A wireless charging system using a symmetric auxiliary receiving coil and a duty cycle modulation to achieve unidirectional shift resistance

Abstract

The application provides a wireless charging system using symmetrical auxiliary receiving coils and duty cycle modulation to realize unidirectional anti-offset, the cross coupling of main and auxiliary coils is eliminated through a group of symmetrical auxiliary coils overlapping with the main receiving coil; the magnetic field decoupling of the main receiving coil and the auxiliary coil is realized through overlapping with the main receiving coil; the symmetrical auxiliary coil receives positive magnetic flux in the overlapping part with the main receiving coil and receives negative magnetic flux in the non-overlapping part, and the positive and negative magnetic fluxes in the area surrounded by the auxiliary coil are offset by adjusting the size of the overlapping area and the non-overlapping area to a certain value, so that the decoupling of the main receiving coil and the symmetrical auxiliary receiving coil is realized.

Description

Technical Field

[0001] This invention belongs to the field of wireless charging technology, and particularly relates to a wireless charging system that utilizes symmetrical auxiliary receiving coils and duty cycle modulation to achieve unidirectional anti-offset wireless charging. Background Technology

[0002] Currently, electric vehicle charging mainly falls into two categories: wired charging and wireless charging. Wired charging physically connects the power source to the vehicle via a cable, offering relatively stable energy transmission and mature technology. However, it also suffers from limitations such as lower charging flexibility and inconvenience. Furthermore, the cable may be damaged or even severed due to external factors during charging, posing a risk of electric shock. Wireless charging, on the other hand, uses a magnetic coupling structure to transmit electrical energy from the power source to the vehicle, achieving magnetic isolation between the power source and the car. It also eliminates the need for manual cable plugging and unplugging, offering greater convenience, flexibility, and safety compared to wired charging. However, wireless charging also has several issues, one of which is the misalignment between the transmitting and receiving coils during parking. In traditional wireless charging coil structures, misalignment between the transmitting and receiving coils leads to drastic changes in transmission inductance, causing fluctuations in output voltage and reducing wireless charging performance. Furthermore, it may affect the lifespan of the electric vehicle battery. Summary of the Invention

[0003] To address the problems of the existing technology, this invention proposes a unidirectional anti-offset wireless charging system utilizing symmetrical auxiliary receiving coils and duty cycle modulation. A set of symmetrical auxiliary coils is added to the original receiving coil, and the cross-coupling between the main and auxiliary coils is eliminated by overlapping with the main receiving coil. Simultaneously, the auxiliary coils are connected to a half-bridge controllable rectifier circuit, and a duty cycle modulation strategy is implemented, connecting them in series with the original receiving circuit topology to jointly output voltage. Through this method, the auxiliary coils compensate for the changes in mutual inductance of the main coil during the offset process, thereby achieving a constant voltage output of the wireless charging system during the offset process and giving the system anti-offset characteristics.

[0004] The technical solution adopted by this invention to solve its technical problem is:

[0005] A wireless charging system that utilizes symmetrical auxiliary receiving coils and duty cycle modulation to achieve unidirectional anti-offset is disclosed. This system eliminates cross-coupling between the main and auxiliary coils by overlapping a set of symmetrical auxiliary coils with the main receiving coil. The magnetic fields of the main receiving coil and auxiliary coils are decoupled by the overlap. The overlapping portion of the auxiliary coil receives positive magnetic flux, while the non-overlapping portion receives negative magnetic flux. By adjusting the size of the overlapping and non-overlapping areas to a certain value, the positive and negative magnetic fluxes within the area enclosed by the auxiliary coil are canceled out, thereby achieving decoupling between the main receiving coil and the symmetrical auxiliary receiving coil.

[0006] Furthermore, by means of the two auxiliary coils, when the main receiving coil and the transmitting coil are offset relative to each other, the mutual inductance between the auxiliary receiving coil and the transmitting coil is used to compensate for the drop in mutual inductance of the main receiving coil.

[0007] Furthermore, the auxiliary coil is connected to a half-bridge controllable rectifier circuit. Utilizing a duty cycle modulation strategy, it is connected in series with the main receiving circuit, which has a full-bridge uncontrolled rectifier, to jointly output voltage. This compensates for the mutual inductance changes of the main coil during the offset process, thereby achieving a constant voltage output from the wireless charging system during the offset process.

[0008] Furthermore, the transmitting side consists of a square wave inverter, an LCC compensation network, and a transmitting coil connected in sequence;

[0009] The receiving side consists of a main receiving circuit and an auxiliary receiving circuit connected in series to the load.

