Transient protection apparatus and method for wireless power transfer systems

Abstract

A method includes, in a switching cycle of a power converter in a wireless power transfer system, the power converter coupled between an input power source and a transmitter coil that is magnetically coupled to a receiver coil, finding a time corresponding to a quarter of the switching cycle, detecting a current flowing through the transmitter coil at the time, the power transferred between the transmitter coil and the receiver coil being proportional to the current flowing through the transmitter coil, comparing the current flowing through the transmitter coil to a plurality of predetermined thresholds to determine whether a transient has occurred, and applying a control mechanism to the power converter in response to the occurrence of the transient.

Description

Technical Field

[0001] The present invention relates to transient protection devices, and in certain embodiments to transient protection devices for wireless power transmission systems. Background Technology

[0002] With further technological advancements, wireless power transfer has become an efficient and convenient mechanism for powering or charging battery-based mobile devices such as mobile phones, tablet PCs, digital cameras, MP3 players, etc. Wireless power transfer systems typically include a primary-side transmitter and a secondary-side receiver. The primary-side transmitter is magnetically coupled to the secondary-side receiver. This magnetic coupling can be implemented as a loosely coupled transformer, which has a primary-side coil formed in the primary-side transmitter and a secondary-side coil formed in the secondary-side receiver.

[0003] A 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 electrical power into wireless power signals. A secondary-side receiver is capable of receiving the wireless power signals via a loosely coupled transformer and converting the received wireless power signals into electrical power suitable for a load.

[0004] As power consumption has become more critical, there is a need for wireless power transmission systems with faster transient response. More specifically, wireless power transmission systems can operate under a variety of operating conditions. For example, a wireless power transmission system can exhibit coupling transients, where the magnetic coupling between the receiver and transmitter changes from loose coupling to tight coupling. Due to this coupling change, the receiver's output voltage can rise significantly. Furthermore, a wireless power transmission system can exhibit load transients, where the receiver's load changes from a heavy load state to a light load state. Due to this load change, the receiver's output voltage can rise significantly.

[0005] The feedback control in conventional wireless power transmission systems is not fast enough to regulate the output voltage under various transients. In practical applications, multiple overvoltage protection devices (such as snubber resistors and clamping capacitors) can be used to limit the output voltage within a predetermined range. However, as the power of wireless power transmission systems tends to increase, transient response becomes a significant problem, posing a challenge to the system design of wireless power transmission systems.

[0006] The goal is to have a simple and reliable control mechanism that can provide fast transient response under a variety of operating conditions. Summary of the Invention

[0007] These and other problems are generally solved or prevented and technical advantages are achieved through preferred embodiments of the present disclosure, which provide transient protection devices and methods for wireless power transmission systems.

[0008] According to an embodiment, an apparatus includes: a transmitter coil configured to be mechanically coupled to a receiver coil; a power conversion device coupled to the transmitter coil; and a controller configured to control operating variables of the power conversion device in response to changes in operating conditions, wherein the controller includes a quarter-cycle detection block configured to establish a current detection moment, and wherein at the current detection moment, a current flowing through the transmitter coil is detected and compared with a plurality of predetermined thresholds to determine which type of transient has occurred.

[0009] According to another embodiment, a method includes: finding a moment corresponding to one-quarter of the switching cycle during a switching cycle of a power converter in a wireless power transmission system; detecting the current flowing through a transmitter coil of the wireless power transmission system at that moment; comparing the current flowing through the transmitter coil with a plurality of predetermined thresholds; and applying a control mechanism to the power converter based on the comparison result of the step of comparing the current flowing through the transmitter coil with the plurality of predetermined thresholds.

[0010] According to yet another embodiment, a method includes: during a switching cycle of a power converter in a wireless power transmission system, finding a moment corresponding to one-quarter of the switching cycle, wherein the power converter is coupled between an input power source and a transmitter coil magnetically coupled to a receiver coil; at that moment, detecting a current flowing through the transmitter coil, wherein the power transmitted between the transmitter and receiver coils is proportional to the current flowing through the transmitter coil; comparing the current flowing through the transmitter coil with a plurality of predetermined thresholds to determine whether a transient has occurred; and applying a control mechanism to the power converter in response to the occurrence of the transient.

