U.S. patent application number 14/975044 was filed with the patent office on 2016-04-14 for space-adaptive wireless power transfer system and method using multiple resonance coils.
The applicant listed for this patent is KOREA ELECTROTECHNOLOGY RESEARCH INSTITUTE. Invention is credited to Ji Myung KANG, Jin Wook KIM, Kwan Ho KIM, Soon Wo LEE, Young Jin PARK.
Application Number | 20160104570 14/975044 |
Document ID | / |
Family ID | 44360749 |
Filed Date | 2016-04-14 |
United States Patent
Application |
20160104570 |
Kind Code |
A1 |
PARK; Young Jin ; et
al. |
April 14, 2016 |
SPACE-ADAPTIVE WIRELESS POWER TRANSFER SYSTEM AND METHOD USING
MULTIPLE RESONANCE COILS
Abstract
A magnetic resonance wireless power transfer method according to
an aspect of the present invention includes transmitting power from
a source coil to the Tx resonant coil using a magnetic induction
method, transmitting the power from the Tx resonant coil to an Rx
resonant coil, having a resonant frequency identical with that of
the Tx resonant coil, via magnetically-coupled resonance, and
transmitting the power from the Rx resonant coil to the device coil
of an electronic device using the magnetic induction method. The Tx
resonant coil and the Rx resonant coil are arranged at a right
angle or a specific angle of inclination relative to each
other.
Inventors: |
PARK; Young Jin; (Anyang,
KR) ; LEE; Soon Wo; (Anyang, KR) ; KANG; Ji
Myung; (Ansan, KR) ; KIM; Jin Wook; (Ansan,
KR) ; KIM; Kwan Ho; (Seoul, KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
KOREA ELECTROTECHNOLOGY RESEARCH INSTITUTE |
Changwon |
|
KR |
|
|
Family ID: |
44360749 |
Appl. No.: |
14/975044 |
Filed: |
December 18, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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13508345 |
Jul 30, 2012 |
|
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PCT/KR2010/006447 |
Sep 17, 2010 |
|
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14975044 |
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Current U.S.
Class: |
307/104 |
Current CPC
Class: |
H02J 7/025 20130101;
H01F 27/006 20130101; H02J 5/005 20130101; H01F 38/14 20130101;
H02J 50/12 20160201; H02J 50/50 20160201; H03H 7/38 20130101 |
International
Class: |
H01F 38/14 20060101
H01F038/14; H03H 7/38 20060101 H03H007/38; H02J 5/00 20060101
H02J005/00 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 4, 2009 |
KR |
10-2009-0105919 |
Sep 15, 2010 |
KR |
10-2010-0090388 |
Claims
1. A magnetic resonance wireless power transfer method, comprising:
transferring power from a source coil to a transmitting (Tx)
resonant coil using a magnetic induction method; transferring the
power from the Tx resonant coil to an intermediate resonant coil,
having a resonant frequency identical with that of the Tx resonant
coil, via magnetically-coupled resonance; transferring the power
from the intermediate resonant coil to an receiving (Rx) resonant
coil, having a resonant frequency identical with the Rx resonant
coil, via magnetically-coupled resonance; and transferring the
power from the Rx resonant coil to a device coil of an electronic
device using a magnetic induction method; wherein the intermediate
resonant coil is placed between Tx resonant coil and Rx resonant
coil in geometrical configuration.
2. The magnetic resonance wireless power transfer method as set
forth in claim 1, wherein the intermediate resonant coil is placed
at a right angle or an angle of inclination relative to the Tx
resonant coil and the Rx resonant coil, or is placed on the
different plane with the Tx resonant coil and the Rx resonant coil,
and the center axes of the intermediate resonant coil, the Tx
resonant coil, and Rx resonant coil are parallel to each other but
not identical with each other.
3. A magnetic resonance wireless power transfer system, comprising:
a source coil configured to be supplied with power from a source; a
transmitting (Tx) resonant coil configured to be supplied with the
power from the source coil using a magnetic induction method; an
intermediate resonant coil supplied with power from the Tx resonant
coil at a resonant frequency identical with that of the Tx resonant
coil using a magnetic resonance mechanism; and an receiving (Rx)
resonant coil configured to be supplied with the power from the
intermediate resonant coil at a resonant frequency identical with
that of the intermediate resonant coil via magnetically-coupled
resonance, wherein the intermediate resonant coil is placed between
Tx resonant coil and Rx resonant coil in geometrical
configuration.
4. The magnetic resonance wireless power transfer system as set
forth in claim 3, wherein the intermediate resonant coil is placed
at a right angle or an angle of inclination relative to the Tx
resonant coil and the Rx resonant coil, or is placed on the
different plane with the Tx resonant coil and the Rx resonant coil,
and the center axes of the intermediate resonant coil, the Tx
resonant coil, and Rx resonant coil are parallel to each other but
not identical with each other, and the Rx resonant coil transfers
the power to a device coil of an electronic device using a magnetic
induction method.
5. The magnetic resonance wireless power transfer system as set
forth in claim 3, wherein at least one of the Tx resonant coil, the
Rx resonant coil, and the intermediate resonant coil comprises; a
lumped inductor or a capacitor whose two electrodes are connected
between both ends of the at least one coil, or whose only one
electrode is connected to one of both ends of the at least one
coil, to both ends of the at least one coil, or to an intermediate
portion of the at least one coil.
6. The magnetic resonance wireless power transfer system as set
forth in claim 3, wherein the Tx resonant coil, the Rx resonant
coil, or the intermediate resonant coil has a helical or spiral
form.
7. The magnetic resonance wireless power transfer system as set
forth in claim 6, wherein the Tx resonant coil, the Rx resonant
coil, or the intermediate resonant coil has a form in which a wire
is wound around a magnetic body.
8. The magnetic resonance wireless power transfer system as set
forth in claim 4, wherein the Tx resonant coil directly transfers
the power to the Rx resonant coil and simultaneously the
intermediate resonant coil transfers the power to the Rx resonant
coil.
9. The magnetic resonance wireless power transfer system as set
forth in claim 3, wherein the Rx resonant coil transfers the power
to the device coil of the electronic device using the magnetic
induction method, and simultaneously the intermediate resonant coil
transfers the power to a device coil of another electronic device
using the magnetic induction method.
