JP7154518B1 - RESONATOR OF COUPLED RESONANCE WIRELESS POWER TRANSMISSION SYSTEM AND COUPLED RESONANCE WIRELESS POWER TRANSFER SYSTEM - Google Patents

Abstract

An object of the present invention is to provide a resonator for a coupled resonance type wireless power transmission system that enables transmission of an appropriate power value by a simpler method.
Kind Code: A1 A resonator applied to a coupled resonance type wireless power transmission system, wherein n sets of divided capacitors including a first divided capacitor and a second divided capacitor connected in parallel to a coil are provided. pairs, the sum of the capacitance value of the first split capacitor and the capacitance value of the second split capacitor is the same in each split capacitor pair of the n sets of split capacitor pairs, and the capacitance of the first split capacitor and the ratio of the capacitance value of the second splitting capacitor is different for each splitting capacitor pair of the n sets of splitting capacitor pairs, and the first switch and the second switch are connected to the n sets of splitting capacitors. A resonator operable to connect either one of a pair to said coil and said power supply or said load.
[Selection drawing] Fig. 5

Description

TECHNICAL FIELD The present disclosure relates to a resonator of a coupled resonance type wireless power transmission system and a coupled resonance type wireless power transmission system.

In recent years, a coupled resonance type wireless power transmission system (hereafter referred to as (abbreviated as "wireless power transmission system") is attracting attention.

FIG. 1 is a conceptual diagram of a wireless power transmission system (here, a wireless power transmission system using a series resonance circuit). In FIG. 1, the power transmitting device UA is drawn on the left side, and the power receiving device UB is drawn on the right side. The power transmission device UA has a resonator composed of a coil 1 and a capacitor 3, and a power supply 5 for transmitting AC power to the resonator. The power receiving device UB also has a resonator configured by the coil 2 and the capacitor 4, and a load 6 that acquires AC power from the resonator.

Because this method uses resonance, it is said that power can be transmitted over long distances several times the size of the coil if the conditions are met. However, in practice, it is difficult to make adjustments for electromagnetic resonance between the two resonators, and stable, high-efficiency transmission cannot be performed. The main reason for this is that the distance between the transmitter and receiver is not fixed in contactless power supply, and the coupling coefficient between the resonators changes due to the fluctuation of the distance.

Non-Patent Document 1 describes in detail how the transmission characteristics between the resonators change due to the change in the coupling coefficient. It is stated therein that it is necessary to vary the external Q of the resonator to match the coupling coefficient.

Incidentally, the Q value of a commonly used resonator is the Q value when no load is connected, and is called unloaded Q. This unloaded Q is the ratio of the characteristic impedance of the resonator and the internal resistance of the coil. On the other hand, the Q value due to the impedance of the power source or load connected to input or output a signal to or from the resonator is called the external Q.

The external Q of a resonator is generally determined by the ratio of the intrinsic impedance of the resonator and the impedance of the load or power source connected thereto. However, the size and structure of the coil that constitutes the resonator is determined by the application, power transmission distance, etc., and since the coil itself is a mechanical component, it is difficult to arbitrarily change its inductance value. In addition, the resonance frequency of the resonator is determined by the inductance of the coil and the capacitance of the capacitor. In principle, the capacitance of the capacitor cannot be freely changed. Moreover, the impedance of the load is almost determined by the application. Also, the impedance of the power supply is determined by the power supply voltage and the desired amount of power.

Thus, in the wireless power transmission system according to the conventional technology, the elements that can change the external Q are limited, and it is difficult to realize and maintain highly efficient resonant power transmission while the k value fluctuates. rice field.

Patent application 2021-143959

I.AwaiandT.Ishizaki, "SuperiorityofBPFtheoryfordesignofcoupledresonatorWPTsystems,"Asia-PacificMicrowaveConference2011, pp. 1889-1892 (2011) INSPEC Accession Number: 12656013

The inventors of the present application have diligently studied the above-mentioned problems of the wireless power transmission system according to the prior art, and configured a resonator as a method of adjusting the external Q of an LC resonator (hereinafter abbreviated as "resonator"). It has been found that it is effective to divide the capacitor to divide the voltage and supply power to the divided points (see FIGS. 3(c) and 3(d) described later). According to such a power supply method, it is possible to freely adjust the external Q while keeping constant the impedance of the power supply and the load connected to the resonator. For details, see Patent Document 1, which is a prior application filed by the applicant of the present application.

In addition, the inventor of the present application has shown in Patent Document 1 that a variable capacitor as shown in FIG. 2 (here, a variable capacitor used for a series resonator) is effective as the capacitor structure. .

The variable capacitors are electrically separated from each other and arranged side by side to face the same direction as the first fixed electrode E1 and the second fixed electrode E2, and the first fixed electrode E1 and the second fixed electrode E2. While maintaining a constant distance between each of the first fixed electrode E1 and the second fixed electrode E2 so as to face each other, the first fixed electrode E1 and the second fixed electrode E2 are arranged so as to be movable along the direction in which the first fixed electrode E1 and the second fixed electrode E2 are arranged. and a movable electrode E3 provided. One divided capacitor is formed between the first fixed electrode E1 and the movable electrode E3, and the other divided capacitor is formed between the second fixed electrode E2 and the movable electrode E3. In this variable capacitor, when the movable electrode E3 is moved, the sum of the area where the first fixed electrode E1 and the movable electrode E3 face each other and the area where the second fixed electrode E2 and the movable electrode E3 face each other is configured to be constant.

By using such a capacitor structure, it is possible to adjust the ratio of the capacitance values while keeping the parallel combined capacitance of the two divided capacitors constant. This makes it possible to adjust the external Q of the resonator while keeping the resonant frequency constant.

One aspect of realizing the capacitor as shown in FIG. 2 is, for example, a capacitor using mechanical rotation called a variable capacitor. In principle, it is possible to adjust the external Q by adjusting the rotation angle of the variable capacitor. Adjustment work is extremely difficult. As a result, a proper external Q cannot be ensured or maintained, and there is a possibility that a proper power value cannot be transmitted from the power transmission side to the power reception side.

