16 (e.g., controller 16M supplies drive signals for inverter 60 at input 74 at a desired AC drive frequency). This causes the output circuit formed from coil 42 and capacitor 70 to produce alternating-current (AC) electromagnetic field (signals 44) that is received by wireless power receiving circuitry 54 formed from coil 48 in device 24. Rectifier 50 can then convert received power from AC to DC and supply a corresponding direct current (DC) output voltage Vrect for powering load 96 in power receiving device 24 (e.g., for charging battery 58, for powering a display and/or other input-output devices 56, and/or for powering other circuitry in load 96). The output voltage Vrect of rectifier 50 is sometimes referred to herein as a rectified voltage.

If desired, power receiving device 24 may include one or more voltage sensors such as voltage sensor 90A and one or more current sensors such as current sensor 90B coupled to output terminals of rectifier 50. Voltage sensor 90A can be configured to measure a voltage level of rectifier output voltage Vrect, whereas current sensor 90B can be configured to measure a current level flowing from the output terminals of rectifier 50 into load 96. The voltage and current sensors 90A and 90B may be used to determine power levels within power receiving device 24. The specific locations of sensors 90A and 90B (e.g., on the DC sides of rectifier 50 in FIG. 2) are merely illustrative. In general, voltage and current sensors 90A and 90B may be positioned at any desired positions within the power receiving circuitry 54 (e.g., on the AC sides of rectifier 50, if desired).

Wireless power transfer coil 48 of power receiving device 24 can be coupled to one or more capacitors. In the example of FIG. 2, coil 48 can have a first terminal coupled to rectifier 50 via capacitor 80-1 and can have a second terminal coupled to rectifier 50 via capacitor 80-2. Capacitor 82-1 can selectively be coupled in parallel with capacitor 80-1 via an associated switch 84-1. When switch 84-1 is activated (i.e., turned on), capacitors 80-1 and 82-1 can be coupled together in parallel. When switch 84-1 is deactivated (i.e., turned off), capacitor 82-1 will be switched out of use. The term “activate” with respect to a switch (or transistor) may refer to or be defined herein as an action that places the switch in an “on” or low-impedance state such that the two terminals of the switch are electrically connected to conduct current. Activating a switch can sometimes be referred to as turning on or closing a switch. The term “deactivate” with respect to a switch (or transistor) may refer to or be defined herein as an action that places the switch in an “off” or high-impedance state such that the two terminals of the switch/transistor are electrically disconnected with minimal leakage current. Deactivating a switch can sometimes be referred to as turning off or opening a switch.

At the other end, capacitor 82-2 can selectively be coupled in parallel with capacitor 80-2 via an associated switch 84-2. When switch 84-2 is activated (i.e., turned on), capacitors 80-2 and 82-2 can be coupled together in parallel. When switch 84-2 is deactivated (i.e., turned off), capacitor 82-2 will be switched out of use. The state of switches 84-1 and 84-2 can be controlled by data transceiver 46 or other control circuitry within power receiving device 24. In some embodiments, the state of switches 84-1 and 84-2 can be a function of a data communications or power transfer mode that is currently employed by system 8 to convey data packets or wireless power between devices 12 and 24. The example of FIG. 2 in which coil 48 is coupled to four capacitors 80-1, 82-1, 80-2, and 82-2 is illustrative. In other embodiments, coil 48 can be selectively coupled to two or more capacitors, three to ten capacitors, or more than ten capacitors. Capacitors 82-1 and 82-1, when switched into use, can alter the impedance of power receiving circuitry 54 and are thus sometimes referred to as impedance adjustment components.

During wireless power transfer operations, while power transmitting circuitry 52 in device 12 is driving AC signals into coil 42 to produce signals 44 at the power transmission frequency, wireless data transceiver circuitry 40 in device 12 can use frequency shift keying (FSK) modulation to modulate the power transmission frequency of the driving AC signals and thereby modulate the frequency of signals 44. As shown in FIG. 2, FSK modulator 40T may modulate the power transmission frequency that is being supplied by controller 16M to input 74 of inverter 60. Operated in this way, FSK data is transmitted in-band from device 12 to device 24. This data can be received in power receiving device 24 by using FSK demodulator 46R (data receiver RX) to perform FSK demodulation operations.

