Efficient wireless power transmission system based on class E power amplifier

Abstract

The invention discloses a high-efficiency wireless power transmission system based on an E-type power amplifier. The high-efficiency wireless power transmission system comprises a transmitting side main circuit, a transmitting side closed-loop feedback circuit, a receiving side main circuit, a receiving side closed-loop feedback circuit and a closed-loop feedback circuit between transmitting and receiving sides, the transmitting side main circuit is connected with the transmitting side closed-loop feedback circuit, the transmitting side main circuit is coupled with the receiving side main circuit through a magnetic field, and the receiving side main circuit is connected with the receiving side closed-loop feedback circuit and the transmitting and receiving side closed-loop feedback circuit. And the closed-loop feedback circuit between the transmitting side and the receiving side is connected with the transmitting side main circuit in a wireless mode. According to the invention, a three-closed-loop control structure is used, so that the wireless power transmission system formed by the E-type power amplifier has the functions of resisting coil position disturbance and load resistance disturbance at the same time, and has constant-voltage output capability at the same time.

Description

Technical Field

[0001] The invention relates to wireless power transmission technology, and in particular to a high-efficiency wireless power transmission system based on a class E power amplifier. Background Art

[0002] With the development of 5G and the Internet, personal portable electronic products have experienced explosive growth. Although wired power transmission technology has been quite mature and widely used in terms of efficiency, reliability and safety, it has the following defects in some application scenarios, which may cause inconvenience:

[0003] High installation and maintenance costs: When equipment needs to be frequently moved or reconfigured, cumbersome wiring is required. When cable damage and failure occur in traditional wired power supply methods, it is very difficult to locate and repair them, especially for cables buried underground or in walls. It is increasingly difficult to meet the needs of productivity development in terms of power supply safety and construction costs.

[0004] Safety hazards: Wired devices present a risk of electric shock, especially in wet environments. Overloaded or damaged cables can cause short circuits, which can cause fire.

[0005] Energy loss: Although high-voltage transmission can reduce losses, the losses during long-distance transmission cannot be ignored, especially in low-voltage or ordinary power transmission.

[0006] Therefore, people hope to find a wireless power transmission method to completely get rid of the constraints of traditional wired power supply methods. However, the existing wireless power transmission technology has certain disadvantages. When the relative positions of the transmitting coil and the receiving coil are slightly offset, the energy transmission efficiency may drop significantly; and when the system load changes, the existing wireless power transmission system often cannot effectively adjust the working state to adapt to the new load conditions, which will lead to energy waste and unstable output power. Therefore, it is urgent to introduce new technologies to improve the performance of wireless power transmission systems. Summary of the invention

[0007] Purpose of the invention: In view of the above problems, the purpose of the present invention is to provide a high-efficiency wireless power transmission system based on a Class E power amplifier, using a three-closed-loop control structure, so that the wireless power transmission system composed of the Class E power amplifier has the function of resisting coil position disturbance and load resistance disturbance, and at the same time has constant voltage output capability.

[0008] Technical solution: A high-efficiency wireless power transmission system based on a class E power amplifier of the present invention comprises: a transmitting side main circuit, a transmitting side closed-loop feedback circuit, a receiving side main circuit, a receiving side closed-loop feedback circuit and a closed-loop feedback circuit between the transmitting and receiving sides; the transmitting side main circuit is connected to the transmitting side closed-loop feedback circuit, the transmitting side main circuit and the receiving side main circuit are coupled through a magnetic field, the receiving side main circuit is respectively connected to the receiving side closed-loop feedback circuit and the transmitting and receiving side closed-loop feedback circuit, and the transmitting and receiving side closed-loop feedback circuit is connected to the transmitting side main circuit in a wireless manner;

[0009] The transmitting side closed-loop feedback circuit, the receiving side closed-loop feedback circuit and the closed-loop feedback circuit between the transmitting and receiving sides constitute three closed-loop feedbacks. The transmitting side closed-loop feedback circuit adjusts the duty cycle of the first switch tube in the transmitting side main circuit, the receiving side closed-loop feedback circuit adjusts the duty cycle of the third switch tube in the receiving side main circuit, and the closed-loop feedback circuit between the transmitting and receiving sides adjusts the duty cycle of the second switch tube in the transmitting side closed-loop feedback circuit.

[0010] Further, the transmitting side main circuit includes: a first DC / DC conversion circuit, a class E power amplifier and a first LC resonant circuit;

[0011] The output end of the first DC / DC conversion circuit is connected to the input end of the class E power amplifier, and the output end of the class E power amplifier is connected to the input end of the first LC resonance circuit.

