Wireless charging system with coil alignment guiding and self-aligning functions and control method thereof

Abstract

The invention discloses a wireless charging system with coil alignment guide and self-alignment and a control method thereof, the system comprises a transmitting end and a receiving end, the receiving end comprises a first receiving module and a second receiving module which are the same in structure, and the output ends of the first receiving module and the second receiving module are both connected with a load; each of the first receiving module and the second receiving module comprises a first secondary side compensation capacitor, a second secondary side compensation capacitor, a receiving coil, a compensation coil and a change-over switch, when the change-over switch is closed, the first secondary side compensation capacitor, the second secondary side compensation capacitor and the compensation coil form an LCC topological structure, and when the change-over switch is disconnected, the first secondary side compensation capacitor and the receiving coil are disconnected from the receiving end circuit. According to the invention, the dislocation direction and dislocation condition of the receiving end are judged through the two compensation coils to realize self-alignment, and the two compensation coils are used as compensation inductors in the normal charging process to realize high-power transmission.

Description

Technical Field

[0001] This invention belongs to the field of wireless power transmission technology, specifically relating to a wireless charging system and its control method that features coil alignment guidance and self-alignment. Background Technology

[0002] Magnetic-coupled wireless power transfer (MC-WPT) technology has attracted widespread attention from scholars both domestically and internationally in recent years due to its advantages such as high security and flexibility. Currently, this technology has been applied to fields such as electric vehicles, automated guided vehicles, and consumer electronics, and is gradually maturing. However, in practical applications, the coupling mechanism in a MC-WPT system may become misaligned due to various factors, resulting in offset. This misalignment can lead to low transmission efficiency, low power, or even failure to charge the wireless charging system. Summary of the Invention

[0003] This invention is proposed to solve the problem that the coupling mechanism of the existing WPT system is prone to misalignment, resulting in low charging efficiency and unstable power transmission. Its purpose is to provide a wireless charging system and its control method with coil alignment guidance and self-alignment.

[0004] This invention is achieved through the following technical solution: A wireless charging system with coil alignment guidance and self-alignment includes a transmitter and a receiver. The receiver includes a first receiver module and a second receiver module with identical structures, which are symmetrically arranged about the transmitter. The output terminals of both the first and second receiver modules are connected to a load. Each of the first and second receiver modules includes a first secondary-side compensation capacitor, a second secondary-side compensation capacitor, a receiving coil, a compensation coil, and a switching switch. When the switching switch is closed, the first secondary-side compensation capacitor, the second secondary-side compensation capacitor, and the compensation coil form an LCC topology. When the switching switch is open, the first secondary-side compensation capacitor and the receiving coil are disconnected from the receiver circuit.

[0005] In the above technical solution, the receiving end further includes a receiving end controller for controlling the switching on and off of the switching switch; the receiving end controller includes a voltage sampling circuit for acquiring the load voltage, a current sampling circuit for acquiring the induced current of the compensation coil, an analog-to-digital conversion module for converting the signal of the sampling circuit, and a switch control module for controlling the switching switch according to the output signal of the analog-to-digital conversion module.

[0006] In the above technical solution, both the first receiving module and the second receiving module include a rectifier and a filter capacitor connected in parallel; the input terminal of the rectifier is connected to one end of the second secondary compensation capacitor and the compensation coil, respectively, and the output terminal of the rectifier and the filter capacitor connected in parallel is connected to the load.

[0007] In the above technical solution, the switching switch includes two MOSFETs connected in series in two directions.

[0008] In the above technical solution, the transmitting end includes a DC power supply, a high-frequency inverter, a primary-side compensation circuit and a transmitting coil connected in sequence, and the first receiving module and the second receiving module are symmetrically arranged about the transmitting coil.

[0009] In the above technical solution, both the transmitting coil and the receiving coil are planar DD-type coils, and the compensation coil is a planar Q-type coil.

[0010] In the above technical solution, the primary-side compensation circuit is an LCC topology circuit.

