Device, control circuit and communication method for wireless power reception and transmission

Abstract

A device, control circuit, and communication method for wireless power reception and transmission. The device includes a receiving coil and a rectifier having a first input and a second input. The first input is coupled to a first terminal of the receiving coil, and the second input is coupled to a second terminal of the receiving coil via a resonant capacitor. The device further includes a first capacitor and a first switching network connected in series between the first input and ground, and a second capacitor and a second switching network connected in series between the second input and ground. Each of the first and second switching networks includes at least a plurality of field effect transistors (FETs) connected in parallel. The first and second switching networks are configured to adjust an impedance coupled to the receiving coil, the impedance being related to amplitude shift keying (ASK) modulation used by the device.

Description

Technical Field

[0001] The present invention relates to a wireless power transfer system and, in a particular embodiment, to in-band communication between a transmitter and a receiver of a wireless power transfer system. Background Art

[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, tablets, digital cameras, and MP3 players. Wireless power transfer systems typically include a primary-side transmitter and a secondary-side receiver. The primary-side transmitter and the secondary-side receiver are magnetically coupled. This magnetic coupling can be implemented as a loosely coupled transformer with a primary-side coil formed in the primary-side transmitter and a secondary-side coil formed in the secondary-side receiver.

[0003] The primary-side transmitter can 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 can convert electrical energy into a wireless power signal. The secondary-side receiver can receive the wireless power signal via a loosely coupled transformer and convert the received wireless power signal into electrical energy suitable for the load.

[0004] In a wireless power transmission system, various control signals can be generated based on operating parameters at the secondary-side receiver. The control signals can be transmitted from the secondary-side receiver to the primary-side transmitter. Specifically, the control signals can be transmitted from the receiving coil to the transmitting coil in the form of a modulated signal using a suitable modulation scheme. The transmission and reception of control signals between the primary-side transmitter and the secondary-side receiver is referred to as in-band communication in a wireless power transmission system. Amplitude shift keying (ASK) is a modulation scheme widely used in receivers of wireless power transmission systems. ASK is achieved by modulating the amplitude of an analog signal in a wireless power transmission system. Information is conveyed through changes in the amplitude of the analog signal. An analog sensing device is used to detect the control signal, which can be included in the current and / or voltage applied to the transmitting coil. A demodulator at the primary-side transmitter can be used to demodulate the signal detected by the analog sensing device, and the demodulated signal is fed to the transmitter controller to better control the operation of the transmitter.

[0005] Communication information can be transmitted from a receiver to a transmitter, and this communication information can be demodulated at the transmitter by changing the transmitter's operating parameters. A relatively simple method for changing the transmitter's operating parameters is based on impedance modulation. For example, a pair of capacitor-switch networks is coupled to the two terminals of a receiver coil. The switches of these capacitor-switch networks are opened and closed during communication, thereby changing the impedance coupled to the receiver coil. This impedance change affects the electrical characteristics of the transmitter. In response to this change, some operating parameters (e.g., the current flowing through the transmitter coil and / or the voltage across the transmitter coil) may change. Control circuitry in the transmitter detects the change in at least one operating parameter and obtains the communication information by demodulating the change in the operating parameter.

[0006] A conventional capacitor-switch network can be connected between the input terminals of a receiver's rectifier. The capacitors in the capacitor-switch network and other capacitors in the receiver form a resonant circuit with the receiver coil. When the capacitor-switch network is conducting, an oscillating current may flow between the rectifier input terminals due to the LC loop characteristics of the resonant circuit. This oscillating current may interfere with the current flow in the rectifier, causing unintended consequences. For example, when the receiver coil has low inductance and the receiver is not coupled to any load or is coupled to a light load, this oscillating current may become large enough to change the direction of the current flow in the rectifier. This interference may cause the rectifier's output voltage to drop suddenly and result in data loss in the in-band communication of the wireless power transfer system. Consequently, the rectifier may shut down, and wireless power transfer may even be unintentionally terminated.

[0007] Therefore, advanced structures are needed to reduce the interference of in-band communication on wireless power transmission and make power transmission more efficient and reliable. Summary of the Invention

[0008] These and other problems are generally solved or circumvented, and technical advantages are generally achieved, by preferred embodiments of the present disclosure, which provide a communication device in a receiver of a wireless power transfer system.

[0009] According to one embodiment, an apparatus for wireless power reception includes a rectifier configured to convert an AC voltage to a DC voltage for coupling to a load of the apparatus. The apparatus further includes a receiving coil and a resonant capacitor connected in series, wherein the combination of the receiving coil and the resonant capacitor is connected between two input terminals of the rectifier. The apparatus further includes a first capacitor and a first switch connected in series, wherein the combination of the first capacitor and the first switch is connected in parallel with the resonant capacitor. The apparatus further includes a second capacitor and a second switch connected in series, wherein the combination of the second capacitor and the second switch is connected in parallel with the resonant capacitor, and wherein the first switch and the second switch are configured to adjust an impedance coupled to the receiver coil, wherein the impedance is related to amplitude shift keying (ASK) modulation used by the apparatus.

