Three-level and adjustable LCC resonant wireless charging system

Abstract

This invention discloses a three-level and adjustable LCC resonant network wireless charging system, including a ground unit and an on-board unit. The ground unit includes a three-level circuit, a ground adjustable LCC resonant network, and a ground transmitting unit, all sequentially coupled, as well as a ground control unit coupled to the three-level circuit and the ground adjustable LCC resonant network. The on-board unit includes an on-board receiving unit, an on-board adjustable LCC resonant network, a synchronous rectification circuit, and an on-board control unit coupled to the on-board adjustable LCC resonant network and the synchronous rectification circuit, all sequentially coupled. The ground / on-board adjustable LCC resonant network includes a variable capacitor whose capacitance is adjusted based on a power transistor. The ground / on-board control unit changes the capacitance of the variable capacitor by controlling the duty cycle of the power transistor, enabling the ground / on-board unit to operate in a magnetically coupled resonant state. This invention ensures efficient charging and reduces energy conversion losses for electric vehicles during magnetically coupled wireless charging, even under conditions of significant coil offset, input voltage, and load variations.

Description

Technical Field

[0001] This invention relates to the field of wireless charging, and more particularly to a three-level and adjustable LCC resonant wireless charging system. Background Technology

[0002] With increasingly severe energy and environmental issues, electric vehicles (EVs) have gained widespread acceptance and use due to their environmental and energy-saving advantages. Wireless charging systems for EVs, with their safety and convenience, are gradually attracting public attention. Enabling both the on-board and ground units of an EV wireless charging system to operate in a magnetically coupled resonant state is of practical significance for improving the system's anti-offset capability and wireless power transmission efficiency. Furthermore, when the input power supply to a wireless charging system is high-power, commonly used power transistors will burn out. Using power transistors that can withstand higher voltages results in lower current handling capacity. Using high-current power transistors would be 4-10 times more expensive than commonly used ones, making the cost too high and uncompetitive in the market. Moreover, commonly used circuits cannot achieve zero-voltage turn-on of the power transistors, subjecting them to significant voltage stress. Summary of the Invention

[0003] The purpose of this invention is to provide a three-level and adjustable LCC resonant wireless charging system. Based on changes in load, input voltage fluctuations, and the offset between the ground and vehicle-mounted coils, the system adjusts the parameters of the ground and vehicle-mounted compensation networks to achieve efficient magnetic coupling resonant charging. Furthermore, when the external input power supply is a high-power source, a voltage reduction and current multiplication function can be achieved through the three-level circuit, enabling zero-voltage turn-on of the power transistor and reducing voltage stress on the power transistor. The circuit used in this invention has low cost, good performance, and a simple control algorithm, making it of practical significance for the large-scale application of wireless charging systems.

[0004] This invention is achieved through the following technical solution:

[0005] A three-level and adjustable LCC resonant wireless charging system includes a ground unit and a vehicle-mounted unit. The ground unit includes a three-level circuit, a ground-adjustable LCC resonant network, and a ground transmitting unit, all sequentially coupled together, as well as a ground control unit coupled to the three-level circuit and the ground-adjustable LCC resonant network. The three-level circuit is used to connect to an external power source and perform voltage reduction and current multiplication on the external power source. The vehicle-mounted unit includes a vehicle-mounted receiving unit, a vehicle-mounted adjustable LCC resonant network, and a synchronous rectification circuit, all sequentially coupled together, as well as a vehicle-mounted control unit coupled to the vehicle-mounted adjustable LCC resonant network and the synchronous rectification circuit. The synchronous rectification circuit is used to couple the charging of the load battery. The ground / vehicle-mounted adjustable LCC resonant network includes at least one variable capacitor whose capacitance value is adjusted based on the power transistor. The ground control unit adjusts the capacitance value of the variable capacitor based on the changes in the external power supply, the voltage of the load battery, and the coil offset. The vehicle control unit adjusts the capacitance value of the variable capacitor based on the changes in the voltage of the load battery and the coil offset. The ground / vehicle-mounted unit adjusts the capacitance value of the variable capacitor by controlling the duty cycle of the power transistor of the ground / vehicle-mounted adjustable LCC resonant network, thereby making the ground / vehicle-mounted unit work in a magnetically coupled resonant state.