[0011] The features and technical advantages of this disclosure have been broadly outlined above to provide a better understanding of the detailed description that follows. Additional features and advantages of this disclosure that form the subject matter of the claims will be described below. Those skilled in the art will understand that the disclosed concepts and specific embodiments can be readily used as the basis for modifying or designing other structures or processes to perform the same purpose as this disclosure. Those skilled in the art will also recognize that such equivalent constructions do not depart from the spirit and scope of this disclosure as set forth in the appended claims. Attached Figure Description

[0012] To gain a more complete understanding of this disclosure and its advantages, reference is now made to the following description taken in conjunction with the accompanying drawings, which include:

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

[0014] Figure 2 Various embodiments according to this disclosure are shown. Figure 1A schematic diagram of the wireless power transmission system shown.

[0015] Figure 3 The following are various embodiments of the present disclosure for controlling Figure 1 The control loop of the wireless power transmission system shown;

[0016] Figure 4 Various embodiments according to this disclosure are shown. Figure 1 Various waveforms of the wireless power transmission system are shown.

[0017] Figure 5 A block diagram of a coupling and load transient protection device according to various embodiments of the present disclosure is shown;

[0018] Figure 6 A schematic diagram of a current detection circuit for detecting current flowing into a wireless power transmission system, according to various embodiments of the present disclosure, is shown.

[0019] Figure 7 Schematic diagrams illustrating comparison and interrupt blocks according to various embodiments of the present disclosure; and

[0020] Figure 8 The following are illustrated in various embodiments of the present disclosure, including control. Figure 1 The flowchart shows a method for a wireless power transmission system.

[0021] Corresponding numbers and reference numerals in the various figures generally denote corresponding parts unless otherwise specified. The figures are drawn to clearly illustrate relevant aspects of the various embodiments, and are not necessarily drawn to scale. Detailed Implementation

[0022] The following describes in detail the making and use of the presently preferred embodiments. However, it should be understood that this disclosure provides many applicable inventive concepts that can be embodied in a wide range of specific contexts. The specific embodiments described are merely illustrative of specific ways of making and using this disclosure and are not intended to limit the scope of this disclosure.

[0023] This disclosure will be described with reference to preferred embodiments in a specific context (i.e., transient protection devices for wireless power transmission systems). However, the invention is also applicable to various power systems. Various embodiments will now be described with reference to the accompanying drawings.

[0024] Figure 1 A block diagram of a wireless power transmission system according to various embodiments of the present disclosure is shown. The wireless power transmission system 100 includes a power stage 104 and a wireless power transmission device 101, cascaded 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 1As shown, transmitter 110 includes a cascaded transmitter circuit 107 and transmitter coil L1. The input of transmitter circuit 107 is coupled to the output of power stage 104. Receiver 120 includes a cascaded receiver coil L2 and rectifier 112. The output of rectifier 112 is coupled to load 114.

[0025] When receiver 120 is placed near transmitter 110, transmitter 110 is magnetically coupled to receiver 120 via a magnetic field. A loosely coupled transformer 115 is formed via transmitter coil L1 (which is part of transmitter 110) and receiver coil L2 (which is part of receiver 120). Therefore, power can be transferred from transmitter 110 to receiver 120.

[0026] In some embodiments, the transmitter 110 may be located inside the charging pad. The transmitter coil is positioned 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, magnetic coupling can 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 transfer occurs 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 the range of approximately 0.05 to approximately 0.9.

[0027] In some embodiments, after magnetic coupling has been established between transmitter coil L1 and receiver coil L2, transmitter 110 and receiver 120 can form a power system through which power is wirelessly transmitted from input power source 102 to load 114.

[0028] Input power source 102 may be a power adapter that converts grid line voltage into direct current (DC) voltage. In other embodiments, input power source 102 may be a regenerative power source, such as a solar panel array. Furthermore, input power source 102 may be an energy storage device, such as a rechargeable battery, fuel cell, etc.

[0029] Load 114 represents the power consumed by a mobile device (e.g., 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.

