U.S. patent application number 12/078147 was filed with the patent office on 2008-08-07 for charged control device and battery pack employing it.
This patent application is currently assigned to ROHM. Invention is credited to Masaaki Fujii.
Application Number | 20080185997 12/078147 |
Document ID | / |
Family ID | 19184895 |
Filed Date | 2008-08-07 |
United States Patent
Application |
20080185997 |
Kind Code |
A1 |
Fujii; Masaaki |
August 7, 2008 |
Charged control device and battery pack employing it
Abstract
A battery pack employing a charge control device includes a
charge detection circuit for checking whether a secondary cell is
in a charged state or not based on at least a charge voltage or a
charge current of the secondary cell; a control circuit for
controlling feeding of electric power to the secondary cell
according to an output of the charge detection circuit; and a
setting circuit for setting a level of the charge voltage or the
charge current at which the charge detection circuit recognizes the
charged state according to control information.
Inventors: |
Fujii; Masaaki; (Kyoto,
JP) |
Correspondence
Address: |
MORGAN LEWIS & BOCKIUS LLP
1111 PENNSYLVANIA AVENUE NW
WASHINGTON
DC
20004
US
|
Assignee: |
ROHM
|
Family ID: |
19184895 |
Appl. No.: |
12/078147 |
Filed: |
March 27, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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|
11092977 |
Mar 30, 2005 |
7372234 |
|
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12078147 |
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10316152 |
Dec 11, 2002 |
6894458 |
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11092977 |
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Current U.S.
Class: |
320/162 |
Current CPC
Class: |
H01M 10/4257 20130101;
Y02E 60/10 20130101; H02J 7/00302 20200101; H02J 7/0031
20130101 |
Class at
Publication: |
320/162 |
International
Class: |
H02J 7/00 20060101
H02J007/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 11, 2001 |
JP |
2001-376771 |
Claims
1. A battery pack employing a charge control device, comprising: a
charge detection circuit for checking whether a secondary cell is
in a charged state or not based on at least a charge voltage or a
charge current of the secondary cell; a control circuit for
controlling feeding of electric power to the secondary cell
according to an output of the charge detection circuit; and a
setting circuit for setting a level of the charge voltage or the
charge current at which the charge detection circuit recognizes the
charged state according to control information.
2. The battery pack as claimed in claim 1, further comprising: a
control information generation circuit receiving a control signal
and generating the control information, wherein the setting circuit
receives the control information and, according to the control
information, sets the level of the charge voltage or the charge
current at which the charge detection circuit recognizes the
charged state.
3. The battery pack as claimed in claim 2, wherein the control
signal is an analog signal.
4. The battery back as claimed in claim 2, wherein the control
information generation circuit generates the control information
based on an output of the control circuit.
5. The battery pack as claimed in claim 1, further comprising: a
detection circuit incorporated in the charge control device and
detecting a state of the charge control device, wherein, according
to a result output from the detection circuit, the setting circuit
sets the level of the charge voltage or the charge current at which
the charge detection circuit recognizes the charged state.
6. The battery pack as claimed in claim 5, further comprising: a
control information generation circuit receiving a signal from the
detection circuit and, according to the signal from the detection
circuit, generates the control information.
Description
[0001] This application is a Continuation of co-pending U.S. patent
application Ser. No. 11/092,977 filed on Mar. 30, 2005, which is a
Continuation-In-Part of U.S. patent application Ser. No. 10/316,152
filed on Dec. 11, 2002 that issued as a U.S. Pat. No. 6,894,458 on
May 17, 2005, and claims the benefit of the Japanese patent
Application No. 2001-376771 filed on Dec. 11, 2001 in Japan.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a charge control device for
controlling the charging of a secondary cell or battery
(hereinafter collectively referred to as a "secondary cell"
throughout the specification and the claims) by monitoring its
charge state, and relates also to a battery pack employing such a
charge control device.