[0006] By adjusting the duty cycle of the power transistors in the vehicle-mounted adjustable LCC resonant network through the ground / vehicle control unit, and adjusting the capacitance value of the variable capacitor in the vehicle-mounted adjustable LCC resonant network, the capacitive reactance value is adjusted, so that the impedance of the ground / vehicle unit is matched, and the ground / vehicle unit operates in a magnetically coupled resonant state. The ground control unit adjusts the on and off of the power transistors in the three-level circuit. After the external power input passes through the three-level circuit, the output voltage is reduced by half and the output current is doubled. The phase shift angle of the three-level circuit can also be adjusted.

[0007] Furthermore, the ground-adjustable LCC resonant network includes an inductor Lp1, a capacitor Cp1, a variable capacitor Cp2, and power transistors Qp1 and Qp2. One end of the inductor Lp1 and one end of the capacitor Cp1 are coupled to one input terminal of the ground transmitting unit. The other end of the inductor Lp1 is coupled to one output terminal of the three-level circuit. The other end of the capacitor Cp1 is coupled to one end of the variable capacitor Cp2 and the drain of the power transistor Qp1. The other end of the variable capacitor Cp2 and the drain of the power transistor Qp2 are coupled to another output terminal of the three-level circuit and another input terminal of the ground transmitting unit. The sources of the power transistors Qp1 and Qp2 are coupled, and the gates of the power transistors Qp1 and Qp2 are coupled to the ground control unit.

[0008] The ground control unit adjusts the duty cycle of power transistors Qp1 and Qp2 based on the impedance changes caused by changes in coil offset distance, external power supply voltage fluctuations, and load changes. This adjusts the capacitance value of variable capacitor Cp2 to achieve impedance matching of the vehicle unit, enabling the ground unit to operate in a resonant state.

[0009] Furthermore, the vehicle-mounted adjustable LCC resonant network includes an inductor Ls1, a capacitor Cs1, a variable capacitor Cs2, and power transistors Qs1 and Qs2. One end of the inductor Ls1 and one end of the capacitor Cs1 are coupled to one output terminal of the vehicle-mounted receiving unit, and the other end of the inductor Ls1 is coupled to one input terminal of the synchronous rectification circuit. The other end of the capacitor Cs1 is coupled to one end of the variable capacitor Cs2 and the drain of the power transistor Qs1. The other end of the variable capacitor Cs2 and the drain of the power transistor Qs2 are coupled to another output terminal of the vehicle-mounted receiving unit and another input terminal of the synchronous rectification circuit. The sources of the power transistors Qs1 and Qs2 are coupled, and the gates of the power transistors Qs1 and Qs2 are used to couple to the vehicle-mounted control unit.

[0010] The vehicle control unit adjusts the duty cycle of power transistors Qs1 and Qs2 based on the impedance changes caused by the coil offset distance and load changes, thereby adjusting the capacitance value of variable capacitor Cs2 to achieve impedance matching of the vehicle unit and enable the vehicle unit to operate in a resonant state.

[0011] Furthermore, the ground transmitting unit includes a ground coil and a ground compensation network. The ground compensation network includes capacitors Cp3 and Cp4 connected in series across the ground coil. The ground control unit adjusts the capacitance value of Cs2 of the adjustable ground LCC resonant network, such that:

[0012]

[0013] Where ω = 2πf, f is the resonant frequency; ωLp1 is the impedance of the resonant inductor Lp1; ωLp is the impedance of capacitors Cp1 and Cp2 connected in series; ωLp is the impedance of the ground coil. The impedance of the ground coil is the impedance minus the impedance of capacitors Cp3 and Cp4 connected in series.

[0014] Furthermore, the vehicle-mounted receiving unit includes a vehicle-mounted coil and a vehicle-mounted compensation network. The vehicle-mounted compensation network includes capacitors Cs3 and Cs4 connected in series across the vehicle-mounted coil. The vehicle-mounted control unit adjusts the capacitive reactance of the vehicle-mounted adjustable LCC resonant network, such that:

[0015]

[0016] Where ω = 2πf, f is the resonant frequency; ωLs1 is the impedance of the resonant inductor Ls1; ωLs is the impedance of capacitors Cs1 and Cs2 connected in series; ωLs is the impedance of the on-board coil. Subtract the impedance of capacitors Cs3 and Cs4 in series from the impedance of the vehicle coil.

