U.S. patent application number 15/838590 was filed with the patent office on 2018-04-12 for semiconductor integrated circuit having battery control function and operation method thereof.
The applicant listed for this patent is Renesas Electronics Corporation. Invention is credited to Takeshi Inoue, Yoko Nakayama.
Application Number | 20180100897 15/838590 |
Document ID | / |
Family ID | 47261168 |
Filed Date | 2018-04-12 |
United States Patent
Application |
20180100897 |
Kind Code |
A1 |
Nakayama; Yoko ; et
al. |
April 12, 2018 |
SEMICONDUCTOR INTEGRATED CIRCUIT HAVING BATTERY CONTROL FUNCTION
AND OPERATION METHOD THEREOF
Abstract
A semiconductor integrated circuit is capable of being supplied
with battery current information and battery voltage information.
The semiconductor integrated circuit includes a memory function, a
current integrating function, a voltage-based state of charge
operating function, a current-based state of charge operating
function, a comparison determination function, a correcting
function, and a resistance deterioration coefficient output
function. The memory function stores the relation between a state
of charge of a battery and an internal resistance deterioration
coefficient thereof. The full charge capacity outputted from the
correcting function and the internal resistance deterioration
coefficient outputted from the resistance deterioration coefficient
output function are stored in the memory function when a
voltage-based state of charge and a current-based state of charge
compared by the comparison determination function are determined to
substantially coincide with each other.
Inventors: |
Nakayama; Yoko; (Chiyoda-ku,
JP) ; Inoue; Takeshi; (Chiyoda-ku, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Renesas Electronics Corporation |
Tokyo |
|
JP |
|
|
Family ID: |
47261168 |
Appl. No.: |
15/838590 |
Filed: |
December 12, 2017 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
14635621 |
Mar 2, 2015 |
9846201 |
|
|
15838590 |
|
|
|
|
13478914 |
May 23, 2012 |
8970174 |
|
|
14635621 |
|
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G01R 31/3648 20130101;
G01R 31/382 20190101; G01R 31/3828 20190101; G01R 31/389 20190101;
G01R 31/367 20190101; G01R 31/392 20190101; G06F 1/263
20130101 |
International
Class: |
G01R 31/36 20060101
G01R031/36; G06F 1/26 20060101 G06F001/26 |
Foreign Application Data
Date |
Code |
Application Number |
May 30, 2011 |
JP |
2011-120119 |
Claims
1-20. (canceled)
21. A method of operating a semiconductor integrated circuit
including a battery control function configured to control a
battery, the method comprising the steps of: (a) storing a relation
between a full charge capacity and an internal resistance
deterioration coefficient of the battery in a memory unit; (b)
supplying current information and voltage information of the
battery to the semiconductor integrated circuit; and (c) storing
the full charge capacity and an internal resistance deterioration
coefficient of the battery in the memory unit when a voltage-based
state of charge and a current-based state of charge have a same
value, wherein: the semiconductor integrated circuit comprises: the
memory unit; a current integrating unit; a voltage-based state of
charge operating unit; a current-based state of charge operating
unit; a comparison determination unit; a correcting unit, and a
resistance deterioration coefficient output unit; and the method
further comprises after step (b): determining a voltage-based state
of charge; determining a current-based state of charge; determining
a comparison output signal based on the voltage-based state of
charge and the current-based state of charge; calculating a
corrected value of the full charge capacity, based on an initial
value of the full charge capacity and the comparison output signal;
and calculating an internal resistance deterioration coefficient,
in response to the corrected value of the full charge capacity.
22. A battery monitoring semiconductor device comprising: (a) a
current detection circuit configured to detect a current of a
battery; (b) a voltage detection circuit configured to detect a
voltage of the battery; and (c) a calculation circuit configured to
calculate a full charge capacity of the battery based on the
current of the battery and the voltage of the battery.
23. The battery monitoring semiconductor device according to claim
22, wherein the calculation circuit comprises: (d) a first capacity
calculation circuit configured to calculate a charged capacity
based on the current of the battery; (e) a second capacity
calculation circuit configured to calculate the charged capacity
based on the voltage of the battery; and (f) a correction circuit
configured to correct the full charge capacity by comparing the
charged capacity based on the current of the battery with the
charged capacity based on the voltage of the battery.
24. The battery monitoring semiconductor device according to claim
23, wherein the calculation circuit determines the full charge
capacity upon a substantially coincident of the charged capacity
based on the current of the battery and the charged capacity based
on the voltage of the battery.
25. A method for monitoring states of a battery, comprising:
detecting a current of the battery; detecting a voltage of the
battery; and calculating a full charge capacity of the battery
based on the current of the battery and the voltage of the
battery.
26. The method according to claim 25, the calculating comprising:
calculating a charged capacity based on the current of the battery;
calculating the charged capacity based on the voltage of the
battery; and correcting the full charge capacity by comparing the
charged capacity based on the current of the battery with the
charged capacity based on the voltage of the battery.
27. The method according to claim 26, further comprising:
determining the full charge capacity upon a substantially
coincident of the charged capacity based on the current of the
battery and the charged capacity based on the voltage of the
battery.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This is a Continuation of U.S. patent application Ser. No.
14/635,621, filed Mar. 2, 2015, now U.S. Pat. No. 9,846,201, which
is a Continuation of U.S. patent application Ser. No. 13/478,914,
filed May 23, 2012, now U.S. Pat. No. 8,970,174, which claims
priority to Japanese Patent Application No. 2011-120119 filed on
May 30, 2011. The contents of the aforementioned applications are
incorporated herein by reference in their entirety.
BACKGROUND
[0002] The present invention relates to a semiconductor integrated
circuit having a battery control function and an operation method
thereof, and particularly to a technology effective in making it
possible to shorten the time taken to calculate a full charge
capacity Qmax and an internal resistance value being parameters
related to deterioration of a battery.
[0003] Portable equipment for consumer use such as a notebook
personal computer (hereinafter referred to as "note PC"), a
cellular phone, a smart phone or the like needs to notify battery's
characteristic information about the degree of deterioration of a
secondary battery used as a power supply, the remaining capacity
and time of the battery at its discharge, or the remaining capacity
and time thereof at its charge, or the like to a user.
[0004] The following Patent Document 1 has described that a
remaining capacity SOCc based on current integration in which
charging and discharging currents of a battery are integrated, and
a remaining capacity SOCv based on an estimated value of an open
voltage of the battery are weighted to calculate a combined
remaining capacity SOC. Further, a current capacity change rate
.sigma. is calculated from a change .DELTA.SOCc in the remaining
capacity based on the current integration and a change .DELTA.SOC
in the combined remaining capacity. When the current capacity
change rate .sigma. reaches a predetermined value or less, it is
determined that the deterioration of the battery has occurred.
Incidentally, the remaining capacity (SOC) is called a charge rate
or a state of charge.
[0005] The following Patent Document 2 has described a method of
determining the deterioration of a battery using a state of charge
(SOC) calculated by integrating charging and discharging currents
of the battery. A current-based state of charge (ISOC) is generated
from the charging and discharging currents of the battery, and a
voltage-based state of charge (VSOC) is calculated from the voltage
of the battery. When the value of either of them is high, the
current-based state of charge (ISOC) is subtracted from the
voltage-based state of charge (VSOC). When the subtracted value
exceeds a first threshold value or when the subtracted value is
less than a second threshold value where the value of either of the
two is low, an additional value is added to a deterioration
coefficient to modify the deterioration coefficient. When the
deterioration coefficient exceeds a third threshold value, it is
determined that the battery has been deteriorated.
[0006] The following Patent Document 3 has described a method of
performing an arithmetic operation on a charging time up to the end
of charge where a secondary battery is charged by constant
current/voltage charge. An open voltage for the secondary battery
is detected. A constant current charging time is calculated from
the open voltage and a voltage drop developed across an internal
resistance of the secondary battery at the constant current charge.
A constant voltage charging time is calculated from a voltage drop
developed across the internal resistance. Then, a charging time
taken up to the end of its charge is arithmetically operated from
the two.
[0007] The following Patent Document 4 has described a method of
calculating a relative remaining capacity of a secondary battery
and a full charge capacity thereof. First, a relative remaining
capacity SOCfull is calculated from a reference table in accordance
with an open circuit voltage OCVfull in the fully charged state of
the secondary battery. Thereafter, a relative remaining capacity
SOC determined from the reference table in accordance with an open
circuit voltage OCV detected upon the stop of discharge of the
secondary battery is corrected based on the relative remaining
capacity SOCfull in the fully charged state, whereby a true
relative remaining capacity SOCtrue is determined. Further, a
discharging current of the secondary battery is integrated to
determine a discharge capacity Q [Ah] from the fully charged state
of the secondary battery to its discharge stop. A full charge
capacity Qfull of the secondary battery is determined as
Qfull=Q/[(100-SOCtrue)/100] based on the discharge capacity Q and
the true relative remaining capacity SOCtrue. A method of
calculating the full charge capacity Qfull is however a general
method.
RELATED ART DOCUMENTS
Patent Documents
[Patent Document 1] Japanese Patent Laid-Open No. 2008-14702
[Patent Document 2] Japanese Patent Laid-Open No. 2003-178811
[0008] [Patent Document 3] Japanese Patent Laid-Open No. Hei
9(1997)-322420
[Patent Document 4] Japanese Patent Laid-Open No. 2011-53088
[0009] The technology described in the Patent Document 1 has shown
that the degree of deterioration of the battery is determined from
the current capacity change rate .sigma.. As described below,
however, the present technology is not capable of calculating the
full charge capacity Qmax and the internal resistance for making it
possible to display the accurate remaining capacity of the
battery.
[0010] In the technology described in the Patent Document 2, when
the current-based state of charge (ISOC) is subtracted from the
voltage-based state of charge (VSOC) and the subtracted value is
not greater than the first threshold value where the value of
either of both the current-based state of charge (ISOC) and the
voltage-based state of charge (VSOC) is high, it is determined
whether the subtracted value is less than a fourth threshold value
smaller than the absolute value of the first threshold value. When
the subtracted value is of the fourth threshold value, the
current-based state of charge (ISOC) is decided as a battery's
state of charge (SOC). Further, when the voltage-based state of
charge (VSOC) is subtracted from the current-based state of charge
(ISOC) and the subtracted value is greater than or equal to the
second threshold value where the value of either of both the
current-based state of charge (ISOC) and the voltage-based state of
charge (VSOC) is low, the current-based state of charge (ISOC) is
decided as a battery's state of charge (SOC). Since the technology
described in the Patent Document 2 executes the complicated
determination process as described above, a calculation convergence
time is required for execution of calculations. The technology
described in the Patent Document 2 is provided assuming a battery
mounted in an electric vehicle (EV), a hybrid electric vehicle
(HEV), etc. It is possible for a semiconductor integrated circuit
for battery control used in this field to shorten the calculation
convergence time with an increase in the processing speed. It has
however been clear as a result of studies by the present inventors
prior to the present invention that it is not easy for a
semiconductor integrated circuit for battery control used in the
field of portable equipment for consumer use such as a notebook PC
or the like to shorten the calculation convergence time.