10. The magnetic resonance wireless power transfer system as set
forth in claim 3, further comprising an impedance matching circuit
between the source and the source coil, or the device coil and a
rectifier circuit or load of the electronic device.
11. The magnetic resonance wireless power transfer system as set
forth in claim 3, wherein impedance matching is performed by
controlling a number of turns and size of the source coil or the Tx
resonant coil and the Rx resonant coil even without using an
impedance matching circuit.
12. The magnetic resonance wireless power transfer system as set
forth in claim 5, wherein a sum of a capacitance of the at least
one coil itself to which the capacitor is additionally coupled and
a capacitance of the added capacitor is equal to or higher than 50
pF and equal to or lower than 10 nF.
13. The magnetic resonance wireless power transfer system as set
forth in claim 3, wherein the Tx resonant coil is embedded in a
wall or a board, the Rx resonant coil is embedded in a desk or a
table, a space, another wall, a pad, or a container near the wall,
and the electronic device near the Rx resonant coil is supplied
with the power.
14. The magnetic resonance wireless power transfer system as set
forth in claim 3, wherein the Tx resonant coil, the intermediate
resonant coil and the Rx resonant coil are arranged so that the
center axes of the Tx resonant coil, the intermediate resonant coil
and the Rx resonant coil are parallel to each other, but the center
axes are not identical with each other.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] The present application is a divisional of U.S. application
Ser. No. 13/508,345 filed on Jul. 30, 2012, which is U.S. National
Stage of International Patent Application No. PCT/KR2010/006447,
filed Sep. 17, 2010, which claims priority to Korean application
number 10-2010-0090388, filed Sep. 15, 2010, and Korean application
number 10-2009-0105919, filed Nov. 4, 2009, which are incorporated
by reference in their entirety.
TECHNICAL FIELD
[0002] The present invention relates generally to a wireless power
transfer system and method using magnetically-coupled resonance of
the evanescent field which is generated around a wireless power
transmitting coil and, more particularly, to a space-adaptive
magnetically-coupled resonance wireless power transfer system and
method, in which the resonant coil of a power receiving unit and
the resonant coil of a power transmitting unit are configured to
have the same resonant frequency so that magnetic field is coupled
between the transmitting (Tx) resonant coil and the receiving (Rx)
resonant coil, and the Tx and Rx resonant coils are placed on a
plane having a right angle or a specific angle so that power
transfer is efficient even when the center axis of the power
receiving unit has not been aligned with the center axis of the
power transmitting unit (i.e., when the center axis of the power
receiving unit has to be vertical to the center axis of the power
transmitting unit or the center axis of the power receiving unit
has to have a specific angle of inclination relative to the center
axis of the power transmitting unit), with the result that power is
stably supplied to an electronic device having the device coil of a
power receiving unit contained therein, such as a mobile phone,
when the electronic device is brought into contact with the power
transmitting unit.
BACKGROUND ART
[0003] Recently, active research is being carried out into wireless
power transfer using magnetic induction in a low frequency band.
However, the method using magnetic induction is disadvantageous in
that power can be transmitted only within a short range of a few
centimeters. Furthermore, there are many difficulties in applying
this method using magnetic induction to wireless power transfer
systems because it has very low efficiency when the arrangements of
Tx and Rx coils are not identical with each other.
[0004] Korean Patent No. 10-0809461 discloses a configuration which
is capable of increasing the power receiving distance by using an
electromagnetic amplification relay employing LC resonance. In this
patent, a method is used of performing LC resonance using a
variable capacitor in a solenoid-type coil in which an induction
coil is wound on a magnetic body to increase magnetic flux. This
method uses separate LC resonant coils in Tx and Rx units, unlike
the existing configuration used for magnetic induction. In this
patent, the distance and efficiency of power transfer can be
increased, as described above. In the invention disclosed in this
patent, the resonant frequencies of the Tx and Rx power resonant
coils are tuned using the variable capacitor. However, this
invention has a disadvantage in that it is difficult to precisely
adjust the value of the variable capacitor to a value which matches
the resonant frequency. Furthermore, this preceding patent
discloses wireless power transfer using only a parallel arrangement
between the resonant coils, and therefore it is difficult to put
this prior patent to practical use in a variety of ways.
[0005] Furthermore, U.S. Patent Application Publication No. US
2009/0224856 A1 discloses a wireless power transfer method using
magnetically coupled resonance. This U.S. patent discloses the
general details of a magnetically coupled resonance method, and
discloses elements related to the Q factor and the resonant
frequency. This patent presents a scheme for improving power
transmission efficiency and transmission distance using a magnetic
resonant structure having the same resonant frequency and very
strong magnetic coupling.
[0006] In U.S. Patent Application Publication No. US 2009/0072629
A1, resonant coils are constructed using a variable capacitor by
means of a method similar to that of a Korean patent (Korean Patent
No. 10-080941).
[0007] U.S. Patent Application Publication No. US 2009/0153273 A1
proposes a method of improving transmission distance and efficiency
by adding additional resonant coils between Tx and Rx resonant
coils that are arranged coaxially with the Tx and Rx power resonant
coils as well. However, this method relates to a serial arrangement
made by taking into consideration higher coupling constant between
the Tx and Rx power resonant coils, and all the resonant coils are
on the same plane. If all the resonant coils are on the same plane,
the coupling constant between the resonant coils is reduced, and
transmission efficiency is deteriorated.
[0008] The four conventional patents do not describe the
arrangement of the coils, and attempt a method of improving power
transfer efficiency and transmission distance on the assumption
that all the coils are in a parallel arrangement (that is, axis of
each coil is identical with one another). If only the parallel
arrangement is used, however, there is the need for a solution
capable of solving difficulties that occur when the parallel
arrangement is applied to real life because of spatial limitations.
Furthermore, in order to freely situate a power receiving unit,
there is the need for a method that enables power transmission even
in a vertical arrangement or various arrangements between the
transmitting and receiving coils, but there has been no solution
for such a method.