[0011] A control method for a wireless charging system with coil alignment guidance and self-alignment, used in the aforementioned wireless charging system, includes the following steps: S1. Initialize the system transmitter circuit and start energy transfer; S2. Control the two switching switches to disconnect, driving the receiver to move closer to the transmitter; S3. Real-time acquisition of load voltage and induced current of the two compensation coils; S4. Adjust the position of the receiving end according to the load voltage and the induced current of the two compensation coils; S5. When the load voltage and the induced current of the two compensation coils meet the preset conditions, the receiving end stops moving, controls the two switching switches to close, and starts charging.

[0012] In the above technical solution, the specific steps in step S4 of adjusting the position of the receiving end based on the load voltage and the induced current of the two compensation coils are as follows: S41. Determine the difference between the induced currents of the two compensation coils: If I f2 - I f1 If >β, then drive the receiver to move forward toward the side of the first receiving module and return to step S3; If I f1 - I f2 If >β, then drive the receiver to move forward toward the side of the second receiver module and return to step S3; If |I f1 - I f2 If |<β, then proceed to step S42; Among them: I f1 I is the induced current in the compensation coil of the first receiving module. f2 β is the induced current of the compensation coil in the second receiving module, and β is the preset current difference threshold. S42. Determine if the load voltage is less than a preset threshold: If not, adjust the receiver position and return to step S3; If so, proceed to step S5.

[0013] The beneficial effects of this invention are: This invention provides a wireless charging system and its control method that features coil alignment guidance and self-alignment. It employs two Q-type coils in a reconfigurable coupling structure to determine the misalignment direction and condition of the receiver, assisting the device in adjusting its position to achieve self-alignment. These coils also serve as compensating inductors for wireless power transmission during normal charging. The self-alignment function ensures that the coils are properly aligned before charging, thereby enabling high-power transmission. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the coupling mechanism in this invention; Figure 2 This is a plan view of the transmitting and receiving ends of the coupling mechanism in this invention; Figure 3 This is a graph showing the mutual inductance variation of the coupling mechanism under different offsets in this invention; Figure 4 This is the equivalent circuit diagram of the wireless charging system of the present invention; Figure 5 This is the equivalent circuit diagram of the wireless charging system of the present invention with LCC-S compensation topology; Figure 6 This is the equivalent circuit diagram of the wireless charging system of the present invention with an LCC-LCC compensation topology; Figure 7 This is a flowchart of the control method of the present invention; Figure 8 This invention relates to four different x-dislocation conditions I f1 The curve showing the change in y-displacement; Figure 9 These are the output current and voltage waveforms measured at two locations according to the present invention. Figure 10 This invention relates to x-alignment and output voltage U under three different y-alignment conditions. L The relationship between them.

[0015] For those skilled in the art, other related figures can be obtained from the above figures without any creative effort. Detailed Implementation

[0016] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0017] Example 1 like Figure 1 and Figure 2 The coupling mechanism shown includes a transmitter and a receiver. The transmitter includes a transmitter coil L. p The receiving end includes a first receiving module and a second receiving module with identical structures. The first receiving module includes a compensation coil L stacked on top of each other. f1 and receiving coil L s1 The second receiving module includes a compensation coil L stacked in layers. f2 and receiving coil L s2 ; The transmitting coil L p and receiving coil L s1 and L s2 All are planar DD-type coils, and the compensation coil L f1 and L f2 It is a planar Q-type coil, and the first and second receiving modules are about the same height as the transmitting coil L. p Symmetrical setup.

[0018] like Figure 1 and Figure 2 As shown, the transmitting end also includes a transmitting magnetic core L. d1 The first receiving module and the second receiving module further include a receiving magnetic core L. d2 ; The receiving magnetic core L d2 The transmitting magnetic core L is stacked with the receiving coil and the compensation coil. d1 It includes a magnetic core base plate and two magnetic core columns mounted on the magnetic core base plate, wherein the magnetic core base plate and the transmitting coil L p The layers are stacked, and the two magnetic core pillars are respectively inserted into the transmitting coil L. p In the two inner holes.

