Dynamic capacitance tuning for wireless power transmission

Abstract

To provide an invention pertaining to dynamic capacitance tuning for wireless power transfer.SOLUTION: A method for operating a wireless power transmitter including a wireless power transmitting coil, an inverter that receives an input voltage and generates an AC output voltage that drives the wireless power transmitting coil, and at least one adjustable capacitance coupled to the wireless power transmitting coil to form a series tuning circuit therewith, can be performed by a control circuit of the wireless power transmitter. The method includes determining, in response to increased power demand from a wireless power receiver, whether the input voltage is at a maximum value and, if so, reducing the at least one adjustable capacitance to increase gain, or determining, in response to decreased power demand from the wireless power receiver, whether the input voltage is at a minimum value and, if so, increasing the at least one adjustable capacitance to decrease gain.SELECTED DRAWING: None

Description

【Technical Field】 【0001】 Cross - Reference to Related Applications This application claims priority to U.S. Provisional Patent Application No. 63 / 585,279, filed on September 26, 2023, entitled "Dynamic Capacitance Tuning For Wireless Power Transfer", U.S. Patent Application No. 18 / 529,564, filed on December 5, 2023, entitled "Dynamic Capacitance Tuning For Wireless Power Transfer", and U.S. Patent Application No. 18 / 613,196, filed on March 22, 2024, entitled "Dynamic Capacitance Tuning For Wireless Power Transfer", each of which is hereby incorporated by reference in its entirety for all purposes. 【Background Art】 【0002】 Wireless power transfer is becoming increasingly popular in a wide variety of electronic devices. For example, many electronic devices such as smartphones, tablet computers, smartwatches, wireless earphones, styluses, etc. can adopt wireless power transfer to facilitate charging of the batteries within the devices. In some applications, for example, in order to perform faster charging, a higher level of wireless power transfer may be desired. Such a higher power transfer level can benefit from techniques for adjusting various system parameters to improve operating efficiency, voltage regulation, etc. 【Summary of the Invention】 【0003】 The wireless power transmitter comprises a wireless power transmitting coil, an inverter that receives an input voltage and generates an AC output voltage to drive the wireless power transmitting coil, at least one adjustable capacitance coupled to the wireless power transmitting coil to form a series-tuned circuit with the wireless power transmitting coil, and a control circuit that operates the inverter and the at least one adjustable capacitance to supply wireless power to a wireless power receiver, wherein the control circuit responds to the power demand from the wireless power receiver by determining whether the input voltage is at its maximum value and, if so, by decreasing the at least one adjustable capacitance to increase the gain, or by determining whether the input voltage is at its minimum value and, if so, by increasing the at least one adjustable capacitance to decrease the gain. 【0004】 At least one adjustable capacitance may include one or more capacitors that can be selectively coupled to a wireless power transmitting coil by one or more switches controlled by a control circuit. At least one adjustable capacitance may include at least one capacitor coupled to the wireless power transmitting coil and at least two capacitors that can be selectively coupled to the wireless power transmitting coil by one or more switches controlled by a control circuit. Determining whether the input voltage is at its maximum value, and if so, decreasing at least one adjustable capacitance to increase the gain, may further include at least temporarily adjusting the input voltage before decreasing at least one adjustable capacitance. At least temporarily adjusting the input voltage before decreasing at least one adjustable capacitance can respond to the operating power level of the wireless power transmitter. Determining whether the input voltage is at its minimum value, and if so, increasing at least one adjustable capacitance to decrease the gain, may further include at least temporarily adjusting the input voltage before increasing at least one adjustable capacitance. At least temporarily adjusting the input voltage before increasing at least one adjustable capacitance can respond to the operating power level of the wireless power transmitter. 【0005】 The wireless power transmitter may further include a control circuit that increases at least one adjustable capacitance to mitigate hard switching events in response to one or more hard switching events. The at least one adjustable capacitance may include one or more capacitors selectively coupled between the inverter output and the wireless power transmitting coil by one or more first switches controlled by the control circuit, and one or more capacitors selectively coupled between the inverter output and ground by one or more second switches controlled by the control circuit. The one or more capacitors selectively coupled between the inverter output and the wireless power transmitting coil may include at least one capacitor coupled between the inverter output and the wireless power transmitting coil, and at least two capacitors selectively coupled between the inverter output and the wireless power transmitting coil by one or more first switches. The one or more capacitors selectively coupled between the inverter output and ground may include at least one capacitor coupled between the inverter output and ground, and a plurality of capacitors selectively coupled between the inverter output and ground by one or more second switches. The wireless power transmitter may further include a control circuit that reduces at least one adjustable capacitance to mitigate hard switching events in response to the absence of one or more hard switching events. 【0006】 A method for operating a wireless power transmitter having a wireless power transmitting coil, an inverter that receives an input voltage and generates an AC output voltage to drive the wireless power transmitting coil, and at least one adjustable capacitance coupled to the wireless power transmitting coil to form a series tuned circuit together with the wireless power transmitting coil may be performed by the control circuit of the wireless power transmitter and includes determining whether the input voltage is at its maximum value in response to an increase in power demand from a wireless power receiver, and if so, decreasing at least one adjustable capacitance to increase the gain, or determining whether the input voltage is at its minimum value in response to a decrease in power demand from a wireless power receiver, and if so, increasing at least one adjustable capacitance to decrease the gain. 【0007】 Determining whether the input voltage is at its maximum value and, if so, decreasing at least one adjustable capacitance to increase the gain may further include at least temporarily adjusting the input voltage before decreasing at least one adjustable capacitance. Determining whether the input voltage is at its minimum value and, if so, increasing at least one adjustable capacitance to decrease the gain may further include at least temporarily adjusting the input voltage before increasing at least one adjustable capacitance. 【0008】 The method may further include increasing at least one adjustable capacitance to mitigate hard switching events in response to one or more hard switching events, and decreasing at least one adjustable capacitance to mitigate hard switching events in response to the absence of one or more hard switching events. 