[0012] Further, the class E power amplifier includes a choke inductor, a first switch tube, a first capacitor and a residual inductor, and the first LC resonant circuit includes a first inductor and a second capacitor;

[0013] Among them, one end of the choke inductor is connected to the output end of the first DC / DC conversion circuit, the other end of the choke inductor is respectively connected to the drain of the first switching tube, one end of the first capacitor and one end of the residual inductor, the source of the first switching tube is connected to the other end of the first capacitor, the other end of the residual inductor is connected to one end of the second capacitor, the other end of the second capacitor is connected to one end of the first inductor, the other end of the first inductor is connected to the source of the first switching tube, and the gate of the first switching tube is connected to the output end of the driving circuit.

[0014] Further, the transmitting side closed-loop feedback circuit includes: a signal detection coil, a voltage follower, an RC phase shift circuit and a comparator, the voltage follower includes a first resistor, a second resistor and a first operational amplifier, the RC phase shift circuit includes a third resistor and a third capacitor, and the comparator includes a fourth resistor, a fifth resistor and a second operational amplifier;

[0015] Among them, the signal detection coil is wound closely against the first inductor coil, one end of the signal detection coil is grounded, the other end of the signal detection coil is connected to one end of the first resistor, the other end of the first resistor is respectively connected to the same-direction input end of the first operational amplifier and one end of the second resistor, and the other end of the second resistor is grounded; the output end of the first operational amplifier is respectively connected to the reverse input end of the first operational amplifier and one end of the third resistor, the other end of the third resistor is respectively connected to one end of the third capacitor and one end of the fourth resistor, the other end of the third capacitor is grounded, the other end of the fourth resistor is respectively connected to the reverse input end of the second operational amplifier and one end of the fifth resistor, the other end of the fifth resistor is grounded, the same-direction input end of the second operational amplifier is grounded, the output end of the second operational amplifier is connected to one end of the sixth resistor through the first level converter, and the other end of the sixth resistor is connected to the input end of the first switch tube driving circuit.

[0016] Further, the receiving side main circuit includes: a second LC resonant circuit, a rectifier circuit and a second DC / DC conversion circuit, the second LC resonant circuit includes a second inductor and a fourth capacitor, and the second DC / DC conversion circuit includes a third switch tube;

[0017] The second inductor is coupled to the first inductor through a magnetic field, one end of the second inductor is connected to one end of the fourth capacitor, the other end of the second inductor and the other end of the fourth capacitor are connected to the input end of the rectifier circuit, the output end of the rectifier circuit is connected to the input end of the second DC / DC conversion circuit, and the output end of the second DC / DC conversion circuit is connected to the load resistor.

[0018] Further, the receiving side closed-loop feedback circuit includes: a voltage and current detection circuit, a square wave signal duty cycle calculator and a square wave generator;

[0019] The voltage and current detection circuit is connected to both ends of the load resistor, and sends the voltage detection value and the current detection value to the square wave signal duty cycle calculator. The square wave signal duty cycle calculator is used to calculate the duty cycle of the third switch tube, and then the square wave generator generates a switch tube control signal to control the duty cycle of the third switch tube.

[0020] Further, the closed-loop feedback circuit between the transmitting and receiving sides includes: a PID controller, a Bluetooth signal transmitting device, a Bluetooth signal receiving device and a square wave control signal generating device;

[0021] The input end of the PID controller is connected to the output end of the summer, the input end of the summer is connected to the voltage and current detection circuit, the output end of the PID controller is connected to the inverting input end of the third operational amplifier through a limiter, the output end of the third operational amplifier is connected to the Bluetooth signal transmitting device through a second level converter, the Bluetooth signal receiving device is connected to the input end of the square wave control signal generating device, and the output end of the square wave control signal generating device is connected to the driving circuit of the second switch tube.

[0022] Furthermore, the closed-loop feedback circuit at the receiving side adjusts the duty cycle of the third switch tube so that the equivalent input impedance R' of the second DC / DC conversion circuit is L Constant, thereby making the equivalent impedance R' of the circuit connected to the second LC resonant circuit L Constant;

[0023] The closed-loop feedback circuit on the transmitting side controls the current of the residual inductor branch in the class E power amplifier and the phase angle difference of the square wave waveform of the first switch tube to be constant at 212.5°, so that the wireless power transmission system has a coupling coefficient k between the primary and secondary coils. 12 When the following equation is satisfied:

[0024]

[0025] The operating frequency of the wireless power transmission system is:

[0026]

[0027] In the formula, parameter Γ2=(r2+R' L ') / (2L2), r2 is the line resistance at the receiving side, L2 is the second inductor in the second LC resonant circuit, R' L ' is the equivalent impedance of the second LC resonant circuit, ω0 represents the frequency of the second LC resonant circuit.

