Phase Modulation Wireless Charger

Abstract

A system, method, and apparatus for wireless charging are disclosed. The charging device includes a resonant circuit including one or more transmit coils, a driver circuit configured to supply a charging current to the resonant circuit, a zero-crossing detector configured to supply a zero-crossing signal including edges corresponding to transitions of a voltage measured across the resonant circuit through a zero volt level or a current in the resonant circuit through a zero ampere level, and a controller. The controller may be configured to cause the driver circuit to supply the charging current to the resonant circuit when a powered device is present on the charging device, and to phase-align the charging current to a phase-modulated signal generated from the zero-crossing signal to control a power level wirelessly transmitted to the powered device.

Description

[Technical Field]

[0001] Priority Claim This application claims priority and interest to patent application no. 16 / 893,417, filed with the United States Patent and Trademark Office on 4 June 2020, which is incorporated herein by reference for all applicable purposes as if its entire contents were fully described below.

[0002] Technical field This invention relates to wireless charging of batteries, including batteries in mobile computing devices in general, and more specifically to the control of wireless power transmission. [Background technology]

[0003] Wireless charging systems are developed to allow certain devices to charge their internal batteries without using physical charging connections. Devices that can utilize wireless charging include mobile devices and / or communication devices. Standards such as the Qi standard set by the Wireless Power Consortium allow devices manufactured by a first supplier to be wirelessly charged with a charger manufactured by a second supplier. Wireless charging standards tend to be optimized for devices with relatively simple configurations and provide basic charging functionality.

[0004] Improvements to wireless charging capabilities are necessary to accommodate increasingly complex mobile devices and evolving form factors. For example, improvements to wireless transmission power control are required. [Brief explanation of the drawing]

[0005] [Figure 1] Figure 1 shows an example of a charging cell that may be employed to provide a charging surface according to a particular embodiment disclosed herein. [Figure 2]Figure 2 shows the arrangement of power transfer areas provided by a charging surface employing a multi-layer charging cell configured according to a particular embodiment disclosed herein. [Figure 3] Figure 3 shows a wireless transmitter that may be provided on a charger base station according to a particular embodiment disclosed herein. [Figure 4] Figure 4 shows a phase-modulated wireless charger configured according to a particular aspect of the present disclosure. [Figure 5] Figure 5 shows an example of a pulse width modulation charger configured according to a particular aspect of this disclosure. [Figure 6] Figure 6 illustrates the operation of the pulse width modulation charger shown in Figure 5. [Figure 7] Figure 7 shows an example of a wireless charging system employing a Class D wireless transmitter configured according to a specific embodiment disclosed herein. [Figure 8] Figure 8 shows the operation of the Class D wireless transmitter shown in Figure 7. [Figure 9] Figure 9 shows a zero-cross slot type foreign object detection according to a particular aspect of the present disclosure. [Figure 10] Figure 10 shows a wireless charging system that employs zero-cross detection to obtain measurements at one or more points in each period of current or voltage in a resonant circuit, according to a particular aspect of this disclosure. [Figure 11] Figure 11 illustrates a phase-based ASK demodulation that supports the use of zero-cross detection in a wireless charging system configured according to a particular aspect of this disclosure. [Figure 12] Figure 12 illustrates a phase-based ASK demodulation that supports the use of zero-cross detection in a wireless charging system configured according to a particular aspect of this disclosure. [Figure 13] Figure 13 shows an example of an apparatus employing a processing circuit that may be adapted according to a particular embodiment disclosed herein. [Figure 14]Figure 14 shows a method of operating a charging device according to a particular aspect of this disclosure. [Modes for carrying out the invention]

[0006] The detailed descriptions provided below in relation to the attached drawings are intended to illustrate various configurations and are not intended to show only the configurations in which the concepts described herein can be implemented. The detailed descriptions include specific details to provide a complete understanding of the various concepts. However, it will be apparent to those skilled in the art that these concepts can be implemented without specific details. Sometimes, well-known structures and components are shown in block diagram form to avoid obscuring such concepts.

[0007] Next, specific embodiments of wireless charging systems are presented with reference to various devices and methods. These devices and methods are described in the following detailed description and are illustrated in the accompanying drawings by various blocks, modules, components, circuits, steps, processes, algorithms, etc. (collectively referred to as “elements”). These elements can be implemented using electronic hardware, computer software, or any combination thereof. Whether such elements are implemented as hardware or software depends on the specific application and the design constraints imposed on the overall system.

[0008] For example, an element, any part of an element, or any combination of elements may be implemented in a “processing system” comprising one or more processors. Examples of processors include microprocessors, microcontrollers, digital signal processors (DSPs), field-programmable gate arrays (FPGAs), programmable logic devices (PLDs), state machines, gate logic, discrete hardware circuits, and other suitable hardware configured to perform the various functions described throughout this disclosure. One or more processors in a processing system may execute software. Software is broadly interpreted to mean instructions, instruction sets, code, code segments, program code, programs, subprograms, software modules, applications, software applications, software packages, routines, subroutines, objects, executable files, execution threads, procedures, functions, etc., whether they are called software, firmware, middleware, microcode, or hardware description languages, etc. Software may reside in a processor-readable storage medium. Processor-readable storage media, also referred to herein as computer-readable media, may include, for example, magnetic storage devices (e.g., hard disks, floppy disks, magnetic strips), optical discs (e.g., compact discs (CDs), digital-purpose discs (DVDs)), smart cards, flash memory devices (e.g., cards, sticks, key drives), near-field communication (NFC) tokens, random-access memory (RAM), read-only memory (ROM), programmable ROM (PROM), erasable PROM (EPROM), electrically erasable PROM (EEPROM), registers, removable disks, carriers, transmission lines, and any other media suitable for storing or transmitting software. Computer-readable media may reside within a processing system, be outside of a processing system, or be distributed across multiple entities including a processing system. Computer-readable media may also be embodied in computer program products.As an example, a computer program product can include a computer-readable medium within a packaging material. Those skilled in the art will recognize the best way to implement the described functionality presented throughout this disclosure in accordance with the particular application and overall design constraints imposed on the overall system.

