U.S. patent application number 10/786493 was filed with the patent office on 2004-08-26 for battery charger and method therefor.
Invention is credited to Hayashi, Isao.
Application Number | 20040164711 10/786493 |
Document ID | / |
Family ID | 32871224 |
Filed Date | 2004-08-26 |
United States Patent
Application |
20040164711 |
Kind Code |
A1 |
Hayashi, Isao |
August 26, 2004 |
Battery charger and method therefor
Abstract
To fully charge a battery by a multi-power-source battery
charger either when a DC power having a voltage corresponding to
the charging voltage of the battery is input or when a DC power
having a voltage higher than the charging voltage of the battery is
input, the supply destination of the input DC power is switched, in
accordance with the voltage of the DC power input to the battery
charger, between a controller which controls charging of the
battery in accordance with the charging voltage of the battery and
a DC/DC converter which controls the voltage and current of the DC
power supplied to the battery through the controller.
Inventors: |
Hayashi, Isao; (Kanagawa,
JP) |
Correspondence
Address: |
MORGAN & FINNEGAN, L.L.P.
345 PARK AVENUE
NEW YORK
NY
10154
US
|
Family ID: |
32871224 |
Appl. No.: |
10/786493 |
Filed: |
February 24, 2004 |
Current U.S.
Class: |
320/134 |
Current CPC
Class: |
H02J 2207/40 20200101;
H02J 7/04 20130101; H02J 7/042 20130101; H02J 7/007 20130101 |
Class at
Publication: |
320/134 |
International
Class: |
H02J 007/00 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 25, 2003 |
JP |
2003-047954 |
Feb 25, 2003 |
JP |
2003-047955 |
Claims
What is claimed is:
1. A battery charger for charging a battery, comprising: a
controller which detects a charging voltage and charging current of
the battery and controls charging of the battery in accordance with
a detection result; a converter which controls a voltage and
current of a DC power supplied to the battery; and a switch which
sets a supply destination of the input DC power to one of said
converter and said controller connected to an output of said
converter in accordance with the voltage of the input DC power.
2. The charger according to claim 1, wherein when a DC power
corresponding to the charging voltage of the battery is input, said
switch sets the supply destination of the input DC power to said
controller, and when a DC power having a voltage higher than the
charging voltage is input, said switch sets the supply destination
of the input DC power to said converter.
3. A battery charger for charging a battery, comprising: a
controller which detects a charging voltage and charging current of
the battery and controls charging of the battery in accordance with
a detection result; a converter which controls a voltage and
current of a DC power supplied to the battery; a first input
connector which supplies the input DC power to said converter; and
a second input connector which supplies the input DC power to said
controller connected to an output of said converter.
4. The charger according to claim 3, further comprising a detector
which detects whether a plug is connected to said second input
connector, wherein said controller sets a quick charging start
voltage of the battery in accordance with a detection result of
said detector.
5. The charger according to claim 4, wherein when the plug is
connected to said second input connector, said controller sets a
higher quick charging start voltage than in a case wherein no plug
is connected to said second input connector.
6. A control method of a battery charger having a controller which
detects a charging voltage and charging current of the battery and
controls charging of the battery in accordance with a detection
result, and a converter which controls a voltage and current of a
DC power supplied to the battery, the method comprising the step of
setting a supply destination of the input DC power to one of the
converter and the controller connected to an output of the
converter in accordance with the voltage of the input DC power.
7. A control method of a battery charger having a converter which
controls a voltage and current of a DC power supplied to a battery
through a switch, a first input connector which supplies the input
DC power to the converter, a second input connector which supplies
the input DC power to the switch, and a detector which detects
whether a plug is connected to the second input connector, said
method comprising steps of: setting a quick charging start voltage
of the battery in accordance with a detection result of the
detector; and detecting a charging voltage and charging current of
the battery and controlling the switch in accordance with a
detection result to control charging of the battery.
8. A computer program product storing a computer readable medium
comprising a computer program code, for a control method of a
battery charger having a converter which controls a voltage and
current of a DC power supplied to a battery through a switch, a
first input connector which supplies the input DC power to the
converter, a second input connector which supplies the input DC
power to the switch, and a detector which detects whether a plug is
connected to the second input connector, said method comprising
steps of: setting a quick charging start voltage of the battery in
accordance with a detection result of the detector; and detecting a
charging voltage and charging current of the battery and
controlling the switch in accordance with a detection result to
control charging of the battery.
