Digital Camera Patent AbstractA digital camera, including a common power supply for supplying
power; a plurality of motors sharing the power supply and driven
by the power supplied from the power supply; and a current detector
for detecting load current supplied to the plurality of motors,
wherein, when either one of the plurality of motors is operated,
other motor is driven not to overlap with a maximum value of the
load current detected by the current detector.
Digital Camera Patent ClaimsWhat is claimed is:
1. A power supply apparatus, comprising a power conversion circuit
which monitors output voltage and controls supply of power according
to increase and decrease of a load; a main load as a cause for generation
of a voltage variation; at least one artificial load for suppressing
the voltage variation caused by the main load; and an artificial
load controlling portion for connecting the artificial load to an
output system of said power conversion circuit and disconnecting
the artificial load from the output system, wherein said artificial
load controlling portion connects said at least one artificial load
to the output system of the power conversion circuit which is connected
with said main load, immediately before said main load operates
and immediately after operation of said main load is completed.
2. The power supply apparatus according to claim 1, wherein said
artificial load is lighter in load than said main load.
3. The power supply apparatus according to claim 1, wherein said
artificial load is structured by a plurality of artificial loads
having a different amount of load, and said artificial load controlling
portion selects any of said plurality of artificial loads in accordance
with a size of load of said main load and connects a selected artificial
load to the output system of the power conversion circuit which
is connected with said main load.
4. The power supply apparatus according to claim 2, wherein said
artificial load is structured by a plurality of artificial loads
having a different amount of load, and said artificial load controlling
portion selects any of said plurality of artificial loads in accordance
with a size of load of said main load and connects a selected artificial
load to the output system of the power conversion circuit which
is connected with said main load.
5. The power supply apparatus according to claim 1, wherein said
artificial load is structured by a plurality of artificial loads
having a different amount of load, and said artificial load controlling
portion connects the artificial load to the output system of the
power conversion circuit which is connected with said main load
by fluctuating the amount of load of the artificial load, by means
of selectively switching over said plurality of artificial loads
in accordance with a size of load of said main load.
6. The power supply apparatus according to claim 2, wherein said
artificial load is structured by a plurality of artificial loads
having a different amount of load, and said artificial load controlling
portion connects the artificial load to the output system of the
power conversion circuit which is connected with said main load
by fluctuating the amount of load of the artificial load, by means
of selectively switching over said plurality of artificial loads
in accordance with a size of load of said main load.
7. The power supply apparatus according to claim 1, wherein said
artificial load is structured by a plurality of artificial loads
in which an amount of load increases step by step, and said artificial
load controlling portion connects the artificial load to the output
system of the power conversion circuit which is connected with said
main load, by increasing the amount of load of said artificial load
step by step at the time immediately before said main load operates
and decreasing the amount of load of said artificial load step by
step at the time immediately after the operation of said main load
is completed, in accordance with a size of load of said main load.
8. The power supply apparatus according to claim 2, wherein said
artificial load is structured by a plurality of artificial loads
in which an amount of load increases step by step, and said artificial
load controlling portion connects the artificial load to the output
system of the power conversion circuit which is connected with said
main load, by increasing the amount of load of said artificial load
step by step at the time immediately before said main load operates
and decreasing the amount of load of said artificial load step by
step at the time immediately after the operation of said main load
is completed, in accordance with a size of load of said main load.
9. The power supply apparatus according to claim 1, wherein said
artificial load is structured by a plurality of artificial loads
having a same amount of load, and said artificial load controlling
portion connects the artificial load to the output system of the
power conversion circuit which is connected with said main load,
by increasing said artificial load at the time immediately before
said main load operates by means of overlapping said artificial
load subsequently, and decreasing said artificial load at the time
immediately after the operation of said main load is completed by
means of disconnecting said artificial load subsequently, in accordance
with a size of load of said main load.
10. The power supply apparatus according to claim 2, wherein said
artificial load is structured by a plurality of artificial loads
having a same amount of load, and said artificial load controlling
portion connects the artificial load to the output system of the
power conversion circuit which is connected with said main load,
by increasing said artificial load at the time immediately before
said main load operates by means of overlapping said artificial
load subsequently, and decreasing said artificial load at the time
immediately after the operation of said main load is completed by
means of disconnecting said artificial load subsequently, in accordance
with a size of load of said main load.
11. The power supply apparatus according to claim 1, wherein said
artificial load is structured by an artificial load in which an
amount of load increases continuously, and said artificial load
controlling portion connects the artificial load to the output system
of the power conversion circuit which is connected with said main
load, by increasing said artificial load continuously at the time
immediately before said main load operates and decreasing said artificial
load continuously at the time immediately after the operation of
said main load is completed, in accordance with a size of load of
said main load.
12. The power supply apparatus according to claim 2, wherein said
artificial load is structured by an artificial load in which an
amount of load increases continuously, and said artificial load
controlling portion connects the artificial load to the output system
of the power conversion circuit which is connected with said main
load, by increasing said artificial load continuously at the time
immediately before said main load operates and decreasing said artificial
load continuously at the time immediately after the operation of
said main load is completed, in accordance with a size of load of
said main load.
13. The power supply apparatus according to claim 1, wherein said
artificial load is structured by an artificial load in which an
amount of load increases discontinuously, and said artificial load
controlling portion connects the artificial load to the output system
of the power conversion circuit which is connected with said main
load, by increasing said artificial load discontinuously at the
time immediately before said main load operates and decreasing said
artificial load discontinuously at the time immediately after the
operation of said main load is completed, in accordance with a size
of load of said main load.
14. The power supply apparatus according to claim 2, wherein said
artificial load is structured by an artificial load in which an
amount of load increases discontinuously, and said artificial load
controlling portion connects the artificial load to the output system
of the power conversion circuit which is connected with said main
load, by increasing said artificial load discontinuously at the
time immediately before said main load operates and decreasing said
artificial load discontinuously at the time immediately after the
operation of said main load is completed, in accordance with a size
of load of said main load.
15. The power supply apparatus according to claim 1, further comprising
a voltage variation detector for detecting the voltage variation
caused by said main load, wherein said artificial load controlling
portion disconnects said artificial load from the output system
of the power conversion circuit which is connected with said main
load when the voltage variation detected by said voltage variation
detector is less than a predetermined amount of variation.
16. The power supply apparatus according to claim 1, further comprising
a voltage variation detector for detecting the voltage variation
caused by said main load, wherein said artificial load controlling
portion does not connect said artificial load to the output system
of the power conversion circuit which is connected with said main
load when the voltage variation detected by said voltage variation
detector is more than a predetermined amount of variation.
17. The power supply apparatus according to claim 1, wherein, when
said artificial load has been connected to the output system of
said power conversion circuit, said artificial load controlling
portion does not carry out new connecting operation with respect
to the connected artificial load.
18. The power supply apparatus according to claim 1, wherein, when
one of said artificial loads has been connected to the output system
of said power conversion circuit, said artificial load controlling
portion carries out connecting operation with respect to an artificial
load other than the connected artificial load.
19. The power supply apparatus according to claim 1, further comprising
a monitor for monitoring a capacity of supplying power of said power
supply apparatus, wherein said artificial load controlling portion
does not carry out connecting operation of said artificial load
when the monitor has judged that the capacity of supplying power
of said power supply apparatus is low. Digital Camera Patent DescriptionBACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a digital camera and a power supply
apparatus suitable therefor.