[0011] A specification called a smart battery system (SBS) has
recently been established in the field of the notebook PC.
Described concretely, an electronic circuit board built in a
battery pack is used and equipped with a function for an accurate
remaining capacity indicator and a function for a safety circuit or
the like relative to overdischarge.
[0012] In order to display the accurate remaining capacity of the
battery of the smart battery system (SBS), there is a need to
calculate a full charge capacity Qmax and an internal resistance as
will be described in detail later. A full charge capacity Qmax
mentioned in the specification of the present application indicates
a capacity taken until a final discharge voltage is reached where
the battery is discharged with an extremely small current
(.apprxeq.0).
[0013] It is however possible for the technology described in the
Patent Document 2 to calculate the deterioration coefficient of the
battery but impossible therefor to calculate the full charge
capacity Qmax and the internal resistance.
[0014] On the other hand, the technology described in the Patent
Document 3 performs the arithmetic operation on the charging time
up to the end of charge of the secondary battery where the
secondary battery is charged by the constant current/voltage
charge, but is nevertheless not capable of calculating the full
charge capacity Qmax. Further, the technology described in the
Patent Document 3 makes use of a charging time table in which times
taken until the open voltage of the secondary battery reaches a
full charge voltage are tabularized, when the constant voltage
charging time is calculated based on an exponential function to
which a change in the open voltage of the secondary battery is made
approximate. Thus, there is a need to provide a nonvolatile memory
having a large storage capacity in order to realize the charging
time table by an actual semiconductor integrated circuit for
battery control.
[0015] On the other hand, the technology described in the Patent
Document 4 is accompanied by problems that it is capable of
calculating the full charge capacity but needs to cause the
secondary battery to definitely reach the fully charged state, and
an accurate calculation cannot be made where the secondary battery
is not fully charged in practical use.
[0016] The present invention has been made as a result of studies
by the present inventors prior to the present invention, such as
described above.
SUMMARY
[0017] An object of the present invention is therefore to enable
shortening of time taken to calculate a full charge capacity Qmax
and an internal resistance that change depending on the
deterioration of a battery.
[0018] Another object of the present invention is to improve the
accuracy of estimation of a remaining capacity of a battery.
[0019] The above and other objects and novel features of the
present invention will be apparent from the description of the
present specification and the accompanying drawings.
[0020] Typical ones of the inventive aspects of the invention
disclosed in the present application will be briefly described as
follows:
[0021] A typical embodiment of the present invention is a
semiconductor integrated circuit (703) having a battery control
function capable of controlling at least either one of discharge
and charge operations of a battery (702).
[0022] The semiconductor integrated circuit is capable of being
supplied with current information generated from a current
detection unit (706) for detecting a current of the battery and
voltage information generated from a voltage detection unit (705)
for detecting a voltage of the battery.
[0023] The semiconductor integrated circuit is equipped with a
memory function (719), a current integrating function (765), a
voltage-based state of charge operating function (764), a
current-based state of charge operating function (766), a
comparison determination function (767), a correcting function
(769), and a resistance deterioration coefficient output function
(768).
[0024] The memory function is capable of storing therein a relation
between a full charge capacity (Qmax) of the battery and an
internal resistance deterioration coefficient (C.sub.Deg) of the
battery.
[0025] The full charge capacity outputted from the correcting
function and the internal resistance deterioration coefficient
outputted from the resistance deterioration coefficient output
function can be stored in the memory function in a state in which a
voltage-based state of charge and a current-based state of charge
compared with each other by the comparison determination function
are determined to substantially coincide with each other (refer to
FIG. 4).
[0026] Further, another typical embodiment of the present invention
is an operation method of a semiconductor integrated circuit (703)
having a battery control function capable of controlling at least
either one of discharge and charge operations of a battery
(702).
[0027] The semiconductor integrated circuit is equipped with a
memory function (719), a current integrating function (765), a
voltage-based state of charge operating function (764), a
current-based state of charge operating function (766), a
comparison determination function (767), a correcting function
(769), and a resistance deterioration coefficient output function
(768).
[0028] The operation method includes a step of storing a relation
between a full charge capacity (Qmax) of the battery and an
internal resistance deterioration coefficient (C.sub.Deg) of the
battery in the memory function, a step of supplying current
information generated from a current detection unit (706) for
detecting a current of the battery and voltage information
generated from a voltage detection unit (705) for detecting a
voltage of the battery to the semiconductor integrated circuit
respectively, and a step of storing in the memory function, the
full charge capacity outputted from the correcting function and the
internal resistance deterioration coefficient outputted from the
resistance deterioration coefficient output function in a state in
which it is determined that a voltage-based state of charge and a
current-based state of charge compared with each other by the
comparison determination function substantially coincide with each
other (refer to FIG. 4).
[0029] An advantageous effect obtained by a typical one of the
inventive aspects of the invention disclosed in the present
application will briefly be explained as follows:
[0030] According to the present invention, it is possible to
shorten the time taken to calculate a full charge capacity Qmax and
an internal resistance that change depending on the deterioration
of a battery.
BRIEF DESCRIPTION OF THE DRAWINGS
[0031] FIG. 1 is a diagram showing a configuration of a
semiconductor integrated circuit 703 for battery control, according
to a first embodiment of the present invention;
[0032] FIG. 2 is a diagram illustrating a configuration of a
voltage detection unit 705 of the semiconductor integrated circuit
703 for battery control shown in FIG. 1 and a configuration of a
battery 702 thereof;
[0033] FIG. 3 is a diagram showing the manner in which information
about the state of detection of a battery remaining capacity or the
like is displayed on a monitor of a notebook personal computer 708
using the semiconductor integrated circuit 703 for battery control
according to the first embodiment of the present invention shown in
FIG. 1;
[0034] FIG. 4 is a diagram for describing the function of an
operation unit 718 of the semiconductor integrated circuit 703 for
battery control according to the first embodiment of the present
invention shown in FIG. 1;
[0035] FIG. 5 is a diagram for describing an operation of the
operation unit 718 shown in FIG. 4, of the semiconductor integrated
circuit 703 for battery control according to the first embodiment
of the present invention;
[0036] FIG. 6 is a diagram for describing an operation of the
operation unit 718 shown in FIG. 4, of the semiconductor integrated
circuit 703 for battery control according to the first embodiment
of the present invention;
[0037] FIG. 7 is a diagram for describing a preferred operation of
the operation unit 718 shown in FIG. 4, of the semiconductor
integrated circuit 703 for battery control according to the first
embodiment of the present invention;
[0038] FIG. 8 is a diagram for describing another preferred
operation of the operation unit 718 shown in FIG. 4, of the
semiconductor integrated circuit 703 for battery control according
to the first embodiment of the present invention;
[0039] FIG. 9 is a diagram showing the manner in which a linear
approximation method is utilized when a charging time Tcv for
constant voltage charge (CV charge) is calculated using the
semiconductor integrated circuit 703 for battery control shown in
FIG. 1;
[0040] FIG. 10 is a diagram illustrating the manner in which a
battery 702 is charged using the semiconductor integrated circuit
703 for battery control shown in FIG. 1;
[0041] FIG. 11 is a diagram for describing in further detail the
linear approximation method used when the charging time Tcv for the
constant voltage discharge (CV charge) shown in FIG. 9 is
calculated;
[0042] FIG. 12 is a diagram showing a flowchart for calculating a
remaining charge time of the battery 702 using the semiconductor
integrated circuit 703 for battery control shown in FIG. 1;
[0043] FIG. 13 is a diagram showing the relationship between the
operation at the discharge of the battery 702 in FIG. 6 according
to the first embodiment of the present invention using the
semiconductor integrated circuit 703 for battery control shown in
FIG. 1, the stored content of nonvolatile memory for a memory 719,
and the operation at the charge of the battery 702, which has been
described in FIGS. 9 through 12 according to a second embodiment of
the present invention; and
[0044] FIG. 14 is a diagram showing the relationship between a
state of charge SOC of the battery 702 and an open-circuit voltage
OCV of the battery 702.
DETAILED DESCRIPTION
1. Summary of the Embodiments
[0045] A summary of typical embodiments of the invention disclosed
in the present application will first be explained. Reference
numerals of the accompanying drawings referred to with parentheses
in the description of the summary of the typical embodiments only
illustrate elements included in the concept of components to which
the reference numerals are given.
[0046] [1] A typical embodiment of the present invention is a
semiconductor integrated circuit (703) having a battery control
function capable of controlling at least either one of discharge
and charge operations of a battery (702).
[0047] The semiconductor integrated circuit is capable of being
supplied with current information generated from a current
detection unit (706) which detects a current of the battery and
voltage information generated from a voltage detection unit (705)
which detects a voltage of the battery.
[0048] The semiconductor integrated circuit is equipped with a
memory function (719), a current integrating function (765), a
voltage-based state of charge operating function (764), a
current-based state of charge calculating function (766), a
comparison determination function (767), a correcting function
(769), and a resistance deterioration coefficient output function
(768).
[0049] The memory function is capable of storing the relationship
between a full charge capacity (Qmax) of the battery and an
internal resistance deterioration coefficient (C.sub.Deg) of the
battery.
[0050] In a state in which it is determined that a voltage-based
state of charge and a current-based state of charge compared with
each other by the comparison determination function are determined
to have coincided with each other, the full charge capacity
outputted from the correcting function and the internal resistance
deterioration coefficient outputted from the resistance
deterioration output function can be stored in the memory function
(refer to FIG. 4).
[0051] According to the above embodiment, it is possible to shorten
the time taken to calculate a full charge capacity Qmax and an
internal resistance that change depending on the deterioration of
the battery.
[0052] In a preferred embodiment, the memory function is capable of
storing an initial value of the full charge capacity and an initial
value of the current-based state of charge therein.
[0053] The current integrating function is supplied with the
current information to thereby enable a current integrated value to
be outputted therefrom.
[0054] The voltage-based state of charge operating function is
supplied with the current information and the voltage information
to thereby enable a voltage-based state of charge (SOC_V) to be
outputted therefrom.
[0055] The current-based state of charge operating function is
supplied with the initial value of the full charge capacity and the
initial value of the current-based state of charge both outputted
from the memory function respectively, and the current integrated
value outputted from the current integrating function to thereby
enable a current-based state of charge (SOC_I) to be outputted
therefrom.
[0056] The comparison determination function is supplied with the
voltage-based state of charge and the current-based state of charge
respectively to thereby enable a comparison output signal
(.DELTA.Qmax) corresponding to a difference between the
voltage-based state of charge and the current-based state of charge
to be outputted therefrom.
[0057] The correcting function is supplied with the comparison
output signal outputted from the comparison determination function
and the initial value of the full charge capacity outputted from
the memory function to thereby enable a corrected calculated value
of the full charge capacity to be outputted therefrom.
[0058] The resistance deterioration coefficient output function is
capable of outputting the internal resistance deterioration
coefficient in response to the corrected calculated value of the
full charge capacity outputted from the correcting function.