DISCLOSURE
Technical Problem
[0009] Accordingly, the present invention has been made keeping in
mind the above problems occurring in the prior art, and an object
of the present invention is to provide a space-adaptive magnetic
resonance wireless power transfer system and method, which are
capable of solving the directionality problem of a magnetic
induction method and allowing for power transfer even in various
spatial arrangements between transmitting (Tx) resonant coil and
receiving (Rx) resonant coil based on the characteristic that
magnetic resonant coils are less influenced by directionality, in
such a way as to present the characteristics of the directionality
of a magnetic resonance method acquired by making quantitative and
qualitative characteristic analysis into the directionality
characteristic the magnetic resonant coils in which there occurs
magnetic resonance of evanescent field generated around a wireless
power transmitting coil.
[0010] Another object of the present invention is to provide a
space-adaptive magnetic resonance wireless power transfer system
and method, which are capable of providing a power transfer method
suitable for various lateral and vertical spaces by arranging
magnetic resonant coils in various ways in order to extend the
energy transmission distance by combining the positions of the
magnetic resonant coils in various ways based on the characteristic
that magnetic resonant coils are less influenced by
directionality.
[0011] Yet another object of the present invention is to provide a
space-adaptive magnetic resonance wireless power transfer system
and method using a coil in helical or spiral form, which are
capable of overcoming the spatial limitations of a parallel
arrangement by arranging resonant coils at a right angle or a
specific angle of inclination, and allowing Tx and Rx resonant
coils to resonate in open form.
Technical Solution
[0012] First, the features of the present invention will be
summarized. In one aspect of the present invention configured to
achieve the objects, a magnetic resonance wireless power transfer
method includes transferring power from a source coil to a Tx
resonant coil using an magnetic induction method; transferring the
power from the Tx resonant coil to an Rx resonant coil, having a
same resonant frequency, via magnetically-coupled resonance of
magnetic evanescent field with non-directive behavior; and
transferring the power from the Rx resonant coil to a device coil
of an electronic device using the magnetic induction method;
wherein in order to transfer the power irrespective of
directionality, the Tx resonant coil and the Rx resonant coil are
arranged at a right angle or a specific angle of inclination
relative to each other so that center axes of the Tx resonant coil
and the Rx resonant coil are not parallel to each other, or the Tx
resonant coil and the Rx resonant coil are arranged so that the
center axes of the Tx resonant coil and the Rx resonant coil are
parallel to each other but the center axes are not identical with
each other.
[0013] In another aspect of the present invention, a magnetic
resonance wireless power transfer method includes transferring
power from a source coil to a Tx resonant coil using a magnetic
induction method; transferring the power from the Tx resonant coil
to an intermediate resonant coil, having a resonant frequency
identical with that of the Tx resonant coil, via
magnetically-coupled resonance of magnetic evanescent field with
non-directive property; transferring the power from the
intermediate resonant coil to an Rx resonant coil, having a
resonant frequency identical with the Rx resonant coil, via
magnetic resonance coupling; and transferring the power from the Rx
resonant coil to a device coil of an electronic device using an
magnetic induction method; wherein the intermediate resonant coil
is placed at a right angle or an angle of inclination relative to
the Tx resonant coil and the Rx resonant coil.
[0014] In still another aspect of the present invention, a
magnetically-coupled resonance wireless power transfer system
includes a source coil configured to be supplied with power from a
source; a Tx resonant coil configured to be supplied with the power
from the source coil using a magnetic induction method; and an Rx
resonant coil configured to be supplied with the power from the Tx
resonant coil at a resonant frequency identical with that of the Tx
resonant coil via magnetically-coupled resonance of magnetic
evanescent field with non-directive property, wherein in order to
transfer the power irrespective of directionality, the Tx resonant
coil and the Rx resonant coil are arranged at a right angle or a
specific angle of inclination relative to each other so that center
axes of the Tx resonant coil and the Rx resonant coil are not
parallel to each other, or the Tx resonant coil and the Rx resonant
coil are arranged so that the center axes of the Tx resonant coil
and the Rx resonant coil are parallel to each other but the center
axes are not identical with each other, and the Rx resonant coil
transfers the power to a device coil of an electronic device using
the magnetic induction method.
[0015] In still another aspect of the present invention, a magnetic
resonance wireless power transfer system, includes a source coil
configured to be supplied with power from a source; a Tx resonant
coil configured to be supplied with the power from the source coil
using a magnetic induction method; an intermediate resonant coil
supplied with power from the Tx resonant coil at a resonant
frequency identical with that of the Tx resonant coil by
magnetically-coupled resonance; and an Rx resonant coil configured
to be supplied with the power from the intermediate resonant coil
at a resonant frequency identical with that of the intermediate
resonant coil via magnetically-coupled resonance, wherein the
intermediate resonant coil is placed at a right angle or an angle
of inclination relative to the Tx resonant coil and the Rx resonant
coil, and the Rx resonant coil transfers the power to a device coil
of an electronic device using an magnetic induction method.
[0016] The magnetic resonance (magnetically-coupled resonance)
wireless power transfer system may further include an impedance
matching circuit between the source and the source coil, or the
device coil and a rectifier circuit or load of the electronic
device.
[0017] Impedance matching may be performed by controlling the
number of turns and size of the source coil or the Tx resonant coil
and the Rx resonant coil even without using an impedance matching
circuit.
[0018] An element, such as a lumped inductor or a capacitor, may be
connected to both ends or intermediate portion of the magnetic
resonant coil or the intermediate resonant coil. In this case, it
is recommended that parasitic resistance of the element, such as an
inductor or a capacitor, be several ohms or less. The element
includes a lumped inductor having a high Q (quality) value (a high
Q lumped inductor) and a capacitor. In addition, a structure
capable of providing a precise capacitance value, such as a coaxial
line, may be used as the element.
[0019] Since the proposed capacitor is used, a relatively low coil
inductance value is required for the same resonant frequency
(f=1/(2.pi.(LC).sup.0.5)) and therefore the length and volume of a
coil can be reduced. In turn, the total volume of a resonant
structure can be reduced. Although there may be a disadvantage in
that efficiency is deteriorated when the capacitor is used, the
tuning of Tx and Rx resonant frequencies that is problematic for
the magnetic resonant structure becomes easy if a proper capacitor
is used.
