Electric field coupling type wireless charging system applied to high-frequency transmission

Abstract

The invention relates to the technical field of wireless power transmission, in particular to an electric field coupling type wireless charging system applied to high-frequency transmission, which comprises a transmitting end and a receiving end, and is characterized in that the transmitting end comprises a power grid power supply, an inverter, a primary side resonance circuit and a transmitting polar plate which are connected in sequence; the receiving end comprises a receiving pole plate, a secondary side resonance circuit, a secondary rectifier and a load which are connected in sequence; the transmitting polar plate and the receiving polar plate are arranged in a coupling manner; the inverter is a class phi 2 series inverter, and the class phi 2 series inverter comprises a first class phi 2 inverter and a second class phi 2 inverter which are connected in series with each other. According to the invention, the class phi 2 inverters are connected in series to form the class phi 2 series inverter, so that the system transmission efficiency during high-frequency transmission is improved. The class phi 2 inverter disclosed by the invention can be well compatible with a gallium nitride (GaN) device. The GaN device has the advantages of low conduction loss, high switching speed, high frequency upper limit and the like, and the efficiency and the power density of the phi2 inverter are further improved.

Description

Technical Field

[0001] The present invention relates to the technical field of wireless power transmission, and in particular to an electric field coupling wireless charging system applied to high frequency transmission. Background Art

[0002] Wireless power transfer (WPT) is a novel power transmission technology that uses electromagnetic or mechanical waves to transfer electrical energy from a power source to a load without electrical contact. Because WPT eliminates any physical connection between the power source and the load during transmission, it avoids the various risks associated with hardware connections compared to traditional contact-based transmission methods and significantly enhances the flexibility of electrical devices. Electric-field-coupled power transfer (ECPT) offers the following advantages: 1) The coupling mechanism uses lightweight metal as the transmitting and receiving electrodes, exhibiting advantages such as thinness and good plasticity; 2) ECPT utilizes an alternating electric field to achieve energy transmission, enabling the system to transmit energy across metallic barriers; and 3) Compared to magnetically coupled wireless power transfer systems, ECPT systems experience negligible eddy current losses caused by surrounding metallic foreign objects. Consequently, electric-field-coupled wireless power transfer has garnered increasing research and attention.

[0003] A typical high-frequency ECPT system consists of a high-frequency inverter circuit, a resonant network, a coupling mechanism, and a rectifier circuit. Two key research areas for ECPT systems are the efficiency of power transmission at high frequencies and the lightweight nature of the system. Existing ECPT systems generally suffer from low power transmission efficiency at high frequencies and these technical challenges. Summary of the Invention

[0004] To address the common technical issues of low power transmission efficiency at high frequencies and lightweighting of ECPT systems in the prior art, the present invention provides an electric field coupling wireless charging system for high-frequency transmission. The specific technical solutions are as follows:

[0005] An electric field coupling wireless charging system for high-frequency transmission includes a transmitter and a receiver. The transmitter includes a grid power supply, an inverter, a primary resonant circuit, and an emitter plate connected in sequence. The receiver includes a receiving plate, a secondary resonant circuit, a secondary rectifier, and a load connected in sequence. The emitter plate and the receiving plate are coupled.

[0006] The inverter is a class Φ2 series inverter, and the class Φ2 series inverter includes a first class Φ2 inverter and a second class Φ2 inverter connected in series with each other.

[0007] Preferably, the first class Φ2 inverter includes a first voltage divider capacitor C in1 , the first choke inductor Lf1 , a first series resonant circuit, a first circuit switch tube S1 and a first shunt capacitor C2;

[0008] The first voltage dividing capacitor C in1 One end of the first choke inductor L f1 One end of each is connected to one end of the grid power supply;

[0009] The first choke inductor L f1 The other end is respectively connected to one end of the first series resonant circuit, one end of the first circuit switch S1, and one end of the first shunt capacitor C2, and serves as an output end of the class Φ2 series inverter;

[0010] The first voltage dividing capacitor C in1 The other end is respectively connected to the other end of the first series resonant circuit, the other end of the first circuit switch tube S1, and the other end of the first shunt capacitor C2, and serves as the first class Φ2 inverter connection end connected to the second class Φ2 inverter.