[0017] Furthermore, in the wireless charging system, the ground coil of the ground transmitter unit is made of multiple Litz wires connected in series or in parallel and wound in a circular or square insulating disk. The size of the ground coil can be adjusted according to different occasions, and different insulation materials can be selected for winding.

[0018] Furthermore, in the wireless charging system, the vehicle-mounted receiver unit's vehicle-mounted coil is made of multiple Litz wires connected in series or in parallel, wound around a circular or square insulating disk. The size of the vehicle-mounted coil can be adjusted according to different occasions, and different insulation materials can be selected for winding.

[0019] Furthermore, the three-level circuit in the wireless charging system includes power transistors Q1-Q4, capacitors C1-C4, capacitor Cs, diodes Df1-Df2, and capacitors Cd1-Cd2. Power transistors Q1-Q4 integrate diodes D1-D4. The drain of power transistor Q1, one end of capacitor C1, and one end of capacitor Cd1 are coupled to the positive terminal of an external power supply. The source of power transistor Q1, the drain of power transistor Q2, the other end of capacitor C1, one end of capacitor C2, and one end of capacitor Cs are coupled to the negative terminal of diode Df1. The source of power transistor Q2, the drain of power transistor Q3, the other end of capacitor C2, and one end of capacitor C3 are coupled to a ground-adjustable LCC resonant network. One input terminal has the source of power transistor Q3, the drain of power transistor Q4, the other end of capacitor C3, one end of capacitor C4, and the other end of capacitor Cs coupled to the positive terminal of diode Df2. The source of power transistor Q4, the other end of capacitor C4, and one end of capacitor Cd2 are coupled to the negative terminal of an external power supply. The other end of capacitor Cd1, the other end of capacitor Cd2, the positive terminal of diode Df1, and the negative terminal of diode Df2 are coupled to the other input terminal of a ground-adjustable LCC resonant network. The gates of power transistors Q1 to Q4 are coupled to a ground control unit. The ground control unit adjusts the phase shift angle, output voltage, and output current of the three-level circuit by adjusting the conduction and cutoff of power transistors Q1 to Q4.

[0020] Furthermore, in the three-level circuit of the wireless charging system, capacitors Cd1 and Cd2 are each composed of three electrolytic capacitors connected in parallel.

[0021] Furthermore, the synchronous rectification circuit in the wireless charging system includes power transistors Qs3 and Qs4, inductors Ls2 and Ls3, and capacitor Ce1. One end of inductor Ls2 and the drain of power transistor Qs3 are coupled to one output terminal of the vehicle-mounted adjustable LCC resonant network. The other end of inductor Ls2 is coupled to one end of inductor Ls3 and one end of capacitor Ce1 for coupling to the positive terminal of the load battery. The source of power transistor Qs3 is coupled to the source of power transistor Qs4 and the other end of capacitor Ce1 for coupling to the negative terminal of the load battery. The drain of power transistor Qs4 and the other end of inductor Ls3 are coupled to the other output terminal of the vehicle-mounted adjustable LCC resonant network. The gates of power transistors Q3 and Q4 are coupled to the vehicle-mounted control unit.

[0022] The present invention has the following technical advantages or beneficial effects:

[0023] In this scheme, the ground control unit adjusts the variable capacitor size by regulating the duty cycle of the power transistor in the adjustable LCC compensation network based on changes in load, coil offset, and input power fluctuations. This adjusts the impedance of the ground unit, enabling it to operate in a resonant state. Similarly, the vehicle-mounted control unit adjusts the capacitor size by regulating the duty cycle of the power transistor in the adjustable LCC resonant network based on impedance changes caused by coil offset and load variations. This adjusts the impedance of the vehicle-mounted unit, also enabling it to operate in a resonant state. The two units work together to achieve efficient magnetic coupling resonant charging for the entire wireless charging system, significantly reducing energy conversion losses. Furthermore, when the external input power supply is at a higher voltage, a three-level circuit can be used to implement a voltage reduction and current multiplication function and zero-voltage turn-on of the power transistor, reducing voltage stress on the power transistor. The circuit used in this invention is low-cost, high-performance, and has a simple control algorithm, making it practically significant for large-scale commercial applications of wireless charging systems. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the module composition and connection relationship of the present invention.

