A multi-wire parallel-wound coil disk for magnetically coupled wireless power transmission

Abstract

The present invention relates to a multi-wire parallel-wound coil disk for magnetically coupled wireless power transmission, including a coupling coil, a high-frequency soft magnetic body, a shielding aluminum plate and other components. The coupling coil is planar, formed by a plurality of wires tightly wound together, and can be a single coil or a plurality of coils. When it is a single coil, the starting and ending points of the plurality of wires wound together are rotationally symmetrically distributed in the coil plane, that is, the single coil wound by each wire has rotational symmetry and has the same inductance and resistance value, and direct parallel connection can balance the current of each wire. When it is a plurality of coils, the encircling parts of each coil constituting the plurality of coils are rotationally symmetrically distributed in the plane of the plurality of coils with the center of the entire coupling coil. Under the premise of satisfying the current density, the present invention realizes the optimal coverage width of the coil and the tight winding of the plurality of wires, which can greatly improve the coupling coefficient and reduce electromagnetic exposure; the number of coil turns (which can be a non-integer) can also be adjusted at will to obtain accurate inductance.

Description

Technical Field

[0001] The invention relates to a multi-wire parallel-wound coil disk for magnetic coupling wireless power transmission, belonging to the technical field of power supply / wireless power transmission. Background Art

[0002] In recent years, wireless power transfer (WPT) technology has received more and more attention. There are many forms of wireless power transfer according to different transmission mechanisms. The more mature wireless power transmission technology in the current electrical field is magnetic field coupling; magnetic field coupling is divided into magnetic induction and magnetic resonance, both of which realize power transfer through the alternating coupling magnetic field between the transmitting coil and the receiving coil.

[0003] In 2008, the Wireless Power Consortium (WPC) was established and launched the Qi standard based on magnetic induction internationally. In 2015, A4PW and PMA merged to form the International Wireless Power Industry Alliance (AirFuel Alliance), which intends to be compatible with magnetic induction and magnetic resonance standards. So far, wireless power transmission technology for small and medium-power electronic products has accelerated its commercialization pace. In 2017, SAE (Society of Automotive Engineers) released SAE J2954_August 2017 "Wireless Power Transmission, Automatic Charging and Calibration Methods for Light Plug-in / Electric Vehicles". my country also began to formulate national standards for wireless charging of electric vehicles in 2017, officially kicking off the industrialization process of wireless charging of electric vehicles.

[0004] The magnetic field coupling wireless power transmission system is mainly composed of the primary device (driving magnetic field), magnetic coupling mechanism and secondary device (receiving energy). Among them, the magnetic coupling mechanism (including the physical structure of the coupling coil and the resonant compensation circuit topology) is the most critical part of the system to achieve long-distance power transmission, which directly affects the power and efficiency of the transmission system.

[0005] According to the description of SAE J2954 (Section 8 of SAE J2954_August 2017), the coupling coil can be designed in a variety of topologies: non-polarized, polarized or multi-coil topology. The coil disk ensures that the magnetic flux exists only on one side by appropriately using ferrite or aluminum backing. 1. The non-polarized topology has a pole in the center of the coil disk and an opposite pole around the outside, which can cause the magnetic flux to leave the center of the coil disk and return to all its outer edges to form a closed loop; when used as a receiving coil, it is mainly sensitive to the vertical magnetic field in space. 2. The polarized topology has N and S poles at both ends of the coil disk, which can cause the magnetic flux to form a closed loop from the N pole to the S pole; when used as a receiving coil, it is mainly sensitive to the horizontal magnetic field. 3. The multi-coil topology usually combines polarized and non-polarized structures, and uses a decoupling coil to be able to generate polarized or non-polarized fields when used as a transmitter, and naturally capture horizontal and vertical magnetic fields when used as a receiver. SAE J2954 lists and recommends five coil topologies: (a) circular / square non-polarized; (b) electromagnetic polarized; (c) DD polarized; (d) multi-coil DDQ; (e) multi-coil bipolar. In addition, the transmitting coil and receiving coil of the wireless power transmission system may or may not be produced by the same manufacturer; to ensure interoperability testing and evaluation, the appendix of SAE J2954 specifies the mechanical and electrical design specifications of all applicable main-receiving coils (M-VA) and reference-transmitting coils (R-GAs).