[0009] Summary Certain aspects of the present disclosure relate to systems, devices, and methods applicable to wireless charging devices. In a wireless charging device, a charging cell can be configured to have one or more induction coils and can provide a charging surface for wirelessly charging one or more devices. The position of the device to be charged can be detected via sensing techniques that associate the position of the device with changes in physical characteristics centered around a known position on the charging surface. Position sensing can be implemented using capacitive, resistive, inductive, contact, pressure, load, strain, and / or another suitable type of sensing.

[0010] In one aspect of the present disclosure, the device includes a battery charging power source, a plurality of charging cells configured in a matrix, a first plurality of switches each configured to couple a row of coils in the matrix to a first terminal of the battery charging power source, and a second plurality of switches each configured to couple a column of coils in the matrix to a second terminal of the battery charging power source. Each charging cell of the plurality of charging cells can include one or more coils surrounding a power transmission area. The plurality of charging cells may be arranged adjacent to the charging surface of the wireless charging device such that the power transmission areas of the charging cells among the plurality of charging cells do not overlap. A device placed on the surface can receive power wirelessly transmitted through one or more charging cells.

[0011] In some cases, this device may also be referred to as a charging surface. Power can be wirelessly transmitted to a power receiving device placed anywhere on the surface of the device. The device can have arbitrarily defined sizes and / or shapes and can be placed regardless of any individual placement that can be charged. Multiple devices can be charged simultaneously on a single charging surface. This device can track the movement of one or more devices across the charging surface.

[0012] The specific embodiments disclosed herein relate to improved wireless charging technology. In various aspects of this disclosure, a method of operating a charging device includes supplying a charging current to a resonant circuit when a power receiving device is present on the surface of the charging device, and providing a zero-crossing signal including an edge corresponding to a transition of a voltage measured across the resonant circuit through a zero-volt level or a transition of a current within the resonant circuit through a zero-ampere level, and controlling a power level wirelessly transmitted to the power receiving device by phase-aligning the charging current with a phase modulation signal generated from the zero-crossing signal.

[0013] Charging cell According to a specific embodiment disclosed herein, a charging device provides a charging surface and uses a charging cell disposed adjacent to this charging surface. In one example, the charging cell is disposed in one or more layers of the charging surface according to a honeycomb package configuration. The charging cell can be implemented using one or more coils capable of inducing a magnetic field along an axis substantially orthogonal to the charging surface adjacent to each coil. As used herein, a charging cell is a component having one or more coils configured to generate an electromagnetic field that is additive to the field generated by other coils within the charging cell, and the electromagnetic fields generate magnetic fluxes oriented along a common axis or in proximity.

[0014] In some implementations, a charging cell includes coils stacked along a common axis and / or overlapping to contribute to an induced magnetic field substantially orthogonal to the charging surface. In some embodiments, a charging cell includes coils positioned within a defined portion of the charging surface and contributing to an induced magnetic field within a substantially orthogonal portion of the charging surface related to the charging cell. In some implementations, a charging cell may be configured by supplying an activation current to coils contained within a dynamically defined charging cell. For example, a charging device may include a stack of multiple coils deployed across the charging surface, and the charging device may detect the position of the device to be charged and select several combinations of the coil stacks to provide charging cells adjacent to the device to be charged. In some embodiments, a charging cell may include a single coil or be characterized as a single coil. However, it should be understood that a charging cell may include multiple stacked coils and / or multiple adjacent coils or stacks of coils. In this specification, coils may be referred to as charging coils, wireless charging coils, transmitter coils, transmission coils, power transmission coils, etc.

[0015] Figure 1 shows an example of a charging cell 100 that may be arranged and / or configured to provide a charging surface for a charging device. As described herein, the charging surface may include an array of charging cells 100 provided on one or more substrates 106. One or more substrates 106 may provide a circuit consisting of one or more integrated circuits (ICs) and / or discrete electronic components. This circuit may include drivers and switches used to control the current supplied to coils used to transmit power to a powered device. This circuit may be configured as a processing circuit including one or more processors and / or one or more controllers that may be configured to perform specific functions disclosed herein. In some embodiments, some or all of the processing circuit may be located outside the charging device. In some embodiments, a power supply or battery may be coupled to the charging device.

[0016] The charging cell 100 can be provided in close proximity to the outer surface area of ​​the charging device, and one or more devices can be placed on it for charging. The charging device may include multiple instances of the charging cell 100. In one example, the charging cell 100 has a substantially hexagonal shape surrounding one or more coils 102 constructed with conductors, wires, or circuit board traces capable of receiving a current sufficient to generate an electromagnetic field in the power transfer area 104. In various embodiments, some coils 102 may have a substantially polygonal shape, including the hexagonal charging cell 100 illustrated in Figure 1. In other embodiments, coils 102 having other shapes are provided. The shape of the coils 102 can be determined at least in part by the capabilities or limitations of the manufacturing technology and / or to optimize the layout of the charging cell on a substrate 106 such as a printed circuit board. Each coil 102 can be mounted using spiral-configured wires, printed circuit board traces, and / or other connectors. Each charging cell 100 can span two or more layers separated by an insulator or substrate 106 such that the coils 102 of different layers have a common axis 108.

[0017] Figure 2 shows the arrangement of power transfer areas provided as a charging surface 200 of a charging device employing a multi-layer charging cell configured according to a particular embodiment disclosed herein. The illustrated charging surface consists of four layers of charging cells 202, 204, 206, and 208. In Figure 2, each power transfer area provided by a charging cell of the first layer charging cell 202 is labeled "L1", each power transfer area provided by a charging cell of the second layer charging cell 204 is labeled "L2", each power transfer area provided by a charging cell of the third layer charging cell 206 is labeled "L3", and each power transfer area provided by a charging cell of the fourth layer charging cell 208 is labeled "L4".

[0018] Figure 3 shows a wireless transmitter 300 that may be installed in a charger base station. A controller 302 can receive a feedback signal that has been filtered by a filter circuit 308 or otherwise processed. The controller can control the operation of a driver circuit 304 that supplies an alternating current (AC) signal to a resonant circuit 306 which includes a capacitor 312 and an inductor 314. The resonant circuit 306 is also referred to herein as a tank circuit, an LC tank circuit, and / or an LC tank, and the voltage 316 measured at the LC node 310 of the resonant circuit 306 is also referred to as the tank voltage.

