Wireless power transmission system and control method thereof

Abstract

The present application discloses a wireless power transmission system and a control method thereof. The wireless power transmission system includes: a transmitter coil configured to be magnetically coupled to a receiver coil; a power conversion device coupled to the transmitter coil; and a controller including a half-cycle detection block, the half-cycle detection block configured to establish a current detection moment, and wherein at the current detection moment, the current flowing through the transmitter coil is detected and compared with a predetermined threshold value for foreign object detection, thereby determining whether a foreign object is coupled to the wireless power transmission system.

Description

Technical Field

[0001] The present invention relates to the technical field of electronic circuits, and more specifically, to a wireless power transmission system and a control method thereof. Background Art

[0002] As technology further advances, wireless power transmission has become an effective and convenient mechanism for powering or charging battery-based mobile devices (such as mobile phones, tablet PCs, digital cameras, MP3 players, etc.). A wireless power transmission system typically includes a primary transmitter and a secondary receiver. The primary transmitter is magnetically coupled to the secondary receiver via magnetic coupling. The magnetic coupling can be implemented as a loosely coupled transformer having a primary coil formed in the primary transmitter and a secondary coil formed in the secondary receiver.

[0003] The primary side transmitter may include a power conversion unit, such as the primary side of a power converter. The power conversion unit is coupled to a power source and is capable of converting power into a wireless power signal. The secondary side receiver is capable of receiving the wireless power signal through a loosely coupled transformer and converting the received wireless power signal into power suitable for the load.

[0004] The power consumption of a wireless power transmission system is a very important parameter. For example, the calculated power consumption can be used for foreign object detection (FOD). Conventional wireless power transmission systems require additional circuits to detect parameters such as input current and coil current to achieve power consumption detection and thus foreign object detection.

[0005] It is desirable to have a simple and reliable control mechanism to reduce the cost of power loss detection. Summary of the invention

[0006] In view of the above problems, an object of the present invention is to provide a wireless power transmission system and a control method thereof.

[0007] According to one embodiment of the present disclosure, a wireless power transmission system is provided, comprising: a transmitter coil configured to be magnetically coupled to a receiver coil; a power conversion device coupled to the transmitter coil; and a controller comprising a half-cycle detection block, wherein the half-cycle detection block is configured to establish a current detection moment corresponding to half of a switching cycle of the power conversion device, and at the current detection moment, a current flowing through the transmitter coil is detected and compared with a predetermined threshold value for foreign object detection, thereby determining whether a foreign object is coupled to the wireless power transmission system.

[0008] According to another embodiment of the present disclosure, a control method for a wireless power transmission system is provided, comprising: in a switching cycle of a power converter of the wireless power transmission system, finding a moment corresponding to one half of the switching cycle; at the moment, comparing a current flowing through a transmitter coil with a predetermined threshold value for foreign object detection, thereby determining whether a foreign object is coupled to the wireless power transmission system.

[0009] According to another embodiment of the present disclosure, a controller is provided, comprising a half-cycle detection block, wherein the half-cycle detection block is configured to establish a current detection moment corresponding to half of the switching cycle of the power conversion device, and at the current detection moment, the current flowing through the transmitter coil is detected and compared with a predetermined threshold value for foreign object detection, thereby determining whether a foreign object is coupled to the wireless power transmission system.

[0010] The above is a fairly broad overview of the features and technical advantages of the present disclosure so that the detailed description of the disclosure that follows may be better understood. Additional features and advantages of the present disclosure that form the subject of the claims of the present disclosure will be described below. It will be appreciated by those skilled in the art that the disclosed concepts and specific embodiments may be readily used as a basis for modifying or designing other structures or processes for the same purpose of performing the present disclosure. It will also be appreciated by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the present disclosure as described in the appended claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] For a more complete understanding of the present disclosure and its advantages, reference is now made to the following description in conjunction with the accompanying drawings, which include:

[0012] Figure 1 A block diagram showing a wireless power transmission system according to various embodiments of the present disclosure;

[0013] Figure 2 Showing various embodiments according to the present disclosure, Figure 1 A schematic diagram of a wireless power transmission system is shown;

[0014] Figure 3 Showing various embodiments according to the present disclosure, Figure 1 Various waveforms of the wireless power transfer system shown;

[0015] Figure 4 A block diagram showing a controller according to various embodiments of the present disclosure;

[0016] Figure 5 A schematic diagram showing a comparison and interruption block according to various embodiments of the present disclosure; and

[0017] Figure 6 According to various embodiments of the present disclosure, control Figure 1 A flow chart of a method of a wireless power transfer system is shown.