9. A battery charger for charging a battery, comprising: a
controller which detects a charging voltage and charging current of
the battery and controls charging of the battery in accordance with
a detection result; a connector which charges the battery from a
detachable plug and receives supply of a DC power that operates
said controller; and a reset unit which resets an operation of said
controller when a voltage supplied to said controller decreases,
wherein said controller executes intermittent charging when the
charging current is not more than a first threshold value
I.sub.th1.
10. The charger according to claim 9, wherein said controller
starts quick charging when the charging voltage exceeds a
predetermined value after a start of charging of the battery,
starts timer-controlled supplemental charging when the charging
current is not more than a second threshold value I.sub.th2, starts
the intermittent charging when the charging current is not more
than a third threshold value I.sub.th3, and ends charging under the
timer control, and wherein the threshold values of the current have
a relationship given by I.sub.th1<I.sub.th3<I.sub.th2.
11. A control method of a controller of a battery charger having a
connector which charges a battery from a detachable plug and
receives supply of a DC power that operates the controller, and a
reset unit which resets an operation of the controller when a
voltage supplied to the controller decreases, said method
comprising steps of: detecting a charging voltage and charging
current of the battery and controlling charging of the battery in
accordance with a detection result; and executing intermittent
charging when the charging current is not more than a threshold
value I.sub.th1.
12. A computer program product storing a computer readable medium
comprising a computer program code, for a control method of a
controller of a battery charger having a connector which charges a
battery from a detachable plug and receives supply of a DC power
that operates the controller, and a reset unit which resets an
operation of the controller when a voltage supplied to the
controller decreases, said method comprising steps of: detecting a
charging voltage and charging current of the battery and
controlling charging of the battery in accordance with a detection
result; and executing intermittent charging when the charging
current is not more than a threshold value I.sub.th1.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a battery charger and, more
particularly, to a battery charger which executes
constant-voltage/consta- nt-current charging of a secondary battery
such as a lithium-ion battery.
BACKGROUND OF THE INVENTION
[0002] FIG. 10 is a view showing the connection form of a charger
and a power supply. Referring to FIG. 10, a charger 201 has a DC
input jack 202 to receive supply of a DC power. The charger 201 can
charge batteries 203 and 204. A car battery cable 205 has, at its
two ends, a plug 206 to be connected to the receptacle of the
cigarette lighter of a car and a DC input plug 207 which supplies
the DC 12- or 24-V power of the car battery to the DC input jack
202. A power adapter 208 converts an AC power supplied from an AC
input plug 209 into a DC 9.5-V power and supplies the DC power to
the DC input jack 202 through a DC input plug 210.
[0003] As shown in FIG. 10, the charger 201 capable of receiving
power from a plurality of power sources has a dedicated 3-terminal
power supply connector (DC input jack 202) and generates the
charging voltage of the battery 203 or 204 through a DC/DC
converter.
[0004] The charger of this type always generates the charging
voltage by using the DC/DC converter. For this reason, when a DC
power equal to the charging voltage of the battery is input from an
external power supply apparatus, the charging voltage of the
battery cannot be obtained. Hence, the battery cannot fully be
charged.
[0005] Charging is sometimes executed by using a power supply
apparatus which can supply a DC power to an electronic device and
simultaneously execute constant-voltage/constant-current control
according to the battery charging conditions. Generally, the power
supply apparatus is designed to cope with a rush current of an
electronic device by canceling constant-current control or changing
the constant-current control value when the output voltage drops.
Hence, under normal quick charging start conditions, an excessively
large charging current may flow to the battery to damage it or
shorten its service life.
[0006] A charger which executes battery charging control by using a
power supply for executing constant-voltage/constant-current
control for battery charging or a power adapter for receiving an AC
power and, for example, a charger shown in FIG. 15 is known.
Referring to FIG. 15, the charger 201 executes
constant-voltage/constant-current control of a DC power supplied
from the plug 206 to charge the battery 203. Generally, backflow of
the DC power from the battery 203 is prevented by arranging a
blocking element such as a diode on the output side of the power
adapter or on the input side of the charger 201.
[0007] However, when a blocking element is inserted to the power
supply line, as described above, a large-capacitance element that
allows the charging current must be used. This is disadvantageous
for cost. In some cases, no sufficient charging voltage can be
supplied to the battery 203 due to a voltage drop in the blocking
element, or the battery cannot fully be charged due to a variation
between elements.
SUMMARY OF THE INVENTION
[0008] The present invention has been made to solve the
above-described problems individually or altogether, and has as its
object to fully charge a battery by using a multi-power-source
battery charger either when a DC power having a voltage
corresponding to the charging voltage of the battery is input or
when a DC power having a voltage higher than the charging voltage
of the battery is input.
