U.S. patent number RE42,114 [Application Number 09/548,213] was granted by the patent office on 2011-02-08 for control system for charging batteries and electronic apparatus using same.
This patent grant is currently assigned to Fujitsu Semiconductor Limited. Invention is credited to Kouichi Matsuda, Hidekiyo Ozawa, Mitsuo Saeki, Nobuo Tanaka.
United States Patent |
RE42,114 |
Matsuda , et al. |
February 8, 2011 |
Control system for charging batteries and electronic apparatus
using same
Abstract
A control system for charging enabling efficient charging of
rechargeable batteries in an electronic apparatus which charges its
rechargeable batteries by using a charger circuit when driving the
apparatus by using an external power source, including first
detecting unit for detecting a differential value between a maximum
permissible charging current allowed by the rechargeable batteries
and a charging current flowing to the rechargeable batteries;
second detecting unit for detecting a maximum usable current by
detecting a differential value between a maximum supplyable current
allowed by the external power source and the current consumption of
the apparatus; third detecting unit for detecting a differential
value between a maximum useable current and the charging current
flowing to the rechargeable batteries; and control unit for
controlling the system in accordance with the differential values
detected by the first and third detecting units so that the charger
circuit generates the maximum charging current within the range
where the charging current flowing to the rechargeable batteries
does not exceed either of the permissible charging current and the
maximum useable current.
Inventors: |
Matsuda; Kouichi (Kawasaki,
JP), Saeki; Mitsuo (Kawasaki, JP), Tanaka;
Nobuo (Kawasaki, JP), Ozawa; Hidekiyo (Kawasaki,
JP) |
Assignee: |
Fujitsu Semiconductor Limited
(Yokohama, JP)
|
Family
ID: |
18138468 |
Appl.
No.: |
09/548,213 |
Filed: |
April 12, 2000 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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Reissue of: |
08578805 |
Dec 26, 1995 |
05739667 |
Apr 14, 1998 |
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Foreign Application Priority Data
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Dec 26, 1994 [JP] |
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6-321970 |
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Current U.S.
Class: |
320/128 |
Current CPC
Class: |
H02J
7/00711 (20200101); H02J 7/0072 (20130101); H02J
9/061 (20130101); H02J 7/007182 (20200101); H02J
7/00714 (20200101) |
Current International
Class: |
H01M
10/46 (20060101); H02J 9/06 (20060101) |
Field of
Search: |
;320/128,161,162,164 |
References Cited
[Referenced By]
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WO |
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WO 93/19508 |
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Sep 1993 |
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WO |
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|
Primary Examiner: Tso; Edward
Attorney, Agent or Firm: Staas & Halsey LLP
Parent Case Text
.Iadd.This application is a reissue of U.S. application Ser. No.
08/578,805, now U.S. Pat. No. 5,739,667. More than one reissue
application has been filed for the reissue of U.S. Pat. No.
5,739,667. The reissue applications are Ser. No. 10/383,068 and the
instant application Ser. No. 09/548,213. .Iaddend.
Claims
We claim:
1. A system for controlling the supply of power from an external
power source to rechargeable batteries in an apparatus which can be
powered either by the external power source or the rechargeable
batteries, comprising: a first detector for detecting a difference
between a maximum permissible charging current allowed by the
rechargeable batteries and a charging current flowing to the
rechargeable batteries; a second detector for detecting a maximum
useable current by detecting a difference between a maximum
suppliable current allowed by the external power source and the
current being consumed by the apparatus; a third detector for
detecting a difference between the maximum useable current and the
charging current flowing to the rechargeable batteries; and a
controller for controlling power supplied from the external power
source to the rechargeable batteries in accordance with the
differences detected by the first and third detectors so that the
charging current flowing to the rechargeable batteries does not
exceed the maximum permissible charging current and does not exceed
the maximum useable current.
2. A system for controlling as set forth in claim 1, further
comprising a fourth detector for detecting a difference between a
maximum permissible supply voltage allowed by said rechargeable
batteries and a voltage applied to said rechargeable batteries,
said control means controlling the power supplied from the external
power source to the rechargeable batteries in accordance wins the
difference detected by the fourth detector so mat the voltage
applied to the rechargeable batteries does not exceed the maximum
permissible supply voltage.
3. A system for controlling the supply of power from an external
power source to rechargeable batteries in an apparatus which can be
powered by either the external power source or the rechargeable
batteries, comprising: a first detector for detecting a difference
between a maximum permissible charging current allowed by the
rechargeable batteries and a charging current flowing to the
rechargeable batteries; a second detector for detecting a
difference between a lowest permissible output voltage allowed by
the external power source and an output voltage which is being
output by the external power source; and a controller for
controlling power supplied from the external power source to the
rechargeable batteries in accordance with the differences detected
by the first and second detectors so that the charging current
flowing to the rechargeable batteries does not exceed the maximum
permissible charging current and the output voltage being output by
the external power source is not less than the lowest permissible
output voltage.
4. A control system for controlling as set forth in claim 3,
further comprising a third detector for detecting a difference
between the maximum permissible supply voltage allowed by the
rechargeable batteries and a voltage applied to said rechargeable
batteries, said control means controlling the power supplied from
the external power source to the rechargeable batteries in
accordance with the difference detected by the third detector so
that the voltage applied to the rechargeable batteries does not
exceed the maximum permissible supply voltage.
5. A system for controlling as set forth in claim 1, wherein said
controller controls the power supplied from the external power
source to the rechargeable batteries by determining if either the
first or third detector detects a negative difference thus
indicating mat the charging current exceeds a maximum, wherein if
either of the first or third detector detects a negative
difference, the controller selects the largest negative difference
and controls the charging current to increase the largest negative
difference to a zero difference, and wherein if neither of the
first or third detector detects a negative difference, the
controller selects the largest positive difference and controls the
charging current to decrease the largest positive difference to a
zero difference.
6. A system for controlling as set form in claim 2, wherein said
controller controls the power supplied from the external power
source to the rechargeable batteries by determining if any of the
first third or fourth detector detects a negative difference thus
indicating that the charging current or the supply voltage exceeds
a maximum, wherein if any of the first third or fourth detector
detects a negative difference, the controller selects the largest
negative difference and controls the charging current to increase
the largest negative difference to a zero difference, and wherein
if none of the first third or fourth detector detects a negative
difference, the controller selects the largest positive difference
and controls the charging current to decrease the largest positive
difference to a zero difference.
7. A system for controlling as set forth in claim 3, wherein said
controller controls the power supplied from the external power
source to the rechargeable batteries by determining if either of
the detector detects a negative difference thus indicating that the
charging current exceeds a minimum or the output voltage is less
then a minimum, wherein if either of the detector detects a
negative difference, the controller selects the largest negative
difference and controls the charging current to increase the
largest negative difference to a zero difference, and wherein if
neither of the detector detects a negative difference, the
controller selects the largest positive difference and controls the
charging current to decrease the largest positive difference to a
zero difference.
8. A system for controlling as set forth in claim 4, wherein said
controller controls the power supplied from the external power
source to the rechargeable batteries by determining if any of the
detector detects a negative difference thus indicating that a
current or a voltage is greater than a maximum or less than a
minimum, wherein if any of the detector detects a negative
difference, the controller selects the largest negative difference
and controls the charging current to increase the largest negative
difference to a zero difference, and wherein if none of the
detector detects a negative difference, the controller selects the
largest positive difference and controls the charging current to
decrease the largest positive difference to a zero difference.
9. A system for controlling the supply of power from a charger
circuit to rechargeable batteries, the rechargeable batteries being
used to supply power to a power supply circuit, comprising: a sense
resistor having two ends, located between the rechargeable
batteries and a connection point for the charger circuit and the
power supply circuit, the sense resistor detecting current flowing
into and out of the rechargeable batteries; a current measurement
device having two inputs connected respectively to the two ends of
the sense resistor, the current measurement device determining
which of the two inputs has a larger voltage and generating a
voltage in accordance with the difference between the voltages of
the two inputs to thereby measure the current flowing into or out
of the rechargeable battery; and a control circuit regulating to a
constant current the current flowing into the rechargeable
batteries, based on the current flowing into the rechargeable
batteries detected by the sense resistor.
10. A system for controlling as set forth in claim 9, wherein the
control circuit has two inputs connected respectively to the two
ends of the sense resistor.
.Iadd.11. An electronic apparatus having an input section for
inputting power from a power source and capable of charging a
battery by using the power from the input section while the
electronic apparatus makes a load operate by applying the power
input from the input section to the load, an output voltage of the
power source being substantially a constant voltage, the output
voltage of the power source falling to less than said constant
voltage when the power source outputs more than a predetermined
current value, the power applied to the load from the input section
varying based on the state of the load, the electronic apparatus
comprising: a power input sensor for obtaining power-input
information by sensing an input of the power from the input
section; a charger for charging the battery by using the power from
the input section; a charge control circuit for controlling the
charging power the charger supplies to the battery based on the
power input information obtained by the power input sensor so that
a sum of the power applied to the load and the power charged to the
battery from the input section is substantially in a current range
in which said output voltage of the power source is substantially
the constant voltage; and a charging voltage detector for detecting
a charging voltage of the battery, wherein the charge control
circuit controls the charging voltage so that the charging voltage
detected by the charging voltage detector becomes a value assigned
to the battery or lower. .Iaddend.
.Iadd.12. An electronic apparatus as set forth in claim 11, further
comprising: a charging current detector for detecting a charging
current of the battery, wherein the charge control circuit controls
the charging current based on the detected charging current so that
the charging current becomes a value assigned to the battery or
lower. .Iaddend.
.Iadd.13. An electronic apparatus as set forth in claim 11, wherein
the power source is able to supply a maximum permissible supply
current of the power source in the current range. .Iaddend.
.Iadd.14. A charging apparatus for an electronic apparatus that has
an input section for inputting power from a power source and is
capable of charging a battery by using the power from the input
section while the electronic apparatus makes a load operate by
applying the power input from the input section to the load, an
output voltage of the power source being substantially a constant
voltage, the output voltage of the power source falling to less
than said constant voltage when the power source outputs more than
a predetermined current value, the power applied to the load from
the input section varying based on the state of the load, the
charging apparatus comprising: a charger for charging the battery
by using the power from the input section; a charge control circuit
for controlling the charging power the charger supplies to the
battery, based on the power input information obtained by power
input sensor for obtaining the power input information by sensing
an input of the power from the input section, so that a sum of the
power applied to the load and the power charged to the battery from
the input section is substantially in a current range in which said
output voltage of the power source is substantially the constant
voltage, wherein the charge control circuit controls the charging
current, based on a charging current detected by a charging current
detector for detecting the charging current of the battery, so that
the charging current becomes a value assigned to the battery or
lower. .Iaddend.
.Iadd.15. A charging apparatus as set forth in claim 14, wherein
the charge control circuit further controls the charging voltage so
that a voltage detected by a charging voltage detector for
detecting the charging voltage of the battery becomes a value
assigned to the battery or lower. .Iaddend.
.Iadd.16. A charging apparatus as set forth in claim 14, wherein
the power source is able to supply a maximum permissible supply
current of the power source in the current range. .Iaddend.