[0025] Figure 2 This is a circuit schematic diagram of an embodiment of the ground unit of the present invention.

[0026] Figure 3 This is a circuit schematic diagram of an embodiment of the vehicle-mounted unit of the present invention. Detailed Implementation

[0027] To facilitate a better understanding of the present invention by those skilled in the art, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The following are merely exemplary and do not limit the scope of protection of the present invention.

[0028] like Figure 1 As shown, the ground unit includes a three-level circuit, a ground-adjustable LCC resonant network ground transmitter unit, and ground control units coupled to the three-level circuit and the ground-adjustable LCC resonant network, respectively, in sequence. The vehicle-mounted unit includes a vehicle-mounted receiver unit, a vehicle-mounted adjustable LCC resonant network, a synchronous rectification circuit, and a vehicle-mounted control unit coupled to the synchronous rectification circuit and the vehicle-mounted adjustable LCC resonant network, respectively, in sequence. The ground transmitter unit includes a ground coil and a ground compensation network, and the vehicle-mounted receiver unit includes a vehicle-mounted coil and a vehicle-mounted compensation network. Energy transfer between the ground coil and the vehicle-mounted coil is achieved using the principle of magnetic coupling resonance.

[0029] The input of the three-level circuit is coupled to an external DC power supply. The ground control unit controls the switching on and off of the power transistors in the three-level circuit, converting the DC voltage into a periodically changing square wave voltage. Under the excitation of the square wave voltage, the ground transmitting unit generates an approximately sinusoidal current, reducing the output voltage by half and doubling the output current. The ground control unit controls the duty cycle of the power transistors in the adjustable LCC compensation network, adjusting the impedance in the adjustable LCC compensation network to achieve impedance matching of the ground unit. The current forms a high-frequency resonant current, which generates an alternating electromagnetic field. The vehicle-mounted receiving unit senses a high-frequency AC voltage, and energy is transferred from the ground end to the vehicle end. Under the excitation of the high-frequency AC voltage, the vehicle-mounted receiving unit generates a high-frequency current. The vehicle control unit controls the duty cycle of the power transistors in the adjustable LCC compensation network, adjusting the impedance in the adjustable LCC compensation network to achieve impedance matching of the vehicle unit, forming a high-frequency resonant current. The current is converted into DC power through a synchronous rectifier circuit to charge the electric vehicle battery.

[0030] The following is in conjunction with the appendix Figure 2 and attached Figure 3 The specific embodiments shown provide a further detailed description of the ground and vehicle-mounted LCC resonant parameter adjustable wireless charging system of the present invention.

[0031] The three-level circuit in this embodiment includes power transistors Q1-Q4, capacitors C1-C4, capacitor Cs, diodes Df1-Df2, and capacitors Cd1-Cd2, each consisting of three filter capacitors connected in parallel. Power transistors Q1-Q4 integrate diodes D1-D4. The drain of power transistor Q1, one end of capacitor C1, and one end of capacitor Cd1 are coupled to the positive terminal of an external power supply. The source of power transistor Q1, the drain of power transistor Q2, the other end of capacitor C1, one end of capacitor C2, and one end of capacitor Cs are coupled to the negative terminal of diode Df1. The source of power transistor Q2, the drain of power transistor Q3, the other end of capacitor C2, and one end of capacitor C3 are coupled to a ground-adjustable LCC resonant circuit. One input terminal of the network has the source of power transistor Q3, the drain of power transistor Q4, the other end of capacitor C3, one end of capacitor C4, and the other end of capacitor Cs coupled to the positive terminal of diode Df2. The source of power transistor Q4, the other end of capacitor C4, and one end of capacitor Cd2 are coupled to the negative terminal of an external power supply. The other end of capacitor Cd1, the other end of capacitor Cd2, the positive terminal of diode Df1, and the negative terminal of diode Df2 are coupled to the other input terminal of the ground-adjustable LCC resonant network. The gates of power transistors Q1 to Q4 are coupled to a ground control unit. The ground control unit adjusts the phase shift angle, output voltage, and output current of the three-level circuit by adjusting the conduction and cutoff of power transistors Q1 to Q4. Preferably, in this embodiment, power transistors Q1, Q2, Q3, and Q4 are NTHL065N65S3F, capacitors C1, C2, C3, and C4 are absorption capacitors of 1uF / 630V, capacitor CS is 1uF / 630V, diodes Df1 to Df2 are STTH30ACS06W, and capacitors Cd1 to Cd2 are 560uF / 450V.