[0009] In order to achieve the above object, according to a
preferred aspect of the present invention, there is provided a
battery charger for charging a battery, comprising:
[0010] a controller which detects a charging voltage and charging
current of the battery and controls charging of the battery in
accordance with a detection result;
[0011] a converter which controls a voltage and current of a DC
power supplied to the battery; and
[0012] a switch which sets a supply destination of the input DC
power to one of the converter and the controller connected to an
output of the converter in accordance with the voltage of the input
DC power.
[0013] It is another object of the present invention to reliably
prevent any disadvantage of stop of DC power input to a battery
charger without using any blocking element.
[0014] In order to achieve the above object, according to another
preferred aspect of the present invention, there is provided a
battery charger for charging a battery, comprising:
[0015] a controller which detects a charging voltage and charging
current of the battery and controls charging of the battery in
accordance with a detection result;
[0016] a connector which charges the battery from a detachable plug
and receives supply of a DC power that operates the controller;
and
[0017] a reset unit which resets an operation of the controller
when a voltage supplied to the controller decreases,
[0018] wherein the controller executes intermittent charging when
the charging current is not more than a first threshold value
I.sub.th1.
[0019] Other features and advantages of the present invention will
be apparent from the following description taken in conjunction
with the accompanying drawings, in which like reference characters
designate the same or similar parts throughout the figures
thereof.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] FIG. 1 is a block diagram showing the arrangement of a
multi-power-source charger according to the first embodiment;
[0021] FIG. 2 is a graph showing a charging control characteristic
by the charger;
[0022] FIG. 3 is a flow chart for explaining the charging operation
of the charger;
[0023] FIG. 4 is a block diagram showing the arrangement of a
charger according to the second embodiment;
[0024] FIG. 5 is a flow chart for explaining the charging-operation
of the charger according to the second embodiment;
[0025] FIG. 6 is a block diagram showing the arrangement of a
charger according to the third embodiment;
[0026] FIG. 7 is a graph showing a charging control characteristic
when a DC power is supplied from a DC input jack 19;
[0027] FIG. 8 is a flow chart for explaining the charging operation
of the charger according to the third embodiment;
[0028] FIG. 9 is a view showing an example of a connection form of
the charger and a power adapter according to the third
embodiment;
[0029] FIG. 10 is a view showing the connection form of a charger
and a power supply;
[0030] FIG. 11 is a block diagram showing the arrangement of a
charger according to the fourth embodiment;
[0031] FIG. 12 is a graph showing a charging control characteristic
by the charger;
[0032] FIG. 13 is a flow chart for explaining the charging
operation of an MPU;
[0033] FIG. 14 is a view showing an example of a connection form of
the charger and a power adapter according to the fourth embodiment;
and
[0034] FIG. 15 is a view showing the connection form of a charger
and a power adapter.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0035] A battery charger according to the present invention will be
described next with reference to the accompanying drawings.
[0036] First Embodiment
[0037] [Arrangement]
[0038] FIG. 1 is a block diagram showing the arrangement of a
multi-power-source charger according to the first embodiment.
[0039] Referring to FIG. 1, a charger 1 has a DC input jack 2 which
receives a DC power supply, a DC input selector switch 3, a voltage
detection section 4 which detects the voltage of the DC input, a
DC/DC converter 5 for constant-voltage/constant-current control, a
regulator 6 which supplies a DC power having a predetermined
voltage to an MPU (microcontroller) 7 and the like, the charging
control MPU, a semiconductor switch 8 which turns on/off quick
charging, a resistor 9 which limits the charging current for
trickle charging, a semiconductor switch 10 which turns on/off
trickle charging, a semiconductor switch 11 which controls quick
charging, a semiconductor switch 12 which controls trickle
charging, a resistor 13 which detects the charging current, and
terminals 14 and 15 to which electrodes 17 and 18 of a battery 16
are connected.
[0040] A power supply having the same voltage as that for charging
the battery 16 or a power supply having a different voltage is
connected to the DC input jack 2. The voltage detection section 4
detects whether the voltage (to be referred to as a "DC input
voltage" hereinafter) Vin input to the DC input jack 2 is higher
than a charging voltage Vcharge of the battery 16. When the DC
input voltage is higher than the charging voltage of the battery 16
(Vin>Vcharge), the voltage detection section 4 connects the DC
input selector switch 3 to the side of the DC/DC converter 5. The
DC/DC converter 5 reduces the DC input voltage to the charging
voltage of the battery 16 so that constant-voltage/constant-curr-
ent control by the charging control MPU 7 can be executed.
