National Semiconductor Corporation

Robert Loke

Vijay Choudhary

One heuristic for tuning a wireless power transfer device includes monitoring a circuit parameter while sweeping a power source frequency; identifying two frequencies related to local maxima of the circuit parameter values; estimating self-resonant frequency of an electromagnetically coupled device based on the two frequencies; determining a value for a tuning component of the wireless power transfer device such that the device self-resonant frequency equals the estimated coupled device self-resonant frequency; and adjusting the tuning component to the determined value. Another tuning heuristic includes monitoring a circuit parameter while sweeping the power source frequency; identifying two frequencies related to two local maximum for the values of the circuit parameter; determining a desired resonance frequency for the wireless power transfer device based on stored information; and adjusting the tuning component to a value that causes the wireless power transfer device when uncoupled to operate at or near the desired resonance frequency.

Resonance tuning

An electrically tunable inductor with an equivalent inductance includes a main winding and a tuning winding magnetically coupled to the main winding. The current through the tuning winding is controlled to adjust the equivalent inductance of the electrically tunable inductor. A device may include an electrically tunable inductor. A system may include multiple devices, one or more of the devices including an electrically tunable inductor. A tuning controller within the system may control the current in tuning windings of one or more of the multiple devices in the system. When an electrically tunable inductor is part of a resonant circuit, the resonant frequency may be controlled by adjusting the equivalent inductance of the electrically tunable inductor through controlling the current in the tuning winding. Controlling the current in the tuning winding includes one or more of controlling the peak, direction, frequency, duty cycle, or phase of the current.

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Sunnyvale, CA, United States of America

Robert Loke