Coil Position Detection in Wireless Power Transfer
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Solution Overview
Problem
Conventional non-contact power supply systems require switching relays to accurately detect the position of the power reception coil, which can be inconvenient and may lead to inaccuracies during alignment.
Innovation Solution
A method and device for coil position detection that utilize alternating current (AC) voltage upstream of the rectifier circuit when the relay is on and direct current (DC) voltage downstream of the rectifier circuit when the relay is off, allowing for accurate alignment without switching the relay.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If relays are switched off to accurately detect voltage at the power reception coil, then measurement precision is improved, but device complexity and ease of operation deteriorate due to required relay switching
Solution Approach 1:
The patent introduces an intermediary measurement approach by detecting voltage at a point upstream of the rectifier circuit (at the AC side) rather than directly at the power reception coil. This intermediary measurement point allows accurate detection without requiring relay switching, as the voltage at this intermediate point correlates with the power reception coil's alignment status while remaining electrically accessible regardless of relay state.
Solution Approach 2:
The patent replaces the mechanical relay switching operation with an electrical measurement substitution. Instead of mechanically switching relays to access measurement points, the system uses voltage detection at an upstream AC side point that provides equivalent alignment information without mechanical intervention, thereby improving ease of operation while maintaining measurement precision.
2Measurement precision
If relays are switched off for accurate voltage detection, then measurement precision is improved, but device complexity increases due to relay control requirements
Solution Approach 1:
The patent extracts the measurement function from the relay-controlled DC side circuit and relocates it to the AC side circuit upstream of the rectifier. This extraction eliminates the need for relay switching in the measurement path, simplifying the control system while preserving measurement accuracy. The measurement is now taken from a part of the system that is always accessible regardless of relay state.
Solution Approach 2:
The upstream AC side voltage measurement acts as an intermediary that provides indirect but accurate information about power reception coil alignment. This intermediary measurement point bypasses the need for complex relay control logic, as the voltage at this point naturally reflects alignment status without requiring system state changes.
3Measurement precision
If relay switching is performed during alignment, then measurement precision is improved, but productivity decreases due to additional switching operations
Solution Approach 1:
The patent enables continuous voltage measurement during the alignment process by selecting a measurement point upstream of the rectifier that remains electrically accessible regardless of relay state. This continuous measurement capability eliminates interruptions caused by relay switching, maintaining productivity while ensuring accurate coil position detection throughout the alignment process.
Solution Approach 2:
The patent substitutes mechanical relay switching operations with continuous electrical measurement at an upstream point. This substitution eliminates the time loss associated with relay switching cycles, thereby improving alignment process efficiency while maintaining detection accuracy through continuous monitoring capability.
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
Enables precise alignment of the power reception coil without switching the relay, improving detection accuracy and simplifying the alignment process.
Implementation Method 1
a power transmission coil provided on the ground and a power reception coil mounted in the vehicle are arranged to face each other and the power transmission coil is excited to supply power to the power reception coil
Implementation Method 2
a coil position is detected based on alternating current (AC) voltage detected upstream of a rectifier circuit configured to rectify AC power received by the power reception coil
Data Source
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AI summary
Provided is a coil position detection method for a non-contact power supply system, configured to supply power from a power transmission coil (12) on a ground side to a power reception coil (22) on a vehicle side, by which a position of the power reception coil (22) is detected. Output terminals of a rectifier circuit (53) configured to rectify AC power received by the power reception coil (22) are connected to a drive circuit (50) and a battery (27). Moreover, a relay switch (26) is provided between the battery (27) and one of the output terminals of the rectifier circuit (53). When the relay switch (26) is on, the coil position is detected based on AC voltage detected by a first voltmeter (51) provided upstream of the rectifier circuit (53) and, when the relay switch (26) is off, the coil position is detected based on DC voltage detected by a second voltmeter (52) provided downstream of the rectifier circuit (53).