JP7532092B2 - Power transmission device and wireless power supply system - Google Patents

Description

The present invention relates to a power transmission device and a wireless power supply system.

In a wireless power supply system, power is transmitted contactlessly from the power transmission coil of a power transmission device to the power receiving coil of a power receiving device, and the power is supplied from the power receiving device to a power supply target such as a battery. Conventionally, technology has been developed to control the output of the power transmission device depending on the state of the power receiving device.

For example, Patent Document 1 describes a technology in which, when the battery is fully charged, the power transmitting device stops normal power transmission and performs intermittent power transmission, and when the battery needs to be recharged, the power transmitting device resumes normal power transmission. At this time, the battery state is detected by a circuit in the power receiving device, and a command according to the battery state is sent from the power receiving device to the power transmitting device, and the power transmitting device that receives the command detects whether the battery is fully charged or needs to be recharged.

Patent Document 2 also describes a technology in which a power transmission device receives information indicating the state of a power receiving device, and the power transmission device transmits power to the power receiving device based on that information. At this time, information is transmitted and received by communication circuits provided in each of the power transmission device and the power receiving device.

Furthermore, Patent Document 3 describes a technology in which, when it is detected that a power receiving device has entered a power supply area, AC power of a predetermined frequency is supplied to the power transmitting antenna of the power transmitting device, and power is transmitted from the power transmitting antenna to the power receiving antenna of the power receiving device. In Patent Document 3, AC power of a plurality of different frequencies is supplied to the transmitting antenna by frequency scanning, and the reflection characteristics of the system including the transmitting antenna and the receiving antenna are detected during frequency scanning. The above-mentioned predetermined frequency is a resonant frequency at which the reflection characteristics are in a resonant state.

JP 2008-178195 A JP 2019-004694 A JP 2011-177009 A

Conventional technologies require additional circuits in addition to the circuits essential for wireless power supply, making the circuits more complex. For example, the technology described in Patent Document 1 requires an additional circuit for detecting the battery state in the power receiving device. In addition, the technology described in Patent Document 2 requires communication circuits to be provided in both the power transmitting device and the power receiving device. Furthermore, the technology described in Patent Document 3 requires a circuit for frequency scanning in the power transmitting device.

It is also preferable that the power transmitting device can control the output by itself without detecting the presence or absence of a power receiving device. However, the technology described in Patent Document 1 requires the power receiving device to notify the power transmitting device of the battery state. Also, the technology described in Patent Document 2 requires the power receiving device to transmit the state of the power receiving device to the power transmitting device. Furthermore, the technology described in Patent Document 3 requires the power transmitting device to detect the presence of a power receiving device within the power supply area.

The present invention aims to provide a power transmission device and a wireless power supply system that can control the output according to the state of the power receiving device by the power transmission device alone, without detecting the presence or absence of the power receiving device, with a simpler configuration.

A power transmission device according to one aspect of the present invention includes a power supply that supplies power to a power transmission coil, a calculation unit that calculates a parameter related to the impedance of a circuit electrically connected to the power supply based on the output voltage and output current of the power supply, and a control unit that controls the output of the power supply based on the parameter.

According to this aspect, the power transmitting device can control the output using the output voltage and output current, so it can control the output according to the state of the power receiving device without receiving information from the power receiving device. In this case, the power transmitting device does not need to detect the presence or absence of the power receiving device. In addition, the information required for control is the output voltage and output current, and a normal power transmitting device naturally includes a device for measuring this output voltage and output current. Therefore, the power transmitting device does not need to include an additional device, and can control the output according to the state of the power receiving device with a simple configuration.

In the above aspect, the power receiving device includes a power receiving coil that receives power from the power transmitting coil in a non-contact manner, and the parameters may include mutual inductance between the power transmitting coil and the power receiving coil.

According to this aspect, the mutual inductance indicates the strength of coupling between the power transmitting coil and the power receiving coil. The power transmitting device can estimate the state of the power receiving device by using the mutual inductance, and can therefore more appropriately control the output according to the state of the power receiving device.

In the above aspect, the power receiving device includes a load connected to a power receiving coil that receives power from the power transmitting coil in a non-contact manner, and the parameters may include a resistance value of the load.