[0059] Immediately after the start of the discharge operation, the
memory function is capable of storing therein the corrected
calculated value of the full charge capacity outputted from the
correcting function in the state in which the voltage-based state
of charge and the current-based state of charge substantially
coincide with each other, and either one of the voltage-based state
of charge and the current-based state of charge in the state in
which the voltage-based state of charge and the current-based state
of charge substantially coincide with each other as the initial
value of the full charge capacity and the initial value of the
current-based state of charge, respectively (refer to FIG. 6).
[0060] In another preferred embodiment, the semiconductor
integrated circuit further includes a resistance parameter output
function (761).
[0061] The resistance parameter output function is comprised of a
table indicative of a relation (f(SOC)) between the voltage-based
state of charge outputted from the voltage-based state of charge
operating function and an internal resistance of the battery. The
resistance parameter output function is capable of outputting a
resistance parameter (f(SOC)) of the internal resistance of the
battery in response to the voltage-based state of charge outputted
from the voltage-based state of charge operating function.
[0062] During the continuation of discharge of the battery, the
internal resistance of the battery is calculated based on a
closed-circuit voltage of the battery generated from the voltage
detection unit and a discharging current of the battery generated
from the current detection unit.
[0063] A method of outputting the resistance parameter of the
internal resistance of the battery from the resistance parameter
output function can be updated in accordance with the result of
calculation of the internal resistance of the battery during the
continuation of the discharge of the battery (refer to FIG. 7).
[0064] Further, in a further preferred embodiment, the full charge
capacity of the battery is calculated based on a state of charge
calculated based on an open-circuit voltage of the battery
generated from the voltage detection unit when a few hours have
elapsed after the end of discharge of the battery, and an
integrated value of the discharging current of the battery
generated from the current detection unit during the discharge of
the battery.
[0065] The internal resistance deterioration coefficient is
calculated based on current and voltage values of the battery
during the discharge of the battery.
[0066] The relation between the full charge capacity and the
internal resistance deterioration coefficient both stored in the
memory function is capable of being updated based on the result of
calculation of the full charge capacity when the few hours have
elapsed after the end of discharge of the battery, and the result
of calculation of the internal resistance deterioration coefficient
during the discharge of the battery.
[0067] In a more preferred embodiment, the semiconductor integrated
circuit calculates a state of charge available, a remaining
capacity and a remaining time of the battery, based on the full
charge capacity and the internal resistance deterioration
coefficient (refer to FIG. 7).
[0068] In another more preferred embodiment, immediately after the
start of the charge operation, the corrected calculated value of
the full charge capacity outputted from the correcting function in
the state in which the voltage-based state of charge and the
current-based state of charge substantially coincide with each
other, and either one of the voltage-based state of charge and the
current-based state of charge in the state in which the
voltage-based state of charge and the current-based state of charge
substantially coincide with each other are respectively stored in
the memory function as the initial value of the full charge
capacity and the initial value of the current-based state of
charge.
[0069] In a further more preferred embodiment, during the
continuation of discharge of the battery, the internal resistance
of the battery is calculated based on the closed-circuit voltage of
the battery generated from the voltage detection unit and the
discharging current of the battery generated from the current
detection unit.
[0070] The method of outputting the resistance parameter of the
internal resistance of the battery at the resistance parameter
output function is capable of being updated in accordance with the
result of calculation of the internal resistance of the battery
during the continuation of the discharge of the battery.
[0071] In a still further more preferred embodiment, when a few
hours have elapsed after the end of charge of the battery, the full
charge capacity of the battery is calculated based on the state of
charge calculated based on the open-circuit voltage of the battery
generated from the voltage detection unit, and the integrated value
of the charging current of the battery generated from the current
diction unit during the charge of the battery.
[0072] The internal resistance deterioration coefficient is
calculated based on the current and voltage values of the battery
during the charge of the battery.
[0073] The relation between the full charge capacity and the
internal resistance deterioration coefficient stored in the memory
function is capable of being updated based on the result of
calculation of the full charge capacity when the few hours have
elapsed after the end of charge of the battery, and the result of
calculation of the internal resistance deterioration coefficient
during the charge of the battery.
[0074] In another more preferred embodiment, as the charge
operation, the charge of a constant current is executed in the
first half of the charge, and the charge of a constant voltage is
executed in the latter half of the charge.
[0075] A state of charge (SOC_change) at a change point when the
constant current charge is switched to the constant voltage charge
is calculated to thereby calculate a constant current charging time
(Tcc) for the constant current charge and a constant voltage
charging time (Tcv) for the constant voltage charge. An added value
of the constant current charging time and the constant voltage
charging time is outputted as a remaining charge time (Tcg)(refer
to FIGS. 9 through 12).
[0076] In a further more preferred embodiment, the relation between
the state of charge of the battery and the charging current for the
constant voltage charge is made to a linear approximation upon the
calculation of the constant voltage charging time to thereby
calculate the constant voltage charging time (refer to FIG.
11).
[0077] In a concrete embodiment, a method for calculating the
change-point state of charge executes at least either the
calculation of the change-point state of charge with a timing at
which the closed-circuit voltage taken during the period of the
constant voltage charge of the battery coincides with a limit
voltage (V_lim) for the constant voltage charge or the calculation
of the change-point state of charge with a timing at which the
charging current taken during the period of the constant voltage
charge of the battery coincides with a constant current (Icc) for
the constant current charge.
[0078] The semiconductor integrated circuit updates the
change-point state of charge calculated by the calculation method
to the value of an actual change-point state of charge calculated
based on a change from the constant current charge to the constant
voltage charge during the actual charge of the battery.
[0079] The semiconductor integrated circuit recalculates the
constant voltage charging time by using the value of the actual
change-point state of charge to thereby update an output value of
the remaining charging time (refer to FIG. 12).
[0080] In the most concrete embodiment, the memory function is
achieved by a nonvolatile memory built in the semiconductor
integrated circuit.
[0081] [2] A typical embodiment according to another aspect of the
present invention is an operation method of a semiconductor
integrated circuit (703) having a battery control function capable
of controlling at least either one of discharge and charge
operations of a battery (702).
[0082] The semiconductor integrated circuit is equipped with a
memory function (719), a current integrating function (765), a
voltage-based state of charge operating function (764), a
current-based state of charge operating function (766), a
comparison determination function (767), a correcting function
(769), and a resistance deterioration coefficient output function
(768).
[0083] The operation method includes the steps of storing a
relation between a full charge capacity (Qmax) of the battery and
an internal resistance deterioration coefficient (C.sub.Deg) of the
battery in the memory function, supplying current information
generated from a current detection unit (706) for detecting a
current of the battery and voltage information generated from a
voltage detection unit (705) for detecting a voltage of the battery
to the semiconductor integrated circuit respectively, and storing
in the memory function, the full charge capacity outputted from the
correcting function and the internal resistance deterioration
coefficient outputted from the resistance deterioration coefficient
output function in a state in which it is determined that a
voltage-based state of charge and a current-based state of charge
compared with each other by the comparison determination function
substantially coincide with each other (refer to FIG. 4).
2. Further Detailed Description of the Embodiments
[0084] Embodiments will next be explained in further detail.
Incidentally, in all of the drawings for explaining the best modes
for carrying out the invention, the same reference numerals are
respectively attached to components having the same function as in
the drawings, and their repetitive description will be omitted.
[First Embodiment] Configuration of Semiconductor Integrated
Circuit for Battery Control
[0085] FIG. 1 is a diagram showing a configuration of a
semiconductor integrated circuit 703 for battery control according
to a first embodiment of the present invention.
[0086] FIG. 1 shows not only the semiconductor integrated circuit
703 but also a battery pack 701, a note PC 708 and an AC/DC
converter 712.
[0087] The battery pack 701 is comprised of a battery 702 having
three series couplings or four series couplings, the semiconductor
integrated circuit 703 for battery control, a protection circuit
704, a voltage detection unit 705, a current detection unit 706,
and a temperature detection unit 707. In the example illustrated in
FIG. 1, the battery 702 has a plurality of battery cells coupled in
series.
[0088] The semiconductor integrated circuit 703 is comprised of a
first A/D converter 709, a second A/D converter 715, a protection
circuit controller 716, a timer 717, an operation part 718, a
memory 719 and an input/output unit 720. The protection circuit
controller 716 is coupled to the protection circuit 704 and
controls the protection circuit 704. Since the input/output unit
720 is coupled to the note PC 708, the semiconductor integrated
circuit 78034 executes the transfer of data through the note PC 708
and the input/output unit 720. The operation part 718 can be
configured by a central processing unit (CPU). The memory 719
includes a volatile memory such as an SRAM for the central
processing unit (CPU) of the operation part 718, and a nonvolatile
memory such as a flash memory or the like.
[0089] As shown in FIG. 1, a power system of the note PC 708
includes first path 710 that supplies power from an AC power supply
731 to the note PC 708 via the AC/DC converter 712, and second path
711 that supplies power from the battery 702 through the DC/DC
converter 721 upon non-coupling of the AC power supply 731. Even in
the case of both of the first path 710 and the second path 711,
power is supplied from a route 725 to the respective units such as
a central processing unit (CPU) 722, a hard disk drive (HDD) 723, a
DVD drive 724 and the like of the note PC 708. During the charge of
the battery 702, the battery 702 is charged from the AC power
supply 731 via the AC/DC converter 721, the first path 710, the
DC/DC converter 721 and the second path 711.
[0090] FIG. 2 is a diagram showing a configuration of the voltage
detection unit 705 for the semiconductor integrated circuit 703
shown in FIG. 1, and a configuration of the battery 702
therefor.
[0091] As shown in FIG. 2, the battery 702 is comprised of a
plurality of battery cells coupled in series, which take the form
of series couplings prepared in plural form and take the form of
parallel couplings of such series couplings. The voltage detection
unit 705 is comprised of a multi-input/one-output multiplexer MPX
configured so as to be capable of selecting an arbitrary coupling
node of the battery 702 and supplying power to an analog input
terminal of the first A/D converter 709. The multi-input terminals
of the multiplexer MPX are coupled to a plurality of coupling nodes
of the battery 702. The single output terminal of the multiplexer
MPX is coupled to the analog input terminal of the first A/D
converter 709.
[0092] The semiconductor integrated circuit 703 shown in FIG. 1 is
coupled to the voltage detection unit 705, the current detection
unit 706 and the temperature detection unit 707. The voltage
detection unit 705 detects a voltage developed across both ends of
the battery 702. The current detection unit 706 detects a current
that flows through the battery 702. The temperature detection unit
707 such as a thermistor, a thermocouple or the like detects the
temperature of the battery 702. Analog signals corresponding to the
detected voltage of the voltage detection unit 705 and the detected
temperature of the temperature detection unit 707 are converted
into digital signals by the first A/D converter 709. The detected
analog current of the current detection unit 706 is converted into
a digital signal by a second A/D converter 715, which is supplied
via a bus to the operation unit 718 and the memory 719.