[0011] Preferably, the second class Φ2 inverter includes a second voltage dividing capacitor C in2 , the second choke inductor L f3 , a second series resonant circuit, a second circuit switch tube S2 and a second shunt capacitor C3;

[0012] The second voltage dividing capacitor C in2 One end of the second choke inductor L f3 One end of each is connected to the first class Φ2 inverter connection end;

[0013] The second choke inductor L f3 The other end is respectively connected to one end of the second series resonant circuit, one end of the second circuit switch tube S2, and one end of the second shunt capacitor C3, and serves as the other output end of the class Φ2 series inverter;

[0014] The second voltage dividing capacitor C in2 The other end of the second series resonant circuit, the other end of the second circuit switch tube S2, and the other end of the second shunt capacitor C3 are respectively connected to the other end of the grid power supply.

[0015] Preferably, the first series resonant circuit includes a first resonant capacitor C f2 and the first resonant inductor L f2 , the first resonant capacitor C f2 One end of the first resonant inductor L f2 and serves as a connection end of the first series resonant circuit; the first resonant inductor L f2The other end of the first choke inductor L f1 Connection; the first resonant capacitor C f2 The other end of the first voltage divider capacitor C in1 connect;

[0016] The second series resonant circuit includes a second resonant capacitor C f4 and the second resonant inductor L f4 , the second resonant capacitor C f4 One end of the second resonant inductor L f4 and serves as a connection end of the second series resonant circuit; the second resonant inductor L f4 The other end of the second choke inductor L f3 Connection; the second resonant capacitor C f4 The other end of the second voltage divider capacitor C in2 connect.

[0017] Preferably, a third series resonant circuit is further included, and the third series resonant circuit includes a third resonant capacitor C1 and a third resonant inductor L1; one end of the third resonant inductor L1 is connected to the connection end of the first series resonant circuit, and the other end is connected to one end of the third resonant capacitor C1, and the other end of the third resonant capacitor C1 is connected to the connection end of the second series resonant circuit.

[0018] Preferably, the primary resonant circuit and the secondary resonant circuit are symmetrically arranged LC topology networks.

[0019] Preferably, the compensating inductor in the secondary resonant circuit is a flexible PCB inductor.

[0020] Preferably, the number of the emitter plates and the number of the receiving plates are both two;

[0021] The two groups of emitter plates are respectively connected to the two output ends of the primary resonant circuit, the two groups of receiving plates are respectively connected to the two input ends of the secondary resonant circuit, and the two groups of emitter plates are respectively arranged opposite to the two groups of receiving plates.

[0022] Preferably, the receiving plates are all cylindrical plates.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1. The present invention improves the system transmission efficiency during high-frequency transmission by connecting class Φ2 inverters in series to form a class Φ2 series inverter.

[0025] 2. The class Φ2 inverter of the present invention is highly compatible with gallium nitride (GaN) devices. GaN devices offer advantages such as low conduction losses, fast switching speeds, and a high upper frequency limit, further improving the efficiency and power density of the Φ2 inverter. GaN devices have higher power density and smaller size, which means that at the same power, GaN devices can be made smaller and lighter. Compared with traditional silicon-based devices, the size and weight of GaN devices can be significantly reduced.

[0026] 3. The compensation inductor in the secondary resonant circuit of the present invention uses a flexible PCB inductor, and the receiving plate uses a cylindrical plate instead of the traditional heavier rigid inductor and rectangular plate. The installation space required is smaller and the volume is smaller, which makes the volume and mass of the receiving end smaller, helps to achieve lightweight receiving end, making it better suitable for wireless charging in scenarios such as drones. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly describes the drawings required for the specific embodiments or the description of the prior art. Similar elements or parts are generally identified by similar reference numerals throughout the drawings. Elements or parts in the drawings are not necessarily drawn to scale.

[0028] Figure 1 Schematic diagram of the structure of the ECPT system of the present invention.

[0029] Figure 2 Schematic diagram of the structure of the class Φ2 series inverter of the present invention.

