U.S. patent application number 13/553189 was filed with the patent office on 2012-11-08 for device housing a battery and charging pad.
Invention is credited to Kyozo Terao, Shoichi TOYA.
Application Number | 20120280651 13/553189 |
Document ID | / |
Family ID | 42991531 |
Filed Date | 2012-11-08 |
United States Patent
Application |
20120280651 |
Kind Code |
A1 |
TOYA; Shoichi ; et
al. |
November 8, 2012 |
DEVICE HOUSING A BATTERY AND CHARGING PAD
Abstract
The charging pad (10) is provided with a position detection
controller (14) that supplies position detection signals to
position detection coils (30), and detects induction coil (51)
position from echo signals output from the induction coil (51). The
device housing a battery (50) is provided with a series capacitor
(55) connected in series with the induction coil (51), a parallel
capacitor (56) connected in parallel with the induction coil (51),
and a switching circuit (57). When the position detection
controller (14) is issuing position detection signals, the parallel
capacitor (56) is connected to the induction coil (51). When power
is transmitted from the power supply coil (11) to the induction
coil (51), the parallel capacitor (56) is not connected to the
induction coil (51) and induction coil (51) AC is output to a
rectifying circuit (53) through the series capacitor (55).
Inventors: |
TOYA; Shoichi; (Minamiawaji
City, JP) ; Terao; Kyozo; (Sumoto Sity, JP) |
Family ID: |
42991531 |
Appl. No.: |
13/553189 |
Filed: |
July 19, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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12765235 |
Apr 22, 2010 |
8248028 |
|
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13553189 |
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Current U.S.
Class: |
320/108 |
Current CPC
Class: |
H02J 50/12 20160201;
H02J 50/90 20160201; H02J 7/0042 20130101; H02J 7/025 20130101;
H02J 50/40 20160201; H02J 50/60 20160201; H02J 7/0027 20130101;
H02J 50/80 20160201 |
Class at
Publication: |
320/108 |
International
Class: |
H02J 7/00 20060101
H02J007/00 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 28, 2009 |
JP |
2009-110176 |
Claims
1. A device housing a battery and charging pad comprising: a
charging pad provided with a power supply coil; and a device
housing a battery containing an induction coil that magnetically
couples with the power supply coil, wherein the internal battery in
the device housing a battery is charged with power transmitted from
the power supply coil to the induction coil, wherein the charging
pad comprises: a case having a charging region where a device
housing a battery can be placed in a removable manner; an AC power
source connected to the power supply coil; a moving mechanism that
moves the power supply coil to a position in close proximity to the
induction coil; and a position detection controller that determines
the position of the device housing a battery placed on the charging
region and controls the moving mechanism to move the power supply
coil close to the induction coil of the device housing a battery,
wherein the position detection controller comprises: position
detection coils fixed to the case; a detection signal generating
circuit that supplies position detection signals to the position
detection coils; a receiving circuit that receives echo signals
output from the induction coil to the position detection coils due
to excitation of the induction coil by position detection signals
supplied to the position detection coils from the detection signal
generating circuit; and a discrimination circuit that determines
induction coil position from the echo signals received by the
receiving circuit; wherein the device housing a battery comprises:
a rectifying circuit connected to the induction coil that converts
AC induced in the induction coil to DC to supply the internal
battery with charging power; a series capacitor connected in series
with the induction coil to input induction coil AC to the
rectifying circuit; and a parallel capacitor connected in parallel
with the induction coil; a switching circuit that switches the
connection of the series capacitor, the parallel capacitor, and the
induction coil, wherein when power is transmitted from the power
supply coil to the induction coil, induction coil AC is output to
the rectifying circuit through the series capacitor.
2. The device housing a battery and charging pad as cited in claim
1 wherein the charging region of the charging pad is the top plate
established on the top of the case.
3. The device housing a battery and charging pad as cited in claim
1 wherein when the position detection controller issues position
detection signals, the parallel capacitor is connected to the
induction coil by the switching circuit; when power is transmitted
from the power supply coil to the induction coil, the parallel
capacitor is disconnected from the induction coil, and induction
coil AC is output to the rectifying circuit through the series
capacitor, and wherein the switching circuit is provided with a
switching device connected in series with the parallel capacitor;
when the switching device is in the ON state, the parallel
capacitor is connected in parallel with the induction coil; when
the switching device is in the OFF state, the parallel capacitor is
disconnected from the induction coil.
4. The device housing a battery and charging pad as cited in claim
3 wherein the switching device is a field effect transistor
(FET).
5. The device housing a battery and charging pad as cited in claim
1 wherein the switching circuit is provided with a pair of
series-connected switching devices; parallel capacitors are
connected in series with the pair of switching devices, the
connection node of the two switching devices is connected to the
ground line, and each switching device is connected to an end of
the induction coil through a parallel capacitor; when the pair of
switching devices is in the ON state, the parallel capacitors are
connected to the induction coil; when the pair of switching devices
is in the OFF state, the parallel capacitors are disconnected from
the induction coil.
6. The device housing a battery and charging pad as cited in claim
5 wherein the pair of switching devices are FETs.
7. The device housing a battery and charging pad as cited in claim
5 wherein the low potential side of the pair of switching devices
is connected to the ground line through a resistor.
8. The device housing a battery and charging pad as cited in claim
5 wherein the rectifying circuit is provided with a diode bridge
circuit, and the induction coil is connected to the ground line
through diodes.
9. The device housing a battery and charging pad as cited in claim
1 wherein the series capacitor and parallel capacitor are
implemented by a single series/parallel capacitor; the switching
circuit is provided with a shorting circuit that short circuits the
rectifying circuit side of the series/parallel capacitor; when the
shorting circuit short circuits the rectifying circuit side of the
series/parallel capacitor, the series/parallel capacitor is
connected in parallel with the induction coil; when the shorting
circuit is not short circuited, the series/parallel capacitor is
connected in series with the rectifying circuit and induction coil
AC is output to the rectifying circuit through the series-connected
series/parallel capacitor.
10. The device housing a battery and charging pad as cited in claim
9 wherein the shorting circuit is made up of a resistance device
and a switching device, and the switching device is controlled ON
and OFF by a control circuit.
11. The device housing a battery and charging pad as cited in claim
10 wherein the resistance device is a positive temperature
coefficient thermistor.
12. The device housing a battery and charging pad as cited in claim
10 wherein the switching device is a phototransistor that is
switched ON and OFF via light.
13. The device housing a battery and charging pad as cited in claim
1 wherein the position detection controller is provided with a
first position detection controller that roughly determines the
position of the induction coil in the device housing a battery, and
a second position detection controller that determines induction
coil position with precision, wherein the first position detection
controller is provided with a plurality of position detection
coils, a detection signal generating circuit, a receiving circuit,
and a discrimination circuit, wherein the power supply coil is
moved close to the induction coil by the first position detection
controller, and subsequently the power supply coil is moved close
to the induction coil by the second position detection
controller.
14. The device housing a battery and charging pad as cited in claim
13 wherein the AC power source has a self-excited oscillator
circuit, and the second position detection controller uses the
frequency of the self-excited oscillator circuit to detect the
induction coil position and control the moving mechanism.
15. The device housing a battery and charging pad as cited in claim
1 wherein the position detection controller is provided with a
plurality of position detection coils fixed to the top plate, a
detection signal generating circuit that supplies position
detection signals to the position detection coils, a receiving
circuit that receives echo signals output from the induction coil
to the position detection coils due to excitation of the induction
coil by position detection signals supplied to the position
detection coils from the detection signal generating circuit, and a
discrimination circuit that determines induction coil position from
the echo signals received by the receiving circuit, wherein the
discrimination circuit is provided with a memory circuit that
stores the amplitude of the echo signal induced in each position
detection coil corresponding to a given induction coil position;
and the discrimination circuit compares the amplitude of the echo
signal induced in each position detection coil with the amplitude
of echo signals stored in the memory circuit to determine the
position of the induction coil.
16. The device housing a battery and charging pad as cited in claim
1 wherein the top plate of the case is large enough to place a
plurality of devices housing a battery; during charging of the
internal battery in a device housing a battery where full-charge
has not been reached, the position detection controller controls
the moving mechanism to move the power supply coil to the position
of the induction coil of another device housing a battery to fully
charge each device housing a battery.
17. The device housing a battery and charging pad as cited in claim
16 wherein the position detection controller can detect at least
one of the following data for the internal battery being charged:
voltage, remaining capacity, and temperature; and using the
detected battery data, the position detection controller can change
the position of the power supply coil to switch the device housing
a battery being charged.
18. The device housing a battery and charging pad as cited in claim
1 wherein the top plate is translucent to allow the power supply
coil position to be visually confirmed from the outside.
19. The device housing a battery and charging pad as cited in claim
18 wherein LEDs can be provided to illuminate the power supply
coil.
20. A charging pad for charging an internal battery of a device
housing a battery comprising: a power supply coil; wherein the
device housing a battery comprises an induction coil that
magnetically couples with the power supply coil, wherein the
internal battery in the device housing a battery is charged with
power transmitted from the power supply coil to the induction coil,
wherein the charging pad further comprises: a case having a
charging region where the device housing a battery can be placed in
a removable manner; an AC power source connected to the power
supply coil; a moving mechanism that moves the power supply coil to
a position in close proximity to the induction coil; and a light
emitting diode disposed around or at a center region of the power
supply coil; wherein the light emitting diode is capable of
emitting light passing through the case corresponding to a movement
of the power supply coil.
Description
[0001] This is a continuation application of application Ser. No.
