Patent Application
20170236638
The present disclosure relates generally to wireless power. More specifically, the disclosure is directed to a wireless power transfer antenna having an auxiliary winding.
An increasing number and variety of electronic devices are powered via rechargeable batteries. Such devices include mobile phones, portable music players, laptop computers, tablet computers, computer peripheral devices, communication devices (e.g., Bluetooth devices), digital cameras, hearing aids, and the like. While battery technology has improved, battery-powered electronic devices increasingly require and consume greater amounts of power, thereby often requiring recharging. Rechargeable devices are often charged via wired connections that require cables or other similar connectors that are physically connected to a power supply. Cables and similar connectors may sometimes be inconvenient or cumbersome and have other drawbacks. Wireless charging systems that are capable of transferring power in free space to be used to charge rechargeable electronic devices may overcome some of the deficiencies of wired charging solutions. As such, wireless charging systems and methods that efficiently and safely transfer power for charging rechargeable electronic devices are desirable.
Various implementations of systems, methods and devices within the scope of the appended claims each have several aspects, no single one of which is solely responsible for the desirable attributes described herein. Without limiting the scope of the appended claims, some prominent features are described herein.
Details of one or more implementations of the subject matter described in this specification are set forth in the accompanying drawings and the description below. Other features, aspects, and advantages will become apparent from the description, the drawings, and the claims. Note that the relative dimensions of the following figures may not be drawn to scale.
One aspect of the disclosure provides a wireless power transfer antenna includes a primary antenna portion configured to develop a primary electric field (E-field) and a primary magnetic field (B-field), and an auxiliary winding coupled to the primary antenna portion by the B-field, the auxiliary winding configured to develop an auxiliary electric field (E-field) that combines with the primary E-field resulting in a net E-field that has a magnitude that is smaller than a magnitude of the primary E-field.
Another aspect of the disclosure provides an antenna structure including a primary antenna portion configured to develop a primary electric field (E-field) and a primary magnetic field (B-field), and an auxiliary winding coupled to the primary antenna portion by the B-field, the auxiliary winding configured to develop an auxiliary electric field (E-field) that combines with the primary E-field, thereby reducing a net electric (E)-field in the antenna structure, and thereby reducing a common-mode signal in the antenna structure.
Another aspect of the disclosure provides a method for wireless power transfer including generating a primary electric field (E-field) and a primary magnetic field (B-field) configured to wirelessly transfer power from a transmitter to a receiver, and generating an auxiliary electric field (E-field) based on the primary B-field, the auxiliary e-field combining with the primary E-field such that a net E-field comprising the primary E-field and the auxiliary E-field has a magnitude that is smaller than a magnitude of the primary E-field.
Another aspect of the disclosure provides a device for wireless power transfer including means for generating a primary electric field (E-field) and a primary magnetic field (B-field) configured to wirelessly transfer power from a transmitter to a receiver, and means for generating an auxiliary electric field (E-field) based on the primary B-field, the auxiliary e-field combining with the primary E-field such that a net E-field comprising the primary E-field and the auxiliary E-field has a magnitude that is smaller than a magnitude of the primary E-field.
In the figures, like reference numerals refer to like parts throughout the various views unless otherwise indicated. For reference numerals with letter character designations such as “102a” or “102b”, the letter character designations may differentiate two like parts or elements present in the same figure. Letter character designations for reference numerals may be omitted when it is intended that a reference numeral encompass all parts having the same reference numeral in all figures.
The various features illustrated in the drawings may not be drawn to scale. Accordingly, the dimensions of the various features may be arbitrarily expanded or reduced for clarity. In addition, some of the drawings may not depict all of the components of a given system, method or device. Finally, like reference numerals may be used to denote like features throughout the specification and figures.
The detailed description set forth below in connection with the appended drawings is intended as a description of exemplary embodiments of the invention and is not intended to represent the only embodiments in which the invention may be practiced. The term “exemplary” used throughout this description means “serving as an example, instance, or illustration,” and should not necessarily be construed as preferred or advantageous over other exemplary embodiments. The detailed description includes specific details for the purpose of providing a thorough understanding of the exemplary embodiments of the invention. In some instances, some devices are shown in block diagram form.
In this description, the term “application” may also include files having executable content, such as: object code, scripts, byte code, markup language files, and patches. In addition, an “application” referred to herein, may also include files that are not executable in nature, such as documents that may need to be opened or other data files that need to be accessed.
As used in this description, the terms “component,” “database,” “module,” “system,” and the like are intended to refer to a computer-related entity, either hardware, firmware, a combination of hardware and software, software, or software in execution. For example, a component may be, but is not limited to being, a process running on a processor, a processor, an object, an executable, a thread of execution, a program, and/or a computer. By way of illustration, both an application running on a computing device and the computing device may be a component. One or more components may reside within a process and/or thread of execution, and a component may be localized on one computer and/or distributed between two or more computers. In addition, these components may execute from various computer readable media having various data structures stored thereon. The components may communicate by way of local and/or remote processes such as in accordance with a signal having one or more data packets (e.g., data from one component interacting with another component in a local system, distributed system, and/or across a network such as the Internet with other systems by way of the signal).
