Abstract: An electronic device includes a wireless charging receive coil configured to transduce, into an alternating current (AC) power signal, a magnetic field generated by a wireless charging transmit coil of an external device; an active rectifier configured to convert the AC signal received at an AC side of the active rectifier into a direct current (DC) power signal output at a DC side of the active rectifier, the active rectifier comprising a plurality of switches; a first modulation capacitor connected to an upper rail of the AC side; a second modulation capacitor connected to a lower rail of the AC side; and a controller configured to adjust an impedance of the computing device to communicate with the external device by at least controlling the plurality of switches to cause the first modulation capacitor and the second modulation capacitor to charge during separate time periods.

Abstract: This disclosure describes apparatuses and techniques for a switched multi-cell battery system for electronic devices. In some aspects, a switched multi-cell battery system may transfer, via a plurality of power control switches electrical power from a power adapter to components of the electronic device by charging battery cells in series and by discharging the battery cells in parallel or as a single battery cell. As a result, the switched multi-cell battery system may reduce or eliminate a voltage step-down conversion stage to increase a power-transfer efficiency of an electronic device. By doing so, charging times may be reduced or operating times may be increased, thereby improving users' experience with their electronic devices.

Abstract: A wireless charging receiver that includes a first coil, a second coil, and a nanocrystalline sheet is disclosed. The first coil is configured to be located within a recess in the nanocrystalline sheet and is positioned between the second coil and the nanocrystalline sheet. The first coil includes first and second terminals and the second coil includes third and fourth terminals. The first terminal is connected to the third terminal and the second terminal is connected to the fourth terminal to electrically connect the first coil to the second coil. The first coil may be formed of a flexible printed circuit board having a continuous trace or may be formed of litz wire. The first coil may be a hybrid coil with a first portion formed of a flexible printed circuit board having a continuous trace and with a second portion formed of litz wire.

Abstract: Shielded electrical transformers and power converters using those transformers are disclosed. In some implementations, a shielded electrical transformer includes a magnetic core, a primary winding, a first secondary winding, and a second secondary winding. The transformer includes a first shielding winding that has a same voltage potential direction as the primary winding and is connected in series with the primary winding to carry current that passes through the primary winding. The transformer also includes a second shielding winding that has a voltage potential direction opposite the primary winding and is connected from primary ground to a floating terminal. The first secondary winding, the second secondary winding, the first shielding winding, and the second shielding winding can each have an approximately equal number of turns.

Abstract: Devices for wireless charging with metal housings. The device comprises a wireless power receiving coil and an associated coil core, wherein the coil core defines a recess and at least a portion of the wireless power receiving coil is disposed in the recess; and a housing comprising one or more metal portions, wherein the housing is configured to receive at least a portion of the wireless power receiving coil and the associated coil core in an opening defined by the one or more metal portions. Alternatively, the device comprises a wireless power receiving coil and an associated coil core; a housing comprising one or more metal portions; and an alignment feature configured to interact with a magnet of a wireless charger to align the device with the wireless charger, wherein the alignment feature comprises a plurality of metal elements that are electrically insulated from each other.

Abstract: An example device (204) includes a wireless charging receive coil (222) configured to transduce, into an alternating current—AC—power signal, a magnetic field generated by a wireless charging transmit coil (218) of an external device (202); an active rectifier (224) configured to convert the AC signal into a direct current—DC—power signal; and circuitry (226) configured to: obtain a target level of the DC power signal; and control the active rectifier (224) to output the DC power signal with the target level.

Abstract: An example device includes a plurality of capacitor and wireless charging coil series pairs that are collectively in parallel; and one or both of: a driver circuit configured to drive the plurality of capacitor and wireless charging coil series pairs with a first common signal; or a sink circuit configured to receive a second common signal from the plurality of capacitor and wireless charging coil series pairs.

Abstract: The present disclosure provides for a wearable device having a wireless power receiving system that may inductively receive or transmit power. The wireless power receiving system includes a receiver coil having a profile that follows a contour of a bottom cover of the wearable device. A transmitter coil from a wireless charging device has a complementary profile that mates with the profile defined by the receiver coil. In one example, the wireless power receiving system includes a shielding, and a receiver coil attached to the shielding. The receiver coil further includes an inner wall and an outer wall connected by a top surface of a coil body. The inner wall defines a center opening in the receiver coil, wherein the receiver coil is conical in shape.

Abstract: An example active stylus includes a core comprising: a main cylinder having a first end, a second end; a first supplemental cylinder disposed at the first end of the main cylinder and having a diameter that is larger than a diameter of the main cylinder; a second supplemental cylinder disposed between the first supplemental cylinder and the second end of the main cylinder and having a diameter that is larger than the diameter of the main cylinder; and a wireless charging receive coil configured to transduce flux of a magnetic field generated by a wireless charging transmit coil into electrical current, wherein the wireless charging receive coil is positioned around a longitudinal axis of the main cylinder of the core and between the first supplemental cylinder and the second supplemental cylinder.

Abstract: Devices for wireless charging with metal housings. The device comprises a wireless power receiving coil and an associated coil core, wherein the coil core defines a recess and at least a portion of the wireless power receiving coil is disposed in the recess; and a housing comprising one or more metal portions, wherein the housing is configured to receive at least a portion of the wireless power receiving coil and the associated coil core in an opening defined by the one or more metal portions. Alternatively, the device comprises a wireless power receiving coil and an associated coil core; a housing comprising one or more metal portions; and an alignment feature configured to interact with a magnet of a wireless charger to align the device with the wireless charger, wherein the alignment feature comprises a plurality of metal elements that are electrically insulated from each other.