[0018] Corresponding numerals and symbols in the different figures generally refer to corresponding parts unless otherwise indicated.The figures are drawn to clearly illustrate the relevant aspects of the various embodiments and are not necessarily drawn to scale. DETAILED DESCRIPTION

[0019] The making and use of the currently preferred embodiments are discussed in detail below. However, it should be understood that the present disclosure provides many applicable inventive concepts that can be embodied in a large number of specific contexts. The specific embodiments described are merely illustrative of specific ways to make and use the present disclosure, and do not limit the scope of the present disclosure. The present disclosure will be described with respect to the preferred embodiments in a specific context (i.e., a foreign object detection device for a wireless power transmission system). However, the present invention may also be applicable to a variety of power systems. The various embodiments will be described below with reference to the accompanying drawings.

[0020] Figure 1 1 is a block diagram of a wireless power transmission system according to various embodiments of the present disclosure. The wireless power transmission system 100 includes a power stage 104 and a wireless power transmission device 101, which are cascade-connected between an input power source 102 and a load 114. The wireless power transmission device 101 includes a transmitter 110 and a receiver 120. Figure 1 As shown, the transmitter 110 includes a transmitter circuit 107 and a transmitter coil L1 connected in cascade. The input of the transmitter circuit 107 is coupled to the output of the power stage 104. The receiver 120 includes a receiver coil L2 and a rectifier 112 connected in cascade. The output of the rectifier 112 is coupled to the load 114.

[0021] When the receiver 120 is placed near the transmitter 110, the transmitter 110 is magnetically coupled to the receiver 120 through a magnetic field. A loosely coupled transformer 115 is formed by a transmitter coil L1 (the transmitter coil L1 is a component of the transmitter 110) and a receiver coil L2 (the receiver coil L2 is a component of the receiver 120). Therefore, power can be transmitted from the transmitter 110 to the receiver 120.

[0022] In some embodiments, the transmitter 110 may be inside the charging pad. The transmitter coil is placed below the top surface of the charging pad. The receiver 120 may be included in a mobile phone. When the mobile phone is placed near the charging pad, a magnetic coupling may be established between the transmitter coil and the receiver coil. In other words, the transmitter coil and the receiver coil may form a loosely coupled transformer through which power is transferred between the transmitter 110 and the receiver 120. The coupling strength between the transmitter coil L1 and the receiver coil L2 is quantified by a coupling coefficient k. In some embodiments, k is in a range from about 0.05 to about 0.9.

[0023] In some embodiments, after magnetic coupling has been established between the transmitter coil L1 and the receiver coil L2 , the transmitter 110 and the receiver 120 may form a power system through which power is wirelessly transmitted from the input power source 102 to the load 114 .

[0024] The input power source 102 may be a power adapter that converts a grid line voltage into a direct current (DC) voltage. In other embodiments, the input power source 102 may be a regenerative power source, such as a solar panel array. In addition, the input power source 102 may be an energy storage device, such as a rechargeable battery, a fuel cell, etc.

[0025] Load 114 represents the power consumed by a mobile device (eg, a mobile phone) coupled to receiver 120. In other embodiments, load 114 may represent a rechargeable battery and / or a battery connected in series / parallel and coupled to the output of receiver 120.

[0026] According to some embodiments, the transmitter circuit 107 may include a primary side switch of a full-bridge power converter. A full bridge is also called an H-bridge. In other embodiments, the transmitter circuit 107 may include a primary side switch of other converters (e.g., a half-bridge converter, a push-pull converter, etc.). Figure 2 The detailed configuration of the transmitter circuit 107 will be described.