The present disclosure has been made in view of the above problems, and a resonator of a coupled resonance type wireless power transmission system that enables transmission of an appropriate power value with a simpler method, and a coupled resonance type wireless power transmission system. intended to provide

The main disclosure that solves the above-mentioned problems is
A resonator applied to a coupled resonance type wireless power transmission system,
having a capacitor and a coil that form a series resonance circuit,
The capacitor has n (where n is a positive integer equal to or greater than 2) sets of divided capacitor pairs each consisting of a first divided capacitor and a second divided capacitor connected in parallel to the coil,
the sum of the capacitance value of the first split capacitor and the capacitance value of the second split capacitor is the same for each split capacitor pair of the n sets of split capacitor pairs;
the ratio of the capacitance value of the first split capacitor to the capacitance value of the second split capacitor is different for each split capacitor pair of the n sets of split capacitor pairs;
a capacitance dividing point of the first divided capacitor and the second divided capacitor is connected to one end of the coil via a first switch;
the other end of the second dividing capacitor is connected to the other end of the power supply or the load via a second switch;
the other end of the first split capacitor is connected to a connection point between the other end of the coil and the other end of the power supply or the load;
the first switch and the second switch operate to connect any one of the n sets of divided capacitor pairs to the coil and the power supply or the load;
It is a resonator.

Also, a resonator applied to a coupled resonance type wireless power transmission system,
having a capacitor and a coil that form a parallel resonant circuit,
The capacitor has n (where n is a positive integer equal to or greater than 2) sets of divided capacitor pairs, each of which consists of a third divided capacitor and a fourth divided capacitor connected in series to the coil,
the sum of the reciprocal of the capacitance value of the third split capacitor and the reciprocal of the capacitance value of the fourth split capacitor is the same for each split capacitor pair of the n sets of split capacitor pairs;
the ratio of the capacitance value of the third split capacitor to the capacitance value of the fourth split capacitor is different for each split capacitor pair of the n sets of split capacitor pairs;
a capacitance dividing point of the third divided capacitor and the fourth divided capacitor is connected to the other end of the power supply or the load via a fourth switch;
the other end of the third dividing capacitor is connected to one end of the coil via a third switch;
the other end of the fourth split capacitor is connected to a connection point between the other end of the coil and the other end of the power source or the load;
the third switch and the fourth switch operate to connect any one of the n sets of divided capacitor pairs to the coil and the power source or the load;
It is a resonator.

According to the resonator of the coupled resonance type wireless power transmission system according to the present disclosure, it is possible to transmit an appropriate power value with a simpler method.

Conceptual diagram of wireless power transmission system A diagram showing the configuration of the variable capacitor described in Patent Document 1 A diagram showing a circuit configuration of an LC resonator Diagram showing configuration of wireless power transmission system FIG. 2 is a diagram showing an example of the configuration of a split capacitor series resonator according to the present embodiment; FIG. 2 is a diagram showing an example of the configuration of a divided capacitance parallel resonator according to this embodiment; FIG. 4 is a diagram showing an example of the behavior of the input impedance of the resonator controlled by adjusting the capacitance ratio a1 in the SS type wireless power transmission system using the divided capacitance series resonator according to the present embodiment; FIG. 4 is a diagram showing the behavior of transmitted power (solid line) controlled by adjusting the capacitance ratio a1 in the SS type wireless power transmission system using the divided capacitance series resonator according to the present embodiment; The figure which shows the result of the simulation performed in order to analyze the imbalance problem of the external Q of the power transmission side resonator and the external Q of the power receiving side resonator. FIG. 4 is a diagram showing an example of the behavior of the input impedance ZS1 of the resonator, which is controlled by adjusting the capacitance ratio b1, in the PP type wireless power transmission system using the split-capacitance parallel resonator according to the present embodiment; FIG. 4 is a diagram showing the behavior of transmitted power (solid line) controlled by adjusting the capacity ratio b1 in the PP-type wireless power transmission system using the split-capacitance parallel resonator according to the present embodiment; Flowchart showing an operation example during system operation of the wireless power transmission system according to the present embodiment

Preferred embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings.

[Schematic configuration of wireless power transmission system]
A wireless power transmission system according to an embodiment of the present disclosure, similarly to the wireless power transmission system shown in FIG. This is a coupled resonance type wireless power transmission system that enables long-distance power transmission by providing two resonators and resonating the two resonators.

Wireless power transmission using resonant circuit resonance is functionally a bandpass filter (BPF) that propagates electromagnetic energy through space. From the design theory of bandpass filters (see, for example, Non-Patent Document 1), if the product of the external Q of both resonators is the square of the reciprocal of the coupling coefficient as shown in equation (10) described later, no reflection occurs. , 100% transmission is possible if loss due to parasitic resistance is excluded.

That is, adjustment of the external Q of the resonator is extremely important in order to realize highly efficient wireless power transmission. In other words, this means keeping the input impedance to the resonator within a certain range in response to changes in the coupling coefficient. In the conventional resonator connection, if the coupling coefficient changes, the input impedance changes significantly, and there was no means for adjusting this.

In order to solve this problem, the inventor of the present application adopts a capacitance division series resonance circuit (see FIG. 3(c)) when using a series resonator in a wireless power transmission system, and divides the capacitance of the capacitor As means for changing the ratio, n sets of split capacitor pairs having different split capacitance ratios are provided, and during system operation, a split capacitor pair having an appropriate split capacitance ratio can be selected from the n sets of split capacitor pairs. (see FIG. 5).

Further, when using a parallel resonator in a wireless power transmission system, a capacitance division parallel resonance circuit (see FIG. 3D) is adopted, and different division capacitances are used as means for changing the division capacitance ratio of the capacitor. A configuration is provided in which n sets of split capacitor pairs having a ratio are provided, and a split capacitor pair having an appropriate split capacitance ratio can be selected from among the n sets of split capacitor pairs during system operation (see FIG. 6).

