JP5319652B2 - Wireless power transmission device - Google Patents

Description

  The present disclosure relates to wireless power transmission.

  2. Description of the Related Art Wireless power transmission technology that uses a power transmission coil and a power reception coil to transmit power in a contactless manner is employed in various devices. In such a wireless power transmission technology, it is indispensable to perform impedance matching between power transmission and reception from the viewpoint of improving transmission efficiency. In particular, in power transmission using a resonance circuit with a high Q factor, transmission over a relatively long distance of several tens of centimeters to several meters is possible, and impedance matching between power transmission and reception must be performed over a wide distance range. . As a method for impedance matching, there are known a method of preparing a number of pickup coils that are electromagnetically coupled to a power transmission / reception coil and operate as an impedance converter, and a method of inserting a variable capacitor in series and parallel.

JP 2010-158151 A JP 2009-60736 A

However, in the above prior art, impedance matching can be easily performed. However, when the coupling between the power transmission coil and the power reception coil is strong, impedance matching cannot be performed at a certain frequency and transmission efficiency is deteriorated. There is a problem of end up.
An object of the present invention is to provide a wireless power transmission device that can perform impedance matching when the coupling between the power transmission coil and the power reception coil varies widely.

  In order to solve the above-described problem, a wireless power transmission device according to an embodiment of the present invention includes a resonable coil connected to a power source, a first variable unit, a second variable unit, and a control unit. The first variable unit is arranged as a π-type circuit or a T-type circuit between the coil and the power supply, and includes a variable circuit element capable of converting the impedance of the power supply load as viewed from the coil side. The second variable unit includes a loop that is electromagnetically coupled to the coil, and converts the impedance of the power supply load and the first variable unit viewed from the coil side by changing a mutual inductance between the coil and the loop. Is possible. The control unit performs impedance conversion using at least one of the first variable unit and the second variable unit to perform impedance matching.

The conceptual diagram of the wireless power transmission apparatus which concerns on 1st Embodiment. The figure which shows another example of the conceptual diagram of the wireless power transmission apparatus which concerns on 1st Embodiment. The block diagram which shows the wireless power transmission apparatus which concerns on 1st Embodiment. The figure which shows an example of the 1st impedance variable part which concerns on 1st Embodiment. The figure which shows an example of a 2nd impedance variable part. The figure which shows an example of the equivalent circuit of the wireless power transmission apparatus which concerns on 1st Embodiment. The figure which shows another example of the equivalent circuit at the time of using a variable circuit element for the wireless power transmission apparatus which concerns on 1st Embodiment. The figure which shows the simulation result of electric power transmission efficiency. The figure which shows another example of the simulation result of electric power transmission efficiency. The flowchart which shows the matching procedure of the impedance of a wireless power transmission apparatus. The flowchart which shows another example of the matching procedure of the impedance of a wireless power transmission apparatus. The figure which shows an example of the equivalent circuit of the wireless power transmission apparatus which concerns on 2nd Embodiment. The figure which shows an example of the trans-pi type element conversion in Norton conversion. The figure which shows another example of the equivalent circuit at the time of using a variable circuit element for the wireless power transmission apparatus which concerns on 2nd Embodiment. The block diagram which shows the wireless power transmission apparatus which concerns on 3rd Embodiment. The figure which shows an example of the equivalent circuit of the wireless power transmission apparatus 1500 which concerns on 3rd Embodiment. The figure which shows an example of the equivalent circuit of a resonance period coupling filter. The block diagram which shows the wireless power transmission apparatus which concerns on 4th Embodiment. The block diagram which shows the wireless power transmission apparatus in the case of switching electric power transmission and wireless communication. The figure which shows the example of arrangement | positioning with the coil for electric power transmission, and the coil for radio | wireless communication. The figure which shows another example of the conceptual diagram of the wireless power transmission apparatus which concerns on 4th Embodiment.

Hereinafter, a wireless power transmission device according to an embodiment of the present disclosure will be described in detail with reference to the drawings. Note that, in the following embodiments, the same numbered portions are assumed to perform the same operation, and repeated description is omitted.
(First embodiment)
A conceptual diagram of a wireless power transmission apparatus according to the first embodiment will be described with reference to FIG.
A wireless power transmission device 100 according to the first embodiment includes a power transmission coil 101 and a power transmission unit 102. Furthermore, the power transmission unit 102 includes a first impedance variable unit 151 (also referred to as a first variable unit), a second impedance variable unit 152 (also referred to as a second variable unit), and a control unit 153.

The power transmission coil 101 is configured by a self-resonant coil or a coil that resonates by adding a capacitor. In addition, when using two or more power transmission coils 101, although it is arbitrary regarding a shape, it is desirable to make the resonant frequency of a power transmission coil the same.
The first impedance variable unit 151 includes a transformer, for example, and can convert the input impedance to a constant multiple.
The second impedance variable unit 152 includes, for example, a pickup coil (hereinafter referred to as a loop), and performs impedance conversion by changing the mutual inductance of the coupling between the loop and the power transmission coil 101 (hereinafter referred to as loop coupling). be able to.
The control unit 153 performs impedance conversion using at least one of the first impedance variable unit 151 and the second impedance variable unit 152 to perform impedance matching.

