CN104993614A - Asymmetric wireless power transmission system with relay coil inserted therein, and method - Google Patents

Abstract

The invention discloses an asymmetric wireless power transmission system with a relay coil inserted therein, and a method, and relates to the field of a magnetically-coupled resonant wireless power transmission technology. The relay coil and an emission coil are coaxial and are disposed at the same plane. The system and the method mainly solve the problem of low transmission efficiency of a wireless power transmission system whose emission coil is larger than a receiving coil in terms of dimension over an intermediate and long distance. According to the method, through inserting the relay coil which is coaxial and disposed at the same plane with the emission coil in the system, the mutual inductance coefficient between adjacent coils is enhanced, the coupling degree between the coils is improved, the transmission efficiency of the system is improved, the coaxial and same-plane structure of the relay coil and the emission coil helps to save space dimension, and application of the wireless power transmission system in reality is better facilitated.

Description

Asymmetric wireless power transmission system and method with relay coil inserted

technical field

The invention belongs to the technical field of magnetic coupling resonance wireless power transmission, and relates to an asymmetric wireless power transmission system inserted with a relay coil, in particular to a relay coil in an asymmetric wireless power transmission system in which the size of the transmitting coil is larger than that of the receiving coil A new design method, the relay coil and the transmitting coil are coaxial and in the same plane, so as to save space and improve the transmission efficiency of the wireless power transmission system.

Background technique

With the development of science and technology, wireless power transmission technology has attracted more and more people's attention, especially in November 2006, Marin Soljacic of the Massachusetts Institute of Technology and his research group used The principle of magnetic coupling resonance successfully lit a 60W light bulb about 2m away from the power supply. Later, this technology was called WiTricity, which aroused a wave of research on wireless power transmission systems. With the in-depth research on magnetic coupling resonance technology, experts and scholars from various countries have successively developed high-power wireless energy transmission devices, such as maglev trains, tailless home appliances, implanted medical equipment, electric vehicles and mobile devices.

At present, there are three ways to realize wireless power transmission at home and abroad:

1. Radio-wave Wireless Power Transmission (RWPT) - the basic principle is to use radio waves (such as microwaves) instead of wires to realize the transmission of electric energy. It can realize high-power and long-distance electric energy transmission. It is a radio wave energy transmission method that has been studied more at present, but its transmission attenuation is serious, the efficiency of energy transmission is not high, and it has a great impact on the biological environment.

2. Electromagnetic Induction Wireless Power Transmission (EI-WPT) - its basic principle is to use the principle of electromagnetic induction to transmit electric energy from the primary winding to the secondary winding, the two windings are tightly coupled, and the transmission efficiency is very high High, but the transmission distance is short and can only be limited to the range of millimeters or centimeters. At the same time, the structural dimensions of the two coil windings require precise dimensions.

3. Magnetically-coupled resonant wireless power transmission (MCR-WPT) - the principle is to adjust the transmitting coil and receiving coil into a resonant system, when the oscillation frequency of the transmitting coil and the natural frequency of the receiving coil At the same time, the system will generate resonance, so that the energy only oscillates between the transmitting coil and the receiving coil with the same resonance frequency, so as to transmit energy, and there will be no energy interaction with other non-resonant objects. It makes up for the shortcomings of the short transmission distance of the electromagnetic induction wireless power transmission technology, increases the transmission distance to the range of meters, and also overcomes the low transmission efficiency of the microwave wireless power transmission method, greatly improving the transmission efficiency of the system.

The transmission efficiency is one of the main performance indicators of the magnetically coupled resonant wireless power transfer system, and the mutual inductance coefficient between the coils will affect the transmission efficiency of the system.

The study found that the transmission efficiency of the wireless power transmission system with the size of the transmitting coil larger than the size of the receiving coil is lower than that of the wireless power transmission system in which the transmitting and receiving devices are completely symmetrical under the same circumstances, and its transmission distance will also be affected. However, in the actual wireless power transmission system, the transmitting It is difficult to achieve complete symmetry between the coil and the receiving coil. Adding a relay coil can effectively solve the problem of low transmission efficiency of the system. It improves the mutual inductance coefficient between the coils and enhances the coupling degree between the coils, thereby enabling the system to operate at a higher efficiency. to transfer.