With such a configuration, the external Q of the resonator can be appropriately adjusted in response to a change in the coupling coefficient that occurs when the positional relationship between the resonators changes, and the input impedance of the resonator viewed from the power supply can be kept within a certain range. This can be maintained only by switching the switch, enabling stable non-contact power transmission. In addition, this makes it possible to easily change the ratio of the input impedance to the resonator and the output impedance on the load side in power transmission using resonance.

First, the configuration of the capacitance-dividing series resonant circuit (FIG. 3(c)) and the capacitance-dividing parallel resonant circuit (FIG. 3(d)) shown in Patent Document 1 filed earlier by the applicant of the present application will be briefly described. .

FIG. 3 is a diagram showing the circuit configuration of an LC resonator. Assuming that the inductance of the coil of the resonance circuit is L ₀ and the capacitance is C ₀ , the resonance frequency and resonator impedance of the resonator are ω ₀ and Z _R0 below.

There are a series type (FIG. 3(a)) and a parallel type (FIG. 3(b)) for connecting a power source and a load to the resonator. Assuming that the impedance of the power source or the load is Z _S0 , the external Q can be defined as the following equation (3a) for the series resonant circuit, and can be defined as the following equation (3b) for the parallel resonant circuit.

In the basic LC resonators of FIGS. 3(a) and 3(b), the external Q is determined by the impedance of the connected circuit. In order to make this adjustment possible, the capacitance is divided into two parallel capacitances in the series resonant circuit as shown in FIG. , connect the load to that split point.

The capacitor (FIG. 3(c)) of the capacitance-dividing series resonant circuit is divided into two in parallel when viewed from the coil, and power is transmitted only to one of the two divided capacitors formed by dividing into two. It has a configuration in which a power source as a unit or a load as a power receiving unit is connected in series. For convenience of explanation, one of the two divided capacitors will be referred to as a "first divided capacitor" and the other as a "second divided capacitor".

Also, as shown in FIG. 7B, the capacitor (FIG. 3(d)) applied to the capacitance-divided parallel resonant circuit is divided into two parts in series when viewed from the coil, and is formed by dividing into two parts. A power supply as a power transmission unit or a load as a power reception unit is connected in parallel only to one divided capacitor of the capacitors. In the following description, one of the two divided capacitors will be referred to as the "third divided capacitor" and the other as the "fourth divided capacitor" for convenience of explanation.

Here, in the capacitance division series resonance circuit, it is necessary to satisfy the following equation (4a) in order to keep the resonance frequency unchanged when adjusting the capacitance of the first division capacitor and the second division capacitor. be. In addition, in the capacitance division parallel resonance circuit, when adjusting the capacitance of the third divided capacitor and the fourth divided capacitor, in order to keep the resonance frequency unchanged, it is necessary to satisfy the following equation (4b). .

Here, the capacitance ratio a ₀ of the first divided capacitor and the second divided capacitor of the capacitance-dividing series resonant circuit is defined as in the following equation (5a), and the third divided capacitor and the fourth divided capacitor of the capacitance-divided parallel resonant circuit is defined as the following equation ( _5b ).

By dividing the capacitor in this way and connecting the load and the power supply to one side of the divided capacitor, in the series resonant circuit, from the circuit equation, Z _S0 is replaced with a ² Z _S0 in Equation (3a). Therefore, the external Q is approximately represented by the following equation (6a). Similarly, in the parallel resonant circuit, Z _S0 is replaced with b ² Z _S0 in Equation (3b) from the circuit equation, so the external Q is approximately represented by Equation (6b) below.

FIG. 4 is a diagram showing the configuration of a wireless power transmission system. FIG. 4(a) shows a mode in which both the power transmitting side resonator and the power receiving side resonator are configured by general series type (S type) resonators, and FIG. Both the resonator and the power-receiving-side resonator are configured by capacitance division series type (S-type) resonators. Further, FIG. 4(c) shows a mode in which both the power transmitting side resonator and the power receiving side resonator are configured by general parallel type (P type) resonators, and FIG. Both the power transmitting side resonator and the power receiving side resonator are configured by capacitance-divided parallel type (P-type) resonators.

Note that the power transmission side resonator and the power reception side resonator do not need to have the same configuration, so there are four types of configurations for the wireless power transmission system. (1) SS type: series type on both transmitting and receiving sides, (2) SP type: series type on transmitting side: parallel type on receiving side, (3) P-S type: parallel type on transmitting side: series type on receiving side (4) PP type; parallel type on both the power transmission side and the power receiving side.

Next, for each of the SS type wireless power transmission system and the PP type wireless power transmission system, the relationship between the external Q and the resonator coupling between the power transmitting side resonator and the power receiving side resonator will be analyzed.

When two LC resonators are set to the same resonance frequency and electromagnetically resonate by bringing the coils close to each other, a high-frequency signal is transmitted between the resonators. be a characteristic.

Assuming that the power transmitting side resonator is 1 and the power receiving side resonator is 2, the inductances of the respective coils are L ₁ and L ₂ and the capacitances are C ₁ and C ₂ , the resonant frequency ω ₀ of the resonator is given by the following formula (7 ), and the characteristic impedances Z _R1 and Z _R2 of the resonator are given by the following equation (8).

Here, let Z _S1 be the impedance of the power source on the power transmission side, and let Z _S2 be the impedance of the load on the power reception side. The coupling coefficient k between resonators plays an important role in resonant power transmission using resonators. The coupling coefficient is given by the mutual inductance L _M between the coils in terms of the circuit, and is given by the following equation (9). This coupling coefficient takes a value between 0 and 1 depending on the positional relationship between the coils.

According to Non-Patent Document 1, if there is a relationship of the following equation (10) between the external Q and the coupling coefficient k of both resonators, the signal is transmitted without reflection.