[0028] Furthermore, the relationship between the duty cycle D of the second switch tube and the voltage at the load resistor terminal is:

[0029]

[0030] Where V I is the input DC voltage of the second DC / DC conversion circuit, V o is the voltage across the load resistor.

[0031] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages:

[0032] 1. The present invention improves the anti-disturbance performance against the position change of the primary and secondary coils of the system. By adopting the constant phase angle difference closed-loop control on the transmitting side, the system can automatically adjust the operating frequency of the system as the relative position of the primary and secondary sides changes when the coupling coefficient requirement is met, so that the transmission efficiency and output power of the system remain stable;

[0033] 2. The present invention improves the anti-disturbance performance against changes in system load resistance. By adopting closed-loop control of the input impedance on the receiving side, the system can make the front-stage E-class power amplifier and the wireless power transmission part work in the best working state under any load impedance, thereby ensuring efficient and stable operation of the system.

[0034] 3. The present invention is based on the closed-loop feedback on the receiving side and the closed-loop feedback structure between the transmitting and receiving sides, so that the system output can show a constant voltage output characteristic to the outside, and when the load impedance changes, the output voltage of the system can be stabilized at a set value. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 The system schematic diagram of a high-efficiency wireless power transmission system based on a class E power amplifier;

[0036] Figure 2 It is a schematic diagram of the structure of a high-efficiency wireless power transmission system based on a class E power amplifier;

[0037] Figure 3 It is the topological structure diagram of the class E power amplifier;

[0038] Figure 4 This is a COMSOL simulation diagram of the wireless power transmission coil;

[0039] Figure 5 The output power varies with the operating frequency ω and the coil coupling coefficient k 12 The changing relationship curve diagram;

[0040] Figure 6 The transmission efficiency varies with the operating frequency ω and the coil coupling coefficient k 12 The changing relationship curve diagram;

[0041] Figure 7 It is the relationship curve between the operating frequency and the load resistance;

[0042] Figure 8 It is the curve diagram of the relationship between output voltage and load resistance;

[0043] Fig. 9 It is a curve diagram showing the relationship between the working frequency and the coupling coefficient between the primary and secondary coils;

[0044] Fig.10 It is the curve diagram of the relationship between the output voltage and the coupling coefficient of the primary and secondary coils;

[0045] Fig.11 This is the simulation waveform. DETAILED DESCRIPTION

[0046] In order to make the objectives, technical solutions and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments.

[0047] The structure diagram of a high-efficiency wireless power transmission system based on a class E power amplifier described in this embodiment is as follows: Figure 1 to Figure 2As shown, it includes: a transmitting side main circuit, a transmitting side closed-loop feedback circuit, a receiving side main circuit, a receiving side closed-loop feedback circuit and a closed-loop feedback circuit between the transmitting and receiving sides; the transmitting side main circuit is connected to the transmitting side closed-loop feedback circuit, the transmitting side main circuit and the receiving side main circuit are coupled through a magnetic field, the receiving side main circuit is respectively connected to the receiving side closed-loop feedback circuit and the transmitting and receiving side closed-loop feedback circuit, and the transmitting and receiving side closed-loop feedback circuit is connected to the transmitting side main circuit in a wireless manner;

[0048] The transmitting side closed-loop feedback circuit, the receiving side closed-loop feedback circuit and the closed-loop feedback circuit between the transmitting and receiving sides constitute three closed-loop feedbacks. The transmitting side closed-loop feedback circuit adjusts the duty cycle of the first switch tube in the transmitting side main circuit to form feedback adjustment 1. The receiving side closed-loop feedback circuit adjusts the duty cycle of the third switch tube in the receiving side main circuit to form feedback adjustment 2. The closed-loop feedback circuit between the transmitting and receiving sides adjusts the duty cycle of the second switch tube in the transmitting side closed-loop feedback circuit to form feedback adjustment 3, so that the wireless power transmission system has the ability to resist coil position disturbance, load resistance disturbance and constant voltage output.

[0049] The transmitting side main circuit includes: a first DC / DC conversion circuit, a class E power amplifier and a first LC resonant circuit;

[0050] The output end of the first DC / DC conversion circuit is connected to the input end of the class E power amplifier, and the output end of the class E power amplifier is connected to the input end of the first LC resonance circuit.

[0051] The first DC / DC conversion circuit can be composed of any switching power supply topology or linear power supply topology that supports output voltage regulation. In this example, a second switch tube D2 is provided in the first DC / DC conversion circuit, and the duty cycle of the second switch tube D2 is controlled and adjusted by a closed-loop feedback circuit between the transmitting and receiving sides. The first LC resonant circuit is composed of an inductor coil and a series capacitor. The series capacitor can be realized by using a single lumped parameter capacitor element or multiple lumped parameter elements dispersedly placed in the coil or directly using the parasitic capacitance parameters of the coil.

