System and method for three-dimensional wireless power charging

Abstract

The present invention relates to an operation method of a transmitter configured to transmit power to a receiver through three orthogonal transmission coils, the method comprising the steps of: calculating a target transmission current in a transmission module including each transmission coil for maximum transmission efficiency; determining the magnitude and phase of an input voltage capable of inducing the target transmission current in each transmission module by considering the mutual inductance between the transmission coils; and inducing the target transmission current in each transmission module through the input voltage determined for each transmission module.

Description

3D wireless power charging system and method

[0001] The present disclosure relates to wireless power charging (WPC).

[0002] Wireless power transfer (WPT) research has been conducted in a wide range of fields, including biomedical devices, electric vehicles, and portable devices. In particular, 3D WPT is being studied to ensure a wide charging area according to the various positions of the receiver. Among various transmitters for 3D WPT, the tri-orthogonal structure can independently generate magnetic fields centered on three axes. Therefore, depending on the phase difference between the transmitting currents, the magnetic field is concentrated in one of the four quadrants, expanding the charging area. Furthermore, the orthogonal structure can implement six degrees of freedom (6DoF) for the receiver by controlling the magnitude of the transmitting current.

[0003] A 3D WPT system using orthogonal TX coils has a large charging area because the receiving coil is loosely coupled to the transmitting coil over a large area. Due to the orthogonality between the transmitting coils, the mutual inductance (M) between the transmitting coils is theoretically TX ) is 0, but because slight changes in dimensions occur during the manufacturing process, M TX It is difficult to make M equal to 0. TX Even if the mutual inductance between the transmitting coil and the receiving coil is not 0, it can significantly worsen the transmission efficiency because it has a low value. Therefore, even if an orthogonal structure is used in 3D WPT, the mutual inductance M between the transmitting coils must be increased to improve performance. TX should be considered.

[0004] Meanwhile, research has been conducted to overcome interference between transmitter coils in tightly coupled systems. For example, a method for calculating the optimal capacitance to improve efficiency by considering interference is known, but a variable capacitor is required because the capacitance of the transmitter must change whenever the receiver moves. In addition, M TX Considering the optimal magnitude and phase of the input sinusoidal voltage for optimal efficiency, studies on controlling the phase synchronization and magnitude of the transmission current, and studies on controlling the magnitude and phase of the inverter in steps by detecting the phase of the transmission current and input impedance through a feedback loop have been introduced. However, these studies are about a tightly coupled system, so in a system where the transmission coil and the receiving coil are loosely coupled, M TX A new method is needed to improve efficiency when interference by .

[0005] The present disclosure provides a three-dimensional wireless power charging system and method for charging a receiver using a transmitter composed of three orthogonal coils.

[0006] The present disclosure provides a three-dimensional wireless power charging system and method that calculates the magnitude and phase of an input voltage capable of inducing a desired transmission current by considering mutual inductance between transmission coils and applies this to each transmission module to improve power efficiency.

[0007] A method of operating a transmitter configured to transmit power to a receiver through three orthogonal transmitting coils according to one embodiment, the method comprising: calculating a target transmitting current in a transmitting module including each transmitting coil for maximum transmitting efficiency; determining a magnitude and a phase of an input voltage capable of inducing the target transmitting current in each transmitting module by considering mutual inductance between the transmitting coils; and inducing the target transmitting current in each transmitting module through the input voltage determined for each transmitting module.

[0008] The step of calculating the target transmission current may include a step of tracing the mutual inductance between each transmitting coil and receiving coil, a step of calculating an equivalent load impedance and a transmission current ratio using the mutual inductance between each transmitting coil and receiving coil, and a step of calculating a target transmission current in each transmitting module using the equivalent load impedance and the transmission current ratio.

[0009] The step of determining the magnitude and phase of the input voltage may include a step of classifying modes according to the input voltage on / off of each transmission module in an equivalent circuit including mutual inductance between the transmission coils, a step of obtaining current equations that can calculate the transmission current of each transmission module by superimposing the transmission current induced in each mode, and a step of calculating the magnitude and phase of the input voltage for the target transmission current of each transmission module using the current equations in an equivalent circuit for extracting the input voltage.

[0010] The mutual inductance between the above transmitter coils can be obtained through EM simulation of the equivalent circuit related to the two transmitter coils.

