WO2013002488A1

WO2013002488A1 - Wireless power transmission apparatus and wireless power transmission method thereof

Info

Publication number: WO2013002488A1
Application number: PCT/KR2012/003674
Authority: WO
Inventors: Su Ho Bae; Woo Kil Jung
Original assignee: Lg Innotek Co., Ltd.
Priority date: 2011-06-29
Filing date: 2012-05-10
Publication date: 2013-01-03
Also published as: KR20130007173A

Abstract

Disclosed is a wireless power transmission apparatus to transmit power to a receiver in wireless. The wireless power transmission apparatus includes an impedance converting unit comprising at least one variable capacitor, and an impedance adjusting unit to acquire at least one of a distance and an angle made together with the receiver and adjust capacitance of the variable capacitor by using the at least one of the distance and the angle.

Description

WIRELESS POWER TRANSMISSION APPARATUS AND WIRELESS POWER TRANSMISSION METHOD THEREOF

The disclosure relates to a wireless power transmission apparatus. In more particular, the disclosure relates to a wireless power transmission apparatus and a wireless power transmission method thereof, capable of improving power transmission efficiency by analyzing the phase difference between voltage and current of the wireless power transmission apparatus.

Recently, as IT technologies have been developed, various portable electronic products have been launched and extensively spread. Accordingly, the battery performance of the portable electronic products has become an important issue due to the nature of the portable electronic products. Meanwhile, home appliances as well as the portable electronic products are equipped with a function of wirelessly transmitting data. However, power is supplied through a power line.

Recently, researches and studies on a wireless power transmission technology have been carried out to supply power in wireless.

According to the wireless power transmission technology, due to the nature of wireless environments, the distance or the angle between a wireless power transmission apparatus and a wireless power receiving apparatus may be significantly varied according to times, and the matching condition between the wireless power transmission apparatus and the wireless power receiving apparatus may be changed.

The disclosure suggests a novel structure and a novel method capable of increasing wireless transmission efficiency under the variable situation.

The disclosure is to provide a wireless power transmission apparatus and a wireless power transmission method thereof, capable of matching impedance varied according to the distance or the angle between a wireless power transmission apparatus and a wireless power receiving apparatus.

The disclosure is to provide a wireless power transmission apparatus and a wireless power transmission method thereof, capable of maximizing the power transmission efficiency by performing the matching of impedance varied according to a coupling coefficient between the wireless power transmission apparatus and a wireless power receiving apparatus.

According to one embodiment of the disclosure, there is provided a wireless power transmission apparatus to transmit power to a receiver in wireless. The wireless power transmission apparatus includes an impedance converting unit comprising at least one variable capacitor, and an impedance adjusting unit to acquire at least one of a distance and an angle made together with the receiver and adjust capacitance of the variable capacitor by using the at least one of the distance and the angle.

According to another embodiment of the disclosure, there is provided a wireless power transmission apparatus to transmit power to a receiver in wireless. The wireless power transmission apparatus includes an impedance converting unit comprising at least one variable capacitor, and an impedance adjusting unit to acquire a coupling coefficient between the wireless power transmission apparatus and the receiver and adjust capacitance of the variable capacitor by using the coupling coefficient.

According to a still embodiment of the disclosure, there is provided a wireless power transmission method including checking a state of power transmitted from a transmitter to a receiver, acquiring at least one of a distance and an angle between the transmitter and the receiver according to the checked state of the power, and performing impedance matching by using the at least one of the distance and the angle.

As described above, according to the embodiment of the disclosure, the wireless power transmission apparatus performs impedance matching by checking the distance and the angle made together with the wireless power receiving apparatus according to the phase difference between the voltage and the current of the transmitted power. Accordingly, due to the transceiving of the stable power of the wireless power transmission apparatus, the power matching circuit not only can be stabilized, but also stable and efficient power can be transmitted and received.

As described above, according to the embodiment of the disclosure, the wireless power transmission apparatus performs impedance matching by checking a coupling coefficient made together with the wireless power receiving apparatus according to the phase difference between the voltage and the current of the transmitted power. Accordingly, due to the transceiving of the stable power of the wireless power transmission apparatus, the power matching circuit not only can be stabilized, but also stable and efficient power can be transmitted and received.