Next, another example of the wireless power transmission apparatus will be described with reference to FIG.
For example, as illustrated in FIG. 2A, when transmitting using a plurality of power transmission coils 101, the power transmission unit 102 includes a first impedance variable unit 151 and a second impedance variable unit for each of the plurality of power transmission coils 101. 152 may be included. 2B, the power transmission unit 102 may include a second impedance variable unit 152 for each power transmission coil 101, and may include only one first impedance variable unit 151. On the other hand, as shown in FIG. 2C, the power transmission unit 102 may include a first impedance variable unit 151 for each power transmission coil 101, and may include only one second impedance variable unit 152. Further, as illustrated in FIG. 2D, transmission may be performed using a plurality of power transmission coils 101 and a plurality of power transmission units 102.

Next, the wireless power transmission apparatus will be described with reference to FIG.
The wireless power transmission apparatus 300 includes a power transmission coil 101, a first impedance variable unit 151, a second impedance variable unit 152, a voltage source 301, and a voltage source load 302.
Since a general voltage source may be used as the voltage source 301, description thereof is omitted here.
The voltage source load 302 is a load that the voltage source 301 can have. Note that the wireless power transmission device 300 is used as a power transmission device, but when used as a power reception device, the voltage source and the voltage source load can be replaced with a power reception side load.

Next, an example of the first impedance variable unit 151 will be described with reference to FIG.
The first impedance variable unit 151 converts the impedance viewed from the power transmission coil 101 side (here, the impedance of the voltage source load) into a constant multiple. Specifically, for example, a transformer as shown in FIG. 4 is assumed. When the winding ratio between the primary side and the secondary side of the transformer is 1: N, the primary-side impedance and the secondary-side impedance have the relationship of Equation 1.

  Therefore, by adjusting the winding ratio of the transformer, it is possible to convert the impedance to an arbitrary constant multiple. The first impedance variable unit 151 may be anything as long as it can convert the impedance to a constant multiple, such as a transformer.

Next, the second impedance variable unit 152 will be described with reference to FIG.
The second impedance variable unit 152 converts the power load and the impedance of the first impedance variable unit 151 viewed from the power transmission coil 101 side by changing the loop coupling. As a method of changing the loop coupling, there is a method of changing the distance between the loop and the power transmission coil 101 by moving the loop, or using a magnetic material inserted between the loop and the power transmission coil 101. . The method is not limited to the above method, and any method may be used as long as the coupling between the loop and the power transmission coil 101 can be arbitrarily changed.
When the loop coupling is expressed by an equivalent circuit, where M is the mutual inductance of the loop coupling between the loop 501 and the power transmission coil 502 as shown in FIG. 5A, a symmetrical T-type circuit as shown in FIG. Become. This symmetric T-type circuit is called a K inverter and is known to operate as an impedance inverter having a four-terminal matrix as shown in Equation 2.

  That is, the impedance is converted corresponding to the mutual inductance between the loop and the power transmission coil. Hereinafter, the coupling between the power transmission coil and the power receiving coil of the receiving device is referred to as coil coupling.

Next, an equivalent circuit of the wireless power transmission apparatus 300 according to the first embodiment will be described with reference to FIG.
It is assumed that the first impedance variable unit 151 uses a transformer (transformer) and the second impedance variable unit 152 uses a loop. Although the first impedance variable unit 151 and the second impedance variable unit 152 are independent, a structure in which the first impedance variable unit 151 and the second impedance variable unit 152 are integrated may be used. For example, a transformer with a transformer inserted in the middle of a loop or a single-turn transformer (variable transformer) with a plurality of winding loops may be used.
Therefore, even when the coil coupling between the power transmission coil and the power reception coil is changed by the impedance conversion by the first impedance variable unit 151 and the second impedance variable unit 152 independently or alternately, the impedance matching can be performed flexibly. It becomes possible.

Next, another example of an equivalent circuit of the wireless power transmission apparatus 300 according to the first embodiment will be described with reference to FIG.
Although the first impedance variable unit 151 is configured by a variable transformer, a variable transformer such as a single-winding transformer or a method of switching a plurality of transformers by switching may be used. In accordance with the strength of the coil coupling, the control unit 153 determines the optimum value of the voltage source load impedance and the optimum value of the loop coupling as viewed from the power transmission coil side 101 so that the power transmission efficiency is maximized.
In addition, impedance matching needs to be performed when the power transmission of the wireless power transmission apparatus 300 starts, when the coil coupling changes, or when the power transmission efficiency deteriorates. In this case, the first impedance variable unit 151 uses a variable transformer as shown in FIG. 7 to adjust the winding ratio so that the power transmission efficiency is maximized. Then, the second impedance variable unit 152 performs impedance matching so that the power transmission efficiency is maximized at a desired frequency by changing the loop coupling.

In addition, as a method of detecting the coil coupling, for example, there is a method in which the power receiving side load impedance is short-circuited and detected by a difference between two frequencies at which the power transmission side reflectance is minimized. Moreover, as a method for detecting the deterioration of the power transmission efficiency, for example, it can be detected by monitoring the received power supplied to the power receiving side load, and this may be used.
Further, the power receiving side load may fluctuate in the power receiving apparatus. In that case, if the voltage source load impedance viewed from the power transmission coil 101 side is converted using the first impedance variable unit 151 and the second impedance variable unit 152 so that the power transmission efficiency is maximized with respect to the power receiving side load, Good. By doing so, it is possible to follow a state in which impedance matching is achieved even with respect to fluctuations in the power receiving side load.