[0052] The class E power amplifier includes a choke inductor RFC, a first switch tube D1, a first capacitor C1 and a residual inductor L X , the first LC resonant circuit includes a first inductor L1 and a second capacitor C2;

[0053] One end of the choke inductor RFC is connected to the output end of the first DC / DC conversion circuit, and the other end of the choke inductor RFC is respectively connected to the drain of the first switch tube D1, one end of the first capacitor C1 and the residual inductor L X The source of the first switch tube D1 is connected to the other end of the first capacitor C1, and the residual inductance L XThe other end of is connected to one end of the second capacitor C2, the other end of the second capacitor C2 is connected to one end of the first inductor L1, the other end of the first inductor L1 is connected to the source of the first switch tube D1, and the gate of the first switch tube D1 is connected to the output end of the driving circuit.

[0054] In one example, the topology of a Class E power amplifier is as follows: Figure 3 As shown, I dc is the input current, i(t) and u(t) are the switch and capacitor C respectively. P The current and voltage of the parallel part are both time functions; i sw (t) and i c Through the switch and capacitor C P The current is a function of time; I rf cos(ωt) is the time function of the RF current, and the peak value of the RF current is the coefficient I rf .

[0055] The transmitting side closed-loop feedback circuit includes: a signal detection coil L3, a voltage follower, an RC phase shift circuit and a comparator, the voltage follower includes a first resistor R1, a second resistor R2 and a first operational amplifier A1, the RC phase shift circuit includes a third resistor R3 and a third capacitor C3, and the comparator includes a fourth resistor R4, a fifth resistor R5 and a second operational amplifier A2;

[0056] Among them, the signal detection coil L3 is wound closely to the inductor coil L1, one end of the signal detection coil L3 is grounded, the other end of the signal detection coil L3 is connected to one end of the first resistor R1, the other end of the first resistor R1 is respectively connected to the same-direction input end of the first operational amplifier A1 and one end of the second resistor R2, and the other end of the second resistor R2 is grounded; the output end of the first operational amplifier A1 is respectively connected to the reverse input end of the first operational amplifier A1 and one end of the third resistor R3, the other end of the third resistor R3 is respectively connected to one end of the third capacitor C3 and one end of the fourth resistor R4, the other end of the third capacitor C3 is grounded, the other end of the fourth resistor R4 is respectively connected to the reverse input end of the second operational amplifier A2 and one end of the fifth resistor R5, the other end of the fifth resistor R5 is grounded, the same-direction input end of the second operational amplifier A2 is grounded, the output end of the second operational amplifier A2 is connected to one end of the sixth resistor R6 through the first level converter K1, and the other end of the sixth resistor R6 is connected to the input end of the first switch tube D1 driving circuit.

[0057] The closed-loop feedback circuit on the transmitting side can be implemented by an analog circuit, but at the same time, the closed-loop feedback structure on the transmitting side can also be implemented by using a digital method, and both need to ensure that the phase angle difference of the ineffective power transmission system is 212.5°. The typical phase shift angle of the RC phase shift circuit is 212.5°. Depending on the type of signal collected by the signal detection coil, that is, current or voltage may be collected, the phase shift angle of the RC phase shift circuit needs to be increased or decreased by 90° on the typical phase shift angle.

[0058] The voltage-dividing resistors R1 and R2 are very large, and the detection coil L3 collects a voltage signal, which is 90° out of phase with the primary L1 loop current. Therefore, the phase shift angle that needs to be designed for the RC phase shift circuit is: 360°-212.5°-90°=57.5°.

[0059] The receiving side main circuit includes: a second LC resonant circuit, a rectifier circuit and a second DC / DC conversion circuit, the second LC resonant circuit includes a second inductor L2 and a fourth capacitor C4, and the second DC / DC conversion circuit includes a fifth capacitor C5, a third switch tube D3, a fourth inductor L4, a fourth switch tube D4 and a sixth capacitor C6;

[0060] The second inductor L2 is coupled to the first inductor L1 through a magnetic field, one end of the second inductor L2 is connected to one end of the fourth capacitor C4, the other end of the second inductor L2 and the other end of the fourth capacitor C4 are connected to the input end of the rectifier circuit, the output end of the rectifier circuit is connected to the input end of the second DC / DC conversion circuit, and the output end of the second DC / DC conversion circuit is connected to the load resistor R7.

