CN115967193A - Capacitor-free self-resonant bidirectional wireless energy transmission array device - Google Patents
Capacitor-free self-resonant bidirectional wireless energy transmission array device Download PDFInfo
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- CN115967193A CN115967193A CN202211511846.2A CN202211511846A CN115967193A CN 115967193 A CN115967193 A CN 115967193A CN 202211511846 A CN202211511846 A CN 202211511846A CN 115967193 A CN115967193 A CN 115967193A
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Abstract
The invention improves a structure without an external capacitance coil, and discloses a capacitance-free self-resonant bidirectional wireless energy transmission array device, which comprises a rectangular spiral multi-turn coil and an alternating current power supply which are connected with each other, can realize bidirectional transmission, and has a better effect in the scenes of industrial application; the device does not need external capacitors, has small size, can become a basic unit for constructing a large array, and can also be used for applications needing small-size implantation equipment.
Description
Technical Field
The invention relates to the technical field of wireless energy transmission, in particular to a capacitor-free self-resonant bidirectional wireless energy transmission array device.
Background
Due to the advantage of Wireless wires, wireless Power Transfer (WPT) technology has been applied to various fields such as charging, detection, and the like. With the rapid development of the times, especially the rapid development of portable electronic equipment, implantable medical equipment and electric vehicles, the WPT technology gets more and more attention; resonant wireless energy transfer utilizes magnetic field coupling between a transmitting coil (Tx) and a receiving coil (Rx) to transfer energy, and most resonant WPTs require tuning using an additional compensation capacitor, but adding a compensation capacitor increases the complexity, size and cost of the system and reduces the reliability of the system. Therefore, a WPT structure without an extra compensation capacitor appears, and the WPT structure replaces the extra compensation capacitor with a capacitor, called self-capacitor for short, of the coil to generate coupling with the coil, so that resonance with a required frequency can be generated without using the extra capacitor. The prior art generally adopts a double-coil topological structure to form a self-resonant circuit; the method is mainly realized by the following two technical schemes:
1. the turn-to-turn spacing between the multi-turn coils is reduced to increase the turn-to-turn capacitance thereof to obtain a desired capacitance value.
2. The number of coils is increased to increase the inductance.
Most self-resonant coil designs are designed around both of the above-mentioned solutions, but both solutions have certain limitations. For the first solution, the value of the inter-turn capacitance cannot become large due to the restriction of the thickness of the coil (0.035 mm), so another method for increasing the self-capacitance is required; for the second solution, increasing the number of coils will increase the weight of the system.
Therefore, based on the shortcomings in the above solutions, a coil structure similar to a parallel capacitor is proposed.
Disclosure of Invention
The invention overcomes the defects of the prior art, and aims to overcome the defects and make the following improvements and optimizations.
The purpose of the invention is realized by the following technical scheme:
the capacitor-free self-resonant bidirectional wireless energy transmission array device comprises rectangular spiral multi-turn coils and an alternating-current power supply which are connected with each other, wherein the number of the rectangular spiral multi-turn coils is 2, a medium substrate is arranged between the two rectangular spiral multi-turn coils, and the medium substrate is used for storing various media; the alternating current power supply is used for inputting alternating current with the frequency required by the device.
Preferably, the number of turns N of the rectangular spiral multi-turn coil is at least 2 and the spacing between each turn is s.
Preferably, the calculation formula of the resonant frequency f of the rectangular spiral multi-turn coil is as follows:
wherein, L is the equivalent inductance of the two rectangular spiral multi-turn coils, and C is the equivalent capacitance of the two rectangular spiral multi-turn coils.
Preferably, the calculation formula of the equivalent capacitance C is as follows:
wherein epsilon is the dielectric constant of the medium filled in the medium substrate, S is the quotient of the surface areas of the two rectangular spiral multi-turn coils, and d is the thickness of the medium substrate, and the capacitance between the two coils can be increased by increasing the dielectric constant of the medium, so that the resonant frequency is reduced; reducing the dielectric constant of the medium reduces the capacitance between the two coils, which increases the resonant frequency.