[0010] The main receiving circuit uses an S-type compensation network and a full-bridge uncontrolled rectifier to output voltage; the main receiving coil is connected to the full-bridge uncontrolled rectifier via a series compensation capacitor.

[0011] The auxiliary receiving circuit uses an S-type compensation network and two parallel half-bridge fully controlled rectifiers to output voltage; the two auxiliary receiving coils are connected in series with compensation capacitors to the two half-bridge fully controlled rectifiers.

[0012] Furthermore, the transmitter-side inverter achieves square wave inversion by injecting a drive signal with a duty cycle of 0.5 into the four inverter switches. The first inverter switch S1 and the fourth inverter switch S4 are simultaneously turned on, as are the second inverter switch S2 and the third inverter switch S3. The first inverter switch S1 and the fourth inverter switch S4 are complementary to the second inverter switch S2 and the third inverter switch S3, which are turned on alternately. By switching on or off the drive signal corresponding to the two bridge arms of the symmetrical auxiliary receiving coil, different operating modes are switched to achieve voltage compensation for different transmitter and receiving coil offset conditions.

[0013] Furthermore, the switching of different working modes enables voltage compensation for different transmit and receive coil offsets, specifically divided into three working modes;

[0014] When the transmitting coil and the receiving coil are facing each other, the wireless charging system operates in mode 1. The two arms of the auxiliary receiving circuit work simultaneously, and the driving signals of the two switches in the same arm are complementary and output in parallel. The main receiving circuit and the auxiliary receiving circuit are connected in series to output voltage to power the electric vehicle battery.

[0015] When the receiving coil shifts to the left relative to the transmitting coil, the wireless charging system operates in mode 2. In this mode, only the right bridge arm of the auxiliary receiving circuit is active; the drive signals for the left bridge arm switches are off, and the drive signals for the right bridge arm switches are complementary. The mutual inductance of the right auxiliary receiving coil is greater than that of the left auxiliary receiving coil, and the current in the left auxiliary receiving loop is... I R1 The voltage is 0; the auxiliary receiving circuit is connected in series with the main receiving circuit to output voltage, so that the voltage drop in the main receiving circuit is compensated by the voltage increase in the auxiliary receiving circuit;

[0016] When the receiving coil is offset to the right relative to the transmitting coil, the wireless charging system operates in mode 3; only the left bridge arm of the auxiliary receiving circuit is active, the drive signal of the right bridge arm switch is off, and the drive signals of the left bridge arm switch are complementary; the mutual inductance of the left auxiliary receiving coil is greater than that of the right auxiliary receiving coil, and the current in the right auxiliary receiving loop is... I R2 The voltage is 0; the auxiliary receiving circuit is connected in series with the main receiving circuit to output voltage, so that the voltage drop of the main receiving circuit is compensated by the voltage increase of the auxiliary receiving circuit.

[0017] Furthermore, by controlling the duty cycle of the complementary drive signal of the auxiliary rectifier bridge arm, the output voltage of the auxiliary receiving circuit is increased to achieve constant voltage under unidirectional offset conditions:

[0018] The superposition of mutual inductance between the transmitting coil and the main receiving coil, and between the transmitting coil and the working auxiliary receiving coil, is taken as the equivalent mutual inductance. The output voltage is proportional to the equivalent mutual inductance. As the duty cycle of the upper transistor drive signal of the auxiliary receiving rectifier bridge arm gradually decreases from 0.5, and the lower transistor drive signal remains complementary to the upper transistor, the output voltage of the auxiliary receiving circuit is further increased. The overall output voltage when the equivalent mutual inductance of the magnetic coupling structure reaches its maximum value during the offset process is selected as the reference value. Under other offset conditions, the duty cycle of the upper transistor drive signal of the working bridge arm is adjusted, and the lower transistor remains complementary, raising the output voltage of the auxiliary receiving circuit so that the overall output voltage rises to the reference value, achieving a stable output voltage of the wireless charging system under coil misalignment.

[0019] Furthermore, when the wireless charging system is in working mode 1, the high-level duration of the drive signal of the upper bridge arm switch of the auxiliary receiving circuit rectifier is shortened in the middle of the axis of symmetry with the midline of the drive signals of the first inverter switch S1 and the fourth inverter switch S4 of the transmitting side inverter, so that the system output voltage rises to be on par with the reference value.

