Patent Description:
Wireless charging systems have been deployed to enable certain types of devices to charge internal batteries without the use of a physical charging connection. Devices that can take advantage of wireless charging include mobile processing and/or communication devices. Standards, such as the Qi standard defined by the Wireless Power Consortium enable devices manufactured by a first supplier to be wirelessly charged using a charger manufactured by a second supplier. Standards for wireless charging are optimized for relatively simple configurations of devices and tend to provide basic charging capabilities.

Conventional wireless charging systems typically use a "Ping" to determine if a receiving device is present on or proximate to a transmitting coil in a base station for wireless charging. The transmitter coil has an inductance (L) and, a resonant capacitor that has a capacitance (C) is coupled to the transmitting coil to obtain a resonant LC circuit. A Ping is produced by delivering power to the resonant LC circuit. Power is applied for a duration of time (<NUM> in one example) while the transmitter listens for a response from a receiving device. The response may be provided in a signal encoded using Amplitude Shift Key (ASK) modulation. This conventional Ping-based approach can be slow due to the <NUM> duration, and can dissipate large and significant amounts of energy, which may amount to <NUM> mJ per Ping. In one example, a typical transmitting base station may ping as fast as <NUM> times a second (period = <NUM>/<NUM>) with a power consumption of (<NUM> mJ * <NUM>) per second = 1W. In practice most, designs trade off responsiveness for a lower quiescent power draw by lowering the ping rate. As an example, a transmitter may ping <NUM> times a second with a resultant power draw of <NUM> mW.

Tradeoffs are generally possible for base stations that employ a single transmitting coil, because a ping rate of <NUM> times a second is usually sufficient to detect a device within <NUM> second of its placement on a charging pad. However, for a multi-coil free position charging pad, responsiveness and quiescent power draw characteristics may be impaired. For example, <NUM> pings per second would be required to produce <NUM> pings per second on each transmitting coil of a <NUM>-coil, free position charging pad scanning. Given the power limits defined by design specifications, the <NUM>-coil free position charging pad has a response rate that is greater than <NUM> seconds, which is typically unacceptable for user experience and may violate regulatory power standards or power budgets for battery powered designs. <CIT> discloses to determine placement of a device on a plurality of transfer coils by determining a difference of the Q-factor over the plurality of coils and thus guides to another solution. <CIT> discloses method and apparatus to determine a foreign object based on Q- measurement (Fig.<NUM>-<NUM>) via pulses transmitted to the resonance circuit in combination with a filter circuit (Fig. <NUM>). The Q-factor is selected as the maximum value determined out of plural measurements on various frequencies (Fig. <NUM>). A foreign object is detected based on a comparison of the determined Q-factor with a threshold value which is communicated to the foreign substance detection unit (Fig.<NUM>).

Improvements in wireless charging capabilities are required to support continually increasing complexity of mobile devices and changing form factors. For example, there is a need for a faster, lower power detection techniques.

Several aspects of wireless charging systems will now be presented with reference to various apparatus and methods. These apparatus and methods will be described in the following detailed description and illustrated in the accompanying drawing by various blocks, modules, components, circuits, steps, processes, algorithms, etc. (collectively referred to as "elements").

The software may reside on a processor-readable storage medium. A processor-readable storage medium, which may also be referred to herein as a computer-readable medium may include, by way of example, a magnetic storage device (e.g., hard disk, floppy disk, magnetic strip), an optical disk (e.g., compact disk (CD), digital versatile disk (DVD)), a smart card, a flash memory device (e.g., card, stick, key drive), Near Field Communications (NFC) token, random access memory (RAM), read only memory (ROM), programmable ROM (PROM), erasable PROM (EPROM), electrically erasable PROM (EEPROM), a register, a removable disk, a carrier wave, a transmission line, and any other suitable medium for storing or transmitting software. The computer-readable medium may be resident in the processing system, external to the processing system, or distributed across multiple entities including the processing system. Computer-readable medium may be embodied in a computer-program product. By way of example, a computer-program product may include a computer-readable medium in packaging materials. Those skilled in the art will recognize how best to implement the described functionality presented throughout this disclosure depending on the particular application and the overall design constraints imposed on the overall system.

Certain aspects of the present disclosure relate to a method of detecting an object and a charging device as set out in the appended set of claims. Charging cells may be configured with one or more inductive coils to provide a charging surface that can charge one or more devices wirelessly. The location of a device to be charged may be detected through sensing techniques that associate location of a device to changes in a physical characteristic centered at a known location on the charging surface. Sensing of location may be implemented using capacitive, resistive, inductive, touch, pressure, load, strain, and/or another appropriate type of sensing.

One aspect of the present disclosure relates to systems, apparatus and methods that enable fast, low-power detection of objects placed in proximity to a charging surface. In one example, an object may be detected when a pulse provided to a charging circuit stimulates an oscillation in the charging circuit, or in some portion thereof. A frequency of oscillation of the charging circuit responsive to the pulse or a rate of decay of the oscillation of the charging circuit may be indicative or determinative of presence of a chargeable device has been placed in proximity to a coil of the charging circuit. Identification of a type or nature of the object may be made based on changes in a characteristic of the charging circuit. The pulse provided to the charging circuit may have a duration that is less than half the period of a nominal resonant frequency of the charging circuit.

In one aspect of the disclosure, an apparatus for detecting objects near a charging surface has a resonant circuit that includes a charging coil attached to the charging surface, a circuit configured to provide a measurement signal representative of the quality factor of the resonant circuit based on a measured response of the resonant circuit to a passive ping, a filter configured to provide a filtered version of the measurement signal that changes at a slower rate than the measurement signal, and comparison logic configured to generate a detection signal that switches when a difference between the measurement signal and the filtered version of the measurement signal exceeds a threshold level. The detection signal may indicate whether an object is positioned proximate to the charging coil.

According to certain aspects disclosed herein, a charging surface may be provided using charging cells that are deployed adjacent to the charging surface. In one example the charging cells are deployed in accordance with a honeycomb packaging configuration. A charging cell may be implemented using one or more coils that can each induce a magnetic field along an axis that is substantially orthogonal to the charging surface adjacent to the coil. In this description, a charging cell may refer to an element having one or more coils where each coil is configured to produce an electromagnetic field that is additive with respect to the fields produced by other coils in the charging cell, and directed along or proximate to a common axis.

In some implementations, a charging cell includes coils that are stacked along a common axis and/or that overlap such that they contribute to an induced magnetic field substantially orthogonal to the charging surface. In some implementations, a charging cell includes coils that are arranged within a defined portion of the charging surface and that contribute to an induced magnetic field within the substantially orthogonal to portion of the charging surface associated with the charging cell. In some implementations, charging cells may be configurable by providing an activating current to coils that are included in a dynamically-defined charging cell. For example, a charging device may include multiple stacks of coils deployed across a charging surface, and the charging device may detect the location of a device to be charged and may select some combination of stacks of coils to provide a charging cell adjacent to the device to be charged. In some instances, a charging cell may include, or be characterized as a single coil. However, it should be appreciated that a charging cell may include multiple stacked coils and/or multiple adjacent coils or stacks of coils.