[0061] The rectifier circuit can be implemented by any rectifier topology such as a half-bridge controlled rectifier topology, a full-bridge controlled rectifier topology, a full-bridge uncontrolled rectifier topology, etc. The second DC / DC conversion circuit takes a switching type DC / DC converter as an example, which is composed of a switching tube, a freewheeling diode, an inductor, and a filter capacitor, but the second DC / DC conversion circuit can be composed of any circuit topology that supports output level conversion.

[0062] The receiving side closed-loop feedback circuit includes: a voltage and current detection circuit, a square wave signal duty cycle calculator and a square wave generator;

[0063] The voltage and current detection circuit is connected to both ends of the load resistor R7, and sends the voltage detection value and the current detection value to the square wave signal duty cycle calculator. The square wave signal duty cycle calculator is used to calculate the duty cycle of the third switch tube D3, and then the square wave generator generates a switch tube control signal to control the duty cycle of the third switch tube D3.

[0064] The closed-loop feedback circuit on the receiving side can be implemented by an analog circuit, and can also be implemented by a digital method. The basic requirement is to ensure that the equivalent impedance of the circuit connected to the LC resonant circuit on the receiving side is constant.

[0065] One implementation of the primary and secondary closed-loop control structure is as follows:

[0066] The voltage sensor installed in the load resistance branch collects the load branch voltage signal and sends it to the DSP. In the DSP, the collected voltage signal is subtracted from the given signal to obtain an error signal.

[0067] The closed-loop feedback circuit between the transmitting and receiving sides includes: a PID controller, a Bluetooth signal transmitting device, a Bluetooth signal receiving device and a square wave control signal generating device;

[0068] The input end of the PID controller is connected to the output end of the summer, the input end of the summer is connected to the voltage and current detection circuit, the output end of the PID controller is connected to the inverting input end of the third operational amplifier A3 through a limiter, the output end of the third operational amplifier A3 is connected to the Bluetooth signal transmitting device through a second level converter K2, the Bluetooth signal receiving device is connected to the input end of the square wave control signal generating device, and the output end of the square wave control signal generating device is connected to the driving circuit of the second switch tube D2.

[0069] The Bluetooth signal transmitting device and the Bluetooth signal receiving device can communicate with each other using the 2.4GHz frequency band. The Bluetooth signal receiving device is located on the primary side and is connected to the input end of the square wave control signal generating device, and the output end of the square wave control signal generating device is connected to the switch tube driving circuit of the DC / DC converter on the primary side.

[0070] The three closed loops cooperate with each other to make the wireless power transmission system have the anti-disturbance characteristics of the primary and secondary coil positions, the anti-disturbance characteristics of the load impedance change, and the constant voltage output characteristics of the system. The closed-loop feedback circuit on the receiving side uses the impedance conversion characteristics of the DC / DC converter to detect the load impedance value connected to the converter in real time. The closed-loop feedback circuit on the receiving side adjusts the duty cycle of the third switch tube to make the equivalent input impedance R' of the second DC / DC conversion circuit L Constant, thereby making the equivalent impedance R' of the circuit connected to the second LC resonant circuit L 'Constant;

[0071] The equivalent impedance R' of the circuit connected to the LC resonator on the receiving side L On the basis of constant, the closed-loop feedback circuit on the transmitting side controls the current of the remaining inductor branch in the class E power amplifier and the phase angle difference of the square wave waveform of the first switch tube to be constant at 212.5°, so that the wireless power transmission system has a coupling coefficient k between the primary and secondary coils. 12 When the following equation is satisfied:

[0072]

[0073] The operating frequency of the wireless power transmission system is:

[0074]

[0075] In the formula, parameter Γ2=(r2+R' L ') / (2L2), r2 is the line resistance at the receiving side, L2 is the second inductor in the second LC resonant circuit, R' L ' is the equivalent impedance of the second LC resonant circuit, ω0 represents the frequency of the second LC resonant circuit.

[0076] Based on the closed-loop feedback circuit on the receiving side and the closed-loop feedback circuit on the transmitting side, the closed-loop feedback structure between the transmitting and receiving sides detects the voltage across the system load resistor and adjusts the output voltage of this link by adjusting the duty cycle of the switch tube in the DC / DC converter on the transmitting side, thereby achieving the purpose of controlling the voltage across the system load resistor. The relationship between the duty cycle D of the second switch tube and the voltage at the load resistor terminal is:

[0077]

[0078] Where V I is the input DC voltage of the DC / DC converter circuit on the transmitting side, V o is the voltage across the load resistor.