[0004] 2. Background of the Related Art
[0005] FIG. 6 is a diagram showing circuit configuration of a
related art battery pack incorporating a charge control device. The
battery pack 1' shown in this figure is composed of a rechargeable
secondary cell 2', a charge control IC 3' for controlling the
charging of the secondary cell 2' by monitoring its charge state,
feed terminals 4a' and 4b' to which direct-current electric power
is fed from a charger (not shown), a switch device 5' connected
between the feed terminal 4a' and the positive electrode of the
secondary cell 2', and a sense resistor 6' connected between the
negative electrode of the secondary cell 2' and the feed terminal
4b' (ground line). The sense resistor 6' has a very low resistance
(generally a few tens of m.OMEGA.), which permits the charge
current flowing through the secondary cell 2' to be detected as a
voltage.
[0006] The charge control IC 3' is built by sealing into a single
package a first full charge detection circuit 31' for checking
whether the secondary cell 2' is in the fully charged state or not
by comparing its charge voltage with a predetermined reference
voltage, a direct-current voltage source 32' for generating the
reference voltage, a second full charge detection circuit 34' for
checking whether the secondary cell 2' is in the fully charged
state or not by comparing the voltages at both ends of the sense
resistor 6', and a control circuit 35' for controlling the feeding
of electric power to the secondary cell 2' by turning on and off
the switch device 5' according to the output signals of the first
and second full charge detection circuits 31'and 34'.
[0007] As described above, the charge control IC 3' can monitor the
charge state of the secondary cell 2' and control its charging in a
considerably satisfactory manner in this battery pack 1'.
[0008] However, in the charge control IC 3' configured as described
above, the reference voltage generated by the direct-current
voltage source 32' (i.e., the level of the charge voltage at which
the first full charge detection circuit 31' recognizes the fully
charged state) is fixed at the time of circuit fabrication. This
makes it impossible to cancel factors that cause variations in the
reference voltage after the circuit fabrication (for example, the
influence of stress occurring when the charge control IC 3' is
packaged or mounted on a circuit board) and fabrication-associated
variations in the secondary cell 2' itself, which is the target of
monitoring by the charge control IC 3'. Thus, in the charge control
IC 3' configured as described above, the fully charged state
voltage level needs to be set rather low to ensure safe charging
operation. This makes it impossible to make the most use of the
charge capacity of the secondary cell 2'.
[0009] On the other hand, the second full charge detection circuit
34' is so configured to check whether the secondary cell 2' is in
the fully charged state or not by comparing the voltages at both
ends of the sense resistor 6', which is connected external to the
charge control IC 3'. Therefore, by setting the resistance of the
sense resistor 6' appropriately, it is possible to vary the level
of the charge current at which to recognize the fully charged
state. However, since the sense resistor 6' has a very low
resistance, it tends to be influenced by variations in connection,
wiring resistances, and other factors. Accordingly, this makes it
extremely difficult to correct a variation in the voltage level at
which the fully charged state is recognized. Thus, in the charge
control IC 3' configured as described above, the level of the
charge current at which the fully charged state is recognized also
needs to be set rather low to ensure safe charging operation. And,
this makes it impossible to make the most use of the charge
capacity of the secondary cell 2'. Moreover, the sense resistor 6',
connected externally, hampers the scaling-down and cost reduction
of the battery pack 1'.
SUMMARY OF THE INVENTION
[0010] Accordingly, the present invention is directed to a charge
control device and battery pack employing it that substantially
obviates one or more of the problems due to limitations and
disadvantages of the related art.
[0011] An object of the present invention is to provide a charge
control device that can accurately control the charging of a
secondary cell by canceling the influence of stress occurring when
an IC is packaged or mounted on a circuit board and other factors,
and to provide a battery pack employing such a charge control
device.
[0012] Additional features and advantages of the invention will be
set forth in the description which follows, and in part will be
apparent from the description, or may be learned by practice of the
invention. The objectives and other advantages of the invention
will be realized and attained by the structure particularly pointed
out in the written description and claims hereof as well as the
appended drawings.
[0013] To achieve these and other advantages and in accordance with
the purpose of the present invention, as embodied and broadly
described, the charge control device and battery pack employing it
includes a charge control device having a charge detection circuit
for checking whether a secondary cell is in a charged state or not
based on at least a charge voltage or a charge current of the
secondary cell; a control circuit for controlling feeding of
electric power to the secondary cell according to an output of the
charge detection circuit; and a setting circuit for setting a level
of the charge voltage or the charge current at which the charge
detection circuit recognizes the charged state according to control
information fed in directly from outside.