Here, the simulation result of the power efficiency characteristic at the time of impedance matching will be described with reference to FIGS.
8 and 9 are examples in which the equivalent circuit of the power transmission device in the first embodiment is calculated by an equivalent circuit simulator. In the simulation, S21 is calculated when the voltage source load and the power-receiving-side load are 50Ω, and the power transmission efficiency is obtained. Further, the normalized frequency Δf normalized by a constant frequency is taken as the horizontal axis. When Δf = 0, it means that there is no frequency shift.

  FIG. 8 shows power efficiency characteristics when the coupling coefficient k of the loop coupling is fixed to 0.1 and the coil coupling is varied. As shown in FIG. 8, when the coupling coefficient kc of the coil coupling is varied from 0.001 to 0.009, the power transmission efficiency becomes maximum when kc = 0.005 and the normalized frequency Δf = 0. I understand. That is, in a configuration that cannot follow the fluctuation of the frequency and cannot tolerate the fluctuation of Δf, the power transmission efficiency is deteriorated when the distance between the coils is short and the coil coupling is strong. Note that by making the loop coupling k close to 1, impedance matching can be performed even when the coil coupling kc is high. However, when the loop coupling k is high, the resonance frequency increases, and therefore when the normalized frequency Δf = 0. This is not realistic because the power transmission efficiency is significantly degraded.

  FIG. 9 shows the relationship between coil coupling and power transmission efficiency when the voltage source load and the power receiving side load are increased to 1Ω, 30Ω, 80Ω, and 100Ω. It is apparent that the value of the coil coupling coefficient kc that maximizes the power transmission efficiency varies as the voltage source load and the power receiving side load increase. That is, high power transmission efficiency can be maintained by changing the voltage source load and the power receiving side load according to the strength of coil coupling.

Here, the impedance matching procedure in the control unit 153 will be described with reference to the flowcharts of FIGS. 10 and 11.
Impedance matching has an optimal procedure depending on the use situation and device configuration, and is roughly divided into two types. First, FIG. 10 shows an impedance matching procedure when the coil coupling is high.

  When the coil coupling is high, it is necessary to increase the loop coupling of the second impedance variable unit 152 so as to match the coil coupling. In this case, the frequency at which the power transmission efficiency is maximized becomes high, and thus high power transmission at a desired frequency. It becomes difficult to achieve efficiency. Therefore, after the impedance conversion is performed by the first impedance variable unit 151, the impedance conversion may be performed within a range in which high power transmission efficiency can be achieved at the frequency used for transmission in the second impedance variable unit 152.

In step S1001, the set power comparison value _{P now,} first impedance value _{imp1 now,} the initial value of the second impedance value _{IMP2 now} to "0", the initial value of the increase or decrease flag Up_flag impedance to "1" . The power comparison value _Pnow is a parameter for storing the received power value before the impedance conversion by the first impedance variable unit 151 and the second impedance variable unit 152.
In step S1002, it is determined whether the impedance increase / decrease flag Up_flag is 1. If Up_flag is 1, the process proceeds to step S1003, and if Up_flag is not 1, the process proceeds to step S1004.

In step S1003, the first impedance variable unit 151 converts the voltage source load impedance so as to increase Δa1. Δa1 is a unit value for increasing or decreasing the impedance in the first impedance variable unit 151.
In step S1004, the first impedance variable unit 151 converts the voltage source load impedance so as to decrease Δa1.
In step S1005, a charge trial is performed and the received power is measured.
In step S1006, 'by comparing the Trip P _now has P' receiving power P after the receiving power P _now and impedance transformation before performing the impedance conversion determine if it is greater than. When P _now is larger than P ′, the process proceeds to step S1008, and when P _now is equal to or less than P ′, the process proceeds to step S1007.

In step _S1007, it updates the value of _{P now} to the value of P ', returns to step S1002, and repeats the same processing.
In step S1008, it is determined whether Up_flag is 0. If Up_flag is 0, the process proceeds to step S1011. If Up_flag is not 0, the process proceeds to step S1009.
In step S1009, Up_flag is set to 0 to reduce the impedance.
In step S1010, similarly to step S1004, the voltage source load impedance viewed from the power transmission coil 101 side is converted so as to decrease by Δa1. Then, it returns to step S1002 and repeats the same process.

In step S1011, impedance conversion is performed so that the voltage source load impedance seen from the power transmission coil 101 side is increased by Δa1. As described above, by the processing from step S1002 to step S1011, the first impedance variable unit searches for an impedance that maximizes the received power.
In step S1012, Up_flag is set to 1.
In step S1013, it is determined whether the impedance increase / decrease flag Up_flag is “1”. If Up_flag is 1, the process proceeds to step S1014, and if Up_flag is not 1, the process proceeds to step S1015.
In step S1014, the second impedance variable unit 152 converts the impedance of the voltage source load viewed from the power transmission coil 101 side so as to increase Δa2. Δa2 is a unit value for increasing or decreasing the impedance in the second impedance variable unit 152.
In step S1015, the second impedance variable unit 152 converts the voltage source load impedance viewed from the power transmission coil 101 side so as to decrease Δa2.