[0030] In some embodiments, transmitter circuit 107 may include a primary-side switch of a full-bridge power converter. A full-bridge is also known as an H-bridge. In other embodiments, transmitter circuit 107 may include a primary-side switch of other converters (e.g., a half-bridge converter, a push-pull converter, etc.). The following will focus on... Figure 2This describes the detailed configuration of the transmitter circuit 107.

[0031] It should be noted that the converter described above is merely an example. Those skilled in the art will recognize that other suitable power converters, such as Class E topology-based power converters (e.g., Class E amplifiers), can be used in other embodiments.

[0032] The transmitter circuit 107 may further include a resonant capacitor. The resonant capacitor and the magneto-inductance of the transmitter coil can form a resonant circuit. Depending on design requirements and different applications, the resonant circuit 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.

[0033] Receiver 120 includes a receiver coil L2, which is magnetically coupled to transmitter coil L1 after receiver 120 is placed near transmitter 110. Therefore, power can be transferred to the receiver coil and further to load 114 via rectifier 112. Receiver 120 may include a secondary resonant capacitor.

[0034] 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.

[0035] Furthermore, synchronous rectifiers can be formed using any controllable device, such as metal-oxide-semiconductor field-effect transistor (MOSFET) devices, bipolar junction transistor (BJT) devices, superjunction transistor (SJT) devices, insulated-gate bipolar transistor (IGBT) devices, gallium nitride (GaN) based power devices, etc. The following will focus on... Figure 2 Let's discuss the detailed structure of rectifier 112.

[0036] Power stage 104 is coupled between input power supply 102 and input of wireless power transmission device 101. Depending on design requirements and different applications, power stage 104 may include many different configurations. In some embodiments, power stage 104 may be a non-isolated power converter, such as a buck converter. In some embodiments, power stage 104 may be implemented as a linear regulator. In some embodiments, power stage 104 may be an isolated power converter, such as a forward converter.

[0037] The implementation of power stage 104 described above is merely an example and should not unduly limit the scope of the claims. Many variations, substitutions, and modifications will be apparent to those skilled in the art. Furthermore, depending on the application and design requirements, power stage 104 may be an optional component of the wireless power transmission system 100. In other words, input power supply 102 may be directly connected to transmitter circuitry 107.

[0038] Figure 2 Various embodiments according to this disclosure are shown. Figure 1 The diagram shows a schematic of a wireless power transmission system. The wireless power transmission device 101 includes a cascaded transmitter circuit 107, a resonant capacitor Cp, a loosely coupled transformer 115, a resonant capacitor Cs, and a rectifier 112. The loosely coupled transformer 115 is formed via a transmitter coil L1 and a receiver coil L2. The transmitter circuit 107 is implemented as follows: Figure 2 The full bridge shown. In the following text, Figure 2 The full-bridge converter shown is also known as a power converter or full-bridge power converter.

[0039] The full-bridge 107 includes four switching elements: S1, S2, S3, and S4. For example... Figure 2 As shown, switching 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 1 The output of power stage 104 is shown. Similarly, switching elements S3 and S4 are connected in series between the input voltage bus VIN and ground. The common junction (SW1) of switching elements S1 and S2 is coupled to the first input terminal of the transmitter coil L1. The common junction (SW2) of switching elements S3 and S4 is coupled to the second input terminal of the transmitter coil L1 via the resonant capacitor Cp. The voltage between SW1 and SW2 is denoted as VSW. The following will address... Figure 4 The waveform of VSW is shown.

[0040] In some embodiments, switching elements S1, S2, S3, and S4 are implemented as MOSFETs or MOSFETs connected in parallel, any combination thereof, etc. In other embodiments, the switching element (e.g., switch S1) can be an insulated-gate bipolar transistor (IGBT) device. In still 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.

[0041] It should be noted that although the examples in this description are based throughout on a full-bridge converter (e.g., Figure 2 The bridge shown is 107, but... Figure 2The implementation of the transmitter circuit 107 shown can have many variations, substitutions, and modifications. For example, in other embodiments, a half-bridge converter, a push-pull converter, or a Class E-based power converter (e.g., a Class E amplifier) ​​may be used. Furthermore, when the transmitter coil L1 is tightly coupled to the receiver coil L2 in some applications, an inductor-inductor-capacitor (LLC) resonant converter may be formed.