【0009】 The wireless power receiver comprises a wireless power receiving coil, a rectifier that receives an AC voltage induced in the wireless power receiving coil by a wireless power transmitter and generates a DC output voltage therefrom, at least one adjustable capacitance coupled to the wireless power receiving coil to form a series-tuned circuit with the wireless power receiving coil, and a control circuit that operates the rectifier and the at least one adjustable capacitance to supply power to a load coupled to the DC output voltage of the rectifier. The control circuit can respond to power demand by determining whether the DC input voltage of the inverter of the wireless power transmitter is at its maximum value and, if so, decreasing the at least one adjustable capacitance to increase the gain, or by determining whether the DC input voltage of the inverter of the wireless power transmitter is at its minimum value and, if so, increasing the at least one adjustable capacitance to decrease the gain. The DC input voltage may be determined by the control circuit in response to one or more messages received from the wireless power transmitter. 【0010】 At least one adjustable capacitance may include one or more capacitors that can be selectively coupled to a wireless power receiving coil by one or more switches controlled by a control circuit. At least one adjustable capacitance may include at least one capacitor coupled between the wireless power receiving coil and the rectifier, and at least one capacitor that can be selectively coupled between the wireless power receiving coil and the rectifier by one or more switches controlled by a control circuit. 【0011】 Determining whether the DC input voltage of the inverter is at its maximum value, and if so, decreasing the gain by decreasing at least one adjustable capacitance, may further include decreasing the rectifier power at least temporarily before decreasing at least one adjustable capacitance, depending on the rectifier power. Determining whether the DC input voltage of the inverter is at its minimum value, and if so, increasing the gain by increasing at least one adjustable capacitance, may further include decreasing the rectifier power at least temporarily before increasing at least one adjustable capacitance, depending on the rectifier power. 【0012】 A method for operating a wireless power receiver having a wireless power receiving coil, a rectifier that receives an AC voltage induced in the wireless power receiving coil by a wireless power transmitter and generates a DC output voltage therefrom, and at least one adjustable capacitance coupled to the wireless power receiving coil to form a series tuned circuit together with the wireless power receiving coil may be performed by the control circuit of the wireless power receiver and may include determining whether the DC input voltage of the inverter of the wireless power transmitter is at its maximum value in response to an increase in power demand, and if so, decreasing at least one adjustable capacitance to increase the gain, or determining whether the DC input voltage of the inverter of the wireless power transmitter is at its minimum value in response to a decrease in power demand, and if so, increasing at least one adjustable capacitance to decrease the gain. The DC input voltage is determined by the control circuit in response to one or more messages received from the wireless power transmitter. 【0013】 Determining whether the DC input voltage of the inverter is at its maximum value, and if so, decreasing the gain by decreasing at least one adjustable capacitance, may further include decreasing the rectifier power at least temporarily before decreasing at least one adjustable capacitance, depending on the rectifier power. Determining whether the DC input voltage of the inverter is at its minimum value, and if so, increasing the gain by increasing at least one adjustable capacitance, may further include decreasing the rectifier power at least temporarily before increasing at least one adjustable capacitance, depending on the rectifier power. [Brief explanation of the drawing] 【0014】 [Figure 1] A simplified block diagram of a wireless power transmission system is shown. 【0015】 [Figure 2A] A schematic diagram of a wireless power transmission system is shown. [Figure 2B] A schematic diagram of a wireless power transmission system is shown. [Figure 2C] A schematic diagram of a wireless power transmission system is shown. [Figure 2D] A schematic diagram of a wireless power transmission system is shown. [Figure 2E] A schematic diagram of a wireless power transmission system is shown. 【0016】 [Figure 3A] A flowchart of the capacitance tuning technology for wireless power transmitters is shown. [Figure 3B] A flowchart of the capacitance tuning technology for wireless power transmitters is shown. [Figure 3C] A flowchart of the capacitance tuning technology for wireless power transmitters is shown. 【0017】 [Figure 4] This shows a flowchart of the capacitance tuning technology for wireless power receivers. 【Best Mode for Carrying Out the Invention】 【0018】 In the following description, for the sake of convenience of explanation, in order to deepen the understanding of the disclosed concepts, many specific details are described. As part of this description, some of the drawings of the present disclosure represent structures and devices in the form of block diagrams in order to avoid obscuring the present invention. From the point of clarity, not all features of the actual implementation form are described in this specification. Furthermore, the language used in this specification is selected solely for the purpose of readability and explanation, and is not selected to limit or restrict the disclosed subject matter. Rather, the appended claims are intended for such purposes. 【0019】 Various embodiments of the disclosed concepts are shown in the accompanying drawings by way of example and not as a limitation, and like reference numerals indicate like elements. For the sake of simplicity and clarity of illustration, where appropriate, reference numerals are repeatedly used in different drawings to indicate corresponding and / or similar elements. In addition, in order to provide a complete understanding of the implementation forms described in this specification, a number of specific details are described. In other examples, methods, procedures, and components are not described in detail so as not to obscure the related functions being described. References to "an", "one", or "another" embodiment in the present disclosure do not necessarily refer to the same or different embodiments, but mean at least one. A given drawing is used to illustrate multiple embodiments or multiple species of the present disclosure, and not all elements in the drawing may be required in a given embodiment or species. When reference numerals are provided in a given drawing, they refer to the same elements throughout some of the drawings, but are not repeatedly used in all drawings. The drawings are not to scale unless otherwise indicated, and the ratios of specific components may be exaggerated to better show the details and features of the present disclosure. 【0020】 Figure 1 shows a simplified block diagram of the wireless power transmission system 100. The wireless power transmission system includes a power transmitter (PTx) 110 that wirelessly transmits power to a power receiver (PRx) 120 via inductive coupling 130, etc. The power transmitter 110 can receive input power which is converted by an inverter 114 into an AC voltage having specific voltage and frequency characteristics. The inverter 114 may be controlled by a controller / communication module 116 which operates as will be further described below. In various embodiments, the inverter controller and communication module may be implemented in a common system such as a system based on a microprocessor, microcontroller, etc. In other embodiments, the inverter controller may be implemented by a separate controller module and communication module having means of communication between them. The inverter 114 may be constructed using any suitable circuit topology (e.g., full bridge, half bridge, etc.) and may be implemented using any suitable semiconductor switching device technology (e.g., MOSFETs, IGBTs, etc., fabricated using silicon, silicon carbide, or gallium nitride devices). 