2. Description of the Related Art
Recently, a digital camera has been used often in place of a conventional
camera utilizing a film. Additionally, in the digital camera, it
has been aimed to allow a lens-barrier motor, a zoom motor and a
focus motor and the like to complete their predetermined operation
as soon as possible at the time of activation or photographing to
reduce the time lag and thereby to enhance user convenience. As
one of the ways to accomplish the aim, for example, motor driving
power is increased to drive the motor at high speed, or a plurality
of motors is driven simultaneously, to achieve reduction of operating
time of the camera. As a result, load power at the time of operation
of the motor is increased and hence a large load is applied to a
power supply.
As conventional technique to reduce such load in the power supply,
JP-A 2001-208956 discloses a digital camera capable of adjusting
the time required for starting-up thereof corresponding to capacity
of a power supply currently used. According to this conventional
technique, it discloses the technique in which the capacity and
kind of the power supply are judged on the basis of a voltage value
of the power supply inputted through a bus to control the driving
of a DC motor as a motor for zooming and a stepping motor as a motor
for focus in accordance with the capacity and the kind of the power
supply judged.
However, as well as in the conventional technique disclosed in
the above mentioned JP-A 2001-208956, there are many portions in
the digital camera that require large load power such as a DSP (Digital
Signal Processor) and a memory, other than the load power for the
motor. Accordingly, in the digital camera in which same power source
is used with respect to those portions, there is a possibility that
power supply voltage drops by increase in the load power of the
motor and thereby operation of the digital camera itself cannot
be carried out. Even if the digital camera is barely operated in
such case, the problem occurs that the life of battery is shortened
in a case where a battery is used as the power supply.
Also, as disclosed in Japanese Patent No. 2794631, measures have
been taken in which, when driving the plurality of motors simultaneously,
each load current is reduced so as not to increase the load power.
However, this makes a period of operating the motor long.
Meanwhile, there are three reasons for generation of a voltage
variation in the power supply due to load fluctuation, first, for
lack of supply capacity of the power supply, second, for lack of
conversion capacity of a power conversion circuit in the power supply,
and third, for too much loads. Among these reasons, it can be said
that the lack of capacity of the power conversion circuit is the
major technological issue with respect to the power supply.
The power conversion circuit constantly monitors output voltage,
and operates in such a manner as to increases supply of power when
the load is increased and decreases the supply of power when the
load is decreased. However, in the rapid change of the load, for
example if the load is increased drastically, the output voltage
falls since the power cannot be supplied sufficiently, whereas if
the load is decreased drastically, the output voltage rises due
to excessive supplying of power. There are methods to change oscillation
cycle and change duty of ON/OFF oscillation, in order to correspond
to the drastic load fluctuation. However, there is a limitation
in terms of software and hardware to allow the oscillation cycle
to be faster, and 100% is the limitation to make "ON-duty"
to be longer in the changing of the duty, thus the fall of the output
voltage cannot be suppressed at some point. Therefore, it can be
said that the operational limitation in terms of the software and
the hardware is the limitation of the capacity in the power conversion
circuit.
As conventional technique for the power supply, JP-A H6-119074
discloses the technique for reducing a variation in output voltage
and a variation in input voltage caused by the load fluctuation.
According to this conventional technique, a conventional power supply
apparatus is combined with a flow diverter and an alternating current
detecting circuit to construct a power supply apparatus. The variation
in output current flowing through a load is detected by the alternating
current detecting circuit, while the alternating current detecting
circuit outputs an output signal which complies with the load fluctuation
to the flow diverter. The flow diverter changes amplitude of the
output signal in accordance with the output signal from the alternating
current detecting circuit to divert current to be supplied from
the power supply apparatus to the load.
In order to correspond to such voltage variation, the conventional
power supply apparatus provided with the power conversion circuit
uses a large capacity of condenser for the output or accelerates
a response of feedback of the output as a way to suppress the voltage
variation caused by the load fluctuation. However, use of the large
capacity of condenser causes various adverse effects to generate
such as increase of rush current, delay in rising and falling, rise
in cost and increase in mounting spaces. In addition, there is a
limitation to make the response of the feedback of the output faster,
and even if the acceleration of the response in the feedback of
the output is obtained, there is a problem that power consumption
increases significantly because the response is accelerated.
Also, since the conventional technique disclosed in the above mentioned
JP-A H6-119074 is the technique which carries out the feedback by
regarding that the degree which the load fluctuates is the alternating
current-like variation, and there is the limitation in order to
accelerate the response in the feedback of the output, it also has
the problem similar to the above described conventional technique.
SUMMARY OF THE INVENTION
The present invention has been made in view of the above mentioned
problems. Therefore, it is a first object of the present invention
to provide a digital camera capable of eliminating a factor that
interferes with operation of a camera, shortens the life of battery
or hinders power saving and enhancing user convenience.
In addition, it is a second object of the present invention to
provide a power supply apparatus suitable for the above digital
camera which is low in cost and capable of achieving reduction of
space and reducing a voltage variation by power saving, without
undermining an electrical characteristic.
To solve the above mentioned problems, the present invention provides
a power supply apparatus, comprising: a power supply for supplying
power to a plurality of devices or circuits to operate the plurality
of devices or circuits; and a moderation mechanism for controlling
the power supplied to the plurality of devices or circuits, wherein
the moderation mechanism controls the power supplied to the plurality
of devices or circuits such that the plurality of devices or circuits
does not operate simultaneously at the time when the plurality of
devices or circuits initiates its operation or stops, and also provides
a digital camera having the power supply apparatus.
Also, to accomplish the first object, the present invention provides
a digital camera, comprising: a common power supply for supplying
power; a plurality of motors sharing the power supply and driven
by the power supplied from the power supply; and a current detector
for detecting load current supplied to the plurality of motors,
wherein, when either one of the plurality of motors is operated,
other motor is driven not to overlap with a maximum value of the
load current detected by the current detector.
A plurality of motors is generally used in a camera. When the motors
are driven, drive current corresponding to a load flows to each
of the motors. In a case where the power supply is shared by the
motors, a total amount of drive current flows out from the power
supply if the motors are driven simultaneously. This is equivalent
to a case that the load is increased from the viewpoint of the power
supply, and thus a burden of the power source becomes increased.
In order to prevent such case, the present invention carries out
operation to avoid the plurality of motors to operate simultaneously
and shift operating time thereof.
According to the present invention, since the plurality of motors
are driven by shifting timing of driving thereof, it is possible
to avoid the load of the power supply to be increased in the extreme,
and thereby to reduce the load of the power supply.
Also, generally there are direct current and pulse motors for the
motors used in the camera. In particular, in the direct current
motor, largest current flows in the initial stage of driving when
it starts up and then the current gradually decreases. Therefore,
a characteristic of the current of the direct current motor is previously
grasped and the pulse motor is driven after predetermined time has
elapsed from the initiation of driving of the direct current motor.
Accordingly, overlapping of the large current flowing at the time
of start-up of the direct current motor and drive current of the
pulse motor is avoided, in order that high current does not flow
out from the power supply.
According to the present invention, since the pulse motor is driven
after the predetermined time has elapsed from the time of initiation
of driving of the direct current motor, it is possible to avoid
the overlapping of the large current flowing at the time of start-up
of the direct current motor and the drive current of the pulse motor,
and thereby to reduce the load of the power supply.