[0011] A transmitter for transmitting power to a receiver may include a first transmitting module including a first transmitting coil, a second transmitting module including a second transmitting coil, a third transmitting module including a third transmitting coil, and a control unit that calculates a target transmitting current for maximum transmission efficiency for each transmitting module, determines a magnitude and phase of an input voltage capable of inducing the target transmitting current for each transmitting module by considering mutual inductance between transmitting coils, and transmits a control signal for applying the magnitude and phase of the input voltage to the corresponding transmitting module.

[0012] The first transmitting coil, the second transmitting coil, and the third transmitting coil may be configured to be orthogonal to each other.

[0013] The above control unit tracks the mutual inductance between each transmitting coil and receiving coil,

[0014] Using the mutual inductance between each of the above transmitting coils and receiving coils, the equivalent load impedance and the transmitting current ratio can be calculated, and using the equivalent load impedance and the transmitting current ratio, the target transmitting current in each transmitting module can be calculated.

[0015] The control unit classifies modes according to the on / off input voltage of each transmission module in an equivalent circuit including mutual inductance between the transmission coils, obtains current equations for calculating the transmission current of each transmission module by superimposing the transmission current induced in each mode, and calculates the magnitude and phase of the input voltage for the target transmission current of each transmission module using the current equations in an equivalent circuit for extracting the input voltage.

[0016] The control unit can transmit a first control signal to the corresponding transmission module to make the output voltage of the voltage amplifier included in the corresponding transmission module a voltage for the target transmission current, and transmit a second control signal for phase control to the corresponding transmission module to make the target transmission current having a desired phase induced in the voltage amplifier.

[0017] The mutual inductance between the above transmitter coils can be obtained through EM simulation of the equivalent circuit related to the two transmitter coils.

[0018] According to the present disclosure, the problem of reduced transmission efficiency due to mutual inductance between transmission coils caused by process errors in the manufacturing process of orthogonal coils can be solved.

[0019] According to the present disclosure, even if interference due to mutual inductance between the transmitting coils exists in a loosely coupled system in which the transmitting coil and the receiving coil are loosely coupled, a decrease in transmission efficiency can be prevented.

[0020] According to the present disclosure, the magnitude and phase of the input voltage for a desired target transmission current can be simply calculated without a feedback loop.

[0021] FIG. 1 is a configuration diagram of a three-dimensional wireless power charging system according to one embodiment.

[0022] FIG. 2 is a diagram illustrating input voltage control considering mutual inductance between transmitter coils according to one embodiment.

[0023] FIG. 3 is a diagram explaining the error correction results of transmission currents considering mutual inductance between transmission coils according to one embodiment.

[0024] Figure 4 is a configuration diagram of a transmitter according to one embodiment.

[0025] FIG. 5 is an exemplary circuit of a wireless power charging system according to one embodiment.

[0026] FIG. 6 is an example of an equivalent circuit of a three-dimensional wireless power charging system according to one embodiment.

[0027] FIG. 7 is a flowchart illustrating an operation method of a transmitter of a three-dimensional wireless power charging system according to one embodiment.

[0028] Below, with reference to the attached drawings, embodiments of the present disclosure are described in detail so that those skilled in the art can easily implement the present disclosure. However, the present disclosure may be implemented in various different forms and is not limited to the embodiments described herein. In addition, in the drawings, parts irrelevant to the description are omitted for clarity of explanation, and similar parts are designated with similar reference numerals throughout the specification.

[0029] In the description, drawing symbols and names are attached for convenience of explanation, and the devices are not necessarily limited to drawing symbols or names.

[0030] In the description, when a part is said to "include" a component, this does not exclude other components, but rather implies that other components may be included, unless otherwise specifically stated. Furthermore, terms such as "part," "unit," and "module" used in the specification mean a unit that processes at least one function or operation, which may be implemented using hardware, software, or a combination of hardware and software.

[0031] In the description, expressions described in the singular may be interpreted as either singular or plural, unless explicitly stated as "one" or "single." Terms containing ordinal numbers, such as "first," "second," etc., may be used to describe various components, but the components are not limited by these terms. These terms may be used to distinguish one component from another.

[0032] FIG. 1 is a diagram illustrating a configuration of a three-dimensional wireless power charging system according to one embodiment, FIG. 2 is a diagram illustrating input voltage control considering mutual inductance between transmission coils according to one embodiment, and FIG. 3 is a diagram illustrating a result of error correction of transmission currents considering mutual inductance between transmission coils according to one embodiment.

[0033] Referring to FIG. 1, a three-dimensional wireless power charging system (10) includes a transmitter (100) composed of three orthogonal coils, and a receiver (200) that receives power transmitted from the transmitter (100).