[0042] In summary, the full-bridge 107 shown herein is limited only for the purpose of clearly illustrating the inventive aspects of the various embodiments. The invention is not limited to any particular power topology.

[0043] It should also be noted that, although Figure 2 Four switches S1-S4 are shown, but various embodiments of this disclosure may include other variations, modifications, and alternatives. For example, a separate capacitor may be connected in parallel with each switch of the full bridge 107. Such a separate capacitor helps to better control the timing of the resonant process of the full bridge 107.

[0044] The output of receiver coil L2 is coupled to load RL via resonant capacitor Cs, rectifier 112, and capacitor Co. The rectifier converts the alternating polarity waveform received from the output of receiver coil L2 into a unipolar waveform. Capacitor Co is used to attenuate noise and provide a steady-state output voltage. Resonant capacitor Cs helps to achieve soft switching in the wireless power transmission system.

[0045] In some embodiments, rectifier 112 is implemented as a synchronous rectifier. Rectifier 112 includes four switching elements, namely S5, S6, S7, and S8. Figure 2 As shown, switching elements S5 and S6 are connected in series between the output terminal of rectifier 112 and ground. Similarly, switching elements S7 and S8 are connected in series between the output terminal of rectifier 112 and ground. Figure 2 As shown, the common junction of switching elements S5 and S6 is coupled to the first terminal of receiver coil L2. The common junction of switching elements S7 and S8 is coupled to the second terminal of receiver coil L2 via resonant capacitor Cs.

[0046] According to some embodiments, the switching elements S5, S6, S7 and S8 are implemented as MOSFETs or MOSFETs connected in parallel, or any combination thereof.

[0047] During operation, multiple transients may occur. The occurrence of transients can affect... Figure 1-2The illustrated wireless power transmission system 100 has an effect. In some embodiments, a coupling transient (change-step condition) may occur. During a coupling transient, the magnetic coupling between the receiver and transmitter changes from loose coupling to tight coupling. Due to this coupling transient, the receiver's output voltage may rise significantly. Furthermore, the power transmitted between the transmitter and receiver also increases. In other embodiments, a load transient (load-step condition) may occur. During a load transient, the receiver's load changes from a heavy load state to a light load state. Due to this load transient, the receiver's output voltage may rise significantly. The power transmitted between the transmitter and receiver decreases during the load transient.

[0048] During the aforementioned transient period, the receiver's output voltage increases significantly. To prevent excessive stress on the receiver's output voltage, a control loop is used to adjust the receiver's output voltage. In some embodiments, the control loop is implemented based on a feedforward control mechanism. The following will focus on... Figure 3 To describe the control loop.

[0049] Figure 3 The following are various embodiments of the present disclosure for controlling Figure 1 The control loop of the wireless power transmission system shown is divided into two parts: a primary side part 310 and a secondary side part 315. The primary side part 310 includes a first adder 302, a frequency adjustment block 312, a second adder 304, a primary side power conversion block 314, and a current gain block 306. The secondary side part 315 includes a secondary side power conversion block 316.

[0050] like Figure 3 As shown, the feedback signal is a current signal Ip(t). In some embodiments, Ip(t) is the current flowing through the transmitter coil. Figure 3 As shown, the feedback signal does not cross the isolation boundary. In other words, the feedback signal is not a feedback signal that crosses from the secondary side to the primary side of the wireless power transmission system.

[0051] like Figure 3As shown, the current signal Ip(t) is fed into a current gain block 306, where a predetermined current gain is applied to the current signal Ip(t). The output of the current gain block 306 and a predetermined current reference REF are fed into a first adder 302. The first adder 302 generates an error signal based on the difference between the predetermined current reference REF and the output of the current gain block 306. The error signal is fed into a frequency adjustment block 312. Based on the error signal, the frequency adjustment block 312 generates a switching frequency signal (f) to set the current flowing through the transmitter coil. In a second adder 304, the switching frequency signal and other operating parameters (e.g., VIN and the duty cycle of the power converter) are combined. The combined signal is applied to a primary-side power conversion block 314, which adjusts the current flowing through the transmitter coil accordingly. Furthermore, the current flowing through the transmitter is magnetically coupled to a secondary power conversion block 316. The secondary power conversion block 316 converts the current flowing through the transmitter into a regulated output voltage for the wireless power transmission system.