[0030] Figure 3 This is the operating voltage and current waveform of the MOSFET of the present invention.

[0031] Figure 4 This is the output voltage waveform of the ECPT system of the present invention. DETAILED DESCRIPTION

[0032] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0033] It will be understood that when used in this specification and the appended claims, the terms “comprises” and “comprising” indicate the presence of described features, integers, steps, operations, elements and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups thereof.

[0034] It should also be understood that the terms used in the present specification are only for the purpose of describing particular embodiments and are not intended to limit the present invention. As used in the present specification and the appended claims, the singular forms "a", "an", and "the" are intended to include the plural forms unless the context clearly indicates otherwise.

[0035] It should be further understood that the term "and / or" used in the present description and the appended claims refers to and includes any and all possible combinations of one or more of the associated listed items.

[0036] Currently, commonly used inverter circuits in systems include full-bridge inverters, half-bridge inverters, Class E inverters, and push-pull inverters. Full-bridge inverters require four switching devices, resulting in higher hardware costs and complex system control. Due to higher voltage and current stresses, switching losses increase significantly at high frequencies, impacting efficiency. Full-bridge inverters have complex drive circuits and suffer from output waveform voltage distortion. Half-bridge inverters can only reach a maximum output voltage of half the input DC voltage, limiting their applicability to high-voltage output applications. Furthermore, they require larger filter capacitors, increasing system size and cost, hindering lightweight design. They are also unsuitable for high-frequency electric field coupled wireless power transmission systems. Class E inverters, operating under zero voltage switching (ZVS) and zero derivative voltage switching (ZVDS) conditions, can operate efficiently at switching frequencies above 1 MHz. They can deliver more power than other inverter types for a given input voltage and are therefore widely used in WPT applications. Adding a parallel or series resonant network to the load network of a Class E inverter can improve inverter efficiency, reduce voltage and current stresses, and improve system energy transfer. Adding an LC resonant network to the load network and applying it to a Class E inverter creates a hybrid inverter called a Φ2 class inverter. Due to the unique circuit structure and design of the Φ2 class inverter, higher efficiency is achieved. In particular, in ultra-high frequency applications, switching losses can be significantly reduced by optimizing the switching process.

[0037] Therefore, based on the Φ2 class inverter, this embodiment provides an electric field coupling wireless charging system for high frequency transmission, such as Figure 1 As shown, it includes a transmitter and a receiver. The transmitter includes a grid power supply, an inverter, a primary resonant circuit, and an emitter plate connected in sequence. The receiver includes a receiver plate, a secondary resonant circuit, a secondary rectifier, and a load connected in sequence. The emitter plate and the receiver plate are coupled. The inverter is a class Φ2 series inverter, which includes a first class Φ2 inverter and a second class Φ2 inverter connected in series.

[0038] In this embodiment, the system uses two class Φ2 inverters connected in series. The DC power of the inverter system is converted into high-frequency AC power to supply the subsequent circuit. The primary-side LC compensation network performs filtering, reactive power compensation, and voltage pumping to generate a high-frequency excitation voltage.

[0039] Furthermore, Φ2 inverters are generally well-compatible with gallium nitride (GaN) devices. GaN devices offer advantages such as low conduction losses, fast switching speeds, and a high upper frequency limit, further improving the efficiency and power density of Φ2 inverters. GaN devices offer higher power density and smaller size, meaning they can be made smaller and lighter for the same power. Compared to traditional silicon-based devices, GaN devices can significantly reduce their size and weight.

[0040] See also Figure 2 , the first classΦ2 inverter includes a first voltage divider capacitor C in1 , the first choke inductor L f1 , a first series resonant circuit, a first circuit switch tube S1 and a first shunt capacitor C2. The first voltage divider capacitor C in1 One end of the first choke inductor L f1 One end of each is connected to one end of the grid power supply. The first choke inductor L f1 The other end is connected to one end of the first series resonant circuit, one end of the first circuit switch tube S1, and one end of the first shunt capacitor C2, and serves as an output end of the class Φ2 series inverter. in1 The other end is respectively connected to the other end of the first series resonant circuit, the other end of the first circuit switch tube S1, and the other end of the first shunt capacitor C2, and serves as the first class Φ2 inverter connection end connected to the second class Φ2 inverter.