[0079] Taking the design of a wireless power transmission system with a coil axial distance disturbance of 0 to 10 cm and a load disturbance range of 5 to 15 Ω as an example, the design method of the parameters of each component in the main circuit of the wireless power transmission system is described in detail, including the following steps:

[0080] Step 1: If Figure 4 As shown in Figure 1, the wireless power transmission system is simulated using the multi-physics field simulation software COMSOL to obtain the self-inductance and mutual inductance of the primary and secondary coils, and to determine the number of turns, turn spacing, number of coil layers and other parameters of the coil. Since the relative position of the two coils can change during actual operation of the system, the simulation scenario needs to ensure that the two coils are weakly coupled and the structures and parameters of the two coils are exactly the same. The coil parameters are shown in Table 1, and the simulation results are shown in Table 2.

[0081] Table 1 Coil structure parameters

[0082] name Numeric describe w / mm 1.83 Wire diameter <![CDATA[r1 / cm]]> 7 Coil 1 Radius <![CDATA[r2 / A]]> 7 Coil 2 Radius <![CDATA[I1 / A]]> 1 Coil 1 Current <![CDATA[I2 / A]]> 0 Coil 2 Current d / m 0.15 Coil spacing zx 12 Number of longitudinal coils Zd / m 0.002 Longitudinal coil turn spacing rx 2 Number of coils in radial direction Rd / m 0.002 Coil turn moment in radial direction

[0083] Table 2 Simulation results

[0084] Mutual inductance between coils 1 and 2 (H) Coil inductance (H) <![CDATA[Coupling coefficient k 12 > 3.813894992861908E-6 1.2990372785850955E-4 0.029359396036855712

[0085] Step 2: Calculate the coupling coefficient k of the two coils based on the self-inductance and mutual inductance of the coils 12 , as shown below:

[0086]

[0087] Where L1 and L2 are the self-inductance of the primary and secondary coils, and M is the mutual inductance of the primary and secondary coils. The primary side corresponds to the transmitting side, and the secondary side corresponds to the receiving side.

[0088] Then determine the critical coupling coefficient k of the system operation c , we need to ensure k c Slightly smaller than k 12 , so that the system can work in the parity-time symmetric state, while limiting the operating frequency of the system to ensure the coverage of the system's near-field area.

[0089] Step 3: According to the selected critical coupling coefficient k c The size of the system is obtained by the natural resonant frequency ω0, and the calculation formula is as follows:

[0090]

[0091] In the formula, R L Represents the load resistance.

[0092] The size of the capacitor C in the primary or secondary resonator is calculated based on the system's natural resonant frequency ω0. The calculation formula is as follows:

[0093]

[0094] Where, L 1 / 2 Represents the inductance in the primary or secondary resonator.

[0095] Step 4: Calculate the residual inductance L in the Class E power amplifier topology b And the first capacitor C1, the calculation formula is as follows:

[0096]

[0097] Among them, the load resistance R L Take the midpoint value of the disturbance range as 10Ω. The calculated C1 value should be the total parallel capacitance between the drain and source of the switch tube, including the parasitic capacitance between the drain and source inside the switch tube.

[0098] Step 5: Determine the size of the choke inductor of the DC power supply branch in the Class E power amplifier. The value of the choke inductor should ensure that there is a sufficiently large impedance at the operating frequency to filter out the high-frequency current in the branch. Generally, an inductor with a larger inductance value is used as the choke inductor.

[0099] The values ​​of the parameters of each component in the system are shown in Table 3 below:

[0100] Table 3 Parameters of each component of the system

[0101] parameter Numeric <![CDATA[Power supply voltage U I / V]]> 70 <![CDATA[High-frequency choke coil L f / mH]]> 0.8 <![CDATA[Residual inductance L b / μH]]> 4.153842 <![CDATA[First capacitor C1 / nF]]> 6.617399 <![CDATA[Resonator capacitor C T , C R / nF]]> 1 <![CDATA[Resonant inductor L T , L R / μH]]> 129.904 <![CDATA[Load resistance R L / Ω]]> 5-15 Coil relative position l / cm 0-10 <![CDATA[Coil coupling coefficient k 12 > 0.03849-1

[0102] Figure 5 is the system output power with the coil coupling coefficient k 12 The relationship between the change of the system operating frequency ω and the system operating point of the magnetic coupling resonant wireless power transmission system under the three-closed-loop control structure is as follows: Figure 5 As shown by the black solid curve, Figure 5 It can be seen that the output power is the maximum output power point under the corresponding coupling coefficient.

[0103] Figure 6 The system transmission efficiency is given by the coil coupling coefficient k 12 And the relationship between the system operating frequency ω, the system is under the three-loop control structure, and its system operating point is as follows Figure 6 The black solid curve in the middle shows the transmission efficiency of the system on the entire working curve:

[0104]

[0105] In the formula, R L is the equivalent impedance of the subsequent circuit connected to the LC resonant circuit on the receiving side, R T , R R They are the equivalent series resistance of the primary and secondary LC resonant circuits respectively.