[0020] When the wireless charging system is in operating modes 2 and 3, the same duty cycle modulation strategy is used. Compared with operating mode 1, in operating mode 2, the drive signal of the left bridge arm switch is turned off, and the corresponding body diode is clamped. In operating mode 3, the drive signal of the right bridge arm switch is turned off, and the corresponding body diode is clamped.

[0021] Furthermore, the specific work process is as follows:

[0022] The system switches operating modes based on the offset between the electric vehicle's receiving coil and the wireless charging device's transmitting coil to achieve stable voltage output and anti-offset effect. When the receiving coil and transmitting coil are directly aligned, the system switches to operating mode 1, with both auxiliary coils operating simultaneously. The duty cycle of the switching transistors on the left and right bridge arms is reduced according to the modulation strategy to increase the output voltage to the reference value. When the receiving coil is deflected to the left relative to the transmitting coil, the system switches to operating mode 2, with the right auxiliary coil receiving and operating, and the left auxiliary coil receiving a stop drive signal and being clamped. The duty cycle of the switching transistor on the right bridge arm is reduced according to the modulation strategy to increase the output voltage to the reference value. When the receiving coil is deflected to the right relative to the transmitting coil, the system switches to operating mode 3, with the left auxiliary coil receiving and operating, and the right auxiliary coil receiving a stop drive signal and being clamped. The duty cycle of the switching transistor on the left bridge arm is reduced according to the modulation strategy to increase the output voltage to the reference value.

[0023] Furthermore, the main receiving coil is a unipolar receiving coil.

[0024] Compared with the prior art, the outstanding features and optimizations of the present invention and its preferred embodiments include at least the following:

[0025] (1) In the case of unidirectional misalignment of the transmitting and receiving coils during the charging process of electric vehicles, the present invention can maintain the same output voltage as when they are aligned, thereby expanding the permissible range of unidirectional coil misalignment of electric vehicles, realizing unidirectional anti-offset, and improving the flexibility and convenience of wireless charging of electric vehicles.

[0026] (2) The proposed magnetic coupling structure only adds a pair of simple auxiliary receiving coils to the common unipolar receiving coil, and eliminates the cross coupling between the two by overlapping the auxiliary receiving coil and the main receiving coil, which simplifies the analysis difficulty and avoids the efficiency drop caused by cross coupling. The scheme is simple.

[0027] (3) The proposed topology only has a single auxiliary receiving coil and its corresponding circuit working when the offset occurs. Even without a driving signal, it can achieve voltage clamping of the other auxiliary receiving coil, avoiding the additional loss caused by loop current when the other auxiliary receiving coil is not working.

[0028] (4) The proposed duty cycle modulation strategy can control the output voltage of the auxiliary circuit without generating reactive power, making the charging voltage more stable and beneficial to the protection of the battery life of electric vehicles. Attached Figure Description

[0029] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments:

[0030] Figure 1 The following is a structural diagram of the receiving coil proposed in the embodiment of the present invention: (a) overall structure of the receiving coil; (b) main receiving coil structure; (c) symmetrical auxiliary receiving coil structure;

[0031] Figure 2 The diagram shows the magnetic coupling structure of the wireless charging system proposed in this embodiment of the invention: (a) facing forward; (b) offset towards the negative Y-axis; (c) offset towards the positive Y-axis.

[0032] Figure 3 This is a voltage-compensated topology diagram of the receiver-side series LCC-S in an embodiment of the present invention;

[0033] Figure 4 This is a topology diagram of the wireless charging system in working mode 1 according to an embodiment of the present invention;

[0034] Figure 5 This is a topology diagram of the wireless charging system in working mode 2 according to an embodiment of the present invention;

[0035] Figure 6 This is a topology diagram of the wireless charging system in working mode 3 according to an embodiment of the present invention;

[0036] Figure 7 The following is a diagram showing the modal analysis of the switching transistor drive signal and circuit during different time periods in the working mode 1 of the wireless charging system according to an embodiment of the present invention: (a) Modulation waveform of the system switching transistor drive signal; (b) Circuit modes during time periods t0~t1 and t2~t3; (c) Circuit modes during time periods t1~t2; (d) Circuit modes during time periods t3~t4.

[0037] Figure 8 The following is a diagram showing the modal analysis of the switching transistor drive signal and circuit during different time periods in the wireless charging system operating mode 2 of this invention: (a) Modulation waveform of the system switching transistor drive signal; (b) Circuit modes during time periods t0~t1 and t2~t3; (c) Circuit modes during time periods t1~t2; (d) Circuit modes during time periods t3~t4.