[0020] Here, it is preferred that in order to prevent the resonant
frequency from changing as a result of the capacitance being
changed by an influence, such as a contact with the human body or
an alien substance, the capacitance value of the capacitor used,
including the capacitance generated in the coil, be 50 pF or
higher. Furthermore, in order to maintain a high Q factor, it is
preferred that the sum of the capacitance generated in a coil and
the capacitance of an added capacitor be 10 nF or lower.
[0021] Furthermore, the added capacitor may be used to minutely
tune the resonant frequencies. That is, the transfer of power may
be directly influenced by the precise tuning of the resonant
frequencies of the Tx and Rx power resonant coils. Accordingly, the
resonant frequencies of the Tx and Rx power resonant coils must be
the same in order to maximize system efficiency, but the resonant
frequency is changed by a parasitic effect even when the Tx and Rx
power resonant coils have been fabricated to have the same
structure, resulting in a sharp drop in efficiency. Thus,
conducting a resonant frequency tuning process on the Tx and Rx
power resonant coils is mandatory.
[0022] In particular, in order to precisely tune the resonant
frequencies of the Tx and Rx power resonant coils, the capacitor
may have a fixed capacitance and an inductor having low loss or a
high Q factor may be used.
[0023] An electronic device may operate its internal circuit using
power induced into the device coil of the electronic device, or may
charge a battery with power obtained by rectifying power induced
into the device coil.
[0024] An electronic device near the resonant coil of a power Rx
unit may be provided with power in such a way that the resonant
coil of a power Tx unit is embedded in an insulator wall and the
resonant coil of the power receiving unit is embedded in a desk, a
table, a space, another insulator wall, a pad or a container near
the insulator wall.
[0025] The Tx resonant coil may directly transfer power to the Rx
resonant coil, and also an intermediate resonant coil may also
transfer stored power to the Rx resonant coil.
[0026] The Rx resonant coil may transfer power to the device coil
of the electronic device using a magnetic induction method, and
also the intermediate resonant coil may transfer power to the
device coil of another electronic device using a magnetic induction
method.
Advantageous Effects
[0027] According to the space-adaptive magnetic resonance wireless
power transfer system and method according to the present
invention, limitations present when applying power transfer to
practical use using the existing parallel arrangement (i.e., when
the center axes of Tx and Rx resonant coils are identical with each
other) can be overcome. In the case of the existing parallel
arrangement, when the distance between transmission and reception
increases, there are frequent occasions in which a new intermediate
coil may not be placed in parallel to Tx and Rx resonant coils
(i.e., when the center axes of coils are identical with each other)
because an obstacle is present between Tx and Rx coils or because
the spatial limitation is imposed on Tx and Rx. For this reason,
there is a limit to the reception of power using the existing
parallel arrangement.
[0028] If the arrangement having a right angle or specific angle of
inclination is used as in the present invention, however, the
existing disadvantages may be negated because the power
transmitting unit is contained in a wall or a place not visible.
That is, since the resonant coils can be arranged to suit the
surrounding environment, the effective power transmitting distance
is greater, and the power transfer efficiency is improved. This is
based on the characteristic that the magnetically-coupled resonance
method is rarely influenced by an obstacle, such as the surface of
a wall or water. A location where there is power transfer can be
used as the position of the Rx resonant coil, and therefore the Tx
resonant coil can be installed in the desired location. The Rx
resonant coil can be placed under a desk or contained in the bottom
because the Rx resonant coil is formed of only a coil in a helical
or spiral form without additionally connecting an electric wire to
the coil.
DESCRIPTION OF DRAWINGS
[0029] FIG. 1 is a circuit diagram showing the equivalent circuit
of a space-adaptive magnetic resonance wireless power transfer
system according to an embodiment of the present invention;
[0030] FIG. 2 is a diagram illustrating a power transfer method in
the space-adaptive magnetically-coupled resonance wireless power
transfer system according to an embodiment of the present
invention;
[0031] FIG. 3 is a diagram illustrating a space-adaptive
magnetically-coupled resonance wireless power transfer system
according to another embodiment of the present invention;
[0032] FIG. 4 is a diagram illustrating magnetic field patterns
when Tx and Rx resonant coils are arranged at a right angle, as
shown in FIG. 2;
[0033] FIG. 5 shows the scattering (S) parameters obtained by the
simulations of FIG. 4;
[0034] FIG. 6 is a diagram illustrating magnetic field patterns
when an intermediate resonant coil is placed at a right angle
relative to Tx and Rx resonant coils, as shown in FIG. 3;
[0035] FIG. 7 shows the variations of evanescent wave modes or
fields over time in coils when an intermediate resonant coil is
used;
[0036] FIG. 8A shows a coordination system in which the resonant
coil of a power transmitting unit and the resonant coil of a power
receiving unit are disposed at a right angle;
[0037] FIG. 8B is a diagram illustrating the variations in
efficiency when the position of the Rx resonant coil is moved along
the z axis;
[0038] FIG. 9 shows a variation of the example of FIG. 2
illustrating a structure in which the Tx and Rx resonant coils are
arranged such that the center axes of the Tx and Rx resonant coils
are parallel to each other because the Tx and Rx resonant coils are
not on the same plane, but the center axes are not identical with
each other;
[0039] FIG. 10 shows a variation of the example of FIG. 3
illustrating a structure in which the intermediate resonant coil is
placed such that the intermediate resonant coil is not on the same
plane as the Tx and Rx resonant coils and the center axes of the
resonant coils are parallel to each other but are not identical
with each other;
[0040] FIG. 11 is a helical coil fabricated to have a resonant
frequency of 900 kHz;
[0041] FIG. 12 is a diagram showing a region (i.e., a 3 dB boundary
line) which exhibits a power transfer efficiency of 50% when a
resonant coil, such as that shown in FIG. 11, is used in the Tx and
Rx power units; and
[0042] FIGS. 13 to 17 show examples in which applicability to
practical use has been improved by arranging the Tx and Rx resonant
coils 114 and 121 at a right angle or a specific angle of
inclination such that they are not in parallel.
BEST MODE
[0043] Although preferred embodiments of the present will be
described in detail with reference to the accompanying drawings and
the descriptions of the drawings, the present invention is not
limited or restricted to the embodiments.
[0044] The present invention will be described in detail below by
describing the preferred embodiments with reference to the
accompanying drawings.
