Abstract: A method of operating a wireless power transmitter having a wireless power transmitting coil, an inverter that receives an input voltage and generates an AC output voltage that drives the wireless power transmitting coil, and at least one adjustable capacitance coupled to the wireless power transmitting coil to form a series tuning circuit therewith, can be performed by control circuitry of the wireless power transmitter and can include: responsive to increased power demand from a wireless power receiver, determining whether the input voltage is at a maximum value and, if so, reducing the at least one adjustable capacitance to increase gain; or responsive to decreased power demand from the wireless power receiver, determining whether the input voltage is at a minimum value and, if so, increasing the at least one adjustable capacitance to decrease gain.

Abstract: A switched capacitor converter can include a switched capacitor stage comprising a flying capacitor and a ladder of three switching devices. A first switching device can be connected between a DC input of the switched capacitor converter and an AC bus. A second switching device is connected between the DC input and a third switching device. The third switching device can be connected between the second switching device and ground. The flying capacitor can be connected between the AC bus and a junction of the second switching device and the third switching device. The switched capacitor converter can further include an inverter stage having an input coupled to the AC bus and an output that delivers an AC voltage.

Abstract: Electronic apparatuses according to embodiments of the present technology may include an electronic device a first surface and a second surface opposite the first. The electronic device may include a battery and a wireless charging coil within an interior volume of the device. The electronic device may include a first magnetic conductor and positioned between the battery and the wireless charging coil. The electronic device may also include an integrated circuit coupled with the battery and the wireless charging coil. The apparatuses may include a case extending about the electronic device. The case may be characterized by a first surface and a second surface. The case may be characterized by a thickness between the first surface of the case and the second surface of the case. The case may include a second magnetic conductor incorporated within the thickness of the case at the second surface of the case.

Abstract: An electronic device (that is capable of both transmitting and receiving wireless power) may be physically and inductively coupled to a removable accessory (that only receives wireless power). The electronic device and removable accessory may optionally be placed on a power transmitting device. In response to the electronic device and removable accessory being placed on a wireless power transmitting device, the electronic device may switch from a power transmitting mode (in which the electronic device transmits wireless power to the removable accessory) to a power receiving mode (in which the electronic device receives wireless power from the wireless power transmitting device). To ensure the electronic device detects the wireless power transmitting device and switches to the power receiving mode in this scenario, the electronic device may transmit wireless power in bursts separated by sleep periods while in the power transmitting mode.

Abstract: Electronic apparatuses according to embodiments of the present technology may include an electronic device a first surface and a second surface opposite the first. The electronic device may include a battery and a wireless charging coil within an interior volume of the device. The electronic device may include a first magnetic conductor and positioned between the battery and the wireless charging coil. The electronic device may also include an integrated circuit coupled with the battery and the wireless charging coil. The apparatuses may include a case extending about the electronic device. The case may be characterized by a first surface and a second surface. The case may be characterized by a thickness between the first surface of the case and the second surface of the case. The case may include a second magnetic conductor incorporated within the thickness of the case at the second surface of the case.

Abstract: An electronic device (that is capable of both transmitting and receiving wireless power) may be physically and inductively coupled to a removable accessory (that only receives wireless power). The electronic device and removable accessory may optionally be placed on a power transmitting device. In response to the electronic device and removable accessory being placed on a wireless power transmitting device, the electronic device may switch from a power transmitting mode (in which the electronic device transmits wireless power to the removable accessory) to a power receiving mode (in which the electronic device receives wireless power from the wireless power transmitting device). To ensure the electronic device detects the wireless power transmitting device and switches to the power receiving mode in this scenario, the electronic device may transmit wireless power in bursts separated by sleep periods while in the power transmitting mode.

Abstract: A wireless power transfer system can include an electronic device including a first wireless power transfer coil and wireless power transfer circuitry coupled to the wireless power transfer coil. The wireless power transfer circuitry can be capable of receiving power and transmitting power wirelessly via the first wireless power transfer coil. The system can further include an accessory device including a second wireless power transfer coil, a rectifier coupled to the second wireless power transfer coil, and an energy storage device coupled to the rectifier by a regulator circuit. The wireless power transfer circuitry can operate in a pulsed or burst wireless power transfer mode to deliver power to the accessory device.