[0019] In this embodiment, as Figure 2 As shown, Figure 2 This is a plan view of the transmitter and receiver, with transmitter coil L. p The length of the first receiving module and the length of the second receiving module, l1, are both 20cm. The distance between the first receiving module and the second receiving module is d1. The lengths of the first receiving module and the second receiving module, as well as the length of the transmitting magnetic core, L... d1 The length of the transmitting coil is (l1-d1) / 2. p The width of a single D-type coil and the receiving coil L s1 Receiver coil L s2 The width l2 of a single D-type coil is 10cm, and the width d2 of the magnetic core column is 1.5cm.

[0020] In this embodiment, in order to reduce the voltage drop across the receiving coil L of the wireless charging system...p The current divides the receiving end into two groups, each absorbing energy separately. To reduce cross-coupling between the receiving coils, the distance between the first and second receiving modules is d1 cm, and the transmitting magnetic core L... d1 and receiving magnetic core L d2 Both are ferrite cores, and the magnetic coupling from the transmitter to the receiver is enhanced through the ferrite core. In this embodiment, the receiving magnetic core L... d2 An aluminum plate is also placed on the side away from the coil to reduce electromagnetic field leakage.

[0021] In this embodiment, the transmitting magnetic core L d1 The ferrite core is positioned only at the center and protrudes from its empty area. Transmitting coil L d1 and two receiving coils L s1 and L s2 The mutual inductance between them is M Lp_Ls1 and M Lp_Ls2 transmitting coil L d1 and two receiving coils L f1 and L f2 The mutual inductance between them is M Lp_Lf1 and M Lp_Lf2 .like Figure 3 As shown, Figure 3 (a) is M Lp_Ls1 M Lp_Ls2 M Lp_Lf1 and M Lp_Lf2 The curves showing the change in mutual inductance at different positions where the x-axis is directly opposite but the y-axis is offset. Figure 3 (b) Mutual inductance M under three different y-direction offset conditions (y=0, 4, and 8cm). Lp_L1f and M Lp_Lf2 .

[0022] Example 2 like Figure 4 The wireless charging system shown includes coil alignment guidance and self-alignment, comprising the coupling mechanism described in Embodiment 1, and the transmitting end further includes a DC power supply U connected in sequence. dc The high-frequency inverter includes four MOSFETs (Q1 to Q4), and the primary-side compensation circuit includes a primary-side compensation inductor L1, a primary-side first compensation capacitor C1, and a primary-side second compensation capacitor C2. p Primary-side compensation inductor L1, primary-side first compensation capacitor C1, and primary-side second compensation capacitor C p This constitutes the LCC topology.

[0023] The receiving end also includes a first receiving circuit and a second receiving circuit with identical structures, both of which are connected to the load R. L connect; The first receiving circuit includes a first secondary-side compensation capacitor C s1 Secondary compensation capacitor C f1 Switch S1, first rectifier and filter capacitor C d1 The second receiving circuit includes a first secondary-side compensation capacitor C. s2 Secondary compensation capacitor C f2 Switch S2, second rectifier and filter capacitor C d2 ; In this embodiment, when the switching switch S1 is closed, the first secondary compensation capacitor C s1 Secondary compensation capacitor C f1 and compensation coil L f1 This constitutes an LCC topology; when the switching switch S2 is closed, the first secondary-side compensation capacitor C... s2 Secondary compensation capacitor C f2 and compensation coil L f2 This constitutes an LCC topology; when the switching switch S1 is open, the first secondary-side compensation capacitor C... s1 and receiving coil L s1 Disconnected from the receiving circuit; when the switching switch S2 is disconnected, the first secondary compensation capacitor C s2 and receiving coil L s2 Disconnected from the receiving circuit, both switching switches S1 and S2 include two MOSFETs connected in series in two directions.

[0024] In this embodiment, the first rectifier and the filter capacitor C d1 The output terminals after parallel connection, as well as the second rectifier and filter capacitor C d2 The output terminals of the parallel connection are all connected to the load R. L Connection. First rectifier D 1-1 ~D 1-4 There are a total of 4 diodes, and the second rectifier D... 2-1 ~D 2-4 There are a total of 4 diodes.