【0021】 The inverter 114 can deliver the generated AC voltage to the transmitter coil 112. In addition to the wireless coil that enables magnetic coupling to the receiver, the transmitter coil block 112 shown in Figure 1 may include tuning circuit components such as additional inductors and capacitors to facilitate the operation of the transmitter under different conditions, such as different degrees of magnetic coupling to the receiver and different operating frequencies. The wireless coil itself can be constructed in a variety of different ways. In some embodiments, the wireless coil may be formed as a winding of wire wound on a suitable bobbin. In other embodiments, the wireless coil may be formed as a trace on a printed circuit board. Other arrangements are also possible and can be used in conjunction with the various embodiments described herein. The wireless transmitter coil may also include a core of a permeable material (e.g., ferrite) configured to influence the magnetic flux pattern of the coil in a manner suitable for a particular application. The teachings herein can be applied in conjunction with any of the wide variety of transmitter coil arrangements suitable for a given application. 【0022】 The PTx controller / communication module 116 can monitor the power transmission coil and use the information derived therefrom to control the inverter 114 appropriately for a given situation. For example, the controller / communication module can be configured to operate the inverter 114 at a given frequency or output voltage according to a particular application. In some embodiments, the controller / communication module can be configured to receive information from the PRx device and control the inverter 114 accordingly. This information may be received via the power transmission coil (i.e., in-band communication), or via a separate communication channel (not shown, i.e., out-of-band communication). In the case of in-band communication, the controller / communication module 116 can detect and decode signals (such as voltage, frequency, or load variations) imposed on the magnetic link by the PRx to receive information, and can command the inverter to modulate the delivered power by manipulating various parameters (such as voltage, frequency, etc.) of the generated voltage to transmit information to the PRx. In some embodiments, the controller / communication module can be configured to employ frequency shift keying (FSK) communication in which the frequency of the inverter signal is modulated to communicate data to the PRx. The controller / communication module 116 can be configured to detect amplitude shift keying (ASK) communication or load modulation-based communication from the PRx. In either case, the controller / communication module 126 can be configured to vary the current drawn on the receiver side and manipulate the waveform seen on the Tx coil to deliver information from the PRx to the PTx. In the case of out-of-band communication, an additional module enabling communication between the PTx and the PRx, such as WiFi, Bluetooth®, or other wireless link, or any other suitable communication channel, can be provided. 【0023】 As described above, the controller / communication module 116 may be, for example, a single module on a single integrated circuit, or it may be constructed from multiple modules / devices on different integrated circuits, or from a combination of integrated circuits and discrete circuits having both analog and digital components. The teachings herein are not limited to any particular arrangement of controller / communication circuit components. 【0024】 The PTx device 110 may optionally include other systems and components, such as a separate communication module 118. In some embodiments, the communication module 118 can communicate with the corresponding module in the PRx via a power transmission coil. In other embodiments, the communication module 118 can communicate with the corresponding module using a separate physical channel 138. 【0025】 As described above, the wireless power transmission system also includes a wireless power receiver (PRx) 120. The wireless power receiver may include a receiver coil 122 that can be magnetically coupled to the transmitter coil 112. Similar to the transmitter coil 112 described above, the receiver coil block 122 shown in Figure 1 may include tuning circuit components such as additional inductors and capacitors to facilitate the operation of the transmitter under different conditions, such as different degrees of magnetic coupling to the receiver and different operating frequencies. The wireless coil itself can be constructed in a variety of different ways. In some embodiments, the wireless coil may be formed as a winding of wire wound on a suitable bobbin. In other embodiments, the wireless coil may be formed as a trace on a printed circuit board. Other arrangements are also possible and can be used in conjunction with the various embodiments described herein. The wireless receiver coil may also include a core of a permeable material (e.g., ferrite) configured to influence the magnetic flux pattern of the coil in a manner suitable for a particular application. The teachings herein can be applied in conjunction with any of the wide variety of receiver coil arrangements suitable for a given application. 【0026】 The receiver coil 122 outputs an AC voltage induced internally by magnetic induction via the transmitter coil 112. This output AC voltage can be supplied to a rectifier 124 that provides DC output power to one or more loads associated with the PRx device. The rectifier 124 can be controlled by a controller / communication module 126 that operates as described further below. In various embodiments, the rectifier controller and communication module may be implemented in a common system, such as a system based on a microprocessor, microcontroller, etc. In other embodiments, the rectifier controller may be implemented by a separate controller module and communication module having means of communication between them. The rectifier 124 may be constructed using any suitable circuit topology (e.g., full bridge, half bridge, etc.) and may be implemented using any suitable semiconductor switching device technology (e.g., MOSFETs, IGBTs, etc., fabricated using silicon, silicon carbide, or gallium nitride devices). 【0027】 The PRx controller / communication module 126 can monitor the receiver coil and use the information derived therefrom to appropriately control the rectifier 124 according to a given situation. For example, the controller / communication module may be configured to operate the rectifier 124 to provide a given output voltage according to a specific application. In some embodiments, the controller / communication module may be configured to transmit information to the PTx device in order to effectively control the power delivered to the receiver. This information may be received or transmitted via the power transmission coil (i.e., in-band communication) or transmitted via a separate communication channel (not shown, i.e., out-of-band communication). In the case of in-band communication, the controller / communication module 126 may transmit information to the PTx by modulating, for example, the load current or other electrical parameters of the received power. In some embodiments, the controller / communication module 126 may be configured to detect and decode signals (such as voltage, frequency, or load fluctuations) applied to the magnetic link by the PTx in order to receive information from the PTx. In some embodiments, the controller / communication module 126 may be configured to receive frequency-shift keying (FSK) communications in which the frequency of the inverter signal is modulated to communicate data to the PRx. The controller / communication module 126 may be configured to generate amplitude-shift keying (ASK) communications or load-modulation-based communications from the PRx. In either case, the controller / communication module 126 may be configured to change the current drawn out on the receiver side to manipulate the waveform observed on the Tx coil in order to deliver information from the PRx to the PTx. For out-of-band communications, an additional module may be provided to enable communication between the PTx and the PRx, such as WiFi, Bluetooth®, or other wireless links, or any other suitable communication channel. 