Abstract: A power transmitter (101) for a wireless power transfer system comprises a transmitter coil (103) and a driver (201) generates a drive signal for the transmitter coil (103) employing a repeating time frame with a power transfer time interval and a foreign object detection time interval. A test generator (211) generates a test drive signal for a test coil (209) during the foreign object detection time interval. A foreign object detector (207) performs a foreign object detection test based on a measured parameter for the test drive signal. Prior to entering a power transfer phase, an adapter (213) controls the power transmitter (101) to operate in a foreign object detection initialization mode in which a preferred value of a signal parameter for the test drive signal is determined in response to at least a first message received from the power receiver (105). During the foreign object detection time interval the signal parameter of is set to the preferred value.

Abstract: A wireless power transfer system comprises at least one power receiver (105) for receiving a power transfer from the power transmitter (101) via a wireless inductive power transfer signal. Configurers (207, 306) of the power transmitter and receiver may perform a configuration process to determine a set of power transfer parameter values which are used in a first power transfer. The power transfer parameter values and a first identity for the first power receiver (105) are stored. After a detection of an absence of the power receiver by a first controller (211), a detector (213) may detect a presence of a candidate power receiver. If the candidate power receiver is detected within a given duration and has an identity matching the first identity, an initialization processor (215) initializes a second power transfer using the set of stored parameter values. Otherwise it discards the set of stored parameter values.

Abstract: A power transmitter (101) of a wireless power transfer system provides wireless power to a power receiver (105). The power transmitter (101) comprises a variable resonance circuit (201) generating an inductive power transfer signal in response to a drive signal. The resonance circuit comprises a capacitive and inductive impedance (201, 203), at least one of which is variable. The resonance frequency can be varied by at least one of the impedances being variable in response to a control signal. A driver (205) generates the drive signal with a variable drive frequency. A frequency modulator (305) applies frequency modulation to the drive signal by varying the variable drive frequency in response to data values to be transmitted to the power receiver (105). An adapter (309) generates the control signal in response to the data values such that the variable resonance frequency follows the variations in the drive frequency resulting from the frequency modulation of the drive signal.

Abstract: A power transmitter (101) for a wireless power transfer system comprises a transmitter coil (103) and a driver (201) generates a drive signal for the transmitter coil (103) employing a repeating time frame with a power transfer time interval and a foreign object detection time interval. A test generator (211) generates a test drive signal for a test coil (209) during the foreign object detection time interval. A foreign object detector (207) performs a foreign object detection test based on a measured parameter for the test drive signal. Prior to entering a power transfer phase, an adapter (213) controls the power transmitter (101) to operate in a foreign object detection initialization mode in which a preferred value of a signal parameter for the test drive signal is determined in response to at least a first message received from the power receiver (105). During the foreign object detection time interval the signal parameter of is set to the preferred value.

Abstract: A power transmitter (101) of a wireless power transfer system comprises a resonance including a transmitter coil (103) for generating a power transfer signal for wirelessly transferring power to a power receiver (105). Further, a driver (1303) generates a drive signal for the resonance circuit (201) and a message receiver (1305) is arranged to receive messages from the power receiver (105). A power loop controller (1307) implements a power control loop by adapting the power of the drive signal in response to power control messages received from the power receiver (105). However, the regulation is subject to a constraint of at least one of a current or voltage of the resonance circuit and a power of the drive signal being below a maximum limit. Further, the power transmitter (101) comprises an adapter (1309) which adapts the maximum limit in response to a load indication indicative of a loading of the power transfer signal by the power receiver (105).

Abstract: An inductive wireless power transmitter is presented for transmitting an inductive wireless power signal to at least two inductive wireless power receivers. The power transmitter coordinates communication with the power receivers in time slots. It allocates a measurement time slot for synchronised power measurement by the power transmitter and the power receivers. During the measurement time slot the power transmitter measures the amount of power it transmits. After the end of the measurement time slot it receives from the power receivers the measured amounts of power received. From the measured power transmitted and power received, it determines an amount of power lost. If the amount of power lost exceeds a threshold value, it reduces the power of the inductive wireless power signal.