FIG. 1 is a view showing a wireless power transmission system according to one embodiment of the disclosure;

FIG. 2 is a circuit diagram showing an equivalent circuit of a transmission coil 21 according to one embodiment of the disclosure;

FIG. 3 is a circuit diagram showing an equivalent circuit of a power source 10 and a transmitter 20 according to one embodiment of the disclosure;

FIG. 4 is a circuit diagram showing a receiving resonance coil 31, a receiving coil 32, a rectifier circuit 40, and a load 50 according to one embodiment of the disclosure;

FIG. 5 is a view showing the structure of a coil according to the embodiment of the disclosure;

FIG. 6 is a block diagram showing the structure of a transmit condition setting device according to the embodiment of the disclosure;

FIGS. 7 and 8 are views showing the procedure of checking a transmit environment according to the embodiment of the disclosure; and

FIG. 9 is a flowchart showing the wireless power transmission method according to the embodiment of the disclosure according to the process steps.

Hereinafter, the embodiments of the disclosure will be described with reference to accompanying drawings.

FIG. 1 is a view showing a wireless power transmission system according to one embodiment of the disclosure.

After the power generated from a power source 10 has been transmitted to a transmitter 20, the power is transmitted to a receiver 30 making resonance with the transmitter 20 due to the resonance, that is, having the same resonant frequency.

The power from the transmitter 20 to the receiver 30 is transmitted to a load 50 through a rectifier circuit 40. The load 50 may include a rechargeable battery or other devices requiring power.

In more particular, the power source 10 includes an AC power source to supply AC power having a predetermined frequency.

The transmitter 20 includes a transmission coil 21 and a transmission resonance coil 22. The transmission coil 21 is connected to the power source 10, so that AC current flows through the transmission coil 21. If the AC current flows through the transmission coil 21, the AC current is induced to the transmission resonance coil 22 physically spaced apart from the transmission coil 21 due to the electromagnetic induction. The power transmitted to the transmission resonance coil 22 is transmitted to the receiver 30 constructing a resonance circuit together with the transmitter 20 due to the resonance.

The power transmission by the resonance is to transmit power between two LC circuits subject to impedance matching, and can transmit power with high efficiency farther than the power transmission by the electromagnetic induction.

The receiver 30 includes a receiving resonance coil 31 and a receiving coil 32. The power transmitted from the transmission resonance coil 22 is received by the receiving resonance coil 31 so that AC current flows through the receiving resonance coil 31. The power transmitted to the receiving resonance coil 31 is transmitted to the receiving coil 32 due to the electromagnetic induction. The power transmitted to the receiving coil 32 is rectified by the rectifier circuit 40 and transmitted to the load 50.

The transmitter 20 and the transmission resonance coil 22 can transmit power to the receiver 30 and the receiving resonance coil 31 by a magnetic field.

In more detail, the transmission resonance coil 22 and the receiving resonance coil 31 are magnetically resonance-coupled with each other to operate at the resonance frequency.

The resonance-coupling between the transmission resonance coil 22 and the receiving resonance coil 31 can significantly improve the power transmission efficiency between the transmitter 20 and the receiver 30.

A quality factor and a coupling coefficient are important in the wireless power transmission.

The quality factor refers to an index of energy that may be stored in the vicinity of a transmitter or a receiver.

The quality factor may be varied according to the operating frequency w, a coil shape, a dimension, and a material. The quality factor may be expressed in equation, Q=w*L/R. In Equation, L refers to the inductance of a coil, and R refers to resistance corresponding to the quantity of power loss caused in the coil.

The quality factor may have a value of 0 to infinity.

The coupling coefficient represents the degree of an inductive coupling between a transmission coil and a receiving coil, and has a value of 0 to 1.

The coupling coefficient may be varied according to the relative position and the distance between the transmission coil and the receiving coil.

FIG. 2 is a circuit diagram showing an equivalent circuit of the transmission coil 21 according to the one embodiment of the disclosure. As shown in FIG. 2, the transmission coil 21 may include an inductor L1 and a capacitor C1, and a circuit having desirable inductance and desirable capacitance can be constructed due to the inductor L1 and the capacitor C1. The capacitor C1 may include a variable capacitor, and impedance matching may be performed by adjusting the capacitance of the variable capacitor. The capacitor C1 may constitute an impedance converting unit.

The transmission resonance coil 22, the receiving resonance coil 31, and the receiving coil 32 may have the same equivalent circuit as that shown in FIG. 2.

FIG. 3 is a circuit diagram showing an equivalent circuit of the power source 10 and the transmitter 20 according to one embodiment of the disclosure.

As shown in FIG. 3, the transmission coil 21 and the transmission resonance coil 22 may include inductors L1 and L2 having predetermined inductances and capacitors C1 and C2 having predetermined capacitances.

FIG. 4 is a circuit diagram showing an equivalent circuit of the receiving resonance coil 31, the receiving coil 32, the rectifier circuit 40, and the load 50 according to one embodiment of the disclosure.

