Digital Camera Patent Abstract
There is disclosed an apparatus and a method for forecasting output
voltage of a battery of a digital camera. A dummy load is disconnected
after the digital camera is powered on. An output voltage of the
battery is obtained when he dummy load is off. The dummy load is
then conducted. An output voltage of the battery is obtained when
the dummy load is on. An internal resistance of the battery and
the output voltage of the battery in operating the power consumptive
elements are determined based on the output voltages, so as to obtain
the voltage drop of the output voltage of the battery caused by
power consumptive elements thereby being aware of the remaining
power of the battery and obtaining the maximum power supplying efficiency
for the digital camera. Digital Camera Patent Claims
What is claimed is:
1. An apparatus for forecasting output voltage of a battery of
a digital camera, the apparatus comprising:
a battery voltage detection circuit connected to two output ends
of a battery for outputting a dividing voltage of the battery from
a dividing voltage output end;
an analog-to-digital converter connected to the voltage output
end for converting an analog voltage value to a digital signal to
output from its output end;
a dummy load connected across on the two ends of the battery; and
a central processing unit connected to the output end of the analog-to-digital
converter for controlling whether to conduct the dummy load or not,
so as to obtain output voltages of the dummy load during off condition
and on condition, respectively, and, according to the obtained output
voltage, determining an internal resistance of the battery for further
determining an output voltage of the battery in operating at least
a power consumptive element based on an internal resistance of the
battery and pre-obtained power consumption of the power consumptive
element.
2. The apparatus as claimed in claim 1, wherein the battery voltage
detection circuit is composed of a dividing voltage circuit with
two resistances connected in series.
3. The apparatus as claimed in claim 1, wherein the dummy load
is a resistance and a switch transistor connected in series, the
central processing unit being connected to the base of the switch
transistor for controlling the switch transistor to conduct the
dummy load.
4. The apparatus as claimed in claim 1, wherein the central processing
unit turns off the dummy load first, after the digital camera is
powered on, to obtain the output voltage Vdoff of the battery during
the dummy load is off, and then conducts the dummy load to obtain
the output voltage Vdon of the battery during the dummy load is
on.
5. The apparatus as claimed in claim 4, wherein the internal resistance
of the battery obtained by the central processing unit is (Vdoff-Vdon)*(R.sub.D
/Vdon), wherein R.sub.D is resistance value of the dummy load.
6. The apparatus as claimed in claim 5, wherein the output voltage
of the battery in operating the power consumptive element obtained
by the central processing unit is Vdoff-(Vdoff-Vdon)*(R.sub.D *I(x)/Vdon),
wherein I(x) is pre-obtained current consumption of the power consumptive
element corresponding to the output voltage of the battery.
7. The apparatus as claimed in claim 6, wherein the pre-obtained
current consumption of the power consumptive elements is stored
in a non-volatile memory as a table.
8. A method for forecasting output voltage of a battery of a digital
camera, the camera comprising a dummy load connected across on two
ends of a battery and a plurality of power consumptive elements,
the method comprising the steps of:
(A) disconnecting the dummy load after the digital camera is turned
on;
(B) obtaining an output voltage Vdoff of the battery during the
dummy load is off;
(C) conducting the dummy load;
(D) obtaining an output voltage Vdon of the battery during the
dummy load is on;
(E) determining the internal resistance of the battery by (Vdoff-Vdon)*(RD/Vdon),
wherein RD is resistance value of the dummy load; and
(F) determining the output voltage of the battery in operating
the power consumptive elements is Vdoff-(Vdoff-Vdon)*(RD*I(x)/Vdon),
wherein I(x) is pre-obtained current consumption of the power consumptive
elements corresponding to the output voltage of the battery.
9. The method as claimed in claim 8, filter comprising a step between
steps (C) and (D) for delaying a period of time to stabilize the
electrical signal.
10. The method as claimed in claim 8, wherein in the step (F),
the pre-obtained current consumption of the power consumptive elements
are stored as a table.
11. The method as claimed in claim 8, further comprising a step
(G) for detecting whether the output voltage of the battery in operating
the power consumptive element is lower than the minimum input voltage
capable of enabling the camera to function normally, and if it is
too low, the power consumptive element is powered off and the user
is alarmed, otherwise, the camera can function well.
Digital Camera Patent Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the technology field of digital
camera and, more particularly, to an apparatus and a method for
forecasting output voltage of a battery of a digital camera.
2. Description of the Related Art
Please refer to FIG. 4. FIG. 4 shows a power supply status of a
conventional digital camera. For currently digital camera design,
as shown in FIG. 4, the power consumptive elements of a digital
camera are: a charging circuit of the flash 91, a back-light driving
circuit of LCD display 92, and a driving circuit of lens motor 93.