When the current flows to the motor, a voltage-drop occurs by internal
impedance of the power supply. More specifically, the voltage-drop
is large when the current is large and the voltage-drop is small
when the current is small. This phenomenon can be detected by detecting
the voltage of the power supply. Therefore, the present invention
includes a voltage detector which detects the voltage-drop of the
power supply and decides the timing of driving of the pulse motor
based on a result of the detection.
According to the present invention, since the timing of driving
of the pulse motor is decided based on the result of the detection
of the voltage detector, it is possible to follow fluctuation of
the load steadily.
In a case where the direct current motor and the pulse motor exist
in a mixed manner, the drive current will be doubled if two or more
pulse motors are used and they are driven with same timing, although
condition of load current varies according to the motor. Therefore,
the present invention is capable of avoiding a current value to
be doubled by operating the pulse motors intermittently and shifting
phases that perform respective intermittent operation of those.
According to the present invention, since the pulse motors are
operated intermittently and are driven by shifting the phases that
perform the respective intermittent operation, it is possible to
drive the pulse motor with a constant drive current and thereby
to minimize the load fluctuation from the viewpoint of the power
supply.
Power consumption of the power supply is decided by the product
of current and time. Accordingly, it is necessary to allow the current
value to be as small as possible to shorten the operating time of
the motor, in order to use a battery longer. In addition, there
is a case in which the motors used in the camera are operated simultaneously.
In such case, it is possible to shorten the total operating time
of the motors if operation of the motor which is shorter is completed
within the operating time of the motor which is longer. Thereby,
it is possible to realize the camera in which time required for
manipulation is short and user-friendliness is high.
According to the present invention, since the plurality of motors
is controlled such that total operating time for driving the plurality
of motors becomes shortest, it is possible to realize the camera
in which the time required for manipulation is short and the user-friendliness
is high.
It has been already mentioned in the foregoing that the power consumption
of the power supply is decided by the product of current and time.
However, even if the total operating time is made to be shortest,
the entire power consumption becomes high if the load current is
large. Therefore, the present invention allows the operating time
to be minimum as well as a total of the load current.
According to the present invention, since the total operating time
for driving the plurality of motors is controlled to be shortest
and the total of the load current is controlled to be least, it
is possible to realize the camera in which the time required for
manipulation is short and the user-friendliness is high, and at
the same time, to allow a burden imposed on the power supply to
be minimum.
As the power supply of the camera, there are the battery and an
AC adapter. In addition, there are primary and secondary batteries
for the battery, and there are various kinds with respect to those.
Those kinds of power supply have their own features. For example,
it is needless to worry about the life of power supply with regard
to the AC adapter, but it cannot be taken along. The primary battery
is inexpensive, but it is impossible to reuse it since charging
cannot be carried out. The secondary battery can be reused since
the charging thereof can be carried out, although it is relatively
expensive. In other words, if the kind of power supply loaded in
the camera can be discriminated, it is possible to select the operation
which corresponds to the discriminated kind. Therefore, the present
invention includes a discriminator for discriminating the kind of
power supply.
According to the present invention, since the timing of driving
of each motor is controlled according to the kind of power supply
discriminated by the discriminator, it is possible to realize a
method of driving the motor in accordance with the kind of power
supply and to obtain most suitable operating condition of the camera.
There are loads for the camera other than the motors, which are
a display portion and a circuit. A total of those loads become a
full-load of the camera from the viewpoint of the power supply.
However, it is not necessarily the case that the full-load is always
consumed, depending on modes of the camera. More specifically, the
load is light at the time of activation of the camera, since an
image system and a display system are not in operation at that time.
According to the present invention, since the timing of operating
of the digital camera is controlled according to condition of load
detected by load-condition detector, the load fluctuation of the
power supply becomes virtually constant, thereby it is possible
to allow a voltage variation of the power supply to be small and
allow the circuit in the camera to operate in a stable manner.
In the battery of the power supply, the volume within the battery
changes according to the ambient temperature and hence, a characteristic
of the drive current changes. More specifically, the inner volume
of the battery reduces when the ambient temperature becomes low,
and thereby it becomes impossible to retrieve high current instantaneously
out of the battery. Therefore, in such case, it is necessary to
create the timing of operation in which the high current does not
flow instantaneously. Accordingly, the present invention includes
temperature detector, for detecting the ambient temperature of the
camera to control the timing of driving of the respective motors
in accordance with a result of detection of the ambient temperature.
According to the present invention, since the timing of driving
for the respective motors are controlled according to the temperature
detected by the temperature detector, it is possible to operate
the camera steadily even when surrounding environment has changed.
There are various kinds of modes in the camera such as a normal
mode, a power-saving mode and a high-speed mode. In addition, operation
carried out in the camera varies depending on the modes. For example,
in the high-speed mode, since it is required to operate the plurality
of motors simultaneously, a large burden is applied on the power
supply and hence it is necessary to avoid maximum current to be
overlapped. Therefore, the present invention includes mode-setting
device and controls the timing of driving of the motors according
to the respective modes.
According to the present invention, since the timing of driving
of each of the plurality of motors is controlled according to a
mode set by the mode-setting device, it is possible to select the
operation which does not apply the burden on the power supply with
respect to every mode.
Also, to accomplish the second object, the present invention provides
a power supply apparatus, comprising a power conversion circuit
which monitors output voltage and controls supply of power according
to increase and decrease of a load; a main load as a cause for generation
of a voltage variation; at least one artificial load for suppressing
the voltage variation caused by the main load; and an artificial
load controlling portion for connecting the artificial load to an
output system of the power conversion circuit and disconnecting
the artificial load from the output system, wherein the artificial
load controlling portion connects the at least one artificial load
to the output system of the power conversion circuit which is connected
with the main load, immediately before the main load operates and
immediately after operation of the main load is completed.
The characteristic of the present invention is that the present
invention includes the artificial load for suppressing the load
fluctuation caused by the main load and the artificial load controlling
portion for connecting the artificial load with the main load or
disconnecting it from the main load, other than the main load. Generally,
a power supply is provided with the power conversion circuit which
operates to increase and decrease the supplying of power when the
load is fluctuated, in order to maintain the voltage constant. However,
it cannot help accepting the load fluctuation at some extent since
it is impossible to follow the speed of the load fluctuation. The
drastic generation of the load fluctuation has been a major cause
thereof. Therefore, the present invention suppresses the load fluctuation
caused by the main load, by connecting the artificial load with
the main load immediately before the power is supplied to the main
load and immediately after the supplying of power is disconnected.
According to the present invention, since the artificial load is
connected immediately before the power is supplied to the main load
and immediately after the power is disconnected, the fluctuation
of the load from the viewpoint of the power supply becomes moderate,
and thus consequently, it is possible to suppress the voltage variation
caused by the load fluctuation.
What is important here is that, it is on the premise that the artificial
load should be smaller in load than the main load. In other words,
about half the load of the main load for example is appropriate
in order to allow the load fluctuation from the viewpoint of the
power supply to be moderate.
According to the present invention, since the artificial load is
lighter in load as compared with the main load, it is possible to
allow the load fluctuation from the viewpoint of the power supply
to be moderate, by connecting the artificial load immediately before
the supplying of power to the main load and immediately after the
disconnection of the supplying of power thereto.