[0010] According to one embodiment, a method includes connecting a receiving coil and a resonant capacitor in series. The method further includes connecting the receiving coil and the resonant capacitor combination between two input terminals of a rectifier, wherein the rectifier is configured to convert an AC voltage to a DC voltage for a load of a wireless power transmission system. The method also includes connecting a first capacitor and a first switch in series, and connecting the combination of the first capacitor and the first switch in parallel with the resonant capacitor. The method also includes connecting a second capacitor and a second switch in series, and connecting the combination of the second capacitor and the second switch in parallel with the resonant capacitor. The method further includes configuring the first switch and the second switch to adjust an impedance coupled to the receiving coil, wherein the impedance is related to ASK modulation used by the wireless power transmission system.

[0011] According to one embodiment, a control circuit for a wireless power receiving system includes a first switch and a second switch, wherein the first switch is connected in series with a first capacitor, and the second switch is connected in series with a second capacitor, wherein the combination of the first switch and the first capacitor is connected in parallel with a resonant capacitor, wherein the series combination of the resonant capacitor and a receiving coil of the wireless power receiving system is connected between two input terminals of a rectifier of the wireless power receiving system, wherein the combination of the second switch and the second capacitor is connected in parallel with the resonant capacitor, and wherein the first switch and the second switch are configured to adjust an impedance coupled to the receiving coil, wherein the impedance is related to ASK modulation used by the wireless power receiving system.

[0012] The features and technical advantages of the present disclosure have been summarized quite broadly above so that the detailed description disclosed below may be better understood. Additional features and advantages of the present disclosure will be described below, which form the subject matter of the claims of the present disclosure. It will be understood by those skilled in the art that the concepts and specific embodiments disclosed herein may be readily used as a basis for modifying or designing other structures or processes for achieving the same purposes of the present disclosure. It will also be appreciated by those skilled in the art that such equivalent structures do not depart from the spirit and scope of the present disclosure as set forth in the appended claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] For a more complete understanding of the present invention and its advantages, reference is now made to the following description in conjunction with the accompanying drawings, in which:

[0014] Figure 1 shows a block diagram of a wireless power transfer system according to some embodiments;

[0015] Figure 2 According to some embodiments Figure 1 A block diagram of a receiver is shown;

[0016] Figure 3 A wireless power receiver is shown including a switch implemented as a field effect transistor (FET) according to some embodiments;

[0017] Figure 4 A wireless power receiver including a variable inductor according to some embodiments is shown;

[0018] Figure 5 A wireless power receiver including a variable inductor and multiple capacitor-switch networks is shown according to some embodiments;

[0019] Figure 6 shows a flow chart for controlling in-band communications of a wireless power transfer system according to some embodiments;

[0020] Figures 7A-7C An example of a capacitor-switch network for in-band communication according to some embodiments is shown.

[0021] 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

[0022] The making and using of the presently preferred embodiments are discussed in detail below. However, it should be understood that this disclosure provides many applicable inventive concepts that can be embodied in a variety of specific contexts. The specific embodiments discussed are intended only to illustrate specific ways to make and use the invention and are not intended to limit the scope of the invention.

[0023] The present disclosure will be described with respect to preferred embodiments in a specific context, namely, a communication device in a receiver of a wireless power transmission system. However, the present disclosure may also be applied to various power systems. Various embodiments will be described in detail below with reference to the accompanying drawings.

[0024] Figure 1A block diagram of a wireless power transmission system according to various embodiments of the present disclosure is shown. Wireless power transmission system 100 includes a power converter 104 and a wireless power transmission device 101, connected in cascade between an input power source 102 and a load 114. In some embodiments, power converter 104 is employed to further improve the performance of wireless power transmission system 100. In alternative embodiments, power converter 104 is an optional component. In other words, wireless power transmission device 101 can be directly connected to input power source 102.

[0025] The wireless power transmission device 101 includes a power transmitter 110 and a power receiver 120 (also referred to as a receiver in this disclosure). Figure 1 As shown, the power transmitter 110 includes a transmitter circuit 107 and a transmitter coil L1 connected in cascade. The input terminal of the transmitter circuit 107 is coupled to the output terminal of the power converter 104. The power receiver 120 includes a receiver coil L2 connected in cascade, a resonant capacitor Cs, a rectifier 112, and a power converter 113. Figure 1 As shown, a resonant capacitor Cs is connected in series with the receiving coil L2 and further connected to the input of the rectifier 112. The resonant capacitor Cs can help achieve soft switching of the wireless power transmission system. The output of the rectifier 112 is connected to the input of the power converter 113. The output of the power converter 113 is coupled to the load 114. The power receiver 120 may further include another resonant capacitor Cd connected between the inputs of the rectifier 112. Optionally, the resonant capacitor Cd may be connected in series with the switch. The resonant capacitor Cd can be configured to change the resonant frequency of the resonant circuit formed by the receiver coil L2, the resonant capacitor Cs, and the resonant capacitor Cd, thereby helping the power transmitter 110 detect the presence of the power receiver 120.

[0026] When the power receiver 120 is placed near the power transmitter 110, the power transmitter 110 is magnetically coupled to the power receiver 120 through a magnetic field. The loosely coupled transformer 115 is composed of a transmitting coil L1 as part of the power transmitter 110 and a receiving coil L2 as part of the power receiver 120. As a result, electric power can be transmitted from the power transmitter 110 to the power receiver 120.

[0027] In some embodiments, power transmitter 110 may be located within a charging pad. Transmitter coil L1 is positioned below the upper surface of the charging pad. Power receiver 120 may be embedded within a mobile phone. When the mobile phone is placed near the charging pad, magnetic coupling is established between transmitter coil L1 and receiver coil L2. In other words, transmitter coil L1 and receiver coil L2 form a loosely coupled transformer, through which power is transferred between power transmitter 110 and power receiver 120. The coupling strength between transmitter coil L1 and 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.