These power consumptive elements require large power consumption.
Therefore, they need three switch units 911, 921, 931 to control
the supply of power, respectively. During the operation of the digital
camera, if the functions of these power consumptive elements are
not necessary, the related switch will be turned off to stop supplying
power. The other logic circuit 94 of the digital camera comprises
a digital signal processor, a ROM (read-only memory), and a RAM
(random-access memory). Because of the power consumption of these
elements is less and their functions are always necessary for the
camera operation, there is no power supply restraint for them.
The power of the digital camera is supplied by the battery 95.
After the battery 95 has been used for a while, the output voltage
of the battery 95 will gradually decrease. Therefore, in order to
avoid the camera from being out of function or shut down due to
the insufficient output voltage of the battery, a digital camera
is generally installed with a battery low detection circuit 96.
When the output voltage of the battery is lower than a predetermined
threshold limit value, the digital camera will generate a warning
signal or sound to inform the user to replace the battery. Since,
the digital camera has the aforementioned power consumptive elements,
when one of the power consumptive elements works, the output voltage
of the battery will be decreased differently, which result in the
battery low detection circuit 96 being unable to detect the actual
output voltage of the battery. Therefore, it is desired to improve
the design of the battery low detection circuit of the digital camera.
SUMMARY OF THE INVENTION
The objective of the present invention is to provide an apparatus
and a method for forecasting the output voltage of a battery of
a digital camera, so as to obtain the voltage drop of the output
voltage of the battery caused by power consumptive elements, thereby
being aware of the remaining power of the battery and obtaining
the maximum power supplying efficiency for the digital camera.
In accordance with one aspect of the present invention, there is
provided a n apparatus for forecasting output voltage of a battery
of a digital camera. The apparatus comprises: a battery voltage
detection circuit connected to two output ends of a battery for
outputting a dividing voltage of the battery from a dividing voltage
output end; an analog-to-digital converter connected to the voltage
output end for converting an analog voltage value to a digital signal
to output from its output end; a dummy load connected across on
the two ends of the battery; and a central processing unit connected
to the output end of the analog-to-digital converter for controlling
whether to conduct the dummy load or not, so as to obtain output
voltages of the dummy load during off condition and on condition,
respectively, and, according to the obtained output voltage, determining
an internal resistance of the battery for further determining an
output voltage of the battery in operating at least a power consumptive
element based on an internal resistance of the battery and pre-obtained
power consumption of the power consumptive element.
In accordance with another aspect of the present invention, there
is provided a method for forecasting output voltage of a battery
of a digital camera. The camera comprises a dummy load connected
across on two ends of a battery and a plurality of power consumptive
elements. The method comprises the steps of: (A) disconnecting the
dummy load after the digital camera is turned on; (B) obtaining
an output voltage Vdoff of the battery during the dummy load is
off; (C) conducting the dummy load; (D) obtaining an output voltage
Vdon of the battery during the dummy load is on; (E) determining
the internal resistance of the battery by (Vdoff-Vdon)*(RD/Vdon),
wherein RD is resistance value of the dummy load; and (F) determining
the output voltage of the battery in operating the power consumptive
elements is Vdoff-(Vdoff-Vdon)*(RD*I(x)/Vdon), wherein I(x) is pre-obtained
current consumption of the power consumptive elements corresponding
to the output voltage of the battery.
Other objectives, advantages, and novel features of the invention
will become more apparent from the following detailed description
when taken in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a structure diagram of the apparatus for forecasting
output voltage of a battery of a digital camera of the present invention.
FIG. 2 is a flowchart of the method for forecasting output voltage
of a battery of a digital camera.
FIG. 3 shows a table of the pre-obtained current consumption of
the power consumptive elements.
FIG. 4 shows a power supply status of a conventional digital camera.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Please refer to FIG. 1. FIG. 1 is a structure diagram of the apparatus
for forecasting output voltage of a battery of a digital camera
of the present invention. Two output ends of a battery 11 with an
internal resistance Rs 12 are connected a battery voltage detection
circuit 13. The battery voltage detection circuit 13 is composed
of a dividing voltage circuit with two resistances R1, R2 in series
connection. The voltage output end of the battery voltage detection
circuit 13 is connected to an analog-to-digital converter 14 for
converting an analog voltage value to a digital signal and outputting
from its output end. The output of the analog-to-digital converter
14 is connected to a central processing unit 15. The central processing
unit 15 controls a dummy load 16 that is across on the two output
ends of the battery 11. As shown in FIG. 1, the dummy load 16 is
a resistance R.sub.D and a switch transistor Q1 connected in series.