.Iadd.17. A charge control circuit for an electronic apparatus that
has an input section for inputting power from a power source and a
charger for charging a battery by using the power from the input
section while the electronic apparatus making a load operate by
applying the power input from the input section to the load, an
output voltage of the power source being substantially a constant
voltage, the output voltage of the power source falling to less
than said constant voltage when the power source outputs more than
a predetermined current value, the power applied to the load from
the input section varying based on the state of the load, the
charge control circuit comprising: a control circuit for
controlling the charging power the charger supplies to the battery,
based on power input information obtained by a power input sensor
for obtaining the power input information by sensing an input of
the power from the input section, so that a sum of the power
applied to the load and the power charged to the battery from the
input section is substantially in a current range in which said
output voltage of the power source is substantially the constant
voltage, wherein the control circuit controls the charging voltage
so that a voltage detected by a charging voltage detector for
detecting the charging voltage of the battery becomes a value
assigned to the battery or lower. .Iaddend.
.Iadd.18. A charge control circuit as set forth in claim 17,
wherein the control circuit controls the charging current based a
charging current detected by a charging current detector for
detecting the charging current of the battery so that the charging
current becomes a value assigned to the battery or lower.
.Iaddend.
.Iadd.19. A charge control circuit as set forth in claim 17,
wherein the power source is able to supply a maximum permissible
supply current of the power source in the current range.
.Iaddend.
.Iadd.20. An electronic apparatus having a charger for outputting a
charging current to charge a battery by using power of a power
source and supplying the power from the battery to a load to make
the load operate, the electronic apparatus comprising: a sense
resistor provided between a connection point between the power
source and the charger and the battery, for detecting a charging
current flowing into the battery and for detecting a current
flowing out from the battery; and a controller for controlling the
charging current from the charger based on a current value measured
by using the sense resistor. .Iaddend.
.Iadd.21. An electronic apparatus as set forth in claim 20, further
comprising: a current measuring section for discriminating which
one of two input potentials applied to both ends of the sense
resistor is larger, and for detecting both a charging current and a
discharging current from a voltage generated according to a
difference between the two input potentials. .Iaddend.
.Iadd.22. An electronic apparatus as set forth in claim 20, further
comprising: a remaining-amount determining section for determining
a remaining amount of current charged to the battery based on a
charging current value measured by the sense resistor.
.Iaddend.
.Iadd.23. An electronic apparatus as set forth in claim 20, further
comprising: a remaining-amount determining section for determining
a remaining amount of current charged to the battery based on a
discharging current value measured by the sense resistor.
.Iaddend.
.Iadd.24. An electronic apparatus having a charger for supplying a
charging current to a battery by using power of a power source to
make a load operate based on the power supplied from the battery,
the electronic apparatus comprising: a sense resistor disposed
between the battery and a connection point between the power source
and the charger, for detecting a charging current flowing into the
battery in order to control the charging current of the charger;
and a detector for detecting a discharging current by the sense
resistor when the power from the battery is supplied to the load.
.Iaddend.
.Iadd.25. An electronic apparatus having an input section for
inputting power from a power source and capable of charging a
battery by using the power from the input section while making a
load operate by applying the power input from the input section to
the load, a current applied to the load from the input section
varying based on the state of the load, the electronic apparatus
comprising: a power input sensor which obtains power-input
information by sensing an input of the power from the input
section; a charger which charges the battery by using a current
from the input section; a charge control circuit which controls the
charger to change a current charged to the battery by determining
whether an input current from the power source reaches a
predetermined value or not in accordance with the power-input
information sensed by the power input sensor, so that a sum of the
current applied to the load and the current charged to the battery
from the input section does not exceed the predetermined value; and
a charging voltage detector which detects a charging voltage of the
battery, wherein the charge control circuit controls the charging
voltage so that the charging voltage detected by the charging
voltage detector becomes a value assigned to the battery or lower.
.Iaddend.
.Iadd.26. An electronic apparatus as set forth in claim 25, further
comprising: a charging current detector which detects a charging
current of the battery, wherein the charge control circuit controls
the charging current based on the detected charging current so that
the charging current becomes a value assigned to the battery or
lower. .Iaddend.
.Iadd.27. An electronic apparatus as set forth in claim 25, wherein
the predetermined value is a maximum permissible supply current of
the power source. .Iaddend.
.Iadd.28. A charging apparatus for an electronic apparatus that has
an input section for inputting power from a power source and is
capable of charging a battery by using the power from the input
section while the electronic apparatus making a load operate by
applying the power input from the input section to the load, a
current applied to the load from the input section varying based on
the state of the load, the charging apparatus comprising: a charger
which charges the battery by using the power from the input
section; a charge control circuit which controls the charger to
change a current charged to the battery by determining whether an
input current from the power source reaches a predetermined value
or not in accordance with the power-input information sensed by a
power input sensor which obtains the power input information by
sensing an input of power from the input section, so that a sum of
the current applied to the load and the current charged to the
battery from the input section does not exceed the predetermined
value, wherein the charge control circuit further controls the
charging voltage so that a voltage detected by a charging voltage
detector for detecting the charging voltage of the battery becomes
a value assigned to the battery or lower. .Iaddend.
.Iadd.29. A charging apparatus as set forth in claim 28, wherein
the charge control circuit controls the charging current, based on
a charging current detected by a charging current detector for
detecting the charging current of the battery, so that the charging
current becomes a value assigned to the battery or lower.
.Iaddend.
.Iadd.30. A charging apparatus as set forth in claim 28, wherein
the predetermined value is a maximum permissible supply power of
the power source. .Iaddend.
.Iadd.31. A charge control circuit for an electronic apparatus that
has an input section for inputting power from a power source and a
charger for charging a battery by using the power from the input
section and while the electronic apparatus making a load operate by
applying the power input from the input section to the load, a
current applied to the load from the input section varying based on
the state of the load, the charge control circuit comprising: a
charge control circuit which controls the charger to change a
current charged to the battery by determining whether an input
current from the power source reaches a predetermined value or not
in accordance with the power-input information sensed by a power
input sensor which obtains the power input information by sensing
an input of power from the input section, so that a sum of the
current applied to the load and the current charged to the battery
from the input section does not exceed the predetermined value,
wherein the control circuit controls the charging voltage so that a
voltage detected by a charging voltage detector for detecting the
charging voltage of the battery becomes a value assigned to the
battery or lower. .Iaddend.
.Iadd.32. A charge control circuit as set forth in claim 31,
wherein the control circuit controls the charging current based a
charging current detected by a charging current detector for
detecting the charging current of the battery so that the charging
current becomes a value assigned to the battery or lower.
.Iaddend.
.Iadd.33. A charge control circuit as set forth in claim 31,
wherein the predetermined value is a maximum permissible supply
power of the power source. .Iaddend.
.Iadd.34. An electronic apparatus connected to an AC adapter which
supplies DC power, capable of charging a battery by using power
from the AC adapter while making a load operate by using the DC
power supplied from the AC adapter, the power given to the load
varying based on the state of the load, the electronic apparatus
comprising: a connector which receives the DC power from the AC
adapter; a charger, connected to the battery, which supplies
charging power to the battery by using the power from the
connector; and a charge control circuit which controls the charger
to control the charging power the charger supplies to the battery
so that a sum of the power applied to the load and the power
charged to the battery becomes a value assigned in advance.
.Iaddend.
.Iadd.35. An electronic apparatus as set forth in claim 34, further
comprising a charging current detector which detects a charging
current supplied to the battery, wherein the charge control circuit
controls the charging current so that the charging current becomes
equal to or lower than a value assigned to the battery, based on a
value of the charging current to the battery detected by the
charging current detector. .Iaddend.
.Iadd.36. An electronic apparatus as set forth in claim 34, further
comprising a charging voltage detector which detects a charging
voltage supplied to the battery, wherein the control circuit
controls the charging voltage so that the charging voltage becomes
equal to or lower than a value assigned to the battery, based on a
value of the charging voltage to the battery detected by the
charging voltage detector. .Iaddend.
.Iadd.37. An electronic apparatus as set forth in claim 34, wherein
the value assigned in advance is a maximum permissible supply power
of the AC adapter. .Iaddend.
.Iadd.38. An electronic apparatus as set forth in claim 34, wherein
the charge control circuit controls the charging power the charger
supplies to the battery, based on sensed information on the power
input from the connector, so that a sum of the power applied to the
load and the power charged to the battery becomes the value
assigned in advance. .Iaddend.
.Iadd.39. A charging apparatus for charging a battery for an
electronic apparatus that is connected to an AC adapter and that is
capable of charging the battery by using power from the AC adapter
while the electronic apparatus making a load operate by using DC
power supplied from the AC adapter, the power given to the load
varying based on the state of the load, the charging apparatus
comprising: a charger, connected to the battery, which supplies
charging power to the battery by using the power from a connector
that is connected to the AC adapter to receive the DC power from
the AC adapter; and a charge control circuit which controls the
charger to control the charging power the charger supplies to the
battery so that a sum of the power applied to the load and the
power charged to the battery becomes a value assigned in advance.
.Iaddend.
.Iadd.40. A charging apparatus as set forth in claim 39, wherein
the charge control circuit controls the charging current so that a
charging current becomes equal to or lower than the value assigned
to the battery, based on a detected value of the charging current
to the battery. .Iaddend.
.Iadd.41. A charging apparatus as set forth in claim 39, wherein
the charge control circuit controls a charging voltage so that the
charging voltage becomes equal to or lower than a value assigned to
the battery, based on a detected value of the charging voltage to
the battery. .Iaddend.
.Iadd.42. A charging apparatus as set forth in claim 39, wherein
the value assigned in advance is a maximum permissible supply power
of the AC adapter. .Iaddend.
.Iadd.43. A charging apparatus as set forth in claim 39, wherein
the charge control circuit controls the charging power the charger
supplies to the battery so that a sum of the power applied to the
load and the power charged to the battery becomes the value
assigned in advance, based on sensed information on the power input
from the connector. .Iaddend.
.Iadd.44. A charge control circuit for controlling a charger in an
electronic apparatus having a connector connected to an AC adapter
to receive DC power from the AC adapter, the charger being
connected to a battery and supplying charging power to the battery
by using the power from the connector, the electronic apparatus
making a load operate by using the DC power supplied from the AC
adapter, the power given to the load varying based on the state of
the load, the charge control circuit comprising: a control circuit
which controls the charger to control the charging power the charge
supplies to the battery so that a sum of the power applied to the
load and the power charged to the battery becomes a value assigned
in advance. .Iaddend.
.Iadd.45. A charge control circuit as set forth in claim 44,
wherein the control circuit controls a charging current based on a
detected value of the charging current to the battery so that the
charging current becomes equal to or lower than a value assigned to
the battery. .Iaddend.
.Iadd.46. A charge control circuit as set forth in claim 44,
wherein the control circuit controls a charging voltage based on a
detected value of the charging voltage to the battery so that the
charging voltage becomes equal to or lower than a value assigned to
the battery. .Iaddend.
.Iadd.47. A charge control circuit as set forth in claim 44,
wherein the value assigned in advance is a maximum permissible
supply power of the AC adapter. .Iaddend.
.Iadd.48. A charge control circuit as set forth in claim 44,
wherein the control circuit controls the charging power the charger
supplies to the battery, based on sensed information on the power
input from the connector, so that a sum of the power applied to the
load and the power charged to the battery becomes the value
assigned in advance. .Iaddend.
