A megahertz Class E2 wireless power transfer system based on a series capacitor double resonant network

Abstract

This invention discloses a megahertz E2 class wireless power transfer system based on a series capacitor double resonant network. The invention constructs a design model for a series capacitor E2 class wireless power transfer system, its innovation lying in utilizing a third harmonic suppression network composed of a series capacitor and a parallel resonant network. When applied to drone wireless charging scenarios, it effectively reduces interference from the wireless power transfer system to the drone control system, as well as power device losses and temperature rise, thereby improving system efficiency. Simulations using ADS and PSIM demonstrate a significant reduction in third harmonic content compared to traditional series resonant networks. The simulated system efficiency curve shows a peak efficiency of 91%, effectively enhancing harmonic suppression and efficiency improvement. This provides a high-power-density, low-electromagnetic-interference solution for drone wireless charging, possessing significant engineering application value.

Description

Technical Field

[0001] This invention relates to the field of wireless power transmission technology, and more specifically to a megahertz E2 class wireless power transmission system based on a series capacitor double resonant network. Background Technology

[0002] With the increasing demand for contactless power supply from devices such as drones, portable electronic devices, implantable medical devices, and smart sensors, traditional wired power supply methods are gradually revealing problems such as inconvenient connection, contact wear, insulation aging, maintenance difficulties, and insufficient safety. Especially in application scenarios requiring high reliability, lightweight design, or continuous power supply during movement, traditional wired power supply methods are no longer sufficient to meet actual needs.

[0003] Wireless power transfer is a power supply method that can transfer energy without direct electrical contact using metal wires. Among these, magnetically coupled resonant wireless power transfer has become an important research direction in the field of wireless power supply due to its advantages such as relatively long transmission distance, high transmission efficiency, and strong adaptability. For megahertz-band wireless power transfer systems, the high-frequency power conversion unit on the transmitting side and the rectifier unit on the receiving side have a decisive impact on system efficiency, power density, and electromagnetic compatibility performance. Class E power amplifiers and Class E rectifiers are suitable for constructing megahertz Class E2 wireless power transfer systems due to their relatively simple structure, high operating frequency, and ease of soft switching.

[0004] However, existing research on wireless power transfer systems largely focuses on coil structure, coupling mechanism arrangement, offset tolerance improvement, or compensation parameter optimization, while research on the output network of the front-end Class E power amplifier and its harmonic suppression capabilities is relatively insufficient. Traditional Class E wireless power transfer systems typically employ a single series resonant network or a conventional load network. When operating in the megahertz frequency band, the system is prone to generating high-order harmonics, especially the third harmonic component, due to factors such as parasitic parameters of switching devices, resonant network parameter deviations, and changes in coupling state.

[0005] These higher harmonics not only propagate along the transmitting network and magnetic coupling mechanism, leading to enhanced electromagnetic interference, but also increase the voltage and current stress on power devices, causing additional switching losses and temperature rise, thus reducing the overall system efficiency and operational stability. In applications such as wireless charging for drones, strong harmonic components may also adversely affect flight control systems, communication modules, or other sensitive electronic units, thereby limiting the engineering application of the system.

[0006] Furthermore, existing megahertz E2 wireless power transfer systems often struggle to balance efficient fundamental frequency transmission, third harmonic suppression, and efficient rectification at the receiver, resulting in limitations in efficiency improvement, insufficient harmonic suppression, and poor electromagnetic compatibility under high-frequency operating conditions. Therefore, it is necessary to propose a novel megahertz E2 wireless power transfer system to effectively suppress third harmonic components and improve system transmission efficiency and operational stability. Summary of the Invention

[0007] The purpose of this invention is to address the above-mentioned deficiencies or improvement needs of existing technologies by providing a megahertz E2 class wireless power transfer system based on a series capacitor double resonant network. The aim is to solve the technical problems of existing megahertz band wireless power transfer systems, such as high high-order (especially third) harmonic content, increased voltage and current stress on power devices, additional switching losses and temperature rise, and easy to cause adverse electromagnetic interference to sensitive electronic units (such as UAV flight control systems), thereby leading to reduced overall system efficiency and unstable operation.

[0008] Technical Solution: To achieve the above objectives, the present invention provides a megahertz E2 class wireless power transmission system based on a series capacitor double resonant network. The system includes: a DC power supply, a transmitting-side E class power amplifier unit, a double resonant network, a coupling coil, a receiving-side E class rectifier unit, and a load.

[0009] The DC power supply is connected to the input terminal of the transmitting-side Class E power amplifier unit. The output terminal of the transmitting-side Class E power amplifier unit is connected to the coupling coil via the double resonant network. The output terminal of the coupling coil is connected to the input terminal of the receiving-side Class E rectifier unit. The output terminal of the receiving-side Class E rectifier unit is connected to the load.

