Wireless charging system and control method thereof

Abstract

The invention relates to a wireless charging system and a control method thereof, the wireless charging system comprises a direct current power supply, a transmitting end, a receiving end, a coupling structure for coupling the transmitting end and the receiving end, and a switch unit arranged at the transmitting end, and the switch unit has two working states. When the two states are switched, the switch unit enables the wireless charging system to be switched between a first topological structure for providing constant current output and a second topological structure for providing constant voltage output. The flexible conversion between the constant-voltage charging stage and the constant-current charging stage in the wireless charging process can be flexibly met through the two working states of the switch unit, the system structure is effectively simplified, and the hardware cost and the potential power loss are reduced. And the method is particularly suitable for application scenes with high requirements on reliability and environmental adaptability, such as underwater detectors.

Description

Technical Field

[0001] This invention relates to the field of wireless power transmission technology, and in particular to a wireless charging system and its control method. Background Technology

[0002] Wireless power transfer technology, especially inductive power transfer (IPT), achieves contactless energy transfer through the principle of electromagnetic induction, demonstrating enormous application potential in fields such as underwater detectors, automated guided vehicles, and consumer electronics. Taking underwater detectors as an example, they typically use lithium batteries for power, but traditional wired charging methods face inherent drawbacks in the underwater environment, including interface corrosion, sealing difficulties, and inconvenient maintenance. Wireless charging technology provides a fully enclosed, highly reliable charging solution for such devices. However, to achieve safe and efficient charging of lithium batteries, the charging process must strictly adhere to the "constant current (CC) followed by constant voltage (CV)" charging protocol, which poses a challenge to the design of wireless charging systems.

[0003] Existing technologies for achieving constant current / constant voltage charging typically have certain drawbacks. One common approach is to add an additional DC-DC converter to the system, achieving the target output through precise converter control. However, this undoubtedly increases the system's hardware cost, size, and power consumption. Another approach is frequency conversion control, enabling the system to achieve constant current or constant voltage output at different operating frequencies. However, this method often suffers from frequency splitting, resulting in complex control strategies. Other solutions employ hybrid compensation topologies, using multiple switches and inductors to achieve mode switching, but this also increases system complexity and power consumption. Furthermore, many control schemes rely on establishing a wireless communication link between the transmitter and receiver to provide load status feedback. This not only increases costs but also makes communication reliability difficult to guarantee in special environments such as underwater. Summary of the Invention

[0004] The purpose of this invention is to provide a wireless charging system and control method, which aims to solve the problems of complex structure, high cost and difficult control caused by the existing wireless charging system in order to achieve constant current and constant voltage charging.

[0005] This invention provides a wireless charging system, including a transmitter, a receiver, and a coupling structure connecting the transmitter and the receiver. The wireless charging system also includes a switching unit having two operating states. The switching unit is disposed at the transmitter. When switching between the two states, the switching unit causes the wireless charging system to switch between a first topology providing constant current output and a second topology providing constant voltage output.

[0006] Furthermore, the transmitting end includes an inverter circuit and a first compensation circuit. The first compensation circuit includes a first series compensation inductor connected in series with the inverter circuit. The switching unit is connected in parallel across the first series compensation inductor. The switch has two operating states: on and off. The wireless charging system is configured such that when the switching unit is in the on state, the first series compensation inductor is short-circuited, and the wireless charging system exhibits the first topology. When the switching unit is in the off state, the first series compensation inductor is connected to the circuit, and the wireless charging system exhibits the second topology.

[0007] Furthermore, the first topology is a PS / S topology, and the second topology is an LCC-S topology.

[0008] Furthermore, the coupling structure includes a primary coil connected to the transmitting end, a first magnetic core for winding the primary coil, a secondary coil connected to the receiving end, and a second magnetic core for winding the secondary coil. The first magnetic core and / or the second magnetic core include a plate-shaped base body and two flanges extending in the same direction perpendicular to the base body from opposite ends of the base body. The primary coil and / or the secondary coil are wound around the base body.

[0009] Furthermore, the switching unit is configured as a relay.

[0010] Furthermore, the inverter circuit is a high-frequency full-bridge inverter circuit.

[0011] Furthermore, the wireless charging system also includes a controller configured to control the switching unit to switch between two states according to a preset charging strategy.

