Wireless Power Transmission Coil Temperature Control for Foreign Object Detection
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Solution Overview
Problem
Existing wireless power transmission systems using the Qi standard face issues with false foreign object detection due to irregular coupling coefficients and measurement errors, which can lead to misalignment being mistaken for foreign objects, resulting in power loss and heating.
Innovation Solution
Incorporating a wireless power transmission apparatus with a transmission coil, driver, first and second temperature sensors, and a control circuit that compares temperature differences between the transmission coil and the interface surface to distinguish between foreign objects and misalignment, allowing for precise detection and power management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If foreign object detection is performed using power transmission and reception measurements, then foreign objects can be detected, but false detection occurs due to coupling coefficient irregularity and measurement errors
Solution Approach 1:
A temperature sensor is introduced as an intermediary detection means. Instead of relying solely on power measurements that are affected by coupling coefficient variations, the system uses temperature measurements of the transmission coil as an intermediate indicator to infer the presence of foreign objects, thereby improving detection reliability while reducing false positives
Solution Approach 2:
The system replaces electrical measurement methods (power transmission/reception measurements) with thermal measurement methods (temperature sensing). This substitution eliminates the sensitivity to coupling coefficient variations and measurement errors inherent in electrical measurements, providing more reliable foreign object detection
2Reliability
If misalignment is mistaken for foreign object, then false positive detection occurs, but power transmission is unnecessarily interrupted
Solution Approach 1:
Temperature measurement serves as an intermediary indicator that is not affected by misalignment. Since the temperature of the transmission coil changes based on foreign object presence rather than alignment, this intermediary measurement allows the system to distinguish between true foreign objects and misalignment scenarios, preventing unnecessary interruption of power transmission
Solution Approach 2:
The system changes the detection parameter from electrical measurements (power transmission/reception) to thermal measurements (temperature). This parameter change makes the detection immune to misalignment effects while maintaining sensitivity to foreign objects, thereby improving both detection accuracy and power transmission continuity
3Reliability
If temperature difference control is implemented, then false foreign object detection is prevented, but system complexity increases
Solution Approach 1:
The temperature sensor serves multiple functions: it monitors the thermal state of the transmission coil for foreign object detection, provides a reference for misalignment detection through temperature difference comparison, and contributes to overall system safety monitoring. This multi-functionality justifies the added component while providing comprehensive detection capabilities
Solution Approach 2:
The transmission coil itself serves as the heat source for temperature measurement. The system utilizes the natural thermal effects that occur during normal operation, requiring no additional heating elements or complex thermal management systems. The temperature difference between the transmission coil and ambient environment naturally indicates foreign object presence
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 solution effectively differentiates between foreign object detection and misalignment, preventing false positives and maintaining power transmission by adjusting power levels based on temperature thresholds, thus protecting the system from overheating and ensuring efficient energy transfer.
Implementation Method 1
The driver 204 applies a driving signal S1, configured as a driving current or otherwise a driving voltage, for example, to the transmission coil 202 such that an electric power signal S2 is generated at the transmission coil 202 in the form of an electromagnetic signal
Implementation Method 2
The reception coil 302 receives the electric power signal S2 from the transmission coil 202
Implementation Method 3
The rectifier circuit 304 and the capacitor 306 rectify and smooth a current S4 induced at the reception coil 302 according to the electric power signal S2, thereby converting the current S4 into a DC voltage
Data Source
AI summary
A transmission antenna includes a transmission coil, and transmits an electric power signal. A driver applies a driving signal to the transmission antenna. A first temperature sensor measures the temperature of the transmission coil, and generates a first temperature signal. A second temperature sensor measures the temperature of an interface surface on which an electronic device mounting a wireless power receiving apparatus is to be placed, and generates a second temperature signal. A control circuit controls the electric power signal according to the difference between the first temperature signal S11 and the second temperature signal.