To sum up, in practical applications of wireless power transfer systems, it is difficult to achieve complete symmetry between the transmitting device and the receiving device. For example, when wirelessly charging mobile devices such as mobile phones, the size of the transmitting coil is larger than that of the receiving coil. In this asymmetric wireless power transmission system, the transmission efficiency will decrease, and with the increase of the transmission distance, the transmission efficiency of the system will drop sharply, and the popularization and application of the wireless power transmission system will be limited. , we must find a technical method to realize the above-mentioned scheme—to allow the wireless power transmission system with the size of the transmitting coil larger than the size of the receiving coil to achieve high-efficiency transmission at medium and long distances.

Contents of the invention

The purpose of the present invention is to propose an asymmetric wireless power transmission system with a relay coil inserted in order to solve the problem that the mutual inductance coefficient is small when the wireless power transmission system with the size of the transmitting coil is larger than the size of the receiving coil for energy transmission, resulting in low system transmission efficiency. method. In the system and method, in a magnetic coupling resonant wireless power transmission system in which the size of the transmitting coil is larger than that of the receiving coil, a relay coil coaxial and coplanar with the transmitting coil is inserted, so that the mutual inductance coefficient between the transmitting end and the receiving end is enhanced, thereby improving the transmission efficiency of the system. At the same time, the present invention can also save space and reduce the volume of the system, which is more conducive to the practical application of wireless power transmission.

In order to achieve the above goals, the technical solution adopted by the present invention is: an asymmetric wireless power transmission system inserted into a relay coil, the wireless power transmission system includes a transmitting device, a relay device and a receiving device; the transmitting device includes a high A high-frequency signal generator, an impedance matching network, a power amplifier and a transmitting coil, one side of the transmitting coil is connected to the high-frequency signal generator through an impedance matching network, and the other side resonates with the receiving coil, so that the energy is transmitted in the form of electromagnetic waves Oscillation between the two coils; the relay device includes a relay coil, the relay coil is coaxial and coplanar with the transmitting coil, has the same number of turns and turn pitch, and the radius of the relay coil is different from that of the transmitting coil; the receiving The device includes a receiving coil, a load device and a power meter. The radius of the receiving coil is smaller than that of the transmitting coil, and the number of turns and the pitch of the turns are the same as that of the transmitting coil. The transmitting coil generates resonance; the transmitting coil, the relay coil and the receiving coil are on the same horizontal axis, and the distance between the transmitting coil and the receiving coil is 1m.

According to the power transmission system of the present invention, the impedance matching network is an active matching network, which is composed of a source follower, an emitter follower and a buffer composed of active and passive devices;

According to the power transmission system of the present invention, the impedance matching network is a passive matching network composed of inductors and capacitors.

According to the power transmission system of the present invention, the relay coil is wound on the outer layer of the transmitting coil.

According to the power transmission system of the present invention, the receiving coil is a multi-turn spiral coil, a matching capacitor is connected in series, and is directly connected to an AC load device; or the receiving coil is supplied to a DC load device or circuit through a rectifier circuit; Rectification circuits include half-wave rectification, full-wave rectification and bridge rectification.

According to the power transmission system of the present invention, the transmitting coil, relay coil and receiving coil utilize their own equivalent resistance at high frequency, parasitic capacitance, matching capacitance and self-inductance to form an oscillation circuit, and the transmitting coil, relay coil and receiving coil The coils have the same resonant frequency.

According to the power transmission system of the present invention, the transmitting coil, the relay coil and the receiving coil are all multi-turn coils.

In order to achieve the above object, another technical solution adopted by the present invention is: an asymmetric wireless power transmission method with a relay coil inserted, the high-frequency signal generator generates a high-frequency sine wave signal, which is amplified by the power amplifier and then loaded into the transmitting Coil, according to which the input power is obtained; the transmitting coil sends the received high-frequency oscillating signal in the form of non-radiating near-field electromagnetic waves; the relay coil receives the high-frequency transmission coil transmitted by the transmitting coil through the near-field coupling The oscillating signal is then sent out in the form of non-radiating near-field electromagnetic waves, and the relay coil acts as a transfer station during the energy transmission process between the transmitting end and the receiving end; the receiving coil is also sent out by the near-field coupling receiving relay coil between the coils The signal, and the output power is measured by the power meter, the ratio of the input power to the output power is the transmission efficiency of the system, thus, the system transmits power with a higher efficiency.