Hereinafter, the processing from step S1016 to step S1022 is the same as the processing from step S1005 to step S1011 and thus the description thereof is omitted. As described above, the second impedance variable unit 152 searches for an impedance that maximizes the received power by the processing from step S1013 to step S1022. Impedance matching is performed by the above procedure.
After the impedance matching procedure is completed, power transmission is started when high power transmission efficiency is achieved after several charging attempts. This power transmission start determination is determined by a threshold value. When coil coupling is obvious, for example, power transmission efficiency that is half the calculated theoretical value is used as a threshold value. If the power transmission efficiency is equal to or higher than the threshold value, power transmission is started. What is necessary is just not to transmit power.

Next, FIG. 11 shows an impedance matching procedure when the coil coupling is low.
When the coil coupling is low, for example, when impedance matching is performed in the second impedance variable unit 152, it is generally possible to perform impedance matching by lowering the loop coupling. When the loop coupling is changed, the frequency at which the power transmission efficiency is maximized also varies. However, when the loop coupling is low, the variation in the frequency at which the power transmission efficiency is maximized is small even when the loop coupling is varied. From the above, when the coil coupling is low, the frequency at which the power transmission efficiency is maximized can be finely adjusted by the impedance adjustment by the second impedance variable unit 152, so that the power transmission efficiency is maximized at the desired frequency. Easy to do. Therefore, when the coil coupling is low, impedance matching may be performed by performing impedance conversion with the second impedance variable unit 152.

  However, when impedance conversion is performed by moving the loop in the second impedance variable unit 152, the range in which the loop can be moved may be limited due to the structure of the apparatus. As described above, when the second impedance variable unit 152 cannot cope with the impedance, the second impedance variable unit 152 may perform impedance matching after the impedance conversion by the first impedance variable unit 151. Thereby, high power transmission efficiency can be achieved.

In step S1101, the second impedance variable unit 152 performs impedance conversion. Specifically, the processing from step S1012 to step S1022 shown in FIG. 10 is performed.
In step S1102, the first impedance variable unit 151 performs impedance conversion. Specifically, the processing from step S1001 to step S1011 shown in FIG. 10 is performed.
Determination of the start of power transmission after the end of the impedance matching procedure is the same as when the coil coupling is strong. In addition, although the order of the impedance variable part which performs impedance conversion is changed with the strength of coil coupling, the control part 153 may perform the determination of order change by threshold value determination, for example. For example, the coupling coefficient of the coil coupling when the error between the frequency at which the power transmission efficiency is maximized and the desired frequency when impedance matching is performed by the second impedance variable unit 152 is 1% may be used as the threshold value. As described above, when the loop coupling is varied, the frequency at which the power transmission efficiency is maximized also increases or decreases, but when the coil coupling is strong, the loop coupling needs to be strengthened, so the frequency at which the power transmission efficiency is maximized increases. As a result, power transmission efficiency deteriorates at a desired frequency. For this reason, when the coil coupling is strong, the error between the frequency at which the power transmission efficiency is maximum and the desired frequency becomes large. Therefore, when the error is, for example, 1% or more, it is determined that the coil coupling is strong. The order in which impedance conversion is performed by the second impedance variable unit 152 after impedance conversion by the first impedance variable unit 151 may be employed.

  According to the first embodiment described above, even when the loop coupling and the coil coupling fluctuate, the voltage source load impedance viewed from the power transmission coil side according to the strength of the coil coupling, By performing impedance matching by the second impedance variable unit, high power transmission efficiency can be maintained at a desired frequency.

(Second Embodiment)
In the first embodiment, the first impedance variable unit includes a transformer. However, the second embodiment is different in that the first impedance variable unit includes a T-type circuit element or a π-type circuit element. By using a T-type circuit element or a π-type circuit element, the circuit scale can be made smaller than when a transformer is used.

A wireless power transmission apparatus according to the second embodiment will be described with reference to FIG.
The wireless power transmission apparatus 1200 according to the second embodiment includes a voltage source 301, a voltage source load 302, a first impedance variable unit 1201 (1201-1 or 1201-2), a second impedance variable unit 152, and a power transmission coil 101. Including. Note that the voltage source 301, the voltage source load 302, the second impedance variable unit 152, and the power transmission coil 101 have the same configurations as those in the first embodiment, and thus description thereof is omitted here.
The first impedance variable unit 1201-1 shown in FIG. 12A is configured by a T-type circuit element, and performs the same operation as the transformer in the first embodiment. Similarly, the first impedance variable unit 1201-2 shown in FIG. 12B is composed of a π-type circuit element, and performs the same operation as the transformer in the first embodiment. Further, the T-type and π-type circuit element constants are determined so that the voltage source load impedance can be varied by a constant multiple when viewed from the power transmission coil 101 side like a transformer, and can be designed by, for example, Norton conversion.