.Iadd.49. An electronic apparatus capable of charging a battery by
using power from a power source while making a load operate by
using the power supplied from the power source, the electronic
apparatus comprising: a charger which supplies charging power to
the battery by using the power from the power source; a detector
which detects the power applied to the load; a charging current
detector detects a charging current to the battery; and a control
circuit which controls the charger to generate the charging power
so that a sum of the charging power supplied to the battery and the
power applied to the load that has been detected becomes a value
assigned in advance, and which controls the charging current based
on the detected charging current so that the charging current to
the battery becomes equal to or lower than a charging current value
assigned in advance to the battery. .Iaddend.
.Iadd.50. An electronic apparatus capable of charging a battery by
using power from a power source while making a load operate by
using the power supplied from the power source, the electronic
apparatus comprising: a charger which supplies charging power to
the battery by using the power from the power source; a detector
which detects the power applied to the load; a charging voltage
detector which detects a charging voltage to the battery; and a
control circuit which controls the charger to generate the charging
power so that a sum of the charging power supplied to the battery
and the power applied to the load that has been detected becomes a
value assigned in advance, and which controls the charging voltage
based on the detected charging voltage so that the charging voltage
becomes within a voltage value assigned in advance to the battery.
.Iaddend.
.Iadd.51. An electronic apparatus capable of charging a battery by
using power from a power source having a prescribed maximum
permissible supply power while making a load operate by using the
power supplied from the power source, the electronic apparatus
comprising: a charger which supplies charging power to the battery
by using the power from the power source; a detector which detects
the power applied to the load; and a control circuit which controls
the charger to adjust the charger to supply the charging power so
that the charging power is the prescribed maximum permissible
supply power minus the detected power applied to the load.
.Iaddend.
.Iadd.52. A charging apparatus for an electronic apparatus capable
of charging a battery by using power from a power source while the
electronic apparatus makes a load operate by using the power
supplied from the power source, the charging apparatus comprising:
a charger which supplies charging power to the battery by using the
power from the power source; and a control circuit which controls
the charger to generate the charging power so that a sum of the
charging power supplied to the battery and the power applied to the
load detected by a detector which detects the power applied to the
load becomes a value assigned in advance, and which controls the
charging current, based on a charging current value detected by a
charging current detector which detects the charging current to the
battery, so that the charging current to the battery becomes equal
to or lower than a charging current value assigned in advance to
the battery. .Iaddend.
.Iadd.53. A charging apparatus for an electronic apparatus capable
of charging a battery by using power from a power source while the
electronic apparatus making a load operate by using the power
supplied from the power source, the charging apparatus comprising:
a charger which supplies charging power to the battery by using the
power from the power source; and a control circuit which controls
the charger to generate the charging power so that a sum of the
charging power supplied to the battery and the power applied to the
load detected by a detector which detects the power applied to the
load becomes a value assigned in advance, and which controls the
charging voltage, based on a charging voltage detected by a
charging voltage detector which detects the charging voltage of the
battery, so that the charging voltage becomes within a voltage
value assigned in advance to the battery. .Iaddend.
.Iadd.54. A charging apparatus for an electronic apparatus capable
of charging a battery by using power from a power source having a
prescribed maximum permissible supply power while the electronic
apparatus makes a load operate by using the power supplied from the
power source, the charging apparatus comprising: a charger which
supplies charging power to the battery by using the power from the
power source; and a control circuit which controls the charger so
that the charger supplies the charging power so that the charging
power is the maximum permissible supply power minus the power
applied to the load that has been detected by a detector which
detects the power applied to the load. .Iaddend.
.Iadd.55. A charge control circuit for controlling a charger for an
electronic apparatus that makes a load operate by using power
supplied from a power source and that has the charger for supplying
charging power to a battery by using the power from the power
source, the charge control circuit comprising: a control circuit
which controls the charger to generate the charging power so that a
sum of the charging power supplied to the battery and the power
applied to the load detected by a detector which detects the power
applied to the load becomes a value assigned in advance, and which
controls a charging current, based on a charging current detected
by a charging current detector which detects the charging current
to the battery, so that the charging current supplied to the
battery becomes equal to or lower than a charging current value
assigned in advance to the battery. .Iaddend.
.Iadd.56. A charge control circuit for controlling a charger for an
electronic apparatus that makes a load operate by using power
supplied from a power source and that has the charger for supplying
charging power to a battery by using the power from the power
source, the charge control circuit comprising: a control circuit
which controls the charger to generate the charging power so that a
sum of the charging power supplied to the battery and the power
applied to the load detected by a detector which detects the power
applied to the load becomes a value assigned in advance, and which
controls the charging voltage, based on a charging voltage detected
by a charging voltage detector which detects the charging voltage
to the battery, so that the charging voltage becomes within a
voltage value assigned in advance to the battery. .Iaddend.
.Iadd.57. A charge control circuit for controlling a charger for an
electronic apparatus that makes a load operate by using power
supplied from a power source having a prescribed maximum
permissible supply power and that has the charger for supplying
charging power to a battery by using the power from the power
source, the charge control circuit comprising: a control circuit
which controls the charger so that the charger supplies the
charging power which is the prescribed maximum permissible supply
power minus the power applied to the load detected by a detector
which detects the power applied to the load. .Iaddend.
.Iadd.58. An electronic apparatus capable of charging a battery by
using power from a power source while making a load operate by
using the power supplied from the power source, the power applied
to the load from the power source varying based on the state of the
load, the electronic apparatus comprising: a charger which supplies
charging power to the battery by using the power from the power
source; a charging current detector which detects a charging
current of the battery; a charge control circuit which controls the
charging power the charger supplies to the battery so that a sum of
the power applied to the load and the power charged to the battery
from the power source becomes a value assigned in advance, and
which controls the charging current based on the charging current
detected by the charging current detector so that the charging
current becomes a limit value assigned to the battery or a lower
value; and a charging voltage detector which detects a charging
voltage of the battery, wherein the charge control circuit further
controls the charging voltage so that the voltage detected by the
charging voltage detector becomes a value assigned to the battery
or lower. .Iaddend.
.Iadd.59. An electronic apparatus as set forth in claim 58, wherein
the pre-assigned value is a maximum permissible supply power of the
power source. .Iaddend.
.Iadd.60. An electronic apparatus as set forth in claim 58, wherein
the charge control circuit controls the charging power the charger
supplies to the battery, based on sensed information on the input
from the power source, so that a sum of the power applied to the
load and the power charged to the battery from the power source
becomes the pre-assigned value. .Iaddend.
.Iadd.61. A charging apparatus for an electronic apparatus that is
capable of charging a battery by using power supplied from a power
source while the electronic apparatus making a load operate by
using the power from the power source, the power applied to the
load from the power source varying based on the state of the load,
the charging apparatus comprising: a charger which supplies
charging power to the battery by using the power from the power
source; and a charge control circuit which controls the charging
power the charger supplies to the battery so that a sum of the
power applied to the load and the power charged to the battery from
the power source becomes a value assigned in advance, and which
controls the charging current, based on a charging current detected
by a charging current detector which detects the charging current
to the battery, so that the charging current becomes a value
assigned to the battery or a lower value, wherein the charge
control circuit further controls the charging voltage so that a
charging voltage detected by a charging voltage detector which
detects the voltage charged to the battery becomes a value assigned
to the battery or lower. .Iaddend.
.Iadd.62. A charging apparatus as set forth in claim 61, wherein
the preassigned value is a maximum permissible supply power of the
power source. .Iaddend.
.Iadd.63. A charging apparatus as set forth in claim 61, wherein
the charge control circuit controls the charging power the charger
supplies to the battery, based on sensed information on the input
from the power source, so that a sum of the power applied to the
load and the power charged to the battery becomes the pre-assigned
value. .Iaddend.
.Iadd.64. A charge control circuit for an electronic apparatus that
makes a load operate by using power supplied from a power source
and that has a charger for supplying charging power to a battery by
using the power from the power source, the power applied to the
load from the power source varying based on the state of the load,
the charge control circuit comprising: a control circuit which
controls the charging power the charger supplies to the battery so
that a sum of the power applied to the load and the power charged
to the battery from the power source becomes a value assigned in
advance, and which controls the charging current based on a
charging current detected by a charging current detector which
detects the charging current to the battery so that the charging
current becomes a value assigned to the battery or a lower value.
.Iaddend.
.Iadd.65. A charge control circuit as set forth in claim 64,
wherein the control circuit further controls the charging voltage
so that a charging voltage detected by a charging voltage detector
which detects the voltage charged to the battery becomes a value
assigned to the battery or lower. .Iaddend.
.Iadd.66. A charge control circuit as set forth in claim 64,
wherein the preassigned value is a maximum permissible supply power
of the power source. .Iaddend.
.Iadd.67. A charge control circuit as set forth in claim 64,
wherein the control circuit controls the charging power the charger
supplies to the battery, based on sensed information on the input
from the power source, so that a sum of the power applied to the
load and the power from the power source charged from the power
source to the battery becomes the pre-assigned value. .Iaddend.
.Iadd.68. A charge control circuit for an electronic apparatus that
has an input section for inputting power from a power source and a
charger for charging a battery by using the power from the input
section while the electronic apparatus makes a load operate by
applying the power input from the input section to the load, an
output voltage of the power source being substantially a constant
voltage, the output voltage of the power source falling to less
than said substantially constant voltage when the power source
outputs more than a predetermined current value, the power applied
to the load from the input section varying based on the state of
the load, the charge control circuit comprising: a control circuit
which controls the charging power the charger supplies to the
battery, based on power input information obtained by a power input
sensor which obtains the power input information by sensing an
input of the power from the input section, so that a sum of the
power applied to the load and the power charged to the battery from
the input section is substantially in a current range in which said
output voltage of the power source is the substantially constant
voltage, wherein the control circuit controls a charging voltage
the charger supplies to the battery so that the charging voltage
detected by a charging voltage detector becomes a value assigned to
the battery or lower, wherein the control circuit controls the
charging power the charger supplies to the battery, based on sensed
information on the input from the power source, so that a sum of
the power applied to the load and the power from the power source
charged from the power source to the battery becomes the
pre-assigned value. .Iaddend.
.Iadd.69. An electronic apparatus connected to an AC adapter which
supplies DC current, capable of charging a battery by using current
from the AC adapter while making a load operate by using the DC
current supplied from the AC adapter, the current given to the load
varying based on the state of the load, the electronic apparatus
comprising: a connector connected to the AC adapter, which receives
DC current from the AC adapter; a charger, connected to the
battery, which supplies charging current to the battery by using
the current from the connector; a charger control circuit which
controls the charger to control the charging current the charger
supplies to the battery so that a sum of the current applied to the
load and the current charged to the battery becomes a value
assigned in advance; and a charging voltage detector which detects
a charging voltage supplied to the battery, wherein the control
circuit controls the charging voltage so that the charging voltage
becomes equal to or lower than a value assigned to the battery,
based on a value of the charging voltage to the battery detected by
the charging voltage detector. .Iaddend.
.Iadd.70. An electronic apparatus as set forth in claim 69, further
comprising a charging current detector which detects a charging
current supplied to the battery, wherein the charge control circuit
controls the charging current so that the charging current becomes
equal to or lower than a value assigned to the battery, based on a
value of the charging current to the battery detected by the
charging current detector. .Iaddend.
.Iadd.71. An electronic apparatus as set forth in claim 69, wherein
the value assigned in advance is a maximum permissible supply
current of the AC adapter. .Iaddend.