[0019] The wireless transmitter 300 can be used by a charging device to determine whether a compatible device has been placed on the surface of the charging device. For example, the charging device may determine that a compatible device has been placed on the surface of the charging device by transmitting an intermittent test signal (active ping) via the wireless transmitter 300, where the resonant circuit 306 can receive an encoded signal if the compatible device responds to the test signal. The charging device may be configured to activate one or more coils in at least one charging cell upon receiving a response signal specified by a standard, convention, manufacturer, or application. In some examples, a compatible device may respond to the ping by communicating the received signal strength so that the charging device can find the optimal charging cell to use for charging the compatible device.

[0020] Passive ping technology can use voltages and / or currents measured or observed at the LC node 310 to identify the presence of a receiving coil adjacent to the charging pad of a device adapted according to a specific embodiment disclosed herein. Many conventional wireless charger transmitters include circuits to measure voltages at the LC node 310 and currents in the network. These voltages and currents may be monitored for power regulation purposes and / or to support communication between devices. In the example shown in Figure 3, the voltage at the LC node 310 is monitored, but it is intended that currents may be monitored additionally or alternatively to support passive ping. The response of the resonant circuit 306 to passive ping (initial voltage V0) is the voltage (V) at the LC node 310. LC ) can be expressed as follows: (Formula 1) TIFF2023528458000002.tif10170

[0021] According to certain embodiments disclosed herein, coils in one or more charging cells can be selectively activated to provide an optimal electromagnetic field for charging a compatible device. In some embodiments, coils are assigned to charging cells, and some charging cells may overlap with others. In the latter case, an optimal charging configuration can be selected on a per-charging-cell basis. In other embodiments, the charging cells may be defined based on the placement of the device to be charged on the surface of the charging device. In such other embodiments, the combination of coils activated in each charging event may differ. In some implementation examples, the charging device may include a driver circuit that can select one or more cells and / or one or more predetermined charging cells to be activated during a charging event.

[0022] Phase-modulated charging One aspect of this disclosure relates to the use of a phase-modulated wireless charger 400, an example of which is shown in Figure 4. The driver circuit 402 includes a capacitor (C p ) and inductor (L pA charging current 410 is supplied to the resonant circuit 404 which includes ). The charging current 410 may lose some of the AC current 410 due to parasitic capacitance etc., but the current of the inductor (i.e., L p The charging current 410 may be substantially the same as the current. The charging current 410 alternates at a frequency that precisely matches the resonant frequency of the resonant circuit 404, thereby improving power transmission efficiency. According to certain aspects of this disclosure, the level of power transmitted to the powered device via the resonant circuit 404 can be controlled by phase modulation of the charging current 410.

[0023] Timing diagram 420 shows a specific mode of phase modulation applied to the charging current 410 in a particular implementation example. Phase modulation allows for fine control of the power supply level by the driver circuit 402. Timing diagram 420 shows three charging periods 422, 424, and 426 in which power is supplied at different levels, as indicated by the changing amplitude of the charging current 410.

[0024] Phase control is achieved using a zero-cross detector 406 and a phase modulator 408 that responds to a phase control signal 418 provided by a controller or other processor. The zero-cross detector 406 is used to provide timing information used by the phase modulator 408. In one example, the zero-cross detector 406 compares the polarity of a measurement signal 412 representing the current flowing through the resonant circuit 404 with the polarity of a delayed version of the measurement signal 412, thereby detecting the difference in polarity when a zero-cross occurs in the measurement signal 412. The zero-cross detector 406 provides a zero-cross signal 414 (ZC) containing timing information that identifies the zero-cross of the measurement signal 412. In one example, the zero-cross signal 414 includes an edge for each zero-cross of the measurement signal 412. The transition direction of the edge may indicate a positive or negative zero-cross. In another example, the zero-cross signal 414 includes a pulse for each zero-cross of the measurement signal 412.

[0025] The phase modulator 408 uses the zero-crossing signal 414 to generate a phase-modulated signal 416. The phase-modulated signal 416 can change the phase of the modulated current that contributes to the charging current 410. The phase of the modulated current relative to the phase of the current in the resonant circuit can cause an increase or decrease in the charging current 410. In the first charging period 422, the phase-modulated signal 416 is strictly synchronized with the zero-crossing signal 414, and the effect of the modulated current is additive over each period of the charging current 410. In this example, the driver circuit 402 delivers maximum power through the resonant circuit 404. In the second charging period 424, the phase-modulated signal 416 has a phase shift of 90° relative to the zero-crossing signal 414, and the effect of the modulated current alternates between addition and subtraction over a quarter period. In this example, the driver circuit 402 delivers 50% of the maximum available power through the resonant circuit 404. During the third charging period 426, the phase-modulated signal 416 has a phase shift that increases from 90° to 180° relative to the zero-crossing signal 414 in the last drawn period 428. The effect of the modulated current is negative over the increasing portion of each period of the charging current 410, and the driver circuit 402 provides power that decreases from 50% of the maximum available power to no power transfer or minimum power transfer via the resonant circuit 404.

[0026] In a specific implementation example, the zero-crossing signal 414 is provided as a digital signal that provides the timing required by the phase modulator 408 to add a phase lead or phase lag to the input zero-crossing signal when indicated by the phase control signal 418. In one example, the driver circuit 402 includes a half-bridge circuit. In one example, the phase control signal 418 is the amount of power flowing through the resonant circuit 404 (i.e., L pと and C p This is a multi-bit digital signal that indicates the amount of phase shift to be applied to the zero-crossing signal 414 in order to directly affect it.

[0027] Resonant pulse width modulation FIG. 5 shows an example of a PWM charger 500, and timing diagrams 600, 620 of FIG. 6 illustrate certain aspects of the operation of the PWM charger 500. One aspect of the present disclosure relates to the use of a pulse width modulation (PWM) charging system for modulating a charging current 510 supplied to a resonant circuit 504. A driver circuit 502 supplies the charging current 510 to a resonant circuit 504 including a capacitor (C p ) and an inductor (L p ). Although a part of the alternating current 510 may be lost due to parasitic capacitance or the like, the charging current 510 can be substantially the same as the current of the inductor (i.e., the L p current). The charging current 510 alternately changes at a frequency that exactly matches the resonant frequency of the resonant circuit 504, improving the power transmission efficiency. According to a particular aspect of the present disclosure, the level of power transmitted to a power receiving device via the resonant circuit 504 can be controlled by PWM modulation that changes the charging current 510.