Compared with other self-resonant structures, the device structure of the invention has the following advantages:
the device can change the capacitance value by changing the turn-to-turn distance and can also obtain different capacitance values by changing the dielectric medium in the dielectric substrate. There are more ways to obtain the capacitance value and thus lower the resonance frequency of the coil. The method can solve the problem that the size or the weight of the coil device is larger because the coil structure with the traditional low resonant frequency needs larger inductance value due to lower capacitance provided by turn-to-turn capacitance. Under the same resonant frequency, the structure using the method can have smaller size, and no additional capacitor is needed, thereby facilitating the array, and further improving the transmission efficiency and the transmission power.
Drawings
The invention is further illustrated by means of the attached drawings, but the embodiments in the drawings do not constitute any limitation to the invention, and for a person skilled in the art, other drawings can be obtained on the basis of the following drawings without inventive effort.
FIG. 1 is a schematic diagram of a wireless energy transfer array apparatus of the present invention;
FIG. 2 is a top view of a wireless energy transmitting array device according to the present invention;
FIG. 3 is an equivalent circuit diagram of the structure of the wireless energy transmission array device of the present invention;
FIG. 4 is a diagram of a preferred embodiment of the present invention showing a wireless energy transmitting array device with mica as the dielectric substrate material S11;
FIG. 5 is a diagram of magnetic field distribution at different distances for a wireless energy transmitting array device in accordance with a preferred embodiment of the present invention;
FIG. 6 is a far field gain diagram of a wireless energy transfer array apparatus according to a preferred embodiment of the present invention;
fig. 7 is a circuit equivalent diagram of a dual coil system of the wireless energy transmission array device of the present invention;
fig. 8 is a graph of transmission distance versus efficiency for a wireless energy transfer array device in accordance with a preferred embodiment of the present invention.
Detailed Description
A capacitorless self-resonant bidirectional wireless energy transfer array apparatus is described in further detail below with reference to specific embodiments, which are provided for purposes of comparison and explanation only and are not intended to limit the present invention.
In the description of the present invention, it is to be understood that the terms "upper", "lower", "left", "right", "top", "bottom", and the like, indicate orientations or positional relationships based on those shown in the drawings, and are only for convenience in describing the present invention and simplifying the description, but do not indicate or imply that the device or element referred to must have a specific orientation, be constructed in a specific orientation, and be operated, and thus, should not be construed as limiting the present invention.
The invention provides a capacitor-free self-resonant bidirectional wireless energy transmission array device, which comprises rectangular spiral multi-turn coils and an alternating-current power supply, wherein the rectangular spiral multi-turn coils and the alternating-current power supply are connected with each other, the number of the rectangular spiral multi-turn coils is 2, a medium substrate is arranged between the two rectangular spiral multi-turn coils, and the medium substrate is used for storing media; the alternating current power supply is used for inputting alternating current with the frequency required by the device.
Two rectangular spiral multi-turn coils are placed in parallel to form a kind of "polar plate" similar to that in the parallel capacitor plate by using the principle of parallel capacitor plate, and then a dielectric medium is filled between the two rectangular spiral multi-turn coils to play the function of supporting and changing the dielectric constant between the two coils. Finally, one end of each of the two coils is connected, and the other end of each of the two coils is parallel to form a structure which is the same as that of the parallel capacitor plate. The specific structure is shown in fig. 2.
Wherein 1 is an alternating current power supply port, and alternating current with the frequency required by the structure is input and is also the only connection position between the two rectangular spiral multi-turn coils; 2 is the spacing s between each turn of the rectangular spiral multi-turn coil; 3 is a rectangular spiral multi-turn coil, the number of turns N is not fixed, and the material can be any conductive material, such as copper, gold, silver and the like; 4 is a dielectric substrate to fill various dielectrics and function as a physical support.
Preferably, the number of turns N of the rectangular spiral multi-turn coil is at least 2 and the spacing between each turn is s.
The compensation capacitor required by the structure is formed by the coupling capacitor between the upper and lower parallel rectangular spiral multi-turn coils and the inter-turn capacitor of each turn coil, so that the self-resonant transmission required by the target frequency is realized. The equivalent circuit diagram is shown in fig. 3:
wherein, C 1 Is the equivalent coupling capacitance between the two coils; c 2 Is the sum of the inter-turn capacitances between each turn of coil; ZG is the sum of the alternating current impedance and the inductance of the surface coil on the structure; ZL is the sum of the ac impedance and the inductance of the lower surface coil; zin is the input impedance of the structure; the current flows from the upper surface rectangular spiral coil to the parallel connected turn-to-turn capacitors and the upper and lower coilsThe coupling capacitance between the two coils flows through the rectangular spiral coil on the lower surface and finally flows out of the rectangular spiral coil to form a complete circuit loop of the structure.