.Iadd.72. An electronic apparatus as set forth in claim 69, wherein
the charge control circuit controls the charging current the
charger supplies to the battery, based on sensed information on the
power input from the connector, so that a sum of the current
applied to the load and the current charged to the battery becomes
the value assigned in advance. .Iaddend.
.Iadd.73. A charging apparatus for charging a battery for an
electronic apparatus that is connected to an AC adapter and that is
capable of charging the battery by using current from the AC
adapter while the electronic apparatus making a load operate by
using DC current supplied from the AC adapter, the current given to
the load varying based on the state of the load, the charging
apparatus comprising: a charger, connected to the battery, which
supplies charging current to the battery by using the current from
a connector that is connected to the AC adapter to receive the DC
current from the AC adapter; and a charger control circuit which
controls the charger to control the charging power the charger
supplies to the battery so that a sum of the current applied to the
load and the current charged to the battery becomes a value
assigned in advance, wherein the charge control circuit controls a
charging voltage so that the charging voltage becomes equal to or
lower than a value assigned to the battery, based on a detected
value of the charging voltage to the battery. .Iaddend.
.Iadd.74. A charging apparatus as set forth in claim 73, wherein
the charge control circuit controls the charging current so that a
charging current becomes equal to or lower than the value assigned
to the battery, based on a detected value of the charging current
to the battery. .Iaddend.
.Iadd.75. A charging apparatus as set forth in claim 73, wherein
the value assigned in advance is a maximum permissible supply
current of the AC adapter. .Iaddend.
.Iadd.76. A charging apparatus as set forth in claim 73, wherein
the charge control circuit controls the charging current the
charger supplies to the battery so that a sum of the current
applied to the load and the current charged to the battery becomes
the value assigned in advance, based on sensed information on input
from the connector. .Iaddend.
.Iadd.77. A charge control circuit for controlling a charger in an
electronic apparatus having a connector connected to an AC adapter
to receive DC current from the AC adapter, the charger being
connected to a battery and supplying charging current to the
battery by using the current from the connector, the electronic
apparatus making a load operate by using the DC current supplied
from the AC adapter, the current given to the load varying based on
the state of the load, the charge control circuit comprising: a
control circuit which controls the charger to control the charging
current the charger supplies to the battery so that a sum of the
current applied to the load and the current charged to the battery
becomes a value assigned in advance, wherein the control circuit
controls a charging voltage based on a detected value of the
charging voltage to the battery so that the charging voltage
becomes equal to or lower than a value assigned to the battery.
.Iaddend.
.Iadd.78. A charge control circuit as set forth in claim 77,
wherein the control circuit controls a charging current based on a
detected value of the charging current to the battery so that the
charging current becomes equal to or lower than a value assigned to
the battery. .Iaddend.
.Iadd.79. A charge control circuit as set forth in claim 77,
wherein the value assigned in advance is a maximum permissible
supply current of the AC adapter. .Iaddend.
.Iadd.80. A charge control circuit as set forth in claim 77,
wherein the control circuit controls the charging current the
charger supplies to the battery, based on sensed information on
input from the connector, so that a sum of the current applied to
the load and the current charged to the battery becomes the value
assigned in advance. .Iaddend.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a control system for charging
which enables efficient charging of rechargeable batteries, a
control system for charging which enables accurate charging of the
rechargeable batteries, and an electronic apparatus which enables
measurement of the charging/discharging current of the rechargeable
batteries by a simple configuration.
2. Description of the Related Art
A portable electronic apparatus such as a notebook computer carries
batteries as the power supply for the apparatus. Generally,
rechargeable batteries (rechargeable batteries) such as NiCd, NiMH
(nickel metal hydride), or Li+ batteries are mounted due to the
operating costs of the apparatus, the desire for an instantaneously
dischargable current capacity, etc. Also, there are many examples
in which a charger is built in so as to enable easy charging of the
rechargeable batteries mounted inside the apparatus by just
connecting an AC adapter etc. to the apparatus.
In such a portable electronic apparatus, usually the internal
rechargeable batteries are used as the power supply of the
apparatus, but when operating the apparatus on a desk etc., the
apparatus is also operated while drawing power from an external
power source through an AC adapter.
If the power which can be supplied from the AC adapter connected to
the apparatus is sufficiently larger than the maximum power used by
the apparatus and the maximum power necessary for the charging of
the rechargeable batteries, it is possible to simultaneously
operate the apparatus and charge the internal rechargeable
batteries. However, where the capability of the AC adapter is
smaller than this, supply of power for both of the operation of the
apparatus and the charging of the internal batteries becomes
impossible. Therefore, just one of them is performed in accordance
with the status of use of the apparatus. AC adapters actually used
for such apparatuses are limited in the amount of power which they
can supply due to cost and size factors. In general, it is a rare
that both operations are simultaneously carried out
Usually, so as to minimize the cost and size of the AC adapter,
generally the capability of the AC adapter is set to the larger of
the poorer necessary for the charging of the internal rechargeable
batteries and the maximum power to be used by the apparatus. Also,
in an apparatus designed to operate on the batteries, generally the
power for charging the internal rechargeable batteries is larger
than the maximum power consumption of the apparatus. This is
because if the reverse were true, then the time during which the
apparatus could be operated on the batteries would become shorter
than the time required for charging the batteries. This would not
be practical for a commercial apparatus.
In view of this situation, up until now the method has been adopted
of having the charger which is mounted inside the apparatus
constantly monitor the status of the apparatus and charge the
rechargeable batteries when the power switch of the apparatus is
turned OFF, stop the charging to the rechargeable batteries when
the power switch of the apparatus has been turned ON, and restart
the charging when the power switch of the apparatus is returned to
the OFF position. Namely, in this configuration, the charging to
the rechargeable batteries was earned out when the apparatus was
not being operated and the charging to the rechargeable batteries
was stopped when the apparatus was being operated.
With this setup, however, when there is excess capability of the AC
adapter, efficient charging cannot be performed. Therefore,
recently, the method has been adopted wherein, where the capability
of the AC adapter is larger by a certain extent than the maximum
power to be used by the apparatus, when the power switch of the
apparatus is turned ON, the current for charging the rechargeable
batteries is lowered and the charging is continued, and when the
power switch of the apparatus is turned OFF, the charging is
carried out by the original charging current. Namely, in this
configuration, when the apparatus is not being operated, a large
charging current is generated for charging the rechargeable
batteries, while when the apparatus is being operated, a small
charging current is generated for charging the rechargeable
batteries.
In a conventional charging system having such a configuration, as
will be explained in detail later with reference to the drawings,
usually the completion of the charging is detected by using the
"history control technique", that is, monitoring the elapse of
time, and "maximum temperature control technique", that is,
monitoring the maximum temperature. Between these two, the most
widely used technique has been the detection of the completion of
charging by monitoring the elapse of time from the start of the
charging.
Further, there are sometimes demands for measurement of the
discharging current of the rechargeable batteries as well in such
charging processing. Conventionally, such demands have been met by
the technique of preparing, separately from a first sense resistor
for detecting the charging current of the rechargeable batteries, a
second sense resistor for detecting the charging current of the
rechargeable batteries and detecting the discharging current of the
rechargeable batteries using this second sense resistor.
However, there was a problem in that efficient charging was not
possible when, as in the related art, a larger of two levels of
charging current was generated for charging the rechargeable
batteries when the power switch of the apparatus is turned OFF and
a smaller of two levels of charging current was generated for
charging the rechargeable batteries when the power switch of the
apparatus is turned ON.
Namely, according to this related art the magnitude of the charging
current must be set irrespective of the magnitude of the current
consumed by the apparatus, so the charging current when the power
switch of the apparatus is turned ON must be set to the lowest
level, that is, the one for when the current consumption becomes
the greatest. Due to this, there was a problem in mat the charging
was not performed using the capability of the external power source
such as the AC adapter to the fullest extent.
Also, when the power switch of the apparatus was left in the ON
position, irrespective of whether or not the apparatus was actually
being operated, the rechargeable batteries were charged with a
small charging current. Therefore, there was a problem that
efficient charging was not performed.
If a method of detecting the completion of charging of the
rechargeable batteries by monitoring the elapse of time from the
start of the charging is adopted as in the related art where the
charging current generated by the charger dynamically changes,
there was a problem that the completion of charging of the
rechargeable batteries could not be accurately detected.
Further, if the method is adopted of preparing a sense resistor for
detecting the charging current of the rechargeable batteries and a
separate sense resistor for detecting the discharging current of
the rechargeable batteries as in the related art, there was a
problem mat two sense resistors became necessary and therefore the
charging/discharging current of the rechargeable batteries could
not be measured by a simple configuration.
SUMMARY OF THE INVENTION
The present invention was made in consideration with this situation
and has as its object to provide a novel control system for
charging which enables efficient charging of rechargeable
batteries, to provide a novel control system for charging which
enables accurate charging of the rechargeable batteries, and to
provide a novel electronic apparatus which enables the
charging/discharging current of the rechargeable batteries to be
measured by a simple configuration.
To attain the above object the present invention provides a control
system for charging in an electronic apparatus which charges its
rechargeable batteries by using a charger circuit when driving the
apparatus by using an external power source, including a first
detecting means for detecting a differential value between a
maximum permissible charging current allowed by the rechargeable
batteries and a charging current flowing to the rechargeable
batteries; a second detecting means for detecting a maximum usable
current by detecting a differential value between a maximum
supplyable current allowed by the external power source and the
current consumption of the apparatus; a third detecting means for
detecting a differential value between a maximum useable current
and the charging current flowing to the rechargeable batteries; and
a control means for controlling the system in accordance with the
differential values detected by the first and third detecting means
so that the charger circuit generates the maximum charging current
within the range where, the purging current flowing to the
rechargeable batteries does not exceed either of the maximum
permissible charging current and the maximum useable current
BRIEF DESCRIPTION OF THE DRAWINGS
The above object and features of the present invention will be mare
apparent from the following description of the preferred
embodiments with reference to the accompanying drawings,
wherein:
FIG. 1 is a view of the configuration of a first embodiment of the
present invention;
FIG. 2 is a view of the configuration of a second embodiment of the
present invention;
FIGS. 3A and 3B are views of the configurations of third and fourth
embodiments of the present invention;
FIG. 4 shows a concrete example of the present invention;
FIG. 5 shows a concrete example of a control circuit;
FIG. 6 shows a concrete example of a PWM comparator;
FIGS. 7A and 7B are views for explaining the operation of the PWM
comparator;
FIG. 8 shows a concrete example of a current measuring circuit;
FIGS. 9A and 9B show the flow of processing to be executed by a
microcontroller;
FIG. 10 is a graph of the characteristics of an AC adapter;
FIG. 11 shows a fifth embodiment of the present invention;
FIG. 12 shows another concrete example of the control circuit;
FIG. 13 is a view for explaining the related art; and
FIG. 14 is another view for explaining the related art.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Before describing the preferred embodiments of the present
invention, the related art and the disadvantages therein will be
described with reference to the related drawings.
A conventional configuration is illustrated in FIG. 13.