Apply this relationship to various wireless power transfer systems (that is, substitute equation (6a) or equation (6b) for external Q in equation (10)). Letting the load impedance Z _S2 be R _L , in the SS type, it means the impedance of the load side as seen from the power supply side (that is, the input impedance at the entrance of the resonator on the power transmission side). Impedance”) is given by the following equation (11). When the relationship of formula (10) is satisfied, impedance matching is established from the power supply to the load. Therefore, according to the impedance matching condition, the input impedance of the resonator entrance on the power transmission side and the impedance of the power supply have the same value Z is _S1 .

Similarly, in the SP type, the input impedance at the entrance of the resonator on the transmission side is given by the following equation (12).

Similarly, in the PS type, the input impedance at the entrance of the resonator on the transmission side is given by the following equation (13).

Similarly, in the PP type, the input impedance at the entrance of the resonator on the transmission side is given by the following equation (14).

In either case, when R _L is connected to the load, the input impedance at the entrance of the resonator on the power transmission side is Z _S1 in each of the above equations, and is determined by the resonator impedances Z _R1 and Z _R2 , the coupling coefficient k, and the capacitance ratios a _and b. I understand. Thus, the resonator coupling acts as an impedance transformer between the load and power source.

The resonant power transmission circuit is an impedance transformation circuit, but the problem is that its ratio changes greatly with the coupling coefficient k. In particular, in the case of wireless power transmission, the coupling coefficient k changes greatly due to changes in the positional relationship of the resonators. As a result, the input impedance at the entrance of the resonator is greatly changed, and the power that can be extracted from the power supply is reduced, and there is a risk of destroying the load due to excessive power. That is, in wireless power transmission, it is necessary to keep the input impedance at the entrance of the resonator within a certain range in order to keep the transmitted power within a predetermined range.

Therefore, in the wireless power transmission system according to the present embodiment, the capacitance ratio a, b is changed by using a capacitance division series resonance circuit (FIG. 3(c)) or a capacitance division parallel resonance circuit (FIG. 3(d)). , the input impedance at the entrance of the resonator is changed, thereby maintaining an appropriate transmission power.

Note that the impedance transformation ratio of the resonance power transmission circuit is determined by the impedances Z _R1 and Z _R2 of the resonators, the impedance Z _S2 of the load on the power receiving side, and the like, as shown in equations (11) to (14). If the capacitance ratio on the power receiving side is fixed, in the case of the SS type, the input impedance Z _S1 of the resonator from equation (11) is the k value and the capacitance ratio on the input side a represented by ₁ . Here, the fixed value portion (Z _R1 Z _R2 /R _L ) is designated as Z _A .

The same is true for the PP configuration. If the capacitance ratio on the power receiving side is fixed, in the case of the PP type, the input impedance Z _S1 of the resonator from equation (14) is the k value and the capacitance ratio b on the input side as shown in equation (16) below. represented by ₁ .

As can be seen from the equations (15) and (16), if the appropriate capacitance ratios a ₁ and b ₁ can be prepared, it is possible to always maintain a constant input impedance Z _S1 with respect to variations in the k value.

[Specific Configuration of Resonator]
FIG. 5 is a diagram showing an example of the configuration of the divided capacitor series resonator according to the present embodiment (here, showing the power transmission side resonator).

The divided capacitance series resonator according to this embodiment is
having a capacitor 3 and a coil 1 that form a series resonance circuit,
The capacitor 3 includes n (where n is a positive integer equal to or greater than 2) sets of divided capacitor pairs 31, 32, 33, each of which consists of a first divided capacitor and a second divided capacitor connected in parallel to the coil 1. ...has 3n,
the sum of the capacitance value of the first split capacitor and the capacitance value of the second split capacitor is the same for each of the n sets of split capacitor pairs 31, 32, 33, . . . 3n;
The ratio of the capacitance value of the first split capacitor to the capacitance value of the second split capacitor is different for each of the n sets of split capacitor pairs 31, 32, 33, . . . 3n, and
A capacitance dividing point of the first divided capacitor and the second divided capacitor is connected to one end of the coil 1 via the first switch 7,
The other end of the second dividing capacitor is connected to the other end of the power supply 5 (the load in the case of the power receiving resonator) via the second switch 8,
The other end of the first split capacitor is connected to the connection point of the other end of the coil 1 and the other end of the power supply 5 (the load in the case of the resonator on the power receiving side),
In the first switch 7 and the second switch 8, any one of n sets of divided capacitor pairs 31, 32, 33, . . . act to connect,
It is a resonator.

Here, the reason why the sum of the capacitance value of the first split capacitor and the capacitance value of the second split capacitor is the same for each split capacitor pair of the n sets of split capacitor pairs is that each split capacitor pair has the same resonance frequency. It is for

The reason why the ratio of the capacitance value of the first split capacitor and the capacitance value of the second split capacitor is different for each split capacitor pair of the n sets of split capacitor pairs is that an appropriate a value can be set during system operation. This is to enable the selection of the split capacitor pair that has. More specifically, the k _{- th} split capacitor pair among the n sets of split capacitor pairs 31, 32, 33, . is set so that the ratio C _B /(C _A +C _B ) (that is, the value of a) is the value of (17) below.

FIG. 6 is a diagram showing an example of the configuration of the split capacitor parallel resonator according to the present embodiment (here, showing the power transmission side resonator).