[0038] Figure 9The following is a diagram showing the modal analysis of the switching transistor drive signal and circuit during different time periods in the working mode 3 of the wireless charging system according to an embodiment of the present invention: (a) Modulation waveform of the system switching transistor drive signal; (b) Circuit mode during time periods t0~t1 and t2~t3; (c) Circuit mode during time periods t1~t2; (d) Circuit mode during time periods t3~t4. Detailed Implementation

[0039] To make the features and advantages of this patent more apparent and understandable, specific embodiments are provided below for detailed explanation:

[0040] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used in this specification have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0041] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0042] The specific details of the solution provided in this embodiment of the invention are as follows:

[0043] (1) Magnetic coupling structure of wireless charging system

[0044] The receiving coil structure proposed in this invention is as follows: Figure 1 As shown, where Figure 1 (a) shows the overall structure of the receiving coil and the stacking arrangement of the main receiving coil and the symmetrical auxiliary coils. Figure 1 (b) The main receiving coil (a common unipolar coil). Figure 1 (c) The proposed symmetrical auxiliary coil (composed of two unipolar coils symmetrically along the midline). The magnetic field decoupling between the main receiving coil and the auxiliary coils is achieved by overlapping the two auxiliary coils at a certain distance from the main receiving coil. (Specification) Figure 1 If the current direction is positive, a positive magnetic flux will be generated inside the main receiving coil and a negative magnetic flux will be generated outside. The part of the auxiliary coil that overlaps with the main receiving coil receives the positive magnetic flux, and the part that does not overlap receives the negative magnetic flux. By adjusting the size of the overlapping area and the non-overlapping area to a suitable value, the positive and negative magnetic fluxes inside the area enclosed by the auxiliary coil can be canceled out, thereby achieving decoupling between the main receiving coil and the symmetrical auxiliary receiving coil.

[0045] The proposed magnetic coupling structure for the wireless charging system is as follows: Figure 2As shown. When the receiving coil and the transmitting coil are directly opposite each other (e.g. Figure 2 In the case shown in (a), the mutual inductance between the main receiving coil and the transmitting coil is at its maximum. At this point, the mutual inductance between the symmetrical auxiliary receiving coil and the transmitting coil is much smaller, allowing the main power to be transmitted through the main receiving coil. When the receiving coil is along the negative Y-axis (e.g., ... Figure 2 (b) As the offset gradually occurs, the area of ​​the main receiving coil and the transmitting coil facing each other gradually decreases, and the mutual inductance between them weakens rapidly. Meanwhile, the area of ​​the auxiliary receiving coil and the transmitting coil facing each other on the right increases, and the mutual inductance between them gradually strengthens. This mutual inductance can be used to compensate for the drop in mutual inductance of the main receiving coil, thus achieving anti-offset in this misalignment direction. Similarly, when the receiving coil is along the positive Y-axis direction (e.g., ... Figure 2 (c) As the offset gradually occurs, the mutual inductance between the main receiving coil and the transmitting coil decreases in the same trend; at the same time, the area of ​​the left auxiliary receiving coil and the transmitting coil increases, and the mutual inductance between the left auxiliary receiving coil and the transmitting coil gradually increases. This mutual inductance can also be used to compensate for the drop in mutual inductance of the main receiving coil, thereby achieving anti-offset in the misalignment direction.

[0046] (2) Wireless charging system circuit topology

[0047] Based on the above magnetic coupling structure, this invention proposes a receiver-side series LCC-S voltage compensation topology, such as... Figure 3 As shown. The transmitting side of this topology consists of a square wave inverter, an LCC compensation network, and a transmitting coil, wherein... V INV S1-S4 are the inverter's DC input voltage and the inverter's switching transistors. L F For series compensation inductance, C F For parallel compensation capacitors, C T For series compensation capacitors, L T For the self-inductance of the transmitting coil, I F , I T They are respectively L F The corresponding current on the transmitting coil. The receiving side of this topology consists of a main receiving topology and an auxiliary receiving topology connected in series to the load. The main receiving topology uses an S-type compensation network and a full-bridge uncontrolled rectifier to output voltage, while the auxiliary receiving topology uses symmetrical auxiliary receiving coils connected in parallel to an S-type compensation network and a half-bridge fully controlled rectifier to output voltage. L Rm , L R1 andL R2 These are the self-inductances of the main receiving coil and the auxiliary receiving coils on the left and right sides, respectively. I Rm , I R1 and I R2 These are the corresponding branch currents, C Rm , C R1 and C R2 These are the series compensation capacitors for the main receiver and the auxiliary receivers on the left and right sides, respectively. D1-D4 are the diodes of the uncontrolled rectifier of the main receiver full-bridge. S 11 S 12 and S 21 S 22 These are the switching transistors of the left and right auxiliary receiving half-bridge fully controlled rectifiers, respectively. C Om and C O12 These are the output filter capacitors for the rectifiers of the main receiving topology and the auxiliary receiving topology, respectively. R L Equivalent load resistance for charging electric vehicles V Om , V O12 and V REC They are respectively C Om , C O12 and R L Voltage at both ends. M TRm , M TR1 and M TR2 These are the mutual inductances between the transmitting coil and the main receiving coil, the left auxiliary receiving coil, and the right auxiliary receiving coil, respectively. The mutual inductance between the main receiving coil and the symmetrical auxiliary receiving coils can be ignored due to overlapping decoupling. The mutual inductance generated by the cross coupling of the left and right auxiliary receiving coils can be simply decoupled by adding a transformer to the winding of another coil nested outside or in the dual auxiliary receiving circuit, so it can also be ignored.