In the figure, the rechargeable batteries are constituted by
series-connected battery cells. The DC connector is a connector for
receiving power from the outside when operating the apparatus on an
external power source such as an AC adapter or charging the
rechargeable batteries mounted inside the apparatus by the external
power source such as an AC adapter. The DC/DC converter is the
power supply circuit for the apparatus which receives power from
the external power source supplied via the DC connector or the
rechargeable batteries and produces the voltage required by the
apparatus.
The charger is a constant current source for producing the power
necessary for charging the rechargeable batteries when power is
supplied from the outside via the DC connector. The charging
control portion is a control mechanism for controlling the start of
the charging of the rechargeable batteries or end of the charging
in accordance with the state of the power supply from the DC
connector or the operation of the apparatus and, at the same time,
for controlling the magnitude of the charging current which is
generated by the charger.
D.sub.1 and D.sub.4 are protection diodes for preventing reverse
current which prevent the flow of power from the rechargeable
batteries to the outside when the AC adapter is not operating due
to the fact no AC power is being supplied to the AC adapter etc.
D.sub.2 is a protection diode for supplying power from the
rechargeable batteries to the DC/DC converter when power is not
being supplied from the outside and, at the same time, preventing
the supply of any voltage supplied from the outside via the DC
connector to the rechargeable batteries.
The charger is a DC-DC circuit which operates under a FWM control
mode. It is constituted by an ON.cndot.OFF controlled main
transistor Tr.sub.1 for switching, a choke coil L.sub.1, a
fly-wheel diode D.sub.3, a smoothing capacitor C.sub.1, resistors
R.sub.0, R.sub.1, R.sub.2, R.sub.3, and R.sub.4 for controlling the
current, and a DC/DC control portion for handling constant current
control processing. The resistor R.sub.0 is a sense resistor for
measuring the current charged to the rechargeable batteries. The
voltage drop caused by this current is divided by the resistor
R.sub.1 and the resistor R.sub.2 and, at the same time, divided by
the resistor R.sub.3 and resistor R.sub.4 and input to the DC-DC
control portion. The resistor R.sub.5 is a voltage-dividing
resistor for controlling the sense potential of the charging
current measured by the resistor R.sub.0 and switches the magnitude
of the current which is generated by changing the resistance value
of the resistor R.sub.4 which is connected in parallel.
This charger operates so as to generate arbitrarily determined
currents by the resistance values of the resistors R.sub.0,
R.sub.1, R.sub.2, R.sub.3, and R.sub.4. It operates under two
current modes in accordance with the valid or invalid state of the
resistor R.sub.5 indicated by the charging control portion. This
constant current operation is the same as that of a regulator of a
switching mode. Here, when the microcontroller side of the resistor
R.sub.5 is in the open state and low level state, the resistor
R.sub.5 becomes valid and invalid, respectively.
When the system is constituted in this way, when power is supplied
from the outside by connection of the AC adapter or the like to a
DC connector, the external power is supplied to the DC/DC converter
via the diode D.sub.1. The DC/DC converter produces the voltage
required by the apparatus in accordance with this. At this time,
the external power is blocked by the diode D.sub.2 from being
applied to the rechargeable batteries.
On the other hand, when power is supplied from the outside, the
power is supplied to the rechargeable batteries and the charging
carried out only when charging has been instructed and the charger
is operating. When the charger stops, the circuit is cut by the
main transistor Tr.sub.1 and no power is supplied to the
rechargeable batteries. If the supply of power from the outside is
interrupted, the power of the rechargeable batteries is supplied to
the DC/DC converter via the diode D.sub.2, and the DC/DC converter
produces the voltage required by the apparatus in accordance with
it. At this time, the power is blocked by the diodes D.sub.1 and
D.sub.4 from flowing to the outside.
When the charger operates by the supply of power from the outside,
the power produced by the charger is given to the rechargeable
batteries via the diode D.sub.4, whereby the rechargeable batteries
are charged. At this time, the diode D.sub.2 is in a backward
biasing state since the voltage which is input from the DC
connector is higher than the voltage of the charger. Therefore, the
charging current of the rechargeable batteries will not leak to the
DC/DC converter side.
During this charging processing, the charging control portion
controls the ON.cndot.OFF state of the charger and controls the
switching of the charging current by constantly monitoring the
presence/absence of supply of power from the DC connector and the
ON.cndot.OFF state of the power switch of the apparatus. Namely,
when power is supplied from the outside via the DC connector, when
the power switch of the apparatus is in the OFF state and thereby
the apparatus is not being operated, it controls the voltage on the
microcontroller side of the resistor R.sub.5 so as to generate a
larger of two levels of charging currents and charge the
rechargeable batteries, while when the power switch of the
apparatus is in the ON state and thereby the apparatus is being
operated, it controls the voltage on the microcontroller side of
the resistor R.sub.5 to generate the smaller of the two levels of
charging currents and charge the rechargeable batteries.
With such charging processing, if the charging is not terminated by
accurately grasping the completion of the charging, there would be
a problem of an adverse effect exerted upon the rechargeable
batteries, which would lead to a reduction of the service life of
the batteries. For example, if there is insufficient charging, this
means that the full capacity of the batteries could not be drawn
upon and the operating time of the apparatus on the batteries would
be reduced. Also, in rechargeable batteries such as NiCd, NiMH, and
Li+ batteries, the only problem with insufficient charging would be
that the rated capacity could not be obtained, but in rechargeable
batteries such as lead-acid batteries, insufficient charging would
cause actual deterioration of the batteries. Also, conversely, when
the charging is excessively increased so as to try to fully utilize
the capacity of the batteries, the batteries became overcharged,
which is a cause of deterioration of batteries.
As a means for determing when the rechargeable batteries are
adequately charged, there are the method of monitoring the elapse
of time from the start of the charging, the method of monitoring
when the voltage of the rechargeable batteries reaches the maximum
voltage value, the method of monitoring when the temperature of the
rechargeable batteries reaches a maximum temperature value, the
method of monitoring when the rate of temperature change of the
rechargeable batteries reaches a maximum rate of temperature
change, and the method of using the characteristic that the voltage
of the rechargeable batteries slightly drops when charging is
completed (so-called -.DELTA.V characteristic). However, when
charging over a long time, that is, charging with a small charging
current in comparison with the charge capacity, control by
monitoring the maximum voltage, control by monitoring the maximum
rate of temperature change, and control by monitoring the -.DELTA.V
characteristic are not possible.
In view of this, conventionally, as previously mentioned, usually
there is adopted the method of detecting the completion of charging
by using the "history control technique" and the "maximum
temperature control technique". Between these two, the former, that
is, the technique of detecting the completion of charging by
monitoring the elapse of time from the start of charging has been
particularly widely used.
Also, as previously mentioned, there are sometimes demands for
measurement of the discharging current of the rechargeable
batteries as well in such charging processing. Conventionally, as
shown in FIG. 14, such demands have been met by the technique of
preparing, separately from the sense resistor R.sub.0 for detecting
the charging current of the rechargeable batteries, a sense
resistor R.sub.x for detecting the discharging current of the
rechargeable batteries and detecting the discharging current of the
rechargeable batteries using this sense resistor R.sub.x.
The above conventional configurations, however, suffered from the
problems mentioned above.
The present invention provides a novel control system for charging
which enables efficient charging of rechargeable batteries, a novel
control system for charging which enables accurate charging of the
rechargeable batteries, and a novel electronic apparatus which
enables the charging/discharging current of the rechargeable
batteries to be measured by a simple configuration.
The basic configurations of the embodiments of the present
invention will be illustrated in FIG. 1 through FIG. 3A and 3B.
In the figures, 1 is an electronic apparatus provided with the
present invention. It is provided with a load circuit 2 for
executing the signal processing, a rechargeable battery 3 for
supplying power to the load circuit 2, and a charger circuit 4 for
generating a charging current for the rechargeable battery 3 by
using power from an external power source.
The electronic apparatus 1 illustrated in FIG. 1 is provided with a
charging current detecting means 10 for detecting the charging
current flowing to the rechargeable battery 3; a current
consumption detecting means 11 for detecting the current consumed
by the load circuit 2; a first detecting means 12 for detecting a
differential value between a maximum permissible charging current
allowed by the rechargeable battery 3 and the charging current
which is detected by the charging current detecting means 10; a
second detecting means 13 for detecting a maximum useable current
by detecting a differential value between a maximum supplyable
current allowed by the external power source and the current
consumption detected by the current consumption detecting means 11;
a third detecting means 14 for detecting a differential value
between the maximum useable current detected by the second
detecting means 13 and the charging current detected by foe
charging current detecting means 10; a fourth detecting means 15
for detecting a differential value between the maximum permissible
supply voltage allowed by the rechargeable battery 3 and the
voltage applied to the rechargeable battery 3; and a control means
16 for controlling the charging current generated by the charger
circuit 4.
The electronic apparatus 1 illustrated in FIG. 2 is provided with a
charging current detecting means 20 for detecting a charging
current flowing to the rechargeable battery 3; a first detecting
means 21 for detecting a differential value between the maximum
permissible charging current allowed by the rechargeable battery 3
and the charging current detected by the charging current detecting
means 20; a second detecting means 22 for detecting a differential
value between the lowest permissible output voltage allowed by the
external power source and the voltage which is output by the
external power source; a third detecting means 23 for detecting a
differential value between the maximum permissible supply voltage
allowed by the rechargeable battery 3 and the voltage which is
applied to the rechargeable battery 3; and a control means 24 for
controlling the charging current which is generated by the charger
circuit 4.
The electronic apparatus 1 illustrated in FIG. 3A is provided with
a detecting means 30 for detecting the charging current flowing to
the rechargeable battery 3; an integrating means 31 which
integrates the charging current which is detected by the detecting
means 30; and an issuing means 32 for issuing a charging end
command to the charger circuit 4.
The electronic apparatus 1 illustrated in FIG. 3B is provided with
a sense resistor 40 for detecting the charging current flowing to
the rechargeable battery 3 on the rechargeable battery 3 side from
the connection point between the charger circuit 4 and the power
simply circuit of the apparatus and, at the same time, provided
with a current measuring means 41 for receiving the voltages at the
two ends of the sense resistor 40 as inputs, discriminating which
of the two input voltages is bigger, and producing a voltage in
accordance with the differential value between these two input
voltages.
In the first embodiment illustrated in FIG. 1, when the apparatus
is driven using power supplied from an external power source, the
control means 16 performs the control according to the differential
values detected by the first detecting means 12, third detecting
means 14, and the fourth detecting means 15 so that the charger
circuit 4 generates the maximum charging current within the range
where the charging current flowing to the rechargeable battery 3
does not exceed either of the minimum permissible charging current
and the maximum useable current and the voltage to be applied to
the rechargeable battery 3 does not exceed the maximum permissible
supply voltage.
Namely, when one or more of the differential values detected by the
first detecting means 12, third detecting means 14, and the fourth
detecting means 15 exceeds the limit value, the differential value
which exceeds the limit value to the most extent is specified. When
none exceeds the limit value, the differential value nearest zero
is specified. The charging current which is generated by the
charger circuit 4 is controlled so that the specified differential
value becomes the zero value.
According to the control processing of this control means 16, in
the first embodiment illustrated in FIG 1, the rechargeable battery
3 is charged with the maximum charging current within a range
allowed by both of the rechargeable battery 3 and the external
power source, and therefore rapid charging of the rechargeable
battery 3 at the time of operation of the electronic apparatus 1
becomes possible.