Wirelessly transferring power may refer to transferring any form of energy associated with electric fields, magnetic fields, electromagnetic fields, or otherwise from a transmitter to a receiver without the use of physical electrical conductors (e.g., power may be transferred through free space). The power output into a wireless field (e.g., a magnetic field) may be received, captured by, or coupled by a “receiving antenna” to achieve power transfer.
Devices that use wireless power transfer are becoming smaller and smaller. As these devices become smaller, it is desirable to reduce the size of the electronic circuits inside of the device. For example, one way of reducing the size of a device that can use wireless power transfer is to convert the electronics from an electrically balanced (also referred to as “differential”) configuration or structure to an electrically unbalanced (also referred to as a single-ended) configuration or structure. For example, converting a wireless power transmitter or wireless power receiver from one having a balanced circuit to one having a single-ended circuit reduces the overall size of the circuit, but may give rise to increased levels of electro-magnetic interference (EMI) emanating from the wireless power transmit antenna or the wireless power receiver antenna. The increased EMI results from converting the antenna from an electrically balanced configuration (one in which two signals having opposite polarity are connected to opposite ends of the antenna and the electric and geometric center of the antenna may or may not be grounded) to a single-ended configuration (one in which one end of the antenna is grounded and a single signal is present at the opposite end, resulting in a higher common mode signal at the antenna). Wireless power transfer EMI compliance poses a significant challenge in terms of managing common mode signals at a wireless power transfer antenna. The antenna is electrically exposed to free space and the common mode component of the input signal projects displacement currents in the antenna that can result in high levels of EMI.
A prior approach to reducing common mode signals, and improving common mode rejection, is to interface to the wireless power transmit antenna with balanced electronics and to construct the antenna in symmetrical fashion, achieving electrical and geometric balance, which results in high common mode rejection. However, it is desirable to provide the electronics with a single-ended configuration to reduce the size and cost of the electronic circuits inside of the device. Unfortunately, single-ended circuitry generally gives rise to elevated levels of EMI as a result of a common-mode voltage signal generated by the single-ended circuitry. The common-mode voltage signal gives rise to elevated levels of common-mode noise at the wireless power antenna.
It is also generally cost effective to fabricate a wireless power transfer antenna as a single-ended structure, typically formed as a single layer spiral on a printed circuit board. Unfortunately, such a single-ended structure is inherently electrically unbalanced for at least the reasons mentioned above.
A prior solution uses a symmetrically wound antenna, but this solution typically requires at least a two-layer printed circuit board and multiple lines having signal crossings, thus increasing manufacturing complexity and cost.
The disclosure describes a wireless power transfer antenna having an auxiliary winding. In an exemplary embodiment, the auxiliary winding can be part of a wireless power transmit antenna or a wireless power receiver antenna. In an exemplary embodiment, the auxiliary winding will be described herein in the context of a wireless power receiver antenna. In an exemplary embodiment, the auxiliary winding can at least partially balance the electric field (E-field) of the wireless power transfer antenna and minimize a common-mode signal in the antenna. The auxiliary winding can extend from the end of the wireless power transfer antenna at which the source signal is applied or taken, or can extend from the end of the wireless power transfer antenna that is coupled to ground. Alternatively, the auxiliary winding can take the form of a single or multi-element shield that can be formed in the vicinity of the wireless power transfer antenna. In an exemplary embodiment, the wireless power transfer antenna structure induces a primary voltage in a primary antenna portion that induces a primary electric field (E-field) and a primary magnetic field (B-field) via a magnetic coupling, and induces an auxiliary voltage in the auxiliary winding. The voltage induced in the auxiliary winding generates an electric (E) field that, when combined with the electric (E) field induced in the primary antenna portion of the wireless power transfer antenna, reduces the net electric (E)-field in the wireless power transfer antenna structure, thereby reducing the common-mode signal in the wireless power transfer antenna structure.
The receiver 108 may receive power when the receiver 108 is located in a magnetic field 105 produced by the transmitter 104. The field 105 corresponds to a region where energy output by the transmitter 104 may be captured by a receiver 108. The transmitter 104 may include a transmit antenna 114 (that may also be referred to herein as a coil) for outputting an energy transmission. The receiver 108 further includes a receive antenna 118 (that may also be referred to herein as a coil) for receiving or capturing energy from the energy transmission. The near-field may correspond to a region in which there are strong reactive fields resulting from the currents and charges in the transmit antenna 114 that minimally radiate power away from the transmit antenna 114. In some cases the near-field may correspond to a region that is within about one wavelength (or a fraction thereof) of the transmit antenna 114.