[0052] Figure 3 An advantageous feature of the control method shown is that it implements a feedforward control mechanism without requiring feedback control signals that isolate the primary and secondary sides. This technique enables fast transient response.

[0053] Figure 3 The control loop used to regulate the output voltage of the receiver is shown. Based on Figure 3 The control loop shown allows different control mechanisms to be used to adjust the receiver's output voltage according to different transients. For example, coupled transients occur in a time range of approximately 10 milliseconds to approximately 100 milliseconds. Coupled transients are slow transients. Load transients occur in a time range of approximately 1 microsecond to approximately 10 microseconds. Load transients are fast transients. In some embodiments, load transients are much faster than coupled transients. Taking into account the speed difference between these two transients, two different control mechanisms (e.g., proportional-integral-derivative (PID)) can be used to adjust the receiver's output voltage. A first PID control mechanism is designed for coupled transients. A second PID control mechanism is designed for load transients. In some embodiments, the second PID control mechanism provides a fast control loop. Due to this fast control loop, the transient response of the second PID control mechanism is faster than that of the first PID control mechanism.

[0054] In operation, the power transmitted between the transmitter and receiver during coupling transients differs from that during load transients. More specifically, during coupling transients, the power transmitted between the transmitter and receiver increases significantly. On the other hand, during load transients, the power transmitted between the transmitter and receiver decreases significantly. This difference can be used to determine which type of transient has occurred and to apply the corresponding control mechanism accordingly.

[0055] The power transmitted between the transmitter and receiver is proportional to the current flowing through the transmitter coil. Specifically, the power transmitted between the transmitter and receiver is proportional to a specific current value (the current value detected one-quarter of the switching cycle of the power converter). The following will address... Figure 4 This describes the relationship between the power transmitted between the transmitter and receiver and the current flowing through the transmitter coil.

[0056] Figure 4 Various embodiments according to this disclosure are shown. Figure 1 The diagram shows various waveforms of the wireless power transmission system. Figure 4 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.

[0057] like Figure 4 As shown, the current flowing through the transmitter coil lags behind the voltage (the fundamental frequency waveform of the first waveform 402). The phase difference between the voltage and the current is expressed as... like Figure 4 As shown.

[0058] During operation, power is transferred from the transmitter to the receiver. The voltage of the second waveform 404 can be expressed as:

[0059]

[0060] In equation (1), U is the root mean square (rms) value of the voltage of the second waveform 404. U can be expressed by the following formula:

[0061]

[0062] like Figure 4 As shown, the current flowing through the transmitter coil (waveform 406) lags behind the voltage (waveform 404). The current flowing through the transmitter coil can be expressed by the following formula:

[0063]

[0064] In equation (3), Ipk is the peak current flowing through the transmitter coil. The root mean square (rms) value of the current flowing through the transmitter coil can be expressed by the following formula:

[0065]

[0066] The power transmitted between the transmitter and receiver coils can be obtained by calculating the integral of the voltage-current product over a period from 0 to 2π. The average power transmitted between the transmitter and receiver coils during one switching cycle can be expressed as follows:

[0067]

[0068] Equation (5) can be simplified to the following equation:

[0069]

[0070] From equation (4) above, the current satisfies the following equation:

[0071]

[0072] Considering equation (3), equation (7) can be simplified to:

[0073]

[0074] Considering equations (2) and (8), equation (6) above can be expressed as:

[0075]

[0076] Equation (9) shows that during the switching cycle, the power transmitted between the transmitter and receiver is proportional to the current flowing through the transmitter coil at a time corresponding to a quarter of the switching cycle.

[0077] During operation, in each switching cycle, a counter is used to find the moment corresponding to one-quarter of the switching cycle. At this moment, the current flowing through the transmitter coil is detected. Based on the detected current, the power transmitted from the transmitter to the receiver can be calculated accordingly.