In power receiving device 24, coil 48 is used to receive signals 44. Power receiving circuitry 54 in device 24 uses the received signals on coil 48 and rectifier 50 to produce DC power. At the same time, wireless transceiver circuitry 46 (e.g., FSK demodulator 46R) in device 24 uses FSK demodulation to extract the transmitted in-band data from signals 44. This approach allows FSK data (e.g., FSK data packets) to be transmitted in-band from device 12 to device 24 with coils 42 and 48 while wireless power is simultaneously being conveyed from device 12 to device 24 via coils 42 and 48. Transceiver circuitry 46 may be coupled to coil 48 (e.g., via one or more capacitors). Measurement circuitry 43 may also be coupled to coil 48 or some other node in power receiving circuitry 54 to make impedance measurements, impulse response measurements, or other desired measurements for external object detection.

Such in-band communications between device 24 and device 12 can also use ASK modulation and demodulation techniques. Wireless transceiver circuitry 46 includes ASK modulator 46T coupled to coil 48 to modulate the impedance of power receiving circuitry 54 (e.g., to adjust the impedance at coil 48). This, in turn, modulates the amplitude of signals 44 and the amplitude of the AC signals passing through coil 42. ASK demodulator 40R monitors the amplitude of the AC signal passing through coil 42 and, using ASK demodulation, extracts the transmitted in-band data from these signals that was transmitted by wireless transceiver circuitry 46. ASK demodulator 40R may be coupled to a node 71 between coil 42 and capacitor 70 or may be coupled to some other node in power transmitting circuitry 52. Similarly, measurement circuitry 41 may optionally be coupled to node 71 or some other node in power transmitting circuitry 52 to make impedance measurements, impulse response measurements, or other desired measurements for external object detection. The use of ASK communications allows ASK data bits (e.g., ASK data packets) to be transmitted in-band from device 24 to device 12 via coils 48 and 42 while wireless power is simultaneously being conveyed from device 12 to device 24 via coils 42 and 48. Data transceiver 40 of power transmitting device and data transceiver 46 of power receiving device 24 that are used for conveying in-band data packets via wireless power transfer coils 42 and 48 are therefore sometimes referred to herein as data “communication(s)” transceiver circuitry.

Power transmitting device 12 can be configured to transfer wireless power to power receiving device 24 in accordance with one or more charging modes. Power transmitting device 12 can be operable in at least first and second charging modes. In the first charging (power transfer) mode, power transmitting device 12 can employ power transmitting circuit 52 to transmit wireless power when inverter 60 is operating at a first power carrier frequency F1 (e.g., inverter 60 is driving AC signals at frequency F1). Power carrier frequency F1 is thus sometimes referred to and defined herein as a first “inverter” frequency. In the second charging (power transfer) mode, power transmitting device 12 can employ power transmitting circuit 52 to transmit wireless power when inverter 60 is operating at a second power carrier frequency F2 different than F1 (e.g., inverter 60 is driving AC signals at a different frequency F2). Power carrier frequency F2 is thus sometimes referred to and defined herein as a second “inverter” frequency. Inverter frequencies F1 and F2 can sometimes be referred to herein collectively as wireless power transmitting inverter frequencies.

As an example, the first inverter frequency F1 may be less than the second inverter F2. In such a scenario, the first charging mode can be considered a slow(er) power transfer mode, whereas the second charging mode can be considered a fast(er) power transfer mode relative to the first charging mode. The example above in which system 8 is operable in two different charging modes with two different charging speeds (wattage) is illustrative. In general, wireless power transfer system 8 can be configured to support three or more power transfer modes with different charging speeds, four or more power transfer modes with different charging speeds, five or more power transfer modes with different charging speeds, six to ten power transfer modes with different charging speeds, or more than ten power transfer modes with different charging speeds (wattage).

To switch between different the charging modes, power receiving device 24 can output a frequency transition request, which can subsequently direct power transmitting device 24 to transition to a charging mode that uses a different inverter frequency. In certain situations, such as when devices 12 and 24 are not properly aligned (e.g. if the wireless power transfer coils 42 and 48 are misaligned or if the housings of devices 12 and 24 are misaligned), system 8 can inadvertently hop back and forth between the different charging modes, which can result in suboptimal wireless power transfer efficiency.

In accordance with some embodiments, frequency transition techniques are provided that mitigate such wireless power transfer inefficiencies that can arise when devices 12 and 24 are misaligned or detached from one each other. FIG. 3 is a flowchart of illustrative steps for adjusting the wireless power transmitting inverter frequency of power transmitting device 12. During the operations of block 100, power transmitting device 12 can operate in a foreign object detection (FOD) mode and can detect the presence of a power receiving device 24 on its charging surface. For example, power transmitting device 12 may use low-power external object detection or analog pings to detect the presence of a foreign object. As another example, power transmitting device 12 may perform impedance measurements, impulse response measurements, or other suitable foreign object detection schemes to detect when device 24 has been placed on the charging surface of device 12.