<FIG> illustrates an example of a charging cell <NUM> that may be deployed and/or configured to provide a charging surface. In this example, the charging cell <NUM> has a substantially hexagonal shape that encloses one or more coils <NUM> constructed using conductors, wires or circuit board traces that can receive a current sufficient to produce an electromagnetic field in a power transfer area <NUM>. In various implementations, some coils <NUM> may have a shape that is substantially polygonal, including the hexagonal charging cell <NUM> illustrated in <FIG>. Other implementations may provide coils <NUM> that have other shapes. The shape of the coils <NUM> may be determined at least in part by the capabilities or limitations of fabrication technology, and/or to optimize layout of the charging cells on a substrate <NUM> such as a printed circuit board substrate. Each coil <NUM> may be implemented using wires, printed circuit board traces and/or other connectors in a spiral configuration. Each charging cell <NUM> may span two or more layers separated by an insulator or substrate <NUM> such that coils <NUM> in different layers are centered around a common axis <NUM>.

<FIG> illustrates an example of an arrangement of charging cells from two perspectives <NUM>, <NUM> when multiple layers are overlaid within a segment of a charging surface that may be adapted in accordance with certain aspects disclosed herein. Layers of charging cells <NUM>, <NUM>, <NUM>, <NUM> provided within a segment of a charging surface. The charging cells within each layer of charging cells <NUM>, <NUM>, <NUM>, <NUM> are arranged according to a honeycomb packaging configuration. In one example, the layers of charging cells <NUM>, <NUM>, <NUM>, <NUM> may be formed on a printed circuit board that has four or more layers. The arrangement of charging cells <NUM> can be selected to provide complete coverage of a designated charging area that is adjacent to the illustrated segment.

In accordance with certain aspects disclosed herein, location sensing may rely on changes in some property of the electrical conductors that form coils in a charging cell. Measurable differences in properties of the electrical conductors may include changes in capacitance, resistance, inductance and/or temperature when an object is placed in proximity to one or more coils. In some examples, placement of an object on the charging surface can affect the measurable resistance, capacitance, inductance of a coil located near the point of placement. In some implementations, circuits may be provided to measure changes in resistance, capacitance, and/or inductance of one or more coils located near the point of placement. In some implementations, sensors may be provided to enable location sensing through detection of changes in touch, pressure, load and/or strain in the charging surface. Conventional techniques used in current wireless charging applications for detecting devices employ "ping" methods that drive the transmitting coil and consume substantial power (e.g., <NUM>-200mW). The field generated by the transmitting coil is used to detect a receiving device.

Wireless charging devices may be adapted in accordance with certain aspects disclosed herein to support a low-power discovery technique that can replace and/or supplement conventional ping transmissions. A conventional ping is produced by driving a resonant LC circuit that includes a transmitting coil of a base station. The base station then waits for an ASK-modulated response from the receiving device. A low-power discovery technique may include utilizing a passive ping to provide fast and/or low-power discovery. According to certain aspects, a passive ping may be produced by driving a network that includes the resonant LC circuit with a fast pulse that includes a small amount of energy. The fast pulse excites the resonant LC circuit and causes the network to oscillate at its natural resonant frequency until the injected energy decays and is dissipated. In one example, the fast pulse may have a duration corresponding to a half cycle of the resonant frequency of the network and/or the resonant LC circuit. When the base station is configured for wireless transmission of power within the frequency range <NUM> to <NUM>, the fast pulse may have a duration that is less than <NUM>.

The passive ping may be characterized and/or configured based on the natural frequency at which the network including the resonant LC circuit rings, and the rate of decay of energy in the network. The ringing frequency of the network and/or resonant LC circuit may be defined as: <MAT>.

The rate of decay is controlled by the quality factor (Q factor) of the oscillator network, as defined by: <MAT>.

Equations <NUM> and <NUM> show that resonant frequency is affected by L and C, while the Q factor is affected by L, C and R. In a base station provided in accordance with certain aspects disclosed herein, the wireless driver has a fixed value of C determined by the selection of the resonant capacitor. The values of L and R are determined by the wireless transmitting coil and by an object or device placed adjacent to the wireless transmitting coil.

The wireless transmitting coil is configured to be magnetically coupled with a receiving coil in a device placed within close proximity of the transmitting coil, and to couple some of its energy into the proximate device to be charged. The L and R values of the transmitter circuit can be affected by the characteristics of the device to be charged, and/or other objects within close proximity of the transmitting coil. As an example, if a piece of ferrous material with a high magnetic permeability placed near the transmitter coils can increase the total inductance (L) of the transmitter coil, resulting in a lower resonant frequency, as shown by Equation <NUM>. Some energy may be lost through heating of materials due to eddy current induction, and these losses may be characterized as an increase the value of R thereby lowering the Q factor, as shown by Equation <NUM>.

A wireless receiver placed in close proximity to the transmitter coil can also affect the Q factor and resonant frequency. The receiver may include a tuned LC network with a high Q which can result in the transmitter coil having a lower Q factor. The resonant frequency of the transmitter coil may be reduced due to the addition of the magnetic material in the receiver, which is now part of the total magnetic system. Table <NUM> illustrates certain effects attributable to different types of objects placed within close proximity to the transmitter coil.

<FIG> illustrates a wireless transmitter <NUM> that may be provided in a charger base station. A controller <NUM> may receive a feedback signal filtered or otherwise processed by a filter circuit <NUM>. The controller may control the operation of a driver circuit <NUM>. The driver circuit <NUM> provides an alternating current to a resonant circuit <NUM> that includes a capacitor <NUM> and inductor <NUM>. The frequency of the alternating current may be determined by a charging clock signal <NUM> provided by timing circuits <NUM>. A measurement circuit may obtain a measurement signal <NUM> indicative of current flow or voltage <NUM> measured at an LC node <NUM> of the resonant circuit <NUM>. The measurement signal <NUM> may be used to calculate or estimate Q factor of the resonant circuit <NUM>.

The timing circuits <NUM> may provide the controller with one or more clock signals <NUM>, including a system clock signal that controls the operation of the controller <NUM>. The one or more clock signals <NUM> may further include a clock signal used to modulate or demodulate a data signal carried on a charging current in the resonant circuit <NUM>. The timing circuits <NUM> may include configurable clock generators that produce signals at frequencies defined by configuration information, including the charging clock signal <NUM>. The timing circuits <NUM> may be coupled to the controller through an interface <NUM>. The controller <NUM> may configure the frequency of the charging clock signal <NUM>. In some implementations, the controller <NUM> may configure the duration and frequency of a pulsed signal used for passive ping in accordance with certain aspects disclosed herein. In one example, the pulsed signal includes a number of cycles of the pulsed signal.

Passive ping techniques may use the voltage and/or current measured or observed at the LC node <NUM> to identify the presence of a receiving coil in proximity to the charging pad of a device adapted in accordance with certain aspects disclosed herein. Many conventional wireless charger transmitters include circuits that measure voltage at the LC node <NUM> or measure the current in the network. These voltages and currents may be monitored for power regulation purposes and/or to support communication between devices. In the example illustrated in <FIG>, voltage at the LC node <NUM> may be measured, although it is contemplated that a circuit may be adapted or provided such that current can additionally or alternatively be monitored to support passive ping. A response of the resonant circuit <NUM> to a passive ping (initial voltage V<NUM>) may be represented by the voltage (VLC) at the LC node <NUM>, such that: <MAT>.