[0027] It should be noted that the above-mentioned converters are only examples. Those skilled in the art will appreciate that other suitable power converters may be used in other embodiments, such as a power converter based on a class E topology (eg, a class E amplifier).

[0028] The transmitter circuit 107 may further include a resonant capacitor. The resonant capacitor and the magnetic inductance of the transmitter coil may form a resonant loop. Depending on design requirements and different applications, the resonant loop may further include a resonant inductor. In some embodiments, the resonant inductor may be implemented as an external inductor. In other embodiments, the resonant inductor may be implemented as a connecting wire.

[0029] The receiver 120 includes a receiver coil L2 that is magnetically coupled to the transmitter coil L1 after the receiver 120 is placed near the transmitter 110. Therefore, power may be transferred to the receiver coil and further delivered to the load 114 through the rectifier 112. The receiver 120 may include a secondary resonant capacitor.

[0030] The rectifier 112 converts the alternating polarity waveform received from the output of the receiver coil L2 into a unipolar waveform. In some embodiments, the rectifier 112 is implemented as a synchronous rectifier including four switches. In other embodiments, the rectifier 112 includes a full-wave diode bridge and an output capacitor.

[0031] In addition, the synchronous rectifier can be formed by any controllable device (such as a metal oxide semiconductor field effect transistor (MOSFET) device, a bipolar junction transistor (BJT) device, a super junction transistor (SJT) device, an insulated gate bipolar transistor (IGBT) device, a gallium nitride (GaN) based power device, etc.). Figure 2 The detailed structure of the rectifier 112 will be discussed.

[0032] The power stage 104 is coupled between the input power source 102 and the input of the wireless power transmission device 101. Depending on the design needs and different applications, the power stage 104 can include many different configurations. In some embodiments, the power stage 104 can be a non-isolated power converter, such as a buck converter. In some embodiments, the power stage 104 can be implemented as a linear regulator. In some embodiments, the power stage 104 can be an isolated power converter, such as a forward converter.

[0033] The above implementation of the power stage 104 is only an example and should not unduly limit the scope of the claims. Those skilled in the art will know many variations, substitutions and modifications. In addition, depending on different applications and design requirements, the power stage 104 can be an optional element of the wireless power transmission system 100. In other words, the input power supply 102 can be directly connected to the transmitter circuit 107.

[0034] Figure 2 Showing various embodiments according to the present disclosure, Figure 1 Schematic diagram of a wireless power transmission system shown in FIG. The wireless power transmission device 101 includes a transmitter circuit 107, a resonant capacitor Cp, a loosely coupled transformer 115, a resonant capacitor Cs, and a rectifier 112 connected in cascade. The loosely coupled transformer 115 is formed by a transmitter coil L1 and a receiver coil L2. The transmitter circuit 107 is implemented as follows Figure 2 In the following text, Figure 2 The full bridge shown is also called a power converter or a full-bridge power converter.

[0035] The full bridge 107 includes four switching elements, namely, S1, S2, S3 and S4. Figure 2 As shown, switch elements S1 and S2 are connected in series between the input voltage bus VIN and ground. The input voltage bus VIN is connected to Figure 1The output of the power stage 104 is shown. Similarly, the switching elements S3 and S4 are connected in series between the input voltage bus VIN and ground. The common node (SW1) of the switching elements S1 and S2 is coupled to the first input terminal of the transmitter coil L1. The common node (SW2) of the switching elements S3 and S4 is coupled to the second input terminal of the transmitter coil L1 through the resonant capacitor Cp. The voltage between SW1 and SW2 is denoted as VSW. Figure 4 The waveform of VSW is shown.

[0036] According to some embodiments, the switching elements S1, S2, S3 and S4 are implemented as MOSFETs or MOSFETs connected in parallel, any combination thereof, etc. According to other embodiments, the switching element (e.g., switch S1) can be an insulated gate bipolar transistor (IGBT) device. In other embodiments, the primary switch can be any controllable switch, such as an integrated gate commutated thyristor (IGCT) device, a gate turn-off thyristor (GTO) device, a silicon controlled rectifier (SCR) device, a junction gate field effect transistor (JFET) device, a MOS controlled thyristor (MCT) device, a gallium nitride (GaN)-based power device, etc.