[0006] In the coil topology, mechanical and electrical design specifications recommended by SAE, and other existing designs, the coil conductor mostly uses a single conductor. This single-conductor winding design cannot meet the requirements of the optimal coil coverage width and tight winding under certain winding turns and wire diameter. The number of turns is determined by the inductance requirements, and the wire diameter is determined by the current requirements; tight winding can reduce leakage magnetic flux and better meet the manufacturing process, and the optimal coverage width is for high coupling coefficient. Improving the coupling coefficient of magnetic coupling coils is of great significance, which not only improves the efficiency of power transmission but also reduces electromagnetic exposure, which is one of the key requirements for the industrialization and promotion of magnetic coupling wireless power transmission technology. In order to meet the optimal coverage width and tight winding at the same time, a multi-wire parallel winding technology route is proposed, but the existing multi-wire parallel winding is that the starting point and the end point of multiple wires are at the same place, so that the inductance of the inner circle wire is small and the inductance of the outer circle wire is large. This difference in inductance leads to unbalanced current flowing through different wires after parallel connection. In order to compensate for this difference in inductance, a design scheme has emerged in which the inner ring wire is connected in series to compensate for the inductance and then connected in parallel with the outer ring wire, but this increases cost, weight, loss and design complexity.

[0007] It can be seen that optimizing the design of coupling coils under the premise of interoperability is one of the key core issues of magnetically coupled wireless power transmission technology. Summary of the invention

[0008] The purpose of the present invention is to overcome the deficiencies of the above-mentioned prior art and provide a multi-wire parallel-wound coil disk for magnetically coupled wireless power transmission, which can achieve optimal coverage width and multi-wire tight winding while meeting the inductance and current density, so as to achieve the purpose of improving coupling coefficient, reducing electromagnetic exposure and balancing conductor current.

[0009] The technical solution of the present invention is as follows:

[0010] A multi-wire parallel-wound coil disk for magnetically coupled wireless power transmission includes a coupling coil, a high-frequency soft magnetic body, a shielding aluminum plate and other components. The coupling coil is planar and is formed by winding multiple wires in parallel. It can be a single coil or multiple coils (it can be a single output or multiple outputs when used as a receiving end); the high-frequency soft magnetic body is a rectangular (or circular or polygonal) flat magnetic sheet that is integral or spliced; the shielding aluminum plate is a pure aluminum plate with a thickness of about 1 mm.

[0011] One side of the high-frequency soft magnet is close to the coupling coil, and the other side is close to the shielding aluminum plate. The coupling coil is used to excite or capture the magnetic field to transfer electrical energy; the high-frequency soft magnet is used to conduct magnetic flux and improve the coupling coefficient while ensuring that the magnetic field only exists on one side of the component; the shielding aluminum plate is used to reduce electromagnetic exposure.

[0012] The characteristics are as follows: 1. When the coupling coil is a single coil, the starting and ending points of the multiple wires wound into the single coil are rotationally symmetrically distributed in the plane of the coil, and the center of rotational symmetry is the center of the coupling coil. Then, the single coils wound by each wire are connected in parallel to form a single coil. In this way, the single coils wound by each wire wound in parallel also have rotational symmetry, so they have the same inductance and resistance values. After being directly connected in parallel, the current in each wire can be naturally balanced. 2. When the coupling coil is a multi-coil, the surrounding parts of each coil constituting the multi-coil are rotationally symmetrically distributed in the plane of the multi-coil, and the center of rotational symmetry is the center of the entire coupling coil; if each coil of the multi-coil is multi-wire wound in parallel, the starting and ending points of the multiple wires of each coil are respectively distributed in the plane of each coil rotationally symmetrically with the center of each coil, and then connected in parallel to form each coil.

[0013] The design steps adopted by the coupling coil are: first, to achieve a high coupling coefficient, select the optimal coverage width of the coil (i.e., the distance between the inner and outer sides of the coil); second, calculate the number of turns of the coil within the optimal coverage width according to the required inductance (which can be a non-integer); third, calculate the wire diameter and number of wire cores of the Litz wire (determined by the equivalent cross-sectional area) according to the required current density; finally, divide the required Litz wire into multiple strands in accordance with the requirement of dense winding of the wire. The calculation formula is: optimal coverage width ÷ number of turns = wire diameter × number of wires. The Litz wire is divided equally and the wire diameter is optimized and adjusted so that the number of wires is an integer, thereby achieving the optimal coverage width of the coupling coil and the dense winding of multiple wires using the technical solution of the present invention.

[0014] Compared with the prior art, the present invention has the following advantages:

[0015] 1. Achieving the optimal coverage width of the coil and tightly winding multiple wires can greatly improve the coupling coefficient and reduce electromagnetic exposure.

[0016] 2. Within the optimal coverage width, the number of coil turns can be adjusted at will (can be a non-integer) to obtain accurate inductance.

[0017] 3. Multiple coils wound in parallel have rotational symmetry, so they have the same inductance and resistance. After being connected in parallel, they can naturally balance the current in each wire and eliminate the adverse effects of non-integer turns on electrical performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of a three-wire parallel-wound single coil disk for magnetically coupled wireless power transmission.

[0019] Figure 2 It is a schematic diagram of a bifilar wound single coil disk for magnetically coupled wireless power transmission.

[0020] Figure 3 It is a schematic diagram of a four-wire parallel-wound four-coil disk for magnetically coupled wireless power transmission.

[0021] Figure 4 It is a schematic diagram of a four-wire parallel-wound double-coil disk for magnetically coupled wireless power transmission.