The divided capacitance parallel resonator according to this embodiment is
having a capacitor 3 and a coil 1 that constitute a parallel resonance circuit,
The capacitor 3 includes n (where n is a positive integer equal to or greater than 2) sets of divided capacitor pairs 31, 32, 33, each of which consists of a third divided capacitor and a fourth divided capacitor connected in series to the coil 1. ...has 3n,
The sum of the reciprocal of the capacitance value of the third split capacitor and the reciprocal of the capacitance value of the fourth split capacitor is the same for each of the n sets of split capacitor pairs 31, 32, 33, . . . 3n, and
The ratio of the capacitance value of the third split capacitor to the capacitance value of the fourth split capacitor is different for each of the n sets of split capacitor pairs 31, 32, 33, . . . 3n, and
A capacitance dividing point of the third dividing capacitor and the fourth dividing capacitor is connected to the other end of the power supply or the load through the fourth switch 10,
The other end of the third dividing capacitor is connected to one end of the coil via a third switch 9,
The other end of the fourth split capacitor is connected to the connection point of the other end of the coil 1 and the other end of the power supply 5 (the load in the case of the resonator on the power receiving side),
In the third switch 9 and the fourth switch 10, any one of n sets of divided capacitor pairs 31, 32, 33, . act to connect,
It is a resonator.

Here, the sum of the reciprocal of the capacitance value of the third split capacitor and the reciprocal of the capacitance value of the fourth split capacitor is the same for each split capacitor pair of the n sets of split capacitor pairs because each split capacitor pair resonates. This is for making the frequencies the same.

The reason why the ratio of the capacitance value of the third split capacitor and the capacitance value of the fourth split capacitor is different for each split capacitor pair of the n sets of split capacitor pairs is that an appropriate b value can be set during system operation. This is to enable the selection of the split capacitor pair that has. More specifically, the k _{- th} split capacitor pair among the n sets of split capacitor pairs 31, 32, 33, . is set so that the ratio (C _C +C _D )/C _C (that is, b value) is the value of the following equation (18).

When using an SS type wireless power transmission system, more preferably, both the power transmitting side resonator and the power receiving side resonator are configured as shown in FIG. Further, when an SP type wireless power transmission system is used, it is more preferable to configure the power transmission side resonator as shown in FIG. 5 and the power receiving side resonator as the configuration shown in FIG. Further, when using a PS type wireless power transmission system, it is more preferable to configure the power transmitting side resonator as shown in FIG. 6 and the power receiving side resonator as the configuration shown in FIG. Further, when using a PP type wireless power transmission system, more preferably, both the power transmitting side resonator and the power receiving side resonator are configured as shown in FIG.

However, in these wireless power transmission systems, only one of the power transmission side resonator and the power reception side resonator is configured as shown in FIG. 5 or 6, and the other is shown in FIG. A basic LC resonator configuration may also be used.

[Transmission characteristics of wireless power transmission system]
FIG. 7 shows the behavior of the input impedance Z _S1 of the resonator, which is controlled by adjusting the capacitance ratio a ₁ in the SS type wireless power transmission system using the divided capacitance series resonator according to this embodiment. It is a figure which shows an example.

In FIG. 7, the range between Z _min and Z _max is an example of the optimum range for the input impedance Z _S1 of the resonator. Hereinafter, Z _min will be referred to as the "target lower limit impedance value", and Z _max will be referred to as the "target upper limit impedance value". Also, p ₁ to p ₁₁ each represent a different a ₁ value.

Generally, in the case of power transmission, a large voltage is applied to the capacitor of the resonator, so a variable capacitance semiconductor element such as a varactor cannot be used for the capacitor. Therefore, when configuring a resonator, individual capacitors such as ceramic capacitors are electrically connected and used. Further, as described above, it is actually difficult from the viewpoint of adjustment accuracy to adjust the capacitance ratio a1 by using _a variable capacitor or the like as a capacitor of the resonator and adjusting the rotational angle position of the variable capacitor. be.

Therefore, in the divided capacitor series resonator according to the present embodiment, as shown in FIG. 5, n sets of divided capacitor _pairs having different capacitance ratios a1 are provided. It is configured so that one can be selected and used.

At this time, a set of split capacitor pairs for maintaining a constant input impedance Z _S1 and transmitting power at a constant level or higher will be examined with respect to fluctuations in the k value.

First, assuming that k changes continuously, when k=k _i , set a ₁ so that the input impedance Z _S1 of the resonator becomes Z _min , and set that value to a _{1 (i)} and That is, it is defined as in the following formula (19).

Here, assuming that the k value increases to k _i+1 and Z _S1 becomes Z _max at that time, the definition is similarly given by the following equation (20).

Here, when a1 is switched to a1 _{(i+1) and} Z _S1 is returned to Z _min , it is expressed as in Equation (21) below.

From these equations (19), (20), and (21), when the k value increases from k _i to k _i+1 , a ₁ changes from a _1(i) to a _1(i+1) The change ratio of a ₁ when changed is represented by the following equation (22).

In other words, if _a large number of a1 values are prepared as a geometric progression at a ratio of √(Zmax/Zmin), the input impedance Z _S1 of the resonator can be obtained without unnecessary overlap and without a break, as shown in FIG. It can be maintained between Z _min and Z _max .

の範囲で変化させることが可能である。 For example, rotary switches are often used to change electrical connections. With 11 widely used contacts, it is possible to switch in ₁₁ stages.

can be changed within the range of

From this point of view, in the divided capacitor series resonator according to the present embodiment, the k-th divided capacitor pair among the n sets of divided capacitor pairs 31, 32, 33, . . . The ratio C _B /(C _A +C _B ) of _A and the capacitance value C _B of the second split capacitor is a geometric progression that increases at the rate of √(Zmax/Zmin) as shown in the above equation (18). prepared to be valued.

In FIG. 7, the a1 value is set so that the input impedance of the resonator is kept within 80Ω to 120Ω when the _k value is changed. Specifically, when the resonator is configured with L=1.59 μH and C=159 pF, the resonance frequency is 10 MHz and the resonator impedance is 100Ω. In a capacitance-divided SS type resonant power transmission circuit (Fig. 4(b)) using two of these resonators, it is assumed that a load of R _L = 1 kΩ is attached and the capacitance ratio a If ₂ is 1, then Z _A is 10Ω. And since Z _min =80Ω and Z _max =120Ω, the ratio of change in a ₁ is √(120/80)=1.225.