An output end of the central processing unit 15 is connected to
the base of the switch transistor Q1 for controlling whether to
conduct the dummy load 16 by turning on or off the switch transistor
Q1.
The battery 11 is used for supplying power for a plurality of power
consumptive elements, such as a charging circuit 17 of the flash,
a back-light driving circuit 18 of the LCD display, a driving circuit
19 of the lens motor, and a logical circuit 20. The supply power
for the power consumptive elements are controlled by switch units
171, 181 and 191, respectively.
The operation of the power consumptive elements will cause different
voltage drop to the output voltage V.sub.B of the battery 11. The
proportion of the voltage drop is decided by the internal resistance
Rs 12. Therefore, in order to know the voltage drop caused by each
power consumptive element, the internal resistance Rs 12 of the
battery 11 needs to be obtained first. However, if the power supply
system of the camera supplies power normally, the output voltage
V.sub.B of the battery 11 has to be higher than a minimum output
voltage V.sub.TH. If the output voltage V.sub.B is lower than the
minimum output voltage V.sub.TH, the user will be informed that
the function of the power consumptive element can not be used.
Please refer to FIG. 2. FIG. 2 is a flowchart of the method of
forecasting output voltage of a battery of a digital camera. After
the power of the digital camera is turned on, the central processing
unit 15 controls the switch transistor Q1 to disconnect the dummy
load 16 (step 201), and indicates the output voltage of the battery
is Vdoff during the dummy load is off. The central processing unit
15 obtains the output voltage of the battery V.sub.B =Vdoff via
the battery voltage detection circuit 13 and the analog-to-digital
converter 14. In order to obtain more accurate voltage value, the
central processing unit 15 may check the output voltage few more
times, for example 5 times, to obtain a average value for being
used as Vdoff (step 202).
In step 203, the central processing unit 15 controls the switch
transistor Q1 to conduct the dummy load 16 and indicates the output
voltage of the battery is Vdon during the dummy load is on. After
a delaying time Td (step 204) to stabilize the electric signal,
the central processing unit 15 obtains the output voltage of the
battery V.sub.B =Vdon via the battery voltage detection circuit
13 and the analog-to-digital converter 14. In order to obtain more
accurate voltage value, the central processing unit 15 may check
the output voltage few more times (ex: 5 times) to obtain a average
value to be Vdon (step 205). If the current of the switch transistor
Q1 is denoted as Id, the value of the internal resistance R.sub.s
of the battery will be obtained by the following formula (step 206):
and
After computing the internal resistance R.sub.s of the battery,
the output voltage of the battery during the operation of the power
consumptive elements can be further computed. Since each power consumptive
element has different power consumption for different output voltage
of the battery, the power consumption needs to be calculated first.
Please refer to FIG. 3. FIG. 3 shows a list of the pre-obtained
power consumption of the power consumptive elements. FIG. 3 shows
the power consumption of the charging circuit 17 of the flash, the
back-lighted driving circuit 18 of the LCD display, the driving
circuit 19 of the lens motor, and the logical circuit 20 for three
different output voltage (6V, 5V, 4V), when the digital camera is
supplied power with four AAA size batteries. When the power consumption
is I(x) and one of the power consumptive elements is turned on,
the voltage drop will be:
Then, replacing R.sub.s by the result of formula (1), the forecasting
value of the output voltage of the battery for that power consumptive
element is:
The pre-obtained current consumption I(x) of the power consumptive
elements are recorded in a table stored in the central processing
unit 15 or an external non-volatile memory. Furthermore, the formulas
(1), (2) and (3) can be implemented in a program and executed by
the central processing unit 15. Therefore, the central processing
unit 15 obtains I(x) of the operating power consumptive element
from the table and computes Vsim (the step 207 in FIG. 2). The step
208 is to detect whether the output voltage Vsim of the battery
during operation of the power consumptive element is lower than
the minimum input voltage V.sub.TH for enabling the camera to function
normally, if it is too low, the digital camera will be turned off
and alarms user (step 209); if it is not, the digital camera can
function well (step 210).
According to the above-mentioned description, the present invention
is able obtain the voltage drop of the output voltage of the battery
caused by power consumptive element to know remaining power of the
battery, thereby obtaining the maximum power supplying efficiency
for the digital camera.
Although the present invention has been explained in relation to
its preferred embodiment, it is to be understood that many other
possible modifications and variations can be made without departing
from the spirit and scope of the invention as hereinafter claimed.
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