Abstract: This disclosure provides systems, methods and apparatus for increasing the efficiency of an amplifier when driven by a variable load. In one aspect a transmitter device is provided. The transmitter device includes a driver circuit characterized by an efficiency. The driver circuit is electrically connected to a transmit circuit characterized by an impedance. The transmitter device further includes a filter circuit electrically connected to the driver circuit and configured to modify the impedance to maintain the efficiency of the driver circuit at a level that is within 20% of a maximum efficiency of the driver circuit. The impedance is characterized by a complex impedance value that is within a range defined by a real first impedance value and a second real impedance value. A ratio of the first real impedance value to the second real impedance value is at least two to one.

Abstract: This disclosure provides systems, methods and apparatus for reducing harmonic emissions. One aspect of the disclosure provides a transmitter apparatus. The transmitter apparatus includes a driver circuit characterized by an efficiency and a power output level. The driver circuit further includes a filter circuit electrically connected to the driver circuit and configured to modify the impedance of the transmit circuit to maintain the efficiency of the driver circuit at a level that is within 20% of a maximum efficiency of the driver circuit when the impedance is within the complex impedance range. The filter circuit is further configured to maintain a substantially constant power output level irrespective of the reactive variations within the complex impedance range. The filter circuit is further configured to maintain a substantially linear relationship between the power output level and the resistive variations within the impedance range.

Abstract: Exemplary embodiments are directed to controlling impedance. A wireless power transmitter for controlling impedance comprises a transmit circuit configured to wirelessly transmit power to a plurality of receivers, each having a load resistance, within a charging region of the transmit circuit. The transmitter also comprises a controller configured to request each receiver of the plurality of receivers to adjust its load resistance to a value that achieves a target total impedance as presented to the controller.

Abstract: This invention describes a method and apparatus to cancel the mutual inductance between mutually coupled transmit coils, each of the transmit coils fed by individual power amplifiers, and the transmit coils all sharing a common ground with the power amplifiers. The methods and systems disclosed consist of coupling the return legs of each transmit coil to a mutual inductance cancellation circuit near a common ground return connection. The cancellation circuit uses a combination of inductors and capacitors to bridge various combinations of the transmit coils without physically connecting the “bridged” transmit coils. Transmit coils “bridged” using inductors have positive mutual inductance added to them, while transmit coils “bridged” using capacitors have negative mutual inductance added to them.

Abstract: An apparatus comprises a first driver circuit having a first output impedance while driving a plurality of couplers with a first current having a first phase to generate a wireless field. A second driver circuit drives the plurality of couplers with a second current having a second phase. A controller causes the second driver circuit to sequentially drive each of the plurality of couplers with the second current while causing the first driver circuit to simultaneously drive the other couplers with the first current. The controller identifies a subset of the plurality of couplers based on detecting a change from the first output impedance in response to each of the plurality of couplers being sequentially driven with the second current. The controller selectively energizes the subset of the plurality of couplers via one or both of the first and second driver circuits to wirelessly transfer the charging power.

Abstract: An apparatus comprises a first driver circuit having a first output impedance while driving a plurality of couplers with a first current having a first phase to generate a wireless field. A second driver circuit drives the plurality of couplers with a second current having a second phase. A controller causes the second driver circuit to sequentially drive each of the plurality of couplers with the second current while causing the first driver circuit to simultaneously drive the other couplers with the first current. The controller identifies a subset of the plurality of couplers based on detecting a change from the first output impedance in response to each of the plurality of couplers being sequentially driven with the second current. The controller selectively energizes the subset of the plurality of couplers via one or both of the first and second driver circuits to wirelessly transfer the charging power.

Abstract: This invention describes a method and apparatus to cancel the mutual inductance between mutually coupled transmit coils, each of the transmit coils fed by individual power amplifiers, and the transmit coils all sharing a common ground with the power amplifiers. The methods and systems disclosed consist of coupling the return legs of each transmit coil to a mutual inductance cancellation circuit near a common ground return connection. The cancellation circuit uses a combination of inductors and capacitors to bridge various combinations of the transmit coils without physically connecting the “bridged” transmit coils. Transmit coils “bridged” using inductors have positive mutual inductance added to them, while transmit coils “bridged” using capacitors have negative mutual inductance added to them.

Abstract: This disclosure provides systems, methods and apparatus for decoupling multiple wireless charging transmitters. In one aspect, a device is configured to transmit wireless power to a first receiver. The device includes a first driver coil and a second driver coil. The device further includes a common reactance element connected to the first driver coil and the second driver coil. The reactance element is configured to at least partially cancel mutual inductance between the first driver coil and the second driver coil.