[0028] Timing diagrams 600, 620 show certain aspects of PWM applied to the charging current 510 in a particular implementation example. Timing diagrams 600, 620 show a limited number of charging periods 602, 604, 606, 622, 624, 626 during which power is supplied at different levels, as indicated by the changing amplitude of the charging current 510, but allow for fine control of the level of power supply by the driver circuit 502 by PWM.

[0029] The power supplied by the charging current 510 can be controlled using a zero-cross detector 506 and a PWM circuit 508 that responds to a control signal 518 provided by a controller or other processor. The zero-cross detector 506 is used to provide timing information used by the PWM circuit 508. In one example, the zero-cross detector 506 can detect the difference in polarity when a zero-cross occurs in the measurement signal 512 by comparing the polarity of a measurement signal 512 representing the current flowing through the resonant circuit 504 with the polarity of a delayed version of the measurement signal 512. The zero-cross detector 506 provides a zero-cross signal 514 (ZC) containing timing information that identifies the zero-cross of the measurement signal 512. In one example, the zero-cross signal 514 includes an edge for each zero-cross of the measurement signal 512. The direction of the edge transition may indicate a positive or negative zero-cross. In another example, the zero-cross signal 514 includes a pulse for each zero-cross of the measurement signal 512.

[0030] The PWM circuit 508 generates a PWM signal 516 using a zero-crossing signal 514. The PWM signal 516 can control the energy contribution to the charging current 510. In one embodiment, a pulse of the PWM signal 516 is used to gate the current supplied to a power inverter circuit that generates an AC output used to provide the charging current 510.

[0031] In the first charging periods 602, 622, the PWM signal 516 includes pulses that match the duration of half a cycle of the charging current 510, providing a charging current 510 with maximum (100%) power. In this example, the driver circuit 502 performs maximum power transfer via the resonant circuit 504. In the second charging periods 604, 624, the PWM signal 516 includes pulses that have a duration of approximately half a cycle of the charging current 510, resulting in a charging current 510 that provides 50% of the maximum available power when supplied to the resonant circuit 504. In the third charging periods 606, 626, the PWM signal 516 includes decreasing pulses that initially have a duration of approximately half a cycle of the charging current 510, decreasing to a state with almost no pulses. The driver circuit 502 provides power via the resonant circuit 504 that decreases from 50% of the maximum available power to no power transfer or minimum power transfer.

[0032] The pulse timing of the PWM signal 516 can be selected based on the method of generating the charging current 510 used in the driver circuit 502. In the first timing example shown by Figure 600 in Figure 6, each pulse starts at a zero crossing and has a duration that can be determined by the amplitude control signal 518. The amplitude control signal 518 may be provided as a multi-bit digital signal that configures a programmable delay circuit or selects the output of a delay line to provide a delay that determines the pulse duration of the amplitude control signal 518.

[0033] In the example shown in the second timing diagram 620 of Figure 6, each pulse of the PWM signal 516 is centered at the midpoint of the corresponding pulse of the zero-crossing signal 514. That is, the center of each pulse lies midway between the zero-crossings of the measurement signal 512. The duration of these pulses can be determined by the amplitude control signal 518. The amplitude control signal 518 can be provided as a multi-bit digital signal, either by configuring a programmable delay circuit or by selecting the output of a delay line to provide a delay that determines the pulse duration of the amplitude control signal 518. The pulse positions can be set using counters, delay lines, lookup tables, and / or other circuits. Centering the pulses of the PWM signal 516 between the zero-crossings of the measurement signal 512 can reduce the distortion of the AC signal of the charging current 510.

[0034] In some implementations, resonant pulse width modulation can use detected zero-crossings as a time reference for initiating the PWM drive cycle. In one example, a timer can be started to control the pulse width. In another example, a delay circuit can be used to control the pulse width. The charging current 510 flowing through the resonant circuit 504 is controlled by the pulse width.

[0035] In some implementations, PWM may be used to control the charging current 510 flowing through the resonant circuit 504 without zero-crossing synchronization. For example, L p Ya C p If other information, such as the value of , is known, the current measurement circuit and the zero-crossing detector 506 may not be necessary.

[0036] Resonant Class D Wireless Transmitter Figure 7 shows an example of a wireless charging system 700 employing a Class D wireless transmitter 702 provided in a particular embodiment disclosed herein. Timing diagram 800 in Figure 8 shows a particular embodiment of the operation of the Class D wireless transmitter 702. The Class D wireless transmitter 702 includes a Class D amplifier that operates as a switching amplifier. The Class D wireless transmitter 702 generates a first signal that switches between voltage rails at a first frequency. The first signal is modulated with a second low-frequency signal. In the illustrated example, the first signal is pulse-width modulated to obtain a PWM signal 718.

[0037] The PWM signal 718 is supplied to the driver circuit 704, which then receives a capacitor (C). p ) and inductor (L p A charging current is generated to drive the resonant circuit 706 which includes an LC tank having ). The charging current is the current in the inductor (i.e., L p The current (802) may be substantially the same. The resonant circuit 706 acts as a low-pass filter, converting the high-frequency PWM signal 718 to obtain an amplified version of the modulated signal, which may be a sine wave. The PWM controller 710 uses cumulative scaling to control the power transmitted to the wireless receiver 730. p It can be operated to control the peak amplitude of current 802. For example, a wide pulse of the PWM signal 718 is L p This can correspond to the peak amplitude of current 802.

