Zero-Crossing Resonant Circuit Sensing for Wireless Charger FOD
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Solution Overview
Problem
Existing wireless charging systems struggle to efficiently manage the increasing complexity of mobile devices and detect foreign objects during charging operations, particularly when placed on or near charging devices, which can affect power transmission.
Innovation Solution
The implementation of zero-crossing slotted foreign object detection techniques, including phase-modulated and resonant pulse-width modulation, to accurately detect foreign objects by monitoring voltage and current transitions in a resonant circuit, allowing for precise control of power transfer and efficient charging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If wireless charging systems use basic charging capabilities optimized for simple device configurations, then ease of operation is improved, but adaptability to increasingly complex mobile devices and changing form factors deteriorates
Solution Approach 1:
The wireless charging system dynamically adjusts transmission power levels and performs foreign object detection at different power stages. The system transitions from basic charging mode to adaptive mode that monitors multiple parameters including voltage, current, and impedance changes to accommodate complex devices with varying power requirements and form factors.
Solution Approach 2:
The system changes operating parameters such as frequency, power level, and detection thresholds based on device characteristics. By monitoring impedance changes and adjusting transmission parameters dynamically, the system adapts to different device configurations while maintaining ease of use through automatic parameter optimization.
2Reliability
If foreign object detection is performed continuously during wireless power transmission, then detection reliability is improved, but energy consumption increases
Solution Approach 1:
The system performs foreign object detection periodically at specific intervals during power transmission rather than continuously. Detection is executed at predetermined time points such as during idle periods between power delivery cycles or at specific power levels, reducing energy consumption while maintaining reliable detection through strategic sampling.
Solution Approach 2:
The system performs preliminary foreign object detection before initiating full power transmission. By conducting initial detection at low power levels or during pre-charging phases, the system identifies foreign objects early, preventing energy waste from charging foreign objects while maintaining safety through continuous monitoring at critical transition points.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables reliable detection of foreign objects and optimal power management, ensuring safe and efficient wireless charging across various device sizes and shapes, while supporting multiple devices on a single charging surface.
Implementation Method 1
a resonant circuit comprising a transmitting coil
Implementation Method 2
a power transmitting coil, a foreign object detector, a magnetic field detector
Data Source
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AI summary
Systems, methods and apparatus for wireless charging are disclosed. A method for operating a charging device includes providing a charging current to a resonant circuit when a receiving device is present on a surface of the wireless charging device, providing a zero-crossing signal that includes edges corresponding to transitions of a voltage measured across the resonant circuit through a zero volt level or to transitions of a current in the resonant circuit through a zero ampere level, providing a measurement slot by decreasing or terminating the charging current for a period of time, and determining whether an object other than the receiving device is present on a surface of the charging device based on measurements of samples of voltage or current captured based on timing provided by the zero-crossing signal, wherein the samples are captured during the measurement slot.