[0012] Furthermore, the controller is configured to estimate the output electrical state of the receiver by monitoring the input electrical parameters of the transmitter, and control the switching of the switching unit based on the output electrical state, wherein the input electrical parameters include DC input voltage and DC input current.

[0013] Furthermore, the controller is also configured to synchronously switch the operating frequency of the transmitter when switching the operating state of the switching unit.

[0014] This application also provides a control method for a wireless charging system, the method comprising:

[0015] The switching unit is controlled to be in a first working state, so that the wireless charging system is in a first topology structure to achieve constant current charging.

[0016] The switching unit is controlled to be in a second working state, so that the wireless charging system is in a second topology structure to achieve constant voltage charging.

[0017] Furthermore, the control method includes:

[0018] Continuously monitor the input DC voltage and / or DC current of the transmitting end;

[0019] Based on the input DC voltage and / or DC current, estimate the output voltage or current of the receiving end;

[0020] The estimated output voltage or current is compared with a preset reference voltage or reference current to determine when to switch the operating state of the switching unit.

[0021] Furthermore, the method also includes:

[0022] When the wireless charging system switches between the constant current charging stage and the constant voltage charging stage, it controls the operating frequency of the transmitting end to switch between a first frequency corresponding to the constant current charging stage and a second frequency corresponding to the constant voltage charging stage.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows: The wireless charging system provided by the present invention, by setting a reconfigurable compensation topology, can change the circuit topology using only a single switching unit, thereby realizing the switching between constant current and constant voltage output modes on a simple hardware system, which greatly simplifies the system structure and reduces hardware costs; The control method provided by the present invention estimates the output state of the receiver by monitoring the input parameters of the transmitter and controls the switching of charging modes accordingly, completely avoiding the dependence on wireless communication between the transmitter and receiver, significantly reducing the complexity and cost of the control system, and improving the reliability and robustness of the system in harsh environments. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the wireless charging system of this application;

[0025] Figure 2 This is the equivalent circuit diagram of the PS / S topology when the switching unit of this application is turned on;

[0026] Figure 3 for Figure 2 Equivalent circuit diagram at zero phase angle;

[0027] Figure 4 This is the equivalent circuit diagram of the LCC-S topology when the switching unit of this application is disconnected;

[0028] Figure 5 for Figure 4 Equivalent circuit diagram at zero phase angle;

[0029] Figure 6 From left to right, the structures are planar CC-type magnetic core structure, EE-type magnetic core structure, and CC-type magnetic core structure.

[0030] Figure 7 This is a flowchart of a control method for a wireless charging system according to this application;

[0031] Figure 8 A schematic diagram of the output waveforms of the battery and inverter circuit under constant voltage charging mode;

[0032] Figure 9 This is a schematic diagram of the output waveform under load variation in constant voltage charging mode.

[0033] Figure 10 A schematic diagram of the output waveforms of the inverter circuit and the rectifier filter circuit in constant current charging mode;

[0034] Figure 11 A schematic diagram of the output waveform under load variation in constant current charging mode;

[0035] Figure 12 A schematic diagram showing the changes in system efficiency and output power throughout the entire wireless charging process;

[0036] Among them, 10 is a wireless charging system; 1 is a DC power supply; 2 is an inverter circuit; 3 is a first compensation circuit; 4 is a coupling structure; 5 is a second compensation circuit; 6 is a switching unit; and 7 is a rectifier and filter circuit. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of the present invention clearer, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0038] This invention provides a wireless charging system 10, see below. Figure 1 The system includes a DC power supply 1, a transmitter, a receiver, a coupling structure 4 connecting the transmitter and the receiver, and a switching unit 6 disposed on the transmitter. The switching unit 6 has two operating states. When switching between the two states, the switching unit 6 causes the wireless charging system 10 to switch between a first topology providing constant current output and a second topology providing constant voltage output.

[0039] Specifically, the transmitting end includes an inverter circuit 2 and a first compensation circuit 3.

[0040] The inverter circuit 2 is a high-frequency full-bridge inverter circuit. Specifically, the high-frequency full-bridge inverter circuit is a single-phase full-bridge inverter circuit composed of a first switch Q1, a second switch Q2, a third switch Q3, and a fourth switch Q4. The positive terminal of the DC power supply 1 is connected to the first switch Q1 and the third switch Q3, and the negative terminal of the DC power supply 1 is connected to the second switch Q2 and the fourth switch Q4. The inverter circuit 2 is used to convert DC power into high-frequency AC power. The two output terminals of the inverter circuit 2 generate high-frequency square wave AC voltage to power the subsequent stage.