Here, FIG. 13 shows circuit element constants when the transformer is converted into a π-type element by Norton conversion.
In Norton conversion, conversion is performed using circuit elements inserted in series. At that time, one or more of the circuit elements inserted in parallel among the converted π-type circuit elements (resistance, capacitor, inductor) are converted into element constants having a negative value. That is, in order to perform Norton conversion in practical use, a circuit for canceling a circuit element constant having a negative value is required in addition to the circuit elements inserted in series. For example, in wireless power transmission, when the resonance frequency of the power transmission resonance circuit (power transmission coil) and the power reception resonance circuit (power reception coil) is shifted, the voltage source and the power reception load are improved in order to improve power transmission efficiency at a desired frequency. The circuit elements are inserted in series and in parallel, but Norton conversion may be performed using the circuit elements inserted in series and in parallel. When a loop is used for the second impedance variable unit 152, the second impedance variable unit 152 may be designed by performing Norton conversion using the inductor value of the loop.

  As described above, the Norton transform can design a π-type circuit that can convert the impedance to a constant multiple like the transformer without changing the resonance frequency of the connected resonance circuit. Note that a circuit converted to π-type can be converted to a T-type circuit by performing π-T circuit conversion.

Next, an example in which a variable circuit element is used in the wireless power transmission apparatus 1200 according to the second embodiment is shown in FIGS. 14 (a) and 14 (b).
FIG. 14A shows a first impedance variable unit 1401-1 of a T-type circuit using a variable circuit element, and FIG. 14B shows a first impedance variable unit of a π-type circuit using a variable circuit element. 1401-2 is shown. The first impedance variable unit 1401 changes the value of each variable circuit element according to the circuit element constant determined from the desired impedance conversion ratio by, for example, Norton conversion as shown in FIG. In addition, the second impedance variable unit 152 performs impedance conversion by changing the loop coupling, and performs impedance matching so that power transmission efficiency is maximized at a desired frequency.

  In wireless power transmission, if a resistor is used as a circuit element of the impedance variable unit 1401 using T-type and π-type circuits, power loss occurs and power transmission efficiency deteriorates. Therefore, it is desirable to use an inductor and a capacitor as circuit elements. However, when communication is performed using the wireless power transmission apparatus 1200 according to the second embodiment, a matching circuit using a resistor may be applied. The impedance matching procedure may be the procedure shown in FIGS. 10 and 11 as in the first embodiment.

  According to the second embodiment described above, impedance matching that maintains high power transmission efficiency at a desired frequency can be performed as in the first embodiment while reducing the circuit scale.

(Third embodiment)
In the third embodiment, in addition to the transmission-side wireless power transmission apparatus having the first and second impedance variable sections, the reception-side wireless power transmission apparatus also includes the first and second impedance variable sections. Different. By performing impedance matching on both the power transmission side and the power reception side, matching can be performed more quickly, and high power transmission efficiency at a desired frequency can be achieved.

A wireless power transmission apparatus according to the third embodiment will be described with reference to FIG.
A wireless power transmission device 1500 according to the third embodiment includes a power transmission device 1501 and a power reception device 1551. Furthermore, the power transmission device 1501 includes a voltage source 301, a voltage source load 302, a first impedance variable unit 151, a second impedance variable unit 152, a control unit 153, and the power transmission coil 101. The power receiving device 1551 includes a power receiving load 1552, a first impedance variable unit 1553, a second impedance variable unit 1554, a control unit 1556, and a power receiving coil 1555. Note that the operation of the configuration included in the power transmission device 1501 is the same as the operation of the above-described configuration, and thus description thereof is omitted here.

The power receiving side load 1552 is a load such as a resistor for taking out the electric power received from the power transmission device.
Similarly to the first impedance variable unit 151 according to the first and second embodiments, the first impedance variable unit 1553 is configured to change the power receiving side load impedance from the power receiving coil 1555 side by a transformer or a π type and T type circuit. It only has to be converted to a constant multiple as seen.
Similar to the second impedance variable unit 152 according to the first embodiment and the second embodiment, the second impedance variable unit 1554 changes the coupling (mutual inductance) between the loop and the power receiving coil to change the mutual inductance. Performs corresponding impedance conversion.
Similarly to the power transmission coil 101, the power reception coil 1555 is configured by a self-resonant coil or a coil that resonates by loading a capacitor.
Similarly to the control unit 153, the control unit 1556 controls the first impedance variable unit 1553 and the second impedance variable unit 1554 to perform impedance matching.

Next, an example of an equivalent circuit of the wireless power transmission apparatus 1500 according to the third embodiment is shown in FIG.
As illustrated in FIG. 16, the first impedance variable unit of the power transmission device and the power reception device may be configured by a transformer, and the second impedance variable unit may be configured by a loop. Moreover, you may integrate a 1st impedance variable part and a 2nd impedance variable part in each of a power transmission apparatus and a power receiving apparatus. As a method of integration, as described above, a transformer inserted in the middle of a loop or a loop wound in a large number may be used like a single-winding transformer (variable transformer). In particular, if a transformer is inserted immediately before the power-receiving-side load in the power receiving device 1551, power loss due to the transformer occurs. Therefore, it is desirable to form a transformer integrated with the loop. In addition, the first impedance variable unit 1553 and the second impedance variable unit 1554 of the power receiving device 1551 may be interchanged.

