Wireless Charging Presence Check Using RF Load-Change Detection
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Solution Overview
Problem
Existing wireless charging systems for small accessories face challenges in efficiently and reliably detecting the presence of listener devices with low power consumption, particularly due to varying signal strengths and interference from other objects, leading to false detections.
Innovation Solution
A method and device that utilize a WLC poller device to transmit RF presence check signals, sample input signals concurrently, measure the rate of change, and adjust attenuation to ensure uniform gain, while discharging the buffer capacitor of the listener device to maintain consistent signal magnitude for accurate detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional RF presence checking methods are used to detect WLC listener devices, then the detection range is extended, but false detections increase due to interference from other objects and varying signal strengths
Solution Approach 1:
The system performs preliminary actions by discharging the buffer capacitor before each presence check and adjusting the attenuator to optimal settings in advance. This ensures that the RF presence check signal starts from a known baseline state, eliminating residual signals that could cause false detections and improving detection reliability.
Solution Approach 2:
The system dynamically changes parameters including attenuator settings and buffer capacitor discharge timing based on detection conditions. By adjusting the attenuator to provide uniform gain and discharging the capacitor at specific intervals, the system adapts to varying signal strengths and environmental conditions, reducing false detections while maintaining detection accuracy.
2Measurement precision
If the RF presence check signal power is increased to improve detection sensitivity, then closer listener devices can be detected, but power consumption increases
Solution Approach 1:
The system uses periodic RF presence check signals instead of continuous transmission. The buffer capacitor is discharged at specific intervals before each presence check, and the attenuator is adjusted periodically to maintain optimal sensitivity. This periodic operation maintains detection sensitivity while significantly reducing average power consumption compared to continuous high-power transmission.
3Stability of the object's composition
If the attenuator is adjusted to provide uniform gain for accurate detection, then detection consistency improves, but device complexity increases
Solution Approach 1:
The system implements self-adjustment mechanisms where the attenuator automatically provides uniform gain based on pre-configured settings, and the buffer capacitor automatically discharges according to timing signals. This self-service approach maintains signal consistency and detection stability without requiring complex manual adjustment circuits, thereby limiting the increase in device complexity.
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 the sensitivity and reliability of detecting WLC listener devices with fewer false alarms, ensuring robust and efficient wireless charging operations.
Implementation Method 1
LPCD uses short RF 'pings' to sense small load changes to identify tags or smartcards in far distance
Implementation Method 2
The secondary device is battery powered which can be recharged by the primary device using RF coupling
Implementation Method 3
When WLC charging is complete and the WLC listener device is withdrawn from the proximity of the WLC poller device, a buffer capacitor of the WLC listener device is rapidly discharged
Data Source
AI summary
A wireless charging (WLC) poller device and WLC listener device are provided. A method for performing a presence check of the WLC listener device includes providing a radio frequency (RF) presence check signal. An input signal from the antenna by the poller device is received concurrently with the transmission of the RF presence check signal. A rate of change of a magnitude of the input signal is measured during the transmission of the presence check signal. A difference between the input signal and an expected input signal is determined. A presence of the listener device is detected if an absolute value of the measured rate of change of the input signal is above a threshold rate of change, and the difference between the input signal and the expected input signal is within a predetermined distance. Prior to the presence check, a capacitor of the WLC listener device may be discharged.