Q-factor determination apparatus and method for wireless power transfer system
AssigneeNuVolta Technologies (Hefei) Co., Ltd.
InventorsZhijun Luo, Yingying Yang
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Abstract
A method includes applying an excitation including a voltage step to a resonant tank comprising a first coil and a capacitor, comparing a damped sinusoidal waveform having a resonant attenuation envelope with a predetermined threshold voltage and detecting a last time instant at which a value of the damped sinusoidal waveform is equal to the predetermined threshold voltage, calculating a quality factor of the resonant tank based on a plurality of parameters derived from the last time instant, and determining whether a foreign object is magnetically coupled to the first coil based on the quality factor.
Claims19
A method for comprising:
- connecting a bias voltage source to a resonant tank of a wireless power transfer system, wherein a current flows from the bias voltage source to ground through the resonant tank and a first low-side switch of a power stage coupled to the resonant tank;
- disconnecting the bias voltage source from the resonant tank, wherein the current flows in a conductive loop comprising the resonant tank, the first low-side switch of the power stage and a second low-side switch of the power stage, wherein after disconnecting the bias voltage source, a damped sinusoidal waveform is generated in the resonant tank comprising a first coil and a capacitor in response to a voltage step applied to the resonant tank;
- comparing the damped sinusoidal waveform with a predetermined threshold voltage and detecting a last time instant at which a value of the damped sinusoidal waveform is equal to the predetermined threshold voltage, wherein prior to the last time instant, the damped sinusoidal waveform crosses the predetermined threshold voltage a plurality of times;
- calculating a quality factor of the resonant tank based on a plurality of parameters derived from the last time instant;
- and
- determining whether a foreign object is magnetically coupled to the first coil of the wireless power transfer system based on the quality factor.
A method comprising:
- connecting a dc voltage source to a power stage of a wireless power transfer system;
- disconnecting the dc voltage source from the power stage, wherein after disconnecting the dc voltage source, a damped sinusoidal waveform is generated in a resonant tank of the wireless power transfer system, and wherein the power stage is connected to the resonant tank;
- detecting a last time instant at which a value of the damped sinusoidal waveform is equal to a predetermined threshold voltage;
- and
- calculating a quality factor of the resonant tank based on a plurality of parameters derived from the last time instant, wherein a controller configured to determine whether a foreign object is magnetically coupled to the first coil based on the quality factor.
An apparatus comprising:
- a power conversion device coupled to a resonant tank comprising a capacitor and a first coil connected in series;
- and
- a controller configured to apply an excitation to the capacitor and the first coil through the power conversion device, detect a signal having a resonant attenuation envelope, compare the signal with a predetermined threshold voltage, and detect a last time instant at which a value of the signal is equal to the predetermined threshold voltage, and wherein the controller is configured to determine a quality factor based on the last time instant.
Dependencies are inferred from the claim text.