Wireless Power Receiver Load Variation for Accurate Presence Detection
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Solution Overview
Problem
Conventional impedance detection methods in wireless charging systems struggle to accurately detect a wireless power receiving unit due to insignificant changes in impedance, leading to false positives or negatives, especially when the difference in impedance between the unit's presence and absence is minimal.
Innovation Solution
A method is introduced where a dummy load is added to the wireless power receiving unit, allowing the wireless power transmitting unit to generate a load variation by switching the dummy load on or off, enabling more significant impedance changes and improving detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional impedance detection methods are used to detect wireless power receiving unit, then the detection process is simple, but the detection accuracy is low due to insignificant impedance changes
Solution Approach 1:
The dummy load is pre-configured in the wireless power receiving unit before actual power reception begins. This preliminary setup ensures that when the receiving unit is detected by the transmitting unit, there is already a significant impedance difference caused by the dummy load, enabling accurate detection without requiring complex detection algorithms or additional hardware modifications.
2Measurement precision
If dummy load is added to wireless power receiving unit, then load variation becomes significant improving detection accuracy, but device complexity increases
Solution Approach 1:
The dummy load modifies the electrical parameters (impedance, power consumption) of the wireless power receiving unit. By changing these parameters significantly when the receiving unit is active, the transmitting unit can easily distinguish between presence and absence of the receiving unit through impedance detection, achieving high detection accuracy with minimal additional hardware.
3Measurement precision
If threshold for impedance change is set low to detect small changes, then detection sensitivity increases, but false positives increase
Solution Approach 1:
The dummy load creates a large, predictable change in impedance parameters when the wireless power receiving unit is present. This significant parameter change allows the transmitting unit to set a higher detection threshold that maintains high sensitivity while minimizing false positives, as the dummy load's impedance effect is substantially different from environmental noise or interference.
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 ability of the wireless power transmitting unit to accurately detect the presence of a wireless power receiving unit by creating a noticeable load variation, reducing false detection issues and improving the reliability of the charging process.
Implementation Method 1
A power transmission method using electromagnetic induction transmits electrical power between a primary coil and a secondary coil. When a magnet is moved in a coil, a current is induced in the coil according to the rate of change of the magnetic field.
Implementation Method 2
The induction current then generates a magnetic field at a transferring end to generate energy at a reception end.
Implementation Method 3
Prof. Soljacic of the Massachusetts Institute of Technology (MIT) announced a system in which electricity is wirelessly transferred using an electric power transmission principle of the resonance scheme based on a coupled mode theory even if a device to be charged is separated from a charging device by several meters
Data Source
AI summary
A method of controlling a wireless power receiver. The method includes receiving, by a power receiver, power from a wireless power transmitter; receiving, from the wireless power transmitter, a time set value that is set for checking cross connection; in response to receiving the time set value, generating a power variation in the wireless power receiver by converting a load status from a first load status to a second load status; and maintaining the second load status for a time corresponding to the received time set value.