12/765,235, filed Apr. 22, 2010.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a device housing a battery
(batteries) such as a battery pack or mobile telephone, and to a
charging pad that transmits power by magnetic induction to the
device housing a battery to charge the battery inside.
[0004] 2. Description of the Related Art
[0005] A charging pad (charging stand, charging cradle) has been
developed to charge a battery housed in a device by transmitting
power from a power supply coil (primary coil) to an induction coil
(secondary coil) by magnetic induction. (Refer to Japanese
Laid-Open Patent Publication HEI 9-63655 (1997) and Utility Model
Registration No. 3011829.)
[0006] JP H09-63655 A cites a configuration with a charging pad
housing a power supply coil driven by an alternating current (AC)
power source, and a battery pack housing an induction coil that
magnetically couples with the power supply coil. The battery pack
houses circuitry to rectify the AC power induced in the induction
coil and supply the rectified power to charge the battery. With
this system, a battery pack can be placed on the charging pad to
charge the battery pack battery without direct physical
contact.
[0007] JP 3011829 U cites a configuration with a battery housed in
the bottom part of an electrical device, a secondary-side charging
adapter provided beneath the battery, and an induction coil and
charging circuit housed in the secondary-side charging adapter.
[0008] A charging pad is also cited that is provided with a power
supply coil to magnetically couple with the induction coil. The
device housing a battery is placed on the charging pad to
magnetically couple the secondary-side charging adapter, power is
transmitted from the power supply coil to the induction coil, and
the battery in the device is charged.
SUMMARY OF THE INVENTION
[0009] JP H09-63655 A has the drawback that the battery pack cannot
be charged when it is shifted out of proper position on the
charging pad. This is because if the position of a mobile
electronic device (housing a battery) is shifted relative to the
charging pad, the power supply coil and induction coil cannot
magnetically couple, and AC power cannot be transmitted from the
power supply coil to the induction coil. As described in JP 3011829
U, an alignment projection can be established on the charging pad,
and an alignment hole can be provided in the mobile electronic
device to insert the alignment projection and reduce position shift
between the mobile electronic device and the charging pad. However,
even with this structure, the power supply coil and the induction
coil cannot always be disposed in precise relative positions.
[0010] To further correct this drawback, the present applicants
developed a charging pad configured with a movable power supply
coil. This system detects the induction coil in a device housing a
battery placed on the charging pad, and moves the power supply coil
into close proximity with the induction coil. FIG. 1 is a circuit
diagram showing the charging pad 110 and the device housing a
battery 150 that is placed on the charging pad 110. The charging
pad 110 is provided with a position detection controller 114 to
detect the position of the induction coil 151. FIG. 2 shows a block
diagram of the position detection controller 114. The position
detection controller 114 is provided with a plurality of position
detection coils 130, a detection signal generating circuit 131, a
receiving circuit 132, and a discrimination circuit 133. The
plurality of position detection coils 130 is mounted inside the
charging pad case top plate where a device housing a battery 150 is
placed. The detection signal generating circuit 131 supplies
position detection signal pulses to the position detection coils
130. The receiving circuit 132 receives echo signals from the
position detection coils 130 that result from excitation of the
induction coil 151 by position detection signals supplied to the
position detection coils 130 from the detection signal generating
circuit 131. The discrimination circuit 133 determines the position
of the induction coil 151 from the echo signals received by the
receiving circuit 132. The discrimination circuit 133 is provided
with a memory circuit 137 to store the amplitude of the echo signal
induced in each position detection coil 130.
[0011] The position detection controller determines the position of
the induction coil in the following manner. [0012] (1) The
detection signal generating circuit 131 outputs a pulse detection
signal to a position detection coil 130. [0013] (2) The position
detection coil 130 is excited by the pulse detection signal. As
shown in FIG. 3, an echo signal is output from the induction coil
151 to the position detection coil 130. [0014] (3) The receiving
circuit 132 receives the echo signal. [0015] (4) Each of the
plurality of position detection coils 130 is sequentially switched
to excite each position detection coil 130 with a pulse detection
signal and receive an echo signal with that position detection coil
130. [0016] (5) The discrimination circuit 133 stores the amplitude
of the echo signal induced in each position detection coil 130 in
the memory circuit 137, and compares echo signal amplitudes to
determine the position of the induction coil 151. The amplitude of
the echo signal in a position detection coil 130 close to the
induction coil 151 is high, and echo signal amplitude drops off as
the position of the induction coil 151 becomes further away from
the detection coil 130. Consequently, the discrimination circuit
133 can determine the induction coil 151 position from echo signal
amplitude. The position detection controller 114 of FIG. 2 has
position detection coils 130 disposed in orthogonal x and
y-directions. The position of the induction coil 151 in the
x-direction is determined by x-axis detection coils 130A, and the
position of the induction coil 151 in the y-direction is determined
by y-axis detection coils 130B.
[0017] As shown in the circuit diagram of FIG. 1, a parallel
resonant circuit is formed by connecting a capacitor 153 in
parallel with the induction coil 151, and the position detection
controller 114 triggers resonance with a pulse signal causing an
echo signal to be generated. However, a capacitor 153 connected in
parallel with the induction coil 151 has the drawback that power
efficiency is reduced when the internal battery 152 is charged by
power induced in the induction coil 151.
[0018] The present invention was developed with the object of
further correcting the drawbacks described above. Thus, it is an
important object of the present invention to provide a device
housing a battery and charging pad that connect a parallel resonant
circuit to generate echo signals to accurately determine the
position of the induction coil when the battery is not being
charged, and disconnect the parallel capacitor during battery
charging to enable battery charging in a power efficient
manner.
[0019] The device housing a battery and charging pad of the present
invention have a charging pad 10 provided with a power supply coil
11, and a device housing a battery 50, 60, 70 that contains an
induction coil 51 to magnetically couple with the power supply coil
11. A battery 52 inside the device housing a battery 50, 60, 70 is
charged by power transmitted from the power supply coil 11 to the
induction coil 51. The charging pad 10 is provided with a case 20
having a charging region where a device housing a battery 50, 60,
70 can be placed in a removable manner, an AC power source 12
connected to the power supply coil 11, a moving mechanism 13 that
moves the power supply coil 11 close to the induction coil 51, and
a position detection controller 14, 44 that determines the position
of the device housing a battery 50, 60, 70 and controls the moving
mechanism 13 to move the power supply coil 11 close to the
induction coil 51 of the device housing a battery 50, 60, 70. The
position detection controller 14, 44 is provided with position
detection coils 30 fixed to a top plate 21, a detection signal
generating circuit 31 that supplies position detection signals to
the position detection coils 30, a receiving circuit 32 that
receives echo signals from the position detection coils 30
resulting from excitation of the induction coil 51 by position
detection signals supplied to the position detection coils 30 from
the detection signal generating circuit 31, and a discrimination
circuit 33 that determines induction coil 51 position from the echo
signals received by the receiving circuit 32. The device housing a
battery 50, 60, 70 is provided with a rectifying circuit 53
connected to the induction coil 51 to convert AC power induced in
the induction coil 51 to direct current (DC) to supply the battery
52 with charging power, a series capacitor 55 connected in series
with the induction coil 51 to input induction coil 51 AC to the
rectifying circuit 53, a parallel capacitor 56 connected in
parallel with the induction coil 51, and a switching circuit 57,
67, 77 that switches the connection of the series capacitor 55, the
parallel capacitor 56, and the induction coil 51. When the position
detection controller 14, 44 is issuing position detection signals,
the device housing a battery 50, 60, 70 switching circuit 57, 67,
77 connects the parallel capacitor 56 to the induction coil 51.
When power is transmitted from the power supply coil 11 to the
induction coil 51, the parallel capacitor 56 is disconnected from
the induction coil 51, and AC power is output from the induction
coil 51 to the rectifying circuit 53 through the series capacitor
55.
[0020] The device housing a battery and charging pad described
above have the characteristic that while a parallel resonant
circuit is normally connected for accurate location of the
induction coil, the parallel capacitor is disconnected during
battery charging to allow the internal battery to be charged in a
power efficient manner. This is because during detection of the
induction coil position, echo signal generation depends on
connection of the parallel capacitor to the induction coil. In
addition, during charging of the internal battery, power efficient
battery charging depends on disconnection of the parallel capacitor
to allow induction coil power to be output to the rectifying
circuit through the series-connected capacitor. Power efficiency
during charging is improved by a circuit configuration that
connects a capacitor in series with the induction coil compared to
prior art circuit configurations with a capacitor connected in
parallel with the induction coil. With this configuration, heat
generation during charging can be controlled, and the internal
battery can be charged efficiently, rapidly, and safely.
[0021] In the device housing a battery and charging pad of the
present invention, the charging region of the charging pad 10 can
be a top plate 21 established on the upper surface of the case 20.
This charging pad has the characteristic that a device housing a
battery can be placed anywhere on the top plate to efficiently
charge the battery inside.
[0022] In the device housing a battery and charging pad of the
present invention, the switching circuit 57 can be provided with a
switching device 58 connected in series with the parallel capacitor
56. When the switching device 58 is in the ON state, the parallel
capacitor 56 is connected in parallel with the induction coil 51.
When the switching device 58 is in the OFF state, the parallel
capacitor 56 is disconnected from the induction coil 51. This
device housing a battery has the characteristic that a parallel
resonant circuit can be switched into or out of the induction coil
circuit to increase power efficiency and allow efficient charging
of the internal battery while maintaining a simple circuit
structure.