[0014] In another aspect, a battery pack employing a charge control
device includes a charge detection circuit for checking whether a
secondary cell is in a charged state or not based on at least a
charge voltage or a charge current of the secondary cell, a control
circuit for controlling feeding of electric power to the secondary
cell according to an output of the charge detection circuit; a
control information generation circuit for generating control
information based on an external signal fed in directly from
outside; and a setting circuit for setting a level of the charge
voltage or the charge current at which the charge detection circuit
recognizes the charged state according to the control information
outputted from the control information generation circuit.
[0015] In another aspect, a battery pack employing a charge control
device includes a charge detection circuit for checking whether a
secondary cell is in a charged state or not based on at least a
charge voltage or a charge current of the secondary cell; a control
circuit for controlling feeding of electric power to the secondary
cell according to an output of the charge detection circuit; a
control information generation circuit for generating control
information by converting an analog external signal fed in directly
from outside into digital data; and a setting circuit for setting a
level of the charge voltage or the charge current at which the
charge detection circuit recognizes the charged state according to
the control information outputted from the control information
generation circuit.
[0016] In another aspect, a battery pack employing a charge control
device includes a charge detection circuit for checking whether a
secondary cell is in a charged state or not based on at least a
charge voltage or a charge current of the secondary cell; a control
circuit for controlling feeding of electric power to the secondary
cell according to an output of the charge detection circuit; a
control information generation circuit for generating control
information based on an output result of the control circuit; and a
setting circuit for setting a level of the charge voltage or the
charge current at which the charge detection circuit recognizes the
charged state according to the control information outputted from
the control information generation circuit.
[0017] In another aspect, a battery pack employing a charge control
device includes a charge detection circuit for checking whether a
secondary cell is in a charged state or not based on at least a
charge voltage or a charge current of the secondary cell; a control
circuit for controlling feeding of electric power to the secondary
cell according to an output of the charge detection circuit; a
detection circuit, provided within the charge control device, for
detecting a state of the charge control device; a control
information generation circuit for generating control information
based on a signal outputted from the detection circuit; and a
setting circuit for setting a level of the charge voltage or the
charge current at which the charge detection circuit recognizes the
charged state according to the control information outputted from
the control information generation circuit.
[0018] It is to be understood that both the foregoing general
description and the following detailed description are exemplary
and explanatory and are intended to provide further explanation of
the invention as claimed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] The accompanying drawings, which are included to provide a
further understanding of the invention and are incorporated in and
constitute a part of this specification, illustrate embodiments of
the invention and together with the description serve to explain
the principles of the invention. In the drawings:
[0020] FIG. 1 illustrates a battery pack incorporated with a charge
control device of a first exemplary embodiment of the present
invention;
[0021] FIG. 2 illustrates a battery pack incorporated with a charge
control device of a second exemplary embodiment of the present
invention;
[0022] FIG. 3 illustrates a battery pack incorporated with a charge
control device of a third exemplary embodiment of the present
invention;
[0023] FIG. 4 illustrates a battery pack incorporated with a charge
control device of a fourth exemplary embodiment of the present
invention;
[0024] FIG. 5 illustrates a battery pack incorporated with a charge
control device of a fifth exemplary embodiment of the present
invention; and
[0025] FIG. 6 illustrates a battery pack incorporating a related
art charge control device.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0026] Reference will now be made in detail to the preferred
embodiments of the present invention, examples of which are
illustrated in the accompanying drawings.
[0027] FIG. 1 is a circuit configuration of a battery pack
incorporating a charge control device of a first exemplary
embodiment of the present invention. The battery pack 1 of the
first exemplary embodiment is composed of a rechargeable secondary
cell 2 (for example, a lithium ion cell), a charge control IC 3 for
controlling the charging of the secondary cell 2 by monitoring its
charge state, feed terminals 4a and 4b to which direct-current
electric power is fed from a charger (not shown), and a switch
device 5 (for example, a MOS transistor) connected between the feed
terminal 4a and the positive electrode of the secondary cell 2.