As shown in FIG. 4, the receiving resonance coil 31 and the receiving coil 32 may include inductors L3 and L4 having predetermined inductances and capacitors C3 and C4 having predetermined capacitances. The rectifier circuit 40 may include a diode D1 and a smoothing capacitor C5 to convert AC power into DC power to be output. Although FIG. 4 shows that DC voltage of 1.3V is applied to the load 50, the load 50 may include a rechargeable battery or a device requiring DC power.

FIG. 5 is a view showing the structure of a coil. The coil may be formed by simply winding a wire as shown in FIG. 5(a), or a capacitor may be additionally linked with the coil to ensure a capacitance as shown in FIG. 5(b).

The coil constructed as shown in FIG. 5 may be used for the transmission coil 21, the transmission resonance coil 22, the receiving resonance coil 31, or the receiving coil 32.

Actually, the coil shown in FIG. 5 may be wound in the solenoid type or the spiral type. The solenoid-type coil is formed by mounting a bobbin on a core and winding a wire around the bobbin in a longitudinal direction thereof. The spiral-type coil is formed by winding the wire around the core from the inner portion thereof to the outer portion thereof.

In this case, the power transmitted from the transmitter 20 to the receiver 30 is affected by a transmission environment, and the transmission efficiency of the power is determined according to the transmission environment.

The transmission environment may include various conditions, especially, including the distance or the angle between the transmitter 20 and the receiver 30.

In other words, when the distance or the angle between the transmitter 20 and the receiver 30 is changed, the transmission efficiency of the power must be increased by changing the transmission condition suitable for the distance or the angle between the transmitter 20 and the receiver 30. However, the detection of the transmission environment is difficult, and the transmission condition is not changed according to the transmission environment in the related art.

Therefore, according to the disclosure, when the transmission environment is changed, the transmission condition is changed suitably for the changed transmission environment, so that the transmission condition optimized under the present transmission environment can be set.

Hereinafter, the change of the transmission condition according to the transmission environment will be described in detail.

FIG. 6 is a block diagram showing the structure of a transmission condition setting device according to the embodiment of the disclosure. In this case, the transmission condition setting device may be included in the transmitter 20. However, the disclosure is not limited thereto, and the transmission condition setting device may be provided separately from the transmitter 20, or may be included in the receiver 30.

Referring to FIG. 6, a transmission condition setting device 100 includes an impedance converting unit 110, an impedance adjusting unit 120, and a storage unit 130.

The impedance converting unit 110 includes at least one variable capacitor, and an impedance matching operation is performed by changing the value (capacitance) of the variable capacitor.

The impedance adjusting unit 120 checks the state of the power transmitted from the transmitter 20 to detect the transmission environment of the power and to determine the capacitance to be applied to the impedance converting unit 110 according to the detected transmission environment.

In addition, the impedance adjusting unit 120 allows the impedance converting unit 110 to perform the impedance matching operation by the determined capacitance.

In this case, the impedance adjusting unit 120 includes a checking unit 121, an acquiring unit 122, and a determining unit 123.

The checking unit 121 checks the state of the transmitted power.

In this case, the checking unit 121 is installed at an output terminal of the transmitter 20 to check the state of the power transmitted to the receiver 30 through the output terminal.

In more detail, the checking unit 121 checks the phase difference between current and voltage of the transmitted power.

In other words, as shown in FIG. 7, the phase difference between voltage and current at the power transmission terminal of the transmitter 20 is changed according to the transmission environment of the power. For example, the phase difference between the voltage and the current is changed according to the distance between the transmitter 20 and the receiver 30. In addition, the phase difference between the voltage and the current is changed according to the receive angle and the transmit angle between the transmitter 20 and the receiver 30.

In addition, the phase difference between the voltage and the current is changed according to the coupling coefficient between the transmitter 20 and the receiver 30.

The checking unit 121 checks the difference between the voltage phase and the current phase according to the transmission power and transmits the checking information to the acquiring unit 22. The acquiring unit 122 acquires the information of at least one of the distance and the angle between the transmitter 20 and the receiver 30 according to the phase difference between the voltage and the current checked in the checking unit 121, and transmits the acquired information to the determining unit 123. In this case, the distance and the angle may be defined as follows.

As shown in FIG. 8(a), a linear distance D between the transmitter 20 and the receiver 30 may be defined as a distance between the transmitter 20 and the receiver 30.

In addition, the angle may include a receive angle and a transmit angle. The receive angle represents an angle of the transmitter 20 with respect to the receiver 30, and the transmit angle represents an angle of the receiver 30 with respect to the transmitter 20.