[0022] In the figure, 1 is the coupling coil, 2 is the high-frequency soft magnetic body, 3 is the shielding aluminum plate; 1-1 is the starting point of winding, 1-2 is the ending point of winding. DETAILED DESCRIPTION

[0023] The present invention will be described in detail below with reference to the accompanying drawings in accordance with the best embodiment.

[0024] like Figure 1 to Figure 4As shown, a multi-wire parallel-wound coil disk for magnetically coupled wireless power transmission comprises a coupling coil (1), a high-frequency soft magnetic body (2), a shielding aluminum plate (3) and other components. The coupling coil (1) is planar and is formed by winding a plurality of wires in parallel, and can be a single coil or multiple coils (when used as a receiving end, it can be a single output or multiple outputs); the high-frequency soft magnetic body (2) is a rectangular (or circular or polygonal) flat magnetic sheet that is integral or spliced; and the shielding aluminum plate (3) is a pure aluminum plate with a thickness of about 1 mm.

[0025] One side of the high-frequency soft magnet (2) is close to the coupling coil (1), and the other side is close to the shielding aluminum plate (3). The coupling coil (1) is used to excite or capture the magnetic field to transfer electrical energy; the high-frequency soft magnet (2) is used to conduct magnetic flux and improve the coupling coefficient while ensuring that the magnetic field only exists on one side of the component; the shielding aluminum plate (3) is used to reduce electromagnetic exposure.

[0026] like Figure 1 , Figure 2 As shown, when the coupling coil (1) is a single coil, the starting point (1-1) and the ending point (1-2) of the multiple wires wound into the single coil are rotationally symmetrically distributed in the coil plane, and the rotational symmetry center is the center of the coupling coil (1), and then the single coils wound by each wire are connected in parallel to form a single coil. In this way, the single coils wound by each wire in parallel also have rotational symmetry, so they have the same inductance and resistance value, and can naturally balance the current in each wire after being directly connected in parallel.

[0027] like Figure 3 , Figure 4 As shown, when the coupling coil (1) is a multi-coil, the encircling parts of each coil constituting the multi-coil are rotationally symmetrically distributed in the plane of the multi-coil, and the rotational symmetry center is the center of the entire coupling coil (1); if each coil of the multi-coil is multi-wire wound in parallel, then the starting point (1-1) and the ending point (1-2) of the multiple wires of each coil are respectively distributed rotationally symmetrically in the plane of each coil with respect to the center of each coil, and then connected in parallel to form each coil.

[0028] The design steps adopted by the coupling coil are: first, to achieve a high coupling coefficient, select the optimal coverage width of the coil (i.e., the distance between the inner and outer sides of the coil); second, calculate the number of turns of the coil within the optimal coverage width according to the required inductance (which can be a non-integer); third, calculate the wire diameter and number of wire cores of the Litz wire (determined by the equivalent cross-sectional area) according to the required current density; finally, divide the required Litz wire into multiple strands in accordance with the requirement of dense winding of the wire. The calculation formula is: optimal coverage width ÷ number of turns = wire diameter × number of wires. The Litz wire is divided equally and the wire diameter is optimized and adjusted so that the number of wires is an integer, thereby achieving the optimal coverage width of the coupling coil and the dense winding of multiple wires using the technical solution of the present invention.

Claims

1. A multi-wire parallel-wound coil disk for magnetically coupled wireless power transmission comprises a coupling coil (1), a high-frequency soft magnetic body (2), and a shielding aluminum plate (3); one side of the high-frequency soft magnetic body (2) is close to the coupling coil (1), and the other side is close to the shielding aluminum plate (3); the shielding aluminum plate (3) is a pure aluminum plate with a thickness of 1 mm, and the high-frequency soft magnetic body (2) is a rectangular, circular or polygonal flat magnetic sheet that is integral or spliced; the coupling coil (1) is planar and is formed by winding a plurality of wires in parallel, and can be a single coil or a plurality of coils, and the plurality of coils can output multiple signals when used as a receiving end; Features: When the coupling coil (1) is a single coil, the starting points (1-1) and the ending points (1-2) of the multiple wires wound around the single coil are rotationally symmetrically distributed in the coil plane, and the center of rotational symmetry is the center of the coupling coil (1), so that the single coils wound by each wire wound in parallel also have rotational symmetry, and then the single coils wound by each wire are connected in parallel to form a single coil; when the coupling coil (1) is a multi-coil, the encircling parts of each coil constituting the multi-coil are rotationally symmetrically distributed in the plane of the multi-coil, and the center of rotational symmetry is the center of the entire coupling coil (1); if each coil of the multi-coil is multi-wire wound in parallel, the starting points (1-1) and the ending points (1-2) of the multiple wires of each coil are rotationally symmetrically distributed in the plane of each coil with respect to the center of each coil, and then connected in parallel to form each coil.

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