After power transmitting device 12 detects a potential power receiving device 24 on its charging surface, device 12 can output, during the operations of block 102, a digital ping to communicate with device 24. Digital pings are a type of ping signals. “Digital pings” may refer to and be defined herein as signals having longer pulses than the external object detection analog pings and having sufficient energy to activate or wake power receiving device 24 (e.g., a digital ping has sufficient bandwidth to support in-band communications between devices 12 and 24). For example, FSK and/or ASK data packets may be conveyed between devices 12 and 24 during digital ping operations. These in-band communications can be modulated at some inverter frequency.

During the operations of block 102, power transmitting device 12 can output a digital ping while the inverter 60 is operating at inverter frequency F1. For example, inverter frequency can be equal to about 125 kHz, about 128 kHz, about 200 kHz, about 326 kHz, about 360 kHz, at least 80 kHz, at least 100 kHz, less than 500 kHz, less than 300 kHz, 1.78 MHz, 13.56 MHZ, 110-205 kHz, between 80-300 kHz, between 300-400 kHz, or other suitable wireless power frequency or frequency range. The digital ping, sometimes referred to as a digital ping signal, can be received at power receiving device 24. Such digital ping signal received at coil 48 can result in AC current to flow through coil 48, which can cause rectifier 50 to drive output voltage Vrect high(er). When the rectifier output voltage Vrect exceeds a rectifier output threshold Vthres, one or more load components 96 can power (wake) up, including waking up data communications circuitry 46.

During the operations of block 104, devices 12 and 24 can perform one or more handshake operations. For example, power receiving device 24 can send one or more startup or identification packets providing information such as its power requirements, supported charging standards, and/or other wireless power transfer parameters. Power transmitting device 12 can also send one or more startup or identification packets providing information such as its power capabilities, supported charging standards, and/or other wireless power transfer characteristics to device 24. Based on the exchanged (identification) information, power transmitting device 12 can perform power negotiations operations with power receiving device 24 (e.g. so that device 12 can determine a suitable output for safely charging device 24). If desired, other handshaking, negotiation, or authentication operations can also be performed during block 104.

Subsequently, during the operations of block 106, power transmitting device 12 can optionally begin transmitting wireless power to power receiving device 24. In other words, power transmitting device 12 can be configured to operate in an “active” wireless power transfer mode. During the active wireless power transfer mode, power transmitting device 12 can transmit wireless power while inverter 60 is modulating signals at inverter frequency F1 (e.g., at the same carrier frequency previously used for transmitting the digital ping during block 102). During the active wireless power transfer mode, device 12 may concurrently perform in-band communications with device 24 (e.g., device 12 may use data transmitter 40T to transmit FSK packets to data receiver 46R, whereas device 24 may use data transmitter 46T to transmit ASK packets to data receiver 40R while wireless power is being transferred from device 12 to device 24). During the active wireless power transfer mode, power receiving device 24 can sometimes output a request for dynamically adjust the output power level of device 12 (e.g., by outputting control error packets or other power control request packets to device 12 for adjusting input voltage Vin). Such type of wireless power transfer operation in which device 24 can continuously negotiate desired power levels with device 12 is sometimes referred to as a “closed loop” wireless power transfer.

During the active wireless power transfer mode, power receiving device 24 can optionally obtain additional information from power transmitting device 12 (see, e.g., operations of block 108). As an example, power receiving device 24 can receive information such as a country code from power transmitting device 12. The country code can indicate a location reflecting where system 8 is currently operating. For instance, a country code having a first value might indicate that system 8 is currently located in the United States; a country code having a second value different than the first value might indicate that system 8 is currently located in a European country; and a country code having a third value different than the first and second values might indicate that system 8 is currently located in an Asian country. Additional or alternatively, power receiving device 24 can receive information such as an input voltage limit from power transmitting device 12. The input voltage limit can represent a maximum input voltage Vin that is supported by device 12 (see FIG. 2). If desired, power receiving device 24 can obtain one or more other wireless power transfer parameter(s) from power transmitting device 12 during block 108.