[0034] A transmitter (100) is a multi-transmitter including orthogonal transmission modules (TX#1, TX#2, TX#3) (110: 110-1, 110-2, 110-3) and a control unit (130). Each transmission module may include a transmission coil (TX coil) and a power amplifier connected to the corresponding transmission coil. The control unit (130) may be an MCU (Micro Control Unit), and may be configured in various other types. The transmission coils (TX coil#1, TX coil#2, TX coil#3) of the transmission modules are orthogonal coils arranged in orthogonal planes in a three-dimensional space.

[0035] The receiver (200) may include a receiving coil (RX coil) (210), a rectifier circuit (230), and a DC-DC converter (250). The rectifier circuit (230) may be configured as, for example, a full bridge rectifier.

[0036] The three-dimensional wireless power charging system (10) can charge the receiver (200) using three orthogonal coils of the transmitter (100). Here, since the transmitting coil and the receiving coil are loosely coupled, there is an advantage of a wide charging area. At this time, since the transmitting coils are orthogonal, theoretically, the mutual inductance between the transmitting coils (M) TX ) is 0, but because slight changes in dimensions occur during the manufacturing process, M TX It is difficult to make it 0. The phases of the transmitting currents flowing in the transmitting coils must be synchronized to achieve maximum transmission efficiency, and the mutual inductance M between the transmitting coils TX A transmission current error occurs, and as a result, the transmission efficiency and charging area are reduced. In particular, since the 3D wireless power charging system (10) transmits power in a weak coupling state between the transmitting coil and the receiving coil, M is not 0. TX Efficiency can be greatly affected by .

[0037] Therefore, the transmitter (100) has a non-zero M TX Considering this, the error of the transmission currents in the transmission modules is compensated to generate synchronized transmission currents. The transmission current for maximum power transmission is M TX It can be derived through the magnitude and phase of the input voltage calculated by taking into account .

[0038] Referring to Fig. 2, the transmitter (100) has a mutual inductance M between the transmitting coils in the equivalent circuit of the wireless power charging system. TX Considering this, the magnitude and phase of the input voltage of each transmission module for the desired transmission current (target transmission current) are calculated and applied to the corresponding transmission module, thereby obtaining M TX The transmission current error can be compensated for.

[0039] Referring to Figure 3, non-zero M exists due to process error. TX The actual transmission currents I by TX1 , I TX2 , I TX3 An error occurs between the transmitter (100) and the M TX The desired transmission current is generated by considering the mutual inductance M between the transmitting coils, and as a result, the transmission efficiency can be maximized by the phase-locked transmission currents. TX can be obtained through EM simulation. M TX The ABCD matrix can be derived from the equivalent circuit involving the two transmitting coils and calculated using the formula converted to the S matrix.

[0040] FIG. 4 is a schematic diagram of a transmitter according to one embodiment, and FIG. 5 is an exemplary circuit of a wireless power charging system according to one embodiment.

[0041] Referring to Fig. 4, the transmission module (110) transmits current I according to the control signal of the control unit (130). TX It is composed of a circuit that induces a current. The transmission module (110) can induce a transmission current having a desired size and phase through an input voltage determined by the control of the control unit (130).

[0042] The transmission module (110) may be composed of various circuits, for example, it may include a voltage amplifier (111), a control structure (112) of the voltage amplifier (111), a gate driver (113) of the voltage amplifier (111), a matching circuit (114), and a transmission coil (115). The voltage amplifier (111) may be composed of, for example, a class D inverter circuit.

[0043] The control structure (112) transmits current I from the control unit (130). TXReceives a digital-to-analog converter (DAC) signal for the voltage amplifier (111) and transmits the current I TX Input voltage V for size TX This can be controlled to be output. The control structure (112) can be configured as, for example, a buck converter circuit.

[0044] The gate driver (113) of the voltage amplifier (111) transmits the transmission current I from the control unit (130). TX A pulse width modulation (PWM) signal can be received. The transmission current I of the desired phase is generated by the PWM signal. TX can be induced. The control unit (130) can secure a wide charging area by changing the phase difference of the PWM signal at 180-degree intervals, thereby concentrating the magnetic field in a quadrant based on the receiver position.