[0078] In operation, the detected current is compared to two predetermined thresholds. In some embodiments, the first predetermined threshold is based on a current threshold of approximately 10% power increase. If the detected current is greater than the first predetermined threshold, a coupling transient occurs. A first PID control mechanism is activated to protect the receiver output from excessive output voltage stress. The second predetermined threshold is based on a current threshold of approximately 50% power decrease. If the detected current is less than the second predetermined threshold, a load transient occurs. A second PID control mechanism is activated to protect the receiver output from excessive output voltage stress. The following will address... Figure 5-7 This section describes the detailed implementation of the first PID control mechanism and the second PID control mechanism.

[0079] Figure 5A block diagram of a coupling and load transient protection device according to various embodiments of the present disclosure is shown. The transient protection device includes a microcontroller unit (MCU) 502, a π / 2 detection block 504, a comparison and interrupt block 506, and a current detection block 508.

[0080] MCU 502 establishes an integer equivalent to one-quarter of the switching cycle of the power converter. MCU 502 feeds this integer to π / 2 detection block 504. Current detection block 508 detects the input current of the wireless power transmission system. The detected input current is fed to compare and interrupt block 506, where a first predetermined current threshold and a second predetermined current threshold are determined based on the detected input current.

[0081] In each switching cycle of the power converter, the π / 2 detection block 504 begins counting from the rising edge of a PWM signal applied to the full bridge. The π / 2 detection block 504 continues counting until the value reaches an integer set by the MCU 502. At a quarter of the switching cycle, the current (I_coil) flowing through the transmitter coil is detected. The detected current (current flowing through the transmitter coil) is fed into the compare and interrupt block 506. The detected current is compared with a first predetermined current threshold and a second predetermined current threshold. If a transient occurs, the compare and interrupt block 506 generates a corresponding interrupt and feeds this interrupt to the MCU 502. In response to the interrupt, the MCU 502 applies the corresponding control mechanism to the power converter.

[0082] Figure 6 A schematic diagram of a current detection circuit for detecting current flowing into a wireless power transmission system, according to various embodiments of the present disclosure, is shown. The current detection block 508 includes a current detection amplifier 602 and a detection resistor R. SENSE and capacitor C SENSE Detecting resistor R SENSE It can be placed between VIN and the full-bridge power converter. Flow through the sense resistor R SENSE The current is the input current of the wireless power transmission system.

[0083] The inverting and non-inverting inputs of the current sense amplifier 602 are respectively connected to the sense resistor R. SENSE The two terminals of the capacitor C. SENSE A current-sensing amplifier 602 is connected between its output and its inverting input. The output of the current-sensing amplifier 602 is configured to generate a detected current IIN. The detected current IIN is used to determine the aforementioned first predetermined threshold and second predetermined threshold. Figure 6 The operating principle of the current sensing circuit shown is well known in the art and therefore will not be discussed in this paper.

[0084] It should be noted that this simplified diagram is merely an example and should not unduly limit the scope of the claims. Many variations, substitutions, and modifications will be apparent to those skilled in the art. For example, those skilled in the art will know that... Figure 6 The current sensing circuit shown is just one way to detect the input current, and other embodiments of the current sensing circuit (such as a DC resistor (DCR) current sensing device) can be used for this function.

[0085] Figure 7 A 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, a second comparator 704, and an interrupt generator 706. (As...) Figure 7 As shown, the detected current (the current flowing through the transmitter coil) IIN is fed into a first comparator 702 and a second comparator 704, respectively. The inverting input of the first comparator 702 is coupled to a first predetermined threshold. The first predetermined threshold is a current threshold generated based on the input current flowing into the wireless power transmission system. The first predetermined threshold is used to determine whether a coupling transient has occurred. The non-inverting input of the first comparator 702 is coupled to the current (I_coil) flowing through the transmitter coil.

[0086] The inverting input of the second comparator 704 is coupled to the current (I_coil) flowing through the transmitter coil. The non-inverting input of the second comparator 704 is coupled to a second predetermined threshold. The second predetermined threshold is a current threshold generated based on the input current flowing into the wireless power transmission system. The second predetermined threshold is used to determine whether a load transient has occurred.

