Capacitive Sensor Grid for Wireless Power Coil Alignment
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Solution Overview
Problem
Existing wireless power transmission systems face challenges in aligning receive coils with transmit coils and detecting foreign objects, which affects efficient power transfer.
Innovation Solution
A capacitive sensor system using a grid array of lines with multiplexers and ADC sample and hold circuits to detect voltage changes and locate objects by monitoring the rate of voltage decay, allowing for precise alignment and foreign object detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If resonant inductive coupling is used for wireless power transfer, then power can be transmitted wirelessly to devices, but alignment between transmit and receive coils becomes difficult and foreign object detection is challenging
Solution Approach 1:
A capacitive sensor array is introduced as an intermediary component between the transmit and receive coils. The sensor array includes multiple capacitive sensors arranged in a grid pattern that detect changes in capacitance caused by the position of the receive coil and foreign objects. This intermediary sensing system provides precise alignment information without interfering with the wireless power transfer function.
Solution Approach 2:
The capacitive sensing function is divided into multiple discrete capacitive sensors arranged in a grid array, with each sensor independently detecting local capacitance changes. This segmentation allows for precise spatial resolution of the receive coil position and foreign object locations, enabling accurate alignment while maintaining wireless power transfer efficiency.
2Use of energy by moving object
If resonant inductive coupling is used for wireless power transfer, then power can be transmitted wirelessly to devices, but detection of foreign objects becomes difficult
Solution Approach 1:
The capacitive sensor array serves as an intermediary detection system that specifically monitors for foreign objects without interfering with the wireless power transfer. Each capacitive sensor detects changes in local capacitance that indicate the presence of foreign objects, providing clear detection signals while the power transfer continues through the inductive coupling path.
Solution Approach 2:
Each capacitive sensor in the array independently monitors its local region for foreign objects, creating a distributed detection network. This local quality approach allows precise identification of foreign object positions and enables selective power transfer control for each region, improving overall safety while maintaining efficient power transfer to authorized devices.
3Measurement precision
If capacitive sensor array is added to the wireless power system, then alignment and foreign object detection improve, but device complexity increases
Solution Approach 1:
The capacitive sensor array is designed to perform multiple functions simultaneously: detecting receive coil alignment, identifying foreign objects, and providing feedback for power transfer control. This multi-functionality reduces the need for separate sensing systems, thereby limiting the increase in overall device complexity while achieving high measurement precision for both alignment and foreign object detection.
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
The capacitive sensor system effectively aligns receive coils with transmit coils and identifies foreign objects, enhancing the efficiency and safety of wireless power transfer by maximizing receive coil capacitance and preventing power transfer to foreign objects.
Implementation Method 1
a capacitor sensor can include a first set of lines; a second set of lines intersecting the first set of lines... to detect voltages on each line of the first set of lines... to detect voltages on each line of the second set of lines, wherein an object positioned with respect to the first set of lines and the second set of lines is located
Implementation Method 2
the capacitor sensor uses the receive coil and rectifier circuitry. In power transfer operation, the rectifier circuitry rectifies the AC signal in the receive coil
Data Source
AI summary
A capacitor sensor array (or grid) over a wireless power transmission coil can include a first set of lines; a second set of lines intersecting the first set of lines; a first multiplexer coupled to provide a charge (e.g. in the form of a DC voltage) from a voltage source to the first set of lines and provide first signals to detect voltages on each line; and a second multiplexer coupled to provide a charge from the voltage source to the second set of lines and provide second signals to detect voltages on each line, wherein an object positioned with respect to the first set of lines and the second set of lines is located. According to some embodiments, a wireless power receive coil and a rectifier circuit can be used in forming a capacitor sensor, to sense the capacitance between the receive and transmit coils for better alignment between the two coils. Other embodiments are also provided.