Control method of wireless charging transmitter

Abstract

This invention discloses a control method for a wireless charging transmitter. Step 1: The excitation coil is coupled to the first transmitting coil of the first transmitting unit, and the first control switch is closed. Step 2: Other control switches are closed sequentially, and an AC signal with a frequency of is applied to the excitation coil. Step 3: The first phase difference of the following two parameters is compared: Parameter 1: the voltage of the AC signal applied to the excitation coil; Parameter 2: the total current in the circuit formed by the first transmitting unit and the transmitting units where the control switches are closed each time. Based on the value of the first phase difference, it is determined whether there is a receiving coil at the position corresponding to the transmitting unit where the control switch is closed each time. If so, the corresponding transmitting unit is defined as a working unit. Step 4: During wireless charging, the control switches of all working units are closed. This method can efficiently determine the position of the receiving coil above the transmitting coil group and activate the corresponding transmitting coil.

Description

Technical Field

[0001] This invention relates to the field of wireless charging, and more particularly to a control method for a wireless charging transmitter. Background Technology

[0002] Wireless charging is a technology that transmits electrical energy directly without physical contact. There is generally a certain positional offset between the transmitting and receiving coils in wireless charging. When the offset between the transmitting and receiving coils is significant, the transmission power and efficiency of the wireless charging system will decrease noticeably; especially when the offset exceeds a certain range, charging may even fail. This will affect the user experience and the widespread adoption of wireless charging technology. Therefore, improving the offset range of wireless charging is one of the key issues that needs to be addressed. Summary of the Invention

[0003] This invention provides a control method for a wireless charging transmitter. It enables efficient charging even when the device being charged has a large offset range.

[0004] The control method for the wireless charging transmitter includes the following steps: Step 1, the excitation coil 1 is coupled to the first transmitting coil L1 of the first transmitting unit, the first control switch S1 is closed, and the other control switches S are opened; Step 2, the other control switches S are closed sequentially, one control switch S at a time, and a frequency of [frequency value missing] is applied to the excitation coil 1. The AC signal, where L D2 The equivalent inductance C is formed by the first transmitting unit, the transmitting unit containing the control switch S that is closed each time, the excitation coil 1, and the receiving coil. D2 The equivalent capacitance of the first transmitting unit and the transmitting unit where the control switch S is closed each time is calculated; Step 3, compare the first phase difference Ф1 of the following two parameters: Parameter 1: the voltage of the AC signal applied to the excitation coil 1; Parameter 2: the total current of the circuit formed by the first transmitting unit and the transmitting unit where the control switch S is closed each time in parallel; Based on the value of the first phase difference Ф1, determine whether there is a receiving coil at the position corresponding to the transmitting unit where the control switch S is closed each time. If so, define the corresponding transmitting unit as a working unit; Step 4, when performing wireless charging, close the control switches S of all working units.

[0005] Preferably, a first phase difference threshold Ф is preset. T And divide it into two threshold ranges: the first threshold range is [0°, Ф] T ] indicates that parameter 2 lags behind parameter 1; the second threshold range is [Ф T ',360°],where Ф T =360°-Ф TThis indicates that parameter 2 leads parameter 1; when the first phase difference Ф1 is not within the range of the two thresholds, it is determined that there is no receiving coil at the position of the transmitting unit where the closed control switch S is located, otherwise there is a receiving coil.

[0006] Preferably, the preset phase difference threshold Ф T The method for obtaining it is as follows: Ф T =[(t3-t1) / (t2-t1)]*360° Wherein, t1 is the rising edge trigger time of the first cycle of the AC signal voltage applied to the excitation coil 1; t2 is the rising edge trigger time of the second cycle of the AC signal voltage applied to the excitation coil 1; and t3 is the rising edge trigger time of the first cycle of the total current of the circuit formed by the first transmitting unit and the transmitting unit where the control switch S is closed each time.

[0007] Preferably, the first transmitting unit is located in the central region of the transmitting coil group consisting of all transmitting units.

[0008] Preferably, when the device to be charged is placed in the charging area, the receiving coil and the first transmitting coil L1 are within the working coupling range.

[0009] Preferably, the first transmitting unit is located at any position in the transmitting coil group composed of all transmitting units. Before step 2, it is also determined whether there is a receiving coil at the position of the first transmitting unit. The method is as follows: close the first control switch S1, and apply a frequency of [missing value] to the excitation coil 1. The AC signal, where L D1 C is the equivalent inductance of the first transmitting unit. D1 The equivalent capacitance of the first transmitting unit is used; the second phase difference Ф2 of the following two parameters is compared: parameter 3: the voltage of the AC signal applied to the excitation coil 1; parameter 4: the current of the first transmitting unit; based on the value of the second phase difference Ф2, it is determined whether there is a receiving coil at the position corresponding to the first transmitting unit.

[0010] Preferably, if there is a receiving coil at the position corresponding to the first transmitting unit, proceed to step 2, and the first transmitting unit is defined as a working unit; if there is no receiving coil at the position corresponding to the first transmitting unit, proceed to step 2, and the first transmitting unit is not defined as a working unit.

[0011] The wireless charging transmitter control method of the present invention can efficiently determine the position of the receiving coil above the transmitting coil group and turn on the corresponding transmitting coil to work. Attached Figure Description

[0012] Figure 1This is a flowchart of the control method for the wireless charging transmitter of the present invention; Figure 2 This is a schematic diagram of the corresponding structure of the control method for the wireless charging transmitter of the present invention. Figure 3 This is a schematic diagram of the transmitting unit in the control method of the wireless charging transmitter of the present invention; Figure 4 This is a schematic diagram of the receiving coil and transmitting coil group in the control method of the wireless charging transmitter of the present invention; Figure 5 A schematic diagram illustrating wireless charging of electronic devices. Detailed Implementation

[0013] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0014] This invention discloses a control method for a wireless charging transmitter. To better understand the working process of the method, its structure and the simple principle of wireless charging will be explained first.