During the operations of block 110, power receiving device 24 can perform an action based on the information received during block 108 and/or block 104. As an example, power receiving device 24 can analyze the received country code and/or other power capabilities information received during block 104 and/or block 108 and determine whether power transmitting device 12 can support wireless power transfer using a different inverter frequency. In response to determining that device 12 can support active wireless power transfer using another inverter frequency, power receiving device 24 can output a frequency transition request (packet) to power transmitting device 12 (e.g., via in-band communications). A “frequency transition” request can refer to and be defined herein as a request to adjust an operating frequency such as the wireless power transmission inverter frequency at device 12. The frequency transition request can include information designating a target inverter frequency F2 that is different than the current inverter frequency F1. This example in which power receiving device 24 transmits a frequency transition request to device 12 is illustrative. More generally, power receiving device 24 can transmit a message indicating that device 24 is ready to proceed with a subsequent (further) stage of wireless power transfer (e.g., a message indicating to power transmitting device 24 that it is ready to receive signals at a different carrier frequency).

During the operations of block 112, power transmitting device 12 can receive the frequency transition request (or other message indicating that device 24 is ready to proceed with further stages of wireless power transfer) from device 24 and respond by outputting a corresponding acknowledgement packet back to device 24. Such type of acknowledgement packet is sometimes referred to herein as a frequency transition acknowledgement (ACK) response. After sending the frequency transition ACK response, power transmitting device 12 can terminate current the digital ping modulated at frequency F1. After receiving the frequency transition ACK response packet from device 12, the rectifier output voltage Vrect within power receiving device 24 can fall to a low voltage, marking an end of the active wireless power transfer operation.

Power transmitting device 12 can then output, during the operations of block 112, a digital ping while the inverter 60 is operating at an adjusted inverter frequency F2 in accordance with the received frequency transition request. In general, the adjusted inverter frequency F2 can be greater than F1 or less than F1 and can be equal to about 125 kHz, about 128 kHz, about 200 kHz, about 326 kHz, about 360 kHz, at least 80 kHz, at least 100 kHz, less than 500 kHz, less than 300 kHz, 1.78 MHz, 13.56 MHz, 110-205 kHz, between 80-300 kHz, between 300-400 kHz, or other suitable wireless power frequency or frequency range. Device configurations in which F2 is greater than F1 are sometimes described herein as an example.

Wireless power transfer using higher inverter (power carrier) frequencies generally provide greater charger wattage. Thus, wireless power transfer using inverter frequency F1 can sometimes be referred to herein as a “low(er)-wattage” charging mode, whereas wireless power transfer using a greater inverter frequency F2 can sometimes be referred to herein as a “high(er)-wattage” charging mode. System 8 can support more than two different charging wattages. Modes with higher charging wattage can provide faster charging speeds. The digital ping output during block 112 can be received at power receiving device 24. Such digital ping signal received at coil 48 can result in AC current to flow through coil 48, which can cause rectifier 50 to drive output voltage Vrect high(er). When the rectifier output voltage Vrect exceeds a rectifier output threshold Vthres, one or more load components 96 can power (wake) up, including waking up data communications circuitry 46.

During the operations of block 114, power receiving device 24 can be configured to adjust one or more components in the power receiving circuitry in preparation for wireless power transfer and/or in-band communications at inverter frequency F2. For example, power receiving device 24 can, using control circuitry 30 (see FIG. 1), deactivate switches 84-1 and 84-2 during block 114 to switch capacitors 82-1 and 82-2 out of use. Switches 84-1 and 84-2 might be activated by default, such as during operations when signals modulated at inverter frequency F1 are being conveyed between devices 12 and 24. This is merely illustrative. In other embodiments, switches 84-1 and 84-2 might be deactivated by default and can be activated during the operations of block 114 to selectively couple capacitors 82-1 and 82-2 in parallel with capacitors 80-1 and 80-2, respectively. Such type of component tuning is illustrative. If desired, other components coupled to coil 48 can be adjusted or tuned during block 114 in preparation for operation at the updated frequency.

After tuning the components, devices 12 and 24 can perform one or more handshake operations. For example, power receiving device 24 can send a startup or identification packet providing information such as its power requirements, supported charging standards, and/or other wireless power transfer parameters. Power transmitting device 12 can also send one or more startup or identification packets providing information such as its power capabilities, supported charging standards, and/or other wireless power transfer characteristics to device 24. Based on the exchanged (identification) information, power transmitting device 12 can perform power negotiations operations with power receiving device 24 (e.g. so that device 12 can determine a suitable output for safely charging device 24). If desired, other handshaking, negotiation, or authentication operations can also be performed during block 104.