Abstract: A method of adaptively controlling dead time between turn off of a first switching device of an inverter and turn on of a second switching device of the inverter that is a counterpart of the first switching device can include: monitoring a plurality of switching events of at least one of the first and second switching devices, storing for each monitored switching event an indication whether a dead time associated therewith permitted optimal switching, and adaptively controlling the dead time responsive to the stored indications. Monitoring a plurality of switching events of at least one of the first and second switching devices can further include sampling an output voltage of the inverter and comparing the sampled output voltage to one of a high reference voltage corresponding to a high inverter rail voltage and a low reference voltage corresponding to a low inverter rail voltage.

Abstract: A transmitter device is configured to transfer energy to multiple receiver devices. The transmitter device includes multiple transmitter coils, and a shared power converter is coupled to each transmitter coil. The shared power converter includes a leading half bridge and multiple trailing half bridges. Each transmitter coil is coupled between the leading half bridge and a respective one of the trailing half bridges. The shared power converter is dynamically configurable in that the leading half bridge may be coupled to multiple trailing half bridges when energy is to be transferred wirelessly to two or more receiver devices. The leading half bridge simultaneously operates with each trailing half bridge as an independent full-bridge phase shift inverter. A signal supplied to each transmitter coil is independently regulated by controlling a phase shift of a respective trailing half bridge with respect to the leading half bridge.

Abstract: A wireless power system has a wireless power transmitting device and multiple wireless power receiving devices. The wireless power transmitting device may have a foldable housing. The wireless power transmitting device has wireless power coils that are used in transmitting wireless power to electronic devices such as cellular telephones, wristwatches, ear buds battery cases, ear buds, computer styluses, and other electronic devices. A rectifier can be coupled to a wireless power coil. In a first mode the coil transmits wireless power to a cellular telephone or other device. In a second mode, the coil is used in receiving wireless power from the cellular telephone or other device. The received wireless power can be retransmitted to other devices.

Abstract: An electronic device in a wireless power system may be operable with a removable accessory such as a case. The device may have coplanar power transmitting and power receiving coils. The transmitting coil may be positioned within a central opening of the receiving coil. The removable accessory may have an embedded receiving coil configured to receive wireless power from the transmitting coil of the electronic device. The receiving coil of the electronic device may receive wireless power from a power transmitting device such as charging mat. The receiving coil of the electronic device may operate up to a higher maximum power than the transmitting coil of the electronic device. The power transmitting coil and power receiving coil in the electronic device may operate at different power transmission frequencies. To mitigate crosstalk, the power transmitting coil's operation frequency may be a non-integer multiple of the power receiving coil's operation frequency.

Abstract: A wireless power transfer system can include an electronic device including a first wireless power transfer coil and wireless power transfer circuitry coupled to the wireless power transfer coil. The wireless power transfer circuitry can be capable of receiving power and transmitting power wirelessly via the first wireless power transfer coil. The system can further include an accessory device including a second wireless power transfer coil, a rectifier coupled to the second wireless power transfer coil, and an energy storage device coupled to the rectifier by a regulator circuit. The wireless power transfer circuitry can operate in a pulsed or burst wireless power transfer mode to deliver power to the accessory device.

Abstract: An electronic device (that is capable of both transmitting and receiving wireless power) may be physically and inductively coupled to a removable accessory (that only receives wireless power). The electronic device and removable accessory may optionally be placed on a power transmitting device. In response to the electronic device and removable accessory being placed on a wireless power transmitting device, the electronic device may switch from a power transmitting mode (in which the electronic device transmits wireless power to the removable accessory) to a power receiving mode (in which the electronic device receives wireless power from the wireless power transmitting device). To ensure the electronic device detects the wireless power transmitting device and switches to the power receiving mode in this scenario, the electronic device may transmit wireless power in bursts separated by sleep periods while in the power transmitting mode.