[0041] When Vin is only slightly higher than Vcharge,
constant-voltage/constant-current control by the DC/DC converter 5
may be difficult. In addition, it is not preferable to supply a
voltage higher than Vcharge. However, the present invention assumes
that a DC input voltage Vin1 (>Vcharge) which allows
constant-voltage/constant-current control by the DC/DC converter 5
without any problem, or a DC input voltage Vin2 (<Vin1) that can
be supplied to the battery 16 without any problem is supplied.
Assume that the minimum input voltage that guarantees the operation
of the DC/DC converter 5 is Vcharge+Vm. In this case, when
Vin.gtoreq.Vcharge+Vm, the switch 3 is preferably connected to the
input side of the DC/DC converter 5. When Vin<Vcharge+Vm, the
switch 3 is preferably connected to the output side of the DC/DC
converter 5. The value Vm should appropriately be set in
consideration of the arrangement of the charger 1 including the
DC/DC converter 5, the value Vcharge, and errors and variations in
Vin1 and Vin2.
[0042] Upon detecting that the battery 16 is connected to the
terminals 14 and 15, the MPU 7 controls from trickle charging to
quick charging and supplement charging. After the end of charging
of the battery 16, charging control is ended. The trickle charging
of this embodiment is executed to restore the voltage of the
battery 16, which has reduced by over-discharging. In the trickle
charging, the battery 16 is charged by a smaller current than
normal charging.
[0043] On the other hand, when the DC input voltage is equal to or
lower than the charging voltage of the battery 16
(Vin.ltoreq.Vcharge), the voltage detection section 4 connects the
DC input selector switch 3 to the output side of the DC/DC
converter 5 to directly use the voltage input to the DC input jack
2 as the charging voltage of the battery 16. In this input, the
input DC power is constant-voltage/constant-current-co- ntrolled.
Hence, when the battery 16 is quickly charged, the DC input voltage
varies like the terminal voltage of the battery 16. Charging
control of the MPU 7 is the same as in the case wherein the DC/DC
converter 5 intervenes.
[0044] When the charger 1 has the above arrangement, any decrease
in voltage due to the use of the DC/DC converter 5 for a DC input
voltage equal to or lower than the charging voltage of the battery
16 can be prevented, and the battery 16 can fully be charged. In
FIG. 1, the general circuit components (e.g., the protection
circuit) of the charger 1, which are unnecessary for the
description of the present invention, are not illustrated.
[0045] [Charging Control Characteristic]
[0046] FIG. 2 is a graph showing a charging control characteristic
by the charger 1. Referring to FIG. 2, a lithium-ion secondary
battery is assumed as the battery 16. The upper portion of FIG. 2
represents a change in terminal voltage (to be referred to as a
"battery voltage" hereinafter) of the battery 16 during charging.
The lower portion of FIG. 2 represents a change in charging current
with respect to the change in battery voltage.
[0047] As shown in FIG. 2, the MPU 7 turns on the switches 12 and
10 to execute trickle charging until the battery voltage reaches
the quick charging start voltage. When the battery voltage rises to
the quick charging start voltage (timing A), the switches 12 and 10
are turned off. The MPU 7 turns on the switches 11 and 8 to start
quick charging to supply the quick charging current to the battery
16. After that, the battery voltage rises to the charging voltage
(timing B). During the period (quick charging period) from the
timing A to the timing B, the DC/DC converter 5 executes
constant-current control. From the timing B, the DC/DC converter 5
shifts to constant-voltage control. The charging current decreases
in accordance with the charged state of the battery 16. When the
charging current decreases to a preset value (timing C), the MPU 7
indicates the end of charging by using, e.g., an indicator (not
shown), and supplement charging starts. This supplement charging is
generally controlled by a timer and ended as a set time elapses
(timing D).
[0048] [Charging Control]
[0049] FIG. 3 is a flow chart for explaining the charging operation
of the charger 1 and MPU 7.
[0050] When a DC power is supplied to the DC input jack 2 (S102),
the voltage detection section 4 determines whether the DC input
voltage Vin is higher than the charging voltage Vcharge of the
battery 16 (S103). If the determination result indicates that the
DC input voltage Vin is higher than the charging voltage Vcharge of
the battery 16, the switch 3 connects the DC input jack 2 to the
input side of the DC/DC converter 5 so that power conversion by the
DC/DC converter 5 starts (S104).
[0051] Upon detecting connection of the battery 16, the MPU 7 turns
on the switch 12 for trickle charging control and the switch 10 for
trickle charging ON/OFF control to start trickle charging (S106).
Connection of the battery 16 is detected by detecting the terminal
voltage of the battery 16 or by using a sensor or switch (not
shown) arranged at a portion where the battery 16 is attached to
the charger 1.