[0015] See Figure 2 , Figure 3 and Figure 4 The wireless charging transmitter (also called the transmitting device) in this application comprises a power supply 6, a working circuit, an excitation coil 1, an electrical signal acquisition circuit 2, a controller 3, and a transmitting coil group 4. The working circuit includes an inverter circuit 7 and a compensation circuit 8. During wireless charging, the device to be charged has a receiving device (receiving coil 51), which is coupled to the transmitting coil L in the transmitting coil group 4.

[0016] As an external device, the power supply can be either a DC or AC power source. When using a DC power source, the input DC power is connected to the inverter circuit. The input DC power is converted into high-frequency AC power by the inverter circuit and then output to the input terminal of the compensation circuit. The high-frequency AC power is then applied to the excitation coil 1 after passing through the compensation circuit. When using an AC power source, an AC power supply is used as the input. A rectifier circuit must be added before the inverter circuit. The output of the AC power supply is rectified and converted into DC power before being input to the inverter circuit.

[0017] The receiver's controller interacts with the transmitter's controller 3 via a wireless communication link, and the receiver sends its charging request to the transmitter.

[0018] See also Figure 2 and Figure 3The transmitting coil group 4 consists of multiple transmitting units connected in parallel. Each transmitting unit is formed by a transmitting coil L, a compensation capacitor C, and a control switch S connected in series to form a loop. This loop can also be called a transmitting circuit, meaning that the transmitting unit consists of at least the above three parts forming a transmitting circuit. The inductance of the transmitting coil L and the compensation capacitor C are connected in series to form an LC transmitting circuit, which can also be called an LC transmitting unit. To distinguish the components within multiple different transmitting units, each transmitting unit can be numbered, and its included transmitting coil L, compensation capacitor C, and control switch S can be numbered accordingly. For example, the second transmitting unit includes a second transmitting coil L2, a second compensation capacitor C2, and a second control switch S2, etc. Figure 2 In this diagram, L1-Ln represent the transmitting coils in each transmitting unit, C1-Cn represent the compensation capacitors in each transmitting unit, and S1-Sn represent the control switches in each transmitting unit.

[0019] One end of the compensation capacitor C of each transmitting unit is connected together, and the other end of the compensation capacitor C is also connected together, meaning that all transmitting units are connected in parallel. In other words, multiple transmitting units connected in parallel form transmitting coil group 4.

[0020] Each transmitting unit's control switch S is controlled by the controller 3. By switching the control switch S on or off, the transmitting circuit is connected or disconnected, thus controlling whether the transmitting unit is working. During operation, the receiving coil 51 may couple with the transmitting coils L of some transmitting units. The method of this application can quickly determine which transmitting coils L can couple with the receiving coil 51, and connect the corresponding transmitting units of those that can couple via the control switch S.

[0021] The transmitting coils are arranged in an array, with the transmitting coils placed closely adjacent to each other in parallel on a plane. The transmitting coils have regular shapes, such as one or more combinations of shapes like circles, squares, rectangles, and hexagons. In addition to being arranged in parallel, the transmitting coils can also be arranged with some overlap between adjacent transmitting coils.

[0022] In multiple transmitting units, at least one transmitting unit's transmitting coil L can be coupled to the excitation coil 1. Since there are multiple transmitting units, there are also multiple transmitting coils L, while there can only be one excitation coil 1. In terms of size, the size of one excitation coil 1 is roughly equivalent to the size of one transmitting coil L, so it is not possible for one excitation coil 1 to be coupled to the transmitting coils L in all transmitting units simultaneously. The excitation coil 1 is located below the transmitting coil group 4, that is, on the side relatively far from the receiving coil 51.

[0023] For ease of explanation, the transmitting unit containing the transmitting coil L coupled to the excitation coil 1 will be named the first transmitting unit. This first transmitting unit can be any transmitting unit, but preferably, it is the transmitting unit located in the central part of the transmitting coil group 4.

[0024] The electrical signal acquisition circuit 2 can acquire electrical signals from any transmitting unit, such as current and voltage, or the total current of all parallel transmitting units. The controller 3 is connected to the electrical signal acquisition circuit 2 and can control the on / off relationship of any control switch S based on the acquired current information.

[0025] Combination Figure 2 and Figure 4 The receiving device, also known as the receiving end, generally includes a receiving coil 51, a receiving end controller 52, a receiving end compensation circuit 53, a receiving end rectification and filtering circuit 54, and a battery as a load 55. When the receiving device is above the transmitting coil group 4, the excitation coil 1, the transmitting coil group 4, and the receiving coil 51 above the transmitting coil group 4 form a three-coil structure with a relay coil. The transmitting coil L in the multiple transmitting units serves as a relay coil between the excitation coil 1 and the receiving coil 51.

[0026] For wireless charging systems, the relay coil in a three-coil structure increases the resonant current, resulting in stronger transmission capabilities compared to a conventional two-coil structure with only a receiver and a transmitter. This allows for longer transmission distances, higher transmission efficiency, and greater transmission power. During operation, at the location of the receiver coil 51, within the corresponding transmitter unit, the control switch S closes, enabling the transmitter unit to conduct and complete wireless power transmission. In other words, the receiver coil 51 can couple with the transmitter coil L within the transmitter unit.

[0027] The following describes the control method for the wireless charging transmitter. This method can determine which transmitter coils L can couple with the receiver coil 51, thereby closing the corresponding control switch S.

[0028] See Figure 1 It can be divided into four main steps. These four steps are the basic steps. In the following description, other steps may be interspersed among these four steps.

[0029] Step 1, which can be considered the initial step, involves coupling the excitation coil 1 with the first transmitting coil L1 of the first transmitting unit, closing the first control switch S1, and opening the other control switches S. As explained above, the transmitting unit coupled with the excitation coil 1 is defined as the first transmitting unit.

