Abstract: A wireless power transfer system includes a power receiver and a power transmitter providing power to this using an inductive power signal. The power transmitter comprises a variable resonance circuit (201) having a variable resonance frequency and generating the inductive power signal. A driver (203) generates the drive signal and a load modulation receiver (303) demodulates load modulation of the inductive power signal. An adaptor (305) adapts the operating frequency and the resonance frequency to converge, and specifically is arranged to control the operating frequency and the resonance frequency to be substantially the same. The adaptation of the operating frequency and the resonance frequency is further in response to a demodulation quality measure. The invention may allow improved communication, and in particular may reduce intermodulation distortion.

Abstract: A wireless power transfer system includes a power receiver and a power transmitter providing power using an inductive power signal. The power transmitter comprises a resonance circuit (201) comprising a capacitive impedance (503) and an inductive impedance (501). A driver (203) generates a drive signal for the resonance circuit. A frequency modification circuit (505) controls the resonance frequency of the resonance circuit (201) by slowing a state change for at least one of the capacitive impedance (503) and the inductive impedance (501) for a fractional time interval of at least some cycles of the drive signal. The frequency modification circuit (505) is arranged 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 (203) generates the timing signal to have transitions synchronized to the drive signal. The slowing may be by impeding current flow between the capacitive and inductive impedance (503, 501).

Abstract: A power transmitter (2) for transferring power to a power receiver comprises a first inductor (307) for providing power and a second inductor (407) for receiving data signals from a power receiver. The first (307) and second (407) inductors are separate inductors in a power transfer circuit (701) and a data signal receiving circuit (702). The data signal receiving circuit (702) comprises a data extracting circuit (1007) for extracting the data signals received by the second inductor (407). The power transmitter comprises a control circuit (401) for controlling the power in dependence on the data signals. The power transmitter transfers power during power transfer periods and receives data during communication periods, communication periods corresponding to periods wherein power is low.

Abstract: A wireless power transfer system includes a power receiver (105) and a power transmitter (101) generating a wireless inductive power transfer signal for powering the power receiver (105) during a power transfer phase. An apparatus, often the power transmitter (101) comprises a first communication unit (305) communicating with a second communication unit of an entity using an electromagnetic communication signal. The entity may typically be the power receiver (105). The apparatus comprises a reference processor (307) for measuring and storing a reference value of a characteristic of the communication signal and a measurement unit (309) which repeatedly during the power transfer phase determines a measured value of the characteristic. A comparator (311) compares the measured values to the reference value and an initiator (313) triggers an entity detection process if the comparison indicates that a measured value and the reference value do not meet a similarity criterion.

Abstract: A thermal barrier for a wireless power transfer system comprises a first surface area (807) for coupling to a power receiver (111) to be powered by a first electromagnetic signal and a second surface area (805) for coupling to a power transmitter (101) providing a second electromagnetic signal. The thermal barrier (801) further comprises a power repeater (803) with a resonance circuit including an inductor and a capacitor. The power repeater (803) is arranged to generate the first electromagnetic signal by concentrating energy of the second electromagnetic signal towards the first surface area (807). The thermal barrier may provide thermal protection of the power transmitter (101) without unacceptable impact on the power transfer operation.

Abstract: A wireless power transfer system comprises a power transmitter (101) arranged to generate a wireless inductive power transfer signal for powering a power receiver (105). The system comprises a temperature controlled power loop setting an operating temperature for a heating part of a powered device. The system further comprises a receiver (207) for receiving a first temperature for a part of a powered device where the powered device is powered by the power receiver (105). A comparator (209) compares the measured temperature to a first reference temperature associated with the power transmitter (101). In response to the first temperature exceeding the reference temperature, a controller (213) proceeds to restrict the power of the power transfer signal and/or to generate a user alert.

Abstract: A wireless power transfer system includes a power receiver (105) and a power transmitter (101) generating a wireless inductive power transfer signal for powering the power receiver (105) during a power transfer phase. An apparatus, often the power transmitter (101) comprises a first communication unit (305) communicating with a second communication unit of an entity using an electromagnetic communication signal. The entity may typically be the power receiver (105). The apparatus comprises a reference processor (307) for measuring and storing a reference value of a characteristic of the communication signal and a measurement unit (309) which repeatedly during the power transfer phase determines a measured value of the characteristic. A comparator (311) compares the measured values to the reference value and an initiator (313) triggers an entity detection process if the comparison indicates that a measured value and the reference value do not meet a similarity criterion.

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 transfer signal where the power transfer signal is provided in a power time interval of a repeating power transfer signal time frame. The time frame furthermore comprises a reduced power time interval. An apparatus (typically being the power receiver (105) or the power transmitter (101)) comprises a short range communication unit (305, 405) arranged to communicate data messages with a second entity (which is the complementary unit, i.e. either the power transmitter (101)) or the power receiver (105)) using short range communication. The short range communication has a range not exceeding 20 cm. The apparatus further comprises a synchronization unit (309, 409) arranged to synchronize the short range communication to the power transfer signal time frame such that short range communication is restricted to the reduced power time intervals.

