Wireless Power Transmitter EMI Reduction via Frequency Spread
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Solution Overview
Problem
Wireless power transfer technologies generate electromagnetic interference (EMI) signals due to leakage magnetic fields, which can be harmful and interfere with other signals, and existing solutions either increase manufacturing costs or reduce power transfer efficiency.
Innovation Solution
A wireless power transmission/reception system that varies the frequency spectrum of the power signal and adjusts the impedance of the resonant circuit in the receiver to resonate with the transmitter, using a spread spectrum technique to minimize EMI while maintaining power transfer efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a separate coil is added to remove the EMI signal, then the EMI signal is reduced, but the manufacturing cost and device thickness increase
Solution Approach 1:
The patent extracts the EMI reduction function from a separate physical coil and integrates it into the control algorithm of the existing coil driver. By separating the harmful EMI component from the power transmission function and handling it through signal processing rather than additional hardware, the solution reduces device complexity while maintaining EMI suppression effectiveness
Solution Approach 2:
The patent introduces an intermediary control algorithm that mediates between the power transmission requirement and EMI reduction requirement. The controller adjusts the coil driving parameters dynamically to suppress EMI without needing a separate shielding coil, thus avoiding increased device complexity
2Object-affected harmful factors
If the frequency of the power signal is adjusted to remove the EMI signal, then the EMI signal is reduced, but the power transfer efficiency decreases due to frequency mismatch
Solution Approach 1:
The patent employs dynamic frequency adjustment where the controller continuously monitors and adapts the coil driving frequency to maintain resonance conditions. This dynamic control allows the system to suppress EMI through frequency modulation while simultaneously maintaining optimal power transfer efficiency by preventing frequency mismatch
Solution Approach 2:
The patent implements a feedback mechanism where the controller monitors the power transfer efficiency and EMI levels, then adjusts the driving frequency accordingly. This closed-loop control ensures that EMI reduction actions do not compromise power transfer efficiency, as any frequency drift is corrected in real-time
3Object-affected harmful factors
If the frequency spectrum of the power signal is spread, then the EMI signal is reduced, but the power transfer efficiency may be affected
Solution Approach 1:
The patent applies periodic frequency modulation where the driving frequency is varied in a controlled periodic manner to spread the spectral content of the power signal. This periodic action reduces EMI by distributing energy across multiple frequencies while the controller maintains synchronization with the receiver to preserve power transfer efficiency
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 system effectively reduces EMI signals while maintaining power reception above a specified gain by varying the frequency of the power signal and impedance of the resonant circuit, addressing the challenges of cost and efficiency in existing solutions.
Implementation Method 1
a second resonant circuit that receives the power signal, an impedance varying unit that varies an impedance of the second resonant circuit
Implementation Method 2
a leakage magnetic field generated in a coil for transmitting or receiving wireless power
Data Source
AI summary
Disclosed is a system for transmitting/receiving wireless power, the system includes a wireless power transmitter including an inverter that generates a first current using an input power source, a first resonant circuit to which the first current is applied to transmit a power signal, and a first controller that controls the inverter, and a wireless power receiver including a second resonant circuit that receives the power signal, an impedance varying unit that varies an impedance of the second resonant circuit, and a second controller that controls the impedance varying unit, wherein the first controller controls the inverter to spread a frequency spectrum of the power signal, and the second controller controls the impedance varying unit such that the second resonant circuit resonates with the power signal generated from the first resonant circuit of the wireless power transmitter. Additional various embodiments recognized through the specification are possible.