[0052] Next, the MPU 7 detects the battery voltage (S107). Upon
detecting that the battery voltage has risen to the quick charging
start voltage, the MPU 7 turns off the switch 12 for trickle
charging control, and turns on the switch 11 for quick charging
control, thus the switch 8 for quick charging ON/OFF control is
turned on to start quick charging (S108).
[0053] When the battery voltage has risen to the charging voltage,
and the charging current has decreased to a set value as charging
progresses, the MPU 7 detects the end of charging (S109). The MPU 7
indicates the end of charging (S110) and starts the timer for
supplement charging (S111). When a predetermined time has elapsed
(S112), the MPU 7 turns on the switch 11 for quick charging control
(S113). The flow returns to step S105.
[0054] Upon detecting that the battery 16 is disconnected from the
charger 1, or the charging current has become zero during charging,
the MPU 7 turns on the switches 11 and 12 to end charging (S113).
Then, the flow returns to step S105.
[0055] As described above, according to the first embodiment, the
operation of charging the battery 16 by causing the DC/DC converter
5 to drop the voltage or the operation of charging the battery 16
without intervening the DC/DC converter 5 is selected in accordance
with whether the supplied DC input voltage is higher than the
charging voltage of the battery 16. Even when a DC power equal to
the charging voltage of the battery 16, which is
constant-voltage/constant-current-controlled, is supplied to the
charger 1, the battery 16 can fully be charged.
[0056] Second Embodiment
[0057] FIG. 4 is a block diagram showing the arrangement of a
multi-power-source charger according to the second embodiment. The
same reference numerals as in the first embodiment denote the same
components in the second embodiment, and a detailed description
thereof will be omitted.
[0058] A charger 1 shown in FIG. 4 has a dedicated DC input jack 19
to which a constant-voltage/constant-current-controlled DC power is
supplied to charge a battery 16. The voltage detection section 4
and switch 3 shown in FIG. 1 are omitted. A DC input jack 2 and the
DC input jack 19 have different shapes or sizes so that they can
receive only dedicated plugs. In the first embodiment, use/nonuse
of a DC/DC converter 5 is electrically switched by detecting the
input voltage by the voltage detection section 4. However, in the
second embodiment with the above arrangement, use/nonuse of a DC/DC
converter 5 is switched by the jack to which a DC power is
supplied. The remaining operations of charging control are the same
as in the first embodiment.
[0059] FIG. 5 is a flow chart for explaining the charging operation
of the charger 1 according to the second embodiment. In the first
embodiment, the operation branches in accordance with the DC input
voltage (S103). The second embodiment is different from the first
embodiment in that the operation branches in accordance with the DC
input jack to which the DC power is supplied (S203). The remaining
operations and processes are the same as in the first
embodiment.
[0060] As described above, according to the second embodiment, the
charger 1 has the DC input jack 19 to which a
constant-voltage/constant-current-c- ontrolled DC input voltage
suitable for charging of the battery is supplied, and the DC input
jack 2 to which a DC input voltage sufficiently higher than the
charging voltage of the battery 16 is supplied. The DC input jacks
2 and 19 have different shapes. Hence, in either case, the battery
16 can fully be charged.
[0061] Third Embodiment
[0062] [Arrangement]
[0063] FIG. 6 is a block diagram showing the arrangement of a
multi-power-source charger according to the third embodiment. The
same reference numerals as in the first and second embodiments
denote the same components in the third embodiment, and a detailed
description thereof will be omitted.
[0064] A charger 1 shown in FIG. 6 has a switch 20 which detects
the insertion/removal of a DC input plug, and a pull-up resistor
21. When no DC input plug (not shown) is inserted to a DC input
jack 19, the switch 20 is ON, and a signal Sg having a voltage of 0
V (L level) is input to an MPU 7. When a DC input plug is inserted,
the switch 20 is turned off so that the signal Sg having a voltage
(H level) almost equal to the power supply voltage of the MPU 7 is
input to the MPU 7 through the pull-up resistor 21. Hence, the MPU
7 can know by the signal Sg whether a DC input plug is inserted to
the DC input jack 19.
[0065] When a DC power is supplied from the DC input jack 19, the
MPU 7 sets the quick charging start voltage (to be referred to as a
"quick charging start voltage 2" hereinafter) to be higher than the
quick charging start voltage (to be referred to as a "quick
charging start voltage 1" hereinafter) of a battery 16 in the first
or second embodiment. The MPU 7 switches setting of the charging
start voltage on a program. Alternatively, for example, two voltage
dividers may be prepared on the charging voltage detection line of
the MPU 7. In this case, selection of the voltage divider is
switched by hardware in accordance with the signal Sg to switch
setting of the quick charging start voltage.