[0037] It should be noted that although the examples in this description are based throughout on a full-bridge converter (e.g. Figure 2 The full bridge 107 shown, but Figure 2 The implementation of the transmitter circuit 107 shown may have many variations, alternatives, and modifications. For example, a half-bridge converter, a push-pull converter, a class-E based power converter (e.g., a class-E amplifier) ​​may be employed in other embodiments. In addition, when the transmitter coil L1 is tightly coupled with the receiver coil L2 in some applications, an inductor-inductor-capacitor (LLC) resonant converter may be formed.

[0038] In summary, the full bridge 107 shown herein is limited only to facilitate clear illustration of the inventive aspects of various embodiments. The present invention is not limited to any particular power topology.

[0039] It should also be noted that although Figure 2 Four switches S1-S4 are shown, but various embodiments of the present disclosure may include other variations, modifications, and alternatives. For example, an independent capacitor may be connected in parallel with each switch of the full bridge 107. Such independent capacitors help better control the timing of the resonance process of the full bridge 107.

[0040] The output of the receiver coil L2 is coupled to the load RL through the resonant capacitor Cs, the rectifier 112 and the capacitor Co. The rectifier converts the alternating polarity waveform received from the output of the receiver coil L2 into a unipolar waveform. The capacitor Co is used to attenuate noise and provide a steady-state output voltage. The resonant capacitor Cs helps to achieve soft switching of the wireless power transmission system.

[0041] In some embodiments, the rectifier 112 is implemented as a synchronous rectifier. The rectifier 112 includes four switching elements, namely, S5, S6, S7, and S8. Figure 2 As shown, switch elements S5 and S6 are connected in series between the output terminal of the rectifier 112 and the ground. Similarly, switch elements S7 and S8 are connected in series between the output terminal of the rectifier 112 and the ground. Figure 2 As shown, a common node of switch elements S5 and S6 is coupled to a first terminal of receiver coil L2. A common node of switch elements S7 and S8 is coupled to a second terminal of receiver coil L2 via a resonant capacitor Cs.

[0042] According to some embodiments, the switching elements S5 , S6 , S7 , and S8 are implemented as MOSFETs or MOSFETs connected in parallel, any combination thereof, or the like.

[0043] Return to reference Figure 1 In the related art, foreign object detection is required during the wireless power transmission process. There are many ways to detect foreign objects, such as detecting capacitance, resistance, power loss, etc. Among them, the power loss detection method is to determine whether there are foreign objects around the wireless power transmission system by detecting whether the power loss deltaP between the transmitter 110 and the receiver 120 is less than a threshold value. Specifically, deltaP=Pt-Pr, where Pt is the transmission power of the transmitter 110 and Pr is the receiving power of the receiver 120. When using the power loss detection method for foreign object detection, it is necessary to accurately detect Pt and Pr in order to accurately determine whether there are foreign objects around the wireless power transmission system. However, the accurate detection of Pt and Pr is difficult.

[0044] To this end, the present application improves the power loss detection method and simplifies the calculation of power loss. Specifically, using the power loss formula deltaP = Pt-Pr = [Pi-Pt (loss) ]-[Po-Pr (loss) ], where Pt is the transmission power of the transmitter 110, Pr is the receiving power of the receiver 120, Pi is the input power of the system, and Pt (loss) is the power loss at the input end, Po is the output power of the system, Pr (loss) is the power loss at the output end. This application provides a simple way to calculate Pt (loss) The method can take into account the simplicity and accuracy of the input power loss calculation, and the Pi, Po and Pr (loss) If known, Pt can be easily calculated by (loss)To obtain the power loss deltaP, it is possible to determine whether the power loss is less than the threshold and whether there are foreign objects around the wireless power transmission system. Figure 3 To describe the relationship between the transmitter power loss and the current flowing through the transmitter coil.

[0045] Figure 3 Showing various embodiments according to the present disclosure, Figure 1 Various waveforms of the wireless power transfer system shown. Figure 3 The horizontal axis represents the time interval. The first waveform 402 represents VSW ( Figure 2 The voltage between the two switch nodes SW1 and SW2 is shown. The second waveform 404 represents the fundamental frequency waveform of the first waveform 402. The third waveform 406 represents the current flowing through the transmitter coil.