[0030] Step 2, which can be called the action step, mainly involves the action of the control switches S. While keeping the first control switch S1 closed, the other control switches S are closed sequentially, one switch S at a time. Generally, they are closed in sequence. During each closure, a frequency of [frequency value missing] is applied to the excitation coil 1. The AC signal, denoted by the operating frequency f2, will be explained below as having its origin. Where L... D2 The equivalent inductance C is formed by the first transmitting unit, the transmitting unit where the control switch S is closed each time, the excitation coil 1, and the receiving coil 51. D2 It is the equivalent capacitance of the first transmitting unit and the transmitting unit where the control switch S is closed each time.

[0031] Taking the closed second transmitting unit as an example, the first and second transmitting units form a parallel circuit, and in this circuit, the first transmitting coil L1 has mutual inductance with the excitation coil 1 and the receiving coil 51, and the second transmitting coil L2 has mutual inductance with the receiving coil 51. According to the principles of circuit analysis, this parallel circuit can be equivalently transformed into an LC circuit, then L... D2 The inductance of the equivalent circuit, hereinafter referred to as the equivalent inductance; C D2 The capacitance of the equivalent circuit is referred to below as the equivalent capacitance. Since the inductance value of the transmitting coil L and the capacitance value of the compensation capacitor C in each transmitting unit are known, the above-mentioned L... D2 and C D2 They already knew.

[0032] For ease of explanation, we refer to the transmitting unit connected each time the control switch S is closed as the transmitting unit to be identified, that is, to identify whether there is a receiving coil 51 at its location.

[0033] Generally, each transmitting unit is essentially the same; therefore, regardless of which transmitting unit's control switch S is closed, the equivalent inductance L... D2 and equivalent capacitance C D2 The values ​​are also the same, so the frequency of the AC signal loaded on the excitation coil 1 is consistent each time the control switch S is closed.

[0034] Of course, the parameters of each transmitting unit can be different. These parameters can be known in advance, so the frequency can be adjusted accordingly each time a different control switch S is closed.

[0035] Step 3, the comparison step, is performed after each control switch S is closed in Step 2. That is, a comparison is performed every time a control switch S is closed. Step 3 compares the first phase difference Ф1 between the following two parameters.

[0036] Parameter 1: The voltage of the AC signal applied to the excitation coil 1; Parameter 2: The total current of the circuit formed by the first transmitting unit and the transmitting unit containing the control switch S which is closed each time. Taking the closure of the second control switch S2 as an example, data 2 is: the total current of the circuit formed by the first transmitting unit and the second transmitting unit in parallel. To acquire data 2, sampling resistors can be set at both ends of the parallel connection point of the parallel transmitting units (such as the parallel connection point of the first transmitting unit and the second transmitting unit). The electrical signal acquisition circuit 2 will process the current signal flowing through the sampling resistor, and after amplitude and waveform processing, input the signal to the controller 3, which will then measure the current phase angle.

[0037] Based on the value of the first phase difference Ф1, it is determined whether there is a receiving coil 51 at the position corresponding to the transmitting unit where the control switch S is closed each time. If so, the corresponding transmitting unit is defined as a working unit. The specific values ​​and judgment principles are explained in detail below.

[0038] Step 2 will close all control switches S once, and step 3 will also determine whether there is a receiving coil 51 at the corresponding position of each transmitting unit. All transmitting units determined to have a receiving coil 51 will be defined as working units.

[0039] Step 4, charging step: When wireless charging, close the control switches S of all working units.

[0040] The following explains how to determine whether a receiving coil 51 is present based on the first phase difference Ф1.

[0041] Preset phase difference threshold Ф T And divide it into two threshold ranges: The first threshold range is [0°, Ф]. T ] indicates that parameter 2 lags behind parameter 1.

[0042] The second threshold range is [Ф] T ',360°],where Ф T =360°-Ф T This indicates that parameter 2 precedes parameter 1.

[0043] When the first phase difference Ф1 is not within the range of the two thresholds, it is determined that there is no receiving coil 51 at the position of the transmitting unit where the closed control switch S is located; otherwise, there is a receiving coil 51.

[0044] Preset phase difference threshold Ф T The method for obtaining it is as follows: Ф T =[(t3-t1) / (t2-t1)]*360° Wherein, t1 is the rising edge trigger time of the first cycle of the AC signal voltage applied to the excitation coil 1; t2 is the rising edge trigger time of the second cycle of the AC signal voltage applied to the excitation coil 1; and t3 is the rising edge trigger time of the first cycle of the first transmitting unit current.

[0045] When the control switch S is turned on, the compensation capacitor C of the transmitter to be identified is connected to the transmitting coil L to form a series circuit. When a signal (a low-power AC signal) is applied to the excitation coil 1, the operating frequency of the signal is set so that one transmitter to be identified and the first transmitter are in a resonant state when there is a receiving coil 51 above them. That is, the equivalent inductive reactance and equivalent capacitive reactance in the parallel transmitter to be identified and the first transmitter cancel each other out, and the two parallel transmitters resonate.

[0046] The operating frequency of the AC signal can be determined based on the parameters of the transmitting end. When the transmitting coils of the unit to be identified and the first transmitting unit have a receiving coil 51 above them, there is mutual inductance between the transmitting coil L1 of the unit to be identified and the receiving coil 51. Meanwhile, the transmitting coil L1 of the first transmitting unit has mutual inductance with both the receiving coil 51 and the excitation coil 1. Based on the compensation capacitor values ​​of the unit to be identified and the first transmitting unit, the operating frequency f2 is made to satisfy... The signal applied to the excitation coil 1 at the transmitting end at the working frequency f2 is also an alternating current signal, which can make the two parallel transmitting units resonate.