On the other hand, in the second embodiment illustrated in FIG. 2,
when the apparatus is driven by using power given from an external
power source, the control means 24 performs control according to
the differential values detected by the first detecting means 21,
the second detecting means 22, and the third detecting means 23 so
that the charger circuit 4 generates the maximum charging current
with a range where the charging current flowing to the rechargeable
battery 3 does not exceed the permissible charging current, the
output voltage which is output by the external power source is not
lowered to less than the lowest permissible output voltage, and the
voltage to be applied to the rechargeable battery 3 does not exceed
the maximum permissible supply voltage.
Namely, when one or mare of the differential values detected by the
first detecting means 21, second detecting means 22, and third
detecting means 23 exceeds the limit value, the differential value
that exceeds the limit value to the greatest extent is specified.
When none exceeds the limit value, the differential value nearest
zero is specified. The charging current which is generated by the
charger circuit 4 is controlled so that the specified differential
value becomes the zero value.
According to the control processing of this control means 24, in
the second embodiment illustrated in FIG. 2, the rechargeable
battery 3 is charged with the maximum charging current within a
range allowed by both of the rechargeable battery 3 and the
external power source, and therefore rapid charging of the
rechargeable battery 3 at the time of operation of the electronic
apparatus 1 becomes possible.
On the other hand, in the third embodiment illustrated in FIG. 3A,
when the charger circuit 4 generates a charging current which
changes in accordance with the operating state of the apparatus so
as to charge the rechargeable battery 3, the detecting means 30
detects the charging current flowing to the rechargeable battery 3,
the integrating means 31 receives this detection result and
integrates the detected charging current, and the issuing means 32
receives this integration result and decides whether or not the
total value of the integrated charging current and the current
capacity possessed by the rechargeable battery 3 at the time of
start of the charging has reached the maximum current capacity of
the rechargeable battery 3 and, when deciding it has, issues a
command for ending the charging to the charger circuit 4.
In this way, in the third embodiment illustrated in FIG. 3A, even
if the charging current generated by the charger circuit 4
dynamically changes, it becomes possible to accurately detect the
completion of charging of the rechargeable battery 3 by using the
charging current
On the other hand, in the fourth embodiment illustrated in FIG. 3B,
the charger circuit 4 generates a charging current of a constant
current mode to be used for the charging of the rechargeable
battery 3 by using the charging current detected by the sense
resistor 40. In this sense resistor 40, the discharging current
from the rechargeable battery 3 will also flow. The current
measuring means 41 receives the charging/discharging current
flowing through this sense resistor 40. When it has, for example,
two input ports, the means 41 outputs a voltage in accordance with
the magnitude of the charging current to one input port when the
charging current flows through the sense resistor 40, and outputs a
voltage in accordance with the magnitude of the discharging current
to the other input port when the discharging current flows through
the sense resistor 40.
In this way, in the fourth embodiment illustrated in FIG. 3B, by
making joint use of one resistor for the sense resistor for the
detection of the charging current and the sense resistor for the
detection of the discharging current, it becomes possible to
measure the charging/discharging current of the rechargeable
battery 3 with a simple configuration.
Below, the present invention will be explained in further detail
according to specific examples.
One specific example of the present invention will be illustrated
in FIG. 4.
In the figure, 50 is a rechargeable battery, that is, a
rechargeable battery constituted by the series-connected battery
cells; 51, a DC connector, that is, a connector for receiving power
from the outside when operating the apparatus by an AC adapter or
when charging the rechargeable battery 50 mounted inside the
apparatus by the AC adapter; 52, a DC/DC converter, that is, a
power supply circuit for the apparatus which receives the supply of
power from an external power source supplied via the DC connector
51, or from the rechargeable battery .50 and thereby produces the
voltage required by the apparatus; 53, a charger, that is, a
constant current source for producing the power necessary for
charging the rechargeable battery 50 when the power is supplied
from the outside via the DC connector 51; 54, a control circuit
constructed inside the charger 53, that is, a control mechanism for
executing constant current control under the PWM control mode; 55,
a current measuring circuit, that is, a measuring circuit for
measuring the charging/discharging current of the rechargeable
battery 50; and 56, a microcontroller, that is, a charging control
mechanism for issuing commands for the start and end of the
charging.
D.sub.1 and D.sub.4 are protection diodes for preventing reverse
current which prevent power from flowing out from the rechargeable
battery 50-to the outside when the AC adapter is not being operated
due to the fact AC power is not supplied to the AC adapter etc.
D.sub.2 is a protection diode for supplying the power from the
rechargeable battery 50 to the DC/DC converter 52 when the power is
not supplied from the outside and, at the same time, for preventing
the voltage from being applied to the rechargeable battery 50 when
the power is supplied from the outside via the DC connector 51.
Tr.sub.1 is a main transistor for switching which performs an
ON/OFF operation according to the command from the control circuit
54; L.sub.1, a choke coil; D.sub.3, a fly-wheel diode; and C.sub.1,
a capacitor for smoothing.
R.sub.0 is a sense resistor for measuring the charging current
flowing to the rechargeable battery 50. The voltage drop due to the
charging current flowing through this sense resistor R.sub.0 is
divided by the resistors R.sub.1 and R.sub.2 and, at the same time,
divided by the resistors R.sub.3 and R.sub.4 and input to an ERR1
terminal of the control circuit 54. R.sub.6 is a sense resistor for
measuring the current consumed by the apparatus. The voltage drop
due to the consumption of current flowing through this sense
resistor R.sub.6 is divided by the resistors R.sub.7 and R.sub.8
and, at the same time, divided by the resistors R.sub.9 and
R.sub.10 and input the ERR2 terminal of the control circuit 54.
A voltage e.sub.1 which is given to the ACADP-terminal of the
control circuit 54 is for notifying the supplyable maximum current
of the AC adapter to the control circuit 54 and is given as a
voltage value corresponding to the current value, e.sub.2, which is
given to a MAXC-terminal of the control circuit 54, is for
notifying the maximum charging current allowed by the rechargeable
battery 50 to the control circuit 54 and is given as a voltage
value corresponding to the current value e.sub.3, which is given to
a Vr terminal of the control circuit 54, is for notifying the
maximum supply voltage allowed by the battery to the control
circuit 54 and is given as the voltage value.
Tr.sub.2 is a switch circuit for protection for preventing the
voltage of the rechargeable battery 50 from being supplied to the
control circuit 54 and, at the same time, preventing the power from
leaking from the rechargeable battery 50 via the resistors R.sub.1
to R.sub.4 by opening the ground side of the control circuit 54
when the power is not supplied from the DC connector 51. R.sub.21
and R.sub.22 are voltage detecting resistors for turning OFF the
switch circuit Tr.sub.2 when the power is not supplied from the DC
connector 51 by detecting this.
A concrete example of the control circuit 54 will be illustrated in
FIG. 5.
As shown in this figure, the control circuit 54 is constituted by
six error amplifiers 540-1 (i=1 to 6), a triangular wave generator
541, a FWM comparator 542, and a driver 543.
This first error amplifier 540-1 (ERA.sub.1) is an amplifier for
measuring the voltage drop across the sense resistor R.sub.0 and
outputs a voltage proportional to the charging current flowing
through the sense resistor R.sub.0. The fourth error amplifier
540-4 (ERA.sub.4) amplifies a differential value between the
charging current which is output by the first error amplifier 540-1
and the maximum charging current (e.sub.2) allowed by the
rechargeable battery 50 to be given to the MAXC-terminal and inputs
the amplified differential value to the PWM comparator 542.
The second error amplifier 540-2 (ERA.sub.2) is an amplifier for
measuring the voltage drop across the sense resistor R.sub.6 and
outputs a voltage proportional to the value of the consumption of
the current flowing through the sense resistor R.sub.6. A fifth
error amplifier 540-5 (ERA.sub.3) amplifies a differential value
between the current consumption value output by the second error
amplifier 540-2 and the maximum supply current value (e.sub.1)
supplyable by the AC adapter to be given to the ACADP-terminal and
outputs the same as the maximum useable current value.
A sixth error amplifier 540-6 (ERA.sub.6) amplifies a differential
value between the charging current which is output by the first
error amplifier 540-1 and the maximum useable current which is
output by the fifth error amplifier 540-5 and inputs the same to
the PWM comparator 542. A third error amplifier 540-3 (ERA.sub.3)
amplifies a differential value between the apply voltage to the
rechargeable battery 50 which is input to the first error amplifier
540-1 and the maximum supply voltage (e.sub.3) allowable by the
rechargeable battery 50 which is given to the Vr terminal and
inputs the amplified differential value to the PWM comparator
542.
Here, the error amplifier 540-i, receiving as its input the limit
value, operates so as to output the prescribed voltage when the
measured value and the limit value are equal, output a voltage
larger than the prescribed voltage thereof when the limit value is
larger than the measured value, and output a negative value or "0"
when the measured value is larger than the limit value.
The triangular wave generator 541 produces a triangular wave
voltage having a prescribed period and inputs the same to the PWM
comparator 542. The PWM comparator 542 receives as its inputs the
voltages output by the fourth error amplifier 540-4, sixth error
amplifier 540-6, and the third error amplifier 540-3 and the
triangular wave voltage output by the triangular wave generator 541
and generates a pulse having a pulse width according to the input
voltage. The driver 543 is a driver circuit for driving the main
transistor Tr.sub.1, turns ON the main transistor Tr.sub.1 during a
period when the PWM comparator 542 outputs a high level and, at the
same time, turns the main transistor Tr.sub.1 OFF during a period
when the PWM comparator 542 outputs the low level.
A concrete example of me PWM comparator 542 is illustrated in FIG.
6.
The PWM comparator 542 of this concrete example is constituted by
comparison circuits which are provided corresponding to the input
voltages from three error amplifiers, compare the output voltages
of the error amplifiers and the triangular wave voltage generated
by the triangular wave generator 541, and output a high level when
the input triangular wave voltage is smaller, and output a low
level when the input triangular wave voltage is larger, and an AND
gate which calculates the AND value of the output values of all
comparison circuits and outputs the resultant value. Due to this,
the comparison circuits generate a pulse having a pulse width
according to the output voltage of the error amplifier. The
comparison circuit corresponding to the error amplifier with the
measured value exceeding the limit value will operate so as not to
generate a pulse since the error amplifier outputs a negative value
or "0".
According to this configuration, the comparison circuits in the PWM
comparator 542 produce a long pulse at a higher level as the margin
is larger when the input voltage from the error amplifier is within
the range of the limit value and, at the same time, do not produce
a pulse when it is not within the range. The AND gate inside the
PWM comparator 542 receives the outputs of the comparison circuits
and outputs a pulse matching the output from the comparison circuit
which outputs the highest level as shown in FIG. 7B.
Namely, the PWM comparator 542 docs not generate a pulse when one
of the input voltages from the three error amplifiers exceeds the
limit and, at the same time, specifies the one nearest the limit
value when mere is no input voltage exceeding the limit value and
generates a pulse of the high level having a length in accordance
with this.
Responding to the generation of pulse of this PWM comparator 542,
the driver 543 turns the main transistor Tr.sub.1 ON during a
period when the PWM comparator 542 outputs an high level, and while
turns the main transistor Tr.sub.1 OFF during a period when the PWM
comparator 542 outputs a low level, thereby to control the
magnitude of the charging current which is generated by the charger
53 so that the output voltage of the error amplifier which becomes
the origin of generation of the pulse from the PWM comparator 542
becomes a zero value.
