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: 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: 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: 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 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: 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: In general, techniques are described that are directed to a device having a first power storage device and a second power storage device connected in series. A first power converter may generate, using electrical energy sourced from the first power storage device and the second power storage device, a first power signal to power a first set of components. A second power converter may generate, using electrical energy sourced from the first power storage device and not the second power storage device, a second power signal to power a second set of components.

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: 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: This document describes techniques and apparatuses directed at reducing inductive-charging power loss. In aspects, a mobile device includes a multi-layer flexible printed circuit board (FPCB) coil that forms a receiver coil having a Litz-wire structure. The FPCB coil includes a multi-trace bundle, having traces systematically routed throughout the different layers of the FPCB coil to reduce eddy current losses.

Abstract: Methods, systems, and techniques for safely controlling wireless charging in the presence of a foreign object are presented. A method includes determining a power difference between a power transmitted by a wireless charger and a power received by an electronic device, determining a level of misalignment of the electronic device with respect to the wireless charger; estimating an amount of power difference due to the level of misalignment of the electronic device with respect to the wireless charger, adjusting a power difference threshold for the wireless charger based on the estimated amount of power difference, and controlling operation of the wireless charger based on the power difference and the adjusted power difference threshold.

Abstract: This document describes techniques and apparatuses directed at reducing inductive-charging power loss. In aspects, a mobile device includes a multi-layer flexible printed circuit board (FPCB) coil that forms a receiver coil having a Litz-wire structure. The FPCB coil includes a multi-trace bundle, having traces systematically routed throughout the different layers of the FPCB coil to reduce eddy current losses.

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 power adapter includes a rectifier configured to convert an input alternating current (AC) power signal on an AC bus into an input direct current (DC) power signal on an input DC bus; a split differential mode (DM) choke connected to the input DC bus, wherein the split DM choke comprises a first DM choke on a high side of the input DC bus and a second DM choke on a low side of the input DC bus; and a switched mode power converter configured to output, using the input DC power signal, an output DC power signal on an output DC bus.

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.