[0023] In the device housing a battery and charging pad of the
present invention, the switching circuit 67 can be provided with a
pair of series-connected switching devices 68. Parallel capacitors
56 can be connected in series with the pair of switching devices
68, and the connection node of the two switching devices 68 can be
connected to the ground line 63. Each switching device 68 is
connected to an end of the induction coil 51 through a parallel
capacitor 56. When the pair of switching devices 68 is in the ON
state, the parallel capacitors 56 are connected to the induction
coil 51. When the pair of switching devices 68 is in the OFF state,
the parallel capacitors 56 are disconnected from the induction coil
51. This device housing a battery can connect a parallel resonant
circuit for accurate location of the induction coil without making
a common connection between the induction coil and the rectifying
circuit ground line. Further, this device housing a battery has the
characteristic that power efficiency can be increased to enable
efficient charging of the internal battery.
[0024] In the device housing a battery and charging pad of the
present invention, the pair of switching devices 68 can be field
effect transistors (FETs).
[0025] In the device housing a battery and charging pad of the
present invention, the rectifying circuit 53 can be provided with a
diode bridge, and the induction coil 51 can be connected to the
ground line 63 through the diodes. In this device housing a
battery, neither end of the induction coil is connected to the
ground line on the output-side of the diode bridge. This allows
induction coil output to be efficiently rectified by the diode
bridge for efficient charging of the internal battery.
[0026] In the device housing a battery and charging pad of the
present invention, the series capacitor 55 and parallel capacitor
56 can be implemented by a single series/parallel capacitor 75, and
the switching circuit 77 can be a shorting circuit 73 that short
circuits the rectifying circuit 53 side of the series/parallel
capacitor 75. When the shorting circuit 73 short circuits the
rectifying circuit 53 side of the series/parallel capacitor 75, the
series/parallel capacitor 75 is connected in parallel with the
induction coil 51. When the shorting circuit 73 is not short
circuited, the series/parallel capacitor 75 is connected in series
with the rectifying circuit 53 to output induction coil 51 AC power
to the rectifying circuit 53 through the series-connected
series/parallel capacitor 75. In this device housing a battery, a
single capacitor is switched to allow its use as both a series
capacitor and a parallel capacitor. Consequently, the device
housing a battery has the characteristic that a parallel resonant
circuit can be switched into or out of the induction
coil-rectifying circuit to improve internal battery charging
efficiency while maintaining a simple circuit structure.
[0027] In the device housing a battery and charging pad of the
present invention, the position detection controller 14 can be
provided with a first position detection controller 14A that
roughly determines the position of the induction coil 51 in the
device housing a battery 50, 60, 70, and a second position
detection controller 14B that determines induction coil 51 position
with precision. The first position detection controller 14A can be
provided with a plurality of position detection coils 30, a
detection signal generating circuit 31, a receiving circuit 32, and
a discrimination circuit 33. This charging pad can move the power
supply coil 11 close to the induction coil 51 with the first
position detection controller 14A, and subsequently move the power
supply coil 11 closer to the induction coil 51 with the second
position detection controller 14B.
[0028] The device housing a battery and charging pad described
above is provided with a first position detection controller that
roughly determines the position of the induction coil of the device
housing a battery, and a second position detection controller that
determines the position of the induction coil with precision. Since
the first position detection controller moves the power supply coil
close to the induction coil and the second position detection
controller then moves the power supply coil closer to the induction
coil, this charging pad is characterized by the ability to
accurately locate the induction coil. The first position detection
controller of the charging pad described above sends position
detection signals to the plurality of position detection coils
fixed to the top plate, the parallel resonant circuit formed by the
induction coil and parallel capacitor is excited by the position
detection signals to output echo signals back to the position
detection coils, and the echo signals are received by the receiving
circuit to determine the position of the induction coil. As a
result, the position of the induction coil can be determined
electrically over a wide detection region with the plurality of
position detection coils. Since this configuration can efficiently
locate an induction coil over a wide region, it is extremely
effective as the first position detection controller that roughly
determines the position of the induction coil of the device housing
a battery.
[0029] In the device housing a battery and charging pad of the
present invention, the AC power source 12 has a self-excited
oscillator circuit, and the second position detection controller
14B uses the frequency of the self-excited oscillator circuit to
determine the induction coil 51 position and control the moving
mechanism 13. In the charging pad described above, the second
position detection controller accurately determines the position of
the induction coil from the oscillating frequency of the AC power
source self-excited oscillator circuit.
[0030] Therefore, this charging pad has the characteristic that
induction coil position can be determined with precision by the
second position detection controller.
[0031] In the device housing a battery and charging pad of the
present invention, the position detection controller 44 can be
provided with a plurality of position detection coils 30, a
detection signal generating circuit 31 that supplies position
detection signals to the position detection coils 30, a receiving
circuit 32 that receives echo signals from the position detection
coils 30 resulting from excitation of the induction coil 51 by
position detection signals supplied to the position detection coils
30 from the detection signal generating circuit 31, and a
discrimination circuit 43 that determines induction coil 51
position from the echo signals received by the receiving circuit
32. The discrimination circuit 43 can be provided with a memory
circuit 47 to store the amplitude of the echo signal induced in
each position detection coil 30 corresponding to a given induction
coil 51 position. The discrimination circuit 43 can compare the
amplitude of the echo signal induced in each position detection
coil 30 with the amplitude of echo signals stored in the memory
circuit 47 to determine the position of the induction coil 51.
[0032] In the device housing a battery and charging pad described
above, the discrimination circuit compares the amplitude of the
echo signal induced in each position detection coil with the
amplitude of echo signals stored in the discrimination circuit
memory circuit to determine the position of the induction coil.
Consequently, the discrimination circuit can accurately determine
the position of the induction coil from the amplitude of the echo
signals induced in the position detection coils. This charging pad
can accurately determine induction coil position with the position
detection controller to rapidly move the power supply coil close to
the induction coil and efficiently charge the internal battery.
[0033] In the device housing a battery and charging pad of the
present invention, the top plate 21 of the case 20 can be made
large enough to place a plurality of devices housing a battery 50.
During charging of the battery 52 in a device housing a battery 50
where full-charge has not been reached, the position detection
controller 14 can control the moving mechanism 13 to move the power
supply coil 11 to the position of the induction coil 51 of another
device housing a battery 50. Repetition of this action can fully
charge each device housing a battery 50.
[0034] In the device housing a battery and charging pad described
above, a battery in the next device housing a battery is charged
before the battery previously being charged has reached
full-charge. Since this procedure is repeated to charge the battery
in a plurality of devices housing a battery, the charging time of
each battery can be reduced, power transmitted from the power
supply coil to the induction coil can be increased, and the
plurality of devices housing a battery can be fully charged in a
short time period. In particular, by switching the device housing a
battery under charge, this system can increase the battery charging
current to fully charge the battery rapidly while reducing
induction coil and battery heating.
[0035] In the device housing a battery and charging pad of the
present invention, the position detection controller 14 can detect
at least one of the following data from the internal battery 52
being charged: battery voltage, battery remaining capacity, and
battery temperature. Using the detected battery data, the position
detection controller 14 can change the position of the power supply
coil 11 to change the device housing a battery 50 under charge.
Since this system changes the device housing a battery being
charged based on battery data detected during charging, a battery
can be fully charged rapidly while protecting the battery under
charge.
[0036] In the device housing a battery and charging pad of the
present invention, the top plate 21 can be translucent to allow the
power supply coil 11 position to be visually confirmed from the
outside. In this system, since close positioning of the power
supply coil to the device housing a battery can be confirmed
visually, the system can be used with confidence while reliably
confirming device housing battery charging.
[0037] The device housing a battery and charging pad of the present
invention can be provided with light emitting diodes (LEDs) to
illuminate the power supply coil 11. Since the moving power supply
coil and the vicinity around the power supply coil is brightly
illuminated by the LEDs in this system, power supply coil movement
can be clearly shown while achieving an aesthetically pleasing
design.
[0038] The above and further objects of the present invention as
well as the features thereof will become more apparent from the
following detailed description to be made in conjunction with the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0039] FIG. 1 is a block diagram of a device housing a battery and
charging pad for a patent application previously submitted by the
present applicant;
[0040] FIG. 2 is a circuit diagram showing the position detection
controller of the charging pad shown in FIG. 1;
[0041] FIG. 3 is a waveform diagram showing an example of an echo
signal output from the parallel resonant circuit due to pulse
signal excitation of the induction coil and parallel capacitor of
that resonant circuit;
[0042] FIG. 4 is an oblique view of the charging pad for an
embodiment of the present invention;
[0043] FIG. 5 is an abbreviated oblique view showing the internal
structure of the charging pad shown in FIG. 4;
[0044] FIG. 6 is a horizontal cross-section view showing the
internal structure of the charging pad shown in FIG. 4;
[0045] FIG. 7 is a lengthwise vertical cross-section view of the
charging pad shown in FIG. 6
[0046] FIG. 8 is a widthwise vertical cross-section view of the
charging pad shown in FIG. 6
[0047] FIG. 9 is a circuit diagram showing the position detection
controller of the charging pad for an embodiment of the present
invention;
[0048] FIG. 10 is a block diagram of a device housing a battery and
charging pad for an embodiment of the present invention;
[0049] FIG. 11 is a block diagram showing another example of a
device housing a battery;
[0050] FIG. 12 is a block diagram showing another example of a
device housing a battery;
[0051] FIG. 13 is a waveform diagram showing an example of an echo
signal output from the parallel resonant circuit due to position
detection signal excitation of the induction coil and parallel
capacitor of that resonant circuit;
[0052] FIG. 14 is a graph showing oscillation frequency as a
function of displacement between the power supply coil and the
induction coil;
[0053] FIG. 15 is a circuit diagram showing the position detection
controller of the charging pad for another embodiment of the
present invention; and
[0054] FIG. 16 is a schematic and graph showing the signal levels
of echo signals induced in the position detection coils of the
position detection controller shown in FIG. 15.