[0041] The first compensation circuit 3 includes a first series compensation inductor Lin and a first parallel compensation capacitor Cp. The first series compensation inductor Lin is connected in series with the inverter circuit 2. The first parallel compensation capacitor Cp is connected in parallel with the primary coil of the coupling structure 4 and then connected in series with the first series compensation inductor Lin as a whole.

[0042] In one embodiment, the first switch Q1, the second switch Q2, the third switch Q3, and the fourth switch Q4 in the inverter circuit 2 can all be configured as MOSFETs.

[0043] The receiving end includes a second compensation circuit 5 and a rectifier and filter circuit 7 consisting of four diodes. This is used to convert the received high-frequency AC power into DC power to charge the load.

[0044] The second compensation circuit 5 is connected in series between the secondary coil of the coupling structure 4 and the rectifier filter circuit 7.

[0045] The rectifier-filter circuit 7 is specifically composed of a first diode D1, a second diode D2, a third diode D3, a fourth diode D4, and a filter capacitor. The first diode D1 and the fourth diode D4 form one group of diodes, and the second diode D2 and the third diode D3 form another group of diodes. The two groups of diodes conduct alternately to rectify the input AC power into DC power. The filter capacitor is connected to the output terminal of the rectifier-filter circuit 7 for filtering.

[0046] In this application, the wireless charging system 10 is configured with a reconfigurable compensation topology. Reconfigurable in this application means that the topology and electrical characteristics of the first compensation circuit 3 can be changed; that is, the topology and electrical characteristics of the first compensation circuit 3 can be reconfigured by controlling the switching unit 6.

[0047] Specifically, the switching unit 6 is connected in parallel across the first series compensation inductor Lin. The switching unit 6 is configured to have two operating states to change the electrical connection state of the first series compensation inductor Lin in the first compensation circuit 3, thereby allowing the wireless charging system 10 to switch between a first topology for providing constant current output and a second topology for providing constant voltage output.

[0048] The switch has two operating states: on and off. The wireless charging system 10 is configured such that when the switch unit 6 is in the on state, the first series compensation inductor Lin is short-circuited, and the wireless charging system 10 is in the first topology; when the switch unit 6 is in the off state, the first series compensation inductor Lin is connected to the circuit, and the wireless charging system 10 is in the second topology.

[0049] This application can flexibly meet the switching between constant voltage charging stage and constant current charging stage during wireless charging by using two working states of the switching unit 6, which effectively simplifies the system structure and reduces hardware costs and potential power loss.

[0050] In one specific implementation, the first topology is a PS / S topology, and the second topology is an LCC-S topology.

[0051] Specifically, in the PS / S topology, P refers to the primary coil, the first S is the series compensation capacitor at the transmitter, and the second S is the series compensation capacitor at the receiver; in the LCC-S topology, L refers to the compensation inductor at the transmitter, the first C refers to the series compensation capacitor at the transmitter, the second C refers to the parallel compensation capacitor at the transmitter, and S refers to the series compensation capacitor at the receiver.

[0052] Switching unit 6 is represented by switch S1 in the circuit diagram.

[0053] When switch S1 is turned on, the first series compensation inductor Lin is short-circuited, which is equivalent to removing the first series compensation inductor Lin from the first compensation circuit 3. The wireless charging system 10 then adopts a PS / S topology, which has constant current output characteristics. See the equivalent circuit diagram of the PS / S topology when switch S1 is turned on. Figure 2 .

[0054] When operating in constant current charging mode at zero phase angle, its equivalent circuit is as follows: Figure 3 At this time, the output voltage of the rectifier filter circuit 7 is:

[0055]

[0056] Among them, R ac It is the AC equivalent resistance of the output resistance, and M is the mutual inductance between the primary and secondary sides. L p and L S These are the self-inductances of the primary coil and the secondary coil, respectively.

[0057] When switch S1 is off, the first series compensation inductor Lin is connected in series with inverter circuit 2. See the equivalent circuit diagram of the LCC-S topology when switch unit 6 is off. Figure 4 .

