Megahertz-level low-voltage large-current wireless electric energy transmission system based on symmetric planar coil

Abstract

The invention discloses a megahertz-level low-voltage large-current wireless electric energy transmission system based on symmetrical planar coils, which comprises a transmitting end and a receiving end, and is characterized in that a transmitting coil of the transmitting end and a receiving coil of the receiving end both adopt a completely symmetrical planar spiral structure consisting of a plurality of rotationally symmetrical conductor sections; a magnetic coupling transformer at a receiving end comprises a primary winding and a plurality of secondary windings, each secondary winding is of a completely symmetrical planar spiral structure composed of a plurality of rotationally symmetrical conductor sections, and each secondary winding is connected with a GaN synchronous rectifier. And the leakage inductance of the magnetic coupling transformer is multiplexed as a receiving end series compensation inductor, so that the integration level of the system is improved, and wireless electric energy transmission under megahertz-level low-voltage large current is realized.

Description

Technical Field

[0001] This invention belongs to the field of wireless power transmission, specifically relating to a megahertz-level low-voltage high-current wireless power transmission system based on symmetrical planar coils. Background Technology

[0002] Wireless power transmission (WPT) is gaining increasing attention in AGVs and mobile robots due to its advantages in safety, automation, and low maintenance. Compared to the high-voltage WPT systems (such as 400 V or 800 V) commonly found in electric vehicles, low-voltage and high-current (LVHC) WPT systems operating at 24 V or 48 V offer advantages such as safer electric shock protection, simplified insulation requirements, and easier system integration, making them particularly suitable for compact platforms requiring high-frequency charging. However, the need to obtain high power at low voltage (e.g., approximately 125 A at 24 V for 3 kW) results in extremely low equivalent load resistance (approximately 0.2 Ω), posing a significant challenge to power device stress, system compactness, and overall efficiency.

[0003] To further improve power density and extend transmission distance, increasing the operating frequency to the megahertz (MHz) range is an important direction for LVHC-WPT. However, achieving MHz operation under low voltage and high current conditions introduces several challenges. First, the extremely low load resistance leads to significant conduction losses and voltage drops, making it difficult to maintain high efficiency under high current. Second, the enhanced effects of parasitic parameters—especially inter-turn capacitance and coil-to-ground capacitance—severely limit the tuning flexibility of the high-frequency resonant network and complicate impedance matching.

[0004] To achieve high output current, recent research has proposed various structural and topological innovations, including dual receivers for current shunting, anti-coupled current multiplication rectifier structures, and partial power handling control strategies. While these methods are effective in certain aspects, they typically operate at low frequencies (around 100 kHz) and often require large magnetic components, complex secondary-side structures, or additional control overhead, limiting their applicability in compact, modular wireless power transfer (WPT) platforms. Especially for low-voltage high-current (LVHC) wireless power transfer (WPT) systems for Automated Guided Vehicles (AGVs), key challenges remain regarding efficiency, compactness, and current carrying capacity under extreme output conditions. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide a megahertz-level low-voltage high-current wireless power transfer system based on symmetrical planar coils, which provides a compact and efficient solution for megahertz-level LVHC-WPT systems.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] A megahertz-level low-voltage high-current wireless power transfer system based on symmetrical planar coils, characterized in that it comprises: a transmitter and a receiver, wherein,

[0008] The transmitter includes a transmitting coil, an inverter, and a transmitter resonant compensation network, which are electrically connected.

[0009] The receiving end includes a receiving coil and a magnetic coupling transformer.

[0010] The transmitting coil adopts a fully symmetrical planar spiral structure composed of n rotationally symmetrical conductor segments, and a compensation capacitor is connected in series between adjacent conductor segments in the transmitting coil;

[0011] The receiving coil adopts a fully symmetrical planar spiral structure composed of m rotationally symmetrical conductor segments, and a compensation capacitor is also connected in series between adjacent conductor segments in the receiving coil.

[0012] The magnetically coupled transformer includes one primary winding and L secondary windings. The primary winding is electrically connected to the receiving coil. The L secondary windings adopt a fully symmetrical planar helical structure composed of L rotationally symmetrical conductor segments. The L secondary windings are magnetically coupled to the primary winding through the transformer core.