[0028] The charge control IC 3 is built by sealing into a single
package a first full charge detection circuit 31 for checking
whether the secondary cell 2 is in the fully charged state or not
by comparing its charge voltage with a predetermined reference
voltage, a variable direct-current voltage source 32 for generating
the reference voltage, a sense resistor 33 connected between the
negative electrode of the secondary cell 2 and the feed terminal 4b
(ground line), a second full charge detection circuit 34 for
checking whether the secondary cell 2 is in the fully charged state
or not by comparing the voltages at both ends of the sense resistor
33, a control circuit 35 for controlling the feeding of electric
power to the secondary cell 2 by turning on and off the switch
device 5 according to the output signals of the first and second
full charge detection circuits 31 and 34, an offset circuit 36 for
offsetting the level at which the second full charge detection
circuit 34 inverts its output, and the feed terminal 4c feeding the
control information steadily from outside the charge control device
to the variable direct-current voltage source 32 and the offset
circuit 36.
[0029] The output signal level of the first full charge detection
circuit 31 is low (at the logical low level) or high (at the
logical high level) according to whether the charge voltage of the
secondary cell 2 is lower or higher, respectively, than the
reference voltage generated by the variable direct-current voltage
source 32. On the other hand, the output signal level of the second
full charge detection circuit 34 is low or high according to
whether the voltage across the sense resistor 33 is higher or
lower, respectively, than the offset level set by the offset
circuit 36.
[0030] When one of the output signal levels of the first and second
full charge detection circuits 31 and 34 becomes high, the control
circuit 35 recognizes that at least one of the charge voltage and
charge current of the secondary cell 2 indicates the fully charged
state, and opens the switch device 5. With this configuration, it
is possible to prevent the secondary cell 2 from being
overcharged.
[0031] Here, the variable direct-current voltage source 32 of the
first exemplary embodiment can set the aforementioned reference
voltage (i.e., the level of the charge voltage at which the first
full charge detection circuit 31 recognizes the fully charged
state) according to the control information read from outside the
charge control device through the feed terminal 4c. Moreover, the
offset circuit 36 of this embodiment can set the aforementioned
offset level (i.e., the level of the charge current at which the
second full charge detection circuit 34 recognizes the fully
charged state) likewise according to the control information read
from outside the charge control device through the feed terminal
4c.
[0032] With the above described configuration, the charge control
IC 3 of the first exemplary embodiment of the present invention can
easily change the set levels of the charge voltage and charge
current at which the fully charged state is recognized, even after
the charge control IC 3 is packaged or mounted on a circuit board,
or after the secondary cell 2 is connected.
[0033] Accordingly, even after the charge control IC 3 is built
into the battery pack 1, it is possible to optimize the levels of
the charge voltage and charge current at which to recognize the
fully charged state by canceling all factors that cause variations
in the reference voltage after the fabrication of the circuit (for
example, the influence of stress occurring when the charge control
IC 3 is packaged or mounted on a circuit board) and all
fabrication-associated variations in the secondary cell 2 itself,
which is the very target of monitoring by the charge control IC
3.
[0034] In the related art charge control IC 3' (FIG. 6), the fully
charged state levels are set rather low to ensure safe charting
operation, because approximately .+-.0.5% variations are inevitable
in the charge voltage detected level and charge current detected
level. However, in the preferred embodiments of the present
invention, when detected levels are reduced to .+-.0.1% or smaller,
it is not necessary to lower the levels of the fully charged state
of both circuits 31 and 34. This makes possible to use of the
charge capacity of the secondary cell 2 more effectively.
[0035] FIG. 2 is a circuit configuration of a battery pack
incorporating a charge control. device of a second exemplary
embodiment of the present invention. The numbers appearing in FIG.
2, which are identical to those of FIG. 1, correspond to the same
circuit elements as described in reference to the first exemplary
embodiment of the present invention. Accordingly, written
descriptions for identical circuit elements in FIG. 2 are
omitted.