With a control circuit 54 of this configuration, the charger 53
charges the rechargeable battery 50 by a charging current limited
by whichever of the charging current which is detected by the sense
resistor R.sub.0 (with a limit value which is the maximum charging
current allowed by the rechargeable battery 50 and the maximum
useable current value which is output by the fifth error amplifier
540-5) and, the voltage applied to the rechargeable battery 50
(with a limit value which is the maximum supply voltage allowed by
the rechargeable battery 50) reaches the limit value first.
In this way, the rechargeable battery 50 is charged by the maximum
charging current within the range allowed by both of the
rechargeable battery 50 and the AC adapter, and therefore it
becomes possible to rapidly charge the rechargeable battery 50 at
the time of the operation of the electronic apparatus 1.
Further explaining the charging operation of the concrete example
of FIG. 4, since the AC adapter is connected to the DC connector
51, when power is supplied from the outside, the external power is
supplied to the DC/DC converter 52 via D.sub.1, and the DC/DC
converter 52 produces the voltage (OUT) required by the apparatus
in accordance with this.
At this time, if an instruction for charging is issued from the
microcontroller 56 to the control circuit 54, the control circuit
54 starts the following operation to generate the charging
current
Namely, when current consumption through the DC/DC converter 52 is
detected by the sense resistor R.sub.6, the maximum useable current
of the AC adapter which becomes useable in that current consumption
state is found. By this, it performs control so that the charging
current of the rechargeable battery 50 which is detected by the
sense resistor R.sub.0 does not exceed the minimum useable current
value thereof and, at the same time, performs control so that the
charging current thereof does not exceed the maximum charging
current allowed by the rechargeable battery 50. Then, it performs
control so that the voltage supplied to the rechargeable battery
50, which is detected by the sense resistor R.sub.0, does not
exceed the maximum supply voltage allowed by the rechargeable
battery 50.
Assume that in the embodiment of FIG. 4, the maximum charging
current allowed by the rechargeable battery 50 is 1000 mA, the
capacity of the rechargeable battery 50 is 1000 mAH, the maximum
current supplyable by the AC adapter is 1500 mA, the maximum value
of the consumption of current to be used when the apparatus
operates is 1100 mA, an average value of the consumption of current
to be used by the apparatus at the time of operation is 400 mA, and
me current consumption when the apparatus does not operate is 0 mA.
At the same time, assume that there is no limitation on the supply
voltage in the rechargeable battery 50.
When the apparatus is not operating, all of the current which is
supplied from the AC adapter can be used as the charging current of
the rechargeable battery 50, and therefore charging at the minimum
current value 1000 mA allowable by the battery becomes possible.
Accordingly, the charging ends in about 1 hour at this time.
On the other hand, when the apparatus is operating, the current
consumption dynamically changes in a range of from 0 to 1100 mA. In
the present invention, charging will be carried out while
dynamically changing the charging current in a range of from 1000
mA to 400 mA matching with this dynamic change. The average current
consumption of the apparatus is 400 mA, and therefore also this
charging current becomes 1000 mA on the average. This charging
current of 1000 mA is a value no different from that when the
apparatus is not operating. Accordingly, even if the apparatus is
operating, the charging can be carried out in about 1 hour.
In this way, the present invention adopts a method of charging by
the minimum capability of the AC adapter by dynamically changing
the charging current of the charger 53 in accordance with the
current consumption on the apparatus side by providing a function
of measuring the current consumption on the apparatus side. Thus,
it becomes possible to greatly shorten the charging time of the
rechargeable battery 50.
Contrary to this, the related art does not adopt a configuration
for dynamically detecting the dynamically changing power
consumption on the apparatus side, therefore is designed
considering the maximum power consumption. Due to this, when the
maximum power consumption at the time of the operation of the
apparatus is 1100 mA and the maximum current supplyable by the AC
adapter is 1500 mA, the current value which can be used by the
charger 53 becomes 400 mA. As a result, irrespective of the current
consumption, the charging is always carried out at 400 mA at the
time of operation of the apparatus and therefore a charging time of
about 3 hours becomes possible.
In this way, in the present invention, by charging in accordance
with the capability of the external power source, it becomes
possible to greatly shorten the charging time of the rechargeable
battery 50.
Next, an explanation will be made of the function of the current
measuring circuit 55 provided in the embodiment of FIG. 4 and the
microcontroller 56.
The current measuring circuit 55 is provided for measuring the
magnitude of the current flowing through the sense resistor
R.sub.0.
This sense resistor R.sub.0 acts as a resistor for controlling the
constant current of the charger 53 as mentioned above, and further,
as seen from the circuit configuration of FIG. 4, is provided in
the path of the discharging current of the rechargeable battery 50.
Namely, at the time of the charging of the rechargeable battery 50,
the charging current flows through this sense resistor R.sub.0,
while when the AC adapter is not connected to the DC connector 51,
the power of the rechargeable battery 50 is given to the DC/DC
converter 52. Accordingly, the discharging current will flow
through this sense resistor R.sub.0. Thus, this current measuring
circuit 55 will measure both of the charging current flowing to the
rechargeable battery 50 and the discharging current flowing out of
the rechargeable battery 50.
A concrete example of this current measuring circuit 55 will be
illustrated in FIG. 8.
As shown in this figure, the current measuring circuit 55 is
constituted by a first operational amplifier 550-1 (OP.sub.1), a
second operational amplifier 550-2 (OP.sub.2), a third operational
amplifier 550-3 (OP.sub.3) and a fourth operational amplifier 550-4
(OP.sub.4). This first operational amplifier 550-1 (OP.sub.1)
receives as input one of the voltages of the two ends of the sense
resistor R.sub.0 at a plus (non-inverting) terminal, while connects
fee minus terminal to a minus (inverting) terminal of the second
operational amplifier 550-2 via the resistor R.sub.31. The second
operational amplifier 550-2 receives as input the other voltage of
the sense resistor R.sub.0 at the plus terminal, while connects the
minus terminal to the minus terminal of the first operational
amplifier 550-1 via the resistor R.sub.31. The third operational
amplifier 550-3 receives as input the output voltage of the first
operational amplifier 550-1 at the minus terminal via the resistor
R.sub.34, while connects the plus terminal to the ground via the
resistor R.sub.37. The fourth operational amplifier 550-4 receives
as input the output voltage of the second operational amplifier
550-2 at the minus terminal via the resistor R.sub.41, while
grounds the plus terminal via the resistor R.sub.44.
By this configuration, the current measuring circuit 55 amplifies a
differential value between the value input to the plus terminal of
the first operational amplifier 550-1 and the voltage input to the
plus terminal of the second operational amplifier 550-2 and outputs
the result.
Namely, the third operational amplifier 550-3 amplifies the voltage
difference when the input voltage of the plus terminal of the first
operational amplifier 550-1 is higher than the input voltage of the
plus terminal of the second operational amplifier 550-2. Due to
this, it outputs a voltage proportional to the discharging current
flowing through the sense resistor R.sub.0. Also, the fourth
operational amplifier 550-4 amplifies the voltage difference and
outputs the result when the voltage at the plus terminal of the
first operational amplifier 550-1 is lower than the input voltage
at the plus terminal of the second operational amplifier 550-2. Due
to this, it outputs a voltage proportional to the charging current
flowing through the sense resistor R.sub.0.
In this way, the current measuring circuit 55 is designed to
measure both of the charging current and the discharging current
flowing through the sense resistor R.sub.0 and discriminates
whether the current flowing through the sense resistor R.sub.0 is
the charging current or the discharging current and produces a
voltage in accordance with the magnitude of the current.
On the other hand, the microcontroller 56 performs the charging
control processing by controlling the control circuit 54 in
accordance with the result of measurement of this current measuring
circuit 55.
FIGS. 9A and 9B show the flow of processing executed by the
microcontroller 56.
First, at step 1 (ST) as shown in the flow of processing of FIGS.
9A and 9B, the microcontroller 56 detects whether or not (he AC
adapter is attached. This processing is executed by monitoring the
output voltage of the AC adapter although this was omitted in the
embodiment of FIG. 4.
When it is detected at this step 1 that the AC adapter is attached,
the processing routine goes to step 2, at which charging of the
rechargeable battery 50 is indicated by activating the control
circuit 54. In the subsequent step 3, the remaining amount of
battery power of the rechargeable battery 50 is read out.
Subsequently, at step 4, the output voltage of the current
measuring circuit .[.50.]. .Iadd.55 .Iaddend.is read to read the
charging current flowing through the sense resistor R.sub.0 and
this is integrated to update the remaining amount of battery power
of the rechargeable battery 50.
Next, at step 5, it is detected whether or not an instruction for
stopping the apparatus has been issued. When it is detected that no
command for stopping the apparatus has been issued, the processing
routine goes to step 6, at which it is decided whether or not the
remaining amount of battery power has reach full charge. When it is
decided that it has not reached full charge the processing routine
returns to step 4, at which the remaining amount of battery power
continues to be updated. When it is decided that it has reached
full charge, the processing routine goes to step 7, at which the
control circuit 54 is stopped. At the subsequent step 8, the
remaining amount of battery power is saved and the processing is
ended.
Next at step 5, when it is detected that an instruction for
stopping the apparatus has been issued, the processing routine
immediately goes to step 7, at which the control circuit 54 is
stopped. At the subsequent step 8, the remaining amount of battery
power is saved and the processing is ended.
On the other hand, when it is detected at step 1 that the AC
adapter has not been attached, that is, when the power of the
rechargeable battery 50 is supplied to the DC/DC converter 52, the
processing routine goes to step 9, at which the remaining amount of
battery power of the rechargeable battery 50 which has been saved
is read out. Subsequently, at step 10, the output voltage of the
current measuring circuit 55 is read to read the discharging
current flowing through the sense resistor R.sub.0 and this is
integrated, thereby to update the remaining amount of battery power
of the rechargeable battery 50. Subsequently, at step 11, it is
detected whether or not an instruction for stopping the apparatus
has been issued. When it is detected that no instruction for
stopping the apparatus has been issued, the processing routine
returns to step 10, at which the remaining amount of battery power
continues to be updated. When it is detected mat an instruction for
stopping the apparatus has been issued, the processing routine goes
to step 8, at which the remaining amount of battery power is saved
and the processing is ended.
In this way, the microcontroller 56 stops the charging by
accurately detecting the completion of charging of the rechargeable
battery 50 even if the charging current which is generated by the
charger circuit 53 dynamically changes.
The example of FIG. 4 adopted a configuration of inputting the
maximum current supplyable by the AC adapter to the ACADP-terminal
of the control circuit 54 in advance, but by utilizing the
characteristic of the AC adapter, it is also possible to
automatically detect the power supply capability of this AC
adapter. According to this, it is possible to make the present
invention further practical.
An example of the correspondence between the output current [A] and
the output voltage [V] possessed by the AC adapter will be
illustrated in FIG. 10. This shows that the AC adapter has a rated
output voltage of 16.0V and a rated output current of 1500 mA.
As shown in this figure, the AC adapter maintains a voltage output
of the rated output voltage when the output current is less man the
rated output current, such as 0 to 1500 mA. If a current more than
the rated output current is required, by lowering the output
voltage to for example 15.0V, an overload state is notified to the
load side. This has the function of cutting off the voltage output
after the ultra-overload state is reached when a further larger
current is required.