[0041] See also Figure 2 The second classΦ2 inverter includes a second voltage divider capacitor C in2 , the second choke inductor L f3 , the second series resonant circuit, the second circuit switch tube S2 and the second shunt capacitor C3. The second voltage divider capacitor C in2 One end of the second choke inductor L f3 One end of each is connected to the first class Φ2 inverter connection end. The second choke inductor L f3 The other end is connected to one end of the second series resonant circuit, one end of the second circuit switch tube S2, and one end of the second shunt capacitor C3, and serves as the other output end of the class Φ2 series inverter. in2The other end of the second series resonant circuit, the other end of the second circuit switch tube S2, and the other end of the second shunt capacitor C3 are respectively connected to the other end of the grid power supply.

[0042] See also Figure 2 , the first series resonant circuit includes a first resonant capacitor C f2 and the first resonant inductor L f2 The first resonant capacitor C f2 One end of the first resonant inductor L f2 One end of the first resonant inductor L is connected to the first series resonant circuit. f2 The other end of the first choke inductor L f1 Connect the first resonant capacitor C f2 The other end of the first voltage divider capacitor C in1 connect.

[0043] The second series resonant circuit includes a second resonant capacitor C f4 and the second resonant inductor L f4 The second resonant capacitor C f4 One end of the second resonant inductor L f4 One end of the second resonant inductor L is connected to the second series resonant circuit. f4 The other end of the second choke inductor L f3 Connect the second resonant capacitor C f4 The other end of the second voltage divider capacitor C in2 connect.

[0044] See also Figure 2 The system of the present invention further includes a third series resonant circuit, which includes a third resonant capacitor C1 and a third resonant inductor L1. One end of the third resonant inductor L1 is connected to the connection end of the first series resonant circuit, and the other end is connected to one end of the third resonant capacitor C1. The other end of the third resonant capacitor C1 is connected to the connection end of the second series resonant circuit.

[0045] Adding a parallel or series resonant network to the load network of a Class E inverter to form a Class Φ2 inverter can improve the inverter's efficiency and reduce the inverter's voltage or current stress. Class Φ2 inverters have a second-harmonic series resonant filter connected in parallel with the switching devices, and these series resonant filters approximately short-circuit the second harmonic. This additional circuit can improve the shape of the transistor waveform, reducing peak voltage or reducing the root mean square current. Class Φ2 converters typically have lower voltage stress on the main switch tube, which helps reduce energy losses during switching and improve the overall efficiency of the converter. Compared to Class EF2 amplifiers, Class Φ2 amplifiers do not require large choke inductors, which speeds up transient response.

[0046] As a preferred embodiment of the present invention, the primary resonant circuit and the secondary resonant circuit are symmetrically arranged LC topology networks.

[0047] As a preferred embodiment of the present invention, the compensating inductor in the secondary resonant circuit is a flexible PCB inductor.

[0048] As a preferred embodiment of the present invention, the number of the emitting plates and the number of the receiving plates are both two;

[0049] The two groups of emitter plates are respectively connected to the two output ends of the primary resonance circuit, the two groups of receiving plates are respectively connected to the two input ends of the secondary resonance circuit, and the two groups of emitter plates are respectively arranged opposite to the two groups of receiving plates.

[0050] As a preferred embodiment of the present invention, the receiving plates are all cylindrical plates.

[0051] In this embodiment, a flexible PCB inductor is used as the compensation inductor in the secondary side resonant circuit, and a cylindrical plate is used as the receiving plate, rather than the traditional heavier rigid inductor and rectangular plate. The installation space required is smaller and the volume is smaller, which makes the volume and mass of the receiving end smaller, helps to achieve the lightweight of the receiving end, making it better suitable for wireless charging in scenarios such as drones.