[0048] This transmitter-side inverter achieves square wave inversion by injecting drive signals with a duty cycle of 0.5 into S1-S4. S1 and S4 are simultaneously turned on, as are S2 and S3, with S1 and S4 conducting alternately with S2 and S3. Different operating modes can be switched by applying or cutting off the drive signals to the two bridge arms corresponding to the symmetrical auxiliary receiving coils, achieving voltage compensation for different transmitter-receiver coil offsets. Specifically, there are three operating modes.

[0049] When the transmitting coil and receiving coil are directly aligned (e.g.) Figure 2 (a) shows that the wireless charging system operates in mode 1, and the topology diagram is as follows. Figure 4 As shown. At this time, both arms of the auxiliary receiving topology are working simultaneously, and the switch S... 11 S 21 Simultaneously activated, S 21 S 22 Simultaneously activated, S 11 With S 12 Complementary drive signals, S 21 and S 22 The drive signals are complementary. The mutual inductance values ​​between the two symmetrical auxiliary receiving coils and the transmitting coil are similar, corresponding to the parallel output of the two auxiliary receiving bridge arms. Finally, the auxiliary receiving topology and the main receiving topology are connected in series to output a voltage that powers the electric vehicle battery.

[0050] When the receiving coil is offset to the left relative to the transmitting coil (e.g.) Figure 2 (b) shows that the wireless charging system operates in mode 2, and the topology diagram is as follows. Figure 5 As shown. At this time, only the right bridge arm is working, and the switch S is turned off. 11 With S 12 The drive signal, the switching transistor S 21 and S 22 The drive signals are complementary. Due to the leftward offset of the receiving coil, the mutual inductance between the main receiving coil and the transmitting coil decreases, and the output voltage of the main receiving topology... V Om The voltage decreases, while the mutual inductance between the right auxiliary receiving coil and the transmitting coil increases, resulting in a decrease in the output voltage of the auxiliary receiving topology. V O12 The current rises. Furthermore, because the mutual inductance of the right auxiliary receiving coil is greater than that of the left auxiliary receiving coil, the body diode of the left auxiliary receiving bridge arm clamps, increasing the current in the left auxiliary receiving circuit. I R1 The output voltage is 0. By connecting the auxiliary receiving topology in series with the main receiving topology, the voltage drop in the main receiving topology is compensated by the voltage increase in the auxiliary receiving topology, thereby maintaining the overall system output voltage. V REC The fluctuation is reduced due to the offset, thus achieving the effect of resisting the offset.

[0051] When the receiving coil is offset to the right relative to the transmitting coil (e.g.) Figure 2 (c) shows that the wireless charging system operates in mode 3, and the topology diagram is as follows. Figure 6 As shown. At this time, only the left bridge arm is working, and the switching transistor S... 11 With S 12 Complementary drive signals turn off the switching transistor S. 21 and S 22 The drive signal. Due to the rightward offset of the receiving coil, the mutual inductance between the main receiving coil and the transmitting coil decreases, and the output voltage of the main receiving topology... V Om The voltage decreases, while the mutual inductance between the left auxiliary receiving coil and the transmitting coil increases, resulting in a decrease in the output voltage of the auxiliary receiving topology. V O12 The current rises. Furthermore, because the mutual inductance of the left auxiliary receiving coil is greater than that of the right auxiliary receiving coil, the body diode of the right auxiliary receiving bridge arm clamps, increasing the current in the right auxiliary receiving circuit. I R2 The value is 0. Similarly, by connecting the auxiliary receiving topology in series with the main receiving topology, the voltage drop in the main receiving topology is compensated by the voltage increase in the auxiliary receiving topology, thereby maintaining the overall system output voltage. V REC The fluctuation is reduced due to the offset, thus achieving the effect of resisting the offset.