Abstract: A wireless power transfer system comprises a power transmitter (101) arranged to generate a wireless inductive power transfer signal for powering a power receiver (105). The system comprises a temperature controlled power loop setting an operating temperature for a heating part of a powered device. The system further comprises a receiver (207) for receiving a first temperature for a part of a powered device where the powered device is powered by the power receiver (105). A comparator (209) compares the measured temperature to a first reference temperature associated with the power transmitter (101). In response to the first temperature exceeding the reference temperature, a controller (213) proceeds to restrict the power of the power transfer signal and/or to generate a user alert.

Abstract: A power transmitter (501) transfers power to a power receiver (505) using a wireless inductive power signal between inductors of the devices. In the power transmitter (501) a power source (601) provides a power source signal which may have level variations. A power signal generator (603) generates a drive signal from the power source signal by means of a frequency converter (605) which increases the frequency of the drive signal relative to the power source signal. A limiter (607) for restricts the power of the drive signal fed to the inductor (503) to be below a threshold in repeating time intervals. A synchronizer (611) synchronizes the repeating time intervals to the power source signal. In the power receiver(505) a load coupler (1001) decouples the power load (1003) from the inductor (507) during the repeating time intervals and a synchronizer (1005) synchronizes the repeating time intervals of the receiver to the power signal.

Abstract: The power toothbrush includes a toothbrush body and a stem portion extending from the toothbrush body which has a workpiece with a flexible membrane at a remote end thereof, and a flexible membrane at a near end thereof as well. A movable piston is positioned in the stem portion, as well as a fluid which is in communication with the flexible membrane at the workpiece end of the toothbrush and the flexible membrane at the near end of the stem portion. The body includes a solenoid coil which, when actuated, moves the piston in opposing directions in a controlled manner within the stem, which acts on the fluid in the stem and moves the flexible membrane at the workpiece in and out at a desired frequency and amplitude.

Abstract: A low power portable device includes a terminal (2) for connection of the device to a power source. A rectifier (3) is connected to the terminal and a half-bridge circuit (4) is connected to the rectifier in order to generate an a.c. switching voltage and includes a half-bridge point (5). A control circuit (6) controls the half-bridge circuit from a power supply (7) which derives a supply voltage for the control circuit from the switching AC voltage supplied by the half-bridge circuit. The power supply comprises a charging capacitor (10) connected to the half-bridge point. A load circuit (8) is connected to the half-bridge point and the charging capacitor is connected to the half-bridge point through an impedance (13, 16).

Abstract: To improve the performance of an inductive coupling system, the magnetic coupling between the primary (4) and secondary (8) windings is increased by adding auxiliary windings (26,28) on the primary (2) and/or secondary (6) yokes of the assembly near the air gap (18) between the yokes. Capacitors (30,32) are connected to the auxiliary windings (26, 28) which, together with the inductance of the auxiliary windings, resonate at the operating frequency of the primary AC voltage (Vp). The effect is an improved magnetic coupling between the primary and secondary windings (4, 8) without increasing the size of the magnetic assembly.

Abstract: The invention relates to a device (1, 14, 17) comprising: a terminal (2) for connection of the device to a power source; a rectifier (3) connected to the terminal; a half-bridge circuit (4) connected to the rectifier in order to generate an a.c. switching voltage, and having a half-bridge point (5); a control circuit (6) for controlling the half-bridge circuit; a power supply (7) for deriving a supply voltage for the control circuit from the switching AC voltage supplierd by the half-bridge circuit, said supply comprising a charging capacitor (10) connected to said half-bridge point; and a load circuit (8) connected to the half-bridge point, wherein the charging capacitor is connected to the half-bridge point through an impedance (13, 16).

Abstract: To improve the performance of an inductive coupling system, the magnetic coupling between the primary (4) and secondary (8) windings is increased by adding auxiliary windings (26,28) on the primary (2) and/or secondary (6) yokes of the assembly near the air gap (18) between the yokes. Capacitors (30,32) are connected to the auxiliary windings (26, 28) which, together with the inductance of the auxiliary windings, resonate at the operating frequency of the primary AC voltage (Vp). The effect is an improved magnetic coupling between the primary and secondary windings (4, 8) without increasing the size of the magnetic assembly.

Abstract: A motor speed control for controlling the speed of an electric induction motor by modulating the amplitude and frequency of the driving voltage. When the load increases the speed control controls the speed so as to be relatively constant with respect to the frequency of the driving voltage. Preferably, the speed control controls the amplitude of the driving voltage in proportion to the square of the frequency.

Abstract: A motor speed control for controlling the speed of an electric induction motor by modulating the amplitude and frequency of the driving voltage. When the load increases the speed control controls the speed so as to be relatively constant with respect to the frequency of the driving voltage. Preferably, the speed control controls the amplitude of the driving voltage in proportion to the square of the frequency.

Abstract: A piezoelectric transformer has a body made of a piezoelectric material polarized in segments. The segments each have diametrically opposed polarization sides (23-28) transverse to the direction of polarization. A pair of input electrodes (13, 14) and a pair of output electrodes (15, 16) are disposed on a first and a second pair of diametrically opposed polarization sides of the body (19). At least one of the electrodes (14, 32, 33) extends beyond the polarization side (28) on which this electrode is disposed, in order to increase a capacitance between this input electrode and one or both output electrodes (15, 16) and thereby reduce common mode currents.