[0028] In some embodiments, after establishing magnetic coupling between the transmitting coil L1 and the receiving coil L2, the power transmitter 110 and the power receiver 120 may form a power system through which power is wirelessly transferred from the input power source 102 to the load 114.

[0029] Input power source 102 may be a power adapter that converts utility line voltage to direct current (DC) voltage. Alternatively, input power source 102 may be a renewable power source, such as a solar panel array. Furthermore, input power source 102 may be any suitable energy storage device, such as a rechargeable battery, a fuel cell, any combination thereof, and / or the like.

[0030] Load 114 represents the power consumed by a mobile device (e.g., a mobile phone) coupled to power receiver 120. Alternatively, load 114 may refer to a rechargeable battery and / or series / parallel connected batteries coupled to the output of power receiver 120. Additionally, load 114 may be a downstream power converter, such as a battery charger.

[0031] According to some embodiments, the transmitter circuit 107 may include a primary-side switch of a full-bridge converter. Alternatively, the transmitter circuit 107 may include a primary-side switch of any other suitable power converter (e.g., a half-bridge converter, a push-pull converter, or any combination thereof and / or the like).

[0032] It should be noted that the above power converters are merely examples. One of ordinary skill in the art will recognize that other suitable power converters, such as a power converter based on a Class E topology (eg, a Class E amplifier), may be used instead depending on design requirements and different applications.

[0033] Transmitter circuit 107 may also include a resonant capacitor (not shown). The resonant capacitor and the magnetic inductance of the transmitter coil may form a resonant circuit. Depending on design requirements and different applications, the resonant circuit may also include a resonant inductor. In some embodiments, the resonant inductor may be implemented as an external inductor. In alternative embodiments, the resonant inductor may be implemented as a connecting wire.

[0034] The power receiver 120 includes a receiving coil L2 that is magnetically coupled to the transmitting coil L1 after the power receiver 120 is placed near the power transmitter 110. Therefore, power can be transferred to the receiving coil and further transferred to the load 114 through the rectifier 112. The power receiver 120 may include Figure 1 The secondary resonant capacitor Cs is shown. In this document, the secondary resonant capacitor Cs may alternatively be referred to as a receiver resonant capacitor. The power receiver 120 may further include a circuit configured to perform in-band communication between the power transmitter 110 and the power receiver 120 (not shown, but may be referred to as a circuit). Figure 2 (see instructions in the text).

[0035] Rectifier 112 converts the alternating polarity waveform received from the resonant tank including receiver coil L2 and receiver resonant capacitor Cs into a unipolar waveform. In some embodiments, rectifier 112 includes a full-wave diode bridge and an output capacitor. In alternative embodiments, the full-wave diode bridge can be replaced by a full-wave bridge formed by switching elements such as n-type metal oxide semiconductor (NMOS) transistors.

[0036] In addition, the rectifier 112 may be formed by other types of controllable devices, such as metal oxide semiconductor field effect transistor (MOSFET) devices, bipolar junction transistor (BJT) devices, super junction transistor (SJT) devices, insulated gate bipolar transistor (IGBT) devices, gallium nitride (GaN)-based power devices, and / or the like. The detailed operation and structure of the rectifier 112 are well known in the art and will not be discussed here.

[0037] Power converter 113 is coupled between rectifier 112 and load 114. Power converter 113 can be used to further regulate the voltage / current applied to load 114. Power converter 113 is a non-isolated power converter. In some embodiments, power converter 113 is implemented as a step-down power converter, such as a buck converter. In alternative embodiments, power converter 113 is implemented as a four-switch buck-boost power converter.

[0038] Furthermore, the power converter 113 may be implemented as a hybrid power converter. A hybrid converter is a non-isolated power converter. By controlling the on / off state of a switch of the hybrid converter, the hybrid converter may be configured as a buck converter, a charge pump converter, or a hybrid converter.

[0039] Depending on design requirements and different applications, the hybrid converter can operate in different operating modes. More specifically, when the load current is less than a predetermined current threshold and / or the input voltage is less than a predetermined voltage threshold, the hybrid converter can operate in buck mode. In buck mode, the hybrid converter is configured as a buck converter. When the input voltage is greater than a predetermined voltage threshold and / or the load current is greater than a predetermined current threshold, the hybrid converter can operate in charge pump mode or hybrid mode. More specifically, in some embodiments, when the ratio of the output voltage of the hybrid converter to the input voltage of the hybrid converter is less than 0.5, the hybrid converter can operate in charge pump mode or hybrid mode. In charge pump mode, the hybrid converter is configured as a charge pump converter. In hybrid mode, the hybrid converter is configured as a hybrid converter.

[0040] In some embodiments, the hybrid converter includes a first switch, a capacitor, and a second switch connected in series between the output of the rectifier 112 and the input of the load 114. The hybrid converter also includes a third switch and a fourth switch. The third switch is connected between a common node between the first switch and the capacitor and a common node between the second switch and the output of the hybrid converter. The fourth switch is connected between a common node between the capacitor and the second switch and ground.

