Spread-Spectrum Wireless Power Transfer for EMI Reduction
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Solution Overview
Problem
Constant-switching power converters generate discrete harmonics that cause significant electromagnetic interference (EMI) within the communication bandwidth of wireless communication devices, affecting both the devices and the power transfer system, due to concentrated harmonic power at specific frequencies.
Innovation Solution
Implementing a spread-spectrum technique in power transfer devices, such as wireless charging pads, to vary switching parameters like frequency, pulse position, and pulse width, thereby distributing harmonic energy across a wide spectrum, reducing interference signals and maintaining energy efficiency during power transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If constant-frequency switching is used in power converters, then power transfer efficiency is maintained, but discrete harmonics cause significant electromagnetic interference within communication bandwidth
Solution Approach 1:
The patent applies dynamics by varying the switching frequency of the power converter over time rather than maintaining a constant frequency. The switching frequency is modulated to spread the harmonic energy across a broader spectrum, preventing concentration at discrete frequencies that would interfere with communication bands. This dynamic frequency adjustment resolves the contradiction by maintaining power transfer efficiency through continuous switching while eliminating EMI through frequency distribution.
Solution Approach 2:
The patent changes the switching frequency parameter from a fixed value to a variable parameter that spans a range of frequencies. By modifying this critical parameter, the harmonic spectrum is transformed from discrete concentrated lines to a distributed spread spectrum, thereby reducing electromagnetic interference while preserving the power conversion function and efficiency.
2Object-affected harmful factors
If spread-spectrum technique is used to reduce harmonic concentration, then electromagnetic interference is minimized, but switching parameters must be varied which increases system complexity
Solution Approach 1:
The patent implements periodic action by using periodic frequency modulation of the switching signal. The switching frequency varies in a periodic manner across the designated frequency range, which spreads the harmonic energy distribution periodically over time. This periodic variation achieves spread-spectrum EMI reduction while using relatively simple periodic control functions rather than complex random or chaotic modulation schemes.
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 spread-spectrum technique effectively minimizes interference within the communication bandwidth of wireless communication devices, preventing signal degradation and ensuring efficient power transfer by dispersing harmonic energy, thus reducing the average power of interference signals to insignificant levels.
Implementation Method 1
the power transfer device wirelessly charges the wireless communication device using induction
Data Source
AI summary
The present invention provides a power transfer device for charging a wireless communication device having a communication bandwidth, and an associated method of transferring power. The device and method of the invention use a spread-spectrum technique to reduce or minimize interference signals within the communication bandwidth and within the power transfer device.