[0045] Referring to FIG. 5, each transmission module (110-1, 110-2, 110-3) of the transmitter (100) transmits a transmission current I according to a control signal of the control unit (130). TX It is composed of a circuit that induces. Taking the transmitter module #1 (TX#1) (110-1) as an example, each transmitter module may include a class D inverter (111), a control structure (112), a gate driver (113) of the inverter (111), a matching circuit (114), and a transmitter coil (115). The class D inverter (111) may be configured as a differential structure. Meanwhile, the transmitter (100) may monitor the status of the receiver (200) in real time through BLE communication to control the size and phase of the transmission current for optimal efficiency.

[0046] The control unit (130) controls the mutual inductance M between the transmitting coils in the equivalent circuit of the three-dimensional wireless power charging system. TX Considering that, the desired transmission current I in each transmission moduleTX It is possible to calculate the magnitude and phase of the input voltage that can induce the signal, and generate control signals for applying them to the corresponding transmission module.

[0047] The control unit (130) transmits a DAC signal for current control to the control structure (112), so that the output voltage of the voltage amplifier (111) is the transmission current I TX It can be made to be a voltage for .

[0048] The control unit (130) transmits a PWM signal for phase control to the gate driver (113), so that the voltage amplifier (111) transmits a transmission current I having a desired phase. TX can be made to be induced.

[0049] FIG. 6 is an example of an equivalent circuit of a three-dimensional wireless power charging system according to one embodiment.

[0050] Referring to FIG. 6, each transmitting module and receiving module of the 3D wireless power charging system (10) can be expressed as an equivalent circuit (20) composed of transmitting circuits and receiving circuits.

[0051] V TXn is the input voltage (transmission voltage) of the nth transmission module, which is described in this disclosure as the output voltage of a class D inverter, and the input voltage can be provided by various circuits. M n is the mutual inductance between the nth transmitting coil and the receiving coil. M TX is the mutual inductance between the transmitting coils. Z Eq is the equivalent load impedance of the transmitter.

[0052] Transmission current I of the transmitter (100) for maximum transmission efficiency TX1 , I TX2 , I TX3 must be set.

[0053] First, the transmission efficiency (η) can be defined as in Equation 1. In Equation 1, α TXn Silver I TX1 and ITXn is the transmission current ratio between them.

[0054] [Mathematical Formula 1]

[0055]

[0056] To derive the optimal transmission current for maximum transmission efficiency, the optimal current ratio α TXn,opt and the optimal equivalent load impedance Z Eq,opt We need to calculate the transmission efficiency η as α TXn Differentiate it as in Equation 2 to obtain the optimal transmission current ratio α TXn,opt can be obtained. The transmission efficiency η is Z Eq Differentiate it to obtain the optimal equivalent load impedance Z as in Equation 3. Eq,opt Assuming that an ideal diode is used in the rectifier, the input DC voltage of the DC-DC converter is V Eq And Z Eq can be expressed as in mathematical expression 4. In mathematical expression 4, D is the duty cycle of the DC-DC converter, and V L is the load voltage.

[0057] [Equation 2]

[0058]

[0059] [Equation 3]

[0060]

[0061] [Equation 4]

[0062]

[0063] Using Equations 1 to 4, the optimal transmission current I TXn,opt can be expressed as in mathematical expression 5. That is, the optimal transmission current I of transmission module #1 TX1,opt is the optimal equivalent sub-wave impedance Z Eq,opt , equivalent receiving resistance R RX , load voltage V L , optimal transmission current ratio α TXn,opt, mutual inductance M n can be calculated using . The optimal transmission current of the remaining transmission modules is I TX1,opt can be calculated as the transmission current ratio.

[0064] [Equation 5]

[0065]

[0066] The maximum efficiency of mathematical expression 1 is It can be organized as in mathematical equation 6 using I. Here, I TXn silver can be defined as, can be expressed as in mathematical formula 7. Here, is the phase of the nth transmitting module.

[0067] [Equation 6]

[0068]

[0069] [Equation 7]

[0070]

[0071] Referring to mathematical expression 6, in order to maximize transmission efficiency, should be minimized, and also, referring to Equation 7, to maximize the transmission efficiency, the transmission current I TXn It can be seen that the phases must be synchronized.

[0072] Meanwhile, if Kirchhoff's voltage law is applied to each transmitter circuit, as in Equation 8, M TX The transmission current is affected by the , and as a result, it is difficult to satisfy the optimal transmission current size of Equation 5, and the transmission currents become unsynchronized.

[0073] [Equation 8]

[0074]

[0075] Therefore, M TXIt is necessary to compensate for the error in the transmission current caused by M, and for this purpose, the magnitude and phase of the input voltage of each transmission circuit are adjusted so that the desired optimal transmission current can be output. TX It can be calculated by considering . In the present disclosure, it is assumed that the control unit (130) calculates this, but of course, it is also possible for a separate computing device to calculate this.