[0025] like Figure 4 As shown, the receiving end includes a receiving end controller for controlling the switching on and off of the switching switch; The receiver controller includes a voltage sampling circuit for acquiring load voltage, a current sampling circuit for acquiring induced current of compensation coil, an analog-to-digital converter module for converting signals from the sampling circuit, and a switch control module for controlling the switching switch based on the output signal of the analog-to-digital converter module.

[0026] In this embodiment, to simplify the calculation, let: (1) First primary-side compensation capacitor C1, second primary-side compensation capacitor C P First secondary side compensation capacitor C S Secondary compensation capacitor C f To compensate for the capacitor, the following formula must be satisfied: (2) In the formula, ω is the operating angular frequency of power transmission, which satisfies ω=2πf, and f is the operating frequency of the system.

[0027] The operating principle of the circuit was analyzed using the first harmonic approximation (FHA) method. Based on the characteristics of the full-bridge inverter and full-bridge rectifier, the relationship between the root mean square (RMS) values ​​of the DC voltage Udc and the inverter output AC voltage Uin can be expressed as: (3) When the device needs charging, it slowly extends to the charging area, switches S1 and S2 are disconnected, and the system enters self-calibration mode. The equivalent circuit is as follows: Figure 5 As shown.

[0028] Using Kirchhoff's Voltage Law (KVL), and based on the relationship between the input and output voltages of the rectifier, the following equation can be derived: (4) In the formula, M3 and M4 are respectively M Lp_Lf1 and M Lp_Lf2 .

[0029] Then, substituting (2) and (3) into (4), we can get: (5) Further derivation yields: (6) In the formula, I f1 I f2 U s1 and U s2 They are respectively , , and The RMS value.

[0030] This application connects two sets of rectifiers in parallel at the receiving end, and the LCC-S is a constant voltage output system. Considering the reverse cutoff characteristics of the diodes, U L Will follow U s1 and U s2 And change.

[0031] When U s1 > Us2 hour: (7) When U s1 < U s2 hour: (8) It can be seen from formulas (7) and (8) that U L With parameters M3, M4, L1 and U respectively dc Related. When L1 and U dc Constant, the fluctuations of M3 and M4 on the x-axis are as follows Figure 3 As shown in (b), U L There will also be corresponding fluctuations. This application utilizes this characteristic to detect U L This is to determine if the coils are accurately aligned.

[0032] After the receiver self-alignment phase is completed, S1 and S2 are closed, and the system enters the normal charging phase. Its equivalent circuit is as follows: Figure 6 As shown.

[0033] Similarly, by using KVL, the following equation can also be derived: (9) In the formula, M1 and M2 are respectively M Lp_Ls1 and M Lp_Ls2 .

[0034] Then, substituting (1) and (2) into (9), we can get: (10) (11) In the formula, I f1 and I f2 They are respectively and The RMS value.

[0035] As can be seen from (11), the output current I L With load R L Irrelevant, I L The value is determined by parameter U dc , ω, L f The decision is made by M1 and M2.

[0036] Example 3 like Figure 7 As shown, a control method for a wireless charging system with coil alignment guidance and self-alignment is provided for controlling the wireless charging system with coil alignment guidance and self-alignment described in Embodiment 2. The specific method is as follows: S1. Initialize the system transmitter circuit and start energy transfer; S2. Control the two switching switches to disconnect, driving the receiver to move closer to the transmitter; S3. Real-time acquisition of load voltage and induced current of the two compensation coils; S4. Adjust the position of the receiving end according to the load voltage and the induced current of the two compensation coils; The specific steps are as follows: S41. Determine the difference between the induced currents of the two compensation coils: If I f2 - I f1 If >β, then drive the receiver to move forward toward the side of the first receiving module and return to step S3; If I f1 - I f2 If >β, then drive the receiver to move forward toward the side of the second receiver module and return to step S3; If |I f1 - I f2 If |<β, then proceed to step S4.2, where: I f1 I is the induced current in the compensation coil of the first receiving module. f2 β is the induced current of the compensation coil in the second receiving module, and β is the preset current difference threshold. S42. Determine if the load voltage is less than a preset threshold: If not, adjust the receiver position and return to step S3; If so, proceed to step S5.

