Multiplexed Detection Circuit for EV Wireless Charging Alignment
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Solution Overview
Problem
Inductive wireless charging systems for electric vehicles face challenges in efficiently detecting foreign metallic objects, living objects, and determining vehicle position due to high magnetic field strengths, which can cause undesirable induction heating and exceed safe electromagnetic field exposure limits.
Innovation Solution
A multi-purpose detection circuit incorporating inductive and capacitive sense circuits with impedance matching elements, a measurement circuit for sequential electrical characteristic measurement, and a control and evaluation circuit to determine the presence of metallic objects, living objects, vehicle type, and vehicle position, using a time multiplexing scheme to optimize detection accuracy and safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If inductive wireless power transfer is used to provide sufficient power transfer (3.3 kW, 7 kW, 11 kW), then power transfer capability is improved, but magnetic flux density reaches high levels (above 2 mT) causing undesirable induction heating of metallic objects
Solution Approach 1:
The system performs foreign object detection (FOD) before initiating power transfer and continuously monitors during operation. By detecting metallic objects in advance and warning users before high power levels are activated, the system prevents induction heating from occurring, thus resolving the contradiction between providing sufficient power transfer capability and preventing harmful induction heating effects
2Ease of operation
If inductive power transfer structure is made open and accessible for domestic and public parking zones, then ease of operation is improved, but detection of foreign objects and living objects becomes more critical due to exceeded electromagnetic field exposure limits
Solution Approach 1:
The system performs living object detection (LOD) and foreign object detection (FOD) before activating the inductive power transfer and continuously monitors during operation. By detecting objects in advance and providing warnings or preventing activation, the system enables open and accessible parking zones while maintaining safety within electromagnetic field exposure limits
Solution Approach 2:
The system continuously monitors the inductive power region during operation and provides real-time feedback about detected objects. This feedback mechanism allows the system to adjust power levels or shut down when objects are detected, maintaining safety while preserving ease of operation in public and domestic settings
3Measurement precision
If separate detection circuits are used for foreign object detection, living object detection, and vehicle position determination, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent employs a single multi-purpose detection circuit that performs foreign object detection (FOD), living object detection (LOD), vehicle detection (VD), and position determination (PD) functions. By using one circuit to execute multiple detection tasks through different measurement modes and signal processing techniques, the system achieves comprehensive detection capability while minimizing hardware complexity and avoiding the need for separate dedicated circuits for each function
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 solution enables efficient detection and positioning of vehicles and objects within the inductive wireless charging system, ensuring safety by preventing induction heating and adhering to safe electromagnetic field exposure limits, while reducing hardware complexity and costs by integrating multiple detection functions into a single circuit.
Implementation Method 1
An alternating current passing through the coil e.g., of a primary wireless power transfer structure produces an alternating magnetic field. When a secondary wireless power transfer structure is placed in proximity to the primary wireless power transfer structure, the alternating magnetic field induces an electromotive force (EMF) into the secondary wireless power transfer structure according to Faraday's law
Implementation Method 2
metallic objects or other objects present in the magnetic field can experience undesirable induction heating
Implementation Method 3
Each of the plurality of inductive sense circuits includes at least one inductive sense element (e.g., a sense coil) and an associated capacitive element
Implementation Method 4
a measurement circuit for selectively and sequentially measuring an electrical characteristic (e.g., an impedance) in each of the plurality of inductive and capacitive sense circuits according to a predetermined time multiplexing scheme
Data Source
AI summary
A multi-purpose detection circuit for object detection and vehicle position determination is described. For example, the circuit is configurable for detecting foreign metallic objects, living objects, and a vehicle or type of vehicle above an inductive wireless power transmitter. The circuit is also configurable for determining the vehicle's position relative to the inductive wireless power transmitter. An example apparatus includes a measurement circuit including a multiplexer, electrically connected to a plurality of inductive and capacitive sense circuits, for measuring one or more electrical characteristics in each of the inductive and capacitive sense circuits according to a predetermined time multiplexing scheme. The apparatus further includes a control and evaluation circuit for evaluating the measured electrical characteristics and determining at least one of a presence of a metallic object, a living object, a vehicle, or a type of vehicle, and a vehicle position based on changes in the measured electrical characteristics.