In accordance with the above therefore, in accordance with more particular embodiments, the transmitter 104 may be configured to output a time varying magnetic field 105 with a frequency corresponding to the resonant frequency of the transmit antenna 114. When the receiver is within the field 105, the time varying magnetic field 105 may induce a voltage in the receive antenna 118 that causes an electrical current to flow through the receive antenna 118. As described above, if the receive antenna 118 is configured to be resonant at the frequency of the transmit antenna 114, energy may be more efficiently transferred. The AC signal induced in the receive antenna 118 may be rectified as described above to produce a DC signal that may be provided to charge or to power a load.
The receiver 208 may include receive circuitry 210 that may include a matching circuit 232 and a rectifier and switching circuit 234 to generate a DC power output from an AC power input to charge a battery 236 as shown in
The receiver 208 may initially have a selectively disablable associated load (e.g., battery 236), and may be configured to determine whether an amount of power transmitted by transmitter 204 and received by receiver 208 is appropriate for charging a battery 236. Further, receiver 208 may be configured to enable a load (e.g., battery 236) upon determining that the amount of power is appropriate.
The antenna 352 may form a portion of a resonant circuit configured to resonate at a resonant frequency. The resonant frequency of the loop or magnetic antenna 352 is based on the inductance and capacitance. Inductance may be simply the inductance created by the antenna 352, whereas, capacitance may be added to create a resonant structure (e.g., a capacitor may be electrically connected to the antenna 352 in series or in parallel) at a desired resonant frequency. As a non-limiting example, capacitor 354 and capacitor 356 may be added to the transmit or receive circuitry 350 to create a resonant circuit that resonates at a desired frequency of operation. For larger diameter antennas, the size of capacitance needed to sustain resonance may decrease as the diameter or inductance of the loop increases. As the diameter of the antenna increases, the efficient energy transfer area of the near-field may increase. Other resonant circuits formed using other components are also possible. As another non-limiting example, a capacitor (not shown) may be placed in parallel between the two terminals of the antenna 352. For transmit antennas, a signal 358 with a frequency that substantially corresponds to the resonant frequency of the antenna 352 may be an input to the antenna 352. For receive antennas, the signal 358 may be the output that may be rectified and used to power or charge a load.
Transmit circuitry 406 may include a fixed impedance matching circuit 409 for matching the impedance of the transmit circuitry 406 (e.g., 50 ohms) to the impedance of the transmit antenna 414 and a low pass filter (LPF) 408 configured to reduce harmonic emissions to levels to prevent self-jamming of devices coupled to receivers 108 (
Transmit circuitry 406 may further include a controller 415 for selectively enabling the oscillator 423 during transmit phases (or duty cycles) for specific receivers, for adjusting the frequency or phase of the oscillator 423, and for adjusting the output power level for implementing a communication protocol for interacting with neighboring devices through their attached receivers. It is noted that the controller 415 may also be referred to herein as a processor. The controller may be coupled to a memory 470. Adjustment of oscillator phase and related circuitry in the transmission path may allow for reduction of out of band emissions, especially when transitioning from one frequency to another.
The transmit circuitry 406 may further include a load sensing circuit 416 for detecting the presence or absence of active receivers in the vicinity of the near-field generated by transmit antenna 414. By way of example, a load sensing circuit 416 monitors the current flowing to the driver circuit 424, that may be affected by the presence or absence of active receivers in the vicinity of the field generated by transmit antenna 414 as will be further described below. Detection of changes to the loading on the driver circuit 424 are monitored by controller 415 for use in determining whether to enable the oscillator 423 for transmitting energy and to communicate with an active receiver. The transmit antenna 414 may be implemented with a Litz wire or as an antenna strip with the thickness, width and metal type selected to keep resistive losses low.
The transmitter 404 may gather and track information about the whereabouts and status of receiver devices that may be associated with the transmitter 404. Thus, the transmit circuitry 406 may include a presence detector 480, an enclosed detector 460, or a combination thereof, connected to the controller 415 (also referred to as a processor herein). The controller 415 may adjust an amount of power delivered by the driver circuit 424 in response to presence signals from the presence detector 480 and the enclosed detector 460. The transmitter 404 may receive power through a number of power sources, such as, for example, an AC-DC converter (not shown) to convert AC power present in a building, a DC-DC converter (not shown) to convert a DC power source to a voltage suitable for the transmitter 404, or directly from a DC power source (not shown).
As a non-limiting example, the presence detector 480 may be a motion detector utilized to sense the initial presence of a device to be charged that is inserted into the coverage area of the transmitter 404. After detection, the transmitter 404 may be turned on and the power received by the device may be used to toggle a switch on the receiver device in a pre-determined manner, which in turn results in changes to the driving point impedance of the transmitter 404.