According to this aspect, the calculated resistance value of the load changes depending on, for example, the connection state of the load. Therefore, by using the resistance value of the load, the power transmitting device can more appropriately control the output according to the state of the power receiving device.

In the above aspect, the power receiving device includes a power receiving coil that receives power from the power transmitting coil in a non-contact manner, and a load connected to the power receiving coil, and the calculation unit may calculate the magnitude and phase difference of the impedance based on the measured output voltage and output current, and calculate the mutual inductance between the power transmitting coil and the power receiving coil and the resistance value of the load, which are included in the parameters, based on the calculated magnitude and phase difference of the impedance.

According to this aspect, the power transmission device can calculate the mutual inductance and the load resistance value included in the impedance-related parameters through simpler processing.

In the above aspect, the control unit may control the output of the power supply based on a table that associates parameters with the control contents of the output of the power supply.

According to this aspect, the power transmission device can control the output of the power source through simple processing.

In the above aspect, the control unit may compare the parameter with a predetermined threshold value and control the output of the power source based on the comparison result.

According to this aspect, the power transmission device can control the output of the power source through simple processing.

A wireless power supply system according to another aspect of the present invention includes a power receiving device, a power transmission coil that transmits power to the power receiving device in a non-contact manner, a power source that supplies power to the power transmission coil, a calculation unit that calculates a parameter related to the impedance of a circuit electrically connected to the power source based on the output voltage and output current of the power source, and a control unit that controls the output of the power source based on the parameter.

According to this aspect, the power transmitting device can control the output using the output voltage and output current, and can therefore control the output according to the state of the power receiving device without receiving information from the power receiving device. In this case, the power transmitting device does not need to detect the presence or absence of the power receiving device. In addition, the information required for control is the output voltage and output current, and a normal power transmitting device naturally includes a device for measuring this output voltage and output current. Therefore, the power transmitting device does not need to include an additional device, and can control the output according to the state of the power receiving device with a simple configuration.

The present invention provides a power transmission device and a wireless power supply system that can control output according to the state of the power receiving device by the power transmission device alone, without detecting the presence or absence of a power receiving device, with a simpler configuration.

1 is a schematic diagram of a configuration of a wireless power supply system according to an embodiment of the present invention. 2 is a schematic diagram illustrating a configuration of a power transmitting device according to the embodiment. FIG. FIG. 2 is a diagram showing an equivalent circuit of the circuit shown in FIG. 1 . FIG. 4 shows a circuit in which the load is removed from the circuit shown in FIG. 3. FIG. 1 is a diagram showing a simplified configuration of a wireless power supply system. FIG. 6 is a diagram showing an equivalent circuit of the circuit shown in FIG. 5 . FIG. 11 illustrates an example of a control table. 5 is a flowchart illustrating an example of a process performed by a power transmitting device according to an embodiment of the present invention.

A preferred embodiment of the present invention will be described with reference to the attached drawings. In each drawing, the same reference numerals are used to denote the same or similar configurations.

Figure 1 is a schematic diagram of a wireless power supply system 1 according to one embodiment of the present invention. The wireless power supply system 1 according to this embodiment includes a power transmitting device 10 and a power receiving device 20.

The power transmission device 10 is a device that transmits AC power to the power receiving device 20 in a non-contact manner. The power receiving device 20 is a device that receives AC power from the power transmission device 10 and supplies power to a load 30 connected to the power receiving device 20. The load 30 is, for example, a power storage device that can store the power supplied from the power receiving device 20.

In this embodiment, the wireless power supply system 1 is described as having one power transmission device 10, but the wireless power supply system 1 may have multiple power transmission devices 10. Also, in this embodiment, the wireless power supply system 1 is described as having one power receiving device 20, but the wireless power supply system 1 may have multiple power receiving devices 20.

The power transmission device 10 according to this embodiment mainly comprises a power source 100, a control device 110, and a power transmission coil 120. The power source 100 is a voltage source that supplies high-frequency AC power to the power transmission coil 120. The control device 110 is a device that controls the output of the power source 100. The power transmission coil 120 is a coil that transmits AC power to the power receiving device 20 in a non-contact manner.