[0010] Furthermore, the transmit-side Class E power amplifier unit includes an RF choke inductor RFC, a switch Q, and a parallel capacitor C1; one end of the switch Q and the parallel capacitor C1 is connected in parallel to the negative terminal of the DC power supply and then grounded together; one end of the RF choke inductor RFC is connected to the positive terminal of the DC power supply, and the other end is connected to the other end of the switch Q and the parallel capacitor C1.

[0011] Furthermore, the double resonant network consists of a parallel resonant capacitor Cs, a resonant inductor Ls, and a series resonant capacitor Co. The parallel resonant capacitor Cs and the resonant inductor Ls are connected in parallel to form a parallel resonant branch. One end of the parallel resonant capacitor Cs and the resonant inductor Ls is connected to the non-grounded end of the parallel capacitor C1, and the other end of the parallel resonant capacitor Cs and the resonant inductor Ls is connected to one end of the series resonant capacitor Co. The other end of the series resonant capacitor Co is connected to one end of the primary side of the coupling coil, and the other end of the primary side of the coupling coil is grounded.

[0012] Furthermore, the receiving-side Class E rectifier includes an input-side parallel inductor L1, a rectifier diode D1, a harmonic shaping capacitor C2, an output filter capacitor C3, and a load resistor R. The two ends of the input-side parallel inductor L1 are respectively connected to the two ends of the secondary side of the coupling coil, and one end is grounded. The rectifier diode D1 is connected in parallel with the harmonic shaping capacitor C2, and one end of the rectifier diode D1 and the harmonic shaping capacitor C2 is connected to the non-grounded end of the input-side parallel inductor L1. The output filter capacitor C3 is connected in parallel with the load R, and one end is grounded. The other end of the rectifier diode D1 and the harmonic shaping capacitor C2, and the output filter capacitor C3 are connected to the non-grounded end of the load R.

[0013] Furthermore, let the system's operating angular frequency be... The parallel resonant capacitor Cs and resonant inductor Ls satisfy the following at the third harmonic angular frequency: ;

[0014] The equivalent inductance of the parallel resonant branch at the fundamental frequency is Leq, and Leq satisfies the following relationship with the series capacitor Cb: .

[0015] Furthermore, the parallel capacitor The series resonant capacitor The load resistor , wherein Where R is the system operating angular frequency, Q is the load resistance, Pout is the quality factor, and Vcc is the DC power supply voltage.

[0016] Under the third harmonic, the condition for Cs and Ls to resonate in parallel is:

[0017] ;

[0018] At fundamental frequency, Cs and Ls are equivalent to Leq. It forms a series resonance with C0:

[0019] ;

[0020] Combining the above formulas, we get:

[0021] ;

[0022] ;

[0023] The final optimized resonant network parameters are as follows:

[0024] ;

[0025] ;

[0026] ;

[0027] In the case of the third harmonic, the parallel resonant capacitor Cs and the resonant inductor Ls are equivalent to an open circuit, so that they exist in the parallel resonant circuit in the form of circulating current and will not flow to the external circuit. In the case of the fundamental frequency, Cs and Ls are equivalent to the series resonant inductor Leq, which resonates in series with the series resonant capacitor C0, and are equivalent to a short circuit for the fundamental frequency.

[0028] Beneficial effects: Compared with the prior art, the technical solution of the present invention has the following beneficial technical effects:

[0029] (1) Effectively suppresses high-order harmonics and reduces system electromagnetic interference. This invention uses a double resonance mechanism composed of a series capacitor and a parallel resonant network to allow the third harmonic energy to circulate within the loop without flowing into the load, resulting in a significant reduction in the third harmonic content in the circuit compared to traditional single resonant networks. This structure can effectively reduce the interference of high-frequency wireless power transmission systems on peripheral equipment, providing a high standard of electromagnetic compatibility (EMC) protection for application scenarios (such as drone charging).

[0030] (2) Achieving soft switching and low heat loss significantly improves system transmission efficiency. Through optimized design of double resonant network and load network parameters, the switching transistors of the front-end Class E power amplifier can successfully achieve zero-voltage switching (ZVS) and zero-voltage derivative switching (ZVDS) at extremely high frequencies. The voltage across the switching transistor and the drain current exhibit ideal timing interleaving characteristics, and the waveform overlap area is significantly reduced compared to the traditional hard-switching mode, thereby greatly reducing the instantaneous power density and switching losses of power devices. The peak system additional efficiency (PAE) can reach 91%. Attached Figure Description

[0031] Figure 1 This is a diagram of a magnetically coupled resonant wireless power transfer system according to the present invention;

[0032] Figure 2 Figures showing the results from the double resonant network and the traditional resonant network are provided.

[0033] Figure 3 The simulation yields the voltage and current waveforms across the switching transistor.