[0087] The outputs of the first comparator 702 and the second comparator 704 are fed into the interrupt generator 706. Based on different transients, the interrupt generator 706 generates different interrupts and sends them to the MCU 502. The MCU 502 applies the corresponding control mechanism to the power converter. The operating principles of the interrupt generator and the MCU are well known in the art and therefore will not be discussed herein to avoid unnecessary repetition.

[0088] It should be noted that the comparison and interrupt block 506 described herein is provided for illustrative purposes only and is given only as an example of functionality that may be included in the comparison and interrupt block 506. Those skilled in the art will recognize that the comparison and interrupt block 506 may be implemented in many different ways and may include other functional blocks.

[0089] Figure 8 The following are illustrated in various embodiments of the present disclosure, including control. Figure 1 The flowchart shows a method for a wireless power transmission system. Figure 8The flowchart shown is merely an example and should not unduly limit the scope of the claims. Those skilled in the art will recognize many variations, substitutions, and modifications. For example, Figure 8 The various steps shown can be added, removed, substituted, rearranged, and repeated.

[0090] A 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.

[0091] In operation, two distinct transients can be applied to a wireless power transmission system. When a coupling transient occurs, the power transmitted between the transmitter and receiver, as well as the receiver's output voltage, increases. When a load transient occurs, the power transmitted between the transmitter and receiver decreases, while the receiver's output voltage increases.

[0092] The control device detects the current flowing through the transmitter coil at a point one-quarter of the power converter's switching cycle. The power transmitted between the transmitter and receiver is proportional to the detected current value. Therefore, the detected current is used to determine what type of transient has occurred. Specifically, a coupling transient occurs when the detected current is greater than a first threshold. On the other hand, a load transient occurs when the detected current is less than a second threshold. Based on the type of transient, an appropriate control mechanism is applied to the power converter to prevent excessive stress on the receiver's output voltage.

[0093] In step 802, during the switching cycle of the power converter in the wireless power transmission system, appropriate circuitry (e.g., a counter) is used to find the moment corresponding to one-quarter of the switching cycle.

[0094] In step 804, at a time corresponding to one-quarter of the switching cycle, the current flowing through the transmitter coil of the wireless power transmission system is detected. The detected current is fed into the compare and interrupt block.

[0095] In step 806, the detected current (the current flowing through the transmitter coil) is compared with a plurality of predetermined thresholds. Specifically, the detected current is compared with a first predetermined threshold indicating whether a coupling transient has occurred and with a second predetermined threshold indicating whether a load transient has occurred. A coupling transient occurs when the detected current is greater than the first predetermined threshold. Conversely, a load transient occurs when the detected current is less than the second predetermined threshold.

[0096] In step 808, the control mechanism is applied to the power converter based on the comparison result of the step of comparing the current flowing through the transmitter coil with a plurality of predetermined thresholds. Specifically, a first PID control mechanism is applied to the power converter when a coupling transient occurs. A second PID control mechanism is applied to the power converter when a load transient occurs. In some embodiments, the transient response of the second PID control mechanism is faster than that of the first PID control mechanism.

[0097] While embodiments of the present disclosure and their 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 present disclosure as defined by the appended claims.

[0098] Furthermore, the scope of this application is not intended to be limited to the specific embodiments of the processes, machines, manufactures, compositions of matter, components, methods, and steps described herein. As will be readily understood by those skilled in the art from the disclosure of this publication, existing or future processes, machines, manufactures, compositions of matter, components, methods, or steps that perform substantially the same function or achieve substantially the same results as the corresponding embodiments described herein can be utilized according to this disclosure. Accordingly, the appended claims are intended to encompass such processes, machines, manufactures, compositions of matter, components, methods, or steps within their scope.

Claims

1. An apparatus comprising: The transmitter coil is configured to be magnetically coupled to the receiver coil; A power conversion device is coupled to the transmitter coil; as well as A controller configured to control the operating variables of the power conversion device in response to changes in operating conditions, wherein the controller includes a quarter-cycle detection block configured to establish a current detection moment corresponding to one-quarter of the switching cycle of the power conversion device, and wherein at the current detection moment, the current flowing through the transmitter coil is detected and compared with a plurality of predetermined thresholds to determine which type of transient has occurred.