As another non-limiting example, the presence detector 480 may be a detector capable of detecting a human, for example, by infrared detection, motion detection, or other suitable means. In some exemplary embodiments, there may be regulations limiting the amount of power that a transmit antenna 414 may transmit at a specific frequency. In some cases, these regulations are meant to protect humans from electromagnetic radiation. However, there may be environments where a transmit antenna 414 is placed in areas not occupied by humans, or occupied infrequently by humans, such as, for example, garages, factory floors, shops, and the like. If these environments are free from humans, it may be permissible to increase the power output of the transmit antenna 414 above the normal power restrictions regulations. In other words, the controller 415 may adjust the power output of the transmit antenna 414 to a regulatory level or lower in response to human presence and adjust the power output of the transmit antenna 414 to a level above the regulatory level when a human is outside a regulatory distance from the wireless charging field of the transmit antenna 414.
As a non-limiting example, the enclosed detector 460 (may also be referred to herein as an enclosed compartment detector or an enclosed space detector) may be a device such as a sense switch for determining when an enclosure is in a closed or open state. When a transmitter is in an enclosure that is in an enclosed state, a power level of the transmitter may be increased.
In exemplary embodiments, a method by which the transmitter 404 does not remain on indefinitely may be used. In this case, the transmitter 404 may be programmed to shut off after a user-determined amount of time. This feature prevents the transmitter 404, notably the driver circuit 424, from running long after the wireless devices in its perimeter are fully charged. This event may be due to the failure of the circuit to detect the signal sent from either the repeater or the receive antenna 218 that a device is fully charged. To prevent the transmitter 404 from automatically shutting down if another device is placed in its perimeter, the transmitter 404 automatic shut off feature may be activated only after a set period of lack of motion detected in its perimeter. The user may be able to determine the inactivity time interval, and change it as desired. As a non-limiting example, the time interval may be longer than that needed to fully charge a specific type of wireless device under the assumption of the device being initially fully discharged.
Receive antenna 518 may be tuned to resonate at the same frequency, or within a specified range of frequencies, as transmit antenna 414 (
Receive circuitry 510 may provide an impedance match to the receive antenna 518. Receive circuitry 510 includes power conversion circuitry 506 for converting received energy into charging power for use by the device 550. Power conversion circuitry 506 includes an AC-to-DC converter 520 and may also include a DC-to-DC converter 522. AC-to-DC converter 520 rectifies the RF energy signal received at receive antenna 518 into a non-alternating power with an output voltage. The DC-to-DC converter 522 (or other power regulator) converts the rectified energy signal into an energy potential (e.g., voltage) that is compatible with device 550 with an output voltage and output current. Various AC-to-DC converters are contemplated, including partial and full rectifiers, regulators, bridges, doublers, as well as linear and switching converters.
Receive circuitry 510 may further include RX matching and switching circuitry 512 for connecting receive antenna 518 to the power conversion circuitry 506 or alternatively for disconnecting the power conversion circuitry 506. Disconnecting receive antenna 518 from power conversion circuitry 506 not only suspends charging of device 550, but also changes the “load” as “seen” by the transmitter 404 (
When multiple receivers 508 are present in a transmitter's near-field, it may be desirable to adjust the loading and unloading of one or more receivers to enable other receivers to more efficiently couple to the transmitter. A receiver 508 may also be cloaked in order to eliminate coupling to other nearby receivers or to reduce loading on nearby transmitters. This “unloading” of a receiver is also known herein as a “cloaking.” Furthermore, this switching between unloading and loading controlled by receiver 508 and detected by transmitter 404 may provide a communication mechanism from receiver 508 to transmitter 404. Additionally, a protocol may be associated with the switching that enables the sending of a message from receiver 508 to transmitter 404. By way of example, a switching speed may be on the order of 100 μsec.
In an exemplary embodiment, communication between the transmitter 404 and the receiver 508 may take place either via an “out-of-band” separate communication channel/antenna or via “in-band” communication that may occur via modulation of the field used for power transfer.
Receive circuitry 510 may further include signaling detector and beacon circuitry 514 used to identify received energy fluctuations that may correspond to informational signaling from the transmitter to the receiver. Furthermore, signaling and beacon circuitry 514 may also be used to detect the transmission of a reduced signal energy (i.e., a beacon signal) and to rectify the reduced signal energy into a nominal power for awakening either un-powered or power-depleted circuits within receive circuitry 510 in order to configure receive circuitry 510 for wireless charging.
Receive circuitry 510 further includes controller 516 for coordinating the processes of receiver 508 described herein including the control of RX matching and switching circuitry 512 described herein. It is noted that the controller 516 may also be referred to herein as a processor. Cloaking of receiver 508 may also occur upon the occurrence of other events including detection of an external wired charging source (e.g., wall/USB power) providing charging power to device 550. Controller 516, in addition to controlling the cloaking of the receiver, may also monitor beacon circuitry 514 to determine a beacon state and extract messages sent from the transmitter 404. Controller 516 may also adjust the DC-to-DC converter 522 for improved performance.
The signal output by the filter circuit 626 may be provided to a transmit circuit 650 comprising an antenna 614. The transmit circuit 650 may include a series resonant circuit having a capacitance 620 and inductance (e.g., that may be due to the inductance or capacitance of the antenna or to an additional capacitor component) that may resonate at a frequency of the filtered signal provided by the driver circuit 624. The load of the transmit circuit 650 may be represented by the variable resistor 622. The load may be a function of a wireless power receiver 508 that is positioned to receive power from the transmit circuit 650.