DETAILED DESCRIPTION OF THE EMBODIMENT(S)
[0055] The following describes embodiments of the present invention
based on the figures.
[0056] FIGS. 4-10 are schematic and diagrammatic views illustrating
the structure and operating principles of the charging pad 10. As
shown in FIGS. 4, 5, and 10, devices housing a battery 50 are
placed on the charging pad 10, and the internal battery 52 is
charged utilizing magnetic induction. A device housing a battery 50
contains an induction coil 51 that magnetically couples with the
power supply coil 11, and a battery 52 that is charged by power
induced in the induction coil 51.
[0057] FIGS. 10-12 show circuit diagrams of a device housing a
battery 50, 60, 70. The device housing a battery 50, 60, 70 is
provided with a rectifying circuit 53 connected to the induction
coil 51 that converts AC induced in the induction coil 53 to DC to
supply power to the internal battery 52. The rectifying circuit 53
converts AC input from the induction coil 51 to DC and outputs that
DC power to a charging control circuit 54 that controls internal
battery 52 charging. The charging control circuit 54 fully charges
the internal battery 52 with power input from the rectifying
circuit 53. The charging control circuit 54 detects full-charge of
the internal battery 52 and stops charging. A charging control
circuit 54 for a lithium ion internal battery 52 charges the
battery 52 to full-charge by constant voltage-constant current
charging. A charging control circuit for a nickel hydride internal
battery charges the battery to full-charge by constant current
charging.
[0058] Further, the device housing a battery 50, 60, 70 of FIGS.
10-12 is provided with a series capacitor 55 connected in series
with the induction coil 51 to efficiently input induction coil 51
AC to the rectifying circuit 53, a parallel capacitor 56 connected
in parallel with the induction coil 51, and a switching circuit 57,
67, 77 to switch connection of the series capacitor 55, the
parallel capacitor 56, and the induction coil 51.
[0059] When position detection signals are output from the position
detection controller 14, the switching circuit 57, 67, 77 connects
the parallel capacitor 56 to the induction coil 51. The induction
coil 51 and parallel capacitor 56 form a parallel resonant circuit
that is excited by position detection signals issued from the
position detection controller 14 position detection coils 30 to
generate echo signals. Resonance resulting in echo signal
generation cannot be achieved by induction coil 51 connection to a
series capacitor 55 alone, and connection of a parallel capacitor
is necessary. Therefore, when the device housing a battery 50, 60,
70 is placed on the charging pad 10 and the position detection
controller 14 is determining the position of the device housing a
battery 50, 60, 70, the switching circuit 57, 67, 77 connects the
parallel capacitor 56 to the induction coil 51.
[0060] However, an induction coil 51 connected to a parallel
capacitor 56 has the drawback that power efficiency is reduced
because the induced power cannot be efficiently output to the
rectifying circuit 53. The power efficiency of power transferred
from the induction coil 51 to the rectifying circuit 53 is improved
with connection of a series capacitor 55 compared to a parallel
capacitor 56. Consequently, after the induction coil 51 position
has been detected and the power supply coil 11 has been moved close
to the induction coil 51, the switching circuit 57, 67, 77 connects
the series capacitor 55 to the induction coil 51 to output induced
power from the induction coil 51 to the rectifying circuit 53.
Specifically, when the power supply coil 11 transmits power to the
induction coil 51, the switching circuit 57, 67, 77 disconnects the
parallel capacitor 56 from the induction coil 51 to leave the
series capacitor 55 connected instead. In this configuration, AC
induced in the induction coil 51 is output to the rectifying
circuit 55 through the series capacitor 55.
[0061] The switching circuit 57 shown in FIG. 10 is provided with a
switching device 58 connected in series with the parallel capacitor
56. The series-connected parallel capacitor 56 and switching device
58 are connected in parallel with the induction coil 51. The
switching device 58 is a semiconductor switching device such as a
FET that is controlled ON and OFF by a control circuit 59. When the
switching circuit 57 switching device 58 is in the ON state, the
parallel capacitor 56 is connected in parallel with the induction
coil 51. When the switching device 58 is in the OFF state, the
parallel capacitor 56 is disconnected from the induction coil 51.
The series capacitor 55 is connected in series with the induction
coil 51 and connects the induction coil 51 to the rectifying
circuit 53.
[0062] The control circuit 59 controls the gate voltage of the FET,
which is the switching device 58, to switch the switching device 58
ON and OFF. When the position of the induction coil 51 is being
detected, the control circuit 59 holds the switching device 58 in
the ON state to connect the parallel capacitor 56 to the induction
coil 51. The induction coil 51 connected in parallel with the
parallel capacitor 56 outputs a large amplitude echo signal when
excited by a position detection signal from a position detection
coil 30. Even with the switching device 58 in the ON state, the
series capacitor 55 is connected between the induction coil 51 and
the rectifying circuit 53. However, with the switching device 58 in
the ON state, the induction coil 51 is connected in parallel with
the parallel capacitor 56 to establish a parallel resonant circuit
that outputs a large amplitude echo signal when excited by a
position detection signal.
[0063] After the induction coil 51 position has been detected and
the power supply coil 11 has been moved close to the induction coil
51, the control circuit 59 switches the switching device 58 OFF to
disconnect the parallel capacitor 56 from the induction coil 51.
Specifically, when power is transmitted from the power supply coil
11 to the induction coil 51, the control circuit 59 holds the
switching device 58 in the OFF state to disconnect the parallel
capacitor 56 from the induction coil 51. In this configuration, AC
power induced in the induction coil 51 is efficiently output to the
rectifying circuit 53 through the series capacitor 55.
[0064] The switching circuit 67 of FIG. 11 is provided with a pair
of switching devices 68 that are connected in series. The two
switching devices 68 of the figure are semiconductor switching
devices such as FETs. The pair of FETs 68A, 68B have their sources
connected together to connect the devices in series. In addition,
the connection node of the pair of switching devices 68, which is
the sources of the two FETs, is connected to the ground line 63
through a high resistance resistor 64 (for example, 100 K.OMEGA.)
to put the connection node essentially at ground potential. A
parallel capacitor 56 is connected in series with each of the two
switching devices 68. Each of the FETs 68A, 68B, which are the pair
of switching devices 68, is connected to an end of the induction
coil 51 through a drain-connected parallel capacitor 56. The
switching circuit 67 of this figure connects the series-connection
of a parallel capacitor 56, FET 68A, FET 68B, and another parallel
capacitor 56 in parallel with the induction coil 51.
[0065] The series capacitor 55 can be connected on the rectifying
circuit 53 side of the parallel capacitor 56 as shown by the solid
lines of the figure, or as shown by the broken lines, it can also
be connected between the parallel capacitor 56 and the induction
coil 51. A series capacitor 55 connected between the parallel
capacitor 56 and the induction coil 51 is connected in series with
the parallel capacitor 56 when the switching devices 68 are in the
ON state. Consequently, the total capacitance connected to the
induction coil 51 to form the parallel resonant circuit is
equivalent to the series combination of the series capacitor 55 and
the two parallel capacitors 56.
[0066] The two FETs 68A, 68B of the pair of switching devices 68
are switched ON and OFF together by the control circuit 69. The
control circuit 69 controls the gate voltages of both FETs in the
same manner to simultaneously switch the pair of switching devices
68 ON and OFF. The control circuit 69 connects the parallel
capacitors 56 in parallel with the induction coil 51 by switching
the pair of FET switching devices 68 to the ON state. When the
control circuit 69 switches the pair of switching devices 68 to the
OFF state, the parallel capacitors 56 are disconnected from the
induction coil 51.
[0067] When the position of the induction coil 51 is being
detected, the control circuit 69 described above holds the pair of
switching devices 68 in the ON state to connect the parallel
capacitors 56 to the induction coil 51. The induction coil 51
connected in parallel with the parallel capacitors 56 outputs an
echo signal when excited into parallel resonance by a position
detection signal from a position detection coil 30.
[0068] After the induction coil 51 position has been detected and
the power supply coil 11 has been moved close to the induction coil
51, the control circuit 69 switches the pair of switching devices
68 OFF to disconnect the parallel capacitors 56 from the induction
coil 51. Specifically, when power is transmitted from the power
supply coil 11 to the induction coil 51, the control circuit 69
holds the pair of switching devices 68 in the OFF state to
disconnect the parallel capacitors 56 from the induction coil 51.
In this configuration, AC power induced in the induction coil 51 is
efficiently output to the rectifying circuit 53 through the series
capacitor 55.
[0069] In the switching circuit 67 of FIG. 11, since one end of the
pair of switching devices 68 is essentially at ground, the circuit
structure of the control circuit 69 can be simplified. In
particular, when the rectifying circuit 53 is a diode bridge,
neither end of the induction coil 51 is at ground potential.
Specifically, the induction coil 51 is connected to the ground line
63 through the diodes. In this case, the circuit structure of the
control circuit 69 that controls the pair of switching devices 68
ON and OFF can be simplified.
[0070] Further, the device housing a battery 70 of FIG. 12 has a
series capacitor 55 and parallel capacitor 56 that are a single
series/parallel capacitor 75. In this device housing a battery 70,
the switching circuit 77 switches the series/parallel capacitor 75
to use it as a series capacitor 55 or as a parallel capacitor 56.