Normally, the load varies according to each output system in the
power supply in which a plurality of output systems exists. In such
case, it is necessary to optimize the artificial loads in accordance
with size of the load. Therefore, the present invention provides
a plurality of artificial loads having various kinds of amount of
load, and selects the most suitable artificial load in accordance
with size of the main load.
According to the present invention, since any of the plurality
of artificial loads is selected in accordance with the size of the
main load, it is possible to connect the most suitable artificial
load corresponding to the size of the main load.
The present invention provides a plurality of artificial loads
having different amount of load to each other, and fluctuates the
amount of load by a combination of the artificial loads. It is disadvantageous
in terms of cost and space if the artificial loads become large
in variety. Therefore, the present invention connects the artificial
load to the main load by fluctuating the amount of load, by combining
a least variety of artificial loads.
According to the present invention, since the least artificial
loads are provided, and the amount of load is fluctuated by their
combination, it is possible to establish the structure which occupies
small space and the cost is inexpensive.
In a case where there is a plurality of artificial loads in which
the amount of load increases step by step, the present invention
connects the artificial load to the main load, by increasing the
amount of load of the artificial load step by step at the time immediately
before the main load operates and decreasing the amount of load
of the artificial load step by step at the time immediately after
the operation of the main load is completed, in accordance with
the size of load of the main load. Accordingly, the load varies
before initiation of the operation of the main load and after the
completion thereof, step by step.
According to the present invention, since the artificial load is
connected by increasing the amount of load of the artificial load
step by step at the time immediately before the main load operates
and is connected by decreasing the amount of load of the artificial
load step by step at the time immediately after the operation of
the main load is completed, the load fluctuation of the main load
fluctuates apparently smoothly, and thereby it is possible to minimize
the voltage variation caused by the load fluctuation.
The present invention provides a plurality of artificial loads
in which the amount of load is same to each other, and increases
the artificial load by subsequently connecting the artificial loads
in parallel to the main load at the time immediately before the
main load operates, and decreases the artificial load by subsequently
disconnecting the artificial loads from the main load at the time
immediately after operation of the main load is completed. Accordingly,
the load fluctuation of the main load fluctuates apparently smoothly,
and thereby it is possible to minimize the voltage variation caused
by the load fluctuation.
According to the present invention, since the artificial load is
increased by subsequently connecting the artificial loads in parallel
at the time immediately before the main load operates, and the artificial
load is decreased by subsequently disconnecting the artificial loads
at the time immediately after operation of the main load is completed,
it suffices even when the number of artificial load is small, and
can establish the structure in which the cost is inexpensive.
The power supply apparatuses described above are based on a method
to fluctuate the artificial load in a so-called digital manner,
but the present invention carries out the fluctuation continuously.
For example, it may be considered to adopt a variable resistor or
a method to convert a variation in an amount of light into a resistance
change with a Cds, or the like as a way to fluctuate the amount
of load continuously. In addition, the present invention increases
the artificial load continuously (decreases resistance of the variable
resistor) at the time immediately before the main load operates,
and decreases the artificial load continuously (increases the resistance
of the variable resistor) at the time immediately after operation
of the main load is completed.
According to the present invention, since the artificial load is
increased continuously at the time immediately before the main load
operates and is decreased continuously at the time immediately after
the operation of the main load is completed, it is possible to carry
out the fluctuation of the main load even more smoothly.
A digital signal is easier to handle when controlling the load
with a PC. Therefore, the present invention constructs a way to
fluctuate the load by changing a width of pulse. The present invention
gradually widens the width of pulse at the time immediately before
the main load operates to increase the artificial load continuously,
and gradually narrows the width of pulse at the time immediately
after operation of the main load is completed to decrease the artificial
load continuously.
According to the present invention, since the artificial load is
increased continuously by gradually widening the width of pulse
at the time immediately before the main load operates and is decreased
continuously by gradually narrowing the width of pulse at the time
immediately after operation of the main load is completed, it is
possible to carry out control with the PC easily.
The present invention is capable of judging whether a value of
varied voltage is to the extent that gives an adverse effect on
a circuit or not, by further including a voltage variation detector
for detecting the voltage variation caused by the load fluctuation
of the main load. Accordingly, when the value of the varied voltage
is not to the extent that gives the adverse effect on the circuit,
the present invention disconnects the connection to make the load
of the power supply light, since there is no necessity of connecting
the artificial load.
According to the present invention, since the artificial load is
disconnected from the output system of the power conversion circuit
which is connected with the main load in a case where the voltage
variation detected by the voltage variation detector is less than
a predetermined amount of variation, it is possible to minimize
unnecessary power consumption.
On the contrary, in a case where the voltage variation exceeds
the predetermined amount of variation, in other words, where the
load exceeds a range in which the load fluctuation is to be suppressed,
the operation of suppressing the load fluctuation by the artificial
load is configured not to be carried out, since the load fluctuation
cannot be suppressed even when the artificial load is connected
in such case.
According to the present invention, since the artificial load will
not be connected to the output system of the power conversion circuit
which is connected with the main load in a case where the voltage
variation detected by the voltage variation detector is more than
the predetermined amount of variation, it is possible to minimize
the power consumption due to the unnecessary operation.
For example, in a case where a plurality of systems of the loads
exists and where one of the main loads is connected with one artificial
load, the operation of suppressing the fluctuation of other main
loads cannot be carried out when a request for the operation of
suppressing the fluctuation of other main loads is made, due to
the fact that the necessary artificial load is in use. In other
words, there is a possibility that addition of further load with
respect to the artificial load while the artificial load is in operation
makes control on the artificial load complicated and impairs accuracy.
Furthermore, there is a possibility that entire load becomes too
large and thus the power supply cannot supply the power, prior to
the suppression of the voltage variation. The present invention
is capable of avoiding such circumstance.
According to the present invention, since the artificial load controlling
portion does not carry out new connecting operation with respect
to the connected artificial load in a case where the artificial
load has been connected to the output system of the power conversion
circuit, it is possible to simplify the control of the artificial
load, and to avoid the possibility that the entire load becomes
too large and thus the power supply cannot supply the power, prior
to the suppression of the voltage variation.
In a case where a plurality of main loads and a plurality of artificial
loads exist, and the request for the operation of suppressing the
fluctuation of other main loads is made when one of the artificial
loads is connected to the main load, it is configured to select
the artificial load other than the connected one and connect the
selected artificial load with the main load.
According to the present invention, since the artificial load controlling
portion carries out connecting operation with respect to an artificial
load other than the connected artificial load in a case where one
of the artificial loads has been connected to the output system
of the power conversion circuit, it is possible to simplify the
control of the artificial load.
When a capacity of supplying the power is deteriorated, for example
when the power supply is the battery and it is consumed, it is configured
not to carry out the operation of the artificial load for suppressing
the voltage variation even if the voltage variation caused by the
load fluctuation of the main load is generated, by judging that
the power supply has no capacity of supplying the power.
According to the present invention, since the artificial load controlling
portion does not carry out connecting operation of the artificial
load in a case where a monitor has judged that the capacity of supplying
power of the power supply apparatus is low, it is possible to avoid
excessive application of load on the power supply.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram of a digital camera according to an embodiment
of the present invention.
FIGS. 2A to 2G are diagrams showing current waveforms in respective
motors and current waveform in a power supply of the digital camera
according to the present invention.