[0076] The three-dimensional wireless power charging system (10) can be assumed to be a linear system since the transmitting coil and the receiving coil are weakly coupled. Based on the characteristics of the linear system, the magnitude and phase of the input voltage that can induce a specific transmitting current can be calculated by applying the superposition principle.

[0077] The equivalent circuit (20) can be classified into three modes according to the on / off input voltage of each transmission module. Mode 1 is a state in which only transmission module #1 operates, i.e., V TX1 Assume that this is on and the remaining input voltages are off. Mode 2 is the state in which only the transmitter module #2 operates, i.e., V TX2 Assume that this is in the on state and the remaining input voltages are in the off state. Mode 3 is the state in which only the transmitter module #3 operates, i.e. V TX3 Assume that this is in the on state and the remaining input voltages are in the off state.

[0078] In the equivalent circuit of each mode, an equation can be derived for each transmission circuit through Kirchhoff's voltage law, and the current equation for each transmission circuit can be derived through simultaneous equations.

[0079] By applying the principle of superposition to the current induced in each mode, the transmission current equation and the reception current equation can be derived, as in mathematical equation 9.

[0080] [Equation 9]

[0081]

[0082] The magnitude and phase of the input voltage for the desired transmission current of each transmission module can be calculated using the corresponding current equation in the equivalent circuit for extracting the input voltage. When a certain angle change occurs, V TX1 , V TX2 , V TX3 The optimal size and phase can be calculated as, for example, 2.46V∠0°, 2.9V∠-9.4°, 2.6V∠0.6°, and synchronized transmission currents can be induced to increase transmission efficiency by these voltages.

[0083] When the control unit (130) calculates an input voltage (target voltage) for a desired transmission current (target transmission current), it can control the transmission module to use the target voltage as an input voltage by transmitting a control signal to the corresponding transmission module. For example, the control unit (130) can control the transmission module to output an input voltage having a size for the transmission current by transmitting a control signal (e.g., a DAC signal) for the transmission current. In addition, the control unit (130) can control the transmission module to output an input voltage having a phase calculated for the transmission current by transmitting a control signal (e.g., a PWM signal) for the transmission current.

[0084] FIG. 7 is a flowchart illustrating an operation method of a transmitter of a three-dimensional wireless power charging system according to one embodiment.

[0085] Referring to Fig. 7, a transmitter (100) configured to transmit power to a receiver (200) through three orthogonal coils tracks the mutual inductance between each transmitting coil and the receiving coil (S110). The transmitter (100) can first check the status of the receiver through a low-power transmitting current.

[0086] The transmitter (100) calculates the equivalent load impedance and transmission current ratio required to calculate the transmission current (target transmission current) for maximum transmission efficiency by using the mutual inductance between each transmitting coil and receiving coil (S120). The transmitter (100) calculates the optimal equivalent load impedance Z of mathematical expression 3 based on the equivalent circuit. Eq,opt and the optimal transmission current ratio α of mathematical expression 2 TXn,opt can be calculated. The transmission current ratio of a specific transmission module can be defined as the ratio of the transmission current of the reference transmission module (transmission module #1) to the transmission current of the corresponding transmission module.

[0087] The transmitter (100) calculates the target transmission current in each transmission module using the equivalent load impedance and the transmission current ratio (S130). The transmitter (100) calculates the transmission current I of the transmission module #1 using the optimal equivalent load impedance and the optimal transmission current ratio, as in mathematical expression 5. TX1,opt can be calculated, I TX1,opt Using the transmission current ratio with , the transmission current of transmission module #2 and the transmission current of transmission module #3 can be calculated.

[0088] The transmitter (100) determines the magnitude and phase of the input voltage for inducing the target transmission current in each transmission module in an equivalent circuit including mutual inductance between transmission coils (S140). The mutual inductance between each transmission coil can be obtained through EM simulation. The transmitter (100) classifies modes according to the input voltage on / off of each transmission module in an equivalent circuit including mutual inductance between transmission coils, and obtains current equations that can calculate the transmission current of each transmission module by superimposing the transmission current induced in each mode. The transmitter (100) can calculate the magnitude and phase of the input voltage for the target transmission current of each transmission module by using the current equations in the equivalent circuit for extracting the input voltage.