[0034] Figure 4 The waveforms of the voltage and current across the load are shown.

[0035] Figure 5 To simulate additional efficiency curves;

[0036] Figure 6 The diagram shows the simulation analysis of the overall wireless power transfer system using PSIM. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0038] like Figure 1 As shown, this invention provides a megahertz Class E2 wireless power transfer system based on a series capacitor double resonant network. The system includes: a DC power supply, a transmitting-side Class E power amplifier unit, a double resonant network, a coupling coil, a receiving-side Class E rectifier unit, and a load. The DC power supply is connected to the input terminal of the transmitting-side Class E power amplifier unit, the output terminal of the transmitting-side Class E power amplifier unit is connected to the coupling coil via the double resonant network, the output terminal of the coupling coil is connected to the input terminal of the receiving-side Class E rectifier unit, and the output terminal of the receiving-side Class E rectifier unit is connected to the load.

[0039] Class E power amplifiers are widely used due to their simple construction and single switching element, which simplifies circuit design and facilitates precise control. Compared to inverter circuits, Class E power amplifiers can achieve higher operating frequencies. By selecting the parameters of the circuit components, the switching element can operate in a soft-switching state, which helps reduce losses during high-frequency switching and thus significantly improves the energy efficiency of Class E power amplifiers. Zero-voltage switching (ZVS) refers to the instant when the voltage across the collector or drain of a switching device is exactly zero at the moment it transitions from the off state to the on state. Zero-voltage derivative switching (ZVDS) goes a step further than ZVS, requiring that the derivative of the voltage (i.e., the rate of change of voltage) at the instant the switch is turned on is also zero. This means that the voltage is not only zero, but the voltage waveform at the moment of conduction is at an extreme point (such as a trough), and its change trend is gradual. Considering the above conditions, the following basic parameters are obtained for Class E power amplifiers: the parallel capacitor... The series resonant capacitor The load resistor , wherein Where R is the system operating angular frequency, Q is the load resistance, Pout is the quality factor, and Vcc is the DC power supply voltage.

[0040] To more effectively filter harmonics, this invention designs a double resonant network that achieves efficient fundamental frequency transmission and third harmonic suppression through a frequency-division resonant mechanism. At the fundamental frequency, the parallel-connected Cs and Ls are equivalent to inductive elements, with their equivalent inductance Leq and series capacitance C0 forming a series resonance, providing a low-impedance path for the fundamental frequency, while exhibiting high impedance for the third harmonic. In the case of the third harmonic, Cs and Ls must satisfy the parallel resonance condition, ensuring that the third harmonic energy circulates within the loop and does not flow into the load, further weakening the third harmonic of the system.

[0041] Analyzing the above problem using mathematical language reveals that it can be expressed as two resonance relationships. The condition for parallel resonance of Cs and Ls under the third harmonic is:

[0042] ;

[0043] At fundamental frequency, Cs and Ls are equivalent to Leq. It forms a series resonance with C0:

[0044] ;

[0045] Combining the above formulas, we get:

[0046] ;

[0047] ;

[0048] The final optimized resonant network parameters are as follows:

[0049] ;

[0050] ;

[0051] ;

[0052] In this circuit, Cs and Ls are parallel resonant capacitors. Under the third harmonic, their parallel resonance is equivalent to an open circuit, allowing them to exist as circulating current in the parallel resonant circuit without flowing to the external circuit. At the fundamental frequency, Cs and Ls are equivalent to a series resonant inductor Leq, resonating with the series resonant capacitor Co. This is equivalent to a short circuit for the fundamental frequency and a high impedance for higher harmonics, further reducing the impact of harmonics on the entire wireless power transmission system.

[0053] With E2 Taking a wireless power transfer system as an example, the circuit is simulated, with the following key parameters: the system operating frequency is 6.78MHz, Cb is 67.8pF, Cs is 8.475pF, and Ls is 7221.33nH. The third harmonic content of the optimized double resonant network is compared with that of the traditional resonant network, and the results are... Figure 2 Figure (a) shows the result of the double resonant network. Figure 2 Figure (b) shows the results for the conventional resonant network. It can be observed that the third harmonic content in the optimized circuit is significantly reduced compared to the third harmonic content in the conventional series resonant network.

[0054] Figure 3 To simulate the voltage and current waveforms across the switch, simulation results show that, through optimized resonant network parameter design, the voltage across the switch and the drain current exhibit ideal timing interleaving characteristics. This non-overlapping characteristic significantly reduces the instantaneous power density of the voltage-current product during switching operation, greatly reduces the waveform overlap area compared to traditional hard-switching modes, and brings the losses on the switch to near zero.

[0055] Figure 4 The voltage and current waveforms across the load are shown. Simulation results demonstrate that in the optimized resonant network system, the total harmonic distortion (THD) is very small, and the output voltage and current waveforms are well-formed sine waves, significantly superior to those of traditional series resonant networks. This characteristic also provides crucial assurance for harmonic compliance in subsequent applications.