FIGS. 3A and 3B are flowcharts of operation for generating each
timing with respect to FIGS. 2A to 2G according to the present invention.
FIGS. 4A to 4E schematically show power supply apparatuses according
to embodiments of the present invention.
FIG. 5 is a diagram to show a main load and change in output voltage
caused thereby in a case that operation for suppressing load fluctuation
is not carried out, to explain the operation of the present invention.
FIG. 6 is a diagram for explaining a method for suppressing load
fluctuation according to the present invention.
FIG. 7 is a diagram for explaining other method for suppressing
load fluctuation according to the present invention.
FIG. 8 is a diagram for explaining other method for suppressing
load fluctuation according to the present invention.
FIG. 9 is a diagram for explaining other method for suppressing
load fluctuation according to the present invention.
FIG. 10 is a diagram for explaining other method for suppressing
load fluctuation according to the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Embodiment 1
Hereinafter, a digital camera according to the present invention
will be described in detail in accordance with embodiment 1 shown
in the drawings. However, it should be noted that structural elements,
kinds, combinations, configurations or their relative arrangements
described in this embodiment are merely illustrative by way of example,
thus it is not intended to limit the scope of the present invention
by them unless otherwise specifically stated.
FIG. 1 is a block diagram of a digital camera according to embodiment
1 of the present invention. The digital camera 100 comprises a size
AA battery 30, an exclusive lithium battery 31 being used exclusively
for the digital camera 100, an AC adapter 32 which are power supplies,
a DC/DC converter 33 which converts power voltage to generate various
voltage necessary for the camera, a motor portion 34 which includes
various motors and controls them, a current detecting portion 35
for detecting current flowing from the DC/DC converter 33 through
inside of the camera, and a voltage detecting portion 36 for detecting
each voltage generated from the DC/DC converter 33. The digital
camera 100 further comprises a temperature sensor 37 for detecting
ambient temperature of the camera, a display (DSP) 38 structured
by a LCD (Liquid Crystal Display) monitor or the like, a CCD (Charge
Coupled Device) 39 for converting an light signal from a lens into
an electrical signal, a memory 40 for storing images, and a controller
(CPU, moderation mechanism) 41 which governs entire control of the
camera. In addition, the motor portion 34 is structured by a zoom
motor 34a, a focus motor 34b, a shutter motor 34c, an aperture stop
motor 34d, a lens-barrier motor 34e and a motor driver 34f for controlling
respective motors.
Five types of motors are used in the digital camera 100. When the
motors are driven, drive current corresponding to a load flows to
each of the motors. The current flowing to the motor is detected
by the current detecting portion 35. In a case where a power supply
is shared by the motors, a total amount of drive current flows out
from the power supply if the motors are driven simultaneously. This
is equivalent to a case that the load is increased from the viewpoint
of the power supply, and thus a burden of the power source becomes
increased. In order to prevent such case, the present invention
carries out operation to avoid the plurality of motors to operate
simultaneously and shift operating time thereof by the controller
(CPU) 41.
In addition, a voltage-drop occurs by internal impedance of the
power supply when the current flows to the motor. More specifically,
the voltage-drop is large when the current is large and the voltage-drop
is small when the current is small. This phenomenon can be detected
by detecting the voltage of the power supply. Therefore, the present
invention includes the voltage detecting portion 36 Which detects
the voltage-drop of the power supply and decides the timing of driving
of the focus motor 34b by the controller (CPU) 41 based on a result
of the detection.
Also, power consumption of the power supply is decided by the product
of current that flows to a circuit and time that the current flows
to the circuit. Accordingly, it is necessary to allow a current
value to be as small as possible to shorten the operating time of
the motor, in order to use the size AA battery 30 and the exclusive
lithium battery 31 longer. In addition, there is a case in which
the motors used in the camera are operated simultaneously. In such
case, it is possible to shorten the total operating time of the
motors if operation of the motor which is shorter is completed within
the operating time of the motor which is longer. Thereby, it is
possible to realize the camera in which time required for manipulation
is short and user-friendliness is high.
As the power supply of the camera, there are the size AA battery
30, the exclusive lithium battery 31 and the AC adapter 32. In addition,
there are primary and secondary batteries for the battery, in which
case the size AA battery 30 is the primary battery and the exclusive
lithium battery 31 is the secondary battery. Those kinds of batteries
have their own features. For example, it is needless to worry about
the life of power supply with regard to the AC adapter 32, but it
cannot be taken along. The primary battery is inexpensive, but it
is impossible to reuse it since charging cannot be carried out.
The secondary battery can be reused since the charging thereof can
be carried out, although it is relatively expensive. In other words,
if the kind of power supply loaded in the camera can be discriminated,
it is possible to select the operation which corresponds to the
discriminated kind. Therefore, the present invention discriminates
the kind of power supply by the controller (CPU) 41. As a method
for accomplishing this, for example, such a configuration can be
utilized in which the kind of power supply is detected by a mechanical
system which is not shown, or detects a difference of voltage of
the power supply at the time of being set in the camera to detect
the kind.
In addition, there are loads for the camera other than the motors,
which are the display (DSP) 38, the CCD (Charge Coupled Device)
39 and the memory 40. A total of those loads become a full-load
of the camera from the viewpoint of the power supply. However, it
is not necessarily the case that the full-load is always consumed,
depending on modes of the camera. More specifically, the load is
light at the time of activation of the camera, since the display
(DSP) 38 and the CCD (Charge Coupled Device) 39 are not in operation
at that time. In other words, if such a configuration is employed
in which condition of load of the camera is detected by the controller
(CPU) 41 and the timing of operation of the digital camera is controlled
in accordance with the load condition, the load fluctuation of the
power supply becomes virtually constant, thereby it is possible
to allow the voltage variation of the power supply to be small and
allow a circuit in the camera to operate in a stable manner.
Furthermore, in the battery of the power supply, the volume within
the battery changes according to the ambient temperature and hence
a characteristic of the drive current changes. More specifically,
the inner volume of the battery reduces when the ambient temperature
becomes low, and thereby it becomes impossible to retrieve high
current instantaneously out of the battery. Therefore, in such case,
it is necessary to create the timing of operation in which the high
current does not flow instantaneously. Accordingly, the present
invention includes the temperature sensor 37 for detecting the ambient
temperature of the camera, to control the timing of driving of the
respective motors in accordance with a result of the detection.
In addition, there are various kinds of modes in the camera such
as a normal mode, a power-saving mode and a high-speed mode. In
addition, operation carried out in the camera varies depending on
the modes. For example, in the high-speed mode, since it is required
to operate the plurality of motors simultaneously, a large burden
is applied on the power supply and hence it is necessary to avoid
maximum current to be overlapped. Therefore, the present invention
controls the timing of driving of the motors according to the respective
modes by setting those modes with the DSP 38.
FIGS. 2A to 2G are diagrams showing current waveforms in the respective
motors and current waveform in the power supply of the digital camera
according to the present invention. Vertical axes in the respective
diagrams represent a current value, and horizontal axes represent
the time. FIGS. 2A and 2E are the diagrams of the conventional current
waveforms which are illustrated for comparison, FIGS. 2B through
2D are the diagrams showing cases of the current waveforms generated
by a direct current motor and a pulse motor, and FIGS. 2F and 2G
are the diagrams showing cases of the current waveforms generated
by two pulse motors.
