Magnetic coupling wireless charging system based on parallel resonance E2 converter

Abstract

The invention provides a magnetic coupling wireless charging system based on a parallel resonance E2 converter, which belongs to the field of wireless charging and comprises a direct-current power supply, a parallel resonance E-type inverter, a wireless charging coil, a wireless charging coil S-LCC compensation structure, a parallel resonance E-type rectifier and a load resistor. All the parts are connected in sequence, and the wireless charging system outputs constant direct-current voltage through on-off of a switch S in the E-type inverter under the duty ratio D. According to the invention, constant-voltage wireless charging can be realized without a feedback and control loop.

Description

Technical Field

[0001] The present invention belongs to the field of wireless charging, and in particular relates to a method based on parallel resonance E 2 Magnetic coupling wireless charging system of the converter. Background Art

[0002] In recent years, with the rapid development of wireless charging technology, magnetically coupled wireless power transfer (WPT) systems have been widely used in many application scenarios, such as mobile devices, electric vehicles and other fields. This technology realizes non-contact energy transmission through magnetic field coupling, reducing the inconvenience caused by traditional wired charging. However, the existing wireless charging technology still faces some problems that need to be solved. For example, when the load changes, the output voltage and current of the system are difficult to maintain stability, and the system efficiency is affected. In addition, the use of complex feedback control and power correction modules also increases the design difficulty and cost of the system.

[0003] Existing Class E inverters are widely used in wireless power transmission systems due to their high efficiency and low loss. When the load fluctuates greatly, it is difficult for the Class E inverter to ensure a constant output current or voltage, resulting in a decrease in system efficiency and a negative impact on the stability of the output. In addition, the harmonic content on the rectifier side is high, which increases the complexity of the system design. In order to solve these problems, a variety of solutions including resonant compensation networks (such as S-LCC compensation) have been proposed in the prior art, but it is still difficult to meet the demand for efficient and stable output when the load changes. Summary of the invention

[0004] In order to overcome the shortcomings of the prior art, the present invention proposes a magnetic coupling wireless charging system based on a parallel resonant E² converter, which has the characteristics of simple structure and easy implementation, and can achieve constant voltage output without a feedback control loop. In addition, the rectifier side can be equivalent to a pure resistor, which significantly reduces the harmonic content in the system and improves the stability and efficiency of the system.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is: A parallel resonance E 2 The magnetic coupling wireless charging system of the converter includes: a parallel resonant E-class inverter and a parallel resonant E-class rectifier are symmetrical structures, and the two have time reversal duality; the parallel resonant E-class rectifier is a current-driven rectifier, and the impedance at the operating frequency is a pure resistance characteristic; the parallel resonant E-class inverter is load-independent and provides a constant current source output when the load changes; the S-LCC compensation structure compensates the wireless charging coil, and the input end of the parallel resonant E-class rectifier receives a constant current to ensure that the parallel resonant E-class rectifier outputs a constant DC voltage; the DC voltage source Vin It is converted into a sinusoidal current with a frequency of f through a parallel resonant Class E inverter and transmitted to the secondary side through the wireless charging coil; the rectifier on the secondary side converts the received sinusoidal current into direct current again; the transmitting side coil of the wireless charging coil is connected to the S compensation structure, and the receiving side coil is connected to the LCC compensation structure for energy transfer.

[0006] Furthermore, the parallel resonant class E rectifier includes a parallel resonant capacitor and an inductor L2-C2, a diode D, and a parallel capacitor C at both ends of the diode. D , rectifier input inductance L in2 And filter capacitor C f ; The two ends of the diode D and the parallel capacitor C of the diode D In parallel, one end is connected to the rectifier input inductor L in2 It is connected to the parallel resonant capacitor C2 and the inductor L2, and the other end is connected to the filter capacitor C f connected.

[0007] Furthermore, the S-LCC compensation structure includes a primary compensation capacitor C p , secondary compensation capacitor C s1 , secondary compensation capacitor C s2 , secondary side compensation inductor L c ; Primary compensation capacitor C p Connect in series with the primary side of the wireless charging coil and the secondary side compensation capacitor C s1的 One end is connected in series with the secondary side of the wireless charging coil, and the other end is connected in series with the secondary side compensation capacitor C s2 and the secondary compensation inductor L c connected.

