Object Detection via Programmable Impedance and Wideband Signaling
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Solution Overview
Problem
Conventional object detection systems in wireless charging systems have limitations in sensitivity, power consumption, and accuracy due to narrow frequency ranges, high harmonic distortion, and uncontrollable impedance, which can lead to false activation of foreign objects and inefficiencies in power transfer.
Innovation Solution
The system employs a wider frequency range (10 KHz to 100 MHz) for improved sensitivity, uses capacitive detection and high-resonant-frequency detection, excites coils with low-power low-distortion signals, and controls impedance to match the coil, enabling accurate detection of 'friend' or foreign objects without activating them, and measures background noise for diagnostic purposes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional power inverter circuits are used to execute pings for object detection, then the system can detect foreign objects, but the frequency range is limited and sensitivity is reduced
Solution Approach 1:
The system changes the operating frequency parameter from conventional narrow ranges (100 kHz to 500 kHz) to an extended range (10 KHz to 100 MHz). This allows the detection system to operate at multiple frequencies including resonant frequencies of different objects, thereby improving detection sensitivity while expanding adaptability to detect various types of foreign objects including high-resonant-frequency objects like RFID tags
2Measurement precision
If high power is used to excite the coil for detection, then the detection range is improved, but foreign objects may be overheated
Solution Approach 1:
The system uses periodic low-power ping signals instead of continuous high-power excitation. The coil is excited with brief low-power test signals at various frequencies, and the response is measured. This periodic low-power approach maintains detection accuracy by measuring impedance changes while preventing foreign objects from accumulating enough energy to overheat
Solution Approach 2:
The system applies partial action by using just enough power to detect object presence through impedance measurement, rather than excessive power that would cause heating. The low-power signals are sufficient to measure coil impedance changes caused by foreign objects without transferring harmful energy to them
3Reliability
If the transmitter unit continuously monitors for foreign objects, then safety is improved, but power consumption increases
Solution Approach 1:
The system performs foreign object detection periodically using brief ping signals rather than continuous monitoring. The power inverter executes occasional test pings at different frequencies and measures coil impedance changes. This periodic approach maintains safety by detecting foreign objects when they are present while consuming minimal power during idle periods
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 enhances detection sensitivity and accuracy, reduces power consumption, and prevents overheating of foreign objects, while allowing for efficient power transfer and safety features like human touch detection.
Implementation Method 1
The wireless power transmitter unit uses power inverter circuits to execute a few pings to excite a coil of the wireless charging system and measure a response from the coil
Implementation Method 2
The systems and methods incorporate capacitive detection (e.g., human body) and high-resonant-frequency foreign object detection
Implementation Method 3
The systems and methods incorporate capacitive detection (e.g., human body) and high-resonant-frequency foreign object detection which are not achieved by conventional object detection systems
Data Source
AI summary
Systems and methods for object detection are provided. The system includes at least a coil, a small signal generator, a small signal receiver, and a processor. The small signal generator includes a digital-to-analog converter circuit with programmable impedance. The small signal generator is configured to select an output impedance for the digital-to-analog circuit for capacitive sensing or radio-frequency identification (RFID) tag detection; generate a small signal according to the output impedance; and provide the small signal to the coil. The small signal receiver receives the small signal and a response signal associated with the small signal and measures the response signal to generate a measured signal. The processor compares the measured signal with one or more reference signals and performs capacitive sensing and/or detect a RFID tag according to the comparison.