Wireless Charging Object Detection via Impedance Measurement
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Solution Overview
Problem
Wireless charging systems face challenges in accurately detecting foreign objects and sensitive devices on the charging surface, which can lead to inefficient power transmission and potential damage to sensitive devices.
Innovation Solution
A wireless power transmitting device equipped with signal measurement circuitry, impulse response circuitry, and switching circuitry to detect external objects and sensitive devices, such as RFID devices, by using probe frequencies, impulse signals, and frequency-sweeping operations, allowing for dynamic adjustment of coil activation and power transmission levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If continuous power transmission is performed to ensure efficient charging, then productivity is improved, but foreign objects may be damaged and reliability deteriorates
Solution Approach 1:
The system performs foreign object detection before initiating power transmission by measuring the impedance of transmitting coils. This preliminary detection identifies foreign objects in advance, allowing the system to prevent power transmission to damaged objects while maintaining efficient charging when no foreign objects are present.
Solution Approach 2:
The system continuously monitors coil impedance during charging operations and compares measured values against reference ranges. When foreign objects are detected or abnormal conditions occur, the system provides feedback to adjust or terminate power transmission, ensuring both charging efficiency and foreign object safety through real-time monitoring.
2Reliability
If foreign object detection is performed continuously to improve reliability, then safety is improved, but energy consumption increases
Solution Approach 1:
The system performs foreign object detection periodically at specific intervals during charging operations rather than continuously. Impedance measurements are taken at predetermined times such as before power transmission begins and at scheduled checkpoints during charging, reducing energy consumption while maintaining adequate detection coverage.
Solution Approach 2:
The system changes detection parameters dynamically based on charging state. Detection frequency and measurement intensity are adjusted according to whether the device is in standby, charging, or fast-charging mode, optimizing the balance between detection reliability and energy consumption for different operational conditions.
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 prevents damage to sensitive devices by accurately identifying and avoiding foreign objects and sensitive devices during wireless power transmission, ensuring safe and efficient charging operations.
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
The wireless power receiving device has a wireless power receiving coil in a resonant circuit that resonates at a wireless power receiving circuit resonant frequency
Data Source
AI summary
A wireless power transmitting device transmits wireless power signals to a wireless power receiving device. The wireless power receiving device has a wireless power receiving coil in a resonant circuit that resonates at a wireless power receiving circuit resonant frequency. The wireless power transmitting device has coils. The coils are supplied with a drive signal in bursts to detect external objects. Measurement circuitry includes an oscillator for supplying the drive signals and a peak detector and analog-to-digital converter for gathering measurements on the coils to which the drive signals have been supplied. Rate-based-filtering is applied to output signals from the analog-to-digital converter to distinguish between temperature drift effects and object placement effects. The frequency of the drive signals is slightly greater than the wireless power receiving circuit resonant frequency.