Abstract: A wireless power system has a wireless power transmitting device with a wireless power transmitting coil and an inverter. The inverter and wireless power transmitting coil are used to transmit wireless power signals. The wireless power system also has a wireless power receiving device configured to receive the wireless power signals using a wireless power receiving coil. A rectifier in the wireless power receiving device rectifies alternating-current signals from the wireless power receiving coil and produces corresponding direct-current power. Power loss calculations may be used to help determine whether a foreign object might be present in the vicinity of a coupled wireless power transmitter and receiver. In an ecosystem with multiple models of transmitter and multiple models of receiver, model-dependent scaling factors may be maintained and exchanged between a given coupled transmitter and receiver pair to allow accurate power loss estimates to be made.

Abstract: A wireless power system may have a wireless power transmitting device and a wireless power receiving device. The wireless power receiving device may have a receive coil that receives wireless power signals from the wireless power transmitting device and may have a rectifier that produces direct-current power from the received wireless power signals. The wireless power transmitting device may have an array of transmit coils. Each transmit coil has a respective magnetic coupling coefficient characterizing its magnetic coupling with the receive coil. The wireless power transmitting device may have control circuitry that uses the magnetic coupling coefficient values in selecting transmit coils to use in transmitting wireless power to the wireless power receiving device.

Abstract: An electronic device in a wireless power system may be operable with a removable accessory such as a case. The device may have coplanar power transmitting and power receiving coils. The transmitting coil may be positioned within a central opening of the receiving coil. The removable accessory may have an embedded receiving coil configured to receive wireless power from the transmitting coil of the electronic device. The receiving coil of the electronic device may receive wireless power from a power transmitting device such as charging mat. The receiving coil of the electronic device may operate up to a higher maximum power than the transmitting coil of the electronic device. The power transmitting coil and power receiving coil in the electronic device may operate at different power transmission frequencies. To mitigate crosstalk, the power transmitting coil's operation frequency may be a non-integer multiple of the power receiving coil's operation frequency.

Abstract: A power system has a wireless power transmitting device and a wireless power receiving device. Coils in the transmitting device may include a circular coil overlapped by first and second rectangular coils at a charging surface. The rectangular coils each include straight segments extending over a central region of the circular coil. Control circuitry can activate the circular coil to transmit wireless power to a first type of wireless power receiving coil using vertical components of the magnetic field generated by the circular coil. The control circuitry can activate the rectangular coils to transmit wireless power to a second type of wireless power receiving coil using horizontal components of the magnetic field generated by the rectangular coils. The circular and rectangular coils wirelessly charge the power receiving device while located at the same position on the charging surface, regardless of the type of wireless power receiving coil that is used.

Abstract: A power converter can be implemented as a series of power conversion stages, including a wireless power conversion stage. In typical embodiments, the power converter receives power directly from mains voltage and outputs power to a battery within an electronic device. A transmitter side of the power converter converts alternating current received from a power source (e.g., mains voltage) to an alternating current suitable for applying to a primary coil of the wireless power conversion stage of the power converter.

Abstract: A wireless power system has a wireless power transmitting device and multiple wireless power receiving devices. The wireless power transmitting device may have a foldable housing. The wireless power transmitting device has wireless power coils that are used in transmitting wireless power to electronic devices such as cellular telephones, wristwatches, ear buds battery cases, ear buds, computer styluses, and other electronic devices. A rectifier can be coupled to a wireless power coil. In a first mode the coil transmits wireless power to a cellular telephone or other device. In a second mode, the coil is used in receiving wireless power from the cellular telephone or other device. The received wireless power can be retransmitted to other devices.

Abstract: A wireless power system has a wireless power transmitting device such as a charging mat with a charging surface and a wireless power receiving device that receives wireless power from coils overlapped by the charging surface. The wireless power transmitting device receives load current and load voltage measurements from the wireless power receiving device and uses this information to produce one or more load lines. The load lines may form a family of load lines each associated with a different respective duty cycle used by inverter circuitry in the wireless power transmitting device in transmitting wireless power signals using the coils. The control circuitry can determine whether the wireless power receiving device has moved by comparing current and voltage information from the wireless power receiving device to the family of load lines and can take appropriate action such as measuring coil inductances for use in subsequent coil selection operations.