[0041] In addition, the power converter 113 may include a first power stage and a second power stage connected in cascade. The first power stage is configured to operate in different modes to efficiently charge the load 114 (e.g., a rechargeable battery). In some embodiments, the first stage can be implemented as a step-down power converter (e.g., a buck converter), a four-switch buck-boost converter, a hybrid converter, and any combination thereof. The second power stage is configured as a voltage divider or an isolation switch.

[0042] Figure 2 1 illustrates a block diagram of a receiver 120 according to various embodiments of the present disclosure. Figure 2As shown, receiver 120 includes a receive coil L2, a receiver resonant capacitor Cs, a resonant capacitor Cd, a rectifier 112, and a power converter 113. Rectifier 112 may include two input terminals 214 and 216 and two output terminals 218 and 220. The series combination of receive coil L2 and receiver resonant capacitor Cs is connected between input terminal 214 and input terminal 216 of rectifier 112. More specifically, input terminal 214 is connected to receiver resonant capacitor Cs, while input terminal 216 is connected to receive coil L2. Receive coil L2 is configured to be magnetically coupled to a transmitter coil (not shown). Receiver resonant capacitor Cs and receive coil L2 form a receiver resonant tank. Resonant capacitor Cd is connected between input terminal 214 and input terminal 216 of rectifier 112. Alternatively, resonant capacitor Cd is connected in series with optional switch 210, with the series combination of Cd and switch 210 connected between input terminals 214 and 216. The resonant capacitor Cd may be configured to enable the receiver 120 to operate at a specific resonant frequency so that the power transmitter 110 (eg Figure 1 The presence of the receiver 120 can be detected by the rectifier 112 (as shown). The output terminals 218 and 220 of the rectifier 112 are connected to the input terminals of the power converter 113. The output terminal of the power converter 113 is connected to the load 114.

[0043] In some embodiments, the rectifier 112 is implemented as a synchronous rectifier. The rectifier 112 may include four switching elements, namely Q1, Q2, Q3 and Q4. Figure 2 As shown, switching elements Q1 and Q2 are connected in series between output terminals 218 and 220 of the rectifier 112. Similarly, switching elements Q3 and Q4 are connected in series between output terminals 218 and 220. The common node of switching elements Q1 and Q2 is connected to input terminal 214, which is coupled to the first end of the receiving coil L2 via resonant capacitor Cs. The common node of switching elements Q3 and Q4 is connected to input terminal 216, which is coupled to the second end of the receiving coil L2. According to some embodiments, the switching elements of the rectifier 112 are implemented as metal oxide semiconductor field effect transistors (MOSFETs) or MOSFETs connected in parallel, any combination thereof, and / or similar combinations. It should be noted that although the examples herein are based on a full-wave rectifier (e.g., Figure 2 rectifier 112 shown in FIG), but Figure 2 The implementation of the receiver shown in FIG. 1 may be subject to many variations, alternatives, and modifications. For example, a half-wave rectifier may be used. In summary, the rectifier 112 described herein is limited only for the purpose of clearly illustrating the inventiveness of various embodiments. The present disclosure is not limited to any particular power supply topology.

[0044] In some embodiments, the receiver 120 includes one or more capacitor-switch networks configured for in-band communication. Each of the one or more capacitor-switch networks can be independently controlled. In operation, the receiver is configured to send one or more control signals (communication information) to a transmitter magnetically coupled to the receiver. The one or more control signals are transmitted using an appropriate modulation scheme, such as amplitude shift keying (ASK). The ASK modulation scheme can be implemented by adjusting the impedance coupled to the receiving coil L2. As a result of adjusting the impedance coupled to the receiving coil L2, the gain of the wireless power transmission system changes accordingly. The controller on the transmitter side detects the change in gain by analyzing the current flowing through the transmitting coil and / or the voltage on the transmitting coil. The change in gain can be demodulated to retrieve the control signal sent from the receiver.

[0045] In a conventional power receiver, a capacitor-switch network for in-band communication may be connected between input 214 and input 216 (at Figure 2 (not shown) This design may result in oscillating currents that interfere with the function of the rectifier. Specifically, when the capacitor-switch network between input terminals 214 and 216 is turned on, the capacitors in the capacitor-switch network and some other capacitors in the receiver may form a resonant circuit with the receiver coil. Due to the LC loop characteristics of the resonant circuit, an oscillating current may be generated between input terminals 214 and 216. When the oscillating current is large and the current in the rectifier is small, this oscillating current may interfere with the current flow within the rectifier and have unintended consequences for the rectifier's operation. For example, the receiver coil can use a smaller inductor to reduce heat generated by the receiver during power transmission. At the same time, the capacitor-switch network can use capacitors with larger capacitance values to generate sufficient impedance change for in-band communication or to support high charging capacity. As a result, the resonant frequency increases, and the oscillating current between input terminals 214 and 216 also increases. When the receiver is not coupled to any load or is only coupled to a light load, the current in rectifier 112 is low. The oscillating current may become large enough to change the direction of the current in the rectifier. For example, the current flowing from input terminal 214 through Q1 to output terminal 218 may be affected by the oscillating current between input terminal 214 and input terminal 216 and may change direction. Reverse current flowing from output terminal 218 to input terminal 214 may cause the rectifier's output voltage to drop suddenly, resulting in data loss during in-band communication within the wireless power transfer system. Consequently, the rectifier may shut down, and wireless power transfer may even be inadvertently terminated.