The series/parallel capacitor 75 is connected between the induction
coil 51 and the rectifying circuit 53. The switching circuit 77 is
a shorting circuit 73 that short circuits the rectifying circuit 53
side of the series/parallel capacitor 75. The shorting circuit 73
is made up of a resistance device 74 such as a positive temperature
coefficient (PCT) thermistor and a switching device 78, and the
switching device 78 is controlled ON and OFF by a control circuit
79. The switching device 78 is a phototransistor such as photo
MOS-FET that is switched ON and OFF via light. When the control
circuit 79 switches the switching device 78 ON, the shorting
circuit 73 short circuits the rectifying circuit 53 side of the
series/parallel capacitor 75 to connect the series/parallel
capacitor 75 in parallel with the induction coil 51. When the
control circuit 79 switches the switching device 78 OFF, the
shorting circuit 73 is not short circuited but rather is open
circuited. This connects the series/parallel capacitor 75 in series
with the rectifying circuit 53 to output induction coil 51 AC power
to the rectifying circuit 53 through the series/parallel capacitor
75.
[0071] As shown in FIGS. 4-10, the charging pad 10 is provided with
a power supply coil 11 connected to the AC power source 12 to
induce electromotive force (EMF) in the induction coil 51, a case
20 housing the power supply coil 11 and having a top plate 21 to
place a device housing a battery 50, a moving mechanism 13 housed
in the case 20 to move the power supply coil 11 along the inside
surface of the top plate 21, and a position detection controller 14
that detects the position of a device housing a battery 50 placed
on the top plate 21 and controls the moving mechanism 13 to move
the power supply coil 11 close to the induction coil 51 of the
device housing a battery 50. The power supply coil 11, AC power
source 12, moving mechanism 13, and position detection controller
14 are housed inside the case 20.
[0072] The charging pad 10 charges the battery 52 inside a device
housing a battery 50 in the following manner. [0073] (1) When a
device housing a battery 50 is placed on the top plate 21 of the
case 20, the position detection controller 14 detects its position.
[0074] (2) The position detection controller 14, which has detected
the position of the device housing a battery 50, controls the
moving mechanism 13 to move the power supply coil 11 along the
inside of the top plate 21 and position it in close proximity to
the induction coil 51 of the device housing a battery 50. [0075]
(3) The power supply coil 11, which has been moved close to the
induction coil 51, is magnetically coupled to the induction coil 51
and transmits AC power to the induction coil 51. [0076] (4) The
device housing a battery 50 converts the induction coil 51 AC power
to DC and charges the internal battery 52 with that DC power.
[0077] The charging pad 10, which charges the battery 52 in a
device housing a battery 50 by the procedure described above,
houses the power supply coil 11 connected to the AC power source 12
inside the case 20. The power supply coil 11 is disposed beneath
the top plate 21 of the case 20 in a manner that allows it to move
along the inside of the top plate 21. The efficiency of power
transmission from the power supply coil 11 to the induction coil 51
is improved by narrowing the gap between the power supply coil 11
and the induction coil 51. With the power supply coil 11 moved into
close proximity with the induction coil 51, the gap between the
power supply coil 11 and the induction coil 51 is preferably less
than or equal to 7 mm. Therefore, the power supply coil 11 is
disposed under the top plate 21 and positioned as close as possible
to the top plate 21. Since the power supply coil 11 is moved close
to the induction coil 51 of a device housing a battery 50 placed on
the top plate 21, the power supply coil 11 is disposed in a manner
that allows it to move along the inside surface of the top plate
21.
[0078] The case 20 that houses the power supply coil 11 is provided
with a planar top plate 21 where a device housing a battery 50 can
be placed. The charging pad 10 of FIGS. 4 and 5 has an overall
planar top plate 21 that is disposed horizontally. The top plate 21
is made large enough to allow placement of devices housing a
battery 50 having different sizes and shapes. For example, the top
plate 21 can have a rectangular shape with a side having a length
of 5 cm to 30 cm. However, the top plate 21 can also have a
circular shape with a diameter of 5 cm to 30 cm. The charging pad
10 of FIGS. 4 and 5 has a large top plate 21 that allows
simultaneous placement of a plurality of devices housing a battery
50. Here, a plurality of devices housing a battery 50 is placed on
the top plate 21 at the same time to allow sequential charging of
their internal batteries 52. Further, the top plate can also be
provided with side-walls or other barriers around its perimeter,
and devices housing a battery can be placed inside the side-walls
to charge the internal batteries.
[0079] The top plate 21 of the case 20 is translucent to allow
visual confirmation of the internal movement of the power supply
coil 11 from the outside. Since the user can visually confirm that
the power supply coil 11 is in close proximity to the device
housing a battery 50, the user can dependably confirm charging of
the device housing a battery 50. As a result, the user can operate
the charging pad 10 with confidence. Further, LEDs 19 can be
provided to illuminate the moving power supply coil 11 and its
vicinity. This can accentuate power supply coil 11 movement and
create an aesthetically pleasing design. In addition, the LEDs 19
can be configured to shine through the top plate 21 to illuminate
the device housing a battery 50. The charging pad 10 shown in FIGS.
5 and 6 has four LEDs 19 disposed at equal intervals around the
power supply coil 11. As shown in FIG. 10, these LEDs 19 are
energized by power supplied from a DC power supply 18 housed in the
charging pad 10. However, LEDs can also be disposed at the center
region of the power supply coil. In addition, the number of LEDs
used to show the power supply coil position can be three or less,
or five or more. With this charging pad 10, the device housing a
battery 50 can be illuminated during charging, or visual effects
such as the color or blinking pattern of the LEDs 19 can be changed
during charging. This type of charging pad 10 can clearly indicate
to the user the state of charging of a device housing a battery
50.
[0080] The power supply coil 11 is wound in a plane parallel to the
top plate 21, and radiates AC magnetic flux above the top plate 21.
This power supply coil 11 emits AC magnetic flux perpendicular to,
and beyond the top plate 21. The power supply coil 11 is supplied
with AC power from the AC power source 12 and radiates AC magnetic
flux above the top plate 21. Wire can be wound around a magnetic
material core 15 to make a power supply coil 11 with high
inductance. The core 15 is magnetic material with a high magnetic
permeability such as ferrite and has the shape of an open end
container. The core 15 has a solid circular cylinder 15A at the
center of the spiral wound power supply coil 11 and a circular
cylindrical enclosure 15B around the outside that are joined by a
bottom section (refer to FIGS. 7 and 8). A power supply coil 11
with a core 15 can focus magnetic flux in a specific region to
efficiently transmit power to the induction coil 51. However, a
magnetic material core is not always required in the power supply
coil, and a coil with no core can also be used. Since a coil with
no core is light, the moving mechanism that moves the power supply
coil inside the top plate can be simplified. The power supply coil
11 is made with essentially the same outside diameter as the
induction coil 51 to efficiently transmit power to the induction
coil 51.
[0081] The AC power source 12 supplies high frequency power, for
example 20 kHz to several MHz, to the power supply coil 11. The AC
power source 12 is connected to the power supply coil 11 via
flexible lead wires 16. This is because the power supply coil 11
has to be moved close to the devices housing a battery 50 that are
placed on the top plate 21. Although not illustrated, the AC power
source 12 is provided with a self-excited oscillator circuit, and a
power amplifier to amplify the AC power output from the
self-excited oscillator circuit. The self-excited oscillator
circuit uses the power supply coil 11 as an oscillator circuit
inductor. Consequently, the oscillator frequency changes with the
inductance of the power supply coil 11. The inductance of the power
supply coil 11 changes with the relative position of the power
supply coil 11 with respect to the induction coil 51. This is
because the mutual inductance of the power supply coil 11 and the
induction coil 51 changes with the relative position of the power
supply coil 11 with respect to the induction coil 51. Therefore,
the frequency of the self-excited oscillator circuit, which uses
the power supply coil 11 as an oscillator circuit inductor, changes
as the power supply coil 11 approaches the induction coil 51. As a
result, the self-excited oscillator circuit can detect the relative
position of the power supply coil 11 with respect to the induction
coil 51 from the change in oscillating frequency, and can be used
with the dual purpose as a position detection controller 14.
[0082] The power supply coil 11 is moved in close proximity to the
induction coil 51 by the moving mechanism 13. The moving mechanism
13 of FIGS. 5-8 moves the power supply coil 11 along the inside of
the top plate 21 in the X-axis and Y-axis directions to position it
close to the induction coil 51. The moving mechanism 13 of the
figures rotates threaded rods 23 via servo motors 22 controlled by
the position detection controller 14 to move nut blocks 24 that are
threaded onto the threaded rods 23. The nut blocks 24 are moved to
move the power supply coil 11 close to the induction coil 51. The
servo motors 22 are provided with an X-axis servo motor 22A to move
the power supply coil 11 in the X-axis direction, and a Y-axis
servo motor 22B to move the power supply coil 11 in the Y-axis
direction. The threaded rods 23 are provided with a pair of X-axis
threaded rods 23A to move the power supply coil 11 in the X-axis
direction, and a Y-axis threaded rod 23B to move the power supply
coil 11 in the Y-axis direction. The pair of X-axis threaded rods
23A are disposed parallel to each other, and are connected via
belts 25 to rotate together when driven by the X-axis servo motor
22A. The threaded nut blocks 24 are provided with a pair of X-axis
nut blocks 24A that are threaded onto each X-axis threaded rod 23A,
and a Y-axis nut block 24B that is threaded onto the Y-axis
threaded rod 23B. Both ends of the Y-axis threaded rod 23B are
connected to the X-axis nut blocks 24A in a manner allowing
rotation. The power supply coil Ills mounted on the Y-axis nut
block 24B.