[0093] The temperature detection unit 707 may preferably be
disposed in the neighborhood of the surface of the battery 702 and
at a high-temperature heat storage portion near the central
processing unit (CPU) 722 of the note PC 708. The protection
circuit controller 716 executes control for securing the safety of
the battery 702, such as protection of overcharge, protection of
overdischarge, etc. in response to the values of the detected
current, the detected voltage and the detected temperature and
outputs a control command to the protection circuit 704. On the
other hand, the operation unit 718 calculates a full charge
capacity Qmax, an internal resistance R, a remaining capacity and
the like using information about the detected current, voltage and
temperature, and various information stored in the memory 719 and
thereby executes the detection of a state of the battery 702. That
is, since the result of calculation by the operation unit 718 is
supplied to the central processing unit (CPU) 722 of the note PC
708 through the input/output unit 720, it is possible to display
the remaining capacity of the battery, the remaining time
available, etc. on the monitor of the note PC 708.
[0094] FIG. 3 is a diagram showing the manner in which information
about the state of detection of a battery remaining capacity or the
like is displayed on the monitor of the note PC 708 using the
semiconductor integrated circuit 703 shown in FIG. 1.
[0095] For example, when the battery 702 is in use, the battery
remaining capacity and the remaining time available are displayed
in small font and/or symbols at the lower portion of the monitor as
shown in a simplified display 751 of FIG. 3. Further, when a
detailed display screen 750 is set up differently from above by the
operation of the note PC 708, detailed information about a battery
deterioration rate, a message for battery replacement, etc. for
example are displayed. Incidentally, although the battery remaining
capacity and the like are not illustrated in the drawing 751, they
can be level-displayed using bars or the like implemented by a
plurality of light emitting diodes (LEDs) disposed at the side face
of the battery pack 701.
[0096] Function of Operation Unit
[0097] FIG. 4 is a diagram for describing the function of the
operation unit 718 of the semiconductor integrated circuit 703 for
battery control according to the first embodiment of the present
invention shown in FIG. 1.
[0098] The function of calculating a full charge capacity Qmax by
the function of the operation unit 718 is particularly shown in
detail in FIG. 4. As shown in FIG. 4, the operation unit 718 is
comprised of an adder 769, a Qmax-R deterioration coefficient
operation part 768, an R temperature coefficient table 763, an
internal resistance operation part 762, an internal resistance
table 761, a voltage based charge-rate operation part 764, a
current integrating part 765, a current based charge-rate operation
part 766 and a comparison determination part 767. The respective
functions of the Qmax-R deterioration coefficient operation part
768, the internal resistance operation part 762, the voltage based
charge-rate operation part 764, the current integrating part 765,
the current based charge-rate operation part 766 and the comparison
determination part 767 in the operation unit 718 can actually be
achieved by software processing of the central processing unit
(CPU) that configure the operation unit 718. Further, the
respective functions of the R temperature coefficient table 763,
the internal resistance table 761 and the Qmax-R deterioration
coefficient operation part 768 in the operation unit 718 can
actually be achieved by the nonvolatile memory 719 such as the
flash memory or the like for the operation unit 718.
[0099] As described at the outset, the full charge capacity Qmax
indicates a capacity taken until a final discharging voltage is
reached where discharge is done with a minimum current
(.apprxeq.0). The full charge capacity is generally calculated from
a post-discharge end state of charge SOC, a pre-discharge start
state of charge SOC_ini and a discharging current integrated value
Quse like the following (equation 1):
Q max = - .intg. Idt SOC - SOC_ini = - Q use SOC - SOC_ini ( 1 )
##EQU00001##
[0100] where I indicates a discharging current of the battery 702,
Quse indicates a discharging charge calculated by time integration
of the discharging current from the battery 702, SOC indicates a
charge amount or a state of charge after the discharge completion,
and SOC_ini indicates a state of charge SOC immediately before the
discharge, respectively. The state of charge SOC_ini taken
immediately before the discharge herein may preferably use a recent
voltage-based state of charge SOC_V in a state in which the voltage
of the battery 702 after a predetermined time has elapsed after the
end of charge and discharge is kept substantially stable. The
voltage-based state of charge is stored in the nonvolatile memory
or the volatile memory immediately before the start of charge and
discharge and used therefrom.
[0101] A current-based state of charge SOC_I is generally
calculated as shown below (equation 2).
SOC_I = SOC_ini - Q use Q ma x * 100 ( 2 ) ##EQU00002##
SOC_ini, which is taken as the initial value of the current-based
state of charge, is determined from the voltage developed
immediately before the charge/discharge on a voltage basis, as
determined by equation 3 below.
[0102] On the other hand, the voltage-based state of charge can be
calculated from an open-circuit voltage of the battery. Since a
closed-circuit voltage CCV of the battery 702 is lower than an
open-circuit voltage OCV of the battery 702 by a voltage drop
developed between a discharging current I of the battery and its
internal resistance R upon discharge of the battery 702, the
voltage-based state of charge is given as the following (equation
3) from the relationship of CCV=OCV-IR.
SOC_V = f ( OCV ) = f ( CCV + IR ) ( 3 ) ##EQU00003##
[0103] where f indicates a function, OCV indicates an Open-Circuit
Voltage, CCV is a Closed-Circuit Voltage, I is a discharging
current of the battery 702, and R is an internal resistance of the
battery 702, respectively. Incidentally, in order to calculate the
function f(OCV), a relation table indicative of the relationship
between a state of charge SOC and an open-circuit voltage OCV such
as shown in FIG. 14 is provided separately in the nonvolatile
memory for the operation unit 718.
[0104] On the other hand, the internal resistance R of the battery
702 is given by the following (equation 4):
R=f(SOC)*C.sub.Deg*C.sub.Temp (4)
where f indicates a function and is calculated by the relation
table 761 indicative of the correspondence between the state of
charge SOC and the internal resistance R of the battery 702.
C.sub.Deg is a deterioration coefficient of the internal resistance
R of the battery 702 and depends on the full charge capacity Qmax.
C.sub.Temp is a temperature coefficient of the internal resistance
R of the battery 702. That is, the above (equation 4) indicates
that the value of the internal resistance R of the battery 702
depends on the state of charge SOC, the full charge capacity Qmax
and the temperature.
[0105] Thus, in the operation unit 718 shown in FIG. 4, the initial
value of the full charge capacity Qmax stored in its corresponding
memory area of the nonvolatile memory for the memory 719 is
supplied to the Qmax-R deterioration coefficient operation part 768
via the adder 769. The deterioration coefficient C.sub.Deg of the
internal resistance R of the battery 702 is therefore outputted
from the Qmax-R deterioration coefficient operation part 768.
[0106] On the other hand, since digital temperature information
from the first A/D converter 709 about the detected temperature of
the temperature detection unit 707 is supplied to the R temperature
coefficient table 763 as temperature information Temp, the
temperature coefficient C.sub.Temp of the internal resistance R of
the battery 702 is outputted from the R temperature coefficient
table 763.
[0107] On the other hand, since digital closed voltage information
from the first A/D converter 709 about the closed-circuit voltage
CCV of the battery 702, which is detected by the voltage detection
unit 705, is supplied to the voltage based charge-rate operation
part 764 as closed voltage information CCV, the voltage based
charge-rate operation part 764 further calculates a voltage-based
state of charge SOC_V in accordance with the above (equation 3)
using the internal resistance R and the current value I and
supplies the result of calculation to the internal resistance table
761. Thus, the internal resistance table 761 outputs the value of
the function f(SOC) corresponding to the first term of the right
side in the above (equation 4) in response to the voltage-based
state of charge SOC_V.
[0108] As a result, the internal resistance operation part 762 is
supplied with the deterioration coefficient C.sub.Deg of the
internal resistance R of the battery 702, which is output from the
Qmax-R deterioration coefficient operation part 768, the
temperature coefficient C.sub.Temp of the internal resistance R of
the battery 702, which is output from the R temperature coefficient
table 763, and the function f(SOC) of the battery 702, which is
output from the internal resistance table 761. Thus, the internal
resistance operation part 762 calculates the internal resistance R
of the battery 702 in accordance with the above (equation 4) using
the function f (SOC), the deterioration coefficient C.sub.Deg and
the temperature coefficient C.sub.Temp.
[0109] On the other hand, digital current information from the
second A/D converter 715 about the detected analog current of the
current detection unit 706 is supplied to the voltage based
charge-rate operation part 764 as current information I. Digital
closed voltage information from the first A/D converter 709 about
the closed-circuit voltage CCV of the battery 702, which is
detected by the voltage detection unit 705, is supplied to the
voltage based charge-rate operation part 764 as closed voltage
information CCV. Thus, the voltage based charge-rate operation part
764 calculates a voltage-based state of charge SOC_V of the battery
702 subsequent to the start of discharge in accordance with the
above (equation 3) using the internal resistance R of the battery
702 from the internal resistance operation part 762, the current
information I from the second A/D converter 715, and the closed
voltage information CCV from the first A/D converter 709.
[0110] On the other hand, the initial value SOC_ini of the
current-based state of charge SOC_I calculated on a voltage basis
from the open-circuit voltage OCV immediately before the start of
discharge has been stored in the memory 719. The initial value
SOC_ini of the current-based state of charge SOC_I read from the
memory 719 is supplied to the current based charge-rate operation
part 766. The initial value of the full charge capacity Qmax stored
in the memory area of the nonvolatile memory for the memory 719 is
supplied to the current based charge-rate operation part 766
through the adder 769. Further, the discharging current subsequent
to the start of discharge of the battery 702 is supplied to the
current integrating part 765 as the digital current information I
from the second A/D converter 715 about the detected analog current
of the current detection unit 706. Thus, the current integrating
part 765 executes time integration of the discharging current and
thereby calculates a discharging charge Quse subsequent to the
start of discharge, of the battery 702. As a result, the current
based charge-rate operation part 766 calculates a current-based
state of charge SOC_I in accordance with the above (equation 2)
using the initial value SOC_ini of the current-based state of
charge SOC_I, the discharging charge Quse of the battery 702 and
the initial value of the full charge capacity Qmax.
[0111] Ideally, the value of the voltage-based state of charge
SOC_V of the battery 702 subsequent to the start of discharge
thereof, which is calculated in accordance with the above (equation
3) by the voltage based charge-rate operation part 764, and the
value of the current-based state of charge SOC_I of the battery 702
subsequent to the start of discharge thereof, which is calculated
in accordance with the above (equation 2) by the current based
charge-rate operation part 766, coincide with each other.
[0112] In fact, however, the value of the voltage-based state of
charge SOC_V and the value of the current-based state of charge
SOC_I often do not coincide with each other. As the cause of this
non-coincidence or inconsistency, it is assumed that, for example,
an error is contained in the internal resistance R of the battery
702 when the voltage-based state of charge SOC_V is calculated,
i.e., an error in battery deterioration is contained in the
function f(SOC) of the first term, in the deterioration coefficient
C.sub.Deg of the second term or in the temperature coefficient
C.sub.Temp of the third term in the right side of the above
(equation 4) for determining the internal resistance R of the
battery 702.