[0038] The power supplied by the driver circuit 704 can be controlled using a zero-cross detector 708 and a PWM controller 710, which may respond to a control signal 720 provided by the controller or other processor. The PWM controller 710 receives a sinusoidal signal from a reference source 712 that provides a PWM modulated carrier signal. The zero-cross detector 708 is used to provide timing information for use by the PWM circuit 710. In one example, the zero-cross detector 708 can detect the difference in polarity when a zero-cross occurs in the measurement signal 714 by comparing the polarity of a measurement signal 714 representing the current flowing through the resonant circuit 706 with the polarity of a delayed version of the measurement signal 714. The zero-cross detector 708 provides a zero-cross signal 716 (ZCS) containing timing information that identifies the zero-cross of the measurement signal 714. In one example, the zero-cross signal 716 includes an edge for each zero-cross of the measurement signal 714. The transition direction of the edge may indicate a positive zero-cross or a negative zero-cross. In another example, the zero-crossing signal 716 contains a pulse for each zero-crossing of the measurement signal 714. The PWM controller 710 can use the zero-crossing signal 716 to generate a PWM signal 718, in which case the PWM signal 718 is L p The current 802 is in phase with the current 802.

[0039] Zero-cross slot type foreign object detection Slot-type foreign object detection can be used to detect foreign objects (FO) on the surface of a wireless charger. The driver circuit of the wireless charger is periodically switched off for short periods called slots, during which time the energy of the resonant circuit driven by the driver circuit is attenuated. The Q factor of the resonant circuit can be determined by measuring this attenuation rate. To accurately measure the AC waveform of the tank circuit without generating aliasing or artifacts that impair the accuracy of the Q factor measurement, a high sample rate is generally required. The sample rate can be 10 to 20 times the frequency of the resonant circuit current, and generally requires the use of a high-speed, expensive analog-to-digital converter (ADC).

[0040] In certain aspects of this disclosure, a zero-crossing detector is used to provide timing information in a slot provided for foreign object detection, enabling a low-cost ADC to reliably obtain accurate measurements of the voltage at the same point in each period of the AC waveform in a resonant circuit. The zero-crossing slot type foreign object detection can be used to detect zero-crossings of voltage and / or current in a resonant circuit. When a zero-crossing is detected, a hold-off timer starts, triggering the sample-and-hold circuit of the ADC. As an example, the hold-off timer triggers the sample-and-hold circuit after 1 / 4 of a period of the AC waveform in the resonant circuit. In this example, the ADC reads the sample taken at the peak of the AC wave. A sampling frequency lower than the fundamental frequency of the AC waveform can be used.

[0041] Figure 9 includes timing diagrams 900, 920 illustrating specific embodiments of zero-crossing, slot-type foreign object detection. Measurement slots 906, 926 are provided during normal charging operation periods 904, 908 or 924, 928. The first timing diagram 900 relates to an embodiment of a signal 902 representing energy, voltage, or current in a resonant circuit when no foreign object is present, where the slow decay 912 in the signal 902 corresponds to a resonant circuit with a high Q factor. The second timing diagram 920 relates to an embodiment of a signal 922 representing energy, voltage, or current in a resonant circuit when a foreign object 1030 (see Figure 10) is present, where the decay 932 corresponds to a resonant circuit with a low Q factor. The zero-crossing, slot-type foreign object detection technique according to specific embodiments of the present disclosure uses sample points 914, 934 identified based on detected zero-crossings identified by zero-crossing signals 910, 930.

[0042] Figure 10 shows an example of a wireless charging system 1000 that employs zero-cross detection to obtain measurement values ​​1028 at one or more points in each period of current or voltage in a resonant circuit 1004. As an example, the measurement values ​​may be used for slot-type foreign object detection according to certain embodiments disclosed herein. The wireless charging system 1000 uses a capacitor (C p) and inductor (L p The system includes a driver circuit 1002 that generates a charging current to drive a resonant circuit 1004 which includes an LC tank circuit having ). The charging current may be substantially the same as the current in the inductor. In some implementations, a voltage measurement signal 1006 representing the voltage across the resonant circuit 1004 is supplied to a first zero-crossing detector 1012. The first zero-crossing detector 1012 generates a zero voltage signal (ZVS1016) as an output indicating the timing of the zero-crossing of the voltage across the resonant circuit 1004. In some implementations, a current measurement signal 1008 representing the current across the resonant circuit 1004 is supplied to a second zero-crossing detector 1014. The second zero-crossing detector 1014 generates a zero current signal (ZCS1018) as an output indicating the timing of the zero-crossing of the current across the resonant circuit 1004.

[0043] A capture timing circuit 1020 may be used to track zero crossings and determine or control the sample-and-hold circuit 1024. In one example, the capture timing circuit 1020 may include or utilize a hold-off timer 1022 that can pinpoint the peak amplitude of voltage or current across the resonant circuit 1004 that occurs after a period corresponding to half a cycle of the resonant circuit 1004. In another example, the capture timing circuit 1020 may include or utilize a hold-off timer 1022 that can pinpoint one or more points of voltage or current across the resonant circuit 1004. The sample-and-hold circuit 1024 provides an output digitized by the ADC 1026 to obtain measurement values ​​1028. The measurement values ​​1028 can be used to track the rate of energy decay of the resonant circuit 1004.

[0044] Zero-crossing amplitude shift modulation demodulation Measurements obtained using the zero-cross detection technique illustrated in Figure 10 can be used for ASK (Amplitude Shift Keying) demodulation. ASK modulation is commonly used to transmit messages defined by the Qi protocol, which is used to wirelessly interconnect power transmitters and power receivers. The Qi protocol allows the receiving side to wirelessly control the transmitting side. Measurements 1028 obtained at one or more points in each period of current or voltage in the resonant circuit 1004 can be used for ASK demodulation. One or more zero-cross detectors 1012, 1014 provide reference timing for sampling the voltage or current associated with the resonant circuit 1004. The sampled data can be used to extract ASK data modulated to the carrier power signal in the receiving device.

[0045] Even signals with frequencies much higher than the sampling frequency can be extracted by timing the sampling using zero-cross detection. In some embodiments, sampling can be performed at the fundamental frequency of the current or voltage associated with the resonant circuit 1004, or at twice the frequency of the current or voltage associated with the resonant circuit 1004. Conventional sampling circuits operate at 10 times or more the fundamental frequency of the current or voltage associated with the resonant circuit 1004 to avoid aliasing and other distortion artifacts.