[0083] Further, the moving mechanism 13 of the figures has a guide
rod 26 disposed parallel to the Y-axis threaded rod 23B to move the
power supply coil 11 in the Y-axis direction while retaining it in
a horizontal orientation. The guide rod 26 is connected at both
ends to the X-axis nut blocks 24A and moves together with the pair
of X-axis nut blocks 24A. The guide rod 26 passes through a guide
block 27 attached to the power supply coil 11 to allow power supply
coil 11 movement along the guide rod 26 in the Y-axis direction.
Specifically, the power supply coil 11 is moved with horizontal
orientation in the Y-axis direction via the Y-axis nut block 24B
and guide block 27 that move along the parallel disposed Y-axis
threaded rod 23B and guide rod 26.
[0084] When the X-axis servo motor 22A rotates the X-axis threaded
rods 23A of this moving mechanism 13, the pair of X-axis nut blocks
24A move along the X-axis threaded rods 23A to move the Y-axis
threaded rod 23B and the guide rod 26 in the X-axis direction. When
the Y-axis servo motor 22B rotates the Y-axis threaded rod 23B, the
Y-axis nut block 24B moves along the Y-axis threaded rod 23B to
move the power supply coil 11 in the Y-axis direction. Here, the
guide block 27 attached to the power supply coil 11 moves along the
guide rod 26 to maintain the power supply coil 11 in a horizontal
orientation during movement in the Y-axis direction. Consequently,
rotation of the X-axis servo motor 22A and Y-axis servo motor 22B
can be controlled by the position detection controller 14 to move
the power supply coil 11 in the X-axis and Y-axis directions.
However, the charging pad of the present invention is not limited
to a moving mechanism with the configuration described above. This
is because any configuration of moving mechanism can be used that
can move the power supply coil in the X-axis and Y-axis
directions.
[0085] Further, the charging pad of the present invention is not
limited to a moving mechanism that moves the power supply coil in
the X-axis and Y-axis directions. This is because the charging pad
of the present invention can be provided with a straight-line guide
wall on the top plate, the devices housing a battery can be aligned
along the guide wall, and the power supply coil can be moved in a
straight-line along the guide wall. Although not illustrated, this
charging pad can move the power supply coil in a straight-line
along the guide wall with a moving mechanism that moves the power
supply coil in one direction such as in the X-axis direction
only.
[0086] The position detection controller 14 detects the position of
a device housing a battery 50 that is placed on the top plate 21.
The position detection controller 14 of FIGS. 5-8 detects the
position of the induction coil 51 housed in the device housing a
battery 50, and moves the power supply coil 11 close to the
induction coil 51. Further, the position detection controller 14 is
provided with a first position detection controller 14A that
roughly determines the position of the induction coil 51, and a
second position detection controller 14B that determines the
position of the induction coil 51 with precision. In this position
detection controller 14, the first position detection controller
14A roughly determines the position of the induction coil 51 and
controls the moving mechanism 13 to move the power supply coil 11
close to the induction coil 51. Subsequently, the second position
detection controller 14B detects the induction coil 51 position
with precision while controlling the moving mechanism 13 to move
the power supply coil 11 more accurately to the position of the
induction coil 51. This charging pad 10 can quickly move the power
supply coil 11 close to the induction coil 51 with precision.
[0087] As shown in FIG. 9, the first position detection controller
14A is provided with a plurality of position detection coils 30
fixed to the inside of the top plate 21, a detection signal
generating circuit 31 that supplies position detection signals to
the position detection coils 30, a receiving circuit 32 that
receives echo signals from the position detection coils 30
resulting from excitation of the induction coil 51 by position
detection signals supplied to the position detection coils 30 from
the detection signal generating circuit 31, and a discrimination
circuit 33 that determines induction coil 51 position from the echo
signals received by the receiving circuit 32.
[0088] The position detection coils 30 are made up of a plurality
of coils in rows and columns. The plurality of position detection
coils 30 is fixed with specified intervals between each coil on the
inside surface of the top plate 21. The position detection coils 30
are provided with a plurality of X-axis detection coils 30A that
detect induction coil 51 position on the X-axis, and a plurality of
Y-axis detection coils 30B that detect induction coil 51 position
on the Y-axis. Each X-axis detection coil 30A is a long narrow loop
extending in the Y-axis direction, and the X-axis detection coils
30A are fixed to the inside of the top plate 21 at specified
intervals. The interval (d) between adjacent X-axis detection coils
30A is smaller than the outside diameter (D) of the induction coil
51, and preferably the interval (d) between X-axis detection coils
30A is from 1 times to 1/4 times the induction coil 51 outside
diameter (D). The position of the induction coil 51 on the X-axis
can be detected more accurately by reducing the interval (d)
between X-axis detection coils 30A. Each Y-axis detection coil 30B
is a long narrow loop extending in the X-axis direction, and the
Y-axis detection coils 30B are also fixed to the inside of the top
plate 21 at specified intervals. In the same manner as the X-axis
detection coils 30A, the interval (d) between adjacent Y-axis
detection coils 30B is smaller than the outside diameter (D) of the
induction coil 51, and preferably the interval (d) between Y-axis
detection coils 30B is from 1 times to 1/4 times the induction coil
51 outside diameter (D). The position of the induction coil 51 on
the Y-axis can also be detected more accurately by reducing the
interval (d) between Y-axis detection coils 30B.
[0089] The detection signal generating circuit 31 issues pulse
signals, which are the position detection signals, with a specified
timing. A position detection coil 30, which has input a position
detection signal, excites a nearby induction coil 51 via the
position detection signal. The induction coil 51, which has been
excited by a position detection signal, outputs an echo signal,
which is generated by the energy of the induced current flow, and
that echo signal is detected by the position detection coil 30.
Specifically, as shown in FIG. 13, following a given delay time
after a position detection signal has been input, the induction
coil 51 generates an echo signal, and that echo signal is induced
in the position detection coil 30 near the induction coil 51. The
echo signal induced in the position detection coil 30 is sent from
the receiving circuit 32 to the discrimination circuit 33. The
discrimination circuit 33 uses the echo signal input from the
receiving circuit 32 to determine if the induction coil 51 is close
to the position detection coil 30. When echo signals are induced in
a plurality of position detection coils 30, the discrimination
circuit 33 determines that the position detection coil 30 with the
largest amplitude echo signal is closest to the induction coil
51.
[0090] The position detection controller 14 shown in FIG. 9
connects each position detection coil 30 to the receiving circuit
32 via a switching matrix 34. Since this position detection
controller 14 can connect a plurality of position detection coils
30 by sequential switching, echo signals from a plurality of
position detection coils 30 can be detected with one receiving
circuit 32. However, a receiving circuit can also be connected to
each position detection coil to detect the echo signals.
[0091] In the position detection controller 14 of FIG. 9, the
discrimination circuit 33 controls the switching matrix 34 to
sequentially switch each of the position detection coils 30 for
connection to the receiving circuit 32. Since the detection signal
generating circuit 31 is connected outside the switching matrix 34,
it outputs position detection signals to each position detection
coil 30. The amplitude of the position detection signals output
from the detection signal generating circuit 31 to the position
detection coils 30 is extremely large compared to the echo signals
from the induction coil 51. The receiving circuit 32 has a diode
connected to its input-side that forms a voltage limiting circuit
35. Position detection signals input to the receiving circuit 32
from the detection signal generating circuit 31 are voltage limited
by the limiting circuit 35. Low amplitude echo signals are input to
the receiving circuit 32 without voltage limiting. The receiving
circuit 32 amplifies and outputs both position detection signals
and the echo signals. An echo signal output from the receiving
circuit 32 is a signal that is delayed from the position detection
signal by a given delay time such as several .lamda.sec to several
hundred .mu.sec. Since the echo signal delay time from the position
detection signal is constant, a signal received after the constant
delay time is assumed to be an echo signal, and the proximity of a
position detection coil 30 to the induction coil 51 is determined
from the amplitude of that echo signal.
[0092] The receiving circuit 32 is an amplifier that amplifies echo
signals input from the position detection coils 30. The receiving
circuit 32 outputs each position detection signal and echo signal.
The discrimination circuit 33 determines if the induction coil 51
is placed next to a position detection coil 30 from the position
detection signal and echo signal input from the receiving circuit
32. The discrimination circuit 33 is provided with an
analog-to-digital (ND) converter 36 to convert the signals input
from the receiving circuit 32 to digital signals. Digital signals
output from the A/D converter 36 are processed to detect the echo
signals. The discrimination circuit 33 detects a signal that is
delayed from the position detection signal by a given delay time as
an echo signal, and determines if the induction coil 51 is close to
the position detection coil 30 from the amplitude of the echo
signal.
[0093] The discrimination circuit 33 controls the switching matrix
34 to sequentially connect each of the plurality of X-axis
detection coils 30A to the receiving circuit 32 to detect the
position of the induction coil 51 along the X-axis. For each X-axis
detection coil 30A connected to the receiving circuit 32, the
discrimination circuit 33 outputs a position detection signal to
that X-axis detection coil 30A and determines if the induction coil
51 is close to that X-axis detection coil 30A by detection or lack
of detection of an echo signal after a given delay time from the
position detection signal. The discrimination circuit 33 connects
each one of the X-axis detection coils 30A to the receiving circuit
32, and determines if an induction coil 51 is close to any of the
X-axis detection coils 30A. If an induction coil 51 is close to one
of the X-axis detection coils 30A, an echo signal will be detected
when that X-axis detection coil 30A is connected to the receiving
circuit 32. Consequently, the discrimination circuit 33 can
determine the position of the induction coil 51 along the X-axis
from the X-axis detection coil 30 that outputs an echo signal. When
the induction coil 51 straddles a plurality of X-axis detection
coils 30, echo signals can be detected by a plurality of X-axis
detection coils 30A. In that case, the discrimination circuit 33
determines that the induction coil 51 is closest to the X-axis
detection coil 30A that detects the strongest echo signal, which is
the echo signal with the largest amplitude. The discrimination
circuit 33 controls the Y-axis detection coils 30B in the same
manner to determine the position of the induction coil 51 along the
Y-axis.