2. The device as claimed in claim 1, wherein: The power conversion device is a full-bridge converter.

3. The device as claimed in claim 1, wherein: The controller is configured to adjust the switching frequency of the power conversion device in response to transients.

4. The device as claimed in claim 3, wherein: The transient is a coupled transient, wherein under the coupled transient, the controller is configured to apply a first control mechanism to the power conversion device.

5. The device as claimed in claim 4, wherein: The transient is a load transient, wherein under the load transient, the controller is configured to apply a second control mechanism to the power conversion device.

6. The device as claimed in claim 5, wherein: The transient response of the second control mechanism is faster than that of the first control mechanism.

7. The device as claimed in claim 1, further comprising: A current sensing block is configured to detect the input current flowing into the power conversion device, wherein the input current is used to generate a first threshold for determining whether a coupling transient has occurred and a second threshold for determining whether a load transient has occurred.

8. The device as claimed in claim 1, wherein: At the current detection moment, the power transmitted from the transmitter coil to the receiver coil is proportional to the current flowing through the transmitter coil.

9. A method comprising: In the switching cycle of the power converter in the wireless power transmission system, find the moment corresponding to one-quarter of the switching cycle; At the stated moment, the current flowing through the transmitter coil of the wireless power transmission system is detected; The current flowing through the transmitter coil is compared with a plurality of predetermined thresholds; as well as A control mechanism is applied to the power converter based on the comparison result of comparing the current flowing through the transmitter coil with a plurality of predetermined thresholds.

10. The method of claim 9, further comprising: The current flowing through the transmitter coil is compared with a first predetermined threshold indicating a coupling transient; as well as The current flowing through the transmitter coil is compared with a second predetermined threshold indicating load transients.

11. The method of claim 10, further comprising: When the coupling transient is applied to the wireless power transmission system, the first control mechanism is applied to the power converter; as well as When the load transient is applied to the wireless power transmission system, a second control mechanism is applied to the power converter, wherein the transient response of the second control mechanism is faster than that of the first control mechanism.

12. The method of claim 9, wherein: At that moment, the power transmitted from the transmitter to the receiver of the wireless power transmission system is proportional to the current flowing through the transmitter coil of the wireless power transmission system.

13. The method of claim 9, further comprising: Detect the input current of the wireless power transmission system; as well as The plurality of predetermined thresholds are determined based on the input current.

14. The method of claim 9, further comprising: During the switching cycle of the power converter, the rising edge of the gate drive signal of the power converter is used as the starting point to begin counting until the moment corresponding to one-quarter of the switching cycle is found.

15. A method comprising: In the switching cycle of the power converter in the wireless power transmission system, find the moment corresponding to one-quarter of the switching cycle, wherein the power converter is coupled between the input power supply and the transmitter coil, and the transmitter coil is magnetically coupled to the receiver coil. At the stated moment, the current flowing through the transmitter coil is detected, wherein the power transmitted between the transmitter coil and the receiver coil is proportional to the current flowing through the transmitter coil; The current flowing through the transmitter coil is compared with a plurality of predetermined thresholds to determine whether a transient has occurred; and A control mechanism is applied to the power converter in response to the occurrence of the transient.

16. The method of claim 15, further comprising: The current flowing through the transmitter coil is compared with a first predetermined threshold to determine whether a coupling transient has occurred; as well as The first control mechanism is applied to the power converter in response to the occurrence of the coupling transient.

17. The method of claim 16, further comprising: The current flowing through the transmitter coil is compared with a second predetermined threshold to determine whether a load transient has occurred; as well as A second control mechanism is applied to the power converter in response to the occurrence of the load transient.

18. The method of claim 17, wherein: The transient response of the second control mechanism is faster than that of the first control mechanism.

19. The method of claim 17, further comprising: Detect the input current of the wireless power transmission system; as well as The first predetermined threshold and the second predetermined threshold are determined based on the input current of the wireless power transmission system.

20. The method of claim 15, further comprising: The counting begins with the rising edge of the gate drive signal of the power converter as the starting point, until the moment corresponding to one-quarter of the switching cycle is found.

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