In an exemplary embodiment, an auxiliary winding for a wireless power transfer resonator reduces the level of a common-mode signal in the wireless power transfer resonator, and may be suited in particular for single-ended resonator circuits. Wireless charging systems can transfer charge to a charge receiving device by magnetic field coupling or by electric field coupling. A magnetic field coupling is also referred to as an inductive coupling and generally uses what is referred to as an H-field, or B-field, coupling. An electric field coupling is also referred to as capacitive coupling and generally uses what is referred to as an E-field coupling. The auxiliary winding can be incorporated into an antenna or resonator structure that controls both the magnetic field and the electric field.
The antenna structure 700 may be implemented in a wireless power transmitter or a wireless power receiver. If implemented in a wireless power transmitter, a transmit input signal may be applied to the conductor 718 by, for example, the transmit circuitry 406 (
In an exemplary embodiment, the primary antenna portion 712 generates a primary electric field (E-field) and a primary magnetic field (B-field). The primary magnetic field (B-field) generated by the primary antenna portion 712 induces a voltage (via electromotive force (EMF)) on the auxiliary winding 715. The voltage induced on the auxiliary winding 715 may comprise an EMF induced voltage at the fundamental power transfer frequency, may include an EMF induced voltage at other frequencies, and may include an EMF induced voltage at harmonics of the fundamental power transfer frequency. In an exemplary embodiment, the auxiliary winding 715 does not necessarily carry a current as a result of an applied input signal or a generated output signal, but the voltage induced in the auxiliary winding 715 generates an auxiliary electric field (E-field) in the auxiliary winding 715. The auxiliary electric field (E-field) generated in the auxiliary winding 715 is substantially 180 degrees out of phase with respect to the primary E-field in the primary antenna portion 712 and opposes the primary E-field in the primary antenna portion 712, thereby reducing the net electric (E)-field in the antenna structure 700, and thereby reducing the common-mode signal of the antenna structure 700 including the primary antenna portion 712 and the auxiliary winding 715. When the magnitude of the auxiliary E-field generated in the auxiliary winding 715 is substantially equal to the magnitude of the primary E-field generated by the primary antenna portion 712, then the auxiliary E-field substantially cancels the primary E-field. When the phase of the E-field in the auxiliary winding 715 is substantially 180 degrees out of phase with respect to the phase of the E-field in the primary antenna portion 712, and the magnitude of the auxiliary E-field generated in the auxiliary winding 715 is less than the magnitude of the primary E-field generated by the primary antenna portion 712, then the net E-field in the antenna structure 700 is the difference in magnitude between the magnitude of the primary E-field and the magnitude of the auxiliary E-field.
The reduction in the common mode voltage allows the use of single-ended circuitry, such as, for example, half-bridge rectification circuitry, thus reducing circuit footprint, and component cost, and facilitating miniaturization.
In an alternative exemplary embodiment, the auxiliary winding may be configured as part of a resonant circuit that may carry current. For example, an end of the auxiliary winding may be capacitively coupled in parallel to the primary antenna portion 712, thus forming a parallel resonant circuit that could modify the net impedance of the antenna structure 700. This may be beneficial for modifying the impedance of the resonator but generally degrades the EMI and common-mode cancellation aspect due to a narrowing of operation frequency.
In an exemplary embodiment, the auxiliary winding 815 may extend around the inside of the primary antenna portion 812 from the point 816 to a point 817 in the same direction in which the primary antenna portion 812 is wound (along an inner edge). In this exemplary embodiment, the auxiliary winding 815 may be referred to as “co-wound” with respect to the primary antenna portion 812. The auxiliary winding 815 may be a fraction of the number of turns of the primary antenna portion 812 or may be a multiple of the number of turns of the primary antenna portion 812.