In FIG. 2A, the direct current motor (a) has a characteristic in
which a large current flows thereto in the initial stage of the
driving and then the current gradually decreases. Also, in the pulse
motor (b), pulse current in which the current values are substantially
constant flow thereto. The current, in which the current values
of the direct current motor and the pulse motor are totalized, flows
out from the power supply as shown by (c) when those are driven
simultaneously, and thus it is obvious that the large load is applied
to the power supply.
In order to improve this circumstance, the timing of driving of
the pulse motor (b) is shifted at virtually center as shown in FIG.
2B, so as to drive the pulse motor after the current of the direct
current motor (a) is decreased. Accordingly, although the current
in which the current values of the direct current motor and the
pulse motor are totalized flows out from the power supply as shown
by (c), it is obvious that its peak value is decreased as compared
with FIG. 2A.
In order to further improve the above mentioned circumstance, the
timing of driving of the pulse motor (b) is shifted to the point
just before the operation of the direct current motor (a) is completed
as shown in FIG. 2C, so as to drive the pulse motor after the current
of the direct current motor (a) is decreased utmost. Accordingly,
although the current in which the current values of the direct current
motor and the pulse motor are totalized flows out from the power
supply as shown by (c), it is obvious that the peak value is decreased
even more as compared with FIG. 2B.
In order to improve the above mentioned circumstance more at the
sacrifice of the time at some extent, the timing of driving of the
pulse motor (b) is further shifted from the point of the completion
of the operation of the direct current motor (a) as shown in FIG.
2D, so as to drive the pulse motor immediately before the current
of the direct current motor (a) decreases utmost and the direct
current motor goes off. Accordingly, although the current in which
the current values of the direct current motor and the pulse motor
are totalized flows out from the power supply as shown by (c), it
is obvious that the peak value is decreased furthermore as compared
with FIG. 2C.
FIG. 2E shows the case that phases of the timing of operation of
the two pulse motors (a) and (b) at the time of movement are the
same. It is obvious from this case that double the amount of current
in which the current values of two pulse motors are totalized flows
out from the power supply as shown by (c) if those are driven simultaneously,
and thereby the large load is applied to the power supply.
In order to improve this circumstance, FIG. 2F shows a case in
which the phases of the timing of operation of the two pulse motors
(a) and (b) at the time of movement are shifted at 180.degree..
When those are driven simultaneously, the current values of two
pulse motors are totalized as shown by (c). However, since the phases
are shifted from each other, the same current flow out from the
power supply and thus it is obvious that the peak value is reduced
as compared with FIG. 2E.
FIG. 2G shows a case that the pulse motor (b) is allowed to carry
out predetermined operation at the timing of OFF of the pulse motor
(a) when the pulse motor is moved. Although the current values of
two pulse motors are totalized as shown by (c) when they are driven
simultaneously, the drive current and operating current flow out
from the power supply alternately as shown in the drawing, since
the phases are shifted from each other. Therefore, it is obvious
that the peak value is reduced as compared with FIG. 2E.
FIGS. 3A and 3B are flowcharts of operation for generating each
timing with respect to FIGS. 2A to 2G. FIG. 3A is a flowchart in
which the timing of driving is generated based on a lapse of time,
while FIG. 3B is a flowchart in which the timing of driving is generated
by monitoring the voltage of the power supply.
First, to explain FIG. 3A, when a zoom motor (for example, direct
current motor) starts its activation (S1), a timer is started to
count the time (S2). Then, it is monitored whether the timer has
counted a predetermined time or not (S3), and if the predetermined
time has elapsed, next, the focus motor (for example, pulse motor)
is activated (S4). In this flowchart, it is necessary to previously
find out how long is the predetermined time required and set that
time.
Next, to explain FIG. 3B, when a zoom motor (for example, direct
current motor) starts its activation (S11), monitoring of voltage
of the power supply is initiated (S12). Then, it is monitored whether
or not the monitored voltage is over a predetermined voltage (S13),
and when detecting that it is over the predetermined voltage, next,
the focus motor (for example, pulse motor) is activated (S14). In
this flowchart, it is necessary to previously find out how much
does the voltage of the power supply drop when the voltage is dropped
by the load current and set that voltage.
Hereinafter, a power supply apparatus according to the present
invention will be described in detail in accordance with embodiments
2 to 6 shown in the drawings. However, it should be noted that structural
elements, kinds, combinations, configurations or their relative
arrangements described in these embodiments are merely illustrative
by way of example, thus it is not intended to limit the scope of
the present invention by them unless otherwise specifically stated.
FIGS. 4A to 4E schematically show the power supply apparatuses
which are suitable for the above described digital camera according
to embodiments of the present invention. Meanwhile, in the drawings,
a power supply, a power conversion circuit, a main load, an artificial
load, and an artificial load controlling portion are represented
as PS, PCNV, ML, VL and VLCNT, respectively. As a matter of simplification
of explanation, the descriptions of cases will be given below in
which one main load ML is provided. In addition, although the power
supply apparatus is suitable for the digital camera in the above
described embodiment, it should be noted that it is possible to
apply the power supply apparatus to other digital cameras, or to
any devices.
Embodiment 2
FIG. 4A is a diagram showing the power supply apparatus according
to the embodiment 2, which comprises a power supply 201 constructed
by a battery or an AC adapter or the like, a power conversion circuit
202 (moderation mechanism) for converting the power from the power
supply 201 into predetermined voltage and controlling the supplying
of power according to increase and decrease of a load by monitoring
the output voltage, a main load 203 which structures a principal
load such as a motor and an electronic circuit and so on, an artificial
load 205 structured by a load which is lighter in load than the
main load 203, and an artificial load controlling portion 204 for
connecting the artificial load 205 with the main load 203 and disconnecting
the artificial load from the main load 203. Meanwhile, although
it is described here as if the artificial load controlling portion
204 is controlled by the power conversion circuit 202, the artificial
load controlling portion may be controlled by a control circuit
which is not shown. The characteristic of the present embodiment
is that it includes the artificial load 205 for suppressing the
load fluctuation caused by the main load 203 and the artificial
load controlling portion 204 for connecting the artificial load
with the main load 203 or disconnecting it from the main load 203,
other than the main load 203. Generally, a power supply apparatus
is provided with the power conversion circuit 202 which operates
to increase and decrease the supplying of power when the load is
fluctuated, in order to maintain the voltage constant. However,
it cannot help accepting the load fluctuation at some extent since
it is impossible to follow the speed of the load fluctuation. The
drastic generation of the load fluctuation has been a major cause
thereof (see FIG. 5). Therefore, the present embodiment suppresses
the load fluctuation caused by the main load 203, by connecting
the artificial load 205 with the main load immediately before the
power is supplied to the main load 203 and immediately after the
supplying of power is disconnected.
Embodiment 3
FIG. 4B is a diagram showing the power supply apparatus according
to the embodiment 3. In this embodiment, since the same reference
numeral is attached to the component part similar to the above embodiment,
the overlapping explanation will be omitted here. The points that
FIG. 4B differs from FIG. 4A are that the artificial load shown
in FIG. 4A has turned into artificial loads 207 208 having different
amount of loads, respectively, and an artificial load controlling
portion 206 selects either one of those artificial loads. More specifically,
normally, the load varies according to each output system in the
power supply in which a plurality of output systems exists. In such
case, it is necessary to optimize the artificial loads in accordance
with size of the load. Therefore, the present embodiment includes
a plurality of artificial loads 207 208 having the various kind
of amount of load, and selects the most suitable artificial load
with the artificial load controlling portion 206 in accordance with
size of the main load 203. For example, it selects the artificial
load in such a manner that the load fluctuation becomes small, such
as selecting the artificial load having 50 mA when the main load
is a motor (100 mA), or the artificial load having 25 mA when the
load is a CCD (50 mA).