The power receiving device 20 according to this embodiment mainly includes a power receiving coil 200, a rectifier circuit 210, and a smoothing circuit 230. The power receiving device 20 also includes a wiring inductor 220. The power receiving coil 200 receives AC power contactlessly from the power transmitting coil 120 of the power transmitting device 10. The rectifier circuit 210 can rectify the AC power received by the power receiving coil 200. The smoothing circuit 230 can smooth the output power of the rectifier circuit 210. The power receiving coil 200 is connected to a load 30 via the rectifier circuit 210 and the smoothing circuit 230, and the power smoothed by the smoothing circuit 230 is supplied to the load 30.

The configuration of the power transmission device 10 according to this embodiment will be described in more detail with reference to FIG. 2. The power transmission device 10 further includes a voltmeter 102 (measurement unit) that measures the output voltage of the power source 100 and an ammeter 104 (measurement unit) that measures the output current of the power source 100. The measurement results of the voltmeter 102 and the ammeter 104 are transmitted to the control device 110.

The control device 110 can control the output of the power source 100. The operation of the control device 110 is performed by the processing unit 111 and the memory unit 118 working together.

The processing unit 111 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory). The ROM included in the processing unit 111 stores processing programs for executing various processes. The CPU executes the processing programs stored in the ROM or the various programs stored in the storage unit 118 to execute various processes. The RAM included in the processing unit 111 stores data that is temporarily used during the execution of the various programs.

The memory unit 118 includes a storage device including a static random access memory (SRAM), a flash memory, a hard disk, or the like. The memory unit 118 stores various data, various computer programs executed by the CPU, and information for controlling the output of the power supply 100 (e.g., a control table, which will be described later), and the like.

The processing unit 111 performs various processes related to controlling the output of the power supply 100. The operation of the processing unit 111 is performed by the acquisition unit 112, the calculation unit 114, and the control unit 116 working together.

The acquisition unit 112 can acquire the measurement results from the measurement unit. In this embodiment, the acquisition unit 112 can acquire the output voltage measured from the voltmeter 102 and the output current measured from the ammeter 104. The acquisition unit 112 transmits the acquired output voltage and output current to the calculation unit 114.

The calculation unit 114 can calculate parameters related to the impedance of a circuit electrically connected to the power source 100 based on the output voltage and output current of the power source 100. Specifically, the calculation unit 114 calculates parameters related to the impedance of a circuit including the power transmission coil 120 connected to the power source 100 by wiring, the power receiving device 20 connected to the power transmission coil 120, and the load 30. Note that the circuit electrically connected to the power source 100 does not have to be mechanically connected to the power source 100. Therefore, the circuit electrically connected to the power source 100 includes the power receiving device 20 and the load 30 to which power is supplied in a non-contact manner.

The parameters calculated by the calculation unit 114 will be described with reference to FIG. 3. FIG. 3 is a diagram showing an equivalent circuit of the circuit shown in FIG. 1. A circuit including the wireless power supply system 1 can generally be represented by an equivalent circuit in which a power transmission coil 120 and a power receiving coil 200 are coupled, as shown in FIG. 3.

In the equivalent circuit shown in Fig. 3, the transmitting coil 120 and the receiving coil 200 in Fig. 1 are replaced with a circuit including three inductances (first inductor 122, second inductor 124, and third inductor 126). Here, if the inductance of the transmitting coil 120 is L _S and the inductance of the receiving coil 200 is L _L , the inductances of the first inductor 122, second inductor 124, and third inductor 126 are expressed as L _S -M, L _L -M, and M, respectively. Here, M is the mutual inductance between the transmitting coil 120 and the receiving coil 200.

The mutual inductance M is expressed by the following formula.
M=k√(L _S L _L )...(1)

The coupling coefficient k is a value ranging from 0 to 1, and indicates the degree of coupling between the power transmission coil 120 and the power receiving coil 200. When the dimensions of the power transmission coil 120 and the power receiving coil 200 and the surrounding environment of each do not change, the coupling coefficient k changes depending on the relative positional relationship between the power transmission coil 120 and the power receiving coil 200. Specifically, the smaller the distance between the power transmission coil 120 and the power receiving coil 200, the stronger the coupling between the power transmission coil 120 and the power receiving coil 200, and the closer the coupling coefficient k is to 1. On the other hand, the greater the distance between the power transmission coil 120 and the power receiving coil 200, the weaker the coupling between the power transmission coil 120 and the power receiving coil 200, and the closer the coupling coefficient k is to 0.