The antenna structure 800 may be implemented in a wireless power transmitter or a wireless power receiver. If implemented in a wireless power transmitter, a transmit input signal may be applied to the conductors 818 and 819 by, for example, the transmit circuitry 406 (
In an exemplary embodiment the primary antenna portion 812 generates a primary electric field (E-field) and a primary magnetic field (B-field). The primary magnetic field (B-field) generated by the primary antenna portion 812 induces a voltage (via electromotive force (EMF)) on the auxiliary winding 815. The voltage induced on the auxiliary winding 815 may comprise an EMF induced voltage at the fundamental power transfer frequency, may include an EMF induced voltage at other frequencies, and may include an EMF induced voltage at harmonics of the fundamental power transfer frequency. In an exemplary embodiment, the auxiliary winding 815 does not necessarily carry a current as a result of an applied input signal or a generated output signal, but the voltage induced in the auxiliary winding 815 generates an auxiliary electric field (E-field) in the auxiliary winding 815. The auxiliary electric field (E-field) generated in the auxiliary winding 815 is substantially 180 degrees out of phase with respect to the primary E-field in the primary antenna portion 812 and opposes the primary E-field in the primary antenna portion 812, thereby reducing the net electric (E)-field in the antenna structure 800, and thereby reducing the common-mode signal of the antenna structure 800 including the primary antenna portion 812 and the auxiliary winding 815. When the magnitude of the auxiliary E-field generated in the auxiliary winding 815 is substantially equal to the magnitude of the primary E-field generated by the primary antenna portion 812, then the auxiliary E-field substantially cancels the primary E-field. When the phase of the E-field in the auxiliary winding 815 is substantially 180 degrees out of phase with respect to the phase of the E-field in the primary antenna portion 815, and the magnitude of the auxiliary E-field generated in the auxiliary winding 815 is less than the magnitude of the primary E-field generated by the primary antenna portion 812, then the net E-field in the antenna structure 800 is the difference in magnitude between the magnitude of the primary E-field and the magnitude of the auxiliary E-field. In an exemplary embodiment, the reduction in the common mode voltage improves the performance of a near-balanced differential circuit.
The antenna structure 900 may be implemented in a wireless power transmitter or a wireless power receiver. If implemented in a wireless power transmitter, a transmit input signal may be applied to the conductors 918 and 919 by, for example, the transmit circuitry 406 (
In an exemplary embodiment the primary antenna portion 912 generates a primary electric field (E-field) and a primary magnetic field (B-field). The primary magnetic field (B-field) generated by the primary antenna portion 912 induces a voltage (via electromotive force (EMF)) on the auxiliary winding 915. The voltage induced on the auxiliary winding 915 may comprise an EMF induced voltage at the fundamental power transfer frequency, may include an EMF induced voltage at other frequencies, and may include an EMF induced voltage at harmonics of the fundamental power transfer frequency. In an exemplary embodiment, the auxiliary winding 915 does not necessarily carry a current as a result of an applied input signal or a generated output signal, but the voltage induced in the auxiliary winding 915 generates an auxiliary electric field (E-field) in the auxiliary winding 915. The auxiliary electric field (E-field) generated in the auxiliary winding 915 is substantially 180 degrees out of phase with respect to the primary E-field in the primary antenna portion 912 and opposes the primary E-field from the primary antenna portion 912, thereby reducing the net electric (E)-field in the antenna structure 900, and thereby reducing the common-mode signal of the antenna structure 900 including the primary antenna portion 912 and the auxiliary winding 915. When the magnitude of the auxiliary E-field generated in the auxiliary winding 915 is substantially equal to the magnitude of the primary E-field generated by the primary antenna portion 912, then the auxiliary E-field substantially cancels the primary E-field. When the phase of the E-field in the auxiliary winding 915 is substantially 180 degrees out of phase with respect to the phase of the E-field in the primary antenna portion 915, and the magnitude of the auxiliary E-field generated in the auxiliary winding 915 is less than the magnitude of the primary E-field generated by the primary antenna portion 912, then the net E-field in the antenna structure 900 is the difference in magnitude between the magnitude of the primary E-field and the magnitude of the auxiliary E-field. In an exemplary embodiment, the reduction in the common mode voltage improves the performance of a near-balanced differential circuit.
In an exemplary embodiment, the auxiliary winding 1015 may extend around the outside of the primary antenna portion 1012 to point 1017 in the same direction in which the primary antenna portion 1012 is wound. In this exemplary embodiment in which the winding of the primary antenna portion 1012 begins at point 1008, the auxiliary winding 1015 may be referred to as “co-wound” with respect to the primary antenna portion 1012. The auxiliary winding 1015 may be a fraction of the number of turns of the primary antenna portion 1012 or may be a multiple of the number of turns of the primary antenna portion 1012. In an exemplary embodiment, the auxiliary winding 1015 may be referred to as an “isolated shield” because it is not directly electrically coupled to the primary antenna portion 1012.