[0046] The present disclosure provides a technique for reducing oscillatory currents that interfere with rectifiers by avoiding connecting a capacitor-switch network for in-band communication between the input terminals of the rectifiers. In various embodiments, the capacitor-switch network for in-band communication can be connected in parallel with the resonant capacitor Cs instead of being connected between the input terminals of the rectifiers. Figure 2 As shown, a capacitor-switch network for receiver in-band communication includes a plurality of capacitors 202, ..., 204 and a plurality of switches 206, ..., 208. The capacitor-switch network includes at least one first capacitor-switch network (including capacitor 202 connected in series with switch 206) and a second capacitor-switch network (including capacitor 204 connected in series with switch 208). Each capacitor-switch network is connected in parallel with a resonant capacitor Cs. The series combination of capacitor 202 and switch 206 is connected in parallel with the resonant capacitor Cs, and the series combination of capacitor 204 and switch 208 is connected in parallel with the resonant capacitor Cs.

[0047] Multiple capacitors 202, ..., 204 and multiple switches 206, ..., 208 can be configured to produce multiple impedance variations. The receiver 120 can select two different impedances from the multiple impedance variations it is configured to produce and switch between the two impedances during communication based on ASK modulation. Half of the waveform of the voltage between the output terminals of the rectifier 112 can be referred to as Vrect. The amplitude of Vrect is affected by the impedance coupled between the first input terminal and the second input terminal of the rectifier 112. Therefore, one of the two selected impedances will result in a low level amplitude of Vrect, while the other will result in a high level amplitude of Vrect. In other words, the low level amplitude of Vrect is associated with the low state of ASK modulation, while the high level amplitude of Vrect is associated with the high state of ASK modulation.

[0048] In various embodiments, receiver 120 may include control circuit 212. Control circuit 212 may be a single chip. Multiple capacitors 202, ..., 204 may be located outside of control circuit 212. Multiple switches 206, ..., 208 may be located inside control circuit 212 and may be controlled by control signals provided by control circuit 212. In some embodiments, control circuit 212 may include rectifier 112 and power converter 113. Alternatively, in various embodiments, rectifier 112 and power converter 113 may be located outside of control circuit 212. Control circuit 212 may be configured to open or close any of multiple switches 206, ..., 208 to produce multiple impedance changes.

[0049] In various embodiments, the plurality of switches 206, ..., 208 may be implemented as field effect transistors (FETs), such as Figure 3As shown. In some embodiments, the gate drive voltage of FETs 206, ..., 208 can be adjusted so that each field-effect transistor can function as a switch, a resistor, or both. In various embodiments, depending on the gate drive voltage, each FET 206, ..., 208 can operate in one of at least three modes: a saturation mode, in which the FET acts as a switch, turned on with a small on-resistance; an off mode, in which the FET acts as a switch that is turned off; and an ohmic mode, in which the FET acts as a resistor whose resistance is controlled by the gate drive voltage. Thus, the capacitor-switch network can be a capacitor-resistor network. The capacitor-resistor network includes one or more control variables, namely the resistance of the FET. The resistance of each field-effect transistor can be adjusted by adjusting the corresponding gate drive voltage. Thus, the capacitor-resistor network can be an adjustable impedance network coupled to the receiving coil. The control circuit 212 can generate multiple impedance variations by adjusting the capacitor-resistor network. During communication, the receiver 120 or the control circuit 212 can select two appropriate impedances from the multiple impedance variations and associate the selected impedances with the low and high states of the ASK modulation.

[0050] In various embodiments, the receiver 120 or the control circuit 212 can adjust the corresponding gate drive voltage of at least one of the plurality of FETs 206, ..., 208 to switch the configuration of the capacitor-switch network when the corresponding drain-source voltage of at least one of the plurality of FETs 206, ..., 208 is close to 0. When the drain-source voltage of the FETs 206, ..., 208 is close to 0, the voltage on the resonant capacitor Cs is also small. Therefore, when the voltage on Cs is low, the switching configuration of the capacitor-switch network can reduce the impact on the function of the rectifier 112.

[0051] In one embodiment, the switch 210 in series with the resonant capacitor Cd can be located external to the control circuit 212. In another embodiment, the switch 210 can be included in the control circuit 212. During in-band communication, the control circuit 212 can turn off the switch 210 to further reduce the oscillating current that may interfere with the operation of the rectifier 112. In various embodiments, the switch 210 can also be implemented as a FET.

[0052] The present disclosure further provides other techniques for reducing oscillating currents that interfere with rectifiers. Figure 4 A power receiver including a variable inductor according to some embodiments is described. Figure 1-3 The receiver coil L2 in FIG4 can be replaced with a variable inductor 402. The inductance of the variable inductor 402 can be adjusted to provide multiple impedance variations for in-band communication between the transmitter and receiver, rather than relying on a capacitor-switch network. The receiver can configure the variable inductor in different ways, and associate two of the configurations with the low and high states of ASK modulation, respectively.

[0053] In one embodiment, variable inductor 402 may be implemented as an inductor-switch network. Figure 4 As shown, variable inductor 402 may include inductor 404 and inductor 406 connected by two switches 408 and 410. In a first configuration, switch 410 is open and switch 408 is closed. The first inductance of variable inductor 402 is provided by the series connection of inductor 404 and inductor 406. In a second configuration, switch 408 is open and switch 410 is closed. The second inductance of variable inductor 402 is provided by inductor 404. Alternatively, switch 408 may be removed. In this case, one terminal of inductor 406 is connected to inductor 404, while the other terminal of inductor 406 is directly connected to input terminal 216. Switch 410 is open in the first configuration and closed in the second configuration. In the second configuration, the second inductance of variable inductor 402 is still provided by inductor 404 because inductor 406 is short-circuited when switch 410 is closed. The receiver 120 may apply the first configuration to the low state of the ASK modulation and the second configuration to the high state of the ASK modulation, or vice versa. Figure 4 The embodiment described in the present invention is merely illustrative and should not be construed as limiting in scope. Any suitable embodiment known in the art may be applied to variable inductor 402 .