[0032] In this embodiment, the ground-adjustable LCC resonant network includes an inductor Lp1, capacitors Cp1 and Cp2, and power transistors Qp1 and Qp2. One end of the inductor Lp1 is coupled to the source of power transistor Q2 and the drain of power transistor Q3 in the three-level circuit. The other end of the inductor Lp1 is coupled to one end of capacitor Cp1 and one end of Cp3 in the ground transmitting unit. The other end of capacitor Cp1 is coupled to one end of capacitor Cp2 and the drain of power transistor Qp1. The other end of capacitor Cp2 is coupled to the drain of power transistor Qp2, one end of capacitor Cp4 in the ground transmitting unit, and the diode in the three-level circuit. The cathode of Df2 is coupled to the anode of the three-level circuit diode Df1, and the sources of power transistors Qp1 and Qp2 are coupled. The gates of power transistors Qp1 and Qp2 are used to couple to the ground control unit. The ground-adjustable LCC resonant network adjusts the duty cycle of power transistors Qp1 and Qp2 through the ground control unit according to changes in output load, coil offset distance, and fluctuations in external input power, controlling their conduction time and indirectly adjusting the capacitance value of capacitor Cp2. This ensures that inductor Lp1 and capacitors Cp1 and Cp2 resonate in the optimal state, maximizing the inductive reactance ωLp1 and capacitive reactance in the circuit. Equal. Preferably, in this embodiment, power transistors Qp1 and Qp2 are SPW55N80C3FKSA1, the inductor Lp1 of the ground-adjustable LCC resonant network is 20uH, the capacitor Cp1 is 390nF, and the adjustable capacitor Cp2 is 330nF.

[0033] In this embodiment, the ground transmitting unit includes a ground compensation network and a ground coil. The ground compensation network includes capacitors Cp3 and Cp4. One end of capacitor Cp3 is coupled to one end of the ground coil Lp, and the other end of Lp is coupled to one end of capacitor Cp4. The other end of capacitor Cp3 is coupled to one end of the inductor Lp1 of the ground LCC resonant network, and the other end of capacitor Cp4 is coupled to one end of capacitor Cp2 of the ground LCC resonant network. Capacitors Cp3 and Cp4 are connected in series with the ground coil Lp to form a series compensation network, used to compensate for the impedance of the ground coil Lp changed by load variations. Preferably, in this embodiment, capacitors Cp3 and Cp4 are 100nF, and the inductance of the ground coil Lp is 47uH. To ensure that the resonant impedances of the ground units are equal, the following conditions must be met:

[0034] As a preferred embodiment, the ground coil is made of multiple strands of Litz wire connected in series or in parallel and wound in a circular or square insulating disk. The size of the ground coil is adjusted according to different occasions, and different insulation materials are selected for winding.

[0035] In this embodiment, the vehicle-mounted receiving unit includes a vehicle-mounted compensation network and a vehicle-mounted coil. The vehicle-mounted compensation network includes capacitors Cs3 and Cs4. One end of capacitor Cs3 is coupled to one end of the vehicle-mounted coil Ls, and the other end of inductor Ls is coupled to one end of capacitor Cs4. The other end of capacitor Cs3 is coupled to one end of inductor Ls1 of the vehicle-mounted LCC resonant network, and the other end of capacitor Cs4 is coupled to one end of capacitor Cs2 of the ground LCC resonant network. Capacitors Cs3 and Cs4 are connected in series with the vehicle-mounted coil Ls to form a series compensation network, used to compensate for the changed impedance of the vehicle-mounted coil Lp when the load changes. Preferably, in this embodiment, capacitors Cs3 and Cs4 are 47nF, and the inductance of the vehicle-mounted coil Ls is 120uH.