[0052] Simulation and verification:

[0053] To verify that this novel inverter topology can be applied to high-frequency electric field coupled wireless charging technology and that the energy transmission of the entire ECPT system can achieve high efficiency under high-frequency conditions, a circuit model of the entire wireless charging system was built and simulated using the Matlab / Simulink simulation platform. The system's resonant network was set to an LC-LC type, and the system switching frequency was set to 6.78 MHz.

[0054] Depend on Figure 3 The MOSFET operating voltage and current demonstrate excellent zero-voltage switching (ZVS) performance. This means that switching losses are significantly reduced at the moment the switch turns on, as no energy is consumed during the on-state. ZVS technology is widely used in circuits such as high-frequency switching power supplies and resonant converters to improve circuit efficiency and reliability. This topology achieves ZVS at high frequencies, significantly improving the system's power transmission efficiency compared to other inverters, resulting in a better output waveform. The parameter settings for class Φ2 are shown in Table 1.

[0055] Table 1 Parameter settings of class Φ2 inverter

[0056] parameter Numerical parameter Numerical <![CDATA[C in1 / uH]]> 50 <![CDATA[C in2 / uH]]> 50 <![CDATA[L f1 / uH]]> 8.0916 <![CDATA[L f3 / uH]]> 8.0916 <![CDATA[L f2 / nH]]> 87.841 <![CDATA[L f4 / nH]]> 87.841 <![CDATA[C f2 / nF]]> 1.5692 <![CDATA[C f4 / nF]]> 1.5692 <![CDATA[L1 / pH]]> 22.96 <![CDATA[C3 / nF]]> 1.3596 <![CDATA[C2 / nF]]> 1.3596 <![CDATA[C1 / uF]]> 6 <![CDATA[L x / nH]]> 108.67 <![CDATA[L x1 / uH]]> 670 <![CDATA[C x 2 / pF]]> 822.44

[0057] The system's secondary compensation inductor utilizes flexible PCB inductors to achieve lightweight design. Compared to traditional coil-wound inductors and rigid PCB inductors, flexible PCB technology offers high wiring density, light weight, and thinness. Furthermore, its increased flexibility and foldability facilitate optimized circuit layout in specific experiments, further reducing the required weight and achieving lightweight design goals.

[0058] The system of the present invention adopts a bilateral LC compensation topology working in constant current mode. The system can achieve a power transmission of 624.7W and an efficiency of 85.3%. The system output voltage waveform is as follows: Figure 4 As shown, a relatively stable state can be achieved, and the system parameters are shown in Table 2.

[0059] Table 2 System parameters

[0060] parameter Numerical parameter Numerical <![CDATA[E dc / V]]> 100 <![CDATA[L1 / uH]]> 1.4447 f / MHz 6.78 <![CDATA[L2 / uH]]> 1.4569 <![CDATA[C M / pF]]> 46.05 <![CDATA[C ex1 / pF]]> 330 <![CDATA[C in1 / pF]]> 56.96 <![CDATA[C ex2 / pF]]> 330 <![CDATA[C in2 / pF]]> 53.69 C0 / uF 5 D 0.5 R0 / Ω 30

[0061] In summary, the present invention improves the system transmission efficiency during high-frequency transmission by connecting classΦ2 inverters in series to form a classΦ2 series inverter. The classΦ2 inverter is well compatible with gallium nitride (GaN) devices. Compared with traditional silicon-based devices, the volume and weight of GaN devices can be greatly reduced. At the same time, the compensation inductor in the secondary resonant circuit of the present application uses a flexible PCB inductor, and the receiving plate uses a cylindrical plate, rather than the traditional heavier rigid inductor and rectangular plate. The space required for its installation is smaller and the volume is smaller, which makes the volume and mass of the receiving end smaller, helps to achieve lightweight receiving end, and makes it better suitable for wireless charging in scenarios such as drones.

[0062] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention, and they should all be included in the scope of the claims and description of the present invention.

Claims

1. An electric field coupling wireless charging system for high frequency transmission, comprising a transmitter and a receiver, characterized in that: The transmitting end includes a grid power supply, an inverter, a primary resonant circuit and an emitter plate connected in sequence, and the receiving end includes a receiving plate, a secondary resonant circuit, a secondary rectifier and a load connected in sequence; the emitter plate and the receiving plate are coupled; The inverter is a class Φ2 series inverter, and the class Φ2 series inverter includes a first class Φ2 inverter and a second class Φ2 inverter connected in series with each other.