[0054] In various embodiments, control circuit 212 may include circuitry configured to adjust variable inductor 402 (e.g., switches 408 and 410). Control circuit 212 may include rectifier 112 and power converter 113. Alternatively, rectifier 112 and power converter 113 may be located outside of control circuit 212. Control circuit 212 may further include an optional switch 210.

[0055] Figure 5 A power receiver including both a variable inductor and multiple capacitor-switch networks is shown, according to some embodiments. Receiver 120 includes multiple capacitor-switch networks connected in parallel with resonant capacitor Cs. The multiple capacitor-switch networks include at least a first capacitor-switch network including capacitor 202 connected in series with switch 206 and a second capacitor-switch network including capacitor 204 connected in series with switch 208. Receiver 120 further includes a variable inductor 402 connected between input 216 and the parallel combination of resonant capacitor Cs and the multiple capacitor-switch networks.

[0056] The plurality of capacitor-switch networks and variable inductor 402 may be configured to provide a plurality of capacitors for the transmitter 110 (in Figure 5In-band communication between the controller 212 and the receiver 120 generates multiple impedance changes. The control circuit 212 may include circuitry configured to control capacitors 202, ..., 204 (e.g., switches 206, ..., 208) and circuitry configured to control variable inductor 402 (e.g., switches 408 and 410). The control circuit 212 may further include an optional switch 210. In various embodiments, the control circuit 212 may further include a rectifier 112 and a power converter 113.

[0057] Figure 2-5 The specific embodiments described herein are illustrative only and should not be construed as limiting in scope. In receiver 120, any suitable number of capacitors, inductors, or switches may be used for in-band communication. For example, receiver 120 may use only one capacitor-switch network comprising a series combination of one capacitor and one switch. In another example, receiver 120 may use three or more capacitor-switch networks for in-band communication. Additionally, those skilled in the art may utilize Figure 2-5 Any of the embodiments shown implements a specific device, or combines all or a subset of these embodiments in a single device.

[0058] In various embodiments, the control circuit 212 may configure the capacitors 202, ..., 204 or the variable inductor 402 based on local measurements performed in the receiver 120. The local measurement may include a measurement of the output voltage of the rectifier, i.e., Vrect between the output terminals 218 and 220. For example, the control circuit 212 may further include a measurement circuit, a detection circuit, and a driver circuit. The measurement circuit may be coupled to the output terminals 218 and 220. The measurement circuit may include at least one digital-to-analog converter (ADC) and may be configured to measure the output voltage between the output terminals 218 and 220. The detection circuit may be configured to determine the difference between the low-level amplitude and the high-level amplitude of Vrect and output the determined difference to the driver circuit. The driver circuit may be configured to generate a control signal for the capacitors 202, ..., 204 and / or the variable inductor 402 based on the output of the detection circuit.

[0059] Figure 6 A flowchart for controlling in-band communication of a wireless power transmission system according to various embodiments of the present disclosure is shown. This flowchart is merely an example and should not unduly limit the scope of the claims. A person of ordinary skill in the art will recognize many variations, alternatives, and modifications. For example, Figure 6 The various steps described in the drawings may be added, deleted, replaced, rearranged, and repeated.

[0060] A wireless power transfer system (e.g. Figure 1The wireless power transmission system shown in FIG. 1 includes a transmitter and a receiver. The transmitter includes a full bridge, a transmitter resonant capacitor, and a transmitting coil. The receiver includes a receiving coil, a resonant capacitor (e.g., receiving resonant capacitor Cs), and a rectifier. The transmitting coil and the receiving coil are magnetically coupled. The wireless power transmission system may further include a control circuit disposed in the receiver.

[0061] In step 602, a receiving coil and a resonant capacitor are connected in series.

[0062] At step 604, the combination of the receiving coil and the resonant capacitor is configured to be connected between two input terminals of a rectifier. The rectifier is configured to convert an AC voltage into a DC voltage for coupling to a load of the wireless power transmission system.

[0063] At step 606, a first capacitor and a first switch are connected in series. The combination of the first capacitor and the first switch is configured to be connected in parallel with the resonant capacitor.

[0064] At step 608, the second capacitor and the second switch are connected in series. The combination of the second capacitor and the second switch is configured to be connected in parallel with the resonant capacitor.

[0065] At step 610, a first switch and a second switch are configured to adjust an impedance coupled to a receiving coil. The impedance is associated with amplitude shift keying (ASK) modulation used by the wireless power transfer system.

[0066] In various embodiments, the first switch and the second switch are included in a control circuit.The control circuit can configure the first switch and the second switch to provide a plurality of impedances coupled to the receive coil.

[0067] In various embodiments, each of the plurality of switches 206 , . . . , 208 in the capacitor-switch network for in-band communication described herein may be a FET network implemented using a plurality of FETs. Figures 7A-7C Various examples of capacitor-switch networks in receivers are described.