[0013] Furthermore, each secondary winding is connected to a GaN full-bridge rectifier, the outputs of each GaN full-bridge rectifier are connected in parallel, and the leakage inductance of the magnetic coupling transformer is reused as the series compensation inductor at the receiving end, thereby realizing wireless power transmission under megahertz-level low voltage and high current.

[0014] Furthermore, the n conductor segments of the transmitting coil are rotationally symmetrical about the transmitting center, and the rotational symmetry angle between two adjacent conductor segments is 2π / n; the m conductor segments of the receiving coil are rotationally symmetrical about the receiving center, and the rotational symmetry angle between two adjacent conductor segments is 2π / m.

[0015] Furthermore, the inner and outer diameters of the conductor segment in the transmitting coil are the same as the inner and outer diameters of the conductor segment in the receiving coil, respectively.

[0016] Furthermore, the L conductor segments in the secondary winding are distributed in a rotationally symmetrical manner with respect to the center of the secondary winding. The rotational symmetry angle between two adjacent conductor segments is 2π / L, and the helical angle of each conductor segment is an integer multiple of 2π.

[0017] Furthermore, the receiving end also includes a bottom support plate, a shielding ferrite layer, and a cover plate, wherein the bottom support plate, receiving coil, shielding ferrite layer, primary winding, secondary winding, and transformer core are stacked in sequence, and a first through hole is provided on the cover plate, and the magnetic coupling transformer is disposed in the first through hole to form a compact integration.

[0018] Furthermore, the shielding ferrite layer and the cover plate are provided with corresponding second through holes for connecting the conductor segment of the receiving coil and the compensation capacitor between the conductor segment of the receiving coil.

[0019] Furthermore, the transformer core is provided with a third through hole for connecting each secondary winding to the corresponding GaN full-bridge rectifier.

[0020] Furthermore, the conductor segments in the transmitting coil and the receiving coil are wound with Litz wire having a first preset diameter and a first preset number of strands;

[0021] The primary winding adopts a planar helical structure made of a single Litz wire, wherein the single Litz wire has a second preset diameter and a second preset number of strands;

[0022] The conductor segment of the secondary winding is made of Litz wire with a third preset diameter and a third preset number of strands.

[0023] The present invention also provides a wireless power transmission receiver, comprising all the structures of the receiver as described above.

[0024] The present invention also provides a wireless power transmission transmitter, including the entire structure of the transmitting coil as described above, and the transmitter further includes an upper support plate, a lower support plate and a transmitting end shielding ferrite layer. The lower support plate, the transmitting coil, the transmitting end shielding ferrite layer and the upper support plate are stacked in sequence, and the transmitting end shielding ferrite layer and the upper support plate are provided with corresponding through holes for connecting the conductor segment of the transmitting coil and the compensation capacitor between the conductor segment of the transmitting coil.

[0025] The beneficial effects of this invention are:

[0026] This invention proposes a compact and efficient LVHC-WPT system operating in the MHz band. In this system, both the transmitting and receiving coils employ a fully symmetrical planar spiral structure composed of multiple rotationally symmetrical segments, with segmented series capacitors inserted between adjacent conductors. This design reduces the resonant voltage of each segment, weakens the effects of parasitic capacitance, and enhances tunability in the MHz range. Furthermore, a magnetic coupling structure with multiple secondary symmetrical windings is used at the receiving end to achieve high voltage drop and natural current shunting; each secondary winding is connected to a GaN-based synchronous rectifier, enabling multi-channel power output. Simultaneously, this invention incorporates leakage inductance into the receiving-side compensation network, eliminating the need for additional discrete inductors and thus improving system integration.

[0027] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will now be described in further detail with reference to the accompanying drawings, wherein:

[0029] Figure 1 It is a traditional LCC-compensated WPT topology;

[0030] Figure 2 This invention proposes a megahertz-level LVHC-WPT topology.

[0031] Figure 3 Figure (a) is a schematic structural diagram of the transmitting coil and the receiving coil;

[0032] Figure 3 Figure (b) is a schematic structural diagram of the secondary winding of a transformer;

[0033] Figure 4 This is a schematic physical implementation diagram of the receiver;

[0034] Figure 5 It is an equivalent circuit based on magnetically coupled inductors;

[0035] Figure 6 It is the equivalent model for receiving integrated leakage inductance compensation;

[0036] Figure 7 This is a graph showing the experimental results. Detailed Implementation

[0037] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be understood that the preferred embodiments are for illustrative purposes only and are not intended to limit the scope of protection of the present invention.