The beneficial effects of the present invention are:

1. The asymmetric wireless power transmission system and method of inserting the relay coil proposed by the present invention can enhance the mutual inductance coefficient of adjacent coils between the magnetically coupled resonant wireless power transmission systems in which the transmitting coil is larger than the receiving coil size, so that the system can use higher transmission efficiency.

2. Compared with the prior art, the asymmetric wireless power transmission system and method inserted in the relay coil proposed by the present invention can maintain a high mutual inductance between adjacent coils during medium and long-distance transmission, thereby making the transmission efficiency significantly The improvement of the system further solves the problem that the transmission efficiency of the system is restricted by the size of the transmitting coil and the receiving coil, and improves the utilization efficiency of electric energy in the system.

Description of drawings

FIG. 1 is a structural diagram of an asymmetric magnetic coupling resonant wireless power transmission system.

Fig. 2 is a schematic diagram of the relay coil and the transmitting coil being coaxial and coplanar in the present invention.

Fig. 3 is an equivalent circuit model diagram of an asymmetric wireless power transmission system inserted with a relay coil according to the present invention.

Fig. 4 is a simulation diagram of the transmission efficiency of the asymmetric wireless power transmission system inserted with the relay coil according to the present invention.

Fig. 5 is an experimental diagram of the transmission efficiency of the asymmetrical wireless power transmission system inserted with a relay coil according to the present invention.

Fig. 6 is a simulation and experiment comparison diagram of the transmission efficiency of the asymmetric wireless power transmission system inserted with a relay coil according to the present invention.

Detailed ways

In order to make the content and advantages of the technical solution of the present invention more clear, the asymmetric wireless power transmission system and method of the present invention with a relay coil inserted will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be emphasized that the following description is only exemplary and not intended to limit the scope of the invention and its application.

The wireless power transmission system of the present invention includes a transmitting device, a relay device and a receiving device. The transmitting device comprises a high-frequency signal generator, an impedance matching network, a power amplifier and a transmitting coil, one side of the transmitting coil is connected to the high-frequency signal generator through an impedance matching network, and the other side resonates with the receiving coil, so that Energy oscillates between the two coils in the form of electromagnetic waves; the relay device includes a relay coil, the relay coil is coaxial and coplanar with the transmitting coil, has the same number of turns and pitch, and has different radii; the receiving device It includes a receiving coil, a load device and a power meter. The radius of the receiving coil is smaller than that of the transmitting coil, and its parameters such as the number of turns and the distance between turns are the same as those of the transmitting coil. Generate resonance with the transmitting coil; the transmitting coil, relay coil and receiving coil are on the same horizontal axis.

The transmitting coil, relay coil and receiving coil utilize their equivalent resistance at high frequency, parasitic capacitance, matching capacitance and their own inductance to form an oscillation circuit, and the transmitting coil, relay coil and receiving coil have the same resonant frequency. The centers of the transmitting coil, the receiving coil and the relay coil are on the same horizontal axis, when the distance and the transmission distance between the transmitting coil and the receiving coil change, due to the strong interaction between the transmitting coil and the relay coil, and between the relay coil and the receiving coil mutual inductance, the system can still transmit with high efficiency.

As shown in Figure 1, the transmitting coil is on the left and the receiving coil is on the right. The size of the transmitting coil is larger than that of the receiving coil, that is, the transmitting device and the receiving device are not completely symmetrical, and their transmission efficiency will be lower than that of the same size. In actual life and applications, people put forward greater requirements for the dexterity and convenience of electronic products, and the same is true for the application of wireless power transmission. The size of the receiving end is often smaller than that of the transmitting end.

As shown in Figure 2, the coaxial and coplanar structure of the relay coil and the transmitting coil of the present invention greatly enhances the mutual inductance between the relay coil and the transmitting coil, realizes the amplification of the source current, improves the transmission efficiency of the system, and saves The size of the space is reduced, the volume of the system is reduced, and it is more conducive to practical application.

As shown in Figure 3, the transmitting coil is on the left, the relay coil is in the middle, and the receiving coil is on the right. Both the transmitting end and the receiving end of the system adopt a series structure, M ₁₂ is the mutual inductance coefficient of the transmitting coil and the relay coil, and M ₂₃ is the relay coil and the mutual inductance coefficient of the receiving coil, Vs is the high frequency voltage source, Rs is the internal resistance of the voltage source, R ₁ , R ₂ , R ₃ are the equivalent internal resistances of the transmitting coil, relay coil and receiving coil respectively, C ₁ , C ₂ and C ₃ are the external capacitances of the three coils, L ₁ , L ₂ , and L ₃ are the self-inductances of the three coils, and R _L is the load resistance of the system.