[0068] exist Figure 7AIn an example depicted in FIG, a capacitor-switch network includes a first capacitor-switch network (including a capacitor 202 and a switch 206 connected in series) and a second capacitor-switch network (including a capacitor 204 and a switch 208 connected in series). The first capacitor-switch network and the second capacitor-switch network are both connected in parallel with the resonant capacitor Cs. Switch 206 is a FET network including four FETs 704, 706, 708, and 710 connected in parallel. Switch 208 is another FET network including four FETs 714, 716, 718, and 720 connected in parallel. By turning on or off one or more FETs in switches 206 and 208, multiple impedance changes can be generated. When all FETs 704, 706, 708, 710, 714, 716, 718, and 720 are turned on, a first impedance is generated. When FETs 704 and 714 are disconnected and FETs 706, 708, 710, 716, 718, and 720 are turned on, a second impedance can be generated. When FETs 704, 706, 714, and 716 are turned off and FETs 708, 710, 718, and 720 are turned on, a third impedance is generated. When FETs 704, 706, 708, 714, 716, and 718 are turned off and FETs 710 and 720 are turned on, a fourth impedance is generated. When FETs 704, 708, 714, and 718 are turned off and FETs 706, 710, 716, and 720 are turned on, a fifth impedance is generated. Similarly, when different FETs in switches 206 and 208 are turned off and other FETs in switches 206 and 208 are turned on, some other different impedances may be generated. In various embodiments, FETs 704, 706, 708, 710, 714, 716, 718, and 720 can be located in control circuit 212.

[0069] Figure 7BAnother example is described, in which the capacitor-switch network includes a first capacitor-switch network (including capacitor 202 and switch 206 connected in series), a second capacitor-switch network (including capacitor 722 and switch 726 connected in series), a third capacitor-switch network (including capacitor 204 and switch 208 connected in series), and a fourth capacitor-switch network (including capacitor 724 and switch 728 connected in series). The first capacitor-switch network, the second capacitor-switch network, the third capacitor-switch network, and the fourth capacitor-switch network are all connected in parallel with the resonant capacitor Cs. Switch 206 includes two FETs 740 and 742 connected in parallel. Switch 208 includes two FETs 748 and 750 connected in parallel. Switch 726 includes two FETs 744 and 746 connected in parallel. Switch 728 includes two FETs 752 and 754 connected in parallel. By turning on or off one or more FETs in switches 206, 726, 208, and 728, multiple impedance changes can be generated. When all FETs 740, 742, 744, 746, 748, 750, 752, and 754 are turned on, a first impedance may be generated. When FETs 740 and 748 are turned off and FETs 742, 744, 746, 750, 752, and 754 are turned on, a second impedance may be generated. When FETs 740, 742, 748, and 750 are turned off and FETs 744, 746, 752, and 754 are turned on, a third impedance may be generated. When FETs 740, 742, 744, 748, 750, and 752 are turned off and FETs 746 and 754 are turned on, a fourth impedance may be generated. When FETs 740, 748, 744, and 752 are turned off and FETs 742, 750, 746, and 754 are turned on, a fifth impedance may be generated. Likewise, some other different impedances may be generated when different FETs in switches 206, 726, 208, and 728 are turned off, while other FETs in switches 206, 726, 208, and 728 are turned on. In various embodiments, FETs 740, 742, 744, 746, 748, 750, 752, and 754 may be located in control circuit 212.

[0070] exist Figure 7CIn another example shown in , the capacitor-switch network includes a first capacitor-switch network (including a capacitor 202 and a switch 206 connected in series) and a second capacitor-switch network (including a capacitor 204 and a switch 208 connected in series). Switch 206 includes FET 760 and FET 764 connected in parallel. Switch 208 includes FET 762 and FET 766 connected in parallel. Each FET 760, 762, 764 and 766 can act as a switch, or a resistor, or both, depending on its gate drive voltage. In one example, FET 760 and FET 762 can act as switches, while FET 764 and FET 766 can operate in ohmic mode. Therefore, by turning on or off one or more FETs 760 and 762, and providing various gate drive voltages to FET 764 and FET 766, respectively, multiple impedance changes can be generated. In another example, FETs 760, 762, 764 and 766 can all operate in ohmic mode. By providing gate drive voltages of various configurations to these FETs, multiple impedance changes can be generated. In various embodiments, FETs 760 , 762 , 764 , and 766 may be located in control circuit 212 .

[0071] Figures 7A-7C The rectifier 112, the power converter 113 and the load 114 are omitted. Figures 7A-7C The specific embodiments described herein are illustrative only and should not be construed as limiting in scope. Figures 7A-7C These embodiments can be applied to Figure 2-5 Receiver 120 is shown in FIG. Any suitable number of capacitors and FETs can be used in the capacitor-switch network for in-band communication. In addition, those skilled in the art can utilize Figures 7A-7C Any of the embodiments shown implements a specific device, or combines all or a subset of these embodiments in a single device.

[0072] 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.

[0073] Furthermore, the scope of the present application is not intended to be limited to the particular embodiments of the processes, machines, manufacture, compositions of matter, means, methods, and steps described in the specification. As will be readily understood by one of ordinary skill in the art from the disclosure herein, processes, machines, manufacture, compositions of matter, means, methods, or steps that perform substantially the same functions now exist or will later be developed or that achieve substantially the same results as the corresponding embodiments described herein may be utilized in accordance with the present disclosure. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.