[0045] FIG. 1 shows the equivalent circuit of a space-adaptive
magnetic resonance wireless power transfer system 100 according to
an embodiment of the present invention.
[0046] Referring to FIG. 1, the space-adaptive magnetic resonance
wireless power transfer system 100 according to an embodiment of
the present invention includes a power transmitting (Tx) unit 110
and a power receiving (Rx) unit 120. The power transmitting unit
110 includes a source 111, a matching circuit 112, a source coil
113, and a Tx resonant coil 114 in helical or spiral form. The
power receiving unit 120 includes a Rx resonant coil 121 in helical
or spiral form, a device coil 122, a rectifier circuit 123, and
load 124. Each of the Tx resonant coil 114 and the Rx resonant coil
121 may be formed of Litz wire, and may have various shapes in
addition to the helical or spiral form. The Tx resonant coil 114
and the Rx resonant coil 121 may be made of super-conducting
material in order to reduce electrical resistance or ohmic loss. In
order to reduce the size of the Tx resonant coil 114 and the Rx
resonant coil 121, a magnetic body on which a wire is wound may be
used for both the Tx resonant coil 114 and the Rx resonant coil
121. The Tx resonant coil 114 and the Rx resonant coil 121 may have
a specific self-capacitance. If necessary, a lumped specific
capacitor of a high Q value or an inductor of a high Q value may be
additionally connected to both the Tx resonant coil 114 and the Rx
resonant coil 121. For example, both electrodes of the capacitor or
the inductor connected to the Tx resonant coil 114 or the Rx
resonant coil 121 may be connected between both ends of the Tx
resonant coil 114 or the Rx resonant coil 121, but the connection
is not limited thereto. For example, only one of the electrodes of
the capacitor or the inductor may be connected to both ends or one
end of the Tx resonant coil 114 or the Rx resonant coil 121, or may
be connected to the intermediate portion of the Tx resonant coil
114 or the Rx resonant coil 121. Here, the total capacitor C.sub.t
of each of the Tx resonant coil 114 and the Rx resonant coil 121
includes a capacitor C.sub.o resulting from the coil itself and a
capacitor C.sub.a additionally attached in order to perform
resonant frequency tuning and to reduce the susceptibility to an
external influence (only C.sub.t is shown in the drawing). Here, it
is preferred that the sum of the capacitance of the capacitor
C.sub.o and the capacitance of the capacitor C.sub.a be 50 pF or
higher in order to prevent the resonant frequency from changing as
a result of the capacitances of the capacitors being changed by an
influence, such as a contact with human body or an alien substance.
It is preferred that the sum of the capacitance of the capacitor
C.sub.o and the capacitance of the capacitor C.sub.a be 10 nF or
lower in order to maintain a high Q factor. The sum of the
capacitance of the capacitor C.sub.o and the capacitance of the
capacitor C.sub.a is not limited to the examples. For example, the
sum of the capacitance of the capacitor C.sub.o and the capacitance
of the capacitor Ca may be 50 pF or lower or 10 nF or higher
depending on the system environment.
[0047] The power transfer mechanism is as follows. Power supplied
from the source 111 is applied to the source coil 113 via the
matching circuit 112. The source coil 113 transfers power to the Tx
resonant coil 114 using a magnetic induction method based on a
time-varying current applied via the matching circuit 112. The Tx
resonant coil 114 continues to store power through self-resonance.
When the Rx resonant coil 121 having the same resonant frequency is
present, the Tx resonant coil 114 forms an energy transfer channel
via strong magnetic coupling of evanescent magnetic field between
the Tx and Rx resonant coils 114 and 121 and then transfers the
stored power to the Rx resonant coil 121. The Tx resonant coil 114
and the Rx resonant coil 121 may transfer power over a low
frequency band ranging from several hundreds of kHz to several
MHz.
[0048] In the power transmitting unit 110, the matching circuit 112
is used between the source 111 and the source coil 113 to carry out
impedance matching between the source coil 113 and the Tx resonant
coil 114. However, impedance matching may be made to be
automatically performed at the resonant frequency by controlling
the number of turns and size (e.g., diameter) of the Tx resonant
coil 114 and the Rx resonant coil 121 or the source coil 113 while
taking into consideration the number of turns and size of the
source coil 113 even in the absence of the matching circuit 112.
Likewise, although not shown, an impedance matching circuit may be
placed between both ends of the device coil 122 (e.g., between the
device coil 122 and the rectifier circuit 123 or between the device
coil 122 and the load 124), and the rectifier circuit 123 and the
load 124 may be placed behind the impedance matching circuit. Even
in this case, impedance matching may be automatically performed at
the resonant frequency by controlling the number of turns and size
of the device coil 122.
[0049] FIG. 2 is a diagram illustrating a power transfer method in
the space-adaptive magnetic resonance wireless power transfer
system 100 according to an embodiment of the present invention.
[0050] In FIG. 2, energy is transmitted through
magnetically-coupled resonance between the Tx and Rx resonant coils
114 and 121 arranged at a right angle or a specific angle of
inclination. For example, the Tx resonant coil 114 may store energy
that is received from the source coil using a magnetic induction
method and, if the Rx resonant coil 121 having the same resonant
frequency is present, the Tx resonant coil 114 may form an energy
transfer channel via strong coupling of evanescent magnetic field
with non-directive property between the Tx and Rx resonant coils
114 and 121 and transfer the stored power to the Rx resonant coil
121. The power transferred to the Rx resonant coil 121 may be
induced in the device coil 122 near the Rx resonant coil 121, and
power rectified by the rectifier circuit 123 may be used by the
load 124 of a device. The device coil 122, the rectifier circuit
123, and the load 124 may be contained in the device (e.g., an
electrical device), and the load 124 may be a battery, such as a
secondary battery for charging power supplied via the rectifier
circuit 123.
[0051] As may be seen from FIGS. 1 and 2, the power reception
method proposed by the present invention refers to a power
reception method which is performed when the Tx and Rx resonant
coils 114 and 121 are arranged at a right angle or a specific angle
of inclination and are not in a parallel arrangement as is common.
In order for power irrespective of directionality to be efficiently
transferred even at a right angle or a specific angle of
inclination, the magnetic resonance method using the Tx and Rx
resonant coils 114 and 121 having the same resonant frequency is
used.