The antenna structure 1000 may be implemented in a wireless power transmitter or a wireless power receiver. If implemented in a wireless power transmitter, a transmit input signal may be applied to the conductors 1018 and 1019 by, for example, the transmit circuitry 406 (
In an exemplary embodiment the primary antenna portion 1012 generates a primary electric field (E-field) and a primary magnetic field (B-field). The primary magnetic field (B-field) generated by the primary antenna portion 1012 induces a voltage (via electromotive force (EMF)) on the auxiliary winding 1015. The voltage induced on the auxiliary winding 1015 may comprise an EMF induced voltage at the fundamental power transfer frequency, may include an EMF induced voltage at other frequencies, and may include an EMF induced voltage at harmonics of the fundamental power transfer frequency. The auxiliary winding 1015 does not necessarily carry a current as a result of an applied input signal or a generated output signal, but the voltage induced in the auxiliary winding 1015 generates an auxiliary electric field (E-field) in the auxiliary winding 1015. The auxiliary electric field (E-field) generated in the auxiliary winding 1015 is substantially 180 degrees out of phase with respect to the primary E-field in the primary antenna portion 1012 and opposes the primary E-field in the primary antenna portion 1012, thereby reducing the net electric (E)-field in the antenna structure 1000, and thereby reducing the common-mode signal of the antenna structure 1000 including the primary antenna portion 1012 and the auxiliary winding 1015. When the magnitude of the auxiliary E-field generated in the auxiliary winding 1015 is substantially equal to the magnitude of the primary E-field generated by the primary antenna portion 1012, then the auxiliary E-field substantially cancels the primary E-field. When the phase of the E-field in the auxiliary winding 1015 is substantially 180 degrees out of phase with respect to the phase of the E-field in the primary antenna portion 1015, and the magnitude of the auxiliary E-field generated in the auxiliary winding 1015 is less than the magnitude of the primary E-field generated by the primary antenna portion 1012, then the net E-field in the antenna structure 1000 is the difference in magnitude between the magnitude of the primary E-field and the magnitude of the auxiliary E-field. In an exemplary embodiment, the reduction in the common mode voltage improves the performance of a near-balanced differential circuit.
In an exemplary embodiment in which the antenna structure 1100 is implemented in a balanced or near-balanced circuit, the auxiliary winding 1115 may comprise a first portion 1127 that is located around the outer circumference of the primary antenna portion 1112 and a second portion 1129 that is located around the outer circumference of the primary antenna portion 1112. The first portion 1127 and the second portion 1129 extend around the outside of the primary antenna portion 1112 in opposite directions, and leave a gap or split 1128. In an exemplary embodiment in which the winding of the primary antenna portion 1112 begins at point 1108, the first portion 1127 may be referred to as “co-wound” with respect to the primary antenna portion 1112 and the second portion 1129 may be referred to as “counter-wound” with respect to the primary antenna portion 1112. In an exemplary embodiment, the auxiliary winding 1115 may be referred to as a “split shield” because the first portion 1127 generally extends from the conductor 1119 of the primary antenna portion 1112 and the second portion 1129 generally extends from the conductor 1118 of the primary antenna portion 1112, where the first portion 1127 and the second portion 1129 extend around the periphery of the primary antenna portion 1112 leaving the gap 1128. In an exemplary embodiment, the gap 1128 may be located substantially opposite the conductors 1118 and 1119 as shown in
The antenna structure 1100 may be implemented in a wireless power transmitter or a wireless power receiver. If implemented in a wireless power transmitter, a transmit input signal may be applied to the conductors 1118 and 1119 by, for example, the transmit circuitry 406 (
In an exemplary embodiment the primary antenna portion 1112 generates a primary electric field (E-field) and a primary magnetic field (B-field). The primary magnetic field (B-field) generated by the primary antenna portion 1112 induces a voltage (via electromotive force (EMF)) on the auxiliary winding 1115. The voltage induced on the auxiliary winding 1115 may comprise an EMF induced voltage at the fundamental power transfer frequency, may include an EMF induced voltage at other frequencies, and may include an EMF induced voltage at harmonics of the fundamental power transfer frequency. The auxiliary winding 1115 does not necessarily carry a current as a result of an applied input signal or a generated output signal, but the voltage induced in the auxiliary winding 1115 generates an auxiliary electric field (E-field) in the auxiliary winding 1115. The auxiliary electric field (E-field) generated in the auxiliary winding 1115 is substantially 180 degrees out of phase with respect to the primary E-field in the primary antenna portion 1112 and opposes the primary E-field in the primary antenna portion 1112, thereby reducing the net electric (E)-field in the antenna structure 1100, and thereby reducing the common-mode signal of the antenna structure 1100 including the primary antenna portion 1112 and the auxiliary winding 1115. When the magnitude of the auxiliary E-field generated in the auxiliary winding 1115 is substantially equal to the magnitude of the primary E-field generated by the primary antenna portion 1112, then the auxiliary E-field substantially cancels the primary E-field. When the phase of the E-field in the auxiliary winding 1115 is substantially 180 degrees out of phase with respect to the phase of the E-field in the primary antenna portion 1115, and the magnitude of the auxiliary E-field generated in the auxiliary winding 1115 is less than the magnitude of the primary E-field generated by the primary antenna portion 1112, then the net E-field in the antenna structure 1100 is the difference in magnitude between the magnitude of the primary E-field and the magnitude of the auxiliary E-field. In an exemplary embodiment, the reduction in the common mode voltage improves the performance of a near-balanced differential circuit.
In an exemplary embodiment, the auxiliary winding 1115 develops a substantially balanced electro-motive force (EMF), i.e., an induced voltage, symmetrically on both the first portion 1127 and the second portion 1129. The auxiliary winding 1115 reduces the exposed EMF and the balanced nature of the auxiliary winding 1115 cancels a significant portion of the common mode signal in the primary antenna portion 1112. Moreover, in an exemplary embodiment where the auxiliary winding 1115 may not develop a completely balanced EMF, but may develop an EMF lower than an EMF developed by the primary antenna portion 1112, the auxiliary winding 1115 still reduces electromagnetic interference emissions from the primary antenna portion 1112.