Subsequently, during the operations of block 116, power transmitting device 12 can begin performing closed-loop wireless power transfer to power receiving device 24. During the active wireless power transfer mode of block 116, power transmitting device 12 can transmit wireless power while inverter 60 is modulating signals at inverter frequency F2 (e.g., using the new/target inverter frequency indicated by the frequency transition request). During the active wireless power transfer mode, device 12 may concurrently perform in-band communications with device 24 (e.g., device 12 may use data transmitter 40T to transmit FSK packets to data receiver 46R, whereas device 24 may use data transmitter 46T to transmit ASK packets to data receiver 40R while wireless power is being transferred from device 12 to device 24). Power transmitting device 12 may continue to transfer wireless power to device 24 until a battery level of battery 58 (see FIG. 1) exceeds a first battery threshold. The battery level of battery 58 is sometimes referred to herein as a state of charge or “SOC.” The first battery threshold is thus sometimes referred to as a first state of charge threshold. The first battery threshold can be equal to or represent at least 80% of a full SOC, at least 90% of a full SOC, at least 95% of a full SOC, or 95-100% of a full SOC. The term “full SOC” can refer to a state at which battery 58 is fully (100%) charged.

The operations of FIG. 3 are illustrative. In some embodiments, one or more of the described operations may be modified, replaced, or omitted. In some embodiments, one or more of the described operations may be performed in parallel. In some embodiments, additional processes may be added or inserted between the described operations. If desired, the order of certain operations may be reversed or altered and/or the timing of the described operations may be adjusted so that they occur at slightly different times. In some embodiments, the described operations may be distributed in a larger system.

The operations of FIG. 3 illustrate a scenario when system 8 is able to successfully transition from operating at inverter frequency F1 to a different inverter frequency F2. In certain scenarios, such as when devices 12 and 24 are at least partially misaligned (e.g., when the wireless power transfer coils 42 and 48 are not properly aligned or when the housings of devices 12 and 24 are not properly aligned), system 8 may not always be able to successfully change inverter frequencies. FIG. 4 is a flowchart of illustrative steps for operating system 8 when the frequency transition fails. The operations leading up to and including block 110 of FIG. 4 are identical to those already described in connection with blocks 100-110 of FIG. 3 and need not be reiterated to avoid obscuring the present embodiment.

During the operations of block 112 in FIG. 4, power transmitting device 12 can receive the frequency transition request (or other message indicating that device 24 is ready to proceed with further stages of wireless power transfer) from device 24 and respond by outputting a corresponding frequency transition acknowledgement (ACK) packet back to device 24. After sending the frequency transition ACK response, power transmitting device 12 can terminate current the digital ping modulated at frequency F1. Upon termination of the digital ping, the rectifier output voltage Vrect within power receiving device 24 can fall to a low voltage, marking an end of the active wireless power transfer operation. Subsequently, power transmitting device 12 can output, during the operations of block 112, a digital ping while the inverter 60 is operating at an adjusted inverter frequency F2 in accordance with the received frequency transition request.

Ideally, such as when devices 12 and 24 are properly aligned for optimal wireless power transfer, the rectifier output voltage Vrect at device 24 will rise to a higher voltage level exceeding Vthres, which can cause device 24 to tune one or more components and begin performing handshaking operations with device 12, as described in connection with block 114 of FIG. 3. However, when devices 12 and 24 are not properly aligned and/or in the presence of foreign external objects such as coins, paper clips, or other conductive objects that might interfere with the wireless power transfer operation, the digital ping might not result in Vrect exceeding Vthres. As a result, power receiving device 24 will not begin handshake operations, send any acknowledgement or identification packets, or otherwise respond to device 12. Power transmitting device 12 may output the digital ping for a certain digital ping duration to wait for a response from device 24. For example, the digital ping duration can be less than 20 ms (millisecond), less than 30 ms, less than 40 ms, less than 50 ms, less than 100 ms, 10-20 ms, 20-50 ms, 50-100 ms, 100-500 ms, less than one second, or other suitable ping duration.

If power transmitting device 12 fails to receive any response from device 24 during the digital ping duration, power transmitting device 12 can terminate the digital ping and wait for a silent period before sending another digital ping (see operations of block 200). Power transmitting device 12 does not output any in-band signals to device 24 during the silent period. After the silent period, power transmitting device 12 can attempt again to communicate with device 24 by sending a second digital ping while the inverter 60 is operating at the adjusted inverter frequency F2. Power transmitting device 12 may output the second digital ping for the digital ping duration to wait for a response from device 24. If power transmitting device 12 fails to receive any response from device 24 during the digital ping duration of the second digital ping, power transmitting device