In this embodiment, the calculation unit 114 can calculate the mutual inductance M and the resistance value R L of the load ₃₀ , which are included in the parameters related to the impedance of a circuit (hereinafter also referred to as the "load side circuit 22") electrically connected to the power supply 100, based on the output voltage and output current of the power supply 100. More specifically, the calculation unit 114 can calculate the magnitude and phase difference of the impedance of the load side circuit 22, and calculate the mutual inductance M and the resistance value R _L based on the calculated magnitude and phase difference of the impedance. Details of the method in which the calculation unit 114 calculates the parameters will be described later. The calculation unit 114 transmits the calculated parameters to the control unit 116.

The control unit 116 can control the output of the power supply 100 based on the parameters calculated by the calculation unit 114. In this embodiment, the control unit 116 can control the output of the power supply 100 based on at least one of the mutual inductance M and the resistance value R _L calculated by the calculation unit 114. The method of controlling the output of the power supply 100 by the control unit 116 will be described in detail later.

The following provides a more detailed explanation of the parameters of the load side circuit 22 calculated by the calculation unit 114. The circuit electrically connected to the power supply 100 may be in, for example, the following three states.
First state: A state in which the power transmitting coil 120 and the power receiving coil 200 are electromagnetically coupled, and power is being supplied to the load 30. Second state: A state in which the power transmitting coil 120 and the power receiving coil 200 are not electromagnetically coupled at all. Third state: A state in which the power transmitting coil 120 and the power receiving coil 200 are electromagnetically coupled, but no power is being supplied to the load 30.

The first state is the state of the circuit shown in FIG. 1 and FIG. 3 described above. The second state will be explained based on the first state. The second state can be considered to be a state in which the power transmitting device 10 is present but the power receiving device 20 is not present. The second state can be considered to be a state in which the mutual inductance M is 0 in the circuit of FIG. 3. At this time, the third inductor 126 is short-circuited, so the power output from the power source 100 returns to the power source 100 through the path of the first inductor 122 and the third inductor 126.

Next, the third state will be described. Fig. 4 is a diagram showing a circuit in which the load 30 has been removed from the circuit shown in Fig. 3. The state of the circuit shown in Fig. 4 is an example of the third state. In general, when the load 30 is removed, the impedance between the two terminals to which the load 30 was connected (i.e., the first terminal 302 and the second terminal 304) can be considered to be infinite. Therefore, the state in Fig. 4 is the state in Fig. 3 where R _L is infinite.

As described above, the circuits (load side circuits 22, 26) electrically connected to the power source 100 are different in the first to third states. When the power source 100 supplies high-frequency AC power, the difference in the load side circuits is manifested as a difference in the absolute value and phase difference of the output voltage and output current of the AC power. In other words, the power transmission device 10 can estimate the state of the load side circuit by acquiring the output voltage and output current of the power source 100.

The following describes a method in which the calculation unit 114 derives a relational expression between the output voltage and the output current and calculates parameters related to the impedance of the load side circuit. In this description, in order to simplify the calculation, the rectifier circuit 210, the inductor 220, and the smoothing circuit 230 are not present in the power receiving device 20. Specifically, the description will be made using the circuit diagram shown in FIG. 5. FIG. 5 is a simplified diagram showing the configuration of the wireless power supply system 2. It is assumed that a load 32 is connected to the wireless power supply system 2, and that the wireless power supply system 2 supplies power to the load 32.

Even if the power receiving device 20 includes a rectifier circuit 210 and a smoothing circuit 230 and AC power is converted to DC power, the power transmitting device 10 can calculate parameters related to the impedance of the load side circuit using the method described below and control the output of the power source 100.

Fig. 6 is a diagram showing an equivalent circuit of the circuit shown in Fig. 5. Here, the impedance of the third inductor 126 is _Z2 , and the impedance of the series circuit of the second inductor 124 and the load ₃₂ is _Z3 . Since this series circuit and the third inductor 126 are connected in parallel, the combined impedance _Z23 of Z2 and _Z3 is expressed by the following equation.
Z ₂₃ = Z ₂ Z ₃ / (Z ₂ + Z ₃ )...(2)
_Z23 is the impedance of the parallel circuit 27 of the third inductor 126 and the above-mentioned series circuit.