[0046] In one example, ASK demodulation is performed using a measured voltage captured with timing provided by ZVS1016 output by the first zero-cross detector 1012 to time the trigger of the sample-and-hold circuit 1024. In another example, ASK demodulation is performed using a measured current captured with timing provided by ZCS1018 output by the second zero-cross detector 1014 to time the trigger of the sample-and-hold circuit 1024. ASK demodulation can be performed using a single sample acquired at the peak of the voltage or current period. Zero-cross ASK demodulation can reject communication channels in the same domain if the phase and / or frequency of the interfering carrier differs from that of the target carrier.

[0047] Figures 11 and 12 illustrate specific embodiments of a wireless charging system 1200 that utilize zero-cross detection to support phase-based ASK demodulation. Referring to the timing diagram 1100 in Figure 11, zero-cross phase demodulation involves detecting the phase difference between the zero-volt cross of voltage 1108 and current 1106 in the resonant circuit 1204. The phase shift between voltage 1108 and current 1106 may correspond to different modulation levels 1102 when the powered device 1206 encodes data by load or resonant shift using ASK modulation. A digital phase detector 1212 can identify the phase difference between the current zero-cross signal (ZCS 1220) and the voltage zero-cross signal (ZVS 1222) provided by the corresponding zero-cross detector circuits 1208, 1210, respectively. The phase difference can be measured at one or more points in each period of the current or voltage in the resonant circuit 1204. The wireless charging system 1200 includes a driver circuit 1202 that generates a charging current 1104 to drive a resonant circuit 1204, which is a capacitor (C p ) and inductor (L p) includes. The charging current 1104 may be substantially the same as the current in the inductor. In some implementations, a voltage measurement signal 1218 representing the voltage across the resonant circuit 1204 is supplied to a first zero-crossing detector 1210. The first zero-crossing detector 1210 generates a zero-crossing signal 1220 with an output indicating the timing of the zero-crossing of the voltage across the resonant circuit 1204. A current measurement signal 1216 representing the current in the resonant circuit 1204 is supplied to a second zero-crossing detector 1208. The second zero-crossing detector 1208 generates a zero-crossing signal 1220 with an output indicating the timing of the zero-crossing of the voltage in the resonant circuit 1204.

[0048] The phase detection circuit 1212 supplies a signal indicating the phase difference between ZCS1220 and ZVS1222 to the ASK demodulator 1214.

[0049] Example of a processing circuit Figure 13 shows an example of a hardware implementation of device 1300, which can be incorporated into a charging or receiving device that enables wireless charging of a battery. In some examples, device 1300 can perform one or more of the functions disclosed herein. According to various aspects of this disclosure, elements, any part of elements, or any combination of elements disclosed herein can be implemented using a processing circuit 1302. The processing circuit 1302 may include one or more processors 1304 controlled by some combination of hardware modules and software modules. Examples of processors 1304 include microprocessors, microcontrollers, digital signal processors (DSPs), SoCs, ASICs, field-programmable gate arrays (FPGAs), programmable logic devices (PLDs), state machines, sequencers, gate logic, discrete hardware circuits, and other suitable hardware configured to perform the various functions described throughout this disclosure. One or more processors 1304 may include dedicated processors that perform specific functions and may be configured, augmented, or controlled by one of the software modules 1316. One or more processors 1304 may be configured through a combination of software modules 1316 that are loaded during initialization, and may be further configured by loading or unloading one or more software modules 1316 during operation.

[0050] In the illustrated example, the processing circuit 1302 may be implemented in a bus architecture generally represented by bus 1310. Bus 1310 may include any number of interconnection buses and bridges depending on the specific application and overall design constraints of the processing circuit 1302. Bus 1310 links various circuits, including one or more processors 1304 and storage 1306. Storage 1306 may include memory devices and mass storage devices, also referred herein as computer-readable media and / or processor-readable media. Storage 1306 may include temporary storage media and / or non-temporary storage media.

[0051] Bus 1310 may link various other circuits, such as timing sources, timers, peripherals, voltage regulators, and power management circuits. Bus interface 1308 can provide an interface between bus 1310 and one or more transceivers 1312. For example, transceivers 1312 may be provided to enable device 1300 to communicate with a charging device or powered device according to a standard protocol. Depending on the nature of device 1300, a user interface 1318 (e.g., keypad, display, speaker, microphone, joystick) may also be provided and can be connected to bus 1310 directly or via bus interface 1308 for communication.

[0052] The processor 1304 can be responsible for managing the bus 1310 and for overall processing, including the execution of software stored on a computer-readable medium, including the storage 1306. In this regard, the processing circuit 1302, including the processor 1304, can be used to implement any of the methods, functions, and techniques disclosed herein. The storage 1306 can be used to store data manipulated by the processor 1304 when the software is executed, and the software can be configured to perform any one of the methods disclosed herein.

[0053] One or more processors 1304 of the processing circuit 1302 can execute software. Software is broadly interpreted to mean instructions, instruction sets, code, code segments, program code, programs, subprograms, software modules, applications, software applications, software packages, routines, subroutines, objects, executable files, execution threads, procedures, functions, algorithms, etc., regardless of whether they are called software, firmware, middleware, microcode, or hardware description languages. The software may reside in storage 1306 in a computer-readable format or on external computer-readable media. External computer-readable media and / or storage 1306 may include non-temporary computer-readable media. Non-temporary computer-readable media may include, for example, magnetic storage devices (e.g., hard disks, floppy disks, magnetic strips), optical discs (e.g., compact discs (CDs), digital multipurpose discs (DVDs)), smart cards, flash memory devices (e.g., "flash drives", cards, sticks, key drives), RAM, ROM, programmable read-only memory (PROM), erasable PROM (EPROM) including EEPROM, registers, removable disks, and any other suitable media for storing software and / or instructions that a computer can access and read. The computer-readable media and / or storage 1306 may also include, for example, carrier waves, transmission lines, and any other suitable media for transmitting software and / or instructions that a computer can access and read. The computer-readable media and / or storage 1306 may reside in the processing circuit 1302, reside in the processor 1304, be outside the processing circuit 1302, or be distributed across multiple entities including the processing circuit 1302. The computer-readable medium and / or storage 1306 may be embodied in a computer program product.As an example, a computer program product may include computer-readable media within the packaging material. Those skilled in the art will recognize the best way to implement the functions described throughout this disclosure, depending on the specific application and the overall design constraints imposed on the entire system.