[0047] The first transmitting unit is located in the central area of ​​the transmitting coil group 4, which consists of all the transmitting units. This ensures that when placing the device to be charged, the first transmitting unit is generally always near the receiving coil 51. Taking wireless charging of a mobile phone or other electronic device as an example... Figure 5 As shown, outer frame A is the area where the mobile phone is placed, and inner frame B is the area where the transmitting coil group 4 is located. Figure 5 The receiving coil 51 (shown as dashed in the image) is also... Figure 5 (Represented by dashed lines) is generally located in the center area of ​​the mobile phone. Therefore, as long as the mobile phone is placed inside the outer frame A, the receiving coil 51 can be coupled with the first transmitting unit.

[0048] The text above mentions that "the transmitting unit where the transmitting coil L coupled to the excitation coil 1 is located is named the first transmitting unit". It can be seen that the first transmitting unit is defined artificially. Combining the explanation in the previous paragraph, the transmitting unit located in the central area of ​​the transmitting coil group 4 is selected, and the transmitting unit is coupled to the excitation coil 1 to make it the first transmitting unit. This ensures that there is a receiving coil 51 at the location of the first transmitting unit.

[0049] Of course, in some embodiments, it is not necessary to place the first transmitting unit in the central area of ​​the transmitting coil group 4. In that case, whether there is a receiving coil 51 above the first transmitting unit needs to be determined by the following method.

[0050] This method is performed before step 2 above. In step 1, the first control switch S1 has already been closed, and then a frequency of [frequency value missing] is applied to the excitation coil 1. The AC signal, the frequency of which is denoted as the operating frequency f1. Wherein, L... D1 The equivalent inductance of the first transmitting unit includes the inductance of the first transmitting coil L1 and the mutual inductance with the excitation coil and the receiving coil, C. D1 This is the equivalent capacitance of the first transmitting unit.

[0051] Compare the second phase difference Ф2 between the following two parameters: Parameter 3: The voltage of the AC signal applied to the excitation coil 1. This parameter is the same as parameter 1, but the specific value may differ. Parameter 4: The current of the first transmitting unit.

[0052] Based on the value of the second phase difference Ф2, it is determined whether there is a receiving coil 51 at the position corresponding to the first transmitting unit. The method of determination is the same as that of determining the first phase difference Ф1, which is to compare it with two divided threshold ranges. When the second phase difference Ф2 is within the two threshold ranges, it is determined that there is a receiving coil 51 above the first transmitting unit.

[0053] If there is a receiving coil 51 at the position corresponding to the first transmitting unit, proceed to step 2, and the first transmitting unit is defined as a working unit; if there is no receiving coil 51 at the position corresponding to the first transmitting unit, proceed to step 2 again, but the first transmitting unit is not defined as a working unit.

[0054] Although step 2 will proceed regardless of the presence of receiving coil 51, the frequency of the AC signal applied to excitation coil 1 may change in step 2. From the formula, it remains... However, since there is no receiving coil above the first transmitting unit, the equivalent circuit consisting of the transmitting unit, the first transmitting unit, the excitation coil 1, and the receiving coil 51 changes each time the control switch S is closed, and therefore their corresponding equivalent inductances also change. Thus, the expression for the frequency remains unchanged, but the numerical values ​​in the formula change.

[0055] For convenience, we will assume that the first transmitting unit is located at the center of the transmitting coil group 4. This ensures that a receiving coil 51 is always present above any device to be charged, thus avoiding the aforementioned numerical variation. Alternatively, the first transmitting unit can be positioned where no receiving coil 51 is present. For example, it can be placed outside the transmitting coil group 4, outside the inner frame B, where no receiving coil 51 is ever above it. In this case, the expression of the formula will not change, only the corresponding values ​​will be altered. Because the receiving coil is absent above the first transmitting unit, the parameters of the equivalent circuit change, leading to a change in the final numerical result.

[0056] In existing technologies, wireless charging systems with multiple transmitting coils typically identify the position of the receiving coil 51 by measuring the reflected impedance generated by the receiving device in the transmitting device, or by measuring the mutual inductance between the transmitting and receiving coils 51. This is because the measurement process involves applying current to both the transmitting and receiving devices and detecting their parameters. This current flows through the power conversion circuit and load in the receiving device, and factors such as different loads can affect the measurement results. To address this issue, existing technologies short-circuit the load in the receiving device when identifying the receiving coil position to avoid the influence of the load. For example, patent CN114050668B connects two points at the output of the impedance matching circuit in the receiving device when measuring the coil mutual inductance value M, thus disconnecting the downstream rectifier filter circuit and the load by short-circuiting these two points.

[0057] In this embodiment, the transmitting coil group 4 is an independent circuit composed of multiple transmitting units connected in parallel. The equivalent impedance of the two parallel transmitting units is related not only to the inductance of the reflecting coil itself and the compensation capacitor, but also to the mutual inductance with the excitation coil 1 and the receiving coil 51. The mutual inductance between the first transmitting coil L1 and the excitation coil 1 is a fixed value, while the mutual inductance between the receiving coil 51 and other transmitting coils is the target parameter to be detected. The result is reflected in the phase difference between the voltage of the transmitting device and the current of the receiving device. During the phase difference measurement process, the parallel working transmitting units are not affected by the power conversion circuit and load of the receiving device. Therefore, the advantage of this embodiment is that it does not require the addition of a switching circuit on the receiving device side, that is, it does not require modification of the receiving device circuit. This reduces the number of system components, lowers cost and complexity, and provides better compatibility with existing mature circuit designs or widely used wireless charging receivers, such as mobile phones.

[0058] After identifying all transmitting units, it is necessary to determine whether the total transmission power of all working units meets the system power transmission requirements. Specifically, this is determined based on the transmission power that each transmitting coil can carry and the number of working transmitting coils (the transmitting coils within a working unit are the working transmitting coils). The transmission power of each transmitting coil is determined by its minimum operating voltage and maximum current carrying capacity. The total transmission power of all working transmitting coils must be greater than the system's maximum transmission power for power transmission to be initiated; otherwise, it cannot be initiated or must be initiated by reducing the transmission power.

