Wireless Power Transmitter LC Tank Q-Factor Calibration
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Solution Overview
Problem
Conventional wireless charging systems face challenges in detecting foreign objects during calibration, which can lead to calibration errors and safety hazards due to the potential for metallic objects to heat up and affect efficiency, especially in scenarios where objects enter the charging field before or during calibration.
Innovation Solution
The system performs on-demand calibration and foreign object detection by measuring the quality factor of the transmitter LC tank, comparing it with a reference value, and interrupting power transmission to detect metallic objects, thereby minimizing the risk of calibration errors and ensuring safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If continuous power transmission is maintained during calibration, then productivity is improved, but foreign objects can cause calibration errors
Solution Approach 1:
The system implements periodic action by interrupting power transmission at specific calibration moments to perform Q-factor measurements. The controller stops power transmission temporarily to measure the Q-factor of the transmitter coil, then resumes transmission. This periodic interruption allows foreign object detection during calibration without significantly impacting overall productivity, resolving the contradiction between continuous operation and accurate detection.
2Reliability
If power transmission is interrupted frequently for detection, then reliability is improved, but productivity deteriorates
Solution Approach 1:
The system applies preliminary action by performing Q-factor measurements at the beginning of calibration and at predetermined moments during calibration, before foreign objects can significantly impact the process. This proactive detection approach ensures reliability by identifying foreign objects early, while minimizing interruptions to productivity by only measuring at critical moments rather than continuously.
3Productivity
If Q-factor measurement is performed during power transmission, then productivity is improved, but measurement precision deteriorates
Solution Approach 1:
The system resolves this contradiction by implementing periodic action where power transmission is temporarily interrupted during calibration to perform accurate Q-factor measurements. The controller stops power transmission at specific calibration moments, allowing precise measurement of the transmitter coil's Q-factor without interference from active power transmission, then resumes transmission to maintain overall productivity.
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 reduces the time window for foreign objects to cause calibration errors by two orders of magnitude, improving safety and efficiency in wireless power transfer by allowing for immediate detection and adjustment of power levels based on object presence.
Implementation Method 1
wireless charging systems use inductive charging operating between 80 kHz and 300 kHz to wirelessly transmit power from a transmitter to a receiver
Implementation Method 2
measuring the quality factor of the transmitter LC tank, comparing it with a reference value
Data Source
AI summary
In an embodiment, a method includes: wirelessly transmitting power using a transmitter LC tank to a wireless power receiver having a receiver LC tank; receiving a first received power packet from the wireless power receiver, the first received power packet including a received power value field indicative of a power level; determining a first power difference between transmitted power and received power based on the first received power packet; calculating a first received power compensation factor based on the first power difference; interrupting wirelessly transmitting power for a first slot period after receiving the first received power packet; performing a first measurement of a first signal associated with the transmitter LC tank during the first slot period; determining a first Q factor value based on the first measurement; comparing the first Q factor value with a reference Q factor value; and detecting a metallic object based on the comparison.