[0094] The discrimination circuit 33 controls the moving mechanism
13 according to the detected X-axis and Y-axis positions to move
the power supply coil 11 close to the induction coil 51. The
discrimination circuit 33 controls the X-axis servo motor 22A to
move the power supply coil 11 to the induction coil 51 position on
the X-axis. The discrimination circuit 33 also controls the Y-axis
servo motor 22B to move the power supply coil 11 to the induction
coil 51 position on the Y-axis.
[0095] The first position detection controller 14A moves the power
supply coil 11 to a position close to the induction coil 51 in the
manner described above. The charging pad of the present invention
can move the power supply coil 11 close to the induction coil 51
with the first position detection controller 14A, and subsequently
transmit power from the power supply coil 11 to the induction coil
51 to charge the battery 52. However, the charging pad can further
refine the position of the power supply coil 11 and move it still
closer to the induction coil 51 to subsequently transmit power and
charge the battery 52. The power supply coil 11 is more precisely
positioned close to the induction coil 51 by the second position
detection controller 14B.
[0096] The second position detection controller 14B has an AC power
source 12 that is a self-excited oscillator circuit, and the second
position detection controller 14B controls the moving mechanism 13
to move the power supply coil 11 to a position accurately
determined by the oscillating frequency of the self-excited
oscillator circuit. The second position detection controller 14B
controls the moving mechanism 13 X-axis servo motor 22A and Y-axis
servo motor 22B to move the power supply coil 11 along the X and
Y-axes while detecting the AC power source 12 oscillating
frequency. Self-excited oscillator circuit oscillating frequency
characteristics are shown in Fig, 14. This figure shows the change
in oscillating frequency as a function of the relative offset
(displacement) between the power supply coil 11 and the induction
coil 51. As shown in this figure, the oscillating frequency of the
self-excited oscillator circuit has a maximum where the power
supply coil 11 and induction coil 51 are closest, and the
oscillating frequency drops off as the two coils become separated.
The second position detection controller 14B controls the moving
mechanism 13 X-axis servo motor 22A to move the power supply coil
11 along the X-axis, and stops the power supply coil 11 where the
oscillating frequency reaches a maximum. Similarly, the second
position detection controller 14B controls the Y-axis servo motor
22A in the same manner to move the power supply coil 11 along the
Y-axis, and stops the power supply coil 11 where the oscillating
frequency reaches a maximum. The second position detection
controller 14B can move the power supply coil 11 in the manner
described above to a position that is closest to the induction coil
51.
[0097] In the charging pad described above, the first position
detection controller 14A roughly detects the position of the
induction coil 51. Subsequently, the second position detection
controller 14B finely adjusts the power supply coil 11 position to
move it still closer to the induction coil 51. However, the
position detection controller 44 shown in FIG. 15 and described
below can move the power supply coil 11 close to the induction coil
51 without fine adjustments.
[0098] As shown in FIG. 15, the position detection controller 44 is
provided with a plurality of position detection coils 30 fixed to
the inside of the top plate, a detection signal generating circuit
31 that supplies position detection signals to the position
detection coils 30, a receiving circuit 32 that receives echo
signals from the position detection coils 30 resulting from
excitation of the induction coil 51 by pulse signals supplied to
the position detection coils 30 from the detection signal
generating circuit 31, and a discrimination circuit 43 that
determines induction coil 51 position from the echo signals
received by the receiving circuit 32. In this position detection
controller 44, the discrimination circuit 43 is provided with a
memory circuit 47 to store the amplitude of echo signals induced in
each position detection coil 30 corresponding to induction coil 51
position. Specifically, this is the amplitude of echo signals
resulting from induction coil 51 excitation that are induced in
each position detection coil 30 after a given delay time, as shown
in FIG. 13. The position detection controller 44 detects the
amplitude of the echo signal induced in each position detection
coil 30, and compares the detected echo signal amplitude with the
echo signal amplitudes stored in the memory circuit 47 to determine
the induction coil 51 position.
[0099] The position detection controller 44 determines induction
coil 51 position from the amplitude of the echo signal induced in
each position detection coil 30 in the following manner. The
position detection coils 30 shown in FIG. 15 are provided with a
plurality of X-axis detection coils 30A that detect induction coil
51 position on the X-axis, and a plurality of Y-axis detection
coils 30B that detect induction coil 51 position on the Y-axis. The
position detection coils 30 are fixed to the inside of the top
plate 21 at specified intervals. Each X-axis detection coil 30A is
a long narrow loop extending in the Y-axis direction, and each
Y-axis detection coil 30B is a long narrow loop extending in the
X-axis direction. FIG. 16 shows the amplitude of the echo signal
induced in each X-axis detection coil 30A as the induction coil 51
is moved along the X-axis. The horizontal axis of FIG. 16 shows the
position of the induction coil 51 on the X-axis, and the vertical
axis shows the amplitude of the echo signal induced in each X-axis
detection coil 30A. This position detection controller 44 can
determine the position of the induction coil 51 on the X-axis by
detecting the amplitude of the echo signal induced in each X-axis
detection coil 30A. As shown in FIG. 16, the amplitude of the echo
signal induced in each X-axis detection coil 30A changes as the
induction coil 51 position along the X-axis changes. For example,
when the center of the induction coil 51 is at the center of the
first X-axis detection coil 30A, the amplitude of the echo signal
induced in the first X-axis detection coil 30A is a maximum as
shown by point A in FIG. 16. When the induction coil 51 is halfway
between the first and second X-axis detection coils 30A, the
amplitude of the echo signals induced in the first and second
X-axis detection coils 30A is equal as shown by point B in FIG. 16.
Specifically, the amplitude of an echo signal detected in an X-axis
detection coil 30A is maximum (strongest signal) when the induction
coil 51 is closest to that detection coil, and the amplitude of the
echo signal decreases as the induction coil 51 is separated from
that detection coil. Therefore, the X-axis detection coil 30A
closest to the induction coil 51 can be determined by which X-axis
detection coil 30A has the largest amplitude echo signal. When echo
signals are induced in two X-axis detection coils 30A, the
direction of induction coil 51 offset from the X-axis detection
coil 30A with the largest echo signal amplitude can be determined
from the direction, relative to the X-axis detection coil 30A with
the largest echo signal, of the other X-axis detection coil 30A
that detects an echo signal. Further, the relative position of the
induction coil 51 between two X-axis detection coils 30A can be
determined from the ratio of the amplitudes of the echo signals
induced in the two X-axis detection coils 30A. For example, if the
ratio between echo signal amplitudes detected in two X-axis
detection coils 30A is one, the induction coil 51 position can be
determined to be halfway between the two X-axis detection coils
30A.
[0100] The discrimination circuit 43 stores in the memory circuit
47 the echo signal amplitude induced in each X-axis detection coil
30A corresponding to induction coil 51 position on the X-axis. When
an induction coil 61 is placed on the charging pad 10, an echo
signal is detected in one of the X-axis detection coils 30A.
Therefore, the discrimination circuit 43 can determine from the
echo signal induced in the X-axis detection coil 30A that an
induction coil 51 has been placed on the charging pad 10; namely,
that a device housing a battery 50 has been placed on the charging
pad 10. Further, by comparing the amplitude of the echo signal
induced in each X-axis detection coil 30A with the amplitudes
stored in the memory circuit 47, the position of the induction coil
51 on the X-axis can be determined. The discrimination circuit can
also store a function in the memory circuit that specifies
induction coil X-axis position corresponding to the ratio of the
amplitudes of echo signals induced in adjacent X-axis detection
coils. Induction coil position can be determined from the function
stored in memory. This function can be determined by moving the
induction coil between two X-axis detection coils and measuring the
ratio of the echo signal amplitudes in the two detection coils.
Here, the discrimination circuit 43 detects the ratio of the
amplitudes of echo signals induced in two X-axis detection coils
30A. Based on the function stored in memory, the X-axis position of
the induction coil 51 between the two X-axis detection coils 30A
can be computed from the detected echo signal amplitude ratio.
[0101] Discrimination circuit 43 detection of induction coil 61
X-axis position from echo signals induced in the X-axis detection
coils 39A is described above. Induction coil 51 position on the
Y-axis can be detected in a similar manner from echo signals
induced in the Y-axis detection coils 30B.
[0102] When the discrimination circuit 43 has detected the
induction coil 51 position on the X and Y-axes, the position
detection controller 44 moves the power supply coil 11 to the
induction coil 51 position based on a position signal issued from
the discrimination circuit 43.
[0103] When an echo signal is detected having a waveform as
described previously, the charging pad discrimination circuit 43
can recognize and distinguish that an induction coil 51 of a device
housing a battery 50 has been placed on the charging pad. When a
waveform is detected and determined to be different from an echo
signal, an object other than the induction coil 51 of a device
housing a battery 50 (for example, a metal foreign object) is
assumed to be on the charging pad and the supply of power can be
terminated. In addition, when no echo signal waveform is detected,
it is assumed that no device housing a battery 50 induction coil 51
has been placed on the charging pad and power is not supplied.