This means that, when the output voltage of the AC adapter is
lowered to the prescribed lowest permissible output voltage, the
limit of the power supply capability of the AC adapter is reached.
By utilizing this characteristic, when the output voltage of the AC
adapter is lowered to the lowest permissible output voltage, the
charging current of the charger 53 is limited. This means that the
maximum supply current of the AC adapter required to be originally
input to the control circuit 54 can be omitted in the example of
FIG. 4.
A fifth embodiment of the present invention using that method is
illustrated in FIG. 11.
In the figure, the same elements as those explained referring to
FIG. 4 are indicated by the same reference numerals.
The point of difference from the embodiment of FIG. 4 is that a
configuration is adopted wherein the resistors R.sub.11 and
R.sub.12 for monitoring the output voltage of the AC adapter which
is connected to the DC connector 51 are provided in place of the
sense resistor R.sub.6 and the resistors R.sub.7 to R.sub.10 and
the output voltage of the AC adapter divided by these resistors
R.sub.11 and R.sub.12 is input to ERR2 minus terminal of the
control circuit 54. Note that, the voltage e.sub.1 corresponding to
the maximum charging current allowable by the rechargeable battery
50 is input to the ERC1 terminal of the control circuit 54. Also,
in the embodiment of FIG. 4, the maximum supply voltage allowable
by the rechargeable battery 50 given from the outside is produced
in an internal portion of the control circuit 54.
FIG. 12 illustrates an embodiment of the control circuit 54 used in
the embodiment of FIG. 11.
As shown in this figure, the control circuit 54 used in the
embodiment of FIG. 11 is constituted provided with four error
amplifiers 544-i (i=1 to 4) in place of the six error amplifiers
540-i (i=1 to 6) provided in the control circuit 54 (shown in FIG.
5) used in be embodiment of FIG. 4.
This first error amplifier 544-1 (ERA.sub.1) is an amplifier for
measuring the voltage drop across the sense resistor R.sub.0 and
outputs a voltage proportional to the charging current charging
current flowing through the sense resistor R.sub.0. The third error
amplifier 544-3 (ERA.sub.3) amplifies a differential value between
the charging current which is output by the first error amplifier
544-1 and the maximum charging current (e.sub.1) allowed by (he
rechargeable battery 50 to be given to the ERC1 terminal and inputs
this amplified differential value to the PWM comparator 542.
The second error amplifier 544-2 (ERA.sub.2) amplifies a
differential value between the voltage supplied to the rechargeable
battery 50 to be input to the first error amplifier 544-1 and the
maximum supply voltage value allowable by the rechargeable battery
50 which is given by the internal battery and inputs this amplified
differential value to the PWM comparator 542. The fourth error
amplifier 544-4 (ERA.sub.4) amplifies a differential value between
the output voltage of the AC adapter which is detected by the
resistors R.sub.11 and R.sub.12 and the lowest permissible output
voltage of the AC adapter which is given by the internal battery
(set to for example 15.0V) and inputs this amplified differential
value to the PWM comparator 542.
Responding to the voltages which are output by the third error
amplifier 544-3, second error amplifier 544-2, and the fourth error
amplifier 544-4 and the triangular wave voltage which is output by
the triangular wave generator 541, the PWM comparator 542 generates
a pulse having a pulse width dependent on the input voltage.
Receiving this pulse, the driver 543 turns the main transistor
Tr.sub.1 ON during the period when the PWM comparator 542 outputs
the high level and, at the same time, turns the main transistor
Tr.sub.1 OFF during the period when the PWM comparator 542 outputs
the low level.
This PWM comparator 542 is constituted by comparison circuits which
are provided corresponding to the input voltages from three error
amplifiers similar to that explained referring to FIG. 6 and which
compare the output voltages of the error amplifiers and the
triangular wave voltage which is generated by the triangular wave
generator 541, output the high level when the input triangular wave
voltage is smaller, and output the low level when the input
triangular wave voltage is higher and an AND gate which calculates
the AND value of the output values of all of the comparison
circuits and outputs the result. Due to this, the comparison
circuits generate pulses having pulse widths in accordance with the
output voltages of the error amplifiers. The comparison circuit
corresponding to (he error amplifier with a measured value
exceeding the limit value operates so as not to generate a pulse
since that error amplifier outputs a negative value or "0".
Due to this configuration, as shown in FIG. 7A, the comparison
circuits in the PWM comparator 542 produce long pulses of a higher
level as me margin is larger when the input voltages from the error
amplifiers are within the range of the limit value and do not
generate pulses when the input voltages are not within that range.
The AND gate inside the PWM comparator 542 outputs a pulse matching
with the output from the comparator outputting the short pulse at
the highest level as shown in FIG. 7B responding to the outputs of
these comparators.
Namely, the PWM comparator 542 does not generate a pulse when one
or more of the input voltages from the three error amplifiers
exceeds the limit value and specifies the one nearest the limit
value when there is none exceeding the limit value and generates a
pulse of the high level having a length in accordance with
this.
Responding to the generation of pulses of this PWM comparator 542,
the driver 543 turns the main transistor Tr.sub.1 ON during the
period when the PWM comparator 542 outputs the high level and turns
the main transistor Tr.sub.1 OFF during the period when the PWM
comparator 542 outputs the low level. Thus, the magnitude of the
charging current which is generated by the charger 53 is controlled
so that the output voltage of the error amplifier which originates
the pulse of the PWM comparator 542 becomes the zero value.
Due to the control circuit 54 of this configuration, the charger 53
charges the rechargeable battery 50 by a charging current limited
by whichever of the charging current which is detected by the sense
resistor R.sub.0 (with a limit value of the maximum charging
current allowed by the rechargeable battery 50), the voltage
supplied to the rechargeable battery 50 (with a limit value of the
maximum supply voltage allowable by the rechargeable battery 50),
and the output voltage of the AC adapter which is detected by the
resistors R.sub.11 and R.sub.12 (with a limit value of the lowest
permissible output voltage of the AC adapter) first reaches the
limit value. That is, the charging current which is generated by
the charger 53 is not limited up to the maximum output current
allowed by the AC adapter.
In this way, the rechargeable battery 50 is charged by the maximum
charging current within a range allowed by both of the rechargeable
battery 50 and the AC adapter, and therefore it becomes possible to
rapidly charge the rechargeable battery 50 at the time of the
operation of the electronic apparatus 1.
Now, in the fifth embodiment of FIG. 11, it is assumed that the
maximum charging current allowable by the rechargeable battery 50
is 1000 mA, the battery capacity of the rechargeable battery 50 is
1000 mAH, the maximum current supplyable by the AC adapter is 1500
mA, the maximum value of the current used when the apparatus
operates is 1100 mA, an average value of the current used by the
apparatus at the time of operation is 400 mA, and the current
consumption when the apparatus is not being operated is 0 mA. Also,
it is assumed that there is no limitation of the supply voltage in
the rechargeable battery 50.
When the apparatus is stopped, all of the current which is supplied
from the AC adapter can be used as the charging current of the
rechargeable battery 50, and therefore the charging at the maximum
current value 1000 mA allowable by the battery becomes possible.
Accordingly, the charging at this time ends in about 1 hour.
On the other hand, when me apparatus is being operated, the current
consumption dynamically changes in a range of from 0 to 1100 mA.
Here, however, it is assumed that the current consumption of the
apparatus is 1000 mA. The charger 53 operates so as to output 1000
mA since the maximum permissible charging current of the
rechargeable battery 50 is 1000 mA. However, when the charging
current which is generated by the charger 53 reaches 500 mA, the
negative current value of the AC adapter becomes 1500 mA, and from
a point of time when exceeding this 1500 mA, the output voltage of
the AC adapter starts to drop. The control circuit 54 operates so
as to limit the output of the charger 53 at the point of time when
the output voltage starts to be lowered by monitoring the output
voltage of this AC adapter, and consequently, the charging current
which is generated by the charger 53 is restricted to the value of
500 mA.
When the current consumption of the apparatus is increased and
becomes 1100 mA, a voltage drop of the AC adapter occurs along with
the increase of this current consumption. Therefore the charger 53
further decreases the charging current to be generated according to
the command of the control circuit 54 and decreases the same down
to 400 mA. Subsequently, when the current consumption of me
apparatus is decreased and becomes 800 mA, the output voltage of
the AC adapter returns to the rated voltage. As a result, the
limitation by the output voltage of the AC adapter is released and
therefore the charger 53 increases the charging current to be
generated according to the command of the control circuit 54 and
meets the voltage drop point of the AC adapter at the point of tame
when increasing the charging current to 700 mA. The current
limitation starts there.
In this way, in the present invention, in accordance with the
capacity of the AC adapter, the charging is carried out along with
the dynamic change of the current consumption of the apparatus
while dynamically changing the charging current in a range of from
1000 mA to 400 mA. The average current consumption of the apparatus
is 400 mA, and therefore also this charging current becomes 1000 mA
on the average. This charging current of 1000 mA is a current no
different from that when the apparatus is stopped, and accordingly
even if the apparatus is operating, the charging can be carried out
in about 1 hour.
In this way, the present invention adopted a method wherein a
function of measuring the current consumption on the apparatus side
by monitoring the output voltage of the AC adapter is provided. In
accordance with the current consumption on this apparatus side, the
charging current of the charger 53 is dynamically changed, thereby
to enable constant charging by the maximum capability of the AC
adapter. Due to this, the charging time of the rechargeable battery
50 can be greatly shortened.
Contrary to this, the related art does not adopt a structure for
dynamically detecting the dynamically changing power consumption on
the apparatus side and therefore is designed considering the
maximum power consumption. Due to this, when the maximum power
consumption at the time of the operation of apparatus is 1100 mA
and the maximum current supplyable by the AC adapter is 1500 mA,
the current useable by the charger 53 becomes 400 mA. As a result,
irrespective of any current consumption of the apparatus, at the
time of the operation of the apparatus, the charging is always
carried out at 400 mA, and a charging time of about 3 hours becomes
necessary.
In this way, in the present invention, by performing the charging
in accordance with the capability of the AC adapter, it becomes
possible to greatly shorten the charging time of the rechargeable
battery 50.
The present invention was explained according to the illustrated
embodiments, but the present invention is not restricted to this.
For example, in the concrete examples, the present invention was
described by using a rechargeable battery 50 in which the supply
voltage is restricted, but it is also possible to use a
rechargeable battery 50 in which the supply voltage is not
restricted. In this case, it is not necessary to constitute the
system so as to limit the charging current by this supply
voltage.
As explained above, according to the present invention, where an
electronic apparatus is provided with a rechargeable battery, it
becomes possible to charge the rechargeable battery by the maximum
charging current within a range allowed by both of the rechargeable
batteries and the external power source, and therefore it becomes
possible to rapidly charge the rechargeable battery at the time of
operation of the electronic apparatus.
Further, according to the present invention, even if the charging
current of the rechargeable batteries dynamically changes, it
becomes possible to accurately detect the completion of charging of
the rechargeable batteries. Further, according to the present
invention, by using the same resistor for the sense resistor for
the detection of the charging current of the rechargeable batteries
and the sense resistor for the detection of the discharging current
of the rechargeable batteries, it becomes possible to measure the
charging/discharging current of the rechargeable batteries with a
simple structure.
* * * * *