[0052] (3) Modulation strategy of auxiliary receiver rectifier in wireless charging system

[0053] When the complementary drive signals of the auxiliary receiving rectifier bridge arms are all set to a duty cycle of 0.5 in the three operating modes, the output voltage of the auxiliary receiving rectifier often cannot accurately compensate for the output voltage of the main receiving rectifier in the event of offset. Overcompensation occurs when the offset distance is small, and undercompensation occurs when the offset distance is large. Therefore, this invention proposes a duty cycle modulation strategy for the auxiliary receiving topology. By controlling the duty cycle of the complementary drive signals of the auxiliary rectifier bridge arms, the output voltage of the auxiliary receiving topology is raised to a suitable value, achieving constant voltage under unidirectional offset conditions.

[0054] The topology proposed in this invention is an LCC-S type compensation network with constant voltage characteristics independent of the load. The superposition of mutual inductance between the transmitting coil and the main receiving coil, and between the transmitting coil and the working auxiliary receiving coil, is used as the equivalent mutual inductance. The output voltage of this topology is proportional to the equivalent mutual inductance. Furthermore, as the duty cycle of the upper transistor drive signal in the auxiliary receiving rectifier bridge arm gradually decreases from 0.5 while the lower transistor drive signal remains complementary to the upper transistor, the output voltage of the auxiliary receiving topology can be further increased. Since the magnetic coupling structure proposed in this invention exhibits the phenomenon of the equivalent mutual inductance first increasing and then decreasing during the offset process, this invention selects the overall output voltage when the equivalent mutual inductance of the magnetic coupling structure reaches its maximum value during the offset process as a reference value. Under other offset conditions, adjusting the duty cycle of the upper transistor drive signal of the working bridge arm while maintaining the complementarity of the lower transistors can raise the output voltage of the auxiliary receiving topology, ensuring that the overall output voltage rises to the reference value. This achieves stable voltage output of the wireless charging system under coil misalignment, achieving a unidirectional anti-offset effect.

[0055] When the wireless charging system is in operating mode 1, the modal analysis of all switching transistor drive signals and circuits at various time periods is as follows: Figure 7 As shown. The upper bridge arm of the auxiliary receiving topology rectifier is set to... θ ( θ <180°), and t 0~ t 1 and t 2~ t 3. Equal duration: The high-level duration of the upper transistor drive signal is shortened in the middle with the midline of the inverter S1 and S4 drive signals as the symmetrical axis. This method avoids the generation of additional reactive power in the system, keeping the system efficiency at a high value. Through this duty cycle modulation strategy, the system output voltage can be raised to the same level as the reference value under this condition.

[0056] When the wireless charging system is in operating modes 2 and 3, the modal analysis of all switching transistor drive signals and circuits at various time periods is as follows: Figure 8 , 9 As shown, the same duty cycle modulation strategy is used. Compared with operating mode 1, the switching transistor S in operating mode 2... 11 With S 12 When the drive signal is off, the corresponding body diode is clamped; in operating mode 3, the switching transistor S... 21 With S 22 When the drive signal is turned off, the corresponding body diode is clamped.

[0057] This invention adds a symmetrical auxiliary receiving coil to the traditional unipolar receiving coil, increases mutual inductance for offset compensation through innovative magnetic coupling structure, achieves output voltage compensation of the main receiving topology through circuit topology innovation, and achieves accurate control of the output voltage compensation by adding a duty cycle modulation strategy. As a result, the output voltage of the wireless charging system remains basically unchanged when the coil is misaligned, thus achieving unidirectional anti-offset.

[0058] The wireless charging system proposed in this invention can switch operating modes according to the offset between the electric vehicle's receiving coil and the wireless charging device's transmitting coil, achieving stable voltage output and anti-offset effect. When the receiving coil and transmitting coil are directly aligned, the system switches to operating mode 1, with both auxiliary receivers operating simultaneously. The duty cycle of the switching transistors on the left and right bridge arms is reduced according to a modulation strategy to increase the output voltage to the reference value. When the receiving coil is offset to the left relative to the transmitting coil, the system switches to operating mode 2, with the right auxiliary receiver operating and the left auxiliary receiver stopping its drive signal and being clamped. The duty cycle of the switching transistor on the right bridge arm is reduced according to a modulation strategy to increase the output voltage to the reference value. When the receiving coil is offset to the right relative to the transmitting coil, the system switches to operating mode 3, with the left auxiliary receiver operating and the right auxiliary receiver stopping its drive signal and being clamped. The duty cycle of the switching transistor on the left bridge arm is reduced according to a modulation strategy to increase the output voltage to the reference value.