Abstract: This disclosure describes apparatuses and techniques for a switched multi-cell battery system for electronic devices. In some aspects, a switched multi-cell battery system may transfer, via a plurality of power control switches electrical power from a power adapter to components of the electronic device by charging battery cells in series and by discharging the battery cells in parallel or as a single battery cell. As a result, the switched multi-cell battery system may reduce or eliminate a voltage step-down conversion stage to increase a power-transfer efficiency of an electronic device. By doing so, charging times may be reduced or operating times may be increased, thereby improving users' experience with their electronic devices.

Abstract: An example device (204) includes a wireless charging receive coil (222) configured to transduce, into an alternating current—AC—power signal, a magnetic field generated by a wireless charging transmit coil (218) of an external device (202); an active rectifier (224) configured to convert the AC signal into a direct current—DC—power signal; and circuitry (226) configured to: obtain a target level of the DC power signal; and control the active rectifier (224) to output the DC power signal with the target level.

Abstract: Methods, systems, and apparatus, including computer programs encoded on computer-storage media, for wireless charging using time-division multiplexing. In some implementations, a wireless charger is configured to concurrently charge multiple devices by providing power wirelessly to individual devices in different time periods. The wireless charger can perform time-division multiplexing by selectively directing the output of a single driver circuit to different power transfer coil segments at different times. The wireless charging sessions of multiple devices can be maintained by repeating a pattern of activating different power transfer coil segments one by one in successive time periods.

Abstract: The present disclosure provides for a wearable device having a wireless power receiving system that may inductively receive or transmit power. The wireless power receiving system includes a receiver coil having a profile that follows a contour of a bottom cover of the wearable device. A transmitter coil from a wireless charging device has a complementary profile that mates with the profile defined by the receiver coil. In one example, the wireless power receiving system includes a shielding, and a receiver coil attached to the shielding. The receiver coil further includes an inner wall and an outer wall connected by a top surface of a coil body. The inner wall defines a center opening in the receiver coil, wherein the receiver coil is conical in shape.

Abstract: This disclosure describes apparatuses and techniques for a switched multi-cell battery system for electronic devices. In some aspects, a switched multi-cell battery system may transfer, via a plurality of power control switches electrical power from a power adapter to components of the electronic device by charging battery cells in series and by discharging the battery cells in parallel or as a single battery cell. As a result, the switched multi-cell battery system may reduce or eliminate a voltage step-down conversion stage to increase a power-transfer efficiency of an electronic device. By doing so, charging times may be reduced or operating times may be increased, thereby improving users' experience with their electronic devices.

Abstract: This document describes a passive adapter for wireless charging of an electronic device and associated methods and systems. The described passive adapter includes two coils connected by a capacitor and separated by a core material that prevents mutual coupling between the coils. These two coils may have differing sizes, such that one coil can size-match to a transmitter coil of an existing wireless charger and the second coil can size-match to a smaller (or larger) receiver coil in a wireless-power receiver to charge a battery of the wireless-power receiver. In aspects, these two coils may be separated by a distance that enables the passive adapter to act as a passive repeater by bridging a space between the transmitter coil and the receiver coil.

Abstract: In general, techniques are described that are directed to a device that includes a power storage device, an electrical load, and a first regulated power converter including components configured to generate, during a first time period and using electrical energy received from a power source external to the device, a first power signal to charge the power storage device. A second regulated power converter includes components configured to determine a charging current at which to charge the power storage device, determine a total amount of current flowing to the power storage device that includes current sourced by the second power converter less current sinked by the electrical load, and generate, during a second time period that is non-overlapping with the first time period, using electrical energy from the power source and based on determined the total amount of current, a second power signal to charge the power storage device.

Abstract: Methods, systems, and apparatus, including computer programs encoded on computer-storage media, for wireless charging using time-division multiplexing. In some implementations, a wireless charger is configured to concurrently charge multiple devices by providing power wirelessly to individual devices in different time periods. The wireless charger can perform time-division multiplexing by selectively directing the output of a single driver circuit to different power transfer coil segments at different times. The wireless charging sessions of multiple devices can be maintained by repeating a pattern of activating different power transfer coil segments one by one in successive time periods.

Abstract: The technology provides for a wearable device including a body and an accessory adapted to be attached to the body. The body includes a first coil configured to inductively transmit power. The body may further include first power management circuitry configured to control the first coil to transmit power according to a wireless charging standard, and to modulate the power transmitted through the first coil to transmit data according to a wireless communication standard. The accessory may include a second coil configured to inductively receive power. The accessory may further include second power management circuitry configured to control the second coil to receive the power transmitted through the first coil according to the wireless charging standard, and to control the second coil to receive the data transmitted through the first coil according to the wireless communication standard.

Abstract: An example active stylus includes a core comprising: a main cylinder having a first end, a second end; a first supplemental cylinder disposed at the first end of the main cylinder and having a diameter that is larger than a diameter of the main cylinder; a second supplemental cylinder disposed between the first supplemental cylinder and the second end of the main cylinder and having a diameter that is larger than the diameter of the main cylinder; and a wireless charging receive coil configured to transduce flux of a magnetic field generated by a wireless charging transmit coil into electrical current, wherein the wireless charging receive coil is positioned around a longitudinal axis of the main cylinder of the core and between the first supplemental cylinder and the second supplemental cylinder.