Here, the operation of the wireless power transmission apparatus 1500 according to the third embodiment will be described.
As shown in FIG. 9, the voltage source load, the optimum value of the power receiving side load impedance, and the optimum value of the loop coupling of the power transmitting device and the power receiving device, in which the power transmission efficiency is maximized according to the strength of the coil coupling. Is determined. As a method of detecting the coil coupling, it may be detected by monitoring the received power as described above. In addition, since impedance matching is required when there is a variation in coil coupling or deterioration in power transmission efficiency at the start of power transmission, the power transmission device 1501 and the power reception device 1551 are independent of the first and second impedances. The variable part performs impedance matching.

  As the impedance matching procedure, the impedance conversion is performed in the first and second impedance variable sections of both the power transmission device 1501 and the power reception device 1551 in the matching procedure shown in FIGS. 10 and 11 as in the first embodiment. Just do it. At this time, impedance matching is performed in the power transmission device 1501 during at least a part of the period in which the impedance of the power receiving device 1551 is converted. Note that the impedance matching periods of the power transmission device 1501 and the power reception device 1551 are preferably the same.

For example, a case where the power receiving side load varies in the power receiving device 1551 is assumed. In this case, the impedance matching is performed by converting the voltage source load impedance viewed from the power transmission coil 101 side in the first impedance variable unit 151 and the second impedance variable unit 152 on the power transmission side so that the power transmission efficiency is maximized. . Further, in the power receiving device 1551, in synchronization with the change of the impedance on the power transmission side, the first impedance variable unit 1553 and the second impedance variable so that the power transmission efficiency of the power receiving side load impedance viewed from the power receiving coil 1555 is maximized. The unit 1554 performs impedance conversion and performs impedance matching. By doing so, it is possible to follow fluctuations in the power receiving side load.
On the other hand, when the load impedance fluctuates in the power transmission device 1501, reverse processing may be performed, and the power receiving coil 1555 so that the power transmission efficiency is maximized in the first impedance variable unit 1553 and the second impedance variable unit 1554 on the power receiving side. The power-receiving side load impedance seen from the side is converted. Then, in synchronization with the power-receiving-side load impedance viewed from the converted power-receiving coil 1555 side, the first impedance variable unit 151 and the second impedance variable unit 152 of the power transmission device 1501 transmit power so that the power transmission efficiency is maximized. What is necessary is just to convert the voltage source load impedance seen from the coil 101 side, and to perform impedance matching.

  Note that when the first impedance variable unit 1553 performs impedance conversion in the power receiving device 1551, the power loss may increase. Therefore, the impedance conversion in the power receiving device 1551 is performed so that the power loss is minimized. desirable. Further, when the power receiving side load impedance fluctuates, the first impedance variable unit 1553 of the power receiving device 1551 converts the impedance so that the impedance viewed from the power receiving coil 1555 and the second impedance variable unit 1554 of the power receiving device 1551 is constant. May be performed. This eliminates the need for the power transmitting apparatus 1501 to follow the variation in the power receiving side load impedance of the power receiving apparatus 1551, and achieves high power transmission efficiency with simpler control.

Next, impedance matching conditions for the wireless power transmission apparatus 1500 according to the third embodiment will be described.
Except for the first impedance variable section of the power transmission device 1501 and the power reception device 1551 shown in FIG. 16, the configuration is similar to the configuration of the inter-resonator coupling filter. Therefore, the impedance matching condition of the inter-resonator coupling filter can be applied to the wireless power transmission apparatus 1500.
An example of an equivalent circuit of the inter-resonator coupling filter is shown in FIG. L ₁ and C ₁ are the inductor value and the conductor value of the power transmission coil, and L ₂ and C ₂ are the inductor value and the conductor value of the power transmission coil. R ₁ and R ₂ correspond to the voltage source load and the power receiving side load. The K inverter described above is described as K _0,1 etc., and is equivalent to the symmetric T-type circuit depicted in FIG. That is, K _0,1 and K _1,2 in FIG. 17 represent loop coupling and coil coupling of the power transmitting device 1501, respectively, and K _2,3 represent loop coupling of the power receiving device 1551.

When the mutual inductance of the loop coupling of the power transmission device 1501 is M ₁ , the mutual inductance of the loop coupling of the power receiving device 1551 is M ₂ , and the coupling coefficient of the coil coupling is k _c , impedance matching of the inter-resonator coupling filter shown in FIG. Is conditioned by a parameter called external k calculated as follows.

In Equation 3, ω ₀ is the resonance frequency of the coil. For example, when a filter having Butterworth characteristics is designed using the power transmission device external k _e1 and the power reception device external k _e2 and the coupling coefficient k _c of the coil coupling, the following conditional expression (4) may be satisfied.

The Butterworth characteristic has the characteristic that the passband is the flattest. This is a characteristic that can be easily used to achieve high power transmission efficiency at a certain frequency in wireless power transmission, and is also suitable for the wireless power transmission apparatus according to the present embodiment. The power transmitting device external k _e1 and the power receiving device external k _e2 can be varied by mutual inductances M ₁ and M ₂ and loads R ₁ and R ₂ , respectively.
In the third embodiment, the mutual inductances M ₁ and M ₂ correspond to the loop coupling between the second impedance variable unit 152 of the power transmitting device 1501 and the second impedance variable unit 1554 of the power receiving device 1551, and the loads R ₁ and R ₂ corresponds to a transformer between the first impedance variable unit 151 of the power transmission device 1501 and the first impedance variable unit 1553 of the power reception device 1551. That is, the first and second impedance variable sections of the power transmission device 1501 and the power reception device 1551 are viewed from the power transmission coil 101 side so that the power transmission device external k _e1 and the power reception device external k _e2 are constant with the coil coupling k _c . Impedance matching can be performed by converting the voltage source load impedance and the power receiving side load impedance viewed from the power receiving coil 1555 side.