[0113] As another cause of this non-coincidence, it is assumed that
the initial value of the full charge capacity Qmax stored in the
memory area of the nonvolatile memory for the memory 719 differs
from the actual full charge capacity Qmax of the battery 702 due to
the degradation of the battery 702, for example.
[0114] Thus, particularly in the operation unit 718 shown in FIG.
4, of the semiconductor integrated circuit 703, the value of the
voltage-based state of charge SOC_V calculated in accordance with
the above (equation 3) by the voltage based charge-rate operation
part 764, and the value of the current-based state of charge SOC_I
calculated in accordance with the above (equation 2) by the current
based charge-rate operation part 766 are respectively supplied to
first and second input terminals of the comparison determination
part 767. As a result, when the voltage-based state of charge SOC_V
supplied to one input terminal is smaller than the value of the
current-based state of charge SOC_I supplied to the other input
terminal, the comparison determination part 767 outputs a
comparison output signal .DELTA.Qmax, which is proportional to the
difference between the two values or on which only the sign is
reflected. That is, the comparison output signal .DELTA.Qmax is
proportional to a value obtained by subtracting the value of the
current-based state of charge SOC_I from the value of the
voltage-based state of charge SOC_V. Thus, the comparison
determination part 767 is configured by a digital subtractor, but
can also be configured by a digital comparator. In either case, the
two input signals are determined to have coincided with each other
where the difference between the two input signals reaches a
predetermined value or less. The comparison output signal
.DELTA.Qmax generated from the comparison determination part 767 is
added to the initial value of the full charge capacity Qmax by the
adder 769 from which a corrected calculated value of the full
charge capacity Qmax is generated.
Simulation Result
[0115] FIG. 5 is a diagram for describing an operation of the
operation unit 718 of the semiconductor integrated circuit 703,
which is shown in FIG. 4.
[0116] FIG. 5 shows the result of simulations using data about the
open-circuit voltage OCV, the closed-circuit voltage CCV, the
discharging current I, the temperature coefficient C.sub.Temp of
the internal resistance R, the temperature of the battery pack 701,
etc. at the usage of the battery pack 701 according to the first
embodiment of the present invention shown in FIG. 1.
[0117] The value of the voltage-based state of charge SOC_V
calculated by the voltage based charge-rate operation part 764, the
value of the deterioration coefficient C.sub.Deg of the internal
resistance R outputted from the Qmax-R deterioration coefficient
operation part 768, and the value of the current-based state of
charge SOC_I calculated by the current based charge-rate operation
part 766, and the corrected calculated value of the full charge
capacity Qmax generated by the adder 769 are shown in FIG. 5 in
order.
[0118] In the simulations, since the value of the voltage-based
state of charge SOC_V is smaller than the value of the
current-based state of charge SOC_I, the value of the comparison
output signal .DELTA.Qmax becomes a negative value. As a result,
the corrected calculated value of the full charge capacity Qmax
generated from the adder 769 is smaller than the stored initial
value of the full charge capacity Qmax.
[0119] The corrected calculated value of the full charge capacity
Qmax generated from the adder 769 is supplied to the Qmax-R
deterioration coefficient operation part 768 and the current based
charge-rate operation part 766. Since the corrected calculated
value is smaller than the initial value, and Qmax is inversely
related to the deterioration coefficient C.sub.Deg of the internal
resistance R of the battery (see FIG. 6), the Qmax-R deterioration
coefficient operation part 768 outputs a new value of C.sub.Deg,
which is larger than the previous value of C.sub.Deg. As a result,
the internal resistance operation part 762 calculates a new
internal resistance R of the battery 702 again in accordance with
the above (equation 4) using the function f(SOC), the temperature
coefficient C.sub.Temp and the new deterioration coefficient
C.sub.Deg having a value which is larger than the previous value.
The recalculated value of the new internal resistance R of the
battery 702 is larger than the previous value. Thus, the voltage
based charge-rate operation part 764 calculates the voltage-based
state of charge SOC_V of the battery 702 subsequent to the start of
its discharge again in accordance with the above (equation 3) using
the current information I from the second A/D converter 715, the
closed voltage information CCV from the first A/D converter 709 and
the new internal resistance R of the battery 702 which has been
calculated by the internal resistance operation part 762. The value
of the recalculated new voltage-based state of charge SOC_V is
larger than the previous value in correspondence with the increase
in the deterioration coefficient C.sub.Deg of the internal
resistance R of the battery 702.
[0120] On the other hand, since the corrected calculated value of
the full charge capacity Qmax generated from the adder 769 is
supplied to the current based charge-rate operation part 766, the
current based charge-rate operation part 766 calculates a new
current-based state of charge SOC_I in accordance with the above
(equation 2) using the initial value SOC_ini of the current-based
state of charge SOC_I, the discharging charge Quse of the battery
702, and the corrected calculated value of the full charge capacity
Qmax. Since the corrected calculated value of the full charge
capacity Qmax is smaller than the initial value of the full charge
capacity Qmax, the value of the current-based state of charge SOC_I
calculated again in accordance with the above (equation 2) is
smaller than the previous value.
[0121] Thus, the new value of the voltage-based state of charge
SOC_V calculated by the voltage based charge-rate operation part
764 increases, whereas the new value of the current-based state of
charge SOC_I calculated by the current based charge-rate operation
part 766 decreases. Accordingly, the value of the voltage-based
state of charge SOC_V and the value of the current-based state of
charge SOC_I which had not coincided with each other at the
beginning, coincide with each other.
[0122] Accordingly, the ideal state that the value of the
voltage-based state of charge SOC_V and the value of the
current-based state of charge SOC_I coincide with each other is
realized by the operation unit 718 of the semiconductor integrated
circuit 703, which is shown in FIG. 4. In the ideal state, the
values of the full charge capacity Qmax and the internal resistance
R each including the error that has become the cause of
non-coincidence between the value of the voltage-based state of
charge SOC_V and the value of the current-based state of charge
SOC_I are calculated without substantially including any error.
Accordingly, the accurate remaining capacity of the battery 702 can
be calculated by accurately calculating such two important
parameters.
[0123] Although the values of the full charge capacity Qmax and the
internal resistance R are calculated using the value of the
voltage-based state of charge SOC_V and the value of the
current-based state of charge SOC_I, both of which change
sequentially during the discharge of the battery 702, current and
voltage values in a time domain in which the discharging current of
the battery 702 is kept stable may be stored in the volatile memory
for the memory 719 and thereby calculated on the basis of data at a
certain timing.
[0124] The above description assumes that the simultaneous
equations of the above (equation 2), the above (equation 3), the
above (equation 4) and "the relational expression of the full
charge capacity Qmax and the internal resistance deterioration
coefficient" apply in an ideal state "SOC_I=SOC_V", and calculates
the value of the current-based state of charge SOC_I, the value of
the voltage-based state of charge SOC_V, the value of the full
charge capacity Qmax and the value of the internal resistance
deterioration coefficient of the internal resistance R, which are
unknown variables.
[0125] In the above description, there has been adopted the method
of sequentially changing the value of the full charge capacity Qmax
to thereby calculate the value of the current-based state of charge
SOC_I, the value of the voltage-based state of charge SOC_V, the
corrected calculated value of the full charge capacity Qmax and the
value of the internal resistance deterioration coefficient of the
internal resistance R. The internal resistance deterioration
coefficient of the internal resistance R may sequentially be
changed or a bisection method or the like can also be adopted.
[0126] After calculating the corrected calculated value of the full
charge capacity Qmax and the internal resistance R described above,
the state of charge SOC to be taken during the discharge is
sequentially calculated by the operation unit 718 in accordance
with the following (equation 5):
SOC = SOC_ini - Q use Q ma x * 100 ( 5 ) ##EQU00004##
[0127] Prior to the calculation of the above (equation 5), the
operation unit 718 reads the initial value SOC_ini of the
current-based state of charge SOC_I and the full charge capacity
Qmax, both of which have been stored in the memory 719, and
calculates the state of charge SOC in accordance with the above
(equation 5) using the current integrated value (i.e., the amount
of charge discharged Quse). As a result, the central processing
unit (CPU) 722 of the note PC 708 calculates a charge rate RSOC, a
remaining time and a remaining capacity actually available, which
are based on a smart battery system, using the calculated state of
charge SOC and full charge capacity Qmax and the internal
resistance R and display them on the monitor.
[0128] Operation of Operation Unit
[0129] FIGS. 6, 7 and 8 are respectively diagrams for describing
operations of the operation unit 718 of the semiconductor
integrated circuit 703, which is shown in FIG. 4.
[0130] The calculation of the full charge capacity Qmax and the
internal resistance R or the like during the discharge is carried
out by three Steps: a process A taken immediately after the start
of discharge, which is shown in FIG. 6, a process B during the
discharge, which is shown in FIG. 7, and a process C after the end
of discharge, which is shown in FIG. 8.
[0131] Process Immediately after the Start of Discharge
[0132] FIG. 6 shows the process A of the operation unit 718
immediately after the start of discharge of the battery 702.
[0133] Since a linear or curvilinear correlation exists between the
full charge capacity Qmax and the internal resistance deterioration
coefficient Cdeg, both of which are affected by deterioration of
the battery 702, this correlation is stored in the nonvolatile
memory in the form of an approximate expression or a look-up table.
As described above, the value of the current-based state of charge
SOC_I and the value of the voltage-based state of charge SOC_V are
respectively calculated using the full charge capacity Qmax and the
internal resistance deterioration coefficient C.sub.deg. Since the
ideal state is taken as "SOC_I=SOC_V", it is possible to estimate
the state of deterioration of the battery. Since both the full
charge capacity Qmax and the internal resistance R change every
moment depending on the deterioration and are unknown, the value of
the full charge capacity Qmax and the value of the internal
resistance deterioration coefficient Cdeg at the point where the
value of the current-based state of charge SOC_I and the value of
the voltage-based state of charge SOC_V coincide with each other as
shown in FIG. 6 using the above calculation method, are
respectively taken to be correct values therefor.
[0134] That is, at the first Step A1 of FIG. 6, the initial value
of the full charge capacity Qmax stored in the memory area of the
nonvolatile memory for the memory 719 is supplied to the Qmax-R
deterioration coefficient operation part 768 via the adder 769
(since .DELTA.Qmax is initially 0). The deterioration coefficient
C.sub.Deg of the internal resistance R of the battery 702 is
therefore outputted from the Qmax-R deterioration coefficient
operation part 768.