[0059] The following explains the potential problem of metal foreign objects during wireless charging.

[0060] Generally, when wireless charging is in progress, the presence of a metal object above the transmitting coil will cause it to be heated by the electromagnetic field generated by the transmitting coil, thereby reducing the system's power transmission performance or preventing it from working properly, and may even lead to safety issues. Therefore, when there is a metal object above the transmitting coil, it needs to be identified by the metal object detection function, and charging should not be started until the metal object is removed.

[0061] In this application, the transmitting unit in the transmitting coil group 4 is equipped with a control switch S. When the control switch S of the non-working unit is turned off, the non-working transmitting coil (the transmitting coil of the non-working unit, i.e., the non-working transmitting coil) will not generate current or electromagnetic field. Therefore, according to this application, after identifying the transmitting coil ("identification" refers to identifying whether there is a receiving coil 51 above), if the total transmission power of the working transmitting coil meets the requirements, wireless power transmission can be directly started without going through the metal foreign object detection process.

[0062] The reason why the phase difference detected during the identification process of the transmitting unit (i.e., the process of detecting the presence of the receiving coil 51 above the transmitting coil) is not within the threshold range is that, in addition to the absence of the receiving coil 51 above the transmitting coil, there is another possibility: the presence of a metallic foreign object on the surface of the transmitting coil. This includes two specific situations: 1. There is no receiving coil 51 above the transmitting coil, but there is a metallic foreign object.

[0063] 2. There is a receiving coil 51 above the transmitting coil, but there is a metallic foreign object between the transmitting coil and the receiving coil 51.

[0064] The total transmission power of the working transmitting coils is insufficient because there are not enough working transmitting coils. In this case, the metal foreign object detection function can be activated to find and remove metal foreign objects above the transmitting coils in order to obtain more working transmitting coils.

[0065] When detecting metallic foreign objects, a method similar to the one described above can be used, namely, the method of identifying the position of the receiving coil 51 on the transmitting coil group 4. Keep the first control switch S1 closed, disconnect other control switches S, and then sequentially connect the control switches S of the non-working transmitting units, connecting only one non-working transmitting unit's control switch S at a time. An AC signal (low power) is applied to the excitation coil 1, causing the total inductive reactance and total capacitive reactance in the parallel non-working transmitting unit and the first transmitting unit to cancel each other out, resulting in resonance between the two parallel transmitting units (the transmitting circuits in the two transmitting units). The operating frequency of the AC signal is determined based on the parameters of the non-working transmitting unit (where there is no receiving coil 51 above it) and the first transmitting unit (where there is a receiving coil 51 above it). Specifically, the non-working transmitting unit only has the inductance of its transmitting coil, while the transmitting coil L1 of the first transmitting unit has mutual inductance with both the receiving coil 51 and the excitation coil 1. Based on the compensation capacitor values ​​of the non-working transmitting unit and the first transmitting unit, the operating frequency f3 is made to satisfy... L D3 The equivalent inductance of the two parallel transmitting units includes the inductance of the non-operating transmitting coil and the first transmitting coil L1, as well as the mutual inductance between the first transmitting coil L1 and the receiving coil 51 and the excitation coil, C. D3 This is the equivalent capacitance of the two parallel transmitting units. The transmitting device applies an AC input to the excitation coil 1 at the operating frequency f3, which can make the two parallel transmitting units resonant when there is no receiving coil 51 above the non-operating transmitting coil.

[0066] Then compare the third phase difference Ф3 between the following two parameters: Parameter 5: The voltage of the AC signal applied to excitation coil 1. It is consistent with parameters 1 and 3, meaning the content is the same, but the numerical value may not be.

[0067] Parameter 6: The total current in the circuit formed by the first transmitting unit and the transmitting units of the control switch S that are closed each time. This parameter 6 is similar to parameter 2, except that it has already been determined which units are non-working and which are working. Therefore, in parameter 6, the transmitting units of the control switch S that are closed each time are all non-working units.

[0068] The third phase difference Ф3 is the same as the first phase difference Ф1 and the second phase difference Ф2 mentioned above. It is compared with two threshold ranges. When the third phase difference Ф3 is within the threshold range, it is determined that there is no receiving coil 51 above the non-working transmitting coil (because the determination of the working frequency f3 at this time is based on the absence of receiving coil 51 above the non-transmitting unit, so being within the threshold range indicates that there is no receiving coil 51 above and no foreign object affecting it); when the third phase difference Ф3 is not within the threshold range, it is determined that there is an abnormality such as a metal foreign object in the transmitting coil of the non-working transmitting unit.

[0069] The wireless charging system reports an abnormality of metal foreign objects through the controller 3. After removing the foreign objects, it re-completes the process of identifying the position of the receiving coil 51 on the transmitting coil group 4. If the removal of foreign objects increases the number of working transmitting coils, and the total transmission power of the working transmitting coils meets the requirements, then wireless power transmission can be started. If the total transmission power of the working transmitting coils still does not meet the requirements, and no metal foreign objects are found after metal foreign object detection, it may be that the number of transmitting coils tightly coupled between the receiving coil 51 and the transmitting coil group 4 is too small, and wireless charging cannot be initiated. It is necessary to change the position of the receiving device to align with the transmitting coil group 4 to couple more transmitting coils, or start by reducing the transmission power after system confirmation.

[0070] Of course, since the excitation coil is located at the center of the transmitting coil group 4 in this embodiment, when the receiving coil 51 is above the first transmitting coil, it will generally cover several other transmitting coils, so the number of working transmitting coils is unlikely to be too small. Furthermore, according to this application, when designing the wireless charging system, the transmittable power of each transmitting coil can be designed to be relatively large. In the event of abnormal situations such as metal foreign objects, the total transmittable power requirement can still be met even if the abnormal transmitting coil is disconnected, thus reducing the number of working transmitting coils. When the number of working transmitting coils exceeds the total transmittable power requirement, the working transmitting units can be selected to optimize power transmission. For example, several working transmitting coils that are relatively concentrated together can be selected, while the remaining working transmitting units can be disconnected to ensure a more concentrated electromagnetic field during power transmission.