The power transmission device external k _e1 and the power reception device external k _e2 can be calculated using the minimum value of reflection and the frequency at the minimum value in the frequency characteristics of reflection in the S parameter, respectively. By this method, impedance matching can be performed more easily by calculating the external k of the power transmission device 1501 and the power reception device 1551 in advance.

  According to the third embodiment described above, by performing impedance matching on both the power transmission side and the power receiving side, it is possible to achieve matching faster and achieve high power transmission efficiency at a desired frequency. Can do.

(Fourth embodiment)
The fourth embodiment is different in that a power transmission device and a power reception device include a modulation / demodulation unit and an information processing unit, and perform wireless communication in addition to power transmission. As in the case of power transmission, by performing impedance matching in the first and second impedance variable sections, the transmission characteristics of the pass band can be flattened over a wide transmission distance. As a result, frequency characteristics without frequency selectivity can be obtained, and a high transmission rate can be achieved when performing wireless communication.

A wireless power transmission apparatus according to the fourth embodiment will be described with reference to FIG.
A wireless power transmission device 1800 according to the fourth embodiment includes a power transmission device 1801 and a power reception device 1851. Furthermore, the power transmission device 1801 includes an information processing unit 1802, a modulation / demodulation unit 1803, a first impedance variable unit 151, a second impedance variable unit 152, and a power transmission coil 101. The power receiving device 1851 includes an information processing unit 1852, a modulation / demodulation unit 1853, a first impedance variable unit 1553, a second impedance variable unit 1554, and a power receiving coil 1555.

The first impedance variable unit 151, the second impedance variable unit 152, the power transmission coil 101 included in the power transmission device 1801, and the first impedance variable unit 1553, the second impedance variable unit 1554, and the power reception coil 1555 included in the power reception device 1851 are Since it is the same as that of the first embodiment, a description thereof is omitted here.
The information processing unit 1802 generates data to be transmitted.
The modulation / demodulation unit 1803 receives data from the information processing unit 1802 and modulates the data to generate a modulated signal. When receiving the modulation signal, the modulation signal is demodulated to generate data. Any modulation method such as ASK, PSK, FSK may be used as the modulation method. The modulation method for communication from the power receiving apparatus 1851 to the power transmitting apparatus 1801 may be load modulation or backscatter that can be modulated by the power receiving apparatus 1851 without a power source.
Similar to the modulation / demodulation unit 1803, the modulation / demodulation unit 1853 receives the modulation signal from the first impedance variable unit and demodulates the modulation signal. When data is received from the information processing unit 1852, the data is modulated.
The information processing unit 1852 receives the demodulated data from the modulation / demodulation unit 1853 and performs processing in the upper layer.

Next, FIG. 19 shows a wireless power transmission apparatus for switching between power transmission and wireless communication.
As shown in FIG. 19, switches are provided in the first impedance variable sections of the power transmission device 1801 and the power reception device 1851 so that the voltage source 301, the voltage source load 302, and the power reception side load 1552 can be connected, respectively. It is also possible to operate as a wireless power transmission device.

Here, the case of using both power transmission and wireless communication will be described with reference to FIG. There are roughly two methods for using power transmission and wireless communication in combination.
(1) A coil different from the power transmission coil 2001 and the wireless communication coil 2002 is used.
(2) The same coil is used for both the power transmission coil 2001 and the wireless communication coil 2002.
In the case of the method (1), at least two coils are required, but power transmission and wireless communication can be performed simultaneously by changing the resonance frequency of the power transmission coil and the wireless communication coil. FIG. 20A shows a case where the diameters of the two coils are changed to make the central axes of the two coils the same, and FIG. 20B shows a case where the central axes of the two coils are separated. .
In the case of FIG. 20A, the loop used in the second impedance variable section can be used in common, and the first impedance variable section may be provided for each coil. Further, since noise during power transmission occurs during wireless communication, it is desirable to take measures against noise. The power transmission coil 2001 is disposed on the outer side and the wireless communication coil 2002 is disposed on the inner side, but the positional relationship may be reversed. In the case of FIG. 20B, the power transmission coil 2001 and the wireless communication coil 2002 are arranged in parallel. However, the present invention is not limited to this, and an appropriate positional relationship may be set according to the application.

In the case of method (1), if the resonance frequency of the power transmission coil 2001 and the wireless communication coil 2002 is the same, noise from the power transmission coil 2001 to the wireless communication coil 2002 and high power error may occur. It is desirable to arrange with care to power supply.
In the case of the method (2), since the power transmission coil 2001 and the wireless communication coil 2002 are used (hereinafter referred to as a combined coil), wireless communication cannot be performed during power transmission, and during wireless communication, Power transmission cannot be performed. That is, it is necessary to perform power transmission and wireless communication in a time-sharing manner. However, for example, power is transmitted at the resonance frequency of the combined coil, and wireless communication is performed using the double resonance frequency or triple resonance frequency of the combined coil, so that power is transmitted by frequency division while sharing the same coil. And wireless communication can be performed simultaneously. In the method (2), the configuration shown in FIG. 19 may be used, and the first impedance variable unit may be provided separately for power transmission and wireless communication.