[0058] L in and C p These are the first series compensation inductor Lin and the first parallel compensation capacitor Cp of the first compensation circuit 3 at the transmitting end. f and C s These are the first and second series compensation capacitors at the transmitting and receiving ends, respectively. V AB This is the input voltage of the wireless charging system 10, which is also the output voltage of the full-bridge inverter, V. ab This represents the output voltage of the wireless charging system 10, which is also the input voltage of the rectifier. AB and I ab This refers to the input and output currents of the wireless charging system 10. R ac It is the AC equivalent resistance of the output resistance. L p and L s These are the self-inductances of the primary and secondary coils, respectively, while M is the mutual inductance between the primary and secondary sides.

[0059] Under zero-phase-angle conditions, the LC resonant network exhibits constant-current output characteristics. Under resonance conditions, the LC series resonant network can be considered as an equivalent resistor. Therefore, according to the principle of duality, the LCC-S topology possesses constant-voltage output characteristics independent of the load. For the equivalent circuit in the specific constant-voltage mode, please refer to [link to relevant documentation]. Figure 5 When the zero phase angle is satisfied, the inverter input current can be derived as:

[0060]

[0061] The PS / S topology and LCC-S topology have excellent constant current and constant voltage output characteristics, respectively, so that the output mode does not depend on complex closed-loop control, thereby enhancing the stability of the wireless charging system 10.

[0062] This application achieves the switching between PS / S topology and LCC-S topology with the simplest system structure, specifically through the switching unit 6 being electrically connected to the first series compensation inductor Lin in the first compensation circuit 3.

[0063] It is understandable that the switching unit 6, as a functional description, can be implemented as a low-cost mechanical relay or a semiconductor switching device such as a MOSFET or IGBT.

[0064] When the switching unit 6 is in the conducting state, that is, when the switch S1 is in the conducting state, for example, when the relay is closed, the first series compensation inductor Lin is short-circuited. At this time, the first series compensation inductor Lin is removed from the compensation topology, thereby forming the PS / S topology. This structure is based on the circuit duality principle and has a constant current output characteristic that is independent of the load. In the figure, the first series compensation inductor Lin is represented by dark gray and does not participate in the electrical connection.

[0065] When the switch S1 is in the open state, for example, when the relay is disconnected, the series compensation inductor is connected to the circuit, thereby forming the LCC-S topology. This structure is also based on the principle of duality and has a constant voltage output characteristic that is independent of the load.

[0066] This application uses only two states of a single switching unit 6 to achieve the conversion between two complex topologies, which has the significant advantages of extremely low hardware cost and simple control logic.

[0067] In one embodiment, the coupling structure 4 includes a primary coil connected to the transmitting end, a first magnetic core for winding the primary coil, a secondary coil connected to the receiving end, and a second magnetic core for winding the secondary coil, wherein the first magnetic core and the second magnetic core are configured as a CC-type magnetic core structure.

[0068] The CC-type magnetic core structure is designed by planarizing the traditional toroidal magnetic core. Specifically, the first magnetic core and / or the second magnetic core include a plate-shaped base body and two flanges extending in the same direction perpendicular to the base body from opposite ends of the base body; the primary coil and / or the secondary coil are wound around the base body and / or the two flanges.

[0069] In one embodiment, the CC-type magnetic core structure can also be configured as a planar CC-type magnetic core structure, that is, the flange extends from the base body and has a first height, the base body has a first length connecting the two flanges, and the ratio of the first length to the first height is in the range of (7,9), so that the magnetic core structure is flattened as a whole, forming a planar CC magnetic core structure.

[0070] In another embodiment, the base body is projected in a similar square shape in its thickness direction, the base body has a first thickness, the first flange and / or the second flange has a second thickness, and the first thickness is set to twice the second thickness.

[0071] When the magnetic flux generated by the coils wound around the transmitting and receiving magnetic cores diffuses on the square-like base body, it radiates almost uniformly in all directions, without preferentially extending in any one direction due to its longer dimension. This ensures a highly uniform magnetic flux density distribution within the base body. The first thickness of the base body is set to twice the thickness of either the first or second flange, resulting in a large magnetic flux carrying capacity along the length of the base body and effectively preventing local magnetic saturation.

[0072] In this application, the planar CC-type magnetic core structure effectively solves the problem of decreased coupling coefficient caused by positional offset by optimizing the magnetic flux path, reducing magnetic leakage, and confining the magnetic field energy more concentrated inside the magnetic core.