Abstract: The invention proposes a method of encoding data packet by encoding type information and size information of said data packet into the same field. The invention also proposes a method of processing data packets received. The data packet comprises a header part and a message part. The header part comprises at least one bit for indicating the type of said data packet, said method comprising a step 101 of obtaining the size information of said data packet based on said at least one bit.

Abstract: A wireless power transfer system includes a power receiver (105) comprising a coil (107) for extracting power from an electromagnetic signal generated by a power transmitter (101). A load controller (305, 309) disconnects a load (303) during a foreign object detection interval and a power controller (307, 311) transmits power control messages reflecting a difference between an induced signal level and a reference level. A message transmitter (307, 313) transmits a predetermined loading indication for the reference level to the power transmitter (101) indicating a predetermined amount of power being extracted from the electromagnetic signal by the power receiver (105) when the load is disconnected and the induced signal is at the reference level.

Abstract: A wireless power transfer system includes a power receiver (105) receiving a power transfer from a power transmitter (101) via a wireless inductive power transfer signal. The power transmitter (101) comprises a transmit power coil (103) generating the power transfer signal. A test signal coil (209) coupled to a test signal generator (211) generates a magnetic test signal. A plurality of spatially distributed detection coils (213) is coupled to measurement unit (215) generating a set of measurement values reflecting signals induced in the detection coils (213) by the magnetic test signal. A processor (217) determines a measurement spatial distribution of the measurement value where the spatial distribution reflects positions of the detection coils (213). A foreign object detector (219) detects a presence of a foreign object in response to a comparison of the measurement spatial distribution to a reference spatial distribution.

Abstract: A method of encoding data packet by encoding type information and size information of the data packet into the same field. The data packet comprises a header part and a message part. The header part comprises at least one bit for indicating the type of the data packet, where the method includes obtaining the size information of the data packet based on the at least one bit.

Abstract: A wireless power transfer system includes a power transmitter (101) providing power to a power receiver (105) via an inductive power signal. The power transmitter (101) and receiver (105) can operate in different modes including a test mode and a power transfer mode. Operating parameters of the power receiver (105) are constrained in the test mode relative (and specifically the loading). A foreign object detector (209) generates a foreign object detection estimate from a comparison of a measured load to an expected load of the inductive power signal when the power receiver is operating in the test mode. A controller (211) enters the power transmitter (101) and receiver (103) into the power transfer mode when the foreign object detection estimate is indicative of no detection of a foreign object. In the power transfer mode, a parasitic power loss detector (207) generates a parasitic power loss detection for the power transfer if a parasitic power loss estimate is outside a range.

Abstract: A power transmitter is configured to transfer power to a power receiver using a wireless inductive power signal. The power transmitter includes a power signal generator configured to drive an inductor to provide the power signal to an inductor of the power receiver. A power loop control is employed by the power receiver for providing power control error messages to the power transmitter, which also includes a query message processor configured to detect a query message from the power receiver using load modulation of the power signal. A modification processor of the power receiver is configured to modify a response of the power loop controller to the power control error messages dependent on the query message. The power receiver is configured to detect the modifications to the operation of the power control and interpret this as a response from the power transmitter to the query message from the power receiver.

Abstract: A power transmitter (101) is arranged to transfer power to a power receiver (105) using a wireless inductive power signal. The power transmitter (101) comprises a power signal generator (207) which drives an inductor (103) to provide the power signal to an inductor of the power receiver (105). A power loop control is employed by the power receiver (105) providing power control error messages to the power transmitter (101). The power transmitter (101) comprises a query message processor (209) which can detect a query message received from the power receiver (105) using load modulation of the power signal. A modification processor (211) is arranged to modify a response of the power loop controller to the power control error messages dependent on the query message. The power receiver (105) can detect the modifications to the operation of the power control and thus can interpret this as a response to the query message.