<FIG> illustrates examples of responses <NUM>, <NUM> to a passive ping. In each of the responses <NUM>, <NUM>, an initial voltage decays according to Equation <NUM>. After the excitation pulse at time = <NUM>, the voltage and/or current is seen to oscillate at the resonant frequency defined by Equation <NUM>, and with a decay rate defined by Equation <NUM>. The first cycle of oscillation begins at voltage level V<NUM> and VLC continues to decay to zero as controlled by the Q factor and ω. The first response <NUM> illustrates a typical open or unloaded response when no object is present or proximate to the charging pad. In this first response <NUM>, the value of the Q factor may be assumed to be <NUM>. The second response <NUM> illustrates a loaded response that may be observed when an object is present or proximate to the charging pad loads the coil. In the illustrated second response <NUM>, the Q factor may have a value of <NUM>. VLC oscillates at a higher frequency in the voltage response <NUM> with respect to the voltage response <NUM>.

<FIG> illustrates a set of examples in which differences in responses <NUM>, <NUM>, <NUM> may be observed. A passive ping is initiated when a driver circuit <NUM> excites the resonant circuit <NUM> using a pulse that is shorter than <NUM>. Different types of wireless receivers and foreign objects placed on the transmitter result in different responses observable in the voltage at the LC node <NUM> or current in the resonant circuit <NUM> of the transmitter. The differences may indicate variations in the Q factor of the resonant circuit <NUM> frequency of the oscillation of V<NUM>. Table <NUM> illustrates certain examples of objects placed on the charging pad in relation to an open state.

In Table <NUM>, the Q factor may be calculated as follows: <MAT> where N is the number of cycles from excitation until amplitude falls below <NUM> V<NUM>.

<FIG> is a flowchart <NUM> that illustrates a method involving passive ping implemented in a wireless charging device adapted in accordance with certain aspects disclosed herein. At block <NUM>, a controller may generate a short excitation pulse and may provide the short excitation pulse to a network that includes a resonant circuit. The network may have a nominal resonant frequency and the short excitation pulse may have a duration that is less than half the nominal resonant frequency of the network. The nominal resonant frequency may be observed when the transmitting coil of the resonant circuit is isolated from external objects, including ferrous objects, non-ferrous objects and/or receiving coils in a device to be charged.

At block <NUM>, the controller may determine the resonant frequency of the network or may monitor the decay of resonation of the network responsive to the pulse. According to certain aspects disclosed herein, the resonant frequency and/or the Q factor associated with the network may be altered when a device or other object is placed in proximity to the transmitting coil. The resonant frequency may be increased or decreased from the nominal resonant frequency observed when the transmitting coil of the resonant circuit is isolated from external objects. The Q factor of the network may be increased or decreased with respect to a nominal Q factor measurable when the transmitting coil of the resonant circuit is isolated from external objects. According to certain aspects disclosed herein, the duration of delay can be indicative of the presence or type of an object placed in proximity to the transmitting coil when differences in Q factor prolong or accelerate decay of amplitude of oscillation in the resonant circuit with respect to delays associated with a nominal Q factor.

In one example, the controller may determine the resonant frequency of the network using a transition detector circuit configured to detect zero crossings of a signal representative of the voltage at the LC node <NUM> using a comparator or the like. In some instances, direct current (DC) components may be filtered from the signal to provide a zero crossing. In some instances, the comparator may account for a DC component using an offset to detect crossings of a common voltage level. A counter may be employed to count the detected zero crossings. In another example the controller may determine the resonant frequency of the network using a transition detector circuit configured to detect crossings through a threshold voltage by a signal representative of the voltage at the LC node <NUM>, where the amplitude of the signal is clamped or limited within a range of voltages that can be detected and monitored by logic circuits. In this example, a counter may be employed to count transitions in the signal. The resonant frequency of the network may be measured, estimated and/or calculated using other methodologies.

In another example, a timer or counter may be employed to determine the time taken for VLC to decay from voltage level V<NUM> to a threshold voltage level. The elapsed time may be used to represent a decay characteristic of the network. The threshold voltage level may be selected to provide sufficient granularity to enable a counter or timer to distinguish between various responses <NUM>, <NUM>, <NUM> to the pulse. VLC may be represented by detected or measured peak, peak-to-peak, envelope <NUM> and/or rectified voltage level. The decay characteristic of the network may be measured, estimated and/or calculated using other methodologies.

If at block <NUM>, the controller determines that a change in resonant frequency with respect to a nominal resonant frequency indicate presence of an object in proximity to the transmitting coil, the controller may attempt to identify the object at block <NUM>. If the controller determines at block <NUM> that resonant frequency is substantially the same as the nominal resonant frequency, the controller may consider the decay characteristic of the amplitude of oscillation in the resonant circuit at block <NUM>. The controller may determine that the resonant frequency of the network is substantially the same as the nominal resonant frequency when the frequency remains within a defined frequency range centered on, or including the nominal resonant frequency. In some implementations, the controller may identify objects using changes in resonant frequency and decay characteristics. In these latter implementations, the controller may continue at block <NUM> regardless of resonant frequency, and may use changes in change in resonant frequency as an additional parameter when identifying an object positioned proximately the transmission coil.

At block <NUM>, the controller may use a timer and/or may count the cycles of the oscillation in the resonant circuit that have elapsed between the initial VO amplitude and a threshold amplitude used to assess the decay characteristic. In one example, VO/<NUM> may be selected as the threshold amplitude. At block <NUM>, the number of cycles or the elapsed time between the initial VO amplitude and the threshold amplitude may be used to characterize decay in the amplitude of oscillation in the resonant circuit, and to compare the characterize decay with a corresponding nominal decay characteristic. If at block <NUM>, no change in frequency and delay characteristic is detected, the controller may terminate the procedure with a determination that no object is proximately located to the transmission coil. If at block <NUM>, a change in frequency and/or delay characteristic has been detected, the controller may identify the object at block <NUM>.

At block <NUM>, the controller may be configured to identify receiving devices placed on a charging pad. The controller may be configured to ignore other types of objects, or receiving devices that are not optimally placed on the charging pad including, for example, receiving devices that are misaligned with the transmission coil that provides the passive ping. In some implementations, the controller may use a lookup table indexed by resonant frequency, decay time, change in resonant frequency, change in decay time and/or Q factor estimates. The lookup table may provide information identifying specific device types, and/or charging parameters to be used when charging the identified device or type of device.

Passive ping uses a very short excitation pulse that can be less than a half-cycle of the nominal resonant frequency observed at the LC node <NUM> in the resonant circuit <NUM>. A conventional ping may actively drive a transmission coil for more than <NUM>,<NUM> cycles. The power and time consumed by a conventional ping can exceed the power and time use of a passive ping by several orders of magnitude. In one example, a passive ping consumes approximately <NUM>µJ per ping with a max ping time of around -<NUM>, while a conventional active ping consumes approximately <NUM> mJ per ping with a max ping time of around <NUM>. In this example, energy dissipation may be reduced by a factor of <NUM>,<NUM> and the time per ping may be reduced by a factor of <NUM>.

Detection and characterization of the decay of the voltage at the LC node <NUM> may require fast, sensitive and/or low-voltage circuits to accommodate the low-power nature of resonant signals at the LC node <NUM> when a short excitation pulse is used to produce resonant signals in the resonant circuit <NUM>. In some instances, passive ping may be implemented using a burst of energy at the nominal resonant frequency of the resonant circuit <NUM>. The burst of energy may have a duration of several periods of the nominal resonant frequency. This burst-mode passive ping necessarily consumes more energy per ping that passive ping that is initiated by short excitation pulses. The additional energy provides additional time to characterize resonant response.