[0037] S5. When the load voltage and the induced current of the two compensation coils meet the preset conditions, the receiving end stops moving, controls the two switching switches to close, and starts charging.

[0038] In this embodiment, since there is no information exchange between the transmitter and receiver, no control is required for the transmitter. The receiver, however, needs to detect and compare voltage and current to control the switching between the system's self-calibration state and normal charging state. In this embodiment, a current transformer is used for the current sampling circuit, and a voltage divider is used for the voltage sampling circuit. The sampled information is converted by an analog-to-digital converter and then analyzed by an STM32F103 MCU. The device will continue to adjust its position until |I f1 -I f2 | and U L They tend towards α and β respectively, meaning the receiving Q-type coil and the transmitting DD-type coil are decoupled, and the equipment reaches a well-aligned position.

[0039] S6. Experimental Simulation: The system parameters are shown in Table 1, where: N p For transmitting coil Lp The number of turns, N s For receiving coil L s The number of turns, N f For compensation coil L f The number of turns, primary compensation inductance L1, transmitting coil L p and compensation coil L f The diameter is 3mm, and the receiving coil L s The diameter is 2mm.

[0040] Table 1 System Parameters Self-alignment method verification: Compensation coil L f1 and L f1 Induced current I f1 and I f2 With DC power supply U dc Compensating inductor L f Load R L It is related to the mutual inductance M between the transmitter and receiver, but the DC power supply U dc and compensation inductor L f It is generally constant, therefore, as long as the load R L It is constant (R in this article) L =2.4Ω), then by comparing I f1 and I f2 The sizes of M3 and M4 are determined, and the direction of the coupling mechanism offset can be determined. Due to the symmetry of the coupling mechanism, this application only tested the positive directions of the x-axis and y-axis.

[0041] Figure 8 The y-dislocation and I-dislocation at different x (x = 0, 5, 10, and 15 cm) during the self-alignment stage are shown. f1 Due to the reverse cutoff of the diode, I f2 It tends towards 0. For example... Figure 9 (a) shows the output measured experimentally (x=5cm, y=3cm), where: blue represents the inverter output voltage U. in The light blue color represents the inverter output current I. in Green represents the compensation coil L. f1 Induced current I f1 Purple represents the compensation coil L. f2 Induced current I f2 After measuring its RMS, the conclusion was reached that I f1 =3.99A, I f2 →0. Therefore, it can be determined that if the current position of the coupling mechanism moves to the left (positive y-axis direction), the device should move its position to the right (negative y-axis direction). For example... Figure 9(b) shows the output measured experimentally (x=5cm, y=0cm). It can be seen that I f1 and I f2 They are essentially equal. It can be determined that, in this state, the coupling mechanism is aligned in the y-direction. This indicates that self-alignment is unaffected by x-alignment, but only related to y-alignment, which is consistent with the theoretical analysis of magnetically coupled structures.

[0042] Due to the symmetry of the coupling structure, this application only tested the positive direction of the y-axis. Figure 10 shows the x-alignment and output voltage U under three different y-alignment conditions (y = 0, 4, and 8 cm). L The relationship between them. Therefore, under three different y-alignment conditions, U L The fluctuations in x-alignment are consistent, indicating that self-alignment is unaffected by y-alignment and depends only on x-alignment. In this application, this fluctuation is utilized for self-alignment in the x-direction. When the x-misalignment approaches 0, U... L It also tends towards 0, and the devices are well aligned.

[0043] In the experiment of this embodiment, the error exponent α was set to 1V and β was set to 0.1A. The designed magnetic coupler can achieve an alignment accuracy of less than 5mm in the x and y directions, that is, during the self-alignment process, the measured U L For 0.937V and |I f1 -I f2 The value is 0.05A, and the receiver is considered to be well aligned.

[0044] In summary, this invention employs two Q-type coils in a reconfigurable coupling structure to determine the misalignment direction and condition of the receiving end, assisting the device in adjusting its position to achieve self-alignment. These coils also serve as compensating inductors for wireless power transmission during normal charging. The self-alignment function ensures that the coils are properly aligned before charging, thereby achieving high-power transmission. Testing on an experimental prototype platform with an output current of 21A and an output voltage of 49V demonstrates that the system can determine the alignment direction and assist in position adjustment, achieving an alignment accuracy within 5mm in both the x and y directions.