The gap 1128 in the auxiliary winding 1115 prevents current from being developed in the auxiliary winding 1115 and attenuates a substantial portion of the electric field in the primary antenna portion 1112, thus attenuating EMI radiating from the coil.
In an exemplary embodiment, the layers 1204, 1206 and 1207 may comprise some or all of the antenna structure 1201. While three exemplary layers 1204, 1206 and 1207 are illustrated in
In an exemplary embodiment, the ferrite layer 1208 and the ground plane 1209 are optional. If they are not present then one or more auxiliary windings may be located on both the top layer 1204 and the bottom layer 1207.
In an exemplary embodiment, the antenna structure 700 of
In an exemplary embodiment, the additional primary antenna winding 1220 can be coupled in series to the primary antenna portion 712 and the additional primary antenna winding 1230 can be coupled in series to the additional primary antenna winding 1220. In an exemplary embodiment, the additional winding 1220 is shown as being located on the layer 1206 and the additional winding 1230 is shown as being located on the layer 1207.
In a multi-layer embodiment, only the outer layers, for example, the layer 1204 when there is a ferrite layer 1208 and a ground plane 1209 present, projects an E-field. The inner layers 1206 and 1207 in this example, are sandwiched by the outer layers and therefore are not externally exposed. In such an embodiment, the outer layer 1204 and the ferrite layer 1208 and ground plane 1209 act as a shield for the inner layers 1206 and 1207. In such an exemplary embodiment, the auxiliary winding 715 is located on an outer layer, such as the layer 1204, thus compensating for the E field generated by the primary antenna portion 712 that is also on the outer layer 1204.
In an exemplary embodiment, the outer turn represented by the auxiliary winding 1355 projects a stronger E-field when the antenna structure 700 is used in conjunction with the ground plane 1351 that is located behind the primary antenna portion 712 and the auxiliary winding 715. In such an implementation, there is also generally a ferrite layer (not shown in
In block 1402, a primary electric field is generated by a primary antenna portion of a wireless power transfer antenna.
In block 1404, an auxiliary electric field is generated by an auxiliary winding. The auxiliary electric field combines with the primary electric field generated by the primary antenna portion of the wireless power transfer antenna resulting in a net electric field that has a magnitude that is smaller than the magnitude of the primary electric field. In an exemplary embodiment in which the auxiliary electric field is substantially 180 out of phase with respect to the primary electric field and is equal in magnitude to the primary electric field, the auxiliary electric field substantially cancels the primary electric field generated by the primary antenna portion of the wireless power transfer antenna, resulting in a net zero electric field.
The apparatus 1500 comprises means 1502 for generating a primary electric field. In certain embodiments, the means 1502 for generating a primary electric field can be configured to perform one or more of the function described in operation block 1402 of method 1400 (
The apparatus 1500 further comprises means 1504 for generating an auxiliary electric field that combines with the primary electric field resulting in a net electric field that has a magnitude that is smaller than the magnitude of the primary electric field. In certain embodiments, the means 1504 for generating an auxiliary electric field that reduces the primary electric field can be configured to perform one or more of the function described in operation block 1404 of method 1400 (
The various operations of methods described above may be performed by any suitable means capable of performing the operations, such as various hardware and/or software component(s), circuits, and/or module(s). Generally, any operations illustrated in the Figures may be performed by corresponding functional means capable of performing the operations.
In view of the disclosure above, one of ordinary skill in programming is able to write computer code or identify appropriate hardware and/or circuits to implement the disclosed invention without difficulty based on the flow charts and associated description in this specification, for example. Therefore, disclosure of a particular set of program code instructions or detailed hardware devices is not considered necessary for an adequate understanding of how to make and use the invention. The inventive functionality of the claimed computer implemented processes is explained in more detail in the above description and in conjunction with the FIGS. which may illustrate various process flows.
In one or more exemplary aspects, the functions described may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored on or transmitted as one or more instructions or code on a computer-readable medium. Computer-readable media include both computer storage media and communication media including any medium that facilitates transfer of a computer program from one place to another. A storage media may be any available media that may be accessed by a computer. By way of example, and not limitation, such computer-readable media may comprise RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that may be used to carry or store desired program code in the form of instructions or data structures and that may be accessed by a computer.
Also, any connection is properly termed a computer-readable medium. For example, if the software is transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (“DSL”), or wireless technologies such as infrared, radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of medium.
Disk and disc, as used herein, includes compact disc (“CD”), laser disc, optical disc, digital versatile disc (“DVD”), floppy disk and Blu-Ray disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above should also be included within the scope of computer-readable media.
Although selected aspects have been illustrated and described in detail, it will be understood that various substitutions and alterations may be made therein without departing from the spirit and scope of the present invention, as defined by the following claims.