[0059] It should be noted that, unless otherwise defined, the technical or scientific terms used in this invention should have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," and similar terms used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0060] This patent is not limited to the above-described preferred embodiment. Anyone can derive various other forms of wireless charging systems that utilize symmetrical auxiliary receiving coils and duty cycle modulation to achieve unidirectional anti-offset based on the teachings of this patent. All equivalent variations and modifications made within the scope of this patent application shall fall within the scope of this patent.

Claims

1. A wireless charging system that utilizes symmetrical auxiliary receiving coils and duty cycle modulation to achieve unidirectional anti-offset, characterized in that: The cross-coupling between the main and auxiliary coils is eliminated by overlapping a set of symmetrical auxiliary coils with the main receiving coil; The magnetic field decoupling between the main receiving coil and the auxiliary coil is achieved by overlapping with the main receiving coil; the part of the auxiliary coil that overlaps with the main receiving coil receives positive magnetic flux, and the part that does not overlap receives negative magnetic flux. By adjusting the size of the overlapping area and the non-overlapping area to a certain value, the positive and negative magnetic fluxes inside the area enclosed by the auxiliary coil are canceled out, thereby achieving decoupling between the main receiving coil and the symmetrical auxiliary receiving coil. The transmitting side consists of a square wave inverter, an LCC compensation network, and a transmitting coil connected in sequence. The receiving side consists of a main receiving circuit and an auxiliary receiving circuit connected in series to the load. The main receiving circuit uses an S-type compensation network and a full-bridge uncontrolled rectifier to output voltage; the main receiving coil is connected to the full-bridge uncontrolled rectifier via a series compensation capacitor. The auxiliary receiving circuit uses an S-type compensation network and two parallel half-bridge fully controlled rectifiers to output voltage; the two auxiliary receiving coils are respectively connected in series with compensation capacitors to the two half-bridge fully controlled rectifiers. The transmitter-side inverter achieves square wave inversion by injecting a drive signal with a duty cycle of 0.5 into four inverter switches. The first inverter switch S1 and the fourth inverter switch S4 are turned on simultaneously, as are the second inverter switch S2 and the third inverter switch S3. The first inverter switch S1 and the fourth inverter switch S4 are turned on alternately with the second inverter switch S2 and the third inverter switch S3. By switching on or off the drive signal corresponding to the two bridge arms of the symmetrical auxiliary receiving coil, different operating modes are switched to achieve voltage compensation for different transmitter and receiver coil offsets. The switching of different working modes enables voltage compensation for different transmit and receive coil offsets, specifically divided into three working modes; When the transmitting coil and the receiving coil are facing each other, the wireless charging system operates in mode 1. The two arms of the auxiliary receiving circuit work simultaneously, and the driving signals of the two switches in the same arm are complementary and output in parallel. The main receiving circuit and the auxiliary receiving circuit are connected in series to output voltage to power the electric vehicle battery. When the receiving coil shifts to the left relative to the transmitting coil, the wireless charging system operates in mode 2. In this mode, only the right bridge arm of the auxiliary receiving circuit is active; the drive signals for the left bridge arm switches are off, and the drive signals for the right bridge arm switches are complementary. The mutual inductance of the right auxiliary receiving coil is greater than that of the left auxiliary receiving coil, and the current in the left auxiliary receiving loop is... I R1 The voltage is 0; the auxiliary receiving circuit is connected in series with the main receiving circuit to output voltage, so that the voltage drop in the main receiving circuit is compensated by the voltage increase in the auxiliary receiving circuit; When the receiving coil is offset to the right relative to the transmitting coil, the wireless charging system operates in mode 3; In the auxiliary receiving circuit, only the left bridge arm is operational; the drive signals for the right bridge arm switches are off, and the drive signals for the left bridge arm switches are complementary. The mutual inductance of the left auxiliary receiving coil is greater than that of the right auxiliary receiving coil, and the current in the right auxiliary receiving loop is... I R2 The voltage is 0; the auxiliary receiving circuit is connected in series with the main receiving circuit to output voltage, so that the voltage drop of the main receiving circuit is compensated by the voltage increase of the auxiliary receiving circuit.