[0038] Figure 1 It is a traditional LCC-compensated WPT topology. For example... Figure 1 As shown, at the transmitting end, the DC power supply V dc The system provides DC power to the entire system, which is then converted into high-frequency AC power by an inverter. The resonant compensation network (i.e., inductor L) f1 and capacitor C f1 ) and capacitance C T and transmitting coil L T The resonant network forming the transmitter resonant network resonates with the high-frequency current output by the inverter, causing the transmitter coil L... T It generates a high-frequency alternating magnetic field, realizing the conversion of electrical energy into magnetic energy, and providing the foundation for wireless power transmission. Inductor L f1 and capacitor C f1 It can be used for filtering, tuning, etc., to optimize the power transmission characteristics on the transmitting side.

[0039] At the receiving end, the receiving coil L R Capacitor C R Inductor L f2 and capacitor C f2 This forms the receiving end resonant network. The receiving coil L... R With transmitting coil L T There is a mutual inductance M between them. When the transmitting coil generates a high-frequency alternating magnetic field, the receiving coil induces a high-frequency alternating current through the principle of electromagnetic induction. R and C R The resonant circuit forming the receiving end (or "receiving side") has the same resonant frequency as the resonant network at the transmitting end (or "transmitting side"), achieving resonant coupling. This allows for efficient energy extraction from the magnetic field on the transmitting side, completing the conversion of magnetic energy into electrical energy. Inductor L f2 and capacitor C f2 It can be used for filtering, tuning, and optimizing the power harvesting characteristics on the receiving side. The rectifier converts the high-frequency AC output from the receiving-side resonant network into DC power for the subsequent load R. L Use. Rectifiers typically consist of diodes or synchronous rectifier devices, utilizing their unidirectional conductivity to achieve AC / DC conversion.

[0040] pass Figure 1 It is known that traditional WPT systems use a single coil (i.e., L) at both the transmitting and receiving ends. T and L R This is achieved through discrete LCC compensation, using mutual inductance M-coupled energy transfer for wireless power transmission.

[0041] The MHz-LVHC-WPT system topology proposed in this invention is as follows: Figure 2 As shown. Reference Figure 2 The MHz-LVHC-WPT system proposed in this invention includes a transmitter and a receiver. The transmitter includes a transmitting coil, an inverter, and a transmitter resonant compensation network, which are electrically connected. The receiver includes a receiving coil and a magnetically coupled transformer. Both the transmitting and receiving coils are divided into multiple segments (e.g.,...). Figure 2 The transmitting coil L in T1 ~L Tn and receiving coil L R1 ~L Rm Where n represents the number of conductor segments in the transmitting coil and m represents the number of conductor segments in the receiving coil), a compensation capacitor is connected in series between adjacent conductor segments in the transmitting coil (e.g., Figure 2 The compensation capacitor C at the transmitter end T1 ~C Tn Compensating capacitors are also connected in series between adjacent conductor segments in the receiving coil (e.g., Figure 2 The compensation capacitor C at the receiving end R1 ~C Rm This segmented approach reduces the impact of parasitic capacitance by lowering the resonant voltage of each segment, thereby improving the resonant robustness at MHz.

[0042] In some embodiments of the present invention, the transmitting coil adopts a fully symmetrical planar spiral structure composed of n rotationally symmetrical conductor segments; the receiving coil adopts a fully symmetrical planar spiral structure composed of m rotationally symmetrical conductor segments. n and m can take any suitable value, for example, 2, 3, 4, 5, 6, etc. n and m can be the same or different.

[0043] In some embodiments of the present invention, the n conductor segments of the transmitting coil are rotationally symmetrical about the transmitting center, with the rotational symmetry angle between two adjacent conductor segments being 2π / n; the m conductor segments of the receiving coil are rotationally symmetrical about the receiving center, with the rotational symmetry angle between two adjacent conductor segments being 2π / m. This geometric symmetry ensures that the self-inductance of each conductor segment in the transmitting and receiving coils is consistent, and that the segments are mutually coupled symmetrically. For both the transmitting and receiving coils, this results in consistent distributed compensation and voltage self-balancing, thereby suppressing parasitic effects and improving the quality factor to adapt to MHz operation.

