circuit to charge the internal secondary
battery. This configuration efficiently charges the battery when
the camera is in its standby state. In addition, in an application
in which the digital camera is connected to the external data processing
device to charge the internal secondary battery in the digital camera
while feeding the power to the components of the camera by the power
supply of the external data processing device, the dedicated charging
period of time can further be reduced. Also, the ability to charge
the secondary battery of the digital camera by the external data
processing device eliminates the need for a special charging unit
such as an AC adapter.
The entire disclosure of Japanese patent application No. 2000-279702
filed on Sep. 14, 2000, including the specification, claims, accompanying
drawings and abstract of the disclosure is incorporated herein by
reference in its entirety.
While the present invention has been described with reference to
the particular illustrative embodiment, it is not to be restricted
by the embodiment. It is to be appreciated that those skilled in
the art can change or modify the embodiment without departing from
the scope and spirit of the present invention. |