[0135] At the next Step A2 of FIG. 6, the comparison determination
part 767 feedback-controls a corrected calculated value of the full
charge capacity Qmax in such a manner that the value of the
voltage-based state of charge SOC_V subsequent to the start of
discharge, which is calculated by the voltage based charge-rate
operation part 764, and the value of the current-based state of
charge SOC_I subsequent to the start of discharge, which is
calculated by the current based charge-rate operation part 766,
coincide with each other. Since the value of the deterioration
coefficient C.sub.Deg of the internal resistance R changes during
the control of the corrected calculated value of the full charge
capacity Qmax at Step A2, the value of the voltage-based state of
charge SOC_V and the value of the current-based state of charge
SOC_I coincide with each other while the process at Step A2 and the
process at Step A1 are being repeated. The corrected calculated
value of the full charge capacity Qmax at this coincidence timing
is used for the correct display of remaining capacity of the
battery 702. At Step A2, the initial value of the full charge
capacity Qmax and the initial value SOC_ini of the current-based
state of charge SOC_I both stored in the nonvolatile memory for the
memory 719 are respectively updated by the state of charge SOC that
has coincided with the corrected calculated value of the full
charge capacity Qmax.
[0136] Process During the Discharge
[0137] FIG. 7 is a diagram for describing a preferred operation of
the operation unit 718 shown in FIG. 4, of the semiconductor
integrated circuit 703.
[0138] FIG. 7 shows the process B of the operation unit 718 during
the discharge of the battery 702.
[0139] During the discharge, a charge rate RSOC, a remaining time
and a remaining capacity available actually are sequentially
calculated on the basis of the full charge capacity Qmax and the
internal resistance R calculated at the process A of FIG. 6. The
internal resistance table 761 important for the calculation of
these remaining capacities is updated during the discharge. This is
because the value of the internal resistance of the battery 702 is
used for the calculation of remaining capacities and important even
for the calculation of a discharge end state of charge SOC_fin, and
the internal resistance of the battery 702 changes due to its
deterioration.
[0140] FIG. 7 shows the manner in which during the continuation of
discharge of the battery 702 subsequent to the start of its
discharge, the content of the internal resistance table 761 which
outputs the value of the function f(SOC) of the first term in the
right side of the above (equation 4) is updated in response to the
voltage-based state of charge SOC_V.
[0141] Since the closed-circuit voltage CCV of the battery 702 is
lower than the open-circuit voltage OCV by a voltage drop developed
by the discharging current I and internal resistance R of the
battery during the discharge of the battery 702 as mentioned above,
the relationship of CCV=OCV-IR is established.
[0142] Thus, even when the SOC characteristic of the internal
resistance R changes due to cycle deterioration or storage
deterioration of the battery 702, the value of the internal
resistance R taken during the discharge can be calculated in
accordance with the following (equation 6) using the closed-circuit
voltage CCV detected by the voltage detection unit 705 and the
discharging current I detected by the current detection unit 706.
The open voltage information OCV is calculated from the
current-based state of charge SOC_I using the relationship between
the state of charge SOC of the battery 702 and the open-circuit
voltage OCV of the battery 702, which relationship is stored in the
memory and exemplified by in FIG. 14.
R = OCV - CCV I ( 6 ) ##EQU00005##
[0143] At that time, the operation unit 718 outputs the value of
the function f(SOC) of the first term in the right side of the
above (equation 4) related to each state of charge SOC using the
deterioration coefficient C.sub.Deg of the internal resistance R
outputted from the Qmax-R deterioration coefficient operation part
768 and the temperature coefficient C.sub.Temp of the internal
resistance R outputted from the R temperature coefficient table
763.
[0144] The value of the function f(SOC) corresponding to each of
the values of the states of charge SOC is stored in the internal
resistance table 761. Therefore, when the value of the function
f(SOC) outputted from the operation unit 718 in correspondence with
a given state of charge SOC is different from the value calculated
in the past and stored in the internal resistance table 761, the
internal resistance table 761 is updated based on a new calculated
value of the function f(SOC) as shown by arrow 744 of FIG. 7. Thus,
even though the deterioration of the battery 702 progresses and the
characteristic of the internal resistance R of the battery 702 with
respect to each state of charge SOC changes, the value of the
function f(SOC) stored in the internal resistance table 761 can be
updated to the latest state.
[0145] Further, the internal resistance table 761 can also be
updated by estimating the value of the function f(SOC)
corresponding to each state of charge SOC not greater than a given
state of charge SOC in accordance with the value of the function
f(SOC) corresponding to the given state of charge SOC as indicated
by arrow 745 of FIG. 7. This estimation is done by multiplying a
pre-update value by the same rate of change as the rate of change
in the value of the function f(SOC) corresponding to the given
state of charge SOC to thereby calculate a post-update value.
[0146] During the discharge, the internal resistance table 761 is
updated at a 10% change step of the state of charge SOC in the
embodiment shown in FIG. 7. When the deterioration of the battery
702 is however large as viewed from the time of previous usage, the
internal resistance taken immediately before the end of discharge
greatly changes and the accuracy of calculation of a discharge-end
state of charge SOC being a parameter important for the estimation
of a remaining capacity is degraded. It is therefore recommended
that the frequency of updating of the internal resistance is
increased immediately before the discharge end.
[0147] Process after the End of Discharge
[0148] FIG. 8 is a diagram for describing another preferred
operation of the operation unit 718 shown in FIG. 4, of the
semiconductor integrated circuit 703 for battery control according
to the first embodiment of the present invention.
[0149] FIG. 8 shows the process C of the operation unit 718 at the
time that a few hours have elapsed after the discharge of the
battery 702 has been ended.
[0150] The process C of FIG. 8 after the end of battery discharge
is used to update the correlation between the full charge capacity
Qmax and the internal resistance deterioration coefficient Cdeg to
be used for the next process A taken immediately after the
discharge start shown in FIG. 6. Thus, the accuracy of calculation
of the full charge capacity Qmax and the internal resistance
deterioration coefficient Cdeg can be improved in the next process
taken immediately after the start of the discharge.
[0151] After the end of the discharge, the correct full charge
capacity Qmax is calculated from the above (equation 1) using the
voltage-based state of charge SOC_V and the integrated charge
quantity Quse taken during the discharge, and the internal
resistance deterioration coefficient Cdeg is also recalculated.
Thus, the correct relation between the full charge capacity Qmax
and the internal resistance deterioration coefficient Cdeg, both
obtained each time the discharge is ended, is calculated by an
approximate expression using the method of least squares, for
example, followed by being updated.
[0152] As is well known, the battery 702 gradually increases in
voltage by being affected by a resistance large in time constant
after the end of its discharge, and the voltage thereof is
stabilized after a few hours. The so-stabilized voltage is an
open-circuit voltage OCV.
[0153] When two hours or so have elapsed after the end of discharge
of the battery 702, the operation unit 718 is capable of
calculating the full charge capacity Qmax in accordance with the
above (equation 1) using the pre-discharge start state of charge
SOC_ini, the discharging current integrated value Quse, and the
state of charge SOC calculated from the open-circuit voltage OCV of
the battery 702 detected by the voltage detection unit 705. The
operation unit 718 also calculates the internal resistance
deterioration coefficient Cdeg from the voltage and current
information at a predetermined time during the discharge. The
operation unit 718 calculates the relation between the so-obtained
internal resistance deterioration coefficient Cdeg and the full
charge capacity with reference to a plurality of times of data at
the discharge prior to the above in accordance with, for example,
the approximate expression using the method of least squares, and
updates the same, followed by being stored into the nonvolatile
memory.
[0154] The updating of the operation method of the Qmax-R
deterioration coefficient operation part 768, which is indicated by
arrow 746 of FIG. 8 can be achieved by rewriting the nonvolatile
memory for the memory 719 having stored therein the software of the
central processing unit (CPU) that configures the operation unit
718. That is, the software of the central processing unit (CPU) is
reprogrammed by rewriting of the nonvolatile memory, and the
approximation expression of the Qmax-R deterioration coefficient
operation part 768 is renewed.
[0155] As described above, the approximation expression of the
Qmax-R deterioration coefficient operation part 768 of the
operation unit 718, which has been updated by the process C of the
operation unit 718 when the few hours have elapsed after the end of
discharge of the battery 707 as shown in FIG. 8 is used in the
first Step A1 of the process A of the operation unit 718
immediately after the start of discharge of the battery 702, which
is shown in FIG. 6.
[0156] Updating the approximation expression of the full charge
capacity Qmax and the internal resistance deterioration coefficient
by the process C after the end of discharge in FIG. 8 as described
above enables an improvement in the accuracy of calculation of the
full charge capacity Qmax and the internal resistance deterioration
coefficient Cdeg at the next process A taken immediately after the
start of discharge shown in FIG. 6. This is because particularly in
the case where the quiescent time of electronic equipment becomes
long and the battery 702 is drastically deteriorated till the next
discharge, the full charge capacity Qmax and the internal
resistance deterioration coefficient Cdeg on which deterioration is
reflected can be calculated by the process C taken after the end of
discharge in FIG. 8 and the next process A taken immediately after
the start of discharge in FIG. 6, thus making it possible to
display more accurate remaining capacity.
[0157] The internal resistance deterioration coefficient Cdeg of
the battery 702 has been used in the first embodiment. When the
deterioration coefficient is however not used, the relational
expression between the full charge capacity Qmax and the internal
resistance of the battery 702 can also be used in the process A
taken immediately after the start of discharge in FIG. 6.
Second Embodiment
[0158] The semiconductor integrated circuit 703 for battery control
shown in FIG. 1 is capable of controlling not only the discharge
operation of the battery 702 but also the charge operation thereof,
as described in the first embodiment.
[0159] The battery 702 can deteriorate due to charge-discharge
cycle deterioration, storage deterioration, or the like. The
battery 702 can also be drastically deteriorated upon the start of
its charge. The semiconductor integrated circuit 703 shown in FIG.
1 is configured so as to carry out the overcharge protection
operation and the overcurrent protection operation during the
charge operation. On the other hand, the remaining charge time may
preferably be displayed during the charge operation. In order to
allow the operation unit 718 to calculate the accurate charging
time, however, the operation unit 718 needs to calculate the
correct full charge capacity Qmax and internal resistance of the
battery 702 being charged.
[0160] Thus, during the charge operation of the battery 702, the
semiconductor integrated circuit 703 shown in FIG. 1 can also
execute a process immediately after the start of charge, similar to
the process A taken immediately after the start of discharge
described in FIG. 6.
[0161] That is, at the Step A1 of the process taken immediately
after the start of charge, the initial value of the full charge
capacity Qmax stored in the memory area of the nonvolatile memory
for the memory 719 is supplied to the Qmax-R deterioration
coefficient operation part 768 via the adder 769 (again with
.DELTA.Qmax=0). Therefore, the deterioration coefficient C.sub.Deg
of the internal resistance R of the battery 702 is outputted from
the Qmax-R deterioration coefficient operation part 768.
[0162] Since there is a case where the charge and discharge of the
battery 702 are different in internal resistance value, there is a
need to multiply the equation for calculation of an internal
resistance at its discharge by a charge correction coefficient
stored separately in the nonvolatile memory for the memory 719 upon
the calculation of the internal resistance of the battery 702 at
its charge.