[0066] FIG. 6 shows that the method switches the setting of the
quick charging start voltage, however, there is a case that the
quick charging start voltage is not switched, when the quick start
charging voltage exceeds the voltage to be supplied to the electric
device.
[0067] [Charging Control Characteristic]
[0068] FIG. 7 is a graph showing a charging control characteristic
when a DC power is supplied from the DC input jack 19.
[0069] The output characteristic of a power adapter connected to
the DC input jack 19 is shown at the upper right corner of FIG. 7.
The output characteristic of the power adapter has a charging
region and a rush region to deal with a rush current generated in
the normal operation of an electronic device. The power adapter is
not only connected to the charger 1 but also designed to be usable
as a power supply for an electronic device to which the battery 16
is attached. However, the rush current of an electronic device
exceeds the maximum permissible charging current (quick chargeable
current) of the battery 16. For this reason, the DC power output
from the power adapter cannot directly be supplied to the battery
16.
[0070] The voltage necessary for an electronic device is generally
higher than the quick charging start voltage (quick charging start
voltage 1) of the battery 16. In the third embodiment, the quick
charging start voltage 2 is used as a condition. When a DC power is
supplied from the DC input jack 19, control is executed such that
quick charging starts simultaneously as the battery voltage exceeds
the quick charging start voltage 2. In other words, when the
battery voltage exceeds the voltage necessary for the electronic
device, the output characteristic of the power adapter enters the
charging region. As shown at the upper right corner of FIG. 7, no
current more than the quick chargeable current is output from the
power adapter. Hence, after the battery voltage exceeds the voltage
necessary for the electronic device by trickle charging and exceeds
the quick charging start voltage 2, quick charging is started. With
this operation, appropriate quick charging can be executed.
[0071] FIG. 7 shows the relationship between the charging voltage
and the charging current under such control. Trickle charging is
performed until the quick charging start voltage 2 (timing A').
Quick charging starts from the timing A'. Constant-current control
(quick charging) is executed until a timing B'. When the battery
voltage has reached the charging voltage of the battery 16, the
control shifts to constant-voltage control. The charging current
decreases in accordance with the charged state of the battery 16.
When the charging current decreases to a preset current value
(timing C'), supplement charging starts. The charging is ended by
the above-described timer control (timing D').
[0072] [Charging Control]
[0073] FIG. 8 is a flow chart for explaining the charging operation
of the charger 1. In the first embodiment, the operation branches
in accordance with the DC input voltage (S103). The third
embodiment is different from the first embodiment in that the
operation branches in accordance with the DC input jack (S203), as
in the second embodiment, and that the quick charging start voltage
is set in accordance with the level of the signal Sg after the
start of trickle charging (S304 to S306). The remaining operations
and processes are the same as in the first embodiment.
[0074] [Connection Form of Charger and Power Adapter]
[0075] FIG. 9 is a view showing an example of a connection form of
the charger 1 and a power adapter according to the third
embodiment.
[0076] Referring to FIG. 9, the charger 1 can charge two batteries
16. A car battery cable 106 has, at its two ends, a plug 107 to be
connected to the receptacle of the cigarette lighter of a car and a
DC input plug 108 which supplies a DC 12- or 24-V power to a DC
input plug 2. A power adapter 109 converts an AC power supplied
from an AC input plug 110 into a DC 9.5-V power and supplies the DC
power to the DC input jack 2 through a DC input plug 111. A power
adapter 112 converts an AC power supplied from an AC input plug 113
into a DC 8.4-V, executes constant-voltage/constant-current-control
for charging of the battery 16, and supplies the DC power, which
has the output characteristic shown in the upper right of FIG. 7,
to the DC input jack 19 through a DC input plug 114.
[0077] As described above, according to the third embodiment, when
the power adapter 112 having an output characteristic that takes
battery charging into consideration is connected to the charger 1,
the quick charging start voltage is set higher than the voltage
necessary for an electronic device. Accordingly, the battery 16 can
fully be charged safely and appropriately.
[0078] Fourth Embodiment
[0079] [Arrangement]
[0080] FIG. 11 is a block diagram showing the arrangement of a
charger according to the fourth embodiment. The same reference
numerals as in the first to third embodiments denote the same
components in the fourth embodiment, and a detailed description
thereof will be omitted.
[0081] A charger 1 shown in FIG. 11 has a charging indicating LED
30.