The equivalent circuit model analysis steps of the asymmetric wireless power transmission system inserted into the relay coil of the present invention are as follows:

1. The equivalent circuit of the system is analyzed to obtain the following equation:

$\left[\begin{array}{c}{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; S</span>}}\\ \mathrm{<span\; class="notranslate">\; 0</span>}\\ \mathrm{<span\; class="notranslate">\; 0</span>}\end{array}\right]<span\; class="notranslate">\; =</span>\left[\begin{array}{ccc}{\mathrm{<span\; class="notranslate">\; Z</span>}}_{\mathrm{<span\; class="notranslate">\; 11</span>}}& \mathrm{<span\; class="notranslate">\; j\&omega;</span>}{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; 12</span>}}& \mathrm{<span\; class="notranslate">\; 0</span>}\\ \mathrm{<span\; class="notranslate">\; j\&omega;</span>}{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; 12</span>}}& {\mathrm{<span\; class="notranslate">\; Z</span>}}_{\mathrm{<span\; class="notranslate">\; twenty\; two</span>}}& \mathrm{<span\; class="notranslate">\; j\&omega;</span>}{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; twenty\; three</span>}}\\ \mathrm{<span\; class="notranslate">\; 0</span>}& \mathrm{<span\; class="notranslate">\; 0</span>}& {\mathrm{<span\; class="notranslate">\; Z</span>}}_{\mathrm{<span\; class="notranslate">\; 33</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; j\&omega;</span>}{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; twenty\; three</span>}}\end{array}\right]\left[\begin{array}{c}{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}\\ {\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}\\ {\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}\end{array}\right]$

Among them, V _S is the output voltage of the high-frequency signal generator, Z ₁₁ , Z ₂₂ , and Z ₃₃ are the loop impedances of the transmitting coil loop, the relay coil loop, and the receiving coil loop respectively, and their expressions are respectively: $Z_{\mathrm{twenty\; two}}=R_2+\mathrm{j\&omega;}{L}_2+\frac{1}{\mathrm{j\&omega;}{C}_2},Z_{33}=R_3+\mathrm{j\&omega;}{L}_3+\frac{1}{\mathrm{j\&omega;}{C}_3}+R_L;$ M ₁₂ is the mutual inductance coefficient of the transmitting coil and the relay coil, M ₂₃ is the mutual inductance coefficient of the relay coil and the receiving coil, i ₁ , i ₂ , and i ₃ are the loop currents of the transmitting coil loop, the relay coil loop and the receiving coil loop respectively. When the system works in the resonance state, it satisfies: $\mathrm{\&omega;}{L}_2=\frac{1}{\mathrm{\&omega;}{C}_2},\mathrm{\&omega;}{L}_3=\frac{1}{\mathrm{\&omega;}{C}_3}.$

2. Solve the determinant in the step 1, i ₁ , i ₂ , i ₃ can be obtained as follows:

${\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; vs.</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; twenty\; three</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; L</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; )</span>}{{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; twenty\; three</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; S</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; 12</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; L</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; S</span>}}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; L</span>}}<span\; class="notranslate">\; )</span>}$

${\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; \&omega;</span>}{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; 12</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; L</span>}}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; S</span>}}}{{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; twenty\; three</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; S</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; 12</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; L</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; S</span>}}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; L</span>}}<span\; class="notranslate">\; )</span>}$

${\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; 12</span>}}{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; twenty\; three</span>}}\mathrm{<span\; class="notranslate">\; vs.</span>}}{{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; twenty\; three</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; S</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; 12</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; L</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; S</span>}}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; L</span>}}<span\; class="notranslate">\; )</span>}$

3. Calculate the loop current in step 2 to obtain the input power, output power and transmission efficiency respectively:

${\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; in</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}\mathrm{<span\; class="notranslate">\; vs.</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; S</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; twenty\; three</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; L</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; )</span>}{{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; twenty\; three</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; S</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; 12</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; L</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; S</span>}}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; L</span>}}<span\; class="notranslate">\; )</span>}$