Abstract: A power transmitter (101) for a wireless power transfer system comprises a transmitter coil (103) and a driver (201) generates a drive signal for the transmitter coil (103) employing a repeating time frame with a power transfer time interval and a foreign object detection time interval. A test generator (211) generates a test drive signal for a test coil (209) during the foreign object detection time interval. A foreign object detector (207) performs a foreign object detection test based on a measured parameter for the test drive signal. Prior to entering a power transfer phase, an adapter (213) controls the power transmitter (101) to operate in a foreign object detection initialization mode in which a preferred value of a signal parameter for the test drive signal is determined in response to at least a first message received from the power receiver (105). During the foreign object detection time interval the signal parameter of is set to the preferred value.

Abstract: The invention proposes a method of encoding data packet by encoding type information and size information of said data packet into the same field. The invention also proposes a method of processing data packets received. The data packet comprises a header part and a message part. The header part comprises at least one bit for indicating the type of said data packet, said method comprising a step (101) of obtaining the size information of said data packet based on said at least one bit.

Abstract: A wireless power transfer system comprises at least one power receiver (105) for receiving a power transfer from the power transmitter (101) via a wireless inductive power transfer signal. Configurers (207, 306) of the power transmitter and receiver may perform a configuration process to determine a set of power transfer parameter values which are used in a first power transfer. The power transfer parameter values and a first identity for the first power receiver (105) are stored. After a detection of an absence of the power receiver by a first controller (211), a detector (213) may detect a presence of a candidate power receiver. If the candidate power receiver is detected within a given duration and has an identity matching the first identity, an initialization processor (215) initializes a second power transfer using the set of stored parameter values. Otherwise it discards the set of stored parameter values.

Abstract: A wireless power transfer system includes a power transmitter (101) arranged to provide a power transfer to a power receiver (105) via a wireless inductive power signal. A parasitic power loss detector (207) is arranged to detect a parasitic power loss for the power transfer, and a user indicator (209) is arranged to initialize a user alert in response to the detection of the parasitic power loss. The system comprises an input (211) for receiving user inputs; and a controller (213) which is arranged to initiate an adaptation of a parasitic power loss detection operation performed by the parasitic power loss detector (207) to detect parasitic power losses if a user input meeting a criterion is not received. Each of the individual features may be implemented in the power transmitter (101), the power receiver (105), or may e.g. be distributed between these. The approach may allow improved foreign object detection in a wireless power transfer system.

Abstract: A power transmitter (501) for a wireless power transfer system includes a parallel resonance circuit (601) comprising at a transmitter coil (503) for generating the power transfer signal. A power source (605) has a current sink terminal and a power source terminal providing current to the parallel resonance circuit (601) with a limited rate of change of the current drawn. A first switch element (607) is coupled between a first end of the parallel resonance circuit (601) and the current sink terminal. A second switch element (609) is coupled between the other end and the current sink terminal. A driver (611) generates a cyclic drive signal such that each cycle comprises a two time intervals in which one switch element (607, 609) is closed and the other (607, 609) is open; and a third time interval in which both the first switch element (607) and the second switch element (609) are closed, the third time interval being between the other two intervals.

Abstract: A wireless power transfer system includes a power receiver and a power transmitter providing power using an inductive power signal. The power transmitter includes a resonance circuit having capacitive and inductive impedances, and a driver configured to generate a drive signal for the resonance circuit. A frequency modification circuit is configured to control the resonance frequency of the resonance circuit by slowing a state change for the capacitive and/or inductive impedance for a fractional time interval of at least some cycles of the drive signal, The frequency modification circuit is configured to align at least one of a start time and an end time for the fractional time interval to transitions of a timing signal. In the power transmitter, the driver is configured to generate the timing signal to have transitions synchronized to the drive signal. The slowing may be by impeding current flow between the capacitive and inductive impedances.

Abstract: A wireless power transfer system includes a power receiver (105) comprising a coil (107) for extracting power from an electromagnetic signal generated by a power transmitter (101). A load controller (305, 309) disconnects a load (303) during a foreign object detection interval and a power controller (307, 311) transmits power control messages reflecting a difference between an induced signal level and a reference level. A message transmitter (307, 313) transmits a predetermined loading indication for the reference level to the power transmitter (101) indicating a predetermined amount of power being extracted from the electromagnetic signal by the power receiver (105) when the load is disconnected and the induced signal is at the reference level.