[0008] Furthermore, when the power semiconductor switch S is switched, the DC power supply is converted into an AC current with a nearly sinusoidal waveform; when the power semiconductor switch S is turned on, the voltage across the switch is 0, achieving zero voltage conduction.

[0009] Furthermore, the parallel resonant capacitor and the inductor LC form a parallel resonant cavity that achieves complete resonance at the operating frequency, blocking the sine wave at the operating frequency f, thereby ensuring that a constant sinusoidal current passes through the wireless charging coil; after compensation by the S-LCC compensation structure, the constant sinusoidal current output by the inverter is transformed into a constant current source flowing into the parallel resonant Class E rectifier, and finally outputs a stable DC voltage.

[0010] Furthermore, the parallel capacitor C D for: ; Where D is the duty cycle of the rectifier diode; Assume that the resonant frequency ratio of the rectifier is q, the quality factor of the parallel resonant cavity is Q, f is the frequency of the system operation, and the angular frequency of the system operation is , the calculation method of the remaining parameters of the parallel resonant E-type rectifier is: , , , capacitor C2 is regarded as capacitor C X With capacitor C2-C X in parallel; ; The equivalent impedance of the parallel resonant class E rectifier and the load resistance R is , V0 is the constant DC voltage output by the rectifier, that is, the voltage obtained by the load resistor R.

[0011] Furthermore, the constant DC voltage V0 output by the rectifier is: ; Through the compensation of the S-LCC supplementary structure, the equivalent impedance of the rectifier and the load at both ends of the inverter is ; Where X is the inductive reactance of the secondary compensation inductor of the S-LCC compensation structure, , I1 is the amplitude of the sinusoidal current output by the parallel resonant class E inverter, and M is the mutual inductance of the wireless charging transmitting coil and the receiving coil.

[0012] Furthermore, the parallel capacitor C across the power semiconductor switch S S for: ; The calculation method for the remaining parameters of the parallel resonant class E inverter is: , , , capacitor C is regarded as capacitor C X2 With capacitor C2-C X2 in parallel: ; When the load resistance is R, the input resistance of the parallel resonant class E inverter is R eq2 .

[0013] The parallel resonant class E inverter of the present invention can achieve zero voltage switching (ZVS) and zero voltage derivative switching (ZVDS) operations under the optimal load resistance Ropt, and output a constant current when the load resistance range is [0, Ropt]. In the wireless power transmission (WPT) system, the inverter input impedance is the equivalent impedance formed by the wireless charging coil, the parallel resonant class E rectifier and the load resistor. Therefore, the class E parallel resonant inverter of the present invention can achieve the optimal working state (simultaneously achieving ZVS and ZVDS) under specific load conditions. When the system load changes, the inverter can still achieve a suboptimal working state, that is, maintain zero voltage switching (ZVS) operation under load changes, thereby ensuring the stability and efficiency of the system.

[0014] The beneficial effects of the present invention are: 1. In the present invention, when the system load changes, the receiving end of the wireless charging system can continuously obtain a constant output voltage, thereby ensuring the stability and reliability of the system under different load conditions.

[0015] 2. The wireless charging coil and the rectifier and load on the receiving side of the present invention can be equivalent to pure resistance, thereby minimizing the influence of the receiving end on the Class E inverter and ensuring the stable operation of the inverter and the optimization of system performance.

[0016] In summary, the power semiconductor devices in the Class E inverter of the present invention can realize zero voltage switching (ZVS) operation, effectively reduce system losses, ensure that the system operates in an efficient state, and further improve the overall energy efficiency of the wireless charging system. This technical solution not only simplifies the system design, but also fills the technical gap of the magnetic coupling wireless charging system based on the parallel resonant E² converter. The present invention can realize constant voltage wireless charging without the need for feedback and control loops. In addition, the rectifier side does not require a power correction module to be equivalent to a pure resistor, thereby significantly reducing the stability and efficiency of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The invention is a parallel resonance E 2 Schematic diagram of the magnetic coupling wireless charging system of the converter; Figure 2 The invention is a parallel resonance E 2 Topology diagram of the magnetically coupled wireless charging system of the converter; Figure 3 It is a simulation waveform diagram under the optimal load in the embodiment; Figure 4 It is a simulation waveform diagram under variable load in the embodiment. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in each embodiment of the present invention described below can be combined with each other as long as they do not conflict with each other. The present invention is further described below in conjunction with the accompanying drawings and specific embodiments.

