Wireless Power Coil Thresholding for Foreign Matter Detection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In non-contact power transmission systems, metal foreign matters between the power transmission coil and the power reception coil can generate heat, leading to safety concerns and potential erroneous detection of foreign matters, which can prevent power transmission.
Innovation Solution
A power transmission device that measures the standby current and sets a foreign matter detection threshold by adding a constant value or ratio to the reference current value, allowing for sensitive detection of metal foreign matters and preventing overheating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the foreign matter determination threshold is made as small as possible to increase detection sensitivity, then metal foreign matter can be detected more accurately, but power transmission may not be started due to erroneous detection
Solution Approach 1:
The patent applies preliminary action by measuring the standby current before power transmission starts and using it to set the foreign matter determination threshold. This preliminary measurement allows the system to establish an accurate baseline specific to each power transmission device, enabling sensitive foreign matter detection without causing erroneous detection that would prevent power transmission startup.
Solution Approach 2:
The patent changes the parameter of the foreign matter determination threshold from a fixed predetermined value to a dynamically set value based on the measured standby current. By adding a predetermined value to the measured standby current, the threshold adapts to individual device characteristics, achieving both high detection sensitivity and reliable operation without erroneous shutdowns.
2Ease of manufacture
If a fixed predetermined threshold is used for foreign matter detection, then the detection method is simple, but detection accuracy varies due to device individual differences
Solution Approach 1:
The patent transforms the detection threshold from a fixed predetermined parameter to a dynamically calculated parameter based on measured standby current. This parameter change maintains simplicity by using a straightforward calculation (standby current plus predetermined value) while significantly improving detection accuracy by accounting for individual device variations in standby current.
Solution Approach 2:
The system performs self-characterization by automatically measuring its own standby current and using this measurement to set its detection threshold. This self-service approach eliminates the need for complex calibration procedures or manual adjustments, maintaining ease of implementation while achieving high detection accuracy tailored to each device's specific characteristics.
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 enables reliable detection of metal foreign matters while minimizing erroneous detection, ensuring safe and efficient power transmission.
Implementation Method 1
a power transmission coil 351 and a power reception coil 231. The power transmission device 35 transmits power in a non-contact manner to the power reception device 23
Implementation Method 2
when power is transmitted with a metal foreign matter being sandwiched between a power transmission coil and a power reception coil, there arises a problem that the metal foreign matter generates heat
Data Source
AI summary
According to an embodiment, a power transmission device performs power transmission without contact with a power reception device. A control circuit of the power transmission device obtains, as a reference value, a standby current in a standby state in which the power transmission to the power reception device is not performed. The control circuit sets, as a foreign matter detection threshold, a value obtained by adding a constant value to the reference value or a value obtained by adding a constant ratio to the reference value. Further, in the standby state, when the current value input to the power transmission circuit and detected by the current detection circuit is equal to or larger than the threshold, the control circuit determines that there is a foreign matter on the power transmission coil.