Preferably, the calculation formula of the resonant frequency f of the rectangular spiral multi-turn coil is as follows:
wherein, L is the equivalent inductance of the two rectangular spiral multi-turn coils, and C is the equivalent capacitance of the two rectangular spiral multi-turn coils, i.e. the sum of the inter-turn capacitance C2 and the coupling capacitance C1 in fig. 3; when L remains unchanged, C increases and the resonant frequency f decreases; c decreases and the resonance frequency f increases.
Preferably, the calculation formula of the equivalent capacitance C is as follows:
wherein epsilon is the dielectric constant of the medium filled in the medium substrate, S is the quotient of the surface areas of the two rectangular spiral multi-turn coils, and d is the thickness of the medium substrate, and the capacitance between the two coils can be increased by increasing the dielectric constant of the medium, so that the resonant frequency is reduced; reducing the dielectric constant of the medium reduces the capacitance between the two coils, which increases the resonant frequency.
In one embodiment, the feasibility of the device was verified by two common materials, the device height h =1mm, by filling the dielectric substrate with mica (mica) with a relative dielectric constant of 5.7 and glass with a relative dielectric constant of 5.5, respectively
(glass) the resonant frequency of the structure is significantly shifted, and the resonant frequency of the mica is: 11.61GHz, i.e. at a frequency of excitation (supply) of 11.61GHz, the imaginary part of the input impedance of the structure is 0 and the overall pack of pits appears purely resistive.
FIG. 4 is a S11 diagram of the device of the invention when the medium substrate material is mica, and the S11 at 11.61GHz is-35.21 dB, which meets the design requirement of S11< -20 dB.
The mica was replaced with glass keeping the other parameters of the structure unchanged. The resonance frequency of the resulting glass was 11.78GHz. By comparing the relative dielectric constant (mica 5.7, glass 5.5) and the resonant frequency (mica 11.61GHz, glass 11.78 GHz) of the two materials, it is concluded, in accordance with the theory described above: the larger the dielectric constant of the material filled in the dielectric substrate in the structure is, the smaller the resonant frequency is; the feasibility of changing the resonant frequency by changing the structural substrate material was demonstrated.
With the other parameters being the same, the magnetic field distribution of the structure at different distances was simulated using electromagnetic simulation software, and the magnetic field distribution plots are shown in FIG. 5, where (a) is the magnetic field distribution plot at a distance of 2mm, (b) is the magnetic field distribution plot at a distance of 5mm, (c) is the magnetic field distribution plot at a distance of 10mm, (d) is the magnetic field distribution plot at a distance of-2 mm, (e) is the magnetic field distribution plot at a distance of-5 mm, and (f) is the magnetic field distribution plot at a distance of-10 mm. On the upper side of the coil on the upper surface of the structure, a magnetic field on a plane which is 2mm away from the structure and is parallel to the structure does not generate obvious Gaussian distribution with strong middle and weak periphery, but only has larger magnetic field intensity; when the distance is 5mm, a magnetic field with Gaussian distribution is completely formed, the magnetic field at the center is circular, and the magnetic field intensity is larger than that at other positions; at a distance of 10mm, the gaussian distribution of the magnetic field has begun to disappear but not completely, there is still a magnetic field distribution similar to 5mm, but the high field circle in the center is compressed very severely and begins to flatten partially. The magnetic field distribution is substantially uniform directly below the coils on the lower surface of the structure and directly above the coils on the upper surface of the structure. But the magnetic field directly below the coils on the lower surface of the structure is stronger than the magnetic field directly above the coils on the upper surface of the structure. From the above results, the two-sided coil using the structure can transmit energy, and the upper surface coil can be used for transmission requiring short distance and high power; the lower surface coil can be used for transmission requiring a long distance (relative to the size of the structure) with high efficiency.
The magnetic field distribution diagram shows that the magnetic field of the structure in the opposite direction of the coil has higher magnetic fields in the upper direction and the lower direction, so that the structure has a bidirectional transmission function, and the upper surface coil can transmit energy even though the lower surface coil has a stronger magnetic field; furthermore, the magnetic field of the structure at the near place does not have strong directivity like the magnetic field at the far place, and only the magnetic field intensity is larger.