[0052] FIG. 3 is a diagram illustrating a space-adaptive magnetic
resonance wireless power transfer system according to another
embodiment of the present invention.
[0053] Referring to FIG. 3, the space-adaptive magnetic resonance
wireless power transfer system according to another embodiment of
the present invention may further include a Tx intermediate unit
130, including an intermediate resonant coil 131 in a helical or
spiral form and an intermediate device coil 132 (the intermediate
device coil may be omitted if needed), between the power Tx unit
110 and the power Rx unit 120, in addition to the power Tx unit 110
and the power Rx unit 120 which are described in conjunction with
FIG. 1. The intermediate resonant coil 131 may also be formed of
Litz wire, and may have various forms in addition to a helical or
spiral form. The intermediate resonant coil 131 may be made of
super-conducting material in order to reduce electrical resistance.
In order to reduce the size of the intermediate resonant coil 131,
a wire may be wound around a magnetic body. Furthermore, although
not shown, the intermediate resonant coil 131 may also have a
specific capacitance component. A lumped specific capacitor of a
high Q value or an inductor of a high Q value may be connected to
the intermediate resonant coil 131 if necessary. For example, both
electrodes of the capacitor or the inductor connected to the
intermediate resonant coil 131 may be connected between both ends
of the intermediate resonant coil 131, but the connection is not
limited thereto. For example, only one of the electrodes of the
capacitor or the inductor may be connected to both ends or one end
of the intermediate resonant coil 131, or may be connected to the
intermediate portion of the intermediate resonant coil 131. Here,
the total capacitor C.sub.t of the intermediate resonant coil 131
includes a capacitor C.sub.o resulting from the intermediate
resonant coil 131 itself and a capacitor C.sub.a of the capacitor
additionally attached in order to tune the resonant frequency and
to reduce the susceptibility to an external influence. Here, it is
preferred that the sum of the capacitance of the capacitor C.sub.o
and the capacitance of the capacitor C.sub.a be 50 pF or higher in
order to prevent the resonant frequency from changing as a result
of the capacitance of the capacitor being changed by an influence,
such as a contact with the human body or an alien substance. It is
preferred that the sum of the capacitance of the capacitor C.sub.o
and the capacitance of the capacitor Ca be 10 nF or lower in order
to maintain a high Q factor. The sum of the capacitance of the
capacitor C.sub.o and the capacitance of the capacitor C.sub.a is
not limited to the examples. For example, the sum of the
capacitance of the capacitor C.sub.o and the capacitance of the
capacitor C.sub.a may be 50 pF or lower or 10 nF or higher
depending on the system environment.
[0054] In FIG. 3, the intermediate resonant coil 131 of the Tx
intermediate unit 130 is arranged at a right angle relative to the
Tx resonant coil 114 and the Rx resonant coil 121. Here, the Tx
resonant coil 114 and the Rx resonant coil 121 may be parallel to
each other. However, the Tx resonant coil 114 and the Rx resonant
coil 121 are not always arranged in parallel because the
intermediate resonant coil 131 may be arranged at a specific angle
of inclination relative to the Tx resonant coil 114 and the Rx
resonant coil 121. The Tx intermediate unit 130 itself may function
as a power receiving unit so that the intermediate resonant coil
131 can relay power from the Tx resonant coil 114 in order to
increase the power transfer distance and can rectify power induced
into the device coil 132 in order for power to be used for load of
a electronic device. Strong magnetic coupling may be generated
between the Tx resonant coil 114 and the intermediate resonant coil
131 at the same resonant frequency via magnetically-coupled
resonance as described above, and power stored in the intermediate
resonant coil 131 may be transferred to the Rx resonant coil 121
via the strong magnetic coupling based on the magnetic resonance.
Furthermore, if the device coil 132 or 122 is placed near the Rx
resonant coil 121 or the intermediate resonant coil 131, power may
be transferred to the device coil 132 or 122 using a magnetic
induction method.
[0055] FIG. 4 is a diagram illustrating magnetic field patterns
when the Tx and Rx resonant coils are arranged at a right angle as
shown in FIG. 2.
[0056] For a contour line distribution of the intensity of a
magnetic field such as that shown in FIG. 4, a reduction in the
interval between contour lines means that the intensity of a
magnetic field is great. From FIG. 4, it may be seen that a very
strong magnetic field is formed only around the Tx resonant coil
114 and the Rx resonant coil 121 and that magnetic resonance is
generated between the two resonant coils. The Tx and Rx resonant
coils 114 and 121 in helical form used for simulations were the
same, the diameter of the coils was 4 mm, the number of turns of
the coils was 5, the diameter of the coils was 20 cm, and the pitch
was 0.54 cm. The resonant frequency was 28 MHz in theoretical
calculations, but was actually found to be 22 MHz. The resonant
frequencies of the theoretical value and the actual value were
different, but it was found that resonance occurred between the Tx
and Rx resonant coils 114 and 121 having the same resonant
frequency. From FIG. 4, it may be seen that a magnetic field is not
radiated between the Tx and Rx resonant coils 114 and 121 having
the same resonant frequency and the tails of evanescent field
present around the coils are interconnected. It may be seen that
this mutual coupling has almost no influence on the arrangement of
the Tx and Rx resonant coils 114 and 121.
[0057] FIG. 5 shows the result of scattering (S) parameters
obtained by the simulations of FIG. 4. The source coil 113 had a
port having an impedance of 50.OMEGA. in order to excite a signal,
and the device coil 122 also had a port having an impedance of
50.OMEGA.. From FIG. 5, it may be seen that impedance is matched at
a reflection coefficient of -7.52 dB in the case of the power
transmitting unit 110 and at a reflection coefficient of -9.4 dB in
the case of the power Rx unit 120 when each of the Tx and Rx
resonant coils 114 and 121 has a resonant frequency of 22 MHz. As
described above, impedance matching may be automatically performed
at the same resonant frequency of the Tx and Rx resonant coils 114
and 121 by controlling the interval between the source coil 113 and
the resonant coil 114 of the power transmitting unit 110 (or
between the device coil and the Rx resonant coil) and the shape (or
the number of turns or size) of the source coil (or device coil)
even without adding an additional impedance matching circuit. The
simulations revealed that the efficiency of power transfer between
the Tx and Rx resonant coils 114 and 121 resulting from magnetic
resonance was about 60% as a result of the influence stemming from
the matching of the power Tx and Rx units 110 and 121 being
compensated for when the distance between the Tx and Rx resonant
coils 114 and 121 was 24 cm.
