Wireless Charging Coil Object Detection via Impulse Response
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Solution Overview
Problem
Wireless charging systems face challenges in accurately distinguishing between wireless power receiving devices and foreign objects, particularly sensitive devices like RFID devices, which can be damaged by excessive power transmission.
Innovation Solution
A wireless power transmitting device equipped with signal measurement circuitry that uses probe frequencies and impulse response measurements to determine the presence of external objects and sensitive devices, dynamically switching coils to avoid damaging transmissions and ensure safe power transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If wireless power transmission is performed without object detection, then power transfer efficiency is improved, but sensitive devices may be damaged by excessive power
Solution Approach 1:
The system performs detection operations at probe frequencies before initiating full power wireless charging transmission. This preliminary detection identifies sensitive devices such as RFID tags in the charging area, allowing the system to adjust or avoid transmitting power to these devices, thereby preventing damage while maintaining efficient charging for compatible devices.
2Measurement precision
If object detection is performed using multiple probe frequencies, then detection precision is improved, but device complexity increases
Solution Approach 1:
The detection circuit is designed to operate at multiple probe frequencies using the same hardware components. The output circuit can be tuned to different frequencies to detect various types of objects including RFID devices, metallic objects, and water. This multi-functional approach achieves high detection precision without proportionally increasing circuit complexity, as the same physical components serve multiple detection purposes across different frequency ranges.
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
Effectively detects and differentiates between compatible devices and foreign objects, preventing potential damage to sensitive devices during wireless charging operations while ensuring efficient power transfer.
Implementation Method 1
a wireless power transmitting device such as a device with a charging surface wirelessly transmits power to a portable electronic device
Implementation Method 2
Impulse response circuitry in the measurement circuitry is coupled to the output circuit and used to measure the response of the output circuit to an impulse signal supplied by an inverter in the wireless power transmitting device. The impulse response circuitry is used to make inductance and Q factor measurements.
Implementation Method 3
a measurement circuit that is coupled to the output circuit and that measures signals while the oscillator circuitry sweeps an alternating-current output signal between a first frequency and a second frequency. Measurements resulting from frequency-sweeping operations are used to detect sensitive devices such as radio-frequency identification devices.
Data Source
AI summary
A wireless power transmitting device transmits wireless power signals to a wireless power receiving device using an output circuit that includes a wireless power transmitting coil. Measurement circuitry is coupled to the output circuit to help determine whether the wireless power receiving device is present and ready to accept transmission of wireless power. The measurement circuitry includes a measurement circuit that is coupled to the output circuit and that measures signals while oscillator circuitry supplies the output circuit with signals at a probe frequency. The measurement circuitry also includes a measurement circuit that is coupled to the output circuit and that measures signals while the oscillator circuitry sweeps signals applied to the output circuit between a first frequency and a second frequency to detect sensitive devices such as radio-frequency identification devices. Impulse response circuitry in the measurement circuitry is used to make inductance and Q factor measurements.