[0019] The invention relates to a parallel resonance E 2 The magnetic coupling wireless charging system of the converter is as follows Figure 1 As shown, including DC power supply V in , parallel resonant class E inverter, S-LCC compensation structure, wireless charging coil and parallel resonant class E rectifier. The transmitting coil and receiving coil of the wireless charging coil are Figure 2 L P and L S , represents the inductance of the coil itself. C P is the series compensation capacitor on the primary side, C s1 , C s2 is the capacitance in the LCC compensation structure on the secondary side, L c is the inductance in the LCC compensation structure on the secondary side.

[0020] The parallel resonant E-type rectifier of the present invention is constructed as follows: a capacitor C is connected in parallel at both ends of a rectifier diode D. D , one end is connected to the rectifier input inductor L in2 The other end is connected to the parallel resonant cavity L2-C2, the load resistor R and the filter capacitor C f In parallel, one end is connected to the parallel resonant cavity L2-C2, and the other end is connected to L in2 The rectifier input current I in2 Constant, a constant output voltage is obtained across the load. By taking the derivative of the voltage across the diode with respect to time as 0 at the turn-on moment, the parallel capacitance C can be obtained. D The duty cycle of the rectifier diode is 50%.

[0021] ; Where D is the duty cycle of the rectifier diode; Set the rectifier resonant frequency ratio , the quality factor of the parallel resonant cavity f is the frequency of the system operation, the angular frequency of the system operation The calculation method of the remaining parameters of the parallel resonant class E rectifier can be obtained: , , , capacitor C2 can be regarded as capacitor CX With capacitor C2-C X in parallel.

[0022] ; The equivalent impedance of the parallel resonant class E rectifier and the load resistance R is , where V0 is the constant DC voltage output by the rectifier; The primary side L of the wireless charging coil P With series compensation capacitor C P Connected, secondary side L S It is connected to the LCC compensation structure, and the LCC compensation structure is connected to the E-class rectifier. Since the output of the parallel resonant E-class inverter is a constant current source, after the S-LCC compensation structure is compensated, the input voltage on the secondary side is , where M is the mutual inductance of the wireless charging transmitting coil and the receiving coil, and I1 is the amplitude of the sinusoidal current output by the parallel resonant class E inverter. Therefore, the input current of the class E rectifier is: , L c It is the secondary compensation inductor of the S-LCC compensation structure. After the coil is compensated, the constant current source is converted into a constant voltage source and then into a constant current source. The voltage obtained by the load resistor R is: .

[0023] Through the compensation of the S-LCC supplementary structure, the equivalent impedance of the rectifier and the load at both ends of the inverter is ; Where X is the inductive reactance of the secondary compensation inductor of the S-LCC compensation structure, .

[0024] The parallel resonant E-type inverter of the present invention is constructed as follows: the two ends of the power semiconductor S are connected to the capacitor C S , one end is connected to the input DC power supply V in The other end is connected to the parallel resonant tank LC. Input inductor L in One end is connected to the input DC power supply V in The positive pole of the parallel resonant cavity LC is connected to the other end. The output stage of the class E inverter is connected to the series S compensation structure of the primary side of the wireless charging coil. The resonant frequency ratio of the parallel resonant class E inverter is set to q=1.29, and the duty cycle of the power semiconductor S is 0.5. According to the working principle of the class E inverter, when the power semiconductor S is turned on, the voltage across its two ends is 0, and the derivative of the voltage across its two ends with respect to time is also 0. It can be concluded that the parallel capacitor C across the power semiconductor S S The values ​​are: ; The calculation method of the remaining parameters of the parallel resonant class E inverter is the same as that of the parallel resonant class E rectifier. , , , capacitor C can be regarded as capacitor C X2 With capacitor C2-C X2 in parallel.