[0044] Figure 3 Figure (a) shows a schematic method for winding a transmitting coil. Figure 3 Figure (a) shows a transmitting coil (L) containing four conductor segments. T1 ~L T4), 1′ to 4′ represent the inner terminals of the corresponding conductor segments, 1 to 4 represent the outer terminals of the corresponding conductor segments, the emission center is o, and the rotational symmetry angle between two adjacent conductors is marked as . In the case of four conductor segments, the rotational symmetry angle is 90° (i.e., π / 2). The helical angle from the outer diameter (corresponding to the outer terminal) to the inner diameter (corresponding to the inner terminal) of each conductor segment is the same (because these conductor segments are perfectly rotationally symmetric). This helical angle can be any suitable value, such as 2π, 2.25π, 2.5π, 3π, etc. Furthermore, the inner terminal of any conductor segment can be connected to the outer terminal of the adjacent segment via a distributed compensation capacitor, i.e., a compensation capacitor (C...). T1 ~C T4 Connect the inner terminal of each segment to the outer terminal of the next segment (e.g., 1′→C). T1 →2,2′→C T2 →3, etc. The configuration of the receiving coil is similar to that of the transmitting coil, so it will not be described in detail here.

[0045] In this invention, the inner and outer diameters of the conductor segment in the transmitting coil can be the same as or different from the inner and outer diameters of the conductor segment in the receiving coil. The specific values ​​of the inner and outer diameters of the conductor segment in the transmitting coil and the conductor segment in the receiving coil can be appropriately adjusted according to the system coupling coefficient and design requirements.

[0046] In this invention, the conductor segments in the transmitting coil and the receiving coil are wound with Litz wire having a first preset diameter and a first preset number of strands (e.g., 0.04 mm × 1500 strands).

[0047] This invention also fundamentally reshapes the magnetic coupling topology. In this invention, each segment (i.e., each conductor segment) at both the transmitter and receiver forms a distributed many-to-many coupling network (L) with all segments at the receiver. Ti L Rj It also has coupling with adjacent segments on the same side (L) Ti L Tj With L Ri L Rj These segment-to-segment couplings stem from planar structures and physical proximity.

[0048] Furthermore, this invention also uses a multi-side transformer (i.e., a magnetically coupled transformer with multiple secondary sides) at the receiving end to replace the discrete inductor L in the traditional topology. f2 The magnetically coupled transformer contains a primary winding L. p With multiple sets of rotationally symmetric secondary windings L s1 ~L sLL represents the number of secondary windings. L can take any suitable value, such as 2, 3, 4, 5, 6, etc. L can be the same as or different from n or m, depending on specific needs. The primary and secondary windings of the transformer achieve strong mutual coupling (L) by sharing a ferrite core (i.e., the transformer core). si L sj ).

[0049] The primary winding is electrically connected to the receiving coil. For example... Figure 2 As shown, the primary winding L p With capacitor C f2 After being connected in parallel, they are connected to both ends of the receiving coil. Each secondary side is connected to a GaN full-bridge synchronous rectifier (SR), and the outputs of each GaN full-bridge rectifier are connected in parallel and then supplied to the load R. L Power supply, thereby enabling wireless power transmission under megahertz-level low voltage and high current.

[0050] In some embodiments of the present invention, multiple secondary windings are located in the same plane, and the L secondary windings adopt a fully symmetrical planar helical structure composed of L rotationally symmetrical conductor segments. The L conductor segments in the secondary windings are rotationally symmetrically distributed with respect to the center of the secondary winding, and the rotational symmetry angle between two adjacent conductor segments is 2π / L. Such symmetry is beneficial for subsequent multi-channel output and inherent current sharing, eliminating the need for active current sharing control.

[0051] In some embodiments of the present invention, the outer end (i.e., outer terminal) to the inner end (i.e., inner terminal) of each conductor segment in the secondary winding forms a continuous spiral, with the spiral angle being an integer multiple of 2π. This layout allows each secondary winding to be directly connected to the GaN full-bridge rectifier from the outer / inner end without additional wiring or interlayer transitions, facilitating integration.