[0104] The charging pad 10 position detection controller 14, 44
controls the moving mechanism 13 to move the power supply coil 11
close to the induction coil 51. In this state, AC power is supplied
to the power supply coil 11 from the AC power source 12. AC power
from the power supply coil 11 is transmitted to the induction coil
51 and used to charge the battery 52. When full-charge of the
battery 52 is detected in the device housing a battery, charging is
stopped and a full-charge signal is sent to the charging pad 10.
The device housing a battery 50 can output a full-charge signal to
the induction coil 51, and the full-charge signal can be sent from
the induction coil 51 to the power supply coil 11 to transmit
full-charge information to the charging pad 10. The device housing
a battery 50 can output an AC signal to the induction coil 51 with
a frequency different from that of the AC power source 12, and the
charging pad 10 can receive that AC signal with the power supply
coil 11 to detect full-charge. The device housing a battery 50 can
output a full-charge signal to the induction coil 51 that is a
modulated carrier wave with a specified frequency, and the charging
pad 10 can receive the carrier wave of specified frequency and
demodulate that signal to detect the full-charge signal. Further,
the device housing a battery can wirelessly transmit a full-charge
signal to the charging pad to send the full-charge information.
Here, the device housing a battery contains a transmitter to send
the full-charge signal, and the charging pad contains a receiver to
receive the full-charge signal. The position detection controller
14 shown in FIG. 10 contains a full-charge detection circuit 17 to
detect full-charge of the internal battery 52. This full-charge
detection circuit 17 detects a full-charge signal sent from the
device housing a battery 50 to detect battery 52 full-charge.
[0105] A charging pad 10, which has a top plate 21 where a
plurality of devices housing a battery 50 can be placed,
sequentially charges the battery 52 in each device housing a
battery 50 to full-charge. As shown in FIG. 4, the charging pad 10
first detects the position of the induction coil 51 in any one of
the devices housing a battery 50 (the first device housing a
battery 50A). The power supply coil 11 is moved close to the
induction coil 51, and the battery 52 in the first device housing a
battery 50A is charged to full-charge. When the battery 52 in the
first device housing a battery 50A reaches full-charge and the
full-charge detection circuit 17 receives a full-charge signal, the
position detection controller 14 detects the position of another
induction coil 51 in a second device housing a battery 50B and
controls the moving mechanism 13 to move the power supply coil 11
to the induction coil 51 of the second device housing a battery
50B. In this state, power is transmitted to charge the battery 52
in the second device housing a battery 50B and that battery 52 is
charged to full-charge. When the battery 52 in the second device
housing a battery 50B reaches full-charge and the full-charge
detection circuit 17 receives a full-charge signal from the second
device housing a battery 50B, the position detection controller 14
detects the position of the induction coil 51 in a third device
housing a battery 50C and controls the moving mechanism 13 to move
the power supply coil 11 to the induction coil 51 of the third
device housing a battery 50C. In this state, power is transmitted
to charge the battery 52 in the third device housing a battery 50C
and that battery 52 is charged to full-charge. In this manner, when
a plurality of devices housing a battery 50 are placed on the top
plate 21, the charging pad 10 sequentially switches from one device
housing a battery 50 to another to fully charge all the internal
batteries 52. This charging pad 10 stores in memory the location of
devices housing a battery 50 that have been fully charged, and does
not charge the batteries 52 in devices that have been fully
charged. When full-charge of the batteries 52 in all the devices
housing a battery 50 placed on the top plate 21 has been detected,
the charging pad 10 suspends operation of the AC power source 12
and stops battery 52 charging. In the embodiments described above
and below, charging of the battery 52 in a device housing a battery
50 is stopped when full-charge is reached. However, it is also
possible to treat a specific battery capacity as full-charge and
stop charging when that specific battery capacity is reached.
[0106] As described above, a charging pad 10 that fully charges
batteries 52 in a plurality of devices housing a battery 50 can
move the power supply coil 11 to the induction coil 51 of the next
device housing a battery 50 to fully charge the battery 52 in the
next device when the battery 52 in the previous device has been
fully charged. This can sequentially charge the batteries 52 in a
plurality of devices housing a battery 50 to full-charge. Further,
a charging pad 10 that charges a plurality of devices housing a
battery 50 can move the power supply coil 11 to the induction coil
51 of another device housing a battery 50 when the battery 52 in
the device housing a battery 50 presently being charged has not
reached full-charge. By repeating this procedure, namely by
switching one after another the device housing a battery 50 that is
being charged, the battery 52 in each device housing a battery 50
can be fully charged. For example, the charging pad 10 can detect
battery data such as battery voltage, remaining capacity, and
battery temperature of the device housing a battery 50 being
charged, and switch the device housing a battery 50 based on the
detected data. The charging pad 10 can also move the power supply
coil to the induction coil of another device housing a battery to
switch the device housing a battery being charged when a specified
time has elapsed. A charging pad that switches the device housing a
battery being charged based on battery voltage switches the device
when battery voltage reaches a predetermined voltage or when the
rate of rise in voltage of the battery being charged becomes equal
to a set value. The charging pad can detect remaining battery
capacity to switch the device housing a battery being charged.
Here, the device housing a battery being charged is switched when
the remaining capacity of the battery being charged reaches a set
capacity or when the change in remaining capacity becomes equal to
a set value. The charging pad can detect battery temperature to
switch the device housing a battery being charged. Here, the device
housing a battery being charged is switched when the temperature of
the battery being charged reaches a set temperature. A charging pad
that switches the device housing a battery being charged when a set
time has elapsed houses a timer, and the device housing a battery
being charged is switched when the timer times out. In addition,
the charging pad can also switch the device housing a battery being
charged based on all the battery data including voltage, remaining
capacity, temperature, and charging time.
[0107] The charging pad 10 described above charges the battery 52
in the next device housing a battery 50 before the previous battery
52 has reached full-charge. Since the charging pad 10 repeats this
procedure to charge the devices housing a battery 50, the power
transmitted from the power supply coil 11 to the induction coil 51
can be increased to fully charge a plurality of devices housing a
battery 50 in a short time period. This is because battery 52
charging current can be increased when charging a single battery 52
for only a short time period. The power transmitted by a charging
pad, which transmits power in a non-contact manner from a power
supply coil 11 to an induction coil 51 in close proximity, is
limited by unavoidable induction coil and battery heat generation
caused by magnetic flux leakage. However, by switching the device
housing a battery 50 during charging, the transmitted power can be
increased while preventing induction coil 51 and battery 52 heat
generation. Specifically, battery 52 charging current can be
increased to rapidly charge the battery 52 to full-charge. This is
because the battery 52 and induction coil 51 are cooled during the
periods when charging is not being performed. Consequently, a
charging pad 10, which switches the device housing a battery 50
being charged prior to reaching full-charge, has the characteristic
that the batteries 52 can be rapidly charged to full-charge while
limiting induction coil 51 and battery 52 heating.
[0108] As shown for example in FIG. 4, where three devices housing
a battery 50 are placed on the top plate 21, the battery 52 in each
device housing a battery 50 can be charged to full-charge in the
following manner. [0109] (1) First, the position of the induction
coil 51 in any one of the devices housing a battery 50 is detected,
and the power supply coil 11 is moved close to the induction coil
51 to charge the battery 52 in the first device housing a battery
50A. [0110] (2) The position detection controller 14 suspends
charging of the battery 52 in the first device housing a battery
50A based on data such as battery voltage, remaining battery
capacity, and battery temperature for the first device housing a
battery 50A. The position of the induction coil 51 in the second
device housing a battery 50B, which is placed in a different
location from the first device housing a battery 50A, is detected.
The moving mechanism 13 is controlled to move the power supply coil
11 close to the induction coil 51 in the second device housing a
battery 50B. In this state, power is transmitted to the second
device housing a battery 50B to charge that battery 52. [0111] (3)
The position detection controller 14 suspends charging of the
battery 52 in the second device housing a battery 50B based on
battery data for the second device housing a battery 50B. The
position of the induction coil 51 in the third device housing a
battery 50C, which is placed in still a different location, is
detected. The moving mechanism 13 is controlled to move the power
supply coil 11 close to the induction coil 51 in the third device
housing a battery 50B to charge the battery 52 in the third device
housing a battery 50B. [0112] (4) Next, The position detection
controller 14 suspends charging of the battery 52 in the third
device housing a battery 50C based on battery data for the third
device housing a battery 50C, and the power supply coil 11 is moved
to the position of the induction coil 51 in the first device
housing a battery 50A to charge the battery 52 in that device.
[0113] (5) In the manner described above, the first device housing
a battery 50A, the second device housing a battery 50B, and the
third device housing a battery 50C are repeatedly charged to charge
their internal batteries 52 to full-charge.
[0114] During the process of battery 52 charging while switching
the devices housing a battery 50, if any one of the batteries 52
becomes fully charged, charging is terminated for that device
housing a battery 50 and the batteries 52 of the next devices
housing a battery 50 are sequentially charged to full-charge. When
full-charge is detected for the batteries 52 in all the devices
housing a battery 50 placed on the top plate 21, the charging pad
10 stops operation of the AC power source 12 and terminates battery
52 charging.
[0115] It should be apparent to those with an ordinary skill in the
art that while various preferred embodiments of the invention have
been shown and described, it is contemplated that the invention is
not limited to the particular embodiments disclosed, which are
deemed to be merely illustrative of the inventive concepts and
should not be interpreted as limiting the scope of the invention,
and which are suitable for all modifications and changes falling
within the spirit and scope of the invention as defined in the
appended claims.
[0116] The present application is based on Application No.
2009-110176 filed in Japan on Apr. 28, 2009, the content of which
is incorporated herein by reference.
* * * * *