[0058] FIG. 6 is a diagram illustrating magnetic field patterns
when the intermediate resonant coil 131 is arranged at a right
angle relative to the Tx and Rx resonant coils 114 and 121 as in
FIG. 3. In FIG. 6, `a` shows a magnetic field pattern when viewed
from the side, and `b` shows a magnetic field pattern when viewed
from the top. FIG. 6 shows the results of the simulations of a
magnetically-coupled resonance phenomenon using a single loop,
connected to a flat type capacitor between both ends of the single
loop, as the intermediate resonant coil 131. Here, an intermediate
resonant coil disclosed in the reference document U.S. Patent
Application Publication No. US 2007/0222542 A1 entitled "Wireless
Non-Radiative Energy Transfer" was used as the intermediate
resonant coil 131. The thickness of the conducting wire was 2 cm,
the diameter of the loop was 60 cm, the interval between the disk
plates of the flat type capacitor was 4 mm, the width of the disk
plate was 138 cm.sup.2, and the dielectric constant was 10. In this
case, the resonant frequency of the loop was 7.8 MHz. It may be
seen that the distance between the Tx and Rx resonant coils 114 and
121 was 1 m, but the power was transferred well up to the power
receiving unit 120 thanks to the intermediate resonant coil 131
arranged at a right angle relative to the Tx and Rx resonant coils
114 and 121.
[0059] The basic principle will now be described in more detail. A
coupling phenomenon between resonance coils having the same
resonant frequency lies in that evanescent waves generated around
the Tx resonant coil 114 are coupled with evanescent field
generated in the Rx resonant coil 121 adjacent to the Tx resonant
coil 114. This coupling phenomenon is shown in FIGS. 4 and 6. The
evanescent waves are coupled at the shortest distance between the
Tx resonant coil 114 and the Rx resonant coil 121. The amount of
the coupling may be small, but a large amount of energy is
transferred to the power receiving unit for a short time even by
the small coupling if the attenuation of the evanescent field is
generated slowly. This result may be the same as that shown in FIG.
7. That is, FIG. 7 shows the variations of evanescent field modes
over time in the resonant coils 114, 121, and 131 when the
intermediate resonant coil 131 of FIG. 6 is used. In FIG. 7, the
evanescent field mode in the Tx resonant coil 114 continues to
oscillate at a resonant frequency, and the size of the evanescent
field gradually decreases. The intermediate resonant coil 131 is
supplied with small amounts of power as described above, and the
energy supplied from the intermediate resonant coil 131 is
transferred to the Rx resonant coil 121. The energy may also be
directly transferred from the Tx resonant coil 114 to the Rx
resonant coil 121, but the amount of the energy is a lot smaller
than the amount of the energy transferred through the intermediate
resonant coil 131. In the existing magnetic induction, however, the
transfer of power in a vertical direction at a small coupling
strength is difficult because a great coupling strength is always
required instead of this coupling phenomenon.
[0060] In the proposed invention, however, unlike in the parallel
arrangement (i.e., the resonant coils are arranged to have the same
central axis), the resonant coils are arranged at a right angle or
a specific angle of inclination. In this case, the transfer of
power may be difficult in a section where coupling is sharply
reduced. FIG. 8 shows a transfer characteristic for the vertical
arrangement between the resonant coils. The Tx resonant coil 114
and the Rx resonant coil 121 were arranged at a right angle
relative to each other as shown in FIG. 8A, and simulations were
performed within one quadrant (1/4). Here, a resonant coil
disclosed in the reference document U.S. Patent Application
Publication No. US 2007/0222542 A1 entitled "Wireless Non-Radiative
Energy Transfer" was used as the resonant coils. The thickness of
the conducting wire was 2 cm, the diameter of a loop was 60 cm, an
interval between the disk plates of a flat type capacitor was 4 mm,
the width of the disk plate was 138 cm.sup.2, and the dielectric
constant was 10. In this case, the resonant frequency of the loop
was 7.8 MHz. From FIG. 8B, it can be seen that the efficiency
varies when the position of the Rx resonant coil 121 is moved along
the z axis. It can also be seen that transmission efficiency is 80%
or higher at a specific distance or less. However, power
transmission efficiency may be small near x=0 because a coupling
coefficient is theoretically very small.
MODE FOR INVENTION
[0061] FIG. 9 shows a variation of the example of FIG. 2 in which
the Tx and Rx resonant coils 114 and 121 may be inclined at a
specific angle so that they are at a right angle or a specific
angle of inclination relative to each other. FIG. 9 shows that the
Tx and Rx resonant coils 114 and 121 may be arranged so that the
center axes of the Tx and Rx resonant coils 114 and 121 are
parallel to each other, but the center axes are not identical with
each other because the Tx and Rx resonant coils are not on the same
plane.
[0062] FIG. 10 shows a variation of the example of FIG. 3 in which
the intermediate resonant coil 131 may be inclined at a specific
angle so that it makes a right angle or a specific angle of
inclination relative to the Tx resonant coil 114 and the Rx
resonant coil 121. FIG. 10 shows that the intermediate resonant
coil 131 may be placed so that the intermediate resonant coil 131
is not on the same plane as the Tx resonant coil 114 and the Rx
resonant coil 121 and the center axes of the resonant coils 131 and
the resonant coils 114 and 121 are parallel to each other, but the
center axes are not identical with each other.
