Dynamic Threshold Control for Contactless Power Transfer Overcurrent Protection
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Solution Overview
Problem
Existing contactless power transfer systems face challenges in accurately detecting overvoltage conditions in the power reception device, leading to potential device damage due to varying coupling states between power transmission and reception coils, which can result in inappropriate power transfer cessation.
Innovation Solution
The system dynamically adjusts the current threshold value based on the coupling state and properties of filters connected to both coils, allowing for precise detection of overcurrent conditions and timely power transfer cessation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a fixed current threshold value is used for detecting overcurrent conditions, then the detection method is simple, but the detection accuracy decreases due to varying coupling states between coils
Solution Approach 1:
The patent applies dynamics by transitioning from a fixed current threshold to a dynamic threshold that adapts to varying coupling states. The system continuously monitors the coupling coefficient between transmission and reception coils and adjusts the current threshold accordingly, ensuring accurate overcurrent detection regardless of coupling variations.
Solution Approach 2:
The patent changes the parameter of current threshold from a constant value to a variable value that depends on the coupling state. By making the threshold a function of the coupling coefficient, the system maintains detection accuracy across different operating conditions while avoiding false positives or negatives.
2Device complexity
If power transfer cessation is triggered by a fixed current threshold, then the control logic is simple, but system reliability decreases due to inappropriate cessation decisions
Solution Approach 1:
The patent implements feedback by continuously monitoring the coupling coefficient and using it to adjust the current threshold dynamically. This feedback mechanism ensures that power transfer cessation decisions are based on accurate, context-aware threshold comparisons, significantly improving the reliability of the control system.
Solution Approach 2:
The control logic transitions from static to dynamic by adapting the current threshold in real-time based on coupling conditions. This dynamic adjustment prevents inappropriate power transfer cessation, ensuring that the system responds accurately to actual overcurrent conditions rather than fixed, potentially misleading thresholds.
3Ease of operation
If the current threshold is not adjusted for coupling state, then the system operation is simple, but device protection becomes ineffective during overvoltage events
Solution Approach 1:
The patent changes the current threshold parameter dynamically based on coupling state to maintain effective device protection. By adjusting the threshold according to real-time coupling measurements, the system ensures that overcurrent detection remains accurate and protective across all operating conditions, preventing device damage during overvoltage events.
Solution Approach 2:
The system performs preliminary action by pre-calculating or pre-establishing the relationship between coupling coefficient and appropriate current threshold values. This allows the system to quickly adjust the threshold in response to coupling changes without complex real-time calculations, maintaining both protection effectiveness and operational simplicity.
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 ensures appropriate power transfer cessation during overvoltage events, effectively protecting devices by accounting for varying coupling states and filter properties, thereby enhancing system reliability and safety.
Implementation Method 1
a power transmission device and a power reception device. In these contactless power transfer system and power transmission device, the threshold value to be compared with the current generated in the power transmission unit for determining whether to stop power transmission is changed in accordance with the coupling state between the power transmission coil and the power reception coil
Implementation Method 2
The power transmission device includes a power transmission coil, and the power reception device includes a power reception coil
Data Source
Figure 1
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AI summary
A contactless power transfer system (1) includes a power supply ECU (250) configured to control an inverter (220) to stop power transmission from a power transmission unit (240) when a current generated in the power transmission unit (240) exceeds a predetermined threshold value due to short-circuiting of a power reception coil comprised in a power reception unit (310). The power supply ECU (250) estimates a coupling state between a power transmission coil comprised in the power transmission unit (240) and the power reception coil, and changes the predetermined threshold value in accordance with the estimated coupling state.