Another example of the wireless power transmission apparatus 1800 according to the fourth embodiment is shown in FIG.
FIG. 21A shows a case where the same frequency is used between the power transmission coils and between the wireless communication coils in the method (1), and FIG. 21B shows the combination coil 2101 in the method (2). The case where the same frequency is used is shown. FIG. 21C shows a case where different frequencies are used in the method (1), and FIG. 21D shows a case where different frequencies are used in the method (2).

For example, in the case of FIG. 21B and FIG. 21D, when the resonance frequencies of the plurality of combined coils 2101 are matched, the magnetic field direction of the space is changed by changing the phase difference of the current supplied to each combined coil 2101. An effect of array control is obtained, and characteristic deterioration due to the direction of the coil on the power receiving side can be improved. However, in the case of arraying, it is necessary to perform power transmission and wireless communication in a time-sharing manner. However, as described above, power transmission is performed if wireless communication is performed using the double resonance frequency or triple resonance frequency of the coil. And wireless communication can be performed simultaneously.
Furthermore, as shown in FIG. 21 (d), when a plurality of methods (2) are used and arranged so that the resonance frequency of the combined coil is different, parallel transmission can be performed by frequency division, and power transmission and wireless communication Can be performed simultaneously by frequency division.

When a plurality of coils of these methods (1) and (2) are used, the voltage source for power transmission or the first and second impedance variable units, the information processing unit for wireless communication, the modulation / demodulation unit, the first And the 2nd impedance variable part may be used with a some coil, and may prepare separately for every coil. However, when arraying or parallel transmission is performed with high efficiency, it is desirable to use a voltage source for wireless power transmission and an information processing unit and modulation / demodulation unit for wireless communication.
When power transmission and wireless communication are performed by frequency division, it is necessary to use a bandpass filter or the like so that a signal in a band used for power transmission is not passed through the wireless communication device. In addition, when power transmission and wireless communication are performed in a time-sharing manner, it should be noted that when switching from power transmission to wireless communication, wireless communication is performed after waiting for a sufficient time in consideration of residual power.

  According to the fourth embodiment described above, power transmission and wireless communication can be performed simultaneously by providing the power transmission coil and the wireless communication coil.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

100, 300, 1200, 1500, 1800 ... wireless power transmission device, 101, 502 ... power transmission coil, 102 ... power transmission unit, 151, 1201, 1401, 1553 ... first impedance variable unit, 152 , 1554 ... 2nd impedance variable part, 153 ... control part, 301 ... voltage source, 302 ... voltage source load, 501 ... loop, 1501, 1801 ... power transmission device, 1556 ··· Control unit, 1551, 1851 ... Power receiving device, 1552 ... Power receiving side load, 1555 ... Power receiving coil, 1802, 1852 ... Information processing unit, 1803, 1853 ... Demodulation unit, 2001 .. Coil for power transmission, 2002... Coil for wireless communication, 2101.

Claims (7)

A resonable coil connected to a power source;
A first variable unit that is arranged as a π-type circuit or a T-type circuit between the coil and the power source, and includes a variable circuit element capable of converting the impedance of the power load viewed from the coil side;
A second variable capable of converting the impedance of the power load and the first variable unit as viewed from the coil side by changing a mutual inductance between the coil and the loop; And
A wireless power transmission apparatus comprising: a control unit that performs impedance conversion using at least one of the first variable unit and the second variable unit and performs impedance matching. A resonable coil connected to a power source;
A first variable unit including a transformer inserted between the coil and the power source and capable of converting an impedance of a power load viewed from the coil side;
A second variable capable of converting the impedance of the power load and the first variable unit as viewed from the coil side by changing a mutual inductance between the coil and the loop; And
A wireless power transmission apparatus comprising: a control unit that performs impedance conversion using at least one of the first variable unit and the second variable unit and performs impedance matching.   3. The radio according to claim 1, wherein the control unit performs impedance matching by performing impedance conversion by the second variable unit after performing impedance conversion by the first variable unit. 4. Power transmission device.   3. The wireless power according to claim 1, wherein the control unit performs impedance matching by performing impedance conversion by the first variable unit after performing impedance conversion by the second variable unit. 4. Transmission equipment.   5. The control unit according to claim 1, wherein the control unit performs impedance matching by performing impedance conversion by the first variable unit during at least a part of a period during which power reception side impedance conversion is performed. The wireless power transmission device according to any one of the above.   2. The control unit according to claim 1, wherein the control unit performs impedance matching by performing impedance conversion by the second variable unit in at least a part of a period in which impedance conversion on the power receiving side is performed. The wireless power transmission device according to claim 1.   The control unit performs impedance conversion on the power receiving side in accordance with fluctuations in impedance of the power load, and then synchronizes with the impedance conversion on the power receiving side, and at least one of the first variable unit and the second variable unit The wireless power transmission device according to any one of claims 1 to 6, wherein impedance matching is performed by performing impedance conversion using any one of the above.

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