Also, the present embodiment structures the artificial load in
such a manner as to increase the amount of load step by step, and
in accordance with the size of the load in the main load 203, connects
the artificial load to the main load by increasing the amount of
load of the artificial load step by step at the time immediately
before the main load 203 operates and disconnects the artificial
load from the main load by decreasing the amount of load of the
artificial load step by step at the time immediately after operation
of the main load is completed. Accordingly, the load changes step
by step at the point before the operation of the main load is initiated
and after the operation is completed. For example, when it is assumed
that the load of the artificial load 201=25 (mA), the load of the
artificial load 202=50 (mA) . . . load of artificial load N=N (mA)>50
(mA) from the artificial load 201 to the artificial load N, respectively,
the load fluctuation by the artificial load for suppressing the
voltage variation is increased step by step, by operating the artificial
load 201 firstly, then switching over the operation to the artificial
load 202, and switching over the operation to the artificial load
N lastly, to increase the artificial load step by step. Alternately,
it is possible to decrease the artificial load step by step, in
an opposite manner thereof.
Embodiment 4
FIG. 4C is a diagram showing the power supply apparatus according
to the embodiment 4. In this embodiment, since the same reference
numeral is attached to the component part similar to the above embodiments,
the overlapping explanation will be omitted here. The point that
FIG. 4C differs from FIG. 4B is that an artificial load controlling
portion 209 is configured to switch over the plurality of loads,
selectively. More specifically, it selects the number of artificial
loads to be connected in parallel and a location of the artificial
loads such that the amount of load of the artificial load changes.
For example, it selects the artificial loads such that the artificial
loads become 50 mA when the main load is the motor (100 mA), and
such that the artificial loads become 25 mA when the main load is
a video amplifier (50 mA).
Also, it includes a plurality of artificial loads in which the
amount of load is same to each other, subsequently connects the
artificial loads in parallel to the main load at the time immediately
before the main load operates to increase the artificial load, and
subsequently disconnects the artificial loads from the main load
at the time immediately after operation of the main load is completed
to decrease the artificial load. Accordingly, the load fluctuation
of the main load 203 fluctuates apparently smoothly, and thereby
it is possible to minimize the voltage variation caused by the load
fluctuation. For example, when it is assumed that the load in the
artificial loads from the artificial load 201 to the artificial
load N is load=25 (mA), respectively, the load fluctuation by the
artificial loads for suppressing the voltage variation is increased
step by step, by operating the artificial load 201 firstly, then
operating the artificial load 202 in such a manner as to be overlapped
with the artificial load 201, and operating the artificial load
N lastly in the overlapping manner, to increase the artificial load
step by step. Alternately, it is possible to decrease the artificial
load step by step, in an opposite manner thereof.
Embodiment 5
FIG. 4D is a diagram showing the power supply apparatus according
to the embodiment 5. In this embodiment, since the same reference
numeral is attached to the component part similar to the above embodiments,
the overlapping explanation will be omitted here. The point that
FIG. 4D differs from FIGS. 4A to AC is that an artificial load controlling
portion 210 is configured to change the load in an analog manner.
The power supply apparatuses according to the embodiments 2 to 4
are based on the method to fluctuate the artificial load in a so-called
digital manner, but the present embodiment carries out the fluctuation
continuously. For example, it may be considered to adopt a variable
resistor or a method to convert a variation in an amount of light
into a resistance change with a Cds, or the like as a way to fluctuate
the amount of load continuously. In addition, the present embodiment
increases the artificial load 210 continuously (decreases resistance
in a case of the variable resistor) at the time immediately before
the main load 203 operates, and decreases the artificial load 210
continuously (increases the resistance in the case of the variable
resistor) at the time immediately after operation of the main load
203 is completed. Furthermore, by increasing or decreasing the load
continuously such as in linear, quadratic curve or logarithm manner
as a load characteristic, it is possible to suppress the voltage
variation.
Embodiment 6
FIG. 4E is a diagram showing the power supply apparatus according
to the embodiment 6. In this embodiment, since the same reference
numeral is attached to the component part similar to the above embodiments,
the overlapping explanation will be omitted here. The point that
FIG. 4E differs from FIGS. 4A to AC is that an artificial load controlling
portion 211 is configured to change the load discontinuously. Although
the embodiment 5 is based on the method to fluctuate the artificial
load continuously, the present embodiment carries out the fluctuation
discontinuously. More specifically, a digital signal is easier to
handle when controlling the load with a PC. Therefore, the present
embodiment constructs the way to fluctuate the load by changing
a width of pulse. The present embodiment gradually widens the width
of pulse at the time immediately before the main load 203 operates
to increase the artificial load 211 continuously, and gradually
narrows the width of pulse at the time immediately after operation
of the main load 203 is completed to decrease the artificial load
continuously.
FIG. 5 is a diagram to show a main load and change in output voltage
caused thereby in a case that operation for suppressing load fluctuation
is not carried out, to explain the operation of the present invention.
When a load of a main load 220 fluctuates drastically at a point
P up to a load L1, a so-called ringing phenomenon is generated in
which voltage lowers largely and rises again in such a manner as
shown by a waveform "a", since the output voltage 221
cannot follow the drastic fluctuation of the main load. The fluctuating
time thereof varies according to whether the load is capacitive
or inductive. The output voltage 221 does not vary when the load
is stable, but a so-called ringing phenomenon is generated in which
the voltage rises largely and lowers again in such a manner as shown
by a waveform "b" when the load of the main load 220 fluctuates
until zero at a point Q, since the output voltage 221 cannot follow
that drastic fluctuation. This peak value becomes a width of voltage
variation.
FIG. 6 is a diagram for explaining a method for suppressing load
fluctuation according to the present invention. The present invention
suppresses the drastic load fluctuation at the time of driving a
main load 222, by previously connecting an artificial load 223 before
and after the driving of the main load 222. Here, it is assumed
that a load L2 of the artificial load 223 has the amount of load
which is approximately half of the load L1 of the main load 222.
More specifically, the artificial load 223 is allowed to fluctuate
up to the load L2 at a point P1 before the main load 222 operates.
Since the load is half of that of the main load, a so-called ringing
phenomenon is generated in which output voltage 225 lowers small
and rises again in such a manner as shown by a waveform "a".