[0071] In addition to the third phase difference Ф3 detection method mentioned above, the detection of metallic foreign objects can also be carried out by the correlation quality factor (Q value) detection method, one of which is as follows.

[0072] When an input voltage is applied to excitation coil 1, the detected transmitting unit will generate current due to induction as the voltage rises. When the input voltage rises to a preset value, the input applied to excitation coil 1 is disconnected.

[0073] Since the transmitting unit is an undisturbed closed LC loop, the energy oscillates freely in the loop of this unit, which manifests as the induced current oscillating and gradually decaying from the peak to 0. By detecting its decay law, the detection of metallic foreign objects can be achieved.

[0074] Specifically, the peak current value I1 and the attenuation current value I2 are predetermined. The time point T1 when the current I1 is generated in the transmitting unit, and the time point T2 when the current I2 is generated, are recorded. The change in the quality factor of the transmitting unit can be determined based on the change in the time difference (T2-T1) of current attenuation. The presence of metallic foreign objects on the transmitting coil will cause the quality factor of the transmitting coil to decrease, resulting in faster attenuation and a smaller attenuation time difference (T2-T1). The measured attenuation time difference (T2-T1) is compared with the time difference when there are no metallic foreign objects. If it exceeds the pre-set threshold of the system, it can be determined that there are metallic foreign objects above the transmitting coil.

[0075] The aforementioned method for measuring oscillation attenuation requires an independent closed loop. If the existing two-coil structure is used, an auxiliary detection LC loop needs to be added to the main circuit. During detection, this auxiliary LC loop is switched to be used independently. Alternatively, a complex switching switch can be added to the main circuit to disconnect the power supply drive circuit, load, and other potentially interfering circuits during detection. These methods increase system complexity and cost. However, based on this application, the parallel loop formed by the transmitting coil group 4 is a relatively independent loop. The system can achieve Q-value-based detection and identification of metallic foreign objects without adding any other circuits or components.

[0076] After the wireless charging operating conditions are met, the control switch S of the transmitting unit where the working transmitting coil is located is turned on, for example... Figure 2 As shown, while keeping the control switch of the first transmitting unit on, the control switches of the xth transmitting unit to the yth transmitting unit are turned on. The transmitting device loads a low-power AC signal onto the excitation coil 1. The operating frequency of the AC signal is set to the operating frequency f4 when wireless charging power transmission is performed. Then, the fourth phase difference Ф4 is determined according to the parameters 7 and 8 below.

[0077] Parameter 7: Total current of the working transmitting coil.

[0078] Parameter 8: The voltage applied to excitation coil 1.

[0079] For example, if an AC signal is applied to the excitation coil 1 at the operating frequency f4, and the operating transmitting unit in the transmitting coil group 4 is in a resonant state, then the recorded phase difference Ф4 should be approximately 0.

[0080] After completing the above steps, the wireless charging system begins power transmission. The DC power from the power supply is converted into high-frequency AC power with an operating frequency of f4 by an inverter circuit. This AC current, after passing through a compensation circuit, generates a high-frequency alternating electromagnetic field around the excitation coil. Since the first transmitting coil L1 is tightly coupled to the excitation coil 1 and is within the range of the high-frequency alternating magnetic field, the first transmitting coil L1 will generate an induced voltage, producing a current in the first transmitting unit. This current, through the parallel working transmitting units, also generates an induced high-frequency alternating electromagnetic field on the first transmitting coil L1 and the remaining working transmitting coils (e.g., transmitting coils Lx to Ly in the figure). The receiving coil 51 generates an induced voltage by inducing the alternating electromagnetic field generated by the excitation coil 1 and the working transmitting coils. After passing through a compensation circuit, this voltage is converted into DC power by a rectifier and filter circuit to charge the battery and other loads. The controllers of the receiving and transmitting devices communicate with each other via a communication link to exchange the charging requirements of the load and the control parameters on both sides. The transmitting device adjusts the power according to the charging requirements.

[0081] During the power transmission process of wireless charging, a high-frequency alternating electromagnetic field is generated above the transmitting coil group 4. It is necessary to continuously monitor whether new metallic foreign objects appear between the transmitting coil group 4 and the receiving coil 51. The presence of metallic foreign objects on the surface of the transmitting coil group 4 will decrease its quality factor, leading to a reduction in transmission capability. While maintaining a constant output power at the load end, this manifests as an increase in input power in the transmitting device, resulting in a larger difference between the input and output power. Normally, the difference between input and output power is due to system losses during power conversion, and theoretically, this power difference can be obtained in advance based on transmission efficiency. Therefore, existing technologies often identify metallic foreign objects by detecting changes in the power difference. That is, when the change in the difference exceeds a correspondingly set threshold, it can be assumed that the change is due to increased power loss caused by the presence of metallic foreign objects, thus indicating the presence of metallic foreign objects on the transmitting coil group 4.

[0082] This application also describes a method for detecting the presence of metallic foreign objects during wireless charging. However, for small metallic foreign objects, the energy loss accounts for a small proportion of the total energy transmitted wirelessly, and the resulting power difference change is negligible compared to the total transmitted power. Therefore, this method of detecting power difference cannot detect them. Furthermore, the power conversion circuit of wireless charging is affected by factors such as voltage, frequency, and temperature, which can cause fluctuations in the difference between input and output power. Additionally, errors in power measurement and misalignment between coils can also lead to the failure of methods for detecting power difference changes.