[0052] In some embodiments of the present invention, the primary winding adopts a planar helical structure wound from a single Litz wire, the single Litz wire having a second preset diameter and a second preset number of strands; the conductor segment of the secondary winding is wound from a Litz wire having a third preset diameter and a third preset number of strands.

[0053] The first preset diameter, the second preset diameter, and the third preset diameter can be the same or different. The first preset number of strands, the second preset number of strands, and the third preset number of strands can be the same or different.

[0054] Each conductor segment of the secondary winding has the same outermost radius and innermost radius.

[0055] The wire diameter and number of strands in each conductor segment of the secondary winding depend on the operating frequency and operating current. For example, at 1 MHz, the skin depth is approximately 0.065 mm, and 0.04 mm fine strands can be used to avoid the skin effect.

[0056] The number of strands in each coil can be determined according to the current carrying capacity. For example, the primary coil can use 0.04 mm × 1500 strands to carry a 1MHz 15A current; while the secondary coil, which carries a larger current, can use 0.04 mm × 3500 strands to carry a 1MHz 30A current.

[0057] Figure 3 Figure (b) shows a transformer containing four secondary windings (L... S1 ~L S4 In the case of ), Figure 3 In Figure (b), 1′ to 4′ represent the inner terminals of the corresponding conductor segments in the secondary winding, and 1 to 4 represent the outer terminals of the corresponding conductor segments. The emission center is o, and the rotational symmetry angle between two adjacent conductors is marked as . In the case of four conductor segments, the rotational symmetry angle is 90° (i.e., π / 2). The helical angle from the outer diameter (corresponding to the outer terminal) to the inner diameter (corresponding to the inner terminal) of each conductor segment is the same (because these conductor segments are perfectly rotationally symmetric), which is 2π.

[0058] Furthermore, in the system proposed in this invention, the transformer leakage inductance is reused as a series compensation inductor on the receiving side (i.e., the L inductance in the traditional WPT system is eliminated). f2 This eliminates discrete inductors and improves system integration.

[0059] The present invention also provides a wireless power transmission receiver, which is the physical implementation of the receiving end. This receiver includes all the structures described above for the receiving end, and further includes a bottom support plate, a shielding ferrite layer, and a cover plate. The bottom support plate, receiving coil, shielding ferrite layer, primary winding, secondary winding, and transformer core are stacked sequentially, and a first through-hole is provided on the cover plate. The magnetically coupled transformer is disposed in the first through-hole to form a compact integration.

[0060] Figure 4 The physical implementation of the proposed compact magnetic structure receiver is presented. The green portion is an acrylic or similar insulating plate, used as the coil substrate (i.e. Figure 4 The bottom support plate and the top cover (i.e.) Figure 4 The cover plate supports the receiving winding and houses the compensation capacitor. From bottom to top, it consists of: four symmetrical receiving coil segments (i.e., four schematic conductor segments), a shielding ferrite layer, the transformer primary winding, four helical secondary windings, and the transformer core. Because the magnetic flux in the central region of the shielding ferrite is relatively small, the lower structure of the transformer can reuse this space to form a compact integration. Therefore, through holes (called "first through holes") can be provided in the cover plate. Figure 4The square through-hole in the middle area of ​​the middle cover plate), the magnetic coupling transformer is set in the first through-hole to form a compact integration. The transformer core forms a closed magnetic circuit with the upper magnetic cover (i.e. the ferrite cover on the top of the core) through the central column (i.e. the central column of the transformer core), and the bottom magnetic circuit is closed by a reused shielding ferrite, thereby achieving strong coupling between the primary and secondary sides.

[0061] In this invention, the shielding ferrite layer and the cover plate are provided with corresponding second through holes for connecting the conductor segment of the receiving coil and the compensation capacitor between the conductor segment of the receiving coil. For example... Figure 4 As shown, the shielding ferrite layer has cutouts (which can also be considered through holes) for connecting each receiving section to the capacitors mounted on the cover plate. The upper magnetic cover has through holes (i.e., the third through hole) for directly connecting the secondary winding to the input terminal of the GaN full-bridge rectifier (GaN-SR).