2. The wireless charging system for unidirectional anti-offset achieved by utilizing symmetrical auxiliary receiving coils and duty cycle modulation according to claim 1, characterized in that: By using the two auxiliary coils, when the main receiving coil and the transmitting coil are offset relative to each other, the mutual inductance of the auxiliary receiving coil and the transmitting coil is used to compensate for the drop in mutual inductance of the main receiving coil.

3. The wireless charging system for unidirectional anti-offset achieved by utilizing symmetrical auxiliary receiving coils and duty cycle modulation according to claim 1, characterized in that: The auxiliary coil is connected to a half-bridge fully controlled rectifier circuit. Using a duty cycle modulation strategy, it is connected in series with the main receiving circuit with a full-bridge uncontrolled rectifier to output a common voltage. This compensates for the change in mutual inductance of the main coil during the offset process, thereby achieving a constant voltage output of the wireless charging system during the offset process.

4. The wireless charging system for unidirectional anti-offset achieved by utilizing symmetrical auxiliary receiving coils and duty cycle modulation according to claim 1, characterized in that: By controlling the duty cycle of the complementary drive signal of the auxiliary rectifier bridge arm, the output voltage of the auxiliary receiving circuit is increased to achieve constant voltage under unidirectional offset conditions. The superposition of mutual inductance between the transmitting coil and the main receiving coil, and between the transmitting coil and the working auxiliary receiving coil, is taken as the equivalent mutual inductance. The output voltage is proportional to the equivalent mutual inductance. As the duty cycle of the upper transistor drive signal of the auxiliary receiving rectifier bridge arm gradually decreases from 0.5, and the lower transistor drive signal remains complementary to the upper transistor, the output voltage of the auxiliary receiving circuit is further increased. The overall output voltage when the equivalent mutual inductance of the magnetic coupling structure reaches its maximum value during the offset process is selected as the reference value. Under other offset conditions, the duty cycle of the upper transistor drive signal of the working bridge arm is adjusted, and the lower transistor remains complementary, raising the output voltage of the auxiliary receiving circuit so that the overall output voltage rises to the reference value, achieving a stable output voltage of the wireless charging system under coil misalignment.

5. A wireless charging system for unidirectional anti-offset operation using a symmetrical auxiliary receiving coil and duty cycle modulation as described in claim 4, characterized in that: When the wireless charging system is in working mode 1, the high-level duration of the drive signal of the upper bridge arm switch of the auxiliary receiving circuit rectifier is shortened in the middle of the axis of the drive signal of the first inverter switch S1 and the fourth inverter switch S4 of the transmitting side inverter, so that the system output voltage rises to the same level as the reference value. When the wireless charging system is in operating modes 2 and 3, the same duty cycle modulation strategy is used. Compared with operating mode 1, in operating mode 2, the drive signal of the left bridge arm switch is turned off, and the corresponding body diode is clamped. In operating mode 3, the drive signal of the right bridge arm switch is turned off, and the corresponding body diode is clamped.

6. A wireless charging system for unidirectional anti-offset operation using a symmetrical auxiliary receiving coil and duty cycle modulation as described in claim 5, characterized in that: The specific work process is as follows: The system switches operating modes based on the offset between the electric vehicle's receiving coil and the wireless charging device's transmitting coil to achieve stable voltage output and anti-offset effect. When the receiving coil and transmitting coil are directly aligned, the system switches to operating mode 1, with both auxiliary coils operating simultaneously. The duty cycle of the switching transistors on the left and right bridge arms is reduced according to the modulation strategy to increase the output voltage to the reference value. When the receiving coil is deflected to the left relative to the transmitting coil, the system switches to operating mode 2, with the right auxiliary coil receiving and operating, and the left auxiliary coil receiving a stop drive signal and being clamped. The duty cycle of the switching transistor on the right bridge arm is reduced according to the modulation strategy to increase the output voltage to the reference value. When the receiving coil is deflected to the right relative to the transmitting coil, the system switches to operating mode 3, with the left auxiliary coil receiving and operating, and the right auxiliary coil receiving a stop drive signal and being clamped. The duty cycle of the switching transistor on the left bridge arm is reduced according to the modulation strategy to increase the output voltage to the reference value.

7. A wireless charging system for unidirectional anti-offset operation using a symmetrical auxiliary receiving coil and duty cycle modulation as described in claim 1, characterized in that: The main receiving coil is a unipolar receiving coil.

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