[0036] As a preferred embodiment, the vehicle-mounted coil is made of multiple strands of Litz wire connected in series or in parallel and wound in a circular or square insulating disk. The size of the vehicle-mounted coil is adjusted according to different occasions, and different insulation materials are selected for winding.

[0037] The vehicle-mounted adjustable LCC resonant network in this embodiment includes inductors Ls1, capacitors Cs1 and Cs2, and power transistors Qs1 and Qs2. One end of inductor Ls1 is coupled to capacitor Cs3 and one end of capacitor Cs1 in the vehicle-mounted receiving unit. The other end of inductor Ls1 is coupled to one end of inductor Ls2 in the synchronous rectifier circuit and the drain of power transistor Qs3. The other end of capacitor Cs1 is coupled to the drain of power transistor Qs1 and one end of capacitor Cs2. The source of power transistor Qs1 is connected to the source of power transistor Qs2. The other end of capacitor Cs2 and the drain of power transistor Qs2 are coupled to capacitor Cs4 in the vehicle-mounted compensation network and one end of Ls3 in the synchronous rectifier circuit. The gates of power transistors Qs1 and Qs2 are coupled to the vehicle-mounted control unit. When the load of the vehicle-mounted unit changes, the duty cycle of power transistors Qs1 and Qs2 is adjusted by the vehicle-mounted control unit to control the conduction time, thereby indirectly adjusting the capacitance value of capacitor Cs2. To make the resonant impedances in the circuit equal, that is Preferably, in this embodiment, power transistors Qs1 and Qs2 are SPW55N80C3FKSA1, and the inductor Ls1 of the on-board adjustable LCC resonant network is 10uH, the capacitor Cs1 is 680nF, and the capacitor Cs2 is 470nF.

[0038] The synchronous rectification circuit in this embodiment includes power transistors Qs3 and Qs4, energy storage inductors Ls2 and Ls3, and capacitor Ce1. The duty cycle of power transistors Qs3 and Qs4 is adjusted by the vehicle control unit, and the energy storage inductors Ls2 and Ls3 and capacitor Ce1 are used for filtering, outputting DC power to charge the load battery B1. Preferably, in this embodiment, power transistors Qs3 and Qs4 are IPW65R045C7, inductors Ls2 and Ls3 are 220uH, and the filter capacitor Ce1 consists of six 470uH / 500V capacitors connected in parallel.

[0039] The fixed frequency for wireless charging of electric vehicles is 85kHz. Both the ground coil and the vehicle-mounted coil have a fixed resonant frequency of 85kHz. When the electric vehicle's lithium battery has a low charge, the charging current is high. The ground / vehicle control unit adjusts the duty cycle of the adjustable LCC resonant network, increasing the variable capacitance and thus increasing the output power of the ground / vehicle unit. When the electric vehicle's lithium battery is fully charged, the required charging current is very low. The ground / vehicle control unit adjusts the duty cycle of the adjustable LCC resonant network, decreasing the variable capacitance and thus reducing the output power of the ground / vehicle unit. The load changes during the electric vehicle battery charging process. Whether the battery is low or fully charged, the ground / vehicle unit operates in resonance, maintaining high transmission efficiency for the wireless charging system. When the external input power is a high-power source, the ground control unit controls the three-level circuit power transistor to adjust the phase shift angle, halving the output voltage and doubling the output current. It can also achieve zero-voltage turn-on of the power transistor, reducing voltage stress on the power transistor.

[0040] Let the direction of the electric car's forward and backward movement be the X-axis, the direction of the electric car's left and right translation be the Y-axis, and the direction perpendicular to the X-axis and Y-axis be the Z-axis.

[0041] As one embodiment, when the offset between the ground coil and the vehicle coil is 0mm in the X and Y axis directions and 150mm in the Z axis direction, and the DC voltage for charging the electric vehicle battery is 390V, the energy transmission efficiency is approximately 92% according to laboratory test results.

[0042] As another embodiment, when the offset between the ground coil and the vehicle coil is 0mm in the X and Y axes and 210mm in the Z axis, and the DC voltage for charging the electric vehicle battery is 420V, the ground / vehicle control unit adjusts the duty cycle of the power transistors of the ground / vehicle adjustable LCC resonant network according to the changes in coil offset distance and charging load, so that both the ground unit and the vehicle unit are in a magnetically coupled resonant state. According to laboratory test results, the energy transmission efficiency is approximately 91%.