<FIG> illustrates an example of frequency response <NUM> of the resonant circuit <NUM> when the resonant circuit <NUM> is stimulated by a ping (here, a passive ping <NUM>) that includes several cycles of a signal that oscillates at or near the nominal resonant frequency (f<NUM> <NUM>) of the resonant circuit <NUM>. A first frequency response <NUM> illustrates the response of the resonant circuit <NUM> when no device is present, while a second frequency response <NUM> illustrates the response of the resonant circuit <NUM> when a chargeable object is present. The chargeable object reduces the Q-factor of the resonant circuit <NUM>. The higher Q-factor of the resonant circuit <NUM> when no device is present causes the resonant circuit <NUM> to produce a significantly higher voltage response <NUM> and draw the maximum current with the longest decay time in response to a passive ping <NUM> at f<NUM> <NUM> than the voltage response <NUM> produced when a chargeable device lowers the Q-factor of the resonant circuit <NUM>, causing the resonant circuit <NUM> to produce lower voltage, draw less current and have a shorter decay time in response to a passive ping at f<NUM> <NUM>. In typical applications, no object is present for a majority of the time a charging device is in operation, and the resonant circuit <NUM> in the charging device has a high Q-factor for a majority of the time. The high Q-factor results in a high power draw. The resonant circuit <NUM> has a slower response time when it has a high Q-factor, since more time is needed for the energy in the passive ping <NUM> to decay thereby delaying initiation of another ping.

An improved passive ping technique implemented in accordance with certain aspects disclosed herein can reduce power consumption associated with passive pings <NUM> and can increase the ping rate. The improved passive ping technique may use a frequency that is significantly different from the resonant frequency of the resonant circuit <NUM>.

<FIG> illustrates an example of frequency responses <NUM> of the resonant circuit <NUM> illustrating the effect of a ping (here, a pulse <NUM>) provided as burst of a stimulation signal that oscillates at a frequency (fp <NUM>) that is greater than the nominal resonant frequency (f<NUM> <NUM>) of the resonant circuit <NUM>. The burst spans two or more cycles of the stimulation signal. In one example, the duration of the burst may be controlled by a timer. In another example, the stimulation may be modulated using a gating signal that causes the stimulation signal to be provided to the resonant circuit at a desired repetition rate and with an active duration that defines the number of cycles of the stimulation signal in the burst. In some implementations, the ping is provided as a multi-cycle burst of a stimulation signal that has a frequency that is lower than f<NUM> <NUM>.

The use of a stimulation signal that has a frequency different from the resonant frequency of the resonant circuit <NUM> can result in the dominant state of the charging device, where no chargeable object is present, to have a lower power draw and faster decay rate than would be expected for a stimulation signal that has a frequency at or near the resonant frequency of the resonant circuit <NUM>. The use of a non-resonant stimulation signal can provide improved performance with respect to the example illustrated in <FIG>. The disclosed ping technique can result in increased decay rates and can limit the occurrence of higher-power draws to pulses <NUM> that lead to detection of a chargeable object. Additional pulses <NUM> are typically superfluous after detection.

The resonant circuit <NUM> may be stimulated during a passive ping procedure by a pulsed signal that includes pulses of a duration that can include several cycles at fp <NUM>. A first frequency response <NUM> illustrates the response of the resonant circuit <NUM> to a pulse <NUM> when no device is present, while a second frequency response <NUM> illustrates the response of the resonant circuit <NUM> to a pulse <NUM> when a chargeable object is present. The effect of the chargeable object on the resonant circuit <NUM> may be exhibited in a reduction in the Q-factor of the resonant circuit <NUM>. The resonant circuit <NUM> produces a significantly lower voltage level <NUM> and draws a lower current with a shorter decay time in response to a ping at fp <NUM> when no device is present than the voltage level <NUM> produced when a chargeable device is present. In typical applications, no object is present for a majority of the time a charging device is in operation, and the resonant circuit <NUM> exhibits a lower power consumption and a faster decay time per ping with respect to the example illustrated in <FIG>.

The frequency spread (fp - f<NUM> or f<NUM> - fp) between the resonant frequency (f<NUM> <NUM>) and the ping frequency (fp <NUM>) may be proportionate to the value of f<NUM> <NUM>. For example, the frequency spread may increase as f<NUM> <NUM> increases. In some implementations, the frequency spread and f<NUM> 808a have a logarithmic (log base <NUM>) relationship. In an example that is compliant or compatible with Qi standards, where <NUM> < f<NUM> < <NUM>, a passive ping frequency may be defined such that <NUM> < fp < <NUM>.

According to certain aspects disclosed herein, frequency spread may be selected as a trade-off between signal-to-noise ratio (SNR) and power consumption or response time. In the example illustrated in <FIG>, an overly-high value for frequency spread may result in lower SNR, while an overly-high value for frequency spread may result in high power draw and/or slow response. The optimal balance between SNR and power draw may vary by application. In some implementations, the lowest power and fast scan rate is obtained by setting fp <NUM> as high as possible while permitting reliable detection of objects given SNR for the system.

The duration of a pulse <NUM> can be defined as a number of fractions of a cycle of fp <NUM>. In one example, the duration of the passive ping pulse may be set to a half-cycle of fp <NUM>. In another example, the duration of the passive ping pulse may be set to multiple cycles of fp <NUM>. In some implementations, the duration of the passive ping pulse includes enough half-cycles of fp <NUM> to obtain a current draw in the detectable range of an analog-to-digital converter (ADC) in microprocessor of a charging device. The passive ping pulse may include additional cycles to accommodate the SNR margin. The number of additional cycles may be the subject of a trade-off to increase the SNR, while limiting power and ping time. In one example, where fp = <NUM> and f<NUM> = <NUM>, the duration of the passive ping pulse is less than <NUM>.

The repetition rate for pulses <NUM> in a pulsed stimulus signal can be determined dynamically when speed of detection is prioritized. In one example, the ADC can be checked to determine when current has fallen back to zero before launching the next pulse <NUM>. In this manner, a detection circuit can determine that no energy remains in the resonant circuit <NUM> from the pulse <NUM> before initiating the next pulse <NUM>. In some implementations, a fixed delay between pulses <NUM> may be implemented. In one example, the fixed delay may be configured to be <NUM> times the longest decay time constant expected or observed in the resonant circuit <NUM>. In one example, the fixed delay may be configured to provide a one millisecond interval between pulses. The one millisecond ping interval may enable an <NUM> coil charging pad to be scanned in <NUM>, permitting sub-second device detection. The fixed time approach can be used if further optimization for speed is not necessary. For example, a dynamic ping interval may be used when larger numbers of charging coils are provided in a charging pad.

<FIG> illustrates a circuit <NUM> that may be used to measure response of a resonant circuit in a passive ping procedure. In the illustrated example, the circuit <NUM> monitors the power <NUM> supplied to an inverter <NUM> that produces the pulse <NUM>. The power <NUM> may be measured as current flow to the resonant circuit <NUM>. In some implementations, power <NUM> may be measured as a voltage across the resonant circuit <NUM>. In the illustrated example, a current sensing circuit <NUM> provides measurements to a controller <NUM> that configures, initiates and/or triggers pulses <NUM> provided to the resonant circuit <NUM>. In one example, the current sensing circuit <NUM> uses a comparator <NUM> to measure the voltage across a low-value resistor <NUM> in the power supply coupling to the inverter <NUM>. A low-pass filter <NUM> may be used to provide an average or root-mean square value as the output <NUM> of the current sensing circuit <NUM>.