[0106] Depend on Figure 6 It can be seen that the transmission efficiency of the system remains unchanged throughout the entire working curve, and it has the anti-disturbance characteristic of output power to changes in load impedance.

[0107] In another example, a circuit simulation solution using simulation software PSIM is provided, and the simulation results are as follows: Figures 7 to 10 As shown, Figure 7 is the relationship curve between the operating frequency and the load resistance. Figure 8 is the relationship curve between output voltage and load resistance. Fig. 9 is the relationship curve between the working frequency and the coupling coefficient of the primary and secondary coils. Fig.10The curve of the output voltage changing with the coupling coefficient of the primary and secondary coils. It can be seen from the figure that when the system load changes from 5Ω to 15Ω, the error between the system's operating frequency and the theoretical frequency of parity time symmetry does not exceed 1%, and its output voltage remains unchanged, indicating that under the three-closed-loop control, the magnetic coupling resonant wireless power transmission topology can work at the parity time symmetry frequency, and the system's efficiency can be maintained at the same level as the working efficiency mentioned in the previous example and remain unchanged; similarly, when the coil coupling coefficient changes between 0.07698 and 0.7698, the error between the system's operating frequency and the theoretical frequency of parity time symmetry does not exceed 3%, and its output voltage remains unchanged, that is, the system can have the ability to adjust the relative position of the coil and the load resistance disturbance under the mutual cooperation of the three-closed-loop control system, and maintain the stability of the system's transmission efficiency and output voltage.

[0108] Select an arbitrary value within the load variation range and the coil coupling coefficient variation range to obtain the steady-state operating waveform of the system as follows: Fig.11 As shown in the figure, it can be seen that when the switch tube of the class E power amplifier in the system is turned on, the terminal voltage at both ends has basically dropped to 0V, that is, the approximate ZVS working condition of the class E power amplifier topology is achieved. From the system steady-state working waveform, it can be obtained that the stable operating frequency of the system is 458.21kHz. According to the calculation formula of the system operating frequency ω, the theoretical operating frequency of the system can be obtained to be 458.44kHz, that is, the magnetically coupled resonant wireless power transmission system approximately operates at the parity-time symmetric frequency.

Claims

1. A high-efficiency wireless power transmission system based on a class E power amplifier, characterized in that: include: A transmitting side main circuit, a transmitting side closed-loop feedback circuit, a receiving side main circuit, a receiving side closed-loop feedback circuit, and a closed-loop feedback circuit between the transmitting and receiving sides; the transmitting side main circuit is connected to the transmitting side closed-loop feedback circuit, the transmitting side main circuit and the receiving side main circuit are coupled through a magnetic field, the receiving side main circuit is respectively connected to the receiving side closed-loop feedback circuit and the transmitting and receiving side closed-loop feedback circuit, and the transmitting and receiving side closed-loop feedback circuit is connected to the transmitting side main circuit wirelessly; The transmitting side closed-loop feedback circuit, the receiving side closed-loop feedback circuit and the closed-loop feedback circuit between the transmitting and receiving sides constitute three closed-loop feedbacks. The transmitting side closed-loop feedback circuit adjusts the duty cycle of the first switch tube in the transmitting side main circuit, the receiving side closed-loop feedback circuit adjusts the duty cycle of the third switch tube in the receiving side main circuit, and the closed-loop feedback circuit between the transmitting and receiving sides adjusts the duty cycle of the second switch tube in the transmitting side closed-loop feedback circuit.

2. A high-efficiency wireless power transmission system based on a class E power amplifier according to claim 1, characterized in that: The transmitting side main circuit includes: a first DC / DC / conversion circuit, a class E power amplifier and a first LC resonant circuit; The output end of the first DC / DC conversion circuit is connected to the input end of the class E power amplifier, and the output end of the class E power amplifier is connected to the input end of the first LC resonance circuit.

3. A high-efficiency wireless power transmission system based on a class E power amplifier according to claim 2, characterized in that: The class E power amplifier includes a choke inductor, a first switch tube, a first capacitor and a residual inductor, and the first LC resonant circuit includes a first inductor and a second capacitor; Among them, one end of the choke inductor is connected to the output end of the first DC / DC conversion circuit, the other end of the choke inductor is respectively connected to the drain of the first switching tube, one end of the first capacitor and one end of the residual inductor, the source of the first switching tube is connected to the other end of the first capacitor, the other end of the residual inductor is connected to one end of the second capacitor, the other end of the second capacitor is connected to one end of the first inductor, the other end of the first inductor is connected to the source of the first switching tube, and the gate of the first switching tube is connected to the output end of the driving circuit.