In other words, as shown in FIG. 8(b), an angle θ1 between a first straight line to link the receiver 30 with the transmitter 20 and a second straight line representing the gradient of the receiver 30 according to the installed state of the receiver 30 may be defined as the receive angle.

In addition, as shown in FIG. 8(c), an angle θ2 between a first straight line along which power is transmitted according to the installed state of the transmitter 20 and a second straight line to link the transmitter 20 with the receiver 30 may be defined as the transmit angle.

In addition, the acquiring unit 122 may acquire the coupling coefficient between the transmitter 20 and the receiver 30 according to the phase difference between the voltage and the current, which is checked in the checking unit 121, and transmit the coupling coefficient to the determining unit 123. The coupling coefficient between the transmitter 20 and the receiver 30 may refer to the coupling coefficient between the transmission resonance coil 22 and the receiving resonance coil 31.

The coupling coefficient between the transmitter 20 and the receiver 30 may be varied according to the distance, the position, and the angle between the transmitter 20 and the receiver 30.

The determining unit 123 determines capacitance to be applied to the impedance converting unit 110 based on the information or the coupling coefficient acquired through the acquiring unit 122.

In other words, the determining unit 123 adjusts the capacitance according to the distance, the transmit angle, and the receive angle between the transmitter 20 and the receiver 30 so that the mismatched impedance can be matched.

In other words, the determining unit 123 adjusts the capacitance according to the coupling coefficient between the transmitter 20 and the receiver 30, so that mismatched impedance can be matched.

In addition, if the impedance matching is performed, the impedance adjusting unit 120 may re-transmit power according to the matched impedance and may perform impedance matching according to the state of the re-transmitted power (power transmission efficiency).

The storage unit 130 may store various information required to perform the impedance matching.

In addition, the storage unit 130 can store information used to acquire the distance, the receive angle, and the transmit angle. In other words, the storage unit 130 may store the information of distances, receive angles, and transmit angles corresponding to all possible phase differences between the voltage and the current.

The storage unit 130 can store coupling coefficients corresponding to all possible phase differences between voltage and current.

The storage unit 130 can store the coupling coefficient corresponding to the distance, the receive angle, and the transmit angle.

The acquiring unit 122 acquires the distance, the receive angle, and the transmit angle by using information stored in the storage unit 130 and provides the distance, the receive angle, and the transmit angle to the determining unit 123.

The acquiring unit 122 acquires the coupling coefficient by using the information stored in the storage unit 130 and provides the coupling coefficient to the determining unit 123.

In addition, the storage unit 130 can store capacitance corresponding to at least one of the distance, the receive angle, and the transmit angle which have been acquired. Therefore, the determining unit 123 can determine capacitance corresponding to the information acquired through the acquiring unit 122 by using the information stored in the storage part 130.

The storage unit 130 can store capacitance corresponding to the coupling coefficient, and the determining unit 123 can determine capacitance corresponding to the coupling coefficient by using the information stored in the storage unit 130.

As described above, according to the embodiment of the disclosure, the wireless power transmission apparatus performs impedance matching by checking the distance and the angle, or a coupling coefficient made together with the wireless power receiving apparatus according to the phase difference between the voltage and the current of the transmitted power. Accordingly, due to the transceiving of the stable power of the wireless power transmission apparatus, the power matching circuit not only can be stabilized, but also stable and efficient power can be transmitted and received.

Referring to FIG. 9, according to the wireless power transmission method, the phase difference between the current and the voltage of the power transmitted from the transmitter 20 to the receiver 30 is checked (step S110).

Thereafter, the distance and the angle (receive angle or transmit angle) between the transmitter 20 and the receiver 30 are acquired by the using the phase difference between the voltage and the current (step S120).

Subsequently, if the distance and the angle are acquired, it is determined if the acquired distance and the acquired angle are equal to or different from previously-acquired distance and angle.

In addition, if the acquired distance and the acquired angle are equal to previously-acquired distance and angle, the previously-set capacitance is maintained.

In addition, if the acquired distance and the acquired angle are different from previously-acquired distance and angle, capacitance is determined according to the acquired distance and the acquired angle (step S130).

Next, the impedance matching is performed by applying the determined capacitance (step S140).

In addition, if the impedance matching is performed, the power may be re-transmitted and the impedance re-matching may be performed according to the state of the re-transmitted power (power transmission efficiency).

Any reference in this specification to “one embodiment,” “an embodiment,” “example embodiment,” etc., means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. The appearances of such phrases in various places in the specification are not necessarily all referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with any embodiment, it is submitted that it is within the purview of one skilled in the art to effect such feature, structure, or characteristic in connection with other ones of the embodiments.