Passive ping procedures may also be coupled with another, reduced-power sensing methodology, such as capacitive sensing. Capacitive sensing or the like can provide an ultra-low power detection method that determines presence or non-presence of an object is in proximity to the charging surface. After capacitive sense detection, a passive ping can be transmitted sequentially or concurrently on each coil to produce a more accurate map of where a potential receiving device and/or object is located. After a passive ping procedure has been conducted, an active ping may be provided in the most likely device locations. An example algorithm for device location sensing, identification and charging is illustrated in <FIG>.

<FIG> is a flowchart <NUM> that illustrates a power transfer management procedure involving multiple sensing and/or interrogation techniques that may be employed by a wireless charging device implemented in accordance with certain aspects disclosed herein. The procedure may be initiated periodically and, in some instances, may be initiated after the wireless charging device exits a low-power or sleep state. In one example, the procedure may be repeated at a frequency calculated to provide sub-second response to placement of a device on a charging pad. The procedure may be reentered when an error condition has been detected during a first execution of the procedure, and/or after charging of a device placed on the charging pad has been completed.

At block <NUM>, a controller may perform an initial search using capacitive proximity sensing. Capacitive proximity sensing may be performed quickly and with low power dissipation. In one example, capacitive proximity sensing may be performed iteratively, where one or more transmission coils is tested in each iteration. The number of transmission coils tested in each iteration may be determined by the number of sensing circuits available to the controller. At block <NUM>, the controller may determine whether capacitive proximity sensing has detected the presence or potential presence of an object proximate to one of the transmission coils. If no object is detected by capacitive proximity sensing, the controller may cause the charging device to enter a low-power, idle and/or sleep state at block <NUM>. If an object has been detected, the controller may initiate passive ping sensing at block <NUM>.

At block <NUM>, the controller may initiate passive ping sensing to confirm presence of an object near one or more transmission coils, and/or to evaluate the nature of the proximately-located object. Passive ping sensing may consume a similar quantity of power but span a greater of time than capacitive proximity sensing. In one example, each passive ping can be completed in approximately <NUM> and may expend <NUM>µJ. A passive ping may be provided to each transmission coil identified as being of-interest by capacitive proximity sensing. In some implementations, a passive ping may be provided to transmission coils near each transmission coil identified as being of-interest by capacitive proximity sensing, including overlaid transmission coils. At block <NUM>, the controller may determine whether passive ping sensing has detected the presence of a potentially chargeable device proximate to one of the transmission coils that may be a receiving device. If a potentially chargeable device has been detected, the controller may initiate active digital ping sensing at block <NUM>. If no potential chargeable device has been detected, passive ping sensing may continue at block <NUM> until all of the coils have been tested and/or the controller terminates passive ping sensing. In one example, the controller terminates passive ping sensing after all transmitting coils have been tested. When passive ping sensing fails to find a potentially chargeable device, the controller the controller may cause the charging device to enter a low-power, idle and/or sleep state. In some implementations, passive ping sensing may be paused when a potentially chargeable device is detected so that an active ping can be used to interrogate the potentially chargeable device. Passive ping sensing may be resumed after the results of an active ping have been obtained.

At block <NUM>, the controller may use an active ping to interrogate a potentially chargeable device. The active ping may be provided to a transmitting coil identified by passive ping sensing. In one example, a standards-defined active ping exchange can be completed in approximately <NUM> and may expend <NUM> mJ. An active ping may be provided to each transmission coil associated with a potentially chargeable device.

At block <NUM>, the controller may identify and configure a chargeable device. The active ping provided at block <NUM> may be configured to stimulate a chargeable device such that it transmits a response that includes information identifying the chargeable device. In some instances, the controller may fail to identify or configure a potentially chargeable device detected by passive ping, and the controller may resume a search based on passive ping at block <NUM>. At block <NUM>, the controller may determine whether a baseline charging profile or negotiated charging profile should be used to charge an identified chargeable device. The baseline, or default charging profile may be defined by standards. In one example, the baseline profile limits charging power to <NUM> W. In another example, a negotiated charging profile may enable charging to proceed at up to <NUM> W. When a baseline charging profile is selected, the controller may begin transferring power (charging) at block <NUM>.

At block <NUM>, the controller may initiate a standards-defined negotiation and calibration process that can optimize power transfer. The controller may negotiate with the chargeable device to determine an extended power profile that is different from a power profile defined for the baseline charging profile. The controller may determine at block <NUM> that the negotiation and calibration process has failed and may terminate the power transfer management procedure. When the controller determines at block <NUM> that the negotiation and calibration process has succeeded, charging in accordance with the negotiate profile may commence at block <NUM>.

At block <NUM>, the controller may determine whether charging has been successfully completed. In some instances, an error may be detected when a negotiated profile is used to control power transfer. In the latter instance, the controller may attempt to renegotiate and/or reconfigure the profile at block <NUM>. The controller may terminate the power transfer management procedure when charging has been successfully completed.

The use of passive ping techniques disclosed herein can enable rapid, low-power detection or discovery of devices or objects that have been placed or positioned proximate to a charging surface. A charging device that employs passive ping can benefit from reduced quiescent power draw, increased detection speed, and reduced radiated EMI. A conventional system that uses passive ping detection operates by providing a stimulating pulse that is used to measure a current or voltage value or rate of decay in order to determine a characteristic of the stimulated the network. Conventional systems, for example, strive to detect changes in Q factor of a resonant circuit stimulated by the stimulating pulse. The value of the Q factor may be calculated or estimated base do a comparison of an electrical or electromagnetic signal to a threshold value.

<FIG> illustrates a system <NUM> that can be used to determine presence of an object that is near or in contact with a resonant circuit. A measuring circuit <NUM> may be used to measure and/or calculate one or more parameters that characterize the resonant circuit used for passive ping detection. The measured parameters may include the Q factor, voltage, current, impedance, frequency of oscillation, and so on. The measuring circuit <NUM> provides a measurement signal <NUM> that has a voltage level or carries a current representative of the measured parameter. The measurement signal <NUM> is compared to a threshold signal <NUM> using a comparator <NUM> that provides a binary object detect signal <NUM>. In the illustrated system <NUM>, the threshold signal <NUM> is produced by a reference circuit <NUM> that is designed to provide a threshold signal with a constant, fixed voltage or current level to enable the system <NUM> to reliably determine when a characteristic of the resonant circuit is changed sufficiently to indicate that an object has is close to a component of the resonant circuit.

In certain implementations, the level of the measurement signal <NUM> or the threshold signal <NUM> can drift. Drift can occur as a result of process, voltage and temperature (PVT) variations. Process variations arise during manufacture of integrated circuit (IC) devices and can cause the reference circuit <NUM> in different devices to produce threshold signals <NUM> with different voltage or current levels. Variations in voltage and temperature may be linked and/or can arise from variations in ambient temperature, power supply, interference, IC operating temperature, loading, stimulation variance, and other factors or causes. In one example, increases in temperature can increase the resistivity of copper, which can then notably affect the Q factor of a resonant circuit.