Moreover, the load side circuit 28 seen from the power supply 100 is a series circuit of the first inductor 122 and the parallel circuit 27. Therefore, if the impedance of the load side circuit 28 is _Z0 and the impedance of the first inductor 122 is _Z1 , _Z0 is expressed by the following equation.
Z ₀ =Z ₁ +Z ₂₃ ...(3)

Here, when the angular frequency of the AC power output by the power supply 100 is ω and the imaginary unit is j, _Z1 is expressed by the following equation.
Z ₁ = jω(L _S -M)...(4)

Further, from the above formula (2), _Z23 is expressed by the following formula.
Z ₂₃ = [{jω(L _L −M)R _L }−ω ² M(L _L −M)]/(R _L +jωL _L )
...(5)

Furthermore, from the above equations (3), (4), and (5), Z ₀ is expressed by the following equation.
Z ₀ = jω(L _S −M) + [{jω(L _L −M)R _L }−ω ² M(L _L −M)]/(R _L +jωL _L )
=Re{Z ₀ }+Im{Z ₀ }
...(6)
Here, Re{Z ₀ } is the real part of Z ₀ expressed on the complex plane, and Im{Z ₀ } is the imaginary part of Z ₀ expressed on the complex plane. Z ₀ having an imaginary component on the complex plane is synonymous with the existence of a phase difference between the voltage applied to the load side circuit 28 (i.e., the output voltage) and the current flowing through the load side circuit 28 (i.e., the output current).

Furthermore, for any Z ₀ , the output voltage V(t) and output current I(t) of the power supply 100 on the complex plane satisfy the following equations.
V(t)=Z ₀ I(t)...(7)
I(t)=(1/Z ₀ )V(t)...(8)

Here, t represents time. For ease of explanation, assume that V(t) is a sinusoidal AC voltage. If _V0 is the maximum value of V(t), then V(t) is expressed by the following equation.
V(t)=V ₀ exp {jωt}...(9)
In a typical power supply 100, V ₀ and ω are set values or the like and are known values.

By substituting equation (9) into equation (8), the following equation is obtained, where θ is the phase difference between the output voltage V(t) and the output current I(t).
I(t)=|V ₀ /Z ₀ |exp{j(ωt-θ)}...(10)

From the above, the calculation unit 114 can calculate the magnitude |Z ₀ | of Z ₀ and the phase difference θ using the measured output voltage V(t) and output current I(t). The calculation unit 114 can also calculate Z ₀ on the complex plane based on |Z ₀ | and θ. Furthermore, the calculation unit 114 can calculate M and R _L based on the calculated Z ₀ and the above-mentioned equation (6).

In this way, in the wireless power supply system according to the present embodiment, the power transmitting device 10 measures the output voltage and output current of the power source 100, and is able to calculate M and _RL based on the measured output voltage and output current. This allows the power transmitting device 10 to estimate the state of the power receiving device 20 without receiving a signal indicating the state of the power receiving device 20 from the power receiving device 20.

Note that devices for measuring the output voltage and output current of the power source 100 (e.g., a voltmeter 102 and an ammeter 104) are naturally implemented in normal power sources for power control and equipment protection. In other words, according to this embodiment, the power transmitting device 10 alone can estimate whether or not it is necessary to supply power to the power receiving device 20 without incurring additional costs.

Next, a method in which the control unit 116 according to this embodiment controls the output of the power source 100 based on the parameters calculated by the calculation unit 114 will be specifically described. The control unit 116 according to this embodiment can control the output of the power source 100 based on a control table that associates the calculated parameters with the control content of the output of the power source 100.

7 is a diagram showing an example of the control table 130. In the control table 130, the values of M and R _L are divided into a plurality of ranks (control No.), and each control No. is associated with a control content. For example, control No. 1, where M is M1 to M2 and R _L is R1 to R2, is associated with a control content of continuing output. This is because, when M and R _L match the values of control No. 1, it is estimated that the wireless power supply system is in an appropriate state for wireless power supply.