[0025] ; When the load resistance is R, the input resistance of the parallel resonant class E inverter is R eq2 The input impedance of the inverter is inversely proportional to the equivalent load resistance on the rectifier side. Therefore, when the load resistance is increased from the optimal load resistance R opt When the input resistance of the inverter changes from 0 to the optimal load, the inverter can achieve constant current output, while the parallel resonant class E rectifier maintains a constant voltage output.

[0026] Example: In this embodiment, the operating frequency of the wireless charging system is set to 1 MHz, and the input DC voltage V in The voltage is 12V, the optimal load resistance of the system is 30Ω, and the resonant frequency ratio q is 1.29. The inductance of the transmitting and receiving sides of the wireless charging coil is 16.2μH, and the mutual inductance M is 2.375μH. Therefore, the coupling coefficient k of the wireless charging coil is 0.1466. The duty cycle of the power semiconductor S and the diode is 0.5, the output current of the class E inverter is set to 1A, and the output current of the class E rectifier is 0.7A. Based on the above parameters, the specific calculation of the system is as follows: The parameters of the parallel resonant class E rectifier are: ; , , .

[0027] The load resistance R of the wireless charging system is 30Ω, so the equivalent impedance of the class E rectifier and the load resistance is R eq It is 40.7246Ω. After S-LCC compensation, the equivalent impedance across the parallel resonant class E inverter is 20Ω.

[0028] The parameters of the parallel resonant class E inverter are: ; , , .

[0029] Based on the above parameters, a simulation system was built in the power electronics simulation software, and the simulation step size was set to 1×10 -9 Under the condition of optimal load resistance of 30Ω, the waveform of the simulation system is as follows Figure 3 As shown. From the simulation results, it can be seen that the theoretically calculated output voltage is 17.3V, and the simulated output voltage is 17.338V, with an error of about 2%. When the load resistance is 30Ω, the MOSFET on the inverter side realizes zero voltage switching (ZVS) and zero voltage derivative switching (ZVDS), and the diode realizes low dv / dt turn-off. The voltage V across the drain and source of the MOSFET is DS First increase and then decrease, when the load deviates from the optimal value, MOSFET can still achieve zero voltage switching (ZVS). As the load resistance increases, the input impedance of the inverter decreases, and the parallel resonant Class E inverter can achieve constant current output within the range of load resistance from 0 to the optimal resistance. Therefore, the present invention sets the working conditions of load resistances of 40Ω, 50Ω, 100Ω and 10kΩ respectively, and the output voltage waveform of the simulation system is as follows Figure 4 As shown. Figure 4 It can be seen that the voltage V across the drain and source of the MOSFET DS It increases first and then decreases, and realizes zero voltage turn-on (ZVS) at the turn-on time. r is the voltage across the inverter parallel resonant tank LC, which is a sine wave. When the resistance increases, V r It gradually decreases, verifying the proposed equivalent impedance formula of the parallel class E rectifier. i1 is the output current of the parallel class E inverter. When the load changes, the output sinusoidal current amplitude remains constant at about 1A. i2 is the input current of the parallel resonant class E rectifier. The input sinusoidal current amplitude is constant at about 0.7A. When the load of the wireless charging system changes from 30Ω to 100Ω, the output current of the inverter always remains constant at about 1A, and the input current of the class E rectifier is maintained at about 0.7A. The system output voltage changes from 17.3V to 17.7V, but the system can still maintain a constant voltage output.

Claims

1. A magnetic coupling wireless charging system, characterized in that: include: The parallel resonant class E inverter and the parallel resonant class E rectifier are symmetrical structures, and both have time reversal duality; The parallel resonant E-class rectifier is a current-driven rectifier, and its impedance at the operating frequency is a pure resistance characteristic; the parallel resonant E-class inverter is load-independent and provides a constant current source output when the load changes; the S-LCC compensation structure compensates the wireless charging coil, and the input end of the parallel resonant E-class rectifier receives a constant current, ensuring that the parallel resonant E-class rectifier outputs a constant DC voltage; the DC voltage source V in It is converted into a sinusoidal current with a frequency of f through a parallel resonant Class E inverter and transmitted to the secondary side through the wireless charging coil; the rectifier on the secondary side converts the received sinusoidal current into direct current again; the transmitting side coil of the wireless charging coil is connected to the S compensation structure, and the receiving side coil is connected to the LCC compensation structure for energy transfer.