The graph <NUM> shows an example of the effect of temperature variance on the measurement signal <NUM>. For simplicity, it is assumed that the level of the threshold signal <NUM> remains constant. Initially, the system <NUM> and the passive pulse resonant circuit are operating during a period of stability <NUM>, when the measurement signal <NUM> is not affected by significant drift. In the illustrated example, the measurement signal <NUM> is at a constant low voltage level <NUM> when no object is placed near the resonant circuit. The measurement signal <NUM> rises to a higher voltage level <NUM> when an object is placed near a component of the resonant circuit, and the object detect signal <NUM> switches active at a first point in time <NUM> when the measurement signal <NUM> rises above the level of the threshold signal <NUM>, indicating that an object has been detected. The system <NUM> remains in an object detected state <NUM> until the level of the measurement signal <NUM> falls below the level of the threshold signal <NUM> at a second point in time <NUM> causing the system <NUM> to exit the object detected state <NUM>.

A period of drift <NUM> commences at a third point in time <NUM>. The drift may be caused by an increase in temperature, for example. The drift may increase the low voltage level <NUM> present when no object is placed near the resonant circuit. At a fourth point in time <NUM>, the measurement signal <NUM> rises above the level of the threshold signal <NUM> causing the object detect signal <NUM> to switch active although no object has been placed near the resonant circuit. The system <NUM> enters a false object detected state <NUM>. In some instances, a decrease in temperature can lower the Q factor and reduce the detection sensitivity of the system <NUM>. In one example, the reduced detection sensitivity can result in the system failing to detect smaller devices.

Other types of PVT variation can cause variance in parameters that are assumed to be fixed by circuit designers and can negatively affect object detection sensitivity. In some conventional systems, compensation circuits may be provided to independently correct for drift in key components. However, the addition of compensation circuits can significantly increase cost and complexity, and other unforeseen sources of drift may arise during mass production and/or under operational conditions.

In accordance with certain aspects of this disclosure, an adaptive passive ping system may be deployed that can eliminate or reduce the effect of drift arising from PVT variations. Adaptive passive ping can be configured to determine presence of an object based on a rate of change of the measurement signal <NUM>, which may be represented algorithmically as a derivative of the measurement signal <NUM>. In one example, detection of an object is signaled when the rate of change of the measurement signal <NUM> exceeds a specified or configured rate or delta (change).

<FIG> illustrates a system <NUM> that may be adapted in accordance with certain aspects disclosed herein to reliably determine presence of an object that is near or in contact with a resonant circuit. The system <NUM> can be configured to be tolerant of drift in voltage or current, where the drift may be attributable to PVT variations. In various implementations, the system <NUM> employs adaptive passive ping thresholding that can be implemented in software, hardware or some combination thereof. In one example, adaptive passive ping thresholding can be implemented in programmable digital hardware using a low pass filter, a Finite Impulse Response (FIR) filter and/or another suitable digital filtering technique used to optimize a low pass filter. A FIR filter typically has an impulse response that has finite duration, and may be configured to settle within a desired, finite time.

The system <NUM> illustrates an example in which adaptive passive ping thresholding is implemented in hardware using a low pass filter <NUM> with a hysteresis comparator. In general, a comparator is a device that is used to differentiate between two signal levels. In one example, a comparator may be used to indicate which of the two signals has the greater voltage level. The comparator <NUM> in <FIG> has one input coupled to a threshold signal <NUM> that is nominally fixed, and the comparator <NUM> output indicates whether a voltage level of the measurement signal <NUM> is greater or less than the voltage level of the threshold signal <NUM>. Multiple transitions can occur when the level of the measurement signal <NUM> is close to the level of the threshold signal <NUM>. A hysteresis comparator may be used to avoid multiple transitions by setting different upper and lower difference thresholds.

In some implementations, the hysteresis comparator includes a comparison circuit <NUM> and a hysteresis circuit <NUM> that compares the difference signal <NUM> to a variable threshold level. The difference signal <NUM> may be representative of difference between two input signals. The hysteresis circuit <NUM> may be configured to suppress response to slow changes in the measurement signal <NUM>. The hysteresis circuit <NUM> may be configured to suppress response to low-voltage changes in the measurement signal <NUM> caused by variations in a voltage or a temperature associated with the apparatus. In some instances, the comparison circuit <NUM> and the hysteresis circuit <NUM> may be provided as separate physical components. In some instances, the comparison circuit <NUM> and the hysteresis circuit <NUM> may implemented in software, hardware or some combination of software and hardware. For example, the comparison circuit <NUM> and the hysteresis circuit <NUM> may be implemented using a digital signal processor or other programmable logic.

In one example, the detection signal <NUM> transitions high when the voltage level of the difference signal <NUM> exceeds a high threshold level defined for positive transitions (e.g., when the difference signal <NUM> is rising), and the detection signal <NUM> transitions low when the voltage level of the difference signal <NUM> is less than a low threshold level defined for negative transitions (e.g., when the difference signal <NUM> is falling). The combination of the low threshold level and the high threshold level may define a delta change threshold.

In the example of the system <NUM> of <FIG>, hysteresis is employed to effectively adjust the threshold voltage that causes the detection signal <NUM> output by the system <NUM> to switch between an object detected state and a no object detected state. The hysteresis circuit <NUM> can be configured to react to large changes in a difference signal <NUM> representing the difference between the measurement signal <NUM> output by a measuring circuit <NUM> and a delayed version of the measurement signal <NUM> provided as the output <NUM> of the low pass filter <NUM>. The low pass filter <NUM> may be configured to closely track drift in the measurement signal <NUM> attributable to PVT variations. Some optimizations may be required to ensure that the system <NUM> can respond quickly to the placement of objects near components of the resonant circuit. A filter constant for the low pass filter <NUM> can be selected to detect changes in object placement within a reasonable time frame as defined by application requirements, and/or with reference to user response times. The detection hysteresis corresponding to the delta change threshold for the hysteresis circuit <NUM> may be configured to define a reasonable change in the measurement signal <NUM> that reliably triggers a change in the detection signal <NUM> when an object is present.

The graph <NUM> shows an example of the response of the system <NUM> to temperature variance on the measurement signal <NUM>. Initially, the system <NUM> and the passive pulse resonant circuit are operating during a period of stability <NUM>, when the measurement signal <NUM> is not affected by significant drift. In the illustrated example, the measurement signal <NUM> is at a constant low voltage level <NUM> when no object is placed near the resonant circuit. The output of the output <NUM> of the low pass filter <NUM> may be at or near the voltage level of the measurement signal <NUM>. In some instances, the output of the output <NUM> of the low pass filter <NUM> may be rising or falling toward the low voltage level <NUM> if recent variations have occurred on the measurement signal <NUM>.

The measurement signal <NUM> rises to a higher voltage level <NUM> when an object is placed near a component of the resonant circuit, and the output <NUM> of the low pass filter <NUM> follows the measurement signal <NUM>. The low pass filter <NUM> blocks higher frequency components of the measurement signal <NUM>, causing a slower rise of the output <NUM> of the low pass filter <NUM> than the rise observed in the measurement signal <NUM>. The difference between the levels of the measurement signal <NUM> and the output <NUM> of the low pass filter <NUM> increases quickly and at some point in time <NUM>, exceeds the positive switching threshold <NUM> for the hysteresis circuit <NUM>. The detection signal <NUM> switches indicating that the system <NUM> is in an object detected state <NUM>. The output of the low pass filter <NUM> continues towards the higher voltage level of the measurement signal <NUM>.