Although embodiments have been described with reference to a number of illustrative embodiments thereof, it should be understood that numerous other modifications and embodiments can be devised by those skilled in the art that will fall within the spirit and scope of the principles of this disclosure. More particularly, various variations and modifications are possible in the component parts and/or arrangements of the subject combination arrangement within the scope of the disclosure, the drawings and the appended claims. In addition to variations and modifications in the component parts and/or arrangements, alternative uses will also be apparent to those skilled in the art.

Claims

A wireless power transmission apparatus to transmit power to a receiver in wireless, comprising:

an impedance converting unit comprising at least one variable capacitor; and

an impedance adjusting unit to acquire at least one of a distance and an angle made together with the receiver and adjust capacitance of the variable capacitor by using the at least one of the distance and the angle.
The wireless power transmission apparatus of claim 1, further comprising:

a transmission coil to generate a magnetic field by using power received from a power source; and

a transmission resonance coil resonance-coupled with the receiver by using the magnetic field to transmit power.
The wireless power transmission apparatus of claim 2, wherein the impedance adjusting unit comprises:

a checking unit to check a state of the power transmitted through the transmission resonance coil;

an acquiring unit to acquire the at least one of the distance and the angle made together with the receiver according to the checked state of the power; and

a determining unit to determine the capacitance of the variable capacitor by using the at least one of the distance and the angle.
The wireless power transmission apparatus of claim 3, wherein the checking unit checks a phase difference between the voltage and the current according to the power transmitted to the receiver.
The wireless power transmission apparatus of claim 4, wherein the acquiring unit acquires at least one of a distance between the wireless power transmission apparatus and the receiver, a power receive angle according to an installation angle of the receiver, and a power transmit angle of the wireless power transmit apparatus according to a position of the receiver.
The wireless power transmission apparatus of claim 5, further comprising a storage unit to store information of at least one of the distance and the angle made together with the receiver corresponding to the phase difference checked through the checking unit, and capacitance corresponding to at least one of the distance, the receive angle, and the transmit angle which are acquired through the acquiring unit.
The wireless power transmission apparatus of claim 3, wherein the impedance adjusting unit re-transmits power by applying the determined capacitance and re-determines the capacitance according to a state of re-transmitted power.
A wireless power transmission apparatus to transmit power to a receiver in wireless, comprising:

an impedance converting unit comprising at least one variable capacitor; and

an impedance adjusting unit to acquire a coupling coefficient between the wireless power transmission apparatus and the receiver and adjust capacitance of the variable capacitor by using the coupling coefficient.
The wireless power transmission apparatus of claim 8, further comprising:

a transmission coil to generate a magnetic field by using power received from a power source; and

a transmission resonance coil resonance-coupled with a wireless power receiving apparatus by using the magnetic field to transmit the power.
The wireless power transmission apparatus of claim 9, wherein the impedance adjusting unit comprises:

a checking unit to check a state of the power transmitted through the transmission resonance coil;

an acquiring unit to acquire the coupling coefficient according to the checked state of the power; and

a determining unit to determine the capacitance of the variable capacitor according to the coupling coefficient.
A wireless power transmission method comprising:

checking a state of power transmitted from a transmitter to a receiver;

acquiring at least one of a distance and an angle between the transmitter and the receiver according to the checked state of the power; and

performing impedance converting by using the at least one of the distance and the angle.
The wireless power transmission method of claim 11, wherein, in the acquiring of the at least one of the distance and the angle between the transmitter and the receiver,

at least one of the distance between the transmitter and the receiver, a receive angle according to a position of the receiver, and a transmit angle of the transmitter according to the position of the receiver are acquired.
The wireless power transmission method of claim 11, wherein the checking of the state of the power comprises checking a phase difference between voltage and current according to the power transmitted to the receiver.
The wireless power transmission method of claim 13, further comprising storing information of at least one of a distance and an angle with the receiver corresponding to the phase difference, wherein the acquiring of the at least one of the distance and the angle between the transmitter and the receiver comprises acquiring information of the at least one of the distance and the angle corresponding to the phase difference by using the stored information.
The wireless power transmission method of claim 12, wherein the performing of the impedance converting comprises:

determining capacitance corresponding to at least one of the acquired distance, the acquired receive angle, and the acquired transmit angle; and

applying the capacitance.
The wireless power transmission method of claim 11, further comprising;

re-transmitting power as the impedance matching is performed; and

re-performing the impedance matching according to transmission efficiency of the re-transmitted power.
A recording medium in which a method claimed according to claims 11 to 16 is realized in a program to execute the method in a computer.