Moreover, control No. 2 in which M is M3 to M4 and R _L is R3 to R4 is associated with a control content for reducing the output. Here, reducing the output may be reducing the output voltage or making the output intermittent. Furthermore, control No. 3 in which M is M5 to M6 and R _L is R5 to R6 is associated with a control content for stopping the output. This is because, when M and R _L match the values of Control No. 2 or Control No. 3, it is estimated that the wireless power supply system is in an inappropriate state for wireless power supply. For example, when M is a value very close to 0 or R _L is a very high value, the combination of M and R _L matches the value of Control No. 2 or Control No. 3.

Note that the control content may be associated with only one of the parameters M and R _L. Also, the control content may be associated with various information in addition to the parameters M and R _L. Furthermore, the control content may include various control contents such as the magnitude of the set output voltage.

The control unit 116 can control the output of the power supply 100 by using the control table 130. Specifically, the control unit 116 can refer to the control table and control the output of the power supply 100 so as to realize the control content associated with the calculated combination of M and R _L. For example, when the value of M is between M1 and M2 and the value of R _L is between R1 and R2, the control unit 116 can cause the power supply 100 to continuously output an appropriate output voltage. Also, when the value of M is between M3 and M4 and the value of R _L is between R3 and R4, the control unit 116 can reduce the output of the power supply 100.

Figure 8 is a flowchart showing an example of processing by the power transmission device 10 according to this embodiment. Below, the flow of processing by the power transmission device 10 will be described with reference to Figure 8. At the time when the processing shown in Figure 8 is started, it is assumed that the power transmission device 10 is transmitting power to the power receiving device 20 in a non-contact manner, and the output voltage and output current of the power source 100 of the power transmission device 10 are being measured.

First, the acquisition unit 112 acquires the measured output voltage and output current of the power supply 100 from the voltmeter 102 and ammeter 104 (step S101).

Next, the calculation unit 114 calculates parameters related to the impedance of the circuit electrically connected to the power supply 100 based on the output voltage and output current acquired in step S101 (step S103). Specifically, the calculation unit 114 calculates the magnitude and phase difference of the impedance based on the output voltage and output current, and calculates the mutual inductance M and the resistance value _RL of the load based on the calculated magnitude and phase difference of the impedance.

Next, the control unit 116 controls the output of the power source 100 based on the parameters calculated in step S103 (step S105). Specifically, the control unit 116 controls the output of the power source 100 so as to realize the control content of the control table in which M and R _L calculated in step S103 match. When the control unit 116 controls the output of the power source, the process shown in Fig. 8 ends. Note that after the process shown in Fig. 8 ends, the process shown in Fig. 8 may be repeatedly performed.

The power transmission device 10 according to this embodiment calculates parameters related to the impedance of the circuit connected to the power source 100 based on the output voltage and output current of the power source 100, and can control the output of the power source 100 based on the calculated parameters. Therefore, the power transmission device 10 can control the output according to the state of the power receiving device 20 by itself, without detecting the presence or absence of the power receiving device 20.

In addition, a typical power transmission device naturally includes a device for measuring the output voltage and output current of the power source 100 and a device for controlling the output of the power source. Therefore, the power transmission device 10 according to this embodiment does not need to include new circuits and devices in addition to the configuration required for wireless power supply, and can control the output according to the state of the power receiving device 20 with a simple configuration.

Furthermore, the power transmission device 10 according to this embodiment is capable of estimating the state of the power receiving device 20 based on the calculated parameters. The power transmission device 10 can control the output of the power source 100 based on the estimation result. Therefore, when no load is connected to the power receiving device 20 or when the power receiving device 20 does not exist, the power transmission device 10 can suppress the power transmission device 10 from emitting power unnecessarily.

As described above, the wireless power supply system 1 according to this embodiment can increase the efficiency of power supply by the power transmission device 10 without incurring the cost of additional equipment.

The above-described embodiments are intended to facilitate understanding of the present invention, and are not intended to limit the present invention. The elements of the embodiments and their arrangements, materials, conditions, shapes, sizes, etc. are not limited to those exemplified, and may be modified as appropriate. In addition, configurations shown in different embodiments may be partially substituted or combined.

In the above embodiment, the power supply 100 is described as a voltage source, but the power supply 100 may be a current source.