[0083] To compensate for the shortcomings of the power difference detection method, this application further employs a phase angle difference detection method to detect metallic foreign objects when the power difference fluctuation is small, i.e., when the power difference change is within a set threshold range. This improves recognition accuracy and reduces blind spots. Specifically, the fifth phase difference Ф5 of the following two parameters is compared: Parameter 9: The voltage of the AC signal applied to excitation coil 1.

[0084] Parameter 10: The electrical signal acquisition circuit detects the total current signal of the first transmitting unit and all working units connected in parallel.

[0085] The fifth phase difference Ф5 has a different comparison benchmark than the first phase difference Ф1 and the third phase difference Ф3 mentioned above. Therefore, a new threshold range is introduced, and the new threshold range is determined as follows: Let the pre-recorded reference phase angle difference be Ф S Let the pre-determined threshold deviation be Ф T Both of these values ​​are baseline values ​​that have been tested and recorded beforehand. Next, the new threshold range Ф can be determined. B ~Ф A , of which Ф A =Ф S +Ф T Ф B =Ф S -Ф T At this time, Ф S This range, neither equal to nor close to 0° and 360°, is referred to as the first range. When the reference phase angle difference Ф S When equal to or close to 0° and 360°, Ф may appear. A Greater than 360° or Ф B The case where the angle is less than 0°. When Ф A When >360°, let Ф A ’ =Ф A -360°, corresponding to two new threshold ranges, with the first new threshold range being 0. ~ Ф A ’ The second new threshold range is Ф B ~ 360 We refer to these two ranges as the second type of range. When Ф B When <0°, let Ф B ’ =Ф B With a +360° angle, the corresponding first and second new threshold ranges change, specifically: the first new threshold range becomes 0. ~ Ф A The second new threshold range becomes ФB ’ ~ 360 When the phase difference Ф5 of the fifth phase falls within this new threshold range (including within the first or second new threshold range), the wireless charging system is considered to be operating normally, and no metallic foreign objects are found above the transmitting coil group 4; otherwise, a metallic foreign object is considered to be found above the operating transmitting coil. The aforementioned new threshold range is equal to Ф5. A and Ф B The value of is related to the range of , and only one of the three ranges mentioned above will occur.

[0086] For example, Ф S =10°、Ф T =2°, therefore Ф A =12°、Ф B =8°, the new threshold range is [8°, 10°], which is the first range.

[0087] If, Ф S =359°、Ф T =2°, therefore Ф A =361°、Ф B =357°、Ф A ’ =1°, the new threshold range becomes two, the first new threshold range [0°, 1°], the second new threshold range [357°, 360°], which is the second type of range.

[0088] If, Ф S =1°、Ф T =2°, therefore Ф A =3°、Ф B =-1°、Ф B ’ =359°, the first new threshold range becomes [0°, 3°], the second new threshold range becomes [359°, 360°], which is the third range.

[0089] Only one of the above three ranges will occur.

[0090] To ensure safe charging transmission, the wireless charging system should immediately stop power transmission upon detecting a metallic foreign object on the surface of the working transmitting coil group 4. After stopping power transmission, the transmitting coil containing the metallic foreign object can be further detected, and the control switch of the circuit containing the transmitting coil with the metallic foreign object can be turned off (the above-mentioned method of using the third phase difference Ф3 detection can determine the location of the metallic foreign object).

[0091] If the number of remaining working transmitting coils can still meet the total transmission power requirements, power transmission can be restored through the remaining working transmitting units; if the number of remaining working transmitting coils can no longer meet the total transmission power requirements, the controller will report the location of the transmitting coil containing the metal foreign object. After the foreign object is removed, wireless power transmission can be started again, that is, power transmission will be restarted after completing the location identification of receiving coil 51 and metal foreign object detection again according to the aforementioned steps.

[0092] In existing technologies, during power transmission in wireless charging systems, changes in the power conversion circuit and load can occur due to system adjustments and charging status, leading to changes in the system's impedance. Therefore, if the aforementioned method of detecting phase difference changes is used, the system cannot distinguish whether the change is caused by a metallic foreign object or by impedance changes in other circuits within the system. To address this issue, existing technologies for detecting metallic foreign objects during power transmission in wireless charging systems, besides detecting changes in power difference, primarily rely on adding an auxiliary detection coil array to the surface of the transmitting coil. For example, patent CN111086401A discloses a wireless charging system and its detection equipment, detection method, and charging method. To avoid interference from the system's power conversion circuit and load, it employs a coil matrix independently of the transmitting and receiving coils to detect metallic foreign objects. By detecting impedance changes in the detection coils within the coil matrix, higher detection accuracy is achieved, compensating for the inability to detect small-volume metallic foreign objects using the power difference detection method.

[0093] In this application, the transmitting coil group 4 is an independent circuit composed of multiple transmitting units connected in parallel. The equivalent impedance of the parallel working transmitting units is related not only to the inductance of the reflecting coil itself and the compensation capacitor, but also to the mutual inductance with the excitation coil and the receiving coil. However, since the position of the receiving coil is fixed during the charging process, the mutual inductance with the excitation coil and the receiving coil is also a fixed value. The equivalent impedance of the parallel working transmitting units remains unchanged during power transmission. The phase difference between voltage and current is not affected by the power conversion circuit and load of the receiving device during operation. The circuit structure of the embodiment can accurately and dynamically detect metallic foreign objects during operation.

[0094] In the detection of metallic foreign objects, the parallel-connected working transmitting units are equivalent to the aforementioned auxiliary detection coil array, but they are also part of the system's power transmission, serving as energy relays and enhancing transmission. On the other hand, using phase difference can distinguish between the leading and lagging states of voltage and current, which is equivalent to distinguishing the real and imaginary parts of the equivalent impedance, making it more accurate than simply measuring the magnitude of the equivalent impedance.