[0056] To evaluate the overall energy efficiency performance of the system, Figure 5 To simulate the additional efficiency curve. As can be seen from the figure, the additional efficiency (PAE) is 91%, indicating that the Class E power amplifier has very little loss during energy conversion and maintains high efficiency.

[0057] Finally, PSIM was used to simulate and analyze the overall wireless power transfer system. The simulation results are as follows: Figure 6 The load waveform shows that the system has completed the work of inversion and rectification, and has achieved wireless power transmission very well.

[0058] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A megahertz E2 class wireless power transfer system based on a series-capacitance double-resonant network, characterized by, The system includes a DC power supply, a transmitting-side Class E power amplifier unit, a double resonant network, a coupling coil, a receiving-side Class E rectifier unit, and a load; The DC power supply is connected to the input terminal of the transmitting-side Class E power amplifier unit. The output terminal of the transmitting-side Class E power amplifier unit is connected to the input terminal of the coupling coil via the double resonant network. The output terminal of the coupling coil is connected to the input terminal of the receiving-side Class E rectifier unit. The output terminal of the receiving-side Class E rectifier unit is connected to the load.

2. The megahertz E-class 2 wireless power transfer system based on series-capacitor double-resonant network according to claim 1, characterized in that, The transmitting-side Class E power amplifier unit includes an RF choke inductor RFC, a switch Q, and a parallel capacitor C1; one end of the switch Q and the parallel capacitor C1 is connected in parallel to the negative terminal of the DC power supply and then grounded together; one end of the RF choke inductor RFC is connected to the positive terminal of the DC power supply, and the other end is connected to the other end of the switch Q and the parallel capacitor C1.

3. The megahertz E-class 2 wireless power transfer system based on series-capacitor double-resonant network according to claim 2, characterized in that, The double resonant network consists of a parallel resonant capacitor Cs, a resonant inductor Ls, and a series resonant capacitor C0. The parallel resonant capacitor Cs and the resonant inductor Ls are connected in parallel to form a parallel resonant branch. One end of the parallel resonant capacitor Cs and the resonant inductor Ls is connected to the non-grounded end of the parallel capacitor C1, and the other end of the parallel resonant capacitor Cs and the resonant inductor Ls is connected to one end of the series resonant capacitor C0. The other end of the series resonant capacitor C0 is connected to one end of the primary side of the coupling coil, and the other end of the primary side of the coupling coil is grounded.

4. The megahertz E-class 2 wireless power transfer system based on series-capacitor double-resonant network according to claim 3, characterized in that, The receiving-side Class E rectifier includes an input-side parallel inductor L1, a rectifier diode D1, a harmonic shaping capacitor C2, an output filter capacitor C3, and a load resistor R. The two ends of the input-side parallel inductor L1 are connected to the two ends of the secondary winding of the coupling coil, with one end grounded. The rectifier diode D1 is connected in parallel with the harmonic shaping capacitor C2, and one end of the rectifier diode D1 and the harmonic shaping capacitor C2 is connected to the non-grounded end of the input-side parallel inductor L1. The output filter capacitor C3 is connected in parallel with the load R, with one end grounded. The other end of the rectifier diode D1 and the harmonic shaping capacitor C2, and the output filter capacitor C3 are connected to the non-grounded end of the load R.

5. The megahertz E-class 2 wireless power transfer system based on series-capacitance double-resonant network according to claim 4, characterized in that, Let the system operating angular frequency be The parallel resonant capacitance Cs and resonant inductance Ls satisfy: at the third harmonic angular frequency. The parallel resonance branch has an equivalent inductance Leq at the fundamental frequency, and the Leq and the series capacitance Cb satisfy: .

6. A megahertz E2 class wireless power transfer system based on series capacitive double resonant network according to any one of claims 1-5, characterized in that, The parallel capacitor The series resonance capacitor The load resistance Wherein, the The R is a load resistance, the Q is a quality factor, the Pout is a system output power, and the Vcc is a direct current power supply voltage value. Under the third harmonic, the condition for Cs and Ls to resonate in parallel is: ； At fundamental, Cs and Ls are equivalent to Leq, In series resonance with Co: ； Combining the above formulas, we get: ； ； The final optimized resonant network parameters are as follows: ； ； ； In the case of the third harmonic, the parallel resonant capacitor Cs and the resonant inductor Ls are equivalent to an open circuit, so that they exist in the parallel resonant circuit in the form of circulating current and will not flow to the external circuit. In the case of the fundamental frequency, Cs and Ls are equivalent to the series resonant inductor Leq, which resonates in series with the series resonant capacitor C0, and are equivalent to a short circuit for the fundamental frequency.

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