[0054] Storage 1306 can maintain and / or organize software such as loadable code segments, modules, applications, and programs, also referred to herein as software modules 1316. Each software module 1316 may contain instructions and data that, when installed or loaded into processing circuit 1302 and executed by one or more processors 1304, contribute to a runtime image 1314 that controls the operation of one or more processors 1304. Certain instructions, when executed, can cause processing circuit 1302 to perform functions according to specific methods, algorithms, and processes described herein.

[0055] Some of the software modules 1316 may be loaded during the initialization of the processing circuit 1302, and these software modules 1316 can configure the processing circuit 1302 to enable the execution of various functions disclosed herein. For example, some software modules 1316 can configure internal devices and / or logic circuits 1322 of the processor 1304 and manage access to external devices such as transceivers 1312, bus interfaces 1308, user interfaces 1318, timers, and numerical coprocessors. The software modules 1316 may include control programs and / or operating systems that interact with interrupt handlers and device drivers and control access to various resources provided by the processing circuit 1302. Resources may include memory, processing time, access to transceivers 1312, user interfaces 1318, and so on.

[0056] One or more processors 1304 of the processing circuit 1302 are multifunctional, thereby loading several software modules 1316 and configuring them to execute different functions or different instances of the same function. Furthermore, one or more processors 1304 may be adapted to manage background tasks initiated in response to inputs from, for example, the user interface 1318, the transceiver 1312, and device drivers. To support the execution of multiple functions, one or more processors 1304 may be configured to provide a multitasking environment, thereby implementing each of the multiple functions as a set of tasks provided by one or more processors 1304 as needed. In one example, the multitasking environment may be implemented using a time-sharing program 1320 that passes control of the processor 1304 between different tasks, thereby returning control of one or more processors 1304 to the time-sharing program 1320 upon completion of any outstanding operations and / or in response to an input such as an interrupt. When a task has control of one or more processors 1304, the processing circuit is effectively specialized for the purposes addressed by the functions associated with the controlled task. The time-sharing program 1320 may include an operating system, a main loop that transfers control in a round-robin manner, a function that assigns control of one or more processors 1304 according to function priority, and / or an interrupt-operated main loop that responds to external events by providing control of one or more processors 1304 to processing functions.

[0057] In one embodiment, the device 1300 includes or operates as a wireless charging device having a battery charging power supply coupled to a charging circuit, a plurality of charging cells, and a controller which may be included in one or more processors 1304. The plurality of charging cells may be configured to provide a charging surface. At least one transmission coil may be configured to guide an electromagnetic field through the charge transmission region of each charging cell. The device 1300 may include a resonant circuit including the transmission coil, a driver circuit configured to supply a charging current to the resonant circuit, and a zero-crossing detector configured to provide a zero-crossing signal including an edge corresponding to a voltage transition measured across the resonant circuit through a zero-volt level, or an edge corresponding to a current transition in the resonant circuit through a zero-ampere level. The controller may be configured to control the power level to which the driver circuit supplies a charging current to the resonant circuit and phase-matches the charging current to a phase-modulated signal generated from the zero-crossing signal for wireless transmission to the powered device when a powered device is present on the surface of the charging device.

[0058] In various examples, the zero-volt level corresponds to a current amplitude midway between the maximum and minimum amplitudes of the AC measured in the resonant circuit. The zero-volt level may also correspond to a voltage level midway between the maximum and minimum amplitudes of the AC voltage measured across the resonant circuit. In one example, the controller is further configured to receive a control signal indicating a desired power level to be wirelessly transmitted to a powered device and to construct a phase-modulated signal to obtain the desired power level.

[0059] In a specific example, the controller is further configured to receive a control signal indicating a phase shift to be applied to the charging current, and to apply the phase shift to the zero-crossing signal to obtain a phase-modulated signal. If no phase shift is applied to the charging current, the maximum level of power may be transmitted to the powered device. If a 180° phase shift is applied to the charging current, the minimum level of power may be transmitted to the powered device.

[0060] In some implementations, storage 1306 holds instructions and information, which instruct one or more processors 1304 to supply a charging current to a resonant circuit when a powered device is on the surface of a charger, to provide a zero-crossing signal that includes edges corresponding to voltage transitions measured across the resonant circuit through zero volt levels or current transitions within the resonant circuit through zero ampere levels, and to control the power level wirelessly transmitted to the powered device by phase matching the charging current to a phase-modulated signal generated from the zero-crossing signal.

[0061] In one example, the zero-volt level corresponds to a current amplitude midway between the maximum and minimum amplitudes of the AC current measured across the resonant circuit. In another example, the zero-volt level could correspond to a voltage level midway between the maximum and minimum amplitudes of the AC voltage measured across the resonant circuit.

[0062] In a specific implementation example, the instruction may be configured to cause one or more processors 1304 to receive or provide a control signal indicating a desired level of power to be wirelessly transmitted to a powered device, and to configure a phase-modulated signal to obtain the desired level of power. The instruction is configured to cause one or more processors 1304 to receive or provide a control signal indicating a phase shift to be applied to the charging current, and to apply the phase shift to the zero-crossing signal to obtain a phase-modulated signal. In one example, if no phase shift is applied to the charging current, the maximum level of power is transmitted to the powered device. In another example, if a 180° phase shift is applied to the charging current, the minimum level of power is transmitted to the powered device.

[0063] Figure 14 is a flowchart 1400 illustrating a method of operating a charging device according to a particular aspect of the present disclosure. This method can be performed by a controller within the charging device. In block 1402, the controller can supply a charging current to a resonant circuit when the powered device is located on the surface of the charging device. In block 1404, the controller can provide a zero-crossing signal that includes an edge corresponding to a voltage transition measured across the resonant circuit through a zero-volt level, or a current transition within the resonant circuit through a zero-ampere level. In block 1406, the controller can control the level of power wirelessly transmitted to the powered device by phase-matching the charging current to a phase-modulated signal generated from the zero-crossing signal.