The far field gain of the device of the present invention in this embodiment is shown in fig. 6, and the structure has little energy transfer in its directions other than the facing direction of the coil, i.e., produces little magnetic leakage. Not only reduces the energy loss, but also ensures that the electromagnetic pollution is less. The energy gain in the opposite direction of its coil follows the gain trend of the two-end transmission. The gain map is in the shape of a lentil as a whole and meets the targets of strong gain at two ends and weak gain at the periphery.
Finally, the transmission characteristics of the inventive device were analyzed. Two units (this structure) are used as the transmitting device and the receiving device in fig. 7, respectively. The parameters are as follows, the number of turns N of the spiral coil is 7, the inter-turn distance s =0.1mm, the thickness of the dielectric substrate is h =1mm, and the size is 4mm multiplied by 4mm.
The equivalent circuit diagram of the dual-coil system is shown in fig. 7, and an input port is formed by an inverter and a direct current power supply, wherein the inverter converts the direct current power supply into alternating current with specific frequency which can enable the coils to generate coupling effect; CT is the compensation capacitance of the transmit coil, resonating the transmit coil at the resonant frequency; LT is a transmitting coil, which together with CT constitutes a transmitting device of a dual coil system; LR is a receive coil, which is the same as the transmit coil, but a smaller coil can also be used as a receive coil to improve the anti-drift capability of the transmission system. CR is the compensation capacitance of the receive coil, which makes the receive coil resonate at the same frequency as the resonant frequency of the transmit coil, and the two coils resonate with each other, maximizing efficiency. The rectifier rectifies the alternating current received by the receiving coil into direct current required by the load RL. M is a coupling coefficient between the transmitting coil LT and the receiving coil LR, and is a parameter expressing transmission capability of both coils numerically, which is related to distance.
The relationship between the measured efficiency and the transmission distance dz is shown in fig. 8, wherein the efficiency is calculated by the following formula:
wherein S 11 2 Power lost to the transmitting coil itself, S 21 2 Is the transmission power of the dual coil.
As shown in fig. 8, the efficiency of the system is 28% when the transmission distance is 1mm, i.e., the transmission distance/structure size =0.25, and gradually decreases as the transmission distance increases, and the efficiency is 3% when the transmission distance is 6mm, i.e., the transmission distance/structure size = 1.5; since the structure has the size of 4mm x 4mm and is small, the efficiency is feasible in engineering application under the transmission distance.
Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention, and not for limiting the protection scope of the present invention, although the present invention is described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions can be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.
Claims (4)
1. A capacitor-free self-resonant bidirectional wireless energy transmission array device is characterized by comprising rectangular spiral multi-turn coils and an alternating current power supply which are connected with each other, wherein the number of the rectangular spiral multi-turn coils is 2, a medium substrate is arranged between the two rectangular spiral multi-turn coils, and the medium substrate is used for storing various media; the alternating current power supply is used for inputting alternating current with the frequency required by the device.
2. The capacitor-less self-resonant type bidirectional wireless energy transmission array device according to claim 1, wherein the number of turns N of the rectangular spiral multi-turn coil is at least 2 and the spacing between each turn is s.
3. The capacitor-free self-resonant bidirectional wireless energy transmission array device according to claim 1, wherein the resonant frequency f of the rectangular spiral multi-turn coil is calculated as follows:
wherein, L is the equivalent inductance of the two rectangular spiral multi-turn coils, and C is the equivalent capacitance of the two rectangular spiral multi-turn coils.
4. The capacitor-free self-resonant bidirectional wireless energy transmission array device according to claim 3, wherein the calculation formula of the equivalent capacitance C is as follows:
wherein epsilon is the dielectric constant of the medium filled in the medium substrate, S is the sum of the surface areas of the two rectangular spiral multi-turn coils, and d is the thickness of the medium substrate, and the capacitance between the two coils can be increased by increasing the dielectric constant of the medium, so that the resonant frequency is reduced; reducing the dielectric constant of the medium reduces the capacitance between the two coils, which increases the resonant frequency.
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| CN202211511846.2A CN115967193A (en) | 2022-11-29 | 2022-11-29 | Capacitor-free self-resonant bidirectional wireless energy transmission array device |
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| CN202211511846.2A CN115967193A (en) | 2022-11-29 | 2022-11-29 | Capacitor-free self-resonant bidirectional wireless energy transmission array device |
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