[0063] FIG. 11 shows the configuration and photograph of a coil in
helical form which was fabricated to have a resonant frequency of
900 kHz. The shape of the Tx resonant coil 114 and the Rx resonant
coil 121 may be the same. The conducting wire used in this case was
Litz wire having a diameter of 1 mm, the diameter of the coil was
26 cm, the height of the coil was 8 cm, and the number of turns of
the coil was 78. The coil had a resistance of 3.2.OMEGA., an
inductance of 2.074 mH, and a Q factor (2 f L/R: L=inductance, R:
conduction resistance+radiation resistance) of 3670. The number of
turns of each of the source coil of the power transmitting unit and
the device coil of the power receiving unit for magnetic induction
with the resonant coil was 1. In particular, in order to obtain the
same resonant frequency for the Tx resonant coil 114, the Rx
resonant coil 121, and the intermediate resonant coil 131, the coil
was wound using a cylindrical structure as shown in FIG. 11. A coil
in helical form, such as that shown in FIG. 7, may be used as the
Tx and Rx resonant coils 114 and 121 or the intermediate resonant
coil 131.
[0064] FIG. 12 is a diagram showing a region (i.e., a 3 dB boundary
line) which exhibits a power transmission efficiency of 50% when a
resonant coil, such as that shown in FIG. 11, is used in the
transmitting and receiving power units. In this drawing, the 3 dB
boundary line in `a` shows efficiency measurements taken when
moving the positions of the Tx and Rx resonant coils 114 and 121 in
the state in which the Tx and Rx resonant coils 114 and 121 were
parallel to each other. The 3 dB boundary line in `b` shows
efficiency measurements taken when moving the Tx and Rx resonant
coils 114 and 121 in the state in which the Tx and Rx resonant
coils 114 and 121 are arranged at a right angle, as shown in FIG.
1. If there is a power transmitting unit having a specific amount,
the power transmitting unit may be supplied with power at an
efficiency of 50% within the 3 dB boundary of the Tx resonant coil
114 even when the power receiving unit is placed in any direction.
In FIG. 12, the space within the dotted line is the 3 dB
region.
[0065] FIGS. 13 to 17 show examples in which the Tx and Rx resonant
coils 114 and 121 are arranged at a right angle or a specific angle
of inclination, not in a parallel arrangement, thereby improving
applicability to practical use. The intermediate resonant coil 113
may be placed at a proper location around the Tx and Rx resonant
coils 114 and 121, as in shown FIG. 3.
[0066] For example, as shown in FIG. 13, the Tx resonant coil 114
may be embedded in an insulator wall, the Rx resonant coil 121 may
be embedded in a desk or a space under a desk that vertically
adjoins the wall, and an electronic device (i.e., a device) may be
supplied with power for purposes, such as charging, even when the
electronic device has been placed in a space over the desk. Here,
the electronic device may be a device including the device coil
122, the rectifier circuit 123, and the load 124, and power
transferred from the Rx resonant coil 121 to the device coil 122
via induction may charge the load 124 (e.g., a battery) via the
rectifier circuit 123.
[0067] Furthermore, as shown in FIG. 14, the Tx resonant coil 114
may be embedded in an insulator wall, a pad having the small-sized
Rx resonant coil 121 contained therein may be placed in a location,
such as a space on a desk vertically adjacent to the wall, and an
electronic device (i.e., a device) may be placed on or near the pad
and supplied with power for purposes, such as charging.
[0068] Furthermore, as shown in FIG. 15, the Tx resonant coil 114
may be embedded in an insulator wall, a container near the wall,
such as a basket or cup having the Rx resonant coil 121 contained
therein, may be place in a location, such as a space on a desk
vertically adjacent to the wall, and an electronic device (i.e., a
device) may be placed in the container and supplied with power for
purposes, such as charging.
[0069] Furthermore, as shown in FIG. 16, the Tx resonant coil 114
may be embedded in an insulator wall on one side, the Rx resonant
coil 121 may be embedded in an insulator wall on the other side
vertical and adjacent to one side, and an electronic device, such
as a wall TV or an electronic frame that may be hung on the wall,
may be supplied with power. Here, the electronic device, such as
wall TV or an electronic frame that may be hung on the wall, may be
a device including the device coil 122, and power transferred from
the Rx resonant coil 121 to the device coil 122 via induction may
be used to operate the internal circuit of the electronic device or
a display device.
[0070] Furthermore, as shown in FIG. 17, the Tx resonant coil 114
may be embedded in an insulator wall, the Rx resonant coil 121 may
be contained in a table near a location close to the wall or the Rx
resonant coil 121 or may be embedded in the table, the Rx resonant
coil 121 and the Tx resonant coil 114 may be arranged at a right
angle relative to each other, and electronic devices, such as a
laptop computer and a mobile phone on the table, may be supplied
with power.
[0071] The Rx resonant coil 121 and the Tx resonant coil 114 are
not necessarily arranged vertically (a direction in which the coil
is wound is vertical), but may not be parallel to each other and
may be inclined at a specific angle if necessary.
[0072] As described above, electronic devices each having the
device coil 122 are placed at locations near the Rx resonant coil
121 so that the electronic devices may be supplied with power via
magnetic induction by using the Rx resonant coil 121 and the Tx
resonant coil 114 that may be arranged at a right angle or a
specific angle of inclination, and power is supplied to the
electronic devices. Accordingly, the electronic devices may be
charged with power or may be operated. This method has a better
advantage than the magnetic induction method or the horizontal
arrangement method in terms of a fine beauty because the Tx
resonant coil 114 is embedded in a wall and thus electric wires may
be fully obviated. Furthermore, in the magnetic resonance method,
power may be transferred without loss because power is less
influenced by an object, such as a wall or desk.
[0073] As described above, in the space-adaptive magnetic resonance
wireless power transfer system 100 according to the present
invention, LC resonance is not generated by adding an artificial
capacitor to a coil, but the Tx and Rx resonant coils 114 and 121
are configured using the magnetic resonance of a coil in helical or
spiral form and the power Tx unit 110 and the power Rx unit 120 are
arranged at a specific angle so that they make a right angle or
specific angle of inclination. Accordingly, a limit inherent in the
conventional parallel arrangement may be overcome, and power may be
transferred more efficiently as compared with the magnetic
induction method.
[0074] Although the present invention has been described in
conjunction with a limited number of embodiments and with reference
to the accompany drawings, the present invention is not limited to
the above-described embodiments, but it will be apparent to those
skilled in the art that a variety of modifications and variations
are possible based on the above description. As a result, the scope
of the present invention should not be determined based on only the
above-described embodiments, but should be determined based on not
only the claims but also equivalents to the claims.
* * * * *