[0082] A constant-voltage/constant-current-controlled DC voltage
suitable for charging of a battery 16 is input to a DC input jack
2. As in the first embodiment, upon detecting that the battery 16
is connected to terminals 14 and 15, a charging control MPU 7
controls from trickle charging to quick charging and supplement
charging. After the end of charging of the battery 16, charging
control is ended.
[0083] The DC power input to the DC input jack 2 is
constant-voltage/constant-current-controlled. Hence, during quick
charging of the battery 16, the input voltage varies almost like
the terminal voltage of the battery 16.
[0084] The arrangement shown in FIG. 11 does not stop charging upon
detecting a decrease in input voltage. For this reason, if the DC
input plug connected to the DC input jack 2 is disconnected during
charging, the power flows back from the battery 16. A switch 8 or
10 is kept. ON, and the backflow continues even though there is no
DC input power. The charging indicating LED 30 is kept ON or
blinked to cause an indication error.
[0085] To prevent this, the MPU 7 detects the voltage across a
resistor 13 for current detection, which is proportional to the
charging current. When the detected voltage is equal to or lower
than a preset voltage, the switch 8 for quick charging or the
switch 10 for trickle charging is repeatedly turned on/off. If the
DC input plug is disconnected during charging, and switches 10 and
8 are turned off, the input voltage to a regulator 6 decreases. A
reset. IC 24 operates to reset the MPU 7 so the charging operation
of the MPU 7 stops. Since the OFF state of the switches 10 and 8 is
maintained, no backflow from the battery 16 occurs. The current
value (threshold value) at which intermittent charging-starts is
decided in consideration of the power consumed by the regulator 6,
MPU 7, and LED 30. In FIG. 11, the general circuit components of
the charger 1, which are unnecessary for the description of the
present invention, are not illustrated.
[0086] [Charging Control Characteristic]
[0087] FIG. 12 is a graph showing a charging control characteristic
by the charger 1. Referring to FIG. 12, a lithium-ion secondary
battery is assumed as the battery 16. The upper portion of FIG. 12
represents a change in battery voltage during charging. The lower
portion of FIG. 12 represents a change in charging current with
respect to the change in battery voltage.
[0088] As shown in FIG. 12, the MPU 7 turns on the switch 10 to
execute trickle charging and indicate during the trickle charging
by, ex., blinking the LED 30 until the battery voltage reaches the
quick charging start voltage. When the battery voltage rises to the
quick charging start voltage (timing A1), the trickle charging is
finished by turning off the switch 10, and quick charging starts to
supply a quick charging current to the battery 16 by turning on the
switch 8. During the period (quick charging period) from the timing
A1 to a timing B1, an external DC/DC converter executes
constant-current control. After that, when the battery voltage
rises to the battery charging voltage (timing B1), the external
DC/DC converter shifts to constant-voltage control. The charging
current decreases in accordance with the charged state of the
battery 16. When the charging current decreases to a value preset
to detect the end of charging (timing C1), the MPU 7 causes the
charging indicating LED 30 to indicate the end of charging (e.g.,
the LED 30 lights up), and supplement charging starts. When the
charging current decreases to a preset value (timing D1),
intermittent charging starts in which the switch 8 repeatedly
turned on/off. The supplement charging is generally controlled by a
timer and ended as a set time elapses (timing E1).
[0089] [Charging Control]
[0090] FIG. 13 is a flow chart for explaining the charging
operation of the MPU 7. Processes in steps S105 to S111, S112, and
S113 are the same as in FIG. 3, and a detailed description thereof
will be omitted. After the start of supplemental charging, the MPU
7 detects that the charging current decreases to the preset
intermittent charging start current value (S401) and starts
intermittent charging (S402). When the supplemental charging timer
detects the elapse of a predetermined time (S112), charging is
ended (S113).
[0091] The intermittent charging is executed at the end of charging
assuming a case wherein the DC input plug is disconnected before
the battery 16 is detached after indicating the end of charging. In
such a satiation, if the charger 1 continues the operation while
keeping the end of charging indicated, the battery 16 is wastefully
discharged. To prevent the wasteful discharging of the battery 16,
intermittent charging is started such that the operation of the
charger 1 is stopped when the DC input plug is disconnected.
[0092] Although not illustrated in FIG. 13, as a measure against
the above-described case wherein the DC input plug is disconnected
during charging, when the voltage across the resistor 13 for
current detection is equal to or lower than a preset voltage, the
MPU 7 makes an interrupt to jump the processing to step S402 to
forcibly start intermittent charging. In FIG. 13, general processes
which are unnecessary for the description of the present invention
are not illustrated.