[0064] In one example, the zero-volt level corresponds to the current amplitude midway between the maximum and minimum amplitudes of the AC current measured across the resonant circuit. In another example, the zero-volt level corresponds to the voltage level midway between the maximum and minimum amplitudes of the AC voltage measured across the resonant circuit.

[0065] In certain implementations, the controller may be configured to receive a control signal indicating a desired power level to be wirelessly transmitted to the powered device, and to construct a phase-modulated signal to obtain the desired power level. The controller may also be configured to receive a control signal indicating a phase shift to be applied to the charging current, and to apply the phase shift to the zero-crossing signal to obtain a phase-modulated signal. In one example, if no phase shift is applied to the charging current, the maximum level of power is transmitted to the powered device. In another example, if a 180° phase shift is applied to the charging current, the minimum level of power is transmitted to the powered device.

[0066] The above-mentioned descriptions are provided to enable a person skilled in the art to carry out the various embodiments described herein. Various modifications to these embodiments will be obvious to a person skilled in the art, and the general principles set forth herein can be applied to other embodiments. For this reason, the claims are not intended to be limited to the embodiments shown herein, but the entire scope consistent with the language of the claims is recognized, and references to singular elements mean "one or more" and not "only" unless otherwise specified. Unless otherwise specified, the term "several" means one or more. All structural and functional equivalents to elements of the various embodiments described throughout this disclosure, known to a person skilled in the art, or to become known to a person skilled in the art, are expressly incorporated herein by reference and are intended to be included in the claims. Furthermore, nothing disclosed herein is intended to be made available to the public, whether such disclosure is expressly contained in the claims or not. No element of a claim should be construed under the provisions of 35 U.S. SC § 112, Chapter 6 unless that element is expressly contained in the phrase "means for" or, in the case of a method claim, in the phrase "step for".

Claims

1. A method of operating a wireless charging device, comprising: providing a charging current to a resonant circuit when a power receiving device is present on a surface of the wireless charging apparatus; providing a zero crossing signal including edges corresponding to transitions of a voltage measured across the resonant circuit through a zero volt level or a current in the resonant circuit through a zero ampere level; and controlling the level of power wirelessly transmitted to the power receiving device by phase-matching a charging current to a phase-modulated signal generated from a zero-crossing signal.

2. 2. The method of claim 1, wherein the zero volt level corresponds to a current amplitude midway between a maximum and minimum amplitude of an alternating current (AC) measured in the resonant circuit.

3. 2. The method of claim 1, wherein the zero volt level corresponds to a voltage level midway between a maximum and minimum amplitude of an AC voltage measured across the resonant circuit.

4. further receiving a control signal indicating a desired power level to be wirelessly transmitted to the power receiving device; 2. The method of claim 1, further comprising configuring the phase modulated signal to obtain the desired power level.

5. further comprising receiving a control signal indicative of a phase shift to apply to the charging current; 2. The method of claim 1, further comprising applying a phase shift to the zero-crossing signal to obtain the phase-modulated signal.

6. The method of claim 5 , wherein a maximum level of power is transferred to the powered device when no phase shift is applied to the charging current.

7. The method of claim 5 , wherein a minimum level of power is transferred to the powered device when a 180° phase shift is applied to the charging current.

8. A charging device, a resonant circuit including a transmission coil; a driver circuit configured to provide a charging current to the resonant circuit; a zero crossing detector configured to provide a zero crossing signal including edges corresponding to transitions of a voltage measured across the resonant circuit through a zero volt level or a current in the resonant circuit through a zero ampere level; a controller, causing the driver circuit to supply a charging current to the resonant circuit when a power receiving device is present on a surface of the charging apparatus; and a controller that controls the level of power wirelessly transmitted to the power receiving device by phase-matching a charging current to a phase-modulated signal generated from the zero-cross signal.

9. 9. The charging device of claim 8, wherein the zero volt level corresponds to a current amplitude midway between a maximum and minimum amplitude of an alternating current (AC) measured in the resonant circuit.

10. 9. The charging device of claim 8, wherein the zero volt level corresponds to a voltage level midway between a maximum and minimum amplitude of the AC voltage measured across the resonant circuit.

11. The controller further comprises: receiving a control signal indicating a desired level of power to be wirelessly transmitted to the power receiving device; 9. The charging device of claim 8, configured to configure the phase modulated signal to obtain the desired power level.

12. The controller further comprises: receiving a control signal indicative of a phase shift to be applied to the charging current; The charging device according to claim 8 , configured to perform a phase shift on the zero-crossing signal to obtain the phase-modulated signal.

13. 13. The charging apparatus of claim 12, wherein a maximum level of power is transferred to the powered device when no phase shift is applied to the charging current.

14. 13. The charging apparatus of claim 12, wherein a minimum level of power is transferred to the powered device when a 180° phase shift is applied to the charging current.

15. 1. A processor-readable storage medium having stored instructions that, when executed by at least one processor of a processing circuit, cause the processing circuit to: providing a charging current to the resonant circuit when the power receiving device is present on a surface of the wireless charging apparatus; providing a zero crossing signal including edges corresponding to transitions of a voltage measured across the resonant circuit through a zero volt level or a current in the resonant circuit through a zero ampere level; and controlling a level of power wirelessly transmitted to the power receiving device by phase-matching a charging current to a phase-modulated signal generated from the zero-crossing signal.

16. 16. The processor-readable storage medium of claim 15, wherein the zero volt level corresponds to a current amplitude midway between a maximum and minimum amplitude of an alternating current (AC) measured in the resonant circuit.

17. 16. The processor-readable storage medium of claim 15, wherein the zero volt level corresponds to a voltage level midway between a maximum and minimum amplitude of an AC voltage measured across the resonant circuit.

18. The instructions further cause the processing circuit to: receiving a control signal indicating a desired level of power to be wirelessly transmitted to the power receiving device; and configuring the phase modulated signal to obtain the desired power level.

19. The instructions further cause the processing circuit to: receiving a control signal indicative of a phase shift to be applied to the charging current; and performing a phase shift on the zero-crossing signal to obtain the phase-modulated signal.

20. 20. The processor-readable storage medium of claim 19, wherein a maximum level of power is transferred to the powered device when no phase shift is applied to the charging current, and a minimum level of power is transferred to the powered device when a 180° phase shift is applied to the charging current.

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