【0028】 As described above, the controller / communication module 126 may be, for example, a single module on a single integrated circuit, or it may consist of multiple modules / devices on different integrated circuits, or a combination of integrated circuits having both analog and digital components and discrete circuits. The teachings herein are not limited to any particular arrangement of controller / communication circuit components. The PRx device 120 may optionally include other systems and components, such as a communications ("comms") module 128. In some embodiments, the communications module 128 can communicate with a corresponding module in the PTx via a power transmission coil. In other embodiments, the communications module 128 can communicate with a corresponding module or tag using a separate physical channel 138. 【0029】 Numerous modifications and extensions are possible for the wireless power transmission system 100 described above, and the following teachings are applicable to any of these modifications and extensions. 【0030】 Figures 2A to 2E show schematic diagrams of a wireless power transmission system. Figure 2A shows an overall schematic diagram 200 of a wireless power transmission system including a wireless power transmitter (PTx) 210 and a wireless power receiver 220, such as those with similar reference numbers (e.g., PTx110 and PRx120) as described above with respect to Figure 1. The wireless power transmitter 210 may include an inverter 114 that can drive the transmitter coil 112. The inverter 114 is shown as a full-bridge inverter, but other inverter configurations may be used depending on the requirements of the application. The inverter 114 can receive an input voltage Vin from an input voltage source represented by a capacitor Cin, and the capacitor Cin may include any suitable DC power source such as a battery, DC-DC converter, or AC-DC converter. The inverter 114 can drive the transmitter coil 112 via a series tuning network 231, which will be described in more detail below with respect to Figure 2B. Figure 2A also shows an optional slew-rate tuning circuit 233, which will be described in more detail below in relation to Figure 2D. Figure 2B also shows parasitic elements 239 that can represent the effects of various wireless charger system implementations, such as capacitance associated with wires / cords. The illustrated representation is merely an example, and other representations may be more appropriate depending on the exact physical configuration of a particular implementation. 【0031】 Figure 2A also shows a wireless power receiver 220. The wireless power receiver 220 may include a rectifier capable of driving a receiver coil 122, which may have a current induced in it by the transmitter coil 112. The rectifier 124 is shown as a full-bridge rectifier, but other rectifier configurations may be used depending on the requirements of the application. The rectifier 124 can generate an output voltage Vrect / Vout from the AC voltage appearing across the receiver coil 122. The rectifier 124 may be driven via a series tuning circuit 235, which will be described in more detail below with respect to Figure 2C. Figure 2A also shows an in-band communication circuit 237, which will be described in more detail below with respect to Figure 2E. 【0032】 Figure 2B shows a schematic diagram of the wireless power transmitter series tuning circuit 231 described above with reference to Figure 2A. The transmitter series tuning circuit may include capacitances such as capacitors Ctx1, Ctx2, and Ctx3, along with the inductance of the transmitter coil 112. Depending on various parameters such as the amount of power transmitted, the operating voltage, and the degree of coupling between PTx and PRx, it may be desirable to tune the series tuning circuit to improve the overall operation. For example, as will be described in more detail below, it may be desirable to tune the series tuning circuit to change the gain of the wireless power transmission system and enable adaptation to various input voltages, power levels, etc. 【0033】 The series tuning circuit 231 may include the base capacitance of capacitor Ctx1, which may always be present in the series tuning circuit, and selectable capacitances from capacitors Ctx2 and Ctx3. These capacitors may be selectively connected in parallel with capacitor Ctx1 to increase their effective capacitance by closing switches Qctx2 and / or Qctx3, respectively. Correspondingly, when one or more of switches Qctx2 and Qctx3 are closed and the corresponding capacitors are connected to the series tuning circuit, opening such switches can decrease the capacitance of the series tuning circuit. By selecting different values ​​for each capacitor, a range of capacitances can be provided. Switches Qctx2 and Qctx3 may be controlled by the wireless power transmitter controller / communication circuit 116 described above with respect to Figure 1. Such control may implement one or more of the control techniques described below with respect to Figures 3A to 3C. The configuration in Figure 2B is merely illustrative; all other configurations, including additional selective capacitors, all selectable capacitors, and series combinations of capacitors (for selectively reducing capacitance), can be implemented if appropriate for a given application. 【0034】 Figure 2C shows a schematic diagram of the wireless power receiver series tuning circuit 235 described above with reference to Figure 2A. The receiver series tuning circuit may include capacitances such as capacitors Crx1 and Crx2, along with the inductance of the receiver coil 122. Depending on various parameters such as the amount of power transmitted, the operating voltage, and the degree of coupling between PTx and PRx, it may be desirable to adjust the series tuning circuit to improve the overall operation. For example, as will be described in more detail below, it may be desirable to adjust the series tuning circuit to change the gain of the wireless power transmission system and enable adaptation to various input voltages, power levels, etc. 【0035】 The series tuning circuit 235 may include the base capacitance of capacitor Crx1, which may always be present in the series tuning circuit, and a selectable capacitance from capacitor Crx2. This capacitor may be selectively connected in parallel with capacitor Ctx1 to increase the effective capacitance by closing switch Qcrx2. Correspondingly, when switch Qcrx2 is closed and the corresponding capacitor is connected to the series tuning circuit, opening such a switch can decrease the capacitance of the series tuning circuit. By selecting different values ​​for each capacitor, a range of capacitances can be provided. Switch Qcrx2 can be controlled by the wireless power receiver controller / communication circuit 126 described above with respect to Figure 1. Such control can implement control techniques as described below with respect to Figure 4. The configuration in Figure 2C is merely illustrative, and all other configurations, including additional selective capacitors, all selectable capacitors, and series combinations of capacitors (for selectively reducing capacitance), can be implemented if appropriate for a given application. 