Claims

1. A device for wireless power reception, comprising: a rectifier configured to convert an AC voltage to a DC voltage for a load connected to the apparatus; a receiving coil and a resonant capacitor connected in series, wherein the combination of the receiving coil and the resonant capacitor is connected between two input terminals of the rectifier; a first capacitor and a first switch connected in series, wherein a combination of the first capacitor and the first switch is connected in parallel with the resonant capacitor, wherein the first switch is configured to operate in an ohmic mode, and a resistance value of a resistor formed by the first switch is adjusted by controlling a gate drive voltage applied to the first switch; as well as A second capacitor and a second switch are connected in series, a combination of the second capacitor and the second switch is connected in parallel with the resonant capacitor, and the first switch and the second switch are configured to adjust an impedance coupled to the receiving coil, wherein the impedance includes at least a first impedance associated with a high state of ASK modulation and a second impedance associated with a low state of ASK modulation. 2 . The apparatus of claim 1 , wherein the first switch and the second switch are configured to provide a plurality of impedances coupled to the receive coil using different ON and OFF combinations.

3. The device according to claim 1, wherein: The first switch is a first field effect transistor (FET); The second switch is a second field effect transistor. 4 . The apparatus of claim 3 , wherein each of the first FET and the second FET is configured to be in a switching configuration when a drain-source voltage of each of the first FET and the second FET is close to zero. 5 . The apparatus of claim 1 , further comprising a third capacitor and a third switch connected in series, a combination of the third capacitor and the third switch being connected in parallel with the resonant capacitor. 6 . The apparatus of claim 1 , wherein the first switch and the second switch are configured to adjust the impedance coupled to the receive coil based on a measurement of an output voltage of the rectifier.

7. The apparatus of claim 1, wherein the receive coil is a variable inductor, and wherein the impedance associated with the ASK modulation is further adjusted by varying the inductance of the receive coil.

8. The apparatus of claim 1, wherein the apparatus is included in a wireless power transfer system, and wherein the wireless power transfer system further comprises a transmitter having a transmit coil magnetically coupled to the receive coil.

9. A communication method for wireless power transmission, comprising: Connecting the receiving coil and the resonant capacitor in series; connecting the combination of the receiving coil and the resonant capacitor between two input terminals of a rectifier, the rectifier being configured to convert an AC voltage into a DC voltage for coupling to a load of a wireless power transfer system; connecting a first capacitor and a first switch in series, and connecting the combination of the first capacitor and the first switch in parallel with the resonant capacitor, wherein the first switch is configured to operate in an ohmic mode, and a resistance value of a resistor formed by the first switch is adjusted by controlling a gate drive voltage applied to the first switch; connecting a second capacitor and a second switch in series, and connecting a combination of the second capacitor and the second switch in parallel with the resonant capacitor; and The first switch and the second switch are configured to adjust an impedance coupled to the receive coil, wherein the impedance includes at least a first impedance associated with a high state of ASK modulation and a second impedance associated with a low state of ASK modulation. 10 . The method of claim 9 , wherein the first switch and the second switch are configured to provide a plurality of impedances coupled to the receive coil using different ON and OFF combinations.

11. The method according to claim 9, wherein: The first switch is a first field effect transistor (FET); The second switch is a second field effect transistor. 12 . The method of claim 11 , wherein each of the first FET and the second FET is configured to switch configuration when a drain-source voltage of each of the first FET and the second FET approaches zero.

13. The method according to claim 9, further comprising: connecting a third capacitor and a third switch in series; and The third capacitor and the third switch are connected in parallel with the resonant capacitor.

14. The method of claim 9, wherein the first switch and the second switch are configured to adjust the impedance coupled to the receive coil based on a measurement of an output voltage of the rectifier.

15. A control circuit for a wireless power receiving system, comprising: a first switch and a second switch, wherein the first switch is connected in series with the first capacitor, and the second switch is connected in series with the second capacitor, wherein: The combination of the first switch and the first capacitor is connected in parallel with a resonant capacitor, and the series combination of the resonant capacitor and the receiving coil of the wireless power receiving system is connected between two input terminals of a rectifier of the wireless power receiving system, wherein the first switch is configured to operate in an ohmic mode, and the resistance of a resistor formed by the first switch is adjusted by controlling a gate drive voltage applied to the first switch; A combination of the second switch and the second capacitor is connected in parallel with the resonant capacitor; and The first switch and the second switch are configured to adjust an impedance connected to the receiving coil, wherein the impedance includes at least a first impedance associated with a high state of ASK modulation and a second impedance associated with a low state of ASK modulation. 16 . The control circuit of claim 15 , wherein the rectifier is configured to convert an AC voltage into a DC voltage for coupling to a load of the wireless power receiving system. 17 . The control circuit of claim 15 , wherein the first switch and the second switch are configured to provide a plurality of impedances coupled to the receive coil using different ON and OFF combinations.

18. The control circuit according to claim 17, wherein: The first switch is a first field effect transistor (FET); The second switch is a second field effect transistor. 19 . The control circuit of claim 18 , wherein each of the first FET and the second FET is configured to switch configuration when a drain-source voltage of each of the first FET and the second FET is close to zero.

20. The control circuit of claim 15, wherein the first switch and the second switch are configured to adjust the impedance coupled to the receive coil based on a measurement of an output voltage of the rectifier.

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