[0046] like Figure 3 As shown, the current flowing through the transmitter coil lags behind the voltage (the fundamental frequency waveform of the first waveform 402), and the phase difference between the voltage and the current is expressed as

[0047] The transmitter power loss includes coil loss, power tube loss and resonant capacitor loss. The losses of the three are equivalent to the AC equivalent resistance of the transmitter coil multiplied by the current. Assuming the AC equivalent resistance is ACR, the transmitter power loss is ACR*Icoil rms ^2, where Icoil rms Indicates the effective value of the transmitter coil current.

[0048] The current flowing through the transmitter coil is defined as formula (1):

[0049]

[0050] The transmitter coil current can be divided into two parts, including active power and reactive power, which can be expressed as formula (2):

[0051] Icoil rms 2 =Icoila rms 2 +Icoilr rms 2 (2)

[0052] Among them, Icoila rms 2 Indicates the active power part, Icoilr rms 2 Represents the reactive power part.

[0053] The active power part of the transmitter coil current can be expressed as formula (3):

[0054]

[0055] Where IIN is the input current of the transmitter coil.

[0056] The current of the transmitter coil at time π can be expressed as formula (4):

[0057]

[0058] Then the reactive power part of the transmitter coil current can be expressed as formula (5):

[0059]

[0060] Therefore, the transmitter coil current can be expressed as formula (6):

[0061]

[0062] In the related art, it is necessary to use a complex formula to calculate the power loss between the transmitter 110 and the receiver 120 (for example, using voltage to calculate the power loss) in order to further perform foreign object detection.

[0063] The present disclosure provides an improved detection circuit, which can easily obtain the power loss at the input end, so as to calculate the power loss deltaP between the transmitter 110 and the receiver 120, thereby achieving the purpose of foreign object detection.

[0064] In operation, in each switching cycle, the moment corresponding to one-half of the switching cycle is found. At this moment, the current flowing through the transmitter coil is detected. Based on the detected current, it is possible to calculate and determine whether the power loss of the transmitter coil is greater than a threshold value, and based on the judgment result, the purpose of foreign object detection is achieved.

[0065] In operation, the detected current is compared with a predetermined threshold. In some embodiments, the threshold of the current cycle is set according to the threshold of the previous cycle. If the detected current is greater than the predetermined threshold, it is determined that there is a foreign object around, and the protection mechanism of foreign object detection is activated. Figure 4-6 To describe the detailed implementation of the detection circuit provided by the present disclosure.

[0066] Figure 4 : A block diagram of a controller according to various embodiments of the present disclosure is shown. The controller includes a microcontroller unit (MCU) 502, a π detection block 504, a comparison and interruption block 506, and a current sampling unit 508. The controller can realize the function of foreign object detection.

[0067] The MCU 502 establishes an integer equivalent to one-half of the switching period of the power converter. The MCU 502 feeds this integer to the π detection block 504. The input terminal of the current sampling unit 508 is directly or indirectly connected to the transmitter coil to detect the current flowing through the transmitter coil.

[0068] In each switching cycle of the power converter, the π detection block 504 detects the falling edge of a PWM signal applied to the full bridge and sends the falling edge to the comparison and interruption block 506. The comparison and interruption block 506 receives the falling edge of the PWM signal and detects the current (Icoil) flowing through the transmitter coil at a time equivalent to half of the switching cycle. The detected current (the current flowing through the transmitter coil) is fed into the comparison and interruption block 506. The detected current is compared with a predetermined threshold. If there is a foreign object around, the comparison and interruption block 506 generates a corresponding interruption signal and feeds this interruption signal to the MCU 502, which applies the corresponding control mechanism to the wireless power transmission system to control the wireless power transmission system not to enter the power transmission mode, or to stop power transmission. For example, the MCU 502 applies the corresponding control mechanism to the power converter so that the power converter stops power conversion.

