Wireless Power Transfer Resonance Switching for Smart Card Detection
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Solution Overview
Problem
Current wireless power transfer systems face challenges in accurately detecting foreign objects, particularly small metal items like smart cards, due to their sensitivity to strong electromagnetic fields, which can lead to damage and unreliable detection using conventional methods.
Innovation Solution
A power transmitter design that employs a repeating time frame with non-overlapping power transfer and object detection intervals, where the communication resonance circuit is adapted to not provide resonance at the first resonance frequency during object detection, allowing for improved detection of objects with resonances close to the communication frequency, such as NFC smart cards, with reduced interference from communication circuitry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the communication resonance circuit provides resonance at the first resonance frequency during communication, then communication efficiency is improved, but detection accuracy of foreign objects deteriorates
Solution Approach 1:
The system implements periodic switching between communication mode and detection mode. During communication time intervals, the communication resonance circuit is coupled to the communicator and provides resonance at the first resonance frequency. During object detection time intervals, the communication resonance circuit is decoupled from the communicator and coupled to the object detector, eliminating resonance interference. This time-division multiplexing resolves the contradiction by ensuring that resonance is active only when needed for communication, not during detection.
Solution Approach 2:
The system dynamically changes the coupling state of the communication resonance circuit based on operational requirements. A controller switches the communication resonance circuit between being coupled to the communicator (during communication) and being coupled to the object detector (during detection). This dynamic reconfiguration allows the same circuit to serve different functions at different times, resolving the contradiction between communication efficiency and detection accuracy.
2Productivity
If the power transfer signal uses high power level, then power transfer efficiency is improved, but foreign object detection reliability deteriorates
Solution Approach 1:
The system uses periodic time-division multiplexing to separate high-power power transfer operations from foreign object detection operations. During power transfer time intervals, high power is delivered to achieve efficient power transfer. During dedicated object detection time intervals, the power level is reduced and the communication resonance circuit is configured for detection rather than power transfer. This periodic switching resolves the contradiction by ensuring that high power is applied only when needed for power transfer, not during detection.
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
This approach enables faster and more accurate detection of foreign objects, including smart cards, by reducing the electromagnetic field strength during object detection intervals and minimizing interference from communication signals, thereby enhancing the reliability and safety of wireless power transfer operations.
Implementation Method 1
power is inductively transferred from a transmitter coil in a power transmitter device to a receiver coil in the individual devices
Implementation Method 2
a communication resonance circuit comprising a communication antenna for transmitting or receiving the electromagnetic communication signal
Implementation Method 3
the communication resonance circuit during communication being arranged to provide a resonance at a first resonance frequency to the communicator
Data Source
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AI summary
A power transmitter (201) conducting power transfer using an electromagnetic power transfer signal employing a repeating time frame comprising a power transfer time interval and an object detection time interval. A power transfer circuit (303) comprises a power transfer coil (203) receiving or generating the power transfer signal during the power transfer time intervals. A communicator (315) communicates with the other device via an electromagnetic communication signal. A communication resonance circuit (317) comprises a communication antenna (319) for transmitting or receiving the electromagnetic communication signal. During the communication, the communication resonance circuit (317) provides a resonance at a first resonance frequency to the communicator (315). A controller (333) adapts the communication resonance circuit to not provide the resonance at the first resonance frequency to the communicator during object detection time intervals. The approach may provide improved detection of resonance objects, such as smart cards (e.g. NFC cards).