FIG. 7 shows the input impedance of the resonator when the initial a ₁ , that is, p ₁ =0.0107, is changed to p ₁₁ =0.0813 at the 11th stage. From Fig. 7, the input impedance of the resonator changes greatly according to the value of _k when a1 is fixed, but by changing the value of a1, _k = 0.03 to 0.28 It can be seen that it can be maintained between the provisions between

Table 1 below shows the values of the capacitance ratios a ₁ of the 11 sets of split capacitor pairs of the power transmitting resonator set to keep the input impedance of the resonator between 80Ω and 120Ω, and the external Q at that time. It is a table. As described above, here, the capacitance ratio of the power receiving side resonator is fixed at a ₂ =1. The k value in Table 1 is the k value when the input impedance of the resonator is 100Ω. Qe1 in Table 1 is the external Q of the power transmitting resonator, and Qe2 is the external Q (fixed value) of the power receiving resonator.

In the split capacitor series resonator according to the present embodiment, as a specific method for selecting one of the n sets of split capacitor pairs during system operation, for example, the power transmission device UA to the power reception device UB: _A method of executing a test of power transmission, monitoring the transmitted power and / or received power at that time, and switching the split capacitor pair to be connected (that is, the a1 value) so that the power value is within the regulation can be used (see FIG. 12 below).

As can be seen from equations (11) and (15), the same can be done with a2 on the power receiving side, and by combining the _two , a wider range of application is possible.

FIG. 8 is a diagram showing the behavior of transmitted power (solid line) controlled by adjusting the capacitance ratio a1 in the SS type wireless power transmission system using the divided capacitance series resonator according to the present embodiment. is.

Here, similarly to FIG. 7, simulation was performed to calculate how the transmitted power would change when the capacity _ratio a1 was adjusted. In this simulation, the parasitic resistance of the coil was set to zero. Also, the power supply is configured to output a sine wave with an effective value of 100V at 10MHz.

First, since it is assumed that there is no internal resistance in the coil, the power sent from the power supply and the power on the load side are the same. In FIG. 7, as the k value increases, the impedance increases, but since the transmitted power is inversely proportional to the impedance, the transmitted power shown in FIG. 8 decreases as the k value increases.

From Fig. 8, it can be seen that the transmission power can be adjusted in the range of 83 to _125W by choosing the value of a1. A rectenna circuit on the power receiving side can sufficiently cope with this level of fluctuation.

In the above, the power transmission (solid line) was described when the parasitic resistance of the coil was set to zero, but in reality, the internal resistance of the coil or the no-load Q of the resonator is an important parameter in resonant power transmission. is.

Therefore, the calculation result when the parasitic resistance of the coil is 0.25Ω and the no-load Q is 400 is shown by the dotted line in FIG. _In FIG. ₈ , the transmission characteristics when the capacitance _ratio a1 is p11, the transmission characteristics when the capacitance _ratio a1 is p10, . From FIG. 8, it can be seen that when the parasitic resistance of the coil is taken into account, the transmitted power is greatly reduced compared to when the parasitic resistance of the coil is zero.

According to Non-Patent Document 1, by adjusting both the external Q of the power transmitting side resonator and the external Q of the power receiving side resonator so as to satisfy the following equation (24), the flattest characteristic is obtained.

The flattest characteristic is a transmission characteristic obtained under the condition of no reflection over a wide frequency band. It represents a transmission characteristic with an efficiency of almost 100% (also called a Butterworth characteristic). The condition (Q _e1 * Q _e2 = 1/k ² ) of formula (10) partially includes the condition (Q _e1 = 1/k and Q _e2 = 1/k) of formula (24), The condition of equation (24) indicates that it is important to balance the external Q of the power transmitting resonator and the external Q of the power receiving resonator to the same degree.

According to Non-Patent Document 1, it is also shown that it is possible to minimize the loss due to the parasitic resistance of the coil by satisfying the flattest characteristics. This is because when the external Q of the power transmitting resonator and the external Q of the power receiving resonator become unbalanced, the internal resistance of the coil is likely to affect the transmission efficiency, resulting in a decrease in transmission efficiency. As shown in Table 1, under the conditions under which the transmitted power in FIG. 8 was calculated, the ratio of the external Q of the power transmitting resonator to the external Q of the power receiving resonator was 1000 times or more, resulting in a large imbalance. Therefore, when the parasitic resistance of the coil is taken into account, it is considered that the transmitted power is greatly reduced compared to the case where the parasitic resistance of the coil is zero.

FIG. 9 is a diagram showing the results of a simulation performed to analyze the problem of imbalance between the external Q of the power transmitting resonator and the external Q of the power receiving resonator. As in FIG. 8, FIG. 9 shows the transmitted power in the SS type wireless power transmission system, which is controlled by adjusting the capacitance _ratio a1 in the split capacitor series resonator according to the present embodiment. there is However, in FIG. 9, the value of the capacitance ratio a2 of the power receiving side resonator is set to 0.135, which is smaller than the capacitance ratio _a2 = ₁ in the case of FIG.

Table ₂ below shows the values of the capacitance ratios a1 of the 11 sets of split capacitor pairs of the power transmitting resonator set to keep the input impedance of the resonator within 80 Ω to 120 Ω in the simulation of FIG. 4 is a table showing the external Q when As described above, here, the capacitance ratio of the power receiving side resonator is fixed at a ₂ =0.135.

In the previous example, the capacitance ratio a1 was changed between _0.0107 and 0.0813, but here, in order to obtain the same output, it is changed between 0.122 and 0.925. Then, as can be seen from FIG. 9, approximately the same transmitted power can be obtained in the same fluctuation range of k as in the previous example.

Also, in this case, as can be seen by referring to the dotted line in FIG. 9, even when the parasitic resistance of the coil is 0.25Ω and the no-load Q is 400, the transmitted power is lower than when the parasitic resistance of the coil is zero. and will not drop significantly. In addition, as shown in Table 2, in this case, the characteristics are the flattest at p ₇ at approximately Q _e1 =Q _e2 , and the external Q of the power transmitting side resonator and the power receiving side resonator within the range of k value fluctuation , the imbalance of the external Q is largely eliminated.