[0163] At the next Step A2 of the process taken immediately after
the start of charge, the comparison determination part 767
feedback-controls a corrected calculated value of the full charge
capacity Qmax in such a manner that the value of a voltage-based
state of charge SOC_V subsequent to the start of charge, which is
calculated by the voltage based charge-rate operation part 764, and
the value of a current-based state of charge SOC_I subsequent to
the start of charge, which is calculated by the current based
charge-rate operation part 766, coincide with each other. The
current integrating part 765 however calculates a charging charge
Qcharge of the battery 702 corresponding to the time integration of
a charging current. Since the value of the deterioration
coefficient C.sub.Deg of the internal resistance R varies during
the control of the corrected calculated value of the full charge
capacity Qmax at this Step A2, the value of voltage-based state of
charge SOC_V and the value of the current-based state of charge
SOC_I coincide with each other while the process at Step A2 and the
process at Step A1 are being repeated. The corrected calculated
value of the full charge capacity Qmax at this coincidence timing
is used for the calculation of the accurate remaining charge time
of the battery 702.
[0164] During the charge, the operation unit 718 calculates the
remaining charge time of the battery 702 using the value of the
calculated full charge capacity Qmax. A concrete method for
calculating the remaining charge time of the battery 702 will be
described in detail later.
[0165] Further, during the period of the charge operation of the
battery 702, the semiconductor integrated circuit 703 shown in FIG.
1 can also carry out a process to estimate the charge duration,
which is similar to the process B to estimate the discharge
duration (remaining capacity) described in FIG. 7.
[0166] That is, the content of the internal resistance table 761
that outputs the value of the function f(SOC) of the first term in
the right side of the above (equation 4) is updated by the process
to estimate the charge duration in response to the voltage-based
state of charge SOC_V. Since the closed-circuit voltage CCV of the
battery 702 is higher than the open-circuit voltage OCV of the
battery 702 by a voltage drop developed between the discharging
current I of the battery and its internal resistance R upon charge
of the battery 702, the relation of CCV=OCV+IR is established.
Thus, the operation unit 718 calculates the internal resistance of
the battery 702 using this relation. Since the process in the
charge duration is identical to the process B in the discharge
duration described in FIG. 7 in other respects, their description
will be omitted.
[0167] Furthermore, when a few hours have elapsed after the end of
charge of the battery 702, the semiconductor integrated circuit 703
shown in FIG. 1 can also execute a process at the time when a few
hours have elapsed after the end of charge, which is similar to the
process C at the time when the few hours have elapsed after the end
of discharge described in FIG. 8. Since the process being processed
at the time when the few hours have elapsed after the end of charge
is identical in other respects to the process C at the time when
the few hours have elapsed after the end of discharge described in
FIG. 8, their description will be omitted.
[0168] The calculation of the full charge capacity Qmax and the
updating process of the internal resistance described above need
not necessarily be executed during the charge. This is because the
value of the full charge capacity Qmax and the value of the
internal resistance can be corrected upon the process of
calculation of the remaining charge time.
[0169] Calculation of Remaining Charge Time
[0170] FIG. 10 is a diagram showing the manner in which the battery
702 is charged using the semiconductor integrated circuit 703 shown
in FIG. 1.
[0171] That is, the battery 702 is capable of being charged from
the AC power supply 731 through the AC/DC converter 712, the DC/DC
converter 721 and the protection circuit 704 using the
semiconductor integrated circuit 703 shown in FIG. 1. When the
battery 702 is a lithium ion battery, the charging of a constant
current/constant voltage is generally often used.
[0172] During the initial first stage of charge as shown in FIG.
10, the battery 702 is charged by a constant current Icc until the
closed-circuit voltage CCV of the battery 702 reaches a
predetermined limit voltage V_lim, and the battery reaches a first
charge amount, called a constant current charge (CC charge).
Thereafter, during a subsequent second stage of charge as shown in
FIG. 10, the battery 702 is further charged at the limit voltage
V_lim, which is a constant voltage, and takes on an additional
second charge, called a constant voltage charge (CV charge). During
the period of the constant voltage charge (CV charge) at the
subsequent stage of charge, the value of a variable charging
current Icy based on the constant voltage charge (CV charge)
decreases gradually. The state of full charge is reached when the
value of the variable charging current Icy has reached a
predetermined prescribed minimum current I_lim.
[0173] A state of charge SOC calculated by the open-circuit voltage
OCV immediately before the charge of the battery 702 is started is
assumed to be a charge initial-value state of charge SOC_ini. A
state of charge SOC in the fully charged state is assumed to be a
fully-charged state of charge SOC_end. A state of charge SOC at the
time the charge operation of the battery 702 changes from the
constant current charge (CC charge) to the constant voltage charge
(CV charge) is taken as a change-point state of charge
SOC_change.
[0174] FIG. 12 is a diagram showing a flowchart for calculating the
remaining charge time of the battery 702 using the semiconductor
integrated circuit 703 shown in FIG. 1. The premise is that
calculating the remaining charge time of the battery 702 may be
carried out immediately after the start of charge using either the
corrected calculated value of the full charge capacity Qmax if it
has already been calculated by executing Steps A1 and A2 of the
process A taken immediately after the start of discharge shown in
FIG. 6, or the full charge capacity Qmax at the previous
discharge.
[0175] At Step 601 of FIG. 12, the operation unit 718 calculates
the change-point state of charge SOC_change in the following
manner.
[0176] That is, since the closed-circuit voltage CCV of the battery
702 is higher than the open-circuit voltage OCV of the battery 702
by a voltage drop developed by a discharging current I and an
internal resistance R of the battery during the charge of the
battery 702, the relationship of CCV=OCV+IR is established.
[0177] Since the relationship of CCV=V_lim is established during
the period of the constant voltage charge (CV charge), the value of
the charging current Icy for the constant voltage charge (CV
charge) is calculated by the operation unit 718 in accordance with
the following (equation 7).
I cv = CCV - OCV R = V _ li m - OCV R ( 7 ) ##EQU00006##
[0178] That is, the value of a limit voltage V_lim, which is a
constant voltage used in the constant voltage charge (CV charge),
is stored in the memory 719. Further, the value of the internal
resistance R of the battery 702 is determined by the above
(equation 6) in a manner similar to the time of discharge, using
the current closed-circuit voltage CCV detected by the voltage
detection unit 705 and the current charging current I detected by
the current detection unit 706, as explained above with respect to
the equation 6. When there is a need to perform a charge
correction, the value of the internal resistance R is calculated by
multiplying the value by an internal resistance charge coefficient
and stored in the memory 719. Further, the open-circuit voltage OCV
is calculated from the state of charge SOC using the relationship
between the state of charge SOC and the open-circuit voltage OCV,
which relationship is exemplified by FIG. 14 and stored in the
memory 719. As a result, the operation unit 718 reads necessary
information from the memory 719, thereby enabling the calculation
of the charging current Icy at the constant voltage charge (CV
charge) in accordance with the above (equation 7).
[0179] Next, the operation unit 718 calculates the change-point
state of charge SOC_change, which is the point where the charging
current Icy for the constant voltage charge calculated by the above
(equation 7) coincides with the constant current Icc for the
constant current charge. The values of the charging current Icy
calculated by the above (equation 7) and the limit voltage V_lim
read from the memory 719, and the value of the internal resistance
R of the battery 702 are supplied to the voltage based charge-rate
operation part 764 of the operation unit 718, so that the
change-point state of charge SOC_change can be outputted from the
voltage based charge-rate operation part 764.
[0180] On the other hand, there is another method by focusing on
the period of the constant current charge (CC charge). The
closed-circuit voltage CCV of the battery 702 at each state of
charge SOC is calculated from the open-circuit voltage OCV and the
internal resistance. The state of charge SOC becomes a change-point
state of charge SOC_change when the closed-circuit voltage CCV
coincides with the limit voltage V_lim. The relation of
CCV=OCV+IccR=V_lim, and I=Icc is established at this coincidence
timing. The charging current Icc for the constant current charge
(CC charge), the limit voltage V_lim for the constant current
charge (CC charge) read from the nonvolatile memory for the memory
719, and the value of the internal resistance R of the battery 702
are supplied to the voltage based charge-rate operation part 764 of
the operation unit 718, which then outputs the change-point state
of charge SOC_change. Incidentally, the value of the charging
current Icc for the constant current charge (CC charge) may be
stored in the memory area of the nonvolatile memory for the memory
719 in advance. Alternatively, the digital current information from
the second A/D converter 715 representing the detected analog
current of the current detection unit 706 can also be utilized.
[0181] Next, at Step 602 of FIG. 12, the operation unit 718
calculates a charge period Tcc for the constant current charge (CC
charge) in the following manner by using the change-point state of
charge SOC_change calculated by the Step 601.
[0182] The full charge capacity Qmax related to the charge
operation of the battery 702 is given like the following (equation
8):
Q ma x = .intg. I cc dt SOC_ini - SOC_chnage = I cc * T cc SOC_ini
- SOC_change ( 8 ) ##EQU00007##
[0183] where Icc is a charging current for the constant current
charge (CC charge) of the battery 702, SOC_ini is an initial value
of a state of charge SOC immediately before the charge, Tcc is a
charge period for the constant current charge (CC charge) which is
to be calculated, and SOC_change is a change-point state of charge
SOC with the timing at which the charge operation of the battery
702 changes from the constant current charge (CC charge) to the
constant voltage charge (CC charge).
[0184] Thus, the charge period Tcc of the constant current charge
(CC charge) is calculated from the above (equation 8) as shown
below (equation 9):
T cc = Q ma x * ( SOC_ini - SOC_change ) I cc ( 9 )
##EQU00008##
[0185] That is, the operation unit 718 reads the full charge
capacity Qmax, and the state-of-charge initial value SOC_ini, the
change-point state of charge SOC_change and the charging current
Icc for the constant current charge (CC charge) taken immediately
before the discharge to thereby calculate the charge period Tcc for
the constant current charge (CC charge) in accordance with the
above (equation 9).
[0186] Next, at Step 603 of FIG. 12, the operation unit 718
calculates a charge period Tcv for the constant voltage charge (CV
charge) in the following manner using the change-point state of
charge SOC_change calculated by the above Step 601. The calculation
of the charge period Tcv for the constant voltage charge (CV
charge) by the following (equation 10) is performed by calculating
and integrating a part charge period Tcv necessary to increase the
state of charge SOC by 0.1% in accordance with an analogy from the
above (equation 9).
T cv = .intg. SOC _ change SOC _ end ( Q ma x . / 1000 ) I cv d (
soc ) ( 10 ) ##EQU00009##
[0187] That is, the operation unit 718 reads the full charge
capacity Qmax and the change-point state of charge SOC_change
stored in advance in the memory area of the nonvolatile memory for
the memory 719 at Step 603 of FIG. 12 and calculates the charge
period Tcv for the constant voltage charge (CV charge) in
accordance with the above (equation 10), based on the charging
current Icy for the constant voltage charge (CV charge) calculated
in accordance with the above (equation 7). Incidentally, since the
fully-charged state of charge SOC_end does not necessarily reach
100% due to the deterioration of the battery 702 at this time, it
is calculated separately by the operation unit 718.