The object is then removed and the measurement signal <NUM> falls rapidly toward the low voltage level <NUM>. The output <NUM> of the low pass filter <NUM> follows the measurement signal <NUM>. The low pass filter <NUM> blocks higher frequency components of the measurement signal <NUM>, causing a slower fall of the output <NUM> of the low pass filter <NUM> than the fall observed in the measurement signal <NUM>. The difference between the levels of the measurement signal <NUM> and the output <NUM> of the low pass filter <NUM> increases quickly and at a point in time <NUM> exceeds the negative switching threshold for the hysteresis circuit <NUM>. The output of the low pass filter <NUM> continues towards the lower voltage level of the measurement signal <NUM>. In this example, the comparator output switches to an object detected state after the object is placed near a component of the resonant circuit and to an object not detected state when the object is removed.

A period of drift <NUM> commences at a third point in time <NUM>. The drift may be caused by an increase in temperature, for example. The drift may cause an increase from the low voltage level <NUM> when no object is placed near the resonant circuit. The output <NUM> of the low pass filter <NUM> converges on the drifting measurement signal <NUM>. In the illustrated example, the output <NUM> of the low pass filter <NUM> is falling when the measurement signal <NUM> begins to rise due to drift. The levels of the measurement signal <NUM> and the output <NUM> of the low pass filter <NUM> may coincide at a point in time <NUM>. The output <NUM> of the low pass filter <NUM> ceases falling and begins to rise, following the measurement signal <NUM> and enabling reliable indication of object detection in the detection signal <NUM>.

In some implementations, the detection signal <NUM> may be switched when a difference is observed between the measurement signal <NUM> and the output <NUM> of the low pass filter <NUM> for a period of time exceeds a threshold minimum time interval. The use of a time interval to judge presence of an object may accommodate lower difference voltages between the measurement signal <NUM> and the output <NUM> of the low pass filter <NUM>, and may enable the system <NUM> to respond more rapidly through a filter constant that reduces the delay introduced by the low pass filter <NUM>.

The adaptive passive ping thresholding techniques disclosed herein can be used to remove or ameliorate the effects of system drift or offsets, regardless of their origin. The adaptive passive ping techniques disclosed herein operate on the system transfer function directly, such that the mechanisms by which drift is caused do not need to be known or understood.

<FIG> is a flowchart <NUM> for a method for detecting objects near a surface of a charging device. In some implementations, the method may be managed or performed by a controller in the charging device. At block <NUM>, the controller may provide a pulsed signal to a charging circuit. Each pulse in the pulsed signal may include a plurality of cycles of a clock signal that has a frequency greater or less than a nominal resonant frequency of the charging circuit. In some instances, a pulse may include an integer number of cycles of a clock signal. In some instances, a pulse may an integer number of cycles of a clock signal and a fraction of a clock signal. The number of clock cycles in a pulse may be determined by a timer that controls the duration of the pulse.

At block <NUM>, the controller may detect a change in resonance of the charging circuit based on a difference in response of the charging circuit to a first pulse in the pulsed signal with respect to a corresponding response of the charging circuit to a second pulse previously transmitted in the pulsed signal. At block <NUM>, the controller may determine that a chargeable device has been placed in proximity to a coil of the charging circuit based on the difference in response.

In one example, the difference in response includes an increase in current flowing in the charging circuit in response to the second pulse with respect to current flowing in the charging circuit in response to the first pulse. In another example, the difference in response includes an increase in voltage across the coil of the charging circuit.

In some implementations, the controller may determine a charging configuration for the chargeable device when the coil of the charging circuit is inductively coupled to a receiving coil in the chargeable device, and provide a charging current to the charging circuit in accordance with the charging configuration. In some implementations, the controller may transmit an active ping in accordance with standards-defined specifications for charging the chargeable device, and identify the chargeable device from information encoded in a modulated signal received from the chargeable device.

In certain implementations, the change in resonance of the charging circuit includes a decrease in Q factor of the charging circuit. The controller may receive a measurement signal representative of the Q factor of the charging circuit, filter the measurement signal to obtain a filtered version of the measurement signal that changes at a slower rate than the measurement signal, and generate a detection signal that switches when a difference between the measurement signal and the filtered version of the measurement signal exceeds a threshold level. The controller may compare the measurement signal and the filtered version of the measurement signal using a comparator that comprises a hysteresis circuit configured to suppress response to slow changes in the measurement signal, including changes in the measurement signal caused by variations in operating voltage or temperature. Filtering the measurement signal may include using a FIR filter to filter the measurement signal or using a low pass filter to filter the measurement signal. The comparison logic may be a hysteresis comparator and/or may have a hysteresis circuit configured to suppress response to slow changes in the measurement signal and/or to suppress response to low-voltage changes in the measurement signal caused by variations in a voltage or a temperature associated with the apparatus.

<FIG> is a diagram illustrating an example of a hardware implementation for an apparatus <NUM> that may be incorporated in a charging device or in a receiving device that enables a battery to be wirelessly charged. In some examples, the apparatus <NUM> may perform one or more functions disclosed herein. In accordance with various aspects of the disclosure, an element, or any portion of an element, or any combination of elements as disclosed herein may be implemented using a processing circuit <NUM>. The processing circuit <NUM> may include one or more processors <NUM> that are controlled by some combination of hardware and software modules. Examples of processors <NUM> include microprocessors, microcontrollers, digital signal processors (DSPs), SoCs, ASICs, field programmable gate arrays (FPGAs), programmable logic devices (PLDs), state machines, sequencers, gated logic, discrete hardware circuits, and other suitable hardware configured to perform the various functionality described throughout this disclosure. The one or more processors <NUM> may include specialized processors that perform specific functions, and that may be configured, augmented or controlled by one of the software modules <NUM>. The one or more processors <NUM> may be configured through a combination of software modules <NUM> loaded during initialization, and further configured by loading or unloading one or more software modules <NUM> during operation.

In the illustrated example, the processing circuit <NUM> may be implemented with a bus architecture, represented generally by the bus <NUM>. The bus <NUM> may include any number of interconnecting buses and bridges depending on the specific application of the processing circuit <NUM> and the overall design constraints. The bus <NUM> links together various circuits including the one or more processors <NUM>, and storage <NUM>. Storage <NUM> may include memory devices and mass storage devices, and may be referred to herein as computer-readable media and/or processor-readable media. The storage <NUM> may include transitory storage media and/or non-transitory storage media.

The bus <NUM> may also link various other circuits such as timing sources, timers, peripherals, voltage regulators, and power management circuits. A bus interface <NUM> may provide an interface between the bus <NUM> and one or more transceivers <NUM>. In one example, a transceiver <NUM> may be provided to enable the apparatus <NUM> to communicate with a charging or receiving device in accordance with a standards-defined protocol. Depending upon the nature of the apparatus <NUM>, a user interface <NUM> (e.g., keypad, display, speaker, microphone, joystick) may also be provided, and may be communicatively coupled to the bus <NUM> directly or through the bus interface <NUM>.