The fluctuating time thereof varies according to whether the load
is capacitive or inductive. The output voltage 225 does not vary
when the load is stable, but when the artificial load 223 is at
a point P2 and the load is L2 and the main load 222 fluctuates up
to the load L1 from that point, the amount of variation becomes
substantially as (L1-L2), thereby a so-called ringing phenomenon
is generated in which the output voltage 225 lowers small at the
point P2 and rises again in such a manner as shown by a waveform
"b". This is because of the fact that a total load of
the main load and the artificial load changes as shown by a reference
numeral 224. In addition, the output voltage 225 does not vary when
the load is stable, but when the artificial load 223 fluctuates
up to the load L2 at a point Q1 and at the same time, when the main
load 222 fluctuates to the load L1 from that point, the amount of
variation becomes substantially as (L1-L2), thereby a so-called
ringing phenomenon is generated in which the output voltage 225
rises small at the point Q1 and lowers again in such a manner as
shown by a waveform "c". Finally, the load L2 of the artificial
load 223 fluctuates until zero at a point Q2, and a so-called ringing
phenomenon is generated in which the output voltage rises small
and lowers again in such a manner as shown by a waveform "d".
This peak value becomes a width of voltage variation. It is obvious
that the width of voltage variation is made small as compared with
the width of voltage variation shown in FIG. 5.
Meanwhile, the amount of load of the artificial load is set as
approximately half of the main load as shown in the drawing, but
other values may be employed without limiting the value by approximately
half of the main load. In addition, it may also be recommendable
to provide a plurality of artificial loads to increase and decrease
the loads step by step.
FIG. 7 is a diagram for explaining other method for suppressing
load fluctuation according to the present invention. The present
invention suppresses the drastic load fluctuation at the time of
driving a main load 230, by previously connecting an artificial
load 231 which varies continuously (in the analog manner) before
and after the driving of the main load 230. Here, it is assumed
that a load 231a of the artificial load 231 has the characteristic
of quadratic curve. More specifically, the artificial load 231 is
allowed to fluctuate continuously from a point P1 to a point p2
before the main load 230 operates. Because the load of the artificial
load has the quadratic curve characteristic, output voltage 233
seldom varies nor does the output voltage 233 vary at the time when
the load is stable. In addition, if the artificial load 231 reaches
a load L1 at a point P2 and at the same time, the main load 230
fluctuates up to the load L1 from that point, the amount of variation
becomes substantially as (L1-L1=0), hence the output voltage 233
hardly varies at the point P2. By the operation in which the artificial
load 231 changes in such a manner as shown by a load characteristic
231b from a point Q1 where the main load finishes its operation,
the output voltage 233 seldom varies and can be stabled. This is
because of the fact that a total load of the main load 230 and the
artificial load 231 changes as shown by a reference numeral 232.
FIG. 8 is a diagram for explaining other method for suppressing
load fluctuation according to the present invention. The present
invention suppresses the drastic load fluctuation at the time of
driving a main load 235, by previously connecting an artificial
load 236 which varies discontinuously (in a pulse manner) before
and after the driving of the main load 235. Here, it is assumed
that a width of pulse is modulated with respect to the artificial
load 236. More specifically, the artificial load 236 is allowed
to fluctuate discontinuously from a point P1 to a point p2 before
the main load 235 operates. Because the load has a characteristic
in which the width of the pulse is changed, output voltage 238 seldom
varies nor does the output voltage 238 vary at the time when the
load is stable. This is because of the fact that a total load of
the main load 235 and the artificial load 236 changes as shown by
a reference numeral 237. In addition, if the artificial load 236
reaches a load L1 at a point P2 and at the same time, the main load
235 fluctuates up to the load L1 from that point, the amount of
variation becomes substantially as (L1-L1=0), hence the output voltage
238 hardly varies at the point P2. By the operation in which the
artificial load 236 changes in such a manner as shown by a load
characteristic 237 from a point Q1 where the main load finishes
its operation, the output voltage 238 seldom varies and can be stabled.
FIG. 9 is a diagram for explaining other method for suppressing
load fluctuation according to the present invention. The present
invention suppresses the drastic load fluctuation at the time of
driving a main load 240, by previously connecting an artificial
load 241 which varies continuously (in the analog manner) before
and after the driving of the main load 240. A point that FIG. 9
differs from FIG. 7 is that the connection of the artificial load
241 to the main load is ceased in mid-course of the operation, since
the characteristic of the fluctuation of the main load 240 is not
drastic and fluctuates smoothly at some extent. Other operations
are same as that of FIG. 7 and explanations thereof are omitted
here accordingly. More specifically, the present embodiment further
includes a voltage variation detector for detecting the voltage
variation caused by the load fluctuation of the main load 240, to
judge whether a value of varied voltage is to the extent that gives
an adverse effect on a circuit or not, and when the value of the
varied voltage is not to the extent that gives the adverse effect
on the circuit, disconnects the connection in the mid-course to
make the load of the power supply light, since there is no necessity
of connecting the artificial load 241. In this example shown in
the drawing, the artificial load 241 is changed continuously in
a region "a" and the artificial load 241 is disconnected
in a region "b", since the load fluctuation of the main
load 240 is moderate in that region.
FIG. 10 is a diagram for explaining other method for suppressing
load fluctuation according to the present invention. The present
invention suppresses the drastic load fluctuation at the time of
driving a main load 245, by previously connecting an artificial
load 246 which varies discontinuously (in the pulse manner) before
and after the driving of the main load 245. A point that FIG. 10
differs from FIG. 8 is that the connection of the artificial load
246 to the main load is ceased in mid-course of the operation. Other
operations are same as that of FIG. 8 and explanations thereof are
omitted here accordingly. More specifically, the present embodiment
further includes a voltage variation detector for detecting the
voltage variation caused by the load fluctuation of the main load
245, to judge whether a value of varied voltage is to the extent
that gives an adverse effect on a circuit or not, and when the value
of the varied voltage is not to the extent that gives the adverse
effect on the circuit, disconnects the connection in the mid-course
to make the load of the power supply light, since there is no necessity
of connecting the artificial load 246. In this example shown in
the drawing, the artificial load 246 is changed discontinuously
in a region "a" and the artificial load 246 is disconnected
in a region "b", since the load fluctuation of the main
load 245 is moderate in that region.
Also, opposite of the cases in FIGS. 9 and 10, in a case where
the voltage variation exceeds a predetermined amount of variation,
in other words, where the load exceeds a range in which the load
fluctuation is to be suppressed, the operation of suppressing the
load fluctuation carried out by the artificial load is configured
not to be carried out, since the load fluctuation cannot be suppressed
even when the artificial load is connected in such case.
In the foregoing explanations, for example, in a case where a plurality
of systems of the loads exists and where one of the main loads is
connected with one artificial load, the operation of suppressing
the fluctuation of other main loads cannot be carried out when a
request for the operation of suppressing the fluctuation of other
main loads is made, due to the fact that the necessary artificial
load is in use. In other words, there is a possibility that addition
of further load with respect to the artificial load while the artificial
load is in operation makes control on the artificial load complicated
and impairs accuracy. Furthermore, there is a possibility that entire
load becomes too large and thus the power supply cannot supply the
power, prior to the suppression of the voltage variation.
However, in a case where a plurality of main loads and a plurality
of artificial loads exist, and the request for the operation of
suppressing the fluctuation of other main loads is made when one
of the artificial loads is connected to the main load, it is effective
to select the artificial load other than the connected one and connect
it with the main load.
Also, when a capacity of supplying the power is deteriorated, for
example when the power supply is the battery and it is consumed,
it is also effective not to carry out the operation of the artificial
load for suppressing the voltage variation even if the voltage variation
caused by the load fluctuation of the main load is generated, by
judging that the power supply has no capacity of supplying the power.
The entire disclosure of Japanese application Nos. 2003-307544
and 2003-329086 are hereby incorporated by reference. |