2. The electric field coupling wireless charging system for high frequency transmission according to claim 1, characterized in that: The first class Φ2 inverter includes a first voltage dividing capacitor C in1 , the first choke inductor L f1 , a first series resonant circuit, a first circuit switch tube S1 and a first shunt capacitor C2; The first voltage dividing capacitor C in1 One end of the first choke inductor L f1 One end of each is connected to one end of the grid power supply; The first choke inductor L f1 The other end is respectively connected to one end of the first series resonant circuit, one end of the first circuit switch S1, and one end of the first shunt capacitor C2, and serves as an output end of the class Φ2 series inverter; The first voltage dividing capacitor C in1 The other end is respectively connected to the other end of the first series resonant circuit, the other end of the first circuit switch tube S1, and the other end of the first shunt capacitor C2, and serves as the first class Φ2 inverter connection end connected to the second class Φ2 inverter.

3. The electric field coupling wireless charging system for high frequency transmission according to claim 2, characterized in that: The second class Φ2 inverter includes a second voltage dividing capacitor C in2 , the second choke inductor L f3 , a second series resonant circuit, a second circuit switch tube S2 and a second shunt capacitor C3; The second voltage dividing capacitor C in2 One end of the second choke inductor L f3 One end of each is connected to the first class Φ2 inverter connection end; The second choke inductor L f3 The other end is respectively connected to one end of the second series resonant circuit, one end of the second circuit switch tube S2, and one end of the second shunt capacitor C3, and serves as the other output end of the class Φ2 series inverter; The second voltage dividing capacitor C in2 The other end of the second series resonant circuit, the other end of the second circuit switch tube S2, and the other end of the second shunt capacitor C3 are respectively connected to the other end of the grid power supply.

4. The electric field coupling wireless charging system for high frequency transmission according to claim 3, characterized in that: The first series resonant circuit includes a first resonant capacitor C f2 and the first resonant inductor L f2 , the first resonant capacitor C f2 One end of the first resonant inductor L f2 and serves as a connection end of the first series resonant circuit; the first resonant inductor L f2 The other end of the first choke inductor L f1 Connection; the first resonant capacitor C f2 The other end of the first voltage divider capacitor C in1 connect; The second series resonant circuit includes a second resonant capacitor C f4 and the second resonant inductor L f4 , the second resonant capacitor C f4 One end of the second resonant inductor L f4 and serves as a connection end of the second series resonant circuit; the second resonant inductor L f4 The other end of the second choke inductor L f3 Connection; the second resonant capacitor C f4 The other end of the second voltage divider capacitor C in2 connect.

5. The electric field coupling wireless charging system for high frequency transmission according to claim 4, characterized in that: The present invention also includes a third series resonant circuit, which includes a third resonant capacitor C1 and a third resonant inductor L1; one end of the third resonant inductor L1 is connected to the connection end of the first series resonant circuit, and the other end is connected to one end of the third resonant capacitor C1, and the other end of the third resonant capacitor C1 is connected to the connection end of the second series resonant circuit.

6. The electric field coupling wireless charging system for high frequency transmission according to claim 1, characterized in that: The primary resonant circuit and the secondary resonant circuit are symmetrically arranged LC topology networks.

7. The electric field coupling wireless charging system for high frequency transmission according to claim 1 or 6, characterized in that: The compensation inductor in the secondary side resonant circuit is a flexible PCB inductor.

8. The electric field coupling wireless charging system for high frequency transmission according to claim 1, characterized in that: There are two groups of emitter plates and two groups of receiving plates; The two groups of emitter plates are respectively connected to the two output ends of the primary resonant circuit, the two groups of receiving plates are respectively connected to the two input ends of the secondary resonant circuit, and the two groups of emitter plates are respectively arranged opposite to the two groups of receiving plates.

9. The electric field coupling wireless charging system for high frequency transmission according to claim 1 or 8, characterized in that: The receiving plates are all cylindrical plates.

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