【0036】 Figure 2D shows the optional slew-rate tuning circuit 233 described above in relation to Figure 2A. For improved operating efficiency, it may be preferable to operate the inverter 114 with zero-voltage switching (ZVS), which can reduce switching losses associated with inverter operation. Depending on various parameters such as operating voltage and operating power level, ZVS may not be possible for a given inverter circuit configuration, including, but not limited to, the overall capacitance coupled to the inverter. To enable ZVS over a wider operating range, the slew-rate tuning circuit 233 can be provided. More specifically, if one or more hard switching events (i.e., lack of ZVS) are detected, the capacitance can be reduced. Alternatively, if no hard switching events are detected over a given period (which may correspond to a larger-than-required ZVS margin), the capacitance can be increased, thereby increasing the voltage slew rate of the inverter. 【0037】 The slew-rate tuning circuit may include the base capacitance of capacitor Csw1, which may always be present, and selectable capacitances from capacitors Csw2, Csw3, and Csw4. These capacitors may be selectively connected in parallel with capacitor Csw1 to increase the effective capacitance by closing switches Qcsw2, Qcsw3, and Qcsw4. Correspondingly, if one or more of switches Qcrx2 are closed and the corresponding capacitors are connected to the series tuning circuit, opening such switches can decrease the capacitance of the series tuning circuit. The corresponding slew-rate capacitors and associated switches may be connected to each inverter leg, as shown in Figure 2A. By selecting different values ​​for each capacitor, a range of capacitances can be provided. Switches Qcsw2, Qcsw3, and Qcsw4 may be controlled by the wireless power transmission controller / communication circuit 116 described above with respect to Figure 1. Such control can implement various control techniques depending on the implementation. In some embodiments, the slew rate capacitance can be adjusted along with a change to the series tuned capacitance, as will be described in more detail below. The configuration in Figure 2D is illustrative only, and all other configurations, including additional selective capacitors, all selectable capacitors, and series combinations of capacitors (for selectively reducing capacitance), can be implemented if appropriate for a given application. 【0038】 Figure 2E shows the in-band communication circuit 237 described above with respect to Figure 2A. The in-band communication circuit 237 is just one example of the many types of in-band communication circuits associated with the corresponding in-band communication method. In many embodiments, various forms of load modulation can be used. Such load modulation may be used to implement amplitude switch keying ("ASK") communication, in which the connection or disconnection of additional load elements may be used to change the received power, which may be detected by the transmitter in relation to the corresponding change in transmitted power. As an example, the in-band communication circuit 237 includes switches Qcc1 and Qcc2 that can selectively connect / disconnect capacitors Ccomm1 and Ccomm2 to / from the respective legs of the (full-bridge) rectifier 124 shown in Figure 2E by switches 224a and 224b. This configuration is just one example, and many other configurations of such a circuit can be implemented. 【0039】 Figures 3A and 3C show flowcharts of the capacitance tuning technique for wireless power transmitters. The PTx input voltage Vin (Figure 2A) can be varied to adjust the output power of the inverter, and therefore the power supplied to the wireless power receiver. Increasing the input voltage Vin can increase the power delivered, and vice versa. Thus, the wireless power transmitter can adjust the supplied power by changing the input voltage Vin, for example, by modifying the control signal provided to the DC-DC converter supplying the input voltage. Depending on the output voltage supplied as Vin and the power level required by the wireless power receiver, the system may operate in a region where adjusting the output voltage to the desired level becomes difficult or impossible. This can be overcome, at least under some conditions, by tuning the series tuned capacitance using the circuit described above with reference to Figures 2A and 2B. 【0040】 Figure 3A shows a flowchart 300a of the high-level wireless power transmitter capacitance tuning technique. Starting from block 341, the transmitter controller (e.g., controller / communication circuit 116) can determine whether the input voltage Vin has reached its maximum value (i.e., high threshold). This may occur, for example, in response to a request for increased power from a wireless power receiver when the wireless power transmitter is already operating at its maximum input voltage. If so, the controller can decrease Ctx to increase the gain of the wireless power transmission system while continuing to monitor the input voltage (block 342). Decreasing Ctx can be achieved, for example, by opening one or more of the switches Qctx2, Qctx3 (Figure 2B) to disconnect one or more of the selectable capacitors Ctx2, Ctx3 coupled to the transmitter coil. If, in block 341, the transmitter controller determines that the input voltage is not at its maximum value / high threshold, the controller can determine in block 343 whether the input voltage has reached its minimum value (i.e., low threshold). This may be done, for example, in response to a decrease in transmitted wireless power or a request to reduce transmitted wireless power. If so, the controller can increase Ctx to reduce the gain of the wireless power transmission system while continuing to monitor the input voltage (block 344). Increasing Ctx can be achieved, for example, by closing one or more of the switches Qctx2, Qctx3 (Figure 2B) to couple one or more of the selectable capacitors Ctx2, Ctx3 to the transmitter coil. Thus, the transmitter controller can adjust or adjust the input voltage and series tuned capacitance in response to the power demand from the wireless power receiver. 【0041】 As described above, different capacitance values ​​can be achieved by different combinations of capacitors Ctxn. Furthermore, different numbers of resonant capacitors Ctxn can be provided, and each capacitor can have a different capacitance value (or the same capacitance value). Therefore, the system can be designed to provide any range of capacitance values ​​that respond to the input voltage. 【0042】 Figure 3B shows a flowchart 300b of a modified wireless power transmitter capacitance tuning technique, which has optional additional steps that may be advantageous under various conditions, such as relatively high transmission power levels. As before, in block 341, the transmitter controller (e.g., controller / communication circuit 116) can determine, for example, whether the input voltage Vin has reached its maximum value (i.e., high threshold) in response to an increase in power demand from the wireless power receiver. If so, the controller can first adjust (e.g., reduce) Vin (block 345a) and, in some cases, at least temporarily reduce the power level being transmitted before making any changes to the series tuning capacitance. Adjusting the input voltage before changing the input capacitance can prevent overvoltage events from occurring in the wireless power receiver due to the capacitance change on the transmitter side. The controller can then decrease Ctx to increase the gain of the wireless power transmission system while continuing to monitor the input voltage (block 342). As explained above, reducing Ctx can be achieved, for example, by opening one or more of the switches Qctx2, Qctx3 (Figure 2B) and disconnecting one or more of the selectable capacitors Ctx2, Ctx3 coupled to the transmitter coil. Then, for example, if a higher power level is requested by the wireless power receiver, the transmitted power level can be increased again to a relatively high value. 