[0093] Generally, current ripple noise is superposed on the
charging current. Hence, a circuit arrangement without any
detection error or detection considering the current ripple noise
is necessary for current detection. Especially, at a late time of
quick charging or during the supplemental charging period when the
charging current is small, intermittent charging may start before
the timing D1, or the operation may return to normal supplemental
charging after the start of intermittent charging due to the
influence of the current ripple noise. For stable start and
continuation of intermittent charging, a hysteresis is prepared in
the threshold value (current value) at which intermittent charging
starts at the end of charging. More specifically, the intermittent
charging start current value is set small to prevent any transition
to intermittent charging before the timing D1. After the start of
intermittent charging, the threshold value is set large to prevent
return to normal supplemental charging.
[0094] Let I.sub.th1 be the threshold value of the charging current
at which intermittent charging is forcibly started, I.sub.th2 be
the threshold value of the charging current at which supplemental
charging starts, and I.sub.th3 be the threshold value of the
current at which intermittent charging starts during supplemental
charging. These threshold values normally have a relationship given
by
I.sub.th1<I.sub.th3<I.sub.th2
[0095] [Connection Form of Charger and Power Adapter]
[0096] FIG. 14 is a view showing an example of a connection form of
the charger 1 and a power adapter according to the fourth
embodiment.
[0097] Referring to FIG. 14, a power adapter 112 converts an AC
power supplied from an AC input plug 113 into a DC 8.4-V power and
supplies the DC power constant-voltage/constant-current-controlled
for charging of the battery 16 to the DC input jack 2 through a DC
input plug 114.
[0098] As described above, the charger 1 according to the fourth
embodiment has no blocking element. However, even when the DC input
plug is disconnected during charging, no power backflow from the
battery 16 occurs, and the battery 16 is not wastefully discharged.
In addition, intermittent charging is executed at the end of
charging. Accordingly, even when the DC input plug is disconnected
before the battery 16 is detached, the battery 16 is not wastefully
discharged.
[0099] <Other Embodiments>
[0100] Note that the present invention can be applied to an
apparatus comprising a single device or to system constituted by a
plurality of devices.
[0101] Furthermore, the invention can be implemented by supplying a
software program, which implements the functions of the foregoing
embodiments, directly or indirectly to a system or apparatus,
reading the supplied program code with a computer of the system or
apparatus, and then executing the program code. In this case, so
long as the system or apparatus has the functions of the program,
the mode of implementation need not rely upon a program.
[0102] Accordingly, since the functions of the present invention
are implemented by computer, the program code installed in the
computer also implements the present invention. In other words, the
claims of the present invention also cover a computer program for
the purpose of implementing the functions of the present
invention.
[0103] In this case, so long as the system or apparatus has the
functions of the program, the program may be executed in any form,
such as an object code, a program executed by an interpreter, or
scrip data supplied to an operating system.
[0104] Example of storage media that can be used for supplying the
program are a floppy disk, a hard disk, an optical disk, a
magneto-optical disk, a CD-ROM, a CD-R, a CD-RW, a magnetic tape, a
non-volatile type memory card, a ROM, and a DVD (DVD-ROM and a
DVD-R).
[0105] As for the method of supplying the program, a client
computer can be connected to a website on the Internet using a
browser of the client computer, and the computer program of the
present invention or an automatically-installable compressed file
of the program can be downloaded to a recording medium such as a
hard disk. Further, the program of the present invention can be
supplied by dividing the program code constituting the program into
a plurality of files and downloading the files from different
websites. In other words, a WWW (World Wide Web) server that
downloads, to multiple users, the program files that implement the
functions of the present invention by computer is also covered by
the claims of the present invention.
[0106] It is also possible to encrypt and store the program of the
present invention on a storage medium such as a CD-ROM, distribute
the storage medium to users, allow users who meet certain
requirements to download decryption key information from a website
via the Internet, and allow these users to decrypt the encrypted
program by using the key information, whereby the program is
installed in the user computer.
[0107] Besides the cases where the aforementioned functions
according to the embodiments are implemented by executing the read
program by computer, an operating system or the like running on the
computer may perform all or a part of the actual processing so that
the functions of the foregoing embodiments can be implemented by
this processing.
[0108] Furthermore, after the program read from the storage medium
is written to a function expansion board inserted into the computer
or to a memory provided in a function expansion unit connected to
the computer, a CPU or the like mounted on the function expansion
board or function expansion unit performs all or a part of the
actual processing so that the functions of the foregoing
embodiments can be implemented by this processing.
[0109] As many apparently widely different embodiments of the
present invention can be made without departing from the spirit and
scope thereof, it is to be understood that the invention is not
limited to the specific embodiments thereof except as defined in
the appended claims.
* * * * *