[0069] Figure 5 Schematic diagram of a comparison and interrupt block according to various embodiments of the present disclosure is shown. The comparison and interrupt block 506 includes a first comparator 702 and a first interrupt generator 708. Figure 5 As shown, the inverting input of the first comparator 702 is coupled to a predetermined threshold. In each current cycle, the predetermined threshold is set, for example, according to the predetermined threshold of the previous cycle. The predetermined threshold is used to determine whether there is a foreign object around the wireless power transmission system. The non-inverting input of the first comparator 702 is coupled to the current (Icoil) flowing through the transmitter coil.

[0070] It should be noted that the comparison and interrupt block 506 described herein is provided only for ease of illustration and is provided only as an example of functionality that may be included in the comparison and interrupt block 506. Those skilled in the art will appreciate that the comparison and interrupt block 506 may be implemented in many different ways and that it may include other functional blocks.

[0071] Figure 6 According to various embodiments of the present disclosure, control Figure 1 A flow chart of a method of a wireless power transfer system is shown. Figure 6 The flowchart shown is merely an example and should not unduly limit the scope of the claims. Many variations, substitutions, and modifications will occur to those skilled in the art. For example, Figure 6 The various steps shown may be added, removed, substituted, rearranged and repeated.

[0072] The wireless power transmission system includes a transmitter and a receiver. The transmitter includes a power converter and a transmitter coil. The receiver includes a receiver coil and a rectifier. The transmitter coil is magnetically coupled to the receiver coil.

[0073] In operation, when foreign matter exists around the wireless power transmission system, power consumption of the wireless power transmission system becomes large.

[0074] The controller is used to detect the current flowing through the transmitter coil at a time corresponding to one-half of the switching cycle of the power converter. The detected current at this time can indicate whether there is a foreign object around the wireless power transmission system. When the detected current is greater than a predetermined threshold, it is determined that there is a foreign object around the wireless power transmission system.

[0075] In step 802, in a switching cycle of a power converter of the wireless power transmission system, a time corresponding to one half of the switching cycle is found. For example, in the switching cycle of the power converter, a falling edge of a gate drive signal of the power converter is used as the time corresponding to one half of the switching cycle.

[0076] In step 804 , at a time corresponding to one-half of the switching period, the current flowing through the transmitter coil of the wireless power transmission system is detected.

[0077] In step 806, the current flowing through the transmitter coil is compared with a predetermined threshold to perform foreign object detection, thereby determining whether a foreign object is coupled to the wireless power transmission system. For example, the predetermined threshold of the current cycle is updated according to the predetermined threshold of the previous cycle.

[0078] In step 808, when it is determined that a foreign object is coupled to the wireless power transmission system, a control mechanism is applied to the wireless power transmission system. For example, when it is determined that a foreign object is coupled to the wireless power transmission system, an interrupt signal is generated and sent to the power conversion device to control the wireless power transmission system not to enter the power transmission mode, or to stop power transmission.

[0079] In some other embodiments, the wireless power transmission system is controlled not to enter the power transmission mode or to stop the power transmission according to the comparison result of comparing the current flowing through the transmitter coil with a predetermined threshold.

[0080] Although the embodiments of the present disclosure and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the disclosure as defined by the appended claims.

[0081] In addition, the scope of the present application is not intended to be limited to the specific embodiments of the processes, machines, manufactures, compositions of matter, components, methods, and steps described in this specification. As will be readily understood by those skilled in the art through the disclosure of this disclosure, processes, machines, manufactures, compositions of matter, components, methods, or steps currently existing or to be developed in the future that perform substantially the same functions as the corresponding embodiments described herein or achieve substantially the same results may be utilized in accordance with this disclosure. Accordingly, the appended claims are intended to include such processes, machines, manufactures, compositions of matter, components, methods, or steps within their scope.

Claims

1. A wireless power transmission system, characterized in that: include: a transmitter coil configured to magnetically couple to a receiver coil; a power conversion device coupled to the transmitter coil; as well as The controller includes a half-cycle detection block, the half-cycle detection block is configured to establish a current detection moment corresponding to half of the switching cycle of the power conversion device, and at the current detection moment, the current flowing through the transmitter coil is detected and compared with a predetermined threshold value for foreign object detection, thereby determining whether a foreign object is coupled to the wireless power transmission system.