[0043] The data above shows that, even with increased offset distance, fluctuating external input voltage, and significant load changes, the wireless charging system in this embodiment maintains efficient magnetic coupling resonance charging and reduces energy conversion losses by adjusting the capacitance value of the adjustable LCC resonant network on the ground / vehicle side. This is achieved by ensuring the ground / vehicle unit operates in an impedance-matched resonant state. When using a high-power external power supply, the three-level circuit of the wireless charging system in this embodiment can halve the output voltage and double the output current, achieving zero-voltage turn-on of the power transistor and reducing voltage stress on the power transistor. The circuit used in this invention is low-cost, high-performance, and has a simple control algorithm, enabling large-scale application.

[0044] The above description of the embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A three-level and adjustable LCC resonant wireless charging system, characterized in that: The system includes a ground unit and a vehicle-mounted unit. The ground unit comprises a three-level circuit, a ground-adjustable LCC resonant network, and a ground transmitting unit, sequentially coupled together, and a ground control unit coupled to the three-level circuit and the ground-adjustable LCC resonant network. The three-level circuit is used to couple to an external power supply and perform voltage reduction and current multiplication conversion on the external power supply. The vehicle-mounted unit comprises a vehicle-mounted receiving unit, a vehicle-mounted adjustable LCC resonant network, and a synchronous rectification circuit, sequentially coupled together, and a vehicle-mounted control unit coupled to the vehicle-mounted adjustable LCC resonant network and the synchronous rectification circuit. The synchronous rectification circuit is used to... The ground / vehicle-mounted adjustable LCC resonant network includes at least one variable capacitor whose capacitance is adjusted based on a power transistor. The ground / vehicle-mounted control unit changes the capacitance of the variable capacitor by controlling the duty cycle of the power transistor of the ground / vehicle-mounted adjustable LCC resonant network based on parameter changes during the charging process, thereby adjusting the capacitive reactance of the ground / vehicle-mounted adjustable LCC resonant network so that the ground / vehicle-mounted unit operates in a magnetically coupled resonant state. The parameter changes during the charging process include changes in the external power supply, the voltage of the load battery, and / or the coil offset. The ground control unit controls the power transistor of the three-level circuit to adjust the phase shift angle of the three-level circuit; The ground-adjustable LCC resonant network includes an inductor Lp1, a capacitor Cp1, a variable capacitor Cp2, and power transistors Qp1 and Qp2. One end of the inductor Lp1 and one end of the capacitor Cp1 are coupled to one input terminal of the ground transmitting unit. The other end of the inductor Lp1 is coupled to one output terminal of the three-level circuit. The other end of the capacitor Cp1 is coupled to one end of the variable capacitor Cp2 and the drain of the power transistor Qp1. The other end of the variable capacitor Cp2 and the drain of the power transistor Qp2 are coupled to another output terminal of the three-level circuit and another input terminal of the ground transmitting unit. The sources of the power transistors Qp1 and Qp2 are coupled, and the gates of the power transistors Qp1 and Qp2 are coupled to the ground control unit. The vehicle-mounted adjustable LCC resonant network includes an inductor Ls1, a capacitor Cs1, a variable capacitor Cs2, and power transistors Qs1 and Qs2. One end of the inductor Ls1 and one end of the capacitor Cs1 are coupled to one output terminal of the vehicle-mounted receiving unit, and the other end of the inductor Ls1 is coupled to one input terminal of the synchronous rectification circuit. The other end of the capacitor Cs1 is coupled to one end of the variable capacitor Cs2 and the drain of the power transistor Qs1. The other end of the variable capacitor Cs2 and the drain of the power transistor Qs2 are coupled to another output terminal of the vehicle-mounted receiving unit and another input terminal of the synchronous rectification circuit. The sources of the power transistors Qs1 and Qs2 are coupled, and the gates of the power transistors Qs1 and Qs2 are coupled to the vehicle-mounted control unit. The ground transmitting unit includes a ground coil and a ground compensation network, wherein the ground compensation network includes capacitors Cp3 and Cp4 connected in series across the two ends of the ground coil; The vehicle-mounted receiving unit includes a vehicle-mounted coil and a vehicle-mounted compensation network. The vehicle-mounted compensation network includes capacitors Cs3 and Cs4 connected in series across the two ends of the vehicle-mounted coil. Both the ground coil and the vehicle-mounted coil are made of multiple strands of Litz wire connected in series or in parallel, wound around a circular or square insulating disc, and their size is adjusted according to different occasions, and different insulation materials are selected for winding.