[0062] This invention also provides a wireless power transmission receiver, which is the physical implementation of the receiving end. It includes all the structures of the transmitting end described above, and the transmitting end structure is similar to the receiving end, but does not include the transformer section. Specifically, the transmitter also includes an upper support plate, a lower support plate, and a transmitting end shielding ferrite layer. The lower support plate, transmitting coil, transmitting end shielding ferrite layer, and upper support plate are stacked sequentially, and the transmitting end shielding ferrite layer and the upper support plate have corresponding through holes for connecting the conductor segment of the transmitting coil and the compensation capacitor between the conductor segments of the transmitting coil.

[0063] To analyze the resonance condition and output characteristics, an AC-AC equivalent model is established based on structural symmetry. For example... Figure 5 As shown, the segmented transmitting / receiving coils and distributed series capacitors can be equivalent to a lumped inductance L. T L R and concentrated capacitor C T C R This forms a dual LCC compensation network. The two ports are connected via mutual inductance M. TR Magnetic coupling, coupling coefficient is A transformer stage consists of a primary winding and multiple secondary windings, which can be simplified to a coupled inductor pair (L...). P L S ) and mutual inductance M PS The coupling coefficient is With multiple secondary sides connected in parallel, the GaN full-bridge synchronous rectifier is equivalent to an AC load resistance R. o =8 / π 2 R L .

[0064] To facilitate resonance analysis, Figure 6 The model uses a comprehensive transformer model (i.e., an integrated transformer model) to decompose the transformer into primary leakage inductance L. lkMagnetizing inductance L m With an effective ratio n e An ideal transformer has the following equivalent parameters:

[0065] (1)

[0066] In this model, the leakage inductance of the transformer is reused as the series compensation inductor at the receiving end, eliminating the need for the discrete L inductor used in traditional LCC topologies. f2 (See) Figure 1 ).

[0067] To achieve resonance, the following parameter relationship can be obtained:

[0068] (2)

[0069] in, This represents the resonant angular frequency.

[0070] based on Figure 5 Based on the model and the resonance condition in equation (2), the steady-state relationship between the input voltage and the output current can be derived as follows:

[0071] , (3)

[0072] in, The system resonant angular frequency is represented by the value in equation (2). .

[0073] The advantages of the present invention will be further illustrated by the following specific experiments.

[0074] In this experiment, both the transmitting and receiving coils are formed by connecting four adjacent conductor segments sequentially to create a symmetrical spiral (see reference for details). Figure 3 (Figure (a)). Each conductor segment in the transmitting and receiving coils is wound with 0.04 mm × 1500 strands of Litz wire. The outer diameter (ports 1-4) of each segment is 150 mm, and the inner diameter (ports 1′-4′) is 105 mm. The helical angle from the outer diameter to the inner diameter of each segment is 2.25π, allowing the inner terminal of any segment to be connected to the outer terminal of the adjacent segment via a distributed compensation capacitor.

[0075] The shielding cores of the transmitting / receiving coils and the transformer core are both made of 5 mm thick PC95 ferrite. The outer diameter and inner diameter of the primary / secondary windings of the transformer are 50 mm and 15 mm, respectively. The primary winding uses 11 turns of 0.04 mm × 1500 strand Litz wire; the secondary winding consists of four sets of symmetrical windings (see...). Figure 3(Figure b) shows that each group uses 0.04 mm × 3500 strands of Litz wire. The spiral angle of each secondary side from the outside to the inside is 2π, which facilitates direct connection to the GaN full-bridge synchronous rectifier (model INN100EQ016A) and minimizes the trace size. The compensation network includes C f1 C f2 C T1 ~C T4 C R1 ~C R4 All capacitors are NP0 type 1 nF capacitors, which are combined in series and parallel to improve their voltage and current withstand capabilities. The key physical and electrical parameters used in the experiment are summarized in Table 1.

[0076] Table 1 System Parameter Settings

[0077]

[0078] Figure 7 The inverter waveform and the system DC-DC efficiency are given. Figure 7 As shown in Figure (a), the system operates at a resonant frequency of 1 MHz, achieving zero-voltage turn-on (ZVS) on the inverter side. The full-load output reaches 3.134 kW / approximately 127 A, corresponding to a DC-DC efficiency of 95.192%. At half load (70 A), the efficiency reaches 96.22%. Figure 7 Figure (b) shows the efficiency curves over the entire power range, from... Figure 7 As can be seen from Figure (b), this system can maintain an efficiency of over 91% in the range from light load to full load, demonstrating excellent performance.