[0073] The planar CC-type magnetic core proposed in this application can maintain a higher and more stable coupling coefficient within a large offset range in the three-dimensional X, Y, and Z directions, effectively enhancing the anti-offset capability and environmental adaptability of the wireless charging system 10, and ensuring stable and efficient energy transmission even in the case of misalignment.

[0074] To achieve automated control of the charging process, the system further includes a controller, such as a DSP28335 chip. The controller is configured to control the switching unit 6 to switch between at least two operating states according to a preset charging strategy.

[0075] The preset charging strategy can be a strategy of constant current charging followed by constant voltage charging during wireless charging, or a strategy that switches between the two modes based on a preset time. Of course, other charging strategies can also be set according to actual needs, and this application does not impose specific restrictions.

[0076] This application also provides a control method for a wireless charging system 10, wherein the controller is configured to estimate the output electrical state of the receiver by monitoring the input electrical parameters of the transmitter, and control the switching of the switching unit 6 based on the output electrical state.

[0077] Specifically, the controller collects the DC input voltage and DC input current of the transmitter in real time and calculates the output voltage or current value of the receiver.

[0078] exist Figure 1 In the schematic diagram of the wireless charging system 10, the midpoint voltage U of the full-bridge inverter is... AB Expanded into a Fourier series, it is represented as:

[0079]

[0080] Where n is the harmonic order and φ is the phase angle. In wireless power transmission systems, the quality factor of the compensation network is relatively high. Therefore, the fundamental frequency analysis method can be used in the proposed system. In this case, since only the fundamental frequency component is considered, we let n = 1. The input components of DC power supply 1 and the resonant network (RMS value) have the following relationship:

[0081]

[0082] The relationship between the rectifier input (root mean square value) and the battery pack output can be expressed as:

[0083]

[0084] Therefore, the DC / AC and AC / DC relationships between the input and output terminals of the entire wireless charging system 10 can be obtained through formulas (3) and (4) above. AC equivalent resistance R ac It can be done through formula R ac =8R o / π 2 It is derived that R0 is the output resistance, and both the AC voltage and current are root mean square values.

[0085] In constant current charging mode, the battery output voltage can be derived by combining equations (1), (3) and (4); in constant voltage charging mode, the output current can be calculated by equations (2), (3) and (4).

[0086] By monitoring the input electrical parameters of the transmitter to estimate the output electrical state of the receiver, and controlling the switching of the switching unit 6 based on the output electrical state, the dependence on the wireless communication link between the transmitter and receiver is eliminated, which greatly simplifies the system design, reduces manufacturing costs, and improves the reliability and robustness of the system in harsh communication environments such as underwater.

[0087] In another embodiment, the controller is further configured to synchronously change the operating frequency of the inverter circuit 2 from a first frequency f when switching the operating state of the switching unit 6. cc Switch to the second frequency f cv Wherein, the first frequency f cc Corresponding to the first topology, the second frequency f cv This corresponds to the second topology.

[0088] Wireless power transmission systems typically require Bluetooth, Wi-Fi, or ZigBee wireless communication devices on both the primary and secondary sides. This not only places high demands on transmission accuracy but also increases system cost and controller design complexity. This application predicts the output electrical state by monitoring the DC input voltage and current, and flexibly adjusts the system's operating frequency based on the real-time output voltage value. Specifically, when the system output voltage is lower than the battery's reference voltage, the controller automatically enters a constant current charging mode. In this mode, switch S1 remains on, and the operating frequency is set to f0. cc When the output voltage reaches or exceeds the battery reference voltage, the controller switches to constant voltage charging mode. At this time, switch S1 is turned off, and the operating frequency is adjusted to f. cv Once the output current decreases to the preset minimum level, the charging process is considered complete.

[0089] For example, in a 200W prototype, the first frequency f cc It can be set to 137kHz, the second frequency f cv It can be set to 149kHz.

[0090] By synchronously switching the first frequency f during the transition between the first and second topologies. cc With the second frequency f cv This ensures that the wireless charging system 10 can operate near its optimal soft switching point in both topologies, thereby reducing switching losses, optimizing the operating efficiency in different modes, and improving the average operating efficiency of the system throughout the entire charging process.