[0045] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A wireless charging system with coil alignment guidance and self-alignment, comprising a transmitter and a receiver, characterized in that: The receiving end includes a first receiving module and a second receiving module with identical structures. The first receiving module and the second receiving module are symmetrically arranged about the transmitting end. The output terminals of the first receiving module and the second receiving module are both connected to the load. Both the first receiving module and the second receiving module include a first secondary-side compensation capacitor, a second secondary-side compensation capacitor, a receiving coil, a compensation coil, and a switching switch. When the switching switch is closed, the first secondary-side compensation capacitor, the second secondary-side compensation capacitor, and the compensation coil form an LCC topology. When the switching switch is open, the first secondary-side compensation capacitor and the receiving coil are disconnected from the receiving circuit.

2. The wireless charging system with coil alignment guidance and self-alignment as described in claim 1, characterized in that: The receiving end also includes a receiving end controller for controlling the switching on and off of the switching switch; the receiving end controller includes a voltage sampling circuit for acquiring the load voltage, a current sampling circuit for acquiring the induced current of the compensation coil, an analog-to-digital converter module for converting the signal of the sampling circuit, and a switch control module for controlling the switching switch according to the output signal of the analog-to-digital converter module.

3. The wireless charging system with coil alignment guidance and self-alignment as described in claim 1, characterized in that: Both the first receiving module and the second receiving module include a rectifier and a filter capacitor connected in parallel; the input terminal of the rectifier is connected to one end of the second secondary compensation capacitor and the compensation coil, respectively, and the output terminal of the rectifier and the filter capacitor connected in parallel is connected to the load.

4. A wireless charging system with coil alignment guidance and self-alignment as described in claim 1, characterized in that: The switching device includes two MOSFETs connected in series in both directions.

5. A wireless charging system with coil alignment guidance and self-alignment as described in claim 1, characterized in that: The transmitting end includes a DC power supply, a high-frequency inverter, a primary-side compensation circuit, and a transmitting coil connected in sequence. The first receiving module and the second receiving module are symmetrically arranged about the transmitting coil.

6. A wireless charging system with coil alignment guidance and self-alignment as described in claim 5, characterized in that: Both the transmitting coil and the receiving coil are planar DD-type coils, and the compensation coil is a planar Q-type coil.

7. A wireless charging system with coil alignment guidance and self-alignment as described in claim 5, characterized in that: The primary-side compensation circuit is an LCC topology circuit.

8. A control method for controlling a wireless charging system comprising coil alignment guidance and self-alignment according to any one of claims 1 to 7, characterized in that: Includes the following steps: S1. Initialize the system transmitter circuit and start energy transfer; S2. Control the two switching switches to disconnect, driving the receiver to move closer to the transmitter; S3. Real-time acquisition of load voltage and induced current of the two compensation coils; S4. Adjust the position of the receiving end according to the load voltage and the induced current of the two compensation coils; S5. When the load voltage and the induced current of the two compensation coils meet the preset conditions, the receiving end stops moving, controls the two switching switches to close, and starts charging.

9. The control method for a wireless charging system with coil alignment guidance and self-alignment according to claim 8, characterized in that: The specific steps for adjusting the receiver position based on the load voltage and the induced current of the two compensation coils in step S4 are as follows: S41. Determine the difference between the induced currents of the two compensation coils: If I f2 - I f1 If >β, then drive the receiver to move forward toward the side of the first receiving module and return to step S3; If I f1 - I f2 If >β, then drive the receiver to move forward toward the side of the second receiver module and return to step S3; If |I f1 - I f2 | < β, then go to step S42; Among them: I f1 I is the induced current in the compensation coil of the first receiving module. f2 β is the induced current of the compensation coil in the second receiving module, and β is the preset current difference threshold. S42. Determine if the load voltage is less than a preset threshold: If not, adjust the receiver position and return to step S3; If so, proceed to step S5.

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