Abstract: This disclosure provides systems, methods and apparatus for reducing harmonic emissions. One aspect of the disclosure provides a transmitter apparatus. The transmitter apparatus includes a driver circuit characterized by an efficiency and a power output level. The driver circuit further includes a filter circuit electrically connected to the driver circuit and configured to modify the impedance of the transmit circuit to maintain the efficiency of the driver circuit at a level that is within 20% of a maximum efficiency of the driver circuit when the impedance is within the complex impedance range. The filter circuit is further configured to maintain a substantially constant power output level irrespective of the reactive variations within the complex impedance range. The filter circuit is further configured to maintain a substantially linear relationship between the power output level and the resistive variations within the impedance range.

Abstract: This disclosure provides systems, methods and apparatus for reducing harmonic emissions. One aspect of the disclosure provides a transmitter apparatus. The transmitter apparatus includes a driver circuit characterized by an efficiency and a power output level. The driver circuit further includes a filter circuit electrically connected to the driver circuit and configured to modify the impedance of the transmit circuit to maintain the efficiency of the driver circuit at a level that is within 20% of a maximum efficiency of the driver circuit when the impedance is within the complex impedance range. The filter circuit is further configured to maintain a substantially constant power output level irrespective of the reactive variations within the complex impedance range. The filter circuit is further configured to maintain a substantially linear relationship between the power output level and the resistive variations within the impedance range.

Abstract: This disclosure provides systems, methods and apparatus for tuning a wireless power transmitter. In one aspect an apparatus configured to wirelessly provide power to a load is provided. The apparatus includes a transmit circuit including a transmit coil. The transmit circuit is configured to wirelessly provide power to the load. The transmit coil is configured to resonate at a resonant frequency. The transmit circuit has a reactance. The apparatus further includes a detection circuit configured to detect a change in the resonant frequency while providing power to the load. The apparatus further includes a tuning circuit configured to adjust the reactance based on the change.

Abstract: Exemplary embodiments are directed to controlling impedance. A wireless power transmitter for controlling impedance comprises a transmit circuit configured to wirelessly transmit power to a plurality of receivers, each having a load resistance, within a charging region of the transmit circuit. The transmitter also comprises a controller configured to request each receiver of the plurality of receivers to adjust its load resistance to a value that achieves a target total impedance as presented to the controller.

Abstract: This disclosure provides systems, methods and apparatus for reducing harmonic emissions. One aspect of the disclosure provides a transmitter apparatus. The transmitter apparatus includes a driver circuit characterized by an efficiency and a power output level. The driver circuit further includes a filter circuit electrically connected to the driver circuit and configured to modify the impedance of the transmit circuit to maintain the efficiency of the driver circuit at a level that is within 20% of a maximum efficiency of the driver circuit when the impedance is within the complex impedance range. The filter circuit is further configured to maintain a substantially constant power output level irrespective of the reactive variations within the complex impedance range. The filter circuit is further configured to maintain a substantially linear relationship between the power output level and the resistive variations within the impedance range.

Abstract: This disclosure provides systems, methods and apparatus for decoupling multiple wireless charging transmitters. In one aspect, a device is configured to transmit wireless power to a first receiver. The device includes a first driver coil and a second driver coil. The device further includes a common reactance element connected to the first driver coil and the second driver coil. The reactance element is configured to at least partially cancel mutual inductance between the first driver coil and the second driver coil.

Abstract: This disclosure provides systems, methods and apparatus for tuning a wireless power transmitter. In one aspect an apparatus configured to wirelessly provide power to a load is provided. The apparatus includes a transmit circuit including a transmit coil. The transmit circuit is configured to wirelessly provide power to the load. The transmit coil is configured to resonate at a resonant frequency. The transmit circuit has a reactance. The apparatus further includes a detection circuit configured to detect a change in the resonant frequency while providing power to the load. The apparatus further includes a tuning circuit configured to adjust the reactance based on the change.

Abstract: This disclosure provides systems, methods and apparatus for increasing the efficiency of an amplifier when driven by a variable load. In one aspect a transmitter device is provided. The transmitter device includes a driver circuit characterized by an efficiency. The driver circuit is electrically connected to a transmit circuit characterized by an impedance. The transmitter device further includes a filter circuit electrically connected to the driver circuit and configured to modify the impedance to maintain the efficiency of the driver circuit at a level that is within 20% of a maximum efficiency of the driver circuit. The impedance is characterized by a complex impedance value that is within a range defined by a real first impedance value and a second real impedance value. A ratio of the first real impedance value to the second real impedance value is at least two to one.

Abstract: This disclosure provides systems, methods and apparatus for managing a temperature of a wireless power receiver. In one aspect a wireless power transmitter is provided. The wireless power transmitter includes a transmit circuit including a transmit coil. The transmit circuit is configured to wirelessly transmit power to a wireless power receiver. The wireless power transmitter further includes a communication circuit configured to receive information based on a temperature measurement of the wireless power receiver. The wireless power transmitter further includes a transmit controller circuit configured to adjust an operating point of power transfer based on the information.