[0091] Accordingly, the present invention also provides a control method for a wireless charging system 10, applied to the aforementioned wireless charging system 10. The method includes:

[0092] The switching unit 6 is controlled to be in a first working state so that the compensation topology is configured as a first topology structure to achieve constant current charging.

[0093] The switching unit 6 is controlled to be in a second working state so that the compensation topology is configured as a second topology structure to achieve constant voltage charging.

[0094] Specifically, see Figure 7 The control steps include:

[0095] S1: Continuously monitor the input DC voltage and / or DC current of the transmitter;

[0096] S2: Estimate the output voltage or current of the receiving end based on the input DC voltage and / or DC current;

[0097] S3: Compare the estimated output voltage or current with a preset reference voltage or reference current to determine when to switch the operating state of the switching unit 6.

[0098] For example, when the estimated output voltage is lower than a preset reference voltage, the system maintains constant current charging; when the estimated output voltage reaches or exceeds the reference voltage, the system switches to constant voltage charging. This method provides a low-cost and highly reliable charging mode switching decision mechanism.

[0099] The preset reference voltage can be the battery's reference voltage.

[0100] In another embodiment, the control method for the wireless charging system 10 further includes:

[0101] When the wireless charging system 10 switches between the constant current charging stage and the constant voltage charging stage, it controls the operating frequency of the inverter circuit 2 at a first frequency f. cc With the second frequency f cv Switching between, wherein the first frequency f cc Corresponding to the first topology, or in other words, the first frequency f cc Corresponding to the constant current charging mode, the second frequency f cv Corresponding to the second topology, or in other words, the second frequency f cv This corresponds to the constant voltage charging mode.

[0102] For example, when the wireless charging system 10 switches from the constant current charging stage to the constant voltage charging stage, the operating frequency of the inverter circuit 2 is changed from the first frequency f. cc Switch to the second frequency f cv Conversely, this is to ensure the optimal energy conversion efficiency throughout the entire charging process.

[0103] To verify the actual performance of the wireless charging system in the wireless transmission system, a 200-watt prototype was built, using a DSP28335 as the main controller. The switching transistors Q1-Q4 in the inverter circuit 2 are IPB031N08N5, and the diodes D1-D4 in the rectifier-filter circuit 7 are DSA30I 100PA. A Chroma 63200A was used as the electronic load to simulate changes in the equivalent battery load. Specifically, the prototype parameters are shown in Table 1.

[0104] Table 1: Parameters of the prototype

[0105]

[0106]

[0107] During the experiment, in order to reduce the adverse effects of reactive power, the operating frequency was fine-tuned to a position slightly off from the resonant point, so as to maintain appropriate reactive power while achieving smooth switching.

[0108] For detailed experimental results, please refer to Figures 8-12 .

[0109] Figure 8 The experimental results of the battery and full-bridge inverter output waveforms in constant voltage charging mode are presented, with the output voltage set at 52V and the maximum output power reaching 200W. In constant voltage charging mode, the operating frequency is set to 149kHz to achieve soft switching.

[0110] Figure 9 The output waveform under varying load conditions in constant voltage charging mode is shown. Specifically, when the output resistance is adjusted from 13Ω to 24Ω, the output power decreases from 200W to 110W, and correspondingly, the output current decreases from 3.8A to 2.2A. Notably, even under varying load conditions, the battery output voltage remains stable at 52V, thus meeting the design requirement of a constant output voltage.

[0111] Figure 10 The output waveforms of the inverter circuit and rectifier filter circuit are displayed in constant current charging mode, and the output power is the same as in constant voltage charging mode.

[0112] Figure 11 The output waveform is displayed under constant current charging mode with varying load. When the output resistance increases from 10Ω to 13Ω, the output power increases from 110W to 200W, the output voltage increases from 38V to 51V, and the output current remains constant.

[0113] Figure 12 The diagram illustrates the system's efficiency and output power throughout the wireless charging process. The average efficiency in constant current charging mode is higher than in constant voltage charging mode. The system's overall maximum efficiency reaches 87%. Maximum output power is achieved at the critical point between constant current and constant voltage charging modes, fluctuating between 46W and 200W.

[0114] Experiments clearly demonstrate that the wireless charging system and wireless power transmission system provided in this application have a simplified structure and better system stability.