[0036] As shown in FIG. 2, a control information generation circuit
37 receives an external signal from outside through the feed
terminal 4c, and the control information generation circuit 37
feeds the control information to the variable direct-current
voltage source 32 and the offset circuit 36. In the second
exemplary embodiment of the present invention, the external signal
fed from outside to the control information generation circuit 37
includes a history signal (i.e., a history signal indicating the
number of times that the cell has been charged thus far). The
control information generation circuit may include a
microcomputer.
[0037] FIG. 3 is a circuit configuration of a battery pack
incorporating a charge control device of a third exemplary
embodiment of the present invention. The numbers appearing in FIG.
3, which are identical to those of FIG. 1, correspond to the same
circuit elements as described in reference to the first exemplary
embodiment of the present invention. Accordingly, written
descriptions for identical circuit elements in FIG. 3 are
omitted.
[0038] As shown in FIG. 3, a control information generation circuit
37 receives an external signal from outside through the feed
terminal 4c, and the control information generation circuit 37
feeds the control information to the variable direct-current
voltage source 32 and the offset circuit 36. In the third exemplary
embodiment of the present invention, the external signal fed from
outside to the control information generation circuit 37 includes
an analog signal (i.e., a temperature signal indicating the ambient
temperature). The control information generation circuit may
include an A/D conversion circuit that converts the analog external
signal into a digital signal.
[0039] FIG. 4 is a circuit configuration of a battery pack
incorporating a charge control device of a fourth exemplary
embodiment of the present invention. The numbers appearing in FIG.
4, which are identical to those of FIG. 1, correspond to the same
circuit elements as described in reference to the first exemplary
embodiment of the present invention. Accordingly, written
descriptions for identical circuit elements in FIG. 4 are
omitted.
[0040] As shown in FIG. 4, a control information generation circuit
37 receives a feedback signal from the control circuit 35, and the
control information generation circuit 37 feeds the control
information to the variable direct-current voltage source 32 and
the offset circuit 36. In the fourth exemplary embodiment of the
present invention, the control information generation circuit may
include a microcomputer.
[0041] FIG. 5 is a circuit configuration of a battery pack
incorporating a charge control device of a fifth exemplary
embodiment of the present invention. The numbers appearing in FIG.
5, which are identical to those of FIG. 1, correspond to the same
circuit elements as described above in reference to the first
exemplary embodiment of the present invention. Accordingly, written
descriptions for identical circuit elements in FIG. 5 are
omitted.
[0042] As shown in FIG. 5, a control information generation circuit
37 receives a signal from a detection circuit 38 provided within an
LSI, and the control information generation circuit 37 feeds the
control information to the variable direct-current voltage source
32 and the offset circuit 36. In the fifth exemplary embodiment of
the present invention, a plurality of detection circuits may be
provided in the LSI, and one of the plurality of detection circuits
38 include a temperature detection circuit. In addition, the
control information generation circuit 37 may include an A/D
conversion circuit that converts the analog signal (i.e.,
temperature) into a digital signal.
[0043] As discussed in the preferred embodiments of the present
invention, the variable direct-current voltage source 32 of each of
the preferred embodiment can set the reference voltage (i.e., level
of the charge voltage at which the first full charge detection
circuit 31 recognizes the fully charged state) according to the
control information received. In addition, the offset circuit 36 of
each of the preferred embodiments can set the offset level (i.e.,
level of the charge current at which the second full charge
detection circuit 34 recognizes the fully charged state) likewise
according to the control information received.
[0044] Moreover, adopting the charge control IC 3 of the preferred
embodiments eliminate the need to connect a sense resistor
externally outside the charge control device for detecting the
charge current of the secondary cell 2. This helps realize the
scaling-down and cost reduction of the battery pack 1. In addition,
switch device 5 may be formed within the charge control IC 3.
[0045] Accordingly, the charge control device of the preferred
embodiments can accurately control the charging of a secondary cell
by canceling the influence of stress occurring when an IC is
packaged or mounted on a circuit board and other factors.
[0046] It will be apparent to those skilled in art that various
modifications and variations can be made in the charge control
device and battery pack employing it of the present invention
without departing from the spirit or scope of the invention. Thus,
it is intended that the present invention cover the modifications
and variations of this invention provided they come within the
scope of the appended claims and their equivalents.
* * * * *