[0079] To quantitatively evaluate the system proposed in this invention, Table 2 summarizes a comparison of representative LVHC-WPT designs of this invention and existing methods, with key indicators including output power, frequency, air gap, output current, and full-load efficiency. To provide a unified benchmark among different schemes, the Wireless Power Transfer Comprehensive Evaluation Index (WPTFOM) is adopted.

[0080] , (4)

[0081] Where P is the system transmission power, d is the air gap distance between the transmitting and receiving coils, η is the system dc–dc efficiency, and S is the geometric mean of the coupler areas (i.e., the geometrically average effective coupling area between the transmitting and receiving coils). For example, if the area of ​​the transmitting coil coil is S1 and the area of ​​the receiving coil coil is S2, then... This metric characterizes the system's ability to efficiently transfer energy within a compact coil area and at a certain distance.

[0082] Table 2 Comparison of the present invention with existing methods

[0083]

[0084] In Table 2, “Comparison 1” represents a low-harmonic tightly coupled design, which can be found in the reference “F. Lu et al., A Tightly Coupled Inductive Power Transfer System for Low-Voltage and High-Current Charging of Automatic Guided Vehicles,” in IEEE Transactions on Industrial Electronics, vol. 66, no. 9, pp. 6867-6875, Sept. 2019”; “Comparison 2” represents a dual-receiver design with partial power processing, which can be found in the reference “S. Liu et al., Efficiency Improvement of Dual-Receiver WPT Systems Based on Partial PowerProcessing Control,” in IEEE Transactions on Power Electronics, vol. 37, no. 6, pp. 7456-7469, June 2022”; and “Comparison 3” represents a multiphase interleaved current source (IPT) design, which can be found in the reference “Y. Wang, S. Zhao, R. Kheirollahi, A. Mostafa, H. Zhang and F. Lu, "Multiphase Interleaved IPT Based Current-Source Converter for High-Current Application," in IEEE Journal of Emerging and Selected Topics in Industrial Electronics, vol. 3, no. 3, pp. 583-593, July 2022; "Comparison 4" represents a series capacitor full-bridge + current multiplier design scheme, which can be found in the reference "X. Li et al.""A High-Efficiency IPT System With Series-Capacitor Full-Bridge Configuration and Inverse Coupled CurrentDoubler Rectifier for High-Input, Low-Voltage, and High Output Current Applications," in IEEE Transactions on Power Electronics, vol. 39, no. 9, pp.11849-11861, Sept. 2024; "Comparison 5" represents a multi-channel interleaved current multiplier design scheme, which can be found in the reference "Y. Zhang, H. Ouyang, Y. Zhuang, X. Cheng, X. Chen and X. Mao, "A Multi-Channel High Current AGV Wireless Charging System based on Perpendicular DD Coil Array and Current Multiplier Rectifier," in IEEE Transactions on Power Electronics, doi: 10.1109 / TPEL.2025.3614467".

[0085] As shown in Table 2, the WPTFOM of the system proposed in this invention reaches 2425 W / m², which is significantly better than existing work. Benefiting from megahertz-level operation, symmetrical segmented coils, and magnetic integration, the system achieves 95.192% efficiency and high power density with a 100 mm air gap and 127 A output. This system demonstrates the advantages of compactness and high performance in LVHC-WPT applications.

[0086] In summary, this invention proposes a compact and efficient WPT system operating at megahertz frequencies for low-voltage, high-current applications. Parasitic effects are suppressed and MHz resonance is achieved through a fully symmetrical segmented coil structure. At the receiving end, a multi-side transformer is used to achieve natural current shunting and high voltage drop, and leakage inductance is integrated into the receiving-side compensation to reduce size and improve magnetic utilization. The fabricated 3 kW prototype achieves 24 V / 127 A output at 1 MHz with a 100 mm air gap, with a DC-DC efficiency of 95.192% and a peak efficiency of 96.22%. Compared with existing solutions, the system of this invention has significant advantages in power density and compactness, as verified by WPTFOM = 2425 W / m², demonstrating its potential application in AGVs and mobile robots.