[0095] In the described embodiment, the excitation coil 1 is positioned at the center of the transmitting coil group 4. This allows the receiving device, when placed above the transmitting coil group 4, to cover the excitation coil and thus its emitted electromagnetic field, reducing electromagnetic field leakage. In reality, since the transmitting units of the transmitting coil group 4 are connected in parallel, changing the position of the excitation coil, while still coupling it with one or more other transmitting coils in the group, results in the same equivalent circuit for the wireless charging system. In other words, the excitation coil does not necessarily need to be positioned at the center of the transmitting coil group 4; changing its position does not affect the system characteristics or the corresponding control method.

[0096] Existing technologies often employ multiple transmitting coil switching schemes to expand the rechargeable area, such as the three-coil charging structure for mobile phones. It should be noted that here, "three coils" refers to selecting only one transmitting coil for power transmission after identification; it's essentially still a two-coil structure. While this method expands the rechargeable area to some extent, in many cases, the receiving coil cannot be perfectly aligned with any of the coils, instead selecting the coil with the best coupling to transmit power. Therefore, optimal charging performance is often not achieved during each charging session. The design of this application avoids this problem. By setting multiple transmitting coils, this application effectively increases the transmission area, ensuring greater coupling between the receiving coil and the transmitting coils. This improves the positional deviation tolerance of the receiving device while achieving better charging performance. Furthermore, the solution in this application uses a single power supply drive circuit through parallel transmitting units, eliminating the need for multiple power supply drive units and reducing the number of system components, cost, and control complexity. The solution proposed in this application uses a three-coil structure for the relay, which does not connect the power supply drive circuit to the parallel transmitting unit group. This effectively isolates the influence between the power supply drive circuit and the receiving device. Therefore, a complex switching mechanism is not required to detect the phase difference. Based on this, the position of the receiving coil can be identified, as well as metallic foreign objects can be identified before and during power transmission. Furthermore, better compatibility with the receiving device can be achieved.

[0097] The above description, based on the embodiments shown in the figures, details the structure, features, and effects of the present invention. The above description is only a preferred embodiment of the present invention, but the present invention is not limited to the scope of implementation shown in the figures. Any changes made in accordance with the concept of the present invention, or equivalent embodiments modified to have equivalent changes, that do not exceed the spirit covered by the specification and figures, should be within the protection scope of the present invention.

Claims

1. A control method for a wireless charging transmitter, characterized in that, Step 1: The excitation coil (1) is coupled to the first transmitting coil (L1) of the first transmitting unit, the first control switch (S1) is closed, and the other control switches (S) are opened; Step 2: Close the other control switches (S) in sequence, one control switch (S) at a time, and apply a frequency of to the excitation coil (1). The AC signal, where L D2 The equivalent inductance of the first transmitting unit, the transmitting unit containing the control switch (S) that is closed each time, the excitation coil (1), and the receiving coil (51) is C. D2 The equivalent capacitance of the first transmitting unit and the transmitting unit where the control switch (S) is closed each time; Step 3, compare the first phase difference (Ф1) of the following two parameters: Parameter 1: The voltage of the AC signal applied to the excitation coil (1); Parameter 2: The total current in the circuit formed by connecting the first transmitting unit in parallel with the transmitting unit containing the control switch (S) that is closed each time; Based on the value of the first phase difference (Ф1), determine whether there is a receiving coil (51) at the position of the transmitting unit where the control switch (S) is closed each time; if so, define the corresponding transmitting unit as the working unit. Step 4: When wireless charging is performed, close the control switches (S) of all working units; a preset first phase difference threshold value T and divide two threshold ranges: The first threshold range is [0°, Ф]. T ] indicates that parameter 2 lags behind parameter 1; The second threshold range is [Ф] T ',360°],where Ф T =360°-Ф T This indicates that parameter 2 precedes parameter 1; When the first phase difference (Ф1) is not within the range of the two thresholds, it is determined that there is no receiving coil (51) at the position of the transmitting unit where the closed control switch (S) is located; otherwise, there is a receiving coil (51). Preset phase difference threshold Ф T The method for obtaining it is as follows: F T =[(t3-t1) / (t2-t1)]*360° Wherein, t1 is: the rising edge trigger time of the first cycle of the voltage of the AC signal applied to the excitation coil (1); t2 is the rising edge trigger time of the second cycle of the AC signal voltage applied to the excitation coil (1); t3 is the rising edge trigger time of the first cycle of the total current of the circuit formed by the first transmitting unit and the transmitting unit where the control switch (S) is closed each time.

2. The control method for the wireless charging transmitter according to claim 1, characterized in that, The first transmitting unit is located in the central region of the transmitting coil group (4) which consists of all the transmitting units.

3. The control method for the wireless charging transmitter according to claim 2, characterized in that, When the device to be charged is placed in the charging area, the receiving coil (51) and the first transmitting coil (L1) are within the working coupling range.

4. The control method for the wireless charging transmitter according to claim 1, characterized in that, The first transmitting unit is located at any position in the transmitting coil group (4) composed of all transmitting units. Before step 2, it is also determined whether there is a receiving coil (51) at the position of the first transmitting unit. The method is as follows: Close the first control switch (S1) and apply a frequency of to the excitation coil (1). The AC signal, where L D1 C is the equivalent inductance of the first transmitting unit. D1 This is the equivalent capacitance of the first transmitting unit; Compare the second phase difference (Ф2) of the following two parameters: Parameter 3: The voltage of the AC signal applied to the excitation coil (1); Parameter 4: Current of the first transmitting unit; Based on the value of the second phase difference (Ф2), determine whether there is a receiving coil (51) at the position corresponding to the first transmitting unit.

5. The control method for the wireless charging transmitter according to claim 4, characterized in that, If there is a receiving coil (51) at the position corresponding to the first transmitting unit, proceed to step 2, and the first transmitting unit is defined as a working unit; If there is no receiving coil (51) at the position corresponding to the first transmitting unit, proceed to step 2. The first transmitting unit is not defined as a working unit.

Images