Wireless Charging Power Level Calculation for Foreign Object Detection
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Solution Overview
Problem
Conventional wireless charging systems face inaccuracies in power level measurement during power-transfer sessions due to disruptions from packet transfers, leading to potential false detection of foreign objects and heat generation hazards.
Innovation Solution
A power-transmitting node continuously accumulates data for transmitted power levels throughout a power-transfer session, using a subset of this data to generate accurate power levels by identifying the end of received packets and applying specific timing window parameters, ensuring accurate comparison with received power levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the TX and RX measure power levels during packet transfer periods, then real-time power monitoring is achieved, but measurement accuracy deteriorates due to current and voltage disruptions
Solution Approach 1:
The system performs power level measurements during intervals between packet transfers rather than during packet transfers. The TX accumulates transmitted power data continuously, and both TX and RX measure power levels in the intervals between CEP/RP packet exchanges, ensuring measurements are taken when current and voltage levels are stable and not disrupted by packet transfer activities
Solution Approach 2:
The system maintains continuous power monitoring capability by accumulating transmitted power data throughout the power-transfer session and selectively using measurements from appropriate intervals. The TX continuously accumulates transmitted power level data, and both nodes continuously monitor their respective power levels during measurement intervals, ensuring uninterrupted monitoring capability while avoiding packet transfer disruptions
2Reliability
If the TX compares transmitted power level with received power level to detect foreign objects, then foreign object detection capability is achieved, but false positive detections occur due to timing mismatches in fluctuating power levels
Solution Approach 1:
The RX transmits RP packets containing its measured received power level to the TX, which then compares this feedback with its own transmitted power level measurement. This feedback mechanism enables the TX to detect foreign objects by comparing power levels while accounting for the timing and fluctuation characteristics of the wireless power transfer
Solution Approach 2:
Both the TX and RX perform their power level measurements during the same interval between packet transfers, ensuring temporal alignment before comparison. The TX accumulates transmitted power data and identifies the specific interval for measurement, while the RX simultaneously measures received power in that same interval, ensuring both measurements correspond to the same time period despite power level fluctuations
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 enhances the accuracy of power level calculations, reducing false positive foreign object detections and ensuring safe operation by maintaining accurate power level measurements even during packet transfers.
Implementation Method 1
a power source (referred to herein as a power-transmitting node or TX) transmits power wirelessly via inductive coupling to a power sink (referred to herein as a power-receiving node or RX)
Implementation Method 2
The inductive coupling between a TX and an RX is achieved via resonant transducer circuitry in each node having similar if not identical resonant frequencies
Implementation Method 3
If a metal foreign objected (FO), like a coin, a key, or other metal object, is placed on or at least near the TX during a power-transfer session, inductive coupling between the TX and the FO may result in the generation of heat in the FO
Data Source
AI summary
In a wireless charging system, a power-transmitting node (TX) has a transmitter for transmitting power wirelessly to a power-receiving node (RX), and a signal receiver for receiving signals from the RX. During a power-transfer session, the TX accumulates data corresponding to its transmitted power level, detects an end of a received power (RP) packet from the RX, and then identifies a subset of the accumulated data. The TX calculates its transmitted power level using the subset of the accumulated data. The TX extracts a received power level of the RX from the received RP packet and compares its calculated transmitted power level with the RX's received power level to determine a presence of a foreign object. Accuracy of FO detection when packets from the RX are not properly received by the TX is improved.