[0087] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A megahertz-level low-voltage high-current wireless power transfer system based on symmetrical planar coils, characterized in that, include: The transmitter and receiver, among which, The transmitter includes a transmitting coil, an inverter, and a transmitter resonant compensation network, which are electrically connected. The receiving end includes a receiving coil and a magnetic coupling transformer. The transmitting coil adopts a fully symmetrical planar spiral structure composed of n rotationally symmetrical conductor segments, and a compensation capacitor is connected in series between adjacent conductor segments in the transmitting coil; The receiving coil adopts a fully symmetrical planar spiral structure composed of m rotationally symmetrical conductor segments, and a compensation capacitor is also connected in series between adjacent conductor segments in the receiving coil. The magnetically coupled transformer includes one primary winding and L secondary windings. The primary winding is electrically connected to the receiving coil. The L secondary windings adopt a fully symmetrical planar helical structure composed of L rotationally symmetrical conductor segments. The L secondary windings are magnetically coupled to the primary winding through the transformer core. Furthermore, each secondary winding is connected to a GaN full-bridge rectifier, the outputs of each GaN full-bridge rectifier are connected in parallel, and the leakage inductance of the magnetic coupling transformer is reused as the series compensation inductor at the receiving end, thereby realizing wireless power transmission under megahertz-level low voltage and high current.

2. The megahertz-level low-voltage high-current wireless power transfer system based on symmetrical planar coils according to claim 1, characterized in that, The n conductor segments of the transmitting coil are rotationally symmetrical about the transmitting center, and the rotational symmetry angle between two adjacent conductor segments is 2π / n; the m conductor segments of the receiving coil are rotationally symmetrical about the receiving center, and the rotational symmetry angle between two adjacent conductor segments is 2π / m.

3. The megahertz-level low-voltage high-current wireless power transfer system based on symmetrical planar coils according to claim 1, characterized in that, The inner and outer diameters of the conductor segment in the transmitting coil are the same as those of the conductor segment in the receiving coil.

4. The megahertz-level low-voltage high-current wireless power transfer system based on symmetrical planar coils according to claim 1, characterized in that, The L conductor segments in the secondary winding are distributed in a rotationally symmetrical manner with respect to the center of the secondary winding. The rotational symmetry angle between two adjacent conductor segments is 2π / L, and the helical angle of each conductor segment is an integer multiple of 2π.

5. The megahertz-level low-voltage high-current wireless power transfer system based on symmetrical planar coils according to claim 1, characterized in that, The receiving end also includes a bottom support plate, a shielding ferrite layer and a cover plate, wherein the bottom support plate, receiving coil, shielding ferrite layer, primary winding, secondary winding and transformer core are stacked in sequence, and a first through hole is provided on the cover plate, and the magnetic coupling transformer is disposed in the first through hole to form a compact integration.

6. The megahertz-level low-voltage high-current wireless power transfer system based on symmetrical planar coils according to claim 5, characterized in that, The shielding ferrite layer and the cover plate are provided with corresponding second through holes for connecting the conductor segment of the receiving coil and the compensation capacitor between the conductor segment of the receiving coil.

7. The megahertz-level low-voltage high-current wireless power transfer system based on symmetrical planar coils according to claim 5, characterized in that, The transformer core is provided with a third through hole for connecting each secondary winding to the corresponding GaN full-bridge rectifier.

8. The megahertz-level low-voltage high-current wireless power transfer system based on symmetrical planar coils according to claim 1, characterized in that, The conductor segments in the transmitting coil and the receiving coil are wound with Litz wire having a first preset diameter and a first preset number of strands; The primary winding adopts a planar helical structure made of a single Litz wire, wherein the single Litz wire has a second preset diameter and a second preset number of strands; The conductor segment of the secondary winding is made of Litz wire with a third preset diameter and a third preset number of strands.

9. A wireless power transmission receiver, characterized in that, Includes the entire structure of the receiver as described in any one of claims 1 to 8.

10. A wireless power transmission transmitter, characterized in that, The transmitter includes the entire structure of the transmitting coil as described in any one of claims 1 to 8, and the transmitter further includes an upper support plate, a lower support plate, and a transmitting end shielding ferrite layer. The lower support plate, the transmitting coil, the transmitting end shielding ferrite layer, and the upper support plate are stacked in sequence, and the transmitting end shielding ferrite layer and the upper support plate are provided with corresponding through holes for connecting the conductor segment of the transmitting coil and the compensation capacitor between the conductor segment of the transmitting coil.

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