[0089] The transmitter (100) applies an input voltage with a determined magnitude and phase to each transmission module, thereby inducing a target transmission current in each transmission module (S150). The transmission currents have an error in the mutual inductance between the transmission coils, and by compensating for the error by considering the mutual inductance between the transmission coils, transmission efficiency can be maximized.

[0090] In this way, according to the present disclosure, the problem of reduced transmission efficiency due to mutual inductance between transmission coils caused by process errors in the manufacturing process of orthogonal coils can be solved.

[0091] According to the present disclosure, even if interference due to mutual inductance between the transmitting coils exists in a loosely coupled system in which the transmitting coil and the receiving coil are loosely coupled, a decrease in transmission efficiency can be prevented.

[0092] According to the present disclosure, the magnitude and phase of the input voltage for a desired target transmission current can be simply calculated without a feedback loop.

[0093] The embodiments of the present disclosure described above are not implemented only through devices and methods, but may also be implemented through a program that realizes a function corresponding to the configuration of the embodiments of the present disclosure or a recording medium on which the program is recorded.

[0094] Although the embodiments of the present disclosure have been described in detail above, the scope of the present disclosure is not limited thereto, and various modifications and improvements made by those skilled in the art using the basic concepts of the present disclosure defined in the following claims also fall within the scope of the present disclosure.

Claims

1. A method of operating a transmitter configured to transmit power to a receiver through three orthogonal transmitting coils, For maximum transmission efficiency, a step of calculating the target transmission current in the transmission module including each transmission coil, A step of determining the magnitude and phase of the input voltage capable of inducing the target transmission current in each transmission module by considering the mutual inductance between the transmission coils, and A step of inducing the target transmission current in each transmission module through an input voltage determined for each transmission module. A method of operation comprising:

2. In paragraph 1, The step of calculating the above target transmission current is A step of tracking the mutual inductance between each transmitting coil and receiving coil, A step of calculating the equivalent load impedance and the transmission current ratio using the mutual inductance between each of the above transmitting coils and receiving coils, and A step of calculating the target transmission current in each transmission module using the above equivalent load impedance and the above transmission current ratio. A method of operation, comprising:

3. In paragraph 1, The step of determining the magnitude and phase of the above input voltage is In an equivalent circuit including mutual inductance between the above transmitter coils, a step of classifying modes according to the on / off input voltage of each transmitter module, A step of obtaining current equations that can calculate the transmission current of each transmission module by superimposing the transmission current induced in each mode, and A step of calculating the magnitude and phase of the input voltage for the target transmission current of each transmission module by using the above current equations in an equivalent circuit for extracting the input voltage. A method of operation, comprising:

4. In paragraph 1, The mutual inductance between the above transmitting coils is obtained through EM simulation, and the method of operation.

5. As a transmitter that transmits power to a receiver, A first transmitting module comprising a first transmitting coil; a second transmitting module comprising a second transmitting coil; a third transmitting module including a third transmitting coil, and A control unit that calculates a target transmission current for maximum transmission efficiency for each transmission module, determines the magnitude and phase of an input voltage that can induce the target transmission current for each transmission module by considering mutual inductance between transmission coils, and transmits a control signal to apply the magnitude and phase of the input voltage to the corresponding transmission module. A transmitter including:

6. In paragraph 5, A transmitter, wherein the first transmitting coil, the second transmitting coil, and the third transmitting coil are configured to be orthogonal to each other.

7. In paragraph 5, The above control unit Track the mutual inductance between each transmitting coil and receiving coil, Using the mutual inductance between each of the above transmitter coils and receiver coils, the equivalent load impedance and the transmission current ratio are calculated. A transmitter that calculates the target transmission current in each transmission module using the equivalent load impedance and the transmission current ratio.

8. In paragraph 5, The above control unit In the equivalent circuit including the mutual inductance between the above transmitter coils, the modes are classified according to the on / off input voltage of each transmitter module, By superimposing the induced transmission currents in each mode, current equations are obtained that can calculate the transmission current of each transmission module. A transmitter which calculates the magnitude and phase of the input voltage for the target transmission current of each transmission module by using the above current equations in an equivalent circuit for extracting the input voltage.

9. In paragraph 5, The above control unit By transmitting a first control signal to the corresponding transmission module, the output voltage of the voltage amplifier included in the corresponding transmission module becomes a voltage for the target transmission current, A transmitter that transmits a second control signal for phase control to the corresponding transmitter module, thereby inducing the target transmission current having a desired phase in the voltage amplifier.

10. In paragraph 5, The mutual inductance between the above transmitter coils is obtained through EM simulation.

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