2. The wireless power transmission system according to claim 1, characterized in that: The power conversion device is a full-bridge converter, a half-bridge converter or a push-pull converter.

3. The wireless power transmission system according to claim 1, characterized in that: The controller is configured to control the wireless power transmission system not to enter a power transmission mode or to stop power transmission when it is determined that a foreign object is coupled to the wireless power transmission system.

4. The wireless power transmission system according to claim 1, characterized in that: The controller further includes a comparison and interruption block, wherein the comparison and interruption block is configured to compare the current flowing through the transmitter coil with a predetermined threshold value at the current detection time to perform foreign object detection, When the comparison and interruption block determines that a foreign object is coupled to the wireless power transmission system, an interruption signal is generated to control the wireless power transmission system not to enter the power transmission mode or to stop power transmission.

5. The wireless power transmission system according to claim 1 or 4, characterized in that: The controller is configured to update the predetermined threshold of the current cycle according to the predetermined threshold of the previous cycle.

6. The wireless power transmission system according to claim 4, characterized in that: The compare and interrupt block includes: a comparator for comparing the current flowing through the transmitter coil with a predetermined threshold; a latch, for latching a comparison result of the comparator, wherein an enable terminal of the latch is connected to the half-cycle detection block to provide the comparison result at the current detection moment; and An interrupt generator is used to provide the interrupt signal according to the comparison result.

7. The wireless power transmission system according to claim 4, characterized in that: The controller further comprises: a current sampling unit configured to detect the current flowing through the transmitter coil; The micro control unit is configured to control the wireless power transmission system to perform power transmission according to the interrupt signal.

8. A control method for a wireless power transmission system, characterized in that: The wireless power transmission system includes a transmitter coil and a power converter, the transmitter coil is magnetically coupled to a receiver coil, the power converter is coupled to the transmitter coil, and the control method includes: In a switching cycle of the power converter, finding a time corresponding to one half of the switching cycle; At the moment, the current flowing through the transmitter coil is compared with a predetermined threshold value to perform foreign object detection, thereby determining whether a foreign object is coupled to the wireless power transmission system.

9. The control method according to claim 8, characterized in that: When it is determined that a foreign object is coupled to the wireless power transmission system, an interrupt signal is generated and sent to the wireless power transmission system to control the wireless power transmission system not to enter a power transmission mode or to stop power transmission.

10. The control method according to claim 8, characterized in that: The predetermined threshold value of the current cycle is updated according to the predetermined threshold value of the previous cycle.

11. The control method according to claim 8, characterized in that: In the switching period of the power converter, a falling edge of a gate driving signal of the power converter is used as a time corresponding to one half of the switching period.

12. The control method according to claim 8, characterized in that: The current flowing through the transmitter coil is compared with a predetermined threshold value. When it is determined that a foreign object is coupled to the wireless power transmission system, an interrupt signal is generated and sent to the wireless power transmission system to control the wireless power transmission system not to enter a power transmission mode or to stop power transmission.

13. The control method according to claim 8, characterized in that: The foreign object detection is performed before the wireless power transmission system enters a power transmission mode, or when the wireless power transmission system performs power transmission.

14. A controller for a wireless power transmission system, characterized in that: The wireless power transmission system includes a transmitter coil and a power conversion device, the transmitter coil is magnetically coupled to a receiver coil, the power conversion device is coupled to the transmitter coil, the controller includes a half-cycle detection block, the half-cycle detection block is configured to establish a current detection moment corresponding to half of the switching cycle of the power conversion device, and at the current detection moment, the current flowing through the transmitter coil is detected and compared with a predetermined threshold for foreign object detection, thereby determining whether a foreign object is coupled to the wireless power transmission system.

15. The controller according to claim 14, characterized in that: Also includes: a current sampling unit configured to detect the current flowing through the transmitter coil; a comparison and interruption block configured to compare the current flowing through the transmitter coil with a predetermined threshold value at the current detection moment to perform foreign object detection, and generate an interruption signal when the comparison and interruption block determines that a foreign object is coupled to the wireless power transmission system; The micro control unit is configured to control the wireless power transmission system to perform power transmission according to the interrupt signal.

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