[0115] This application relates to a wireless charging system, including a DC power supply 1, a transmitter, a receiver, a coupling structure 4 connecting the transmitter and receiver, and a switching unit 6 disposed on the transmitter. The switching unit 6 has two operating states. When switching between the two states, the switching unit 6 causes the wireless charging system 10 to switch between a first topology providing constant current output and a second topology providing constant voltage output. The two operating states of the switching unit 6 flexibly meet the switching needs between the constant voltage charging stage and the constant current charging stage during wireless charging, effectively simplifying the system structure and reducing hardware costs and potential power losses. It is particularly suitable for applications with high reliability and environmental adaptability requirements, such as underwater detectors.

[0116] In the description of this specification, references to terms such as "an embodiment," "some embodiments," "specifically," or "optional embodiments," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of those different embodiments or examples.

[0117] This application has been described with reference to the above-mentioned embodiments; however, the above embodiments are merely examples for implementing this application. It must be noted that the disclosed embodiments do not limit the scope of this application. On the contrary, any modifications and refinements made without departing from the spirit and scope of this application are within the scope of patent protection of this application.

Claims

1. A wireless charging system, comprising a transmitter, a receiver, and a coupling structure coupling the transmitter and the receiver, characterized in that, The wireless charging system also includes a switching unit, which has two working states, and the switching unit is disposed at the transmitting end. When the two operating states are switched, the switching unit causes the wireless charging system to switch between a first topology that provides constant current output and a second topology that provides constant voltage output.

2. The wireless charging system according to claim 1, characterized in that, The transmitting end includes an inverter circuit and a first compensation circuit. The first compensation circuit includes a first series compensation inductor connected in series with the inverter circuit. The switching unit is connected in parallel across the first series compensation inductor. The two working states of the switch include on and off. The wireless charging system is configured such that when the switching unit is in the ON state, the first series compensation inductor is short-circuited, and the wireless charging system exhibits the first topology; when the switching unit is in the OFF state, the first series compensation inductor is connected to the circuit, and the wireless charging system exhibits the second topology.

3. The wireless charging system according to claim 2, characterized in that, The first topology is a PS / S topology, and the second topology is an LCC-S topology.

4. The wireless charging system according to claim 1, characterized in that, The coupling structure includes a primary coil connected to the transmitting end, a first magnetic core for winding the primary coil, a secondary coil connected to the receiving end, and a second magnetic core for winding the secondary coil. The first magnetic core and / or the second magnetic core include a plate-shaped base body and two flanges extending in the same direction perpendicular to the base body from opposite ends of the base body. The primary coil and / or the secondary coil are wound around the base body.

5. The wireless charging system according to claim 1, characterized in that, The switching unit is configured as a relay.

6. The wireless charging system according to claim 2, characterized in that, The inverter circuit is a high-frequency full-bridge inverter circuit.

7. The wireless charging system according to any one of claims 1 to 6, characterized in that, The wireless charging system also includes a controller configured to control the switching unit to switch between two states according to a preset charging strategy.

8. The wireless charging system according to claim 7, characterized in that, The controller is configured to estimate the output electrical state of the receiver by monitoring the input electrical parameters of the transmitter, and to control the switching of the switching unit based on the output electrical state. The input electrical parameters include DC input voltage and DC input current.

9. The wireless charging system according to claim 8, characterized in that, The controller is also configured to synchronously switch the operating frequency of the transmitter when switching the operating state of the switching unit.

10. A control method for a wireless charging system, applied to the wireless charging system as described in any one of claims 1 to 9, characterized in that, The method includes: The switching unit is controlled to be in a first working state, so that the wireless charging system is in a first topology structure to achieve constant current charging. The switching unit is controlled to be in a second working state, so that the wireless charging system is in a second topology structure to achieve constant voltage charging.

11. The control method according to claim 10, characterized in that, The control method includes: Continuously monitor the input DC voltage and / or DC current of the transmitting end; Based on the input DC voltage and / or DC current, estimate the output voltage or current of the receiving end; The estimated output voltage or current is compared with a preset reference voltage or reference current to determine when to switch the operating state of the switching unit.

12. The control method according to claim 10, characterized in that, The method also includes: When the wireless charging system switches between the constant current charging stage and the constant voltage charging stage, it controls the operating frequency of the transmitting end to switch between a first frequency corresponding to the constant current charging stage and a second frequency corresponding to the constant voltage charging stage.

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