In the above embodiment, the control unit 116 has been described as controlling the output of the power source 100 based on the control table 130, but the control unit 116 may control the output of the power source 100 without using the control table 130. For example, the control unit 116 may continue to calculate parameters (e.g., M and R _L ) in real time and control the output of the power source 100 in accordance with the calculated parameters.

The control unit 116 may also compare the calculated parameter with a predetermined threshold value and control the output of the power source 100 based on the comparison result. The threshold value may be set in advance and stored in the storage unit 118. The control unit 116 may reduce or stop the output of the power source 100 when the calculated parameter is equal to or less than the threshold value (or equal to or more than the threshold value). For example, the control unit 116 may reduce or stop the output of the power source 100 when M is equal to or less than the threshold value. The control unit 116 may also reduce or stop the output of the power source 100 when R _L is equal to or more than the threshold value. This allows the power transmission device 10 to suppress unnecessary power supply and reduce power loss according to the state of the power receiving device 20, without communicating with the power receiving device 20 or receiving a signal related to power control from the power receiving device 20.

In the above embodiment, the control unit 116 has been described as controlling the output of the power source 100 based on M and R _L included in the parameters related to impedance. The parameters used by the control unit 116 to control the output of the power source 100 are not limited to M and R _L , and may be various parameters related to impedance. For example, the control unit 116 may set the magnitude or phase of the impedance as a parameter and control the output of the power source 100 based on the parameter.

1, 2...wireless power supply system, 10...power transmission device, 100...power source, 102...voltmeter, 104...ammeter, 110...control device, 111...processing unit, 112...acquisition unit, 114...calculation unit, 116...control unit, 118...storage unit, 120...power transmission coil, 122...first inductor, 124...second inductor, 126...third inductor, 130...control table, 20...power receiving device, 22, 28...load side circuit, 200...power receiving coil, 210...rectifier circuit, 230...smoothing circuit, 30, 32...load

Claims (6)

a power transmitting coil for transmitting power to a power receiving device in a non-contact manner;
a power source that supplies power to the power transmitting coil;
a calculation unit that calculates a parameter related to the impedance of a circuit electrically connected to the power supply based on an output voltage and an output current of the power supply;
A control unit that controls an output of the power source based on the parameters;
Equipped with
The power receiving device includes a power receiving coil that receives power from the power transmitting coil in a non-contact manner, and a load connected to the power receiving coil,
the calculation unit calculates a magnitude and a phase difference of the impedance based on the measured output voltage and the measured output current, and calculates a mutual inductance between the transmitting coil and the receiving coil and a resistance value of the load, which are included in the parameters, based on the calculated magnitude and phase difference of the impedance;
The control unit controls whether to continue, reduce, or stop the output of the power source based on the mutual inductance and a resistance value of the load . the power receiving device includes a power receiving coil that receives power from the power transmitting coil in a non-contact manner,
The parameters include a mutual inductance between the transmitting coil and the receiving coil.
The power transmitting device according to claim 1 . the power receiving device includes a load connected to a power receiving coil that receives power from the power transmitting coil in a non-contact manner;
The parameters include a resistance value of the load.
The power transmitting device according to claim 1 or 2. The control unit controls the output of the power source based on a table in which the parameters are associated with control contents of the output of the power source.
The power transmitting device according to claim 1 . The control unit compares the parameter with a predetermined threshold value and controls an output of the power source based on a comparison result.
The power transmitting device according to claim 1 . A power receiving device;
A power transmitting coil that transmits power to the power receiving device in a non-contact manner;
a power source that supplies power to the power transmitting coil;
a calculation unit that calculates a parameter related to the impedance of a circuit electrically connected to the power supply based on an output voltage and an output current of the power supply;
A control unit that controls an output of the power source based on the parameters;
Equipped with
The power receiving device includes a power receiving coil that receives power from the power transmitting coil in a non-contact manner, and a load connected to the power receiving coil,
the calculation unit calculates a magnitude and a phase difference of the impedance based on the measured output voltage and the measured output current, and calculates a mutual inductance between the transmitting coil and the receiving coil and a resistance value of the load, which are included in the parameters, based on the calculated magnitude and phase difference of the impedance;
The control unit controls whether to continue, reduce, or stop the output of the power source based on the mutual inductance and the resistance value of the load .