【0043】 Alternatively, in block 341, if the transmitter controller determines that the input voltage is not at its maximum value / high threshold, the controller may, in block 343, determine whether the input voltage has reached its minimum value (i.e., low threshold), for example, in response to the decrease in power demand by the wireless power receiver. If so, the controller may (optionally) first adjust Vin (block 345b) and, if applicable, at least temporarily reduce the transmitted power level before making any changes to the series tuning capacitance. As described above, adjusting the input voltage (and associated transmitted power level) before changing the input capacitance can prevent overvoltage events from occurring in the wireless power receiver due to capacitance changes on the transmitter side. The controller may then increase Ctx to reduce the gain of the wireless power transmission system while continuing to monitor the input voltage (block 344). Increasing Ctx can be achieved, for example, by closing one or more of the switches Qctx2, Qctx3 (Figure 2B) to couple one or more of the selectable capacitors Ctx2, Ctx3 to the transmitter coil. Subsequently, if, for example, a higher power level is requested by the wireless power receiver, the transmitted power level can again be increased to a relatively high value. 【0044】 The input voltage regulation described above can be achieved in various ways. For example, in at least some embodiments, voltage regulation can be achieved by modifying a feedback control signal provided to a DC-DC converter or other regulator providing Vin. In other embodiments, such as those where the input voltage is supplied by a USB-PD power adapter, the supplied voltage can be modified by providing the adapter with an appropriate USB-PD control signal. 【0045】 As explained above, certain operating regimes, for example, at higher power levels, may require input voltage adjustment before transmitting capacitance changes, while other operating regimes, for example, at lower transmitted power levels, may not necessarily benefit from such operation. Therefore, the technique described above can be modified to selectively provide input voltage adjustment before switching the capacitor depending on the transmitted power level. As an example, the input voltage adjustment function may be enabled when the power level exceeds a first threshold power level and disabled when the power level falls below a second threshold power level. The first and second threshold power levels may be the same or different, providing some degree of hysteresis in the operation. 【0046】 Figure 3C shows a flowchart 300c of a further modified wireless power transmitter capacitance tuning technique, which has optional additional steps that may be advantageous in addressing inverter hard-switching (i.e., non-ZVS) events that could lead to increased losses and reduced operating efficiency. Starting from block 346, the control circuit can determine whether a hard-switching condition exists. This may be the occurrence of a single hard-switching event, or more preferably, in at least some cases, the detection of multiple hard-switching events and / or multiple consecutive hard-switching events within a period of time. Such hard-switching events may present an opportunity to improve operating efficiency by increasing the capacitance coupled to the inverter, which may include either adjusting the series-tuned capacitance Ctx and / or adjusting the slew-rate-tuned capacitance, as described above with respect to Figure 3D. 【0047】 In either case, if a hard switching condition is detected, the controller may increase the series tuned capacitance (block 347) or adjust both the slew rate capacitance Csw and the series tuned capacitance Ctx to provide an overall increase in capacitance. For example, the adjustment may include increasing the slew rate capacitance Csw and decreasing the series tuned capacitance Ctx while still providing an overall increase in capacitance. In addition (and potentially optionally), the controller may adjust the input voltage Vin before changing the capacitance to prevent a receiver-side overvoltage event (as described above) (block 345c). Although not shown in Figure 3C, there is a procedure for decreasing capacitance if the conditions leading to the capacitance triggered by the preceding hard switching no longer exist. Such a change can be made, for example, by detecting that no hard switching events have been detected for a period of time. The system can then decrease the capacitance (by adjusting the series tuned capacitance Ctx and / or slew rate capacitance Csw). If the decrease triggers a hard switching event, the capacitance adjustment can be reversed (i.e., the capacitance increases again). Alternatively, capacitance reduction can be maintained if the reduction does not trigger hard switching conditions. 【0048】 If the hard switching condition does not trigger capacitance adjustment in block 346, the technique shown in flowchart 300c may be similar to that described above with reference to Figures 3A and 3B. As before, in block 341, the transmitter controller (e.g., controller / communication circuit 116) can determine, for example, whether the input voltage Vin has reached its maximum value (i.e., high threshold) in response to an increase in power demand from the wireless power receiver. If so, the controller can first adjust Vin (decrease it, since it is already at the maximum voltage) (block 345a) (optionally, depending on the transmitted power level), and can also reduce the transmitted power level at least temporarily before making any changes to the series tuned capacitance. Adjusting the input voltage (e.g., reducing it) before changing the input capacitance can prevent overvoltage events from occurring in the wireless power receiver due to the capacitance change on the transmitter side. The controller can then reduce Ctx to increase the gain of the wireless power transmission system while continuing to monitor the input voltage (block 342). As explained above, reducing Ctx can be achieved, for example, by opening one or more of the switches Qctx2, Qctx3 (Figure 2B) and disconnecting one or more of the selectable capacitors Ctx2, Ctx3 coupled to the transmitter coil. Then, for example, if a higher power level is requested by the wireless power receiver, the transmitted power level can be increased again to a relatively high value. 【0049】 Alternatively, in block 341, if the transmitter controller determines that the input voltage is not at its maximum / high threshold, the controller may, in block 343, determine whether the input voltage has reached its minimum (i.e., low threshold), for example, in response to a reduced power demand from the wireless power receiver. If so, the controller may first adjust Vin (increase it, since it is already at the minimum voltage) (block 345b) (optionally, for example, depending on the transmitted power level), and may also potentially temporarily reduce the transmitted power level before making any changes to the series tuning capacitance. As described above, adjusting (increasing) the input voltage (and associated transmitted power level) before changing the input capacitance can prevent overvoltage events from occurring in the wireless power receiver due to capacitance changes on the transmitter side. The controller may then increase Ctx to reduce the gain of the wireless power transmission system while continuing to monitor the input voltage (block 344). Increasing Ctx can be achieved, for example, by closing one or more of the switches Qctx2, Qctx3 (Figure 2B) to couple one or more of the selectable capacitors Ctx2, Ctx3 to the transmitter coil. Then, for example, if a higher power level is requested by the wireless power receiver, the transmitted power level can again be increased to a relatively high value. 