Next, the input impedance and transmission characteristics of the resonator in the PP type wireless power transmission system using the divided capacitance parallel resonator according to this embodiment will be described. A PP-type wireless power transmission system using a split-capacitance parallel resonator can also obtain results similar to those described above.

FIG. 10 shows the behavior of the input impedance Z _S1 of the resonator, which is controlled by adjusting the capacitance ratio b ₁ in the PP type wireless power transmission system using the divided capacitance parallel resonator according to this embodiment. It is a figure which shows an example.

In FIG. 10, the range between Z _min and Z _max is an example of the optimum range for the input impedance Z _S1 of the resonator. Also, q ₁ to q ₁₁ each represent a different b ₁ value.

In FIG. 10, similarly to the above, if the resonator is configured with L=1.59 μH and C=159 pF, and R _L =1 kΩ and b ₂ =1 on the receiving side, Z _A will be 10Ω. In FIG. 10, the b ₁ value for keeping the input impedance of the resonator within 80Ω to 120Ω is calculated when the k value is changed in this configuration. In the case of the parallel type (P type), the coupling coefficient k and the capacitance ratio b come to the numerator. Therefore, as k increases, the impedance drops, and b must be decreased to restore it.

In the split capacitor parallel resonator according to the present embodiment, the k _- th split capacitor pair among the n sets of split capacitor pairs 31, 32, 33, . . . The ratio (C _C + C _D )/C _C (that is, b ₁ value) of the capacitance value C _D of the dividing capacitor increases at a rate of √(Zmax/Zmin) as shown in the above equation (19), etc. It is prepared to be the value of the ratio series.

FIG. 10 shows the input impedance of the resonator when the initial b ₁ , that is, q ₁ =1.25, is changed to q ₁₁ =9.45 in the 11th stage. Also in this case, the ratio of change in b ₁ √(Zmax/Zmin) is 1.225. As a result, as shown in FIG. ₁₀ , it can be seen that the input impedance of the resonator can be maintained within the specified range from k=0.03 to 0.3 by switching the b1 value.

Table 3 below shows the values of the capacitance ratios b1 of the 11 sets of split capacitor pairs of the power transmitting resonator set to keep the input impedance of the resonator within 80 Ω to ₁₂₀ Ω in the simulation of FIG. 4 is a table showing the external Q when As described above, the capacitance ratio of the power receiving side resonator is fixed at b ₂ =1 here. The k value in Table 2 is the k value when the input impedance of the resonator is 100Ω. Q _e1 in Table 2 is the external Q of the power transmitting side resonator, and Q _e2 is the external Q (fixed value) of the power receiving side resonator.

FIG. 11 shows the behavior of transmitted power (solid line) controlled by adjusting the capacitance ratio b ₁ in the PP-type wireless power transmission system using the split-capacitance parallel resonator according to the present embodiment. It is a diagram.

Here, similarly to FIG. 10, simulation was performed to calculate how the transmitted power would change when the capacity ratio b ₁ was adjusted. In this simulation, the parasitic resistance of the coil was set to zero. Also, the power supply is configured to output a sine wave with an effective value of 100V at 10MHz.

From FIG. 11, it can be seen that the transmission power can be adjusted in the range of 83 to 125W by choosing the value of b ₁ . A rectenna circuit on the power receiving side can sufficiently cope with this level of fluctuation.

The transmission characteristics control described above can be similarly performed in the SP _type wireless power transmission system and the PS _type wireless power transmission system. _The impedance transformation ratio can be changed by _a2 and b2. That is, in _order to maintain the input impedance of the resonator _{between Z min and} Z _max , n sets of dividing capacitor pairs 31, 32, 33, . It is sufficient to set the capacity ratio of

[Example of operation during system operation of wireless power transmission system]
FIG. 12 is a flowchart showing an operation example during system operation of the wireless power transmission system according to this embodiment. Here, only an operation example of the SS type wireless power transmission system is shown. The flowchart shown in FIG. 12 is, for example, processing executed by a control unit (not shown) of the power transmission device UA according to a computer program.

In step S1, the control unit of the power transmitting device UA communicates with the control unit of the power receiving device UB, and starts conducting a power transmission test.

In step S2, the control unit of the power transmission device UA measures the transmission efficiency in the power transmission test. At this time, the control unit of the power transmitting device UA measures the transmission efficiency based on, for example, the power transmitted from the power transmitting device UA and the received power measured by the power receiving device UB.

In step S3, the control unit of the power transmission device UA determines whether or not the transmission efficiency measured in step S2 is greater than a threshold value (95%, for example). If the transmission efficiency measured in step S2 is greater than the threshold (step S3: YES), the process proceeds to step S5, and if less than the threshold (step S3: NO), the process proceeds to step S4.

In step S4, the control unit of the power transmission device UA switches the first switch 7 and the second switch 8, and among the n sets of divided capacitor pairs 31, 32, 33, . switch the dividing capacitor pairs of . At this time, the control unit of the power transmission device UA selects _one of the n sets of split capacitor pairs 31, 32, 33, . , select the split capacitor pair to be connected. Then, returning to step S1, power transmission and transmission efficiency are measured again.

In the wireless power transmission system according to this embodiment, the processing of steps S1 to S4 is repeatedly executed to specify the capacitance ratio a ₁ (ie, the split capacitor pair) that can ensure high transmission efficiency.

In step S5, the control unit of the power transmitting device UA causes the power receiving device UB to perform the actual power transmission from the power transmitting device UA.

In step S6, the control unit of the power transmission device UA waits for satisfaction of conditions for terminating power transmission (S6: NO). Then, if the termination condition is satisfied (S6: YES), the processing of the flowchart of FIG. 12 is terminated. Note that the control unit of the power transmission device UA determines that the termination condition is satisfied, for example, when the battery, which is the load of the power reception device UB, reaches a fully charged state.