2. A method based on parallel resonance E according to claim 1. 2 The magnetic coupling wireless charging system of the converter is characterized in that: The parallel resonant E-type rectifier includes a parallel resonant capacitor and an inductor L2-C2, a diode D, a parallel capacitor C D , rectifier input inductance L in2 And filter capacitor C f ;Diode D and parallel capacitor C D In parallel, one end is connected to the rectifier input inductor L in2 It is connected to the parallel resonant capacitor C2 and the inductor L2, and the other end is connected to the filter capacitor C f connected.

3. A method based on parallel resonance E according to claim 1. 2 The magnetic coupling wireless charging system of the converter is characterized in that: The S-LCC compensation structure includes a primary compensation capacitor C p , secondary compensation capacitor C s1 , secondary compensation capacitor C s2 , secondary side compensation inductor L c ; Primary compensation capacitor C p Connect in series with the primary side of the wireless charging coil and the secondary side compensation capacitor C s1 One end is connected in series with the secondary side of the wireless charging coil, and the other end is connected to the secondary side compensation capacitor C s2 and the secondary compensation inductor L c connected.

4. A method based on parallel resonance E according to claim 2 2 The magnetic coupling wireless charging system of the converter is characterized in that: When the power semiconductor switch S is switched, the DC power supply is converted into an AC current with a nearly sinusoidal waveform; when the power semiconductor switch S is turned on, the voltage across its two ends is 0, achieving zero voltage conduction.

5. A method based on parallel resonance E according to claim 2 2 The magnetic coupling wireless charging system of the converter is characterized in that: The parallel resonant capacitor and inductor LC form a parallel resonant cavity that achieves complete resonance at the operating frequency, blocking the sine wave at the operating frequency f, thereby ensuring that a constant sinusoidal current passes through the wireless charging coil; after compensation by the S-LCC compensation structure, the constant sinusoidal current output by the inverter is transformed into a constant current source flowing into the parallel resonant Class E rectifier, and finally outputs a stable DC voltage.

6. A method based on parallel resonance E according to claim 2 2 The magnetic coupling wireless charging system of the converter is characterized in that: Parallel capacitor C D for: ； Where D is the duty cycle of the rectifier diode; Assume that the resonant frequency ratio of the rectifier is q, the quality factor of the parallel resonant cavity is Q, f is the frequency of the system operation, and the angular frequency of the system operation is , the calculation method of the remaining parameters of the parallel resonant E-type rectifier is: , , , capacitor C2 is regarded as capacitor C X With capacitor C2-C X in parallel; ； The equivalent impedance of the parallel resonant class E rectifier and the load resistance R is , V0 is the constant DC voltage output by the rectifier, that is, the voltage obtained by the load resistor R.

7. A method based on parallel resonance E according to claim 6. 2 The magnetic coupling wireless charging system of the converter is characterized in that: The constant DC voltage V0 output by the rectifier is: ； Through the compensation of the S-LCC supplementary structure, the equivalent impedance of the rectifier and the load at both ends of the inverter is ; Where X is the inductive reactance of the secondary compensation inductor of the S-LCC compensation structure, , I1 is the amplitude of the sinusoidal current output by the parallel resonant class E inverter, and M is the mutual inductance of the wireless charging transmitting coil and the receiving coil.

8. A method based on parallel resonance E according to claim 6. 2 The magnetic coupling wireless charging system of the converter is characterized in that: The parallel capacitor C across the power semiconductor switch S S for: ； The calculation method for the remaining parameters of the parallel resonant class E inverter is: , , , capacitor C is regarded as capacitor C X2 With capacitor C2-C X2 in parallel: ； When the load resistance is R, the input resistance of the parallel resonant class E inverter is R eq2 .

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