【0050】 The above describes various techniques for adjusting the series tuned capacitance of a wireless power transmitter according to input voltage and load conditions in order to achieve improved voltage regulation. Additionally or alternatively, to achieve similar effects, series tuned capacitance adjustment can also be performed on the wireless power receiver side. Figure 4 shows a flowchart of a wireless power receiver capacitance tuning technique 400 in which the receiver-side resonant gain associated with a receiver-side resonant circuit including a receiver coil and series tuned capacitance Crx is adjusted based on the power level and the transmitter-side input voltage. Starting from block 451, a receiver controller (e.g., receiver controller / communication circuit 126) can determine whether increased power is required or desired. If so, in block 452, the receiver controller can send an increased power request (PTx) to the wireless power transmitter. If PTx can send an increased power level, PTx can send it, for example, by increasing its input voltage Vin. Alternatively, if the PTx is unable to transmit the increased power level, it can communicate with the wireless power receiver by, for example, sending a NAK (Negative Response) message in response to a request from the receiver for increased power. This NAK message (and the preceding message from the receiver requesting increased power) may conform to one or more standard protocols, such as the Qi wireless charging standard published by the Wireless Power Consortium, or it may be any other format suitable for communication between the PTx and PRx, such as a proprietary protocol. 【0051】 If no NAK message is received (block 453), the power is increased by PTx only, and the process can return to block 451. Otherwise, if a NAK message is received (block 453), the receiver controller can determine whether PTx is unable to transmit the increased power because PTx is already at its maximum input voltage Vin. For example, the NAK message received from PTx may include an indication of why the increased power is unavailable (e.g., because PTx is already at its maximum input voltage), or may be followed by a subsequent message indicating such information. If the NAK message indicates a reason other than already being at its maximum input voltage that the increased power cannot be provided, the receiver may optionally engage in other compensation or negotiation with PTx to attempt to increase the received power (block 457), after which control returns to block 451. Such other compensation or negotiation is beyond the scope of this application and is therefore not discussed in detail. 【0052】 If a NAK message is received (block 453) and the reason for the NAK is that PTx has reached its maximum input voltage Vin (block 454), the receiver controller may decrease the receiver-side series tuned capacitance Crx to increase the gain, and therefore the received power (block 456). Before doing so, the receiver controller may optionally decrease its power level to prevent overvoltage (block 455). This is similar to the transmitter-side process described above. In certain operating regimes, for example, at relatively high power levels, a change in series tuned capacitance to increase the gain, and therefore the received power, may cause an overvoltage event on the receiver side. To mitigate this, the power may be temporarily reduced before changing the capacitance. The power level can then be increased after the change in capacitance. The capacitance on the receiver side can be changed in a similar manner to that on the transmitter side, and one or more additional receiver-side resonant capacitors Crx2 are optionally isolated from the receiver coil 122 by opening switch Qcrx2 and decreasing the capacitance, thereby increasing the gain and thus increasing the power received in block 456. Control can then be returned to block 451. 【0053】 In block 451, if the receiver controller determines that an increase in the wireless power transmitter is not needed or desired, the receiver controller can determine whether it is at a low power level (block 458). Otherwise, control can return to block 451. If, instead, the receiver controller determines that the receiver is operating at a low power level (block 458), the receiver controller can increase the receiver series resonant capacitance back to its nominal value. The capacitance increase can be achieved by closing switch Qcrx2 to connect the resonant capacitor in parallel with capacitor Crx1, thereby increasing the capacitance and decreasing the system gain. As with the transmitter-side adjustments, the power levels associated with increasing or decreasing the capacitance may be associated with one or more threshold power levels, which may be the same value or different values ​​that allow for hysteresis in the transition. 【0054】 All of the above operations refer to various voltage levels and thresholds, power levels and thresholds, etc. The teachings herein can be applied to various systems operating at different voltage levels, different power levels, etc. For example, in some embodiments, the input voltage may be controllable to be in the range between about 16V and 20V, whether or not by manipulating the control signal for the DC-DC converter. Such a voltage range may, but is not required, correspond to a USB-PD power supply providing a 20V input voltage to such a DC-DC converter. However, operation in other voltage ranges corresponding to other USB-PD voltage levels may also be appropriate. For example, an input voltage range between about 10V and 15V or 12V and 15V may be used with a 15V USB-PD power supply. Alternatively, if a buck boost converter is used to provide Vin from the power supply, the upper limit of the supplied voltage range may exceed the voltage supplied to such a DC-DC converter. Similarly, with respect to power thresholds, a 15W power threshold can serve as a boundary between low-power and high-power regimes. Operating above this threshold can be used to selectively enable or disable features such as input voltage reduction before capacitance changes begin on either the PTx or PRx side. However, 15W is merely an example of such a threshold, which could be 10W, 12W, 16W, 18W, 20W, 22W, 25W, 28W, 30W, 32W, 35W, 38W, 40W, 45W, 50W, or any other suitable value. If some degree of hysteresis is desired, an additional power threshold can be used to indicate a return to a low-power regime. Such a threshold could be 9W, but any value below the high-power threshold, such as 12W, 10W, 7.5W, 5W, etc., may be used. Unless otherwise specified herein or in the appended claims, any of the above values ​​may be used. However, in at least some applications, there may be advantageous reasons to adopt a particular threshold. 【0055】 The above describes various features and embodiments relating to dynamic capacitance tuning in wireless power transmission systems. Such configurations can be used in a variety of applications, but may be particularly advantageous when used with electronic devices such as mobile phones, tablet computers, laptops or notebook computers, and accessories such as wireless headphones and styluses. Furthermore, while numerous specific features and various embodiments have been described, it should be understood that these features and embodiments can be combined in various permutations in a particular implementation unless otherwise stated to be mutually exclusive. Therefore, the various embodiments described above are provided for illustrative purposes only and should not be construed as constituting the scope of this disclosure. Various modifications and changes can be made to the principles and embodiments herein without departing from the scope of this disclosure or the claims. 