[0188] In particular, a linear approximation method to be described
below is used for the calculation of the charge period Tcv for the
constant voltage charge (CV charge) according to the above
(equation 10).
[0189] FIG. 9 is a diagram showing the manner in which the linear
approximation method is utilized when the charge period Tcv for the
constant voltage charge (CV charge) is calculated using the
semiconductor integrated circuit 703 shown in FIG. 1.
[0190] Strictly speaking, the charging current Icy for the constant
voltage charge (CV charge) exponentially decreases with respect to
a change in time as shown in a curved line 650 of FIG. 10. The
charging current Icy for the constant voltage charge (CV charge)
however decreases approximately linearly with respect to a change
in the state of charge SOC as shown in a straight line 651 of FIG.
9. Further, the constant voltage charge (CV charge) is carried out
in an area in which the state of charge SOC at the latter half of
the charge period of the battery 702 is high. Furthermore, in the
above (equation 7) for determining the value of the charging
current Icy for the constant voltage charge (CV charge), the
charging voltage V_lim being the closed-circuit voltage CCV of the
battery 702 is a constant voltage, and the internal resistance R
can also be assumed to be a constant value without a large change
in an area in which the state of charge SOC is high.
[0191] On the other hand, FIG. 14 is a diagram showing the
relationship between the state of charge SOC of the battery 702 and
the open-circuit voltage OCV of the battery 702.
[0192] As shown in a characteristic 660 of FIG. 14, the
open-circuit voltage OCV and the state of charge SOC are placed in
a substantially linear type correlation in an area in which the
state of charge SOC is high.
[0193] Thus, in the above (equation 7), the open-circuit voltage
OCV is used to predict the value of the charging current Icy for
the constant voltage charge (CV charge) by using the relation in
which the open-circuit voltage OCV is approximately linear with the
state of charge SOC.
[0194] FIG. 11 is a diagram for describing in further detail the
linear approximation method used when the charging time Tcv for the
constant voltage charge (CV charge) shown in FIG. 9 is
calculated.
[0195] As shown in FIG. 11, the operation unit 718 calculates the
gradient `a` of a approximate straight line shown in FIG. 11 from
the value of the constant current Icc used in the constant current
charge (CC charge), the value of a prescribed current I_lim of the
charging current Icy for determining the attainment of a fully
charged state, the change-point state of charge SOC_change
calculated at Step 601 of FIG. 12, and the fully-charged state of
charge SOC_end like the following (equation 11).
a = I cc - I _ li m SOC_end - SOC_change ( 11 ) ##EQU00010##
[0196] Thus, the operation unit 718 calculates the value of the
charging current Icy for the constant voltage charge (CV charge)
like the following (equation 12) using the gradient a calculated
like the above (equation 11), based on the current-based state of
charge SOC_I momentarily calculated by the current based
charge-rate operation part 766 according to the approximate
straight line shown in FIG. 11.
I.sub.cv=I.sub.--lim+a*(SOC_end-SOC_I) (12)
[0197] Accordingly, the value of the charging current Icy for the
constant voltage charge (CV charge) calculated by the above
(equation 12) is used for the calculation of the charging time Tcv
for the constant voltage charge (CV charge) of the above (equation
10), thereby making it possible to calculate the charging time Tcv
from the change-point state of charge SOC_change to the
fully-charged state of charge SOC_end.
[0198] Next, at Step 604 of FIG. 12, the operation unit 718 adds
the charging time Tcc for the constant current charge (CC charge)
calculated at Step 602 of FIG. 12 and the charging time Tcv for the
constant voltage charge (CV charge) calculated at Step 603 of FIG.
12 like the following (equation 13), thereby calculating a
remaining charge time Tcg.
T.sub.cg=T.sub.cc+T.sub.cv (13)
[0199] Thus, the remaining charge time Tcg calculated by the
operation unit 718 at Step 604 of FIG. 12 can be shown in a
simplified display 751 or on a detailed display screen 750 like the
monitor display of FIG. 3 during the charge of the battery 702.
[0200] Next, at Step 605 of FIG. 12, the change-point state of
charge SOC_change is calculated for when the closed-circuit voltage
CCV of the battery 702 actually coincides with the limit voltage
V_lim.
[0201] This means that either one of the value of the voltage-based
state of charge SOC_V outputted from the voltage based charge-rate
operation part 764 and the value of the current-based state of
charge SOC_I outputted from the current-based charge-rate operation
part 766 is calculated as the change-point state of charge
SOC_change when the closed-circuit voltage CCV of the battery 702
(which is the detected voltage of the voltage detection unit 705)
coincides with the limit voltage V_lim.
[0202] The value of the change-point state of charge SOC_change
calculated at Step 601 of FIG. 12 was a predicted value calculated
using the value of the internal resistance R of the battery 702 or
the like. On the other hand, since the value of the change-point
state of charge SOC_change calculated at Step 605 of FIG. 12 is
calculated for when the closed-circuit voltage CCV of the battery
702 actually coincides with the limit voltage V_lim, it is an
actually measured value of the change-point state of charge
SOC_change.
[0203] Thus, in a more preferred embodiment, the charge coefficient
of the internal resistance R of the battery 702 stored in the
memory area of the nonvolatile memory for the memory 719 is
corrected using the value of the change-point state of charge
SOC_change calculated at Step 605 of FIG. 12. That is, at Step 606
of FIG. 12, the operation unit 718 corrects the charge coefficient
of the internal resistance of the battery 702 stored in the memory
area of the nonvolatile memory for the memory 719, based on the
difference between the value of the change-point state of charge
SOC_change calculated at Step 605 of FIG. 12, and the value of the
change-point state of charge SOC_change calculated at Step 601 of
FIG. 12.
[0204] Next, at Step 607 of FIG. 12, the gradient `a` calculated in
accordance with the above (equation 11) is recalculated using the
value of the change-point state of charge SOC_change calculated at
Step 605 of FIG. 12. Further, the value of the charging current Icy
for the constant voltage charge (CV charge) calculated in
accordance with the above (equation 12) is recalculated. During the
period for the constant voltage charge (CV charge), the values of
the calculated charging current Icy and the actually-measured
charging current Icy are compared with each other. When there is a
large difference therebetween, the charging current Icy is
corrected by correcting the full charge capacity Qmax, for example,
thereby allowing the actually-measured value and the calculated
value to approach each other, whereby the accuracy of calculation
of the next constant voltage charging time is improved. The
corrected full charge capacity Qmax is capable of being stored in
the nonvolatile memory and utilized next time. Using the value of
the charging current Icy for the constant voltage charge (CV
charge) recalculated as part of step 607 using the above (equation
12), the operation unit 718 recalculates the value of the charging
time Tcv for the constant voltage charge (CV charge) in accordance
with the above (equation 10).
[0205] Thus, after Step 607 of FIG. 12, the value of the charging
time Tcv for the constant voltage charge (CV charge) recalculated
at Step 607 of FIG. 12 can be represented in the simplified display
751 or by the detailed display screen 750 like the monitor display
of FIG. 3 as the remaining charge time.
Third Embodiment
[0206] FIG. 13 is a diagram showing the relationship between the
operation at the discharge of the battery 702 in FIG. 6 according
to the first embodiment of the present invention using the
semiconductor integrated circuit 703 for battery control shown in
FIG. 1, the stored content of nonvolatile memory for the memory
719, and the operation at the charge of the battery 702, which has
been described in FIGS. 9 through 12 according to the second
embodiment of the present invention.
[0207] The discharge operation 810, the stored content 820 of
nonvolatile memory for the memory 719, and the charge operation 830
for charging the battery 702 are interrelated.
[0208] The discharge operation 810 begins with Process A 811, which
commences immediately after the start of discharge. Process A uses,
as inputs, the following: (a) the relation between an open-circuit
voltage OCV of the battery 702 and a state of charge SOC thereof at
the stored content 820 of nonvolatile memory for the memory 719,
and the internal resistance table 761 (f(SOC)), (b) the initial
value of a full charge capacity Qmax, and (c) an approximate
expression of the full charge capacity Qmax and an internal
resistance deterioration coefficient. As output, Process A updates
the value of the full charge capacity Qmax in the nonvolatile
memory, based on the stored content 820 of nonvolatile memory for
the memory 719.
[0209] Next, the discharge operation 810 continues with Process B
812. Process B uses, as inputs, the following: (a) the relation
between the open-circuit voltage OCV of the battery 702 and the
state of charge SOC thereof at the stored content 820 of
nonvolatile memory for the memory 719, and the internal resistance
table 761 (f(SOC)), and (b) the full charge capacity Qmax. As
output, Process B updates the internal resistance table 761
(f(SOC)) in the nonvolatile memory, based on the stored content 820
of nonvolatile memory for the memory 719.
[0210] The discharge operation 810 then continues with Process C
813, which may take place after a few hours have elapsed after the
end of discharge of the battery 702 (i.e., after the end of Process
B). Process C uses, as inputs, the following: (a) the relation
between the open-circuit voltage OCV of the battery 702 and the
state of charge SOC thereof at the stored content 820 of
nonvolatile memory for the memory 719, which may be stored in the
internal resistance table 761 (f(SOC)), and (b) the approximate
expression of the full charge capacity Qmax and the internal
resistance deterioration coefficient. As output, Process C updates
the approximate expression of the full charge capacity Qmax and
internal resistance deterioration coefficient, based on the stored
content 820 of nonvolatile memory for the memory 719.
[0211] The charge operation 830 for charging the battery 702
includes (a) calculations of the change-point state of charge
SOC_change and (b) calculations of a first charging time Tcc for
the constant current charge (CC charge) and a second charging time
Tcv for the constant voltage charge (CV charge).
[0212] The change-point state of charge SOC_change is first
calculated using the internal resistance charge coefficient, the
internal resistance table 761 (f(SOC)) and the full charge capacity
Qmax at the stored content 820 of nonvolatile memory for the memory
719 (process 831). The calculated change-point state of charge
SOC_change is stored in the nonvolatile memory for the memory
719.
[0213] After the change-point state of charge SOC_change has been
calculated, the charging time Tcc for the constant current charge
(CC charge) and the charging time Tcv for the constant voltage
charge (CV charge) are calculated using the full charge capacity
Qmax and the change-point state of charge SOC_change, both of which
are stored in the nonvolatile memory for the memory 719 (process
832).
[0214] After the charge operation 830, the internal resistance
table 761 (f(SOC)) and the full charge capacity Qmax can also be
updated as indicated by broken-line arrows shown in FIG. 13.
[0215] While the invention made above by the present inventors has
been described specifically on the basis of the various
embodiments, the present invention is not limited to the
embodiments referred to above. It is needless to say that various
changes can be made thereto within the scope not departing from the
gist thereof.
[0216] For example, the present invention can be applied not only
to a battery for a note PC but also to a semiconductor integrated
circuit for battery control, which is used in a PDA (Personal
Digital Assistant), a hand-held game console, a cellular phone and
the like.
* * * * *