In the wireless power transmission system according to the present embodiment, the series of processes described above enables power transmission from the power transmission device UA to the power reception device UB with high transmission efficiency.

Note that in the flowchart of FIG. 12, the transmitted power is adjusted by adjusting _only the capacitance ratio a1 of the capacitors of the power transmission side resonator under the condition that the capacitance ratio _a2 of the capacitors of the power reception side resonator is fixed. showed that. Such an embodiment is useful in that it is not necessary to adjust the capacitance ratio _a2 of the capacitors of the power receiving side resonator during system operation.

However, in order to obtain the flattest characteristics, it is more preferable to adjust _both the capacitance ratio a1 of the capacitors of the power transmitting _side resonator and the capacitance ratio a2 of the capacitors of the power receiving side resonator. _In this case, for example, in the processing of steps S1 to S4 in the flowchart of FIG. A similar process is performed for the resonator. That is, under the condition that the capacity ratio a ₁ of the power transmission side resonator is fixed, the capacity ratio a ₂ of the power reception side resonator (that is, the split capacitor _pair ) is switched in stages to maximize the transmission efficiency. should be specified.

This enables power transmission from the power transmission device UA to the power reception device UB with higher transmission efficiency.

[effect]
As described above, according to the resonator according to the present disclosure (see FIG. 5 or FIG. 6), the external Q of the resonator is changed to It is possible to properly adjust and maintain the input impedance of the resonator as seen from the power source within a certain range simply by switching the switch, thereby enabling stable wireless power transmission.

In addition, if the transmitted power can be monitored, it is possible to adjust the resonator only in one of the power transmission and reception. Furthermore, if this device is used for both power transmission and reception, it is possible to set a condition that the loss due to the internal resistance is small, that is, the flattest characteristics at all times. In this way, according to the resonator according to the present disclosure (see FIG. 5 or 6), resonance power transmission, which has been difficult to control and has not been widely used, can be achieved with a simple method and high transmission efficiency. can be realized.

Although specific examples of the present invention have been described in detail above, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.

According to the resonator of the coupled resonance type wireless power transmission system according to the present disclosure, it is possible to transmit an appropriate power value with a simpler method.

UA power transmission device UB power reception device 1 power transmission side coil 2 power reception side coil 3 power transmission side capacitors 31, 32, 33, . 4th switch

Claims (8)

A resonator applied to a coupled resonance type wireless power transmission system,
Having a capacitor and a coil that form a series resonance circuit,
having a first switch, a second switch, and a power source as a power transmission unit or a load as a power reception unit;
The capacitor has n (where n is a positive integer equal to or greater than 2) sets of divided capacitor pairs each consisting of a first divided capacitor and a second divided capacitor connected in parallel to the coil,
the sum of the capacitance value of the first split capacitor and the capacitance value of the second split capacitor is the same for each split capacitor pair of the n sets of split capacitor pairs;
the ratio of the capacitance value of the first split capacitor to the capacitance value of the second split capacitor is different for each split capacitor pair of the n sets of split capacitor pairs;
a capacitance dividing point of the first divided capacitor and the second divided capacitor is connected to one end of the coil via the first switch;
the other end of the second dividing capacitor is connected to a first end of the power supply or the load through the second switch;
the other end of the first split capacitor is connected to a connection point between the other end of the coil and a second end of the power supply or the load;
the first switch and the second switch operate to connect any one of the n sets of divided capacitor pairs to the coil and the power supply or the load;
resonator. The k-th split capacitor pair among the n sets of split capacitor pairs has a ratio C _B /(C _A +C _B ) between the capacitance value C _A of the first split capacitor and the capacitance value C _B of the second split capacitor. is set to be the value of the following formula (1),
A resonator according to claim 1 .

A resonator applied to a coupled resonance type wireless power transmission system,
Having a capacitor and a coil that constitute a parallel resonant circuit,
having a third switch, a fourth switch, and a power source as a power transmission unit or a load as a power reception unit;
The capacitor has n (where n is a positive integer equal to or greater than 2) sets of divided capacitor pairs, each of which consists of a third divided capacitor and a fourth divided capacitor connected in series to the coil,
the sum of the reciprocal of the capacitance value of the third split capacitor and the reciprocal of the capacitance value of the fourth split capacitor is the same for each split capacitor pair of the n sets of split capacitor pairs;
the ratio of the capacitance value of the third split capacitor to the capacitance value of the fourth split capacitor is different for each split capacitor pair of the n sets of split capacitor pairs;
a capacitance dividing point of the third divided capacitor and the fourth divided capacitor is connected to a first end of the power supply or the load through the fourth switch;
the other end of the third dividing capacitor is connected to one end of the coil through the third switch;
the other end of the fourth split capacitor is connected to a connection point between the other end of the coil and a second end of the power supply or the load;
the third switch and the fourth switch operate to connect any one of the n sets of divided capacitor pairs to the coil and the power source or the load;
resonator. The k-th split capacitor pair among the n sets of split capacitor pairs has a ratio of the capacitance value C _C of the third split capacitor to the capacitance value C _D of the fourth split capacitor (C _C +C _D )/C _C is set to be the value of the following formula (2),
4. A resonator according to claim 3.

A power transmission-side resonator is composed of the resonator according to claim 1, and
wherein the resonator on the power receiving side is composed of the resonator according to claim 1,
Coupling resonance type wireless power transmission system. A power transmission-side resonator is composed of the resonator according to claim 3, and
wherein the resonator on the power receiving side is composed of the resonator according to claim 1,
Coupling resonance type wireless power transmission system. A power transmission-side resonator is composed of the resonator according to claim 1, and
wherein the resonator on the power receiving side is composed of the resonator according to claim 3,
Coupling resonance type wireless power transmission system. A power transmission-side resonator is composed of the resonator according to claim 3, and
wherein the resonator on the power receiving side is composed of the resonator according to claim 3,
Coupling resonance type wireless power transmission system.

Images