【0056】 The above describes an exemplary embodiment of a wireless power transmission system that can transmit certain information between PTx and PRx within the system. This disclosure intends that the transmission of this information improves the ability of devices to provide wireless power signals to each other in an efficient manner to facilitate battery charging, such as by sharing the power processing capabilities of the devices with each other. Entities implementing this technology should take care to ensure that well-established privacy policies and / or privacy practices are adhered to to the extent that any sensitive information is used in a particular implementation. Specifically, such entities would be expected to implement and consistently apply privacy practices that are generally recognized as meeting or exceeding industry or government requirements for maintaining user privacy. Implementers should inform users where personally identifiable information is expected to be transmitted in the wireless power transmission system and allow users to "opt in" or "opt out" of participation. For example, such information may be presented to a user when they place a device on a power transmitter if the power transmitter is configured to poll for sensitive information from power receivers. 【0057】 Risks can be minimized by limiting data collection and deleting data when it is no longer needed. Additionally, and where applicable, data de-identification can be used to protect user privacy. For example, device identifiers can be partially masked to convey device characteristics without uniquely identifying the device. De-identification can be facilitated, where appropriate, by removing identifiers, controlling the amount or specificity of stored data (e.g., collecting location data at the city level rather than the address level), controlling how data is stored (e.g., aggregating data across users), and / or by other means such as differential privacy. Robust encryption can also be used to reduce the possibility of inductively coupled device-to-device communication being spoofed.

Claims

[Claim 1] A wireless power transmission device, Wireless power transmission coil and An inverter that receives an input voltage and generates an AC output voltage to drive the wireless power transmission coil, At least one adjustable capacitance coupled to the wireless power transmission coil, The wireless power receiver comprises an inverter and a control circuit for operating the at least one adjustable capacitance to supply wireless power to the wireless power receiver, wherein the control circuit is Determine whether the input voltage is at its maximum value, and if so, To increase the gain, reduce the at least one adjustable capacitance, By adjusting the input voltage at least temporarily before reducing the at least one adjustable capacitance, an overvoltage event in the wireless power receiver caused by reducing the at least one adjustable capacitance is prevented. Or, Determine whether the input voltage is at its minimum value, and if so, To reduce the gain, increase the at least one adjustable capacitance, Responding to power demands from the wireless power receiver by preventing overvoltage events in the wireless power receiver caused by increasing the at least one adjustable capacitance, by at least temporarily adjusting the input voltage before increasing the at least one adjustable capacitance. Wireless power transmitter. [Claim 2] The wireless power transmitter according to claim 1, wherein the at least one adjustable capacitance includes one or more capacitors that can be selectively coupled to the wireless power transmitting coil by one or more switches controlled by the control circuit. [Claim 3] The wireless power transmitter according to claim 1, wherein the at least one adjustable capacitance includes at least one capacitor coupled to the wireless power transmitting coil and at least two capacitors that can be selectively coupled to the wireless power transmitting coil by one or more switches controlled by the control circuit. [Claim 4] The wireless power transmitter according to claim 1, wherein the control circuit performs at least a temporary adjustment of the input voltage before reducing the at least one adjustable capacitance, depending on the operating power level of the wireless power transmitter. [Claim 5] The wireless power transmitter according to claim 1, wherein determining whether the input voltage is at a minimum value and, if so, increasing the at least one adjustable capacitance to reduce the gain further comprises at least temporarily adjusting the input voltage before increasing the at least one adjustable capacitance. [Claim 6] The wireless power transmitter according to claim 1, wherein the control circuit adjusts the at least one adjustable capacitance to maintain zero-voltage switching of the inverter. [Claim 7] The at least one adjustable capacitance is One or more capacitors that can be selectively coupled between the inverter output and the wireless power transmission coil by one or more first switches controlled by the control circuit, The wireless power transmitter according to claim 6, comprising one or more capacitors that can be selectively coupled between the inverter output and ground by one or more second switches controlled by the control circuit. [Claim 8] The one or more capacitors that can be selectively coupled between the inverter output and the wireless power transmission coil include at least one capacitor coupled between the inverter output and the wireless power transmission coil, and at least two capacitors that can be selectively coupled between the inverter output and the wireless power transmission coil by one or more first switches, The wireless power transmission according to claim 7, wherein the one or more capacitors that can be selectively coupled between the inverter output and ground include at least one capacitor coupled between the inverter output and ground, and a plurality of capacitors that can be selectively coupled between the inverter output and ground by one or more second switches. [Claim 9] A method for operating a wireless power transmitter having a wireless power transmitting coil, an inverter that receives an input voltage and generates an AC output voltage to drive the wireless power transmitting coil, and at least one adjustable capacitance coupled to the wireless power transmitting coil, wherein the method is performed by a control circuit of the wireless power transmitter. In response to the increased power demand from the wireless power receiver, determine whether the input voltage is at its maximum value, and if so, To increase the gain, reduce the at least one adjustable capacitance, By adjusting the input voltage at least temporarily before reducing the at least one adjustable capacitance, an overvoltage event in the wireless power receiver caused by reducing the at least one adjustable capacitance is prevented. Or, In accordance with the reduced power demand from the wireless power receiver, it is determined whether the input voltage is at its minimum value, and if so, To reduce the gain, increase the at least one adjustable capacitance, To prevent overvoltage events in a wireless power receiver caused by increasing the at least one adjustable capacitance, by adjusting the input voltage at least temporarily before increasing the at least one adjustable capacitance, A method that includes doing so. [Claim 10] The method according to claim 9, further comprising adjusting the at least one adjustable capacitance to maintain the zero-voltage switching operation of the inverter.

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