4. The high-efficiency wireless power transmission system based on a class E power amplifier according to claim 3, characterized in that: The transmitting side closed-loop feedback circuit includes: a signal detection coil, a voltage follower, an RC phase shift circuit and a comparator, the voltage follower includes a first resistor, a second resistor and a first operational amplifier, the RC phase shift circuit includes a third resistor and a third capacitor, and the comparator includes a fourth resistor, a fifth resistor and a second operational amplifier; Among them, the signal detection coil is wound closely against the first inductor coil, one end of the signal detection coil is grounded, the other end of the signal detection coil is connected to one end of the first resistor, the other end of the first resistor is respectively connected to the same-direction input end of the first operational amplifier and one end of the second resistor, and the other end of the second resistor is grounded; the output end of the first operational amplifier is respectively connected to the reverse input end of the first operational amplifier and one end of the third resistor, the other end of the third resistor is respectively connected to one end of the third capacitor and one end of the fourth resistor, the other end of the third capacitor is grounded, the other end of the fourth resistor is respectively connected to the reverse input end of the second operational amplifier and one end of the fifth resistor, the other end of the fifth resistor is grounded, the same-direction input end of the second operational amplifier is grounded, the output end of the second operational amplifier is connected to one end of the sixth resistor through the first level converter, and the other end of the sixth resistor is connected to the input end of the first switch tube driving circuit.

5. The high-efficiency wireless power transmission system based on a class E power amplifier according to claim 4, characterized in that: The receiving side main circuit includes: a second LC resonant circuit, a rectifier circuit and a second DC / DC conversion circuit, the second LC resonant circuit includes a second inductor and a fourth capacitor, and the second DC / DC conversion circuit includes a third switch tube; The second inductor is coupled to the first inductor through a magnetic field, one end of the second inductor is connected to one end of the fourth capacitor, the other end of the second inductor and the other end of the fourth capacitor are connected to the input end of the rectifier circuit, the output end of the rectifier circuit is connected to the input end of the second DC / DC conversion circuit, and the output end of the second DC / DC conversion circuit is connected to the load resistor.

6. A high-efficiency wireless power transmission system based on a class E power amplifier according to claim 5, characterized in that: The receiving side closed-loop feedback circuit includes: a voltage and current detection circuit, a square wave signal duty cycle calculator and a square wave generator; The voltage and current detection circuit is connected to both ends of the load resistor, and sends the voltage detection value and the current detection value to the square wave signal duty cycle calculator. The square wave signal duty cycle calculator is used to calculate the duty cycle of the third switch tube, and then the square wave generator generates a switch tube control signal to control the duty cycle of the third switch tube.

7. A high-efficiency wireless power transmission system based on a class E power amplifier according to claim 6, characterized in that: The closed-loop feedback circuit between the transmitting and receiving sides includes: a PID controller, a Bluetooth signal transmitting device, a Bluetooth signal receiving device and a square wave control signal generating device; The input end of the PID controller is connected to the output end of the summer, the input end of the summer is connected to the voltage and current detection circuit, the output end of the PID controller is connected to the inverting input end of the third operational amplifier through a limiter, the output end of the third operational amplifier is connected to the Bluetooth signal transmitting device through a second level converter, the Bluetooth signal receiving device is connected to the input end of the square wave control signal generating device, and the output end of the square wave control signal generating device is connected to the driving circuit of the second switch tube.

8. The high-efficiency wireless power transmission system based on a class E power amplifier according to claim 7, characterized in that: The closed-loop feedback circuit on the receiving side adjusts the duty cycle of the third switch tube so that the equivalent input impedance R' of the second DC / DC conversion circuit L Constant, thereby making the equivalent impedance R' of the circuit connected to the second LC resonant circuit L Constant; The closed-loop feedback circuit on the transmitting side controls the current of the residual inductor branch in the class E power amplifier and the phase angle difference of the square wave waveform of the first switch tube to be constant at 212.5°, so that the wireless power transmission system has a coupling coefficient k between the primary and secondary coils. 12 When the following equation is satisfied: The operating frequency of the wireless power transmission system is: In the formula, parameter Γ2=(r2+R' L ') / (2L2), r2 is the line resistance at the receiving side, L2 is the second inductor in the second LC resonant circuit, R' L ' is the equivalent impedance of the second LC resonant circuit, ω0 represents the frequency of the second LC resonant circuit.

9. The high-efficiency wireless power transmission system based on a class E power amplifier according to claim 8, characterized in that: The relationship between the duty cycle D of the second switch tube and the voltage at the load resistance terminal is: Where V I is the input DC voltage of the second DC / DC conversion circuit, V o is the voltage across the load resistor.

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