One or more processors <NUM> in the processing circuit <NUM> may execute software. Software shall be construed broadly to mean instructions, instruction sets, code, code segments, program code, programs, subprograms, software modules, applications, software applications, software packages, routines, subroutines, objects, executables, threads of execution, procedures, functions, algorithms, etc., whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise. The software may reside in computer-readable form in the storage <NUM> or in an external computer-readable medium. The external computer-readable medium and/or storage <NUM> may include a non-transitory computer-readable medium. A non-transitory computer-readable medium includes, by way of example, a magnetic storage device (e.g., hard disk, floppy disk, magnetic strip), an optical disk (e.g., a compact disc (CD) or a digital versatile disc (DVD)), a smart card, a flash memory device (e.g., a "flash drive," a card, a stick, or a key drive), RAM, ROM, a programmable read-only memory (PROM), an erasable PROM (EPROM) including EEPROM, a register, a removable disk, and any other suitable medium for storing software and/or instructions that may be accessed and read by a computer. The computer-readable medium and/or storage <NUM> may also include, by way of example, a carrier wave, a transmission line, and any other suitable medium for transmitting software and/or instructions that may be accessed and read by a computer. Computer-readable medium and/or the storage <NUM> may reside in the processing circuit <NUM>, in the processor <NUM>, external to the processing circuit <NUM>, or be distributed across multiple entities including the processing circuit <NUM>. The computer-readable medium and/or storage <NUM> may be embodied in a computer program product. By way of example, a computer program product may include a computer-readable medium in packaging materials. Those skilled in the art will recognize how best to implement the described functionality presented throughout this disclosure depending on the particular application and the overall design constraints imposed on the overall system.

The storage <NUM> may maintain software maintained and/or organized in loadable code segments, modules, applications, programs, etc., which may be referred to herein as software modules <NUM>. Each of the software modules <NUM> may include instructions and data that, when installed or loaded on the processing circuit <NUM> and executed by the one or more processors <NUM>, contribute to a run-time image <NUM> that controls the operation of the one or more processors <NUM>. When executed, certain instructions may cause the processing circuit <NUM> to perform functions in accordance with certain methods, algorithms and processes described herein.

Some of the software modules <NUM> may be loaded during initialization of the processing circuit <NUM>, and these software modules <NUM> may configure the processing circuit <NUM> to enable performance of the various functions disclosed herein. For example, some software modules <NUM> may configure internal devices and/or logic circuits <NUM> of the processor <NUM>, and may manage access to external devices such as a transceiver <NUM>, the bus interface <NUM>, the user interface <NUM>, timers, mathematical coprocessors, and so on. The software modules <NUM> may include a control program and/or an operating system that interacts with interrupt handlers and device drivers, and that controls access to various resources provided by the processing circuit <NUM>. The resources may include memory, processing time, access to a transceiver <NUM>, the user interface <NUM>, and so on.

In one implementation, the apparatus <NUM> may be implemented in a wireless charging device that has a battery charging power source coupled to a charging circuit, a plurality of charging cells and a controller, which may include the one or more processors <NUM>. The plurality of charging cells may be configured to provide a current to one or more charging coils near a surface of the charging device. At least one coil may be configured to direct an electromagnetic field through a charge transfer area of each charging cell.

The apparatus <NUM> may include a pulse generating circuit configured to provide a pulsed signal to the charging circuit. Each pulse in the pulsed signal may include a plurality of cycles of a clock signal that has a frequency greater or less than a nominal resonant frequency of the charging circuit. In one example, the pulse generating circuit includes a logic circuit that gates a clock signal under the control of a timer. The controller may be configured to detect a change in resonance of the charging circuit based on a difference in response of the charging circuit to a first pulse in the pulsed signal with respect to a corresponding response of the charging circuit to a second pulse previously transmitted in the pulsed signal. The controller may be configured to determine that a chargeable device has been placed in proximity to the charging coil based on the difference in response. In one example, the difference in response includes an increase in current flowing in the charging circuit in response to the second pulse with respect to current flowing in the charging circuit in response to the first pulse. In another example, the difference in response includes an increase in voltage across the coil of the charging circuit.

In some implementations, the controller can be configured to determine a charging configuration for the chargeable device when the coil of the charging circuit is inductively coupled to a receiving coil in the chargeable device, and cause the charging circuit to provide a charging current to the charging circuit in accordance with the charging configuration. In one example, the controller can be configured to cause the charging circuit to transmit an active ping in accordance with standards-defined specifications for charging the chargeable device, and identify the chargeable device from information encoded in a modulated signal received from the chargeable device.

In certain implementations, the apparatus <NUM> has a measurement circuit configured to provide a measurement signal representative of the resonance of the charging circuit based on the response of the charging circuit to the pulsed signal. In some examples, a change in resonance of the charging circuit includes a decrease in Q factor of the charging circuit. The apparatus <NUM> may include a filter configured to provide a filtered version of the measurement signal that changes at a slower rate than the measurement signal, and comparison logic configured to generate a detection signal that switches when a difference between the measurement signal and the filtered version of the measurement signal exceeds a threshold level. The detection signal may indicate whether an object is positioned proximate to the charging coil. The filter may be implemented as a finite impulse response filter or a low pass filter. The comparison logic may include a hysteresis circuit configured to suppress response to low-voltage changes in the measurement signal caused by variations in a voltage or a temperature associated with the apparatus.

In some implementations, the storage <NUM> maintains instructions and information where the instructions are configured to cause the one or more processors <NUM> to provide a pulsed signal to a charging circuit, wherein each pulse in the pulsed signal comprises a plurality of cycles of a clock signal that has a frequency greater or less than a nominal resonant frequency of the charging circuit, detect a change in resonance of the charging circuit based on a difference in response of the charging circuit to a first pulse in the pulsed signal with respect to a corresponding response of the charging circuit to a second pulse previously transmitted in the pulsed signal, and determine that a chargeable device has been placed in proximity to a coil of the charging circuit based on the difference in response. The difference in response includes an increase in voltage across the coil of the charging circuit or an increase in current flowing in the charging circuit in response to the second pulse with respect to current flowing in the charging circuit in response to the first pulse.

In some implementations, the instructions may be configured to cause the one or more processors <NUM> to determine a charging configuration for the chargeable device when the coil of the charging circuit is inductively coupled to a receiving coil in the chargeable device, and provide a charging current to the charging circuit in accordance with the charging configuration. In some implementations, the instructions may be configured to cause the one or more processors <NUM> to transmit an active ping in accordance with standards-defined specifications for charging the chargeable device, and identify the chargeable device from information encoded in a modulated signal received from the chargeable device.

Claim 1:
A method for detecting an object (<NUM>), comprising:
providing a pulsed signal to a charging circuit (<NUM>, <NUM>), wherein each pulse in the pulsed signal comprises a plurality of cycles of a clock signal that has a frequency greater or less than a nominal resonant frequency of the charging circuit; characterised by:
detecting a change in resonance of the charging circuit (<NUM>);
the method is characterised by further comprising: wherein the change in resonance of the charging circuit includes a decrease in Q factor of the charging circuit, based on a difference in response of the charging circuit to a first pulse in the pulsed signal with respect to a corresponding response of the charging circuit to a second pulse previously transmitted in the pulsed signal (<NUM>); and
determining that a chargeable device has been placed in proximity to a coil of the charging circuit (<NUM>) based on the difference in response, wherein detecting the change in resonance of the charging circuit includes:
receiving a measurement signal (<NUM>) representative of Q factor of the charging circuit;
filtering the measurement signal to obtain a filtered version of the measurement signal that changes at a slower rate than the measurement signal; and
generating an indication of change in resonance in a detection signal that switches when a difference between the measurement signal and the filtered version of the measurement signal exceeds a threshold level.