${\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; out</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; L</span>}}<span\; class="notranslate">\; =</span>\frac{{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; 12</span>}}{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; twenty\; three</span>}}\mathrm{<span\; class="notranslate">\; vs.</span>}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; L</span>}}}{{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; twenty\; three</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; S</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; 12</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; L</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; S</span>}}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; L</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}$

$\mathrm{<span\; class="notranslate">\; \&eta;</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; out</span>}}}{{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; in</span>}}}<span\; class="notranslate">\; =</span>\frac{{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; 12</span>}}{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; twenty\; three</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; L</span>}}}{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; twenty\; three</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; S</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; 12</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; L</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; S</span>}}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; L</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; )</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; twenty\; three</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; L</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; )</span>}$

4. The radii of the transmitting coil, the relay coil and the receiving coil in the system are a, b, and c respectively, the distance between the transmitting coil and the receiving coil is D, and the distance between the transmitting coil and the relay coil is d, then the relay coil and The distance between the receiving coils is Dd, then the mutual inductance between the transmitting coil and the relay coil is: $m_{12}={\mathrm{\&mu;}}_0{\left(\mathrm{ab}\right)}^{\frac{1}{2}}{\&Integral;}_0^{\frac{\mathrm{\&pi;}}{2}}\frac{(2{\sin }^2\mathrm{\&theta;}-1)\mathrm{d\&theta;}}{{(1-{k_1}^2{\sin }^2\mathrm{\&theta;})}^{\frac{1}{2}}},$ in $k_1^2=\frac{4\mathrm{ab}}{d^2+{(a+b)}^2};$ The mutual inductance between the relay coil and the receiving coil is: $m_{\mathrm{twenty\; three}}={\mathrm{\&mu;}}_0{\left(\mathrm{bc}\right)}^{\frac{1}{2}}{\&Integral;}_0^{\frac{\mathrm{\&pi;}}{2}}\frac{(2{\sin }^2\mathrm{\&theta;}-i)\mathrm{d\&theta;}}{{(1-{k_2}^2{\sin }^2\mathrm{\&theta;})}^{\frac{1}{2}}},$ in $k_2^2=\frac{4\mathrm{bc}}{{(\mathrm{D.}-d)}^2+{(b+c)}^2}.$

In the asymmetric wireless power transmission system with relay coils inserted in the present invention, since the transmitting coil and the relay coil are coaxial and in the same plane, d=0, then the mutual inductance M12 between the transmitting coil and the relay coil is enhanced, which is determined by the step ₃ The expression of system transmission efficiency shows that the efficiency is related to M ₁₂ and M ₂₃ , and M ₁₂ and M ₂₃ are related to d and Dd respectively. When the distance d between the transmitting coil and the relay coil decreases, the distance between the relay coil and the receiving coil When the distance Dd increases, M ₁₂ increases and M ₂₃ decreases. When other parameters of the system remain unchanged, the transmission efficiency changes with the change of d. From the expression of efficiency, it can be seen that when d increases, the efficiency η is almost unchanged at first , and then with the increase of d, the efficiency decreases sharply. It can be seen that when the distance d between the transmitting coil and the relay coil is very close, the transmission efficiency can reach a large value. Considering the size and volume constraints of the actual system, The invention maintains the relay coil and the transmitting coil on the same axis and plane, which not only makes the transmission efficiency of the system reach a higher value, but also saves the volume of the system, which is more conducive to the actual application of the system.

The radii of the transmitting coil and the receiving coil of the present invention are respectively a=30cm, c=10cm, the radius of the relay coil is b=50cm, the turn pitch P ₀ =2cm, the number of turns is N=8 turns, and the radius of all copper wires is r=3mm, The excitation source frequency is set to f ₀ =10.6MHz, the distance between the transmitting coil and the receiving coil, that is, the system transmission distance D=1m, and the centers of all coils are on the same horizontal axis. The transmitting coil, the receiving coil and the capacitor form an LC series resonant circuit, so that the coil resonance occurs near 10.6MHz.

As shown in Figure 4, the transmission efficiency of the system reaches the highest value near the resonant frequency point, and its value is close to 1, which greatly improves the transmission of this asymmetric magnetic coupling resonant wireless power transmission system in which the size of the transmitting coil is larger than that of the receiving coil efficiency.

In the experimental model of the present invention, the sine wave signal of 10.6 MHz is produced by the signal generator, and loaded into the transmitting coil after being amplified by the power amplifier, so that the input power can be obtained, the receiving coil is connected to the power meter, and the output power is measured by the power meter, two The ratio of the two is calculated to obtain the transmission efficiency of the system.