2. The wireless charging system according to claim 1, characterized in that: The ground control unit adjusts the capacitive reactance of the adjustable LCC resonant network based on changes in the voltage of the external power supply, the voltage of the load battery, and the coil offset, so that: ； Where ω = 2πf, f is the resonant frequency; ωLp1 is the impedance of inductor Lp1; ωLp is the impedance of capacitors Cp1 and Cp2 connected in series; ωLp is the impedance of the ground coil. The impedance of the ground coil is the impedance minus the impedance of capacitors Cp3 and Cp4 connected in series.

3. The wireless charging system according to claim 1, characterized in that: The on-board control unit adjusts the capacitive reactance of the on-board adjustable LCC resonant network based on the voltage change of the load battery, so that: ； Where ω = 2πf, f is the resonant frequency; ωLs1 is the impedance of inductor Ls1; ωLs is the impedance of capacitors Cs1 and Cs2 connected in series; ωLs is the impedance of the on-board coil. Subtract the impedance of capacitors Cs3 and Cs4 in series from the impedance of the vehicle coil.

4. The wireless charging system according to any one of claims 1-3, characterized in that: The three-level circuit includes power transistors Q1-Q4, capacitors C1-C4, capacitor Cs, diodes Df1-Df2, and capacitors Cd1-Cd2. Power transistors Q1-Q4 internally integrate diodes D1-D4. The drain of power transistor Q1, one end of capacitor C1, and one end of capacitor Cd1 are coupled to the positive terminal of an external power supply. The source of power transistor Q1, the drain of power transistor Q2, the other end of capacitor C1, one end of capacitor C2, and one end of capacitor Cs are coupled to the negative terminal of diode Df1. The source of power transistor Q2, the drain of power transistor Q3, the other end of capacitor C2, and one end of capacitor C3 are coupled to one input terminal of a ground-adjustable LCC resonant network. The source of power transistor Q3, the drain of power transistor Q4, the other end of capacitor C3, one end of capacitor C4, and the other end of capacitor Cs are coupled to the positive terminal of diode Df2. The source of power transistor Q4, the other end of capacitor C4, and one end of capacitor Cd2 are coupled to the negative terminal of an external power supply. The other end of capacitor Cd1, the other end of capacitor Cd2, the positive terminal of diode Df1, and the negative terminal of diode Df2 are coupled to the other input terminal of a ground-adjustable LCC resonant network. The gates of power transistors Q1 to Q4 are coupled to a ground control unit. The ground control unit adjusts the phase shift angle, output voltage, and output current of the three-level circuit by adjusting the conduction and cutoff of power transistors Q1 to Q4.

5. The wireless charging system according to claim 4, characterized in that: The capacitors Cd1 and Cd2 are each composed of three electrolytic capacitors connected in parallel.

6. The wireless charging system according to claim 4, characterized in that: The synchronous rectification circuit includes power transistors Qs3 and Qs4, inductors Ls2 and Ls3, and capacitor Ce1. One end of inductor Ls2 and the drain of power transistor Qs3 are coupled to one output terminal of the vehicle-mounted adjustable LCC resonant network. The other end of inductor Ls2 is coupled to one end of inductor Ls3 and one end of capacitor Ce1, and is used to couple to the positive terminal of the load battery. The source of power transistor Qs3 is coupled to the source of power transistor Qs4 and the other end of capacitor Ce1, and is used to couple to the negative terminal of the load battery. The drain of power transistor Qs4 and the other end of inductor Ls3 are coupled to the other output terminal of the vehicle-mounted adjustable LCC resonant network. The gates of power transistors Qs3 and Qs4 are coupled to the vehicle-mounted control unit.

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