As shown in Fig. 5, the transmission efficiency of the experimental model of the present invention reaches the highest value near the resonant frequency point, and its value is close to 0.9, that is, the system can transmit with higher efficiency.

As shown in FIG. 6 , the simulation of the asymmetric wireless power transmission system inserted in the relay coil of the present invention is basically consistent with the experimental data, and is also consistent with the theoretical analysis results. It shows that in an asymmetric system, the method of inserting a relay coil coaxial and coplanar with the transmitting coil greatly improves the transmission efficiency of the system.

The present invention designs a method for inserting a relay coil coaxial and in the same plane as the transmitting coil in a magnetically coupled resonance wireless power transmission system in which the transmitting coil is larger than the receiving coil, thereby enhancing the mutual inductance coefficient between the coils, thereby enhancing the coupling coefficient and transmission of the system Efficiency, and save space size, more conducive to the practical application of the wireless power transmission system.

The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto, any equivalent modification or transformation made by those skilled in the art within the technical scope disclosed in the present invention is acceptable. Should be covered within the protection scope of the present invention.

Claims (8)

1. An asymmetric wireless power transmission system inserted into a relay coil, characterized in that the wireless power transmission system includes a transmitting device, a relay device and a receiving device; The transmitting device comprises a high-frequency signal generator, an impedance matching network, a power amplifier and a transmitting coil, one side of the transmitting coil is connected to the high-frequency signal generator through an impedance matching network, and the other side resonates with the receiving coil, so that Energy oscillates between the two coils in the form of electromagnetic waves; The relay device includes a relay coil, the relay coil is coaxial and coplanar with the transmitting coil, has the same number of turns and pitch, and the radius of the relay coil is different from that of the transmitting coil; The receiving device includes a receiving coil, a load device and a power meter. The radius of the receiving coil is smaller than that of the transmitting coil, and the number of turns and the pitch of the turns are the same as those of the transmitting coil. One side of the receiving coil is connected to the load device and the power meter. Meter, the other side resonates with the transmitting coil; The transmitting coil, relay coil and receiving coil are on the same horizontal axis, and the distance between the transmitting coil and the receiving coil is 1m. 2. An asymmetric wireless power transmission system inserted with a relay coil according to claim 1, characterized in that the impedance matching network is a passive matching network consisting of capacitors and inductors. 3. A kind of asymmetrical wireless power transmission system inserted into a relay coil according to claim 1, wherein the impedance matching network is an active matching network, a source follower composed of active and passive components, Emitter follower and buffer form. 4. An asymmetric wireless power transmission system with a relay coil inserted according to claim 1, wherein the relay coil is wound on the outer layer of the transmitting coil. 5. An asymmetric wireless power transmission system with a relay coil inserted according to claim 1, wherein the receiving coil is a multi-turn helical coil connected in series with a matching capacitor and directly connected to an AC load device. 6. An asymmetrical wireless power transmission system inserted into a relay coil according to claim 1, wherein the receiving coil is supplied to a DC load device through a rectification circuit, and the rectification circuit includes half-wave rectification and full-wave rectification and bridge rectification. 7. According to claim 1, an asymmetric wireless power transmission system inserted into a relay coil is characterized in that, the transmitting coil, the relay coil and the receiving coil utilize their own equivalent resistance at high frequency, parasitic capacitance, The matching capacitor and its own inductance form an oscillation circuit. The transmitting coil, relay coil and receiving coil have the same resonant frequency. 8. A power transmission method using the wireless power transmission system as claimed in claim 1, wherein the high-frequency signal generator produces a high-frequency sine wave signal, which is amplified by the power amplifier and then loaded into the transmitting coil, according to This obtains the input power; the transmitting coil sends the received high-frequency oscillation signal in the form of non-radiating near-field electromagnetic waves; the relay coil receives the high-frequency oscillation signal transmitted by the transmitting coil through the near-field coupling between the coils, Then it is sent out in the form of non-radiating near-field electromagnetic waves, and the relay coil plays the role of a transfer station during the energy transmission process between the transmitting end and the receiving end; the receiving coil also receives the signal sent by the relay coil through the near-field coupling between the coils, The output power is measured by a power meter, and the ratio of the output power to the input power is the transmission efficiency of the system. Therefore, the system transmits power with high efficiency.